Saving Energy and Tray Numbers in Ethylene-Ethane Distillation Towers by Vapor Permeation Membrane Load Sharing

Abstract

Currently the separation of light hydrocarbon binaries, like ethylene-ethane mixture, is achieved almost exclusively by cryogenic distillation. However the process is highly energy intensive because of close relative volatilities (near unity), necessitating increased reflux ratio and number of stages, with the attendant increased energy consumption in the form of condenser and reboiler duties. It was also shown that the use of membrane separators alone will require excessive feed pressure, hence very high compressor power to drive the system, hence are constrained to small scale separations due to the large areas needed. Thus for difficult separations involving mixtures with very close relative volatilities like ethane-ethylene mixture, it was shown that the use of a distillation vapor membrane hybrid to share the load  leads to significant reduction in the overall energy expenditure for the process while still  achieving the desired petrochemical grades of 99% in each product stream.

Keywords: Distillation, Membrane, Hybrid, Load-sharing, Energy-saving