Hydrogen purification method from reformed gas containing high concentration of CO by using metal hydride

Abstract

The Metal Hydride Intermediate-Buffer (MIB) method has been proposed as a measure to enable flexible load following operation and immediate start-up of PEFC system with a reformer. In this method, using the property of metal hydride to absorb hydrogen selectively, hydrogen is stored and purified simultaneously from reformed gas with impurities and subsequently supplied to PEFC stack. In this paper, using the fluorinated LmNL^Mno.sAlo.j metal hydride, we have investigated to improve resistivity of the metal hydride against CO to simplify the reformer. If the resistivity against CO rises to the 1%, preferential oxidation (PROX) process in reformer can be removed. Important consideration in this method is to keep CO concentration of released hydrogen from metal hydride below 10ppm. To investigate the effect of CO, absorption and release experiments of hydrogen from simulated reformed gas containing 100, 100ppm or 1% CO were carried out with the specimen. The result of the absorption experiment shows that, when the specimen temperature is set to 50°C or higher, hydrogen absorption rate remains nearly unaffected by existence of 1% CO. The result of the release experiment shows that, when the specimen temperature exceeds 120°C, CO concentration of released hydrogen is approximately kept below 10ppm.