Time resolved pyrolysis product distributions of softening coals.

Time-resolved product distributions of four softening coals pyrolyzed in an electrically heated grid are presented. The data collected over a broad range of temperatures and pressures, satisfy a mass balance despite the small sample size (ca. 15 mg). Gaseous products composition as well as the weight of tar evolved were determined during heat-up at 100C/s and for extended isothermal periods (0-30s) at various temperatures (450-950C). Pressures studied range from .01 to 25 atm of either helium or hydrogen. The quench, a liquid nitrogen- cooled helium stream allows precise time-resolution of the pyrolysis reaction over the entire operating range without loss of product. Based on model compound studies in the literature and relative bond strength, we interpret the time resolved behavior of various gaseous products in terms of the decomposition of particular functional groups present in the coal molecule.