(76b) High-Pressure Hydrogen Purification USING Electrical Swing Adsorption

The University of North Dakota Energy & Environmental Research Center (EERC) is developing technologies for hydrogen production and use at U.S. military installations. Hydrogen will be produced from JP-8 and renewable feedstocks. The work is being funded by the U.S. Army Corps of Engineers Engineering Research and Development Center (ERDC) at the Construction Engineering Research Laboratory (CERL) in Champaign, Illinois.

In initial work, a high-pressure water-reforming (HPWR) concept for on-demand production of high-pressure proton exchange membrane fuel cell-quality hydrogen from JP-8 has been developed at the bench scale. Tests on aromatics- and sulfur-free Syntroleum-produced ?S-8? fuel as feedstock produced hydrogen concentrations of up to 56%. The HPWR system operates at up to 600 standard cubic feet/hour (1.5 kilograms/hour) hydrogen production capacity and is currently being upgraded to operate at 12,000 psi. By reforming liquid hydrogen carriers and purifying the gas stream at pressure, 10,000 psig hydrogen for use in fuel cell vehicles can be created with up to a 15% energy savings over low-pressure production followed by compression of the hydrogen. To purify the hydrogen, a bench-scale system is being built and tested to also operate at 12,000 psi. The purification method being tested is electrical swing adsorption (ESA), which was developed at the Oak Ridge National Laboratory. The process is similar to pressure swing adsorption in that the gas is passed through a material that adsorbs contaminants, allowing purified hydrogen to flow through. However, instead of regenerating the adsorber by reducing the pressure in the system, pressure is maintained, and an electric current is passed through the adsorber, causing desorption of the contaminant gases. To permit the flow of electric current through the adsorber, it must be monolithic and electrically conductive. To reduce the large standard volume of hydrogen that would be used to purge the system at such high pressures, the monolith must also have a much higher density than standard granular adsorbers which may contain as much as 80% porosity on a bulk basis.

The EERC has developed a method for making electrically conductive high-surface-area activated carbon monoliths that are approximately twice as dense as granular adsorbers. Initial tests of the ESA process are being performed in a small laboratory-scale rig with a 1"-diameter by 4"-long monolith operating at up to 1000 psi. Concurrently, the 12,000-psi system is being built that can operate with a 1.5"-diameter by 24"-long monolith or a 2.5"-diameter by 30"-long monolith. In this paper, we will describe the overall research program, provide results of testing with the laboratory rig, and give a general system description of the larger bench-scale rig, which is undergoing shakedown testing.