Property Impacts on Heat Exchanger Design in CO2 Cryogenic Process of Carbon Capture and Storage

Abstract: Carbon capture and storage (CCS) is one of the most promising technologies which can significantly reduce CO2 emissions. A better understanding of thermo-physical properties of CO2 mixtures is required for the design and operation of different CCS processes. Before the gaps being filled, the most important properties need to be identified, and the performances of current property models should be evaluated.In this thesis, the status and progress of property impacts on CCS processes were reviewed by literature survey. The studied CCS processes include CO2 conditioning, transport and storage. The results show that heat capacity and density are most important in pumping process, while heat capacity and compressibility have greater impacts on compression process. In addition, density and heat capacity are treated most important in CO2 pipeline transport. For CO2 storage, density and viscosity should be prioritized.According to the knowledge gaps, the property impacts on the design of multi-stream heat exchanger in CO2 cryogenic capture process were investigated. The design model of the heat exchanger was proposed and developed by an in-house code in MATLAB. The property impacts on heat exchanger size and annual capital cost were identified by sensitivity study. The results show that thermal conductivity has the most significant impact. In addition, the heat exchanger design is less sensitive to viscosity than heat capacity, however, the higher deviation range of viscosity models may lead to a higher impact.Regarding to property model evaluation, the performances of viscosity models and thermal conductivity models of CO2 mixtures with non-condensable impurities were evaluated. Recommendations for property model selection were given as well. The results show that KRW model is recommended for predicting viscosity. For estimating thermal conductivity, GERG model is most accurate.