Gas-phase polymerization Processes are widely used to produce polyolefins. They use either continuous-flow stirred-bed or fluidized-bed reactors. Unlike slurry and solution processes, in WERNA PP process (Novolen Technology) no liquid phase is present in the reactors, only vapor and soLids. This makes the gas-phase process simpler, because there is no solvent or liquid monomer to separate from the polymer, purify, and recycle

The polymerization in the WERNA PP reactor is carried out in gas phase utilizing evaporative cooling at a production rate of 10 t/h for homopolymers in a 50 m3 reactor. The reaction Temperature is adjusted to 80°C. Reactor pressure is adjusted to about 30 barg and is controlled by adjusting the fresh propylene flow rate

For the production of homopolymers, fresh propylene after being purified in C3-splitter, is fed to the reactor via bottom header and dome spray. Hydrogen is also added to the reactor bottom through recycle gas header. Co-catalysts (TEA and external stereomodifier) are fed to the reactor via the same header.

The Z/N catalyst is provided via separate feeding system and is flushed with White Oil into the reactor either via the reactor wall or alternatively to the top feed nozzles.Propylene vapor is continuously removed from the top of the reactor, condensed and pumped back to the reactor.

Liquid propylene that is fed back into the mixed polymer powder evaporates immediately, thus removing the heat of polymerization.The polypropylene product is discharged to the discharge vessel by reactor pressure. In the discharge vessel, polymer powder and the carrier gas are separated and the pressure is reduced to generally less than 2 bar.

The carrier gas is directed through a cyclone to remove the major amount of solid carry-over and then filtered to remove residual polymer fines.Depending on the downstream requirements, TEA is deactivated by adding steam or Isopropanol to product.The deactivated carrier gas is compressed and sent to the monomer recovery unit or recycled to the reactor.

A rotary feeder transfers polymer powder from the discharge vessel to the purge vessel. Residual monomer is removed from the powder with a nitrogen purge. The monomer is sent to monomer recovery unit.

Polymer powder from the purge vessel is pneumatically conveyed by nitrogen to the elevated powder silos upstream Extruder.

PP-powder is fed together with solid additives to the extruder for homogenization and pelletization. Liquid or molten additives are added downstream the degassing barrel. The extruder applied is twin screw extruders (co-rotating).

In contrast to other technologies, NOVOLEN deactivates the catalyst by adding water to the extruder, using the High temperature for fast decomposition and a vacuum degassing for the volatiles generated during extrusion. They are collected and sent to either the flare (gas) or to the wastewater treatment plant (liquids).

The PP pellets from extruder are sent to deodorizer where the hydrocarbon content of pellets in presence of steam and nitrogen will be dropped sufficiently giving FDA assurance for food and medical grades. From deodorizer, PP pellets are conducted to pellet cooler. Downstream of the pellet cooler, blending silos are installed to ensure lot–to–lot conformity for product delivery. Depending on the logistics strategy, these silos can also be used as bagging silos.

After being fully blended, PP pellets are sent to bagging silos from which they will be let bagged and packed into 25 and 750 kg bags. In parallel, the facilities of truck loading of PP pellets have been foreseen inside plant.