Experimental investigation on the poisoning characteristics of methane as impurity in La0.9Ce0.1Ni5 based hydrogen storage and purification system

Abstract

In the present work, poisoning effect of CH4 as gaseous impurities in La0.9Ce0.1Ni5 based “Metal Hydride Hydrogen Purification System (MHHPS)” was investigated by varying the impurity level between 10% and 50% by weight, in the H2 gas mixture and by performing cyclic test with 10% impurity. Prototype reactor with 6 embedded cooling tube (ECT) was fabricated and filled with 1.2 kg of La0.9Ce0.1Ni5 for purification study. The experimentation comprises of three steps i.e. absorption, flushing and desorption of gas mixture. The gas samples from each purification stages were analysed using Gas Chromatograph (GC). The system delivered 99.9995% pure hydrogen for 10–20% impure gas mixture. While, for higher impurity level, the purity level of desorbed hydrogen was in the range of 95.9%–99.6%. According to the cyclic study, the amount of hydrogen absorbed was decreased in the range of 0.6 wt% to 0.9 wt% for 50%–90% hydrogen content. For pure hydrogen, the absorption capacity was 1.2 wt%, for absorption condition of 20 °C and 10 bar. The regeneration of the poisoned “Metal Hydride (MH)” bed was performed in two regeneration cycles. The bed poisoning can be decreased significantly, if the desorption temperature is maintained above 90 °C.