Natural gas drying and cleaning of carbon dioxide by membrane gas separation

To solve the problem of dehydration and CO2 removal in natural gas purification, a membrane process scheme consisting of a two-stage countercurrent recirculation cascade has been proposed. The first stage is an ordinary separator, and the second stage is a two-module separator with recycle. This scheme allows natural gas cleaning to remove highly permeable impurities with any desired level of methane recovery. Optimal values of the main parameters of the given process flowsheet have been determined. Energy efficiency has been evaluated with taking account of the operating costs of interstage compression and methane loss (in energy units).