Polyvinyl Chloride Production from VCM (Bulk Polymerization)

The process under analysis comprises 2 major sections: (1) Polymerization; and (2) Classification & Storage.

Polymerization. In the first stage, the vinyl chloride monomer (VCM) is polymerized in an autoclave reactor, under vigorous agitation promoted by a turbine agitator. The reaction is initiated by acetyl cyclohexyl sulfonyl peroxide (ACSP). When the VCM conversion rate reaches approximately 10% by weight, the polymer slurry is transferred to a second polymerization step. The polymer slurry, along with VCM feed and initiators, are then fed to vertical reactors. The reaction is also conducted under agitation. The molecular weight of the polymer being formed is controlled according to reaction media temperature. The reaction is continued until 80–85% of the vinyl chloride monomer is converted, when PVC grains reach 130 - 160 µm diameter. Off-gases from polymerization, composed primarily of unreacted VCM, are compressed and then passed through heat exchangers using cooling water and chilled water, in such a way that the VCM is condensed and is recycled to the polymerization.

Classification & Storage. The PVC powder from the Polymerization is dropped into a hopper, from which it is classified by means of screeners. The PVC product is directed to the Product Silos, while oversize polymer particles are diverted to a grinder and returned to the screens. The PVC powder is pneumatically conveyed to the blending silos for homogenization. Subsequently, part of the PVC is packed in begs, while the other part is directly sent to storage silos.