US2040048A - Method of treating hydrocarbon oil - Google Patents

Description

May 5,- 3.9%. I A. c. .HAMPTON METHOD OF TREATING HYDROCARBON OIL Filed May lO, 1933 Km. EM.

`|NvENToR ATTORNEY:

Patented May 5, 1936 UNlTE STATES PATENT OFFICE METHOD OF TREATING HYDRO- CARBON OIL Application May 10, 1933, Serial No. 670,218

7 Claims.

This invention relates to processes for the treatment of hydrocarbon oils and pertains more particularly to processes for the production of intermediate products such as Diesel fuel oil or furnace oil, as a by-product in the formation of gasoline from heavier hydrocarbon oils,

Diesel fuel oil is generally accepted as having the following characteristics, approximately: Flash point, above 150 F.; bottom sediment and water, less than .1%; carbon residue, less than .5 insoluble in hexane, less than 5%. Furnace oil may have a gravity of about 38.2 A. P. I., an initial boiling point of 214 F. approximately, and an end point of about 500 F.

It is an object of my invention to provide a process whereby oil of these general characteristics may be made, as a separate product, in a conventional oil cracking unit adapted for the productionof gasoline, without interfering seriously with the primary function of that unit.

, This invention permits the simultaneous production of intermediate products such as Diesel fuel oil or furnace oil, and gasoline, even when the fractionating apparatus, adapted to segregate the gasoline, is operated at relatively high pressure, such as those in excess of 100 pounds per square inch, for example, 200 pounds per square inch. Relatively high pressures in ordinary systems, of the type known heretofore, make it dimcult, if not impossible, to obtain an intermediate product directly from the fractionating system, having the necessary ash point to meet the usual specifications. In a great many cases it is mpossible, or at best undesirable, to introduce steam or water into the high pressure system n order to strip this intermediate cut of light ends. In accordance with my invention relatively heavy oil, such for example, as gas oil of Mid- Continent characteristics and having a gravity of about 34 A. P. I., is subjected to cracking of conventional intensity for the production of `gasoline and other light distillates. The resulting cracked products are separated into vapors and an unvaporized residue, in an evaporating zone. The residue is withdrawn to a tar flashing zone of lower pressure, wherein the lighter constituents thereof are vaporized and freed from residual tar, the latter product being withdrawn from the process. The lighter constituents mentioned are subjected to fractionation in the upper portion of said ashing zone, which acts as a secondary fractionating Zone, to produce relatively light and clean vapors, and reflux condensate which mingles with the residual tar. The vaporsseparated Vin the evaporating zone are fractionated in a primary fractionating zone with the resultant separation of light vapors in the gasoline boiling range, which are removed as a desired product, and `reflux condensate.

During the treatment of the cracked products in the evaporating zone an intermediate condensate may be formed and withdrawn as a side stream. This side stream and/or reflux condensate from the primary fractionating Zone constitute the immediate source of the intermediate product e. g. Diesel fuel oil or furnace oil. Either or both liquids are introduced into a condensate or Diesel'oil flashing zone of reduced pressure, wherein lighter portions thereof ,are vaporized, the character of the remaining unvaporized oil being determined by the back pressure held on the products in the condensate flashing zone just mentioned. Light products liberated as vapors in the condensate flashing Zone are preferably introduced into the secondary fractionating zone inmixture with the lighter constituents from the flashed residue, `and therein are similarly separated into relatively light and clean vapors and reflux condensate. Theseclean vapors are then condensed and introduced into an intermediate point in the primary fractionating zone for further treatment, the products remaining unvaporized in the Diesel oil flash drum being withdrawn and passed through a cooler to storage, as a desired product.

The above mentioned and further objects and advantages of my invention and the manner of attaining them will be made clear in the following description and accompanying drawing.

The single Vgure of the drawing represents schematically an oil treating system embodying my invention.

ReferringV more particularly to the drawing, fresh charging'stock, such, for example, as 34 A. P. I. Mid-Continent gas oil, is introduced through charging line l, having pump 2, into cracking furnace V3, wherein it is heated to a conversion temperature, Which may vary considerably in accordance with known principles. This temperature may be in the range of 800 to 1000 F. or more, but is preferably about 850 F., While the pressure maintained on the oil in the furnace ,may also vary considerably. The outlet pressure on the furnace'may be, for example, to 1000 lbs. per square inch, or even higher, but is preferably in the neighborhood of pounds per square inch. The time of passage of the oil through the furnace is preferably great enough to produce a moderate amount of conversion of the oil therein, the highly heated oil passing from the furnace through line 4 into reaction chamber 5 wherein additional conversion takes place, the digested products subsequently passing through line. 6, having reducing valve 'I, into the lower part of evaporator 8, which is maintained under a lower pressure than that of the reaction chamber, for example, about 200 pounds per square inch. This evaporator is illustrated as having two trap out trays 9 and IIJ, baille plates II, and cooling coils I2 and I3. The introduced products separate into vapors and a liquid residue, the residue being collected in the base of the evaporator, while the vapors pass upwardly. The rising vapors are cooled by action of the cooling coils I2 and I3, through which any cooling medium, such as fresh charge, may be passed in the well known manner, resulting condensate collecting on the trap out trays 9 and I0, while uncondensed vapors pass off from the top of the evaporator through vapor line I4 into a low point in the fractionator or bubble tower I5. A portion of the condensate from trap-out trays 9 and IIJ may be directed through line 2| and 2U into the base of fractionator I5, if desired.

In the fractionator, which is equipped with bubble'trays or any other well known form of fractionating devices, further partial condensation of the vapors takes place, as a result of the cooling action of cooling coil I6 located at the top of the tower. Fresh charge or any other suitable cooling medium may be passed through this coil in the usual manner. Condensate formed in the fractionator is collected in the base thereof, as well as on trap-out trays I5' and I6', if desired, while uncondensed vapors pass ofl through vapor line I'I Yand condenser I8, the relatively light -distillate being collected in receiving drum I9, having gas draw-off pipe I9. This distillate is a final desired product such as gasoline, the end point being regulated by proper adjustment of the fluid flow through coil I6 or in any other equivalent manner. Condensate withdrawn from the fractionator through lines 20 or 20, or both, and/or condensate removed from one. or both of trays 9 and I0, through line 2|, is introduced through line 22, having pressure reducing valve 23, into condensate or Diesel oil flash drum 24, which is maintained at a desired pressure by adjustable relief valve 25 located in the outgoing vapor line 26, which prevents the pressure in the drum 24 from exceeding a predetermined value. The flash drum is equipped with suitable fractionating devices 21,'of any well known type, which are adapted partially to fractionate the vapors liberated in the drum, from the introduced products. These vapors pass off through vapor line 26, past the back pressure or relief valve 25, into tar flasher 28, through either of inlets 28 or 30. Residue of a tar like character is withdrawn from the base of evaporator 8 and passed through line 30, having reducing valve 3|, into the base of the tar flasher 28, which is maintained at a much lower pressure than that of the evaporator, this pressure being subject to considerable variation, but most suitably being within the limits of atmospheric to twenty-five pounds per square inch. j 4 I The resulting flashed vapors, mingled with those entering the tar flasher from pipe 26, rise through the drum` and are subjected to fractionation by action of the fractionating devices 32 of any well known type located in the upper portion of the drum and serving as a fractionating zone. A separate fractionating chamber might be provided, if desired for treating the vapors flashed from the tar in drum 28, and in this case part or all of the fractionating elements in drum 28 could be removed. Vapors remaining uncondensed pass off through vapor line 33, heat exchanger 34, and auxiliary cooler or condenser 35, and are introduced in condensate form into the distillate receiver 35. Distillate so collected is removed through pipe 31 and forced by pump 38, through heat exchanger 34, into an intermediate point in the fractionator I5 or evaporator 8. The point of introduction may be, for example, two trays above the vapor inlet to the fractionator I5.

Branch lines 38 and 39 having respectively control valves 4U and 4| serve to supply refluxing liquid to the Diesel oil flash drum 24, and tar flasher 28, in the order named.

The pressure in the flash drum 24 is maintained at a value somewhat higher than that of tar flasher 28 so that the vapors may flow under their own pressure from the drum to the flasher. The pressure maintained on the flash drum 24, by adjustment of the back pressure valve 25 is held substantially constant by the inherent action of the valve, and is so selected that only sufiicient light fractions will be separated in vapor form, from the introduced products, to leave an unvaporized liquid of the desired characteristics, the liquid being withdrawn from the process through draw-off line 42 and cooler 42. The liquid so withdrawn from the flash drum 24 has the desired characteristics, e. g. those of Diesel fuel oil or furnace oil, any of the undesirable light products present in the condensate withdrawn from the fractionator or from the trap out trays Sand I0 being removed in the flash drum 24, and returned to the fractionator I5 or evaporator 8, after treatment in the tar flasher 28. If desired the vapors from flash drum 24 may be separately condensed and returned to fractionator I5 as a refluxing medium, valves 50 and 5I, pipe 52, condenser 53, receiving drum 54, pump 55 and conduit 56, being provided for this purpose. By closing valve 5| and opening valve 5I! all vapors from drum 24 mayv be directed into condenser 53. If desired condensate may be withdrawn from an intermediate point in the flash drum 24, as a desired product, trap-out trays 24 being provided for this purpose. The condensate so withdrawn may be further stripped if necessary, the resultingI vapors being treated similarly to those from line 26 or discarded, while the stripped condensate has the desired characteristics as a final product.

Heavy tar residue may be withdrawn from the tar flasher 28 through draw-off line 43. All or part of the condensate segregating in the bottom of the fractionator I5 may be recycled through line 44, having pump 45, to the cracking furnace 3 for retreatment with the fresh charge. In case all of the condensate is so recycled the products introduced to the Diesel oil flash drum will be Withdrawn from either one of the trays 9 and I0 in the evaporator 8, or from trays I5 and IIA in the fractionator I5. The characteristics of th products collecting on the two trays 9 and I0, and the condensate collected in the fractionator I5, may be controlled by proper adjustment of the flow of cooling fluid through the heat exchange coils I2, I3, and I6, as well as by regulation of the amount of refluxing medium supplied. The vapors from the flash drum 24 are preferably in. troduced into the tar flasher 28 for further fractionation, so that they may be clean enough for introduction into the fractionator I5. Howeverj in certain linstances these vapors may be suitable for such introduction without retreatment inthe chamber 28, and in this case the vapors may be directed through cross over line 44, having valve 45, and forced directly through the heat eX- changer 34, and Condenser 35, into the distillate receiver 35.

Other charging stocks than that mentioned may be used if desired, such, for example, as a lighter or heavier gas oil, or other crude distillate. Crude oil might also be so treated, but in that case the amount of cracking carried out on the oil introduced into the evaporator 8 would have to be limited to prevent undesirable carbon formation. The cracking system and the conditions disclosed I consider to be preferable for the charging stock specically mentioned, but I do not wish to be limited thereto since other cracking apparatus and methods may be used. This process is particularly applicable where a considerable pressure is maintained on the fractionator column I5, such, for example, as pounds per square inch, but the invention is also applicable where higher or lower pressures are used, the characteristics of the intermediate product withdrawn from the base of flash drum 24 being controlled by adjustment of the back pressure valve 25. Relatively high pressures on the fractionator I5 are desirable since they keep down the quantity of desirable light gasoline distillate withdrawn from the receiver I9 through the gas drawoff pipe I9', but pressures of a lower value may be used, such as from 40 to 60 pounds per square inch, for example.

While I have described a particular embodiment of my invention for the purposes of illustration it should be understood that various modiiications and adaptations thereof may be made within the spirit of the invention as set forth in the appended claims.

I claim:

l. The process of treating hydrocarbon oil which comprises subjecting relatively heavy oil to cracking temperature under superatmospheric pressure to produce conversion thereof, introducing the resulting cracked products into a vapor separating zone wherein vapors separate from liquid residue, cooling said vapors to condense heavier fractions thereof, fractionating the uncondensed vapors in a fractionating zone to produce gasoline, expanding said residue into a first zone of reduced pressure wherein partial vaporization thereof takes place, condensing resulting vapors and introducing condensate so produced into said fractionating zone, expanding the condensed heavier fractions into a second zone of reduced pressure wherein partial vaporization thereof takes place, leaving an unvaporized liquid, introducing resulting vapors into said first zone, and withdrawing said liquid from the process.

2. A process in accordance with claim 1 wherein the pressure of said fractionating zone is in excess of one hundred pounds per square inch, and wherein the pressure in said second zone is adjusted to effect evaporation from said condensed heavier fractions, of sufficient lighter components to give the unvaporized liquid withdrawn from said second zone, the characteristics of ordinary Diesel fuel oil.

3. The process of treating hydrocarbon oil which comprises subjecting relatively heavy oil to cracking temperature under superatmospheric pressure to produce conversion thereof, separating resulting vapors, cooling said vapors to condense heavier fractions thereof, fractionating the uncondensed vapors in a fractionating zone to condense products heavier than gasoline, expanding condensed products into a zone of reduced pressure wherein partial vaporization thereof takes place, removing the unvaporized portion thereof from the process, introducing the vapors ofxsaid partial vaporization into a separate flashing Zone wherein heavy residue is expanded to separate vaporizable portions therefrom, removing vapors from said separate ashing Zone, condensing said vapors, and introducing the resulting condensate into an intermediate point in said fractionating zone.

4. The process of treating hydrocarbon oil which comprises subjecting relatively heavy oil to cracking temperature under superatmospheric pressure to produce conversion thereof, introducing the `resulting cracked products into a vapor separating Zone wherein vapors separate from liquid residue, cooling said vapors to condense heavier fractions thereof, fractionating the uncondensed vapors in a fractionating zone to produce gasoline, expanding said residue into a rst Zone of reduced pressure wherein partial vaporization thereof takes place; condensing resulting vapors and introducing condensate so produced, into said fractionating zone, expanding a portion of the condensed heavier fractions into a second zone of reduced pressure, wherein partial vaporization thereof takes place, leaving an unvaporized liquid, introducing resulting vapors into said first zone of reduced pressure, withdrawing said unvaporized liquid from the process as a desired product, and combining another portion of said condenser heavier fractions with said relatively heavy oil for cracking therewith.

5. The process of treating hydrocarbon oil which comprises subjecting relatively heavy oil to cracking temperature under superatmospheric pressure to produce conversion thereof, introducing resulting cracked products into a vapor separating Zone wherein vapors are separated from a liquid residue, partially condensing said vapors in said zone and removing resulting condensate, free from said residue, transferring uncondensed vapors to a fractionating zone wherein heavier fractions are condensed and a desired light product is separated in vapor form and subsequently condensed, removing said liquid residue from said separating zone, introducing the condensate removed from said separating zone directly into a Zone of reduced pressure, wherein partial vapori- Zation of said condensate, by its contained heat, takes place, leaving unvaporized liquid oil, preventing the pressure in said zone of reduced pressure from exceeding a predetermined value, removing said unvaporized liquid oil and diverting it from the process as a desired product, passing liquid residue from said separating Zone into a tar flashing Zone of low pressure wherein partial vaporization of said residue takes place, leaving uncondensed vapors, mingling vapors from the expanded condensate with said uncondensed vapors just mentioned, cooling the resulting vapor mixture to form a condensate and introducing condensate so formed into an intermediate point in said fractionating zone.

6. The process of treating hydrocarbon oil which comprises subjecting relatively heavy oil to cracking temperatures under superatmospheric pressure to produce conversion thereof, introducing resulting cracked products into a vapor separating zone wherein vapors are separated from a liquid residue, partially condensing said vapors in said zone and removing resulting condensate, free from said residue, transferring uncondensed vapors to a fractionating zone wherein heavier fractions are condensed and a desired light product is separated in vapor form and subsequently condensed, removing said liquid residue from said separating zone, introducing the condensate removed from said separating zone directly into a zone of reduced pressure, wherein partial vaporization of said condensate, by its contained heat, takes place, leaving unvaporized liquid oil, preventing the pressure in said zone of reduced pressure from exceeding a predetermined value, removing said unvaporized liquid oil and diverting it from the process as a desired product, removing liquid residue from said separating zone and expanding it into a tar flashing zone of lower pressure wherein partial vaporization of said residue takes place, leaving uncondensed vapors, mingling vapors from the expanded condensate with said uncondensed vapors just mentioned, cooling the resulting vapor mixture to form a condensate, introducing condensate so formed into an intermediate point in said fractionating zone and combining condensed heavier fractions removed from said fractionating zone with said relatively heavy oil for further cracking.

7. The process of treating hydrocarbon oil which comprises subjecting relatively heavy oil to cracking temperature under superatmospheric pressure to produce conversion thereof, introducing resulting cracked products into a vapor separating zone wherein vapors are separated from a liquid residue, partially condensing said vapors, leaving uncondensed relatively light vapors, removing said uncondensed vapors and passing them through a fractionating zone to condense undesirably heavy constituents thereof as reux condensate, removing the fractionated vapors and condensing them as a desired product, returning the reiiux condensate for further cracking in mixture with said relatively heavy oil, expanding condensate, formed by the partial condensing step, into a zone of reduced pressure wherein vaporization of the lighter constituents of the condensate takes place, maintaining a substantially constant back pressure on said zone of reduced pressure, removing the unvaporized condensate, and diverting it from the process as a iinal desired product, removing the vaporized lighter constituents from said zone of reduced pressure, condensing them and combining resulting condensate with said vapors separated from said resulting cracked products for further treat'- ment.

ARTHUR C. HAMPTON.

CERTIFICATE OF CORRECTION.

Patent No. 2,040,048. May 5, 1956.

ARTHUR C. HAMPTON.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, second column, line 25, claim 4, strike out the semicolon after "place" and insert a comma instead; and line 55, same claim, for "condenser" read condensed; same column, line 69, claim 6, for "temperatures" read temperature; and that the said Lettere Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this lst day of September, A. D. 1956.

Leslie Frazer (Seal) Acting Commissioner of Patents.

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