| The Compound tray researched in this paper consists of dual-flow tray and 50-1 ^Omm high structural packing which is directly put under the dual-flow tray. It has three mass transfer sections that is the foam section on the tray, the film section in the packing layer and the shower section under the packing, so it has very high mass transfer efficiency. The compound tray has no down comer, gas and liquid counter flow through the holes of on the tray. This paper analyzed the mechanism that gas and liquid flow through the holes according to the fluid characteristics of the compound tray, and put forward that there are three states of liquid flowing, gas flowing and blocked for the holes because of the foam fluctuating on the tray while the compound tray operates . Liquid flows through the holes under wave crest, gas flows through the holes under trough and neither liquid nor gas flows through the holes under the wave middle that means the holes are blocked. The state of the holes changes continuously along with the moving waves. At the same time the number of holes for liquid flowing, gas flowing and blocked to the number of total holes was defined as liquid flowing ratio, gas flowing ratio and blocked ratio.The experiment was made with in-diameter 500mm column using water-air system, the ratio was first delected in detail by multi-path conductivity gauge for the compound tray with free area 20% and 25% respectively. The basic regulation of the ratio which changes along with the flo\v rate of liquid and gas was obtained; besides, the experiments discovered that the real velocity of the holes at flooding point is about llm's under different liquid flow rate, according to this the up limit of the compound tray can be reckoned .The pressure drop of the compound tray can be regarded as consisting of dry plate pressure drop, clear liquid resistance, liquid surface tension resistance, and packing pressure drop. The model that has established can fairly predict the pressure drop of the compound tray, the value calculated by the model compared with that detected by experiment is less than 20%. so the model can be used for designing of the compound tray: besides, a calculating method was gained for operating region of the compound tray on the basis of its characteristics .The test was made on the compound tray, dual flow tray, sieve tray and valve tray for mass transfer efficiency with in-diameter 300 mm column using ethanoi and water system. The total efficiency, plate efficiency, foam efficiency, film efficiency of compound tray, and the total efficiency of the other thee types of plate was detected. The experiment's results show that the total and plat efficiency of the compound tray is over 100%, the highest efficiency can be up to 122% within the range of F factor I~2.5m/s(kg/m3)i/2, it is far higher than the efficiency of dual flow tray , sieve tray and valve tray . The efficiency of compounded packing can reach 0.2~0.53 theoretical plate according to the different height of packing.The special area of foam was detected for the compound tray of 20% free area by CCD camera and computer identification technology of gas and liquid two phase flow in column . with the rectangular plexiglass tower in 200mm X 300mm, and it's correlation was obtained .This experiment offered data of special area for establishing mass transfer model of foam.The mass transfer model of the foam was established on the basis of the penetration theory, and the mass transfer model of the compound tray was obtained according to the mass transfer model of the foam and FRB model in packing. The error of the model value comparing to the experiment value is less than +20% and -15%.
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