The pyrolysis of a Wyoming coal in different nonreactive atmospheres

This study investigated how differing nonreactive atmospheres affected the properties of chars produced by coal pyrolysis. Samples of a Wyoming subbituminous coal were first heated at 586°C in helium for 6 hr. They were then heated for another 6 hr at 300°C higher in helium, argon or nitrogen. Weight losses in the chars during the second step were apparently unaffected by the choice of inert environment. Surface characteristics, pore structures, and reactivities of the resulting chars were, however, significantly different as shown by the results of scanning electron microscopy, nitrogen adsorption, carbon dioxide adsorption, and reactivity of the chars in carbon dioxide. Smoothness of the surface, adsorption capacities, N₂ and CO₂ surface areas, and reactivity during gasification all decreased in the direction (in order of inert atmospheres employed) He >Ar >N₂. In addition, there were strong indications that trace contaminants in the inert gases could alter the characteristics of the resulting char markedly.