Optimization Of Three/Four-Pass Trays

Tray column plays a major role in chemical separation equipment. In recentyears, novel trays appear frequently, the requirements of processing capability are alsogetting higher and higher. There are two main points on research and development ofcolumn tray, one is to improve the efficiency, the other is for some specialrequirements, such as low pressure drop, high flux, etc. Multipass tray has a goodadvantage for processing large liquid load, its longer overflow weir can effectivelysolve the problem of high overflow on the tray. However, design of multipass tray isstill one of chemical equipment design difficulty. Two kinds of design method forthree/four-pass tray are introduced in this paper: equal bubbling area method andequal flowpath length method. Different optimization of the two methods is puttedforward,for example, installing auxiliary weir and fence weir to change height of theliquid layer on the tray, sealing part of the downcomer clearance to balance the liquidflow of each channel. Through the comparison of different optimization designmethod of multipass tray, it can be seen that the results of optimization of equalbubbling area method and the equal flowpath length method for three/four-pass trayare reliable. For three-pass tray, equal flowpath length method with installingauxiliary weir and fence weir can better meet the requirements for uniform gas-liquiddistribution and mass transfer, compared with equal bubbling area method, itsoperation flexibility has obvious advantages. For four-pass tray, there is no significantdifference between equal flowpath length method with installing auxiliary weir andfence weir and equal bubbling area method with adjusting weir height, Designer canchoose either method according to the actual situation. A model for predicting the hydrodynamics and flow distribution of three-passtrays is presented. The model predicts good distribution at larger operation load, butits operation flexibility is bad. When designing three-pass tray, maldistribution doesnot have significant effect on mass transfer efficiency and hydraulic performance ofthree-pass tray. If we choose the optimization proposed in the article, and the designis reasonable, maldistribution can be reduced to acceptable levels.