4, the body method - gas phase combination process
The bulk-gas phase combination process mainly includes the Spheripol process of Basel, the Hypol process of Mitsui Chemicals of Japan, and the Borstar process of Borealis.
(1) Spheripol process. The Spheripol process was developed by Basell Polyolefins. Since its first industrialization in 1982, this technology has been the most successful and widely used polypropylene production process to date. The Spheripol process is a polymerization process combining liquid phase prepolymerization with liquid phase homopolymerization and gas phase copolymerization. The process uses a high-efficiency catalyst. The particle size of the PP powder produced by the catalyst is spherical, and the particles are large and uniform. Can be adjusted, both wide and narrow. It can produce a wide range of products for a wide range of applications. Its homopolymerized and random copolymerized products are characterized by high clarity, good optical properties and no odor. The liquid phase loop reactor used in the Spheripol process has the following advantages:
(a) High reactor-space rate (up to 400kg PP/h.m3), smaller reactor volume and less investment;
(b) The reactor has a simple structure, low material requirements, and can be designed and manufactured with low-temperature carbon steel. Due to the small diameter (DN500 or DN600), even if the pressure is high, the pipe wall is thin;
(c) The jacketed leg portion of the reactor can serve as a support for the reactor frame. This structural design reduces investment;
(d) Due to the small volume of the reactor, the residence time is short, the product is switched quickly, and the transition material is small;
(e) The polymer particles are suspended in the propylene liquid, and there is good heat transfer between the polymer and the propylene. The heat transfer area per unit volume of the reaction heat is removed by the cooling jacket, the heat transfer coefficient is large, and the overall heat transfer coefficient of the loop reactor is as high as 1600 W/(m 2 · ° C);
(f) The slurry in the loop reactor is circulated at high speed by an axial flow pump, and the fluid flow rate is as high as 7 m/s, so that the polymer slurry can be uniformly stirred, the catalyst system is uniformly distributed, the polymerization reaction conditions are easily controlled, and the control can be accurately controlled. The product quality is uniform, it is not easy to produce hot spots, it is not easy to stick to the wall, and the energy consumption of the axial flow pump is also low;
(g) The concentration of the polymer slurry in the reactor is high (mass fraction is greater than 50%), the single pass conversion of the reactor is high, and the single pass conversion of homopolymerized propylene is 50%-60%. These features make the loop reactor suitable for the production of homopolymers and random copolymers. The Spheripol process initially uses high-efficiency catalysts such as GF-2A, FT-4S, and UCD-104. The catalyst activity reaches 40kgPP/gcat, and the product isotacticity is 90%-99%, which can be used without deashing or randomization.
The technology has now evolved to the second generation. Compared to the first generation technology using a single loop reactor, the second generation technology uses a double loop reactor with significantly improved operating pressure and temperature to produce bimodal polypropylene. The catalyst system adopts the fourth-generation or fifth-generation ZN high-efficiency catalyst, which increases the hydrogen separation and recovery unit, improves the high-pressure and low-pressure degassing equipment of the polymer, and improves the steaming, drying and propylene accident discharge units, and increases the operation. Flexibility, increased efficiency, and significant reductions in raw material and utility costs. The resulting product has a more uniform particle size and a wider melt flow index (from 0.3-1600.0 g/10 min), which produces new PP grades with high stiffness, high crystallinity and low heat seal temperature. The impact copolymerization of the Spheripol process is produced by a gas phase process, and the reactor is one or two dense phase fluidized bed reactors connected in series. The reactor was a gas phase dense phase fluidized bed. A gas phase reactor system can be used to produce impact copolymers with an ethylene content of 8% to 12% (mass fraction), if needed to produce special impact copolymers with higher rubber phase content and possibly more than one dispersed phase (eg low For stress whitening products, two gas phase reactor systems need to be designed to maintain the gas phase composition and operating conditions in the two gas phase reactor systems independently, and two different copolymers can be added to the homopolymer.
By treating the polymer by steaming and drying in two steps, the vapor in the steam exhaust gas can be easily condensed to separate the pure hydrocarbon monomer, and the hydrocarbons in the tail gas can be completely recovered and the monomer consumption can be reduced. A closed circuit nitrogen drying system also reduces the nitrogen consumption of the unit. In addition, the Spheripol process adopts a modular design to meet the requirements of different users, and is easy to build step by step (such as first on the homopolymer production system, adding gas phase reaction system in time), and the production capacity of the device is also easy to expand. The Spheripol process has a rigorous safety system design that gives the unit high operational stability and safety. The new generation of Spheripol process uses pure additives to join the system, making the product quality more uniform and stable, and convenient for product switching. Spheripol process technology offers a full range of products including homopolymers, random copolymers, impact copolymers, terpolymers (ethylene-propylene-butene copolymers). The MFR range of the homopolymer product is 0.1-2000 g/10 min, the MFR of the industrial product reaches 1860 g/10 min (special non-granulated product), and the flexural modulus of the high rigidity product reaches 2300 MPa. The industrially produced random copolymer product has an ethylene content of up to 4.5% (mass fraction) and an ethylene-propylene-butene terpolymer product. The film sealing initiation temperature is as low as 110 ° C, which can be produced by a gas phase process. The competition for high ethylene content random copolymerization. The impact copolymer product has a combination of good rigidity and impact resistance. The product has an ethylene content of up to 25% (40% rubber phase) and has the ability to reach 40% ethylene content (60% rubber phase). In addition, the Spheripol process can flexibly adjust the molecular weight distribution of the product between polymer dispersion index (PI) 3.2-12 according to product requirements by adding peroxide and double loop reactor. It can directly produce MFR up to 1800g/ in the reactor. 10min products and large
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