Performance optimization of hydrogen purification reactor based on catalytic Methanation: From methanation kinetics to optimization of reactor structure and operating conditions

The hydrogen separation and purification method based on metal hydride (MH) is considered as one of the efficient methods for recovering hydrogen from industrial waste gases. However, CO in industrial waste gas express poisoning effect, which reduce the hydrogen storage capacity of MH. Without considering adding equipment, elimination of CO with chemical reaction during the operation process constitutes a cost-effective and efficient solution to the problem. Given the composition of the feed gases and the toxicity of the products, the methanation of CO is identified as the optimal reaction. Accordingly, the study selected MH(LaNi_4.3Al_0.7), which could catalyst the conversion of CO into CH₄. This work formulated a kinetics model of catalyzed methanation and combines it with hydrogen storage reactions in order to establish a multi-physical field coupling model, which will describe the dehydrogenation phenomenon under impurity atmosphere more accurately. Moreover, the design of the purification reactor was optimized. Further research was conducted on the influence of design parameters of the reactor and operating parameters on hydrogen purity and hydrogen loss during methanation reaction. The results showed that after optimization of geometric and operating parameters, under the dehydrogenation conditions of heating at 388 K, the reactor could complete methanization at a safe temperature. At the same time, after blowing pure hydrogen at a flow rate of 0.01 kg/s for 180 s, CH₄ and CO are blown out. The purity of the outlet hydrogen gas could reach over 99.999 %. This work explores the elimination of CO from methanation, providing a solution for hydrogen purification in complex atmospheres.