Froth Heights on Dual-Flow Trays with a Heterogeneous Binary Azeotropic System and a Heterogeneous Ternary System with a Homogeneous Azeotrope

Abstract

Visual froth height measurements and the clear liquid heights on 20% free area dual-flow trays, operated at total reflux, have been obtained on the homogeneous system of water−steam, on the heterogeneous systems of ethyl acetate−water and ethyl acetate−ethanol−water, and in the homogeneous region near the homogeneous ternary azeotrope of that ternary system. The experimental results were obtained under distilling conditions at a total pressure of 101.3 kPa for a range of liquid and vapor densities and vapor velocities. The churn flow conditions on the dual-flow trays at total reflux were found to have the characteristic of constant volume fraction liquid in the froth for all systems investigated: ΦL = 0.291; hf < 0.300. A correlating equation for the froth height that contains the impact pressure was found for all systems investigated to be hf = 2.625(1/2ρVu2) with hf < 0.300. A dimensionless correlating form, based on a modified Froude number, was found to be suitable for all systems: FrM = 280.0 × 10-6(ρV/ρL)-1/2 with hf < 0.300. The clear liquid height was found for all systems to follow hCL = ΦLhf with hf < 0.300. The dimensionless correlation for froth heights for all systems could be converted to a flooding vapor velocity relationship at total reflux for dual-flow trays by ufl = 0.0283√Z(ρV/ρL)-3/4 with Z < 0.300.