Soluble Organic Matter Affecting Low-Temperature Oxidation of Coal with Different Ranks

Abstract

Soluble organic matters in three different ranks of coal were extracted by the tetrahydrofuran. After treatment the product ingredients in the extract and microstructure change at the coal surface were measured. During the process of heating, the emissions released from the coal before and after extraction also be considered as indicators for evaluating the role played by the soluble organic matters. The results show that the extracts mainly contain aromatic and oxygenated compounds. It is noted that the active groups in the residual coal significantly reduced compared to the raw coal. By contrast, the total pore-volume and specific surface-area in the residual coal grow in varying degrees. Especially, the lower the coal rank is, the more obvious these variations are. In the procedure of low-temperature oxidation, the oxygen consumptions of residual coal with different rank all decrease. Regarding the soft coal and coking coal, the emissions of CO, CO₂, C₂H₄ and C₂H₆ also decline. However, for the anthracite, the emissions of CO₂ and C₂H₆ increase at the temperature from 110-130 °C. Further, the apparent activation energy of soft coal, coking coal and anthracite boosts after the extracted processing, which suggested that the existence of soluble organic matters is propitious to the occurring of spontaneous combustion of coal.