An Energy-Economic-Environment Tri-Objective Evaluation Method for Gas Membrane Separation Processes of H₂/CO₂

For pre-combustion carbon capture, the high syngas pressure provides a sufficient mass transfer driving force to make the gas membrane separation process an attractive option. Comparisons of combined different membrane materials (H₂-selective and CO₂-selective membranes) and membrane process layouts are very limited. Especially, the multi-objective optimization of such processes requires further investigation. Therefore, this paper proposes 16 two-stage combined membranes system for pre-combustion CO₂ capture, including 4 two-stage H₂-selective membrane systems, 4 two-stage CO₂-selective membrane systems, and 8 two-stage hybrid membrane systems. A tri-objective optimization method of energy, economy, and environment is proposed for comprehensive evaluation of the proposed systems. Results show that with the targets of 90% CO₂ purity and recovery, six gas membrane separation systems could be satisfied. After further multi-objective optimization and comparison, the C1H2-4 system (the hybrid system with H₂-selective membranes and CO₂-selective membranes) has the best performance. Feed composition and separation requirements also have an important influence on the multi-objective optimization results. The effects of selectivity and permeance of H₂-selective and CO₂-selective membranes on the performance of the C1H2-4 system are also significant.