Hydrogen pumping and compression by superpermeation through iron

Hydrogen superpermeation through a very pure iron membrane exposed to H-atoms on its upstream side and the compression of the released H2-molecules on the downstream side have been investigated at various driving pressures (10-7≤p1≤10-3 mbar) and in the presence of helium. The compression runs have been extended to downstream pressures between 1 and 10 mbar corresponding to a maximum compression factor of 6x105. That is not the highest possible factor because the time slopes of the pressure increase in this range reveal no saturation tendency. The dependence on time of the pressure increase is nearly linear up to 10-1 mbar. Hydrogen throughput and pump speed have been evaluated from the initial pressure slopes. Helium inlet upstream to a partial pressure of 10-3 mbar has no distinguishable influence on the pressure slope. This observation has been confirmed by supplementary measurements of the hydrogen permeation flux at various compositions of the hydrogen/helium driving gas. (orig.)