Bubble column reactors for high pressures and high temperatures operation

Bubble column reactors are multiphase contactors based on the dispersion of a gas phase in the form of bubbles inside a cylindrical vessel where a liquid or a suspension circulates. Those reactors present many advantages such as good heat and mass transfer rates, no moving parts, compactness, easy operating and low maintenance and operating costs. Their main drawback is the significant backmixing which can affect selectivity and conversion of reaction products. They have gained particular attention in the field of wastewater treatment for Wet Air Oxidation (WAO) processes application. Those processes are operated at high pressures (up to 30 MPa) and temperatures (up to 573 K). In order to efficiently operate those processes, conversion, heat and mass transfer must be optimised. Those parameters depend themselves on operating conditions such as pressure, temperature, superficial gas and liquid velocities and on design parameters such as sparger and column design. This review is aimed to find the relevant parameters for operating bubble column at high pressures and temperatures in continuous mode. The main mechanisms governing the bubble column will be described. The influence of the different parameters on gas holdup, mass transfer properties and on liquid axial dispersion coefficient will be extensively studied.