No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Mitigation approaches and techniques for combustion power plants flue gas emissions: A comprehensive review
Abstract
Population growth and urbanization are driving energy demand. Despite the development of renewable energy technologies, most of this demand is still met by fossil fuels. Flue gases are the main air pollutants from combustion power plants. These pollutants include particulate matter (PM), sulfur oxides (SOx), nitrogen oxides (NOx), and carbon oxides (COx). The release of these pollutants has adverse effects on human health and the environment, including serious damage to the human respiratory system, acid rain, climate change, and global warming. In this review, a wide range of conventional and new technologies that have the potential to be used in the combustion power plant sector to manage and reduce flue gas pollutants have been examined. Nowadays, conventional approaches to emissions control and management, which focus primarily on post-combustion techniques, face several challenges despite their widespread use and commendable effectiveness. Therefore, studies that have proposed alternative approaches to achieve improved and more efficient methods are reviewed. The results show that new advances such as novel PM collectors, attaining an efficiency of nearly 100 % for submicron particles, microwave systems, boasting an efficiency of nearly 90 % for NO and over 95 % for SO2, electrochemical systems achieving above 90 % efficiency for NOx reduction, non-thermal plasma processes demonstrating an efficiency close to 90 % for NOx, microalgae-based methods with efficiency ranging from 80 % to 99 % for CO2, and wet scrubbing, exhibit considerable potential in addressing the shortcomings of conventional systems. Furthermore, the integration of hybrid methods, particularly in regions prioritizing environmental concerns over economic considerations, holds promise for enhanced control and removal of flue gas pollutants with superior efficiency.
... The International Energy Agency predicts that under the Sustainable Development scenario goal, the world will achieve net-zero emissions by 2070, and carbon capture, utilization, and storage will contribute to a cumulative carbon reduction of 15%. 1 Because of the depletion of coal resources and the continuous advancement of the global "carbon neutrality" plan, domestic and foreign coal mines are scaling back production or shuttering operations, rapidly increasing the number of closed/abandoned coal mines. 3 Flue gas constitutes the primary air pollutant in combustion power plants, including particulate matter, sulfur oxides, nitrogen oxides, and carbon dioxide. 2 In the face of the increasingly severe global greenhouse effect and the growing demand for clean energy, the absorption and storage of flue gas from abandoned mines are effective ways to solve the above problems. Given the challenges associated with treating power plant flue gas and its substantial impact on the greenhouse effect, injecting it into abandoned mines for CO 2 storage and facilitating the displacement of available energy CH 4 holds practical significance. ...
... The absolute adsorption volume error ranges for RK, SRK, PR, and Lee compression factor calculation methods are 0.069−0.226 cm3 at 29.4°C and 0.004− 0.0547 cm 3 at 49.7°C. The absolute adsorption volumes obtained from the Beggs−Brill method and the other four compression factor calculation methods exhibit significant errors at both temperatures, rendering them unsuitable for modeling coal flue gas adsorption in power plants. ...
To minimize errors in calculating coal flue gas adsorption capacity due to gas compressibility and to preclude prediction inaccuracies in abandoned mine flue gas storage capacity for power plants, it is imperative to account for the influence of compression factor calculation accuracy while selecting the optimal theoretical adsorption model. In this paper, the flue gas adsorption experiment of a power plant with coal samples gradually pressurized to close to 5 MPa at two different temperatures is carried out, and the temperature and pressure data obtained from the experiment are substituted into five different compression factor calculation methods to calculate different absolute adsorption amounts. The calculated adsorption capacities were fitted into six theoretical adsorption models to establish a predictive model suitable for estimating the coal adsorption capacity in power plant flue gas. Results reveal significant disparities in the absolute adsorption capacity determined by different compression factors, with an error range of 0.001278–7.8262 (cm³/kg). The Redlich–Kwong equation of state emerged as the most suitable for the flue gas of the selected experimental coal sample and the chosen composition ratio among the five compression factors. Among the six theoretical adsorption models, the Brunauer–Emmett–Teller model with three parameters demonstrated the highest suitability for predicting the adsorption capacity of coal samples in power plant smoke, achieving a fitting accuracy as high as 0.9922 at 49.7 °C.
... ESPs have proven effective in mitigating PM emissions from biomass boilers, but their adoption in small-scale applications encounters economic challenges. While the investment cost of ESPs is considered reasonable for industrial power plants [54], the investment poses a substantial financial burden on a small-scale [11,25]. For example, the investment cost for an ESP suitable for wood burners with a thermal power below 50 kW typically ranges from e1000 to e3300 [28,29,[55][56][57][58]. ...
... In case of the 240 kW boiler investigated in this study, the additional investment required to integrate the ESP is e4250, which can be considered substantial, although this represents a rather modest relative investment increase of 6.2% compared to the same boiler without ESP [56]. ESPs also entail operational costs attributed to their power consumption, albeit these costs are generally considered low [11,21,54]. For instance, the investigated boiler exhibits a 57% increase in electrical power consumption when the ESP is activated [39]. ...
Electrostatic precipitators (ESP) are an effective means of reducing particulate matter emissions from biomass combustion. This study presents a comprehensive evaluation of the performance of an ESP integrated in a 240 kW wood chip boiler. The boiler-integrated ESP is commercially available and is evaluated in-situ using two types of wood chips, unlike previous studies, which mainly focuses on prototypes or lab-based constructions. The obtained results indicate a mass-based ESP efficiency of 94-96%, surpassing previously reported values for small-scale boiler-integrated ESPs. Furthermore, the number-based ESP efficiency is 83-92%, which is in line with values reported in literature. Despite the promising performance, the widespread adoption of integrated ESPs in small-scale appliances faces challenges due to the lack of financial, regulatory and energetic incentives. Nevertheless, the application of ESPs in this context remains crucial in addressing local air pollution and reducing the overall environmental impact of small-scale biomass combustion. To facilitate broader implementation, further research and policy initiatives are necessary. This study provides valuable insights into the true effectiveness of a small-scale ESP in mitigating particulate matter emissions.
... Then the BSF method has the lowest potential impact of all methods of 2.003E-1 or 1%. Sulfur dioxide (SO2), nitrogen oxides (NOx), and ammonia (NH3) are anthropogenic emissions that are created in the exhaust gas from scrubbers due to combustion, the use of diesel, and the use of ammonia to reduce NOx emissions (Larki et al., 2023;Shelyapina et al., 2020). These emissions cause air pollution, acid rain, and health issues, and they come from combustion processes and the disposal of gas. ...
1.3 billion tons of the food produced for human consumption is wasted in the food supply chain as a result of a number of issues. A high proportion of food waste occurs during consumption, primarily influenced by consumer behavior. In Semarang City, Black Soldier Fly, incineration, and composting are alternatives to food waste management. This research aims to analyze alternative food waste management methods that yield reusable resources and materials because currently unknown which method has the smallest environmental impact. Life Cycle Assessment method can be used to examine the environmental impact of the food waste management system from every phase 1 ton food waste analyze. BSF has proven superior to composting, incineration and landfilling methods in analyzes of potential environmental impacts that reduce 90% environmental impact. Landfills cover a large area and the effect of global warming is significant until of 1.704E+03 CO2-eq, this issue needs more attention in the management of the generated CH4. Incineration needs to make advances in the method such as producing new resources and emissions so that can be reused because incineration impact eutrophication potential until 2.438E+00 . For reasons environmental concerns, efficient food waste management is crucial to realizing the Sustainable Development Goals.
... This increasing need for energy has caused a worrying trend-the consumption of primary resources at an alarming rate, raising serious environmental concerns and acceleration of the fossil fuels depletion [2]. Despite notable progress in renewable energy technologies, an astonishing 80% of the world's energy consumption still relies on fossil fuels and combustion facilities [3]. In this context, our world finds itself at a pivotal point where the imperative for change is clear-a significant global shift towards renewable energy sources is not just a choice but a necessity [4]. ...
The increasing global demand for energy, environmental concerns and the depletion of fossil fuel reserves, necessitates a paradigm shift towards sustainable energy solutions. Cogeneration emerges as a versatile approach to address these
challenges. This article explores a solar-thermal natural gasdriven polygeneration system. The proposed system integrates solar-thermal heliostat energy and natural gas for power generation, hydrogen production, freshwater production, and
domestic hot water. Using energy, exergy, and exergoeconomic analyses, the study examines the efficiency, cost-effectiveness, and environmental impact, contributing vital insights to enhance cogeneration systems' efficacy and applicability. The Pareto front diagram, utilizing the LINMAP method, showcases optimal points for the system, balancing exergy efficiency and total cost rate as objective functions. The best point achieved through optimization exhibits an exergy efficiency of 36.24% and a total cost of 1208 $/hr.
... In recent years, the problem of treating gas emissions of industrial enterprises and vehicles has become increasingly relevant, leading to the development and diversification of various technologies aimed at reducing pollution. Depending on the type of harmful components, the treatment methods can be based on absorption, adsorption, as well as catalytic and membrane technologies and their combinations [1,2]. Among them, post-combustion technologies using various liquid and solid sorbents for carbon dioxide capture have recently gained particular importance among capture and purification technologies [3,4]. ...
In order to establish the formation patterns of the Co–Mg oxide system, samples with different Co:Mg ratios and heat treatment temperatures were synthesized and studied. Study of the sam-ples confirmed the phase transition of MgxCo2–xO4 spinels into corresponding solid solutions at 800–900 °C. The similarity of formation patterns for different compositions is shown. The rock-salt oxide in low-temperature samples is an anion-modified paracrystalline phase that forms a “true” solid solution only upon spinel decomposition. TPR profiles of decomposed Co3O4 spinel show surface Co3O4 peaks and a wide peak corresponding to well-crystallized CoO, while par-tial Co3O4 TPR up to 380 °C results in dispersed and amorphous CoO. High-temperature non-stoichiometric samples are poorly reduced, indicating their low oxygen reactivity. Spinel reoxidation after heat treatment to 1100 °C by calcination at 750 °C showed complete regenera-tion for MgCo2O4–Co3O4 samples and its absence in case of an excess of MgO relative to stoi-chiometry. Based on the data obtained, it can be concluded that the processes governing the formation of Co–Mg oxide systems are determined by both Co:Mg ratio and the heat treatment conditions, potentially providing the possibility of fine tuning for specific catalytic processes.
... Estimating emission loads is essential for establishing the applicability of permitting and control programs, designing emission control strategies, discovering the effects of sources and appropriate techniques of mitigation, and other valuable applications by related stakeholders. Implementing stricter emission regulations for coal-fired power plants, gradually removing high-emission power generation units, and installing air pollution control devices on existing units have led to enhancements in reducing air pollutants through fuel switching and various methods [12,13]. ...
Continuous Emission Monitoring System (CEMS) is generally used for monitoring compliance with emission standards set by the government regulations and has not been optimally used for other additional purposes yet. If operated CEMS can produce reliable and accurate data, they can develop further specific data such as emission factors. These emission factors can be used for estimating pollutant emission loads from coal combustion activity in Coal-Fired Power Plants (CFPPs) without conducting direct source measurements. In this study, hourly 1 yr CEMS data from several units of CFPPs were processed to develop specific emission factors for principal air pollutants (SO2, NOx, particulates) and greenhouse gases (represented by CO2). Emission factors were determined by dividing the emission load of each pollutant by the amount of combusted coal during 1 yr. The results showed that emission factor ratings for this study could not be classified as A ratings due to the limited number of investigated CEMS facilities. According to the variability of the derived emission factor values, SO2 and CO2 emission factors can be rated as B or above average (with fewer variability values). In comparison, NOx and particulate emission factors can be placed as C or average (with more variability values).
... Implementing a few exhaust gas treatment technologies is one approach to reducing emissions. Even though it is thought that exhaust gas treatment processes may decrease NOx and PM emissions in more significant quantities, installing these technologies will be expensive due to the investment and maintenance costs [53], [80]. Some methods could be used to improve fuel-air mixing and diffuse combustion diesel engines to minimize the formation of NOx and PM such as increasing fuel injection pressure to control fuel pressure at the fuel injector to achieve optimal performance and reduce fuel consumption [81], using gaseous fuels [82], using fuel additives [83], [84]. ...
Environmental pollution from transportation means and natural resource degradation are the top concern globally. According to statistics, NOx and PM emissions from vehicles account for 70% of total emissions in urban areas. Therefore, finding solutions to reduce NOx and PM emissions is necessary. Changing the engine's internal combustion method is considered promising and influential among the known solutions. One of the research directions is a combustion engine using the Premixed Charge Compression Ignition (PCCI) method combined with biofuels to improve the mixture formation and combustion process, reducing NOx and PM emissions. Therefore, this study presents the mechanism of the formation of PM and NOx emissions in the traditional combustion and the low-temperature combustion process of internal combustion engines. Besides, the theoretical basis of flame spread during combustion is also introduced. The key feature of this research is that it has modeled the combustion process in diesel engines under the PCCI modes. This was accomplished using blends of waste cooking oil (WCO)-based biodiesel and diesel fuel, as well as the ANSYS Fluent software. The results showed that PCCI combustion using B20 fuel can significantly reduce NOx and PM emissions, although HC and CO emissions tend to increase, and thermal efficiency tends to decrease. In further studies, different modes of the PCCI combustion process should be thoroughly examined so that this process can be implemented in practice to reduce pollutant emissions.
... Nitrogen oxides (NO X ) are formed when nitrogen in the air reacts with oxygen at high temperatures. Flue gas temperature is directly related to combustion efficiency [34]. ...
Currently, the modeling of complex chemical-physical processes is drastically influencing industrial development. Therefore, the analysis and study of the combustion process of the boilers using machine learning (ML) techniques are vital to increase the efficiency with which this equipment operates and reduce the pollution load they contribute to the environment. This work aims to predict the emissions of CO, CO2, NOx, and the temperature of the exhaust gases of industrial boilers from real data. Different ML algorithms for regression analysis are discussed. The following are input variables: ambient temperature, working pressure, steam production, and the type of fuel used in around 20 industrial boilers. Each boiler's emission data was collected using a TESTO 350 Combustion Gas Analyzer. The modeling, with a machine learning approach using the Gradient Boosting Regression algorithm, showed better performance in the predictions made on the test data, outperforming all other models studied. It was achieved with predicted values showing a mean absolute error of 0.51 and a coefficient of determination of 99.80%. Different regression models (DNN, MLR, RFR, GBR) were compared to select the most optimal. Compared to models based on Linear Regression, the DNN model has better prediction performance. The proposed model provides a new method to predict CO2, CO, NOx emissions, and exhaust gas outlet temperature.
... The majority of countries have made an effort to lower air pollution emissions due to concerns about climate change and global warming [2]. Nitrogen oxides (NO x ), comprising nitrogen oxide (NO 2 ), nitric oxide (NO), and carbon monoxide (CO), are considered the primary atmospheric pollutants due to they can be harmful to humans when inhaled in high concentrations [3], and cause environmental problems such as acid rain, photochemical smog, tropospheric ozone, Energy and ultimately global warming [4]. The combustion process in many different industries, such as gas turbines and boilers in power plants, is a key contributor to the hazardous pollutants (NO x , CO, and PM, etc.) emitted into the environment [5,6]. ...
Electrical energy is now widely recognized as an essential part of life for humans, as it powers many daily amenities and devices that people cannot function without. Examples of these include traffic signals, medical equipment in hospitals, electrical appliances used in homes and offices, and public transportation. The process that generates electricity can pollute the air. Even though natural gas used in power plants is derived from fossil fuels, it can nevertheless produce air pollutants involving particulate matter (PM), nitrogen oxides (NO x), and carbon monoxide (CO), which affect human health and cause environmental problems. Numerous researchers have devoted significant efforts to developing methods that not only facilitate the monitoring of current air quality but also possess the capability to predict the impacts of this increasing rise. The primary cause of air pollution issues associated with electricity generation is the combustion of fossil fuels. The objective of this study was to create three multiple linear regression models using artificial intelligence (AI) technology and data collected from sensors positioned around the energy generator. The objective was to precisely predict the amount of air pollution that electricity generation would produce. The highly accurate forecasted data proved valuable in determining operational parameters that resulted in minimal air pollution emissions. The predicted values were accurate with the mean squared error (MSE) of 0.008, the mean absolute error (MAE) of 0.071, and the mean absolute percentage error (MAPE) of 0.006 for the turbine energy yield (TEY). For the CO, the MSE was 2.029, the MAE was 0.791, and the MAPE was 0.934. For the NO x , the MSE was 69.479, the MAE was 6.148, and the MAPE was 0.096. The results demonstrate that the models developed have a high level of accuracy in identifying operational conditions that result in minimal air pollution emissions, with the exception of NO x. The accuracy of the NO x model is relatively lower, but it may still be used to estimate the pattern of NO x emissions.
... Notwithstanding these advantages, challenges persist in the efficient processing and storage of hydrogen, hindering the full realization of a hydrogen-based energy economy. Notably, security issues about hydrogen storage, transportation, and transportation remain common [10][11][12][13][14][15][16][17]. Current conventional hydrogen storage methods, employing various metal hydrides, fall short in terms of storage capacity. ...
This review paper reports on the use of Delafossite as a layer between perovskite-based solar cells to improve hydrogen production efficiency and make the process easier. The investigation delves into the possible breakthroughs in sustainable energy generation by investigating the synergistic interplay between Delafossite and solar technology. This investigation covers copper-based Delafossite material’s properties, influence on cell performance, and function in the electrolysis process for hydrogen production. Some reports investigate the synthesis and characterizations of delafossite materials and try to improve their performance using photo electrochemistry. This work sheds light on the exciting prospects of Delafossite integration using experimental and analytical methodologies.
... The progressive tightening of global standards for industrial wastewater treatment has led to an inexorable shift towards achieving zero discharge of desulfurised wastewater (FGD wastewater) [1]. The eventual convergence of sulfur oxides, hydrogen chloride, and other pollutants in the flue gas from coal-fired power plants into FGD wastewater depends on the quality of the coal, limestone, and desulfurisation processes [2]. The high salt content and strong corrosiveness of FGD wastewater present challenges for wastewater treatment in the vast majority of thermal power plants. ...
An important method that coal-fired power plants use to realise low-cost zero discharge of desulfurisation wastewater (FGD wastewater) is to utilise wet slag removal systems. However, the high Cl− content of FGD wastewater in wet slag removal systems causes environmental damage. In this study, the corrosion behaviour of the inner guide wheel material, 20CrMnTi, was studied using dynamic weight loss and electrochemical methods. X-ray diffraction, scanning electron microscopy, and energy spectroscopy were used to analyse the organisational and phase changes on the surfaces and cross sections of the samples at different Cl− concentrations. The corrosion rate increased with the Cl− concentration up to 20 g/L, but it decreased slightly when the Cl− concentration exceeded 20 g/L. In all the cases, the corrosion rate exceeded 0.8 mm/a. The corrosion product film density initially increased and then decreased as the Cl− concentration increased. The corrosion products comprised mainly α-FeOOH, γ-FeOOH, β-FeOOH, Fe3O4, and γ-Fe2O3.
... The increase in population and the ongoing urbanization process are propelling the need for more energy . Even though renewable energy technologies have advanced, the majority of this energy demand is still satisfied through the use of fossil fuels Larki et al., 2023). In today's world, where we are all striving for cleaner energy and sustainability, there is a smart way to make use of the heat that is typically wasted by diesel engines. ...
Thermoelectric generators hold immense promise in addressing the ever-increasing global energy demands and environmental concerns. Harnessing waste heat from various sources, such as exhaust gases from internal combustion engines, represents a vital avenue for improving energy efficiency and reducing emissions. In light of this, the present study introduces a comprehensive model for evaluating the performance of thermoelectric generators in heat recovery from diesel engine exhaust, shedding light on the potential of this technology to contribute to sustainable energy solutions. In this study, a model is presented for evaluating a thermoelectric generator's performance in heat recovery. The model is validated using experimental data from the literature. In this setup, 14 thermoelectric modules are placed at both the bottom and top of a rectangular gas channel of a diesel engine to recover heat from the exhaust gas. The hot head is heated by the exhaust gas, while the cold head is cooled by water, maintaining a constant temperature of 293 K. However, the temperature of the hot head varies depending on the engine's speed and load. The study investigates 12 different engine operating modes, including three motor speed modes (1000, 1500, and 2000 rpm) and five motor load modes (0.2, 0.4, 0.6, 0.8, and 1.0 MPa). Numerical analysis is performed concurrently with finite element simulations. The numerical and experimental finite element results are compared, and the findings confirm the consistency of the results.
... In recent decades, as the demand for electricity has continued to grow, there has been a rising rate of consumption of primary resources, leading to environmental issues and the depletion of fossil fuels [1]. Therefore, there is a significant global shift towards renewable energy sources, driven in part by the increasing prevalence of Artificial Intelligence (AI) and the Internet of Things (IoT) technologies in various sectors [2,3]. These advancements resulted in a demand for compact, adaptable, and portable systems that can adequately meet the evolving needs of the both electronics industry and society overall. ...
Carbon capture utilization and storage (CCUS) technologies are regarded as an economically feasible way to minimize greenhouse gas emissions. In this paper, various aspects of CCUS are reviewed and discussed, including the use of geological sequestration, ocean sequestration and various mineral carbon mineralization with its accelerated carbonization methods. By chemically reacting CO2 with calcium or magnesium-containing minerals, mineral carbonation technology creates stable carbonate compounds that do not require ongoing liability or monitoring. In addition, using industrial waste residues as a source of carbonate minerals appears as an option because they are less expensive and easily accessible close to CO2 emitters and have higher reactivity than natural minerals. Among those geological formations for CO2 storage, carbon microbubbles sequestration provides the economic leak-free option of carbon capture and storage. This paper first presents the advantages and disadvantages of various ways of storing carbon dioxide; then, it proposes a new method of injecting carbon dioxide and industrial waste into underground cavities.
Electricity plays a vital role in the economic development and welfare of countries. Examining the electricity situation and defining scenarios for developing power plant infrastructure will help countries avoid misguided policies that incur high costs and reduce people’s welfare. In the present research, three scenarios from 2021–2040 have been defined for Iran’s electricity status. The first scenario continues the current trend and forecasts population, electricity consumption, and carbon dioxide emissions from power plants with ARIMA and single and triple exponential smoothing time series algorithms. As part of the second scenario, only non-hydro renewable resources will be used to increase the electricity supply. By ensuring the existence of potential, annual growth patterns have been defined, taking into account the renewable electricity generation achieved by successful nations. The third scenario involves integrating operating gas turbines into combined cycles in exchange for buyback contracts. Economically, this scenario calculates return on investment through an arrangement of various contracts for the seller company and fuel savings for the buyer.
Nitrogen oxide (NOx) is a major gaseous pollutant in flue gases from power plants, industrial processes, and waste incineration that can have adverse impacts on the environment and human health. Many denitrification (de-NOx) technologies have been developed to reduce NOx emissions in the past several decades. This paper provides a review of the recent literature on NOx post-combustion purification methods with different reagents. From the perspective of changes in the valence of nitrogen (N), purification technologies against NOx in flue gas are classified into three approaches: oxidation, reduction, and adsorption/absorption. The removal processes, mechanisms, and influencing factors of each method are systematically reviewed. In addition, the main challenges and potential breakthroughs of each method are discussed in detail and possible directions for future research activities are proposed. This review provides a fundamental and systematic understanding of the mechanisms of denitrification from flue gas and can help researchers select high-performance and cost-effective methods.
Considerable seawater bittern is produced during salt production. Seawater bittern can be used to reduce CO2 and SOx because of the presence of valuable mineral ions, such as K⁺ and Mg²⁺, which react with the carbonate and sulfate ions present in high concentrations. In this study, a novel seawater bittern recovery process is proposed for CO2 and SOx utilization. The proposed process has the following steps: (1) metal ion separation of the seawater bittern to produce KOH and Mg(OH)2; (2) SOx capture and utilization using the generated Mg(OH)2; (3) CO2 capture and utilization using the generated KOH. The pay-back period (PBP) was calculated to verify the economic feasibility of the proposed process. The results revealed an SOx and a CO2 capture efficiency of approximately 99 % and 98 %, respectively. Furthermore, the annual net revenue was approximately 153,439 USD/y based on the profit obtained from the generated product and savings on absorbent. Thus, the PBP was approximately 6.2 y.
Coal is expected to remain a significant power supply source worldwide and shifting to carbon-neutral fuels will be challenging because of growing electricity demand and booming industrialization. At the same time, coal consumption results in severe air pollution and health concerns. Improvement in emission control technologies is a key to improving air quality in coal power plants. Many scientists reported removing air pollutants individually via conventional control methods. However, controlling multiple pollutants combinedly using the latest techniques is rarely examined. Therefore, this paper overviews the current and advanced physical technologies to control multi-air pollutants synergistically, including carbon control technologies. Also, the paper aims to examine how potential air pollutants (e.g., PM2.5, SO2, NOx, CO2), including mercury from the coal-fired power plants, cause environmental impacts. The data synthesis shows that coal quality is the most significant factor for increasing air emissions, regardless of power plant capacity. It is found that selecting techniques is critical for new and retrofitted plants depending on the aging of a power plant and other socio-economic factors. Considering the future perspective, this paper discusses possible pathways to transform from linear to a circular economy in a coal power plant sector, such as utilizing energy losses through energy-efficient processes and reuse of syngas. The article provides an in-depth analysis of advanced cost-effective techniques that would help to control the air pollution level. Additionally, a life cycle assessment-based decision-making framework is proposed that would assist the stakeholders in achieving net-zero emissions and offset the financial burden for air pollution control in coal-fired power plants.
Graphical abstract
Air pollution is a worldwide and a local issue caused by energy generation. It refers to global warming deterioration in human environmental health and local-global sustainability. This review provides information on the generation and consumption of energy with their air pollution mixture of many pollutants; gases, liquids and particles. These pollutants have become one of the leading environmental hazards to human and planet health. The components of pollutants that result from burning fossil fuels (oil and gas) and coal have been studied, such as sulfur dioxide, carbon dioxide, nitrogen oxides and particles. Both sulfur dioxide and nitrogen oxides interact with water to produce acid rain. Both gas and oil-fired thermal power plants emission today and in the future might be transformed to work on renewable energy sources. The results stated that gas-fired power plants are more generally faster efficient, less pollution than oil and coal power plants. A complete assessment of exhaust gas treatment was conducted. Carbon dioxide capture, desulfurization, denitrification, and particle collection were all successful as treatment control mechanisms. So, previous studies presented some methods for reducing nitrogen oxides and sulfur oxides through water injection and exhaust gas recycling. The addition of nano-additives in diesel emulsion fuel (W/D) has recently been shown to increase the characteristics and performance of the fuel while reducing the quantity of emitted hydrogen chloride (HC) and carbon monoxide (CO). It was determined that the best nano-additives for W/D were Aluminum Oxide (Al2O3), copper(ii) oxide, magnesium oxide (MgO), manganese oxide (MnO), and zinc oxide (ZnO), among others (E10).
The inland navigation sector makes a significant contribution to the growth of the global economy as well as to climate change due to pollutants emitted by diesel engines. NOx emissions are very high in port areas where, due to traffic, the ships run at idling regimes. Selective catalytic reduction (SCR) represents one of the most suitable technologies, in terms of cost effectiveness, but does not perform well if the temperature during vessel operation is lower than 180 °C. Microwave technology can support preheating of the ceramic core of SCR in order to increase the temperature towards the optimal interval for the best NOx reduction. Research has focused on coupling a magnetron head to a SCR device in order to evaluate to what extent the technology can meet the requirements of Stage V of the European Directive related to NOx emissions. Measurements of NOx emitted have been performed on engines with 603.5 kW nominal power and 1500 rpm that operate at a lower engine speed (700–1200 rpm) and output power (58–418 kW). The values recorded for emissions using microwave heating of ceramic core of SCR have decreased by 89% for a constant load of engine and idling engine speed.
The paper presents and discusses modern methods and technologies of CO2 capture (pre-combustion capture, post-combustion capture, and oxy-combustion capture) along with the principles of these methods and examples of existing and operating installations. The primary differences of the selected methods and technologies, with the possibility to apply them in new low-emission energy technologies, were presented. The following CO2 capture methods: pre-combustion, post-combustion based on chemical absorption, physical separation, membrane separation, chemical looping combustion, calcium looping process, and oxy-combustion are discussed in the paper. Large-scale carbon capture utilization and storage (CCUS) facilities operating and under development are summarized. In 2021, 27 commercial CCUS facilities are currently under operation with a capture capacity of up to 40 Mt of CO2 per year. If all projects are launched, the global CO2 capture potential can be more than ca. 130–150 Mt/year of captured CO2. The most popular and developed indicators for comparing and assessing CO2 emission, capture, avoiding, and cost connected with avoiding CO2 emissions are also presented and described in the paper.
: Evaluation of economic aspects is one of the main milestones that affect taking rapid actions in dealing with GHGs mitigation; in particular, avoiding CO2 emissions from large source points, such as power plants. In the present study, three kinds of capturing solutions for coal power plants as the most common source of electricity generation have been studied from technical and economic standpoints. Aspen HYSYS (ver.11) has been used to simulate the overall processes, calculate the battery limit, and assess required equipment. The Taylor scoring method has been utilized to calculate the costliness indexes, assessing the capital and investment costs of a 230 MW power plant using anthracite coal with and without post-combustion, pre-combustion, and oxy-fuel combustion CO2 capture technologies. Comparing the costs and the levelized cost of electricity, it was found that pre-combustion is more costly, to the extent that the total investment for it is approximately 1.6 times higher than the oxy-fuel process. Finally, post-combustion, in terms of maturity and cost-effectiveness, seems to be more attractive, since the capital cost and indirect costs are less. Most importantly, this can be applied to the existing plants without major disruption to the current operation of the plants.
Concentrated animal feeding operations (both slaughter and dairy cattle) lead to land, water, and air pollution if waste storage and handling systems are not effectively managed. At the same time, cattle biomass (CB), which includes both slaughter/feedlot biomass (FB) and dairy biomass (DB), have the potential to be a source of green energy at coal-fired power plants. Part I presented results on NOx reductions with pure FB or Coal: FB blends as reburn fuels. Part II deals with results from reburning with pure DB or Coal: DB blends as reburn fuels. A mixture of NG with a small amount of NH3 was used to generate the baseline NOx of 400–420 ppm (or 185–194 g/GJ). NOx emissions were found to be reduced by as much as 96% when reburning with FB. The effects of reburn fuel type, equivalence ratio (ERRBZ) in the reburn zone, vitiated air, several injection configurations of reburn fuel and initial NO concentrations on NOx emissions were investigated. The ERRBZ shows a significant effect on the NOx reduction. The 20% heat input by reburning was the better operating condition for the long-term operation due to its ash production. The results reveal that reburn with DB fuels is an effective technology for NOx emission control when the initial NOx emission is higher than 275 ppm (or 127 g/GJ or 0.3 lb/MMBtu).
Operation of marine diesel engines causes significant emission of sulphur and nitrogen oxides. It was noticed worldwide and the regulations concerning harmful emissions were introduced. There were several solutions elaborated; however, emission control for both SO x and NO x requires two distinctive processes realized in separated devices, which is problematic due to limited space on ship board and high overall costs. Therefore, the electron beam flue gas treatment (EBFGT) process was adopted to ensure the abatement of the problem of marine diesel off-gases. This novel solution combines two main processes: first the flue gas is irradiated with electron beam where NO and SO 2 are oxidized; the second stage is wet scrubbing to remove both pollutants with high efficiency. Laboratory tests showed that this process could be effectively applied to remove SO 2 and NO x from diesel engine off-gases. Different compositions of absorbing solution with three different oxidants (NaClO, NaClO 2 and NaClO 3 ) were tested. The highest NO x removal efficiency (>96%) was obtained when seawater-NaClO 2 -NaOH was used as scrubber solution at 10.9 kGy dose. The process was further tested in real maritime conditions at Riga shipyard, Latvia. More than 45% NO x was removed at a 5.5 kGy dose, corresponding to 4800 Nm ³ /h off-gases arising from ship emission. The operation of the plant was the first case of examination of the hybrid electron beam technology in real conditions. Taking into account the experiment conditions, good agreement was obtained with laboratory tests. The results obtained in Riga shipyard provided valuable information for the application of this technology for control of large cargo ship emission.
The iron and steel industry is the largest energy-consuming sector in the world. It is responsible for emitting 4–5% of the total anthropogenic CO2. As an energy-intensive industry, it is essential that the iron and steel sector accomplishes important carbon emission reduction. Carbon capture is one of the most promising alternatives to achieve this aim. Moreover, if carbon utilization via power-to-gas is integrated with carbon capture, there could be a significant increase in the interest of this alternative in the iron and steel sector. This paper presents several simulations to integrate oxy-fuel processes and power-to-gas in a steel plant, and compares gas productions (coke oven gas, blast furnace gas, and blast oxygen furnace gas), energy requirements, and carbon reduction with a base case in order to obtain the technical feasibility of the proposals. Two different power-to-gas technology implementations were selected, together with the oxy blast furnace and the top gas recycling technologies. These integrations are based on three strategies: (i) converting the blast furnace (BF) process into an oxy-fuel process, (ii) recirculating blast furnace gas (BFG) back to the BF itself, and (iii) using a methanation process to generate CH4 and also introduce it to the BF. Applying these improvements to the steel industry, we achieved reductions in CO2 emissions of up to 8%, and reductions in coal fuel consumption of 12.8%. On the basis of the results, we are able to conclude that the energy required to achieve the above emission savings could be as low as 4.9 MJ/kg CO2 for the second implementation. These values highlight the importance of carrying out future research in the implementation of carbon capture and power-to-gas in the industrial sector.
Many countries have put in place, various legislations that govern air emission limits/pollutants from the industries. The common pollutants being monitored are Sulphur Oxides (SO x ), Nitrogen Oxides (NOx), Carbon Monoxide (CO), Carbon Dioxide (CO 2 ), Volatile Organic Compounds (VOC s ), particulate matters and dioxins. In Malaysia, the regulatory requirement aims to regulate emissions of air pollutants from industrial activities including oil and gas, power plants, waste fuel plants and asphalt mixing plants. One of the emission limits under Clean Air Regulation (CAR2014) is emission level for SO x should be less than 600 mg/m ³ (reference condition at 3 % of O 2 , 273 K, 101.3 kPa) whereby sum of SO 2 and SO 3 expressed as SO x . Excessive SO x emission can affect both health and the environment. Aligning with the regulation requirement, Group Technical Solution (GTS) under PETRONAS has embarked on assessment of technology solutions to meet the emission limit on SO x emission limit for thermal oxidizers which cover new and existing facilities. This paper describes on the work methodology and approach adopted during the assessment. The objective of the assessment is to determine the suitable process technology to reduce SO x emission in order to achieve the desired emission limit for flue gas at outlet stream of thermal oxidizer. Thorough evaluation was carried out based on proposal submission from various technology providers and Vendors. The selection criteria was developed and established. For existing thermal oxidizers, the assessment is more complex taking into consideration the nature of brownfield project and to ensure the proposed modification has minor impact to operability and maintainability of existing facilities. This study has successfully enabled identification of feasible process technologies such as Caustic Scrubber, Seawater Flue Gas Desulfurization and Ammonia based Desulfurization to meet the desired emission limit at thermal oxidizer outlet for Oil and Gas Industry and supporting environmental protection. The selected technology is varies based on plant/project specific requirement. Among main considerations are the by-product management, consumable and utility consumption as well as compatibility of the technology with existing plant on shutdown requirement.
Multiple noble metals-modified micrometric TiO2-based photocatalysts were prepared by a cheap and sustainable approach based on the use of metal-enriched wastewaters (Ag, Au, Pt) and used for the photodegradation of propionic acid (PA) and NOx under LED. Properly tuning the metal decoration step, the material's photoactivity was optimized. 0.1%Pt @Ag/TiO2 led to 60% PA removal, whereas the strong PA adsorption on the 0.1%Au @Ag/TiO2 surface caused a partial deactivation. In contrast, 0.1%Au @Ag/TiO2 showed the highest photoactivity in the NOx decomposition (90%) due to the high tolerance of Au to HNO3 produced on the catalyst surface.
With the introduction of innovative solutions aimed at reducing environmental impact and increasing internal combustion engine efficiency, water injection is
considered an interesting solution to decrease the risk of knock, reduce charge temperature and employ dilute combustion operation. It allows to use extreme
downsizing for engines with higher compression ratio as well as increased margins for optimal spark timing. The present work aims to explore the effects of applying
water injection on combustion and emissions in an optically accessible spark ignition engine fueled with commercial gasoline. For this study, the water mass is equal
to 30% of the gasoline mass, and is delivered through two injectors placed in the intake manifold. A 3D-CFD study is carried out using the G-equation turbulent
combustion model in a RANS framework, properly calibrated against available experimental data. Experimental and numerical results are compared in terms of OH
radical concentration obtained by UV emission spectroscopy and by CFD simulations, around the spark plug and in two regions of interest near the intake and exhaust valves. Furthermore, the 3D-CFD model allows to have more in-depth information on the processes inside the combustion chamber: in this context, an investigation on the mechanisms of soot formation was carried out, focusing on the effect of water injection on this phenomenon. The water injection produces a less homogenous distribution of the charge in the combustion chamber to such an extent that the flame struggles to reach the area close to the intake valves, leading to the production of a greater quantity of soot than in the case without water injection.
Herein, we employ an aerosol-assisted method (AA-CVD) to produce TiO2 on window glass and study how the process parameters affect their photocatalytic activity towards NOx (NO + NO2) remediation. A range of process parameters are explored to produce 50 unique TiO2 coatings with wide ranging physicochemical properties. The physicochemical properties were examined using X-ray diffraction (XRD), atomic force microscopy (AFM), UV–visible transmission spectroscopy and transient absorption spectroscopy (TAS), and the photocatalytic activity towards NO gas was measured using protocol akin to the ISO (22197-1:2016). The most active sample showed an NO removal of ∼14.4 ± 1.7 % and NOx removal of ∼5.4 ± 0.77 %, which was ∼40 and ∼25 times higher than that of a commercially available self-cleaning window. The links between the process parameters, physicochemical properties and photocatalytic activity were studied in depth, where it was seen that the three most influential physicochemical properties on the observed activity were surface roughness, charge carrier population and charge carrier lifetime. Therefore, we recommend that these properties be targeted in the rational design of more active coatings for applications in photocatalytic NOx remediation.
Background
Exposure to fine particulate matter (PM2.5) is associated with adverse health outcomes but communities are not randomly exposed to PM2.5. Previous cross-sectional environmental injustice analyses in Canada found disproportionately higher exposure to PM2.5 in low-income populations, visible minorities and immigrants. Beyond static surveillance, it is also important to evaluate how changes in PM2.5 exposure over time may differentially impact disadvantaged communities. We examine whether communities with different sociodemographic characteristics benefited equitably from the overall decreases in ambient concentrations of PM2.5 from 2001 to 2016 in Canada.
Methods
We derived census tract level estimates of average annual PM2.5 using validated satellite-based estimations of annual average PM2.5 concentration surfaces. We investigated how the spatial distribution of PM2.5 has evolved over 15 years (2001–2016) by comparing absolute values and rank percentiles of census tract level annual average PM2.5 concentrations in 2001 and 2016. Using decennial census data and multivariable linear regression, we determined if sociodemographic characteristics are associated with changes in exposure to PM2.5, accounting for geographic boundary changes between census periods.
Results
Overall, ambient PM2.5 concentrations decreased from 2001 (median of 9.1 μg/m³) to 2016 (median of 6.4 μg/m³), with varying provincial patterns. Across communities, ranked census tract specific PM2.5 in 2001 and in 2016 are highly correlated (Spearman's rho = 0.75). We found that, on average and accounting for provincial differences and baseline PM2.5, communities with greater density of aboriginal population, lower education, higher shelter-cost-to-income ratio, unemployment or lower income experienced smaller absolute decreases in PM2.5 from 2001 to 2016.
Conclusions
Identifying sociodemographic groups that benefit least from decreasing exposure to PM2.5 highlights the need to consider environmental injustice when designing or revising air pollution policies.
Great interest has been directed toward developing catalytic desulfurization and denitrification to remove toxic or environmentally harmful gases before atmospheric emission. The burning of fossil fuels produces sulfur dioxide (SO2) and nitrogen oxides (NOX). The most cost-effective technologies for reducing SOx and NOx emissions are imperative to mitigate greenhouse gas emissions produced by burning fossil fuels. A huge number of the research paper was published on greenhouse gas mitigation technology over the past two decades, which demonstrates both its importance and its rapid advancement. The various interested research communities would benefit greatly from a review covering key features of new and advanced SOx/NOx mitigation techniques. Thus, the leading SOx and NOx mitigation technologies available for emission and cleaning control of coal-fired power plant flue gases using novel materials have been reviewed in this study. Various physical and chemical properties in the solid catalytic desulfurization and denitrification process, specifically the structure and active functional groups as well as the stability of the catalyst were highlighted. Research directions for overcoming the challenges involved in SOx and NOx mitigation using solid catalysts/sorbents interface adsorption were suggested. Then the results are clear and compelling with reducing SOx and NOx emissions to mitigate greenhouse gas emissions which will contribute to the practical value of scientific knowledge.
Biomass is considered a renewable and cleaner energy source alternative to fossil fuels. In recent years, industrial biomass boilers have been rapidly developed and widely used in the industrial field. This work makes a review on the fuel types used in industrial biomass boilers, the fuel characteristics and the characteristics of air pollutants emitted from the combustion of industrial biomass boilers and other contents in different studies. However, the existing research still has many deficiencies. In the future, further research on biomass fuel, industrial biomass boiler combustion process and the pollutants emitted by industrial biomass boiler combustion, especially the carbonaceous aerosol emitted by industrial biomass boiler and carbonaceous aerosol optical properties still need to be made. At the same time, the potential harm of carbonaceous aerosols emitted from industrial biomass boiler sources to human health and climate change needs to be studied in depth. This review provides a scientific basis for the accurate evaluation of industrial biomass boilers and the effective prevention and control of various pollutants of industrial biomass boilers.
Air pollution and climate issues are becoming serious, and particularly NOx cause acid rain, ozone hole and disease of respiratory system for humans, which mainly come from automobile and industrial exhaust emissions. Selective catalyst reduction (SCR) with NH3 as reducing agent is widely employed to eliminate NOx, and the selection of catalyst has a decisive effect in the final conversion. The modification methods of catalysts, such as addition of second metal, replacement of support, optimization of structure, pretreatment and post-treatment are systematically reviewed. For zeolite catalysts, the reaction mechanism and SO2 poisoning theory are analyzed. In addition, effects of catalyst parameters on denitrification efficiency are summarized, including Si/Al ratio, Cu or Fe loading, specific surface area, coordination structure and calcination temperature. Effects of spatial structure of spinel and perovskite catalysts on catalytic effect are analyzed, and the performance of catalysts with different components is compared. Finally, the current problems of catalyst research are summarized and the development of NH3-SCR technology are prospected.
According to World Health Organization (WHO) survey, air pollution has become the major reason of several fatal diseases, which had led to the death of 7 million people around the globe. The 9 people out of 10 breathe air, which exceeds WHO recommendations. Several strategies are in practice to reduce the emission of pollutants into the air, and also strict industrial, scientific, and health recommendations to use sustainable green technologies to reduce the emission of contaminants into the air. Photocatalysis technology recently has been raised as a green technology to be in practice towards the removal of air pollutants. The scientific community has passed a long pathway to develop such technology from the material, and reactor points of view. Many classes of photoactive materials have been suggested to achieve such a target. In this context, the contribution of conjugated polymers (CPs), and their modification with some common inorganic semiconductors as novel photocatalysts, has never been addressed in literature till now for said application, and is critically evaluated in this review. As we know that CPs have unique characteristics compared to inorganic semiconductors, because of their conductivity, excellent light response, good sorption ability, better redox charge generation, and separation along with a delocalized π-electrons system. The advances in photocatalytic removal/reduction of three primary air-polluting compounds such as CO2, NOX, and VOCs using CPs based photocatalysts are discussed in detail. Furthermore, the synergetic effects, obtained in CPs after combining with inorganic semiconductors are also comprehensively summarized in this review. However, such a combined system, on to better charges generation and separation, may make the Adsorb & Shuttle process into action, wherein, CPs may play the sorbing area. And, we hope that, the critical discussion on the further enhancement of photoactivity and future recommendations will open the doors for up-to-date technology transfer in modern research.
The co-removal of CO2 while removing SO2 and NOx from industrial flue gas has great potential of carbon emission reduction but related research is lacking. In this study, a wet scrubbing process with various urea solutions for desulfurization and denitrification was explored for the possibility of CO2 absorption. The results showed that the urea-additive solutions were efficient for NOx and SO2 abatement, but delivered < 10% CO2 absorption efficiency. The addition of Ca(OH)2 dramatically enhanced the CO2 absorption, remained the desulfurization efficiency, unfortunately restricted the denitrification efficiency. Among various operating parameters, pH of solution played a determining role during the absorption. The contradictory pH demands of CO2 absorption and denitrification were observed and discussed in detail. A higher pH of solution than 10 was favorable for CO2 absorption, while the oxidizing of NO to NO2, NO2⁻ or NO3⁻ by NaClO2 was inhibited in this condition. When 7 < pH < 10, it was favorable for the conversion and absorption of NO and NOx. However, the conversion of HCO3⁻to CO3²⁻ was significantly inhibited, hence preventing the absorption of CO2. Large part of Ca(OH)2 became CaCO3 with a finer particle size, which covered the unreacted Ca(OH)2 surface after the reaction. Kinetic analysis showed that the CO2 absorption in urea-NaClO2Ca(OH)2 absorbent was controlled by chemical reaction in early stage, then by ash layer diffusion in later stage.
NOx emissions belong to the most critical gaseous emissions in thermal conversion of biomass and non-recyclable waste. Yet the role of air staging on NOx reduction is not fully understood in most combustion systems. This study investigates the effect of air staging on the NOx reduction in an industrial bubbling fluidized bed by means of a detailed kinetic mechanism and assuming gradual entrainment of flue gases (with NOx precursors) into the air jets. The computed data is compared to unique non-published experimental industrial-scale data, from a 107 MWth biomass-fired fluidized bed boiler. The air was staged via primary air (through the bed), and secondary and tertiary air jets with a high inlet velocity. NO, HCN and NH3 concentrations were measured inside the furnace at a depth of 1.8 m, below the secondary air jets, above the secondary air jets and above the tertiary air jets. The computed NOx values were in good agreement with the experimental values. Above the bed, the total NO + HCN + NH3 concentration was 1169 ppm. After the tertiary air staging the total NO + HCN + NH3 concentration was 76 ppm. The conversion of fixed nitrogen (NO + HCN + NH3) to N2 reached 65 % after the secondary air jets, and 90 % after the tertiary air jets. The study shows that exceptional reduction of NOx emissions can be achieved with air staging in this type of industrial combustion systems for biomass.
In this study, the performance of a large number of anionic (SDS, SLS, and SDBS), cationic (CTAB), and non-ionic (Triton X-100 and Tween 80) surfactants on the surface activity, emulsion size, and surface charge of five oil samples was investigated in aqueous solution with two different salinities, with the aid of interfacial tension (IFT) measurement, zeta potential, and dynamic light scattering (DLS) analysis. In addition, the most important parameters that can affect the IFT of crude oil/surfactant solutions (i.e. charge of the hydrophilic group and chain length of the hydrophobic hydrocarbon group of the surfactants and different characteristics of crude oil such as ˚API, acidity, weight percentage of the asphaltene and resin fractions, their aromaticity and polarity, and asphaltene stability parameter) were comprehensively analyzed. The results showed that IFT values, surface charge of the aggregates, and the size of microemulsions depend on the crude oil type, ionic strength, and type of surfactants, however, without any straightforward proportionality with the examined parameters. Among the considered surfactants, the cationic and non-ionic surfactant showed the lowest and highest dependency to the crude oil type, respectively. A paramount efficiency was obtained for CTAB cationic surfactant with the microemulsion size of 102 nm and surface charge at near isoelectric point (zeta potential of 3.5 mV).
Sulfur fixation technology for raw coal can reduce SO2 emission during coal combustion. A method combining microwave irradiation and ultrafine Ca(OH)2 slurry was proposed, where raw coal was pulverized to mix with the slurry, and then treated by microwave irradiation. For anthracite coal (sulfur content = 1.90 wt%) with particle size distributed in the range of 75–180 μm, the treatment fixed 67.98 % of the sulfur in coal ash. Results prove that there is a synergy between microwave irradiation and ultrafine Ca(OH)2 for coal pretreatment, and finer coal particles had higher fixation rate. Under the same treatment condition, the sulfur fixation rate was increased to 74.68 % by adding 1 mol/L NaOH. Applying more NaOH or less Ca(OH)2 both made the fixation rate decrease. The combined treatment was also applied to bituminous coal (sulfur content = 0.79 wt%), and a fixation rate of 87.93 % was obtained. A continuous pretreatment system was developed for practical utilization of the method. Coal treated by the system was made into honeycomb briquette and burnt in a domestic coal stove, where a sulfur fixation rate of 74.97 % was obtained, compared to that of 4.55 % from untreated coal briquette.
This study proposes a design and optimization framework for a membrane-integrated absorption CO2 capture process for a coal-fired power plant. A modeling framework was developed for the hybrid capture process. The design was made by considering different flow-rate distributions between the combustion and sweep air for the membrane, as well as series and parallel configurations in an integrated manner. Sensitivity analysis was performed to understand the impact of the ratio of the combustion air being fed to the membrane on the capture performance and its economics under a hybrid configuration. As a case study, a coal-fired power plant was selected to implement the membrane-integrated absorption CO2 capture process, which was simulated with Unisim® and MATLAB®. A techno-economic assessment was used to understand the capital investment and operating expenditure related to the capture process. Compared to a stand-alone absorption process, 4.73% energy savings could be identified with a hybrid series configuration, whereas the parallel configuration offered 6.11% savings in capital cost from the reduction in equipment size. Although economic benefits can be obtained from hybrid processes through the development of membrane performance, the hybrid processes considered in this work are marginally more expensive than a stand-alone absorption process.
This review discusses the cryogenic capture system from the perspective of constructing new cryogenic capture system structures, exploring the optimal system parameters, and analyzing the challenges faced by different cryogenic capture systems. The gas that needs to remove CO2 undergoes desulfurization, denitrification and dust removal treatment, which can effectively reduce impurities and remove, and ensure the progress of the subsequent carbon capture process. Among the cryogenic technologies of carbon capture, cryogenic distillation is restricted by the concentration of carbon dioxide (CO2) in the gas and cost, and it cannot be widely popularized. Cryogenic condensation offers a wide range of industrial applications because it may immediately liquefy CO2 for oil displacement. Currently, the most concerned cryogenic sublimation can capture low-concentration CO2 at a rate of 99.9% at 13.5 vol%, and energy consumption and annual investment costs can also be effectively reduced. In general, cryogenic CO2 capture technology provides remarkable cost and efficiency benefits compared with other carbon capture technologies. By 2030, China’s CO2 capture cost will be 13–57$/t, and it will be 3–19$/t in 2060. Combining fixed costs and operating costs, the total abatement cost is 65$/t CO2, which is similar to the cost of 54$/ton CO2 in Japan and 60–193$/t CO2 in Australia. By 2060, the carbon emission reduction ratio of carbon capture, utilization, and storage (CCUS) will account for about 10% of the total emission reduction, so the research on CCUS is very urgent. It must break through the extreme utilization of cold energy and energy consumption barriers as well as increase the efficiency of the system.
A dielectric barrier discharge (DBD) coupling MnCu/Ti oxidation and postpositioned wet electrostatic precipitator (WESP) system was built. The experimental results showed that WESP can significantly enhance the simultaneous conversion efficiency(ηC) of NO, SO2 and Hg⁰ by the DBD coupling MnCu/Ti reactor. The best simultaneous removal efficiency(ηR) of NO, SO2 and Hg⁰ reached 94.5%, 100% and 100%, respectively. The ratio of catalyst active component (Mn/Cu) and catalyst filling amount were optimized. The effects of catalyst active component ratio, filling amount, flue gas component and energy density (SED) on the ηC of NO, SO2 and Hg⁰ were determined. The effect of sodium humate (HA-Na) in the cleaning water on the ηR was also illustrated. Besides, we clarified the absorption mechanism and how WESP corona discharge oxidized NO, SO2 and Hg⁰, as well as the removal of NO2, SO2, and SO3 by HA-Na. Product analysis showed that NO2, SO2 and SO3 were converted into NO3⁻ and SO4²⁻, part of HgO was converted into Hg²⁺ in the cleaning water, and a small amount of Hg(NO3)2 and HgSO4 were converted into Hg²⁺, NO3⁻ and SO4²⁻.
Urban air quality is a major concern throughout the world. Reduction of environmentally harmful emissions is often a public good in a global context. Some advanced processes or technologies to reduce the pollution in our atmosphere have been introduced to tackle this issue and some have already been commercialized. Plasma-assisted air conditioners to decompose gaseous toxic compounds and TiO2 photocatalytic devices are examples of it. In the future more applications with more compact and enhanced materials are projected to be found. In this section we discuss two advanced processes thoroughly, namely, those of nonthermal plasma and photocatalysis. These two technologies have the same concept of employing the ions coming from the process to initiate the reaction. In some applications the utilization of these technologies could overcome the limitation of conventional thermal-based or adsorption-based techniques to treat air pollution.
Flue gas desulfurization technology for sulfur dioxide removal from exhausts of combustion processes is becoming more widespread as allowed emission levels keep getting lowered. Spray scrubbers have gained traction in coastal and maritime applications, where seawater can be used as a scrubbing liquid. Detailed numerical models are required for accurate replication of processes in these applications, with complex physical and chemical phenomena considered. Among them, mass transfer modeling between phases has proven to be particularly important for obtaining accurate simulation results. Present work investigates a new model for calculating liquid side mass transfer coefficient in falling droplets, which considers additional parameters such as surface renewal rate, Reynolds number, and droplet diameter, compared to simplified and more common approaches. Initial modelling was performed on a single droplet level, followed by the implementation in the computational fluid dynamics framework and expansion to the entire spray. Desulfurization efficiencies for real cases modelled with the new approach were compared with the experimental data and the previously used penetration theory model results. The newly implemented model investigated the influence of operational parameters such as water and gas flow, sulfur dioxide concentration, droplet size, and distribution on desulfurization efficiency. The results obtained by the new model showed the expected trend of increased efficiency with the water flow increase, as well as greater sensitivity to operational conditions in different cases. Furthermore, compared to the previously used model, the present work more accurately replicated removal efficiencies in simulations of seawater spray scrubber applications, which is beneficial in designing new and more efficient equipment.
Fine particulate matters emitted from the industrial flue gas are the primary reason for the serious haze problem. The agglomeration has been proven an effective method to improve fine particle removal efficiency, but the movement characteristics in the process and their effects on the agglomeration are unclear. In this study, the agglomeration and the underlying mechanisms in the various electric fields were investigated. The results showed that the removal efficiency of fine particles can reach near 80% under the coupling effect of turbulence and cross discharge electrode, and the particle size can be increased by 30% simultaneously. The electric field intensity with cross electrode approached 650,000 V/m and higher than another three conventional electrodes with 60,000–200,000 V/m. The residence time of fine particle was extended to 0.2 s in the electric field with cross electrodes, and the deviate distance from the discharge electrode was nearly 3 times than other electrodes. The longer residence time and the more disordered movements can make fine particles carry more charge amounts and have more opportunities to finish coagulations. This study discussed the charged particles movement characteristics under the electric fields coupling with turbulence, and explored the further effects on the agglomeration and removal of fine particles. It’s designed to provide the guidance for the setting and improvement of electric fields in the dust removal equipment.
Aiming at improving the capture performance of internal vortex electrostatic cyclone precipitator (ECP), a theoretical model with mechanics-electric-magnetic coupling was established, the collection efficiency of magnetic confinement ECP under different working voltages was simulated, and the influence of magnetic flux intensity on the removal performance of submicron particles was explored. Results show that the number of particles escaped from the cyclone is greatly reduced after the introduction of magnetic field and electric field, indicating that charging effect and magnetic confinement are more conductive to trap submicron particles in the internal vortex ECP. The lower the working voltage is, the worse the charging lifting effect is, but the stronger the magnetic confinement characteristics are. Furthermore, the contributions of charging effect to collection efficiency and magnetic confinement characteristics are more obvious at a weaker magnetic flux density. The research results can provide a practical new idea for the innovative design of ECP.
Flue gas emission from combustion of fossil fuel is a growing environmental concern. In this study the effect of flue gas recirculation and Fe(II)EDTA addition on CO2 and NO removal from flue gas was explored in a biofilter. The effect of SO2 on CO2 and NOx removal efficiencies were also studied herein. The optimal removal efficiencies of CO2 (88.1%) and NO (85.8%) were achieved with the flue gas recirculation of 2:1. The presence of SO2 showed little impact on CO2 or NO removal while induced the decline of NO removal. The addition of Fe(II)EDTA clearly enhanced NO removal (~85%). The Illumina sequencing results showed that abundant sulfur-associated bacteria (Desulfobulbus, Desulfococcus, Sulfurovum, Chlorobium), nitrogen-associated bacteria (Thauera), fermentative bacteria (Longilinea and Anaerovorax), and various iron-reducing bacteria (Geobacter) were detected in the biofilter with Fe(II)EDTA addition. The synergistic effect of denitrifying/iron-reducing bacteria dedicated to the sustainable NO removal.
A cascade-arch-firing low-NOx and high-burnout configuration (CLHC) was developed as a solution for a 600 MWe W-shaped flame furnace suffering from poor burnout under ultra-low NOx combustion conditions. Under the comprehensive low-NOx combustion conditions regulated by the CLHC, overfire air (OFA) was first positioned at the furnace throat in a uniformly flattening OFA port form along the furnace breadth direction. In order to disclose the OFA angle’s effect on the furnace performance and meanwhile establish an appropriate angle for the OFA with the above original designs, the in-furnace flow field, coal combustion, and NOx emissions were evaluated at various OFA angles of θ = 10°, 20°, 25°, 30°, and 35°. Increasing θ only changed a little the symmetry of flow field and combustion morphology, i.e., the symmetry generally deteriorating first and then improving. The OFA penetration in the furnace throat zone initially increased but then worsen as θ increased. In the upper furnace strongly affected by OFA, gas temperatures, high-temperature zone area, and levels of O2 and CO all descended first and then increased with θ, while NO generally undergone an increase-to-decrease trend. Trends of furnace outlet’s performance indexes with θ showed that the residual O2 and CO emission generally decreased first and then increased, NOx emissions initially increased but then decreased, while carbon in fly ash undergone an increase-to-decrease trend prior to an increase at θ = 35°. In view of the above findings and the gained optimal low-NOx and high-burnout performance (NOx emissions of 667 mg/m³ at 6% O2 and carbon in fly ash of 5.31%), θ = 30° was taken as an appropriate OFA angle for the CLHC furnace. Compared with a currently advanced low-NOx combustion art, the CLHC reduced further NOx emissions by 26.3% while remained a high burnout achievement.
Due to the energy crisis and pollution caused by fossil fuels, the development of renewable fuels is an increasing demand to meet energy needs. Biodiesel fuel, which results from the transesterification process between vegetable or animal oils and alcohols, has a high potential to replace diesel fuels. However, the conventional transesterification processes are costly, time-consuming, and inefficient. Many researchers have accomplished a lot of researches about novel intensification methods to improve the yield of biodiesel production. Therefore, many researchers have considered strong electric fields an advanced molecular decomposition process in recent years. The present study provides an overview of different non-thermal plasma reactors reported in the transesterification process. Also, the effect of design and various operational parameters on energy efficiency has been investigated. The data reported in this study can optimize non-thermal plasma reactors and develop new reactor systems.
Semi-dry circulating fluidized bed flue gas desulfurization(CFB-FGD) is a major industrial FGD technology. Assuming that only one desulfurizer particle is wrapped in each droplet for mass transfer and dissolution, this study proposed a two-film theory-based simplified desulfurization model, with which CFB desulfurization was performed. After model verification, this study simulated the hydrodynamics and desulfurization reaction characteristics and explored the effects of inlet SO2 concentration(A), gas velocity(B), circulating particle mass flux(C), and jet water volumetric flux(D) on the desulfurization efficiency. Simulation results coupling with response surface methodology (RSM) analysis could not only quantitatively reflect the effect degree of a single variable but also apply to the interaction between parameters, thus determining the optimal parameters. RSM results showed that D and CD were the independent and interaction parameters, respectively, that most significantly affected desulfurization efficiency. The simulation under the optimal operating parameters showed that the desulfurization efficiency was greatly improved, reaching 99.69%.
Carbon capture and utilization (CCU) is an emerging technology with commercial potential to convert atmospheric carbon dioxide (CO2) into net zero or negative emission products. In microalgae-based CCU, microalgae utilize CO2 and sunlight to generate biomass for commercial applications. This paper reviews the current state of microalgal culture development for CCU and highlights its potential contribution to addressing climate change challenges. Current microalgal culture systems have not been designed for high throughput biomass growth and carbon capture. Raceways, high-rate algal ponds, and photobioreactors are the most widely used for microalgal cultivation at a large-scale. The limitations of these systems are related to microalgal growth requirements. Ponds are operated at narrow depth to ensure sufficient light distribution and thus need a large land surface. CO2 gas needs to be in a dissolved form for efficient utilization by microalgae. Innovative system designs to achieve optimized distribution of light, nutrient, and CO2 utilization for enhanced biomass production are crucial to achieve large-scale CO2 capture by microalgae. Data corroborated in this review highlights several innovative techniques to deliver CO2 effectively and enhance light illumination to microalgal cells. Submerged and internal illuminations can enhance light distribution without compromising culture volume and land requirements. CO2 delivery technique selections mainly depend on CO2 sources. The carbonation column appears to be the best option regarding efficiency, easy operation, and simple design. The downstream processes of microalgal culture (i.e. harvesting, biomass utilization, and water reuse) are important to make microalgae-based CCU a significant contribution to global carbon mitigation solutions.
This review summarizes the characteristics, preparation methods, modification methods, and application of MOFs for CO 2 capture from post-combustion coal-fired flue gas, and machine learning used in the development and screening of MOFs.
Electrochemical removal of nitrogen oxides (NOx) by perovskite electrodes is a promising method due to its low cost, simple operation and no secondary pollution. In this study, a series of La0.8Sr0.2Mn1-xCuxO3 (x = 0, 0.05, 0.1 and 0.15) perovskites are fabricated as the improved electrodes of solid electrolyte cells (SECs) for NOx removal and the effects of Cu doping are investigated systematacially. Multiple characterization methods are carried out to analyze the physicochemical properties of perovskites firstly. Then the performances of cells based on various perovskites are evaluated by the measurements of electrochemical properties and NOx conversions. The results show that the Cu-doped electrode has more surface oxygen vacancies and a better redox property, thus having a higher NOx conversion and smaller polarization resistance. The electrode based on La0.8Sr0.2Mn0.9Cu0.1O3 has the maximum 70.8% NOx conversion and the lowest 36.3 Ω cm² Rp value in the atmosphere of 1000 ppm NO at 700 °C. First-principle calculation reveals that the Cu-doped electrode is easier to form surface oxygen vacancy, while the surface oxygen vacancy plays an important role on electron transfer between electrode and NOx molecule. This study not only provides a new strategy to enhance the electrode performance for NOx removal in SECs but reveals the fundamental effect of Cu doping on the properties of La0.8Sr0.2MnO3 perovskites.
Fine particles emitted from coal-fired power plant is one of the main sources in China, causing serious harm to the atmospheric environment and human health. By promoting the fine particles to form larger aggregates, chemical agglomeration technology is more beneficial for fine particles to be captured by electrostatic precipitator (ESP). The experimental results showed that the concentration and particle size of fly ash particles were significantly enhanced after the addition of sesbania gum (SBG) and styrene-butadiene emulsion (SBE), and the total dust removal efficiency was up to 89.45% and 91.05%. Moreover, as the surfactant (T-100) was added, the removal efficiency could be further increased to 93.58% and 94.42%. Simultaneous, the contact angle of the complex solution formed by surfactant T-100 and 0.1% SBE, which reached the lowest value of 23.6°, showed better wetting performance. The SEM-EDS results suggested that the fine particles were formed new larger aggregate with a size larger than 10 μm. Simultaneous, the surface of fly ash particles was covered by an organic layer and further adhered to some submicron fine particles. The result has useful guidelines in future applications for optimizing operating parameters of chemical agglomeration in coal-fired power plants.
Since pollen is a major cause of allergies, collecting it from the environment seems to be beneficial. In this study, a new electro cyclone is proposed and simulated for collecting pollen from indoor environments. In this cyclone, an electrode is added to a traditional cyclone to apply additional force to particles that have already been pre-charged. The obtained results showed an increase of 14, 33 and 53 (%) in separation efficiency for pollen particle sizes of 10, 8 and 6 µm. Moreover, at lower inlet velocity, high electrostatic voltage enhances the efficiency, with the effect being more noticeable on finer particles. The validity of the simulation results was confirmed by comparing it with experimental and simulation findings of our previous study. It is also concluded that small electro cyclone systems are more efficient in removing fine particles from various gas streams.
Heterogeneous agglomeration (HA) is a very potential technology for coal-fired flue gas treatment. In this paper, the distribution and migration mechanisms of trace elements (TEs) such as Se, As and Pb in CFPPs were studied on a 30,000 m³/hr pilot-scale experimental platform. The influences of HA on the removal efficiency of gaseous and particulate TEs were well analyzed. The results showed that Se, As and Pb were enriched in fly ash, and their sensitivity to particle size is quite different. The content of Se was the highest in PM1, reaching 193.04 mg/kg at the electrostatic precipitator (ESP) outlet. The average particle size of the total dust before ESP increased significantly from 21.686 to 62.612 μm after injecting the heterogeneous agglomeration adsorbent, conducive to its further removal by ESP. In addition, the concentrations of gaseous Se, As and Pb in the flue gas decreased after adsorbent spray, and accordingly, their contents in the hierarchical particles increased, indicating that the adsorbent could effectively promote the adsorption of gaseous trace elements in fly ash and reduce the possibility of their escape to the atmosphere. Total concentrations of Se, As and Pb emitted by wet flue gas desulfurization (WFGD) are 0.223, 0.668 and 0.076 μg/m³, which decreased by 59.98%, 47.69% and 90.71%, respectively. Finally, a possible HA mechanism model was proposed, where chemical adsorption, physical condensation and collision agglomeration of gaseous TEs and fine particles with adsorbent droplets occurred to form larger agglomerates.
Sulfuric pollutants (SO2, SO3/sulfuric acid mist, sulfate, etc.) generated in coal-fired power plants (CFPPs) have been receiving more and more attention due to their adverse effects on the operation of power plant and environment. In order to abate air pollutants including sulfur (S) substance in flue gas, ultra-low emission (ULE) control technology was exploited to collaboratively capture these pollutants by using air pollutants control devices (APCDs), while S present in different occurrence in coal and various chemical speciation in flue gas when passing through APCDs. Therefore, it is necessary to clarify the transition and fate of S from in coal pre-combustion to in flue gas after APCDs. This paper reviews the transformation of S in the sequence of flowing in to flowing out in typical ULE-CFPPs, including the basic principles, influencing factors and recent studies on S pollutants generation, transformation and control. Firstly, the occurrence of S in coal and transition mechanism of S in boiler combustion are analyzed. Then, the mechanism and influencing factors of S substances deposited on heat recovery device, selective catalytic reduction (SCR), electrostatic precipitator (ESP), wet flue gas desulfurization (WFGD) and wet electrostatic precipitator (WESP) are discussed, and the influence of different S on the operation performance of each device is also discussed. Furthermore, the factors affecting the removal efficiency of S in APCDs are analyzed, and some suggestions are put forward for the optimal operation of APCDs.
Selective catalytic reduction is a common technology to control nitrogen oxides (NOx) in coal-fired industries, diesel engines, etc., among which, selective catalytic reduction of NOx by NH3 (NH3-SCR) has been commercially applied. However, its drawbacks such as the ammonia slipping, air heater fouling, catalyst poisoning, high investment and cost of operating have stimulated the development of new-type DeNOx technology. Nowadays, selective catalytic reduction with H2 (H2-SCR) has been regarded as a promising DeNOx technology. This review begins with the reaction mechanism of H2-SCR and then the noble metal SCR catalysts (Pt-based and Pd-based ones) and the non-noble metal catalysts for NOx removal are reviewed. Then, the effects of different preparation methods and different supports for H2-SCR performance are discussed. What follows is the homogeneous reactions of H2-SCR catalysts with O2, H2, H2O, SO2, CO, CO2, etc. And the recent progress of SCR mechanism by DFT calculations is summarized. Finally, the challenges and prospects for H2-SCR catalysts with the corresponding effective strategies are proposed. Hopefully, this article may provide insights into the gap between the newly developed H2-SCR catalysts and the practical demand in NOx removal, thus promoting their future commercial application.
For a domestic 350 MW coal-fired power plant, the effect of heterogeneous agglomeration technology on the migration and emission of three trace elements of arsenic, selenium and lead in tail flue gas was studied. The results show that heterogeneous agglomeration technology can promote the attachment of gaseous harmful trace elements to particulate matter effectively. The reduction rates of gaseous As, Se and Pb concentrations at the ESP outlet were 24.10%, 61.08%, and 70.38%, respectively. Under the synergistic effect of ESP, more As, Se, and Pb are enriched in fly ash, and the concentration of As, Se, and Pb in fine particles below 10 μm at the ESP outlet is reduced by 54.48%, 56.47%, and 75.17%, respectively. In addition, after spraying the agglomerating agent, the final As, Se, and Pb concentrations in the atmosphere were 1.29 μg/m³, 2.01 μg/m³, and 1.12 μg/m³, which were far lower than those of the relevant EPA emission limits.
Hydrate-based CO2 separation technology is limited by complex formation conditions and low separation efficiency, makes it temporarily unable to realize commercial application. In this review, according to the superiority of additives in strengthening hydrate formation, the effects of different additives on the thermodynamics-kinetics of hydrate formation were systematically summarized, and the strengthening mechanism was further elaborated from the perspectives of hydrate structure change and gas selectivity. Among them, quaternary ammonium salt is more environmentally friendly, and the separation factor reached 37 with TBAF, more than 90 mol% CO2 captured by the two-stage hydrate + membrane separation method. In addition, based on the characteristics of nanoparticles in enhancing heat and mass transfer, the impact of nanoparticles on the formation of CO2 hydrate was summarized, which provided a new idea for the research of additives. More importantly, the effects of experimental conditions and process flow on separation efficiency were also summarized. Energy analysis showed that the use of thermodynamic additives significantly reduced the investment cost of the system by more than 50%. However, higher hydrate formation heat leads to higher energy consumption, and the presence of kinetic additives improves significantly, emphasizing the urgency of developing more stable and lower formation heat thermodynamic additives and exploring the effect of mixed additives on commercial applications. At present, stirring methods were mostly used to strengthen hydrate formation with higher energy consumption. Future research should also strive to carry out experimental measurements under static conditions, and constantly optimize the reaction vessel and process.