An Improved CO₂ Separation and Purification System Based on Cryogenic Separation and Distillation Theory

In this study, an improved CO₂ separation and purification system is proposed based on in-depth analyses of cryogenic separation and distillation theory as well as the phase transition characteristics of gas mixtures containing CO₂. Multi-stage compression, refrigeration, and separation are adopted to separate the majority of the CO₂ from the gas mixture with relatively low energy penalty and high purity. Subsequently, the separated crude liquid CO₂ is distilled under high pressure and near ambient temperature conditions so that low energy penalty purification is achieved. Simulation results indicate that the specific energy consumption for CO₂ capture is only 0.425 MJ/kgCO₂ with 99.9% CO₂ purity for the product. Techno-economic analysis shows that the total plant investment is relatively low. Given its technical maturity and great potential in large-scale production, compared to conventional MEA and Selexol^TM absorption methods, the cost of CO₂ capture of the proposed system is reduced by 57.2% and 45.9%, respectively. The result of this study can serve as a novel approach to recovering CO₂ from high CO₂ concentration gas mixtures.