solvent regeneration to recover a polar hydrocarbon selective solvent substantially free of hydrocarbons and other impurities from a solvent - rich stream containing selective solvent , heavy hcs , and polymeric materials generated from reactions among thermally decomposed or oxidized solvent , heavy hcs , and additives is provided . a combination of displacement agent and associated co - displacement agent squeezes out the heavy hcs and pms from the extractive solvent within a solvent clean - up zone . simultaneously , a filter equipped with a magnetic field is positioned in a lean solvent circulation line to remove paramagnetic contaminants . the presence of the co - displacement agent significantly enhances the capability of the displacement agent in removing the heavy hcs and pms from the extractive solvent . as a result , the solvent regeneration system operates under milder conditions and minimizes or eliminates the need for including a high temperature , energy intensive and difficult - to - operate thermal solvent regenerator .