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CO2 capture and sorbent regeneration performances of some wood ash materials
Abstract
Wood ash, which is recognized as an environmental pollutant, is tried as a new material for CO2 capture in this work. Five wood ash samples obtained from different raw materials were chosen, and an experimental demonstration of the CO2 capture performances of these wood ash samples was present in detail in a modified fixed bed reactor system. The CO2 capture and the sorbent regeneration performances of wood ash were investigated under different conditions by changing the temperature, H2O concentration, gas flow rate and the heating rate. The CO2 capture capacities are in the range of 0.35-0.54 mmol CO2/g for different wood ash samples under the condition of 60 degrees C, 10% CO2 + 12% H2O. The CO2 capture processes contain two parts for these samples. One is the physical adsorption process, and another is the chemical reaction of K2CO3 with CO2 and H2O to form KHCO3, K2CO3.1.5H(2)O and K4H2(CO3)(3).1.5H(2)O The desired wood ash is proved to be regenerable and stable during 10-cycle CO2 sorption-desorption tests. The deactivation model and the Avrami-Erofeyev model are adopted to evaluate the CO2 sorption and desorption kinetics of this sample respectively. Considering the low cost, and the recycling of environmental pollutants, wood ash is a nice choice for CO2 capture.
... A elevada habilidade de remoção de dióxido de carbono do biogás está relacionada com o alto teor de CaO nas cinzas de madeira. A extração do CO 2 pela cinza de madeira é realizada por processo de carbonatação acelerada (GUO et al., 2015). ...
... No entanto, é necessário avaliar a adsorção com cinzas em escala piloto antes da sua utilização, pois foram Durante a adsorção do CO 2 pelas cinzas de madeira, o pH é reduzido devido a conversão de carbonatos em bicarbonatos. As reações acontecem de forma mais eficiente quando o processo é realizado por via úmida do que de maneira seca, por isso, a água é um requisito fundamental no processo (GUO et al., 2015). ...
... Alta capacidade de remoção de CO2 do biogás (GUO et al., 2015). ...
Biogas, among the options currently available, presents itself as an important source of renewable and sustainable energy. To improve its usability, biogas needs to go through the purification process, which corresponds to the removal of CO2 and other elements such as hydrogen sulfide. This article aimed to review in the literature the use of low-cost natural materials that have the potential to be used in the purification of biogas, pointing out their adaptations in terms of adsorption capacity and methods of obtaining them. The methodology adopted was the literature review, carried out through an electronic search of scientific articles in the ScienceDirect database from 2017 to 2021. Adsorption-based processes have been widely used and studied in biogas purification due to their requirements for relatively low energy, easy control and low operating costs. The use of natural materials, with local availability and low cost, such as fly ash, zeolites and biomass materials are effective for use in biogas purification. Natural materials are easily adjusted and simple to operate, making them suitable for use as carbon dioxide adsorbents. However, to make natural materials more competitive, greater investments in research on suitability for specific uses for removing pollutants from biogas are needed.
... For example, the bark and wood residues can be used as a raw material for particle board and chemical pulp production. Furthermore, energy can be produced by burning wood waste from the debarking plant, black liquor from the pulp making process, and bio sludge from wastewater treatment plants, as a forest fertilizer, or a raw material for the synthesis of a porous, ceramic composite [2 -7], material for CO 2 capture [3]. ...
... The chemical composition of wastes is the first step and initial approach for characterization. It was found repeatedly that biomass shows a wide diversity and its composition is significantly or highly variable [2,3,11,13]. The composition of natural biomass depends on various factors, name type of biomass, plant species or part of plants, growth processes, growing conditions, location, seasons, blending of different biomass types some similarities or differences in common chemical characteristics for biomass varieties, reported in almost all investigations [13]. ...
The main part of companies in Bulgaria are built, however in the 70s, and upgraded last decade. The countrysupplies around 80 % of its supplies of paper, paperboard and pulp with own production. Integrated treatment ofwastes is a priority for realizing closed life cycle of materials. The aim of the present work is to investigate thecomposition and other important characteristics of biomass wood ash wasted from paper industry. The correlationsand associations among the chemical characteristics are also studied to find some basic trends and importantrelationships between two similar wastes from different enterprises. It was proved that all samples taken containedBa, Cr, Mn, Ni, Co, Al, Fe, Cu and Zn far below the legal limits for such type of products. A product has a certain anti-acidic effect. The other positive result was that the content of iron is between 34 to 60 mg per 1 kg dry waste. The microscopic photos confirmed that the particles are close to the nano-size materials. The content of the elements C, N, H is in good quantities and ratios, which is a prerequisite for their use as a soil improver. By the results of this study, it was confirmed that all samples produced as a result of the thermal treatment and final low water content achieved are free from pathogen microorganisms and different weed seeds, affecting the yield and soil sustainability. That allows determining the optimal ratio between the used components with a view to obtain products with desired thermal stability and physico-chemical properties as soil improvers.
... In principle, thermal treatment changes the structural properties and adsorption capacity by eliminating hydrogen and heteroatoms and disintegrating carbon frameworks, depending on the applied temperature, feedstock type, and mineral concentration. For instance, thermally modified wood ash samples at 280 °C caused the carbon framework to burn, leaving Si particles that resulted in higher surface area and Si concentration [37]. ...
... The high initial pH of the slurry and the presence of CaO in the wood ash caused CO 2 adsorption due to the reaction between calcium bases and CO 2 . The CO 2 was captured by wood ash adsorbents in a two-part process: physical adsorption and chemical interaction of K 2 CO 3 with CO 2 and H 2 O [37]. Similarly, ash generated by wood combustion was evaluated for CO 2 capture [110]. ...
Purpose of Review
Wood-based adsorbents are increasingly used for environmental applications. They demonstrate considerable advantages, including renewable feedstock, relatively simple preparation processes, and advantageous structural and surface properties. In short, they provide environmentally friendly, effective, and economical sources for contaminant removal. This review summarizes recent advances in the preparation and use of selected modified wood-based residues (biochar, ash, and cellulose) as adsorbents for environmental applications (water, air, and soil remediation).
Recent Findings
Although chemical modifications have produced better results for wood-based adsorbents, the inherent corrosion problems and safety issues have made physical modifications more feasible on an industrial scale. For environmental remediation, inorganic contaminants can be removed by raw and modified wood-based adsorbents, mainly via electrostatic interaction, surface complexation, pore filling, and ion exchange. Organic contaminants are removed via van der Waals forces between unsaturated polycyclic molecules, pore filling, and hydrogen bonding. Specific surface area and porosity are critical parameters for effective contaminant adsorption, mostly from water and air. A comparison of wood-based residues used for wastewater treatment ranked the efficiency as ash > cellulose > biochar versus cellulose > biochar > ash for air remediation. Adding modified wood residues to soil enhances the fertility and biological characteristics in addition to remediation. Moreover, spent wood-based adsorbents can be used in construction materials, soil fertilizers, and catalysts.
Summary
This review summarizes classical and new physical and chemical methods for modifying wood adsorbents and the impacts on physiochemical characteristics such as porosity, pore volume, surface area, and surface functional groups. Also addressed are the adsorption capacity and efficiency of raw and modified wood adsorbents for removing contaminants from synthetic effluents, mine water, air, and soil. Valorization methods for spent modified wood-based adsorbents are then outlined. Suggestions and prospects are given for future studies on environmental decontamination by wood residues.
... Recently, enormous studies on the synthesis of activated carbons from distinct biomass materials have been reported as CO 2 adsorbents. Some of the commonly used biomass precursors are rice husk [21], coconut shell [22,23], orange peel [24], rubber-seed shell [25,26], shrimp shell [27], almond shell [28], hazelnut shell [29], walnut shell [30], pistachio-nut shell [31], palm kernel shell [32], and wood ash [33]. Despite its huge applicability, it is still a challenging task to attain activated carbons with excellent textural features and favorable surface heterogeneity, simultaneously, from a complex 3D biomass structure attributed to the high oxygen content and strong chemical bonding [34]. ...
... Biomass-an organic, renewable, and sustainable carbon-rich material generally composed of plants with complex natural polymers such as hemicellulose (15-30 wt.%), lignin (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33) wt.%), cellulose (40-50 wt.%), and other extractive materials (1-10 wt.%) which function as structural organizing ingredients [35]. Fig. 2 demonstrates the typical chemical structure of biomass i.e., lignocellulosic biomass. ...
Solid adsorbents are considered very attractive for selective CO2 removal from main emission sites, and this method was found suitable for post-combustion carbon capture owing to its cost-effective and retrofit...
... A milestone in the application of fly ash in CO 2 adsorption is the regeneration of the materials, which is typically influenced by temperature, heating rate, and flow rates [14,16]. Thus, it was demonstrated that a maximum temperature of 473 K (with an increment of 10 K/min) is sufficient for a complete regeneration of the ash in about 30 min [16], while, in other studies the temperature was below 423 K and the time shorter [14]. ...
... A milestone in the application of fly ash in CO 2 adsorption is the regeneration of the materials, which is typically influenced by temperature, heating rate, and flow rates [14,16]. Thus, it was demonstrated that a maximum temperature of 473 K (with an increment of 10 K/min) is sufficient for a complete regeneration of the ash in about 30 min [16], while, in other studies the temperature was below 423 K and the time shorter [14]. This difference could be explained by the applied gas flow rates. ...
In order to obtained high selective membrane for industrial applications (such as natural gas purification), mixed matrix membranes (MMMs) were developed based on polysulfone as matrix and MCM-41-type silica material (obtained from coal fly ash) as filler. As a consequence, various quantities of filler were used to determine the membranes efficiency on CO2/CH4 separation. The coal fly ash derived silica nanomaterial and the membranes were characterized in terms of thermal stability, homogeneity, and pore size distribution. There were observed similar properties of the obtained nanomaterial with a typical MCM-41 (obtained from commercial silicates), such as high surface area and pore size distribution. The permeability tests highlighted that the synthesized membranes can be applicable for CO2 removal from CH4, due to unnoticeable differences between real and ideal selectivity. Additionally, the membranes showed high resistance to CO2 plasticization, due to permeability decrease even at high feed pressure, up to 16 bar.
... 32.0 R 2 : coefficient of determination; CK 1 : no stover addition; CK 2 : maize stover; CK 2 + WA: maize stover + wood ash; CK 2 + OS: maize stover + oil shale; C s : slowly mineralizable C pool; C r : rapidly mineralizable C pool; k s : mineralization rate constant for C s ; k r : mineralization rate constant for C r . active components, such as alkaline and alkaline earth metal oxides and their carbonates, as well as a larger contact area for the reactant gas with these active components (Guo et al. 2015). The CO 2 emission in CK 2 + OS was lower than that in CK 2 , although the difference was not significant, indicating that oil shale did not have a positive effect on CO 2 emission, possibly because the oil shale amendment reduced native SOC mineralization. ...
... Soil CO 2 and Ca 2+ content, pH, and water conditions influence the formation of calcium carbonate. Similarly, other studies have reported that wood ash from bark, sawdust, and branches containing high CaO content are low-cost options for CO 2 sequestration (Guo et al. 2015). The major elements of wood ash from various sources include high amounts of Ca (7-33%) and moderate amounts of K (3-4%), Mg (1-2%), and P (0.3-1.4%) (Vance and Mitchell 2000). ...
Soil organic carbon (SOC) and inorganic carbon (SIC) are important carbon reservoirs in terrestrial ecosystems. A large portion of carbon from stover enters the atmosphere after stover return. However, there is little information on soil carbon sequestration during stover decomposition. In this study, a 54-day incubation experiment was conducted in calcareous soil to investigate the effects of wood ash or oil shale application (1.2 w/w%) on CO2 emissions, soil C content, and other soil chemical properties. Four treatments were compared: (i) no maize stover addition; (ii) 1.5% maize stover; (iii) 1.5% maize stover plus 1.2% wood ash; and (iv) 1.5% maize stover plus 1.2% oil shale. Wood ash addition decreased CO2 emission as a result of enhanced SIC sequestration in soil amended with maize stover; oil shale enhanced SOC due to increased carbon input from recalcitrant oil shale. Wood ash addition also significantly increased soil pH and soil microbial biomass carbon. The addition of wood ash to soil may be a potential strategy for promoting inorganic carbon storage and mitigating CO2 emissions after stover return. In addition, oil shale is a very stable C source and oil shale amendment could be an efficient, long-term strategy to sequester organic C in soils.
... Importantly, due to the massive global production (7.6−15 Gt/a) of BA, 22,23 it can meet the large quantities for BS treatment. Previously, BA was successfully adopted for simultaneous CO 2 sequestration and BS decrement. ...
Upgrading biogas to biomethane via CO2 sequestration is an affordable technology to achieve negative carbon emissions, where minimizing energy consumption is a significant issue. Herein, a novel agriculture-friendly green absorbent, composed of biomass ash (BA) and biogas slurry (BS), is put forward as a medium to transport CO2 from biogas into plants due to CO2 reactions with Ca2+ in BA and free ammonia in BS, and the low physiological toxicity of BA and BS. We further identified the simultaneous CO2 and H2S removal performance of the BA–BS absorbent and evaluated the negative carbon emission of biomethane production based on a biogas plant with a capacity of 10,000 m3-biogas/d. Under the conditions on CO2 partial pressure of 400 kPa, a temperature of 25 °C and a mass ratio of BS to BA of 4:1, amaximum CO2 absorption capacity of 23.72 g-CO2/kg-absorbent and an H2S removal efficiency of 100% could be achieved. Moreover, compared to the inexpensive pressurized water scrubbing system, the biogas upgrading system with the proposed novel absorbent could achieve a lower cost ($0.30/Nm3-biogas) but a higher negative carbon emission (501.33 g-CO2E/Nm3-biogas) and systemic energy efficiency (96.4%). It might provide a practical strategy for biomethane production with low cost and negative carbon emission.
... Renewable energy resources are only a solution to reduce the problems related to conventional resources. Globally, it is expected that bioenergy will reach 20% by 2050 [2]. Bioenergy is mostly composed of biodiesel, bioethanol, and biogas. ...
The availability of pollutants in biogas especially carbon dioxide hinders its application in the enginery parts by minimizing its calorific standards. The presence of CO2 contributes to global warming which is a worry globally. Thus, upgrading technologies is needed for safe utilization on small-scale and wide-range. The commercial technologies mostly discussed in the literature are pressure swing adsorption, membrane separation, physical scrubbing, and water scrubbing. These techniques are costly concerning investment, and operation costs, and are energy-intensive, especially on a small scale. Thus, difficult to apply especially in low-income economies, and necessitates the development of natural, low-cost sorbents for biogas upgrading like biomass, eggshell waste, and clay soil. The current review critically evaluates the potentiality of new approaches using low-cost sorbents for biogas upgrading. The review proposed that activating and additional of pore-forming materials in the adsorbents is necessary to significantly enhance their performance.
... The results of grey water before and after treatment by using ash of leaves of tulsi (Ocimum tenuiflorum) and subabul (Leucaena leucocephala) are shown satisfactory and in an average of 34 % of pollutants were minimized and nearly about same results were found in some selected research paper/articles written by researchers [11,2a,12] and some parameters results were nearly same were found in this research article [13]. ...
Plants are very useful every time in an environment. Greywater generation is not in the control of humans, but the treatment of greywater is in our hands. This study was based on greywater treatment and minimizing its impact using the ash of plant leaves of tulsi (Ocimum tenuiflorum) and subabul (Leucaena leucocephala) as eco-friendly tactics towards sustainable greywater management. This study focused on using plant leaves as adsorbents to minimize unwanted substances in grey water. The leaves of plants can burn at high temperatures in a controlled environment to obtain ash, which is used to minimize and remove pollutants like nutrients, organic compounds, and impurities, from grey water. The study aims to investigate the efficiency of plant leaf ash as an adsorbent, and the potential of the plant leaf for grey water treatment. The study could have significant implications for the development of low-cost and eco-friendly greywater treatment technologies. The use of plant leaf ash for greywater treatment could provide a sustainable and natural alternative to conventional greywater treatment methods. It will minimize the biochemical oxygen demand, chemical oxygen demand, organic matter load, and NPK also at a certain level and it helps to minimize the toxicity of greywater. The results showed that plant leaf ashes were effective in reducing the levels of pollutants.
... Particularly, the CO 2 sorption efficiencies of the regenerated coupled samples which go through 1-5 cycles are all much higher than that of the newly prepared sample which keeps 100% efficiency for only 1650 s as mentioned above. That should be attributed to the structure-property change of the coupled samples during the regeneration [43][44][45][46]. Furtherly, the accumulated CO 2 sorption amount of the regenerated sample in each round was summarized and depicted in Fig. 13b. ...
Deactivation of catalyst for the oxidation of carbon monoxide in the impurity gases such as CO2, SO2, and NOx are common issues in practical use. In this work, Cu–Mn–Ce composite oxide catalysts (CMCO) were coupled with K2CO3 (KC) to inhibit the poisoning effect of these gases. The CMCO/KC composite catalysts, prepared by multi-step impregnation method, were tested for CO catalytic oxidation and CO2 chemical absorption in the presence of SO2 (0.004% and 0.04%) or NO2 (0.0025% and 0.025%), and further characterized by XRD and XPS. The results showed that CMCO/KC could catalyze CO efficiently at low temperatures, and proper K2CO3 addition (10–50 wt%) could even promote CMCO catalytic activity owing to the CO2 sorption. Among them, CMCO/50KC showed the highest CO catalytic performance with the T50 of 114.5 °C. More importantly, K2CO3 doping treatment could reduce or eliminate the catalyst deactivation caused by SO2 and NO2, due to the competitive sorption reaction of the alkali toward the acid gases. Further regeneration experiments revealed that CMCO/KC also had fine regeneration activity and stability for CO/CO2 removal.
Graphical Abstract
... Wood ash with high carbon content and large surface area is similar to activated carbon and can be used to control odors associated with wastewater and biosolids [71]. Even wood ash can be used as a catalyst and carbon dioxide adsorbent [72,73]. ...
Wood resources, including wood materials and wood fuel, have been widely used since the beginning of human society. Today’s surging demand for buildings and energy has made people more dependent on wood, and as a result, the world produces tens of millions of tons of wood ash every year. How to manage and reuse these wastes has gradually aroused people’s concern. Among many beneficial management options, this paper focuses on civil engineering, the world’s most energy-intensive and resource-consuming sector. Through reviewing the research on using wood ash in concretes and mortars, geopolymers and alkali-activated materials, road construction and soil stabilization, bricks, panels, and other green construction materials, this paper explores the possibility and potential of using wood ash in civil engineering. Given the current situation of preferentially studying mechanical properties, this review further discusses some research questions, such as the limitation of wood ash itself, costs, environment, and standards and regulations, hoping to improve the commercialization and valorization of wood ash.
... Wood ash can also be used to improve the properties of concrete such as removal of water and enhancement of its strength (Siddique, 2012). The main chemical components of wood ash include; CaO, SiO 2 , Al 2 O 3 , Fe 2 O 3 , K 2 O, MgO, MnO, Na 2 O, P 2 O 5 and TiO 2 (Guo et al., 2015). ...
Carbon dioxide and hydrogen sulfide are the main contaminants in biogas, which reduce its calorific value and cause wear on metallic appliances through corrosion. There are no comparative studies on the potential of dry adsorption and wet wood ash (carbonation) process on biogas upgrade. The current study for the first time investigates the effects of different process parameters on the use of wood ash for purification of biogas and compares the performance of the two processes. The chemical composition of wood ash was characterized using X-ray fluorescence (XRF) while biogas was analysed using gas chromatography and a digital biogas analyser. The effects of process parameters on biogas carbonation method were investigated. The highest CO2 uptake and methane increment achieved by use of wood ash slurry was 2.30 mmol/g-wood ash and 88%, respectively. This high CO2 uptake was possibly due to the high content of oxides (46% TS) in natural wood ash. The optimum conditions of adsorbent/water ratio and biogas flow rate for methane enhancement were 1:4, and 100 ml/min, respectively. In dry adsorption processes, an increase in mass of activated wood ash from 2.5 to 35 g increased CO2 removal from 8.9 to 67.9%. Furthermore, the evaluation of carbonation adsorption indicated that the process followed pseudo-first order kinetics. Activation of wood ash did not significantly improve its CO2 uptake by carbonation while the uptake by activated wood through dry adsorption was comparable to that of raw wood ash through carbonation process. Conclusively, raw wood ash by carbonation process is a good candidate recommendable for purifying biogas in household digesters.
... However, as the unburnt carbon content of wood ashes is one of the limiting factors [262], the ash from modern commercial biomass power stations where there is careful combustion control may be more suitable than the ash used many older studies. Another proposed application of wood ash that exploits its Ca-alkalinity is to produce sorbents for end-of-pipe CO2 separation and capture [267,268]. Surface modification, such as surface coating by alkaline metal salts or amines, can enhance the CO2 capture ability of wood ash [236,267]. ...
Use of biomass for energy production is increasing, so management of the resultant ash is important. This review compares current and future production, chemical composition, and reuse options for ash from common feedstocks (agricultural residues, energy crops, woody biomass, forest residues, recovered wood, paper sludge, sewage sludge and municipal solid waste). Global production is ~170 Mt/yr, but could increase to ~1000 Mt/yr if all available biomass were exploited. Current production is dominated wood and waste derived ashes, but there is capacity to greatly increase use of agricultural residues. Combustion of virgin biomass in modern furnaces can produce ash with negligible persistent organic pollutants and low contaminant metals concentrations, so application to land is possible. Agricultural residue ashes contain abundant potassium and useful phosphate, so could potentially be used as fertiliser. Forestry ashes are rich in CaO, but slightly higher contaminant metals levels may restrict their use to forestry soils. Recovery of potassium from these ashes, and their use in cementitious materials have also been demonstrated. Biomass containing waste ashes potentially contain more persistent organic pollutants and contaminant metals. However, municipal solid waste bottom ash is routinely used as a construction aggregate for prescribed applications. Paper sludge ash is suitable for restricted use as a soil conditioner and possibly as a secondary pozzolan. However, controlled disposal may be required for recovered wood ash and sewage sludge incineration ash. As persistent organic pollutants tend to partition to the flue gases, fly ash and air-pollution control residues are likely to require controlled disposal.
... Therefore, the reuse of ash has gained an increased interest. Depending on the composition and geographical region, ash has been used in agriculture (soil amendment), as forest soil amendment, to control the odor and pH of some wastes, to remove pollutants from water and to produce ceramics and building materials (cement base and road base material) [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. ...
The sustainable economy framework imposes the adoption of new ways for waste reuse and recycling. In this context, this paper proposes a new alternative to obtain glass fertilizers (agriglasses) by reusing two cheap and easily available wastes, wood ash and manganese rich sludge resulting from drinking water treatment processes for groundwater sources. Glasses were obtained using different amounts of wastes together with (NH4)2HPO4 and K2CO3 as raw materials. The P-K-Mn nutrient solubilization from the obtained glasses was investigated using a citric acid solution. The kinetics of the leaching process was studied after 1, 7, 14, 21 and 28 days, respectively. The intraparticle diffusion model was used to interpret kinetic data. Two distinct stages of the ion leaching process were recorded for all of the studied compositions: first through intraparticle diffusion (the rate-controlling stage) and second through diffusion through the particle–medium interface. The fertilization effect of the obtained agriglasses was studied on a barley crop. The specific plant growth parameters of germination percentage, average plant height, biomass and relative growth rate were determinate. The positive impact of the agriglasses upon the plants biomass and relative growth rate was highlighted. The effects of agriglasses can be tuned through glass compositions that affect the solubility of the nutrients.
... MgO sites form from the magnesium nitrate hexahydrate which dehydrates to the anhydrous salt Mg(NO 3 ) 2 between 110 • C and 190 • C; over 400 • C these decompose to MgO. The formation of carbonates is an additional avenue that is seeing increased focus especially in the context of producing adsorbents from waste such as wood ash, biomass ash, coal ash, solid refuse fuel ash and steel slag to name a few [368][369][370][371][372]; the process of carbonation however and the methods to improve such are not within the scope of this review. ...
The mitigation of climate change, abatement of greenhouse gas emissions and thus, fundamentally, the separation of CO2 from various gas streams are some of the most pressing and multifaceted issues that we face as a society. De-carbonising our entire civilisation will come at a great cost and requires vast amounts of knowledge, initiative and innovation; yet, no matter how much time or money is spent, some sectors simply cannot be de-carbonised without the deployment of carbon capture and storage technologies. The technical challenges associated with the removal of CO2 are not universal – there exists no single solution. Capturing the CO2 on solid sorbents has been gaining traction in recent years given its cost-effectiveness as a result of its ease of application, relatively small energy requirements and applicability in a wide range of processes. Even with the myriad materials such as zeolites, carbons, metal organic frameworks, mesoporous silicas and polymers, the challenge to identify a sorbent with optimal capacity, kinetics, selectivity, stability and ultimately, viability, still persists. By tailoring these solid materials through comprehensive campaigns of surface modification, the pitfalls of each can be mollified and the strengths enhanced. This highly specific tailoring must be well informed so as to understand the mechanisms by which the CO2 is adsorbed, the surface chemistry that has influence on this process, and what methods exist to facilitate the improvement of this. This review endeavours to identify the surface functional groups that interact with the CO2 molecules during adsorption and the methods by which these functional groups can be introduced. It also provides a comprehensive review of the recent attempts and advancements made within the scientific community in the experimental applications of such methods to enhance CO2 capture via adsorption processes. The primary search engine employed in this critical review was Scopus. Of the 421 references cited that embody the literature focussed on surface modification for enhancing the selective adsorption of CO2, 370 are original research papers, 43 are review articles and 7 are conference proceedings.
... 4,5,7,8 Another promising application is the use as adsorbent for the removal of various pollutants from wastewater. 9,10 Manganese is one of the most abundant metals in nature having an essential role for the human body, enzymes activation and for plants growth. [11][12][13] It is mostly used in industry, with application in metallurgy, ceramics, dry battery cells, electrical coils, food and pharmaceutical production. ...
BACKGROUND
In the circular economy context, the present article proposes a green technical solution by manganese ions adsorption on oak wood ash and the reuse of the new waste generated by the adsorption process as soil amendment.
RESULTS
The influence of the main process variables: pH, adsorbent dose and contact time was investigated for optimal manganese ions adsorption. The highest adsorption efficiency of the wood ash (more than 98%) was recorded at pH 6, adsorbent dose of 10 g L⁻¹ and contact time 15 min. The ion adsorption process is best described by Langmuir isotherm and pseudo second‐order kinetic model. Maximum adsorption capacity, 54.94 mg g⁻¹, is better than other adsorbent materials previously used for manganese adsorption. The exhausted wood ash, resulted after the manganese adsorption was used as soil amendment for barley crop, Hordeum vulgare L. The beneficial effect upon the studied plants was highlighted using the specific parameters: germination percent (up to 10% higher), plant average length (higher by 14–35%), biomass (up to 200%) and relative growth rate (higher by 6–12%) compared to those obtained for the control sample.
CONCLUSION
These results show that all the wastes involved have been used successfully and support the proposed eco‐friendly technical solution for some industrial wastes management. © 2020 Society of Chemical Industry
... Biomass based porous carbons, for example, derived from almond shells/olive stones [13], wood ash [14], and plastic [15] proved to be highly effective for CO 2 adsorption. Additionally, the regeneration of such porous carbons is expected to be less energy intensive requiring mild temperatures for a much shorter duration, which in combination with the CCS could bring down the regeneration heat requirements even below 40%. ...
The energy penalties associated with the liquid amines carbon dioxide absorption are huge which could be minimised by using materials based carbon capture adsorption. A facile one-step approach for the preparation of activated porous carbon spheres through direct carbonization of d-glucose with a novel non-corrosive chemical, potassium acetate for carbon dioxide capture is presented here. The amount of potassium acetate is varied to control the chemical structure, morphology, porosity and textural features. The potassium acetate/d-glucose impregnation ratio of 3 is optimum condition for obtaining activated porous carbon spheres with high specific surface area (1917 m² g⁻¹), spherical morphology, and specific pore volume (0.85 cm³ g⁻¹). The activated porous carbon spheres prepared using different glucose to potassium acetate ratios are employed as carbon dioxide adsorbents. Among all, activated porous carbon spheres prepared with the potassium acetate/d-glucose of 3 registers the best performance and exhibits carbon dioxide adsorption capacities of 1.96 and 6.62 mmol g⁻¹ at 0 °C/0.15 bar and 0 °C/1 bar. It also shows impressive carbon dioxide adsorption at 0 °C/30 bar (20.08 mmol g⁻¹) and 25 °C/30 bar (14.08 mmol g⁻¹). This performance is attributed to highly developed porous structure of the optimized material. Low isosteric heat of adsorption (24.8–23.04 kJ mol⁻¹) means physisorption which suggests lower energy penalties for material regeneration. A non-complicated synthesis and high carbon dioxide capture demonstrate the importance of this work. This synthesis strategy may be utilized to prepare porous carbons from other precursors which could find potential in energy-related applications.
... kJ mol À1 ) led to the conclusion that both chemical and physical modes of adsorption are at play in this case. Wood ash based activated porous carbon has been recently proposed for CO 2 capture with chemical sorption being the main operating mode in the adsorption process [149]. Analysis before and after CO 2 adsorption indicated that the presence of alkali and alkaline earth metals in the wood ash leads to a chemical reaction with CO 2 and H 2 O resulting in the formation of various carbonate products. ...
The quest for producing cost-effective and efficient adsorbents for CO 2 capture has received enormous attention in recent times. Biomass-derived porous carbons are considered to be the most preferred adsorbent materials for CO 2 capture owing to their excellent textural properties, tunable porosity and low cost. Different type of activation processes including solid-state activation possess generate appropriate morphology and other physico-chemical properties in these materials which enable them to act as effective adsorbents for CO 2 capture. In this review, the key scientific results from published literature have been consolidated and critical commentary has been provided to give a broad insight into the production of biochar and activated porous carbons and their application in CO 2 capture. A thorough review of the mechanism of pyrolysis for cellulose, hemicellulose and lignin has been presented in detail. The ability of different activating agents to produce activated porous carbons has been discussed. A summary of the application of biochar and activated porous carbons for CO 2 capture has been included. The review concludes with an overview of future outlook and potential research direction that could be undertaken for advancing the utilization of biomass-derived porous carbon materials for applications including CO 2 capture and energy storage.
... The studies on the use of ashes from coal-fired power generation are carried out in many countries (noack et al. 2014;Mayoral et al. 2013;Siriruang et al. 2016;Ukwattage et al. 2013Ukwattage et al. , 2015Guo et al. 2015;Ebrahimi et al. 2017;Ji et al. 2017;Jo et al. 2012;Dananjayan et al. 2016;Mazzella et al. 2016;Wee 2013;Bobicki et al. 2012), including Poland (Uliasz--Bocheńczyk et al. 2006a, b, 2007, 2008, 2011, Uliasz-Bocheńczyk 2008, 2011. ...
As a result of energy production processes, the power industry is the largest source of CO2 emissions in Poland. Emissions from the energy sector accounted for 52.37% (162 689.57 kt) of the total emissions in 2015, which was estimated at 310.64 million tons of CO2. In recent years, the tightening of regulations on the use of renewable energy sources has resulted in an increased amount of biomass used in the professional energy industry. This is due to the fact that the CO2 emissions from biomass combustion are not included in the total emissions from the combustion of fuels, resulting in the zero- emission factor for biomass. At the same time, according to the hierarchy of waste management methods, recycling is the preferred option for the management of by-products generated during energy production. The fly ashes resulting from the biomass combustion in pulverized boilers (which, due to their chemical composition, can be classified as silicate ash) were subjected to analysis. These ashes can be classified as waste 10 01 17 - fly ash from co-firing other than mentioned in 10 01 16 according to the Regulation of the Minister of the Environment of December 9, 2014 on waste catalogues. The maximum theoretical carbon dioxide binding capacity for the analyzed fly ashes resulting from the co-combustion of biomass is 8.03%. The phase composition analysis of the fly ashes subjected to carbonation process has shown, in addition to the components identified in pure fly ash samples (SiO
... The CO2 sorption capacity increased when increasing the amount of K2CO3. Yafei et al. [5] investigated the CO2 capture performance of some wood materials by using fluidized bed reactor. The component of employed wood materials was investigated by XRD which showed high K2CO3 component. ...
Alternative energy is one of the methods for decreasing fossil fuel consumption. However, conventional fossil fuel process improvement is also considerably interesting issue due to the fact that adjusting existing process is easier and cheaper comparing to the development of the process compatible with the alternative energy. At present, the global warming and climate change phenomenon cause the increasing of average earth temperature. The CO2 emission to the atmosphere is mainly produced by fossil fuel combustion from power industry. This is because the CO2 has high heat capacity. Therefore, in order to use the conventional fossil fuel process efficiently, CO2 should be eliminated from the flue gas before releasing it to the environment. Currently, there are many methods that use to capture CO2 such as using circulating fluidized bed riser with solid sorbent. The advantages of circulating fluidized bed riser are uniform solid particle and temperature distributions, high contacting area between gas-solid particle and suitable for continuous operation. In this study, the effect of operating parameters on CO2 capture in circulating fluidized bed riser with solid sorbent is investigated using 2D computational fluid dynamics model. The basic simulation step has to find the suitable computational mesh cells or grid independency test (5,000, 10,000, 15,000 and 20,000 cells) and compare the simulation result with the real experimental result. According to the simulation results, the suitable mesh cell is 10,000 cells and the obtained result is matched with the experimental results. Then, the effect of operating parameters on the CO2 capture conversion is optimized.
... Pour avoir une structure bien plus légère au lieu d'utiliser une structure en béton, on peut utiliser à sa place une structure en acier dont l'impact a été déjà étudié par (Olmez et al. 2016). Mais il est mieux de prendre le bois grâce à son aptitude de stocker le CO2 (Guo et al. 2015). Le fait de ne pas utiliser beaucoup de plastique diminue l'impact de la couche de protection. ...
De nos jours, la protection de l’environnement est un défi international. Le toit vert est l’un des concepts innovants pour faire face à cette bataille. On observe une augmentation de son utilisation dans les zones urbaines à travers le monde. Mais une question se pose : quelles sont les conséquences sur l’environnement du cycle de vie du toit vert ? Dans cet article, les performances environnementales de deux systèmes complets de toits verts léger et lourd implantés à Antananarivo-Madagascar sont analysées et comparées dans le but de déterminer les impacts potentiels des deux systèmes de toit vert. Des solutions sont avancées pour diminuer les charges environnementales des toits verts. L’approche d’Analyse de Cycle de Vie (ACV) a été utilisée pour réaliser l’étude. Les différentes phases de l’approche : 1-définition des objectifs, 2-inventaire de cycle de vie, 3-caractérisation des impacts, 4-interprétation des résultats, ont été déroulées sur le système du toit vert. Les calculs ACV ont été effectués avec le logiciel OpenLCA. Les résultats de l’étude montrent que, les matériaux vierges et/ou importés sont les plus impactant : 1- L’utilisation du ciment, gravillon, matière plastique vierge, terre est à éviter; 2- Diminuer au maximum l’importation des matériaux surtout s’il s’agit d’un transport aérien ; 3- Choisir des engrais naturels et de l’eau de puits pour l’arrosage au cours de l’utilisation du toit vert.
... The characterization of these white layers using sterol and phytosterol is quite difficult in this scenario due to the absence of COP, EpiCOP, and Stigtanol (or low concentration) in all the white samples. Furthermore, these layers indicative of burning can absorb the compounds leaching from layers above due to its composition which could explain the existence of some compounds in some of the white layers [47,48]. ...
The characterization of ancient lipids from prehistoric organic residues (fumiers) located in rock-shelters has been possible after the optimization of an analytical method based on the microwave-assisted extraction and solid-phase extraction clean-up step and a final derivatization step followed by gas chromatography with mass spectrometry. Eight sterols and two bile acids were detected just in the partially burned and unburned layers of the fumiers (animal organic residues deriving from manure/dung). The relationship between some of these compounds can be used to distinguish the biogenic origin of the samples, concluding that these strata (from Early Neolithic to Chacolithic period) can be classified as ruminants residues. Three main periods of activity are observed over a period of 2000 years: one from 3990±40 BP (4530-4410 cal. BP) to 4100±40 BP (4820-4750/4730-4510/4470-4450 cal. BP), the second from 4470±40 BP (5300-4970 cal. BP) to 5490±30 BP (6310-6275/6230-6220 cal. BP) and the third from 5880±30 BP (6775-6765/6750-6645 cal. BP) to 6010±30 BP (6940-6780/6765-6755 cal. BP). The data obtained are in concordance with the previous results obtained in the area.
... Recently, considerable research efforts have been devoted to developing various technologies for CO 2 capture. Examples of this include solvent absorption of CO 2 [5][6][7], solid sorbent adsorption of CO 2 [8][9][10], and membrane separation of gases to isolate CO 2 from flue gases [11] and so on. Among these technologies, chemical absorption using alkanolamines as the absorbents for CO 2 capture is presently the most frequently used and commercially mature technology for CCS [3,[12][13][14][15]. ...
In this work, the regeneration of rich CO2-loaded monoethanolamine (MEA) solvent with two catalysts (e.g. SAPO-34 and SO4²⁻/TiO2) was investigated in order to reduce the energy requirement for solvent regeneration. The regeneration behavior with and without catalyst of a 5M MEA solution with an initial CO2 loading of 0.5 mol CO2/mol amine at 96 °C was studied to compare their CO2 desorption rate and heat duties. The results show that the two solid acid catalysts can reduce the heat duty for solvent regeneration and increase the CO2 desorption rate in comparison with blank test. The mechanism of CO2 desorption with catalyst in 5M MEA was proposed based on the result of catalyst characterization (e.g. N2 absorption/desorption experiment, Py-IR, NH3-TPD, FT-IR and XRD) to better understand the desorption process. The results indicate that SAPO-34 with the higher joint value of Brϕnsted/Lewis acid sites ratio (B/L) and mesopore surface area (MSA) shows the faster CO2 desorption rate and lower heat duty than SO4²⁻/TiO2. Based on the experimental results, the addition of solid acid catalysts into amine solution could be considered as one of choices to reduce the heat duty for CO2 desorption from CO2-loaded amine solvent.
Кремний-резорцин-формальдегидные аэрогели получены золь-гель методом с использованием сушки в среде сверхкритического СO. Исследована зависимость между условиями получения образцов и их структурными и физическими характеристиками. Полученные аэрогели могут рассматриваться в качестве сорбентов СO и теплоизоляционных материалов.
Silica-resorcinol-formaldehyde aerogels were synthesized using a sol-gel method followed by drying in supercritical CO. Correlations between the conditions of synthesis and the structural and physical characteristics of the synthesized samples were analyzed. The obtained aerogels can be considered as sorbents of CO and thermal insulation materials.
Ex-situ mineralization processes leverage the reaction of alkaline materials with CO 2 to form solid carbonate minerals for carbon capture, utilization, and storage. Annually, enough alkaline waste is generated to reduce global CO 2 emissions by a significant percentage via mineralization. However, while the reaction is thermodynamically favorable and occurs spontaneously, it is kinetically limited. Thus, a number of techniques have emerged to increase the efficiency of mineralization to achieve a scalable process. In this review, we discuss mineralization of waste streams with significant potential to scale to high levels of CO 2 sequestration. Focus is placed on the effect of operating parameters on carbonation kinetics and efficiency, methods, cost, and current scale of technologies.
Nano-biochar, characterized by its environmentally friendly nature and unique nanostructure, offers a promising avenue for sustainable carbon materials. With its small particle size, large specific surface area, abundant functional groups and tunable pore structure, nano-biochar stands out for its distinct physical and chemical properties compared to conventional biochar. This paper aims to provide an in-depth exploration of nano-biochar, covering its sources, transformation mechanisms, properties, applications, and areas requiring further research. The discussion begins with an overview of biomass sources for nano-biochar production and the conversion processes involved. Subsequently, primary synthesis methods and strategies for functionalization enhancement are examined. Furthermore, the applications of nano-biochar in catalysis, energy storage, and pollutant adsorption and degradation are explored and enhanced in various fields.
Endüstri Devrimi ile birlikte başlayan ve gelecekte de hızlı bir şekilde devam edeceği düşünülen kırsaldan kente göç hareketi kentsel, sosyal ve ekonomik açıdan birtakım olumsuzluklar doğurmaktadır. Kentlerdeki hızlı nüfus artışının beraberinde getirdiği konut ihtiyacı, kentsel yaşam alanlarındaki yeşil dokunun azalmasına sebep olurken kırsal alanlarda da tarımsal faaliyetlerin azalmasına sebep olmuştur. Bu gibi nedenler kentlerde hem yeşil doku oluşturacak hem de tarımsal faaliyetlerde kullanılacak alanlara ihtiyacı gündeme getirmiştir. Bitki çatılar çok eski yıllardan beri çeşitli sebeplerle yapıların çatılarında kullanılmaya başlanmış olup günümüzde de kullanımı devam etmektedir. Bununla birlikte kentsel tarım, çatı tarımı, topraksız tarım gibi kavramlarla ortaya çıkan ve kullanıcısının yerel gıda ihtiyacının bir bölümünü karşılayan, tarımsal faaliyetlerin binaların çatılarında yapıldığı uygulamalar son dönemlerde önem taşımaktadır. Çatı tarımı ile hem kent alanlarında yeşil doku artırılmış olup hem de yerel gıda ihtiyacı karşılanarak güvenilir gıdaya ekonomik bir şekilde ulaşım sağlanmış olacaktır. Daha gelişmiş bir yeşil çatı türü olan çatı tarımının kentsel alanlarda kullanımını örnek projeler üzerinden inceleyen bu çalışmada; çatı tarımının kent ekonomisine katkı sağlayacağı, yerel gıda tüketimini arttıracağı, insanların psikolojisi üzerinde olumlu etki yaratarak daha mutlu bir toplum yaratacağı ve sosyalleşme imkanlarını arttıracağı görülmüştür. Yapılacak olan çatı tarımı projeleri ve çalışmaları ile halkın ve tasarımcıların teşvik edilmesi, üretici firmaların bilgilendirme toplantıları yapması ve çatı tarımı uygulamalarının kentsel dönüşüm ve sürdürülebilir kent çalışmaları kapsamında ele alınarak planlamalara entegre edilmesi önerilmektedir.
This review explores the potential of using different types of ash, namely fly ash, biomass ash, and coal ash etc., as mediums for CO2 capture and sequestration. The diverse origins of these ash types—municipal waste, organic biomass, and coal combustion—impart unique physicochemical properties that influence their suitability and efficiency in CO2 absorption. This review first discusses the environmental and economic implications of using ash wastes, emphasizing the reduction in landfill usage and the transformation of waste into value‐added products. Then the chemical/physical treatments of ash wastes and their inherent capabilities in binding or reacting with CO2 are introduced, along with current methodologies utilize these ashes for CO2 sequestration, including mineral carbonation and direct air capture techniques. The application of using ash wastes for CO2 capture are highlighted, followed by the discussion regarding challenges associated with ash‐based CO2 absorption approach. Finally, the article projects into the future, proposing innovative approaches and technological advancements needed to enhance the efficacy of ash in combating the increasing CO2 levels. By providing a comprehensive analysis of current strategies and envisioning future prospects, this review aims to contribute to the field of sustainable CO2 absorption and environmental management.
In line with the objectives of the circular economy, the conversion of waste streams to useful and valuable side streams is a central goal. Ash represents one of the main industrial side-products, and using ashes in other than the present landfilling applications is, therefore, a high priority. This paper reviews the properties and utilization of ashes of different biomass power plants and waste incinerations, with a focus on the past decade.
Possibilities for ash utilization are of uttermost importance in terms of circular economy and disposal of landfills. However, considering its applicability, ash originating from the heat treatment of chemically complex fuels, such as biomass and waste poses several challenges such as high heavy metal content and the presence of toxic and/or corrosive species. Furthermore, the physical properties of the ash might limit its usability. Nevertheless, numerous studies addressing the utilization possibilities of challenging ash in various applications have been carried out over the past decade. This review, with over 300 references, surveys the field of research, focusing on the utilization of biomass and municipal solid waste (MSW) ashes. Also, metal and phosphorus recovery from different ashes is addressed.
It can be concluded that the key beneficial properties of the ash types addressed in this review are based on their i) alkaline nature suitable for neutralization reactions, ii) high adsorption capabilities to be used in CO2 capture and waste treatment, and iii) large surface area and appropriate chemical composition for the catalyst industry. Especially, ashes rich in Al2O3 and SiO2 have proven to be promising alternative catalysts in various industrial processes and as precursors for synthetic zeolites.
The study based on wastewater treatment using different plant materials like neem (Azadirachta indica) and mango (Mangifera indica) plant leaves ash are innovative and eco-friendly approaches towards sustainable wastewater management. This work focuses on using the plant materials as adsorbents for removing pollutants from wastewater. The plant materials are subjected to high temperature in a controlled environment to obtain ash, which are used for the removal of pollutants such as heavy metals, organic compounds, and nutrients from wastewater. The study aims to investigate the efficiency of each plant material as an adsorbent, and the potential of the mixture of plant materials for wastewater treatment. The study could have significant implications for the development of low-cost and eco-friendly wastewater treatment technologies. The use of plant materials ash for wastewater treatment could provide a sustainable and natural alternative to conventional wastewater treatment methods. The results showed that, plant leaves ashes were effective in reducing the levels of pollutants.
Rice husk ash-derived Ca-Mg-modified silicate as support for Ni-Co catalyst developed for Hydrogen production by Sorption-Enhanced Steam Reforming
of Bioethanol
Recently, biomass has been understood and investigated to develop adsorbents for carbon dioxide (CO2) adsorption due to their non-hazardous nature, availability, low disposal cost, and thermal stability. In this perspective, the sustainable approach of converting biomass into activated carbon (BAC) for the adsorption of CO2 is promising for solid waste management while reducing anthropogenic greenhouse gas emissions. Among other biomass adsorbents, metal oxide impregnated activated carbon (MBAC) has demonstrated excellent adsorption affinity for CO2 adsorption. Therefore, in this review, an evaluation and detailed study of various MBACs for CO2 adsorption is presented for the first time. BAC synthesize method, including various carbonization techniques, surface activation and functionality approaches have been discussed. This study also provides detailed overview of MBAC in the context of various preparation methods, critical factors and operating parameters for a high CO2 adsorption capacity. Besides, the solid-gas reactor configuration, cyclic regeneration techniques, CO2 adsorption process mechanism, and CO2 adsorption kinetics also have been discussed. Finally, concluding remarks and future perspectives for biomass-derived MBAC for CO2 adsorption capture were addressed. This review will also assist in the search for alternatives to CO2 absorption technology, which is both cost-effective and environmentally friendly.
Five long-term stored biomass ashes (BAs) from beech wood chips, corn cobs, sunflower shells, plum pits, and walnut shells produced at 500 °C were thermally treated at 900 °C and subsequently weathered to evaluate their CO2 capture and storage (CCS) potential by mineral carbonation. A combination of different mineralogical, chemical and thermal analyses was used for that purpose. The BAs studied are highly enriched in alkaline-earth and alkaline oxides (52–91%) and they belong to diverse chemical ash types. The minerals responsible for CCS of these BAs include Ca, K, K-Ca and Ca-Mg carbonates and bicarbonates such as calcite, fairchildite, kalicinite, dolomite, and butschliite. The formation of these minerals is a result of interactions between alkaline-earth and alkaline oxyhydroxides in BA and flue CO2 gas during residual char combustion and especially atmospheric CO2 during BA storage and weathering. It was found that the BAs studied show significant CCS capacity, namely about 19–33% (mean 27%). It was emphasized that the renewable and carbon-neutral biomass also has some extra CCS potential due to the sequestration of atmospheric CO2 during BA storage and weathering. Therefore, the future large-scale bioenergy production in a sustainable way can contribute greatly for decreasing CO2 emissions in the atmosphere and can reduce the use of costly CCS technologies.
The effective capture of waste and diluted CO2 by porous carbon materials is extremely challenging. Herein, a facile one-step strategy was developed to prepare activated N/O-rich multilayer ultramicropores carbon composite materials for capturing waste and diluted CO2 effectively by directly carbonizing urea and d-glucose with a novel non-corrosive and non-toxic chemical activator of potassium acetate. Especially, the diluted CO2 adsorptive capacity of the porous carbon material reached 1.38 mmol/g and 0.57 mmol/g at 0.15 bar and 0.05 bar (0 °C) respectively. Meanwhile, the retention time up to 85 min in the diluted CO2 breakthrough experiment further confirms the outstanding adsorptive property of the materials, implying their potential for CO2/N2 separation in the industrial field.
In this work, a biomethane fuel was obtained from biogas, using a solid matrix of ashes obtained from a central heating plant fed by wood. Biomethane composition was studied in an experimental pilot plant that treats organic waste through dry anaerobic digestion. European limits were considered and respected for the biomethane injection into the gas grid. The process was able to completely remove carbon dioxide (CO2) during its initial phase. After 50 h of test CO2 concentration started to appear in the outlet gas. This behaviour is related to the ash content, reactive phases (e.g., Ca hydroxides) and fine particle size (<0.2 mm). Coupled with the CO2 removal, European limits for the biomethane injection into the gas grid must consider also trace compounds (Limits for Sulfur 150 mg/Nm³ and CO2 3%vol.). After 95 h of the experimental test, the gas injection limits are still maintained both for total sulfur trace compounds and both for CO2 limits. Uptake of 0.7 g/kg for H2S and 115 gCO2/kgash were registered from the pilot plant.
Short-term stored, long-term stored, and weathered biomass ashes (BAs) produced from eight biomass varieties were studied to define their composition, mineral carbonation, and CO2 capture and storage (CCS) potential by a combination of methods. Most of these BAs are highly enriched in alkaline-earth and alkaline oxides, and the minerals responsible for CCS in them include carbonates such as calcite, kalicinite, and fairchildite, and to a lesser extent, butschliite and baylissite. These minerals are a result of reactions between alkaline-earth and alkaline oxyhydroxides in BA and flue CO2 gas during biomass combustion and atmospheric CO2 during BA storage and weathering. The mineral composition of the short-term stored, long-term stored, and weathered BAs is similar; however, there are increased proportions of carbonates and especially bicarbonates in the long-term stored BAs and particularly weathered BAs. The carbonation of BAs based on the measurement of CO2 volatilization determined in fixed temperature ranges is approximately 1–27% (mean 11%) for short-term stored BAs, 2–33% (mean 18%) for long-term stored BAs, and 2–34% (mean 22%) for weathered BAs. Hence, biomass has some extra CCS potential because of sequestration of atmospheric CO2 in BA, and the forthcoming industrial bioenergy production in a sustainable way can contribute for decreasing CO2 emissions and can reduce the use of costly CCS technologies.
The main contaminants in biogas namely carbon dioxide, hydrogen sulfide, and siloxanes limit its application especially in engines by reducing energy density and causing corrosion on machine parts. Furthermore, the carbon dioxide in biogas contributes highly to global warming. Therefore, biogas should be upgraded to increase its safe application. Most commercial methods of biogas cleaning are expensive for small and medium scale digesters. There is no review documentation detailing the usage of natural materials in the purification of biogas. The aim of the current study was to systematically and critically review recent developments in the applications of natural materials in the purification and upgrade of biogas. Documented literature indicate that the low-cost natural adsorbents have potential in purification of biogas. The adsorption capacity of biogas contaminants for most materials can be enhanced by physical and chemical activation. The two mechanisms through which these material eliminate carbon dioxide in biogas namely surface adsorption and wet carbonation process have been discussed. In addition, the study looked at the factors that affect the removal of carbon dioxide from biogas using natural materials. The adsorption capacity of biogas contaminants for different natural and modified materials were reviewed. Furthermore, a summary of the merits and demerits of different natural adsorbents for biogas purification is presented. Future studies should investigate the methane loss during upgrading process using low-cost adsorbents. Comparative investigations of the process cost-effectiveness of using natural materials to upgrade biogas should be carried out to determine their suitability against the commercial processes.
Development of innovative methodologies to convert biomass ash into useful materials is essential to sustain the growing use of biomass for energy production. Herein, a simple chemical modification approach is employed to functionalize biomass fly ash (BFA) with 3-aminopropyltriethoxy silane (APTES) to develop an inexpensive and efficient adsorbent for water remediation. The amine-functionalized BFA (BFA–APTES) was fully characterized by employing a range of characterization techniques. Adsorption behavior of BFA–APTES was evaluated against two anionic dyes, namely, alizarin red S (ARS) and bromothymol blue (BTB). In the course of experimental data analysis, the computation tools of data fitting for linear and nonlinear form of Langmuir, Freundlich, and the modified Langmuir–Freundlich adsorption isotherms were used with the aid of Matlab R2019b. In order to highlight the misuse of linearization of adsorption models, the sum of the squares of residues (SSE) values obtained from nonlinear models are compared with R² values obtained from the linear regression. The accuracy of the data fitting was checked by the use of SSE as an error function instead of the coefficient of determination, R². The dye adsorption capacity of BFA–APTES was also compared with the nonfunctionalized BFA. The maximum adsorption capacities of BFA–APTES for ARS and BTB dye molecules were calculated to be around 13.42 and 15.44 mg/g, respectively. This value is approximately 2–3 times higher than the pristine BFA. A reasonable agreement between the calculated and experimental values of qe obtained from the nonlinear form of kinetic models verified the importance of using equations in their original form. The experimentally calculated thermodynamic parameters including molar standard Gibbs free energy (ΔadGm⁰) and molar standard enthalpy change (ΔadHm⁰) reflected that the process of adsorption of dye molecules on the BFA–APTES adsorbent was spontaneous and exothermic in nature. Moreover, the used BFA–APTES adsorbent could be regenerated and reused for several cycles with significant dye adsorption capacity. The remediation capability of the BFA–APTES adsorbent against ARS dye was also demonstrated by packing a small column filled with the BFA–APTES adsorbent and passing a solution of ARS through it. Overall, we provide a simple and scalable route to convert BFA into an efficient adsorbent for water remediation applications.
Sorption-enhanced steam reforming of ethanol (SE-SRE) with in-situ CO2 removal is an environmentally friendly and sustainable approach for hydrogen production. Researches on continuous production of high-purity H2 by SE-SRE over the modified Li4SiO4 sorbent were conducted using two parallel reactor in this work. The low cost Li4SiO4 derived from rice husk ash (RHA) is a promising high-temperature CO2 sorbent. However, the poor adsorption kinetics of RHA-Li4SiO4 sorbent at low CO2 concentration is the major challenge. The metallic elements (K, Ca, Al, Mg) were employed to modify the RHA-Li4SiO4 for efficient CO2 capture. The developed sorbents were characterized and tested to study the role of dopants on the crystal, textural, microstructure and CO2 adsorption kinetics and cyclic stability. Results indicated that K doping effectively inhibited the growth of crystal aggregation and resulted in a fluffy morphology with abundant pores and higher specific surface area, while the addition of Ca, Al and Mg formed a nubby structure with larger particle size. K-doped RHA-Li4SiO4 exhibited the best CO2 uptake properties and the optimal K doping molar content was 0.02 with the maximum capture capacity of 34.16 wt%, which is higher than 27.1 wt% of pure RHA-Li4SiO4. Then, the effect of operating conditions on the enhancement behaviors was considered in the SE-SRE system. High-purity H2 (above 96%) was achieved by coupling K(0.02)/RHA-Li4SiO4 sorbent with Ni-based catalyst under the optimum condition (T: 525 °C, liquid hourly space velocity: 0.9 mL/(g·h), sorbent/catalyst: 4 and steam/carbon: 8.0). The adsorption activity of K(0.02)/RHA-Li4SiO4 maintained at a high level in ten SE-SRE/regeneration cycles. Finally, a scheme including two parallel fixed-bed reactors was designed and operated periodically for continuous production of high-purity H2. The reaction switching time was shown to depend strongly on the pre-breakthrough time and operating conditions. As the reaction switching time was 40 min, the products were always only H2 and CH4 (no CO and CO2 appear) and the H2 purity remained above 90% during 400 min, confirming high purity hydrogen stream can be obtained continuously.
Eight biomass ashes (BAs) produced at 500 and 900 °C were studied to definite their composition, phase transformations, carbonation-decarbonation behavior, and CO2 capture and storage (CCS) potential. Light microscopy, powder X-ray diffraction, scanning electron microscopy, as well as differential-thermal, thermo-gravimetric and chemical analyses were used for that purpose. It was found that most of the BAs studied have high contents of alkaline-earth and alkaline elements represented by carbonates, bicarbonates, oxyhydroxides, chlorides, sulphates, phosphates, and inorganic amorphous material, and such minerals and phases have a key role for CCS by BA. There is an intensive formation of newly formed carbonates as a result of solid–gas reactions between alkaline-earth and alkaline oxyhydroxides and volatile CO2 formed during biomass combustion. Subsequently, additional post-combustion carbonates and bicarbonates are formed by both solid–gas and solid-liquid reactions between the unreacted oxyhydroxides and carbonates in BA and CO2 occurring in air and water during BA storage. The decomposition temperature of carbonates is mostly at 600–900 °C and the mass loss measured in this temperature range approximately determines the CO2 volatilization from the carbonates in BAs. The measured CO2 volatilization (or CCS) for the BAs studied is between 1 and 27% (mean 11%). It was emphasized that the biomass energy can be not only carbon-neutral, but also with some extra CCS potential due to fixation and immobilization of atmospheric CO2 in BA. Therefore, the future large-scale bioenergy production can contribute enormously for reducing CO2 emissions and can decrease or eliminate the application of expensive technologies for CCS.
Co-firing of coal and biomass blends provides a promising route for clean energy utilization with high efficiency and mitigated pollutants emission. However, the technology meets an important challenge in effective utilization of the co-firing fly ashes. Efforts have been made to valorize the co-firing fly ash residues as potential CO 2 sorbents. To achieve enhanced CO 2 sorption performance, the samples were modified with tetraethylenepentamine (TEPA). Effects of amine loading, CO 2 sorption temperature, initial CO 2 concentration and gas flow rate on CO 2 sorption behaviors of the amine-tethered sorbents were investigated. The desired sorbent with 25% TEPA loading presented the highest CO 2 sorption capacity of 1.19 mmol CO 2 /g when tested under 60 °C and 15%CO 2 with a total gas flow rate of 1200 ml min ⁻¹ . The effects of regeneration temperature and ramping rate on sorbent regeneration performance were demonstrated. The maximum sorbent regeneration efficiency of 97.2% was achieved under the regeneration condition of 110 °C and 5 °C min ⁻¹ . CO 2 sorption capacity of the amine-tethered sorbent kept stable within 5 repeated cycles. These findings indicate that the amine-tethered sorbent could be a good candidate for on-site CO 2 capture from flue gas in co-firing power plants.
Carbon Capture, Utilization and Storage, also referred to as Carbon Capture, Utilization and Sequestration (CCUS), is one of novel climate mitigation technologies, by which CO2 emissions are captured from sources such as fossil power generation and industrial processes, and further either reused or stored.
Carbon monoliths with bimodal porosity were obtained through nanocasting technique from silica mono- liths (hard template) and furfuryl alcohol (precursor). These carbon adsorbents were evaluated as sor- bents for CO 2 capture by using a fixed-bed adsorption set up under dynamic conditions. Carbonization at different temperatures (550 to 950 °C) was carried out that resulted in the generation of different carbon adsorbents containing oxygen functional groups. The textural characterization results reveal the effect of nanocasting technique, which is confirmed from the generation of mesopores (0.41), microp- ores (0.85 cm 3 g −1 ) and high surface area (1225.1 m 2 g −1 ) of adsorbent synthesized at 950 °C, as shows highest CO 2 uptake of 1.0 mmol g −1 at 30 °C and 12.5% CO 2 concentration. The increase in the adsorption capacity with increasing CO 2 concentration and decrease with the increasing adsorption temperature con- firms the physisorption process. Five adsorption–desorption cycles show established materials with excel- lent regeneration stability as an adsorbent. Furthermore, three kinetic models along with three isotherms were used in the present study to analyze the adsorption data and found that fractional order kinetic model and Temkin isotherm fitted best. Thermodynamic studies suggested the exothermic, spontaneous as well as the feasibile nature of the adsorption process.
An amine-functionalized adsorbent was prepared by loading pentaethylenehexamine (PEHA) into the pores of KIT-6 mesoporous silica. Nitrogen adsorption/desorption, thermogravimetric analysis, and X-ray powder diffraction were employed to analyze the structural properties of the prepared adsorbents. The results reveal that the pore size, pore volume, and surface area of the adsorbents decrease after PEHA loading in KIT-6, while the basic KIT-6 pore structure remains unchanged. The CO2 adsorption performance of amine-functionalized KIT-6 was studied by isothermal CO2 adsorption, adsorption/desorption cycle regeneration testing, and multiple cycle tests. The amount of CO2 absorbed increased with increasing temperature in the temperature range of 303–343 K, achieving a maximum adsorption capacity of 3.2 mmol/g-adsorbent at 343 K. For temperatures greater than 343 K, the adsorption capacity decreased with increasing temperature. The amount of CO2 adsorbed remained nearly constant after 10 adsorption/desorption cycles. The CO2 adsorption/desorption kinetics of the PEHA-impregnated KIT-6 were investigated using three kinetics models. The results indicate that the CO2 adsorption process by the amine-functionalized adsorbent is dominated by intra-particle diffusion, and the adsorption rate is restricted by the intra-particle diffusion process. In addition, high CO2 partial pressure facilitates the adsorption of CO2. The CO2 adsorption breakthrough curves obtained by the deactivation model were in good agreement with the results of this study. The adsorbents were regenerated by vacuum and temperature swing adsorption regeneration. The results indicate that increasing the desorption temperature is an effective means of reducing the regeneration time. The absolute value of the activation energy obtained from the Arrhenius equation for CO2 desorption was 81.992 kJ·mol⁻¹, which was greater than that obtained for adsorption.
Reusable nitrogen-doped carbon derived from coconut shell was prepared as a sustainable alternative for carbon dioxide (CO2) adsorption from gas streams. The procedure is based on carbonization and chemical activation with coconut shell, glucosamine, and KOH as the activating agent. The textural properties, as well as the fixed-bed adsorption and regeneration performance of the adsorbent were investigated using the fixed-bed adsorption column. The surface nature and properties of the adsorbent changed remarkably due to the surface modification that enhanced the adsorption process. The adsorbent showed a maximum CO2 uptake of 4.23 mmol/g at 30 °C and 1 bar. CO2 adsorption capacity increased with initial concentration and decreased with increases in temperature and flowrate. The adsorption capacity and physiochemical properties of the adsorbent were preserved after 20 adsorption–desorption cycles without significant loss in capacity. This finding suggests that the synthesized adsorbent is a good candidate for CO2 capture from post-fossil fuel combustion processes.
Large quantities of wood ashes derived from biomass materials combustion potentially threaten the ecological environment. Recycling of the wood ashes as solid sorbents for pollutants control is an economical and environmentally friendly route. In this work, waste wood ashes (WAs) were modified with tetraethylenepentamine (TEPA), monoethanolamine (MEA), diethanolamine (DEA), polyethyleneimine (PEI), and diethylenetriamine (DETA) to synthesize solid sorbents with enhanced CO2 capture performances. CO2 capture behaviors of the synthesized sorbents were tested under 60 °C, 5.0%CO2 + 5%H2O using a fixed-bed reactor, and sorbent regeneration behaviors were evaluated under 120 °C, 10 °C/min and 100%N2. The sorbent synthesized of ashes collected from straw-fired power plants modified with TEPA (TEPA-WA-1) is identified as the optimum candidate with superior capability for CO2 capture and sorbent regeneration. CO2 capture capacity of TEPA-WA-1 increases first and then decreases with the increase of amine loading. Sufficient amine loading can provide substantive active sites for enhanced CO2 chemisorption, whereas excessive loading will cause particle aggregation and pore structure blockage and affect its CO2 capture capacity adversely. The maximum CO2 capture capacity of 2.02 mmol CO2/g is obtained with an amine loading of 45 wt.%. The desired sorbent is demonstrated to be stable during 10 cyclic operations. Moreover, the presence of acid impurities (SO2 and NO2) exerts negative effect on the cyclic CO2 capture and sorbent regeneration performances of the synthesized sorbent. It is mainly attributed to sorbent deactivation induced by the formation of byproducts and weakened physical properties for the sorbent exposed in acid impurities.
Stringent discharge requirements call for advanced methods of wastewater treatment to take on where biological treatment fails to succeed. Here, the adsorption potential of fly ash, an on-site available and cheap material, was tested in batch and continuous flow fixed bed experiments using bleaching effluent from an integrated mill producing mechanical pulp. Various models were fitted to the experimental data to find the best description of the adsorption system and to obtain important model parameters: the Freundlich model yielded the highest correlation and indicated that the process was favorable. The bed depth service time model suggested that the adsorption in the column setup involved more than one rate limiting step, and the Thomas and Clark models generated similar curves which satisfactorily described adsorption at short bed depth. The fly ash showed good adsorptive properties of wood derived substances: both lignin and extractives were effectively separated from the effluent. ■ INTRODUCTION Biological treatment has become the most widely applied method to reduce the discharge of wood derived substances released during processing of the raw material into the final lignocellulosic-based product. Although this has proven a cost efficient method to remove oxygen consuming substances in wastewater, stringent discharge requirements demand measures to eliminate also substances which resist biological treatment. One such compound is lignin which is released from the wood during pulping and bleaching operations. Adsorption is a potent method for separation of pollutants in industrial wastewater, well-established in the pharmaceutical and chemical industry. However, the method seems rarely adopted in other areas, such as the pulp and paper industry. In order to make adsorption a competitive alternative to other available options for advanced wastewater treatment, such as membrane filtration, advanced oxidation processes, and various phys-icochemical treatments, a low-cost and readily available adsorbent must be sifted out. A variety of ashes have been investigated as potential low-cost adsorbents by numerous authors and have been found to possess interesting properties for the adsorption of organic pollutants. 1−4 Necessary information for large-scale adsorption design can be obtained by evaluating the breakthrough characteristics of an adsorbent bed in a column setup. 1,5 Before experiments are run in continuous columns, a preliminary screening of adsorbents in batch experiments is recommended. Batch experiments and the use of adsorption isotherms provide a measure of the effectiveness of adsorption for removing specific adsorbates, as well as the maximum adsorption capacity. However, the equilibrium conditions of batch experiments do not account for hydrodynamics and mass transfer occurring in a fixed-bed continuous adsorption column: the conditions at any cross section in the fixed adsorbent bed is affected by the upstream behavior. 1,5 Column operations create a continuous concen-tration gradient in the adsorption zone as the liquid passes through the column, whereas in batch experiments, the concentration gradient between the solid and aqueous phases decreases with time. In theory, continuous flow over a fixed bed therefore increases the adsorbent capacity by maintaining the mass transport of solute across the liquid/solid interface. In earlier publications, 6,7 we have demonstrated in batch experiments the good sorptive properties of fly ash in the removal of aqueous lignin isolated from mechanical pulping effluent. The Redlich-Peterson as well as the Langmuir and Freundlich equilibrium models were found to provide adequate descriptions of the experimental data. Kinetic studies showed that equilibrium between the adsorbate in solution and on the adsorbent surface was essentially achieved after 30 min and that pseudo-second-order rate kinetics best described the exper-imental data. In the present study, the practical applicability of adsorption for treating process wastewater in mechanical pulping was evaluated. Bleaching effluent was treated with fly ash and the removal of wood derived organic compounds such as lignin and extractives was investigated. Batch-experiments, similar to the previous tests with aqueous lignin samples, were performed, and the fit of sorption isotherms was evaluated to find the most suitable model. Finally, fixed bed continuous column experi-ments were run to obtain the breakthrough characteristics in an attempt to find the most suitable adsorption model: the bed depth service time, Thomas, and Clark models were fitted to the experimental data.
Mineral carbonation of alkaline waste materials is being studied extensively for its potential as a way of reducing the increased level of CO2 in the atmosphere. Carbonation converts CO2 into minerals which are stable over geological time scales. This process occurs naturally but slowly, and needs to be accelerated to offset the present rate of emissions from power plants and other emission sources. The present study attempts to identify the potential of coal fly ash as a source for carbon storage (sequestration) through ex-situ accelerated mineral carbonation. In the study, two operational parameters that could affect the reaction process were tested to investigate their effect on mineralization. Coal fly ash was mixed with water to different water-to-solid ratios and samples were carbonated in a pressure vessel at different initial CO2 pressures. Temperature was kept constant at 40 °C. According to the results, one ton of Hazelwood fly ash could sequester 7.66 kg of CO2. The pressure of CO2 inside the vessel has an effect on the rate of CO2 uptake and the water-to-solid ratio affects the weight gain after the carbonation of fly ash. The results confirm the possibility of the manipulation of process parameters in enhancing the carbonation reaction.
For the first time, amino acid (AA) and AA-complex based solid sorbents for CO2 removal were investigated by immobilizing AAs and AA-complexes into porous polymethylmethacrylate (PMMA) microspheres. Deposition of pure AAs into porous PMMA supports led to limited CO2 adsorption in sorbents, because large AA particles or crystals were formed during deposition of pure AAs into PMMA microspheres and some pores of the PMMA microspheres were clogged. Among the AA sorbents studied, Arginine (Arg) solid sorbents had the highest CO2 adsorption capacity. Interestingly, by forming AA-complexes with other polymers, we substantially improved AA water solubility, achieved uniform immobilization of AAs inside PMMA microspheres, and obtained high CO2 adsorption capacity. We found that the types of AA-complexes, complex loading capacity, and ratio of AAs in the complexes could have significant effects on CO2 adsorption properties. Especially, complexing Arg with a strong polyelectrolyte (i.e. polystyrene sulfonate) resulted in substantially improved AA water solubility and high CO2 adsorption capacity. Our developed AA-complex based solid sorbents could be innovative since they could eliminate concerns related to potential equipment corrosion as well as high heat duty associated with aqueous solvent regeneration all the while retaining the advantageous properties (high thermal stability, excellent biocompatibility, and negligible volatility) of AAs.
This work reviews the advantages and disadvantages of using mineral wastes for CCS and their potential in CO2 abatement, highlighting the potential applications and scenarios. This study indicates that a variety of inorganic waste materials such as pulverised fuel ash, municipal solid waste ash, cement kiln dust, biomass and paper sludge ash and sewage sludge ash are available feedstocks for Carbon Capture and Storage by Mineralisation (CCSM) in the UK. The high variability of both the waste amounts and chemical composition represent a major obstacle to the deployment of these materials in CCSM. Currently, mineral waste resources for mineral carbonation have the theoretical potential to capture about 1 Mt/year CO2 in the UK, considering only the materials not recycled that are currently sent to landfill. Moreover, inorganic waste as a CCSM resource is in many ways more complex than the use of natural minerals due to uncertainty on future availability and high chemical variability and might be viable only in niche applications. For example, the use of inorganic wastes (concrete waste and steel slag) and buffer solutions in spray trickle bed systems (able to sequester 50% of the CO2 entering the system) was estimated to have costs competitive with geological storage.
The ashes from lignite combustion are characterized by high CaO and free CaO contents and are a potentially interesting material for CO2 bonding, more particularly as theirs economical use is limited. The findings of CO2 absorption by suspensions prepared on the basis of ash from lignite combustion are presented in the paper. On these grounds CO2 sequestration potential via mineral carbonation in ash aqueous suspensions in Poland will be estimated.
Potassium carbonate was used as a sorbent to capture CO2 from a gaseous stream of carbon dioxide, nitrogen, and moisture. The breakthrough data of CO2 were measured in a fixed bed to observe the reaction kinetics of the CO2-carbonate reaction. Several models, such as the shrinking-core model, the homogeneous model, and the deactivation model, in the non-catalytic heterogeneous reaction systems were used to explain the kinetics of the reaction between CO2, K2CO3, and moisture using analysis of the experimental breakthrough data. A good agreement of the deactivation model was obtained with the experimental breakthrough data. The sorption rate constant and the deactivation rate constant were evaluated through analysis of the experimental breakthrough data using a nonlinear least squares technique and described in the Arrhenius form.
Coal fly ash is a potential candidate for CO2 mineral sequestration. If calcium is extracted selectively from coal fly ash prior to carbonation (namely indirect carbonation), a high-purity and marketable precipitated calcium carbonate (PCC) can be obtained. In the extraction process, recyclable ammonium salt (i.e., NH4Cl/NH4NO3/CH3COONH4) solution was used as a calcium extraction agent in this study. The influence of time, temperature, agent concentration, and solid-to-liquid ratio on calcium extraction efficiency was explored. NH4Cl/NH4NO3/CH3COONH4 are confirmed to be effective calcium extraction agents for the high-calcium coal fly ash investigated, and about 35–40% of the calcium is extracted into the solution within an hour. The calcium extraction performance is best for CH4COONH4, followed by NH4NO3 and NH4Cl. Increasing temperature from 25 to 90 °C and agent concentration from 0.5 to 3 mol/L only subtly increases calcium extraction efficiency for NH4Cl and NH4NO3, while the positive effect of increasing temperature and agent concentration is more obvious for CH3COONH4. In the carbonation process, carbonation efficiency, namely conversion of Ca2+ into precipitated calcium carbonate(PCC), is only 41–47% when the leachate is carbonated by CO2. A newly proposed method of substituting CO2 with NH4HCO3 as the source of CO32– yields much higher carbonation efficiency (90–93%). Furthermore, the carbonation reaction rate is also largely improved when carbonating the leachate by NH4HCO3. In addition to these benefits, CO2 capture and storage can be simultaneously realized on-site if integrating the leachate carbonation process with an ammonia–water CO2 capture process using NH4HCO3 as a connector. In this way, the costs associated with CO2 compression and transportation can be eliminated. PCC with a purity up to 97–98% is obtained, which meets the purity requirement (≥97%) of industrially used PCC. It is estimated based on the experimental results that 0.17 tons of PCC can be produced from 1 ton of coal fly ash by this method, bounding 0.075 tons of CO2 at the same time, and 0.036 tons more CO2 can be avoided if the obtained PCC is substituted for the PCC manufactured by the conventional energy-intensive method.
A solid amine adsorbent for CO2 was developed by carbon nanotubes (CNTs) impregnated with tetraethylenepentamine (TEPA). The adsorption behavior toward CO2 (2.0 vol %) was investigated in a fixed-bed column. After modification, the adsorption capacity of CNTs–TEPA reached 2.97 mmol g–1 at 298 K. Rising temperatures from 283 to 313 K enhanced the CO2 adsorption capacity. The maximum adsorption capacity was approximately 3.56 mmol g–1 at 313 K. The adsorption capacity was also influenced by moisture and reached as high as 3.87 mmol g–1 (2.0% H2O). In comparison to many other types of modified carbon or silica adsorbents in the literature, CNTs–TEPA had a higher adsorption capacity at the same temperature. The adsorption capacity for CO2 remained almost the same after cyclic regeneration experiments. A deactivation model, capable of describing the uptake of CO2, was applied under various conditions. In all cases, the experimental data agreed with the predicted breakthrough model.
The present paper investigates the application of raw coal fly ash (FA) to dry-based CO2 fixation. Dry sorbents are manufactured by mixing FA, NaOH, CaO and a small amount of water and their absorption behavior, performance, regeneration and leaching efficiency are analyzed. The CO2 absorption efficiency (AE) of FA-added sorbent (WNCF) is higher than that of FA-free sorbents (WNC) and its absorption behavior is improved. In addition, CO2 desorption from carbonated WNCF (CWNCF) occurs at 100 °C lower than that from carbonated WNC (CWNC) and its desorption efficiency is 16.5% point higher than that of CWNC, due to the FA addition to the sorbent. However, the AE of regenerated CWNCF is substantially lower than that of fresh WNCF, which indicates that CWNCF cannot easily be regenerated by simple desorption increasing temperature. This is ascribed to the effect of the added FA and water in contributing to the production of Ca- and Na-based carbonated materials that cannot readily be regenerated during the carbonation. Some of the inherent K and Ca components present in the raw FA participate in the carbonation of WNCF, and Cr is co-precipitated during WNCF carbonation to become a stabilized material.
Stringent discharge requirements call for advanced methods of wastewater treatment to take on where biological treatment fails to succeed. Here, the adsorption potential of fly ash, an on-site available and cheap material, was tested in batch and continuous flow fixed bed experiments using bleaching effluent from an integrated mill producing mechanical pulp. Various models were fitted to the experimental data to find the best description of the adsorption system and to obtain important model parameters: the Freundlich model yielded the highest correlation and indicated that the process was favorable. The bed depth service time model suggested that the adsorption in the column setup involved more than one rate limiting step, and the Thomas and Clark models generated similar curves which satisfactorily described adsorption at short bed depth. The fly ash showed good adsorptive properties of wood derived substances: both lignin and extractives were effectively separated from the effluent.
The objective of this study is to develop a new cost-effective CO2 sorbent, K2CO3/TiO(OH)2 or KTi, with inexpensive and widely available K2CO3 and nanoporous TiO(OH)2 as supporting material. The performance of KTi CO2 capture was evaluated using a fixed-bed tubular reactor under different experimental conditions, including sorption temperature, flow rate, and moisture concentration of flue gas. Use of TiO(OH)2 as a support for K2CO3 leads to a significant increase of CO2 sorption capacity per unit of K2CO3 by about 37 times. The optimal K2CO3 loading on TiO(OH)2 is 30 wt %. The highest sorption capacity achieved with KTi is 1.69 mmol of CO2/g of KTi, whereas the theoretical sorption capacity of KTi with the prepared TiO(OH)2 could be as high as 3.32 mmol of CO2/g of KTi. The enthalpy change of the KTi-based CO2 sorption is −28.51 kcal/mol. Moreover, KTi is regenerable and stable. Therefore, KTi is a promising CO2 sorbent.
A new inexpensive inorganic-organic composite sorbent for CO2 capture was prepared by the immobilization of a branched polyethyleneimine (PEI) onto porosity-enhanced clays using the wet impregnation method. In the composite, a low cost and naturally abundant clays (e.g. kaolinite and montmorillonite) was used as the supporting material, which was pre-modified by acid- or alkaline-treatment to improve its textural properties, i.e. pore volume and surface area, for accommodating the CO2-philic PEI. Among the modified clays, the montmorillonite modified by 6 M HCl(Mon_HCl_6M) showed the highest porosity with the pore volume of 0.71 cm(3)/g from 0.16 cm(3)/g, and BET surface area of 253 m(2)/g from 72 m(2)/g. The cost of the Mon_HCl_6M was estimated as $0.14/kg, which was significantly lower than reported supporting materials for the amine-based sorbents for CO2 capture. At the optimal PEI loading of 50 wt% on the Mon_HCl_6M support, the CO2 sorption capacity reached 112 mg CO2/g-sorbent at 75 degrees C under dry condition, which can be further enhanced to 142 mg CO2/g-sorbent with the moisture addition (ca. 3 vol%) due to the change in the interaction mechanism between CO2 and amine in the presence of moisture. Moreover, the PEI/Mon_HCl_6M sorbent showed a good regenerability for 10 sorption-desorption cycles tested and a good thermal stability in the temperature range of CO2 sorption (75 degrees C) and desorption (100 degrees C).
CO2 capture and storage (CCS) has received significant attention recently and is recognized as an important option for reducing CO2 emissions from fossil fuel combustion. A particularly promising option involves the use of dry alkali metal-based sorbents to capture CO2 from flue gas. Here, alkali metal carbonates are used to capture CO2 in the presence of H2O to form either sodium or potassium bicarbonate at temperatures below 100 °C. A moderate temperature swing of 120–200 °C then causes the bicarbonate to decompose and release a mixture of CO2/H2O that can be converted into a “sequestration-ready” CO2 stream by condensing the steam. This process can be readily used for retrofitting existing facilities and easily integrated with new power generation facilities. It is ideally suited for coal-fired power plants incorporating wet flue gas desulfurization, due to the associated cooling and saturation of the flue gas. It is expected to be both cost effective and energy efficient.
Simulating regeneration tests of Potassium-Based sorbents that supported by Suzhou River Channel Sediment were carried out in order to obtain parameters of regeneration reaction. Potassium-based sediment sorbents have a better morphology with the surface area of 156.73 m2·g−1, the pore volume of 357.5×10−3 cm3·g−1 and the distribution of pore diameters about 2–20 nm. As a comparison, those of hexagonal potassium-based sorbents are only 2.83 m2g−1, 7.45×10−3 cm3g−1 and 1.72–5.4 nm, respectively. TGA analysis shows that the optimum final temperature of regeneration is 200 and the optimum loading is about 40%, with the best heating rate of 10 °C·min−1. By the modified Coats-Redfern integral method, the activation energy of 40% KHCO3 sorbents is 102.43 kJ·mol−1. The results obtained can be used as basic data for designing and operating CO2 capture process.
This study examined the factors affecting mineral carbonation to sequester CO2 using coal fly ash (CFA) in aqueous solutions under ambient temperature and pressure conditions. Serial extraction and carbonation tests were conducted on CFA obtained from a coal-fired power plant as the following conditions were varied: solid dosage, CaO content, CO2 flow rate, and solvent type. The solid dosage, CaO content, and solvent type affected the Ca extraction efficiency, which was well correlated with the carbonation efficiency. In addition, at a given Ca extraction efficiency, the CO2 flow rate and the solvent type affected the rate and extent of CFA carbonation. Based on the study results, the CO2 sequestration capacity of CFA under ambient temperature and pressure conditions was approximately 0.008 kg of CO2 per 1 kg of CFA at the experimental test conditions (CaO content: 7 wt.%, solid dosage: 100 g/L, CO2 flow rate: 2 mL/min, and solvent: DI water).
The performance of coal fly-ash based oxygen carriers for chemical looping combustion of synthesis gas has been investigated using both a thermogravimetric analyser and a packed bed reactor. Oxygen carriers with 50 wt% active metal compounds, including copper, nickel and iron oxides, supported on coal fly-ash were synthesised using the deposition–precipitation method. Copper oxide and nickel oxide supported on fly-ash showed high oxygen transfer efficiency and oxygen carrying capacity at 800 °C. The fly-ash based nickel oxide was effective in reforming hydrocarbons and for the conversion of carbon dioxide into carbon monoxide; a nickel complex with silicate was identified as a minor phase following the reduction reaction. The fly-ash based iron oxide showed various reduction steps and resulted in an extended reduction time. The carbon emission at the oxidation stage was avoided by reducing the length of the exposure to the reduction gas.
This work reviews the availability and the potential of the carbon capture and storage (CCS) technology using coal fly ash (FA). Because the technology can be effectively applied on-site to coal fired power plants and as FA contains sufficient alkali components, the technology may be another option of CCS technology to a limited extent.The technology can be divided into wet and dry processes. In the former, the available components for CCS in FA are leached into solution by the solvent where they are subsequently consumed for carbonation to store CO2. Particularly, the CO2 storage capacity of CaO-enriched FA solution mixed with brine under high pressure may be equal to or greater than the true CO2 emission reduction achieved by applying FA as a cement additive.In the dry process, FA can be used as a direct support or as the raw material of the sorbent supports for CO2 capture. The dry process is effectively applied for CO2 capture rather than storage because the sorbents should be regenerated. Another advantage of the technology is the stabilization of the harmful components present in FA, which are mostly co-precipitated with carbonated FA during the process.
In this work spent coffee grounds from single-use capsules were used as the starting material for producing low-cost activated carbons. The activation conditions were selected and optimised to produce microporous carbons with high CO2 adsorption capacity and selectivity, thus with potential to be used as adsorbents in postcombustion CO2 capture applications. Two activation methods are compared: physical activation with CO2 and chemical activation with KOH. The first method is considered less contaminant; however, leads to carbons with lower textural development and thus lower CO2 adsorption capacity than those obtained by activation with KOH. On the other hand, multicomponent adsorption cyclic experiments pointed out that the CO2/N2 selectivity of physically activated carbons is higher than that of chemically activated carbons.
The effects of manganese salts including Mn(NO3)2 and MnCO3 on CO2 capture performance of calcium-based sorbent during cyclic calcination/carbonation reactions were investigated. Mn(NO3)2 and MnCO3 were added by wet impregnation method. The cyclic CO2 capture capacities of Mn(NO3)2-doped CaCO3, MnCO3-doped CaCO3 and original CaCO3 were studied in a twin fixed-bed reactor and a thermo-gravimetric analyzer (TGA), respectively. The results show that the addition of manganese salts improves the cyclic carbonation conversions of CaCO3 except the previous cycles. When the Mn/Ca molar ratios are 1/100 for Mn(NO3)2-doped CaCO3 and 1.5/100 for MnCO3-doped CaCO3, the highest carbonation conversions are achieved respectively. The carbonation temperature of 700–720 °C is beneficial to CO2 capture of Mn-doped CaCO3. The residual carbonation conversions of Mn(NO3)2-doped and MnCO3-doped CaCO3 are 0.27 and 0.24 respectively after 100 cycles, compared with the conversion of 0.16 for original one after the same number of cycles. Compared with calcined original CaCO3, better pore structure is kept for calcined Mn-doped CaCO3 during calcium looping cycle. The pore volume of calcined MnCO3-doped CaCO3 is 2.4 times as high as that of calcined original CaCO3 after 20 cycles. The pores of calcined MnCO3-doped CaCO3 in the pore size range of 27–142 nm are more abundant relative to clacined original one. That is why modification by manganese salts can improve cyclic CO2 capture capacity of CaCO3.
Coal combustion in thermal power plants throughout the world produces large amounts of fly ash. Disposal of fly ash is a serious threat to the environment and hence is a worldwide concern for conversion of these wastes into useful products. Synthesis of mesoporous silica materials from coal fly ash has already been proposed as an option which can be utilized as an adsorbent. Adsorption is considered to be one of the more promising technologies for capturing CO2 from flue gases. This paper reviews the recent development of solid adsorbents from industrial waste materials with special reference to fly ash for post-combustion capture of CO2.
The thermodynamics and kinetics of the thermal decompositions of NaHCO3 and KHCO3 were studied by means of simultaneous TG-DSC. Analysis of the isothermal mass-change traces indicated that the thermal decompositions of NaHCO3 and KHCO3 follow an Avrami-Erofeyev A1.5 law. The A1.5 law was tentatively explained by assuming a combination of the A1 and A2 laws.
It was illustrated that KHCO3 is more stable than NaHCO3 as concerns the thermodynamics and kinetics of the thermal decompositions. The apparent activation energies for the decompositions of the two hydrogencarbonates were a little larger than the corresponding enthalpy changes.
Mineral carbonation is one of the alternatives considered for CO2 sequestration. This consists of inducing the artificial weathering of alkaline minerals to produce stable carbonate solids. This work presents the wet carbonation of lime-rich ashes from the fluidized bed combustion of two different fuels: a Spanish sulfur-rich lignite, with calcium carbonate and quartz as main mineral constituents, and the waste produced during the extraction of the coal. The novelty of the work is its experimental approach, which explores all the variables (pH, temperature, time, liquid to solid ratio, NaCl ratio) from a statistical survey centered on finding optimized conditions that maximize the degree of carbonation. CO2 uptake is determined by direct thermogravimetric tests. The results indicate that high carbonation efficiency (78% efficiency) is achieved for both solids at basic pH and moderate treatment times. Those conditions cause anhydrite to dissolve, increasing the availability of Ca2+ for reprecipitation as carbonate and hydroxide. At neutral pH, 72% conversion efficiency is equivalent to a capture of 8% of the CO2 theoretically emitted in the combustion of coal wastes. The proposed conditions for fly ash carbonation enables rapid CO2 capture that is applicable for upscaling and industrial use.
An extended overview of the phase–mineral and chemical composition and classification of biomass ash (BA) was conducted. Some general considerations related to the composition of BA and particularly problems associated with this issue were discussed initially. Then, reference peer-reviewed data including phase–mineral composition and properties of BAs plus own investigations were used to describe and organise the BA system. It was found that BA is a complex inorganic–organic mixture with polycomponent, heterogeneous and variable composition. The phase–mineral composition of BA includes: (1) mostly inorganic matter composed of non-crystalline (amorphous) and crystalline to semi-crystalline (mineral) constituents; (2) subordinately organic matter consisting of char and organic minerals; and (3) some fluid matter comprising moisture and gas and gas–liquid inclusions associated with both inorganic and organic matter. Approximately 229 forming, major, minor or accessory phases or minerals were identified in BA. These species have primary, secondary or tertiary origin in the combustion residue and they are generated from natural (authigenic and detrital) and technogenic phases or minerals originally present in biomass. Common topics related to BA such as: terminology clarification; chemical composition; contents and concentration trends; correlations and associations; formation and behaviour; fusion temperatures; and leaching; were discussed and compared to coal ash. A general characterization of the phase–mineral composition and description of the occurrence and origin for common constituents in BA, namely: (1) silicates; (2) oxides and hydroxides; (3) sulphates (plus sulphides, sulphosalts, sulphites and thiosulphates); (4) phosphates; (5) carbonates (plus bicarbonates); (6) chlorides (plus chlorites and chlorates); (7) nitrates; (8) glass; (9) other inorganic phases; (10) organic phases; and (11) organic minerals; were also conducted and compared to coal ash. Finally, certain major associations related to the occurrence, content and origin of elements and phases were identified in the BA system and they include: (1) Si–Al–Fe–Na–Ti (mostly glass, silicates and oxyhydroxides); (2) Ca–Mg–Mn (commonly carbonates, oxyhydroxides, glass, silicates and some phosphates and sulphates); and (3) K–P–S–Cl (normally phosphates, sulphates, chlorides, glass and some silicates and carbonates). It was found that these systematic associations in BA have a key importance in both fundamental and applied aspects, namely their potential application for classification and indicator purposes connected with innovative and sustainable processing of BA. The potential utilization, technological and environmental advantages and challenges related to BA using the above classification approach are described in Part 2 of the present work.
An extended overview of the complex phase-mineral and chemical composition and properties of biomass ash (BA) was conducted in Part 1 of the present work. Then, the identified systematic associations, namely (1) Si–Al–Fe–Na–Ti (mostly glass, silicates and oxyhydroxides); (2) Ca–Mg–Mn (commonly carbonates, oxyhydroxides, glass, silicates and some phosphates and sulphates); and (3) K–P–S–Cl (normally phosphates, sulphates, chlorides, glass and some silicates and carbonates); connected with the occurrence, content and origin of elements and phases in the BA system were used for classification of BAs into four types and six sub-types in Part 1. The potential application of BA using the above classification approach is described in the present Part 2. It is demonstrated that such new BA classification has not only fundamental importance, but also has potential applications in prediction of properties and utilisation connected with the innovative and sustainable utilisation of BAs specified in different types and sub-types. The potential advantages and challenges related to utilisation of BA are described. Different aspects connected with BAs such as: (1) bulk utilisation (for soil amendment and fertilisation; production of construction materials, adsorbents, ceramics and other materials; plus synthesis of minerals); (2) recovery of valuable components and their utilisation (char, water-soluble, cenosphere–plerosphere, magnetic and heavy fractions; and elements); and (3) multicomponent utilisation; are described based on the reference investigations, present data and above classification. Subsequently, additional issues related to BAs, namely: (1) technological advantages and challenges (slagging, fouling and corrosion; low ash-fusion temperatures; erosion and abrasion; co-combustion and co-gasification; prediction of phase composition; and others); and (2) some environmental risks and health concerns (air, water, soil and plant contamination; acidity, alkalinity and leaching; volatilisation, retention, capture and immobilisation of hazardous elements and compounds; ash inhalation and disposal); during biomass and BA processing are also discussed. Finally, it is emphasised that the definitive utilisation, technological and environmental advantages and challenges related to BAs associate preferentially with specific BA types and sub-types and they could be predictable to some extent by using the above combined chemical and phase-mineral classification approaches.
A conceptual multi-step process demonstrates the feasibility of CO2 sequestration in an integrated operation utilizing by products primarily obtained from fossil fuel combustion (fly ash) and oil and gas production (brine). This process includes a carbonation reaction utilizing a brine solution and CO2 as reactants under mild reaction conditions. CaO rich fly ashes are added to increase the pH level of the reactant brine, maximizing the reaction efficiency of the carbonation reaction. Furthermore, these materials can also provide a source of Ca in addition to the Ca present in the brine for carbonation. The calcium from fly ashes and brine both contribute to the formation of calcium carbonate during the carbonation reaction.
Accelerated carbonation has been used for the treatment of contaminated soils and hazardous wastes, giving reaction products that can cause rapid hardening and the production of granulated or monolithic materials. This technology provides a route to sustainable waste management and it generates a viable remedy to the problems of a decreasing number of landfill sites in the UK, global warming (due to greenhouse gas emissions) and the depletion of natural aggregate resources, such as sand and gravel. The application of accelerated carbonation (termed Accelerated Carbonation Technology or ACT) to sequester CO2 in fresh ashes from municipal solid waste (MSW) incinerator/combined heat and power plants is presented. The purpose of this paper is to evaluate the influence of fundamental parameters affecting the diffusivity and reactivity of CO2
(i.e. particle size, the reaction time and the water content) on the extent and quality of carbonation. In addition, the major physical and chemical changes in air pollution control (APC) residues and bottom ashes (BA) after carbonation are evaluated, as are the optimum reaction conditions, and the physical and chemical changes induced by accelerated carbonation are presented and discussed.
Adsorption is considered to be one of the more promising technologies for capturing CO2 from flue gases. For post-combustion capture, the success of such an approach is however dependent on the development of an adsorbent that can operate competitively at relatively high temperatures. In this work, low cost carbon materials derived from fly ash, are presented as effective CO2 sorbents through impregnation these with organic bases, for example, polyethylenimine aided by polyethylene glycol. The results show that for samples derived from a fly ash carbon concentrate, the CO2 adsorption capacities were relatively high (up to 4.5wt%) especially at high temperatures (75°C), where commercial active carbons relying on physi-sorption have low capacities. The addition of PEG improves the adsorption capacity and reduces the time taken for the sample to reach the equilibrium. No CO2 seems to remain after desorption, suggesting that the process is fully reversible.
In general, the post-combustion capture of CO2 is costly; however, swing adsorption processes can reduce these costs under certain conditions. This review highlights the issues related to adsorption-based processes for the capture of CO2 from flue gas. In particular, we consider studies that investigate CO2 adsorbents for vacuum swing or temperature swing adsorption processes. Zeolites, carbon molecular sieves, metal organic frameworks, microporous polymers, and amine-modified sorbents are relevant for such processes. The large-volume gas flows in the gas flue stacks of power plants limit the possibilities of using regular swing adsorption processes, whose cycles are relatively slow. The structuring of CO2 adsorbents is crucial for the rapid swing cycles needed to capture CO2 at large point sources. We review the literature on such structured CO2 adsorbents. Impurities may impact the function of the sorbents, and could affect the overall thermodynamics of power plants, when combined with carbon capture and storage. The heat integration of the adsorption-driven processes with the power plant is crucial in ensuring the economy of the capture of CO2, and impacts the design of both the adsorbents and the processes. The development of adsorbents with high capacity, high selectivity, rapid uptake, easy recycling, and suitable thermal and mechanical properties is a challenging task. These tasks call for interdisciplinary studies addressing this delicate optimization process, including integration with the overall thermodynamics of power plants.
The global rise in atmospheric greenhouse gas concentrations calls for practicable solutions to capture CO2. In this study, a mineral carbonation process was applied in which CO2 reacts with alkaline lignite ash and forms stable carbonate solids. In comparison to previous studies, the assays were conducted at low temperatures and pressures and under semi-dry reaction conditions in an 8 L laboratory mixing device. In order to find optimum process conditions the pCO(2) (10-20%), stirring rate (500-3000 rpm) and the liquid to solid ratio (L/S = 0.03-0.36 L kg(-1)) were varied. In all experiments a considerable CO2 uptake from the gas phase was observed. Concurrently the solid phase contents of Ca and Mg (hydr)oxides decreased and CaCO3 and MgCO3 fractions increased throughout the experiments, showing that CO2 was stabilized as a solid carbonate. The carbonation reaction depends on three factors: Dissolution of CO2 in the liquid phase, mobilization of Ca and Mg from the mineral surface and precipitation of the carbonate solids. Those limitations were found to depend strongly on the variation of the process parameters. Optimum reaction conditions could be found for LIS ratios between 0.12 and 0.18, medium stirring velocities and pCO(2) between 10% and 20%. Maximum CO2 uptake by the solid phase was 4.8 mmol g(-1) after 120 min, corresponding to a carbonation efficiency for the alkaline material of 53% of the theoretical CO2 binding capacity. In comparison to previous studies both CO2 uptake and carbonation efficiencies were in a similar range, but the reaction times in the semi-dry process were considerably shorter. The proposed method additionally allows for a more simple carbonation setup due to low T and P, and produces an easier to handle product with low water content.
An in-situ CO(2) sequestration method using coal ash ponds located in coastal regions is proposed. The CO(2) sequestration capacity of coal fly ash (CFA) by mineral carbonation was evaluated in a flow-through column reactor under various conditions (solid dosage: 100-330g/L, CO(2) flow rate: 20-80mL/min, solvent type: deionized (DI) water, 1M NH(4)Cl solution, and seawater). The CO(2) sequestration tests were conducted on CFA slurries using flow-through column reactors to simulate more realistic flow-through conditions. The CO(2) sequestration capacity increased when the solid dosage was increased, whereas it was affected insignificantly by the CO(2) flow rate. A 1M NH(4)Cl solution was the most effective solvent, but it was not significantly different from DI water or seawater. The CO(2) sequestration capacity of CFA under the flow-through conditions was approximately 0.019g CO(2)/g CFA under the test conditions (solid dosage: 333g/L, CO(2) flow rate: 40mL/min, and solvent: seawater).
The use of low-cost adsorbent has been investigated as a replacement for the current expensive methods of removing dyes from wastewater. As such, fly ash generated in National Thermal Power plant was collected and converted into a low-cost adsorbent. The prepared adsorbent was characterized and used for the removal of dyes from wastewater. Adsorption studies were carried out for different temperatures, particle sizes, pH's, and adsorbent doses. The adsorption of each dye was found to increase with increasing temperature, thereby indicating that the process is endothermic in nature. The removal of each dye was found to be inversely proportional to the size of the fly ash particles, as expected. Both the linear and nonlinear forms of the Langmuir and Freundlich models fitted the adsorption data. The results indicate that the Freundlich adsorption isotherm fitted the data better than the Langmuir adsorption isotherm. Further, the data were better correlated with the nonlinear than the linear form of this equation. Thermodynamic parameters such as the free energies, enthalpies, and entropies of adsorption of the dye−fly ash systems were also evaluated. The negative values of free energy indicate the feasibility and spontaneous nature of the process, and the positive heats of enthalpy suggest the endothermic nature of the process. The adsorptions of crystal violet and basic fuschin follow first-order rate kinetics. In comparison to other low-cost adsorbents, the sorption capacity of the material under investigation is found to be comparable to that of other commercially available adsorbents used for the removal of cationic dyes from wastewater.
The ash behavior during suspension firing of 12 alternative solid biofuels, such as pectin waste, mash from a beer brewery, or waste from cigarette production have been studied and compared to wood and straw ash behavior. Laboratory suspension firing tests were performed on an entrained flow reactor and a swirl burner test rig, with special emphasis on the formation of fly ash and ash deposit. Thermodynamic equilibrium calculations were performed to support the interpretation of the experiments. To generalize the results of the combustion tests, the fuels are classified according to fuel ash analysis into three main groups depending upon their ash content of silica, alkali metal, and calcium and magnesium. To further detail the biomass classification, the relative molar ratio of Cl, S, and P to alkali were included. The study has led to knowledge on biomass fuel ash composition influence on ash transformation, ash deposit flux, and deposit chlorine content when biomass fuels are applied for suspension combustion.
The overall objective of the work described in this paper was to determine the behavior of wood ash under entrained-flow gasification conditions. Experimental work in atmospheric and pressurized entrained-flow gasification simulators, combined with thermodynamic equilibrium calculations, has shown that wood ash is not prone to form a molten slag at typical operating conditions of (pressurized, dry-feed, oxygen-blown) entrained-flow gasifiers, in spite of the presence of a relatively high amount of low-melting alkaline elements. This appears mostly due to the formation of mainly high-temperature-melting compounds (e.g., CaO) and only a small fraction of Ca silicates, which are characterized by a lower melting temperature. Phosphor and silicon may contribute to creating a higher melt amount, whereas low-melting alkali metal compounds are mostly partitioned into the vapor phase. Experiments, as well as modeling work performed for three types of wood, have shown consistent results. Addition of a fluxing agent is a promising option to improve the slagging behavior of wood-based systems by reducing the melting point of the slag. Moreover, thermodynamic calculations have shown that slag recycle may represent a feasible option in order to obtain sufficient slag coverage of the refractory wall despite the low ash content of woody fuels (typically 1 order of magnitude lower than in coal). In the present work, the determination of slag viscosity, a parameter critical for continuous operation of a slagging gasifier, has been addressed as well. The results of modeling work, showing the inapplicability of predictive formulas developed in the past for coal slags to wood-based slags, underline that further work is required to allow for a quantitative assessment of the slag viscosity as a function of slag composition and temperature.
The capture of CO 2 from gas streams has been achieved by the utilization of amine-enriched fly ash carbon sorbent system. The initial fly ash carbon sorbents were generated by the chemical treatment of carbon-enriched fly ash concentrates with a 3-chloropropylamine-hydrochloride (CPAHCL) solution at 25 • C. It was determined that these amine-enriched fly ash carbon sorbents performed at a 9% CO 2 capture capacity based on commercially available sorbents. The chemical sorption performance of these amine-enriched fly ash carbon sorbents will be described within this paper.
In this work several Li4SiO4-based sorbents from fly ashes for CO2 capture at high temperatures have been developed. Three fly ash samples were collected and subjected to calcination at 950 °C in the presence of Li2CO3. Both pure Li4SiO4 and fly ash-based sorbents were characterised and tested for CO2 sorption at different temperatures between 400 and 650 °C and adding different amounts of K2CO3 (0–40 mol%). To examine the sorbents performance, multiple CO2 sorption/desorption cycles were carried out. The temperature and the presence of K2CO3 strongly affect the CO2 sorption capacity for the sorbents prepared from fly ashes. When the sorption temperature increases by up to 600 °C both the CO2 sorption capacity and the sorption rate increase significantly. Moreover when the amount of K2CO3 increases, the CO2 sorption capacity also increases. At optimal experimental conditions (600 °C and 40 mol% K2CO3), the maximum CO2 sorption capacity for the sorbent derived from fly ash was 107 mg CO2/g sorbent. The Li4SiO4-based sorbents can maintain its original capacity during 10 cycle processes and reach the plateau of maximum capture capacity in less than 15 min, while pure Li4SiO4 presents a continual upward tendency for the 15 min of the capture step and attains no equilibrium capacity.
Environmentally friendly product, calcium-silica-aluminum hydrate, was synthesized from oil shale fly ash, which is rendered so far partly as an industrial waste. Reaction conditions were: temperature 130 and 160°C, NaOH concentrations 1, 3, 5 and 8M and synthesis time 24h. Optimal conditions were found to be 5M at 130°C at given parameter range. Original and activated ash samples were characterized by XRD, XRF, SEM, EFTEM, (29)Si MAS-NMR, BET and TGA. Semi-quantitative XRD and MAS-NMR showed that mainly tobermorites and katoite are formed during alkaline hydrothermal treatment. Physical adsorption of CO(2) on the surface of the original and activated ash samples was measured with thermo-gravimetric analysis. TGA showed that the physical adsorption of CO(2) on the oil shale fly ash sample increases from 0.06 to 3-4 mass% after alkaline hydrothermal activation with NaOH. The activated product has a potential to be used in industrial processes for physical adsorption of CO(2) emissions.
Highly efficient Li(4)SiO(4) (lithium orthosilicate)-based sorbents for CO(2) capture at high temperature, was developed using waste materials (rice husk ash). Two treated rice husk ash (RHA) samples (RHA1 and RHA2) were prepared and calcined at 800°C in the presence of Li(2)CO(3). Pure Li(4)SiO(4) and RHA-based sorbents were characterized by X-ray fluorescence, X-ray diffraction, scanning electron microscopy, nitrogen adsorption, and thermogravimetry. CO(2) sorption was tested through 15 carbonation/calcination cycles in a fixed bed reactor. The metals of RHA were doped with Li(4)SiO(4) resulting to inhibited growth of the particles and increased pore volume and surface area. Thermal analyses indicated a much better CO(2) absorption in Li(4)SiO(4)-based sorbent prepared from RHA1 (higher metal content sample) because the activation energies for the chemisorption process and diffusion process were smaller than that of pure Li(4)SiO(4). RHA1-based sorbent also maintained higher capacities during the multiple cycles.
Poultry rendering emissions contain volatile organic compounds (VOCs) that are nuisance, odorous, and smog and particulate matter precursors. Present treatment options, such as wet scrubbers, do not eliminate a significant fraction of the VOCs emitted including, 2-methylbutanal (2-MB), 3-methylbutanal, and hexanal. This research investigated the low-temperature (25-160 degrees C) catalytic oxidation of 2-MB and hexanal vapors in a differential, plug flow reactor using wood fly ash (WFA) as a catalyst and oxygen and ozone as oxidants. The oxidation rates of 2-MB and hexanal ranged between 3.0 and 3.5 x 10(-9)mol g(-1)s(-1) at 25 degrees C and the activation energies were 2.2 and 1.9 kcal mol(-1), respectively. The catalytic activity of WFA was comparable to other commercially available metal and metal oxide catalysts. We theorize that WFA catalyzed a free radical reaction in which 2-butanone and CO(2) were formed as end products of 2-MB oxidation, while CO(2), pentanal, and butanal were formed as end products of hexanal oxidation. When tested as a binary mixture at 25 and 160 degrees C, no inhibition was observed. Additionally, when ozone was tested as an oxidant at 160 degrees C, 100% removal was achieved within a 2-s reaction time. These results may be used to design catalytic oxidation processes for VOC removal at poultry rendering facilities and potentially replace energy and water intensive air pollution treatment technologies currently in use.
Solid waste and atmospheric emissions originating from power production are serious problems worldwide. In the Republic of Estonia, the energy sector is predominantly based on combustion of a low-grade carbonaceous fossil fuel: Estonian oil shale. Depending on the combustion technology, oil shale ash contains 10-25% free lime. To transport the ash to wet open-air deposits, a hydraulic system is used in which 10(7)-10(8) cubic meters of Ca(2+)-ion-saturated alkaline water (pH level 12-13) is recycled between the plant and sedimentation ponds. The goals of the current work were to design an ash-water suspension carbonation process in a continuous mode laboratory-scale plant and to search for potential means of intensifying the water neutralization process. The carbonation process was optimized by cascading reactor columns in which the pH progressed from alkaline to almost neutral. The amount of CO(2) captured from flue gases can reach 1-1.2 million ton at the 2007 production level of the SC Narva Power Plants. Laboratory-scale neutralization experiments were carried out to compare two reactor designs. Sedimentation of PCC particles of rhombohedral crystalline structure was demonstrated and their main characteristics were determined. A new method providing 50x greater specific intensity is also discussed.
Novel dynamic equipment with gas in and out continuously was developed to study the capture capacity of CO(2). Municipal solid waste incineration (MSWI) fly ash has a high capture rate of CO(2) in CO(2)-rich gas. Fly ash can sequester pure CO(2) rapidly, and its capacity is 16.3 g CO(2)/100 g fly ash with no water added and 21.4 g CO(2)/100 g fly ash with 20% water added. For simulated incineration gas containing 12% CO(2), the capture rate decreased and the capacity was 13.2 g CO(2)/100 g fly ash with no water added and 18.5 g CO(2)/100 g fly ash with 20% water added. After accelerated carbonation, the C and O contents increased, indicating CO(2) capture in the fly ash; CO(2) combines with Ca(OH)(2) to form CaCO(3), which increased the CaCO(3) content from 12.5 to 54.3%. The leaching of Pb markedly decreased from 24.48 to 0.111 mg/L.
The bagasse fly ash, an industrial solid waste of sugar industry, was used for the removal of cadmium and nickel from wastewater. As much as 90% removal of cadmium and nickel is possible in about 60 and 80 min, respectively, under the batch test conditions. Effect of various operating variables, viz., solution pH, adsorbent dose, adsorbate concentration, temperature, particle size, etc., on the removal of cadmium and nickel has been studied. Maximum adsorption of cadmium and nickel occurred at a concentration of 14 and 12 mg x l(-1) and at a pH value of 6.0 and 6.5, respectively. A dose of 10 g x l(-1) of adsorbent was sufficient for the optimum removal of both the metal ions. The material exhibits good adsorption capacity and the adsorption data follow the Langmuir model better then the Freundlich model. The adsorption of both the metal ions increased with increasing temperature indicating endothermic nature of the adsorption process. Isotherms have been used to determine thermodynamic parameters of the process, viz., free energy change, enthalpy change and entropy change.
The feasibility of reusing wood ash as an inexpensive catalyst in a catalytic ozonation process has been demonstrated. Catalytic ozonation was demonstrated to oxidize H2S, methanethiol (MT), dimethyl sulfide (DMS), and dimethyl disulfide (DMDS) at low temperatures (23-25 degrees C). The process oxidized 25-50% of an inlet MT stream at 70 ppmv without the formation of DMDS (contrary to ash plus oxygen in air), oxidized 90-95% of an 85 ppmv stream of DMS, and oxidized 50% of a 100 ppmv DMDS stream using 2 g of wood ash at a space velocity of 720 h(-1) using ozone concentrations ranging from 100 to 300 ppmv. Similarly, 60-70% conversion of a 70 ppmv H2S stream was achieved with 2 g of ash in 1.1 s without catalytic deactivation (approximately 44 h). The overall oxidation rate of H2S, DMS, and DMDS increased with increasing ozone concentration contrary to the oxidation rate of MT, which was independent of ozone concentration. Dimethyl sulfoxide and dimethyl sulfone were identified as the primary end products of DMS oxidation, and SO2 was the end product of H2S and MT oxidation.
During bottom ash weathering, carbonation under atmospheric conditions induces physico-chemical evolutions leading to the pacification of the material. Fresh bottom ash samples were subjected to an accelerated carbonation using pure CO2. The aim of this work was to quantify the volume of CO2 that could be sequestrated with a view to reduce greenhouse gas emissions and investigate the possibility of upgrading some specific properties of the material with accelerated carbonation. Carbonation was performed by putting 4mm-sieved samples in a CO2 chamber. The CO2 pressure and the humidity of the samples were varied to optimize the reaction parameters. Unsieved material was also tested. Calcite formation resulting from accelerated carbonation was investigated by thermogravimetry and differential scanning calorimetry (TG/DSC) and metal leaching tests were performed. The volume of sequestrated CO2 was on average 12.5L/kg dry matter (DM) for unsieved material and 24 L/kg DM for 4mm-sieved samples. An ash humidity of 15% appeared to give the best results. The reaction was drastically accelerated at high pressure but it did not increase the volume of sequestrated CO2. Accelerated carbonation, like the natural phenomenon, reduces the dangerous nature of the material. It decreases the pH from 11.8 to 8.2 and causes Pb, Cr and Cd leaching to decrease. This process could reduce incinerator CO2 emissions by 0.5-1%.
As a result of the EU Landfill Directive, the disposal of municipal solid waste incineration (MSWI) fly ash is restricted to only a few landfill sites in the UK. Alternative options for the management of fly ash, such as sintering, vitrification or stabilization/solidification, are either costly or not fully developed. In this paper an accelerated carbonation step is investigated for use with fly ash. The carbonation reaction involving fly ash was found to be optimum at a water/solid ratio of 0.3 under ambient temperature conditions. The study of ash mineralogy showed the disappearance of lime/portlandite/calcium chloride hydroxide and the formation of calcite as carbonation proceeded. The leaching properties of carbonated ash were examined. Release of soluble salts, such as SO4, Cl, was reduced after carbonation, but is still higher than the landfill acceptance limits for hazardous waste. It was also found that carbonation had a significant influence on lead leachability. The lead release from carbonated ash, with the exception of one of the fly ashes studied, was reduced by 2-3 orders of magnitude.