Industrial Scale Propylene/Propane Separation Using Pressure Vacuum Swing Adsorption

Conventional propylene/propane separation via distillation is capital- and energy-intensive. Pressure vacuum swing adsorption (PVSA) is a potential low-cost alternative to C3 distillation. In this work, a new 7-step PVSA cycle is developed using 4A zeolite as the adsorbent, capable of separating 84.4/15.6 propylene/propane (wt %) mixture to produce high purity (>99.5 wt %), high recovery (>99%) propylene at a low energy consumption. The proposed PVSA unit is simulated and costed together with its peripheral units using industrially relevant feed condition and product specifications. The lost opportunity cost arising from the presence of propylene in the raffinate product is also included in the costing algorithm. The proposed PVSA unit is optimized using a global stochastic optimizer, giving a minimum total cost of US$20.86 per tonne of propylene. This is significantly lower than the cost of an equivalent distillation unit, which is found to be US$41.07 per tonne of propylene. The use of PVSA for propylene/propane separation can thus lead to a significant improvement in profitability. The net present value (NPV) of PVSA over distillation for a 450 KTA propylene plant is found to be US$76.79M.