Thermodynamic study on the effects of operating parameters on CaO-based sorption enhanced steam gasification of biomass

Sorption enhanced steam gasification of biomass (SESGB) is a promising route for the production of H2-rich syngas. In this work, effects of some critical parameters of SESGB on hydrogen production are studied by means of thermodynamic equilibrium modeling. To improve the model performance, modeling modifications are made by using the carbon conversion efficiency for carbon balance calculation and by calibrating the equilibrium constants of methane reforming, water-gas shift, and CaO carbonation reactions with the experimental data. In addition, a new concept of CaO effective conversion rate is proposed to describe the influence of the CaO with different CO2 sorption capacity on hydrogen production. The root mean square error (RMSE) between the prediction results of the modified model and the experimental results is less than 3.5%, indicating the validity of the modification method. And the prediction results show that increasing temperature and the mass ratio of steam/biomass from 823 K to 923 K and from 0.5 to 1.5 increases the concentration of H2 and gas yield, while increasing the molar ratio between CaO and carbon from 1 to 2 mainly increases the H2 concentration.