Development of a new CO2-rich natural gas to high-purity CO zero carbon emission system employing chemical looping process: Thermodynamic and environmental investigation

Abstract

Offshore natural gas (NG), as an important energy resource, has high CO₂ concentrations widely distributed from 20% to 80%. The effective conversion and utilization of these NG hold substantial environmental value. However, traditional NG conversion technologies, such as dry reforming of methane (DRM), cannot fully convert NG with such high CO₂ concentrations, often requiring decarbonization processes which causes significant energy loss and carbon emissions. In this work, a novel zero-carbon emission system for the efficient and environmentally friendly conversion of CO₂-rich NG is developed. Different from the traditional DRM route to produce syngas, the CO₂-rich NG is converted directly into high-purity CO through metal oxide oxygen carrier chemical looping reactions with CO₂ adsorption enhancement. Through the proposed method, a higher amount of CO₂ can be reduced per unit of methane, showing the capable advantage for higher CO₂ concentration NG. Based on the system configuration, key process experiments were conducted to validate the feasibility and advancement of the proposed system. Furthermore, system integration and parameter analysis were conducted to investigate the thermodynamic and environmental performance of the developed system, verifying its adaptability and conversion capability to various types of NG. The promising results show that, the novel system can convert NG with up to 63.50% CO₂ to CO with 99.10% purity. Compared to the DRM, the amount of CO₂ reduced per unit of CH₄ raises from 0.76 to 1.71, representing 1.25 times increase, with a 17.00% improvement in system energy efficiency. This research significantly improves the utilization efficiency and environmental sustainability of CO₂-rich fuels, such as CO₂-rich NG and biogas, providing a new pathway for reducing greenhouse gas emissions and high valorization utilization of CO₂.