A NEW COAL FLASH PYROLYSIS METHOD SUPPRESSING CROSS-LINKING THROUGH THE SWELLING OF COAL BY PYRIDINE VAPOR

A new coal flash pyrolysis method was presented for increasing the total volatiles and the tar yield through suppressing the cross-linking reactions during the pyrolysis, in which the coal swollen by pyridine vapor was pyrolyzed under a high heating rate. Pyridine molecules interacting strongly with coal were retained during the pyrolysis at low temperatures, and they were completely desorbed without decomposition at 764-degrees-C. Thanks to this peculiar behavior of the pyridine, the cross-linking reactions which occur at temperatures lower than 500-degrees-C were significantly suppressed. The total volatiles and the tar yield of a Morwell brown coal swollen by pyridine vapor increased up to 58 kg/100 kg of coal and 28 kg/100 kg of coal, respectively, indicating the validity of the presented method. The increase in the tar yield was well correlated with the amount of the decreases in the yields of CO, CO2, and H2O, which would be closely related to the extent of the cross-linking reaction suppressed. To increase the total volatiles and the tar yield further by utilizing the hydrogen donability of tetralin, the flash pyrolysis of coal swollen by pyridine and tetralin sequentially was performed. The total volatiles increased up to 64 kg/100 kg of coal at 764-degrees-C, and the tar yield increased up to as high as 42 kg/100 kg of coal, which was 2.3 times larger than that of the raw coal.