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Polymer Grade Propylene & Technical Grade Propylene

The unit / Propane Dehydrogenation unit is based on the production of 350,000 metric ton per year (99.7% purity product per year) of propylene from propane, operating at 330 days per year.

The refining and propylene recovery section of the unit since receiving purge and off gas containing propylene from the other units in the complex have the capacity to produce 450,000 metric ton per year of polymer and technical grade propylene.  The refining and propylene recovery section consist of 2 identical refining and splitter units.

The technology is CATOFIN Process licensed by Lummus.  Plant was commissioned in May, 1995 and was shut down in Jully of 1996.  Appropriate steps were taken to mothball the plant.

Reason for shutdown was over capacity of Polypropylene commodity and high demand of polyethylene. Therefore the propane was switched to the ethylene and ultimately to polyethylene production to satisfy the market demand in that area.

The following is a brief process summary:

The CATOFIN reaction system consists of parallel fixed-bed reactors and a regeneration air system. The reactors are cycled through a sequence consisting of Reaction, Regeneration and Evacuation/ purge steps. Multiple Reactors are used so that the reactor feed / product system and regeneration air system operate in a continuous manner.

There are a total of  ‘7’ reactors, three continuously operative, three in regeneration and one standby unit as spare.

The fresh liquid propane feed is combined with recycled feed from the refined section vaporized, and preheated to the reaction temperature of 690° F in a charge heater and fed to the reactors. The reaction takes place under vacuum over a Chromium – Alumina catalyst to maximize feed conversion and olefin selectivity.  The reaction is the “Catalytic Dehydrogenation” of Propane.

The effluent gas from the reactors, after cooling is compressed in two Elliott steam turbine driven propylene compressors and sent to Recovery system where the inert gases, hydrogen and light hydrocarbons are separated from the compressed reactor effluent.

Then the rich propylene gas from the recovery system is fed to the product purification. In this section the propylene product is separated from unreacted propane.

After a suitable period of on-stream operation, feed to an individual reactor is discontinued and the reactor is reheated / regenerated.  Reheat / regeneration air heated in a regeneration air is heater. The regeneration air serves to restore the temperature profile of the catalyst bed to its initial on-stream condition in addition to burning coke off the catalyst.  When reheat/ regeneration is completed, the reactor is re-evacuated for the next on-stream period.

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