Hydrothermal treatment of Shenhua coal I. Effects on swelling and extraction properties of Shenhua coal

摘要

Hydrothermal treatment as one of important pretreatment can impact on the properties and reactivity of coal. Graff and Brandes[1] reported that exposure of Illinois No. 6 coal to 50 atm of steam at temperatures between 320 and 360 ℃ can improve the yields of liquids obtained by flash pyrolysis and solvent extraction, and suggested that coal is partially depolymerized by this steam exposure. Khan[2] studied the effects of steam pretreatment on the composition and devolatilization of coals with various rank, and revealed that the effects of steam pretreatment of coal on subsequent conversion appear to be a function of feed coal type. Iino et al.[3] thought the occurrence of some chemical reactions and the yield enhancements of treated coal may be due to the relaxation of hydrogen bonds and the removal of oxygen functional groups, such as the breaking of ether bonds. Shui et al.[4] found that the extraction yield of hydrothermal treated coals obviously increased because of the dissociation of the coal aggregation structure due to hydrogen bonds broken. Bienkowski et al[5] reported that steam treatment of Wyodak coal at 200 ℃ increased the conversion of toluene solubles in liquefaction. However, Ross and Hirschon[6] suggested that water treatment of Illinois No. 6 coal at 250 ℃ did not increase toluene solubles in liquefaction. Therefore, the structure and reactivity of hydrothermal treatment coal are influenced by a number of factors, such as conditions of pretreatment and coal rank etc.