US1982091A - Conversion of petroleum oils - Google Patents

Description

Nov. 27, 1934.

A. R. WORKMAN CONVERSION OF PETROLEUM OILS Filed June 1'?, 1929 Sh. www @Y v Q\ \&v wQr No.

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vwenf'oz ARNOLD Fi. WORKMAN omai 1 mvdw I Patented Nov. 27, 1934 UNITED STATES PATENT OFFICE CONVERSION OF PETROLEUM OILS Arnold R. Workman, Malverne, N. Y., assigner to Doherty Research Company, New York, N. Y., a corporation of Delaware Application June 17, 1929, Serial No. 371,416

4 Claims. (Cl. 196-48) This invention pertains to the art of pressure From the pipe 2 the preheated oil passes by a distillation of petroleum oils, and particularly to pipe 10 into a hot oil surge tank 12, from which that portion of the art relating to the conversion it is passed through a pipe 14 and pump 16 of higher boiling point oils into oils of lower under a relatively high superatmospheric presboiling point by cracking the same at higher temsure through a heater 18 of the pipe still furnace 60 peratures under superatmospheric pressure. type. During the passage of the oil through the In the fractional distillation of crude petroheater 18, it is gradually heated to a temperature leum oil or its distillates and residues for the o J.from 750 F. to 925 F., or to a point at production of denite marketable products, conu which the oil will crack. The highly heated siderable care is taken to maintain the products products from the heater 18 are conducted 65 within certain distilling ranges and to remove through a transfer line 20 into an enlarged crackfrom any particular distillate relatively light or ing chamber 22 in which a body of oil may be heavy ends which may be undesirable in the maintained at a cracking temperature for a sufresulting product or desired in a different prodficient time to convert substantial quantities of uct. Commercial cracking processes however are the oil. 70

carried on without regard to the recovery, for In starting up the apparatus the oil from chamexample, of the light en'ds such as gasoline conber 22 may be conducted through a valved pipe tained in the recycle stock, which should be 24 directly back to the surge tank l2 until the removed and not returned to the heating zone cracking unit has been brought to the desired of the cracking unit. cracking temperature and pressure. The cracked 75 The primary object of the present invention is vapors from the chamber 22 are conducted theretherefore, to provide an improved process for from through a valved vapor line 26 into the lower converting petroleum oils in which the recycle portion of the reliux tower 8 through which the stock or any intermediate distillate withdrawn vapors pass and are subjected to rectifying and from the system is stripped of its content of reux conditions. rIhe tower 8 is preferably of 80 light constituents having the character of presthe bubble tray type so that as the vapors pass sure distillate or gasoline. from tray to tray they are brought into an inti- In accordance with this object the invention mate contact with bodies of condensate of gradcomprises a pressure cracking process in which ually decreasing temperature. The tower is pref- 30 the vapors from the cracking zone are rectied erably also provided with overflow pipes for the 85 and subjected to reflux condensation under reltrays so that the condensate collecting on each atively high superatmospheric pressure to protray Will be conducted on to the next lower tray duce reflux condensates which are withdrawn and the condensate from the lowermost tray in While hot and partially vaporized by reducing the tower will be conducted into the base of the the pressure thereon, thereby to remove the lower tower. 90 boiling constituents as vapors. AS the cracking operation proceeds the body of Other objects and advantages of the invention oil in the cracking chamber 22 becomes gradually will be disclosed by the following detailed demore saturated with heavy polymerized tars and scription of the invention taken in connection pitches which must be removed from time to i0 with the accompanying drawing in which: time in order to prevent the formation of ex- 95 The figure is a diagrammatic elevational flow cessive deposits of carbon and coke in this chamsheet of an apparatus embodying features of the ber. Residuum is therefore Withdrawn from improved invention adapted for carrying out the the chamber 22 at suitable intervals through improved process. valved pipes 28 under sudden reduction of pres- Referring to the drawing, the relatively high sure, and conducted through a transfer line 30 100 boiling petroleum oil to be treated which may be into a flash concentrator 32 in which substana gas oil or other suitable distillate or residue is tial quantities of the residuum are vaporized due introduced into the cracking system through a to the reduction in pressure upon release of the feed pipe 2, which connects through suitable residuum from the chamber 22. The pressure valved connections with preheating coils 4 and maintained in the cracking chamber 22 may 105 6 mounted in the upper portion of a reux and range from 125 lbs. per square inch to upwards rectifying tower 8. In the tower 8 the feed of 500 lbs. depending upon the particular type stock may be utilized in the coils 4 and 6 for of oil being treated in the system; while the prescontrolling the cut temperature on the tower and sure in the conoentrator is preferably mainfor preheating the feed stock for the system. tained at approximately atmospheric or not 110 Cir more than about 15 pounds per square inch above atmospheric which is sufcient to provide for rapid flow of vapors and othermaterials from the concentrator 32. In order to facilitate the vaporization in the concentrator, a gas may be introduced into the residuum therein through a distributor 34, while the stripped residuum may be withdrawn through a valved pipe l36.

The vapors produced in the concentrator 32 are conducted through a vapor line 38 into a reflux tower 40 the temperature of which is controlled to condense all constituents of the vapors having boiling points above that of constituents desired in the pressure distillate. The pressure distillate or gasoline vapors, which may comprise as high as 5% of the residuum, are conducted from tower 40 through a vapor line 42 to a condenser 44, and the resulting condensate is recovered' in a receiver 46. A rEhe Acondensate (pressure distillate) may be conducted from the receiver 46 to storage through a valved connection 48,` or portions of this condensate may be returned to the top of tower 40 through a pipe l5G and Ypump 52 .for the purpose of controlling the out temperature on the vapors leaving the tower. f f

The. heavy reflux condensate produced in the tower 40 is passed -through a pipe 54 and pump 56 into the pipe 10 and 'then into the hot oil tank 12, where it forms a portion of the cracking stock passed to the heater 18. The temperature in the lower portion of the tower 40 may be maintained comparatively :high so that the oil passed into the 'tank 12 (which is preferablyf highly insulated) is at a comparatively high temperature.

vwhich may be substantially the same pressure as Athat maintained on the oilin the crackinglchamber 22, or a pressure intermediate that and a pressure substantially above atmospheric. The vapors entering the tower`8 kfrom the vapor line 26 will maintain the lower portion of the tower at a comparatively high temperature so VVthat the reflux condensate collected in the. base ofthe tower will be at a temperature closely approximating the boiling point of itslower boilingconstituents under the pressure maintained in the tower. Likewise the condensate collecting on each tray will contain constituents heated substantially vto their boiling point. Since there 'is a di'ierence in temperature vbetween the 'base and top of the tower 8 of several hundred degrees F. it will be practically impossible lfor cer- Vtain constituents such as kerosene to gravitate to `the bottom of the tower because of .the high temperature, or to pass oil from the top of the tower ybecause of the relatively low temperature. In accordance with the invention `therefore these intermediate reflux condensates which vmay tend to -log the tower are withdrawn through valved .pipes 64and 66, and introduced with sudden reduction of pressure into a low pressure iiiash tower 68 Ain which substantial :portions of Vthe oondensates :are vaporized by the reduction of pressure. In a similar manner the relatively heavy reflux condensate which may be comprised of heavy gas oil constituents is withdrawn' from the base of the tower 8 through a valved pipe 70 and introduced through a valved branch pipe 72 into the lower portion of the ash tower 68.

The condensates withdrawn from the diierent levels of tower 8 gradually increase in average boiling point and are therefore introduced into the low pressure tower 68 at varying vertical :positions corresponding to their relative boiling points, so that the tower 68 is maintained under substantially the same relative temperature gradient as `tower. Furthermore the condensate `introduced through the pipe 64 will contain a :larger proportion-of low boiling constituents than the condensate introduced from lower points of the vtower l8. Theupper part of the tower 68 is maintained at a temperature suitable for the re moval of only the gasoline or pressure distillate lvapors yflashed yfrom the reiiuxicondensate. .These vapors lare withdrawn through .a vapor line 74', condensed in a condenser 76, a-nd passed through a transfer line F18 into a sto-rage .receptacle 80. IPressure vdistillate may -be withdrawn `from the Itank 8G and passed to storage through a valved pipe 82, or portions :thereof may ybe conducted through a valved Ypipe 84 into theupper .portion of reflux tower 4() .for 'the purpose of kmaintaining the proper cut temperaturein this tower. Other portionsof the condensate irom the receiver .80 may be passed by means 'of a pump-86and valved .pipe 88 into `the upper portion of tower f8, `.where it may be'u'sed to aid inmaintaining the 'desired out vtemperature therein. Portions of the condensate conducted through pipe 88 may `also be vpassed through a valved branch pipe `9) -into 'the upper portion of the tower .68 in which it is used as a reflux and cooling :medium for the purpose of holding back the relatively 4high boiling constituents in this tower.

Instead vof :flashing the heaviest condensate from the tower 8 rinfthe 'flash `tower 68, it .maybe passed directly y:through the vvalved pipe v'l0 into the upper portion `of the tower 40 where rit is flashed and used-asl'atemperature oontrolmedium in this tower.

The stripped condensate reiluxed through Ithe tower r68 and `collecting at the base thereof is Withdrawn :through .a valvedipipe y92 and Vpassed lby means of `pump 56 and pipellO yinto vthe hot oilfstorage tank 12. Aiportion-o-f this vcondensate withdrawn through thefpipe 92 may be by-passed through a valvepipe94.andiconducted by means of the pipe into the upper /portion'of the tower l 40 particularly when it is desired tto cool the upper portion `of this tower.

The pressure maintained in tower 68 may be substantially the same as :that maintainedin the tower 40 and both of these .towers are vpreferably constructed with bubble overilow traysso'thatthe vapors formed Iand introduced thereinto fmay 4be thoroughly rectified.

The cracking process described above 4in connection with this invention Imay be `referred to asa liquid phase cracking processi'but the invention is notlimited vto cracking in the liquid phase since the mixture of distillates conducted 4to `the Yheater 18'may be vaporized therein andthe vapors heated to a-cracking `temperature :prior to theirjpla introduction `into the'chamber 22. In this case .the chamber 22 maybe 'used asa Aseparator for heavy polymerized constituents which may condense vfrom lthe vapors, `and yfor carbon and lcoke y:formed 'in the process. yThe temperaturepf .thef

vapors leaving the heater 18 under these conditions is maintained at about 1100 F.

In certain cracking operations in which substantially no logging of the tower 8 is experienced, the whole of the reflux produced therein may be flashed under reduced pressure in the tower 40, and concentrator 32 together with the towers 40 and 68 (or 40 alone) may be employed to treat the reflux condensates and residuum from a plurality of cracking units such as the one shown and described in the drawing.

The superatmospheric pressure maintained on the chamber 22 may be controlled by the valved outlets from the trap 62 or the valves in pipes 26 or 58. The pressure maintained on the tower 8 may be likewise controlled by the valve in pipe 58 to maintain a pressure greater than that maintained in condenser 60, and less than that in chamber 22. The tower 8 is always maintained under a substantially higher pressure than that maintained in towers 68 or 40, and the back pressure held on the tower 68 may be used to control the degree of vaporization therein. The pressure in tower 8 should be at least about 25 lbs. per square inch above that in tower 68, but for ease of operation a dierence of lbs. is preferably maintained.

The various elements of the apparatus shown in the drawing are diagrammatic, and in actual commerical practice the cracking chambers, towers and hot oil and vapor lines will be heavily insulated.

Having described the preferred form of the invention, what is claimed as new is:

1. The process of converting petroleum oils, which comprises passing oil under a relatively high superatmospheric pressure through a heating Zone in which the oil is heated to a conversion temperature, discharging the resulting highly heated products into an enlarged chamber, passing vapors from said chamber into a rectifying tower maintained under a relatively high superatmospheric pressure in which the vapors are passed through a series of zones maintained at gradually decreasing temperature and in each of which a body of condensate is maintained, withdrawing substantially only pressure distillate Vapors from said tower for final condensation and collection, withdrawing a relatively low boiling reflux condensate from a zone in the mid-portion of said tower into the mid-portion of a rectifying Zone of relatively lower pressure than that maintained in said tower, and withdrawing reflux condensate from the lower portion of said tower into the lower part of said rectifying zone, distilling substantial portions of the condensates introduced into said rectifying zone by suddenly reducing the pressure thereon, removing and condensing pressure distillate vapors from said rectifying zone and passing unvaporized condensate collecting in said rectifying zone into said heating zone.

2. In the art of cracking petroleum oils, in which oil is cracked under superatmospheric pressure at a high temperature in a cracking zone, and vapors therefrom are subjected to reflux condensation under a relatively high pressure in a refluxing zone, the improvement which comprises withdrawing residuum from said cracking zone and distilling it under a reduced pressure, passing the vapors from said residuum into a reflux tower, withdrawing reux condensate from said reuxing Zone into a separating zone and vaporizing portions thereof by suddenly reducing the pressure thereon, removing and condensing the relatively low boiling vapors evolved from said reux condensate, passing portions of the resulting distillate into said reflux tower to control the rerluxing of said residuum vapors, and passing unvaporized reflux condensate collecting in said reiiux tower and said separating zone into said cracking zone.

3. The process of converting petroleum oils, which comprises cracking a relatively high boiling point oil under high pressure and temperature in a cracking zone, passing vapors therefrom into a rectifying Zone maintained under a relatively high superatmospheric pressure, withdrawing residuum from said cracking zone, and vaporizing portions thereof by flashing the same under reduced pressure, passing the residuum vapors into a refluxing zone in a tower, withdrawing condensate under sudden reduction of pressure from said rectifying zone into a refluxing zone, in a separate tower, wherein substantial portions of said condensate are vaporized, passing unvaporized portions of said condensate into said rst mentioned refluxing zone in contact with the vapors produced from said withdrawn residuum, and subjecting the combined condensate collecting in said iirst mentioned refluxing zone to cracking conditions of temperature and pressure.

4. In the art of cracking petroleum oils in which oil is cracked under superatmospheric pressure at a high temperature in a cracking zone and vapors therefrom are subjected to reflux condensation under a relatively high pressure in a rectifying tower through which the vapors pass in intimate contact with a series of bodies of condensate of progressively decreasing temperature and boiling point, the improvement which comprises withdrawing substantially only pressure distillate vapors from the upper portion of said tower for final condensation and collection, withdrawing a relatively light reflux condensate from the mid-portion of said tower and a relatively heavy reiiux condensate from the lower portion of said tower, introducing said withdrawn condensates into separate distilling zones maintained at a substantially lower pressure than the pressure maintained in said tower, separately distilling said condensates in said zones by the heat made available on reducing the pressure thereon, separately fractionating the vapors evolved from said condensates to remove hydrocarbons suitable as pressure distillate and produce a relatively low boiling and a relatively high boiling cracking stock.

ARNOLD R. WORKMAN.

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