Yoshinori Shirasaki

Development and Demonstration of Membrane Reformer System for Highly-Efficient Hydrogen Production from Natural Gas

A membrane reformer is composed of a steam reformer equipped with palladium-based alloy modules in its catalyst bed, and can perform steam reforming reaction and hydrogen separation processes simultaneously, without shift converters and purification systems. It thus can be configured much more compactly and can provide much higher efficiency than the conventional technologies. We have manufactured and tested a world-largest scale membrane reformer with a rated hydrogen production capacity of 40 Nm3/h. The operation test has successfully been proceeding for over 3,000 hours in one of the hydrogen refueling stations in Tokyo, which has demonstrated the potential advantages of the membrane reformer: simple system configuration as benefited by single-step production of high-purity (99.999% level) hydrogen from natural gas, compactness and energy efficiency as high as 70 to 76% under both the rated and partial-load operating conditions. The system has thus been proved to give the highest efficiency in producing hydrogen from natural gas among various competing technologies. The paper will present the latest achievements and the future plan of the membrane reformer technology development.

Surface reaction and transport kinetics of hydrogen through palladium-based membranes under gas co-existing with hydrogen atmospheres

In order to understand how gas co-existing with hydrogen affects the hydrogen permeability of a silver 23wt%-palladium membrane, the surface reaction of hydrogen was evaluated from the continuity of the surface reaction rate and the bulk diffusion flux of hydrogen based on the results of hydrogen-permeation measurements. The interference effect of the co-existing species was quantified as a function of temperature, partial pressure and the components of the co-existing gas. In order to investigate the behaviour of the co-existing species on the membrane surface, in situ observation using the Polarisation Modulated Infrared Reflection Absorption Spectroscopy (PM-IRRAS) was carried out. An infrared absorption peak due to the adsorption of carbon monoxide on the membrane was observed under the atmosphere of 7.8% carbon monoxide – 2.3% water vapour – 89.9% hydrogen. From the dependence of the infrared absorption peak on temperature, co-existing carbon monoxide was found to adsorb onto the membrane surface irreversibly.