Study On Ash Fusion Characteristics And Co-gasification Characteristics Of Biomass And Coal

Ash fusion characteristics of coal and biomass are important for the development of entrained flow co-gasification of coal and biomass. In this study, the effects of biomass addition on coal ash fusion temperatures(AFTs) were investigated. Besides, the co-gasification characteristics of biomass and coal were studied in a drop tube reactor.The AFT of coal could be reduced effectively by adding of three kinds of biomass. The AFT of rice straw(RS) and coal blending ash was reduced with the increase of RS ratio. However, in the cotton stalk(CS) and coal blending ash, as well as sargassum (SA) and coal blending ash, the AFT was reduced firstly and then increased with the gradual increase of biomass ratio. At high temperature, the presence of biomass can form low melting eutectic minerals easily, such as leucite and nepheline, which could reduce the AFT of coal. The blending ash had a relative low AFT when the value of base to acid ratio(B/A) is in the range of 0.5-3.0.High temperature images showed that coal ash fusion behaviours were prolonged softening and subsequent melting of solid phases that result in sluggish flow and depressed dissolution of the refractory constituents, and RS ash had more volatile matter release and could form active melts, which could promote the reaction between the minerals and dissolve the residual refractory. The melting process of blending ash was similar to the melting process RS ash. The promotion of the flow behavior in blending ash was enhanced with the rise of RS ratio.In the steam co-gasification experiments, the generation of CO was inhibited with RS ratio of 50% and 80% when gasification temperature was at 1000℃. At 1200℃, the gas yields were according with the weighted average value. At 1400℃, the generation of CO and H2 were promoted with RS ratio at 50% and 80%. The proximate and ultimate analyses of co-gasified solid were different from the weighted average value. In the oxygen co-gasification experiments, when at 1200℃, CO and H2 were inhibited and CO2 was promoted with RS ratio of 20%and 50%. However when RS ratio was 80%, H2 and CO2 were inhibited. At 1400℃, H2 was inhibited and CO2 was promoted with RS ratio of 20%, and CO was promoted when RS ratio were 50% and 80%. The solid ash composition was similar to that of steam co-gasification. The fused ash particle, which was rich of Si, A1, K and Ca et al, was formed during co-gasification of coal and RS.