(332f) Energy and Economic Analyses of a Vapor Recompression Distillation System for I-Butane/n-Butane Separation

The relatively low thermodynamic efficiency of conventional distillation has made distillation processes a prime target of process intensification research. Numerous alternative designs have been explored with the aim to reduce thermodynamic losses in distillation columns and to improve the overall process efficiency. Vapor recompression (VRC) is one such technique that can potentially offer substantial energy and cost savings over conventional distillation.

In this study, we demonstrate the advantage of a VRC-based design over a conventional distillation column (CDC) for the separation of a close-boiling i-butane/n-butane mixture. First, a rigorous simulation model is developed for the CDC in Aspen Plus® and reference cost analysis is performed. Then, alternative VRC configurations are developed and compared with the reference CDC model. In the base VRC configuration, the overhead vapor is mechanically compressed and used to boil the bottoms liquid. Further improvements are made by topological changes including feed location, heat integration, and recycle streams. The optimized VRC system shows up to 38% savings in direct operating/energy costs and up to 24% savings in total annualized cost (TAC) relative to the reference CDC system.