From 09/23/2014 through 6/5/2012
Fluidized Bed Reactors
1. “In a typical polymerisation reaction, monomer, diluent, catalyst, co-catalyst and optionally co-monomer and hydrogen are fed to a reactor where the monomer is polymerised. The diluent does not react but is typically utilised to control solids concentration and also to provide a convenient mechanism for introducing the catalyst into the reactor. The reactor effluent, a mixture of polymer, diluent, unreacted (co-)monomer and hydrogen, is removed from the reactor and fed to a flash tank where the polymer is separated from the diluent and unreacted (co-)monomer and hydrogen. Typically, catalyst will be contained in the polymer.
Polymerisation processes of ethylene may be carried out in loop reactors. In the polymerisation reaction of ethylene, different reactants including the monomer ethylene, a light hydrocarbon diluent such as isobutane, a catalyst and optionally, a co-monomer such as hexene-1 and hydrogen are fed to a reactor. When polymerising ethylene, in the presence of a suspension of catalyst in diluent, said diluent having low solubility for the polymer, the polymer is produced in the form of solid particles, insoluble in the diluent. The contents of the reactor are circulated continuously with a pump to avoid deposition of polymer on the walls of the reactor. Slurry, consisting of the reactants and polyethylene powder, is typically collected in one or more settlings legs of the polymerisation reactor and discharged continuously to a flash tank, through flash lines, where most of the light hydrocarbon diluent and unreacted ethylene evaporates, yielding a dry bed of polyethylene in powder form. The powder is discharged to a purge drier in which the remaining light hydrocarbon and co-monomer are removed. Then the powder of polyethylene is transported to a finishing area where various stabilisers and additives are incorporated. Finally it is extruded into pellets.”
[Vandaele, US Patent 8,192,689 (6/5/2012)]
2. Many polymerization reactions are limited by high viscosity. It is difficult to reach high molecular weights because of slow transport in the viscous media. Chu developed a polymerization process based on two stages, a mechanical stage using deflecting blades or a rotating disk and a second stage based on gravity driven mixing by spinning. The first stage brings viscosity to 150 000 cP at 300 C while the second stage bring viscosity to 400 000 cP or higher at 300 C.
US Patent 8,796,401 (August 5, 2014), “Polymerization of High Viscosity Materials,” Yi-Lin Chu (Princo Middle East FZE, Dubai, Arab Emirates).
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Roger D. Corneliussen
Maro Polymer Links
Tel: 610 363 9920
Fax: 610 363 9921
Copyright 2012 by Roger D. Corneliussen.
No part of this transmission is to be duplicated in any manner or forwarded by electronic mail without the express written permission of Roger D. Corneliussen
* Date of latest addition; date of first entry is 6/19/2012.