Membrane superstructure optimization for carbon capture from cement plants. Water content influence on optimal solution

Abstract

A four-membrane superstructure, embedding different connection alternatives and driving force generation options, was extended to consider a four-component wet flue gas mixture. Three case scenarios were assessed for treating a flue gas stream from a cement plant. By minimizing the specific total annual cost (sTAC), each case converged to a distinct local optimal arrangement, achieving the same separation target (90% CO2 recovery and 95% CO2 purity on the concentrated stream), thus highlighting the versatility of the model. In terms of the same superstructure and cost model, the optimal solution for capturing CO2 from wet flue gases is approximately 1.5 times higher than that of a dry mixture. A commonly published optimal two membrane-stage configuration fails to achieve high separation targets, even with low water content. The most cost-effective approach is to eliminate water at the beginning of the process. The energy consumed for CO2 pumping and compression is offset by energy generated during retentate expansion, resulting in a surplus that reduces the overall energy consumption to drive the process.