CO2 separation by membranes in natural gas processing

Aim of this work is the demonstration of how a proper distribution of the separation load in a multistage membrane system can make more efficient the operation. A single stage and a two membrane stages in cascade have been considered to process ternary mixtures representing natural gas and landfill gas streams. The quality of the separation has been evaluated in terms of purity of the more permeable component and membrane area per feed flow-rate, in correspondence of fixed global recoveries. The influence of different design variables such as feed pressure and pressure ratio, feed concentration, membrane selectivity on the separation extent has been investigated assuming co-current and complete mixing flow modes in the membrane units.