Modeling and debottlenecking of distillation column for C3 fraction for multiple pressure levels

Growing polypropylene production puts pressure on existing propane-propylene separation facilities. While hybrid membrane–distillation configurations have demonstrated energy savings, systematic evaluation of their impact on plant throughput and operational flexibility is missing in literature. In this work, conversion of an existing distillation column (C3 splitter) to a split-feed design and its integration with an upstream membrane unit was investigated for throughput increase without replacing major equipment. Aspen Plus V12 model of a representative C3 splitter (10.32 t/h feed, 82.1 mol% propylene) served as a case study for low-pressure splitter with a heat pump (11 bar, design A) and conventional high-pressure splitter (20 bar, design B). Optimally integrated membrane enabled significant C3 splitter reflux reduction: 40 % (A) and 38 % (B), increasing plant capacity by 56 % (A) or 45 % (B), with further bottlenecks identified in compressor, heat-exchangers, and column hydraulics. Specific energy consumption at increased capacity decreased by only 1.4 % in A and was sensitive to compressor efficiency, whereas it decreased by 30.5 % in B compared to basic operation. Similarly, specific exergy consumption and specific CO2 emissions decreased from 1568 to 1097 kWh/t and from 0.2967 to 0.2076 tCO2/t, respectively. Specific total annual costs amounted to 49.0 to 55.3 EUR/t (A) and to 106.6 to 111.8 EUR/t (B), compared to 51.4 EUR/t (base A) and 126.0 EUR/t (base B) with membrane cost varying from 5000 to 10000 EUR/m2. Hybrid membrane–distillation retrofits proved potential to debottleneck C3 splitters, reusing most existing assets, aiming to advance sustainable and competitive propylene production.