Numerical Simulation Of Co-gasification Of Biomass And Coal In A Fluidized Bed

Biomass energy is a abundant reserves of renewable energy. Gasification is oneof the most effective way for the usage of biomass energy. Biomass is taken as apopular technical route to produce fuel gas. However biomass gasification alone hasmany shortcomings such as supply changes with season, fluidized difficulty inside thefluidized bed and high tar content in the syngas. Co-gasification of coal and biomasscan improve the biomass supply problem, increase the gasification temperature topromote tar crack and also improve the fluidization characteristic inside the fluidizedbed.This thesis takes co-gasification experimental fluidized bed as a subject for study,use Aspen Plus software to establish the fluidized bed gasification model, andperforms the co-gasification of biomass and coal in fluidized bed gasifier. To simulatethe reality in a fluidized bed gasifier, the gasification reaction kinetics is expressed byFORTRAN subroutine in RCSTRS, and then the RSCTRS in series are used tosubstitute the Gibbs reactor．The results indicate that the simulating values are wellagreed with the experimental data. And the effects of biomass blending ratio,equivalence ratio(ER) as well as steam-to-fuel ratio(S/F) on co-gasificationcharacteristic of biomass and coal are systematically studied. The simulation resultsindicate that when the blending ratio of pine sawdust increases, the volumeconcentration of CO increases; the gasification efficiency reaches a maximum at anER of0.29; the increase of S/F value is conductive to improve hydrogen yield. Whenthe S/F value is in range of0.35~0.45, the high gasification efficiency and heatingvalues could be obtained.Based on Aspen Plus, exergy analysis is employed to study the process ofco-gasification of biomass with coal, and the effects of biomass blending rtatio onexergy value, and exergy efficeiency of product gas were studied in this thesis. Theresults show that pine sawdust gasification generates a higher energy efficiency than lignite gasification; when the blending ratio of pine sawdust reached50％, thesynergistic effect is obvious, which shows that co-gasification of biomass and coal isa better gasification technology.