Optimizing methane recovery: Techno-economic feasibility analysis of N2-selective membranes for the enrichment of ventilation air methane

Abstract

Utilization of the low concentration methane from coal-mining ventilation air is challenging but can significantly contribute to the mitigation of methane emissions to the atmosphere. This work focuses on the techno-economic feasibility analysis of N2-selective membrane systems for the enrichment of ventilation air methane (VAM). The feed methane concentration and gas permeance are found to significantly influence the specific methane enrichment cost, while feed pressure has the lest effect. For a stand-alone membrane system, the optimal methane recovery of ca. 70% is identified to achieve a higher methane purity at the same cost, which may gain an economic benefit when it is operated at high plant capacity. Although the SAPO-34 membrane system is technologically feasible for the enrichment of 1.5 vol% VAM, novel membranes with a higher N2/CH4 selectivity of greater than 25 is required to reduce the membrane stages for the pre-concentration of a very diluted VAM of <1 vol%. Considering a large-scale application in the methane recovery from the coal-mining ventilation air, carbon hollow fiber membranes may have the potential to address the challenges of the high production cost and the module up-scaling with large packing density that is faced by zeolite membranes.