In H_2 production from woody biomass by steam gasification using CaO as a CO_2 sorbent, the effect of reaction parameters such as the molar ratio of CaO to carbon in the woody biomass ([Ca]/[C]), reaction pressure, reaction temperature, and molar ratio of oxygen to carbon in the woody biomass ([O_2]/[C]) on H_2 yield was investigated. In the absence of CaO, the product gas contained CO_2. On the other hand, in the presence of CaO ([Ca]/[C]=1, 2, and 4), no CO_2 was detected in the product gas. At a [Ca]/[C] of 2, the maximum yield of H_2 was obtained. The H_2 yield was largely dependent on the reaction pressure, and exhibited the maximum value at 0.6 MPa. It is noteworthy that H_2 could be obtained from woody biomass at a much lower pressure compared to other carbonaceous materials such as coal ( > 12 MPa) and heavy oil ( > 4,2 MPa) in steam gasification using a CO_2 sorbent. H_2 yield increased with increasing reaction temperature. The addition of oxygen had negative effects on the H_2 production. Woody biomass is the one of the most appropriate carbonaceous materials in H_2 production by steam gasification using CaO as a CO_2 sorbent, taking the reaction pressure into account.
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