Effects of cations on the rapid pyrolysis of a Wyodak subbituminous coal

Abstract

The effects of cations on product compositions from rapid pyrolysis of a Wyodak sub-bituminous coal were examined. Raw coal and demineralized coal in acid, Ca, Na and K forms were heated in helium at 1000 K/s to temperature of up to 1400 K, and yields of char, tar and individual gaseous volatile products were determined as a function of time-temperature history. Metal-ion form coals gave lower yields of tar and gaseous hydrocarbon volatiles than did the acid-form coal. CO/sub 2/ yields from acid-form coal reflected stoichiometric decomposition of carboxyl groups, while cation-form coals gave CO/sub 2/ yields that were considerably larger than those from demineralized coal, probably reflecting non-carboxyl coal oxygen decomposition via a metal carbonate intermediate. In all cases, Na and K ions had larger effects than did Ca ions.