Propylene, ethylene and any other required comonomers are fed into the reactor(s). Hydrogen is added to control the molecular weight. Polymerization conditions (temperature, pressure and reactant concentrations) are set by the polymer grade to be produced. The reaction itself is exothermic. Reactor cooling is achieved by evaporation of liquefied reactor gas, which is injected into the reactor. Flash evaporation of the liquid in the polymer bed ensures the most efficient heat removal.
The polymer powder is discharged from the reactor(s) and separated from the gas in a discharge cyclone at atmospheric pressure. Any unreacted monomer separated from the powder is compressed and either recycled or returned to the upstream olefins unit for recovery. The final degassing of the polymer is done in a purge silo by flushing with nitrogen. The purge offgas is sent to a recovery system. Finally, the powder is converted into pellets that incorporate a full range of well-dispersed additives.
For highly demanding applications, which require extremely low levels for volatiles and odor, the gas-phase process offers an optional desorber unit to treat the pellets after extrusion.
Benefits
The Novolen® gas-phase process features an exceptional cost/performance ratio. Due to the simplicity of the gas-phase process, the capital expenditures for inside battery limits (ISBL) of a Novolen technology process plant are the lowest in the industry.
Reports specifically evaluating the competitiveness of all commercial PP processes have concluded that Lummus Technology provides the lowest investment costs for the full range of PP products at lowest operating costs. This investment cost advantage for world-scale plants producing high value products further increases the attractiveness for investors.
The Novolen gas-phase process includes standardized packages for high-efficiency monomer recovery. Proven reliability and minimized equipment count lead to highly competitive maintenance costs.
- Produces a full range of homopolymers, random and impact copolymers in only two identical reactors with Ziegler-Natta and metallocene catalysts, which covers a broad range of products for all markets/applications, including ultra-high rubber content (up to 50%) impact copolymers and terpolymers as well as very high stiffness grades and high clarity random copolymers
- No dedicated reactor for impact copolymer production. Two identical reactors connected in a row allow for impact copolymer production and also for homopolymer production
- Exclusive vacuum degassing at extruder. Products at the lowest edge of volatile content in the marketplace with very low taste and odor level for highly demanding applications (for example, drinking water pipes and food packaging). Can be combined with our exclusive desorber technology
- Simple, solvent-free gas-phase process. Among the lowest operating and maintenance costs in the industry
- Drop-in metallocene catalyst. Novolen process plants are ready to use Novocene® catalyst without any major plant modifications. New polypropylene (PP) grades with outstanding combination of properties
- Small reactor volume = small gas inventory. Rapid grade changes. Minimized inventory results in inherently safer process and in reduced capital investment and operating cost
- No proprietary and no single-vendor equipment, resulting in a lower TIC