Coal-fired Power Plants In China Research Articles

Spatial autocorrelation analysis of the environmental efficiency of coal-fired power plants in China

Spatial autocorrelation analysis of the environmental efficiency of coal-fired power plants in China

Study on the condensable particulate matter removal characteristics of air pollution control devices in a Chinese ultra-low emission coal-fired generating unit

Condensable particulate matter (CPM) belongs to PM25. In addition, it is one of PM2.5 main contributors. But CPM emissions are often overlooked in coal-fired power plants. As a result, this paper studies the removal characteristics of (CPM) from air pollution control devices (APCDs) in a Chinese ultra-low emission coal-fired generating unit. The quality and content of flue gas particles, including CPM and filterable particulate matter (FPM), were measured at four points: the selective catalytic reduction (SCR) input, air preheater (APH) inlet, electric precipitator (ESP) outlet, and wet flue gas desulphurization (WFGD) outlet. The removal characteristics of each APCD were studied. Within the scope of this study, it is found that: ® CPM emission concentration accounts for 94.9% of total particle emission concentration, and is higher than the ultra-low particulate matter outflow guidelines for coal-fired power plants in China; ©WFGD has the highest CPM inorganic component removal radio of 97.02%, and ESP has the highest CPM organic component removal radio of 58.46%, among APCDs; ©SO4 2−, NH4 +, F−, and Cl− are the most abundant water-soluble ions in CPM.

Applicability of coal slag for application as packed bed thermal energy storage materials

Refractory materials are considered as the most suitable high-temperature sensible heat storage materials due to their excellent thermo-mechanical resistance and superior thermophysical properties. Unfortunately, refractories are usually too expensive. To reduce the cost of energy storage materials, the recycling of refractory industrial solid wastes into storage materials is becoming increasingly prevalent. The paper innovatively proposes to use the slags from a liquid slagging furnace of a coal-fired power plant in China as packed bed sensible heat energy storage materials. This paper characterizes the chemical compositions and thermophysical properties of three typical coal slags (Fukang coal slag, Fukang coal granulated slag, Hongshaquan coal granulated slag) and evaluates their potentials as storage materials. The results show that the three kinds of coal slags have good thermophysical properties. At 380 °C, the energy storage densities per unit volume of the three materials are 1037 MJ/m3, 986 MJ/m3 and 920 MJ/m3, respectively. Fukang coal slag has good thermal stability and durability and can be directly used for ultra-high temperature energy storage at 1000 °C. Due to the low crystallization degree, the two granulated slags have poor thermal durabilities and need to be processed at high temperatures before using them for energy storage applications.

Suggestion on further strengthening ultra-low emission standards for PM emission from coal-fired power plants in China

China has established the largest clean coal-fired power generation system in the world by accomplishing the technological transformation of coal-fired power plants (CFPPs) to achieve ultra-low emission. The potential for further particulate matter (PM) emission reduction to achieve near-zero emission for CFPPs has become a hotspot issue. In this study, PM emission from some ultra-low emission CFPPs adopting advanced air pollutant control technologies in China was reviewed. The results revealed that the average filterable particulate matter (FPM) concentration, measured as the total particulate matter (TPM) according to the current national monitoring standard, was (1.67±0.86) mg/m3, which could fully achieve the ultra-low emission standard for key regions (5 mg/m3), but that achieving the near-zero emission standard was difficult (1 mg/m3). However, the condensable particulate matter (CPM), with an average concentration of (1.06±1.28) mg/m3, was generally ignored during monitoring, which led to about 38.7% underestimation of the TPM. Even considering both FPM and CPM, the TPM emission from current CFPPs would contribute to less than 5% of atmospheric PM2.5 concentrations in the key cities and regions in China. Therefore, further reduction in FPM emission proposed by the near-zero emission plan of CFPPs may have less environmental benefit than emission control of other anthropogenic sources. However, it is suggested that the management of CPM emission should be strengthened, and a national standard for CPM emission monitoring based on the indirect dilution method should be established for CFPPs. Those measurements are helpful for optimal operation of air pollutant control devices and continuously promoting further emission reduction.

The co-benefits of clean air and low-carbon policies on heavy metal emission reductions from coal-fired power plants in china

China has implemented a series of measures to address air pollutants and carbon emissions from coal-fired power plants, which can mitigate toxic heavy metal emissions simultaneously. By integrating plant-level information and energy activity data, we investigated the co-benefits of clean air and low-carbon policies by compiling a detailed inventory of historical heavy mental emissions (i.e., Hg, Pb, Cd, Cr, Ni, Sb, Mn, Co, Cu, Zn, As, and Se) for China's coal-fired power plants during 2005–2020. Several scenarios were then designed to assess the evolution of heavy metal emissions for each coal-fired power plant with consideration given to the coal washing rate, air pollution control devices, operational hours and lifetime. The total emissions decreased from 12.9 thousand tons in 2005 to 8.8 thousand tons in 2020, which was mainly due to the widely installation of upgraded end-of-pipe devices and the decommissioning of small and emission-intensive plants, especially in Sichuan, Jiangsu and Zhejiang. Scenario analysis shows that reducing the operational lifetime to 20 years is the most effective measure to reduce national HM emissions, but the effects differ widely between regions. This study provides insights for the precise co-control of both heavy metals and carbon emissions, which is highly important for meeting the requirements of the Minamata Convention and carbon neutrality.

Influence of Dry Sorbent Injection System on Emission Characteristics of Condensable Particulate Matter in Coal-fired Power Plant

To study the effect of dry sorbent injection (DSI) system on the emission characteristics of condensable particulate matter (CPM) in a 600MW unit of an ultra-low emission coal-fired power plant in China, the EPA Method 202A is used to sample the flue gas from its total exhaust. Through sample analysis, the CPM emission concentration and water-soluble ion composition corresponding to the two unit loads and whether the DSI is running are obtained. The results show that the use of DSI system reduces CPM emissions at 600MW and 300MW unit loads, and the CPM emission concentration is reduced by 32% and 9.7%, respectively. For the CPM reduction caused by DSI system under these two loads, SO4 2- and Cl− together contributed 65.7% and 87.3%, respectively. The DSI system achieves the removal of CPM mainly by removing the SO3 and HCl, which are gaseous precursors of SO4 2- and Cl− in CPM. At the same time, water-soluble ions are the main component of CPM. The analysis of its composition shows that the masses of NH4 +, Cl− and SO42- ions are relatively large, and they together account for 95.8%-96.8% of all water-soluble ions mass.

Increasing mercury risk of fly ash generated from coal-fired power plants in China

The trend in mercury (Hg) content of fly ash, the primary solid Hg waste from coal-fired power plants (CFPPs), has not been well evaluated in China. This study integrated a national sampling campaign, a literature survey, and model predictions to investigate the trend in Hg content of fly ash and associated output nationwide. The results demonstrated that Hg content of fly ash from both our campaign conducted in 2020 and the literature survey met the Weibull distribution. The best estimate for the distribution of Hg content in our campaign (401.4 µg/kg) was about two-fold higher than that from the literature survey (236.6 µg/kg). The increasing trend was mainly attributed to the increasing installation of advanced air pollution control devices (APCDs) in CFPPs. The total national Hg output by fly ash was estimated to be 217.7 tons (64.1−501.8 tons) currently. Regarding the disposal of fly ash, a total of 16.1 tons and 105.8 tons of Hg were re-emitted into the air and immobilized in materials, respectively. The increasing trend in the Hg content of fly ash suggested the need for more stringent requirements for the disposal of solid Hg waste from CFPPs in China.

Investigation on the ammonia emission characteristics in coal-fired power plants of China

The coal-fired power plants in China have basically completed the upgrade and transformation for the ultra-low emission, and the reduction in traditional pollutant emission is significant. However, excessive ammonia emission has become one of the major concerns due to its adverse effects on environmental protection facilities and atmospheric environment. In this paper, four typical coal-fired power plants which have completed the ultra-low emission retrofits were measured on site to investigate the whole process emission characteristics of ammonia. The ammonia in the flue gas was classified into the gaseous ammonia, the filterable ammonia or the total ammonia, based on different sampling systems. Besides, the ammonia in the captured fly ash, desulfurization slurry, desulfurization wastewater, and gypsum was also analyzed to provide a quantitative overview of ammonia emission. Results showed that there was only gaseous ammonia detected at the outlet of SCR devices. Most gaseous ammonia was converted into filterable ammonia when it passed through the air preheater. Filterable ammonia, the predominant form of ammonia that made up about 65% to 95% of the total ammonia, could be effectively captured by the dust removers, with over 80% of it being removed. Higher ammonia concentration was measured from the fly ash collected in the rear storehouses. The concentration of ammonia emitted at the WFGD outlet was less than 0.5 mg/Nm3, with no more than 0.3 mg/Nm3 being discharged after the further removal by WESP. Discharging with the captured fly ash was the main pathway for ammonia emission, which should be considered in the further pollution control in coal-fired power plants.

Ready-to-implement low-carbon retrofit of coal-fired power plants in China: Optimal scenarios selection based on sludge and photovoltaic utilization

Currently the flexible demand for high proportion penetration of renewable energy depends on coal-fired units (CFUs), and the large-scale phase-out of CFUs in a short time is not realistic in China. Due to urban expansion, approximately 458 Chinese coal-fired power plants (CFPPs) are now located in cities. Limited by space, urban CFUs face difficulty in becoming equipped with carbon capture and storage systems. This presents a sizeable challenge for the low-carbon transition of urban CFPPs and carbon neutral processes. Here, we present a ready-to-implement method to reduce the carbon emission of CFPPs in limited space: roof photovoltaic-assisted power generation combined with sludge co-combustion for coal-fired power generation systems (PVSCs). We also consider nonurban CFPPs with the method of roof photovoltaic-assisted power generation (PVs) only. Based on remaining life cycle analysis, we find that the PVSCs could save 28.47 Mt of coal, reduce CO2 emissions by 69.76 Mt, treat 125.70 Mt of sludge, and also generate 12.08 billion RMB worth of electricity revenue per year. In addition, our scenario analysis shows that PVSCs are more profitable when choosing an urban CFU with a remaining life of more than 12 years and while the sludge treatment subsidy is set at 100 RMB t−1. Under strict and lenient CFU decommissioning policies, CFUs with a remaining life of between 19 and 30 years and between 13 and 24 years should be selected for PVs, respectively. Thus, we conclude that PVSCs can not only generate economic benefits but also facilitate carbon reduction and solid waste treatment.

Utilization of desulfurization gypsum potentially impairs the efforts for reducing Hg emissions from coal-fired power plants in China

The thermal instability of most mercury (Hg) species in flue gas desulfurization (FGD) gypsum may lead to the release of large amounts of Hg into the atmosphere. In this study, gypsum samples were collected from 13 major coal-fired power plants (CFPPs) for evaluating the Hg thermal stability within a temperature range of 100–200 °C. Results indicated that the release ratio of Hg from FGD gypsum varied considerably among the CFPPs. Such significant differences were caused by different proportions of the major Hg compounds, especially of HgClx (HgCl2 and Hg2Cl2), in the FGD gypsum samples. The release ratio appeared extremely sensitive to changes in the treatment temperature and duration. Wallboard manufacturing and its use as cement retarder are the leading causes of Hg emission (corresponding to greater than 95% of the total) during FGD gypsum resource utilization. The total average Hg emitted due to FGD gypsum resource utilization in China in 2017 was estimated to be 11.42 tons (ranging between 2.15 and 38.35 tons), which accounted for about 23.8 % (ranging between 4.6 and 79.8%) of the stack Hg emissions from CFPPs in that year. The results of this study indicate that the resource utilization processes of FGD gypsum are important Hg emission sources and that they should be considered with care in future emission control policies.

Carbon efficiency and abatement cost of China's coal-fired power plants

In this paper, we propose a new model to investigate the carbon efficiency and carbon abatement cost of coal-fired power plants in China based on the directional distance function with endogenous directional vectors (DVs). We further decompose the change of carbon abatement cost into two contributing factors, i.e., input changes and technical change. The empirical analysis is based on a recent panel dataset comprising 616 Chinese coal-fired power plants from 2011 to 2012. The results show substantial potential for carbon performance improvement in China's coal-fired power plants, with higher carbon efficiency (CE) and lower carbon abatement cost (CAC) associated with non-state-owned enterprises. The decomposition analysis shows that the change in carbon abatement cost is mainly attributed to technical change. However, imposing DVs exogenously can get the opposite results and have a significant impact on the distributions of the estimated results. The findings of this paper provide new insights for better understanding the recent dynamics of the carbon performance of China's coal-fired power plants and have important policy implications.

Location-specific co-benefits of carbon emissions reduction from coal-fired power plants in China

Climate policies that achieve air quality co-benefits can better align developing countries’ national interests with global climate mitigation. Since the effects of air pollutants are highly dependent on source locations, spatially nuanced policies are crucial to maximizing the achievement of co-benefits. Using the coal power industry as a case study, this study presents an interdisciplinary approach to assessing facility level co-benefits at every specific source location in China. We find that co-benefits range from US$51-$278 per ton CO2 reduction nationwide and are highly heterogeneous spatially, with “hotspot” regions that should be the priority of emissions reduction policies, and that provinces should use different techno-economic strategies to reduce emissions. The location-specific co-benefit value plus a carbon price serves as a unified environmental indicator that enables policy makers to more accurately understand the social costs of electricity generation from coal burning and provides a scientific framework for geographically nuanced policymaking.

Post-combustion slipstream CO2-capture test facility at Jiangyou Power Plant, Sichuan, China: performance of a membrane separation module under dynamic power-plant operations

Abstract Membrane-based separation technologies have the potential to lower the cost of post-combustion CO2 capture from power-plant flue gases through reduced energy and capital costs relative to conventional solvent approaches. Studies have shown promise under controlled conditions, but there is a need for data on performance and reliability under field conditions. Coal-fired power plants in China operate in a dynamic manner, with increases and decreases in output causing changes in flue-gas composition. In this paper, we describe the first field test of a membrane-based post-combustion CO2-capture system connected to a dynamically operating power plant in China. We report the performance of a Membrane Technology Research, Inc. (MTR) PolarisTM membrane-based capture system over a range of plant operating loads ranging from 54% to 84% and conducted an operational stability test over a 168-h period during which the power plant was operating at an average load of 55%, but ramped as high as 79% and as low as 55%. Our results confirm the ability of a membrane capture system to operate effectively over a wide range of host-plant operating conditions, but also identity several issues related to plant integration, system control and resilience in the face of host-plant upsets that require attention as membrane separation systems move towards commercial use.

Ash fusion and mineral evolution during the co-firing of coal and municipal sewage sludge in power plants

By coupling the treatment of municipal sewage sludge (MSS) with large coal-fired units not only does it overcome the shortcomings of difficult combustion and the low calorific value of sludge, but it can also use the existing exhaust emission treatment devices of power plants to treat toxic gases and various pollutants discharged in the combustion process. It is a competent method for treating MSS, which has been more frequently used in coal-fired power plants in China in recent years. In this paper, raw coal, municipal sludge, fly ash and slag are sampled and analyzed from three full-scale power plants which are actually mixed with MSS. The melting characteristics and composition of ash obtained from raw coal and MSS at different mixing ratios and various temperatures are analyzed by ash fusion point determination meters, XRF and XRD, and the mineral evolution is simulated by Factsage. The results of the lab-scale study indicate that the ash melting characteristic temperature of MSS in three power plants is obviously lower than that of pulverized coal, and with an increase in the mixing ratio, the ash melting characteristic temperature of the mixed samples gradually decreases. The higher iron content in MSS is the main reason why the ash melting characteristic temperature of MSS and mixed samples is lower than that of coal, and hematite formed from the process is a common fluxing mineral. The analysis results for the slag and ash from three full-scale power plants co-firing MSS indicate that the main composition of slag and ash is mullite, and that co-firing MSS has little effect on the ash melting characteristics. The experimental results can provide reference for practical coal-fired power plants in reasonable mixing sludge, avoiding slagging and improving boiler efficiency.

Simulating optimal development of clean coal-fired power generation for collaborative reduction of air pollutant and CO2 emissions

Over 60% of electricity was produced by coal-fired power plants in China. Apart from accelerating penetration of non-fossil power, clean coal-fired power generation (CCFPG) needs to be largely impelled. The economic and environmental impacts of expanded development of CCFPG industry within the socioeconomic system remain unclear. We develop an integrated input-output model to explore an optimal combination of CCFPG technologies subject to emission constraints and maximization of gross regional production. The trends in CCFPG industries’ outputs and power generation, as well as reductions of NO x , SO 2 , PM 2.5 and CO 2 emissions in Jilin Province during 2021–2030 are simulated in seven scenarios. We found that the timing and scale of development of CCFPG technologies are mainly determined by costs, joint-removal efficiencies, and levels of emission constraints. When CO 2 emission constraint gets stricter, the production of integrated gasification combined cycle with carbon capture and storage will increase for larger CO 2 emission reduction. Industrialization of CCFPG technologies calls for additional investment and subsidies, which would induce reduced investment for some sectors and negative impact on the economy. The quantified economic and environmental impacts of introducing CCFPG technologies are expected to provide government with references for emission mitigation of coal-fired power generation industries.

Characteristics and potential ecological risks of heavy metal pollution in surface soil around coal-fired power plant

The concentrations of heavy metals (As, Cd, Cr, Cu, Hg, Mn, Pb and Zn) in surface soils in the area surrounding a coal-fired power plant in China were measured, the distribution characteristics of heavy metals in different wind directions were analyzed, and the pollution degree of heavy metal in soil was evaluated. The soil around the power plant is generally polluted by heavy metals, and the degree of pollution is heavy pollution and moderate pollution. The comprehensive potential ecological hazard index of heavy metals in the soil around the power plant was 155.09–293.04, and the potential ecological hazard was moderate or strong. Cd, Hg and As contributed more to RI than other heavy metals. The values of Nemerow index and potential ecological risk index are different among different directions and different distances from the power plant. Cd, Hg and As are the mainly contributors for the potential ecological risk. The results revealed that wind direction is important for the distribution of heavy metal around coal-fired power plant. The study can provide a theoretical basis for the prevention and management of soil heavy metal pollution around coal-fired power plant.

A Many-Objective Optimization for an Eco-Efficient Flue Gas Desulfurization Process Using a Surrogate-Assisted Evolutionary Algorithm

The flue gas desulfurization process in coal-fired power plants is energy and resource-intensive but the eco-efficiency of this process has scarcely been considered. Given the fluctuating unit load and complex desulfurization mechanism, optimizing the desulfurization system based on the traditional mechanistic model poses a great challenge. In this regard, the present study optimized the eco-efficiency from the perspective of operating data analysis. We formulated the issue of eco-efficiency improvement into a many-objective optimization problem. Considering the complexity between the system inputs and outputs and to further reduce the computational cost, we constructed a Kriging model and made a comparison between this model and the response surface methodology based on two accuracy metrics. This surrogate model was then incorporated into the NSGA-III algorithm to obtain the Pareto-optimal front. As this Pareto-optimal front provides multiple alternative operating options, we applied the TOPSIS to select the most appropriate alternative set of operating parameters. This approach was validated using the historical operation data from the desulfurization system at a coal-fired power plant in China with a 600 MW unit. The results indicated that the optimization would cause an improvement in the efficiency of desulfurization and energy efficiency but a slight increase in the consumption of limestone slurry. This study attempted to provide an effective operating strategy to enhance the eco-efficiency performance of desulfurization systems.

Environmental efficiency analysis of China's coal-fired power plants considering heterogeneity in power generation company groups

This study conducts an environmental efficiency analysis of 104 coal-fired power plants in China by simultaneously considering multiple undesirable outputs (CO2, SO2, NOx, and PM2.5 emissions) generated during the production process and the heterogeneity caused by differences between the five major power generation companies (Datang, Guodian, Huadian, Huaneng, and Power Investment). In the empirical study, slacks-based data envelopment analysis (DEA) was employed to investigate the “total” and individual CO2, SO2, NOx, and PM2.5 “specific” environmental inefficiency scores for each power plant. These scores allow us to identify which undesirable outputs are the main sources of total environmental inefficiency for each company and power plant. The results show that inefficient PM2.5 and SO2 emissions are the main sources of environmental inefficiency for many plants. Furthermore, a meta-frontier DEA decomposition framework is adopted to identify whether the source of total environmental inefficiency for each power plant is due to technological gaps between the five major power generation companies or managerial gaps within the same power generation company. The results imply that, in most cases, managerial gaps within the same power generation company account for a larger proportion of total environmental inefficiency for each power plant. These findings are used to provide comprehensive policy suggestions for government and corporate managers to improve the environmental efficiency of power plants.

Potential environmental risk of trace elements in fly ash and gypsum from ultra–low emission coal–fired power plants in China

The ultra–low emission retrofitting (ULE) in China's coal–fired power plants (CFPPs) enhances removal efficiencies of trace elements, which may increase their contents in fly ash and gypsum. However, their potential environmental risks in these wastes have been scarcely evaluated. Experiments indicated that the trace elements in fly ash and gypsum accounted for approximately 92.9–98.2% of the total outputs. Most trace elements in these wastes existed mainly as mobile/leachable forms, except for the Hg in fly ash (residual form). We comprehensively evaluated the potential environmental risks of trace elements in fly ash and gypsum from ULE CFPPs in China using a modified risk assessment approach that integrates a trace element enrichment model for waste, and chemical speciation datasets. We found that nationally, trace elements in gypsum represented low levels of potential risk, even after ULE. However, the potential moderate environmental risk of fly ash has aroused attention because of trace element pollution, where Hg and Cd contributed the major risks. The relatively high risks from fly ash are mainly distributed in Guangxi, Hunan and Hebei provinces. The disposal of fly ash in these areas should be given special attention in the future.

Developing effective CO2 and SO2 mitigation strategy based on marginal abatement costs of coal-fired power plants in China

This study proposes a novel analysis framework to investigate the CO2 and SO2 emission efficiency, emission reduction potential, and marginal abatement cost (MAC) of 316 coal-fired power plants in China. The comprehensive analysis framework is based on the combined approach of utilizing the directional output distance function (DODF) and parametric linear programming (PLP). The average emission efficiencies of CO2 and SO2 were 0.48 and 0.61, respectively, which indicates that China’s coal-fired power plants have a large potential to reduce CO2 and SO2 emissions, on average by 52% and 39%, respectively. In 2010, the average CO2 and SO2 emissions reduction potential for the 316 investigated power plants were 1,517 kt and 3,773 t, respectively. The average MAC prices for CO2 and SO2 were estimated to be 598 yuan/tonne and 22,401 yuan/tonne, respectively, indicating that the reduction of such emissions is very expensive. Furthermore, I formulated an optimization problem for maximizing CO2 and SO2 emission reductions under the governmental budget constraint. Solving this optimization problem yielded the total cost for the maximum reductions of CO2 and SO2 emissions, the maximum possible reductions for CO2 and SO2 emissions for each allocated budget scale, and the optimal budget allocation for each power plant at a given budget scale. I finally suggest effective mitigation strategies for CO2 and SO2 emissions generated from China’s coal-fired power plants.