What is tray efficiency?
Calculations are made which indicate the vapor and liquid composition that would result if equilibrium existed at that particular temperature and pressure. One theoretical plate would accomplish these compostitions. By repeating these calculations until the desired terminal compositions are reached, the total number of theoretical plates, or trays, can be calculated. The number of theoretical trays used, divided by the actual trays, results in the tray efficiency for that system and at those operating conditions. In the case of packings, the height of packing to equal a theoretical plate is used (HETP) to express efficiency. If trays on 24″ spacing have 50% efficiency, four feet are required for a theoretical plate. If a packing has an HETP of four feet, the two devices are equal efficiency-wise.
