Impact of CO2 atmosphere on coal pyrolysis in indirectly heated fixed bed with internals

Abstract

To clarify how CO2 affects pyrolysis characteristics in reactor with internals, pyrolysis of Yulin coal under N2 (inert) and CO2 (active) atmospheres is performed in fixed-bed reactors for two kinds of pyrolysis, i.e., with and without internals.CO2 exhibits different impact on tar yield for two types of pyrolysis, i.e., raising tar yield for pyrolysis in reactor without internals but lowering tar yield for that with internals. Tar yield pyrolysis under CO2 atmosphere is 6.31 wt% with internals, which is still higher 15.97% than that without internals at 1000 °C. In addition, CO2 atmosphere can produce more CO, high BET surface area char and high-quality of tar with more light tar (<C10), but less char, H2 and CH4 for both types of pyrolysis. The different impact of CO2 may be ascribed to the various flow routes for two kinds of reactors, and the extent of CO2-inclusive reactions, such as CO2-char gasification and reverse water gas shift (RWGS), is weakened by the adoption of internals due to occurring at lower temperatures and shorter residence time.