摘要
The sorption-enhanced steam methane reforming (SE-SMR) process is promising for in situ CO 2 capture and high-purity hydrogen production with a low CO concentration. SE-SMR using a CaO-based sorbent was operated at a temperature of 600-750 °C. High-purity H 2 production (defined as the H 2 molar fraction at outlet ≥90%) by SE-SMR using a CaO sorbent is generally not achievable at a temperature of 550 °C with a commonly used steam/methane molar ratio (S/C) of 3. CO 2 is the main greenhouse gas. The utilization of CO 2 to improve high-purity H 2 production through SE-SMR by adding CO 2 at the inlet in a fixed-bed reactor at 550 °C and S/C = 3 is numerically studied. The results show that high-purity H 2 production is achieved when the extra CO 2 addition at the inlet is at least 12% of the original mass flow rate (denoted as ≥12% CO 2,in ), based on the parameters in this work. The remarkably higher reaction rate of the strongly exothermic CO 2 sorption reaction is obtained for CO 2,in ≥ 12% in the inlet region of the catalyst/sorbent bed for the earlier time stage. Consequently, the temperature and the rate of steam methane reforming are significantly enhanced by the CO 2 sorption reaction. CH 4 conversion, the rates of H 2 production and CaO conversion, and total H 2 production (based on per unit mass of supplied CH 4 ) are enhanced by an increase in the level of CO 2,in