(363b) A Purge Bin Model for the Recovery of Polyolefins

In the manufacturing of polyolefins, the product purge bin is a challenging unit operation to model because of the counter-current mass transfer at low concentrations of residual components in the gas/solid system.

After the reactions of monomer (and co-monomer) over a catalyst in the presence of inerts (including a condensing agent) in a gas phase reactor, the product polymer is generated in solid particle form. These solid particles contain a sizable amount of condensing agent, monomer, and undesired species that need to be removed before the polymer can be sent to downstream units for processing and shipment. The removal of the hydrocarbons and impurities is done by counter-currently contacting the polymer particles with stripping nitrogen in a tower called the product purge bin, which can be challenging to model accurately.

This work focuses on the development of a practical model that can capture the major characteristics of the polyethylene product recovery process in the purge bin so they can be easily incorporated into Aspen Plus. The model can be applied to polyolefins (polyethylene, polypropylene) production to increase capacity, optimize performance, and guide plant operations to achieve sustainability targets.