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NOx reduction in waste incinerators by SCR instead of SNCR compared from a life cycle perspective: a case study
Abstract
In most modern waste incinerators selective non catalytic reduction (SNCR) is applied to remove NOx from the combustion gas to reach the European emission limit value (ELV) of 200mg/Nm3. If however the NOx-ELV for waste incinerators would be lowered to e.g. 100mg/Nm3, SNCR, with a typical NOx removal efficiency of around 50%, would not suffice to reach the new ELV. In that case, selective catalytic reduction (SCR), with a NOx removal efficiency of up to 90% in tail-end configuration could be an interesting alternative. However, from a life cycle perspective, the production, construction and operation of SCR equipment including the catalyst, also involve indirect (i.e. not from the process itself but related to other parts of the life-cycle) pollutant emissions and resource consumption with resulting environmental impacts. By means of a case study of a typical hazardous waste incinerator it is illustrated that replacing SNCR by tail-end SCR reduces the direct environmental impact of the incinerator (i.e. environmental impact of the NOx emitted at the stack) in the impact categories acidification, eutrophication and photo-oxidant formation, as expected from the lower NOx emissions in case of SCR. However, mainly due to the need to reheat the combustion gas, SCR has higher indirect impacts than SNCR, most notably in the impact category global warming. Because of these indirect impacts, the mentioned direct environmental impact reductions of SCR in the impact categories acidification, eutrophication and photo-oxidant formation are no net environmental benefits; when e.g. fuel oil is used as an energy source to reheat the flue gas, the indirect impact in the impact categories acidification and photo-oxidant formation is higher than the direct impact reduction related to the lower NOx concentration in the flue gas emitted at the stack of the installation. In this case, there is only a net environmental benefit in the impact category eutrophication. Overall it can be concluded that in the hazardous waste incinerator under study, which is representative in its field, replacing SNCR by SCR to reach a new, lower ELV, increases the net overall environmental impact of the incinerator, particularly in the impact category global warming. From an environmental point of view optimizing SNCR should be preferred over installing tail-end SCR in existing installations such as the considered hazardous waste incinerator.
... SCR technology is an effective method for treating NOx that utilizes a reductant to react with NOx, converting it into harmless nitrogen gas [5]. Compared to other NOx removal technologies, such as direct decomposition, storage reduction (NSR), and selective non-catalytic reduction (SNCR) [6], SCR offers significant advantages, including high purification efficiency, low secondary pollution, and well-established technological applications [7]. The core of SCR technology lies in the selection of a suitable reductant, which can include hydrogen selective catalytic reduction (H2-SCR), hydrocarbon selective catalytic reduction (HC-SCR), ammonia selective catalytic reduction (NH3-SCR), and carbon monoxide selective catalytic reduction (CO-SCR) [8]. ...
... 2NH3 + 2O2→N2O + 3H2O (4) NO + CO→1/2N2 + CO2 (5) NO2 + 2CO→1/2N2 + 2CO2 (6) The catalytic reactions on the surface of SCR catalysts generally follow the Eley-Rideal (ER) and Langmuir-Hinshelwood (LH) mechanisms [13]. Different catalytic systems and reaction conditions dictate which mechanism is followed, and the reaction mechanism for the same catalyst may also shift with changes in the reaction temperature. ...
Sintering flue gas contains significant amounts of harmful gases, such as carbon monoxide and nitrogen oxides (NOx), which pose severe threats to the ecological environment and human health. Selective catalytic reduction (SCR) technology is widely employed for the removal of nitrogen oxides, with copper-cerium-based bimetallic catalysts and their derivatives demonstrating excellent catalytic efficiency in SCR reactions, primarily due to the significant synergistic effect between copper and cerium. This paper summarizes the main factors affecting the catalytic performance of Cu-Ce-based bimetallic catalysts and their derivatives in the selective catalytic reduction of ammonia and carbon monoxide. Key considerations include various preparation methods, doping of active components, and the effects of loading catalysts on different supports. This paper also analyzes the influence of surface oxygen vacancies, redox capacity, acidity, and specific surface area on catalytic performance. Additionally, the anti-poisoning performance and reaction mechanisms of the catalysts are discussed. Finally, the paper proposes strategies for designing high-activity and high-stability catalysts, considering the development prospects and challenges of Cu-Ce-based bimetallic catalysts and their derivatives, with the aim of providing theoretical guidance for optimizing Cu-Ce-based catalysts and promoting their industrial applications.
... Finally, the off-gas enters the last cleaning unit, an ammonia-based selective catalytic reduction unit for reducing NO x compounds. Aqueous ammonia is injected over a zeolite catalyst, reacting with NO x to produce nitrogen and water vapor (Thomas and Cole, 2016;Van Caneghem et al., 2016). After the final gas cleaning unit, the off-gas roaster is released into the atmosphere containing the listed emission concentrations in Table S1. ...
... The highest contribution of natural gas in impact categories is caused by the combustion of natural gas for heat generation in the units (Van Caneghem et al., 2016). Direct process emissions, energy, and raw material contribution to the gas handling system after roasting are observed in Fig. S4, where mercury scrubber, SO 2 scrubber, and NO x removal were the dominant stages that contributed to almost all the environmental impact categories. ...
Gold has always been regarded as a valuable commodity in high demand throughout history. Nevada is the leading producer of gold in the United States, and gold miningMining contributes to a significant part of Nevada’s economy. Depending on the types of gold ore and its mineralogical characteristics, several beneficiation and extraction methods are available for gold. Gold can be beneficiated by heap leaching, flotation, roasting, autoclave, or a combination of these techniques. Regardless of the rigorous environmental management standards, different gold processingGold processing routes can impact the ecosystem and human health since gold miningMining is a significant source of hazardous chemicals. In this study, a life cycle assessment (LCALife cycle assessment (LCA)) was conducted to evaluate the environmental performance of four main processes. Using the TRACI method, categories of ozone depletion, global warming, smog, acidification, eutrophication, carcinogenics, non-carcinogenics, respiratory effects, ecotoxicity, and fossil fuel depletion were evaluated for the processes that occurred for gold recovery.
... In coal-fired power plants, SCR is used to convert NO x using a catalyst into nitrogen (N 2 ) and water (H 2 O), thus reducing emissions of NO x . Meanwhile, SNCR has a similar technology that works by injecting reagents at high temperature without the need for a catalyst (van Caneghem J et al., 2016). ...
... SNCR is only suitable for the high-temperature reaction range of 850-1100°C. [7] However, in applications such as steel sintering and industrial boilers, where flue gas temperatures typically range from 120-300°C, SNCR is not a feasible option for NO x abatement. On the other hand, SCR technology employs catalysts along with reducing gases like H 2 , NH 3 , or CO to efficiently eradicate NO x , enabling the reaction at moderate temperatures ranging from 300-500°C or even lower. ...
The technology of CO selective catalytic reduction of NOx (CO‐SCR) showcases the potential to simultaneously eliminate CO and NOx from industrial flue gas and automobile exhaust, making it a promising denitrification method. The development of cost‐effective catalysts is crucial for the widespread implementation of this technology. Transition metal catalysts are more economically viable than noble metal catalysts. Among these, Fe emerges as a prominent choice due to its abundant availability and cost‐effectiveness, exhibiting excellent catalytic performance at moderate reaction temperatures. However, a significant challenge lies in achieving high catalytic activity at low temperatures, particularly in the presence of O2, SO2, and H2O, which are prevalent in specific industrial flue gas streams. This review examines the use of Fe‐based catalysts in the CO‐SCR reaction and elucidates their catalytic mechanism. Furthermore, it also discusses various strategies devised to enhance low‐temperature conversion, taking into account factors such as crystal phase, valence states, and oxygen vacancies. Subsequently, the review outlines the challenges encountered by Fe‐based catalysts and offers recommendations to improve their catalytic efficiency for use in low‐temperature and oxygen‐rich environments.
... The emission status of nitrogen oxides is shown in Figure 1. In industrial settings, several methods are employed to mitigate NO x control, with selective catalytic reduction (SCR) emerging as one of the most efficient technical methods [5][6][7]. SCR systems utilize a reducing agent, such as, typically, ammonia (NH 3 ) and convert poisonous NO x into harmless nitrogen (N 2 ) and water vapor (H 2 O) in the presence of a catalyst [8]. The choice between SCR, selective non-catalytic reduction (SNCR), or combined approaches depends on various factors, including emission regulations, cost considerations, space limitations, and specific operating conditions [9]. and improving the catalytic performance [12]. ...
Selective catalytic reduction (SCR) stands out as a pivotal method for curbing NOx emissions from flue gas. The support, crucially, for SCR efficacy, loads and interacts with the active components within the catalyst. The catalysts could be amplified by the denitration performance of the catalyst by enhancements in support pore structure, acidity, and mechanical robustness. These improvements ensure efficient interaction between the support and active materials, thereby optimizing the structure and property of the catalysts. TiO2 is the most commonly used support of the NH3-SCR catalyst. The catalyst with TiO2 support has poor thermal stability and a narrow temperature range, which can be improved. This paper reviews the research progress on the effects of various aspects of TiO2 support on the NH3-SCR catalyst’s performance, focusing on the TiO2 crystal type, TiO2 crystal surface, different TiO2 structures, TiO2 support preparation methods, and the effects of TiO2-X composite support on the NH3-SCR catalyst’s performance. The reaction mechanism, denitrification performance, and anti-SO2/H2O poisoning performance and mechanism of TiO2 support with different characteristics were described. At the same time, the development trend of the NH3-SCR catalyst using TiO2 as the support is prospected. It is hoped that this work can provide optimization ideas for SCR catalyst research.
... For DeNO x technology, the investment and operating costs of SCR are relatively high , and the indirect environmental impact is significantly higher than that of SNCR (Van Caneghem et al., 2016). Therefore, SCR is not suitable to be promoted in China's MSWI industries. ...
... Furthermore, Selective Catalytic Reduction (SCR) devices can reduce the content of nitrogen oxides in exhaust gases. 20 Another technology involves injecting water into the intake manifold of internal combustion engines through a heating evaporator to obtain a high-temperature gas. This process utilizes the high temperature generated by the internal combustion engine to instantly convert water mist into high-temperature gas, which then enters the combustion chamber of the engine to mix with fuel and burn. ...
The rail transit construction process produces a large quantity of carbon emission. The carbon emission could be divided into two sources, including direct carbon emission from the construction process and indirect carbon emission by raw material utilization. With the promotion of China National carbon peaking and carbon neutrality goals, it is an industry trend for the rail transit construction company to reduce carbon emission during the construction event. This study provides a detailed overview of the possible carbon emission process and carbon mitigation process during the rail transit construction event and puts forward preliminary carbon mitigation suggestions and strategy for the rail transit construction process. The predominant carbon emission section during rail transit construction is the raw material (including the steel, cement, concrete, tunnel segment), electricity, and fuel consumption during construction. It is suggested that the rail transit construction process could achieve carbon emission mitigation from the following prospects: make careful plans for the raw material selection (such as using recycled concrete, recycled steel, and so forth), improve the construction process to reduce energy waste, and optimize the equipment selection during the mechanical and electrical installment process. By this, the carbon emission could be mitigated during the rail transit construction.
... The approach suffers from the disadvantage of requiring high temperature (800-1100 • C) and lower NO x removal efficiency (ca. 50 %) [16]. The use of heterogeneous catalysts enables more efficient reduction reaction (>90 %) and allows reaction operation at lower temperatures (300-450 • C). ...
... In view of the NO x generation characteristics of coal combustion, the existing technical means to control NO x in the combustion process mainly include reasonably adjusting the combustion temperature, the oxygen concentration, the proportion, location, time and temperature of fuel and air input, etc., so as to suppress the generation of NO x and reduce partial NO x in the combustion process, thus achieving the purpose of NO x emission inhibition, such as air-staged technology [8], fuelstaged technology [9], flue gas recirculation technology [10], low temperature and low oxygen combustion technology [11], etc. Nevertheless, the application of these mentioned technologies will inevitably sacrifice the combustion efficiency, and the degree of NO x reduction is limited, which leads to Published by Francis Academic Press, UK -15-the fact that the existing units have to use flue gas aftertreatment technologies such as selective catalytic reduction (SCR) or selective non catalytic reduction (SNCR) to reduce NO x emissions [12]. While in the course of SCR and SNCR operation, there will also be quite a few issues such as high cost, catalyst poisoning, ammonia escape, narrow stable operation window and so on, which can not meet the demand of renewable energy peak shaving [13]. ...
... Molecules 2024, 29, 574 2 of 16 long lifespan and a wide range of active temperatures, they do not have high denitration efficiency. Therefore, the SCR catalyst is costly and technical [9]. Of course, to comprehend the NO oxidation trends in SACs, Li et al. ...
Theoretical and experimental investigations have shown that biochar, following KOH activation, enhances the efficiency of NO removal. Similarly, NaOH activation also improves NO removal efficiency, although the underlying mechanism remains unclear. In this study, zigzag configurations were employed as biochar models. Density functional theory (DFT) was utilized to examine how Li and Na single adsorption and OH co-adsorption affect the reaction pathways of NO reduction on the biochar surface. The rate constants for all reaction-determining steps (RDSs) within a temperature range of 200 to 1000 K were calculated using conventional transition state theory (TST). The results indicate a decrease in the activation energy for NO reduction reactions on biochar when activated by Li and Na adsorption, thus highlighting their beneficial role in NO reduction. Compared to the case with Na activation, Li-activated biochar exhibited superior performance in terms of the NO elimination rate. Furthermore, upon the adsorption of the OH functional group onto the Li-decorated and Na-decorated biochar models (LiOH-decorated and NaOH-decorated chars), the RDS energy barriers were higher than those of Li and Na single adsorption but easily overcome, suggesting effective NO reduction. In conclusion, Li-decorated biochar showed the highest reactivity due to its low RDS barrier and exothermic reaction on the surface.
... Numerous studies have examined NOx emissions from incinerators [24][25][26]. NOx plays a vital role in Korea's air quality management policies. In 2019, Korean incinerators emitted NOx at 30.5 ppm, which is 43.5% of the corresponding emission limit (70 ppm) [27]. ...
Waste incineration is a crucial component of waste management as it is the final stage of circular utilization and the initial phase of disposal. Effective waste management prioritizes energy recovery from waste and substantial waste volume reduction while committing to minimizing air pollutant emissions, particularly nitrogen oxides (NOx). This study involves an in-depth analysis of operational data from 44 incineration facilities in South Korea spanning 5 years, supplemented by empirical measurements from 14 sites. This study aimed to assess three key aspects of these incineration facilities: (1) waste volume reduction characteristics, (2) energy recovery capabilities, and (3) NOx emission reduction performance. We examined how these elements interact within the policy framework governing incinerator management in South Korea. Quantitatively, incinerating 100 tons of municipal waste resulted in a gain of 338.7 m3 in landfill capacity and recovery of 637.5 GJ of energy in the form of heat or electricity. Notably, South Korean incineration facilities significantly extend the lifespan of landfill sites, aligning closely with the objectives of the South Korean Ministry of Environment’s “No More Direct Landfilling of Household Waste Policy”. This positive outcome is further reinforced by the “Incineration Tax Reduction Policy”, which incentivizes active efforts toward energy recovery during incineration. Our study provides decision-makers with valuable insights for achieving a harmonious equilibrium between environmental sustainability and resource utilization, thereby contributing to the continuous improvement of policies aimed at South Korea’s vision of achieving a circular economy.
... Hence, the so-called typical APCDs of semi-dry scrubber (SDS) + activated carbon injection (ACI) + fabric filter (FF) reported by Lu et al. (2017) and Yang et al. (2020) are outdated. Generally speaking, the deNO x rates of selective non-catalytic reduction (SNCR) and SCR were 34-46 % and 80-90 %, respectively (Fu et al., 2022;Han et al., 2019;Van Caneghem et al., 2016). At present, the average NO x concentration from China's MSWI plants is 136.89 mg/m 3 (Ma et al., 2023). ...
China is the largest developing country in the world, and its municipal solid waste (MSW) has increased with a compound annual growth rate of 5.1 % since 1980. Incineration, which has the advantages of mass- and volume-reduction as well as energy and heat recovery, has become the mainstream environmentally sound treatment method in China. However, air pollution emissions are the primary reason for limiting MSW incineration (MSWI). Currently, the Chinese government is devoted to comprehensively implementing MSW classification. However, the classification model and the future MSW reduction rate are not yet clear. In this study, we project scenarios of air pollution emissions until 2030 based on the different MSW classification models (MSW reduction rates) and diffusion rates of ultra-low emission technology. A total of 6011 tons (t) of particulate matter, 25,881 t of SO2, 14,915 t of CO, 17,167 t of HCl, and 200,166 t of NOx will be emitted in 2030 under the business-as-usual (BAU) scenario, and air pollutants will not peak under this scenario. Air pollutants will reduce by 11 % of the BAU scenario by only implementing an MSW reduction of 20 % (JPN-model). The optimal scenario (DEU-model, increasing the efficiency of material recovery and upgrading air pollution control devices) means that air pollutants will be reduced by 83.2–96.2 % from the base amount under the BAU scenario. These results provide references for MSW management and air pollution emission reduction from the aspects of MSW classification and technology upgrades
... In cement kilns, NOx are primarily formed in the rotary kiln and the precalciner, and more than 95% of the nitrogen oxides produced is NO [2]. At present, low NOx combustion (LNC), selective non-catalytic reduction (SNCR), and selective catalytic reduction (SCR) have been widely applied to remove the NOx emitted from cement industrial processes [3][4][5]. The efficiency of LNC is not sufficient to meet the air emission standards set by the cement industry. ...
NOx emission from the cement industry have received much attention. In order to reduce the NOx emission in cement kilns, nickel slag was used to prepare the non-ammonia denitrification material, and a denitrification mechanism was proposed in this study. The results showed that the denitrification material prepared at pH 7 exhibited the best denitrification performance. At low temperature, the highest denitrification performance was achieved between 200 and 300 °C with a NO decomposition rate of approximately 40%. Then, the NO decomposition rate increased as the temperature increased, reaching over 95% above 700 °C. The physicochemical characteristics showed that the material had the highest specific surface area and the highest relative Fe content, which benefited the denitrification performance. The divalent iron of the denitrification material was considered the active site for the reaction, and trivalent iron was not conducive to denitrification performance at a low temperature range. After the denitrification reaction, the Fe3+/Fe2+ increased from 0.89 to 1.31. The proposed denitrification mechanism was the redox process between divalent iron and trivalent iron. This study not only recycles industrial waste to reduce solid waste pollution but also efficiently removes nitrogen oxides from cement kilns without ammonia.
... However, the use of O 3(g) has a negative effect on the midpoint indicators, except MDP. Catalytic reduction of NOx in flue gas cleaning produces secondary pollutant emissions and material consumption and ammonia discharge, which has an environmental impact (Van Caneghem et al. 2016). ...
Resource recovery is crucial for small- and medium-sized enterprises to attain a circular economy. The economic benefits of recovering precious metals from electronic waste, such as waste printed circuit boards (WPCBs), are hindered by secondary pollutant emissions from pretreatment processes. This study aims to recover copper from the WPCB acid leaching process and reduce NOx emissions through the use of a high gravity rotating packed bed (RPB). The results indicate that the copper recovery ratio increases to 99.75% through the displacement reaction between iron powder and copper nitrate. The kinetic analysis of copper dissolution was employed to simulate the NOx emissions during acid leaching, with an R-squared value of 0.872. Three oxidants, including H2O2(aq), ClO2(aq), and O3(g), with pH adjusted to different NaOH concentrations, were used to remove NOx. The greatest NOx removal rate was achieved using a 0.06 M NaOH solution, with a removal rate of 91.2% for ozone oxidation at a 152-fold gravity level and a gas-to-liquid (G/L) ratio of 0.83. The gas-side mass transfer coefficients (KGa) for NOx range from 0.003 to 0.012 1/s and are comparable to previous studies. The results of a life cycle analysis indicate that the NOx removal rate, nitric acid recycling rate, and copper recovery rate are 85%, 80%, and 100%, respectively, reducing the environmental impact on the ecosystem, human health, and resource depletion by 10% compared to a scenario with no NOx removal.
... In MSW flue gas incinerator contains 95% NOx (NO + NO2). NO is a gas that is relatively dangerous when released into the atmosphere because it can react with O2 and form NO2. NO2 is brown gas, acid, and causes irritation which when it reacts with rain water will cause acid rain [26]. SCR works by spraying ammonia onto the flue gas so that it can react with NO and produce N2 (reaction 1) on the surface of the TiO2 / V2O5 / WO3 catalyst at a typical lower temperature between 030007-6 200-350 °C [27]. ...
Hungary produces nearly 2 million tons of food waste every year and produces municipal solid waste (MSW) of about 4.1 million tons per year. If it translates into the term of the energy, it will be equal to the value of 6275 kJ (high heating value/HHV), and it will produce a potential of 748.9 billion kJ per day, on a national scale. However, the amount of energy produced by waste depends on the composition of the waste. Moreover, in practice, the conversion of waste into electrical energy is not as direct as converting coal or natural gas. Many technologies have been developed and methodologies in dealing with MSW. In several European countries, the handling of MSW is mostly done by mechanical way, biological waste management (MBT) and waste incineration. In this study, some methods for managing MSW into energy, which are suitable in Hungary MSW energy recovery, will be elaborated. In Hungary it-self there is a MSW incineration plant located in the capital city of Budapest with a processing capacity of 420 thousand tons of MSW, which can produce 24 MW of power. In the process of burning waste in a boiler that requires high temperature and pressure, the incinerator produces high concentrations of chlorine and sulfur because it is caused by a high temperature corrosion. To reduce the impact caused by the MSW incinerator, flue gas treatment is needed. The most commonly used methods are fabric filter and selective catalytic reduction (SCR) system.
... Cyanuric acid (CNOH)3 has also been studied in some laboratory tests [1]. A detailed review on the studied issue of NOx emission reduction in flue gas is given by sources such as [2], [3], [4], [5], [6], [7]. While NOx reductions of up to 90 % have been achieved under laboratory conditions, in real operations the SNCR efficiency varies much less due to the many parameters that affect the achieved efficiency. ...
The aim of the experiment was to verify the possibility of nitrogen oxides (NOx) reduction by iron compounds dosed into the flue gas stream under different combustion conditions. The motivation for conducting the experiment was to find cheap and available compounds that could streamline the process of existing denitrification methods in use. Such substances could be, for example, iron scale. The possibility of the catalytic ability of iron compounds in the reduction of nitrogen oxides under certain optimal combustion conditions is also confirmed by some foreign studies. Laboratory combustion tests were carried out on an experimental combustion plant, a periodically operating two-chamber furnace for waste incineration. The experiment was divided into two parts. In the first part, measurements of nitrogen oxide emissions were made when only natural gas was burned and gaseous ammonia (NH3) was simultaneously dosed with iron compounds. In the second part, measurements of the emission composition and the effect of the dosed iron additives on the amount of contained nitrogen oxides during the combustion of refuse derived fuel (RDF) with simultaneous combustion of natural gas in the supporting burner were carried out. The highest and comparable NOx conversion was achieved when two different additives, namely siderite and dried scale, were used under almost identical conditions in the refuse derived fuel combustion regime. The results of the present research confirm that the use of additives in the form of iron compounds can, with appropriate combustion process configuration, reduce the amount of NOx emissions produced, which can thus be crucial in meeting the increasingly stringent legislative requirements for reducing emission limits.
... Many LCA practitioners have only considered CCS due to growing climate change concerns [46][47][48][49]. Various efforts have been made to introduce the LCA methodology to assess pollutant end-of-pipe treatment, such as SCR and FGD [50,51]. However, while achievements have been made in assessing the environmental performance of end-of-pipe treatment processes, reliable results of their inter-independent relationships remain very limited. ...
Coal-fired power generation leads to serious environmental pollution, such as air and water pollution; thus, pollution control or treatment is necessary. However, end-of-pipe treatments are still indispensable approaches to reducing environmental stress, and focusing on each in turn leads to pollutant-by-pollutant features. The present study applies the LCA method to reveal the total direct and indirect environmental impacts from increasing significant pollution control units for a coal-fired power plant. From the results, it was found that increasing the performance of CCS and FGD units may result in higher overall environmental impacts due to their energy costs. Greater energy requirements result in greater global warming potential, human toxicity, and terrestrial acidification effects. LNB & OFA, SCR, and ESP units did not cause any other significant environmental impacts, while activated carbon used in the ACI unit is an additional source of indirect terrestrial acidification. Water depletion effects must be considered when increasing the use of CCS units. Policy makers can use the data from the present study to establish sustainable directions to resolve environmental problems at the macro-economic scale.
... The reduction of NO x in waste incinerators by SNCR and SCR were compared from a life cycle perspective. The conclusion was that incinerators installed with SCR that meet lower emission limit values will significantly increase the impact of global warming [22]. The energy consumption and environmental impact of SCR technology in China was investigated, providing the basis for potential improvements in its environmental performance [23]. ...
Humans are significantly perturbing the global nitrogen cycle, leading to excess reactive nitrogen in the environment. Nitrogen oxides as a key reactive nitrogen species are mainly controlled by selective non-catalytic reduction and selective catalytic reduction. Converting nitrogen oxides to ammonia, defined as ReNOx, emerges as an alternative method under a disparate design concept. However, little is known about its overall environmental performance. In this study, we conducted for the first time a life cycle assessment of ReNOx. Compared with the eco-index in the condition of 200 °C with a conversion rate of 95%, it would increase substantially in the condition of 160 °C with a conversion rate of 80% and in the case without a sound NH3 treatment. Feedstock format change, adsorption material performance deterioration, and recovery rate decline would increase the eco-index by 8%, 12%, and 18%, respectively. The eco-index was decreased by 31% in the optimized scenario with a renewable energy source and an increased conversion rate. The environmental impacts were compared with traditional methods at impact, damage, and eco-index levels. Finally, the implications on process arrangement in the flue gas system, the externality for power generation, and the contribution to the nitrogen circular economy were examined. The results can serve as a reference for its developers to improve the technology from the environmental perspective.
The present study conducts a comparative analysis between selective catalytic reduction (SCR) using a Cu-zeolite catalyst and selective non-catalytic reduction (SNCR) for the removal of NO x from industrial waste gas. The primary objective of this investigation is to computationally explore the removal of NO x using NH 3 at various reactor conditions, along with the study of different hydrodynamic aspects. The study revealed the impact of different porosity of the catalyst (in SCR) and the number of baffles (in SNCR) on the reaction and fluid flow profile. Distinct geometries were employed to model each process, incorporating a turbulent model and kinetic parameters with an eddy-dissipation model (EDM) for simulations. Analyzing the effect of the NH 3 /NO ratio on NO conversion efficiency is a crucial component of the study. With diminishing efficiency at higher ratios, the SCR process demonstrated nearly complete NO conversion at a certain NH 3 /NO ratio, and this value changes with the inlet gas temperature. In contrast, SNCR produced less favorable conversion rates than SCR, indicating that the amount of NH 3 supply affects conversion efficiency. At the SCR system’s optimum NH 3 /NO ratio, SNCR achieved an 83 % conversion, and the conversion rate remained relatively constant as the ratio was increased. The results highlight the various possibilities for optimization of the reactor systems in terms of efficiency and economic feasibility.
In order to control NOx emissions and meet China’s ultralow emission standards, a numerical simulation based on the computational fluid dynamics (CFD) approach is performed for the optimization of the reductant injection volume, number of injection sources, distribution, and injection direction for the flue gas denitrification process of a circulating fluidized bed boiler (CFB) blended with low-water content biomass in a 168 MW unit of a thermal power plant. Using the target power plant boiler entity as a template, a simplified geometric model is established, 1:1, and the mass fractions of each flue gas component set by the inlet boundary conditions are O22, H2O11.6, CO216.2%, and NO0.05%(about 134 ppm), and the reduction reactions under different optimized conditions are numerically simulated using the SNCR model in ANSYS Fluent 2021 R1. The simulation results under each condition were analyzed. The results show that the optimal ammonia-to-nitrogen ratio should be taken as NSR = 1.25, the denitrification efficiencies of 81.00, 81.63, and 82.74% at the three outlets are high, and the ammonia escapes of 1.76, 2.08, and 9.42 mg/s are within a reasonable range; increasing the number of injection sources can significantly reduce the disturbance of the flue gas flow field by reductant injection; the direction of injection is parallel to the direction of the flue gas flow, and the line of the injection source is orthogonal to the direction of the flue gas flow, which is conducive to the mixing of the reductant and flue gas; the optimized boiler denitrification efficiency reaches 74.2%, meeting the ultralow emission requirements of nitrogen oxides and ammonia escape.
Coal-fired power plants (CFPPs) account for > 70% of electricity generation in India, but < 5% of facilities have installed technologies for sulfur dioxide (SO2) and nitrogen oxide (NOX) removal. Emissions of these pollutants lead to the formation of fine particulate matter (PM2.5) and an increased risk of premature mortality for exposed populations. Here, we use a nested version of the GEOS-Chem global chemical transport model (0.5° × 0.625° resolution) for India to estimate reductions in PM2.5 concentrations that could have been achieved by implementing existing emission control technologies like flue-gas desulfurization (FGD) and/or selective catalytic reduction (SCR). We quantify the associated burden of disease using the integrated exposure response (IER) and global exposure mortality model (GEMM) functions and compare the costs of premature mortality to those for FGD installation. Model simulations for 2010 suggest installation of FGD would have reduced mean annual PM2.5 concentrations across India by 8%, compared to 3% with SCR installation, and 11% with both FGD and SCR. A 7–28% reduction in PM2.5 was simulated for local communities closest to CFPPs (same model grid cell), leading to up to 17% reduction in annual premature mortality. Overall, more than 0.21–0.48 million premature deaths would have been avoided over a 10-year period if FGD had been implemented on all CFPPs, compared to 0.09–0.21 million with SCR and 0.22–0.72 million with both FGD and SCR. Benefits associated with such actions are approximately 18.1–604 billion USD per year, which is equivalent to ~ 0.44 to 10% of India’s GDP. These results suggest that monetary benefits from avoided premature mortality far outweigh the capital and operational costs of FGD and/or SCR installation of 32.8 billion per year, respectively. This information is essential because the high costs of installation and operation are often given as reasons for delaying installation and commissioning. We conclude that policy actions to control air pollution from CFPPs are economically justifiable.
Nitrogen waste poses substantial threats to global sustainable development through multiple pathways, prompting the United Nations (UN) to propose halving nitrogen waste as a means to achieve Sustainable Development Goals (SDGs). However, the pathways and potential to improve global SDGs through halving nitrogen waste are less known. Here we show that nitrogen waste is directly and indirectly linked to all 17 UN 2030 SDGs and that halving nitrogen waste could enhance global SDGs overall by 16%. The total social benefits of halving nitrogen waste could be as high as US 1,137 billion, adopting cost-effective strategies could slash these expenses by 72%. Our findings provide crucial insights for policymakers and underscore the urgency of developing cost-effective nitrogen waste reduction strategies to achieve global sustainable development.
In Japan, a Waste To Energy (WTE) plant with a strict NOx emission limit value of 50 ppm (O2 12%-dry) has been operated with selective non-catalytic reduction (SNCR). Ammonia or urea is used as a media for SNCR, but urea is safer than ammonia and is easy to use. However, urea has a problem of lower NOx removal efficiency than ammonia. Therefore, a technology to convert urea to ammonia on-site is necessary. In this work, the basic performance of this urea decomposition system, the operation results of SNCR, and the CO2 reduction by SNCR were studied.The urea decomposition system was a catalytic reactor, and when the catalytic temperature was above 250 °C and the space velocity was below 6000 h−1, the conversion to ammonia was almost 100%. The NOx removal ratio of SNCR was 20% at an ammonia equivalence ratio of 0.4 and about 40% at an equivalence ratio of 0.6, a performance level similar to other plant. Furthermore, it was estimated that CO2 emissions were reduced by 3.1% by applying SNCR instead of SCR, and when combined with other CO2 reduction measures of this plant, CO2 emissions were reduced by 16.2%.
Co-pyrolysis technology containing biomass offers remarkable advantages in reducing NOx emissions economically and efficiently. In this work, it was innovatively introduced to solve the problem of excessive NOx emission during the incineration of waste energetic materials (EMs). The kinetics and NOx emission characteristics of waste double-base propellant (DP), pine sawdust (PS), and their mixtures with different ratios during pyrolysis were investigated by thermogravimetric analysis and fixed-bed experiments. The results showed that there was a significant interaction between DP and PS. Kinetic analysis by Friedman and Kissinger-Akahira-Sunose (KAS) methods demonstrated that the average activation energies of the mixtures with different ratios were smaller than that of DP, indicating that the addition of PS improved the reactivity of co-pyrolysis. In addition, the fixed-bed experiment determined that the lowest NOx emission was achieved during DP pyrolysis alone at 900 ℃. Co-pyrolysis at this temperature was found to have synergistic effects of reduced NOx emissions for different ratios of mixtures. The best synergistic effect was achieved at the mixing ratio of 60 wt% DP and 40 wt% PS, resulting in a 72.11 % reduction in actual NOx emissions compared to the expected value. This study provides a new direction and powerful data support for the clean, efficient and economic treatment of waste EMs, especially for practical engineering strategies.
Resource recovery is vital for small and medium-sized enterprises to achieve a circular economy. The economic benefits of the recovery of precious metals from electronic waste, such as waste printed circuit boards (WPCBs), are reduced by the emission of secondary pollutants emissions from pre-treatment processes. This study recovers copper from the WPCB acid leaching process and removes NOx post-process using a high gravity rotating packed bed (RPB). The results show that the copper recovery ratio increases to 99.75% for the displacement reaction between iron powder and copper nitrate. The kinetic analysis of copper dissolution is used to simulate the NOx emissions during acid leaching with an R-square value equal to 0.872. Three oxidants, including H 2 O 2(aq) , ClO 2(aq) , and ozone solutions with an adjusted pH corresponding to different NaOH concentrations, are used to remove NOx. A significantly greater amount of NOx is removed using a 0.06 M NaOH solution as an absorbent. The highest NOx removal ratio is 91.2% for ozone oxidation, a 152-fold gravity level and a gas-to-liquid (G/L) ratio of 0.83. The gas side mass transfer coefficients ( K G a ) for NOx range from 0.003 to 0.012 1/s and are comparable to the values for previous studies. The results of a life-cycle analysis show that the NOx removal ratio, the nitric acid recycling ratio and the copper recovery ratio are 85%, 80%, and 100% so environmental impact on the ecosystem, human health and resource depletion is reduced by 10%, compared to a situation whereby no NOx is removed.
TiO2/GO with different graphene oxide (GO) composite ratios were prepared by hydrothermal method and characterized by SEM, TEM, XRD, UV-vis, XPS, Raman and photocurrent. The results show that both TiO2 and GO/TiO2 crystal are anatase type. Part of GO is reduced to the reduced graphene oxide (RGO), properties of which are closer to that of graphene, when GO is prepared by hydrothermal reaction with butyl titanate. And such transformation is conducive to photoelectron transfer. Compared with pure TiO2, the composite TiO2/GO catalyst has a smaller grain size and a higher ratio of adsorbed oxygen/lattice oxygen, which is beneficial to the oxidation of NO. Moreover, lower band gap enhances the abilities of absorbing visible light and the photoelectron response over TiO2/GO catalyst. Therefore, the catalyst exhibits more excellent photocatalytic performance. The photocatalytic denitration performance of the composites was evaluated under visible light. When the GO composite ratio is 1.5%, the catalyst possesses the optimal photocatalytic denitration performance. When the ratio of ammonia to nitrogen is 1:1, the denitration efficiency can reach as high as 88.6%, which is 30% higher than that of self-made unmodified TiO2 and 40% higher than that of V-Ti-W catalyst. The anti-interference ability is significantly stronger than that of commercial V-Ti-W catalysts. It is concluded, from the mechanism analysis, that the oxidation rate of NO plays a key role in the process of photocatalytic denitration, and the presence of ammonia can accelerate the reduction of NO2.
The first objective of any waste policy should be to minimize the negative effects of the generation and management of waste on human health and the environment. Re-use and recycling of waste, although of high priority in the waste hierarchy, is not necessarily always the best treatment method. In the case of hazardous waste containing toxic components, thermal treatment with energy recovery constitutes a cost effective treatment option, complying with the pillars of “Sustainability” and the requirements of “Resource Efficient and Cleaner Production”. Iron recovery from the incineration ashes, water recycling, substitution of fossil fuel by high calorific waste in the incineration process, and energy recovery, avoid the use of non-renewable resources. Emissions to air and discharges to water of a typical rotary kiln for the incineration of hazardous waste, are far below the European emission limit values. Furthermore, recent studies on health effects of modern, state-of-the art waste incinerators show that any potential damage to the health of those living close-by or working in a hazardous waste incineration plant, is likely to be very small, if detectable.
To date numerous environmental, economic and societal indicators have been applied to evaluate and compare the sustainability of products and processes. This study presents a set of ad hoc sustainability indicators suitable for assessing and comparing processes for the treatment of industrial waste streams and for allowing to address efficiently all aspects of sustainability. This set consists of the following indicators: energy intensity, material intensity, water consumption, land use, global warming, human toxicity and treatment cost. The application of these indicators to industrial waste treatment processes is discussed in depth. A distinction is made between direct contributions to sustainability, occurring at the process level itself, and indirect contributions related to the production of auxiliaries and the recovery of end products. The proposed sustainability assessment method is applied to treatment processes for automotive shredder residue (ASR), a complex and heterogeneous waste stream with hazardous characteristics. Although different strategies for recycling and valorization of ASR were developed, with some of them already commercialized, large quantities of ASR are still commonly landfilled. This study concludes that for ASR the most sustainable alternative to the present landfill practice, both in short and long term perspective, consists of recycling combined with energetic valorization of the residual fraction.
This paper analyses six strategies for managing the MSW generated in Asturias (Spain) in terms of their environmental impacts applying the Life Cycle Analysis methodology. To this end, the effect of these strategies on Human Health, Ecosystem Quality, Global Warming and Resource Depletion is studied. The analysed management options include direct landfill with recovery of biogas (S-0), direct incineration with energy recovery (S-1), biomethanization of the source-separated organic fraction with direct incineration of the mixed fraction (S-2), biomethanization of the source-separated organic fraction, sorting of the mixed fraction and incineration of the rejected fraction (S-3), biomethanization of the source-separated organic fraction, sorting of the mixed fraction and incineration of the rejected fraction following aerobic stabilization of the organic fraction (S-4) and biomethanization of the source-separated organic fraction, sorting of the mixed fraction and landfill of the rejected following aerobic stabilization of the organic fraction (S-5). The Consortium for Waste Management (COGERSA) provide data regarding on transport and collection of waste and consumption of energy, water, oil and reagents at each processes. The results obtained suggest that Scenario S-3 has the least impact on the analysed damage categories while the scenarios including landfilling produces the greatest impact in all the categories analysed. Regarding involved processes in studied scenarios, the transport produces a significant impact in the environment, biomethanization contributes to reducing the impact in all the damage categories and incineration adversely affects the categories of Human Health and Climate Change, but helps to reduce damage in the Resources category.
An approach to the analysis of the plate-type catalysts for high-dust selective catalytic reduction (SCR) applications is herein presented. Commercial systems were studied in the form of slabs. NOx reduction and SO2 oxidation runs were performed spanning a wide range of operating conditions. The results were analyzed on the basis of a 1D model. The estimates of the intrinsic activity parameters and of the effectiveness factors were found to differ significantly among the catalysts under study. Aspects related to scale-up were also addressed on a preliminary basis. Concerning the SO2 oxidation reaction, the lab-scale analysis of the catalysts can be directly exploited for reactor design. On the contrary, the evaluation of the DeNOx performance of the industrial plate-type monolith requires the study of the interphase mass transfer in the real scale; the NO conversion data collected in the slab-reactor were estimated as not conservative in relation to design applications.
Due to ongoing developments in the EU waste policy, Waste-to-Energy (WtE) plants are to be optimized beyond current acceptance levels. In this paper, a non-exhaustive overview of advanced technical improvements is presented and illustrated with facts and figures from state-of-the-art combustion plants for municipal solid waste (MSW). Some of the data included originate from regular WtE plant operation - before and after optimisation - as well as from defined plant-scale research. Aspects of energy efficiency and (re-)use of chemicals, resources and materials are discussed and support, in light of best available techniques (BAT), the idea that WtE plant performance still can be improved significantly, without direct need for expensive techniques, tools or re-design. In first instance, diagnostic skills and a thorough understanding of processes and operations allow for reclaiming the silent optimisation potential.
Deactivation of vanadium–titanium deNOx SCR (selective catalytic reduction) catalysts in high-dust position have been investigated in three 100 MW-scale boilers during biofuel and peat combustion. The deactivation of the catalyst samples has been correlated to the corresponding flue gas composition in the boilers. Too investigate the effect on catalyst deactivation a sulphate-containing additive was sprayed into one of the furnaces. Increased alkali content on the SCR catalyst samples decreased the catalytic deNOx activity. The study has shown a linear correlation between exposure time in the boilers and alkali concentration (mainly potassium) on the samples. The results imply that mainly alkali in ultra fine particles (<100 nm) in the flue gas increased the alkali accumulation on the catalyst samples. Low correlation was found between particles larger than 100 nm and the catalyst deactivation. It was not possible to decrease the deactivation of the catalyst samples by the sulphate-containing additive. Although the additive had an effect in sulphating potassium chloride to potassium sulphate, it did not decrease the amount of potassium in ultra fine particles or the deactivation of the catalyst samples.
Energy and environment are drawing greater attention today, particularly with the rapid development of the economy and increase consumption of energy in China. At present, coal-fired power plants are mainly responsible for atmospheric air pollution. The selective catalytic reduction (SCR) technology is a highly effective method for NOX control. The present study identified and quantified the energy consumption and the environmental impacts of SCR system throughout the whole life cycle, including production and transportation of manufacturing materials, installation and operation of SCR technology. The analysis was conducted with the utilization of life cycle assessment (LCA) methodology which provided a quantitative basis for assessing potential improvements in the environmental performance of the system. The functional unit of the study was 5454Â t NOX emission from an existing Chinese pulverized coal power plant for 1Â year. The current study compared life cycle emissions from two types of de-NOX technologies, namely the SCR technology and the selective non-catalytic reduction (SNCR) technology, and the case that NOX was emitted into atmosphere directly. The results showed that the environmental impact loading resulting from SCR technology (66810 PET2000) was smaller than that of flue gas emitted into atmosphere directly (164121 PET2000) and SNCR technology (105225 PET2000). More importantly, the SCR technology is much more effective at the elimination of acidification and nutrient enrichment than SNCR technology and the case that NOX emitted into atmosphere directly. This SCR technology is more friendly to the environment, and can play an important role in NOX control for coal-fired power plants as well as industrial boilers.
In the present paper, the validity of the waste hierarchy for treatment of solid waste is tested. This is done by using the tool life cycle assessment on recycling, incineration with heat recovery and landfilling of recyclable waste for Swedish conditions. A waste hierarchy suggesting the environmental preference of recycling over incineration over landfilling is found to be valid as a rule of thumb. There are however assumptions and value choices that can be made that make landfilling more preferable. This is the case for some waste fractions and for some of the environmental impacts studied when only a limited time period is considered. When transportation of waste by passenger car from the households is assumed for the other treatment options but not for landfilling, landfilling also gains in preference in some cases. The paper concludes that assumptions made including value choices with ethical aspects are of importance when ranking waste treatment options. Uncertainties related to the assessment of toxicological impacts can also influence the conclusions.
Caledonian Paper (CaPa) is a major paper mill, located in Ayr, Scotland. For its steam supply, it previously relied on the use of a Circulating Fluidized Bed Combustor (CFBC) of 58 MWth, burning coal, wood bark and wastewater treatment sludge.It currently uses a bubbling fluidized bed combustor (BFBC) of 102 MWth to generate steam at 99 bar, superheated to 465 °C. The boiler is followed by steam turbines and a 15 kg/s steam circuit into the mill. Whereas previously coal, wood bark and wastewater treatment sludge were used as fuel, currently only plantation wood (mainly spruce), demolition wood, wood bark and sludge are used.Since these biosolids contain nitrogen, fuel NOx is formed at the combustion temperature of 850–900 °C. NOx emissions (NO + NO2) vary on average between 300 and 600 mg/Nm3 (dry gas). The current emission standard is 350 mg/Nm3 but will be reduced in the future to a maximum of 233 mg/Nm3 for stand-alone biomass combustors of capacity between 50 and 300 MWth according to the EU LCP standards. NOx abatement is therefore necessary.In the present paper we firstly review the NOx formation mechanisms, proving that for applications of fluidized bed combustion, fuel NOx is the main consideration, and the contribution of thermal NOx to the emissions insignificant.We then assess the deNOx techniques presented in the literature, with an updated review and special focus upon the techniques that are applicable at CaPa. From these techniques, Selective Non-catalytic Reduction (SNCR) using ammonia or urea emerges as the most appropriate NOx abatement solution.Although SNCR deNOx is a selective reduction, the reactions of NOx reduction by NH3 in the presence of oxygen, and the oxidation of NH3 proceed competitively.Both reactions were therefore studied in a lab-scale reactor and the results were transformed into design equations starting from the respective reaction kinetics. An overall deNOx yield can then be predicted for any operating temperature and NH3/NOx ratio.We then present data from large-scale SNCR-experiments at the CFBC of CaPa and compare results with the lab-scale model predictions, leading to recommendations for design and operation. Finally the economic impact is assessed of implementing SNCR-technology when applying an NH3 SNCR or urea SNCR to the CFBC at CaPa.
Life cycle assessment (LCA) is an environmental assessment tool generally applied to products but also to processes. Features of the LCA of processes are presented in this paper. This approach was used to compare two flue gas cleaning processes: the typical wet-type process and the new transported droplets column process. The LCA result shows that the global environmental burden is similar between the two processes, which confirms the viability of the transported droplets column. The distribution of the environmental burden, however, is different between the two processes. The weak points of the transported droplets column are the pollution transfer from air to water and a larger volume to stabilize. Its strong point: it is more efficient in capturing dust particles and toxic pollutants. This process could be improved from an environmental standpoint by adding an electrostatic filter upstream of the transported droplets column to capture the particles. The laboratory results of the transported droplets column need, however, to be confirmed at a larger scale.
Selective non-catalytic reduction (SNCR) of nitrous oxides in a full-scale municipal solid waste incinerator was investigated using LCA. The relationship between NO(x)-cleaning and ammonia dosage was measured at the plant. Un-reacted ammonia - the ammonia slip - leaving the flue-gas cleaning system adsorbed to fly-ash or in the effluent of the acidic scrubber was quantified from the stoichiometric reaction of NO(x) and ammonia assuming no other reaction products was formed. Of the ammonia slip, 37% was associated with the fly-ash and 63% was in the effluent of the acidic scrubber. Based on NO(x)-cleaning efficiency, the fate of the ammonia slip as well as the environmental impact from ammonia production, the potential acidification and nutrient enrichment from NO(x)-cleaning was calculated as a function of ammonia dosage. Since the exact fate of the ammonia slip could not be measured directly, a number of scenarios were set up ranging from "best case" with no ammonia from the slip ending up in the environment to "worst case" where all the ammonia slip eventually ended up in the environment and contributed to environmental pollution. In the "best case" scenario the highest ammonia dosage was most beneficial demonstrating that the environmental load associated with ammonia production is of minor importance. In contrast, in a "worst case" scenario" NO(x)-cleaning using SNCR is not recommendable at all, since the impacts from the ammonia slip exceed the saved impacts from the NO(x) removal. Increased dosage of ammonia for removal of NO(x) is recommendable as long as less than 10-20% of the ammonia slip to the effluent of the acidic scrubber ends up in the environment and less than 40% of the slip to the fly-ash ends up in the environment. The study suggests that the actual fate of the ammonia slip is crucial, but since the release of the ammonia may take place during transport and at the facilities that treat the wastewater and treat the fly-ash this factor depends strongly on local conditions and may be hard to determine. Thus, LCA-modeling proved useful in assessing the balance between ammonia dosage and NO(x)-removal in flue-gas cleaning from waste incineration.
In the EU, emissions from energy from waste plants are largely reduced by applying the Waste Incineration Directive with its limit of 200 mg/m3(s) for NO(x) emissions. The need for further improvement is reflected by new German legislation effective as of 27 January 2009, requiring 100 mg/m3(s). Other countries are expected to follow this example due to the national emission ceilings of the Gothenburg protocol and the concluding EU directive 2001/81/EC. On the other hand, an increase in energy efficiency will be encouraged by the EU Waste Framework Directive. This is why there is a need for new technologies that make it possible to reconcile both requirements: reduced emissions and increased energy efficiency. A new process combining the internal recirculation of flue gas with ammonia or urea injection in order to achieve less then 80 mg/m3(s) of NO(x) is described. Important additional features of the process are an R1 efficiency above the required 0.65 of the EU Waste Framework Directive even with standard steam parameters of 40 bar/380 degrees C as well as low ammonia slip in the flue gas at the boiler outlet of below 10 mg/m3(s).
At international level LCA is being increasingly used to objectively evaluate the performances of different Municipal Solid Waste (MSW) management solutions. One of the more important waste management options concerns MSW incineration. LCA is usually applied to existing incineration plants. In this study LCA methodology was applied to a new Italian incineration line, to facilitate the prediction, during the design phase, of its potential environmental impacts in terms of damage to human health, ecosystem quality and consumption of resources. The aim of the study was to analyse three different design alternatives: an incineration system with dry flue gas cleaning (without- and with-energy recovery) and one with wet flue gas cleaning. The last two technological solutions both incorporating facilities for energy recovery were compared. From the results of the study, the system with energy recovery and dry flue gas cleaning revealed lower environmental impacts in relation to the ecosystem quality. As LCA results are greatly affected by uncertainties of different types, the second part of the work provides for an uncertainty analysis aimed at detecting the extent output data from life cycle analysis are influenced by uncertainty of input data, and employs both qualitative (pedigree matrix) and quantitative methods (Monte Carlo analysis).
The engineering, construction, performance and running costs of a catalytic flue gas cleaning component in the low dust area of a municipal waste incinerator is discussed. For this purpose, the case study of a Flemish incineration plant is presented, covering the history, the design procedure of the catalyst, relevant process data and the financial aspects. A reliable PCDD/F-destruction by means of oxidation by the catalyst to typical values of 0.001 ng TEQ/Nm3 has been demonstrated. At the same time, NOx- and CO-emissions are reduced by 90% and 20% to about 50 mg/Nm3 and below 10 mg/Nm3, respectively.
This article summarises the abatement of NO(x) pollution by using sorbing catalytic materials with special relevance to the challenge presented in fixed installations sources. A general vision of the origins of the different pollutants, with emphasis on nitrogen oxides formation, is presented as introduction. The impact of NO(x) pollution comprises additionally a quick view of its toxicity and environmental effects. Actual solutions are presented especially the case of the selective catalytic reduction (SCR) process with its advantages and difficulties. The new concepts for NO(x) abatement are also analysed. In such a way, updated information on solid sorbents for NO(x) removal is provided by including metal oxides, spinelles, perovskites, double-layered cuprates, zeolites, carbonaceous materials, heteropolyacids (HPAs), and supported heteropolyacids. The possibility of reducing those sorbed NO(x) is also underlined. Sorption mechanisms are analysed and clarified by emphasising convergence and disagreement points.