97/03458 Laser pyrolysis and char oxidation of low-rank coal particles

Abstract

Prior work on the CO{sub 2} laser pyrolysis of separated arrays of bituminous coal particles at high flux levels is now augmented by a study of the pyrolysis and char oxidation processes of lignite and subbituminous coal particles as a function of exposure time at a laser fluxes of 200-300 w/cm{sup 2}. The Beulah lignite and Rosebud subbituminous coals studied were supplied by the Penn State Coal Sample Bank. They had been collected, ground, and packaged in an inert atmosphere. The coal samples were subsequently stored, sieved, carefully dried, and maintained in a glove box under dry nitrogen. The moisture loss of the as-received samples was within experimental error of the supplied ASTM analysis. The mass loss vs. time reported here are for particles that were dried at 120{degrees}C under nitrogen. The morphological changes in the particles with laser exposure was monitored by scanning electron microscopy. Care was taken to insure that mass loss did not reflect loss of particles. Pyrolysis rates were determined for particles in air and in a nitrogen flow, and compared with the results of corresponding laser pyrolysis studies of high and low-volatile bituminous coal particle arrays.