Influence of inherent minerals and pyrolysis temperature on the yield of pyrolysates of some Pakistani coals

An analytical method has been developed to quantitize tar, liquids and gaseous products resulting from the flash pyrolysis of sub-bituminous Makarwal coal. The method involves the thermal decomposition of 200 mg of 85-mesh size coal at 690 °C under the flow of nitrogen using Shimadzu PYR-2A open tubular pyrolyzer. The resulting tar and liquid fractions were separated using two traps at the exit of the pyrolyzer while the gaseous products leaving the traps were on line injected to gas chromatograph equipped with porapak Q column and flame ionization detector for the analysis. Effect of demineralization on the yields of products was investigated by treating raw samples with 2 M HCl. Removal of inherent minerals from coal by acid wash decreased the yield of total volatiles indicating catalytic properties of mineral under the condition used in present study. The influence of pyrolysis temperature on the yield of pyrolysates and hydrocarbon gases, resulting from raw coal samples, was studied over the temperature range of 500–770 °C.