(348e) Polymeric Vs High Performance Inorganic Membrane Materials for of Biogas Upgrading Membrane Systems

Membrane separation is a key technology for biogas purification. Multistaged processes based on either cellulose acetate (CA) or polyimide (PI) materials are classically used for this application [1]. In this study, a systematic process synthesis optimization is performed in order to identify the most cost effective solution for three different membrane materials (CA, PI, and zeolite) and three different outlet pressure levels (5, 10, and 15 Bar). More specifically, the objective is to investigate the possibility of advanced inorganic membranes such as zeolite to compete with polymers; a highly permeable (CO₂ permeance 3500 GPU) and selective (CO₂/CH₄ selectivity = 160) zeolite membrane is compared to polymeric materials (CO₂ permeance 60 PGU, CO₂/CH₄ selectivity 60), with a large cost difference (2000 €/m² for zeolite vs 60 €/m² for polyimide). The key question is to evaluate to what extent high performance materials generate different process configurations and whether they can provide cost effective solutions.

Methods

A general and systematic optimization model for membrane process proposed in [2] is used, which takes into account all the mentioned possibilities as a degrees of freedom in a membrane system (vacuum pumping, self recycling loops) (Figure 1). Moreover, three different outlet pressure levels are taken as constraints, for three different membrane materials. The overall target is to identify to what extent improved commercially available membrane materials, extended connection possibilities and supplementary equipment options (vacuum pump, expander) impact the biogas purification cost.

Results

It is shown that a costly (i.e. 2000 EUR per square meter vs 50 for CA and PI) but high performance

membrane material such a zeolite offers the best cost effective solution compared

to commercially available polymeric membranes (Figure 2.a). Increasing the outlet pressure increases

the purification cost. Two stage processes with recycling loops offer the best balance between

purity, recovery, complexity and cost, whatever the outlet pressure level (Figure 2.b). The use of

vacuum pumping is shown to improve the process economy, while expander and extra feed

compression do not show an interest.

[1] Angelidaki, L. Treu, P. Tsapekos, G. Luo, S. Campanaro, H. Wenzel, P. G. Kougias, Biogas upgrading and utilization: Current status and perspectives, Biotechnology Advances 36 (2018) 452–466.

[2] A. A. Ramirez-Santos, M. Bozorg, B. Addis, V. Piccialli, C. Castel, E. Favre, Optimization of multistage membrane gas separation processes.Example of application to CO2 capture from blast furnace gas, Journal of Membrane Science 566 (2018) 346–366.