Patent GB-700826-A (GB)
Title: Improvements in or relating to condensing systems for distillation columns
IPC: B01D5/00
Filed: 1951-08-28
Abstract: The condensing chamber 2 disposed in the upper portion of distillation column 1 has an open top and side walls 4, 8, 7, 5, spaced from the sides of the column so that the fractionated vapours pass upwards through passages 3 between the outside walls of the chamber and the sides of the column and then flow downwards through the chamber.  This chamber contains 1st stage condenser tubing 12, 12a, 12b, and associated collecting wells 10 for the 1st stage condensate, conduits 27 for discharging the 1st stage condensate from the column, 2nd stage condenser tubing 13 disposed below the 1st stage tubing and having an associated condensate collecting well 11 and withdrawal conduit 28, baffle means 29 between the 1st and 2nd condensing stages, and an offtake conduit 25 for leading uncondensed vapours from the lower portion of the chamber to the exterior of the column.  Baffle plates 29 intercept all the condensate falling from the tube bundles 12, 12a, 12b, and divert it over curbs 30 into the two side wells 10 so that this 1st stage condensate is prevented from reaching the 2nd stage condensing <PICT:0700826/III/1> <PICT:0700826/III/2> stage; undesired cooling of the 1st stage condensate is thereby obviated.  The vapour offtake conduit 25 extends horizontally through chamber 2; one end of it being welded blind to the column and the other end protruding from the column. The upper side of the offtake has a slot 26 extending along most of the length of the offtake within the chamber.  Suction may be applied at the protruding end of of the offtake to obtain a required vacuum within the column.  Baffle plates 32 are mounted over the offtake in order to divert condensate falling from tube bundle 13 away from the offtake into the well 11.  Both sets of baffles 29, 32, reduce entrainments of condensate in the vapour stream by causing abrupt changes in course of the vapour.  Each bank of tubes has headers 16, 17 which are secured to tube sheets 14, 15 respectively.  Each header 16 has an inlet (not shown) and an outlet 19 for circulating cooling fluid through the tubes of each bundle.  The cooling fluid may be circulated through the three upper tube bundles in succession.  Each tube bundle is supported in position by means of horizontally aligned frames 21, 22, welded to opposite sides of the column and flanged at their outer ends. Header 17 is slidably received by frame 22, which is closed by cover 23; and header 16 is secured to frame 21.  Track members 24, secured to the chamber walls 4 or 5 and to the column, extend between frames 21 and 22, and facilitate the endwise withdrawal of the tube bundles from the column, when desired. Reduced crude petroleum may be fractionated in the column in order to separate gas oil required for catalytic cracking.  The temperature of the 1st stage condensate may be in excess of 500 DEG F., while that of the 2nd stage condensate may be about 250 DEG F.  The discharge through conduits 27 may be three times that through conduit 28.  The charge may be preheated by using it as cooling fluid in the 1st condensing stage; it is then supplied to the inlet of bundle 12 and withdrawn from the outlet of bundle 12b.  Water may be used as the cooling fluid in tube bundle 13.