Membrane absorption of separating supercritical carbon dioxide and vapor in geothermal energy utilization based on lattice Boltzmann modeling

Abstract

Supercritical carbon dioxide exhibits potential as a working fluid for electricity generation utilizing geothermal energy, even in the presence of vapor within the reservoir mixture. A membrane absorption separator has been designed to separate the vapor from the mixture and purify the carbon dioxide. To simulate the two-phase flow of the gas mixture and absorption liquid, the multicomponent multiphase lattice Boltzmann method is employed. This method is coupled with the interfacial continuous species transfer model for salt diffusion in liquid water to investigate pore-scale factors influencing vapor absorption. The modeling approach offers detailed insights into the membrane absorption process. Simulation results indicate that strategies to reduce mass transfer resistance, such as increasing porosity, enhancing hydrophobicity, and decreasing membrane thickness, significantly enhance absorption efficiency. Conversely, methods to increase the mass transfer driving force, including elevating the concentration of the absorbing solution, increasing its thickness, and decreasing the gas thickness, provide limited improvements in efficiency compared to the aforementioned strategies. Among the factors examined, membrane porosity emerges as the most significant.