FLASH PYROLYSIS OF COAL IN SOLVENT VAPOR FOR CONTROLLING PRODUCT DISTRIBUTION

A simple method was presented for controlling the product distribution during the flash pyrolysis of coal under mild conditions, in which the coal was pyrolyzed in an atmosphere containing solvent vapors. To examine the validity of this method, an Australian brown coal (Morwell) was pyrolyzed in a nitrogen atmosphere containing the vapor of ethylbenzene, 2-methyl-1-propanol, tetralin, or methanol. In ethylbenzene vapor the char yield decreased by 3-4.5 kg/100 kg of coal, and the tar yield increased by 5.8-8.6 kg/100 kg of coal at 650-750-degrees-C. This clarified that the coal conversion can be increased when the radical donation rate matches the formation rate of tar precursors even if the radical is supplied from the gas phase. In 2-methyl-1-propanol vapor, the BTX yield dramatically increased up to 6.4 kg/100 kg of coal which was 5 times larger than that in an inert atmosphere at 750-degrees-C. It was clarified that the dramatic increase was brought about by the gas-phase reactions of tar with the radicals deriving from 2-methyl-1-propanol. Tetralin and methanol, which decompose at high temperatures, increased the yield of hydrocarbon gas at 850-degrees-C. These results indicate that the product distribution can be controlled by matching the radical donation rate of the solvent vapor with the formation rate of the desired product precursors at a temperature suitable for the desired product. Thus, a simple and effective method was presented to control the product distribution and to increase the conversion of coal pyrolysis.