Improvement of the ultrafiltration of highly viscous liquids by injection of pressurized carbon dioxide

The injection of pressurized carbon dioxide (CO2) (gas or supercritical) in a liquid induces a lowering of viscosity the magnitude of which is a funct ion of temperature and pressure. In this work, the addition of pressurized CO2 to highly viscous liquids is proposed as an ecologically viable and eco nomically competitive technology to increase permeate flux during ultrafilt ration at low temperature. Initially viscosity and phase-equilibrium data o f model compounds, polyethylene glycols (PEG), in the presence of CO2 were studied at high pressure. Then tangential filtration runs with PEG-CO2 mixt ures were conducted on pilot-plant units equipped with mineral membranes. R esults thus obtained were analyzed using the previously measured kinetic an d thermodynamic data.