Polypropylene plant process

Figure 1 shows part of a solvent phase polypropylene plant. The plant consists of three process lines, denoted A, B, and C. During a risk assessment review, a scenario was identified that involved a release of reactor contents from a location near the west end of the A line. Estimates are needed of the blast overpressures that would occur if the resulting cloud of vapor, mist, and power ignites. 

Borstar A catalytic process for polymerizing ethylene or propylene, subdivided into Borstar PE and Borstar PP. Use of two reactors — a loop reactor and a gas-phase reactor — allows better control of molecular weight distribution. The loop reactor operates under supercritical conditions to avoid bubble formation. Either Ziegler-Natta or metallocene catalysts can be used. The latest version, Borstar PE 2G, uses a single, multizone gas-phase reactor to make polymers that have bimodal molecular weight distributions. Developed by Borealis A/S. The first commercial unit, for polyethylene, was installed in Porvoo, Finland, in 1995. The first polypropylene plant was operated by Borealis in Schwechat, Austria, in 2000. In 2005, Borstar s total capacity for PE and PP was 1.3 million tons. 

Petrofin [Process enhancement through recovery of olefins] A process for recovering olefins (ethylene and propylene) from polymerization processes by adsorption on zeolite 4A. Developed by BOC and used at Montell s polypropylene plant at Lake Charles, LA. First demonstrated in 1997. 

VaporSep A family of separation processes, based on membranes that are selectively permeable to organic vapors. Developed by Membrane Technology Research, CA, in the 1990s and used by DSM in its polypropylene plant to separate propylene from nitrogen. The membrane is a three-layer sandwich, packaged in spiral modules. 

Commercial plants Eleven polypropylene plants are in operation or under construction, with capacities ranging from 65,000 tpy to 300,000 tpy. JPP offers processing designs for single-production with capacities reaching 400,000 tpy. 

The monomer consumption data of the HDPE process is slightly different for the polypropylene process due to variable purity of the monomer raw material used by polypropylene plants. 

The SPS polymerization is very unique. Liquid styrene monomer is polymerized with homogeneous catalysts and produces SPS powder in the reactor. This is in contrast to Ziegler-Natta catalysts, which have solid components and powders that can easily be obtained by the growth of the solid components in bulk polyethylene and polypropylene plants. Under limited operational conditions and with a special equipment, SPS powder can be obtained. The SPS polymerization systems are very difficult to design. There are three types of SPS reactor processes from the patent information. 

Synthesis The early polypropylene plants used a slurry process adopted from polyethylene technology. An inert liquid hydrocarbon diluent, such as hexane, was stirred in an autoclave at temperatures and pressures sufficient to keep 10 to 20 percent of the propylene monomer concentrated in the liquid phase. The traditional catalyst system was the crystalline, violet form of TiCla and AlCl (C2Hs)2- Isotactic polymer particles... 

Figure 21.7 Photograph and process flow diagram of a membrane propylene recovery system installed at a modem polypropylene plant. The front portion of the unit is the compressor package. The spiral-wound membrane modules are contained in the horizontal tubes above and behind the compressor. This unit recovers approximately 1000 Ib/h of hydrocarbons.

This is used most often in process plants. It is a tough, low-cost material with probably the widest range of chemical resistance of any of the low-cost plastics. On a volume basis, PVC is more favorable than polypropylene because the modulus of PVC is considerably higher than that of polypropylene, so it will form more rigid structures when used at the same thickness. On a weight basis it is not as favorable as PVC because it has a specific gravity of 1.4 compared with 0.92 for polypropylene. 

Novolen A process for making polypropylene in the gas-phase, using a vertical stirred-bed reactor. Developed by BASF and engineered by Uhde. Eight plants had been licensed as of 1985. A metallocene-catalyzed version was introduced in 1996. The name is used also for the product. 

Fig. 15. Specific power consumed in the process of extrusion of polypropylene filled with 10% (by mass) of chalk (a) and 20% (by mass) of asbestos (b) versus capacity of the plant at core vibration at amplitudes, degr. 1 — 0 2 — 4.8 3 — 11.5 4 — 22.3...

The commercial production of high-density polyethylene started almost at the same time in late 1956 by Phillips using a chromium-based catalyst in a medium-pressure process and by Hoechst using a Ziegler catalyst in a low-pressure process. Polypropylene production began in Montecatini and Hercules plants in 1957. Poly(l-butene) and poly(4-methyl-1-pentene) have been produced in small commercial quantities since about 1965. The commercial production of ethylene/propylene-based rubbers started in 1960 [241]. 

Polymerization plants are now planned with throughputs of up to 70 t/h for polypropylene (PP) and over 100 t/h for different types of polyethylene (PE), and many licensors would like to process and pelletize these volumes to specification with just one processing plant. In addition to intake, melting, and homogenization of the raw materials, there is a need for discharge parts, conveying systems, and post-treatment units of an appropriate size. 

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