Hydrogen rich syngas production from sorption enhanced gasification of cellulose in the presence of calcium oxide

Abstract

Sorption enhanced gasification of biomass is a novel technology for high purity H2 production and simultaneous carbon negative emission. The effect of CaO on the H2 production process was normally qualitatively explained. To quantitatively study the enhancing mechanism of CaO, the sorption enhanced gasification of cellulose for H2 rich syngas production was carried out in a fixed-bed pyrolysis-gasification system, the amount of CO2 absorbed, the carbon conversion rate of volatiles as well as the changes in the role of CaO under different gasification conditions were quantitatively studied. The results showed that CaO acted as a CO2 absorbent and/or a catalyst depending on the gasification temperature. It functioned as both a CO2 absorbent and a catalyst at lower temperatures of 550–700 °C, and a maximum amount of CO2 absorbed by CaO was achieved at 550 °C as 189.88 ml/g cellulose, CaO catalyzed the volatiles gasification to produce more H2 and achieve more sufficiently conversion with increasing temperature. While when the gasification temperature ≥750 °C, CaO acted only as a catalyst. The optimized condition for sorption enhanced pyrolysis-gasification of cellulose was of gasification temperature of 650 °C and of mass ratio of CaO/cellulose of ≥4, under which the actual carbon conversion rate of volatiles achieved ∼90 wt.%.