Membrane separation is highly expected for enriching CO2 from flue gases, but the inadequacy in separation efficiency and production capacity should not be overlooked. Process planning and initial design with multi-product and energy recovery approach is attempted in this work to ameliorate this limitation. Three retrofitting options are considered: the novel constraint mode with the local permeate CO2 concentration that is always higher than the feed stream concentration is proposed for CO2 enrichment to increase the output of the CO2-enriched product (with a general mode, the local permeate stream that is more diluted than the feed stream mixes in the permeate bulk); the turbine unit is used to take back the static energy in membrane residue; and the multi-product option with N-2 purification would have the advantage that N-2 has been enriched greatly after CO2 separation. According to the comprehensive comparison conducted in this study, the retrofitted process involving both the novel constraint mode and the multi-product approach is the most effective for saving energy and enhancing production capacity. Crude CO2 (50 vol%) and N-2 (99 vol%) would be generated simultaneously. In addition, the positive performance has been demonstrated by process simulation and economical analysis with both a normal polysulphone membrane and a novel Polaris membrane. On the whole, membrane separation system retrofitting with multi-product and energy recovery approach together should be an effectual approach to promote carbon capture, storage, and utilization.