Polymerization process using a dual shear mixing element
AssigneeNova Chemical (International) S.A.
InventorsAnnette Lynn Burke, Edward Christopher Foy, John Iatrou, Umesh Karnik, Darwin Edward Kiel, Vaclav George Zboril
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Abstract
A dual shear mixing element for use in a chemical reactor. The device may be used in processes where liquids of different temperatures need to be thoroughly mixed in a short period of time and solute must stay in solution. The present invention is particularly useful in the solution polymerization of polyolefins, especially in the medium pressure process for the preparation of linear low density polyethylene.
Claims5
A process for mixing a cooler liquid having a temperature from 80 to 200° C. into hotter solution having a temperature from 150 to 300° C. in a reactor comprising a closed cylindrical vessel having A) one or more inlets;
- B) one or more outlets;
- C) a ratio of height to diameter from 1.5:1 to 3:1;
- and D) internally a mixing element comprising in cooperating arrangement:
- a. a tube which defines an open interior space, said tube having a cylindrical top section, a flared bottom section, and a fixed stator between said top section and said bottom section, wherein said fixed stator partially constricts said open interior space in the area between said cylindrical top section and said flared bottom section;
- b. a combined auger and impeller comprising:
- b1. a central shaft rotatable within said tube;
- b2. at least one auger flight integrally attached to said central shaft so as to describe a helix about said central shaft, wherein said auger flight is located within, and rotatable within, said open space of said cylindrical top section of said tube;
- and
- b3. a series of impeller blades attached to said shaft below said fixer stator and said at least one auger flight at a distance sufficient to permit clearance between said fixed stator and said at least one auger flight, wherein said impeller blades are located within, and rotatable within, said open space within said flared bottom section of said tube, with the proviso that the rotation diameter of said impeller blades is greater than the rotation diameter of said at least one auger flight,
- said mixing element having a height from 0.75 to 0.90 the internal height of said reactor, at least one of said one or more inlets being located in the bottom of said closed cylindrical vessel and the flared portion of said tube being proximate said at least one inlet;
- wherein said cooler liquid has a temperature of at least 20° C. cooler than said solution;
- said process comprising introducing said relatively cooler liquid into said reactor through said inlet proximate said flared portion of said tube and rotating the central shaft at a speed sufficient to provide turbulent conditions within said flared portion.
Dependencies are inferred from the claim text.