Pressurized catalytic calcium looping hydrogen generation from coal with in-situ CO2 capture

Abstract

Pressurized catalytic calcium looping hydrogen generation (Ca-LHG) of coal with the introduction of K2CO3 catalyst was conducted to produce hydrogen in the autothermal gasification condition. Results showed that the K2CO3 catalyst could significantly improve the gasification reactivity while CaO sorbent mainly played the role as CO2 absorbent and the heat carrier. The final carbon conversion was increased from 31% for raw-char to more than 90% with adding K2CO3 and/or CaO at 700 °C and 3.5 MPa. On the basis of char blended with 10 wt% K2CO3, the H2 concentration was increased from 60 vol% to 77 vol% while the CO2 decreased from 26 vol% to 13 vol% in the presence of CaO. Moreover, CaO was found to reduce the deactivation of the K catalyst by alleviating the interaction of K with Si and Al in coal ash. The CO2 capture and CH4 yield were benefited from the gasification pressure increasing. The reaction heat calculation results indicated that the gasification of Ca-LHG process could shift from endothermic to exothermic as the pressure increasing to higher than 2.0 MPa. The gasification pressure of 3.5 MPa was suggested to achieve fully utilization of char and simultaneously maintain the thermal balance for both gasifier and regenerator. Finally, the multicycle performance of Ca-LHG demonstrated that the H2 content and carbon conversion were maintained above 70 vol% and 90% respectively during the 6 cycles experiment.