Design of mixed refrigerant cycle for low temperature processes using thermodynamic approach

Minimizing the work consumed of refrigeration system is the most effective measure to reduce the cost of products in sub-ambient chemical processes such as olefin plants. A recent advancement has been the introduction of mixed working fluids in refrigeration system in place of pure working fluids. Due to the lack of systematic design method for Mixed Refrigerant Cycle (MRC), conventional approaches are largely trial-and-error and therefore operations can be far away from optimal conditions. In this paper, a novel method for systematic design of MRCs is presented which combines the benefits of thermodynamics approach and mathematical optimization. Based on the success of the proposed systematic method for the optimal selection of refrigerant composition and operating pressures, the method is extended to give optimal arrangement of the cycle components. The procedure is demonstrated using a case study of design of MRC for a typical olefin plant.