High-ash Coal Research Articles

MODERN COMPUTING EXPERIMENTS ON PULVERIZED COAL COMBUSTION PROCESSES IN BOILER FURNACES

The aim of the work is to create new computer technologies for 3D modeling of heat and mass transfer processes in high-temperature physico-chemical-reactive environments that will allow to determine the aerodynamics of the flow, heat and mass transfer characteristics of technological processes occurring in the combustion chambers in the operating coal TPP RK. The novelty of the research lies in the use of the latest information technologies of 3D modeling, which will allow project participants to obtain new data on the complex processes of heat and mass transfer during the burning of pulverized coal in real combustion chambers operating in the CHP of RK. Numerical simulation, including thermodynamic, kinetic and three-dimensional computer simulation of heat and mass transfer processes when burning low-grade fuel, will allow finding optimal conditions for setting adequate physical, mathematical and chemical models of the technological process of combustion, as well as conduct a comprehensive study and thereby develop ways to optimize the process of ignition, gasification and burning high ash coals. The proposed methods of computer simulation are new and technically feasible when burning all types of coal used in pulverized coal-fired power plants around the world. The developed technologies will allow replacing or eliminating the conduct of expensive and labor-consuming natural experiments on coal-fired power plants.

Comparative evaluation of performance of high and low ash coal fuelled chemical looping combustion integrated combined cycle power generating systems

Chemical looping combustion is a novel concept for the inherent capture of CO2 gas. The recent interest of the CLC study is the direct fuelling of coal for the metal-oxy combustion that simplifies the working components of the power plants. In addition, the effect of the ash content of coal in the CLC process is needed to be elucidated for the commercial implementation of this technology. Based on these objectives, the present study is focused on the process simulation of combined cycle power plants using ASPEN plus software. The simulation work intends to perform the CLC process in two different ways, namely, direct and indirect coal fuelled CLC process (without a gasifier). The effect of the gasifying medium (steam and CO2) on the net thermal efficiency of power plants is evaluated. The simulation results show that the direct CLC process with CO2 as the gasifying medium using iron oxide as an oxygen carrier achieved a higher efficiency of 46.8% and 43% in the case of low and high ash coal, respectively. Further, the economic analysis shows a low levelized cost of electricity (LCOE) for the direct CLC process by about 6.2–8.2 $/MWh, compared to the indirect CLC process.

Interaction between sequestered supercritical CO2 and minerals in deep coal seams

This study investigates the interaction between supercritical CO2 (scCO2) and minerals in coal that may occur during CO2 sequestration into deep coal seams. Two low-rank coals with low-ash content, one low-rank coal with high-ash content and one high-rank coal with low-ash content were used to study the interactions. A coal-CO2 geochemical interaction experiment with a typical high-ash coal was conducted to investigate change of the water-soluble elements after scCO2 interaction. X-ray powder diffraction (XRD) was used to determine the effects of scCO2–H2O on the minerals in the four coals. In addition, the influence of scCO2 on pore structure of four coals was studied based on liquid nitrogen adsorption experiment. The results suggest that scCO2 can effectively enhance the solubility of all elements from coal in water because of scCO2 interaction. ScCO2 can significantly improve the solubility of trace elements than that of major elements. Because of the relatively low mineral content in coals and the short experimental period, secondary minerals formed by scCO2-mineral-water interaction were not determined with XRD. However, the content of primary minerals changed; the apparent content of quartz increased and the content of kaolinite, carbonate minerals and pyrite decreased. For the experimental coals in this study, scCO2 can enlarge the pore size of the micropores for low-ash coal and mesopores for low-rank coal, but shrinks that of micropores for high-ash coal and mesopores for high-rank coal.

Co-gasification of high ash biomass and high ash coal in downdraft gasifier

The present work studies gasification of high ash biomass (20–25% w/w), high ash coal (30–35% w/w), and their co-gasification in a downdraft gasifier developed in our earlier study (Siddiqui et al., 2018). TGA studies were performed to examine the change in performance due to the catalytic effect of inorganic content. The effect of biomass ratio (BR) was examined. Higher percentage of biomass increased the conversion to gas on carbon basis, and decreased the conversions to char and tar. The presence of coal enhanced the temperature and hence the rates of the reactions to certain extent. The respective cold gas and thermal efficiencies for BR0 are 33.06% and 49.38%, and for BR1 are 52.22% and 64.15%. BR0.75 gave the best performance with CGE of 57.5% and thermal efficiency of 72.63%. Finally, the clinker formation issue and the preliminary atmospheric emissions measurements are reported for gasifier.

Экспериментальное исследование пульсационных характеристик закрученного потока в модели четырехвихревой топки

Актуальность исследования обусловлена необходимостью вовлечения в топливно-сырьевую базу низкосортных высокозольных углей в связи с ограниченностью запасов высококачественного топлива. Для их эффективного и экологически безопасного использования требуется разработка новых и модернизация имеющихся котельных агрегатов с предварительным физическим и численным моделированием. Целью работы является экспериментальное исследование пульсационных характеристик турбулентного закрученного потока в модели перспективного топочного устройства, использующего четырёхвихревую схему сжигания пылеугольного топлива. Объектом исследования является изотермическая лабораторная модель четырёхвихревой топки, выполненная из оптически прозрачного оргстекла для проведения измерений в рамках современных бесконтактных методов диагностики потоков. Методы: физическое лабораторное моделирование аэродинамики и процессов переноса в четырехвихревой топке; бесконтактное исследование осредненных и пульсационных характеристик в объеме модели топки при различных режимных параметрах; исследование пульсаций давления с использованием конденсаторного микрофона. Результаты. С использованием метода цифровой трассерной визуализации получены распределения осредненных и пульсационных характеристик скорости потока в ряде сечений модели в широком диапазоне режимных параметров. Определено положение зон с высоким значением турбулентных пульсаций и застойных зон, установлены особенности их расположения в зависимости от режимов. С использованием конденсаторного микрофона получены данные о пульсациях давления в локальных областях объема модели. Анализ спектральных характеристик с применением к полученным данным преобразования Фурье показал, что в изучаемой модели отсутствуют нестационарные периодические колебания, связанные с прецессией вихревого ядра потока. Измеренные пульсации давления вызваны акустикой, пульсации скорости носят случайный характер и не связаны с динамикой когерентных структур.

Production of complex alloy from high-silicon manganese ore and high-ash coals of Kazakhstan

The article presents theoretical and technological foundations for the production of complex alumosilicomanganese alloy (ASM) from high-silicon manganese ore, Karaganda high-ash coals and Teniz-Korzhunkol coal basins (Borly and Saryadyr coal deposits), Tekturmas deposit quartzite and long-flame coal of Shubarkol field. Based on the reference data and calculated thermodynamic data (for compounds with unknown thermodynamic data), a mathematical model of the phase structure was constructed by conducting a thermodynamic-diagram analysis of four-component Fe – Si – Al – Mn system. The compositions of alumosilicomanganese obtained from the coals of Karaganda and Teniz-Korzhunkol coal basins, in contrast to ASM alloy from Ekibastuz coals, are shifted in the region of tetrahedra with relatively large volumes. This fact indicates their increased stability and technological predictability. The results of the series of experimental tests carried out in an ore-thermal furnace has shown the possibility of obtaining an ASM alloy with controlled chemical composition using high-ash coals of Borly and Saryadyr fields, the substandard high-silica manganese ore of Zapadny Kamys field, addition of long-flame coal from Shubarkol deposit and quartzite of Tekturmas deposit to the mix by continuous slag-free process. Chemical composition of the alloy was regulated by addition of manganese ore to the sample of charge materials. A complex alloy was obtained with the following chemical composition (% by mass): 32 – 53 % of Si; 15.5 – 25.0 % of Al; 12 – 32 % of Mn; 8 – 20 % of Fe; 0.02 – 0.05 % of P; 0.2 – 0.5 % of C. The resulting metal does not crumble into powder when stored. This is ensured by low phosphorus content and high aluminum content of more than 10 %. Phase components of the experimental alloy were determined. The use of dumping high-ash coals, substandard manganese ores and the complete elimination of coke use ensure a low cost of the alloy. It is proposed to use this alloy for deoxidation and alloying of steel, and also as a reducing agent in the production of refined ferromanganese grades.

Development of the smelting technology of complex aluminum-chrome-silicon-containing ASC alloy from substandard raw materials

Scientists of the Chemical-Metallurgical Institute named after Zh. Abishev develop new types of highly effective alloys based on resource-saving technologies that allow the complex processing of natural and technogenic raw materials, such as carbonaceous waste, chrome ore fines, etc. Therefore, it has led to the creation of a onestage, slag-free and non-waste technology with the maximum use of all useful charge components. With disappearance of rich ore reserves, as well as the expansion of demand for raw materials and the development of technology, the rich ores are replaced by poorer and substandard ones that require new methods of processing. The maximum use of raw materials and industrial waste, if this is economically justified, is one of the basic requirements for the technology. This task is closely intertwined, and in many cases coincides with another task – the development of integrated methods of raw materials processing, which, in the general production cycle, allows using, if possible, all useful elements of raw materials. The main objective of the study is to find ways to improve the use of sub-standard chrome ore. As a reducing agent in the electrothermal smelting of the ACS alloy, instead of expensive coke, without which no process of carbothermic smelting is required, a cheap high-ash Borly coal was used. The coal ash, which mainly consists of silica and alumina, is an additional source of silicon and aluminum in the alloy. This technology will be simple and allows regarding substandard chromium ore as a complex metallurgical raw material, since not only chrome is used, but also the components of the waste rock – silicon and aluminum. As a result of the complete reduction of all charge oxides, this technology will make it possible to obtain a complex alloy of ACS with an approximate chemical composition: 39 – 43 % of chromium, 23 – 27 % of silicon, 7 – 10 % of aluminum. The transition of the main components of the charge to the alloy will be: 82 – 85 % of chromium, 68 – 70 % of silicon, 59 – 60 % of aluminum. In this paper, the results of experimental studies on the production of a complex alloy of ACS (aluminum-chromium-silicon) from high-ash coals of the Borly deposit and chrome ore minerals of the Donskoi GOK are presented. The course of furnace operation is described with a lack, excess, and also the calculated amount of the reducing agent. The ways of eliminating the upset in furnace operation are shown.

An evaluation of machine learning and artificial intelligence models for predicting the flotation behavior of fine high-ash coal

In this study, five different machine learning (ML) and artificial intelligence (AI) models: random forest (RF), artificial neural networks (ANN), the adaptive neuro-fuzzy inference system (ANFIS), Mamdani fuzzy logic (MFL) and a hybrid neural fuzzy inference system (HyFIS) were employed to predict the flotation behavior of fine high ash coal in the presence of a novel “hybrid” ash depressant consisting of polyacrylamide chains grafted onto aluminium hydroxide nanoparticles: Al(OH)3-PAM (Al-PAM). A total of 51 flotation tests were conducted on coal samples with 38% ash-content and a P80 of approximately 49 μm. Different influencing variables of coal flotation including polymer dosage, pH, polymer conditioning time, sodium metasilicate dosage (commercial dispersant), and the impeller speed were used as inputs for the models. The combustible recovery and ash content of coal reported to the concentrate were used as response variables (outputs). For AI model development, 80% of the total data was used for training phase and 20% was used for testing phase. Coefficient of determination (R2) and root-mean-square error (RMSE) were used as performance indicators of the models. The MFL model showed the best accuracy for the prediction of the combustible recoveries and the froth ash contents for this specific feed. However, in case of any significant change in the characteristics of the feed, these models would have to be re-trained using the data obtained through further physical experimentation and/or process model simulations. Moreover as these models are trained on laboratory scale data, these are only good for the predictions at laboratory scale.

Design of experiments to optimize the extraction parameters of a power grade Indian coal

Low grade high ash coals with difficult physical washability characteristics require chemical cleaning techniques such as solvent extraction to obtain super clean coal with lower ash contents. Kedla, an Indian low grade coal has ash content around 44%–50% and there is a need to maximize its solvent extraction yield so as to make this power grade coal industrially useful. This paper highlights the use of definitive screening design and response surface methodology to extract the maximum organic matter from Kedla coal using ethylenediammine (EDA) and N-methyl pyrollidone (NMP) as solvents under mild atmospheric pressure conditions. The coal was pre-treated with acetic acid before extractions were carried out. The parameters such as the acid pre-treatment time, acid concentration, particle size, the co-solvent concentration and the solvent concentration were optimized in this paper. With this design of experiments technique about 40% of the organic matter with minimal ash (less than 2%) content was rendered extractable unlike the already postulated designer solvent system—e, N system (i.e. NMP containing small amount of EDA) that uses coal to solvent ratio as 1:17 (wt/vol) and coal to co-solvent ratio as 1:1(wt/vol) thus only giving 19% extraction yield. Therefore, the present design of experiments technique helps in conserving the number of experiments for process intensification.

Microwave-assisted rapid upgrading of Indian high ash coal and its blending with untreated coal to improve the slurryability and rheological characteristics of blended slurry

ABSTRACT The Indian high ash coal collected from Makum coal fields of Assam is crushed, sieved and air dried using lab scale instruments. Based on the preliminary results, the coal sample is treated in a lab scale microwave oven at 700 W of input power for 120 s. The physical and morphological properties of untreated coal show that there is an increase in the fines upon the treatment. The chemical analysis shows that the carbon and fixed carbon fractions are found to increase by 17.66% and 21.3% respectively whereas the ash and oxygen mass fractions are observed to decrease by 15.56% and 28.91% respectively. Due to this, the maximum settled concentration is observed to decrease by a maximum of 19.8%, and the time to reach maximum settling is observed to increase by a maximum of 58.5%. The rheological characteristics reveal that all the slurries behave like a Newtonian fluid at 10–30% solid concentration whereas a pseudoplastic behavior is observed at 40–60% solid concentration. The apparent viscosity is observed to reduce by a maximum of 46.11%. The optimum proportion of treated coal is observed to be 40% by mass of coal.

Alloy Production from High-Silica Manganese Ore and High-Ash Kazakhstan Coal

Engineering principles are outlined for the production of silicon–aluminum–manganese alloy from high-silica manganese ore and high-ash Kazakhstan coal (from the Borly and Saryadyr fields in the Karaganda and Teniz-Korzhunkol coal basins), Tekturmas quartzite, and Shubarkol long-flame coal. By thermodynamic diagram analysis of the four-component Fe–Si–Al–Mn system on the basis of handbook data (and calculated thermodynamic data where no handbook data are available), a mathematical model of the phase structure may be developed. The aluminum–silicon–manganese composition obtained from the Karaganda and Teniz-Korzhunkol coal, in contrast to the aluminum–silicon–manganese alloy from Ekibastuz coal, is shifted on the thermodynamic diagrams toward tetrahedra with relatively large volume. This indicates increased stability and technological predictability. The results of tests in an ore furnace show that aluminum–silicon–manganese alloy of regular composition may be obtained by a continuous slag-free method from high-ash Borly and Saryadyr coal and unconditioned high-silica manganese ore from the Western Kamys field if Shubarkol long-flame coal and Tekturmas quartzite are added to the batch. The alloy composition may be regulated by adding manganese ore to the weighed batch materials. An alloy with the following composition is obtained: 32–53 wt % Si, 15.5–25.0 wt % Al, 12–32 wt % Mn, 8–20 wt % Fe, 0.02–0.05 wt % P, and 0.2–0.5 wt % C. The resulting alloy does not crumble to powder on storage, thanks to the low phosphorus content and high aluminum content (>10%). The phase components of the experimental alloy are determined. The cost of the alloy is low, since it is produced from high-ash tailings coal and unconditioned high-silica manganese ore, with absolutely no coke. The alloy may be used for the reduction and alloying of steel and also as a reducing agent in the production of refined ferromanganese.

Production of Aluminum–Chromium–Silicon Alloy from Unconditioned Materials

At Abishev Chemical and Metallurgical Institute, highly effective new alloys have been developed on the basis of resource-saving technology. The alloys may be produced from natural and industrial materials such as coal waste and chromium-ore fines. The result is a single-stage, slag-free, and waste-free technology with the maximum utilization of all the useful batch components. As reserves of rich ores are exhausted, alternatives must be sought. The use of leaner and unconditioned ores calls for new processing methods. Such technologies must make the best possible use of the raw materials and production wastes, within the limits of economic feasibility. In many cases, this complex problem is associated with the development of complex processing methods capable of utilizing all the useful components in the raw materials within a single production cycle. In the present work, the goal is to find means of more efficiently utilizing unconditioned chromium ore. In the electrosmelting of aluminum–chromium–silicon alloy, the traditional reducing agent is coke, which is expensive. Our proposal is to use inexpensive high-ash Borly coal. The ash in this coal consists mainly of silica and aluminum and provides an additional source of silicon and aluminum for the alloy. The proposed technology is simple and makes effective use of unconditioned chromium ore, which provides not only chromium but also the silicon and aluminum present in the ash. By complete reduction of all the oxides in the batch, this technology yields aluminum–chromium–silicon alloy with the following approximate composition: 39–43% Cr, 23–27% Si, and 7–10% Al. The extraction of the basic batch components in the alloy is as follows: 82–85% Cr, 68–70% Si, and 59–60% Al. Experimental data are presented for the production of aluminum–chromium–silicon alloy from high-ash Borly coal and chromium-ore fines from Don enrichment facility. Furnace operation is described in the case of deficient, excess, and correct quantities of reducing agent. Methods of eliminating furnace disruption are outlined.

Laboratory-Scale Studies on Humidified O2-Fed High-Ash Coal-Based Underground Coal Gasification

With the depletion of coal reserves all over the world, efforts are being made worldwide to utilize those deep underground coal seams, which are difficult to mine or are not feasible economically. Underground coal gasification (UCG) is a promising technology to achieve that objective and also to reduce the atmospheric pollution that is casued by surface gasification of the mined coal. Based on the previous research performed in this field, it is a well-known fact that the optimum quantity of water influx into coal seam can increase the hydrogen content of the product gas. In our earlier study, a novel method of utilizing humidified oxygen as the gasification agent was conducted for low ash coal gasification. The experimental results had shown the production of substantial quantity of hydrogen in the product gas. In the present study, the laboratory-scale experiments are extended to high-ash Indian coals with increases in the absolute humidity of the feed oxygen by preheating the water (humidifying medium)...

Petrographic and chemical reactivity assessment of Indian high ash coal with different biomass in fluidized bed co-gasification

The reactivity of coal and biomass has been evaluated by comparing the optical and chemical changes in feed material prior and after the co-gasification. The proximate, ultimate, GCV, low-pressure N2 sorption isotherm, micropetrography, SEM and EDX spectroscopy analyses are carried out to assess the reactivity of blends of high ash Indian coal and biomass. The relative changes in parameters like surface area, pore size, and pore volume have been correlated with reacted percentage area of coal macerals and cellulose-lignin cellular structures of biomass. The Optimas image processing software is being used to mark the reacted portion of organic constituents and calculated the reactivity percentage. The bottom ash of pure coal has shown the least reacted organic matters, indicating inefficiency of high ash coal due to a large amount of inorganic and inertinite contents that is resisting the oxidation. The reactivity percentage is determined by the petrographic and SEM images, and varies from 36.34 to 99.64% and 6.61–96.22%, respectively. It is summarised that the estimation of percentage alteration of macerals and other micro-organic constituents can be used as one of the practical approaches for the assessment of the reactivity of coal and biomass. The blending ratio 6:4 of coal and press mud has shown the highest reactivity (>99.64%). The values of petrographic and SEM reactivity have shown good correlations with the carbon contents, unreacted vitrinites, mineral matters and biomass remnants. These relations have been taken into account to formulate the proposed petrographic empirically calculated reactivity (RPEC). The focus has also been made to investigate the influence of feed composition on carbon conversion and heating value of the product gas.

ANALYTICAL EXPRESSIONS FOR Fe – Si – Al – Mn METAL SYSTEM AND PHASE COMPOSITION OF ALUMOSILICOMANGANESE

Calculations of analytical expressions of Fe – Si – Al – Mn quaternary metal system and phase compositions of complex alu­mosilicomanganese alloy are presented in the article. Analytical expressions were obtained by the derivation of transformation equations that show any secondary system through the primary components of the base system. The location of the melt given composition was determined from positive values of coefficients of the equations of certain polytope calculated by Heath equation. Chemical composition of the complex alumosilicomanganese al­loy obtained under semi-industrial conditions corresponds to the tetrahedron FeAl3 – Al – Si – Mn11Si19 with the volume equal to V = 0,216811. It was established that compositions of alumosili­comanganese obtained from coals of the Karaganda coal basin, in contrast to the AMS alloy from Ekibastuz coals, tend to be in the re­gion of tetrahedra with a relatively large volume. The alloy compo­sitions modeled by such large-volume tetrahedrons are more stable and technologically predictable. Practical application of the results of the thermodynamic-diagram analysis (TDA) to the compositions of different grades of alumosilicomanganese reduces to finding of elementary tetrahedra within which their compositions are limited, and the normative distribution of primary phases between second­ary compounds for them is equal to 100 % of the considered tetra­hedron. Based on the normative distribution of the primary phases between the compounds (secondary phases) located on vertices of the Fe – Si – Al – Mn tetrahedron, a metallurgical evaluation of the melts can be made. This will subsequently allow to determine the phase composition of metal products at smelting of various grades of alumosilicomanganese and to limit the residual content of silicon and aluminum in them while using the latter in the recovery of man­ganese from manganese ore, as well as silicon and aluminum from high-ash coal. The derived analytical expressions for estimating the type and number of secondary phases of Fe – Si – Al – Mn system formed in it are universal and can be used both at smelting of vari­ous grades of alumosilicomanganese and in assessing the composi­tions of ferrosilicoaluminum and ferrosilicomanganese.

Pressurized Liquid Extraction of Brazilian Coal Followed by the Extracts Characterization by Gas Chromatography Coupled to Mass Spectrometry.

This work reports a study on the use of Pressurized Liquid Extraction (PLE) for the selective extraction of organic compounds (aliphatic hydrocarbons - AHs, polycyclic aromatic hydrocarbons - PAHs and polycyclic aromatic compounds - PACs) from high-ash Brazilian coal. A homemade PLE system was built and solvents of different polarities (hexane, toluene and ethanol) were employed to extract the organic compounds from coal samples at a pressure of 10 MPa, under temperatures of 80°C and 200°C and extraction times up to 120 min. The selectivity of the extraction process was evaluated by a well-established methodology employed for the characterization of coal extracts (Preparative Liquid Chromatography - PLC 8). The fractions obtained in the PLC-8 method were dried and, after, quantified by gravimetry. Results showed that the proposed method of extraction was selective for the extraction of AHs using hexane at the temperature of 80°C and for the extraction of PAHs at 200°C. Additionally, the method showed to be selective for the extraction of PACs using ethanol at both studied temperatures. The AHs and PAHs fractions were also analyzed by GC-MS, showing that the first was composed mainly by low molecular weight compounds (<31 carbons) while the second by pyrenes, fluoranthenes, crysenes, benzopyrenes, perylenes and benzofluoranthenes. The present method showed to be a powerful tool for selective extraction of organic compounds from coal samples with simplicity, low quantity of solvent and filling other the requirements to be considered a greener method of extraction.

Co-gasification of High Ash Coal–Biomass Blends in a Fluidized Bed Gasifier: Experimental Study and Computational Intelligence-Based Modeling

Co-gasification (COG) is a clean-coal technology that uses a binary blend of coal and biomass for generating the product gas; it is environment-friendly since it emits lesser quantities of pollutants compared to the coal gasification process. Although coals found in many countries contain high percentages of ash, co-gasification studies involving such coals, and the process modeling thereof, are rare. Accordingly, this study presents results of the co-gasification experiments conducted in a fluidized-bed gasifier (FBG) pilot plant using as a feed the blends of high ash Indian coals with three biomasses, namely, rice husk, press mud, and sawdust. Since the underlying physicochemical phenomena are complex and nonlinear, modeling of the COG process has been performed using three computational intelligence (CI)-based methods namely, genetic programming, artificial neural networks, and support vector regression. Each of these formalisms was employed separately to develop models predicting four COG performance variables, namely, total gas yield, carbon conversion efficiency, heating value of product gas, and cold gas efficiency. All the CI-based models exhibit an excellent prediction accuracy and generalization performance. The co-gasification experiments and their modeling presented here for a pilot-plant FBG can be gainfully utilized in the efficient design and operation of the corresponding commercial scale co-gasifiers utilizing high ash coals.

Demineralization mechanism and influence of parameters on high ash Indian coal by chemical leaching of acid and alkali solution

The current research was investigated the mechanism of coal demineralization and the effect of leaching parameters on high ash coal and study the characterization of pre and post-treated coal. The two high ash Indian coal selected from Mahanadi Coalfield Limited, Odisha, pulverized to 375, 230 and 180 µm particle size were undergone simultaneous acid and alkali treatment at a different concentration, temperature and time. The percent demineralization was increased with decrease the size of the particle and rises with leaching parameters. The investigation suggested 180 µm particle size offers efficient demineralization for both coals at 30% NaOH and 30% H2SO4 concentration. The alkali leaching leads to obtaining the demineralization 46% and 42% whereas acid treatment resulted in 34% and 32% of the original coal samples. The extent of demineralization was improved the calorific value of coal. Besides, the degree of demineralization was proved from the FTIR, XRF and FESEM–EDX analysis results. FTIR analysis result showed that the peak intensity of mineral band decreased by the leaching effect and the degree of demineralization was significantly obtained to large extent by the X-ray Fluorescence spectrometer; which elucidates major minerals removed from coal by the leaching effect of acid and alkali solution.

Improving efficiency of CCS-enabled IGCC power plant through the use of recycle flue gas for coal gasification

CO2 capture from coal-fired power plants is necessary for continued use of coal as a fuel. Proven CO2 capture techniques such as amine absorption and oxyfuel combustion entail significant energy penalty leading to considerable decrease in the net thermal efficiency of the power plant. Recent studies of high-ash Indian coals show that CO2 has sufficient reactivity for coal gasification in temperature ranges of interest to IGCC. Against this background, we analyse in the present study, a new power plant layout which uses part of the sequestered flue gas stream for high-pressure gasification of the coal within the framework of an IGCC power plant with CO2 capture. Detailed thermodynamic calculations of the new plant layout, referred to here as Oxy-RFG-IGCC-CC, using commercial power plant simulation software show that the optimized Oxy-RFG-IGCC-CC plant with CO2 capture produces power at an overall thermal efficiency of 34.2%, which is nearly the same as that of current generation of pulverized coal boiler-based power plants without CO2 capture or that of a conventional IGCC with post-combustion capture. The proposed simpler layout is also 1.9% more efficient than a comparable CO2-capture-enabled IGCC plant that uses steam for coal gasification.

Improved Slurryability and Rheological Characteristics of High Ash Indian Coal by Hydrothermal Treatment

ABSTRACT The crushed and sieved high ash coal samples are treated hydrothermally in a 15 l (liters) lab scale autoclave at a temperature of 394 K and residence times of 30, 45, 75 and 120 minutes. The hydrothermal treatment (HTT) of the coal samples leads to the increase in the carbon and fixed carbon fractions whereas a decrease in the oxygen and volatile fractions. A significant decrease in the maximum settled concentration is observed upon HTT and settling time increases by ~48%. All the suspensions behave like a Newtonian fluid up to a solid concentration of 30% (10–30%) and for the concentrations >40% (40–60%), the suspensions behave like a pseudoplastic or shear thinning fluid. The HTT leads to a significant improvement in the rheological characteristics of the CWS. The apparent viscosity shows an increase with solid concentration for raw as well as HTT coals. Whereas a decreasing trend is observed with treatment time and shear rate. The apparent viscosity shows a maximum improvement by 60.1, 50.71, 39.9, 50.55, 65.69 and 75.41% at 10, 20, 30, 40, 50 and 60% solid concentration, respectively. As similar characteristics are observed at residence times of 75 and 120 minutes, the optimum treatment time is observed to be 75 minutes.