One of the distinct advantages associated with gas-phase processes is the relative ease of separating the reacted polymer from the unreacted monomer. However, calling the process simple is quite an understatement as the product discharge system is often more complex than the reactor cycle gas system itself.
This complexity is directly reflected in the demands for the valves as well. Proper valve performance improves the accuracy of throughput control and favorably affects overall plant performance.
Discharge of the product
In a reactor, gaseous monomer, comonomers and proprietary catalysts combine to produce a dry, polymer resin. This resin – along with hydrocarbon vapor, unspent catalyst, and possibly polymer sheets and chunks – flows from the reactor to the product discharge system (PDS) where unreacted gas is separated from the product and returned to the reactor.
The PDS consists of one or more product chambers, as well as an assortment of valves and piping for product conveyance, isolation, and gas venting and recycling. Downstream from the PDS, the product is purged with nitrogen to remove any remaining absorbed hydrocarbons. Finally, the granular polymer is pelletized with application-appropriate additives.