Industrial Preparation of Poly(vinyl Chloride)

Abstract

Vinyl chloride (VCM) is unloaded from railroad tank cars or tank trucks into pressurized storage spheres. VCM, emulsifiers, and catalysts are metered into polymerization vessels wherein PVC is produced through a chemical reaction in an aqueous medium under controlled conditions of temperature and pressure. After the reaction reaches a predetermined completion, the contents are transferred to a secondary vessel wherein steam is injected and the VCM containing vapors are pumped to a recovery system. The VCM-containing vapors are compressed, cooled, condensed, decanted, and recycled to the process for reuse. The stripped PVC resin water slurry is then pumped to blending tanks where the batches from multiple reaction vessels are blended for product uniformity. From the plant tanks the PVC resin water slurry is pumped to a dewatering centrifuge, where approximately 90% of the water is removed and subsequently discharged to the industrial sewer system. The PVC resin wet cake is conveyed from the centrifuge to a flash dryer where essentially all the remaining water is removed. At this point, the dry resin is buoyant in an air stream and enters a two-stage collection system for separation of conveying air. The PVC resin is then screened and air-conveyed to storage for bulk shipment, compounding, or bagging.