Oil shale pyrolysis in a moving bed with internals enhanced by rapid preheating in a heated drop tube

Abstract

The enhanced oil shale pyrolysis in a moving bed with internals (MBI) by rapid preheating in a drop tube was developed to improve the quality of shale oil through reaction regulation in stages. Initially rapid preheating of oil shale in the upper drop tube endowed the generation of massive free radical fragments and volatile precursors, which would simultaneously restrict the remarkable release of volatiles from particles to minimize the gas-phase secondary reactions. The preheated oil shale subsequently fell into the lower MBI to shape a granular bed with the cocurrent flow of heat and volatiles. In the MBI, the oil shale pyrolysis and volatiles reactions were directed and regulated by matching the flow and temperature fields to realize the selective cracking of heavy fraction in shale oil. The granular bed also served as a filter for the in-situ removal of dust entrained by the volatiles. The shale oil yield reached 83.0% of Fischer Assay oil yield, its light fraction was as high as 89.2 wt% and dust content was as low as 0.6 wt%. The advantages of pyrolysis in the MBI enhanced by rapid preheating were further justified by comparison with other pyrolysis processes.