Patent GB-359022-A (GB)
Title: An improved process and apparatus for the cracking or for the cracking and destructive hydrogenation of hydrocarbons
Filed: 1930-07-15
Abstract: In a process for obtaining low-boiling products from petroleum oils e.g. crude oil, kerosene, gas oil, topped crude oil, asphaltic oils, the feed oil, preheated if desired, is admitted to a vaporizing zone at atmospheric or higher pressure, e.g. at 500 lbs. per sq. inch., an intermediate condensate is withdrawn and cracked, the whole of the products of cracking are returned to the vaporizing zone where they meet the unvaporized part of the feed oil, and the vapours and the liquid residue are withdrawn from the vaporizing zone.  The intermediate condensate may be cracked in apparatus of the nature of a coil, or a coil and one or more conversion chambers.  In the former case the cracking is effected largely in the vapour phase.  The temperature in the coil may be from 750 DEG  to about 1500 DEG  F. and the pressure 50-3000 lbs. per sq. in. or more.  The temperature in the conversion <PICT:0359022/III/1> <PICT:0359022/III/2> chambers may be from 750 DEG  to 850 DEG  F. or more, and the pressure may be the same or higher than in the coil.  The pressure in the vaporizer may be lower than in the cracking treatment, e.g. atmospheric, or 500 lbs. per sq. in. or more.  The temperature in the vaporizer is regulated so that the vapours yield gasoline, naphtha, and light kerosene, whilst heavier fractions form the intermediate condensate and residues.  The temperature in the lower part of the vaporizer may be 600-700 DEG  F.  The residue from the vaporizer may be submitted to destructive hydrogenation, or it may be distilled and the vapours returned to the process.  The distillation may be carried to dryness, or a liquid residue may be withdrawn and such residue may be submitted to destructive hydrogenation.  The intermediate condensate from the vaporizer may be admitted, directly or after removing lighter fractions by distillation, at various points of the cracking system and the flow may be regulated in order to control the temperature of the cracked products and of the vaporizer.  Part of the coil may be byepassed for the same purpose.  The vapours from the vaporizer and from the various stills are fractionated, together or separately, to recover gasoline and other products.  As shown in Fig. 1, feed oil is forced by pump A through a preheating coil C in the upper part of the vaporizer D, and thence through a branch S into the vaporizer.  In starting up the process, the feed oil is passed direct to the heating and cracking coil F.  This coil comprises successive sections G, H, J.  The cracked products pass through line K to the vaporizer and are separated into vapours which are led off at L to fractionators and condensers.  An intermediate condensate which collects in the pan N, and a liquid residue which can be withdrawn at M and may pass direct to destructive hydrogenation plant.  Steam may be injected into the liquid in the vaporizer at T.  The intermediate condensate is forced by pump O through line P to the inlet section G of the cracking coil or part may be passed through branch Q to the end section J or through branch R to the outlet end of the coil. Part of the oil may pass from the section G through byepass U to the outlet end of the coil.  A form of the process in which the oil is treated in separate heating and cracking zones is illustrated in more detail in Fig. 4.  Feed oil is forced by pump 2 through a heating coil 4 in a furnace 5 and thence to the vaporizer 7. Valved byepass lines 90, 91, 92 permit passage of part of the oil through cooling coils 8, 9 in fractionators 10, 11 for the cracked vapours, and of part direct to the vaporizer 7.  The coil 4 may also be byepassed at 13.  The <PICT:0359022/III/3> vaporizer 7 and the cracking coil 23 are arranged as described above.  Feed oil may be passed through the cooling coil 16 in the vaporizer direct to the cracking coil whilst starting up. Products from the coil pass through line 29 and branches 31, 33, 34 to the heat-insulated conversion chambers 30, 32 which may be connected in series or in parallel.  Oil in the chambers 30, 32 may be agitated by stirrers or it may be re-circulated by pump 52, through lines 53, 53<1>, or returned through line 45 to the coil 23. The vaporizer may be fitted with bell-capped plates as shown in Fig. 5, arranged so that the heavy unvaporized oil does not mix with the intermediate condensate.  The oil is admitted at S and the part not vaporized in the upper and cooler regions passes from the second plate D<1> through pipe D<11> to the lowest and hottest region, where cracked products are admitted at K.  Vapours liberated in the lower part of the vaporizer pass up through all the plates D<1> and the intermediate condensate collects in the drip-pan N.  The vaporizer may be fitted with cooling coils C<1>, W, and a heating coil V, which are independent of the feed oil.  Intermediate condensate may be recirculated through lines 19, 22, 37, Fig. 4, and branches 38 . . 41, 22<1>.  The residue from the vaporizer may be withdrawn at 44, and it may be pumped through line 45 to the inlet of coil 23 when starting up, or it may be recirculated through branches 47, 48, 40. The vapours leave the vaporizer through the pressure-control valve 55 and pass through line 54 to fractionators 11, 10.  The fractionators are provided with cooling coils 59, 58 independent of the feed oil and with steaminjection pipes 60.  The condensates are returned to the vaporizer 7 by pump 80 or they are passed through coolers 61, 62 to storage; whilst the vapours pass on to a condenser 64.  Gases and uncondensed vapours from 64 may be heated to dissociation temperatures and used in destructive hydrogenation plant. Intermediate condensate from the vaporizer 7 may be distilled, with or without steam, in the still 66 under a higher pressure than that in the vaporizer and fractionators, and the residue from the still may be withdrawn at 68 or returned through lines 68<1>, 37 to the coil 23. Vapour from the still 66 pass through line 69 to the fractionator 11, or through branch 70 to the vaporizer 7.  The residue from the vaporizer may be withdrawn through line 71 by pump 72<1> and heated in stills 74, 75 by steam or direct heat or both, preferably at a higher pressure than in the vaporizer 7.  The final residue may be withdrawn by pump 94 and passed to destructive hydrogenation plant.  The vapours from stills 74, 75 pass through lines 78, 81 to the vaporizer 7, or through branches 82, 83 to the fractionator 11, or through branch 84 to a fractional condenser 85. The condensate from 85 may be returned to the still 66 or the coil 23 and the vapours may pass to the vaporizer 7 or the fractionator 11. In another form of apparatus, Fig. 3, Provisional (not shown), the conversion chambers 30, 32 are dispensed with.  In each form, pumps and valves are provided to control the flow as desired and to permit of the desired pressures in the different parts of the plant, and check-valves prevent back flow into the lines leading to the cracking coils and conversion chambers.  Specifications 359,023 and 359,026 are referred to.