Sulfur fate during in-situ gasification chemical looping combustion (iG-CLC) of coal

Journal article, 2021

Sulfur conversion during in-situ gasification chemical looping combustion (iG-CLC) of coal is consisted by pyrolysis and char gasification. Insight into the fate of sulfur in these two processes is essential for exploring appropriate strategies for sulfur emission control, whereas in most of works the pyrolysis and gasification could not be fully identified. In this case, a two-stage fluidized bed reactor system comprising a lower and a higher reactor was used to generate in-situ and separate gases from pyrolysis and gasification in this work. Sulfurous gases including H2S, COS, CS2 and SO2 were experimentally studied under various conditions by changing operation temperature (T), O/fuel ratio (Φ) and OC reduction degree (XOC), while the solid samples were regularly collected for the characterization using different techniques. It was found that the sol-gel Fe2O3/Al2O3 was a sulfur resistant OC during the iG-CLC process, thus no formation of sulfur components in the material. The values of T and Φ have positive effect on the conversion of sulfurous gases to SO2, whereas a lower XOC value can improve the conversion of H2S. The main components from volatiles (mainly H2S and CS2) and from char (mainly COS) can be effectively converted to SO2 by the OC material. The coal ash exhibited a desulfurization function, as some sulfur contents were retained as CaSO4 during the iG-CLC tests. Finally, the fate of sulfur in coal during iG-CLC was comprehensively mapped, which would be significant for developing strategies for sulfur emission control.