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In the low-temperature oxidation of coal, ·OH can be formed via two pathways: the direct decomposition of ·OOH and the decomposition of ROO·. · OOH is produced when O 2 abstracts H from hydrocarbons or oxygen-containing functional groups, and with an energy barrier of 317.69 kJ/mol, the O-O bond of · OOH is cleaved to form · …
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To analyze the secondary oxidation of the active structures of pulverized coal and reduce risks of coal spontaneous combustion, free radical theory and functional group analysis were combined to study the effects of particle size and oxidation temperature on the active structure of coal molecules. This process was based on electron …
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Coal oxidation at low temperatures is a complicated process, involving four phenomena: oxygen transport to the surfaces of coal particles (convective mass transfer from the bulk to the film surrounding a particle followed by the diffusive mass transfer in the film) and within coal pores (pore diffusion), chemical interaction between coal and O 2, …
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In the process of mechanical crushing, the coal sample not only changes in physical structure but also changes in chemical structure. With the decrease in particle …
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The results showed that the best crushing strength was obtained when the weight ratio of WOR and low-rank coal is 3:7 at 800 °C, and its crushing strength of M 25 (M 25) can reach to 97%, while the thermoplastic properties of WOR is thought to be responsible for the obtained good crushing strength, where WOR can be softened and …
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In this paper, the low-temperature oxidation experiments at different particle sizes of four coal samples were conducted to investigate the effect of particle size on coal spontaneous combustion. The changes of oxygen-containing functional groups and gas composition during the grinding of coal samples under different atmosphere conditions …
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The energy conversion of an outburst mainly occurs among gas expansion energy, coal crushing, and transport energy. The energy dissipation under high gas …
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DOI: 10.1016/J.JLP.2015.08.007 Corpus ID: 110923960; Sources of underground CO: Crushing and ambient temperature oxidation of coal @article{Tang2015SourcesOU, title={Sources of underground CO: Crushing and ambient temperature oxidation of coal}, author={Yibo Tang}, journal={Journal of Loss Prevention in The Process Industries}, …
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The low-temperature oxidation characteristics of coal were studied through temperature-programmed experiments. The results showed that the CO emission of coal samples with antioxidants was ...
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The low temperature oxidation of coal is a contradictory and unified dynamic process of coexisting mass and heat transfer. The thermophysical properties are crucial during coal spontaneous combustion.
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In the process of sample preparation, the coal is firstly crushed with the crusher, screened into the particle size range of 0.074–0.106 mm with a screen and finally placed in vacuum drying oven dried for 24 h at 40 °C for reserve. ... According to the coal low-temperature oxidation method described in Sect. "Low-temperature oxidation of ...
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The results indicate that the average pore size of coal decreases as the temperature increase, with low-metamorphic coal demonstrating a more pronounced …
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Besides, the low-rank coal samples are handled under seven various pretreatment temperatures (ranging from 120 to 300 °C); then, the pore structure characteristics of low-rank coal under various ...
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Abstract. This paper examines the low-temperature oxidation of coal using pore model resembling ordinary tree structures, where the trunk of each effective pore reaches the exterior of the coal particle. Theoretical analysis shows that, at low temperatures and atmospheric pressure, the mean diffusivity of oxygen in a coal …
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Coal. Article. Micro-structure of crushed coal with different metamorphic degrees and its low-temperature oxidation. May 2020. Process Safety and …
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Five macro-characteristic temperatures (critical temperature T 1, xerochasy temperature T 2, activity temperature T 3, mass peak temperature T 4, and ignition temperature T 5) move to the low temperature direction with decreasing particle sizes except T 4. Reaction processes during coal–oxygen interactions are proposed.
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Jingyu Zhao et al. analysed the critical points of the low-temperature oxidation stage of coal, including the critical temperature (97.45 ± 7.15 °C) and crack temperature (149.28 ± 8.32 °C) 17 ...
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A conventional technique to study coal pore structure is low-temperature nitrogen adsorption. ... A conceptual model in Fig. 13 displays the change in pore structure of lignite before and after crushing. The coal particle size significantly affects the original pore structure of the lignite during crushing. Crushing and impacts cause a collapse ...
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This study is aimed at investigating the effect of particle size on the oxygen adsorption capacity and spontaneous combustion and oxidation of coal, so as to provide guidance for the prevention of spontaneous combustion of residual coal in goafs. First, gas adsorption experiments, low-temperature oxidation (LTO) experiments and electron …
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By thermogravimetry (TG) experiments, evolution behaviors and properties of thermal oxidation processes at low temperature of a bituminous coal with five …
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The oxygen concentration in the goaf is low, and in order to study the effect of oxygen concentration on the low temperature oxidation characteristics of coal, the lower low temperature oxidation process of rock/coal mixtures (all x = 50 % of different rock/coal mixtures) under different low-oxygen conditions is analyzed using thermogravimetric ...
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The free radical concentration of oxidized coal is greatly affected by the crushing process. In the particle size range of 0.074-0.125 mm, low-temperature oxidation has the weakest effect on free ...
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The theory holds that coal oxidation at low temperatures is due to the interaction of coal with O 2 in the air (physical adsorption, chemical adsorption, and chemical reaction). When the heat accumulates to the point that it cannot be released in time, the coal will combust spontaneously. ... In the process of coal crushing, a large number of ...
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To this end, a low-ash and high-volatile wetting coal sample from Western China was pretreated by a programmed heating experimental system at isothermal pyrolysis temperatures of 50, 80, 110, 140 ...
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Shenmu (SM) subbituminous coal without caking property was treated by low-temperature rapid pyrolysis (LTRP) to modify its caking and coking properties. The treated samples were characterized by Fourier transform infrared spectrometry, vitrinite reflectance, and X-ray diffraction to determine the modification mechanism. Moreover, …
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This study focuses on the mechanism of gas (such as CO and CO2) generation during low-temperature oxidation of coal to provide a better understanding of the progressive phases of coal spontaneous combustion. Considering the formation of coal bodies, the internal structures of different coal bodies vary; therefore, it is difficult to …
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It can be seen that the crushing performance index of biomass was stable above 95 % from low temperature to high temperature. The crushing performance index of PVC increased with the increase of temperature, and finally tended to be stable, and the crushing performance index was about 95 % above 300 °C.
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Carbon dioxide (CO2) is widely used in the prevention and control of spontaneous coal combustion. In this manuscript, three low-rank coals with different metamorphic degrees were selected as the research objects. The temperature-programmed experiments, in situ infrared cooling experiments, simulation of the …
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Heat release and accumulation in low-temperature oxidation of coal is the fundamental reason responsible for coal spontaneous combustion [8]. Coal with a spontaneous combustion tendency will undergo a slow oxidation process due to physical and chemical absorption after crushing and accumulation during mining.
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The composition of coal tar is complex [14], among which coal tar with pyrolysis temperature between 500 °C and 700 °C is referred to as low-temperature coal tar (LTCT) [15]. The disadvantages of conventional coal-to-oil technology in terms of environmental protection and production costs lead to the emergence of underground in …
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