Effect of Hydrogen Separation on Coal Char Gasification with Subcritical Steam Using a Calcium-Based CO₂ Sorbent

Coal char was gasified using subcritical steam with/without a CO₂ sorbent (CaO) and/or a hydrogen separation membrane (palladium-23% silver) in a batch/semibatch autoclave reactor to investigate the kinetics in terms of the effect of hydrogen separation at 590-650 °C and 1.9-2.4 MPa in order to support a hydrogen production process of the HyPr-RING method. CO₂ sorption by CaO affects the production rate of H₂ but scarcely affected the carbon conversion to gas. Hydrogen separation promotes the hydrogen production in spite of the absence of CO₂ sorption. The effect of hydrogen separation on hydrogen yield and carbon conversion was higher than that of CO₂ sorption. A higher gasification temperature increased the hydrogen yield and carbon conversion. Using a first-order reaction form in parallel, the gasification reaction mechanism was explained for the components of the volatile matter and char in coal char. A higher reaction temperature results in an increase of the values of any kinetic constant for subcritical steam gasification of Adaro coal char with/without CaO and/or a hydrogen separation membrane. CO₂ sorption promoted hydrogen production due to the tar from volatiles with the catalytic effects of CaO, whereas hydrogen separation promoted hydrogen production due to char.