Techno-economic assessment of a chemical looping splitting system for H₂ and CO Co-generation

The natural gas (NG) reforming is currently one of the low-cost methods for hydrogen production. However, the mixture of H₂ and CO₂ in the produced gas inevitably includes CO₂ and necessitates the costly CO₂ separation. In this work, a novel double chemical looping involving both combustion (CLC) and sorption-enhanced reforming (SE-CLR) was proposed towards the co-production of H₂ and CO (CLC-SECLR_HC) in two separated streams. CLC provides reactant CO₂ and energy to feed SECLR_HC, which generates hydrogen in a higher purity, as well as the calcium cycle to generate CO in a higher purity. Techno-economic assessment of the proposed system was conducted to evaluate its efficiency and economic competitiveness. Studies revealed that the optimal molar ratios of oxygen carrier (OC)/NG and steam/NG for reforming were recommended to be 1.7 and 1.0, respectively. The heat integration within CLC and SECLR_HC units can be achieved by circulating hot OCs. The desired temperatures of fuel reactor (FR) and reforming reactor (RR) should be 850 ℃ and 600 ℃, respectively. The heat coupling between CLC and SECLR_HC units can be realized via a jacket-type reactor, and the NG split ratio for reforming and combustion was 0.53:0.47. Under the optimal conditions, the H₂ purity, the H₂ yield and the CH₄ conversion efficiency were 98.76%, 2.31 mol mol^-1 and 97.96%, respectively. The carbon and hydrogen utilization efficiency respectively were 58.60% and 72.45% in terms of the total hydrogen in both steam and NG. The exergy efficiency of the overall process reached 70.28%. In terms of the conventional plant capacity (75×103 t y^-1) and current raw materials price (2500 $ t^-1), the payback period can be 6.2 years and the IRR would be 11.5, demonstrating an economically feasible and risk resistant capability.