Slurry phase processes

Producers use four routes to make polyechylencj the bulk- or high-pressure process, the solution-phase process, the slurry-phase process, and the gas-phase process. Organizing your thinking around processes and products is not all that straightforward. Some of the processes can be used to produce ail the polyethylene forms, some only a few or one. That calls for a few words first by product and then more by process. 

In the bulk process, liquid propylene (polymer grade propylene here too) replaces the hydrocarbon diluent used in the slurry phase process. The PP is continuously withdrawn from the solution and any unreacted monomer is flashed off and recycled. The back end of the process, atactic PP removal and catalyst deactivation and removal, is the same as the slurry process. 

At the 5,000 b/d CANMET demonstration plant in Canada, the pitch is sent to a cement kiln for use as clinker. Other slurry-phase processes include COMBIcracking (developed by Veba Oel), Aurabon (UOP), and HDH Cracking (Intevep). Although several slurry-phase demonstration plants have been built, the pitch-disposal problem has kept it from gaining industry-wide acceptance. 

Shell is already producing ethylene/carbon monoxide polymers using a palladium-based SSC by a slurry phase process. BP and GE are working on similar technologies for the production of E/CO polymers. Norbornene and other cyclic olefins are very interesting and potentially low cost monomers that could be... 

Slurry-phase processes may involve either an inert diluent such as iso-butane or heptane, or condensed monomer such as propylene. In either case the catalyst particles are suspended and well mixed in the liquid medium. Monomer concentrations are high and the liquid provides good removal of the heat produced by the polymerization of the polymer particles. The two main reactors for slurry-phase olefin polymerization are the loop reactor and continuous-stirred tank. Slurry-phase processes are very attractive for high crystalline homopolymer products such as polypropylene and polyethylene. 

A single-step process for DME production from synthesis in which methanol is a co-product was also investi ted recently [8385]. The methanol synthesis, methanol dehydration, and water-gas shift reactions occur simultaneous in the reactor over mixed methanol and alcohol dehydration catalysts. The Air Products slurry-phase process has been tested over a wide range of operating conditions and offers the potential for both lower capital and operating costs compared with a multistep proeess in which methanol synthesis Irom synthesis is the first step of the process [83,85]. Most recently, a DME to methanol selectivity of 7624 mol% was claimed for a mixed-eatalyst system operated at 250°C and 65 mol% CO eonversion [84]. The productivity at these eonditions was 4.7 gmol/k of DME and 1.5 gmol/kgdi of methanol. These values compare with 95% DME selectivity and 51% methanol eonversion over a SAPO-16 catalyst at 425°C for the synthesis of DME from methanol [86]. 

In the Riillips slurry phase process (ref. 4) a hydrocarbon diluent, ethylene, catalyst, and comonomer if required, eu e charged continuously to circulating loop reactors eperating at about 40 atm. The crystalline pxslyethylene forms as discrete, free flowing particles in the presence of the diluent vp to a critical eperating tenperature, vhich depiends mainly on the... 

Most commercial processes produce polypropylene by a Hquid-phase slurry process. Hexane or heptane are the most commonly used diluents. However, there are a few examples in which Hquid propylene is used as the diluent. The leading companies involved in propylene processes are Amoco Chemicals (Standard OH, Indiana), El Paso (formerly Dart Industries), Exxon Chemical, Hercules, Hoechst, ICl, Mitsubishi Chemical Industries, Mitsubishi Petrochemical, Mitsui Petrochemical, Mitsui Toatsu, Montedison, Phillips Petroleum, SheU, Solvay, and Sumimoto Chemical. Eastman Kodak has developed and commercialized a Hquid-phase solution process. BASE has developed and commercialized a gas-phase process, and Amoco has developed a vapor-phase polymerization process that has been in commercial operation since early 1980. 

Eastman Chemical Company has operated a coal-to-methanol plant in Kingsport, Tennessee, since 1983. Two Texaco gasifiers (one is a backup) process 34 Mg/h (37 US ton/h) of coal to synthesis gas. The synthesis gas is converted to methanol by use of ICl methanol technology. Methanol is an intermediate for producing methyl acetate and acetic acid. The plant produces about 225 Gg/a (250,000 US ton/a) of acetic anhydride. As part of the DOE Clean Coal Technology Program, Air Products and Cnemicals, Inc., and Eastman Chemic Company are constructing a 9.8-Mg/h (260-US ton/d) slurry-phase reactor for the conversion of synthesis gas to methanol and dimethyl... 

Sizing, safety relief, 436, 437-441 API liquid valve, 444 Balanced valves, 441 Conventional valves, 438 Critical back pressure, 440 Effects of two-phase flow, 437 Hydraulic expansion, 441 Rupture disks, 434 Sub-critical flow, 449 Slurry flow, process pipe, 142-147 Regimes, 143... 

For the sake of developing commercial reactors with high performance for direct synthesis of DME process, a novel circulating slurry bed reactor was developed. The reactor consists of a riser, down-comer, gas-liquid separator, gas distributor and specially designed internals for mass transfer and heat removal intensification [3], Due to density difference between the riser and down-comer, the slurry phase is eirculated in the reactor. A fairly good flow structure can be obtained and the heat and mass transfer can be intensified even at a relatively low superficial gas velocity. 

Mueller JG, SE Lantz, BO Blattmann, PJ Chapman (1991b) Bench-scale evaluation of alternative biological treatment processes for the remediation of pentachlorophenol- and creosote-contaminated materials slurry-phase bioremediation. Environ Sci Technol 25 1055-1061. 

Another method of manufacturing polypropylene employs the liquid monomer as the polymerization solvent. This process, known as the liquid propylene or bulk-phase process, has a major advantage over the slurry method in that the concentration of the monomer is extremely high. The high concentration increases the rate of the reaction relative to that seen... 

Srivastava [434,435], The process can be carried out under aerobic (KSARC56) or anaerobic conditions (Mic-1). The identified products include methane, lower alcohols, volatile fatty acids, and/or humic acid. For aromatic feeds the main products are phenols (and derivatives), methane and carbon dioxide. The process is carried out in a slurry phase, at pH of 7.8, under moderate stirring using a bacteria concentration less than 20%. The feed concentration could not exceed more than 50%, as stated in the patent document. In the aerobic operation, the thermophilic consortium KSARC56 is operated for 48 hours at a temperature of up to about 60°C. For the anaerobic operation a mixture of N2 C02 of about 80 20 was used. 

Rao, V. U. S., Stiegel, G. J., Cinquegrane, G. J., and Srivastava, R. D. 1992. Iron-based catalysts for slurry-phase Fischer-Tropsch process Technology review. Fuel Process. Technol. 30 83-107. 

EP2 A process for polymerizing olefins in the slurry phase. Developed by Borealis. 

SPD [Slurry phase distillate] A process for making diesel fuel, kerosene, and naphtha from natural gas. Developed by Sasol and first commercialized in South Africa in 1993. A joint venture with Haldor Topsoe for the further development and commercialization of the process was announced in 1996. Commercialization in Nigeria was announced in 1998. 

SSPD [Sasol slurry phase distillate] A process for converting natural gas to diesel fuel, kerosene, and naphtha. Operated by Sasol in South Africa since 1993. Three stages are involved. In the first, natural gas is converted to synthesis gas by reforming. In the second, the synthesis gas is converted to waxy hydrocarbons in a slurry-phase reactor. In the third, the waxes are upgraded to middle distillates. See also Arge. 

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