Separation of polypropylene exhaust gas by alcohol absorption method

The recovery of propylene from polypropylene (PP) exhaust gas has great significance for improving production efficiency and protecting environment. The solubilities of propylene were measured first in various alcoholic solutions, and then the separation of propylene and nitrogen was investigated by alcohol absorption method. On the base of SRK equation of state and Wilson activity coefficients model, the solubilities of propylene in different alcoholic solutions and conditions were calculated. The average absolute relative deviation between the calculated solubilities and experimental values at fixed conditions is 5.30%. The separation experiments were conducted in pure n-butanol and ethylene glycol, respectively, and the influences of temperature and pressure on the separation efficiency were investigated as well. The results indicate that n-butanol shows a better separation performance than ethylene glycol under the same conditions. High pressure and low temperature are conductive to high concentration and recovery of propylene in product gas. Under 303 K and 1.49 MPa, propylene is concentrated from 20 mol% in feed gas to 92.31 mol% with a recovery of 79.69% after separation.