PP Homopolymer from Propane (Oleflex PDH / Spheripol PP)

The process under analysis comprises four major sections: (1) Propane Dehydrogenation; (2) Propylene Purification; (3) Polymerization; and (4) Polymer Degassing and Pelletizing.

Propane Dehydrogenation. Fresh and recycled propane are fed to a depropanizer column for heavy impurities removal and then heated to the reaction temperature in a charge heater. The dehydrogenation reaction takes place on moving bed reactors across multiple stages, which operate in a continuous mode. In this process, a continuous catalyst regenerator (CCR) unit is used to purge the coke accumulated on the surface of the platinum-based catalyst during the reaction.

Propylene Purification. The reactor effluent is compressed, dried and sent to a low-temperature separation system (cold box) for the removal of a hydrogen-rich stream. Subsequenty. light hydrocarbons and hydrogen traces are removed in a deethanizer column and PG propylene is obtained in a propane-propylene (P–P) splitter.

Polymerization. PG propylene is sent to fixed bed dryers for removal of water and other catalyst poisons, and to the prepolymerization reactor. The catalyst and hydrogen are also fed to this reactor. The reactor and dryers outlets are mixed with hydrogen and routed to two loop reactors in series, where the polymerization takes place.

Polymer Degassing and Pelletizing. The slurry from the reactor containing spheres of polypropylene, unreacted monomer, catalyst and other impurities is discharged in a degassing system to separate the unreacted monomer from the polymer. The gas from the degassing sent to a monomer recovery area before being recycled to the reaction area. A fraction of the recycle monomer stream is sent to a propylene-propane splitter column for purification. The degassed polymer is combined with additives and then flows to the pelletizing unit before being sent to product blending and storage.