Combined trapezoid spray tray (CTST) is one of spray trays with special trapezoid structure. The plate has some advantages such as higher flux and efficiency

lower pressure drop

better blockage and foaming resistance.The hydromechanics of CTST was studied.The pressure in the cap was lower than that out of the cap in the zone of cap gap. Therefore CTST is favorable for liquid coming into the cap from the plate. Gas velocity distribution in the cap was studied

and there were two small eddy zones at the bottom of the cap. On the upside in the cap

gas velocity was high owing to the decrease of cross section area

which provided liquid with enough energy to be broken up and sprayed out of the cap. With the cap

gas (or vapor) was capable to lift liquid from the plate up to the space between plates where was the main space of mass transfer. Little liquid was stagnant when passing through the cap

which made liquid holdup small.