Polypropylene film recycling
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Our plant uses a polypropylene production system based on the small-core polypropylene process. Currently, membrane recovery is achieved using 4 membranes connected in parallel; we are about to carry out technical upgrades to add a second stage of membranes (2 membranes). I would like to ask the experts here: what are the differences between series and parallel connection of organic membranes, and what are the advantages of each? I am considering replacing these six organic membranes with a three-stage recycling system, using a 3-2-1 recycling approach. I wonder if this would work? Note: Currently, the propylene content in the membrane off-gas is around 8-20%, and it is being burned in a flare. I earnestly seek advice from those with more experience. !
The series-parallel arrangement of membrane separation on the small unit has little impact on the performance of the entire recovery system. A 4-2 series-parallel conversion is possible; the 3-2-1 configuration should not be considered. Due to too many series connections, the pressure loss is high, which in turn reduces the membrane separation efficiency.
Our company uses membrane technology and equipment from Dalian Ouke. Initially, four membranes were used in pairs, with the two pairs connected in series, and this setup worked well. Later, as the installation was expanded, the level of propylene in the exhaust gases became too high; therefore, an additional pair of membranes was added, resulting in a configuration of three sets connected in series. This approach also proved effective, with the propylene content in the exhaust gases being kept at around 8%.
Our company’s 30,000-ton plant uses membranes from Dalian Ouke, and the parallel operation mode works well; there is no need for three sets in series, as this would result in too high a pressure drop and increase the workload on the compressors. Membrane recovery relies mainly on stability.
The driving force for membrane separation is the pressure difference; without it, separation is not possible. A certain flow rate is also required, and the residence time inside the membrane should not be too long – generally, two stages in series are sufficient.