Coal Components Research Articles

Modes of occurrence of scandium in coals and peats (A review)

The modes of occurrence of scandium in peat and coal from different deposits in Siberia, Russian Far East, Kazakhstan, and Mongolia was studied with the use of a set of methods. The fractions of coal with different densities and the group components of peat and brown coal were considered. The selective leaching of Sc from brown coal and black coal with ammonium acetate and concentrated acids was performed, and a correlation between the Sc content and the ash content was studied. It was established that, at the early stages of a coal-formation process, the bulk of scandium in low- and medium-ash peats and brown coal was bound to organic matter. Humic substances (fulvic acids + humic acids) are the main carriers and concentrators of scandium. In all cases, the scandium content of humic acids was higher than the average concentration in peat and brown coal. A decrease in the yield of humic acid fractions in the coalification process decreases their fraction in the total balance of scandium; however, the fraction of insoluble humic substances increases in this case. The modes of occurrence of scandium changes in the course of coalification. In low-rank black coal (grade D), a considerable fraction of scandium occurs in the organic matter. The mineral forms of scandium predominate in mature black coal. Scandium is a constituent of silicates, aluminosilicates, phosphates, and aluminophosphates; it likely forms its own mineral species.

Analysis of Structural Features of Humic Acids Fractions after Mechanochemical Modification

Humic substances are the major components of soil, peat and brown coal. They can be fractionating into fulvic acids (FA), brown humic acids (BHA) and gray humic acids (GHA). In this work we investigated the influence of mechanochemical modifications on structural composition of HAs main fractions using the methods of IR and 1H MRS spectroscopy. The IR spectroscopy results has shown that HA has different chemical composition in comparison with GHA and BHA. Potentiometric titration showed that mechanoactivation (MA) with thiourea increases the amount of oxygen-containing groups up to 2.5. For the first time we studied the impact of modifying agent of thiourea on the structural composition and acid-base properties of HAs major fractions - GHA and BHA during the mechanoactivation process.

Carbon Isotope Fractionation Behavior of Secondary Biogenic Coalbed Methane Generated from Lignite Samples Based on Parent Methanogen

Simulation experiments on biogenic coalbed methane were conducted under an anaerobic condition provided by an anaerobic glove chamber and using parent anaerobic methanogen. These experiments aimed to analyze the isotope fractionation behavior of secondary biogenic coalbed methane generated from the lignite samples collected from Zhaotong Basin, Yunnan Province, China. Results showed that the δ13C1 values of the simulated biomethane varied from −52.31‰ to −58.41‰, which were in the normal distribution range compared with those of biogenic methane. Given the organic maceral in the parent rock, the methanogen used, and the biological generation pathway of CH4, δ13C1 values continued to decrease as the simulation experiment proceeded. The carbon isotope ratio transferred from raw coals to biogenic methane in the simulation, indicating the significant relationship of source material inheritance. The fractional degree of δ13C1 was probably controlled by the organic maceral component in coal, which was manifested by the positive correlation between δ13C1 and humic matter content, as well as the negative correlation between δ13C1 and inertinite content.

Study on the Preparation of Oil-Coal-Water Slurry

This paper presented a method of a new kind of triplex mixture system of oil-water-coal slurry preparation.Triplex synfuel containing gasoline, water and coal was prepared using nonionic surfactant. Tween 80 was used as emulsifying agent. The ratio of water, gasoline and coal was optimized. The optimum prescription of oil-water-coal slurry was obtained by means of orthogonal experiment. Results showed that stable triplex mixture systems were prepared with the ratio of the components of coal (C) to water (W) to oil (O) by weight was C:W:O=45%:30%:25% when 0.2% Tween 80 were added into the system. Rheological properties of oil-water-coal slurry were also investigated.

Study on occurrence of sulfur in different group components of Xinyu clean coking coal

This paper illustrates the occurrence and distribution of sulfur in coal from the perspective of composition and structure of the coal body. With the organic sulfur-rich Xinyu clean coking coal as the sample, and the method of separating all group components from coal through extraction and stripping process as well as X-ray photoelectron spectroscopy (XPS) and gas chromatography/mass spectrometer (GC/MS) analysis techniques, the content of inorganic sulfur and organic sulfur of different forms in raw coal and various group components is studied and the occurrence of organic sulfur in organic matter of coal is carefully observed. The results show the distribution of inorganic sulfur is mainly dependent upon its particle size and density in coal and has less relationship with the structure of group components of coal. Thiophene sulfur is the major form of organic sulfur either in raw coal or group components. The external environment of molecules dominated by conjugated structure can decrease the electron binding energy of organic sulfur in conjugated structure, while increase that of sulfur in aliphatic structure. The distribution of organic sulfur in coal is balanced as a whole and will not be significantly influenced by structural differences of group components. However, the occurrence of organic sulfur compounds is associated with the structure of group components, showing relatively small difference. And there is only one type of small molecule organic sulfur compounds in light component, with small abundance.

Breaking the limits of structural and mechanical imaging of the heterogeneous structure of coal macerals

The correlation between local mechanical (elasto-plastic) and structural (composition) properties of coal presents significant fundamental and practical interest for coal processing and for the development of rheological models of coal to coke transformations. Here, we explore the relationship between the local structural, chemical composition, and mechanical properties of coal using a combination of confocal micro-Raman imaging and band excitation atomic force acoustic microscopy for a bituminous coal. This allows high resolution imaging (10s of nm) of mechanical properties of the heterogeneous (banded) architecture of coal and correlating them to the optical gap, average crystallite size, the bond-bending disorder of sp2 aromatic double bonds, and the defect density. This methodology allows the structural and mechanical properties of coal components (lithotypes, microlithotypes, and macerals) to be understood, and related to local chemical structure, potentially allowing for knowledge-based modeling and optimization of coal utilization processes.

Utilization of low rank coal as oxidation catalyst by controllable removal of its carbonaceous component

Controlled removal of carbonaceous component in low rank coal by sulfonation followed by calcination demonstrated that it is a simple and effective method to utilize this material as catalyst in the oxidation of styrene. Low rank coal is one of the least utilized categories of coal. However, it shows excellent potential as a catalyst due to high concentrations of carbon and other elements, such as transition metals, which are embedded inside its structure. In this research, the low rank coal was treated by sulfonation followed by calcination in order to activate the transition metals embedded in it. The catalytic activity of the treated low rank coal was tested in the oxidation of styrene by aqueous hydrogen peroxide. The low rank coal showed high catalytic activity after sulfonation and calcination at 700°C, with 3% of styrene conversion and 97% of selectivity toward benzaldehyde. The transition metal active sites in low rank coal that play the most important role in the oxidation of styrene were determined by coal mimicking models. The presence of cobalt oxide and titanium oxide active sites in the low rank coal plays the most significant role in the oxidation of styrene by aqueous hydrogen peroxide.

Effects of Volatile Component in Coal on HighPhosphorus Oolitic Hematite in Direct Reduction Roasting Process

Effects of Volatile Component in Coal on HighPhosphorus Oolitic Hematite in Direct Reduction Roasting Process

Distributed flotation kinetics models – A new implementation approach for coal flotation

Composition-dependent flotation kinetic models with distributed flotation rate constants for predicting the flotation response of the various components of coal have been available for quite some time. However, the full potential of these models have not been realised because the floatability distribution of particles, a key requirement for the utilisation of the models, has not been readily accessible experimentally to allow the validation of these models.A new approach has been developed that allows the coal flotation feed to be fractionated into particles classes of size and composition using a microscopic characterisation tool called Coal Grain Analysis. Previous work had determined the contact angles of discrete coal maceral groups and associated minerals. Combining this information with the particle composition data from the Coal Grain Analysis methodology provides a pathway for estimating the contact angles of heterogeneous coal particles via Cassie’s Equation. The approach provides a unique opportunity to estimate the flotation rate constants for the different particle classes.

Elemental composition of PM2.5 in Shiprock, New Mexico, a rural community located near coal–burning power plants and abandoned uranium mine tailings sites

Fine particulate matter (PM2.5) was collected in Shiprock, New Mexico, a small community located near two coal–fired power plants and numerous abandoned uranium mine tailing sites. Eleven PM2.5 samples were collected for 96h over three sampling periods (April/May 2009, November 2009, and October/November, 2010). Nine samples were analyzed for 64 elements using inductively coupled plasma–mass spectrometry. B, Bi, Cu, Pb, Sb, Sn, and Zn were observed in at least eight samples at levels indicative of anthropogenic enrichment (enrichment factors between 30 and 650). All the seven elements could be explained by coal–combustion processes. B, Bi, and Sb are enriched in coals; Cu, Pb, Sn, and Zn are chalcophile–lithophile or chalcophile elements, all with appreciable affinity for sulfur, a component of coal. Principal component analysis also supported these findings. Four major sources (percent variance) were identified: soil (61%), coal combustion (17%), industrial (11%), and sea salt (5%). Concentrations of elements associated with coal combustion in Shiprock were lower than levels observed in other industrially influenced cities. This was explained by Shiprock’s location west of the power plants. Back trajectories indicated that winds arrive to Shiprock from the W, SW, and NW, but the power plants are located to the east (upwind) of the city. Samples were also analyzed for uranium (0.002–0.02ng/m3) and other metals associated with mine tailings (Sr, Mo). All metals were detected but at low levels, and concentrations did not vary predictably with wind direction. Hence, the tailings sites could not be attributed as the source.

Production of fuel briquettes from anthracite fines

Experimental data on the development of a technology for the production of fuel briquettes from anthracite fines, slack coal, and coal slurries available in the Rostov oblast are presented. The effects of the moisture content and particle size distribution of the coal components, the moisture content of the charge, the composition of a binder, the compacting pressure, and the regime of hardening on the technical properties of the fuel pellets were studied. The possibility of obtaining water-resistant briquettes was demonstrated.

Raman spectroscopy of coal component of Late Permian coals from Southern China

The chemical structural characterization of four samples (M-1, M-5, VS, and BaS) from Southern China was studied by Raman spectroscopy with curve-fitting analysis. Several Raman parameters, e.g., full width at half maximum (FWHM) and intensity ratio (ID1/IG), were obtained. Vitrinite (VS) and barkinite (BaS) were separated from the same coal sample, separately. The results showed that nine bands were assigned from the Raman spectra. Two typical bands, G and D1, have broad peaks, which showed that all the samples have poor order in chemical structure. Barkinite has higher disorder in chemical structure than vitrinite.

Ash-free coal as fuel for direct carbon fuel cell

This work describes the performance of the direct carbon fuel cell (DCFC) fuelled by ash-free coal. Employing coal in the DCFC might be problematic, mainly because of the ash deposition after the cell reactions. In the study, the carbonaceous ash-free component of coal is obtained, which is then evaluated as the DCFC fuel and compared with raw coal, active carbon, carbon black, and graphite. The electrolyte-supported SOFC structure is adapted to build the DCFC. The DCFC based on the ash-free coal fuel exhibits good performance with regard to the maximum power density, day-by-day measurements, and durability at continuous run. When the carbon fuels are internally gasified to H2 and CO, the power density is generally much improved, compared to N2 pyrolysis environment. The power generation is most likely related to the concentration of pyrolyzed gases as well as the electrochemical reactivity of the solid carbon.

Nitrogen doping of ash-free coal and effect of ash components on properties and oxygen reduction reaction in fuel cell

Nitrogen doping of ash-free coal (HPC) and raw coal in a stream of ammonia was studied in application to a cathode catalyst for a fuel cell. The relation to structure morphology, surface properties and catalytic activity for the oxygen reduction reaction (ORR), the effects of addition of the ash components of the raw coal to HPC and the comparison with carbonization in a stream of helium were determined. Tests were carried out with linear sweep voltammetry measurement in streams of oxygen and argon gases and a scan region of 0.04–1.04V using a three-electrode setup. Inorganic elements dominant in the ash of the raw HPC coal were iron, aluminum, potassium, magnesium, silicon and calcium. The nitrogen doping of HPC at 773–1073K decreased the oxygen content and increased the nitrogen content and the pyridinic nitrogen with the treating temperature compared to the carbonization in a stream of helium based on the XPS analysis. The addition of metals to HPC and subsequent nitrogen doping decreased the nitrogen content of HPC but increased the pyridinic nitrogen in the nitrogen distribution except for magnesium and calcium due to interaction with the pyridinic nitrogen. From the Raman analysis, the nitrogen doping at 773–1073K decreased the ID/IG ratio (deficient carbon degree) compared to the carbonization, but the addition of the ash components, especially 0.5% Fe+0.5% Al, increased it, resulting from the formation of many edges of deficient carbons in the presence of the ash. The TEM observation showed that the nitrogen doping of HPC at 1073K created onion-like fullerene structures but the addition of iron and aluminum destroyed this structure and formed a nanocarbon structure. The presence of iron and aluminum increased the pyridinic nitrogen and the disordered defect carbons formed along the edges of the graphite layers. Furthermore, the nitrogen doping at 1073K increased the onset potential of the ORR from 0.37 (carbonizing) to 0.67V. The addition of both iron and aluminum further increased the onset to 0.79V for the ORR which was the same potential as that of the raw HPC containing the ash components. The presence of ash in the raw coal, especially iron and alumina, promoted the electronic performance for the oxygen reduction. Consequently, the nitrogen-doped combined iron and aluminum with nanocarbons were the active species of the HPC catalysts for the ORR.

Log interpretation for coal petrologic parameters: A case study of Hancheng mining area, Central China

Abstract Aiming at a serious obstacle for building a log interpretation model to accurately interpret density and sonic speed value of each coal component which cannot be measured directly in lab scale, a log interpretation method of coal reservoir parameters was studied using the Hancheng mining area as an example. The enumeration method was used to calculate density and sonic speed value of fixed carbon, ash, and volatile according to experimental determination of industrial components, pore, gas content, density and sonic speed value of many coal samples in the Hancheng mining area. On the basis of the relationships of each coal component and its density and sonic speed value, logging response relationships between each component and its compensated density and acoustic travel-time differences were studied using numerical fitting. As fitted carbon content increases and ash content decreases, density decrease and sonic speed difference increase. By combining statistical analysis method and theory model calculation method, interpretation models of industrial components, gas content and pore for coal reservoirs were built and a logging integrated interpretation software was programmed, which have got good effect in actual application.

Instrumental Approach and Diagnosis of Total Inorganics in a Typical Carbonaceous Matter

Typical Carbonaceous matter are often widespread and reveal relatively wide range of dominant organic types. The instrumental diagnosis to subject them to oxidation, combustion and/or incineration serve till date mandatory fundamental requirement in the further pursuance of their mineralogical and wet Chemical Analysis. The results of the Ash content from three (3) carbonaceous coal-and shaly coal samples from Northeastern England and Scottish fife show that the variation and/or the volatilization of the inherent sensitive elements are related to both the techniques and the sample composition. From the two techniques adopted, the high-and low-temperature methods the Ash values observed/obtained for Westfied shaly and Beaumont coal types are dependent on their derived material source-argillaceous and pure coal components. However, of the inorganic components (Ash) values that can be recovered from any carbonaceous matter, Radio-frequency method appears to suggest the accurate and reliable alternative for their subsequent geochemical appraisal.

Technological value of coal used for coking

The technological value of coal used for coking is analyzed, with particular attention to clinkering coal, the coke group, and lean additives, as well as G and GZhO coal. A relation is established between the technological value of the coal components and their permissible content in coking batch so as to produce coke of constant strength (M25 = 87%). The precision in determining the technological value of coal is assessed.

Study on Electrochemical Flotation of Low Rank Coal Macerals

Coal component is the basic unit of coal, each component of coal has its special processing properties, Now under the demand of energy conservation and environmental protection , how to sort coal components reasonably and effectively has become a problem needed to resolve immediately. Picking vitrain and fusain by hand, analyzing the pH and add in different solution under the condition of different drugs both surface potential difference, and through the flotation tests determine the appropriate separation conditions. The results show that the enrichment rate of the maceral have improved by electrochemical flotation method .

Chemical properties of superfine pulverized coals. Part 2. Demineralization effects on free radical characteristics

Inorganic matter in coal significantly influences its chemical properties and potential utilizations. Electron paramagnetic resonance (EPR) characteristics can be affected by inorganic species, and various groups of paramagnetic centers behave differently after demineralization procedures. In this paper, EPR and the power saturation technique were applied to investigate thoroughly the free radical characteristics of acid-treated superfine pulverized coals. Systematic studies were conducted to explore the behaviors of different groups of paramagnetic centers in demineralized and pyrite-free coals. Focus was directed on comparisons of free radical characteristics of coal samples with different particle sizes, indicating that coals with higher maturities and larger particle sizes are much more easily saturated. Compared to raw coals, the acid-treated samples are more susceptible to saturation. Furthermore, the power saturation technique also served as a quantitative analysis method to study the line-broadening mechanism. This technique revealed that the components in coals with higher molecular weights contain more homogeneous components. Worth noticing is that the concentrations of free radicals residues in the acid-treated coals are determined by two competing mechanisms. The oxidation effects would increase the amounts of free radicals while the removal process of certain components in coals has decreasing effects. Multi-component spectra studies reflect that EPR spectra of acid-treated coals are superimposed by one Gaussian and three Lorentzian lines.

Partitioning of mineralogical and inorganic geochemical components of coals from Santa Catarina, Brazil, by industrial beneficiation processes

Comparative studies of the mineral matter and trace elements in 12 pairs of run-of-mine (ROM) and clean-coal products from beneficiation plants in Santa Catarina, southern Brazil, have been carried out using low-temperature oxygen-plasma ashing, X-ray diffraction and chemical analysis techniques with the aim of evaluating the effect of coal preparation on the mineralogy and chemical composition of the final coal products. The results show that substantial reductions in mineral matter and ash percentages are associated with beneficiation of coals mined from the different deposits. These reductions are accompanied by changes in the percentages of Fe2O3 in the respective coal ashes, due to the reduction in the proportion of pyrite in the mineral matter, and also by a reduction in the percentage of Na2O, possibly due to ion exchange within the clay minerals. The relative proportions of quartz, clay minerals, and minor phases such as calcite and feldspar (mainly albite) within the mineral matter are not, however, significantly changed by the beneficiation processes.The concentrations of most trace elements in the beneficiation products are similar to the respective concentrations in the relevant ROM materials, or are reduced to an extent similar to that of the total mineral matter percentage for the respective coal samples. This suggests an association mainly with the clay-rich mineral matter. The concentrations of As and Pb, however, are reduced to a greater extent for most samples by the beneficiation processes, consistent with a pyrite association. Concentrations of Ge, U and Zr are higher in many of the clean coals than in the respective run-of-mine materials, suggesting the possibility of preferential association, at least for some deposits, with the organic-rich fractions of the coals concerned.