Synergy of steam reforming and K2CO3 modification on wood biomass pyrolysis

Abstract

The primary objective of this study was to investigate the synergistic effects of K2CO3 and steam reforming in the gasification process of woody biomass for hydrogen production. The experiment was carried out in a fixed-bed reactor with a continuous feeding system to investigate the effect of steam to biomass (S/B) molar ratio (0–0.4), K2CO3 loading amount (0–10 wt%) and reaction temperature (650–850 °C) as three main factors. The experimental results clearly indicated that both S/B and K2CO3 loadings promoted hydrogen production which could reach from 56 to 66% progressively as temperature increased from 650 to 750 °C, the role of potassium carbonate was mainly to change the path of catalytic cracking of tar and reduce the carbon deposit on the surface of the catalyst. While the role of water vapor mainly promoted shifting the reforming reaction in the direction of hydrogen generation. In addition, the water vapor itself could react with carbon to generate more hydrogen. The synergy of K2CO3 modification and steam reforming alleviated the deposited char and changed the components of tar simultaneously, and the optimum value for hydrogen production was acquired with 7.5% K2CO3 loading biomass while the value of S/B was 0.3 as the result of K2CO3 modification. The yield of rich-hydrogen syngas at 650 °C was similar with that of 850 °C, which evidenced that K2CO3 promoted the cracking of biomass at the low temperature region. It was concluded that K2CO3 modification of wood biomass with steam reforming promoted the hydrogen production and changed the path of catalytic cracking of tar and reduced the carbon deposit on the surface of the catalyst.