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Circulating fluidized beds (CFBs) have been widely used in industrial processes such as combustion, gasification, calcinations etc.

Fushimi Research Group (with collaborators from Univ. of Tokyo, Hirosaki Univ., National Inst. of Adv. Industrial Sci. & Tech., and Kyushu Univ.) has been studying around the technologies of a triple-bed circulating fluidized bed (TBCFB) as a coal gasifier. Coal gasification is a technology of extracting the fuel gas from coal, preventing from emission of adverse affecting gas on the global environment.

It is imperative to increase rate of steam gasification of char at low temperatures and to promote tar decomposition/reforming in the TBCFB gasifier. Tar vapor is a stronger inhibitor of gasification. Some studies so far show a possibility of rapid tar decomposition by circulating a large amount of unreacted char together with inert solid media in the TBCFB. From viewpoint of mass and heat balance, and kinetics of pyrolysis and gasification, it is necessary to circulate a large amount of char and inert solid media with high mass flux. However, there has been no study around such condition.

In this research, flow behaviors of binary mixture of silica sand and nylonshot (coal char substitute) were investigated in a TBCFB.

Through the research, the large amount of nylonshot can be successfully circulated without causing significant segregation in the present TBCFB. Moreover, the modified pressure balance model was successfully set up to predict the mass flux of binary solids mixture.

This research is useful for the “green” energy technologies.

For further reading: Advanced Powder Technology

Research topic from TUAT Chemical Engineering