Polyolefin plant resin degassing

Figure 8.14 Flow diagram showing the use of hydrocarbon-permeable membranes to recover unreacted monomers from a polyolefin plant resin degassing unit. The photograph is of a system installed by MTR in Qatar in 2007.

One of the most successful petrochemical applications is illustrated in Figure 8.14 treatment of resin-degassing vent gas in a polyolefin plant [28]. In these plants, olefin monomer, catalyst, solvents, and other coreactants are fed at high pressure into a polymerization reactor. The polymer product (resin) is removed from the reactor and separated from excess monomer in a flash-separation step. The recovered monomer is recycled to the reactor. Residual monomer is removed from the resin powder by... 

The recovery of hydrocarbon monomers from ethylene in polyethylene and polypropylene plants is actually the largest application of vapor separation membranes. After the production of the polyolefin resin, there are unreacted monomer and hydrocarbon solvents dissolved in the resin powder that must be separated in order to reuse the polymer. The traditional application involves stripping with hot nitrogen in a column known as a degassing bin. The values of nitrogen and monomer are both high therefore, the recovery and reuse of these components are of great interest. For this purpose, a membrane operation is profitably used. It consists of two membrane units in series where the off-gas... 

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