Polymerization reactor for butyl rubber production

摘要

A low temperature polymerization reactor for the production of butyl rubber by catalytic polymerization of isobutylene with small amount of a conjugated diolefin such as isoprene includes: an extended upper head with fluid deflector fixed to the top tube-sheet, the shapes of the head and deflector being optimized in order to reach a very homogeneous slurry velocity in the rows of tubes and to minimize the pressure drop due to the inversion of flow from up-flow to down-flow and to the entrance of the slurry in the tubes; an hemispheric bottom head with fluid deflectors placed between the impeller and the bottom itself and designed to minimize the pressure drop due to the inversion of flow from down-flow to up-flow; and straightening baffles inside the draft tube, which shape and dimensions are optimized to turn the radial velocity components produced by the rotation of the impeller into axial velocity components.

主权项

1. A single pass shell and tubes type polymerization reactor (1), used to produce butyl rubber in slurry, copolymerizing at least 95 wt % of isobutylene with not more than about 5 wt % of isoprene, in concentration of about 35% to 45% by vol. in a solvent, preferably methyl chloride, in presence of 0.015% to 0.15% by weight of catalyst, preferably aluminum chloride, and at a temperature within the range of −104° C. to −90° C., wherein the velocity in the tubes is in the range from 2.4 to 4.5 m/sec, wherein the reaction mixture is introduced from the bottom side near an impeller shaft (5) and the outflow (11) is in the top, with the reaction in tube side and a cooling media in the shell side (19) to remove the heat of reaction, and a circulation pump installed at the bottom (4), to permit high velocity of the rubber slurry in the central draft tube (2) and in downflow smaller tubes (6), the reactor comprising:
a—an extended upper head (3), containing a fluid deflector (15), having an inclined bottom up drop shape cross section partially cut at its bottom portion, wherein the shape of the head and of the deflector are sized to reach a very homogeneous slurry velocity in the rows of tubes (6) and to minimize the pressure drop due to the inversion of flow from up-flow to down-flow and to the entrance of the slurry in the tubes (6); the vortex at the entrance of the tubes being also minimized, while is eliminated any bad slurry distribution occurring in single pass of the old conventional design; b—an hemispheric bottom head (4) with a first fluid deflector (17), having an inclined drop shape cross section partially cut at its upper portion, and a second fluid deflector (18) having a trapezoidal section, located around the first deflector (17), sized to minimize the pressure drop due to the inversion of flow from down-flow to up-flow; c—three straightening baffles (7) in the draft tube (2), having a periodicity of 120° and designed as surfaces with a lower curved part and an upper straight radial part and the curved part is constructed as a sequence of radial segments in order to turn the tangential velocity components produced by the rotation of the impeller (5) into axial velocity components, allowing an increased hydraulic efficiency, wherein such combination improving substantially the homogeneity of the velocity and reducing the overall pressure drop, allows an increased circulation in the bottom pump and longer reactor cycles.