Continuous coater solvent recovery process

Abstract

A process for the recovery of solvent entrained in a water vapor laden exhaust gas stream exhausted from a spray painting system is disclosed. The process includes an oil absorption unit which absorbs and removes all but about 100 parts per million of the solvent from the exhaust gas stream while permitting air and water vapor to be vented from the system and a stripper which in turn removes all but about 0.001 mole fraction of any one solvent component trapped in the oil. The oil, which is substantially free of solvent, is returned to the absorption unit. The stripped solvent can then be condensed and reused by mixing it with the paint solids to be sprayed in the process; or, alternatively, it can be admitted as a vapor into the atmosphere surrounding a workpiece which is being coated in the spray painting system to raise the solvent humidity surrounding the workpiece to above about 70%. By raising the solvent humidity to above about 70% caking of paint on the interior surfaces of the spray booth, plugging of the paint spray nozzles, and rapid evaporation of solvent from the paint are reduced. The present process provides a means to recover and reuse even a complex mixture of solvents where the recovered solvent comprises a mixture of the same components in the same ratio as the solvent mixture originally used in the paint spray system. The system is described in relation to a continuous coater wherein parts to be coated move continuously through an enclosed paint spray area and are coated while the solvent laden atmosphere therein is exhausted from the coater for recovery of the solvent.