Subbituminous Coal Combustion Research Articles

Scientific bases and peculiarities of conversion of CHPP anthracite boilers to sub-bituminous coal combustion

Scientific bases and peculiarities of conversion of CHPP anthracite boilers to sub-bituminous coal combustion Print EmailUser Rating: / 0 PoorBest Category: Content №1 2024 Last Updated on 29 February 2024 Published on 30 November -0001 Hits: 1 SocButtons v1.4 Authors: M.V.Chernyavskyy*, orcid.org/0000-0003-4225-4984, Thermal Energy Technology Institute of National Academy of Sciences of Ukraine, Kyiv, Ukraine, e-mail: mchernyavski@gmail.com O.Yu.Provalov, orcid.org/0000-0002-5191-2259, Thermal Energy Technology Institute of National Academy of Sciences of Ukraine, Kyiv, Ukraine, e-mail: eproval@ukr.net Ye.S.Miroshnychenko, orcid.org/0000-0003-2487-6886, Thermal Energy Technology Institute of National Academy of Sciences of Ukraine, Kyiv, Ukraine, e-mail: yevhenmi@gmail.com O.V.Kosyachkov, orcid.org/0000-0002-9445-8738, Thermal Energy Technology Institute of National Academy of Sciences of Ukraine, Kyiv, Ukraine, e-mail: alexkosoy@ukr.net * Corresponding author e-mail: mchernyavski@gmail.com повний текст / full article Naukovyi Visnyk Natsionalnoho Hirnychoho Universytetu. 2024, (1): 041 - 049 https://doi.org/10.33271/nvngu/2024-1/041 Abstract: Purpose. Development of scientific foundations and generalization of experience in development and implementation of technical solutions for conversion of CHPP anthracite boilers with steam productivity up to 250 t/h for combusting sub-bituminous coal with maximum use of existing equipment. Methodology. Consumption and heat calculations of pulverizing systems, aerodynamic calculations of pulverized coal pipes and burners, thermal calculations of boilers and combustion chambers. Calculation justification of technical solutions to eliminate the risk of coal ignition in pulverizing systems and in the burners. Industrial tests on CHPP boiler units. Findings. Different types of pulverizing systems of anthracite CHPP boilers with ball-drum mills, an intermediate pulverized coal hopper and with hot air as a drying agent were considered, and a classification of pulverizing systems by the method of pulverized coal transport to the burners (with drying agent or hot air), and boilers – by the type and location of the burners and the geometry of the furnace, was performed. The problems were analyzed, the calculations of pulverizing systems, pipes, burners, and boilers were performed according to the applied technical solutions, and the experience was summarized of conversion from anthracite to sub-bituminous coal in the boilers of Myronivska, Darnytska CHPP and of the first line of Slovianska TPP. Recommendations are given on methods of conversion of anthracite boilers with a steam capacity of up to 250 t/h with different types of pulverizing systems for burning sub-bituminous coal with maximum use of existing equipment. Originality. For pulverizing systems with ball-drum mills and an intermediate hopper for pulverized coal with hot air as a drying agent classification was made for the first time by the type of transporting agent, and it was shown that when converting from anthracite to sub-bituminous coal with the air transport of pulverized coal to the burners, it is necessary to use the selection of slightly heated air from the first stage of the air heater. It is substantiated that maintaining the temperature conditions of molten slag removal while reducing the share of hot air consumption to the furnace requires the preferential operation of pulverizing systems in a single-mill mode, which is possible due to the greater grindability of sub-bituminous coal. Practical value. Based on the experience of approving technical solutions at Myronivska, Darnytska CHPPs, and at the first line of Slovianska TPP, recommendations are given on how to transfer anthracite boilers with a steam capacity of up to 250 t/h with different types of pulverizing systems for burning sub-bituminous coal with maximum use of existing equipment.

Converting Slovianska TPP with the central coal pulverizing plant from anthracite to sub-bituminous coal

Purpose. To develop scientific foundations and technical solutions and to implement the converting of the anthracite boiler of the 800 MW unit of Slovianska TPP with central coal pulverizing plant to sub-bituminous coal combustion with maximum use of existing equipment, without stopping the unit’s operation. Methodology. Theoretical and calculational studies on the processes of coal drying and pulverizing at the central coal pulverizing plant. Calculational justification of technical solutions to eliminate the risk of pulverized coal ignition in the pulverized coal supply system and in the boiler unit burners. Trial tests at the coal pulverizing plant and boiler unit. Findings. The technological features of coal pulverizing plant with steam panel dryers designed for anthracite and the peculiarities of the drying process of an individual coal particle were analyzed. It is substantiated that coal drying at the first stages takes place according to the “wet bulb thermometer” mechanism, and safe conditions for sub-bituminous coal pulverizing are determined and confirmed by tests. Technical solutions to eliminate the risk of pulverized coal ignition in the pulverized coal supply system and in the boiler burners were calculated and implemented, which allows the combustion of different coal grades (anthracite, sub-bituminous coal and their mixtures) without changing the composition of the air duct equipment and burners, using only operational measures. Originality. For the first time, it was proved that coal drying at the first stages takes place according to the “wet bulb thermometer” mechanism, and safe conditions for sub-bituminous coal pulverizing at the central pulverizing plant with steam panel dryers and unventilated ball drum mills were determined. Practical value. Technical solutions were developed and implemented to convert the anthracite boiler of the 800 MW unit of Slovianska TPP with a central coal pulverizing plant to sub-bituminous coal burning with maximal use of existing equipment, without stopping the unit’s operation, including safe modes of sub-bituminous coal pulverizing, as well as pulverized coal of various coal grades and their mixtures feeding and combustion. As a result of the implementation of the developed technical solutions, the 800 MW power unit of Slovianska TPP became the first unit in the world capable of using anthracite and sub-bituminous coal separately or in the form of mixtures of a wide range of compositions.

Assessment of combustion residual leachate volume, composition, and treatment costs

Combustion residuals and the resulting leachate from storage sites represent a large volume of wastewater in the United States (U.S.) that has not been quantified. This work estimates the constituents present, volume of wastewater, and costs of treatment for both combustion residual landfill leachate and the leachate from surface impoundment closures. Combustion residual landfill leachate produced from contact with bituminous coal combustion byproducts is generally predicted to be higher in lithium and manganese, whereas landfill leachate produced from contact with subbituminous coal combustion byproducts is generally predicted to be higher in mercury and vanadium. The annual volume of a single landfill with combustion residual leachate can reach more than 800,000 cubic meters. This leachate represents an annual volume of 26.8–42.8 million cubic meters nationally. Closing surface impoundments can yield between 830 and 1040 cubic meters of leachate nationally for a three-year closure period. Costs as low as $1.5/m3 or as high as $95/m3 are observed. Treatment trains will need to remove 72% of total suspended solids (TSS), 87% of arsenic, and 64% of mercury from landfill leachate. When applied to impoundments, these treatment trains would need to remove 97% of arsenic.

Effects of oxygen concentration on devolatilization and combustion behavior of coal particles: A multi-parameter study

The devolatilization and volatile combustion of lignite coal (LC), sub-bituminous coal (SBC) and bituminous coal (BC) with different O2 concentrations (21%-50%) were investigated on a concentrating photothermal experiment platform. The characteristics and mechanism of different coal particle combustion were analyzed by using multiple diagnostics, including Planar Laser Induced Fluorescence (PLIF) of OH radicals and polycyclic aromatic hydrocarbons (PAHs), high-speed cinematography and FT-IR. The results showed that, with increasing O2 concentration, the ignition delay time (tign) of different ranks of coal decreased, which was associated with the increase of OH concentrations during the ignition stage. The good correlation between tign and OH concentration was observed. For the volatile combustion, the OH concentration, volatile release amount and volatile flame duration time (tvol) significantly increased with the increasing of O2 concentration at low O2 concentrations. In the higher O2 concentrations, coals with different PAHs generation amount responded differently on the increasing of O2 concentration. On one hand, for the coals with lower PAHs generation amount, the OH concentration increased with the increasing of O2 concentration, while the tvol was not sensitive to changes of the O2 concentration. On the other hand, for the coals with higher PAHs generation amount, the OH concentration decreased with the increasing of O2 concentration while the tvol increased with the increasing of O2 concentration. It can be concluded that PAHs inhibited the OH generation, and the generation characteristics of OH and PAHs affected the sustained state of volatile combustion. The higher PAHs concentration consumed higher amount of OH during the volatile combustion. Meanwhile, with the increasing of PAHs concentration, the reaction rate of H + O2+M→HO2+M in which PAHs participate was increased, inhibiting the reaction H + O2→OH+O, and the increasing of polymer soot of PAHs will reduce the flame temperature through thermal radiation, which further inhibited the OH formation.

Effects of impregnation sequence for Mo-modified V-based SCR catalyst on simultaneous Hg(0) oxidation and NO reduction

A series of molybdenum (Mo)-modified vanadium (V)-based selective catalytic reduction (SCR) catalyst samples were prepared by incipient impregnation method for the simultaneous removal of elemental mercury (Hg(0)) and nitrogen oxide (NO) under a simulated sub-bituminous coal combustion gas. The Hg(0) oxidation performances of the modified SCR catalysts significantly varied in terms of different formulations and impregnation sequences while NO reduction performance was quite stable. When Mo and tungsten (W) were sequentially doped onto titanium dioxide (TiO2) support followed by V, the modified SCR catalyst showed the best Hg(0) oxidation performance compared to those firstly doped with V onto TiO2 followed by Mo and W or V, Mo and W simultaneously doped onto TiO2. TEM, XPS and XANES results showed that the different impregnation sequences could result in the different particle sizes of MoO3 and the oxidation states of V and Mo speciation, which could lead to different Hg(0) oxidation performances.

Investigation of subbituminous coal and lignite combustion processes in terms of mercury and arsenic removal

The aim of this work was to determine the Hg and As behaviour during coal combustion and flue gas purification process in terms of reducing their emissions into the atmosphere. The distribution of Hg and As between the solid phase (ash) and the gaseous phase was determined. Due to the high volatility, almost all of the mercury introduced into the installation passed to the flue gas. In the case of the As, more than 70% of the As passed to the flue gas, while the rest was recorded in the ashes. Three dusty sorbents were examined in terms of the effectiveness of flue gas purification from Hg and As: powdered activated carbon PAC, coke dust, and filter cake. The average efficiency of mercury removal for subbituminous coal and lignite ranged from 85 to 93% and 61 to 80%, respectively. On the other hand, the efficiency of As removal for subbituminous coal ranged from 21.8% to 90.8% depending on the sorbent used. The research was carried out in a laboratory scale tube furnace. The coal sample was burned in the flow of air and flue gas was directed through the sorbent container or scrubbers. The analysis was performed in defined and controlled conditions which included: combustion temperature, time, temperature of flue gas passing through the sorbent and flow rate.

Microwave-assisted pyrolysis of EFB-derived biochar as potential renewable solid fuel for power generation: Biochar versus sub-bituminous coal

The present study was conducted to study the physico-chemical characteristics (proximate and ultimate analyses, particle size distribution, energy content and ash analyses) and investigate the combustion behaviour of empty fruit bunch (EFB)-derived biochar (EFBC) as potential solid fuel for power generation. The EFBC was produced using a 10 L microwave-assisted pyrolysis system. Proximate analysis was conducted on the EFBC by using a thermogravimetric analyser (TGA) (TGA/SDTA851, Mettler Toledo, USA) to determine the fixed carbon, volatile matter, moisture and ash contents. The ultimate analysis was conducted to determine elemental composition of mature EFBC by using CHNS/O analyser (model LECO CHN628 and 628S, USA) according to ASTM D-5291 standard method. The particle size distribution was determined using particle size distribution analyser (Malvern mastersizer) and the higher heating value (HHV) of EFBC was measured by using Parr 6100 oxygen bomb calorimeter according to BS EN 14918. The ash compositional analysis was measured using energy dispersive X-ray fluorescence spectrometer (EDX, SHIMADZU EDX-720). The combustion tests on both EFBC and sub-bituminous coal (SBC) were conducted using a fluidised bed reactor (370 mm high and 54 mm wide dimension) and the gaseous emissions were analysed using gas chromatography (GC). EFBC exhibited a comparable HHV (6,317.99 kcaL/kg) with almost similar H/C ratio, higher O/C and (N + O)/C ratios compared to SBC signifying a stable burning. Furthermore, EFBC combustion resulted in lower CO and NOx emissions than the SBC combustion by 51.60% and 60.50%, respectively, suggesting that EFBC is a potential solid fuel in power generation.

Control of Spontaneous Combustion of Sub-Bituminous Coal by Means of Heat Exchanger Submersion inside the Piles

The low-rank coal, such as sub-bituminous and lignite has become a widely used alternative fuel for power generation. During the transportation process from mining location to power plant, coal on the barge might be stored for a long period of time. A control mechanism of spontaneous combustion of coal in barge was simulated in laboratory scale by means of submersing heat exchanger inside the coal bed. The low-rank coal is more prone to self-ignition (spontaneous combustion) which is quite difficult to detect, due to the complex event of spontaneous combustion involving many factors from both intrinsic and extrinsic factors, such as particle size, moisture content, ambient temperature, barometric pressure, etc. A laboratory scale experiment was set up to study the smouldering combustion phenomenon of coal samples and means of control by using heat exchanger submersion in a coal bed. The coal sample was placed inside a wire mesh cube with a coiled copper tube installed in the middle of the coal bed. Fresh water was flowed through the coiled copper tube with controlled intake temperature about 28 °C. Approximately 65 grams of coal is heated in the oven at 210 °C until the temperature in the middle of the pile reaches up to 320 °C, then water is discharged through a copper tube to the middle of the pile and cooling it down. It is found that the temperature of coal sample can be brought down to 200 °C depending on the water flow. Thermocouples are used to measure the coal’s temperature in the middle of the pile. This method shows that the heat generated can be reduced to below the critical temperature for spontaneous combustion. The water flow rate has significant impact on temperature reduction of the coal inside the bed. This method has a potential benefit for controlling spontaneous combustion problem during barge transportation of coal.

Promotional effect of CuO loading on the catalytic activity and SO2 resistance of MnOx/TiO2 catalyst for simultaneous NO reduction and Hg0 oxidation

CuO loaded MnOx/TiO2 mixed oxide (CuMnTi) synthesized by an ultrasonic-assisted impregnation method was for the first time employed for simultaneous nitrogen monoxide (NO) reduction and elemental mercury (Hg0) oxidation under selective catalytic reduction (SCR) atmosphere with the presence of NH3. The CuMnTi catalyst exhibited a wide temperature window from 150 to 250 °C for both NO reduction and Hg0 oxidation. At the optimal temperature of 175 °C, CuMnTi reduced 96.4% of the inlet NO and oxidized 100% of the inlet Hg0 at a very high gas hourly space velocity (GHSV) of 40,000 h−1. O2, HCl and NO significantly promoted Hg0 oxidation and offset the adverse effect of detrimental flue gas components such as water vapor, SO2 and NH3. The protection effect of CuO over MnOx reserved enough active sites of CuMnTi for Hg0 oxidation in the presence of NH3 or SO2. Compared with MnOx/TiO2 (MnTi), the superior redox property, enlarged Hg0 adsorption capacity and decent SO2 resistance of CuMnTi ternary system were evidenced to account for its improved catalytic activity. This study indicated future potential for applying CuMnTi catalyst in simultaneous NO reduction and Hg0 oxidation in low-temperature (150–250 °C) and low-rank (sub-bituminous and lignite) coal combustion flue gases.

Active methods of mercury removal from flue gases

Due to its adverse impact on health, as well as its global distribution, long atmospheric lifetime and propensity for deposition in the aquatic environment and in living tissue, the US Environmental Protection Agency (US EPA) has classified mercury and its compounds as a severe air quality threat. Such widespread presence of mercury in the environment originates from both natural and anthropogenic sources. Global anthropogenic emission of mercury is evaluated at 2000 Mg year−1. According to the National Centre for Emissions Management (Pol. KOBiZE) report for 2014, Polish annual mercury emissions amount to approximately 10 Mg. Over 90% of mercury emissions in Poland originate from combustion of coal.The purpose of this paper was to understand mercury behaviour during sub-bituminous coal and lignite combustion for flue gas purification in terms of reduction of emissions by active methods. The average mercury content in Polish sub-bituminous coal and lignite was 103.7 and 443.5 μg kg−1. The concentration of mercury in flue gases emitted into the atmosphere was 5.3 μg m−3 for sub-bituminous coal and 17.5 μg m−3 for lignite. The study analysed six low-cost sorbents with the average achieved efficiency of mercury removal from 30.6 to 92.9% for sub-bituminous coal and 22.8 to 80.3% for lignite combustion. Also, the effect of coke dust grain size was examined for mercury sorptive properties. The fine fraction of coke dust (CD) adsorbed within 243–277 μg Hg kg−1, while the largest fraction at only 95 μg Hg kg−1. The CD fraction < 0.063 mm removed almost 92% of mercury during coal combustion, so the concentration of mercury in flue gas decreased from 5.3 to 0.4 μg Hg m−3. The same fraction of CD had removed 93% of mercury from lignite flue gas by reducing the concentration of mercury in the flow from 17.6 to 1.2 μg Hg m−3. The publication also presents the impact of photochemical oxidation of mercury on the effectiveness of Hg vapour removal during combustion of lignite. After physical oxidation of Hg in the flue gas, its effectiveness has increased twofold.

No.20 亜瀝青炭の高比率混炭時の燃焼特性(ガス化・燃焼・液化(2))

No.20 亜瀝青炭の高比率混炭時の燃焼特性(ガス化・燃焼・液化(2))

Development of Sulfur Release and Reaction Model for Computational Fluid Dynamics Modeling in Sub-Bituminous Coal Combustion

Pulverized coal-fired boilers applying low-NOx combustion technologies commonly suffer from high-temperature corrosion due to high-concentration H2S. Accurate prediction of sulfur species, especially H2S, is of great importance for the optimized design and operation of boilers and burners to reduce such problems. The sulfur release characteristics from coal and subsequent sulfur species gas-phase reaction mechanism are two critical steps controlling sulfur species evolution. In this study, first, a global sulfur species gas-phase reaction mechanism consisting of 10 reactions is proposed based on a detailed mechanism considering hundreds of elementary reactions. Kinetic parameters of the global mechanism are determined via a rigorous mathematical optimization process. Second, the sulfur release characteristics during coal pyrolysis and char burning of five kinds of sub-bituminous coals are investigated in a drop tube furnace (DTF). Equations describing the relationship between sulfur release and coal consu...

Glycerol effect on the inhibition of spontaneous combustion of subbituminous coal

Factors favoring the phenomenon of spontaneous combustion in coal mainly depend on the intrinsic properties such as coal particle size, moisture content, among others; the medium in which it is located and how it is stored. Consistent with this, the objective of this work is to evaluate the effect of glycerol on the inhibition of self-combustion as water re-adsorption reducer through the addition of glycerol in different amounts (4, 8, 18 and 28% wt). The coal sample was extracted from the Córdoba department, Colombia. Incipient impregnation method was used to perform the addition of glycerol to the desired quantities. Characterizing the coal samples was performed by: TGA-DTG, nitrogen adsorption at -196 °C, C-H-N-O, FTIR, and SEM. The TGA of the coals evaluated in an air atmosphere, show changes in combustion properties of each sample. Di ignition index is reduced as the coal is impregnated with glycerol, obtaining its lowest value for 8wt% of glycerol. The effect of glycerol in inhibiting the spontaneous combustion of coal is exposed in the adsorption equilibrium; the sample with 8wt% glycerol shows the highest reduction of water adsorption in coal validating the proposed technology as inhibitor agent spontaneous combustion phenomenon found in Colombian coal.

Lignites and subbituminous coals combustion in Polish power plants as a source of anthropogenic mercury emission

Coal combustion is one of the main anthropogenic sources of mercury emission to the atmosphere. A total of 121 subbituminous coal samples and 29 lignite samples representative for coals burned in Polish power and heat and power plants were acquired and examined. The average mercury content in subbituminous coal samples was 104μgkg−1 (4.591gHgTJ−1), varying from 18 to 518μgkg−1. The average chlorine and bromine content were 2200ppm and 12ppm, respectively. For lignite samples the average mercury content was 197μgkg−1 (21.380gHgTJ−1), varying from 60 to 665μgkg−1. Lignite samples contained significantly less chlorine (40ppm on average) and bromine (4ppm) than coal samples. The Cl·Hg−1 ratio for subbituminous coal samples varied between 103 and 105. For lignite samples this ratio was around 10. Mercury mass balances were performed for two subbituminous coal-fired plants and one lignite-fired plant. The chemical composition of each type of coal had a significant influence on mercury concentration and speciation in the flue gas. The proportion of oxidized mercury (Hg2+) correlated with chlorine content. The relatively large proportion of particulate-bound mercury (Hgp) and Hg2+ measured favored mercury removal by the electrostatic precipitator (65% on average), and by the wet flue gas desulfurization units (32%). Results of mercury emissions from the stack to the atmosphere were 2.0–5.0 and 15.1μgm−3, for plants burning subbituminous coal and lignite, respectively. The mercury leaving the stack from three plants was over 90% elemental mercury (Hg0). Calculated mercury emission factors for plants burning subbituminous coal and lignite were: 0.71–1.80gHgTJ−1 (subbituminous coal) and 6.09gHgTJ−1 (lignite).

Catalytic Destruction of a Surrogate Organic Hazardous Air Pollutant as a Potential Co-benefit for Coal-Fired Selective Catalytic Reduction Systems

Catalytic destruction of benzene (C6H6), a surrogate for organic hazardous air pollutants (HAPs) produced from coal combustion, was investigated using a commercial selective catalytic reduction (SCR) catalyst for evaluating the potential co-benefit of the SCR technology for reducing organic HAP emissions. Bench-scale experiments were performed using simulated coal combustion flue gases under a broad range of SCR reaction conditions. C6H6 was added at 1 or 17 ppm into the flue gas mixtures with different concentrations of sulfur dioxide (SO2), nitrogen oxide (NO), hydrogen chloride (HCl), and ammonia (NH3) to simulate the combustion of bituminous and sub-bituminous coals. The destruction of the C6H6 across the catalyst was measured by a total hydrocarbon analyzer and a resonance-enhanced multiphoton ionization time-of-flight mass spectrometer (REMPI–TOFMS) for the experiments with high (17 ppm) and low (1 ppm) concentrations of C6H6, respectively. The operating parameters of the SCR process, including the ...

Evaluation of interactions between soil and coal fly ash leachates using column percolation tests

The aim of this work was the assessment of the environmental impact of different origin fly ashes with regard to their final disposal. The experimental procedure included the performance of single column tests and column tests of fly ash and soil in series. The appraisal of the potential environmental hazards was implemented using physicochemical analyses and bioassays. Two different fly ash samples were examined, one fly ash produced from the combustion of sub-bituminous coal (CFA) and one fly ash produced from the combustion of lignite (LFA). Single column percolation tests were performed according to NEN 7343 protocol, while fly ash/soil experiments were conducted incorporating slight modifications to this protocol. The study focused on the release of metals Ba, Cr, Cu, Mo, Se and Zn and the ecotoxic behavior of leachates on crustacean Daphnia magna and bacteria Vibrio fischeri. The infiltration of the leachates of both fly ashes through soil affected considerably their leaching profile. The transport of Cu and Zn was facilitated by the dynamic leaching conditions and influenced by the pH of the leachates. Moreover, the release and bioavailability of Cr, Cu and Zn was probably altered during the infiltration experiments and organisms’ response was not always correlated with the concentration of metals. Nevertheless, the results are signalling that possible manipulations and final disposal of fly ash should be considered when environmental threats are investigated.

Thermogravimetric analysis of the behavior of sub-bituminous coal and cellulosic ethanol residue during co-combustion

The influence of the addition of cellulosic ethanol residue (CER) on the combustion of Indonesian sub-bituminous coal was analyzed by non isothermal thermo-gravimetric analysis (TGA). The effect of blends ratio (5%, 10%, 15% and 20%), interaction mechanism, and heating rate (5°C/min, 10°C/min, 15°C/min, 20°C/min) on the combustion process was studied. The results show that the increase of the blending ratio allows to achieve the increase of the combustibility index from 7.49E−08 to 5.26E−07 at the blending ratio of 20%. Two types of non-isothermal kinetic analysis methods (Ozawa–Flynn–Wall and Vyazovkin) were also applied. Results indicate that the activation energy of the blends decreases with increasing the conversion rate. In particular, the blending ratio of 20% confirms to have the better combustion performance, with the average value of the activation energy equal to 41.10kJ/mol obtained by Ozawa–Flynn–Wall model and 31.17kJ/mol obtained by Vyazovkin model.

Calorimetry in testing waste materials from the brown coal combustion

The calorimetric measurements were applied in testing the wastes collected from different furnaces in electric power plants as materials to be used in civil engineering. The fly ash materials were collected from two power stations based on different brown coal deposits and working with conventional and fluidized bed installation. The reactivity of high calcium fly ash from sub-bituminous coal combustion has been proved in calorimetric, conductometric, chemical shrinkage, and rheological measurements before their practical implementation on larger scale. Highly soluble components of fly ash contribute to the hydration products and structure formation, followed by setting and hardening of fly ash–cement mixture. These results have been the base of research project aimed in the innovative solutions dealing with the management of deposits of wastes generated as a result of coal combustion. The standardization and potential use on larger scale of these materials, necessary from the environmental point of view, seems to be the question of nearest future.

Numerical simulation of sub-bituminous coal and bituminous coal mixed combustion employing tabulated-devolatilization-process model

To investigate the cause of the increase in the unburned fraction when sub-bituminous coal is mixed with bituminous coal observed in previous experimental research using a 100 kg-coal/h-class coal combustion test furnace, numerical simulations of the mixed combustion of sub-bituminous coal and bituminous coal are performed. To take into account the effect of the particle heating rate on the devolatilization parameters, the tabulated-devolatilization-process model (TDP model) is employed. The results show that the simulation could qualitatively reproduce the experimental results, which are an increase in flame lift-off with increasing sub-bituminous coal mixing ratio and a maximum value of the unburned fraction at a sub-bituminous coal mixing ratio of 25%. Furthermore, it is clarified from the simulation results that the nonlinear increase in the overall unburned fraction in the case of sub-bituminous coal mixing with bituminous coal is caused by the steep increase in the unburned fraction of bituminous coal particles with increasing sub-bituminous coal mixing ratio.

Understanding selected trace elements behavior in a coal-fired power plant in Malaysia for assessment of abatement technologies

The Proposed New Environmental Quality (Clean Air) Regulation 201X (Draft), which replaces the Malaysia Environmental Quality (Clean Air) 1978, specifies limits to additional pollutants from power generation using fossil fuel. The new pollutants include Hg, HCl, and HF with limits of 0.03, 100, and 15 mg/N-m3 at 6% O2, respectively. These pollutants are normally present in very small concentrations (known as trace elements [TEs]), and hence are often neglected in environmental air quality monitoring in Malaysia. Following the enactment of the new regulation, it is now imperative to understand the TEs behavior and to assess the capability of the existing abatement technologies to comply with the new emission limits. This paper presents the comparison of TEs behavior of the most volatile (Hg, Cl, F) and less volatile (As, Be, Cd, Cr, Ni, Se, Pb) elements in subbituminous and bituminous coal and coal combustion products (CCP) (i.e., fly ash and bottom ash) from separate firing of subbituminous and bituminous coal in a coal-fired power plant in Malaysia. The effect of air pollution control devices configuration in removal of TEs was also investigated to evaluate the effectiveness of abatement technologies used in the plant. This study showed that subbituminous and bituminous coals and their CCPs have different TEs behavior. It is speculated that ash content could be a factor for such diverse behavior. In addition, the type of coal and the concentrations of TEs in feed coal were to some extent influenced by the emission of TEs in flue gas. The electrostatic precipitator (ESP) and seawater flue gas desulfurization (FGD) used in the studied coal-fired power plant were found effective in removing TEs in particulate and vapor form, respectively, as well as complying with the new specified emission limits.Implications:Coals used by power plants in Peninsular Malaysia come from the same supplier (Tenaga Nasional Berhad Fuel Services), which is a subsidiary of the Malaysia electricity provider (Tenaga Nasional Berhad). Therefore, this study on trace elements behavior in a coal-fired power plant in Malaysia could represent emission from other plants in Peninsular Malaysia. By adhering to the current coal specifications and installation of electrostatic precipitator (ESP) and flue gas desulfurization, the plants could comply with the limits specified in the Malaysian Department of Environment (DOE) Scheduled Waste Guideline for bottom ash and fly ash and the Proposed New Environmental Quality (Clean Air) Regulation 201X (Draft).