Experimental analysis and system design of a novel autothermal moderate-temperature chemical looping hydrogen production process with steam enhancement

Hydrogen is recognized as a clean and versatile energy carrier critical to global decarbonization. Among various production routes, steam methane reforming (SMR) dominates but suffers from high energy consumption, catalyst degradation, and substantial CO 2 emissions. Chemical looping hydrogen production (CLHP) process has emerged as a promising alternative for its inherent CO 2 capture and autothermal potential. In conventional CLHP, CH 4 complete oxidation to CO 2 is required for effective CO 2 separation, necessitating high temperatures, limiting H 2 yield, and causing significant irreversible energy losses. To address these limitations, this study proposes a novel moderate-temperature chemical looping hydrogen production process with steam enhancement (CLHP-SE) that co-feeds CH 4 and steam during the reduction reaction stage to modulate the reaction pathway, thereby enhancing CH 4 conversion and H 2 yield while simultaneously reducing the reaction temperature. Steam is fed to suppress CH 4 complete oxidation while participating in H 2 production. A series of fixed-bed experiments were conducted to validate the feasibility of the co-fed strategy. At 650 °C, the CH 4 conversion rate remained stable between 85% and 93%, with H 2 yield reaching 2.12-2.65 mol-H 2 /mol-CH 4 in the reduction stage. The experimental results are further integrated into a system model for comprehensive performance evaluation. The results show that the proposed CLHP-SE system achieved a H 2 yield of 2.65 mol-H 2 /mol-CH 4 under self-heating operation, which was about 21% and 15% higher than the traditional SMR system (2.19 mol-H 2 /mol-CH 4 ) and CLHP system (2.30 mol-H 2 /mol-CH 4 ), respectively. Moreover, the energy and exergy efficiencies of the CLHP-SE system reached 77.71% and 68.70%, respectively—6.56% and 6.08% higher than those of the reference CLHP system. This work demonstrates a promising pathway toward efficient and low-carbon H 2 production from natural gas at mild operating conditions.