A new realization of periodic cycled separation is presented which enables continuous vapor flow also during liquid drainage from the trays. With the proposed design a new operation form is thus introduced, where the trays are drained sequentially rather than simultaneously, such that the vapor flow is not interrupted during the liquid drainage.
Separation factors and column efficiencies are compared for a column, stripping ammonia from water with air, using three different sets of internals: Conventional sieve trays, Sulzer BX gauze packings and periodically cycled trays. The periodic trays are advantageous compared to their predecessors. For different ratios of countercurrent vapor/liquid flow rates, column efficiencies are two times greater for periodically cycled columns than for columns with sieve trays. Depending upon the holdup and gas flow, the tray efficiency of a single periodic tray can be up to 300 % of an ideal stage.