Thin film membrane for CO₂ separation with sweeping gas method

Different from gases separation technology using membranes and solvent, solvent-free gas separation technology is more economically and energy efficient. Due to its inherent low permeance of the membrane, the means using sweeping or vacuum are two main options to increase the mass flow rate of the fast gas (with higher selectivity) on the permeate side. This study models a typical membrane for CO₂ separation and investigates the effects of different parameters on the total mass flow rate, mass fraction of CO₂ and the mass flow rate of CO₂ in the permeate outlet. These parameters are the permeate outlet pressure, mass flow rate of mixed feeding and sweeping gases, membrane length and the height of gases zones. The results show that the mass flow rate of CO₂ in the permeate side can be enhanced dramatically by using sweeping gas method. But the mass fraction of CO₂ in permeate outlet is also significantly affected by this method. The increase of membrane length enhances both the mass fraction and mass flow rate of CO₂ in permeate outlet. But mass fraction of CO₂ on permeate outlet reaches its peak when membrane length exceeds 150 mm. The height of gases zones, however, have very limited effects on both the mass fraction and mass flow rate of CO₂ in the permeate outlet. This study provides a good guideline for designing industrial gases separation systems using membranes.