Secondary cracking of volatile and its avoidance in infrared-heating pyrolysis reactor

Abstract

This study aims to compare the pyrolysis behavior of Huadian oil shale in two infrared heating fixed bed reactors with different directions of infrared beam. Our previous work has shown that fast pyrolysis of oil shale conducted in the shallow fixed bed infrared heating reactor (co-current) presented the massive secondary reactions, which lowered the shale oil production (Siramard et al., 2017). Conversely, the cross-current infrared achieved shale oil yields higher than the Fischer Assay oil yield (13.07 wt% of dry basis), such as 117.7% of the Fischer Assay yield at our realized highest heating rate of 7 °C/s under a specified pyrolysis temperature of 550 °C. The shale oil from the cross-current infrared heating reactor was obviously heavier than the oil obtained from the co-current heating reactor. Thus, the infrared cross heating evidently suppressed the secondary reactions toward volatile. Our realized shale oil yield could reach 13.67 wt% or 122.5% of the Fischer Assay yield under reducing pyrolysis pressure of 0.6 atm, indicating that lower pressure is also beneficial to the release of volatile and reduction of the secondary cracking reactions. This work shows essentially that the infrared cross heating provides an effective merge of the advantages from quick heating and minimization of secondary cracking reactions to enable the shale oil yields being higher than the Fischer Assay oil yield. Keywords: Pyrolysis, Secondary cracking, Volatile, Infrared heating, Oil shale