Coal-fired Industrial Boilers Research Articles

Non-negligible environmental risks of typical hazardous trace elements in wastes from Chinese coal-fired industrial boilers

Coal-fired industrial boilers (CFIBs) that provide heat for industrial production operate to produce large quantities of wastes containing hazardous trace elements (HTEs), threatening the quality of the environment. Based on the established facility-level material flow inventory of five typical HTEs (Hg, As, Cd, Cr, and Pb) of Chinese CFIBs in 2020, we explored the enrichment characteristics and environmental risks of HTEs in wastes at the regional scale from the perspective of substance flow and enrichment levels. Results showed that the shares of HTEs entering the waste stream were 2.2–16.8 % higher in the focus regions of continuous improvement of air quality compared to the non-focus regions, explained by the higher synergistic control efficiencies of their air pollution control facilities (ACPFs), at 86.6–90.4 % (Hg), 98.6–99.1 % (As), 95.1–95.9 % (Cd), 93.2–94.8 % (Cr), and 97.1–98.0 % (Pb), respectively. In addition, the national averages of HTEs in slag, fly ash, and flue gas desulphurisation (FGD) were simulated to be 0.15–0.87 g/t, 3.25–18.44 g/t, 0.30–0.96 g/t, 19.76–70.11 g/t, and 15.85–73.74 for Hg, As, Cd, Cr, and Pb, respectively. Nationally, the integrated environmental risks of the five HTEs in slag, fly ash, and FGD residue exhibited Considerable, Very High, and Very High level of environmental risk, with the cumulative environmental risk indexes of 171, 317, and 281, respectively. Hg and Cd were the major contributors to the environmental risks of slag, fly ash, and FGD residue, with environmental risk contributions ranging from 23.8 to 82.3 % and 16.0 to 66.1 %, respectively. Results can provide data support for modelling the environmental release of HTEs from wastes and formulating control strategies for environmental management agencies.

Air quality and health benefits for different heating decarbonization pathways in China

The urgent need for decarbonization in China's heating system, comprised of approximately one hundred thousand boilers, is imperative to meet climate and clean air objectives. To formulate national and regional strategies, we developed an integrated model framework that combines a facility-level emission inventory, the Community Multiscale Air Quality (CMAQ) model, and the Global Exposure Mortality Model (GEMM). We then explore the air quality and health benefits of alternative heating decarbonization pathways, including the retirement of coal-fired industrial boilers (CFIBs) for replacement with grid-bound heat supply systems, coal-to-gas conversion, and coal-to-biomass conversion. The gas replacement pathway shows the greatest potential for reducing PM2.5 concentration by 2.8 (2.3–3.4) μg/m3 by 2060, avoiding 23,100 (19,600–26,500) premature deaths. In comparison, the biomass replacement pathway offers slightly lower environmental and health benefits, but is likely to reduce costs by approximately two-thirds. Provincially, optimal pathways vary – Xinjiang, Sichuan, and Chongqing favor coal-to-gas conversion, while Shandong, Henan, Hebei, Inner Mongolia, and Shanxi show promise in CFIBs retirement. Henan leads in environmental and health benefits. Liaoning, Heilongjiang, and Jilin, rich in biomass resources, present opportunities for coal-to-biomass conversion.

Spatiotemporal variation and inter-transport of atmospheric speciated mercury between Kaohsiung Harbor and neighboring urban areas

This study investigated the spatiotemporal variation, gas-particle partition, and source resolution of atmospheric speciation mercury (ASM) in Kaohsiung Harbor and neighboring Metro Kaohsiung. Four sampling sites were selected to determine the pollution characteristics and inter-transport of ASM between the port and urban areas. The yearly average GEM, GOM, and PBM concentrations were 7.13 ± 2.2 ng/m3, 331 ± 190 pg/m3, and 532 ± 301 pg/m3, respectively. Notably, GEM emerged as the predominant ASM species (85–94%), primarily originating from anthropogenic emissions from the harbor area and nearby industrial complex. The study revealed a distinct seasonal variation in ASM concentrations in the Kaohsiung Area in the following order: winter > fall > spring > summer. Concerning spatial distribution, ASM concentrations in the port areas were generally higher than those in the urban areas. This disparity was chiefly attributed to the influence of the prevailing winds, local sources, and atmospheric dispersion. Backward trajectory simulation revealed that polluted air masses blown from the northeast in winter and spring, moving along the western in-land part of Taiwan Island, were likely influenced by local sources and long-range transport (LRT). In summer, air pollutants originating from the south were likely transported from the coastal industrial sources. During fall, air masses blown from the western offshore waters transported air pollutants from Kaohsiung Harbor to neighboring Metro Kaohsiung. The results obtained from principle component analysis (PCA) indicated that primary sources in the port areas included ship emissions, vehicular exhausts, and nearby industrial complex, which align with the primary source factors identified by positive matrix factorization (PMF), which were mobile sources and coal-fired industrial boilers. Meanwhile, mobile sources and sulfur-containing fuel/waste combustion were identified as the primary sources in the urban areas.

Analysis of emission characteristics and driving forces of air pollutants and GHG from coal-fired industrial boilers in China

Coal burning is considered to be the main anthropogenic source of air pollutants, which can cause serious environmental pollution. As one of the important coal burning sources, coal-fired boilers have become the important challenges of the policy of “carbon peaking” and “carbon neutrality” of Chinese government. In this paper, the emission inventory of air pollutants (TSP, SO2, NOX, VOCs), and greenhouse gases (GHG, including CO2, CH4, N2O) from coal-fired industrial boilers (CFIB) from 2006 to 2020 are established by using the “bottom-up” emission factor method. Besides, Kaya identical equation and Logarithmic mean Divisia index (LMDI) model are used to quantify the driving forces of the changing tendency in pollutants emission based on five driving factors, which include pollution production coefficient (f), control technology level (β), economy (GOV), industrial energy intensity (e) and coal consumption structure of industrial boilers (s). Combined with existing relevant policies, the future emission tendency of air pollutants and GHG in 2025 and 2030 is projected. The result shows that policy adjustment has a significant impact on pollutant emission trends. In 2020, emissions of TSP, SO2, NOX, VOCs and GHG from CFIB in China are 679.5 kt, 644.7 kt, 603.9 kt, 40.7 kt and 4.4 × 105 kt CO2e, respectively. Control technology level is the main factor to the emission reduction of SO2 and TSP, which has caused a decrease of 4278.6 kt and 3337.3 kt in emissions of SO2 and TSP compared to those of 2006 respectively, while the influencing effect on NOX, GHG and VOCs was relatively weak. In addition, in the scenario of improved control technology, pollutant emissions could be reduced by 62.6%–94.9% until 2030.

Use of La-Co@NPC for Sulfite Oxidation and Arsenic Detoxification Removal for High-Quality Sulfur Resources Recovery in Desulfurization Process.

Ammonia desulfurization is a typical resource-recovery-type wet desulfurization process that is widely used in coal-fired industrial boilers. However, the sulfur recovery is limited by the low oxidation rate of byproduct (ammonium sulfite), leading to secondary SO2 pollution due to its easy decomposability. In addition, the high toxic arsenic trace substances coexisting in desulfurization liquids also reduce the quality of the final sulfate product, facing with high environmental toxicity. In this study, nitrogen-doped porous carbon coembedded with lanthanum and cobalt (La-Co@NPC) was fabricated with heterologous catalytic active sites (Co0) and adsorption sites (LaOCl) to achieve sulfite oxidation and the efficient removal of high toxic trace arsenic for the recovery of high-value ammonium sulfate from the desulfurization liquid. The La-Co@NPC/S(IV) catalytic system can generate numerous strongly oxidizing free radicals (·SO5- and ·O2-) for the sulfite oxidation on the Co0 site, as well as oxidative detoxification of As(III) into As(V). Subsequently, arsenic can be removed through chemical adsorption on LaOCl adsorption sites. By using the dual-functional La-Co@NPC at a concentration of 0.25 g/L, the rate of ammonium sulfite oxidation reached 0.107 mmol/L·s-1, the arsenic (1 mg/L) removal efficiency reached 92%, and the maximum adsorption capacity of As reached up to 123 mg/g. This study can give certain guiding significance to the functional material design and the coordinated control of multiple coal-fired pollutants in desulfurization for high-value recovery of sulfur resources.

Experimental study on NOx reduction performance by ammonia solution injection into the fuel-rich zone in a 75 t/h coal-fired industrial boiler

Industrial-scale trials of NOx reduction by ammonia solution injection into the fuel-rich zone were conducted in a 75 t/h corner-tangentially coal-fired boiler, and impacts of SOFA ratio, secondary air distribution modes, and ammonia solution injector configurations on the NOx reduction performance were discussed in detail. Results indicated that the waist air distribution mode and the increase in SOFA ratio could reduce the oxygen concentration in the reduction zone, which was conducive to the NOx reduction performance of injected ammonia solution. Ammonia solution injector configurations also had a remarkable influence on NOx reduction performance. Ammonia solution injected from injectors in the top layer and at four corners yielded lower NOx emissions than that in the bottom layer and on four walls, respectively. Meanwhile, more ammonia solution injectors in service were favorable for the reducing agent mixing with flue gas, thereby enhancing the NOx reduction performance. The lowest NOx emissions of 48 mg/m3 and a corresponding maximum NOx reduction efficiency of 86.09 % were achieved under the optimized conditions, i.e., 30 % SOFA ratio, the waist air distribution mode, and all 16 ammonia solution injectors in service. However, the boiler efficiency test indicated that the retrofit led to a reduction of 0.28 % in the boiler thermal efficiency simultaneously, necessitating further studies to mitigate the adverse effects.

Experimental study of gas-particle flow in the coal-fired industrial boiler applied radial air staging at variable over-fired air distributions

Radial air staging is an innovative method for reducing NOx emissions from coal-fired boilers compared to conventional axial air staging. However, an important issue in using this method is to set the over-fired air (OFA) distribution rationally to achieve good boiler performance. This paper aims to optimize the OFA distribution by evaluating important gas-particle (GP) parameters that influence the pulverized coal (PC) combustion performance. The GP flow experiment is conducted in a laboratory furnace model of a coal-fired boiler with different OFA distributions. The experimental results show that as RIO (Two-level OFA distribution ratio) changes from 0:1 to 1:0, the mixture of the OFA jet and airflow in the main combustion zone is advanced, which is conducive to PC burnout. Meanwhile, the size of the central recirculation zone decreases, resulting in poor PC ignition. It is worth noting that at RIO of 1:0, the central recirculation zone disappears at section y/d = 2.5, indicating that there is no high-temperature flue gas downstream to heat the fresh PC particles, which is extremely unfavorable for the stable combustion of the PC. In addition, at RIO of 0:1, compared to other cases, there are more particles in the central recirculation zone, which promotes the reduction reaction of N element released from PC particles, thus reducing NOx emission. According to the comprehensive evaluation, it is recommended that the RIO of the two-level OFA be set to 1:1 when using radial air staging in a coal-fired boiler. The results provide new insights into the application of the air staging method for efficient and clean PC utilization.

Influence of over-fired air location on gas-particle flow characteristics within a coal-fired industrial boiler under radial air staging

To achieve low-NOx emission in the coal-fired industrial boiler, the radial air staging method is proposed. The location of the over-fired air (OFA) is an essential parameter as it affects the combustion stability, NOx generation, burnout, and slagging trend. These are related to the gas-particle flow such as the recirculation region, gas mixture, and gas-particle mixture. Therefore, in this paper, taking a coal-fired industrial boiler with radial air staging method as an object, in a cold-modeling furnace, the gas-particle flow characteristics under various OFA locations (LD of 1.29, 1.43, 1.72, and 2.00) are studied. When OFA is radially arranged, the OFA jet diffuses towards the furnace center. As the LD increases, the size of the central recirculation region increases, thereby improving combustion stability. When the LD is 2.00, the mixing of the OFA jet and PCC jet obviously is delayed. Moreover, an increase in LD leads to more returned particles in the furnace center, promoting the reduction reaction of NOx. In addition, as the LD increases from 1.29 to 1.72, the gas-particle mixing uniformity is enhanced, which is beneficial to the uniform temperature distribution. Comprehensively, the LD of 1.43–1.72 is recommended when radial air staging is adopted in coal-fired industrial boilers.

Emission Characteristics, Speciation, and Potential Environmental Risks of Heavy Metals from Coal-Fired Boilers: A Review

Coal-fired boilers, including coal-fired power plants (CFPPs) and coal-fired industrial boilers (CFIBs), are an important area for achieving sustainability globally as they are one of the globally important sources of anthropogenic emissions of heavy metals (HMs) due to huge amount of coal consumption. To date, the investigation of atmospheric emission characteristics, speciation, and potential environmental risks of HMs from coal-fired boilers has received widespread attention and achieved significant progress. To characterise the emissions of HMs from coal-fired boilers, research is currently being carried out in the areas of (1) studying the release of HMs from coal combustion processes, (2) developing emission factors and emission inventories, and (3) revealing the cross-media partitioning of HMs between different output streams. Research on the chemical forms of HMs in waste from coal-fired boiler is currently focused on chemical valence and speciation components. The sequential chemical extraction method is currently the most widely used method for investigating the chemical fractionations of HMs in wastes from coal-fired boilers. Studies indicate that different HM elements display differentiated characteristics of speciation in waste from coal-fired boilers. Early studies on potential environmental risk and ecological risk caused by HMs are usually based on actual monitoring values of HMs in the target environmental media. The risk assessment code method and the leaching toxicity method are the most widely used method to study the potential environmental risk of HMs in waste from coal-fired boilers. With the implementation of global carbon emission reduction strategies, the scale of coal-fired boilers and air pollution control technologies are bound to change in the future. Therefore, as an important component of global efforts to achieve sustainable development, more research is needed in the future to improve the accuracy of emission inventories, reveal the mechanisms of HM chemical transformation, and establish methods for potential environmental risk assessment at regional scales.

Operation analysis and its performance optimizations of the spray dispersion desulfurization tower for the industrial coal-fired boiler

As a relatively new type of desulfurization system, long-term high-efficiency desulfurization is a critical issue for commercial spray dispersion system applications. To analyze the coupling effects of different operation parameters, a series of operation performance predictions with their optimizations are implemented. Through the analysis of the operating influencing factors based on artificial intelligence, the key influencing factors of the operation performance are determined. For instance, the tube immersion depth accounts for 46% of the factors that affect the desulfurization efficiency. Moreover, the system stability analysis determines not only the system's fine operation stability, but also identifies several factors, such as the PH and inlet gas temperature, that require key control for operational stability. For instance, the phase margin of the PH, flue gas temperature, and SO2 concentration in flue gas is greater than 0 when the amplitude margin reaches 1 point, allowing the PH control system to demonstrate excellent system operating stability. Then, after a systematic analysis of the operation, several optimizations of the operation are provided. Finally, in recent applications, the optimized spray dispersion has demonstrated excellent desulfurization performance: the desulfurization efficiency was greater than 99%, and the outlet SO2 concentration was less than 15 mg/m3 in three years of operation, which means that near-zero SO2 emissions in long cycles were essentially achieved, and 1/3 and 1/5 of the energy and cost consumption were reduced.

Catalytic Oxidation Activity of NO over Mullite-Supported Amorphous Manganese Oxide Catalyst.

Nitric oxide (NO) can pose a severe threat to human health and the environment. Many catalytic materials that contain noble metals can oxidize NO into NO2. Therefore, the development of a low-cost, earth-abundant, and high-performance catalytic material is essential for NO removal. In this study, mullite whiskers on a micro-scale spherical aggregate support were obtained from high-alumina coal fly ash using an acid-alkali combined extraction method. Microspherical aggregates and Mn(NO3)2 were used as the catalyst support and the precursor, respectively. A mullite-supported amorphous manganese oxide (MSAMO) catalyst was prepared by impregnation and calcination at low temperatures, in which amorphous MnOx is evenly dispersed on the surface and inside of aggregated microsphere support. The MSAMO catalyst, with a hierarchical porous structure, exhibits high catalytic performance for the oxidation of NO. The MSAMO catalyst, with a 5 wt% MnOx loading, presented satisfactory NO catalytic oxidation activity at 250 °C, with an NO conversion rate as high as 88%. Manganese exists in a mixed-valence state in amorphous MnOx, and Mn4+ provides the main active sites. The lattice oxygen and chemisorbed oxygen in amorphous MnOx participate in the catalytic oxidation of NO into NO2. This study provides insights into the effectiveness of catalytic NO removal in practical industrial coal-fired boiler flue gas. The development of high-performance MSAMO catalysts represents an important step towards the production of low-cost, earth-abundant, and easily synthesized catalytic oxidation materials.

Effect of coal preparation on atmospheric emissions of trace elements and their cross-media environmental risk from Chinese coal-fired industrial boilers

Effect of coal preparation on atmospheric emissions of trace elements and their cross-media environmental risk from Chinese coal-fired industrial boilers

Distribution, chemical fractionation, and potential environmental risks of Hg, Cr, Cd, Pb, and As in wastes from ultra-low emission coal-fired industrial boilers in China

This study conducted a comprehensive investigation of the distribution, chemical fractionation, and potential environmental risks of Hg, Cd, Cr, Pb, and As in waste based on new data from five ultra-low emission (ULE) coal-fired industrial boilers (CFIBs). The results showed that fly ash was enriched with Cd, Pb, As, and Hg, while its Cr contents were not invariably higher than those of slag. Fly ash was the predominant output flow for Hg, Cd, Cr, Pb, and As in the tested ULE boilers, with higher proportions of HTEs in the fly ash and lower proportions of HTEs in the flue gas than in the non-ULE boilers. The average proportions of residual Hg, Cd, Cr, Pb, and As in wastes revealed the following order: slag > fly ash > flue gas desulfurization (FGD) by-products. The potential environmental risks of Hg, Cd, Cr, Pb, and As in the fly ash, slag, and FGD by-products of CFIBs at the county level in the Beijing-Tianjin-Hebei Air Pollution Transmission Channel Cities (“2 +26 cities”) region showed spatial heterogeneity. It is predicted that the potential release of Pb, Cr, and Cd in the fly ash would increase and that of the FGD by-products would decrease after the implementation of the ULE retrofitting of all CFIBs.

Unit-based emissions and environmental impacts of industrial condensable particulate matter in China in 2020.

The emission of condensable particulate matter (CPM) and its environmental impacts are arousing concern in China with the effective control of filter particulate matter (FPM). This study established an up-to-date and unit-based CPM emission inventory for industrial sectors and systematically evaluated the effects of CPM on primary and secondary PM2.5 in China. In 2020, the national CPM emissions total for industrial sectors was estimated to be 0.98Tg with uncertainty from -49% to 66%, including 0.62Tg of organic CPM (CPMorg) and 0.36Tg of inorganic CPM (CPMin). Totals of 62%, 23% and 8% CPM were emitted from coal-fired power plants, coal-fired industrial boilers and sinter plants, respectively. By filling CPM emissions in PM2.5 simulation, the normalized mean bias (NMB) of model to observation was improved from -27% to -14% in East, North and Central China. The 4μg/m3 PM2.5 concentration was attributed to CPM emissions in this region, accounting for 10% of observations. On "polluted" days (PM2.5>75μg/m3), industrial CPM emissions can contribute 7μg/m3 PM2.5 in North China. Therefore, China should focus on controlling CPM from coal combustion to ensure continuous air quality improvement.

Effect of nitriding treatment on char reducing nitric oxide at high temperature

To reduce nitric oxide (NO) emissions from coal-fired industrial boilers, char waste could be collected from the tail flue and fed into the furnace to reduce NO, which would also decrease the incomplete combustion loss. Nitriding treatment could be used to enhance the NO reducibility of char waste. In this paper, char with nitriding treatment (nitriding char) was prepared from Shenhua char and urea. The effect of nitriding treatment on char reducing NO at high temperatures (700 °C–900 °C) was studied using a fixed-bed experimental system and various urea masses and pretreatment times. Increasing the urea mass and decreasing the pretreatment time resulted in more urea residue being present in the char, which increased the nitrogen complex which existed in the form of C(N) and caused the surface enrichment of nitrogen element, but blocked the pore structure. In an inert atmosphere, the NO reduction rates of all the nitriding chars were higher than that of the raw char, but there was an optimal limit parameter for the urea mass and pretreatment time. The presence of 2 vol% O2 was not conducive to the NO reduction by nitriding char because of the higher char-nitrogen (char-N) content resulting from the nitriding treatment, which generated more NO and offset the benefit of the nitriding treatment. This paper provides a useful NO control strategy in coal-fired industrial boilers, and the relevant process route has achieved a 20%–35% decrease in NO emissions in engineering applications.

Mercury distribution and emission reduction potentials of Chinese coal-fired industrial boilers

Mercury distribution and emission reduction potentials of Chinese coal-fired industrial boilers

Gas or electricity? Regional pathway selection under carbon neutrality target: A case study of industrial boilers

Scattered coal combustion in industrial boilers is one of the main sources of CO2 emissions in China. With their lower emission intensity, electric and gas-fired boilers are recognized as effective alternatives to coal-fired boilers. Therefore, with the promise of reaching a peak in carbon emissions and attaining carbon neutrality, due to the differences in power structures, fuel prices, and energy resources in different regions, it is significant to identify the most suitable regional alternatives for coal-fired boiler retrofitting and the influences of policy on the effect of CO2 emission mitigation. In this paper, an optimization model combined with power structures, fuel prices, and energy resources is developed to analyze the CO2 emission mitigation performances of coal-to-gas (C2G) and coal-to-electricity (C2E) retrofits for coal-fired industrial boilers in regions of China. Based on life-cycle data, the regional substitution portfolio of C2G and C2E in each region in 2017 is optimized with the objective of maximizing the CO2 emission reduction efficiency, and the policy effects of fuel price subsidies and CO2 emission fees are discussed by scenario analysis. Based on the perspective of the local electricity structure, the optimized future pathway of low-carbon development for industrial boilers in various regions is studied. The results indicate that, in 2017, C2G retrofitting is suitable for most regions in China, while both C2G and C2E retrofits are suitable for Fujian, Guangxi, Hubei, Yunnan, Sichuan, and Qinghai. Only Yunnan's optimal portfolio is suitable for a 100% C2E retrofit without any supporting policies. “Thresholds” of electricity price subsidy exist for enterprises to adopt a C2E retrofit. It is easier to implement C2E in Fujian with a relatively low electricity price subsidy, while it is difficult to implement C2E in Qinghai as it requires a high electricity price subsidy. The effect of CO2 emission fees on improving CO2 emission reduction efficiency is only remarkable for Qinghai. Until 2050, 100% C2G retrofitting is still suitable in Henan, Hunan, and Jiangxi; in contrast, Yunnan, Fujian, Guangdong, Shaanxi, Guangxi, and Xinjing could benefit from a 100% C2E retrofit. If carbon capture and storage (CCS) is implemented, Beijing and Henan would also benefit from a 100% C2E retrofit. This study not only could help decision-makers to formulate a detailed policy for CO2 reduction but also could provide a suggested pathway for CO2 reduction in the future. As a result, preparatory work for technologies and policies could be conducted to achieve the goal of reaching peak carbon emissions and of attaining carbon neutrality.

Highly-resolved spatial-temporal variations of air pollutants from Chinese industrial boilers

Industrial boilers are a significant anthropogenic source of air pollutant emissions. In this study, a county-based atmospheric emission inventory of particulate matter (PM), PM10, PM2.5, SO2, NOx, organic carbon (OC) and elemental carbon (EC) from industrial boilers over mainland China in 2017 was developed for the first time, based on county-level activity data from ~61,000 coal-fired industrial boilers (CFIBs), ~44,000 biomass-fired industrial boilers (BFIBs), ~71,000 gas-fired industrial boilers (GFIBs) and ~9300 oil-fired industrial boilers (OFIBs), updated emission factors (EFs) and air pollution control device (APCD) efficiencies. The total national PM, PM2.5, PM10, SO2, NOx, OC and EC emissions from industrial boilers in 2017 were estimated to be 1,240, 347, 761, 1,648, 1,340, 13.1 and 15.8 kilotons (kt), respectively. Intensive air pollutant emissions from industrial boilers of more than 1000 kg/km2 were predominantly in north-eastern, northern and eastern China. CFIBs contributed the most (77.6–94.0 %) to air pollutant emissions because of their high air pollutant EFs and the large amounts of coal consumed. BFIBs were the second-highest contributor to national air pollutant emissions, with the contribution of BFIBs to PM2.5, OC and EC emissions in central and southern China reaching up to 42.1 %, 61.7 % and 45.5 %, respectively. There were seasonal peaks in monthly air pollutant emissions in heating regions. The overall uncertainty realting to the new emission inventory was estimated as −25.9 %–22.7 %. Significant air pollutant emission reductions were obtained from 2017 to 2030, and by 2030 the PM, PM10, PM2.5, SO2 and NOx emissions were forecast to decrease by 40.1–84.0 %, 41.6–84.3 %, 44.5–75.2 %, 44.5–75.2 % and 19.5–46.8 % compared to 2017, respectively, under four proposed scenarios. The results of this study showed that differentiated industrial boiler management measures should be developed according to the actual emission characteristics.This work developed a county-based atmospheric emission inventory of PM, PM10, PM2.5, SO2, NOx, OC and EC from Chinese industrial boilers in 2017 for the first time.

Emission characteristics of PM2.5 and components of condensable particulate matter from coal-fired industrial plants

Particulate matter (PM), including condensable particulate matter (CPM) and filterable particulate matter (FPM), emitted from coal combustion is one of the major contributors to air pollution. In this study, CPM and FPM were sampled from two coal-fired industrial boilers with air pollution control devices (APCDs). The emission concentration of total PM (CPM and FPM) and inorganic components of CPM were studied. The organic fractions in CPM and raw coal were analyzed using a gas chromatograph/mass spectrometer (GC/MS). The concentrations of total PM in the flue gas decreased from 1475.61 to 7.68 mg/Nm3 in unit 1, and from 2451.62 to 29.38 mg/Nm3 in unit 2 after the flue gas passed through the APCDs. CPM accounted for 51.42–91.93% of total PM emitted from stacks, of which organic components (73.87–96.30%) were one of the main constituents. Although aromatic hydrocarbons are one of the major components of raw coal, they were almost nonexistent in the CPM emitted from coal combustion. Saturated hydrocarbons accounted for the largest proportion of organic components in CPM, 49.19% in unit 1 and 61.16% in unit 2. The proportion of esters in the oxygen-containing derivatives of CPM emitted from two units was relatively high. SO42− was the inorganic component with the largest concentration in CPM emitted from the boiler units. This study will improve the understanding of the emissions levels of PM2.5 and the properties of CPM that originate from the coal-fired industrial processes.

Investigation of factors affecting thermal performance in a coal - fired boiler and determination of thermal losses by energy balance method

In this study, a coal-fired industrial type boiler's performance and emission tests were performed using the energy balance method. During the experiments, the directives in the test standard (ASME PTC - 4) were followed. This tested boiler has a capacity of 75 t/h and is used in the mining industry. This boiler is a steam drum boiler equipped with an atmospheric circulating fluidized bed furnace. The furnace chamber with a rectangular cross-section has its width of 4250 mm and a depth of 4100 mm. In order to minimize the height of the furnace chamber and whole boiler, the middle wing walls are built-in the furnace chamber. As a result of the performance test, the boiler efficiency (indirect method) was found to be 93.07% (base on the lower heating value of fuel). According to the indirect method, the first three significant losses in total boiler losses were, respectively; the conversion of H2 in the fuel to water after combustion by 4.036%, the loss of dry flue gas by 3.231%, and the proportion of unburned carbon in residual products at the end of combustion with 1.653%. Due to the fluidized bed boiler's structural characteristics, it was also shown in the test results that emissions were suppressed in the combustion chamber, which was kept in the temperature range of 850–950 °C.