GAS HOLDUP AND HEAT TRANSFER FROM IMMERSED SURFACES IN TWO- AND THREE-PHASE SYSTEMS IN BUBBLE COLUMNS

Abstract

Two experimental slurry bubble column facilities comprising of 10.8 and 30.5 cm diameter columns and appropriate for conducting hydrodynamic and heat transfer studies are described. The average and local gas holdup data are reported for the air-water system as a function of air velocity. The holdups for the three phases are also reported for the air-water-glass beads system over a range of air velocity values. The air holdup data are compared with the predictions of some of the commonly used correlations. The heat transfer coefficient for a 19 mm diameter cylindrical probe and the two- and three-phase dispersions are measured as a function of air velocity. Most of these hydrodynamic and heat transfer data correspond to the churn turbulent regime and the values obtained on the two columns differ appreciably from each other under similar operating conditions. This fact indicates that the scaleup of slurry bubble columns could be quite difficult on the basis of data obtained on the bench and pilot-plant scale units. The continuing data from these facilities on different systems will shed more light in the future on this important aspect which is crucial to the commercialization of indirect coal liquefaction technology.