Conceptual design and assessment of Integrated capture and methanation of CO2 from flue gas using chemical-looping scheme of dual function materials

Abstract

Integrated Carbon Capture and Methanation (ICCM) with renewable hydrogen is considered a promising Power-to-Gas technology. Although ICCM is expected to reduced CO2 emission, the potentials of net CO2 reduction and economic feasibility are still unrevealed by careful assessments. This study developed three ICCM processes at industrial scale, and performed an assessment in terms of energy conversion efficiency, comprehensive energy consumption, net CO2 emission, and levelized cost of CO2 conversion. Special attentions were paid to investigate the effects from electricity and hydrogen sources, and plant configuration on the technical, environmental, and economic feasibilities. This work also identified the opportunities and challenges as operation pressure, SNG price, and carbon tax are consideredthe primary factors. A comparison was made between ICCM processes and the reference process that combines CO2 capture with aqueous solutions and CO2 catalytic hydrogenation for CH4 fuels. 89.0 % of energy conversion efficiency could be achieved with ICCM processes, much higher than that of reference process. When ICCM processes are driven by renewable energy, the best comprehensive energy consumption is estimated to be –20.68 MJ/kg CO2; negative CO2 emissions could be easily achieved for ICCM processes, and the best net CO2 emissions is –1.57 kg CO2/kg CO2 when powered by wind energy, demonstrating the technical and environmental feasibility as ICCM process is coupled with renewable energy. The levelized costs of CO2 conversion are in the range of 0.98–2.0 US$/kg CO2. The economic feasibility of ICCM process is primarily limited by H2 production cost. But the levelized costs of CO2 conversion decreases rapidly with H2 production cost, and the ICCM processes could become profitable if the cost of H2 production from renewable energy drops to the same level of coal-based hydrogen (<1.4 US$/kg H2). It is possible for European Union to deploy ICCM plants to bring economic revenues because of its high SNG price and carbon tax.