Polyethylene process flow diagram

In 1989, the NDF Company opened a facility in Georgetown, South Carolina to produce low density polyethylene. Manufacturing of the polyethylene is done in two 50-ton reactors that are encased individually within their own 8-story-high process unit. The main raw materials for the manufacturing operations include ethylene, hexane, and hutene. The polymerization is completed in the presence of a catalyst. The hase chemicals for the catalyst are aluminum alkyl and isopentane. The reactor and catalyst preparation areas are on a distributed control system (DCS). A simplihed process flow diagram is attached. 

Figure 7.1 Schematic process flow diagram for autoclave high pressure process for production of low density polyethylene. (Reprinted with permission of John Wiley Sons, Inc., Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley and Sons, Inc., h edition, 2006).

Most of the polyethylene made in gas phase processes employs Ziegler-Natta catalysts. There are, however, a few instances where supported chromium and single site catalysts are used. A simplified process flow diagram for the Unipol gas phase reactor process is shown in Figure 7.4. Principal operating features of the gas phase process are summarized in Table 7.5. 

Fig. 3-18 Flow diagram of high-pressure polyethylene process. After Doak [1986] (by permission of Wiley-Interscience, New York).

Figure 4.11 Flow diagram of the gel-spinning process of making ultra high molecular weight polyethylene fiber.

Solution polymerization is of limited commercial utihty in free-radical polymerization but finds ready applications when the end use of the polymer requires a solution, as in certain adhesives and coating processes [i.e., poly(viityl acetate) to be converted to poly(viityl alcohol) and some acryhc ester finishes]. Solution polymerization is used widely in ionic and coordination polymerization. High-density polyethylene, poly butadiene, and butyl rubber are produced this way. Table 10.2 shows the diversity of polymers produced by solution polymerization, while Figure 10.2 is the flow diagram for the solution polymerization of vinyl acetate. 

The loop reactors, which are recycled tubular reactors, are used by the Phillips Petroleum Co. and Solvay et Cie. The Phillips process is characterized by the use of a light hydrocarbon diluent such as isopentane or isobutane in loop reactors which consist of four jacketed vertical pipes. Figure 1 shows the schematic flow diagram for the loop reactor polyethylene process. The use of high-activity supported chromium oxide catalyst eliminates the need to deash the product. This reactor is operated at about 35 atm and 85-110° C with an average polymer residence time of 1.5 hr. Solid concentrations in the reactor and effluent are reported as 18 and 50 wt %, respectively. The reactor diameter is 30 in. (O.D.) and the length of the reactor loop is about 450 ft. 

Figure 9.18 Flow diagram of a high-pressure polyethylene process (reprinted from ref. 171 with permission from WUey-Interscience).

Figure 4.2 — (A) Schematic diagram of an ammonia-N-sensitive probe based on an Ir-MOS capacitor. (Reproduced from [20] with permission of the American Chemical Society). (B) Pneumato-amperometric flow-through cell (a) upper Plexiglas part (b) metallized Gore-Tec membrane (c) auxiliary Gore-Tec membrane (d) polyethylene spacer (e) bottom Plexiglas part (/) carrier stream inlet (g) carrier stream outlet. (C) Schematic representation of the pneumato-amperometric process. The volatile species Y in the carrier stream diffuses through the membrane pores to the porous electrode surface in the electrochemical cell and is oxidized or reduced. (Reproduced from [21] with permission of the American Chemical Society).

---