Testing of ceramic membranes for PEG separation and preliminary design of a membrane cascade

Abstract The Plasma Exhausts Gases (PEGs) proposed to reduce the power load over the plasma facing components are separated by the Plasma Exhaust Processing System of DEMO. Two kinds of commercial ceramic porous membranes (top layer pore size 0.2 μm and 3–4 nm, respectively) have been tested. Experiments have been carried out at room temperature with feed pressure in the range 100–180 kPa and permeate pressure of 100 kPa by testing Ar, N 2 , He and H 2 . The experimental results validated a gas mass transfer model taking into account the permeation mechanisms of Knudsen and Poiseuille used to assess the permeance of the molecule DT. According to the processing requirements for the PEG separation of DEMO, a membrane system consisting of ceramic membranes followed by a Pd-Ag permeator has been assessed. By vacuum pumping the permeate of the ceramic membrane cascade at 10 mbar maximum Ar concentration in the retentate is 99.95%, while higher Ar concentration of 99.995% can be achieved by vacuum pumping the permeate at 1 mbar. In both the cases, the Pd-permeator downstream the ceramic membrane cascade recovers about the 99% of the DT fed in form of ultrapure gas.