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

Abstract

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-SECLRHC) in two separated streams. CLC provides reactant CO2 and energy to feed SECLRHC, 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 SECLRHC units can be achieved by circulating hot OCs. The desired temperatures of fuel reactor (FR) and reforming reactor (RR) should be 850 °C and 600 °C, respectively. The heat coupling between CLC and SECLRHC 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.

Keywords

• Natural gas reforming
• Chemical looping
• Heat integration coupling
• Techno-economic assessment
• Hydrogen