Study On The Properties Of The Thermal Dissolution Of Gas And Coking Coals And The Use Their Tdsfs In The Coal Blending For Coke-making

The thermal dissolutions(TDs) of gas and coking coals were carried out in different solvents at 340~380 ? for the comparative study of the effects of temperature and solvent on the TD performance of gas and coking coals. TG, ultimate analysis, FTIR and dynamic viscoelastic measurement were used to characterize the structure of the TD soluble fractions(TDSFs) and residues. The effect of addition of TDSF and coal model compounds in coal blending for coke-making on the quality of coke was further investigated. The coking coal blending mechanism was discussed,and the effects of composition and structure on the caking and coking properties of were preliminarily revealed.The results suggest that the TD temperature affects the TD yield of gas and coking coals differently. When 1-MN was used as a solvent, the TD yield of gas coal increased with the temperature rising, and the maximum TD yield was obtained at380 ? as 64.6%. While for coking coal, and the largest TD yield of 61.0% was obtained at 360?. The pyrolysis and condensation deeply occur at 380?, and the free radicals generated can not be stabilized by to obtain the activity H in time,resulting in the condensation themselves, thus forming 1-MN-insoluble compounds.At the same time, the different nature of the solvents has different influence on the TD of gas coal and coking coal. At 360? conditions, the TD yields for the both coals in polar solvent of CMNO were higher than those in non-polar solvent of 1-MN.Addition of 10% methanol in 1-MN the TD yield decreased by 4.1% and 10.7% from gas coal and coking coal respectively. FTIR analyses suggested that the contents of oxygen-containing functional groups and the heavy components with poly aromatic structure in TDSF increased as the polarity of solvent increasing. Similar tendency was found with the TD temperature rising, which is also consistent with the results of ultimate analysis. The TG results showed that the maximum weight loss temperature of TDSF from CMNO was the lowest. Meanwhile, with the rising of TD temperature,the weight loss of TDSF obtained decreased. It was found by ultimate analysis that the contents of C in the TDSFs from coking coal were higher than those in the TDSFs from gas coal. This suggests that the aromatic ring structural compounds in the TDSFs from coking coal were higher than those in the TDSFs from gas coal.The measurement of dynamic viscoelasticity of TDSF showed that the softening temperature of TDSF obtained at 380? was the lowest in the same solvent. Based on the TG and ultimate analyses of different TDSFs and residues, it showed that the side chains of the aliphatic hydrocarbons in the coal were broken into smaller molecular weight compounds as the TD temperature increasing, resulting in the softening temperature of TDSF obtained decreasing gradually. But with the increase of the polarity of the solvent, the softening temperature of TDSF obtained increased. The softening temperatures of TDSFs from coking coal were generally higher than those from gas coal under the same conditions. Based on the TG and ultimate analyses of different TDSFs and residues, it can be speculated that the TDSFs from coking coal contain more polycyclic aromatics, resulting in the higher temperature of liquids phase formation. However the TDSFs from gas coal contain more components with low molecular weight, and the formation of the liquids phase is in the low temperature,resulting in the low softening temperature of the TDSF. This is also one of the causes that the caking property of the TDSF from gas coal is higher than that of TDSF from coking coal.The coking properties of addition of different TDSFs and coal related model compounds in coal blends were investigated. Compared the coke from the standard coal blends, the quality of cokes was improved obviously after adding TDSF and model compounds in the coal belends, and the effects of TDSF are better than model compounds. The TDSF from 1-MN at 360? gave the best improvement to the coke quality because of its best caking property. Due to the TDSFs from polar solvents containing more oxygen functional groups, it limits the stability of the free radicals,and reduces the amounts of plastic materials. Therefore, the improvement of coke quality by the TDSFs from polar solvents decreases. Comparing the coke blending with the TDSFs from gas and coking coals it can be found that, the TDSFs fromcoking coal has a better improvement of the coke quality than that from gas coal. This is because that the coal rank of gas coal is lower than that of coking coal. Gas coal will form more volatile matters and tars in coking process. While coking coal is a low volatile matters with medium caking bituminious coal, the stability of the plastic materials produced by heating is very high. It was found by ultimate analysis that the content of C in the TDSFs from coking coal was higher, and H/C was lower. It means that the TDSFs from coking coal have more aromatic compounds and these aromatic compounds can supply hydrogen donor after pyrolysis. This will make the free radical fragements form liquids thus expanding the range of plastic temperature, improving the caking and coking properties of coal blends, therefore improving the quality of coke.