Study On The Properties Of The Thermal Dissolution Of Shenfu Sub-bituminous And Fat Coals And The Use Their TDSFs In The Coal Blending For Coke-making

The thermal dissolutions(TDs) of Shenfu sub-bituminous(SF) and fat coals were carried out in different solvents at 320~380? for the comparative study of the effects of temperature and solvent on the TD performance of SF and fat coals. TG, ultimate analysis, FTIR and TD soluble fraction(TDSF) char,s optical texture measurement were used to characterize the structure and composition of the TD soluble fractions(TDSFs) and residues. The effect of addition of TDSF and TD insoluble fraction(TDIF) from SF coal in coal blending for coke-making on the quality of coke was further investigated. The mechanism of coking coal blending was discussed, and the effects of composition and structure of TDSF on the caking and coking properties were preliminarily revealed. This will lay the foundation for the developing of a new technology in which low rank coal was modified by TD and used in coal blending and coking.The results suggest that the TD temperature affects the TD yield(TDY) of SF and fat coals differently. When 1-MN was used as a solvent, the TDY of SF trended to increase firstly and then decease as temperature rising, and the maximum TDY was obtained at 360? as 45.6%. However, the TDY for fat coal increased continuously as temperature rising from 320? to 380?, and reached to the highest value of 74.5% at 380?. On the other hand, the different nature of the solvents has different effects on the TD of SF and fat coals. At 360?, the TDYs for SF and fat coals in polar solvent of CMNO were 61.1 and 79.5%, which were higher than those in non-polar solvent of 1-MN respectively. Addition of 10% methanol in 1-MN the TDY increased by 18.1% and decreased by 4.7% for SF and fat coals respectively.The structure of the TDSFs from SF and fat coals is quite different. The content of oxygen functional groups in TDSF from SF coal was more than that in TDSF from fat coal, therefore the amount of hydrogen bond association structure in TDSF from SF coal was also higher than that in TDSF from fat coal. The TDSF of fat coal not only contained aliphatic hydrocarbon structure, but also much of aromatic hydrocarbon structure. There were many of methyl side chains with high degree of branch in aliphatic hydrocarbon structure. The aliphatic hydrocarbon structure was primary in TDSF of SF, and the content of aromatic structure significantly increased at high TD temperatures. Based on the optical texture measurement analysis of TDSF char under different conditions, it was found that the coarse-grained mosaic structure was dominated in the optical texture of TDSF of fat coal. But the fine mosaic structure was dominated in the optical texture of TDSF of SF.The effects of addition of different TDSFs from SF and fat coal instead of fat coal in coal blends on coke properties were investigated. Comparing with the coke from the standard coal blends, the quality of coke was improved obviously after adding TDSF in the coal blends as indicating that the particle reaction index reduced, the particle strength after reaction and the micro strength index increased. It was found that addition of TDSF of SF coal in 1-MN at 340? showed the best modification to the coke properties. The effects of TDSF of CMNO on the quality of coke were better than that of TDSF of 1-MN. For fat coal, the TDSF from nonpolar solvent 1-MN at 360? gave the best improvement to the coke quality than that from other solvents. Comparing the coke blending with the TDSFs from SF and fat coals it can be found that the TDSFs from fat coal has a better improvement to the quality of coke than that from SF. Moderate molecular weight, more fat methyl side chain structure and aromatic structures with moderate molecular weight are the major cause of caking components. Oxygen-containing functional groups decrease the caking property of TDSF. Since the TDSF of SF containing more oxygen-containing functional groups, its improvement to the quality of coke is not as good as the TDSF of fat coke in coking coal blending.The effects of addition of SF raw coal and TDIFs in coal blends on coke property were further investigated. Comparing with the coke from the standard coal blends, the quality of cokes from adding SF raw coal and TDIF in the coal blends became worse obviously, and the effects of TDIF addition are worse than TDSF and better than SF raw coal. The TDIF from CMNO at 360? gave the best coke quality than the others. This suggests that low rank coal can be used for coal blending coking by TD modification, therefore effectively expanding the coking coal sources.