On the Issue of Establishing the Stages of Coal Metamorphism for Predicting the Hazardous Properties of Coal Seams

The characteristic stages of metamorphic transformations of mines are established according to the increase in the elemental content of carbon and changes in other components of organic matter. Stages of metamorphism transformations with an average carbon content of more than 93.6% can significantly differ in properties due to the unpredictability of the ratio between the components of organic matter. At these stages, even a minimal difference between the components can be the reason for the emergence of new properties of the coal seams. As the influence of the processes of metamorphism increases, the boundaries of the stages, determined by the percentage of carbon, narrow. The established stages of the transformation of reservoirs in terms of the individual proportion of the components in carbonization practically do not differ from the boundaries of the stages determined by the elemental composition of organic matter. It is noted that the average carbon content at the stages of seam metamorphism, determined by the yield of coke, in most cases does not coincide with the ranges of changes in the average carbon content, established by the individual content of the components or their share in carbonization. The inconsistency of the boundaries in the stages of seam metamorphism makes it unacceptable to use the coke yield as the main criterion for assessing the conversion of coal and even more so the manifestation of hazardous properties of coal seams.

Effects of Direct Coal Liquefaction Residue Additions on Low-Rank Pulverized Coal during Co-Pyrolysis

This study examined the co-pyrolysis characteristics of low-rank coal (SJC) and direct coal liquefaction residue (DCLR) through thermogravimetric analysis coupled with Fourier transform infrared spectrometry. It also investigated the influences of different mass fractions of DCLR to SJC on the co-pyrolysis characteristics and release regulation of gas phase components. Results showed that with increasing DCLR content, coke yield initially decreased and then increased, but tar and gas yield reversed. Different addition of DCLR changed the composition of the pyrolysis gas in various degrees, and reduced the content of-OH and nitrogen compounds in coke. The H2 content in the gas gradually increased. When 40% DCLR was added, the maximum tar yield was 22.79%, and the maximum H2 yield was 37.12%. At 60% DCLR, the lowest semi-coke yield was 65.01%, and the highest gas yield was 14.65%. The co-pyrolysis of SJC and DCLR can be divided into three stages. The first was the dry degassing stage, during which the adsorbed gas and small-molecule gas were removed on the coal surface at room temperature to 350 °C. The second stage (350 °C–650 °C) was the intense pyrolysis reaction stage, during which a large number of volatiles were obtained. The substantial weight loss rate peak appeared around 450 °C. The weight loss rate of pyrolysis gradually increased with increasing DCLR dosage. The co-pyrolysis of SJC and DCLR was not a simple sum between SJC and DCLR, which indicated a synergistic effect in the co-pyrolysis. The synergistic effect between SJC and DCLR enhances the interaction between free-radical fragments, thereby increasing the yield of pyrolysis tar. The third stage was the shrinkage of semi-coke from 650 °C to the end of the reaction. The polycondensation reaction between free-radical fragments to form solid coke with higher aromaticity, and H2 released.

Ex-Situ Synthesis and Study of Nanosized Mo-Containing Catalyst for Petroleum Residue Hydro-Conversion

This study represents the results of ex-situ synthesis and research of the properties of concentrated suspensions with new catalysts for petroleum residue hydro-conversion. Suspensions were prepared and stabilized in a petroleum residue medium through reverse emulsions containing water-soluble Mo-precursor and S-containing agents (elemental sulfur, thiocarbamide) in the absence of a solid carrier. The resulting ex-situ catalyst dispersions had Mo content of 6–10 wt % and contained nanosized and submicron catalyst particles stabilized in a petroleum residue medium. The effects of S-containing agents on the properties of catalytic particles (sulfidation level, dispersity, structural and morphological features) were studied. The synthesis conditions for the optimal ex-situ catalyst providing the lowest coke yield (0.2 wt %) and the highest conversion (55.5 wt %) during petroleum residue hydro-conversion in a single pass mode have been determined.