Analysis on H2 production process integrated CaO/Ca(OH)2 heat storage and sorption enhanced staged gasification using calcium looping

Abstract

A novel H2 production process integrated CaO/Ca(OH)2 heat storage and sorption enhanced staged gasification of biomass/coal based on calcium looping was proposed. The proposed process consists of four units such as co-pyrolysis of biomass and coal, char gasification with recycled CO2, sorption enhanced H2 production and CaO/Ca(OH)2 heat storage. CaO is used as CO2 sorbent to enhance water gas shift reaction for H2 production. Exhausted CaO experienced the multiple cycles from the sorption enhanced H2 production unit is sent to the CaO/Ca(OH)2 heat storage unit for the reactivation. Then the reactivated CaO is fed into the sorption enhanced H2 production unit again for the next cycle. To evaluate the overall performance of the proposed process, the thermodynamic simulation was performed by using Aspen Plus. The results show that the integrated process is more beneficial for H2 production compared with the normal sorption enhanced staged gasification process. Integrated CaO/Ca(OH)2 heat storage unit reduces the amount of required CaO and promotes H2 production, energy conversion efficiency and exergy efficiency of the normal process. The novel process operated at the optimum conditions achieves 17.4% higher H2 yield than the normal process. At this condition, the corresponding H2 yield of 1.08 Nm3/kg-fuel, energy conversion efficiency of 42.1%, exergy efficiency of 39.4% and CO2 capture efficiency of 96.6% are achieved in the integrated process. Therefore, H2 production process integrated CaO/Ca(OH)2 heat storage and sorption enhanced staged gasification based on calcium looping appears promising.