Scaling-up defect-free asymmetric hollow fiber membranes to produce oxygen-enriched gas for integration into municipal solid waste gasification process

Municipal solid waste (MSW) gasification is an attractive waste-to-energy (WTE) technology with promise for future solid waste management, owing to the production of syngas which can be used as an alternative energy resource. However, quality of produced syngas is not meeting expectation. One promising solution is to use oxygen-enriched gas (OEG) to elevate produced syngas quality but producing OEG is costly. Herein, we demonstrated an asymmetric defect-free hollow fiber membrane made up of Matrimid (R) 5218 polyimide for scaling-up to 2-inch membrane modules. Our modules have an effective surface area up to 2.6 m(2) with a packing density of up to 44% to produce OEG of 45% O-2 purity. The 2-inch membrane module was integrated into a labscale gasification process to produce syngas using refuse derived fuel (RDF) generated from MSWs collected from the university campus. Prior to this, the lab-scale gasification was first optimized by tuning the gasification temperature, O-2 purity and equivalence ratio (ER). Then, MSW gasification using membrane-based OEG was carried out, and compared against air gasification and synthetic OEG of the same O-2 purity. Our results showed that, at O-2 purity of 45%, gasification temperature of 900 degrees C and ER of 0.15, the quality of produced syngas was elevated with a lower heating value (LHV) of 9.15 MJ/m(3) and H-2/CO ratio of 1.43, which was substantially higher than air gasification with LHV and H-2/CO ratio reported at 5.38 MJ/m(3) and 0.81, respectively. Gasification results for membrane-based OEG and synthetic OEG were also comparable, while process simulation evidence suggested that membrane-based separation was at least 2-fold less energy-intensive than cryogenic distillation and pressure swing adsorption. Overall, this proof-of-concept successfully demonstrates the viability and competitiveness of membrane process for producing OEG at medium O-2 purity (i.e., 40-50%) to support MSW gasification for WTE conversion.

Automated summary

Municipal solid waste gasification technology has great potential for waste-to-energy conversion, but the quality of produced syngas is a key challenge. Using oxygen-enriched gas can improve syngas quality, but it is costly. This study successfully demonstrated the use of a specialized hollow fiber membrane to produce oxygen-enriched gas for enhancing syngas quality.