Fast co-pyrolysis of Naomaohu coal with waste tire under negative pressure

Co-pyrolysis of waste tire and low-rank coal is an efficient and clean technology for the utilization of solid wastes. Pyrolysis at negative pressure can minimize the secondary reactions of the pyrolysis volatiles, and is beneficial to understand the co-pyrolysis mechanism. In this study, an infrared-heated fixed-bed coupled with the vacuum pyrolysis equipment via the real-time pyrolysis pressure control was adopted to explore the co-pyrolysis interactions of Naomaohu coal and waste truck tire based on co-pyrolysis products distribution and tar compositions. Result shows that under atmospheric pressure, the highest tar yield of 21.62 wt.% was obtained at the heating rate of 600 C-degrees/min, and the best co-pyrolysis synergistic performance was obtained when the pyrolysis temperature was 550( degrees)C, along with 50% waste tire content. Pyrolysis pressure exerted the influence on the pyrolysis products distribution. When the absolute pyrolysis pressure decreased from 101 kPa to 11 kPa, tar yield exhibited an increasing trend from 38.27 wt.% to 48.72 wt.%, and the best tar synergistic effect was obtained at 550 C-degrees with blend ratio 1/1. The limonene content in co-pyrolysis tar under vacuum pressure reached the maximum 32.10% at the absolute pyrolysis pressure of 11 kPa, which was 9.31% higher than that under atmospheric co-pyrolysis. Co-pyrolysis under negative pressure could inhibit the molten state of waste tire and decrease the secondary reaction of the volatiles, which provides a simple route to improve the tar from copyrolysis of coal with waste tire.