Supercritical fluids are commonly used in industrial processes in order to lower their costs, to improve their efficiency or to replace hazardous organic solvents. One of the applications making use of scCO2 is in food drying technology. Figure 1 below presents general principle of such process, where pressurized CO2 is continuously recirculated through a drying chamber and a dehydration unit.
Figure 1: Scheme of continuous drying process using scCO2
The reason of using CO2 is its easily achievable critical point (Figure 2) and properties like non-toxic, non-flammable, cheap and available in high purity and bulk quantities.
Figure 2: Phase diagram of CO2
Currently, zeolite beds are being used to remove water from drying fluid. However, as their regeneration demands a very high energy input and there is possibility of premature zeolite saturation, another CO2 regeneration technique is needed.
The aim of the project is water removal from carbon dioxide streams using water selective membranes. The main challenge is development of technology with adequate separation performance (high flux and selectivity) under operating conditions in the range of 40 to 60 °C and 100 to 200 bar. The research includes identification of a membrane materials which are stable at supercritical CO2 conditions, preparation of organic and inorganic membranes, membrane characterization, development and their performance evaluation for water separation from CO2, mass transport studies and process design.
This is a Wetsus Institute project.