US1791114A - Process and apparatus for cracking petroleum oils - Google Patents

Description

D. G. BRANDT Feb. 3, 1931.

PROCESS AND APPARATUS FOR CRACKING PETROLEUM OILS Filed May 5, 1927 MUFmI XSI-LUM ww mokwmmw Q xm.

|lSnam/1Mo@ n DAV/D e. BRA/V07 @ZM /1/'5' @Into/1MM?? Patented Febc 3, 41931i DAVID G. BRANDT, F WFSTFIELD, NEW JERSEY, ASSIGNOR TO DOHERTY RESE'lRCIFlC COMPANY, OF NEW YORK, N. Y., A CORPORATION 0F DELAWARE PROCESS AND' .APPARATUS FOR CRACEING PETROLEUM OILS Application filed May 3, 1927. Serial N0. 188,416.

T his invention relates to an improved process and apparatus for the treatment of petroleum oils and more particularly for the cracking of high boiling point oils to produce oils having lower boiling points.

The usual practice in cracking oil is to employ a gas oil as a raw cracking stock. rlhere is an urgent desire to crack heavy fuel oil but the cracking of the heavy oil has been limited on account of the amount of deposition of carbon which occurs While the oil is being circulated through the furnace. In practically all the cracking processes now in commercial use7 the raw oil7 even though it be fuel oil, is circulated through a pipe still and heated to a comparatively high temperature. vWhen fuel oil is circulated through the ppe still the coils soon clog with carbon.

rlhe primary object of the present invention is to provide a process and apparatus by which the charging stock may be effectively cracked in a cracking chamber without subjecting it directly to the high temperature of the heating furnace.

A further object of the invention is to control the amount of oil vaporized in the crackin;l chamber and consequently the amount of reflux condensate produced.

These as well as other objects and advantages, which will be apparent from the detailed description given hereafter, are accomplished by preheating` the charging oil and passing it to the cracking chamber where 1t cracked by contact with hot vapors and oil from highly heated reflux condensate and residuum distillate which have been independently heated in separate pipe still furnaces,'the amount of reflux condensate produced being controlled by supplying a regulated quantity of gas along with the oil (reflux or residuum distillate) being passed to the furnaces.

The invention will now be described in-detail, reference being made to the accompanying drawing forming a part of this specification and in which The figure is a diagrammatic side elevational view of the apparatus with certain parts broken away and shown in section, in

which the preferred process of the invention may be carried out.

The oil to be cracked which is preferably a fuel oil, a topped crude oil or a high gravity crude oil of a paraffin or asphaltic base, is

introduced into the system under pressure from a pump (not shown) through the pipe 2 which connects with a series of heat interchange coils 4 mounted in a dephle mating section 6 of a combined cracking and ephlegmating tower 8. ln the dephlegmator G the charging stock is heated by hot vapors passing upward through the perforated or bubble capped trays 10 and a reflux condensate is produced which flows from tray to tray and finally collects in the lower part of the dephlegmating section on a partition 12 in which are mounted pipes 14 having open upper ends through which the vapors enter the dephlegmator. The lreflux condensate is withdrawn from the lower part of the dephlegmator by a pipe 16 and pump 18 and passed under high pressure through conduit 2O and reflux heater 22 where the oil is heated to a temperature sufficiently high to crack the major portion of the condensate. From the heater 22 the highly heated reflux is delivered by valved pipe 24 to the upper end of a vapor-liquid separator 2G. This separator is preferably of the vertical cylindrical type7 in the upper part of which is a funnel-like partition 28 with the neck of the funnel extending nearly to the bottom of the chamber so that the oil separated from the vapors in the upper compartment flows out the funnel tip 29 at the bottom and upward around the same where it is discharged near the top of the separator by a conduit 30. rlhe oil leaving the separator 26 by the conduit 30 is passed direct to the upper portion of a cracking chamber 32 which comprises the-lower part of the tower 8. Although the reflux condensate is'heated above its cracking temperature in the heater 22 there is only a comparatively small amount of cracking carried on in the heater 22 because the oil is circulated so rapidly through the heater. The major portion of the cracking takes place as a time re1 action, while the oil is circulating downwardly through the funnel 28, upwardly through of the cracking chamber, to the lower part of the cracking chamber Where they are distributed into the body ot oil therein by an annular distributor 36, which connects directly with the pipe 84.

The charging stock consisting of the high gravity oil, either a fuel oil or a topped crude, is preheated in the dephlegmating section to substantially its cracking temperature. llt `Will be noted however that the high gravity charging stock Will be cracked at lower tem peratures than the reflux condensate which is heated in the heater 22. After the charging stock has circulated through the coils 4 it passes by means of a conduit 38 into the lower portion of the separator 26 -vvhere it is distributed in the body ot oil derving through the separator 26 by a distributor 40 adjacent the tip 29 of the tunnel 28. When the charging stock is mixed with the hot oil passing through the separator 26, the resulting temperature ot the mixture is suciently high to crack the charging stock oil as the furnace heated stock which is circulating through the separator is mixed with the charging stock. This mixture of oil leaves the separator and passes through the cracking chamber where the cracking reaction is continuously carried on./ 'llhe cracking of this oil mixture is materially assisted by the introduction of high temperature vapors through the distributor 36 in the bottom of the cracking chamber.

Vapors leave the cracking chamber 32 by the pipes 14 referred to above and those vapors not condensed in the dephlegmator (which are preferably only gasoline vapors and Iixed gas) are led by valved vapor line 42 into a `:vater cooled condenser 44 Where the inal condensate is produced, which with the lixed or non-condensable gases pass through jconduit 46 to gas-liquid separator and container 48. Condensate is Withdrawn from container 48 by valved pipe 50 While the xfed gases are Withdrawn by pipe 52 which connects with a pump 54 which in turn is used to supply gas to the cracking system as referred to hereinafter. Excess gas from the system is delivered to any 4desired point ot consumption by valved pipe 56 which connects with gas main 52.

lltesiduum is Withdrawn trom the separator merrie and the cracking chamber by valved pipes 58 and 60 respectively into main 62 by which it is conveyed to the concentrator 64. 'l`his Withdrawn residuum is distilled in the concentrator 64 by releasing the pressure and using the potential heat of the mass to supply the necessary heat. rl`he vapors issuing from the mass of residuum in the lower part of the chamber 64 pass up through a neck 66 of an inverted funnel-like partition 68 into a dephlegmating compartment cont-aining plates T0 yWhich may be provided Wit-h bubble caps and over-tlovv pipes T2. All volatiles distilled from the residuum except ing the gasoline are preferably condensed in the chamber 64 vvhile the vapors containing gasoline are led by a vapor conduit 74 to a xvater cooled condenser T6 from which condensed gasoline is removed to storage by valvcd pipe 78.

'l`he condensate formed in the upper portion of concentrator 64 collects on the partition 68 and is Withdrawn through pipe 80 by pump 82 and passed under high pressure through conduit 84 and heater 86, where the oil is raised to a high temperature, the heated product being passed through a valved conduit 88 into the upper compartment ot the separator 26 where it mingies With the heated products from the heater'22. llrom this point the heated vaporized and unvaporized portions of the residuum distillate follow the same course as that followed by the reux condensate from heater 22, as described above.

The heaters 22 and 86 may be ot any approved construction but are preferably ot the pipe still furnace type in which the oil is passed 1n a single stream through a pipe coil mounted therein. n

llt for anv reason the residuum Withdrawal lines 58 and 60 should become clogged or the valves become inoperative or it is otherwise found desirable, residuum may be Withdrawn through the valved lines 90 and 92 connecting the main 62 respectively with the separator and the cracking chamber.

ln order to control the quantity of oil vaporized in the cracking chamber 32, gas under pressure from pump 54 is passed by a conduit 94 through a heat exchanger 96 where the gas is heated by the residue from the distilled residuum Withdrawn from the lower partof concentrator 64 by valved pipe 98. rlhe cooled residuum which ordinarily is of the fuel oil type is Withdraw-n from the exchanglll@ er 96 by pipe 100 ivhile the heated gas whereby more oil vapor is produced and carried from the cracking chamber into the dephlegmator thus giving an increase in re-` iiuk condensate. Likewise a reduction in the amount ot' gas introduced into the system will reduce the amount of reflux condensate.

Instead of reducing the pressure on the residuum in the concentrator in order to effect its distillation it may be distilled under the same or any lower pressure than the pressure existing in the cracking chamber by introducing gas from was main 102 through valved pipe 108 and distributor 110 placed in the bottom of the concentrator 64. The introduction of a gas into the hot residuum has the same eiect as a physical reduction in pressure because the gas creates a partial pressure of the vapors and at the same time removes them from the mass.

Between the oil eed lines 2() and 84 is shown a valved connecting pipe 112 by which oil may be passed from one line to the other for equalization of pressure if desired or in case of accident with one of the furnaces 22 or 86 the valve in either line 2O or 84 may be closed and all the oil passed through the other heater by opening the valve in pipe 112. However in normal practice it is essential that the oil from the two sources be heated separately since the reflux oil has a lighter gravity than the residuum distillate and therefore can be heated to a higher temperature.

1n carrying out the process of cracking hydrocarbon oils according to the invention, preheated charging stock entering the separator 26 from the distributor 40 is heated substantially to the cracking temperature by the hot vapor and oil in the dephlegmator so that it commences to crack in the separatei' and continues to crack in the cracking chamber since it is further heated by the hot vapor and gas coming direct from the separator'and entering the cracking chamber from the distributor 36. It will be observed that the oil is contacted with the vapors rising from the distributor 36 as soon as it enters the cracking chamber, so that by the time it slowly works its way to the bottom of the cracking chamber, it has had ample time to complete the cracking operation.

In addition to cracking the charging stock a certain proportion of the reflux condensate and the residuum distillate will be crackedto produce gasoline, as a result of being heated to a high temperature under pressure in the heaters.

The pressure used in the cracking chamber may vary from atmospheric to several hundred pounds per square inch but to 200 pounds per square inch has been found to give satisfactory results. Various parts of the apparatus may be maintained under different pressures by proper manipulation of the valves in conduits 24, 88, 42 and 50.

While a large part of the residuum may Abe withdrawn from the cracking chamber it may be desirable when operating under certain conditions, such as under extremely high temperatures in the heaters, to withdraw all the separated oil leaving the tip 29 ot the funnel-like partition 28 directly into the concentrator 64. This may be done by proper regulation oit/the valve in pipe 58 so that residuum is withdrawn equal in amount to the oil discharging from the tip 29. Due to the difference in character of the charging stock and the residuum an imaginary boundary may be maintained near the tip 29 between the two oils by regulation of their flow as pointed out above.

'llhe relative amounts of residuum withdrawn from the chambers 26 and 32 are in any case, preferably regulated so as to control and maintain the proper cracking temperature in each chamber and also to control and regulate the concentration of carbon forming materials in these two chambers so that. as little carbon as possible will be formed. The removal of hot residuum from either chamber naturally has a tendency to reduce the temperature and therefore the withdrawal should be proportioned between the two chambers in order to maintain proper cracking temperatures in each. Likewise the withdrawal of the heavy tar and sludge from the chambers lowers the concentration of these carbon forming materials and therefore the withdrawal should be proportioned between both chambers in order to `keep the concentration of carbon forming materials. below the saturationpoint or below the point at which appreciable amounts of carbon are 'Ulft formed. llt, for example, it is attempted to withdraw all the residuum through the outlet 60, the temperature in chamber 26 may rise relatively higher than in chamber 32. This higher temperature coupled with the non-withdrawal of residuum-rom chamber 26 soon prod-uces a condition of over saturation of carbon forming materials in the oil and as a result large .amounts of carbon and coke will be formed,

By proper regulation of the residuum removal from both chambers defects such as this may be overcome.

Ithas beenidetermined that the production of carbon in the cracking of mineral oils also gives rise to the simultaneous production of fixed gas. In accordance with the present invention applicant makes use of returned fixed gas in the cracking chamber to decrease the formation of like products and to restrain the formation of carbon, in addition to the functions of the gas referred to above. 'llhe formation of xed gas and carbon is prevented or decreased by theoperation of the law of mass action, the introduction of xed gas formed in the process, serving to shift the equilibrium so that the formation of these undesired products is reduced to a minimum. The regulation of the amount of fixed gas returned, together with the residuum withdrawal referred to above gives a vvery effective control on the forniation of carbon in applicants oil cracking system.

A considerable body of reflux condensate may be maintained around the tubes 14, in order to accommodate any fluctuations in the amount of oil passed by the pump 18 to I the heater 22.

rlFhe separator 26, tower 8 and concentrator 64e. are shown as being covered with heat insulating material. Conduitsl carrying hot or preheated oil, vapors or gas may be in.- sulted in the same manner.

Having thus described my invention, what ll claim is:

1. The process of cracking petroleum oils under superatmospheric pressure, which comprises, passing charging stock in heat interchange relation to but out of contact with oil vapors in a dephlegmator whereby a reflux condensate is produced, passing said condensate through a heater under pressure whereby highly heated oil and vapors are produced, separating highly heated vapors from highly heated oil in a separating Zone, passing said highly heated vapors under pressure into a body of oil to crack the same, withdrawing residuum from said body and list-illing it, independently heating the resulting distillate under pressure t-o a high temperature and passing the heated distillate into said separating zone.

2. 1n the method of cracking petroleum oils in which a reflux condensate is produced from vapors from a cracking cham-1 ber and adistillate is produced from residuum withdrawn from the crackingchamber, the improvement which comprises passing said condensate and said distillate` under super'- atmospheric pressure through independent heaters and discharging the resulting heated products into the cracking chamber.

3. The method defined in claim 2 in which the amount of reflux condensate produced is separating zone into said craczking zone, heating the oil in said cracking zonevby intimately mingling therewith the vapors from said separating zone and maintaining a superatmospheric pressure during said heating.

5. T he process defined in claim 4 in which said charging oil isk passed in heat interchange relation to but out of contact with vapors in said dephlegmator.

6. The process of cracking petroleum oils. which comprises preheating a charging oil by pa-ssing it in heat interchange relation to but out of contact wit-h oil vapors from a cracking chamber, passing the preheated charging oil directly into said chamber, withdrawing residuum from said chamber Iand dist-illing it, heating the distillate thereof to a high temperature and cracking said preheated oil by contacting therewith said highly heated distillate.

7. rl`he process defined in claim 6 in which a preheated gas is mixed with said distillate before said heating.

8. ylhe process of cracking petroleum oils, which comprises passing charging stock in heat exchange relation to but out of contact with oil vapors from a cracking chamber whereby said charging stock is preheated and reiuX condensate is produced from' said 'vapors, passing said preheated charging stock into said cracking chamber tomaintain a body of oil therein, withdrawing residuum from said chamber, distilling said residuum, heating said reflux condensate and the re-l siduum distillate under superatmospheric pressure to a cracking temperature and cracking said charging stock in said chamber by contacting therewith said highly heated condensate and distillate.

9. rllhe process of cracking petroleum oils, which comprises maintaining a heating zone and a cracking zone, introducing the oil to be cracked only into said cracking zone, withdrawing residuum from said cracking zone and producing a distillate therefrom,-

heating said distillate to a cracking temperature in said heating zone and cracking the oil introduced into said cracking zone by contacting therewith said highly heated distillate.

10. IThe process defined in claim 9 inwhich said oil to be cracked is preheated prior to its introduction into the cracking zone and a gas is mingled with said distillate prior to said heating.

An apparatus for treating oils comprising a cracking still, a dephlegmator receivmg vapors from said still, aT distilling qll mamie chamber receiving residuum from said still, means for heating refiux condensate from said dephleglnator, independent means for heating distillate from said distilling chamber, a vapor separating chamber. means for passing heated products from said heating means to said separating chamber and means for passing oil and vapors from said separator into said cracking still. Y

12. The apparatus defined in claim 11 in which means are provided for introducing' charging oil into the separating chamber.'

13. An apparatus for treating oils comprising a cracking still, a dephlegmator receiving vapors from said still, a distilling chamber receiving residuum from said still, means forheating reflux condensate from said deephlegmator, independent means for heating distillate from said distilling chamber, and means for passing heated products from said heating means into said cracking still.

14. 1n the method of cracking petroleum oils in which a reflux condensate is produced from vapors from a cracking chamber and a distillate is produced from residuum Withdrawn from the cracking chamber, the improvement which comprises heating the said condensate and distillate to a cracking temperature and introducing the resulting highly heated products into the cracking chamber, passing gas into the oil in the cracking chamber, and regulating the quantity of gas introduced to control the relative quantity of reflux condensate produced and the amount ofvaporizable oil left in said withdrawn residuumvwhich is thereafter Vaporized to produce said distillate.

15. In the process for cracking mineral oils in which oil is passed under pressure through a heating zone then into a separating chamber where vapors are separated from unvaporized oil, and in which the resulting vapors and unvaporized oils are brought into intimate contact in a cracking still, the improvement which comprises introducing fresh charging stock comprising a heavy mineral oil into intimate contact with said unvaporized oil in said separating chamber.

16. The process of cracking petroleum oils7 which comprises maintaining an oil heating zone and a cracking zone, introducing oil to be cracked into said cracking zone and maintaining an-enlarged body of oil therein, withdrawing residuum from said cracking zone into a still, introducing gas into the withdrawn residuum to produce a distillate therefrom, passing the resulting distillate through said heating zone wherein it is heated to a high temperature, and passing the resulting highly heated products into contact with the oil in said cracking zone.

17. In the process of cracking mineral oils y in which a body of oil is maintained at a cracking temperature in a cracking zone and residuum is withdrawn therefrom and distilled, the improvement which comprises passing the distillate produced from said residuum without mixing the same with any other oil, directly through a high temperature heating zone, and passing the resulting highly heated product into said cracking zone into contact with the body of oil therein.

18. The process of cracking petroleum oils, which comprises preheating a charging oil by passing it in heat interchange relation to but out of contact With oil vapors from a cracking chamber, passing the preheated charging oil directly into said chamber, withdrawing residuum from said chamber and distilling it, subjecting the vapors produced from said residuum to reflux condensation to produce a reflux distillate therefrom. heating the said distillate to a cracking temperature, and cracking said preheated oil by coutacting therewith the highly heated products of said distillate.

19. rlhe process of cracking petroleum oils, Which comprises maintaining a heating Zone and a cracking Zone, introducing fresh feed oil to be cracked into said cracking zone, Withdrawing residuum from said cracking zone and distilling the same, subjecting the vapors from said residuum to reflux condensation to produce a reflux distillate therefrom, heating said distillate to a cracking temperature in said heating zone, and cracking the oil introduced into said cracking zone by contacting therewith the highly heated products of said distillate.

20. 1n the method of cracking petroleum voils in which a reflux condensate is produced from vapors from a cracking zone and a distillate is produced from residuum withdrawn from said cracking Zone, the nnprovement which comprises passing said condensate through one heating Zone and said distillate through a second heating zone under superatmospheric pressure, heating the said condensate and the said distillate to a high teinperature in said heating zones, and discharging the resulting highly heated products from said heating zones into said cracking zone.

In testimony whereof I aiiix my signature.

DAVID G. BRANDT.

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