Capacity factors in the performance of perforated‐plate columns

Abstract

AbstractA study was made of factors affecting the vapor‐handling capacity of perforated‐plate liquid‐vapor contacting columns. Vapor‐phase pressure drop across plates, liquid entrainment upward from plate to plate, and plate stability were investigated as functions of operational and geometric column parameters.Gas‐phase pressure drop across dry perforated plates was observed to follow functional relationships predicted from available information for single perforations. The presence of liquid on a plate increased the total pressure drop by the equivalent clear‐liquid head plus a small residue which is nearly constant for a given liquid.Entrainment was observed to be a function of column gas velocity, independent of gas velocity in the perforations. Weight rate of entrainment was also found to be proportional to the gas density, independent of liquid density, and inversely proportional to the liquid‐surface tension. For a given system, entrainment was observed to be proportional to approximately the third power of the group, gas velocity divided by the distance between the liquid surface and the plate above.The stability of perforated plates was observed to be adequate for many industrial and experimental applications, as also reported in recently published studies, but contrary to qualitative statements found in the earlier literature. Stability was found to increase with decreasing perforation diameter and decreasing total perforation area relative to column cross‐sectional area; to increase with greater gas density, liquid surface tension, and liquid wetting power; and to be virtually independent of liquid density and viscosity.Operating limits of vapor and liquid throughput are shown for a typical application of perforated plates in liquid‐vapor contacting columns.