Coal Components Research Articles

Relationship between thermal properties and structure, composition of briquette through grey relational analysis

The effective thermal conductivity of coal is tested by Hot disk, and the specific heat of coal is measured by differential scanning calorimetry. The results show that the higher the volatile content of coal is, the lower the effective thermal conductivity and the higher the specific heat. However, the ash content is positively correlated with the effective thermal conductivity and specific heat. The greater the P-wave and S-wave are, the greater the effective thermal conductivity. The calculation results of the grey relational analysis show that the main factor affecting the effective thermal conductivity is the mechanical properties of coal, and the main factor affecting the specific heat is the fixed carbon in coal. Compared with sandstone and mudstone, the linear correlation coefficient between the industrial components of coal and both the thermal conductivity and specific heat are lower, and the effective thermal conductivity is more affected by the structure.

Hierarchical porous N-TiO2/carbon foam composite for enhancement of photodegradation activity under simulated sunlight

Nitrogen doped TiO2 (N-TiO2) photocatalyst was synthesized via sol-gel combined with low temperature reflux method using urea as nitrogen source. Hierarchical porous carbon foam (HPCF) with the characteristics of micro/mesopores and micron-sized macropores was made by steam activation of a new type of thin-walled carbon foam which was produced from the loose medium component of coal. N-TiO2/HPCF was synthesized by loading N-TiO2 onto the HPCF via impregnation method. The synthesized catalysts were characterized by N2 adsorption, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), diffuse reflection spectrometry (DRS) and photoluminescence spectroscopy (PL). Phenol was used as a simulated pollutant in wastewater to evaluate the photodegradation performances of naked TiO2, N-TiO2 and N-TiO2/HPCF. The N-TiO2/HPCF composite removed 97 % of phenol in 2 h of simulated sunlight irradiation and displayed the highest photocatalytic activity, which was 4.9 times that of N-TiO2 and 10.8 times that of naked TiO2. The enhanced activity of N-TiO2/HPCF can be ascribed to the combination of both extended visible light adsorption of N-TiO2 and the concentrating effect brought by HPCF. This work demonstrates a facile approach to synthesis an inexpensive and efficient N-TiO2 coated coal-based carbon foam for the treatment of wastewater.

Mechanism of Methane Adsorption/Desorption in Low-Rank Vitrain and Durain Coal Affected by Pore Structure and Wettability: A Case Study in Dafosi Area, South Ordos Basin, China

Water content and water–coal interface wettability are always the difficult issues of coalbed methane adsorption/desorption. In order to study the effects of the pore structure and wettability of different macro coal components on methane adsorption and desorption, we compared and analyzed the wettability difference between vitrain and durain, and revealed the influence of wettability on methane adsorption and desorption through a pore structure analysis, wettability measurements, an adsorption–desorption experiment and adsorption heat calculations under different conditions, taking the No. 4 coal in Dafosi Coal Mine of the Huanglong coalfield as the research object. The results show that both vitrain and durain are relatively hydrophilic substances. However, vitrain has a low ash content, high volatility, and less oxygen, and the pores are mainly semi-closed pores compared with dark coal. Vitrain also has poor connectivity, poor sorting, a small pore diameter, and a coarser surface, resulting in poor surface wettability. The large specific surface area (SSA) and relatively poor wettability of vitrain leads to more adsorption sites in methane, which makes the adsorption capacity of vitrain greater than that of durain, but the good pore connectivity of durain causes the strong desorption capacity of durain. The isosteric adsorption heat of the adsorption process is greater than that of the desorption process, indicating that there is a desorption hysteresis phenomenon which is essentially due to the lack of energy in desorption. Surfactants change the wettability of the coal surface, and different surfactants have different effects on methane adsorption and desorption. Relatively speaking, the methane desorption of coal samples treated with G502 and 6501 are better. The research results provide scientific reference for the study of gas–water transport in the desorption process of low-rank CBM, and provide evidence for the methane desorption model of vitrain and durain.

Desensitization effect of chemically induced coal components at room temperature: An experimental study

This study was conducted to address the rock burst problem caused by serious stress concentrations in coal seams. Based on the principle of inducing agent corrosion affecting coal components to soften coal, different inducers were selected to study the desensitization effect of acid leaching induction on coal components. The microscopic behavior characteristics of coal under acid leaching were analyzed, and the qualitative and quantitative laws were obtained for different acid leaching times and microscopic behavior characteristics. The results show the following: (1) The mixed acid solution as an inducer has the effect of immersion, dissolution, and fracture on coal. During the reaction process, the internal pores of the coal expand, and the height of the external liquid decreases. The mixed acid solution had the best effect in terms of the removal of minerals in coal. (2) Under microscopic conditions, the internal crack width of the coal body expanded several times after mixed acid soaking; the difference in the unevenness before and after compression fracture was stable at 25–27%, and the mixed acid expanded the gap in the coal. (3) This practical study shows that the characterization changes of the mixed acid solution, injected into the borehole, combines the characteristics of the citric acid and phosphoric acid solution. The minerals around the borehole are dissolved, and the debris fuses with the solution. The liquid is viscous and forms a film on the surface of the solution. The mixed acid has a more obvious effect on the immersion and dissolution of coal.

Experimental study of advantages of coalbed gas bioengineering

Coalbed gas bioengineering (CGB) is a special fermentation engineering that converts some organic components of coal to methane, which enhances coalbed gas production. To verify the feasibility and superiority of CGB, three different rank coals were used to simulate the anaerobic fermentation for biomethane production in laboratory. The SEM, XPS, MIP and Isothermal adsorption experiments were used to characterize coal surface modification and pore structure changes of coal before and after bioconversion. Firstly, the different rank coals have potential for biomethane production, and the biomethane production of HN coal as low rank coal is 1.43 times and 2.45 times higher than that of HB and ZG coals. The injection of CO2 in the later stage of HN anaerobic fermentation can realize the CO2 biomethanation with a methane yield of 1.85 mL/g. Secondly, the decrescent of Langmuir volume of residual coal after bioconversion determine the enhancement of coal seam desorption capacity for methane. Thirdly, the increase rate in the proportion of macropores in HN, HB, and ZG coals is 5.86%, 4.23%, and 11.76%, the increase in coal permeability is consistent with the increase in the distribution ratio of macropores in the coal, as well as the increase in total pore volume. The multiple advantages of “four enhancements and one reduction” (production enhancement, liquids enhancement, desorption enhancement, permeability enhancement, and emission reduction) are summarized. A framework system of CGB covering three phases is briefly described: acquisition of efficient microorganisms, laboratory simulations and field tests. CBGB is expected to positively impact the stagnant commercial development of coalbed methane.

The main pathogenetic mechanisms of pneumosclerotic changes in the lungs of coal industry workers

Introduction. Occupational dust pathology of respiratory organs in Kuzbass remains relevant due to its high prevalence among workers of the coal industry. Entering the body, the components of coal cause the development of pneumoconiotic fibrosis. Innovative ideas about the morphogenesis of fibrosis in recent years have shifted to the molecular level and appeal to the state of cellular receptors, the expression of some genes and the repression of others, a radical change in the cellular phenotype, which is the platform on which complex pathological processes occur. The study aims to research the mechanisms of fibroplastic changes in the lung tissue of miners from the position of epithelial-mesenchymal transformation. Materials and methods. The authors carried out histological and immunohistochemical studies of the respiratory system obtained during fifty autopsy operations of a group of Kuzbass miners working in underground. We studied the bronchial mucosa, respiratory lung tissue, arteries and veins of the small and large circulatory circles. The scientists perfomed immunohistochemical study using monoclonal antibodies (marker of proliferation Ki-67; oncogene of proapoptotic activity Bcl-2; endothelial function factors CD-31 and CD-34; marker of epithelial tissue cytokeratin; muscle tissue markers: actin, desmin, vimentin; connective tissue markers: type III collagen; muscle tissue collagenization marker: EMA; intercellular adhesion molecules E and N-cadherins; macrophage antigen (HAM5600)). Results. Epithelial cells of bronchi of coal industry workers partially lose the ability to express cytokeratins with the replacement of individual cell clusters with cells with non-core expression of maternal epithelial tissue of muscle antigens (vimentin, desmin, actin). When exposed to dust, the epithelial phenotype changes with changes in the quantity, shape and quality of the tissue structures of the lung tissue. Epithelial cells become elongated, fusiform, lose polarity and intercellular connections, acquire mobility and the ability to migrate beyond the tissue histione. Hyperactivation of cellular signaling pathways leads to disorganization and partial disintegration of the cytoskeleton with the appearance of functional mobility of cellular elements. A significant decrease in intercellular adhesive contacts under conditions of prolonged exposure to coal-rock dust leads to suppression of the expression of E-cadherin with partial substitution for N-cadherin contacts. Meanwhile, epithelial cells go through the process of epithelial-mesenchymal transformation, participate in the processes of fibrosis.Activated myofibroblasts are the main source of fibrosis in the lungs , their precursors can be both resident and bone marrow fibroblast-like cells. Dedifferentiated epithelial cells can act as decompensation of the regenerative capacity of lung tissue. Conclusion. The concepts of epithelial-mesenchymal transformation as a mechanism of the main pathological changes in pneumoconiosis should serve as a foundation for further in-depth study and understanding of the complex pathogenetic aspects of this problem in medicine. Ethics. The authors conducted all the studies of the dead miners with the help of a secondary examination of blocks and ready-made histological micro-preparations (glasses) of the material of the Bureau of Forensic Medical examination in Novokuznetsk, Osinniki, Prokopyevsk. The researchers carried out studies of pathomorphological material strictly on the basis of Federal Law No. 323-FZ of 21.11.2011 "On the basics of protecting the health of citizens in the Russian Federation", in particular Article 67 "Conducting pathoanatomic autopsies", Federal Law No. 8-FZ of 12.01.1996 "On Burial and Funeral Business" (Article 5, paragraph 1, 2), as well as in accordance with the Order of the Ministry of Health of April 29, 1994 No. 82 "On the procedure for conducting a pathoanatomical autopsy" (appendix to the order of the Ministry of Health and Medical Industry of 29.04.1994 No. 82), Order of the Ministry of Health of Russia of 24.03.2016 No. 179n "On the rules for conducting pathoanatomical studies".

Rheology, ignition, and combustion performance of coal-water slurries: Influence of sequence and methods of mixing

This paper presents the results obtained from a comprehensive study of how the conditions and methods of preparing three-component fuel slurries affect their ignition, combustion, emissions, as well as viscosity and static stability. The data obtained for slurry fuels based on bituminous coal and water with added waste hydrocarbon oil and wood biomass as well as a slurry based on coal slime. A tubular muffle furnace was used for combustion at 700–900 °C. The influence of the mixing conditions of the components on the ignition and combustion behavior was moderate. It was established that surfactants should not be added to composite slurry fuels at the final stage of component mixing. To provide more uniform burnout of a blend with wood biomass, the latter should first be mixed with water and then the coal component should be added. Iterative mixing can provide a 10–15% improvement of ignition and burnout characteristics. To obtain a more homogeneous and stable blend, it is advisable to use a cavitator (colloid mill) rather than a homogenizer or a magnetic stirrer. Based on a set of parameters (viscosity, stability, cost, ignition and combustion characteristics), a dimensionless efficiency indicator was calculated using Weighted Sum Method. The calculated values of the relative efficiency indicator of the fuel blends based on coal dust ranged from 0.67 to 0.73. The relative efficiency of a slurry was found to increase by 25–30% when coal dust is replaced by coal slime due to the economic parameter.

Effect of Coal Gasification Slag on Improving Physical Properties of Acid Soil

Coal gasification slag (CGS) is a coal-based solid waste formed by the transformation of inorganic mineral components and carbon components in raw coal into slag during coal gasification. To explore its influence on the physical characteristics of acid soil and study the influence mechanism on the water holding capacity of acid soil, the coarse and fine CGS were used as materials to mix with acid soil in different proportions. The volume weight, particle size composition, and water retention performance of the mixed soil were tested, and the changes of soil water characteristic curve were analysed. The results showed that, after mixing the acid soil with CGS, the particle size composition of acid soil was significantly improved, the sand content increased by 13.27–195.46%, the clay and silt content decreased by −2.14–38.62% and 3.22–40.06%, respectively; and the soil bulk density decreased significantly (P < 0.05), with a decrease range of 3.38–28.12%. The soil texture also changed from silty loam to sandy loam, and the water retention performance showed an upward trend, which significantly affected the soil saturated water content, capillary water capacity and field water capacity, with an increase range of 2.87–38.09%, 1.73–27.92% and 4.18–22.27%, respectively. The Van Genuchten (VG) model could fit the soil water characteristic curve well, indicating that the water retention of acid soil was significantly improved by adding CGS. In conclusion, CGS could improve the water physical properties effectively, and improve the water retention and water holding properties of acid soil significantly. This feature is conducive to the environmentally friendly utilization of CGS to improve agricultural acid soil.

Enhancement of dewatering performance of vitrinite-rich and inertinite-rich coals by surfactants: Experiment and simulation

The high moisture content of fine coals, especially flotation clean coals has affected the production of coal processing plants for a very long time. The two main components of fine coals are vitrinite and inertinite. The percentage of these two macerals present in the coal has an impact on the dewatering process. In this paper, the influence of surfactants on the dewatering effect of two samples with different maceral contents is studied. The results demonstrate that non-ionic surfactants have an excellent dewatering effect on vitrinite-rich coal, and it reduced the filter cake moisture by 1.84%, while cationic surfactants have an outstanding dewatering effect on inertinite-rich coal, and it reduced the filter cake moisture by3.81%. For both the coals, surfactant adsorption reduces the hydrophobicity of the coal. The best dewatering effect corresponds to the lowest filtrate surface tension and the loosest filter cake structure. Surfactants can reduce the pressure required to remove water from the filter cake by lowering the surface tension of the filtrate. In addition, surfactants have an agglomeration effect on fine coals, which increases the porosity of the coal and facilitates a low-moisture product. This study will help engineers select the suitable filter aid for the maceral content of coal and contribute to the development of efficient filter aids.

Electrospun carbon nanofibers from PAN and a loose medium component of coal as binder-free electrodes for supercapacitors

BackgroundDespite the significant progress of co-spinning strategy to prepare 1D hierarchical porous carbon nanofibers, reducing raw material cost and improving specific surface area (SSA) utilization ratio still needs further improvement. MethodsThe binder-free and flexible carbon nanofibers (CNFs) are fabricated using a blend of polyacrylonitrile (PAN) and a loose medium component (LMC) of coal via electrospinning, followed by pre-oxidation and carbonization process. Significant findingsLMC, an effective pore-enhancing modifier for CNFs, can increase pore volume and improve electrochemical performance while retaining the basic characteristics of good pore structure and pore size distribution (PSD). The prepared materials have higher SSA utilization, mainly due to the dominant pore distribution of 0.9 nm and the special fibrous properties, which are different from ordinary porous carbon. The supercapacitor electrodes prepared from LCNF3 possess a high specific capacitance (227.4 F g−1 at 1 A g−1) and outstanding cycling stability (104.3% capacitance retention after 10,000 cycles). This work provides a new perspective for increasing the pore volume of CNFs prepared by electrospinning and realizing coal's high value-added utilization.

A comparison between multivariate linear model and maximum likelihood estimation for the prediction of elemental composition of coal using proximate analysis

The elemental composition of coal is essential for analysing the overall process of energy conversion systems. Simultaneous information regarding the elemental composition of coal fed into a boiler is of increasing interest for plant operation. In this study, methods of estimating the elemental composition of coal using proximate analysis and a higher heating value were developed to meet requirements in boiler operation. A novel method was developed to formulate the multivariate linear model (MLM) for predicting the elemental composition of coal by solving a set of simultaneous equations with extensive correlations between coal components and an elemental composition constraint. The maximum likelihood estimation (MLE) approach for predicting carbon, hydrogen, oxygen, nitrogen, and sulphur contents was also developed based on a series of extensive correlations among coal components. The maximum likelihood estimator employs more correlations and considers the performance of prediction residuals for each correlation, offering a better prediction accuracy than the MLM, which is based on fewer correlations and neglects prediction residuals. A total of 743 data points was used to derive the MLM and MLE models, which were validated and verified by another set of data that included the same variety of coal types. The proposed methods can estimate the complete elemental composition of coal (C, H, O, N, and S) with acceptable prediction accuracy for engineering purposes. Another important finding is that average absolute error corresponding to the measured values of nitrogen is only 14.14%, although the predicted nitrogen contents did not follow the trends of the measured values.

Experimental study on the evolutionary characteristics of silicified coal functional groups during oxidation/pyrolysis

ABSTRACT In order to study the influence of silicification on coal components and the spontaneous combustion of silicified coal and its functional group change characteristics, the coal components of silicified coal and nonsilicified coal were analyzed by proximate analyzer; the oxygen absorption capacity of silicified coal and nonsilicified coal was tested by coal spontaneous combustion tendency tester, the oxygen absorption of coal at room temperature can directly reflect the degree of spontaneous combustion of coal and the generation of related gases in the reaction process of low temperature and oxygen of silicified coal and nonsilicified coal was measured by temperature programmed experimental device; In situ diffuse reflectance Fourier transform infrared spectrometer was used to test silicified coal and nonsilicified coal in nitrogen and air atmosphere. The evolution characteristics of different chemical bonds in the process of coal oxidation were studied. The surface active group changes of two different coal samples under different gas conditions were obtained, and the oxidative spontaneous combustion characteristics of silicified coal were microscopically proved. The results show that the oxygen absorption of silicified coal is higher than that of nonsilicified coal. During the reaction of silicified coal with oxygen, with the increase of coal temperature, the amount of oxidation gas and pyrolysis gas, oxygen consumption rate and exothermic intensity are higher than those of nonsilicified coal; the changes of related functional groups were mainly manifested in the hydroxyl groups at the peak positions of 3697–3625 cm−1 and 3624–3610 cm−1, the methyl and methylene groups at the peaks of 2975–2915 cm−1 and 2870–2845 cm−1, the aromatic ring C = C double bond at the position of 1604–1599 cm−1, the aromatics and the oxygen-containing functional groups at the spectral segment of 3060–3032 cm−1. Thus, the transformation rules of the related microstructure of silicified and nonsilicified coal under two gas atmospheres were obtained. This study has key significance for revealing the characteristics of silicified coal oxidation at lower temperature.

Experimental and simulation investigations of the impact of polyacrylamide on CBM ad-/desorption

Slickwater is commonly used during hydraulic fracturing in coalbed gas well, which is often prepared with polyacrylamide as the friction reducer. To investigate the impact of polyacrylamide on CBM ad-/desorption after a fracturing operation, slickwater with different concentrations of polyacrylamide were prepared and used to treat Illinois coal samples. Both isothermal ad-/desorption experiments and molecular simulations were conducted to investigate the impact of slickwater. Nuclear magnetic resonance measurements were performed to analyse the evolution of surface functional groups of coal during slickwater treatment. The results show that there is no significant chemical reaction between the coal component and polyacrylamide. Because of the porosity of the polyacrylamide coating adhered onto the surface of the pore, polyacrylamide has a significant sorption capacity of methane. The methane sorption amount of the ‘coal-slickwater’ system is higher than that of raw coal. However, with the increase of the amount of residue entering the pores, the porous structure of the polyacrylamide coating becomes denser, blocking some pores and the pore surface area is reduced; thus, the overall sorption capacity of the ‘coal-polyacrylamide’ system decreases.

Primary studies on the effect of coal bio-gasification in situ in the Qinshui basin

AbstractCoal bio-gasification is one in situ coal gasification technology that utilizes the digestion of organic components in coal by methanogenic bacteria. It is not only an effective technology to enhance the recoverable reserves of coalbed methane, but also an important technical method to promote clean coal utilization. Relevant laboratory researches have confirmed the technical feasibility of anthracite bio-gasification. However, in the complex environment of coal bed, whether in situ gas can be yield with methanogenic bacteria needs to be verified by in situ experiments. In this study, a vertical well and a horizontal well were used in Qinshui basin to perform field experiments to confirm the technical industrial feasibility. The concentration of Cl− ion and number changes of Methanogen spp. were used to trace nutrition diffusion. Gas production changes and coalbed biome evolution were used to analyze technical implementation results. The trace data and biome evolution identified that: (1) The development of Methanoculleus spp. has a significant positive correlation with culture medium diffusion; (2) the structure of coalbed microbial community was significantly changed with the injection of nutrition, and the newly constructed methanogenic community was more suitable for fermentation of coal; and (3) the evolution of dominant microflora has further enhanced bio-gasification of coal. Gas production data showed that the gasification of coal lasted 635 and 799 days and yielded 74,817 m3 and 251,754 m3 coalbed methane in Z-159 and Z-7H wells, respectively. One nutrition injection in coalbed achieved an average of 717 days of continuous gas production in experimental wells. Results confirmed that coalbed methane enhancement with bio-gasification of coal is a potential technology to achieve the productivity improvement of coalbed methane wells. And the findings of this study can help to further understand the mechanism of in situ coal bio-gasification and provide theoretical support for the development of biomining of coal.

The characteristics of maceral in Huangling coal and its in-situ pyrolysis

In order to reveal the pyrolysis and coking characteristics of different components in coal, the macerals in Huangling coal were enriched by centrifugation, and the pyrolysis characteristics of macerals were studied. The transformation characteristics of macerals during pyrolysis were observed in-situ by heating stage microscope. The purities of vitrinite and inertinite are more than 90% and 80%, respectively, while the purity of liptinite is nearly 70%. The initial pyrolysis temperature of liptinite is about 385°C, and those of the other macerals are all about 410°C. The maximum pyrolysis temperatures are between 470–480°C for all macerals studied. The maximum weight loss rate and the total weight loss rate decrease in the order of liptinite, vitrinite, semi-vitrinite and inertinite. The softening temperature of the liptinite (including sapropelic groundmass) is 350–370°C, while that of vitrinite is about 410–420°C as shown by the in-situ pyrolysis in a heating stage microscope. The pyrolysis process of vitrinite goes through the stages of edge shrinking, pore formation, surface softening, the formation of liquid phase, and solidification. Only slight morphological changes are observed in semi-vitrinite, while no changes are observed in inertinite. The active components in Huangling coal are vitrinite and liptinite, and the liptinite can promote the softening and melting characteristics of the adjacent vitrinite.

Understanding the adsorption behaviors of naphthalene sulfonate formaldehyde in coal water slurry

Naphthalene sulfonate formaldehyde (NSF) has been widely used as a dispersant for coal water slurry (CWS) preparation. However, the adsorption behaviors of NSF on different components were scarcely discussed due to the complex nature of coal. In this study, the adsorption kinetics and isotherms of NSF on the particle surfaces of carbonaceous matter, kaolinite, quartz, pyrite were investigated, along with X-ray photoelectron spectroscopy (XPS) and contact angle meter were conducted to clarify the adsorption mechanism of NSF on each particle surface. The adsorption measurements showed that the saturated adsorption capacities of NSF on the surfaces of kaolinite, pyrite and carbonaceous matter were much higher than that of quartz. Further single-layer adsorption occurred for the NSF adsorbed by all particles except quartz, where multi-layer adsorption was observed. The XPS and contact angle results showed that the interaction between the hydrophobic tail of NSF and carbonaceous matter is mainly attributed to hydrophobic force, concurrently the combination of the hydrophilic groups in NSF with Al elements of kaolinite and Fe elements of pyrite. The findings are significant to elucidate the adsorption mechanism of dispersants on the coal-water interface and proposed a reference for dispersants utilization based on different coal components.

2-10 TEMおよびXRDを用いたVietnam炭中結晶質灰分の高温挙動の解析

2-10 TEMおよびXRDを用いたVietnam炭中結晶質灰分の高温挙動の解析

Functionalized ionic liquids for lignite dissolution and treatment

AbstractBACKGROUNDAs a low‐rank coal, lignite (frequently referred to as ‘brown coal’) has a high latent moisture content and low energy density and thus has low value as a solid fuel, often being burned at power stations close to where it is mined. For this reason, an effective pretreatment is essential to the better utilization of low‐rank coal for energy and materials. Ionic liquids (ILs) are alternatives to conventional volatile organic solvents for pretreating coal due to their tailorable structures and physical properties, as well as their ability to partially dissolve/swell coal components. This study aimed to rationally design ionic liquids having a high hydrogen‐bond basicity, based on the acetate anion, paired with ether‐functionalized cations (especially the less‐expensive piperidinium) for lignite dissolution and treatment.RESULTSLignite treated by these functionalized ionic liquids at 105 °C led to the dissolution of 15.7–24.5 wt% lignite with a concomitant increase in coal aromaticity and rank, a reduction in coal decomposition residues, and the production of smaller and more uniform particles. The ether‐functionalized N‐(2‐ethoxyethyl)‐N‐methylpiperidinium acetate is a particularly attractive alternative to conventional imidazolium ILs due to its lower cost, high hydrogen‐bond basicity, and a strong capability for improving the coal aromaticity.CONCLUSIONOur results have demonstrated that pretreatment with functionalized ionic liquids can improve the coal aromaticity and rank, decrease coal decomposition residues, and yield smaller and more uniform particles, which enables a better utilization of low‐rank coal for fuel and materials. © 2021 Society of Chemical Industry (SCI).

Structural difference of gas coal separation components and its effect on sulfur transformation during pyrolysis of high sulfur coal

Two gas coals were respectively separated into four components with different vitrinite content using ZnCl2 solution. The carbon structure, composition of coal macerals and minerals, and plastic layer behavior of separating components were characterized by nuclear magnetic resonance spectrometer (13C NMR), coal petrographic analyzer, X-ray fluorescence spectrometry (XRF) and Gieseler fluidity. Combining with X-ray photoelectron spectroscopy (XPS), effect of different gas coal separation components on sulfur transformation behavior during pyrolysis of high-sulfur coal and distribution of sulfur forms in coke was investigated. The results show that with increase of vitrinite content in gas coal, the relative ratio of aliphatic carbon in coal increases, and the release amount of volatiles increases during pyrolysis; hydrogen free radicals in volatiles promote decomposition of sulfur, stabilize sulfur free radicals in time and release as sulfur-containing gases, and thus sulfur content in coke is reduced. Low density components in gas coal have the largest maximum fluidity and widest plastic range, and stability of plastic layer is the best during co-pyrolysis with high sulfur coal. The basic minerals in gas coal are mainly enriched in high density components, which leads to increase of sulfide sulfur and sulfate sulfur in the coke. For utilization of gas coal in coal-blending pyrolysis, enrichment of vitrinite and selection of coals with easier removal of alkaline minerals are beneficial for reducing sulfur in coke.

Effect of acetic acid concentration and dissolution time on the evolution of coal phases: A case report of bituminous coal

In the environment of high in-situ stress, the closing-up of coal seam pores and fractures has a great influence on the flow of coalbed methane. The acidification method can effectively expand fractures and generate new fractures, which is of great significance to improve the efficiency of coalbed methane mining. In order to investigate the correlation between the components in coal and the time and concentration of acetic acid dissolution, in this paper, Fourier infrared spectroscopy, X-ray diffraction and scanning electron microscopy experiments were performed on bituminous coal after 1, 3, 5, 12, 24, 48 and 72 h of dissolution to obtain the changes of coal components, organic functional group parameters and coal crystal structure. The results show that when acetic acid reacts with coal, kaolinite is recrystallized within 24 h of dissolution, and the recrystallized crystals are corroded by acetic acid within 24–72 h. The sensitivity of different functional groups to acetic acid is different, and the content of C=O and aliphatic group in acidified coal increases. The surface morphology of dissolved coal samples was observed by scanning electron microscope. It was found that the dissolution effect of acetic acid on coal surface cracks increased with the increase of acetic acid concentration. Combined with the specific experimental results, the best effect of 75% acetic acid on the coal samples was obtained after 72 h of dissolution.