CO2/CH4 separation by means of Matrimid hollow fibre membranes

Abstract

CO2/CH4 mixtures separation was investigated using Matrimid®5218 hollow fibre membranes and measuring the membrane flux feeding singly CH4 and CO2 and their mixtures, with CH4 concentration ranging from 5 to 70 %molar. Specific attention was paid to membrane properties at a high temperature (up to 75 °C) and feeding humidified streams, not yet particularly investigated, in a pressure range 400–600 kPa. The membrane properties were restored when water vapour was removed and temperature decreased stating the excellent hydro-thermal stability of these membranes. Maps of the separation performance were also calculated for a range of operating conditions wider than the experimental one paying specific attention to the feed/permeate pressure ratio further to membrane selectivity and permeance. Single and multi-stage membrane separation systems were investigated using these maps. The prepared Matrimid®5218 hollow fibres showed very good performance in terms of flux and selectivity for temperatures up to 60 °C, also in steam saturated conditions, allowing a methane concentration meeting the specification for its injection into the grid.