Optimization of semi-permeable membrane systems for biogas upgrading

This work focuses on the optimization of a biogas upgrading process consisting of three CO2-permeable membranes. A 1-D membrane model, capable of handling multicomponent gas mixtures, is formulated as a set of differential algebraic equations and validated against experimental data. The model is used within a sequential algorithm to solve the simulation of the three-stage system. The key design variables (i.e., areas of each membrane module, stream pressures and recycle mass flow rates) are optimized using the recently developed MO-MCS algorithm, a derivative-free optimizer suitable for multi-objective problems. Results show that the Pareto-optimal solutions have a total plant cost in the range 720-770 (sic)/(Nm(3)/h of feed) and an energy efficiency of 87.7-89.2%.