Gas hold-up and mass transfer in gas-lift reactors operated at elevated pressures

The effect of elevated pressure on the hydrodynamics and mass transfer in t he gas-lift reactor with external liquid circulation loop is examined. Expe riments were performed in a 0.15 m diameter column operated at pressures in the range 0.1-1.0 MPa with nitrogen as gas-phase and water as liquid phase . A clear influence of system pressure on overall gas hold-up in the riser and on the volumetric mass transfer coefficient was found. The observed inc rease of epsilon and k(L)a values was smaller than in a bubble column witho ut liquid circulation, due to the fact that in the gas-lift system the circ ulation velocity increases with pressure. A constant ratio of approximately 0.5 between the volumetric mass transfer coefficient and the gas hold-up w as observed over the pressure range investigated. (C) 1999 Elsevier Science Ltd. All rights reserved.