Research and development of twin-column periodically counter-current beds packed with metal hydride particles

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We built an experimental apparatus for the twin-column type of the hydrogen isotope separation. We obtained the following results through experiments and numerical simulations.(1) Pd and LaNi_<4.7>Al_<0.3> were found to be the most promising materials for the isotope separation from measurements of the hydrogen isotope separation factor, the isotopic exchange reaction rate constant and the hydrogen dissociation pressure. The hight equivalent to a theoretical plate was 0.7cm for both of the two materials.(2) The displacement chromatography using a single Pd bed was proved to be able to concentrate up to 100% deuterium from hydrogen-deuterium mixtures. This result directly assures an outstanding performance of the twin-column type isotope separation system proposed here.(3) The rate-determining step for the isotopic exchange mass transfer in Pd was beta-phase diffusion below 273K and pore diffusion above 273K.That in LaNi_<5-X>Al_X was the intrinsic isotopic exchange reaction on a Ni layr deposited on surfaces.(4) The cycles necessary to establish a steady-state profile in the twin beds were found to be within 100 steps of absorption and desorption from numerical simulations based on the plate thory.(5) After rearrangement of the experimental apparatus, desorption with a reversed flow was found to be more efficient from a viewpoint of the operation time.(6) The experimental result under the total reflux condition showed the deuterium concentration in the LaNi_<4.7>Al_<0.3> bed and the deuterium depletion in the Pd bed. This result assures the efficiency of the twin-column type isotope separation system.