Sulfur Content Of Coal Research Articles

Fine coal desulphurization and microwave energy absorption behaviour by microwave magnetic separation

AbstractMicrowave energy has been used to improve the coal‐pyrite magnetism, while magnetic medium has been added to enhance the microwave energy. Hence, there will be a secondary gradient magnetic chain, which can improve the desulphurization process through magnetic separation. Microwave energy and medium synergistic effects are able to readily improve the magnetic desulphurization process for fine coal. The present paper has studied the impact of microwave energy on the magnetic desulphurization process for fine coal. Intrinsic electromagnetic parameters of different materials were used to analyze and predict the equivalent dielectric parameters of the fine coal layer. The electromagnetic parameter according to the effective medium theory equation for fine coal was established. Coal specific susceptibility is related to pyrite content and pyrrhotite content in pyrite. The specific susceptibility values for the three types of coals were found to be in the following order: Lu'an (LA) coal > Weinan (WN) coal > Yiluo (YL) coal. The most suitable value for LA high‐sulphur coal's sulphur content after being separated by dry type rare earth roll strong magnetic separator appeared to be 60 s delayed in nitrogen atmosphere compared to the corresponding value in an air atmosphere. LA fine coal sulphur content reduced to 2.05 % from 3.66 %, and the microwave magnetic separation desulphurization rate was 44 %.

Sulfur Removal in Bio-Briquette Combustion Using Seashell Waste Adsorbent at Low Temperature

Presently, biomass is mostly utilized as co-fuel in coal combustion in view of energy diversification and emission reduction. However, since the coal content of bio-briquettes is high (up to 80% in this study), gas emissions such as those of SO x still occur. Therefore, the introduction of SO 2 adsorbent is common in coal briquette or bio-briquette combustion. A calcium-based material is usually used for this goal. The aim of this study was to observe the effects of desulfurization temperature and Ca/S ratio (Ca = calcium content in adsorbent; S = sulfur content in coal and biomass) on desulfurization efficiency and kinetics. The ratio of coal to biomass (palm kernel shell/PKS) was fixed at 90:10 (wt/wt) and the ratios of Ca to S were varied at 1:1, 1.25:1, 1.5:1, 1.75:1 and 2:1. The mixtures of coal, PKS and adsorbent were briquetted at a molding pressure of 6 ton/cm 2 with Jatropha curcas seeds and starch mixture as binding agents. Desulfurization was performed within a temperature range of 300 to 500°C for 720 seconds at an airflow rate of 1.2 L/min. The results showed that the highest desulfurization efficiency (90.6%) was associated with the Ca/S ratio of 2:1 and temperature of 400°C. Moreover, the highest reaction rate constant of desulfurization was 0.280 min -1 .

A Novel Approach to Coal Processing - Electrochemical Solutions to Pollution Reduction and Material Synthesis

Several scientific research have shown that the coal industry is responsible for a large array of pollution including small particle pollution near populated areas, toxic heavy metals and acid rains1. In 2011, EPA estimated that power plants are responsible for half of the mercury air pollutant in the U.S.2 These environmental concerns garnered the interest of both the general public and governments to find new ways to effectively reduce the pollution related to coal power plants. Furthermore, the current worldwide electricity generation is heavily reliant on coal comprising 41.3% accentuating the need for clean coal energy3. For decades coal has been seen as a mere inexpensive fuel for generating energy in power plants. However, a closer look at coal reveals that coal is a heterogeneous and complex mixture of hydrocarbons, rich with minerals4. It has been reported that electrolyzing a slurry of fine coal particles in acidic media can produce hydrogen, consuming less energy than water-electrolysis5. The hydrogen produced by this method is pure enough to be used directly in a commercially available hydrogen fuel-cell. Our research group have successfully electrolyzed coal to synthesize graphene by chemical vapor deposition method (CVD)6. Extensive optimization and control of process parameters was required to produce the graphene structure. The findings from the graphene synthesis process motivated the development of a comprehensive process to generate clean energy and produce high value materials from inexpensive coal. The main advantages of the new process proposed in this study to process coal via electrochemical methods are (i) easy adaptation to the existing infrastructure of the coal industry to facilitate quicker and low-cost integration of the new process, (ii) decreasing the sulfur content of coal after each step to reduce pollution, and (iii) retrieving the metallic content leached from coal to the slurry to avoid toxic and heavy metals such as mercury poisoning of the air and also generate revenue to reduce operating cost. Figure 1 represents a brief comparison between the current coal process and the new coal process proposed in this study. Various optimizations in every step of this coal process such as increasing hydrogen generation during electrolysis, decreasing energy consumption during pyrolysis and CVD, and electrochemical-recovery of minerals will be done with the focus on the process economy.

Minimisasi Sulfur Batubara dengan Sodium Karbonat untuk Bahan Baku Briket

Coal is a raw material especially in the cost briquet industry. Coal is a solid with a sulfur content up to 5%, and sulfur has negative effect at exhaust emission. The main objective of this study is to remove sulfur from coal after the coal crushed and screened and then soluted by sodium carbonate (Na 2 CO 3 ) in various concentration. The results of analyzes of sulfur content which has been done. show that the concentration of sodium carbonate has correlation to change sulfur content in coal. An optimum concentration was obteined in 2,5% sodium carbonate which can remove 8,29 % sulfur contained in coal.

Determination of reaction areas for the sulfur conversion during low-metamorphosed coal oxidative desulphurization

Taken into account the global trends of metallurgy, in order to save energy, new technologies in blast furnaces are actively developed in Ukraine, namely, substitution of natural gas for pulverized coal (PC). However, use of this technique is complicated by inconsistencies of characteristics of a large part of domestic coal with requirements that apply to PC raw materials, primarily because of the high sulfur content in it.To solve this problem, it is proposed to use the method of coal oxidative desulphurization that consists in selective conversion of pyritic sulfur by vapor-air mixture. However, the content of sulfur in coal is not the only requirement, so the task of research is determination of process parameters that will enable to minimize the destruction and burning of organic carbon that occurs during its oxidative desulphurization.Series of experiments on detailed determination of patterns for high-sulfur low-metamorphosed coal oxidative desulphurization to produce raw materials for PC are began in this article. The effect of linear velocity of the oxidant and the grain size of raw materials on the process is determined and the values of these factors when oxidative desulphurization isn't limited to diffusion velocity of the oxidant to the coal grain surface are established. The dependence of the process stages from parameters of fluidized bed and mass transfer criteria of the reagent is shown.

Chemistry, mineralogy and distribution of selected trace-elements in the Parvadeh coals, Tabas, Iran

The Parvadeh Coalfield located in the south of Southern Khorasan Province, with an area of 1200km2 is one of the most important coal producing areas in East-Central Iran and contain low to medium volatile bituminous coal (%Ro: 0.9–1.5%). The mineralogical and geochemical data of coals with respect to element partitioning during coal dressing indicated that the main minerals of feed coals are quartz, illite, kaolinite, calcite, dolomite, and pyrite. The element contents of coal-bearing layers are higher than the Clarke of Earth. Cluster statistical analysis indicates that Si, Al, Zn, V, K, Ni and Cr principally occur in the silicates, whereas Cd, Fe, As and Co displays affinity to the sulfide phase. Molybdenum, Li, Cu and Pb mainly occur in the organic fraction of coal. The high sulfur content in coals under study was influenced by seawater during peat deposition. Pyritic sulfur is the main form of sulfur in the coals from Parvadeh. Syngenetic pyrite is present as framboids associated with macerals. The calculated removability index shows that Li, Mo, Pb and Cu are enriched in the cleaned coal and are associated with organic matter in coal. The higher degree of removal for other minor elements during mineral processing however indicates that they are associated with mineral matter in coal. The coal cleaning method in Parvadeh coal-cleaning plant not only removes mineral matter and pyritic sulfur, but also reduces the content of most inorganic elements.

Reduction of Sulfur Dioxide Emissions by Burning Coal Blends

Given that sulfur contents of coals vary widely, this work investigated whether cofiring of high-sulfur coals with low-sulfur coals of different ranks has any distinct advantages on lowering the sulfur dioxide emissions of the former coals, beyond those predicted based on their blending proportions. Such cofiring intends to take advantage of documented evidence in previous investigations at the author's laboratory, which demonstrated that lignite coals of low-sulfur, high-calcium, and high-sodium content undergo massive bulk fragmentation during their devolatilization. This particular behavior generates a large number of small-sized char particles which, upon effective dispersion in the gas, can heterogeneously absorb the emitted sulfur dioxide gases, i.e., act as defacto sorbents, and then retain them in the ash. This study included two high- and medium-sulfur bituminous coals, two low-sulfur lignite coals, and a sub-bituminous coal. Results showed that bituminous coals burning under substoichiometric (fuel-lean) conditions release most of their sulfur content in the form of SO2 gases, whereas low-ranked coals only partly release their sulfur as SO2. Furthermore, the SO2 emission from coal blends is nonlinear with blend proportions, hence, beneficial synergisms that result in substantial overall reductions of SO2 can be attained. Finally, NOx emissions from coal blends did not show consistent beneficial synergisms under the implemented fuel-lean combustion conditions.

Monitoring the sulfur content of coal

Information regarding the sulfur content of the coal is required not only in metallurgy but also when burning coal as a fuel. The traditional method of determining the sulfur content of coal is unsuitable for large-scale monitoring of processes because it is laborious and not sufficiently reliable. Nuclear-physics methods are free of those problems. However, satisfactory precision of the results is only possible with relatively constant composition of the coal or when the matrix effect due to fluctuations in the composition is taken into account. In the present work, the composition of coal is studied by correlation and regression analysis of the ash composition in coal from different deposits. The correlation coefficients between the main ash components (Al2O3, SiO2, SO3, CaO, and Fe2O3) are calculated. For the example, of coal from Kazakhstan and the Minusinsk Basin, statistically significant correlations are established between the contents of sulfur and calcium in the coal; the correlation coefficient is 0.75–0.93. No significant and consistent correlations are found between other ash components. These findings permit optimal development of nuclear-physics methods of monitoring the sulfur content of coal—specifically, in improving the precision of the analysis by taking account of the matrix effect due to redistribution of the mineral components.

Modeling Fireside Corrosion Rate in a Coal Fired Boiler Using Adaptive Neural Network Formalism

In this paper, an efficient artificial neural network (ANN) model using multi-layer perceptron (MLP) philosophy has been proposed to predict the fireside corrosion rate of super heater tubes in coal fire boiler assembly, using operational data of an Indian typical thermal power plant. The input parameters comprise coal chemistry, namely, coal ash and sulfur contents, flue gas temperature, SOX concentrations in flue gas, fly ash chemistry (wt% Na2O and K2O). An efficient gradient based network training algorithm has been employed to minimize the network training errors. Effects of coal ash and sulfur contents, wt% of Na2O and K2O in fly ash and operating variables such as flue gas temperature and percentage excess air intake for coal combustion on the fireside corrosion behavior of super heater boiler tubes have been computationally investigated and parametric sensitivity analysis has been undertaken. It has been observed that ash and sulfur contents of coal, flue gas temperature and fly ash chemistry have a relatively predominant influence on the rate of fireside corrosion with respect to other parameters. Quite good agreement between ANN model predictions and the measured values of fireside corrosion rate has been observed, which is corroborated by the regression fit between these values. © 2016, Sociedade Portuguesa de Electroquimica. All rights reserved. Modeling Fireside Corrosion Rate in a Coal Fired Boiler Using Adaptive Neural Network Formalism. Available from: https://www.researchgate.net/publication/303782462_Modeling_Fireside_Corrosion_Rate_in_a_Coal_Fired_Boiler_Using_Adaptive_Neural_Network_Formalism [accessed Aug 16, 2017].

Qualitative and chemical characteristics of mineral matter in the selected lignite deposits in light of their suitability for clean coal technologies

An analysis of the variability of ash content and chemical composition of coal ash is crucial when assessing the possibility of using this raw material in clean coal technologies (CCS). The paper focuses on chemical, technological and quality characteristics of ash from the combustion of lignite from Polish deposits. Ash content on a dry ash-free basis for the samples from 9 deposits varies from 1 to 50%. The most commonly observed ash content in the studied samples of lignite is in the range between 10–20%. The measured ash melting temperatures from the collected lignite samples have shown that the sintering, softening, melting and flow temperatures, determined in an oxidizing atmosphere (air), are higher than those determined in a reducing atmosphere. In the majority of Polish lignite deposits, the dominant component of ash was SiO2 , followed by CaO. When evaluating the suitability of coal in energy production, with particular emphasis on the combustion and gasification processes, it is also necessary to study the behavior of ash at high temperatures and the impact of ash on the gasification and combustion facilities. Ash fouling and slagging processes, which are heavily dependent on the ash content, composition, melting point and the content of chlorine, phosphorus and sulfur in coal, have a negative effect on the combustion process.

Adoption of SO2 emission control technologies - An application of survival analysis

Using data on coal-fired electric power plants, this article investigates the contributing factors affecting the investment decisions on flue-gas desulfurization (FGD), a capital-intensive emission control technology. The paper makes two contributions to the literature. First, the public regulatory status of electric power plants is found to have a strong influence on whether FGD investment is made. Compared to deregulated power plants, those that are still under rate-of-return regulations by Public Utility Commissions are more likely to install FGD. Second, a higher rate of inspections of polluting facilities (not just electric utility power plants) in a state in the previous year is associated with a higher probability of power plants adopting FGD this year. In addition, sulfur content of coal and plant size are both positively associated with the likelihood of FGD installation. The service length of boilers is negatively associated with the likelihood.

Experimental Study on Greenhouse Gas Emissions Caused by Spontaneous Coal Combustion

There are large areas of spontaneous coal combustion in northern and northwestern China. The quantification of greenhouse gas (GHG) emissions resulting from spontaneous coal combustion is an important step toward determining proper management practices to reduce such emissions in the future. The present study investigated the GHG emission characteristics of the spontaneous combustion of 10 typical coal types. Furthermore, this study examined the estimation method applied to the GHG emissions caused by spontaneous coal combustion. The experimental results showed that the rates of CH4 and CO2 emissions from spontaneous coal combustion resulting from mining activities were greater than the same rates of emissions resulting from mere surface air seepage (by factors of ∼1.8 and ∼1.6, respectively). The emission rate of CH4 was significantly correlated with the volatile content of coal, while the emission rate of CO2 was significantly correlated with the moisture, oxygen, and sulfur contents of coal. Three diff...

Bacterial removal of sulfur from the China lignite by a newly isolated bacterium, Sinomonas flava XL4

The lignite coal collected from Shengli coalfield of Inner Mongolia Autonomous Region in China contains about 5.22% by mass total sulfur with a gross calorific value of 6329 cal g−1. In the present work, the coal sample was subjected to desulfurization by using a new bacterium isolated from the native coal mine site. The native bacterium was identified to be Sinomonas flava XL4 based on the 16S rDNA gene sequence analysis, and reported first time for the capability to remove about 44% of total sulfur from the lignite coal. The influence of various process parameters such as medium pH, incubation time, pulp density, particle size, incubation temperature on sulfur removal from the lignite after S. flava XL4 treatment was investigated, and the experimental results showed that the total sulfur content of lignite coal was reduce to 2.92% under optimum reaction conditions. In addtion, the calorific value of lignite coal after bacterium desulfurization increased from 6329 to 6678 cal g−1, and the ash content was eliminated. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 374–379, 2016

The Formation of Aerosols During the Co-combustion of Coal and Biomass

The global drive to lessen the emission of greenhouse gases in the power industry has seen an increase in the co-combustion of coal with various types of biomass. The practice “represent possibly the best (cheapest and lowest risk) renewable energy option for many power producers”. Most reviews of the practice cite environmental benefits coupled with satisfactory technological performance. One environmental aspect which has been virtually ignored is the formation and release of ultra-fine aerosol particles, which have a damaging effect on the respiratory system. The emission of respirable aerosols during the combustion of both coal and biomass has received considerable attention, but there is little information available for the combustion of their mixture. The available evidence, reviewed here, indicates that the extent of their formation is increased by co-combustion, due to the high ash and sulphur content of coals, and the high alkali metal content of biomass.

Features of Bivalent and Trivalent Iron Oxide Reduction from Slag with Carbon

Liquid-phase reduction of bi- (FeO) and trivalent (Fe 2 O 3 ) iron from slag with activated coal is studied: BAU (wood) and KAD (bituminous). Kinetic relationships are obtained for reduction at 1450°C from slag with an initial overall iron content Fe tot ≈ 5%. It is shown that regardless of the type of coal liquid-phase reduction of iron to metal from slag with a preponderance of Fe 2 O 3 is difficult compared with slag containing mainly FeO and requires preliminary reduction of trivalent to bivalent iron. A relationship is established for the rate of liquid-phase reduction on carbon reducing agent properties (structure porosity, ash content, sulfur content). The greater reducing capacity of BAU coal compared with KAD correlates with the lower ash and sulfur content of BAU coal.

Changes in sulfur form during coal desulfurization with microwave: Effect on coal properties

The changes in sulfur form in coal were analyzed by sulfur K-XANES (K-edge X-ray absorption near edge structures) spectra before and after the coal microwave desulfurization in a NaOH solution. After the desulfurization, the pyritic sulfur content of coal decreased significantly from 53.6% to 39.2%, while the sulfate sulfur content increased from 17.3% to 34.6%. Only a small amount of thiophene sulfur (20.1–16.1%) was removed. Some sulfur-containing components were oxidized to sulfate sulfur. Under the optimum conditions, the ash content decreased, while the volatile content increased. The calorific value of coal slightly decreased with a slight variation in the amplitudes. The overall structure of coal did not change significantly based on Fourier transform infrared (FTIR) spectral analyses. Thus, the desulfurization of coal with microwave irradiation in a NaOH solution did not significantly change the properties of coal.

Geochemistry of the Cretaceous coals from Lamja Formation, Yola Sub-basin, Northern Benue Trough, NE Nigeria: Implications for paleoenvironment, paleoclimate and tectonic setting

The Cretaceous coals of Lamja Formation located in Yola Sub-basin of the Northern Benue Trough, northeastern Nigeria, were analyzed based on a combined investigation of organic and inorganic geochemistry to define the paleodepositional environment condition, organic matter source inputs and their relation to paleoclimate and tectonic setting. The total organic carbon and sulfur contents of Lamja Formation coals ranges from 48.2%–67.8% wt.% and 0.42%–0.76% wt.%, respectively, pointing their deposition in freshwater environment with inferred marine influence during burial. Biomarkers and chemical compositions provide evidence for a major contribution of land-derived organic matter, with minor aquatic organic matter input. Minerals such as quartz, pyrite, kaolinite, illite, montmorillonite and calcite were present in the coals, suggesting that these minerals were sourced from terrigenous origin with slightly marine influence, considered as post-depositional. This is consistent with a significant amount of the oxides of major elements such as SiO2, Fe2O3, Al2O3, TiO2, CaO, and MgO. The investigated biomarkers are characterized by dominant odd carbon numbered n-alkanes (n-C23 to n-C33), moderately high Pr/Ph ratios (1.72–3.75), very high Tm/Ts ratios (18–29), and high concentrations of regular sterane C29, indicating oxic to relatively suboxic conditions, delta plain marine environment of deposition with prevalent contribution of land plants and minor aquatic organic matter input. Concentrations of trace elements such as Ba, Sr, Cr, Ni, V, Co and their standard ratios also suggested that the organic matter was deposited under oxic to relatively suboxic conditions, which is in parts deposited under marine influenced. Some standard binary plots of SiO2 versus (Al2O3+K2O+Na2O) indicate a semi-arid paleoclimatic condition whereas log SiO2 versus (K2O/Na2O) also revealed passive continental margin setting. The inferred tectonic setting is in agreement with the tectonic events witnessed in the West and Central Africa during the Cretaceous period.

Thermodynamic assessment of the possibility of emission of submicron particles in the process of coal combustion

Methods of chemical thermodynamics of multicomponent reactive systems are used to study the distribution of the most volatile components (potassium and sodium) in the products of combustion of 15 types of coal. The effect of the mineral part of coals and various potassium and sodium compounds on the temperature of their transition into the gas phase is investigated. It is shown that the distribution of potassium and sodium in the products of coal combustion depends on the speciation of these elements in the initial coal; the mineral part composition; the ash content of coals; and the sulfur, potassium, and sodium content of the initial coals.

Enrichment and particle size dependence of polonium and other naturally occurring radionuclides in coal ash

Coal fired thermal power contributes 70% of power in India. Coal fired power generation results in huge amounts of fly ash and bottom ash of varying properties. Coal, which contains the naturally occurring radionuclides, on burning results in enrichment of these radionuclides in the ashes. In the present study, coal, bottom ash and fly ash samples collected from six coal-fired power plants in India were measured for 210Po using alpha spectrometry and for natural U, 226Ra, 232Th and 40K by an HPGe γ-ray spectrometer. 210Po in fly ash ranged from 25.7 to 70 Bq/kg with a mean value of 40.5 Bq/kg. The range and mean activities of 238U, 226Ra, 232Th, 40K in fly ash were 38.5–101 (78.1), 60–105.7 (79), 20–125 (61.7) and 43.6–200 (100) Bq/kg respectively. Fly ash and bottom ash contains two to five times more natural radionuclides than feed coal. The results were compared with the available data from earlier studies in other countries. The effect of particle size on enrichment factor of the nuclides in fly ash was studied. 210Po showed the largest size dependence with its concentration favoring the smaller particle size while 232Th showed least size dependence. 238U and 226Ra showed behavior intermediate to that of 210Po and 232Th. Also the correlation between sulfur content of the feed coal and activity of 210Po was investigated. Increased sulfur content in feed coal enhanced enrichment of 210Po in ash.

Biological removal of sulphur and ash from fine-grained high pyritic sulphur coals using a mixed culture of mesophilic microorganisms

Bioleaching of coal’s pyrite is a promising option to reduce sulphur content of high sulphur coals from an economical, technical and environmental point of view. In this research, a mixed culture of acidophilic iron- and sulphur-oxidizing mesophilic microorganisms including Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans was used to remove pyritic sulphur from the high sulphur coal of Mehr Azin, Tabas, Iran. The influence of various parameters, namely nutrient medium type (Norris and 9K), initial pH (1, 1.5 and 2) and the addition of ferrous sulphate on the pyritic sulphur removal and ash content of coal was investigated using an orthogonal array L-18 Taguchi design. Shake flasks experiments were carried out in pulp density of 5% (w/w), particle size of smaller than 500μm, and a stirring rate of 150rpm at 35°C for 30days. Analysis of variance (ANOVA) was used to determine the effects of the variables on sulphur and ash reduction from the coal. The maximum sulphur removal (50.3% total sulphur) was obtained at the initial pH of 1, the ferrous sulphate addition of 0.02M and Norris nutrient medium. Total sulphur and ash content values were decreased from 3.87% to 1.92% and 25.72% to 11.6%, respectively. SEM/EDS and XRD analyses showed that a high level of sulphate and jarosite precipitations could be occurred at the initial pH of 2 when 0.05M ferrous iron addition and 9K nutrient medium were used.