Patent GB-470576-A (GB)
Title: Improvements in the cracking and coking of hydrocarbon oils
Filed: 1936-02-17
Abstract: In a process for cracking and coking oils an intermediate product of the process collected on a tray 78 at the bottom of a fractionating tower 27 is cracked in a coil 1 and the cracked products passed into a converter 5 in which <PICT:0470576/III/1> the vapours are fractionated in the tower 27 to provide the heavy intermediate product referred to above and a lighter fraction collected in a re-boiler 87 and this lighter fraction after passage through the heat-exchanger 24 and lines 96, 97, is subjected to an independently controlled conversion in a coil 100, the products obtained being passed (1) in part through lines 138, 18, 18<1> into the lower part of the coking chambers 16, (2) in part through a line 139 into the upper portion of the converter 5.  When liquids and vapours are withdrawn separately from the converter 5 the vapours are withdrawn through a line 20 and passed through a heat-exchanger 24 and line 25 into the tower 27 while the liquids are directed through lines 7, 13, 14, 14<1>, or 17, 18, 18<1> into the upper or lower parts of the coking chambers.  Alternatively, liquids and vapours may be withdrawn together through lines 7, 9 and flashed in the chamber, the vapours then passing through line 28 to the tower 27, while liquid residues are passed through lines 52, 13 to the coking chambers. Modifications comprise passing the residues in part (1) through lines 52, 57 and cooler 60 to storage, or (2) through line 62 into the line 7. Condensate condensed in the heat-exchanger 24 is stored in accumulator 32 from which it is withdrawn and pumped through line 38 and optionally through cooler 41 either into line 47 or through line 44 into the top of the converter 5. Alternatively, the condensate may be mixed with heavy condensate from the line 83 and with residues from the chamber 11 passed through the line 68, the mixture separation of liquids and vapours takes place, the liquid products with or without flashing in a flash chamber are passed into the upper or lower portions of coking chambers 16, 16<1>, being pumped by the pump 37 through the line 38 as described above.  Raw oil charging stock is supplied through lines 73, 76 to the fractionator 27 from the top of which the vapours of desired end-point are withdrawn through line 102, condensed in cooler 103, and collected in receiver 106. Part of this stock mixed if desired with extraneous fractions supplied by a pump 118 are re-cycled as reflux through lines 112, 114.  Gases are passed through line 122 to a scrubber 123 where condensible constituents, e.g. butane, are removed by scrubbing with an absorber oil and the enriched oil is passed through line 136 to mix with the reflux condensate from the column 87 passing to the coil 100 or through line 136<1> to mix with the fraction passing through line 81 to the coil 1.  The coking chambers are used alternately to permit reconditioning which is carried out by purging with air or steam and then reheating by introducing part of the liquids in the chamber in use through lines 145, 148 into the chamber being reconditioned.  Vapours withdrawn from the coking chambers are passed (1) through lines 149, 151 to the flash chamber 11, or (2) through line 151 to a column 153 from which heavy reflux is re-cycled through line 157 to the coking chambers or the cracking coils while vapours pass off through line 159 heat-exchanger 180 and condenser 161, to receiver 164 from which condensate may be re-cycled to the column 153 or column 27.  Specifications 405,721, 413,927, and 472,304 are referred to.