Characteristics of American coals in relation to their conversion into clean energy fuels. Quarterly technical progress report, October--December 1977

Abstract

The Penn State/DOE Coal Sample Bank has been expanded. A total of 54 characterized coal samples and 232 selected printouts of coal data were provided upon request to the coal research community. Work has been conducted using nitrogen as a pyrolysis medium at 808/sup 0/C and seven size grades of the Texas Darco lignite (PSOC-412) as starting material. This work was intended to extend previous work on the effects of particle size on pyrolysis. A study is being made into the effects of low temperature oxidation on the agglomerating properties of caking coals. The effect of preoxidation in air of a highly caking coal at different temperatures on weight loss during pyrolysis up to 1000/sup 0/C and reactivity of resultant chars to air at 475/sup 0/C has been investigated. Preoxidation has essentially no effect on weight loss during pyrolysis below 450/sup 0/C. At higher temperatures, however, preoxidation results in a decrease in weight loss. Preoxidation markedly enhances subsequent char reactivity. Differential scanning calorimetry and thermogravimetric analysis have been used to study the interaction between oxygen and an unactivated Saran carbon. In the range 125-227/sup 0/C, chemisorption of oxygen, though the predominant process, is associated with a gasification reaction. The rate of the latter reaction is much higher than extrapolated from the Arrhenius plot in the temperature range 450-550/sup 0/C. In the temperature range 450-850/sup 0/C, gasification kinetics have been studied by the TGA technique. Plots of burn-off versus reaction time are linear over the 15-65% burn-off range. The Arrhenius plots consist of three distinct straight lines of different slopes, indicating that the gasification reaction occurs in three different zones.