CEMCAP is an international R&D project under the Horizon 2020 Programme preparing the ground for the large-scale implementation of CO2 capture in the European cement industry. This paper concerns the performance modeling of membrane-assisted CO2 liquefaction as a possible retrofit application for post combustion CO2 capture. For the relatively large CO2 concentrations that are typical for the flue gas in conventional cement kilns, it may be possible to capture CO2 by combining a single membrane unit for bulk separation and a CO2 liquefaction train in which the waste stream is recycled and mixed with the feed to the membrane system. The required membrane surface area is strongly correlated with the CO2 concentration in the cement kiln flue gas, as well as targeted CO2 recovery, pressure ratio across the membrane, membrane separation factor and CO2 permeance. Specifications for flue gas pre-conditioning and an overall techno-economic evaluation are planned to follow the evaluation of experimental results for membrane performance under realistic conditions, as well as for CO2 liquefaction performance. Published by Elsevier Ltd.@en