Distillation has been shown to account for 49% of the industrial separation energy consumption in the U.S. Analysis of separation energy requirements shows that raising product concentrations from, e.g., from 95% to 99.5% or higher takes proportionally much higher energy input than for lower purities. Therefore, an efficient alternative is to feed a less pure product stream from an existing distillation column into a lower-energy separation system, such as a membrane, for finishing.
This paper provides a perspective on implementing retrofitted hybrid separation systems and describes two realistic examples. The focus is on retaining current distillation columns used for high-purity separations by reducing the column product purity and purifying the output stream with a membrane system. Such a hybrid system can help reduce energy consumption, operating costs, and CO2 emissions.