Hydrogen Production in Steam Gasification of Biomass with CaO as a CO2 Absorbent

Abstract

Characteristics of steam gasification of biomass for hydrogen production at ambient pressure in a laboratory-scale external circulating concurrent moving bed (ECCMB) system with CaO as a CO2 absorbent were investigated. In this ECCMB system, steam gasification of biomass, in situ CO2 capture, combustion of the produced char, and calcination of CaCO3 can occur simultaneously. The experimental results verified that the in situ CO2 capture was achieved with calcined limestone as a CO2 absorbent, which increased the extent of the water−gas shift reaction and enhanced the yield of H2. The H2 content of 60−70 mol % in dry gas can be obtained at a steam/biomass weight ratio (S/B ratio) of 0.38–0.59 and a CO2 absorbent/biomass weight ratio (A/B ratio) of 20 at the reactor temperature of 700–800 °C. The results showed that the addition of a CaO-based CO2 absorbent is a good solution to increase hydrogen content in dry gas from the ECCMB process. An irreversible deactivation of the CO2 absorbent occurred in the cyc...