Reaction characteristics of caking coal in jetting pre-oxidation fluidized bed gasifier

Abstract

Considering the difficulty in treating high-ash coking coal by the existing fluidized bed gasification technology, Institute of Process Engineering, Chinese Academy of Sciences has developed a jetting pre-oxidation fluidized bed gasification(JPFBG) technology for gasifying washing middlings and other caking coals. The coal is jetted into the pre-oxidation zone of a fluidized bed gasifier using an O2-containing gas stream to quickly disperse the particles and oxidize the viscous and plastic matter formed during heating. The char falls into the gasification zone to react with gasification agent as in other fluidized beds. This study was devoted to investigating the product distribution of pre-oxidation and the structure as well as reactivity of the formed char with respect to gasification condition parameters like temperature, air equivalence ratio(ER) and steam/coal ratio. The suitable conditions for pre-oxidation were temperature about 950℃ and ER1 about 0.13. The produced char had relatively larger specific surface area and higher gasification reactivity. The suitable gasification conditions were 1000℃, ER2 about 0.17 and mass ratio for steam/coal about 0.09. Then, the produced fuel gas had relatively higher quality and its tar contained more light species that were easier to be eliminated downstream. Obviously, all these results would support the design and scale-up of the JPFBGtechnology.