Optimization analysis of hydrogen separation from an H2/CO2 gas mixture via a palladium membrane with a vacuum using response surface methodology

This study uses a palladium membrane to separate hydrogen from an H2/CO2 (90/10 vol%) gas mixture. Three different operating parameters of temperature (320-380 degrees C), total pressure difference (2-3.5 atm), and vacuum degree (15-49 kPa) on hydrogen are taken into account, and the experiments are designed utilizing a central composite design (CCD). Analysis of variance (ANOVA) is also used to analyze the importance and suitability of the operating factors. Both the H2 flux and CO2 (impurity) concentration on the permeate side are the targets in this study. The ANOVA results indicate that the influences of the three factors on the H2 flux follow the order of vacuum degree, temperature, and total pressure difference. However, for CO2 transport across the membrane, the parameters rank as total pressure difference > vacuum degree > temperature. The predictions of the maximum H2 flux and minimum CO2 concentration by the response surface methodology are close to those by experiments. The maximum H2 flux is 0.2163 mol s-1 m-2, occurring at 380 degrees C, 3.5 atm total pressure difference, and 49 kPa vacuum degree. Meanwhile, the minimum CO2 concentration in the permeate stream is t 643.58 ppm with the operations of 320 degrees C, 2 atm total pressure difference, and 15 kPa vacuum degree. The operation with a vacuum can significantly intensify H2 permeation, but it also facilitates CO2 diffusion across the Pd membrane. Therefore, a compromise between the H2 flux and the impurity in the treated gas should be taken into account, depending on the requirement of the gas product.(c) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study utilizes a palladium membrane to separate hydrogen from an H2/CO2 gas mixture and investigates the effects of temperature, total pressure difference, and vacuum degree on hydrogen permeation. The results demonstrate that vacuum degree has the most significant impact on H2 flux, while total pressure difference has the most influence on CO2 transport. The response surface methodology provides accurate predictions in comparison with experimental results.