Membranes for Olefin Separations

Polymer grade propylene (99.5wt% propylene, 0.5wt% propane) is in high demand because it is used to produce polypropylene, which is used in many industry applications. Polymer grade propylene can be purified either from chemical grade propylene (93wt% propylene, 7wt% propane) produced by a steam cracker reactor or from refinery grade (35wt% propylene, 65wt% propane) propylene produced from a propane dehydrogenation reactor. The conventional distillation separation processes is expensive and energy intensive. This report attempts to explore membrane-only and hybrid systems as possible alternative paths to achieving the desired product purities. A separations process incorporating a membrane presents a unique opportunity for our company to penetrate the market for olefin separations. Possible membrane separation processes include a membrane-only separation process and a hybrid system, the latter consisting of both membranes and distillation columns. The costs and benefits of each process were analyzed to determine the price of the membrane that would make a membrane separation process competitive. More specifically, the conventional distillation processes were examined as base cases to establish the target internal rate of return. Then the price of membrane that would yield the same IRR as the conventional distillation process was calculated for both membrane only and hybrid processes in each of the three cases below. For each of the three cases below, the conventional distillation separation process was established as the base case while the membrane only separation process and the hybrid system were explored as alternatives. The cases below represent the feed and product combinations desired for the various separation processes that were explored. Case A: Chemical grade (93%) to polymer grade (99.5%) propylene, with the chemical grade propylene feed coming from a steam cracker Case B: Refinery grade (35%) to polymer grade (99.5%) propylene, with the refinery grade propylene feed coming from the propane dehydrogenation process Case C: Refinery grade (35%) to chemical grade (93.0%) propylene, with the refinery grade propylene feed coming from the propane dehydrogenation process After examining the three cases, the hybrid system was not considered a viable option for separation in case B and case C. The price of the membrane is obtained when the IRR of the membrane only and/or hybrid process are equal to that of conventional distillation. The price of the membrane was determined to be in the price range of $47-52/m2. This price was capped at the lowest membrane price calculated for any process ($52), for reasons explained in detail in the Conclusion. However, the membrane product must be priced lower than $52, because the IRR of a membrane process must be higher than that of conventional distillation in order to give our clients a compelling enough reason to adopt our membrane technology