The Recovery of Hydrogen from Binary Gas Mixtures Using a Membrane Module Based on a Palladium Foil Taking into Account the Deactivation of the Membrane

Abstract

The recovery of hydrogen from binary gas mixtures with active (deactivating the surface of the membrane) and passive impurities has been studied. Experiments have been carried out on a multifunctional membrane module, the operating area of which consists of gas chambers separated by a thin foil palladium membrane. A dimensionless coefficient of the deactivation of the surface of the membrane has been introduced. An analytical formula has been obtained for the hydrogen flux from binary mixtures at its preset pressures on the opposite sides of the membrane that takes into account adsorption–desorption, breaking to protons on the surface, the diffusion of the latter in the metal lattice, and the recombination of Н+. In the case when the condition are fulfilled, the Н2 flux can be calculated by the modifiable Sieverts equation. This equation and an assumption about the complete mixing of the mixtures in the chambers of the membrane module have made it possible to develop a theoretical model for the recovery of hydrogen from binary mixtures in the membrane module. An analytical dependence for the Н2 flux as a function of the fluxes of the mixtures at the inlet of the chambers, ratio of the pressures on the opposite sides of the membrane, initial composition of the hydrogen mixture, and the coefficient of deactivation has been found. Utilizing this dependence, a procedure for finding this coefficient using additional experiments has been proposed. As an example, the coefficients of deactivation for the products of steam reforming of methane (CO, СО2, СН4, and water vapor) have been calculated for a palladium membrane with a composition Pd–6%Ru. The theoretical model has been subjected to the experimental verification on Н2–5%CO and Н2–20%CO binary mixtures.