Synergistic Effects During Co-pyrolysis And Co-gasification Of Lignite And Bituminous Coal

Co-pyrolysis and co-gasification of YN lignite and DWG bituminous coal were carried out in a fixed bed reactor to investigate the synergistic effects between the two coals and the mechanism underlying the synergistic effect. This study has mainly achieved three following aspects of results:First, it was found that the differences between the char yields obtained from co-pyrolysis the temperature of900℃and those calculated from the results of the pyrolysis of two individual coals were small, but the tar yields obtained from the co-pyrolysis were obviously lower than the calculated ones and the compositions of gaseous products produced from the co-pyrolysis were also different from the calculated ones. The results indicated that there existed a synergistic effect during the co-pyrolysis.Second, the char obtained from the co-pyrolysis was gasified with steam under atmospheric pressure. The gasification rate, carbon conversion and composition of gas were surveyed by way of comparing to the corresponding results of gasification of the blends of chars derived from two individual coals. It was shown that the char obtain from the co-pyrolysis had a higher gasification rate depending on the gasification temperature. The shrinking core model was used to describe the gasification of coal char, and it was found that the activation energy was lower for the char obtained from the co-pyrolysis than the calculated one.Third, demineralization of coal by acid washing was carried out to investigate the effect of mineral matter in coal on the synergy occurring during the co-gasification. It was observed that the mineral matter in coal had an influence on the synergy but it appeared to be not the only reason. Scanning electron microscopy (SEM) and specific surface area measurement (BET) analyses demonstrated that there were some interactions between YN lignite and DWG bituminous coal during the co-pyrolysis, which could cause structural changes of the coal char and thus influenced the gasification activity of the char.