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Biomass pyrolysis and in-line air–steam reforming as a potential strategy to progress towards sustainable ammonia production
... El producto de fondo se obtiene residual de asfáltico que, por excelencia, es carga a procesos de craqueo para la obtención de hidrocarburos livianos [2]. Sin embargo, en la actualidad existen procesos termoquímicos que pueden ser aprovechados a las condiciones de presión de la unidad de destilación de vacío, entre ellas la pirolisis, varios autores han empleado el proceso de pirolisis para estudiar la degradación térmica de muestras complejas entre ellas biomasa, oil shale, polímeros y compuestos orgánicos de residuos de hidrocarburos, como una opción para la producción de hidrocarburos livianos [3,4,5]. [2]. ...
Hydrogen energy plays a vital role in the transition towards a carbon-neutral society but faces challenges in storage and transport, as well as in production due to fluctuations in renewable electricity generation. Ammonia (NH 3), as a carbon-neutral hydrogen carrier, offers a promising solution to the energy storage and transport problem. To realize its potential and support the development of a hydrogen economy, exploring NH 3 synthesis in a decentralized form that integrates with distributed hydrogen production systems is highly needed. In this study, a computational fluid dynamics (CFD) model for the Ruthenium (Ru) catalysts-based Haber-Bosch reactor is developed. First, a state-of-the-art kinetic model comprehensively describing the complex catalytic reaction is assessed for its sensitivity and applicability to temperature, pressure and conversion. Then, the kinetic model is integrated into the CFD model, and its accuracy is verified through comparison with experimental data obtained from different Ru-based catalysts and operation conditions. Detailed CFD results for a given case are presented, offering a visual understanding of thermal gradients and species distributions inside the reactor. Finally, a CFD-based parametric study is performed to reveal the impacts of key operation parameters and optimize the NH 3 synthesis reactor. The results show that the NH 3 production rate is predominantly influenced by temperature, with a twofold difference observed for every 30 • C variation, while pressure primarily affects the equilibrium. Additionally, the affecting mechanism of space velocity is thoroughly discussed and the best value for efficient NH 3 synthesis is found to be 180,000 h −1. In conclusion, the CFD model and simulation results provide valuable insights for the design and control of decentralized NH 3 synthesis reactor and operation, contributing to the advancement of sustainable energy technologies.
A comparative analysis of the ethanol reforming concerning steam and autothermal reformer was conducted to evaluate parametric conditions for a hydrogen‐rich product stream. The present simulation study includes first attempt to report the optimal parametric conditions for ethanol‐steam and ‐autothermal reformer. Various operating parameters, including temperature, pressure, steam‐to‐ethanol ratio, and oxygen‐to‐ethanol ratio, were considered in this analysis. Result illustrated that the hydrogen mole fraction increased with rising temperature in the steam reforming of ethanol, but it remained constant beyond reaction temperature of 750°C. On the other hand, as the pressure and the steam‐to‐ethanol ratio increased, the H2 mole fraction decreased. Furthermore, with an enriched oxygen‐to‐ethanol ratio reactant stream, H2 and CO content in the product effluent was found to be reduced in the autothermal ethanol reforming. The results showed that an autothermal reforming strategy under optimized parameters (temperature: 600°C; steam‐to‐ethanol ratio: 5; oxygen‐to‐ethanol ratio: 0.6) produced the maximum H2 yield (3.78 kmol/h) per mole of ethanol. It was observed that introducing O2 into the reformer helped reduce the amount of energy required for the steam reforming reaction. This study indicates that, although considerable work has been conducted on reforming catalysts development, simulation‐based studies are still useful to help understand the overall process behavior without undertaking laborious, high‐cost involved time‐consuming experiments. This article is protected by copyright. All rights reserved.
In recent decades, the production of H2 from biomass, waste plastics, and their mixtures has attracted increasing attention in the literature in order to overcome the environmental problems associated with global warming and CO2 emissions caused by conventional H2 production processes. In this regard, the strategy based on pyrolysis and in-line catalytic reforming allows for obtaining high H2 production from a wide variety of feedstocks. In addition, it provides several advantages compared to other thermochemical routes such as steam gasification, making it suitable for its further industrial implementation. This review analyzes the fundamental aspects involving the process of pyrolysis-reforming of biomass and waste plastics. However, the optimum design of transition metal based reforming catalysts is the bottleneck in the development of the process and final H2 production. Accordingly, this review focuses especially on the influence the catalytic materials (support, promoters, and active phase), synthesis methods, and pyrolysis-reforming conditions have on the process performance. The results reported in the literature for the steam reforming of the volatiles derived from biomass, plastic wastes, and biomass/plastics mixtures on different metal based catalysts have been compared and analyzed in terms of H2 production.
By testing 92 different biochars, this study had the objective to determine the relations between simple physico-chemical characteristics of biochar (elemental composition, ash fraction, specific surface area, process parameters) and infrared sorption characteristics revealing the presence of specific functional groups. The results of Diffusive Reflection Fourier Transformation Infrared Spectroscopy were statistically analyzed with multiple linear regression techniques and Principal Component Analysis (PCA) with the biochar characterization parameters as model inputs. The dominant parameters affecting the functional group signals were the pyrolysis temperature, the H/C-ratio and specific surface area of the biochar and the ash fraction. Regression models were able to explain 60-90% of data variance for specific peaks in the DRIFTS-spectra. The application of PCA could further reduce the input parameters to three main factors explaining 70.8% of total data variance. Biplots of the first two main factors showed the similarity of infrared spectra of biochars produced at 300 and 450 °C, whereas a pyrolysis temperature of 600 °C lead to a partial and a 750°C to a nearly complete loss of biochar surface functional groups.
Solid waste management needs, increasing pollution level by burning or dumping of waste, and the use of fossil fuels and depleting energy resources are a few of the problems of the decade that need to find answers. Disposal of lots of compound polymers-rich biomass waste is done worldwide by dumping on land or into water bodies or else by incineration or long-term storage in an available facility commonly. This kind of disposal instead becomes a reason to add the soil, water, and air pollution. A lot of multidisciplinary collaboration in different streams of science and technology has added to the efficiency of using such waste for use as an alternative energy form, like biogas and biohydrogen. The use of biogas plants for converting biological waste into methane using municipal solid waste (MSW) is known since a long time. Along with MSW, a lot of other agricultural waste and kitchen waste are also added every day to nature. But the complex components of such waste material like lignocellulosic wastes still don't pass the test of qualifying as a resource for biogas and even more energy-efficient and cleaner biofuel, bio-hydrogen. It may be because of its complicated structure and a lot of parameters that affect its use for converting it into bio-hydrogen. This review is designed to analyze and compare these parameters for optimum lignocellulosic waste conversion, more specifically agriculture and food waste, into cleaner energy forms that would help to tackle the solid waste management and air pollution control more effectively.
More than 27 million tonnes of waste plastics are generated in Europe each year representing a considerable potential resource. There has been extensive research into the production of liquid fuels and aromatic chemicals from pyrolysis-catalysis of waste plastics. However, there is less work on the production of hydrogen from waste plastics via pyrolysis coupled with catalytic steam reforming. In this paper, the different reactor designs used for hydrogen production from waste plastics are considered and the influence of different catalysts and process parameters on the yield of hydrogen from different types of waste plastics are reviewed. Waste plastics have also been investigated as a source of hydrocarbons for the generation of carbon nanotubes via the chemical vapour deposition route. The influences on the yield and quality of carbon nanotubes derived from waste plastics are reviewed in relation to the reactor designs used for production, catalyst type used for carbon nanotube growth and the influence of operational parameters.
Graphic Abstract
A novel integrated biomass-to-energy system was presented based on gasification and pyrolysis for efficient and sustainable energy production. The system combines the advantages of gasification and pyrolysis to convert different types of biomass into electrical energy and hydrogen energy, respectively. The pyrolysis of woody biomass generates bio-oil and accompanying gas that is mixed with gasification-produced syngas to increase its heating value, thereby increasing power generation. The heat generated during gasification is used to provide thermal energy for pyrolysis, increasing the yield of pyrolysis products. The proposed system was thermodynamically and economically evaluated, and it was found that the system achieved high energy efficiency and economic benefits, greatly exceeding the energy utilization efficiency of conventional biomass power plants. The system also had excellent environmental performance with a lower CO2 emission intensity than that of a coal-fired power plant. The effects of the pyrolysis temperature, gasification temperature, and turbine pressure ratio were explored in the novel system, and the results show that increasing the pyrolysis temperature appropriately is beneficial for increasing hydrogen production and power generation, while increasing the gasification temperature increases the hydrogen yield but decreases the system power generation. These results demonstrate that the proposed integrated biomass-to-energy system provides an efficient and sustainable approach for biomass energy utilization.
Ruthenium/nickel ex-solved perovskite catalysts have been synthesized by incipient impregnation. As-synthesized and spent catalysts have been characterized by XRD, TPR-H2, SEM-EDX and TEM analyses. Reduced catalysts have been tested in the autothermal reforming of ethanol, in the temperature range of 600–800 °C. All tested catalysts gave the total conversion of ethanol in the range of investigated temperatures, confirming the oxidative ability and oxygen storage capacity of perovskite, that promotes the catalyst activation. The highest hydrogen yield (83%) is obtained by ruthenium/nickel ex-solved perovskite containing the 0.5 wt% of Ru (SFMN/0.5Ru catalyst) at 600 °C. Increasing the amount of Ru in the catalyst an inhibiting effect is observed: high Ru content modifies the metal species and their reducibility. H2 yield strongly decreases (lower than the 50%) for the catalyst containing the 1 wt% of ruthenium (SFMN/1Ru catalyst), at all the reaction temperatures tested. At 600 °C, were the highest H2 yield is registered, the coke deposition increases with this order: SFMN/1Ru< SFMN/0.5Ru< SFMN, confirming the positive role of noble catalyst toward the inhibition of carbon species formation. By comparison of all catalytic aspects (ethanol conversion, hydrogen yield, coke deposition and stability) the catalyst showing the best performance is ruthenium/nickel ex-solved perovskite with 0.5 wt% of Ru content (SFMN/0.5Ru).
Chemical looping allows for the production of different products, such as syngas, high-purity hydrogen and high concentration CO2, through a single process without the need for separation. In this study, a detailed analysis is investigated by utilizing Aspen Plus software to explore the feasibility of bio-oils efficient utilization in four chemical looping processes. The Sorption Enhanced Steam Reforming (SESR) process for syngas production with CO2 capture can be modified into an autothermal process by combusting a fraction of the syngas, leading to a syngas yield of 11.04 (mol/mol fuel) and a CO2 capture capacity of 4.18 (mol/mol fuel). The Calcium and Chemical Looping Reforming (CaL-CLR) process is a unique approach to attaining the greatest syngas yield of 11.31 (mol/mol fuel) and capturing the highest CO2 of 5.40 (mol/mol fuel) simply by adjusting the flow rate of NiO oxygen carrier to realize autothermic reforming without compromising the syngas output. Nevertheless, the integration of NiO and air reactor (AR) will lead to increased financial and operational outlays. For co-production of syngas and high-purity hydrogen, the Three-Reactors Chemical Looping Hydrogen (TR-CLH) process can produce high-purity hydrogen with 5.70 (mol/mol fuel) under autothermal conditions, but the syngas yield and purity are low. The Chemical Looping Reforming and Water Splitting (CLRWS) process has the potential to create a substantial syngas yield, up to 9.63 (mol/mol fuel), as well as a considerable flow rate of high-purity hydrogen, 8.42 (mol/mol fuel). It is clear that this process is more successful than other processes available; however, the excessively high temperature of the fuel reactor (FR) impedes its further utilization.
Fossil fuels are no longer accepted as the sole energy source with their environmental impacts and fluctuating price. Green hydrogen is considered a potential candidate for fossil fuel soon—however, hydrogen is facing the challenges of storage and transportation. Green ammonia, with its ease of transport and storage, is another promising alternative. Decarbonizing ammonia production is an environmental press toward achieving net-zero emissions by 2050. This work summarizes the up-to-date progress in the green ammonia production methods. An assessment of the different production methods was conducted to highlight the merits and constraints of each approach. Moreover, the promising applications of green ammonia in the energy sectors were discussed. The various barriers, i.e., technical, economic, environmental, and regulations and policies, facing the widespread of green ammonia were also discussed. Finally, the contribution of green ammonia in achieving the different sustainable development goals was elaborated, focusing on the contribution of green ammonia in achieving climate change (SDG 13), clean energy (SDG 7), and other sustainability-related goals. Low efficiencies, high cost, and negative environmental impacts are the common challenges of the various production methods. The progress in green ammonia is essential for achieving SDG2, “Zero hunger”. SDG3 “healthy life and well-being” and SDG13 “Climate action”, will be achieved by eliminating 3.85 kg CO2-eq/kg NH3 emitted from conventional ammonia-based processes. Ease storing of green ammonia in liquid form (at 9 bar or cooling to −33°); makes it the best green energy source, i.e., achieving SDG7 “green and affordable energy”. By 2050, green ammonia is expected to represent 99 % of marine fuel, thus contributing to SDG9 “Industry and Infrastructure”. Moreover, green ammonia production will save 35.2 GJ of natural gas, thus achieving SDG12 “Responsible consumption/production”.
In the current energy scenario, the production of heat, power and biofuels from biomass has become of major interest. Amongst diverse thermochemical routes, gasification has stood out as a key technology for the large-scale application of biomass. However, the development of biomass gasification is subjected to the efficient conversion of the biochar and the mitigation of troublesome by-products, such as tar. Syngas with high tar content can cause pipeline fouling, downstream corrosion, catalyst deactivation, as well as adverse impact on health and environment, which obstruct the commercialization of biomass gasification technologies. Since the reduction of tar formation is a key challenge in biomass gasification, a comprehensive overview is provided on the following aspects, which particularly include the definition and complementary classifications of tar, as well as possible tar formation and transformation mechanisms. Moreover, the adverse effects of tar on downstream applications, human health or environment, and tar analyzing techniques (online and off-line) are discussed. Finally, the primary tar removal strategies are summarized. In this respect, the effect of key operation parameters (temperature, ER and S/B), catalysts utilization (natural and supported metal catalysts) and the improvement of reactor design on tar formation and elimination was thoroughly analyzed.
A large number of process routes is available for the production of sustainable energy carriers from biogenic residues. Benchmarking these routes usually suffers from a lack of comparable performance data. The present work addresses this through a comprehensive model-based comparison of various biomass-to-X routes. Herein, seven routes (methanol, synthetic natural gas, dimethyl ether, Fischer-Tropsch syncrude, ammonia, and hydrogen with and without carbon capture) are modelled in detailed Aspen Plus® simulations. The evaluation itself is based on various key performance indicators, which capture both energetic (i.e. energy yield and usable heat per feedstock) and material-based (i.e. carbon and hydrogen conversion efficiency, and CO 2 emissions) properties of the routes. The results show, that no simple correlations can be drawn between energetic and material-based indicators. In summary across all considered properties, the methanol route exhibits the best combined results, in particular with the highest carbon efficiency of 40 %. Fischer-Tropsch is more suitable for integration into existing industrial parks due to the lowest energy yield of 40 % with a lot of by-product formation and the highest amount of useable heat per feedstock of 211.3 kW MW − 1. Whereas dimethyl ether and synthetic natural gas have potential for integration into heat grids, mainly due to their good conversion and simultaneous large heat dissipation. Ammonia and hydrogen should only be considered in combination with carbon capture. Therefore, the key performance indicators determined herein must be considered together with project-and location-specific requirements and the market outlook for the product.
The emerging study of hydrogen energy is receiving substantial attention in the scientific community due to its efficiency in approaching net zero and environmental sustainability. Meanwhile, bioethanol is a sustainable and carbon–neutral fuel for hydrogen production. This research aims to assess various ethanol reforming routes, including ethanol steam reforming, partial oxidation, and autothermal reforming, and evaluate the differences in hydrogen production as a function of catalyst physicochemistry and experimental parameters. For all three techniques, 75 % hydrogen selectivity is attained at 400 °C. In the ethanol steam reforming, non-noble metals (Co and Ni) are more reactive than noble metals (Rh and Ru). However, the sequence of hydrogen selectivity is featured by Rh > Ir > Ru > Pt > Ni > Co in autothermal reforming of ethanol. The partially filled d-orbitals of various transition metals can uptake or provide electrons to various reagents, thereby controlling reaction activity. Non-noble metals are inexpensive, making these catalysts appealing for a variety of reforming processes. The small crystal size <10 nm and the large Brunauer-Emmett-Teller surface area of the metal-support particles regulate the dispersion and reactivity of the catalyst. Hydrogen selectivity is lower in partial oxidation and autothermal reforming, while CO and CO2 exhibit no specific selectivity trend. The reactivity of intermediate reactions such as dehydrogenation and decarbonylation positively correlated with the reaction temperature and the steam/oxygen/ethanol ratio, which regulates syngas product distributions. Overall, this review provides a vision for sustainable hydrogen production and decarbonization to achieve the net zero target.
Rising global temperature, pollution load, and energy crises are serious problems, recently facing the world. Scientists around the world are ambitious to find eco-friendly and cost-effective routes for resolving these problems. Biochar has emerged as an agent for environmental remediation and has proven to be the effective sorbent to inorganic and organic pollutants in water and soil. Endowed with unique attributes such as porous structure, larger specific surface area (SSA), abundant surface functional groups, better cation exchange capacity (CEC), strong adsorption capacity, high environmental stability, embedded minerals, and micronutrients, biochar is presented as a promising material for environmental management, reduction in greenhouse gases (GHGs) emissions, soil management, and soil fertility enhancement. Therefore, the current review covers the influence of key factors (pyrolysis temperature, retention time, gas flow rate, and reactor design) on the production yield and property of biochar. Furthermore, this review emphasizes the diverse application of biochar such as waste management, construction material, adsorptive removal of petroleum and oil from aqueous media, immobilization of contaminants, carbon sequestration, and their role in climate change mitigation, soil conditioner, along with opportunities and challenges. Finally, this review discusses the evaluation of biochar standardization by different international agencies and their economic perspective.
Chemical looping hydrogen production (CLH2) is a new technology used to produce hydrogen (H2) from fuels while separating CO2 simultaneously. This research aims to build an integrated conversion system of rice husks, a high energy potential biomass, to H2 with high energy efficiency. The developed system mainly consists of superheated steam drying, steam gasification, chemical looping, and Haber-Bosch processes. Three different systems are developed and compared. The first and second systems employ direct chemical looping (DCL) using H2O and CO2 as gas enhancers for the reducer, respectively, while the third system adopts syngas chemical looping (SCL). Exergy recovery and process integration technologies are adopted to enhance energy and exergy efficiencies. A mixture of Fe2O3 and Al2O3 is used as oxygen and heat carriers in the CLH2 module. Process modeling, optimization, and evaluation of both energy and exergy efficiencies are conducted using Aspen Plus. Some crucial operating parameters, including reactor temperature, pressure, the oxygen carrier flow rate, and gas enhancer flow rate, are selected to evaluate the performance of the system, especially in terms of efficiency. The highest achievable H2, NH3, and net power efficiencies are 51.8%, 38.09%, 0.65%, respectively, when DCL is adopted with CO2 as a gas enhancer during the reduction.
Biochar is the solid material produced from the carbonization of organic feedstock biomass. This material has several unique characteristics such as greater carbon content, good electrical conductivity, high stability and large surface area, which can be applied in several research areas such as generation of power and wastewater treatment. In connection with this, recently, the investigations on biochar significantly focus on the removal of toxic heavy metals since the biochar material is easily available and environmentally friendly. According to an environmental analytical device, biochar-derived carbonaceous material has been additionally applied to the synthesis of an effective, sensitive, and low-cost electrochemical sensor. Biochar with an assessment of electrochemical properties has engaged with different redox reactions in water. In this survey, electrochemical ways of behaving of biochar in light of the electrochemical structures were analytically compiled as well as the impact from biomass sources and manufacturing process including carbonization strategies, pre-treatment/changed techniques. This review emphasizes the various synthesis methods of biochar form organic feedstock, properties and different modulations of biochar for the bioremediation of heavy metals. This review study emphasizes the utilization of biochar as sensing platform and supercapacitor for electrode fabrication in electrochemical biosensor to enhance the remediation of toxic contaminants from water streams and by switching the less ecological traditional materials. Brief information on the techniques employed for packaging biochar as carbon electrode is summarized. Scope in the aspect of environmental concern of biochar, future challenges and prospects are proposed in detail.
In the energy system transition, energy storage technology is vital for increasing the penetration of renewables, where chemical energy storage is most suitable for long-term grid-scale energy storage. Green ammonia is selected to replace hydrogen for the sake of storage efficiency, safety, and cost. Most time, ammonia is seen as either an energy storage medium or a fuel. However, the dual identity of ammonia as an energy carrier is discussed less. So, this study conceptualizes power-to-ammonia-to-power (P2A2P) and biomass-to-ammonia-to-power (B2A2P) pathways where ammonia is served as an energy carrier for both energy storage and fuel. Eight scenarios involving recent ammonia production and utilization technologies are technically and economically evaluated based on hourly weather and demand data. The results show that the B2A2P pathway presents a better performance because the average energy and exergy efficiencies are hardly influenced by the supply and demand balance of electricity. They can reach 40–50% in contrast to 27–47% in the P2A2P pathway. Besides, the B2A2P pathway provides a considerable amount of ammonia (around 10,000 t/month), which takes the major part of revenues. Although the CAPEX (603.3–675.1 MUSD) and OPEX (30–40 MUSD) in the B2A2P pathway are much higher than that of P2A2P (159.2–181.1 and 6–9 MUSD, respectively), the optimal scenario of the B2A2P pathway has a shorter discounted payback time (six years), and higher net present value (415.5 MUSD).
To solve the problem of unevenly distributed renewables and increase their penetration, large-scale energy storage is necessary. Green hydrogen is suitable for bulk energy storage; however, it still faces storage problems. Therefore, green ammonia has been proposed as a substitute for hydrogen. The combination of renewables and green ammonia production can achieve cross-sector decarbonization. However, the potential of green ammonia as an energy carrier requires further investigation. This paper reports the design and analysis of a renewable multi-generation system for electricity, heat, and green ammonia, where biomass-to-ammonia-to-power is used as an energy storage method. This concept combines renewable power generation, biomass chemical-looping ammonia production, and direct ammonia fuel cells. The results indicated that the maximum energy and exergy efficiencies were 60.1% and 56.3%, respectively. The system provides 29,582 t·y⁻¹ ammonia and 3,525,305 t·y⁻¹ hot water and captures 171,550 t·y⁻¹ of carbon dioxide. The optimal proportion of key components and relevant design criteria were also determined through sensitivity analysis as well. Compared to systems involving power-to-ammonia-to-power, the higher efficiency, lower electricity consumption for ammonia production, and carbon dioxide capture make biomass-to-ammonia-to-power a promising energy storage method for multigeneration systems.
The growing environmental concerns associated with global warming along with the exponential rise in energy demand are boosting the production of clean energy. The combined process of biomass pyrolysis and in-line catalytic steam reforming is a promising alternative for the selective production of hydrogen from renewable sources. This Primer provides a general overview of the fundamental aspects that influence the hydrogen production potential of the process. Recent research studies and their main findings are highlighted. The current challenges and limitations of the process and ways to optimize the biomass-derived products of steam reforming are discussed. Finally, we evaluate progress toward the industrial scalability of the process. The combined process of biomass pyrolysis and in-line catalytic steam reforming is a promising alternative for the selective production of hydrogen from renewable sources. In this Primer, Lopez et al. outline the main factors influencing hydrogen production, from reactor configurations and operating conditions to product analysis and catalyst development.
Hydrogen is a clean fuel for heat and power generation and can serve as a feedstock for chemical synthesis. This study assesses the hydrogen production from biomass (e.g., cow manure) through integrating psychrophilic anaerobic digestion and dry methane reforming. For the first time, a rigorous model is developed for the low-temperature anaerobic digestion process by implementing the complex kinetics of the fermentation bioreactions. The produced biogas from the anaerobic digestion process is fed to the reforming process for hydrogen production. The kinetics of the dry methane reforming and water gas shift reactions over Co-Ni-Al2O3 catalyst are incorporated into the model. Validating the results of the proposed process using experimental data shows <5% relative deviation. The effects of total solids content, organic loading rate, hydraulic retention time, and digestate recirculation fraction on biogas and CH4 yield are investigated. The optimum values of operating parameters in the anaerobic digestion process as well as the dry methane reforming process are obtained. The process is designed to achieve the highest CH4-to-H2 conversion and the lowest energy consumption. A 48.07 kg/h biogas could produce 8.11 kg/h H2. The biomass-to-H2 process offers an energetic efficiency of 72.85%, revealing its superiority to similar processes, such as steam and auto-thermal reforming. The proposed process highlights a high potential for CO2 emission reduction (e.g., 398,736 t/y), compared to the direct biogas combustion for electricity production. Economic analysis shows that the cost of biogas-to-H2 production is 1.39 USD/kg H2 for a plant capacity of 45.5 kg/h H2.
The fast deactivation of the reforming catalyst greatly conditions H2 production from biomass. In order to alleviate this problem, use of conditioning catalysts in a previous conditioning step has been proposed to modify the pyrolysis volatile stream reaching the reforming catalyst. The experimental runs have been conducted in a two-step reactor system, which includes a conical spouted bed reactor for the continuous pinewood sawdust pyrolysis and an in-line fixed bed reactor made up of two sections: the conditioning and the reforming steps. Biomass fast pyrolysis was conducted at 500 °C and the reforming step at 600 °C. Different conditioning beds (inert sand, γ-Al2O3, spent fluid catalytic cracking (FCC) catalyst and olivine) were used for the conditioning of biomass pyrolysis volatiles and the influence their composition has on the performance and deactivation of a commercial Ni/Al2O3 reforming catalyst has been analyzed.
Considerable differences were noticed between the conditioning catalysts, with the reforming catalyst stability decreasing as follows depending on the type of material used: γ-Al2O3 > olivine > inert sand ≈ no guard bed > spent FCC catalyst.
The high acidity of γ-Al2O3 (with a high density of weak acid centers) is suitable for the selective cracking of phenolic compounds (mainly guaiacol and catechol), which are the main precursors of the coke deposited on the Ni active sites. Although H2 production is initially lower, the reforming catalyst stability is enhanced. These results are of uttermost significance in order to step further in the scaling up of the in-line pyrolysis-reforming strategy for the direct production of H2 from biomass.
Alternative energy sources have been the main interest since past decades due to inclining energy demand and growing environmental consciousness. Hydrogen (H2) which is known as a clean fuel and most viable energy carrier for the future, is highly potential due to its high mass-based energy density. Among the diverse thermochemical techniques introduced to generate H2 in an economical way, steam reforming (SR) emerged as a promising option due to high H2 production ability and economical profit. Presently, the feedstocks for mature SR technology are mostly non-renewable resources such as fossil fuel (coal, diesel, gasoline, and natural gas). H2 can also be produced from SR from alternative feedstocks such as liquid biomass waste and biomass derived oxygenates. This approach will not only solve disposal problem, but also open new breakthrough for renewable resources utilization. In this review, the concept, advantages, prospects and challenges of bio-H2 production via SR process over industrial effluents, solvents, biomass-derived solvents, and lipids are reviewed. These organic-rich feedstocks are mostly waste that caused pollution issues or produced in glut, thus proper utilization of these materials is an urgent need. SR of these alternative feedstocks are viable due to the high H2 yields obtained upon the transformation of their high-water volume content.
A study was carried out on the valorization of different waste plastics (HDPE, PP, PS and PE), their mixtures and biomass/HDPE mixtures by means of pyrolysis and in line oxidative steam reforming. A thermodynamic equilibrium simulation was used for determining steam reforming data, whereas previous experimental results were considered for setting the pyrolysis volatile stream composition. The adequacy of this simulation tool was validated using experimental results obtained in the pyrolysis and in line steam reforming of different plastics. The effect the most relevant process conditions, i.e., temperature, steam/plastic ratio and equivalence ratio, have on H2 production and reaction enthalpy was evaluated. Moreover, the most suitable conditions for the oxidative steam reforming of plastics of different nature and their mixtures were determined. The results obtained are evidence of the potential interest of this novel valorization route, as H2 productions of up to 25 wt% were obtained operating under autothermal conditions.
Currently, ammonia, as a clean and sustainable energy carrier, is intensively synthesized from its elements during the Haber-Bosch technology. This process requires a large amount of energy and emits numerous amounts of carbon dioxide, because hydrogen is dominantly produced from fossil fuels through reforming processes. Biomass-derived glycerol steam reforming is an attractive alternative to traditional reforming for reducing the dependence on hydrocarbon resources and mitigating climate change. This research aims to intensify a heat-integrated process for the co-production of ammonia and syngas from glycerol valorization. In this process, glycerol reforming continuously provides hydrogen needed for ammonia synthesis, and the liquid glycerol is simultaneously vaporized by heat generated from ammonia synthesis. Methane tri-reforming acts as a heat source to drive glycerol reforming; at the same time, the effluent gas produced through glycerol reforming is recycled to the tri-reforming side to reduce the greenhouse gas emissions. The role of different parameters on the process performance is identified by a one-dimensional heterogeneous model. Numerical results show that by adjusting the adequate operating conditions, glycerol and methane conversion >95%, nitrogen conversion >25%, glycerol dryness fraction = 1.0, and syngas with hydrogen to carbon monoxide ratio above 2.0, suitable for the Fischer-Tropsch and methanol synthesis processes, can be achieved. In addition, this heat-integrated intensified process is promising in terms of energy saving, environmental pollution mitigation, feasibility and effectiveness for industrial-scale application; however, experimental proof-of-concept is required to ensure the safe operability of this process.
A two-stage gasification has been proven as an effective and robust approach for converting low-valued and/or highly heterogeneous materials i.e. waste, into hydrogen and/or syngas due to its tight control and flexibility in operation. As the gas yield and gas properties depend upon materials and operating conditions, the interactions of operating conditions should not be ignored. However, these have not been able to fully capture experimentally. In this work, an artificial neural network model was developed and validated using experimental data to predict and optimise the gasification process thereby reducing time and costs in developing and testing. The model can predict accurately gas composition and yield corresponding to the variations at the output with a correlation R² > 0.99. The developed neural network model was then applied for optimising operating conditions of the two-stage gasification for high carbon conversion, high hydrogen yield and low carbon dioxide in nitrogen and carbon dioxide environments. The predicted conditions were tested, and the results agreed well with experimental data. For example, at the optimum operating conditions (900˚C for the 1st stage and 1000 °C for the 2nd stage with a steam/carbon ratio of 3.8 in nitrogen and 5.7 in carbon dioxide environments), the gas yield, hydrogen and carbon dioxide were 96.2 wt%, 70 mol% and 16.4 mol% for nitrogen environment and 97.2 wt%, 66 mol% and 12 mol% for carbon dioxide environment.
This paper focuses on the challenges, opportunities and future potentials with ammonia as a carbon-free fuel, and covers recent technological solutions to overcome the barriers with the production, storage and usage of green ammonia. One way to decarbonize the energy industry is by converting electrical energy into chemical energy via water electrolysis to produce hydrogen. Hydrogen can then be stored, used in a fuel cell to generate electricity, or burnt cleanly with air to generate heat, steam, producing only water as a by-product. However, hydrogen has an extremely low density, even when compressed, which means that its energy density on a volumetric basis remains distinctly substandard to most liquid fuels, hydrogen also has a much wider range of concentrations over which it remains potentially explosive. Ammonia alternatively is ~ 18% hydrogen by weight, which means that in terms of hydrogen density, it is ~ 50% higher than compressed or liquefied hydrogen. One major advantage is that there is an existing infrastructure for the production, transport and distribution of ammonia worldwide. Although ammonia in theory can be combusted to produce only nitrogen and water as emissions, in practice, several challenges arise, nitrous oxides (NOx) are often generated, especially if the combustion happens at higher temperatures and/or under pressure, in vehicle engines, gas turbines and as rocket fuel. To overcome such challenges, further research into ammonia combustion phenomena is required. This review sheds light on recent technological advancements with ammonia from the production point to the utilization end point. Moreover, the study concludes with a techno-economic evaluation and global market trends of ammonia in the COVID-19 crises.
Biomass pyrolysis and the in-line catalytic cracking of the pyrolysis volatile stream has been approached in this study. The pyrolysis step was carried out in a conical spouted bed reactor at 500 °C, whereas the inert sand or the cracking catalysts (γ-Al2O3, spent FCC and olivine) were placed in a fixed bed reactor at 600 °C. Product analysis was carried out on-line by means of chromatographic methods, and the distribution and composition of the main products obtained have been related to the features characterizing each catalyst (physical properties, chemical composition and acidity).
Decarbonylation reactions were favoured over decarboxylation ones when acid catalysts (spent FCC and γ-Al2O3) were used, whereas olivine promoted ketonization and aldol condensation reactions. The Fe species in the olivine structure enhanced reforming and WGS reactions. Bio-oil cracking was more severe as catalyst acidity was increased, leading to an increase in the hydrocarbon fraction. The Al2O3 derived bio-oil was substantially deoxygenated, with a considerable reduction in the phenolic fraction, which accounted mainly for alkyl-phenols. The three materials tested led to a significant decrease in acid and phenolic compounds in the volatile stream, making it suitable for further catalytic valorization for the production of H2, fuels and chemicals.
This paper focuses on a new configuration of biomass gasification based cascaded ammonia synthesis and proposes two different configurations of ammonia synthesis system using the Stoichiometric and Gibbs reactors in the Aspen Plus V11. A new heat recovery technique from biomass gasification using syngas cooling is also proposed in this study. The proposed configuration comprises of a biomass gasifier, a heat recovery unit for syngas cooling, a combined cycle, water gas shift reactor system (WGSRS), pressure swing adsorption (PSA) and ammonia production unit. The ammonia based carbon-capturing system is incorporated to ultimately capture the CO2 emissions. The sensitivity analyses are conducted on each significant subsystem employed in the proposed configuration. The results obtained from the Gibbs reactors show that pressure has a positive effect while very high-temperature effects negative on the ammonia synthesis. The results also reveal that the cascaded ammonia synthesis offers high ammonia conversion rates. The designed system produces 21.9 kmol/h of ammonia and 3405 kW electrical power. The results obtained from the present sensitivity analysis are further presented and discussed.
Ammonia synthesis through renewable energy technology can transform the energy and fertilizer markets of the future. The study deals with the techno economic environmental analysis of conventional ammonia synthesis via natural gas and green ammonia synthesis via onshore wind technology in coastal areas of Germany. The study also investigates the current and futuristic (2030) economic feasibility of different ammonia plants by calculating levelized cost of ammonia production. Major ammonia plants in Germany uses Steam Methane Reforming and Haber Bosch Process plants that requires natural gas as a source of hydrogen and air as a source of nitrogen. Similarly, the green ammonia plant uses water electrolysers (Alkaline/PEM electrolysers), Cryogenic Air Distillation, Water Desalination and Haber Bosch Process plants that are all powered by onshore wind farm.
Ammonia is an indispensable raw material in the chemical industry. A hybrid biomass conversion to ammonia system (HBCAS) is developed by means of the chemical looping process with the assistance of solar energy and wind power. The system consists of six modules: i) biomass gasification, ii) oxy-syngas combustion, iii) chemical looping air separation (CLAS), iv) chemical looping ammonia production (CLAP), v) power generation, and vi) water electrolysis. A simulation was conducted for feasibility analysis and parameter optimization using ASPEN Plus, focusing on the development of a coordinated distribution network of energy and materials. Multi-generation of NH3, N2, and H2 was achieved using biomass cascading. The thermally neutral requirements of HBCAS and the effects of the operating conditions of each module on the selectivity (MnO2, AlN, and NH3), product concentrations, production rates, and reactant conversions were comprehensively considered. The results indicate that ammonia selectivity of 79.36%, a production rate of 34.1 kmol/h, and a concentration of 65.65 vol.% can be obtained under typical conditions with 1 kg/s biomass input, confirming the feasibility of the HBCAS and providing guidance for its use.
Global urbanization has resulted in amplified energy and material consumption with simultaneous waste generation. Current energy demand is mostly fulfilled by finite fossil reserves, which has critical impact on the environment and thus, there is a need for carbon-neutral energy. In this view, biohydrogen (bio-H2) is considered suitable due to its potential as a green and dependable carbon-neutral energy source in the emerging ‘Hydrogen Economy’. Bio-H2 production by dark fermentation of biowaste/biomass/wastewater is gaining significant attention. However, bio-H2 production still holds critical challenges towards scale-up with reference to process limitations and economic viabilities. This review illustrates the status of dark-fermentation process in the context of process sustainability and achieving commercial success. The review also provides an insight on various process integrations for maximum resource recovery including closed loop biorefinery approach towards the accomplishment of carbon neutral H2 production.
Autothermal reforming of methane is one of the most widely reported techniques for syngas production. This thermodynamic analysis discusses two aspects of autothermal reforming: first, to obtain hydrogen to nitrogen in the ratio 3:1, which is the most suitable feed ratio for ammonia production in the Haber–Bosch process, and then to find out the thermoneutral point of the process. Throughout the study, all simulations are carried out at 1 bar pressure and within the temperature range 500–1000°C. Conditions with more than 99% methane conversion and 0.1% coke deposition are considered. Other parameters taken into account for optimization are OMR (oxygen to methane ratio) in range 0.4–0.6, SMR (steam to methane ratio) in range 1.5–3.5 and oxygen enrichment in air from 25% to 40%. This study briefly discusses the water gas shift (WGS) reaction for CO removal and its conversion to H2. The best thermoneutral point for the reformer was found to be at OMR = 0.59845, SMR = 2.105, with an oxygen enrichment level of 39.4%.
Based on the promising results of La2O3- and CeO2-promoted Ni/Al2O3 catalysts in the reforming of biomass pyrolysis volatiles, the performance of these catalysts and the non-promoted one was evaluated in the pyrolysis and in-line steam reforming of polypropylene (PP). The experiments were carried out in a continuous bench scale pyrolysis-reforming plant using two space times of 4.1 and 16.7 gcat min gplastic⁻¹ and a steam/PP ratio of 4. The prepared catalysts and the deposited coke were characterized by N2 adsorption−desorption, X-ray fluorescence (XRF), X-ray diffraction (XRD), temperature-programmed oxidation (TPO), and transmission electron microscopy (TEM). The Ni/Al2O3 catalyst showed suitable performance regarding pyrolysis product conversion and hydrogen production and led to moderate coke deposition. It is to note that La2O3 incorporation remarkably improved catalyst performance compared to the other two catalysts in terms of conversion (>99%), hydrogen production (34.9%), and coke deposition (2.24 wt %).
The influence of the metal selected as catalytic active phase in the two-step biomass pyrolysis-catalytic reforming strategy has been analyzed. The pyrolysis step was carried out in a conical spouted bed reactor at 500 °C, whereas steam reforming was performed in a fluidized bed reactor at 600 °C. Ni/Al2O3, Co/Al2O3 and two bimetallic Ni-Co/Al2O3 catalysts with different metal loadings were synthesized by wet impregnation method, and fresh and deactivated catalysts were characterized by N2 adsorption/desorption, X-ray Fluorescence (XRF), Temperature Programmed Reduction (TPR), X-Ray powder Diffraction (XRD), Temperature Programmed Oxidation (TPO), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Although Ni/Al2O3 and both bimetallic catalysts had similar initial activity in terms of oxygenate conversion, (higher than 98%), the poorer metal dispersion observed in both bimetallic catalysts led to a fast decrease in conversion due to the promotion of coke formation on large particles. This occurred even though Ni–Co alloy formation has a positive influence by hindering the oxidation of Co⁰ species. The main cause for the deactivation of these catalysts is the formation of a coke with amorphous structure. The poor initial performance of Co/Al2O3 catalyst is related to changes in the Co⁰ oxidation state induced by the presence of steam, which led to a fast deactivation of this catalyst.
The performance of fixed and fluidized bed reactors in the steam reforming of biomass fast pyrolysis volatiles was compared, with especial attention paying to the differences observed in catalysts deactivation. The experiments were carried out in continuous regime in a bench scale unit provided with a conical spouted bed for the pyrolysis step. They were carried out on a Ni-Ca/Al2O3 commercial catalyst and under optimum conditions determined in previous studies, i.e., pyrolysis temperature 500 °C, reforming temperature 600 °C and a steam/biomass ratio of 4. Moreover, the influence of space time was analysed in both reforming reactors. The fixed bed reactor showed higher initial conversion and H2 yield, as it allowed attaining a H2 yield higher than 90 % with a space time of 10 gcat min g vol⁻¹. However, a space time of 15 gcat min g vol⁻¹ was required in the fluidized bed to obtain a similar H2 yield. Moreover, the fixed bed also led to lower catalyst deactivation. Catalyst deactivation was mainly related to coke deposition, and higher coke contents were observed in the catalysts used in the fluidized bed reactor (1.2 mgCOKE gcat⁻¹ gbiomass⁻¹) than those in the fixed bed one (0.6 mgCOKE gcat⁻¹ gbiomass⁻¹). Therefore, the differences in the performance of the two reactors were analysed and their practical interest was discussed.
Global ammonia production reached 175 million metric tons in 2016, 90% of which is produced from high purity N2 and H2 gases at high temperatures and pressures via the Haber-Bosch process. Reliance on natural gas for H2 production results in large energy consumption and CO2 emissions. Concerns of human-induced climate change are spurring an international scientific effort to explore new approaches to ammonia production and reduce its carbon footprint. Electrocatalytic N2 reduction to ammonia is an attractive alternative that can potentially enable ammonia synthesis under milder conditions in small-scale, distributed, and on-site electrolysis cells powered by renewable electricity generated from solar or wind sources. This review provides a comprehensive account of theoretical and experimental studies on electrochemical nitrogen fixation with a focus on the low selectivity for reduction of N2 to ammonia versus protons to H2. A detailed introduction to ammonia detection methods and the execution of control experiments is given as they are crucial to the accurate reporting of experimental findings. The main part of this review focuses on theoretical and experimental progress that has been achieved under a range of conditions. Finally, comments on current challenges and potential opportunities in this field are provided.
The joint process of pyrolysis-steam reforming is a novel and promising strategy for hydrogen production from biomass; however, it is conditioned by the endothermicity of the reforming reaction and the fast catalyst deactivation. Oxygen addition may potentially overcome these limitations. A thermodynamic equilibrium approach using Gibbs free energy minimization method has been assumed for the evaluation of suitable conditions for the oxidative steam reforming (OSR) of biomass fast pyrolysis volatiles. The simulation has been carried out contemplating a wide range of reforming operating conditions, i.e., temperature (500–800 °C), steam/biomass (S/B) ratio (0–4) and equivalence ratio (ER) (0–0.2). It is to note that the simulation results under steam reforming (SR) conditions are consistent with those obtained by experiments. Temperatures between 600 and 700 °C, S/B ratios in the 2–3 range and ER values of around 0.12 are the optimum conditions for the OSR under autothermal reforming (ATR) conditions, as they allow attaining high hydrogen yields (10 wt% by mass unit of the biomass in the feed), which are only 12–15% lower than those obtained under SR conditions.
To reduce the fossil-fuel consumption and the impacts of conventional ammonia production on climate change, green ammonia production processes using green hydrogen need to be investigated. For commercial production scale, potential alternatives can be based on biomass gasification and water electrolysis via renewable energy, namely biomass- and power-to-ammonia. The former generally uses entrained flow gasifier due to low CO2 and almost no tar, and air separation units are shared by the gasifier and ammonia synthesis. The latter may use solid-oxide electrolyzer due to high electrical efficiency and the possibility of heat integration with the ammonia synthesis process. In this paper, techno-economic feasibility of these two green ammonia production processes are investigated and compared with the state-of-the-art methane-to-ammonia process, considering system-level heat integration and optimal placement of steam cycles for heat recovery. With a reference ammonia production of 50 kton/year, the results show that there are trade-offs between the overall energy efficiency (LHV) and ammonia production cost for all three cases. The biomass-to-ammonia is the most exothermic but is largely limited by the large heat requirement of acid gas removal. The steam cycles with three pressure levels are able to maximize the heat utilization at the system level. The power-to-ammonia achieves the highest system efficiency of over 74%, much higher than that of biomass-to-ammonia (44%) and methane-to-ammonia (61%). The biomass-to-ammonia reaches above 450 /ton, 5 years). The power-to-ammonia is currently not economically feasible due to high stack costs and electricity prices; however, it can be competitive with a payback time of below 5 years with mass production of solid-oxide industry and increased renewable power penetration.
The effect of La2O3 addition on a Ni/Al2O3 catalyst has been studied in the biomass pyrolysis and in-line catalytic steam reforming process. The results obtained using homemade catalysts (Ni/Al2O3 and Ni/La2O3-Al2O3) have been compared with those obtained using a commercial Ni reforming catalyst (G90LDP). The pyrolysis step has been performed in a conical spouted bed reactor at 500 °C and the reforming one in a fluidized bed reactor placed in-line at 600 °C, using a space time of 20 gcatalyst min gvolatiles⁻¹ and a steam/biomass ratio of 4. The Ni/La2O3-Al2O3 catalyst had a better performance and higher stability than G90LDP and Ni/Al2O3 catalysts, with conversion and H2 yield being higher than 97 and 90%, respectively, for more than 90 min on stream. Nevertheless, conversion and H2 yield decreased significantly with time on stream due to catalyst deactivation. Thus, the deactivated catalysts have been characterized by N2 adsorption-desorption, X-ray diffraction (XRD), temperature programmed oxidation (TPO), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Coke deposition has been determined to be the main cause of catalyst deactivation, with the structure of the coke being fully amorphous in the three catalysts studied.
The performances of the primary catalysts olivine, dolomite, γ-alumina and FCC spent catalyst were evaluated in the continuous steam gasification of sawdust in a bench-scale plant equipped with a fountain confined conical spouted bed reactor. The experiments were carried out at 850 °C, and the efficiency of the gasification process was defined by gas yield, H2 production, tar concentration and composition, and carbon conversion efficiency. The benefits of the fountain confiner not only helped to improve the gas-solid contact, and therefore favoured the primary catalysts’ reforming and cracking activity, but also enhanced H2 production and reduce tar formation. Thus, dolomite and γ-alumina recorded the lowest values of tar, 5.0 and 6.7 g Nm⁻³, respectively, which corresponded to 79% and 72% tar reduction compared to the inert sand, whereas olivine and the FCC spent catalyst recorded higher tar contents, 20.6 and 16.2 g Nm⁻³, respectively. It is noteworthy that light PAHs were the most abundant species in the tar (60 wt% of the whole tar content).
In this study, we design and evaluate a highly efficient energy system for performing an integrated conversion of empty fruit bunches (EFB) to H2 that is stored in the form of ammonia (NH3). The biomass undergoes processes that include supercritical water gasification (SCWG) for H2 production and H2 chemical storage using the Haber-Bosch process to produce NH3. Exergy recovery by heat integration is employed to increase the efficiency of the system. First, EFBs are gasified with steam in the SCWG process to produce H2-rich syngas and to completely remove the pre-drying requirement. Subsequently, a syngas chemical looping (SCL) process involving three reactors is used to produce H2 that is subsequently converted to NH3 by the Haber-Bosch process. Theoretically, the integrated process can achieve a high EFB-to-NH3 conversion efficiency that exceeds 15% with a H2 conversion efficiency of 76.2% and an overall maximum syngas-to-H2 conversion efficiency of 46.3% with 100% CO2 capture capability. Compared to traditional EFB conversion processes, this process can theoretically achieve higher efficiency, and it can improve waste utilization in palm oil processing plants by incorporating exergy recovery and heat integration into the system.
Aqueous-phase reforming (APR) is a quite new technology for the production of hydrogen and light hydrocarbons from aqueous-organic mixtures in a single-stage process. This manuscript analyzes the APR of representative model compounds of bio-oil aqueous fraction, including acetic acid, ethanol, 1-hydroxypropan-2-one (acetol) and benzene-1,2-diol (catechol), as well as a mixture of all of them. The APR experiments were conducted at 230 °C and 3.2 MPa over three different Ni-based catalysts, including spinel NiAl 2 O 4 , and supported Ni/CeO 2 -γAl 2 O 3 and Ni/La 2 O 3 -αAl 2 O 3 . The reactivity of the model compounds varied largely in the order: acetol > ethanol > catechol > acetic acid, whereas the H 2 production decreased in the following order: ethanol ≫> acetol > acetic acid > catechol. Based on the product distribution obtained, the reaction pathways in the APR of each model compound have been proposed. In the APR of the mixture, the Ni/La 2 O 3 -αAl 2 O 3 led to the highest H 2 yield but was affected by Ni leaching, whereas spinel NiAl 2 O 4 showed a much higher stability. Therefore, the Ni-spinel catalyst showed a good potential for H 2 production by APR of bio-oil aqueous fraction.