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Currently spray dust reduction is one of the most widely used dust removal methods in coal mines. The wetting performance of water on coal has a direct impact on spray dust reduction, therefore, adding wetting agents such as surfactants in water can improve the wetting performance of water on coal. In order to investigate the effect of various surfactants on the wettability of bituminous coal dust, four types of surfactants, namely, Rapid Penetrant T, 1227, BS-12 and APG, were used to investigate the wettability of bituminous coal by combining molecular simulation techniques and laboratory experiments. On the one hand, the interfacial system of surfactant aqueous solution was constructed by means of molecular simulation, the hydrophilicity of surfactant itself was analyzed based on the theory of the number of hydrogen bond formation and the radial distribution function, and the surface tension experiments of 4 reagents were carried out, and it was found that the Rapid Penetrant T reagent forms the most number of hydrogen bonds being 398, and the radial distribution function curve peaks at 1.99 ×10−10 m at the earliest time, which is the easiest to be adsorbed with H2O molecules, and the experimental results also showed that the Rapid Penetrant T reagent has the strongest weakening of the surface tension of the water, i.e., the smallest surface tension, which is 24.4 mN/m. On the other hand, through the electrostatic potential calculation, combined with the constructed surfactant/water/bituminous coal ternary adsorption system interaction energy analysis, the effect of four surfactants on the wettability of bituminous coal was investigated, and the experiments on the settlement and contact angle of bituminous coal in 4 reagents were carried out respectively. The results showed that the potential difference between the site and the water molecules after the Rapid Penetrant T molecules combined with the bituminous coal molecules is the largest, being 6.8535 eV, and the interaction energy between it and the bituminous coal is also the largest, being −2705.12 kJ/mol, and the experimental results also showed that the two kinds of bituminous coal have the smallest settling time in the Rapid Penetrant T reagent being 26.3 and 10.22 s respectively, and the smallest contact angle are 25.8° and 21.7° respectively. Thus, the study shown that the molecular simulation results are in agreement with the experimental results, and all of them validate that the anionic surfactant Rapid Penetrant T has the best wettability performance on bituminous coal.

The vitrinite-rich concentrates were extracted respectively from the Datong bituminous coal and the Xinjiang bituminous coal by the density gradient centrifugation method. The activated carbons were prepared by physical activation with carbon dioxide using the above raw coals and vitrinite. The structural properties of vitrinite and the corresponding raw coals were compared, and the characteristics of crystallite and pore structure were analyzed after the carbonization and CO2 activation process. The differences of aromatic and aliphatic hydrocarbon structures of coal and its vitrinite samples were analyzed by Fourier transform infrared spectroscopy. Microcrystalline structure parameters and aromaticity index of coals, chars and activated carbons were analyzed by X-ray diffractometer. The pore structure parameters of chars and activated carbons were studied by the low-temperature nitrogen adsorption method. Compared with raw coals, the crystallite unit sizes of vitrinite were smaller, the length of aliphatic hydrocarbon chain was shorter, and the number of branch chains was larger than those of the corresponding coals, which was beneficial to enhance the fluidity in the carbonization process. Moreover, the weight loss rates of vitrinite were higher, and the weight loss peaks were wider than that of the coals during the carbonization process by thermogravimetric analyzer. The above differences of structural properties and carbonization reactivity of coal and its vitrinite samples could affect the structure characteristics of chars. The results showed that the crystallite lamella size and stacking thickness of vitrinite chars were both increased after carbonization at 850 ℃, while the stacking thickness of crystallite in coal chars was decreased, which indicated that the differences of maceral mainly affected the vertical stacking of crystallite lamella during carbonization. Meanwhile, it led to higher aromaticity and larger BET specific surface area of both vitrinite chars. After the CO2 activation process, the stacking thickness and lamella size of crystallite in activated carbons were lower than that of the corresponding chars, indicating that the crystallite unit got burnt by CO2 activation. The dominant micropore structures were obtained after activation process. The BET specific surface areas of activated carbons from vitrinite reached 744.1 and 797.4 m2/g, respectively, which were significantly higher than that of activated carbons from coals. The micropore and mesopore volumes of vitrinite-based activated carbons were both higher than that of coal-based activated carbons, and the micropore volumes were 1.7−2.2 times more than that of coal-based activated carbons. The above results indicated that the chars with higher aromaticity and more porosity were beneficial to generate micropore structure during activation process.

Underground in-situ pyrolysis of coal is a new trend in the utilization of coal resources in the future. It is especially critical to investigate the coal pore-fissure structure, its spatial distribution and connectivity under different pyrolysis methods, and the existing studies on the pore-fissure structure parameters of coal after pyrolysis are in non-stress condition and lack of the comparison of pore-fissure structure parameters under different pyrolysis methods. Based on the above deficiencies, using the self-made triaxial testing machine of thermo-fluid-mechanical-chemical coupling at high temperature and pressure, combined with the micro-CT technology, the fissure structure differences of bituminous coal under the conditions of natural and steam in-situ pyrolysis (600 ℃) were investigated, and then the mechanism of the differences was explored. The results show that ① After the natural and steam in-situ pyrolysis at 600 °C, the fissure forms generated inside the coal sample are mainly slender cracks and holes, and the fissure scale is further improved after steam pyrolysis. The fissure network is more abundant and complex. ② Under the stress condition of 5 MPa axial pressure and 3 MPa confining pressure, after natural pyrolysis, the fissure rate is 2.68 times of the original fissure rate. However, after steam pyrolysis, the fissure rate is 3.65 times of the original fissure rate, and the fissure rate of each layer is more uniform. ③ Steam pyrolysis makes the bituminous coal heated evenly, with large heat exchange area and more adequate pyrolysis of organic matter. The displacement effect ensures the continuous production of pyrolysis products. The local stress effect of pore pressure not only expands the original pore-fissure volume, but also destroys the weak surface of pore wall, which greatly increases the pore connectivity. The steam denudation effect will “scour and transport” the tar with high viscosity attached to the blind fissures out of the coal body. Hydrogen-rich environment promotes the cracking of heavy tar and enhances the fluidity of oil. ④ There are large differences in the fissure rate and fissure morphology between in-situ and non-stress of coal pyrolysis. Steam pyrolysis is the optimal heating method for the engineering practice of in-situ thermal injection coal mining.

With industrial development and innovation, the demand for key metal minerals dominated by rare earth elements is increasing day by day. More experts believe that coal measures mineral resources have the potential to obtain key metal minerals, and such resources have therefore received high attention at home and abroad. Huaibei coalfield in China is rich in coal resources. In order to study the geochemical characteristics of trace elements in its coal and judge the industrial potential of rare metals, No. 5 coal, No. 8 coal and No. 10 coal in Zhuzhuang Coal Mine were selected as the research objects. The samples were analyzed by means of industrial analysis, XRF and ICP-MS. The results show that compared with the world coal, most trace elements in Zhuzhuang Coal Mine are highly enriched, such as Li, Cr, Co, etc. Compared with 5 coal and 8 coal, the concentration of trace elements in 10 coal is low, and the contents of V, Mn, Rb and Cs belong to the normal range. Through the analysis of w (Al2O3)/ w (TiO2) ratio and element geochemical characteristics, it is concluded that the sedimentary source area of the study area is felsic source rock, the paleosalinity from Shanxi formation to Lower Shihezi Formation changes from marine facies to saline water facies, and the paleoclimate is a warm and humid reduction environment. In addition, rare earth elements are enriched in light and medium rare earth elements, and Eu, Y positive anomalies and Ce negative anomalies all show that the sedimentary environment of Zhuzhuang mine is affected by seawater and magmatic hydrothermal solution. Therefore, the abnormal enrichment of trace elements in Zhuzhuang Coal Mine may be affected by the sedimentary environment, seawater and hydrothermal solution. In addition, the study area is relatively rich in rare earth elements, and its total content is close to or even higher than the industrial grade. Through the comparison of REY prospect coefficient (Coutl) and a variety of sediment minerals, it is considered that the rare earth elements of coal 5 and coal 8 in the sample of the study area are promising as REY raw materials, while the effect of coal 10 is poor.

In order to clarify the adsorption pattern between coal and CO, CO2 and O2, the competition between CO and CO2 and O2 in coal is studied. Qianjiaying bituminous coal is used as the research object, and the molecular unit parameters are calculated by quantitative analysis method based on the experimental results of Fourier transform infrared spectroscopy (FTIR). The molecular cell structure of Qianjiaying bituminous coal is constructed (C1160H860O80N20). To verify the accuracy of the model, the infrared spectrum of molecules is simulated by quantum chemical calculation, and the calculated results are basically consistent with the experimental results. On this basis, the effects of pressure(0−16 MPa) and temperature(20−60 ℃) on the adsorption of CO, CO2 and O2 by coal are investigated by using the Grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) methods. From the experimental results, it can be concluded that the fitted isothermal adsorption curves conformed to the Langmuir equation. Under the same pressure, the adsorption capacity of CO, CO2 and O2 is weaker as the temperature increases. At the same temperature, there is a positive correlation trend between the burial pressure of coal seam and the adsorption amount. The magnitude of adsorption of single gases CO, CO2 and O2 is CO2 > O2 > CO, and CO2 can reach saturation adsorption state in the first. The competitive adsorption results of binary gases show that the adsorption selectivity of CO2/CO has obvious advantages in low-pressure or shallow buried coal seams. However, the adsorption selectivity of O2/CO did not change significantly with the change of pressure. The competitive adsorption capacity of CO2 is greater than that of CO, and the adsorption capacity of CO2 decreases with the increase of CO concentration; The competitive adsorption of O2 is greater than CO when the ratio of CO to O2 molar concentration is ≤ 1, but the adsorption of CO is greater than O2 when the molar concentration of CO is much greater than O2. Therefore, the molar concentration of CO is high, which inhibits the adsorption capacity of CO2 and O2. In other words, in bituminous coal seams with high abnormal CO concentration, the effect of using CO2 injection to control fire extinguishing is not significant, so the amount of air leakage from the working face should also be controlled to prevent CO from desorption to the coal body and to ensure that the CO concentration in the well is within the permissible range.

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C2H4 is used as an indicator gas to evaluate the spontaneous combustion process of coal, and the adsorption of C2H4 by coal will cause the decrease of C2H4 gas volume fraction in mine air, which in turn affects the accuracy of the assessment of the spontaneous combustion process of coal. In order to reveal the microscopic mechanism of C2H4 adsorption in bituminous coal, a molecular model of Wiser bituminous coal was constructed, and the adsorption process of C2H4 in the molecular model of bituminous coal at temperature of 293.15-313.15 K and pressure of 0.1-3 MPa was simulated using Monte Carlo method, and the changes of adsorption heat, adsorption potential energy and adsorption entropy during the adsorption process were analyzed. The results showed that the adsorption of C2H4 in bituminous coal molecules first increased rapidly with increasing pressure and then leveled off; the higher the temperature, the lower the adsorption of C2H4 when the pressure was the same; Langmuir-Freundlich model has the best fitting effect on C2H4 adsorption process, and the maximum adsorption a of C2H4 decreases with increasing temperature; the average heat of adsorption of C2H4 under different temperature conditions is 35.29-37.65 kJ/mol, indicating that the adsorption of C2H4 in bituminous coal is physical adsorption; the adsorption potential energy and entropy of C2H4 decreased

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By establishing the molecular structure model of Pingdingshan bituminous coal（Ｃ108Ｈ71Ｏ4Ｎ）, using the grand canonical ensemble Monte Carlo method, the isobaric adsorption curves of the adsorption capacity at temperature of 298.15 and 303.15 K and the adsorption pressure at saturation and the isobaric adsorption curves of 1 point every 10 ℃ between 10 ℃and 70 ℃ were studied at molecular scale. The results show that the physical adsorption capacity of oxygen is negatively correlated with the equal adsorption heat, and positively correlated with low pressure. Adsorption saturation can be achieved at a certain pressure. The adsorption capacity changes relatively little at normal temperature and pressure. The three-dimensional distribution and energy distribution of the density of physical adsorption of oxygen in coal, the diffusion coefficient of O2 molecule in coal, and the influence of aromatic functional groups and fatty functional groups on the physical adsorption of oxygen are obtained. It is found that pyrrole functional groups have a great influence on the adsorption capacity, so as to intuitively understand the behavior of physical adsorption of oxygen by coal.

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In order to study the influence of different conditions on the particulate matter produced by coal combustion, the particulate matter produced by coal combustion is separated and collected in 11 ranges of 0-18 μm by micro-orifice uniform deposit impactor under laboratory conditions. The effects of combustion temperature, mass, coal type and size on the formation of particulate matter are studied. The results show that the total particle mass of bituminous coal and lignite at low temperature is obviously higher than that at high temperature. At high temperature, the particle size distribution of the two samples increased in the range of 1.0-10 μm, and the peak size appeared in the range of 0.18-0.32 μm and 0.32-1.0 μm respectively. Compared with lignite, the quality of particles produced by bituminous coal combustion is obviously increased, and the quality of particles produced by bituminous coal combustion is proportional to the quality and size of pulverized coal.

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The weak mass number difference of interference elements and target elements can be distinguished by high resolution coupled plasma mass spectrometry which can solve the mass spectrometry of polyatoms and oxides. It has been focused on trace element analysis in coal, but the application is still not mature enough. The challenge of mass spectrometry interference in determination of trace metal elements, especially rare earth elements in coal has not been systematically reported. HNO3-HF mixed acid was used to digest coal sample, pretreatment conditions such as digestion time, evaporation acid and resolution were optimized. The mass spectrometry interference of V, Cr, Mn, Co, Ni, Cu, Ga, Ge, As, Rb, Sr, Y, Nb, Mo, Cd, Sn,Sb,Cs,Ba,La,Ce,Pr,Nd,Sm,Eu,Dy,Gd,Tb, Ho,Er,Lu, Hf,Tl,Pb,Th total 35 trace metal elements at low, midde and high resolution was studied. Ge, Nd, Eu, Gd, Ho, Er, Lu were determined in high resolution pattern, Ga was determined in mid-resolution pattern, the remaining elements were determined in low resolution pattern. A method for measuring 35 trace metal elements in coal with high resolution inductively coupled plasma mass spectrometry was established. Under the optimized experimental conditions, the linear correlation coefficient of each element standard curve is greater than 0.999 9, and the detection limit is 0. 001--0. 082 µg/g. Coal standard sample (SARM 20) was selected for method verification, and elements with no certified value in the standard sample were basically matched with the standard experiment, the relative standard deviation of determination results are 0. 27c--6. 3% and the standard recoveries are 85. 8%-- 117 Four representative sample of other bituminous coal from Russian, other bituminous coal from Australian, coking coal from Mongolian, and other bituminous coal from Indonesia were seeded for testing, and the differences of trace metal element contents in coal from different producing areas were analyzed. The centents of Mn,Ba,Sr and rare earth elements are different in four coals, which can support the analysis of coal origin. [ABSTRACT FROM AUTHOR]

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To study the effect of H2O2 pretreatment combined with biodegradation on coal pores, the bituminous coal was pretreated with 0.05% H2O2, and the high-efficiency methanogenic microflora derived from the produced water of active coalbed methane(CBM) wells was used for anaerobic degradation of coal. The content of biomethane was detected by gas chromatograph and the development of coal pores was characterized by low-temperature liquid nitrogen adsorption. The results showed that H2O2 pretreatment of bituminous coal could significantly enhance biomethane production. Pretreatment had no significant effect on the type of coal pores, but the adsorption capacity of residual coal was reduced, which was conducive to the extraction of in-situ CBM. After pretreatment, the micro-pores and meso-pores volume of coal sample increased, while the transitional pores volume decreased. After biodegradation, the total pore volume and specific surface area of residual coal were significantly reduced; this may be caused by the retention and accumulation of soluble organic matter produced by microbial metabolism in the coal, thus blocking the pores of the coal.

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In order to study the change rule of free radicals in the process of continuous oxygen consumption of coal, four kinds of bituminous coals with different degrees of deterioration were selected and electron paramagnetic resonance apparatus was used to study the change rule of free radicals in the process of continuous oxygen consumption of different bituminous coals from oxygen-rich to oxygen-poor under the condition of variable temperatures. The experimental results show that the species and concentration of free radicals decrease and the symmetry of free radicals increases with the increase of coal metamorphism at room temperature; with the decrease of coal particle size, the concentration of free radical in coal increases, the type remains the same, and the symmetry fluctuates; particle size distribution has great influence on free radicals, concentration, type and symmetry of coal; when the temperature keeps increasing and the oxygen supply keeps decreasing, the concentration of free radicals in coal increases and decreases, while the type and symmetry of free radicals decrease. The continuous oxygen consumption of different types of coal varies with temperature.

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Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

China is rich in crop straw resources, but straw burning is serious and resource utilization is not high. To solved the ecological pollution and resource waste caused by straw burning, and let straw carbonization equipment market promotion. The orthogonal experiment of carbonization process was designed according to the literature and the results of preliminary experiment. The straw biochar produced by process test was analyzed. The thermal characteristic parameters and combustion characteristic parameters were calculated. Straw biochar yield, fuel ratio, hydrocarbon atomic ratio, alkalinity index, high calorific value and dimensionless comprehensive combustion index Z were used as quality evaluation indexes for high quality straw biochar. Grey correlation analysis method and comprehensive quality score method were used to analyze the evaluation indexes and influencing factors, and the response surface method designed by CCD experiment was used to optimize the production process of straw biochar directional regulation. The experiment provides a theoretical basis for improving the energy utilization rate of straw and provides a large number of data support for the popularization and application of continuous straw carbonization equipment. The results showed that temperature was the primary factor affecting the quality of straw biochar. The five evaluation indexes of straw biochar quality except the yield of straw biochar were ranked as follows: Z > H/C >FR >AI >HHV, the quality of straw biochar produced by the equipment is stable and close to the burning quality of bituminous coal. In the orthogonal experiment, the experiment in group 16 and group 12 obtained a higher comprehensive score, and the optimal process parameter combination was A3B4C1. CCD test results after response surface optimization, in the balance of the two response values to meet the maximum, the predicted optimal process parameters are: cut after the corn straw, after 600 ℃ thermal carbonization for 50 min, the production of straw biochar output is 53.05%, its combustion index Z is 0.726 6. The empirical test showed that the difference between the experimental value and the predicted value was less than 0.2%, the fitting model and the response surface optimization method were accurate and feasible, and the combustion quality of straw biochar produced by the optimal carbonization process was greatly improved. The C content and H/C of straw biochar produced under the best technological conditions are increased by nearly 2 times, which is closed to the combustion quality of bituminous coal and anthracite, and far better than the barbecue biochar purchased in the market. Through the carbonization process in this study, the utilization quality of straw biochar can be controlled directionally, forming a reproducible and generalized quasi-directional regulation method of high quality fuelized straw biochar. The analysis methods greatly reduce the experiment times, choose the appropriate fuel straw biochar quality evaluation index, and on the premise of saving the cost of raw materials and energy, quick understanding of high quality energy straw biochar production process parameters, facilitate continuous piecewise uniform crop straw carbonization market-oriented all-round production system of rapid popularization and application.In addition, the experimental design and data analysis method in this paper can also provide data support for the production of straw carbonization process using straw as raw material for adsorption and fertilizer carbon. [ABSTRACT FROM AUTHOR]

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Accurate identification of mine water inrush source is the key technology of mine water disaster prevention and control. According to the composition and content of conventional elements in Feicheng coalfield of Ordovician limestone water and the fifth limestone water is very similar, it is difficult to use the water inrush discrimination problem, twenty water samples from two types of aquifers are selected as discriminant samples, and five trace elements F, Br, I, H3BO3 and Rn are used as discriminant factors of Fisher method, combined with Baizhuang coal in Feicheng coalfield. The typical discriminant function model of Fisher is established by SPSS software in the case of water inrush from the floor of Mine 9603 working face, and the discriminant result is compared with that of the Piper three-line diagram of the conventional element. The results show that the Fisher discriminant model with trace elements can accurately identify similar water inrush sources, and the method is simple and easy to operate. [ABSTRACT FROM AUTHOR]