Enhancing the efficiency of propylene recovery from a polypropylene plant flare

Abstract The growing demand for olefins driven by their widespread use in petrochemical industries, particularly in polypropylene production, has brought attention to inefficiencies in certain operational processes. This study focuses on a polypropylene production plant that experiences significant propylene losses when production rates increase from 16 to 28 tons per hour (hourly production rate), leading to substantial flaring. The main objective is to minimize these losses and improve the separation efficiency between propane and propylene. To address this, the study evaluates advanced, energy-efficient distillation techniques, including conventional distillation, bottom flash distillation, and vapor recompression distillation. In the conventional method, the existing 65-tray (actual tower) vent recovery column was replaced with a taller column containing 129 trays (theoretical). Simulations performed using Aspen HYSYS Version 10 showed that applying these techniques could reduce annual propylene losses from 2,900 tons per year to just 800 tons per year, with the recovered propylene fed back into the production process. Among the evaluated options, bottom flash distillation proved to be the most economical and efficient, offering low operational costs and a rapid payback period. This method not only maximized propylene recovery but also delivered an estimated annual net saving of $2.52 million. An economic analysis confirmed bottom flash distillation as the optimal solution for upgrading the vent recovery system with a total capital investment of $ 7.115 million and a total operating cost of $ 0.235 million.