Flash pyrolysis coal liquefaction process development. Annual report, January-December 1977

Abstract

The Flash Pyrolysis Coal Liquefaction process development unit processed a caking bituminous coal for up to 22 hours continuously without plugging and thus established the technical feasibility of ORC caking coal reactor. Prior to the caking coal tests, we made three extended runs of one week duration and obtained baseline material balance data by pyrolyzing a subbituminous coal. Mass and elemental balance closures in the baseline runs were good. The extended operation of the PDU with the caking coal was hampered by unstable circulation of recycle char to the reactor. This was overcome by the development of a pneumatic char circulation technique using a fluidized-bed lift-tube char feeder. We developed a generalized data reduction routine for computer adjustment of data from the PDU and the BSR. We obtained kinetic parameters for the tar formation and cracking reactions based on the BSR data. The tar yields from subbituminous coal in the PDU baseline runs were found to be lower than those of the bench-scale reactor. The recycle char in the PDU was shown to be responsible for this. The addition of reactive carrier gases such as steam and carbon dioxide resulted in higher tar yields even in the presence of char.more » Apparently, these reactive gases retard the adsorption of tar vapors on the char surface. The processability of the PDU-derived tar in a continuous hydrotreater was demonstrated in a 40-hour test.« less