Effects of Heating Rate and Ion-Exchangeable Cations on the Pyrolysis Yields from a Victorian Brown Coal

Abstract

A Victorian low-rank coal (Loy Yang) was acid-washed and ion-exchanged with Na and Ca to prepare the H-form, Na-form, and Ca-form coal samples. Two more H-form samples were also prepared by rewashing the Na-form and Ca-form samples with acid. These coal samples were pyrolyzed in a wire-mesh reactor where the secondary reactions of the evolved volatiles were minimized. The ion-exchanged coal samples were found to give very different tar yields from those of the raw coal samples. While the tar yields from the pyrolysis of the raw and H-form coal samples were observed to be very sensitive to changes in heating rate, the tar yields from the Ca-form and Na-form samples showed little heating rate sensitivity. Unlike higher rank coals studied previously, the tar yields from the pyrolysis of the raw coal and the H-form coal samples at 600 °C were found to increase much more than the corresponding increases in the total volatile yields as the heating rate was increased from 1 to 2000 K s-1. Reexchanging Na in the ...