Axial mixing and gas absorption in a mechanically agitated absorption tower

Abstract

Axial mixing in the liquid, with and without simultaneous countercurrent flow of air, was measured in a twelve-compartment, six-inch diameter, mechanically agitated tower for gas rates 9 to 94 and liquid rates 1300 to 19,600 lb/hr (sq ft), agitator speeds 200 to 2000 rpm. The corresponding eddy diffusivities and gas holdup were correlated in terms of the variables studied. Attempts to make similar measurements for the gas phase failed to give meaningful data, but the indications are that axial mixing in the gas is of minor importance. The tower was also used to measure the mass-transfer rates during absorption of ammonia from air into water. At 110 lb gas/hr (sq ft), the performance corresponds roughly to that of towers packed with 1- to 2-in conventional packings. The mass-transfer coefficients corrected for axial mixing are roughly 7 to 25 per cent larger than those before correction.