Sorption-enhanced steam gasification of woody biomass assisted by Ca/Na/FS (fine slag) composite sorbents

Abstract

In this research, composite sorbents with high activity in promoting H2 production during sorption-enhanced steam gasification of pine sawdust (PS) were developed by doping coal gasification fine slag (FS) and NaOH into calcined conch shell (CS). The tests performed in a laboratory-scale fixed bed reactor demonstrated that the composite sorbents greatly improved H2 concentration and yield over that achieved with CHCS (CS after hydration and calcination), reaching 73.5% and 600.7 mL/g-PS, respectively. This promotion effect on H2 production was not influenced by the unburned carbon in FS. To obtain high H2 concentration and yield with as little NaOH and as much FS as possible, the optimum sorbent was found to be 3CS-2FS-0.32Na (in mass ratio of CS:FS:NaOH = 3:2:0.32). Under this condition, the H2 concentration and yield reached 74.3% and 572.3 mL/g-PS, respectively. In five cycles of experiment, although the H2 yield of 3CS-2FS-0.32Na decreased from 572.3 mL/g-PS to 416.6 mL/g-PS, it was always higher than with CHCS alone by at least 28%. The results in this study indicate that FS has potential to be an effective inert support material that endows CaO with high activity in H2 production during sorption-enhanced steam gasification. This might help to provide a new approach to minimizing the negative environmental impact of FS.