Propane-propylene splitter design

I had been hired to review the design for a new 12,000 BSD propane-propylene splitter for a chemical plant in Convent, Louisiana. The tower was intended to be a replacement for an existing 10,000 BSD propylene-propane splitter. The incremental capacity of2000 BSD would economically justify the 3,000,000 investment for the new splitter. 

Another very large potential application of membranes in ethylene plants is replacing the C2 and C3 splitters. An example of a possible process design is shown in Fig. 7.15. In this example, a two-step membrane system equipped with propylene-permeable membranes is used to split a 50/50 propylene/propane overhead stream from a depropanizer column into a 90% propylene stream and a 90% propane stream. Both streams could then be sent to distillation units for polishing, but the size of columns required would be much reduced. For this design to be feasible, membranes with an olefin/paraffin selectivity of 5 to 10 are required. Many other designs that combine membranes and distillation columns to achieve good separation are possible [23]. 

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