A review on mercury in coal combustion process: Content and occurrence forms in coal,transformation, sampling methods,emission and control technologies

Mercury, as a global pollutant, has raised worldwide concern due to its high toxicity, long-distance transport, persistence, and bioaccumulation in the environment. Coal-fired power plants (CFPPs) are considered as the major anthropogenic mercury emission source to the atmosphere, especially for China, India, and the US. Studies on mercury in coal combustion process have been carried out for decades, which include content and occurrence forms of mercury in coal, mercury transformation during coal combustion, sampling, co-removal and emission of mercury in CFPPs, mercury removal technologies for CFPPs. This current review summarizes the knowledge and research developments concerning these mercury-related issues, and hopes to provide a comprehensive understanding of mercury in coal combustion process and guidance for future mercury research directions.The average mercury content in the coal from China, the US, and South Africa is 0.20, 0.17, and 0.20 mg/kg, respectively, which is higher than the world's coal average value of 0.1 mg/kg. In general, mercury in coal is in the forms of sulfide-bound mercury (mainly pyritic mercury, dominant), clay-bound mercury, and organic matter-bound mercury, which are influenced by diagenetic, coalification, and post-diagenetic conditions, etc. Mercury transformation in coal combustion includes homogeneous (without fly ash) and heterogeneous (with fly ash) reaction. The transformation is affected by the coal types, flue gas components, flue gas temperature, combustion atmosphere, coal ash properties, etc. The effects of chlorine, NOx, SO₂, H₂O, O₂ NH₃ on elemental mercury (Hg⁰) homogeneous oxidation and the influence of physical structure properties, unburned carbon, and metal oxides in fly ash as well as flue gas components on Hg⁰ heterogeneous transformation are systematically reviewed in detail. For the mercury transformation in oxy-coal combustion, O₂ promotes Hg⁰ oxidation with Cl₂ while NO and CO₂ inhibit or do not favor that reaction. CO₂ increases Hg⁰ oxidation in the atmosphere of NO and N₂. SO₂ will limit Hg⁰ oxidation, while HCl has a higher oxidation effect on Hg⁰ than that in air-coal combustion atmosphere. Fly ash plays an important role in Hg⁰ oxidation. SO₃ inhibits mercury retention by fly ash while H₂O promotes the oxidation.The sampling or analysis principle, sampling requirements, and advantages and disadvantages of the commonly used on-site mercury sampling methods, namely, Ontarion Hydro Method (OHM), US EPA Method 30B, and Hg-CEMS, are compared. The air pollution control devices (APCDs) in CFPPs also have the mercury co-removal ability besides the conventional pollutants, such as NO_x, particulate matter (PM), SO₂, and fine PM. Selective catalytic reduction (SCR) equipment, electrostatic precipitator (ESP) or fabric filter (FF), and wet flue gas desulfurization (WFGD) device are good at Hg⁰ oxidation, particulate mercury (Hg^p) removal, and oxidized mercury (Hg²⁺) capture, respectively. The Hg⁰ oxidation rate for SCR equipment, and the total mercury (Hg^t, Hg^t = Hg⁰ + Hg²⁺ + Hg^p) removal rate for ESP, FF, and WFGD device is 6.5–79.9%, 11.5–90.4%, 28.5–90%, and 3.9–72%, respectively. Wet electrostatic precipitator (WESP) can capture Hg⁰, Hg²⁺, and Hg^p simultaneously. The mercury transformation process in SCR, ESP, FF, WFGD, and WESP is also discussed. Hg^t removal in ESP+WFGD, SCR+ESP+WFGD, SCR+ESP+FF+WFGD, and SCR+ESP+WFGD+WESP is 35.5–84%, 43.8–94.9%, 58.78–73.32%, and 56.59–89.07%, respectively. The mercury emission concentration in the reviewed CFPPs of China, South Korea, Poland, the Netherlands, and the US is 0.29–16.3 µg/m³. Mercury in some fly ash and gypsum, and in most WFGD and WESP wastewater, is higher than the relevant limits, which needs to be paid attention to during their processing.Mercury removal technologies for CFPPs can be divided into pre-combustion (including coal washing technology and mild pyrolysis method), in-combustion (including low-NO_x combustion technology, circulating fluidized bed combustion technology, and halogens addition into coal), and post-combustion (including existing commercial SCR catalyst improvement, inhibiting Hg⁰ re-emission in WFGD, mercury oxidizing catalysts, injecting oxidizing chemicals, carbon-based adsorbents, fly ash, calcium-based adsorbents, and mineral adsorbents) based on the mercury removal position. The mercury removal effects, mercury removal mechanism, and/or influencing factors are summarized in detail. One of the regenerable mercury removal adsorbents, the magnetic adsorbent modified by metal oxides or the metal halides, is the most promising sorbent for mercury removal from CFPPs. It has advantages of high mercury removal efficiency, low investment, easy separation from fly ash, and mercury recovery, etc. Lastly, further works about mercury transformation in coal combustion atmosphere, mercury co-removal by APCDs, the emission in CFPPs, and mercury removal technologies for CFPPs are noted.     

Search for solid acid catalysts aiming at the development of bifunctional tandem catalysts for the one-pass synthesis of lower olefins via CO2 hydrogenation

The development of methodologies for CO₂ utilization is in high demand worldwide. Here, we propose bifunctional tandem catalysts of ZnZrO_x (for CO₂-to-methanol hydrogenation) and a series of solid acid catalysts (for subsequent methanol conversion to light olefins). As solid acid catalysts, we used zeolites and silicoaluminophosphates with different topologies, MOR, FER, MFI, 1BEA, CHA, and ERI, confirmed by X-ray diffraction, electron microscopy, and nitrogen adsorption-desorption. They also showed the corresponding acid properties examined by ammonia adsorption. The tandem catalysts realized a one-pass synthesis of lower olefins, while no hydrocarbons were obtained using ZnZrO_x only. According to the reaction test and ammonia adsorption, there seems to be no correlation between product yields and acid strength. The pore sizes and channel dimensionality of zeolites influence the selectivity of products; zeolites with small pores, such as MOR, SAPO-34 and ERI, are promising, while zeolites with larger pores, such as MFI, produce heavier hydrocarbons. The results provide new insight into the design of innovative catalysts for CO₂ utilization.     

The effect of low-NOx combustion on residual carbon in fly ash and its adsorption capacity for air entrainment admixtures in concrete

Fly ash from pulverized coal combustion contains residual carbon that can adsorb the air-entraining admixtures (AEAs) added to control the air entrainment in concrete. This is a problem that has increased by the implementation of low-NO_x combustion technologies. In this work, pulverized fuel has been combusted in an entrained flow reactor to test the impact of changes in operating conditions and fuel type on the AEA adsorption of ash and NO_x formation.Increased oxidizing conditions, obtained by improved fuel-air mixing or higher excess air, decreased the AEA requirements of the produced ash by up to a factor of 25. This was due to a lower carbon content in the ash and a lower specific AEA adsorptivity of the carbon. The latter was suggested to be caused by changes in the adsorption properties of the unburned char and a decreased formation of soot, which was found to have a large AEA adsorption capacity based on measurements on a carbon black. The NO_x formation increased by up to three times with more oxidizing conditions and thus, there was a trade-off between the AEA requirements of the ash and NO_x formation. The type of fuel had high impact on the AEA adsorption behavior of the ash. Ashes produced from a Columbian and a Polish coal showed similar AEA requirements, but the specific AEA adsorptivity of the carbon in the Columbian coal ash was up to six times higher. The AEA requirements of a South African coal ash was unaffected by the applied operating conditions and showed up to 12 times higher AEA adsorption compared to the two other coal ashes. This may be caused by larger particles formed by agglomeration of the primary coal particles in the feeding phase or during the combustion process, which gave rise to increased formation of soot.     

Removal of NOx by microwave reactor with ammonium bicarbonate and Ga-A zeolites at low temperature

Microwave reactor with the mixture of ammonium bicarbonate (NH₄HCO₃) and Ga-A zeolites was set up to study the removal of nitrogen oxides (NO_x) from waste gas with excess oxygen concentration (14–19%) at low temperature (80–120 °C). The results showed that the microwave reactor filled with NH₄HCO₃ and Ga-A zeolites could reduce NO_x to nitrogen with the best purifying efficiency of 95.45% and the best denitrification amount of 89.28 mg h⁻¹. The optimal microwave power and residence time (RT) on denitrification was 259–280 W and 0.259 s, respectively. Microwave denitrification effect of the experiment using ammonium bicarbonate and Ga-A zeolites was much higher than that using ammonium bicarbonate or Ga-A zeolites only. The mechanism for microwave-induced NO_x reduction can be explained as the microwave-induced catalytic reaction between NO_x and ammonium bicarbonate with Ga-A zeolites being the catalyst and microwave absorbent.     

A review of the interference of carbon containing fly ash with air entrainment in concrete

Industrial utilization of fly ash from pulverized coal combustion plays an important role in environmentally clean and cost effective power generation. Today, the primary market for fly ash utilization is as pozzolanic additive in the production of concrete. However, the residual carbon in fly ash may interfere with air entraining admixtures (AEAs) added to enhance air entrainment in concrete in order to increase its workability and resistance toward freezing and thawing conditions. The problem has increased with implementation of low-_NOx${\mathrm{NO}}_x$ combustion technologies.     

燃煤烟气中汞吸附的研究综述

概述了燃煤烟气中汞的吸附特性,综述了活性炭、飞灰和其它吸附剂对汞的吸附机理和影响因素,探讨了汞的吸附模型。指出活性炭对汞的脱除效率可达到90%以上,但成本高,飞灰吸附成本虽然低但脱除效率有限,其它吸附剂研究尚处于初级阶段,因此寻找廉价高效的吸附剂十分必要,同时开发烟气中污染物的联合脱除技术是研究方向。     

Effects on enrichment characteristics of trace elements in fly ash by adding halide salts into the coal during CFB combustion

The effects on enrichment characteristics of trace elements (TEs) in fly ash by adding halide salts into the coal during coal combustion were conducted on a 6 kW_th circulating fluidized bed (CFB) experimental device. Results show that unburn carbon content in fly ash has little relationship with the concentration of TEs namely Hg, As, Pb, Cr and Mn. All the TEs are enriched in fly ash for the raw coal CFB combustion. Concentration of Hg and Mn increases with increasing the addition amount of CaCl₂, NH₄Cl and NH₄Br. As, Pb and Cr enrich in fly ash more strongly when adding more CaCl₂ into the coal while more addition of NH₄Cl and NH₄Br leads to the decrease of their enrichment compared to addition amount of 0.1 wt%. On the whole, putting halide salts into the coal results in the TEs enriched in fly ash, which benefits for TEs removal during the coal combustion. Combining this method with the chemical sequential extraction or thermal treatment of the fly ash will be a promising way to realize the TEs removal and their recovery.     

Chemical properties of solid biofuels—significance and impact

The chemical composition of solid biofuels (as defined in [Directive 2000/76/EC of the European Parliament and of the Council on the Incineration of Waste. In: European Commission, editor. Official Journal of the European Communities, vol. L 332; 2000. p. 91–111] and [CEN/TC 335—WG2 N94. Final draft. European Committee for standardization, editor. Solid biofuels—fuel specifications and classes. Brussels, Belgium; 2003.] has manifold effects on their thermal utilisation. C, H and O are the main components of solid biofuels and are of special relevance for the gross calorific value, H in addition also for the net calorific value. The fuel N content is responsible for NO_x formation. NO_x emissions belong to the main environmental impact factors of solid biofuel combustion. Cl and S are responsible for deposit formation and corrosion and are therefore relevant for a high plant availability. Furthermore, Cl causes HCl as well as PCDD/F and S SO_x emissions and both elements are involved in the formation of aerosols (submicron particle emissions). The ash content influences the choice of the appropriate combustion technology and influences deposit formation, fly ash emissions and the logistics concerning ash storage and ash utilisation/disposal. Major ash forming elements (Al, Ca, Fe, K, Mg, Na, P, Si, Ti) are of relevance for the ash melting behaviour, deposit formation and corrosion. In addition, volatile elements such as Na and K are main constituents of aerosols. Volatile minor elements (As, Cd, Hg, Pb, Zn) play a major role in gaseous and especially aerosol emissions as well as in deposit formation, corrosion and ash utilisation/disposal. Either partly or non-volatile minor elements (Ba, Co, Cr, Cu, Mo, Mn, V) are of special relevance for ash utilisation. The present paper discusses the influence of chemical fuel properties on biomass combustion plants as well as possibilities and recommendations for controlling them.     

Methanol conversion to dimethyl ether over beta zeolites derived from bagasse fly ash

Catalytic performance of beta zeolites derived from bagasse fly ash for methanol dehydration to dimethyl ether, alternative fuel, was investigated. Amorphous silica extracted from bagasse fly ash, a tetraethylammonium hydroxide (TEAOH) were used as a precursor and a template for synthesis of beta-zeolites, respectively. Beta zeolites could be synthesized at a constant hydrothermal temperature of 135°C and a constant initial pressure of 3 bars under the nitrogen atmosphere. The crystallization time and Si/Al ratio were 48 h and 15, respectively. These conditions gave the highest crystallinity for beta zeolites with a crystal size of 0.51 μm as well as a Brunauer–Emmett–Teller surface area of 844 m² g^?1. Beta zeolites with the Si/Al ratios of 15.8 and 24.6 were used as catalysts for methanol conversion to dimethyl ether. Beta zeolites with the Si/Al ratios of 15.8 and 24.6 have the % yields of 84 and 60, respectively. According to the result of NH₃-TPD, the beta zeolites with the Si/Al ratio of 15.8 showed higher acidity than beta zeolites with a Si/Al ratio of 24.6. Therefore, the beta zeolites with a Si/Al ratio of 15.8 were more efficiency in methanol conversion reaction than beta zeolites with a Si/Al ratio of 24.6.     

燃煤烟气脱汞吸附剂研究进展

概述了目前当今世界燃煤烟气中脱汞吸附剂的研究现状,介绍了碳基吸附剂、钙基吸附剂、石油焦、飞灰,以及一些新型吸附剂对汞的脱除效果。指出活性炭对汞的脱除效率高,但成本也高;飞灰吸附剂对汞脱除的成本低,但脱除效率也低。用于燃煤电厂汞吸附的吸附剂研究处于实验室研究阶段,因此开发价廉和高效脱汞吸附剂和吸附剂的再生等是吸附剂发展过程中的一个重要研究课题。     

Evaluation of activated carbon adsorbent for fuel cell cathode air filtration

The effectiveness of a commercial activated carbon modified by KOH (KMAC) was evaluated as adsorbent for purifying NO_x and SO₂, which are the major contaminants in fuel cell cathode air stream. The N₂ adsorption–desorption isotherms of KMAC samples showed that the surface structure of the activated carbon was changed significantly by KOH impregnation. The sample of KMAC with a loading of 10.1% KOH by weight presented the highest adsorption capacities for both NO_x and SO₂, which were 96 mg g⁻¹ and 255 mg g⁻¹, respectively. A pre-exposure of KMAC to CO₂ caused neither effect on the adsorption of NO_x nor on the adsorption of SO₂. KMAC could fully protect a 250 W proton exchange membrane fuel cell (PEMFC) stack from 1100 ppb of NO_x and 250 ppb of SO₂ for about 130 h.     

Optimization of Process Parameters for the Preparation of CaO/CaSO4/Coal Fly Ash Sorbent for Sulfur Dioxide (SO2) Removal: Part II

A two-step optimization strategy was employed to optimize the surface area of sorbent prepared from coal fly ash, calcium oxide (CaO) and calcium sulfate (CaSO₄) for flue gas desulfurization. In the first step, a 3 level full factorial design of experiment was used to develop a regression model equation to correlate the significant experimental sorbent preparation variables to the surface area of the resulting sorbent. The three experimental sorbent preparation variables studied are hydration period (x ₁), ratio of CaO to fly ash (x ₂) and amount of CaSO₄ (x ₃). In the subsequent step, response surface methodology was used to identify the experimental sorbent preparation variables that maximize the surface area of the sorbent. Through this two-step optimization strategy, it was found that at a hydration period of 10 hrs and drying temperature of 100°C, optimum surface area of 67.0 m²/g could be attained by using 5 grams of CaO, 13.7 grams of fly ash, and 7.4 grams of CaSO₄ in the preparation mixture. The prediction was verified with experimental runs.     

Effect of Two-Level Over-Fire Air on the Combustion and NOx Emission Characteristics in a 600 MW Wall-Fired Boiler

This paper accomplishes a numerical investigation on the effect of two-level over-fire air (OFA) on the combustion and NO_x emission in a supercritical 600 MW wall-fired boiler. Different arrangements of two-level OFA nozzles and different airflow ratios between the two layers are set to examine NO_x emission and the carbon content in fly ash. According to the simulation results, the two-level OFA case releases the NO_x between the single upper layer and the single lower layer of the two-level OFA nozzles in operation. Moreover, the two-level OFA arrangement gives a lower carbon content in fly ash than the single-level OFA cases. In addition, both low NO_x emissions and low carbon content in fly ash can be obtained simultaneously when the two levels of OFAs are injected from Layers 1 and 4 with r_lower at 0.5.     

Characterization of ashes from a 100 kWth pilot-scale circulating fluidized bed with oxy-fuel combustion

Oxy-fuel combustion experiments have been carried out on an oxygen-fired 100 kW_th mini-circulating fluidized bed combustion (CFBC) facility. Coal and petroleum coke were used as fuel together with different limestones (and fixed Ca:S molar ratios) premixed with the fuel, for in situ SO₂ capture. The bed ash (BA) and fly ash (FA) samples produced from this unit were collected and characterized to obtain physical and chemical properties of the ash samples. The characterization methods used included X-ray fluorescence (XRF), X-ray diffraction (XRD), char carbon and free lime analysis, thermogravimetric analysis (TGA), and surface analysis. The main purpose of this work is to characterize the CFBC ashes from oxy-fuel firing to obtain a better understanding of the combustion process, and to identify any significant differences from the ash generated by a conventional air-fired CFBC. The primary difference in the sulfur capture mechanism between atmospheric air-fired and oxy-fuel FBC, at typical FBC temperatures (∼850 °C), is that, in the air-fired case the limestone sorbents calcine, whereas the partial pressure of CO₂ in oxy-fuel FBC is high enough to prevent calcination, and hence the sulfation process should mimic that seen in pressurized FBC (PFBC). Here, the char carbon content in the fly ash was much higher than that in the bed ash, and was also high by comparison with ash obtained from conventional commercial air-firing CFBC units. In addition, measurements of the free lime content in the bed and fly ash showed that the unreacted Ca sorbent was present primarily as CaCO₃, indicating that sulfur capture in the oxy-fuel combustor occurred via direct sulfation. Limestone utilization for oxy-fuel combustion in this unit was generally lower than that in industrial-scale air-firing CFBCs, with better limestone performance found during combustion of petcoke running at relatively higher temperatures. The Brunauer–Emmett–Teller (BET) surface area and also the pore volume in the fly ash were much higher than in the bed ash and smaller size pores predominated in the fly ash samples.     

Oxy-fuel combustion of solid fuels

Oxy-fuel combustion is suggested as one of the possible, promising technologies for capturing CO₂ from power plants. The concept of oxy-fuel combustion is removal of nitrogen from the oxidizer to carry out the combustion process in oxygen and, in most concepts, recycled flue gas to lower the flame temperature. The flue gas produced thus consists primarily of carbon dioxide and water. Much research on the different aspects of an oxy-fuel power plant has been performed during the last decade. Focus has mainly been on retrofits of existing pulverized-coal-fired power plant units. Green-field plants which provide additional options for improvement of process economics are however likewise investigated. Of particular interest is the change of the combustion process induced by the exchange of carbon dioxide and water vapor for nitrogen as diluent. This paper reviews the published knowledge on the oxy-fuel process and focuses particularly on the combustion fundamentals, i.e. flame temperatures and heat transfer, ignition and burnout, emissions, and fly ash characteristics. Knowledge is currently available regarding both an entire oxy-fuel power plant and the combustion fundamentals. However, several questions remain unanswered and more research and pilot plant testing of heat transfer profiles, emission levels, the optimum oxygen excess and inlet oxygen concentration levels, high and low-temperature fire-side corrosion, ash quality, plant operability, and models to predict NO_x and SO₃ formation is required.     

燃煤电厂飞灰碳含量与PAHs有机污染物吸附量之间相关性研究

以五家燃煤电厂为例,实验分析了飞灰总碳、元素碳、有机碳含量,并与飞灰中多环烃类（PAHs）有机污染物吸附量作了相关分析;此外研究了燃煤排放PAHs与炉前煤中PAHs的关联性,从煤化学、煤燃烧学角度探讨了PAHs的吸附反应机制,提出煤粉燃烧过程中PAHs的一种重要形成机制-未燃碳颗粒及吸附反应机制,指出飞灰中的碳位不仅是PAHs的重要吸附位,同时也是PAHs的重要反应位。     

Modeling the behavior of selenium in Pulverized-Coal Combustion systems

The behavior of Se during coal combustion is different from other trace metals because of the high degree of vaporization and high vapor pressures of the oxide (SeO₂) in coal flue gas. In a coal-fired boiler, these gaseous oxides are absorbed on the fly ash surface in the convective section by a chemical reaction. The composition of the fly ash (and of the parent coal) as well as the time-temperature history in the boiler therefore influences the formation of selenium compounds on the surface of the fly ash. A model was created for interactions between selenium and fly ash post-combustion. The reaction mechanism assumed that iron reacts with selenium at temperatures above 1200 °C and that calcium reacts with selenium at temperatures less than 800 °C. The model also included competing reactions of SO₂ with calcium and iron in the ash. Predicted selenium distributions in fly ash (concentration versus particle size) were compared against measurements from pilot-scale experiments for combustion of six coals, four bituminous and two low-rank coals. The model predicted the selenium distribution in the fly ash from the pilot-scale experiments reasonably well for six coals of different compositions.     

The promotional effect of MnOx on (NH4)2S2O8-modified activated coke for selective catalytic reduction of NO with NH3 at low temperature

In this study, Manganese oxide (MnO_x) was supported on activated coke modified by (NH₄)₂S₂O₈ (ACs) to obtain novel MnO_x/ACs catalysts with high NO_x removal performance by excessive impregnation method. The influence of precursor and loading amount of MnO_x on the catalytic efficiency were studied. The Mn₃O₄ supported on ACs samples prepared with manganese acetate tetrahydrate as precursor and the loading amount of 8% Mn is the most effective in NO_x removal among modified samples and its removal efficiency is 97% at 180 °C. And the adsorption state and reaction behaviors of NH₃, NO and O₂ on MnO_x/ACs catalysts were measured by in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) in different conditions in order to study the effect of MnO_x and the reaction mechanism. The results suggested that Eley-Rideal and Langmuir-Hinshelwood mechanism existed simultaneously for the selective catalytic reduction of NO over the MnO_x/ACs catalyst.     

No removal in the selective catalitic reduction process over Cu and Fe exchanged type Y zeolites synthesized from coal fly ash

The nitric oxide (NO) removal capacity of ion-exchanged zeolite Y obtained from coal combustion fly ash was evaluated in this work. Zeolite Y was exchanged either with Cu²⁺ or Fe²⁺ to obtain two different catalysts for the selective catalytic reduction of NOx from flue gas.

The selective catalytic reduction experiments were carried out at temperatures ranging from 50°C to 350°C, water content 0% and 5% and 5% O₂. In the absence of water, a total conversion of NO is obtained at 200°C for both zeolites, but important differences were found between zeolites LY-Cu and LY-Fe in the reduction of NO at temperatures lower than 200°C, and especially in the presence of water, that could be attributed to the different temperatures at which active species Cu²⁺ and Fe³⁺ are available for both ion-exchanged zeolites at the studied conditions. The greater surface area of zeolite LY-Cu can also contribute to its higher activity.     

Study of optimal pulverized coal concentration in a four-wall tangentially fired furnace

The effect of fuel lean/rich conditions (1:1, 1:2, 1:3, 1:4, 1:5 and 1:6) on the furnace core temperatures, carbon in fly ash and slag and NO_x emissions was investigated in a 1 MW four-wall tangentially horizontal bias fired furnace for Yibin anthracite and Shenmu bituminous, respectively. Results shown that furnace core temperatures increased at first and then decreased along the height of the furnace when anthracite burned. The furnace core temperature at the height of primary air nozzles was the highest when the bituminous lean/rich varied from 1:1 to 1:3, and its trend was similar to the anthracite when the bituminous lean/rich was changed from 1:4 to 1:6. The ignition of anthracite required a heating stage, while bituminous could timely ignite due to high volatile. However, when the bituminous lean/rich was too low resulting in the relative lack of oxygen, it still needed a heating stage. With increased coal concentration, the furnace core temperatures in the primary air section went up firstly and then down, but the carbon in fly ash and slag showed adverse behavior. This was due to the high coal concentration corresponding to high volatile concentration leading to the timely ignition and burnout, causing higher furnace core temperature in the primary air section and decreased carbon in fly ash and slag. Corresponding to the highest furnace core temperature in the primary air section and the lowest carbon in fly ash and slag, the optimal pulverized coal concentration of anthracite and bituminous was 0.796–0.810 kg coal/kg air and 0.586–0.607 kg coal/kg air, respectively. In addition, with increased pulverized coal concentration, the NO_x emissions reduced quickly with a slight decrease in the range of the optimal pulverized coal concentration.