US2101088A - Treating hydrocarbon oils - Google Patents

Description

Dec. 7, 1937.

c. w. Nox-'SINGER ET A L TREATING HYDROGARBON OILS Filed' Dec. 1, i931 Patented Dec. 7, 1937 U ETE!) STAT ATENT Fries TREATING HYDROCARBON OILS Application December l, 1931, Serial No. 578,374

7 Claims.

This invention relates to a method of and apparatus for treating hydrocarbon oils.

A major object of the invention is to provide a novel type of treatment in which a number of useful steps are combined in a continuous operation to obtain a maximum ultimate yield of gasoline or other light fractions with a minimum loss due to the formation of carbon in the high temperature units of the apparatus.

A further object is to provide a novel oil treating process in which a heavy oil, such as a crude oil, is rst relieved of any light fraction or fractions and in which the heavy undesired ends are segregated before the main stream is passed to 15 the cracking apparatus.

Another object is to provide a novel oil treating process wherein two different fractions are separately subjected to cracking operations, to be later conjointly subjected to fractionation and other further processing.

A still further object is to separately carry out high pressure cracking operations and low pressure cracking operations, and to conjointly subject the products of such high and low pressure cracking to further treament.

A further object of this invention is to subject a comparatively light fraction to high pressure cracking operations, to subject a heavier fraction to low pressure cracking operations, and to conjointly subject the products of such cracking operations to further treatment.

A still further object is to provide a novel oil treating process in which a common evaporating, dephlegmating and fractie-mating system is combined with a plurality of cracking circuits of the type above set forth, and which also comprises a part, at least, of a stripping system,

With these and other equally important objects in View, which will appear as the invention is described `in more detail, the invention comprehends the concept of treating a stream of a heavy hydrocarbon oil, such as crude oil, in a continuous process, during the different stages of which process the temperature and/or pressure conditions are controlled and regulated so as to effect a stripping of the lighter natural fractions, and the separate treatment of various heavier fractions under cracking conditions most suitable thereto, to produce lighter molecular bodies.

In order to enable a ready understanding of the invention a typical physical embodiment is shown in the accompanying drawing, in which the single figure is a diagrammatic illustration of the system.

In the past, one of the difficulties which has been encountered in cracking operations is the excessive formation of carbon in the high tem- 5 perature apparatus, such as cracking tubes, soaking coils, or reaction chambers. In the present invention this diiiiculty is largely eliminated by permitting only relatively light products, such as clean, condensed fractions, to pass through the high temperature cracking apparatus. This, as well as other advantages, is further secured by separating the fractions to be cracked into a lighter fraction and a heavier fraction, and subjecting, separately, the lighter fraction to high pressure cracking operations and the heavier fraction to low lpressure cracking operations. The heavy ends of the feed oil, moreover, are withdrawn therefrom before the cracking units are reached thereby.

Some of the advantages of stripping off the lighter products from the feed oil vare the relatively immediate recovery of such lighter products, without subjecting them to useless proc- K esses, so far as they are concerned, and the pre- Vention of the breaking up of such lighter products into extremely light, volatile, and undesirable products by their passage through the cracking units. Moreover, the removal of such lighter products before the hydrocarbon is cracked, causes more of such products to be produced in the cracking processes than would otherwise be the case. During cracking, a certain equilibrium tends to be formed between the various fractions, and by the previous removal of the lighter products, as already set forth, more lighter products are formed when such equilibrium tends to establish itself.

As shown in the drawing, the charging stock, which consists of any hydrocarbon oil and preferably a crude, is taken from a source of supply and pumped by pump l through the line 2, to the top of the flash tower 3. Branch pipes, such as pipe il, may be used to supply other units similar to the one illustrated and described.

The flash tower is heated by steam injected through the jets 5, and is divided into an upper section 6 and a lower section 'l by the partition plate 8. In this plate is provided a standpipe 9, protected by the cap Ill and plate Il. The upper portion of section 6 is provided with plates I2 through which the incoming feed oil drips downwardly, while vapors, driven off from the oil as it is heated, pass upwardly. The feedroil is thus stripped of its Ylightest fractions, which pass with any entrained water vapor upwardly in the tower and out pipe i3, while the stripped oil collects about standpipe 9.

In lieu of standpipe 9, an external pipe may be used to permit passage of vapors from section 'l to section 6, in Which case such pipe may be Aconnected to section l just under partition plate the water formerly entrained in the hydrocarbon vapors is separated and drawn off at IS. A pump Il pumps the water-free light hydrocarbons'through pipe i8, valve I9 and pipe 20 to the dephlegmating tower 2l, where it is introduced near the top trays thereof. Thereafter, the light hydrocarbon, dripping down over these trays, Vis at least partially vaporized and the vapors pass out pipe 22 at-the top of the dephlegmator, through heat exchangers 23, 2li and 25, water coolers 25 and 2l, air condenser 28 and water cooler V29 to the gas separator 3l). In the gas separator, fixed gases are separated from the light distillate and drawn olf by pipe 3l, while the distillate comprising the gasoline fractions, is drawn off by pipe 32 and may be led thereby to a stabilizer.

As an alternative to introducing the light fraction in the dephlegmator as just described, valve I9 may be closed, valve 33 in pipe 313 opened, and the light fraction introduced into the evaporator 35; From the evaporator, the vapors of the light fraction pass through pipe 36 vto dephlegmator 3l, andV thence through pipe 38 to dephlegmator 2l, thereafter following the vcourse already described.

Coming back to the stripped feed oil which collects about the standpipe 9, this is pumped by pump 39 through pipe 4B, through heat exchangers 25, 2li and 23, in indirect heat exchange relationship with the vapors leaving dephlegmator .2L to the heat exchangers il and 4l' in dephlegmator 3l, wherein this stripped oil comes in heat exchanging relationship with the vapors leaving dephlegmator 3l. Thence the stripped oil is led by pipe 42 through control valve 43 to the trays in the evaporator 35.V As an alternative, valve 43 may be closed and valve le in pipe 45, opened, whereby the stripped oil is introduced at the bottom of the evaporator, by way or pipe Iii. Such portionsrthereof as are vaporized follow the course of fractionation just outlined with respect to the light fraction when that is introduced from pipe .'i into the evaporator.

4 The heavier portions of the stripped oil collect at the bottom of the evaporator, and are led. by pipe lll, to the lower chamber 'l of the flash tower 3. Here steam is injected into the bottoms, vaporizing any residual light fractions .which pass 'through standpipe 9, and are thus'returned to oi without passing through' the cracking apparatus, thereby enabling the production of more of such fractions in the cracking operations because of the equilibrium which tends to be formed therein. Moreover, the bottoms of the feed oil are also drawn off without passing through the cracking apparatus, which materially reduces the formation of carbon therein.

Coming now to the cracking or conversion operations, only clean, condensed fractions, free from the lightest and heaviest fractions, are subjected to such operations. The fractions are obtained from the bottom of the dephlegmating towers. The heavier of these fractions, obtained at the bottom of dephlegmator 3l, is subjected to a relatively low pressure cracking operation. This fraction is pumped from the dephlegmator by pump through pipe 52 and furnace 53, to one or more soaking drums 54, where conversion takes place at relatively low pressures. After conversion, the cracked products are led to the evaporator 35 by pipe Q6, or by pipe 55 having thethree take-ois, 55, 5l, 58. Thereafter, these products follow the course of fractionation already set forth in regard to the other hydrocarbons delivered to the evaporator. The heavier oilin dephlegmator 3l, while it has little tendency to form. carbon during conversion, yet has more of such a tendency than the lighter fraction obtained from dephlegrnator 2l. Accordingly, this heavier fraction is put through a relatively low pressure conversion process, in which little carbon is formed. The lighter fraction is put through a high pressure conversion process, which, while ordinarily tending to form considerable carbon when heavy stock is used, forms practically none in this instance since a light fraction is used. These refinements reduce the carbon formation to a minimum in this process, with the consequent formation of a high quality, well balanced product.

In such high pressure process, the lighter fraction is drawn off from the bottom of dephlegmater 2i by pipe 55 and pumped by pump '60 through furnace 6i to one or more high pressure reaction chambers-?. Thence, the cracked products are led through pipe 63, provided with a pressure reduction valve Sill, to evaporator 35, and thereafter follow the course of the other hydrocarbons delivered thereto, as hereinafter explained. Reduction valves may be found necessary on pipes 55 and 4S, although the pressure in the soaking drum 54 and in the coils in furnace 53 is much lower than in the correspondn ing parts of the system just described.

Returning to the fractionating system, certain cooling and refluxing systems remain to be described. From the bottom of dephlegmator 31 a portion of the condensate is drawn oi by pipe 65, cooled by the water cooler 66, and pumped by pump 5l to the top of the evaporator 35, to cool and have a refluxing action upon the products therein. Similarly, condensate is drawn by pipe 63 from the bottom of dephlegmator 2l, cooled in the Watercooler $9, and pumped by pump l!! to the top of dephlegmator 31. Finally, a portion of the already cool condensate in tank 35 may be returned through pipe ll, provided with a pump l2, to the top of dephlegmator 2 l.

As to temperatures and pressures maintained during operation, the following are given merely as illustrative of one of the many possible operations` using the system and'process above'described, and are not to be taken as limiting or restrictive. One set of satisfactory approximate (corresponding to No. 37 in the drawing), 725 F.;

bottom of second dephlegmator, 650 F.; oil entering high pressure furnace, 625o F.; oil leaving said furnace, 950 F.; pressure in reaction chamber, 750 pounds per square inch; oil entering low pressure furnace, 790 F.;,oil leaving said furnace, 950 F.; pressure in soaking drum, 125 to 175 lbs. per sq. in.; oil leaving pump corresponding to No. 17, 125 F.

While the conversionof the oil in the illustrated form is confined to the separate'conversion of two fractions thereof, it is of course within the purview of my invention to subject more than two fractions to separate conversion procjesses, wherein the pressure used in such processes will decrease as the specific gravity of the fraction converted increases.

While I have shown and described the preferred embodiment of my invention,I wish it to be understood that I do not confine myself to the precise details of construction herein set forth, by v way of illustration, as it is apparent that many changes and variations may be made therein by those skilled in the art, without departing from the spirit of the invention, orr exceeding the scope of the appended claims.

We claim:

l. The method of simultaneously distilling heavy oil and cracking selected distilled constituents thereof which comprises subjecting a stream consisting of petroleum oil distillate to cracking under superatmospheric pressure and discharging the stream of cracked products into an evaporating zone, simultaneously subjecting an independent stream consisting of a relatively lower boiling petroleum distillate to cracking under materially different conditions, thereafter discharging the latter stream of cracked products into said evaporator Zone, substantially continuously introducing into said evaporating zone preheated heavy oil and causing such oil to be distilled by the aforesaid cracked products discharged thereinto, separately collecting in said evaporating zone all non-vaporous residual products from the said cracked products discharged thereinto and the said heavy oil distilled therein and preventing their return to either of said cracking operations, separately withdrawing separated vapors from said evaporating Zone and subjecting them to a fractionating operation to condense as reiiux condensate higher boiling constituents of said vapors undesired in the final distillate product, withdrawing and collecting the fractionated vapors, separately collecting in said fractionating operation the higher and lower boiling fractions of the said reflux condensate, passing the higher boiling condensate from said fractionating zone to the said first-named cracking Zone, passing the lower boiling condensate to the said second- Vnamed cracking zone, `separately withdrawing collected residual products from said evaporating Zone and passing them to a separate distilling Zone, condensing the evolved vapors therefrom and introducing at least a portion of the resulting condensate directly into said evaporating Zone in counter-current contact with the vapors therein for distillation by aid of the heat of said vapors.

2. The method of simultaneously distilling fresh vcrude oil and cracking selected distilled constituents thereof which comprises subjecting a stream consisting of petroleiun oil distillate to cracking under superatmospheric pressure and discharging the stream of cracked products into an revaporating zone, simultaneously subjecting an independent stream consisting of a relatively lower boiling petroleum distillate to cracking under materially different conditions, thereafter discharging the latter stream of cracked products into said evaporating zone, separately collecting in said evaporating zone all residual products remaining unvaporized therein and preventing their return to either of said' cracking operations, separately withdrawing separated vapors from said evaporating zone and subjecting them to a fractionating operation to condense as reflux condensate higher boiling constituents of said vapors undesired in the nal distillate product, withdrawing and collecting the fractionated vapors, separately collecting in said fractionating operation the higher and lower boiling fractions of the said reiluxcondensate, passing the higher boiling condensate from said fractionating zone to the said first-named cracking Zone, passing the lower boiling condensate to the said secondnamed cracking zone, separately withdrawing collected residual products from ,said evaporating Zone and passing them to a separate distilling Zone, separately withdrawing evolved vapors from the latter distilling zone and fractionating them in another separate fractionating zone by directlyr contacting such vapors with fresh crude oil charging stock being supplied to the operation, withdrawing and collecting the fractionated Vapors, separately withdrawing the resulting reflux condensate and fresh oil mixture from said second-named fractionating zone, and introducing the said condensate fresh oil mixture directly into the said evaporating zone in counter-current contact with the vapors therein for distillation by aid of the heat of said vapors.

3. The method of simultaneously distilling fresh-crude oil and cracking selected distilled constituents thereof which comprises subjecting a stream consisting of petroleum oil distillate to cracking under superatmospheric pressure and discharging the stream of cracked products into an evaporating zone, simultaneously subjecting an independent stream consisting of a relatively lower boiling petroleum distillate to cracking under materially different conditions, thereafter discharging the latter stream of cracked products into said evaporating Zone, separately collecting in said evaporating zone all residual products remaining unvaporized therein, separately withdrawing separated vapors from said evaporating zone and subjecting them to a fractionating operation to condense as reiiux condensate higher boiling constituents of said vapors undesired in the final distillate product, withdrawing and collecting the fractionated vapors, separately collecting in said fractionating operation the higher and lower boiling fractions of the said re- `iiux condensate, passing the higher boiling condensate from said fractionating Zone to the said first-named cracking zone, passing the lower boiling condensate to the said second-named cracking zone, separately withdrawing collected residual products from said evaporating zone and passing them to aseparate distilling-Zone,separately withdrawing evolved vapors from the latter distilling zone and fractionating them in another separate fractionating Zone by directly contacting such vapors with fresh crude oil charging stock being supplied to the operation, withdrawing and collecting the fractionated vapors, separately withdrawing the resulting reflux condensate and fresh oil mixture from said second-named fractionating zone, passing the said mixture in indirect heat exchange relation with the aforesaid cracked vaporous products undergoing fractionation in the aforesaid first-named fractionating opera-` tion, and thereafter introducing the said preheated condensate-fresh oilY mixture into the said evaporating zone for distillation therein by the aforesaid cracked products.

4. The method of simultaneously distilling fresh crude oil and crackingV selected distilled constituents thereof which comprises subjecting astream consisting of petroleum oil distillate to cracking under superatmospheric pressure and discharging the stream of cracked products into an evaporating zone, simultaneously subjecting an independent stream consisting of a relatively lower boiling petroleum distillate to cracking under materially different conditions, thereafter discharging the latter stream of cracked products into said evaporating zone, substantially continuously introducing into said evaporating zone preheated reduced crude oil and causing such oil toV be distilled by the aforesaid cracked products discharged thereinto, separately collecting in said evaporating zone all non-vaporous residual products from the said cracked products discharged thereinto and the said reduced crude oil distilled therein and preventing their return to either of said cracking operations, separately withdrawing separated vapors from said evaporating zone and subjecting them to a fraction- Aating-operation to condense as reflux condensate higher boiling constituents of said vapors undesired in the final distillate product, withdrawing and collecting the fractionated vapors, separately collecting in said fractionating operation the higher and lower boiling fractions of the said reux condensate, passing the higher boiling con densate from said fractionating Zone Vto the said first-named cracking zone, passing the lower boiling condensate Yto the said second-named cracking Zone, separately withdrawing residual products from said evaporating zone and passing them to a separate distilling zone, separately withdrawing evolved vapors from the latter distilling Y Zone and fractionating them in another separate fractionating zone by directly contacting such vapors with fresh crude oil charging stock being supplied to the operation, withdrawing and col, lecting the fractionated vapors, and passing at least a portion of the said fractionated products withdrawn from the said second-named separate fractionating zone to the said first-named fractionating operation in which the said cracked vaporous products are subjected to fractionation.

5. The method of simultaneously distilling fresh crude oil and cracking selected distilled constituents thereof which comprises subjecting a stream consisting of petroleum oil distillate to cracking under superatrnospheric pressure and discharging the stream of cracked products into an evaporating zone, simultaneously subjecting an independent stream consisting of a relatively lower boiling petroleum distillate to cracking under materially different conditions, thereafter discharging the latter stream of cracked products into said evaporating zone, separately collecting in said evaporating zone all residual products remaining unvaporized therein and preventing their return to either of said cracking operations, separately withdrawing separated vapors from said evaporating zone and subjecting them to a fractionating operation to condense as reflux condensate higher boiling constituents of said vapors undesired in the final distillate product, withdrawing and collecting the fractionated vapors, separately collecting in said fractionating operation the higher and lower boiling fractions of the said reflux condensate, passing the higher boiling condensate from said fractionating Zone, to the said first-named cracking zone, passing the lower boiling condensate to the said second-named cracking zone, separately withdrawing residual products from said evaporating VZone and passing them to a separate distilling zone, separately withdrawing evolved vapors from the latter distilling zone and fractionating them in another separate fractionating zone by directly contacting such vapors with fresh crude oil charging stock being supplied to the operation,

withdrawing and collecting the fractionated vapors, separately withdrawing the resulting reiiux condensate and fresh oil mixture from said second-named fractionating zone and introducing it into said evaporating zone, and passing at least a portion of the said fractionated products withdrawn from the said second-named separate fractionating Zone to the said first-named fractionating operation in which the said cracked vaporous products are subjected to fractionation.

6. The process of treating hydrocarbon oil which comprises passing a clean distillate oil through a cracking zone wherein said oil is raised to a cracln'ng temperature and subjected to conversion, introducing the resulting cracked products into a low point in an evaporating zone wherein vapors separate from liquid residue, passing resulting vapors upwardly through said evaporating zone and into a fractionating zone wherein fractional condensation thereof occurs,

.removing the fractionated vapors and condensing them as a desired product, utilizing resulting reiux condensateY as a source of said clean distillate oil first mentioned, removing liquid residue from said evaporating Zone and introducing it into a separate flashing zone wherein vaporization of lighter fractions thereof occurs, contacting fresh relatively heavy charging stock with resulting flashed vapors to cause partial vaporization thereof, collecting unvaporized portions of said fresh charging stock and condensed heavier fractions of the flashed vapors and introducing the resulting mixture, without intermediate passage through a cracking zone, into a higher point in said evaporating Zone above the Vliquid level therein in countercurrent contact with the vapors rising therethrough so that said mixture is subjected to partial vaporization before any portion thereof contacts directly with the hot cracked products at the point of introduction thereof into said evaporating zone and at the same time introducinginto said evaporating zone at a still higher point a lighter, relatively clean distillate oil, as arefluxing medium which serves to wash from the rising vapors undesirably heavy constituents.

7. VThe process of treating hydrocarbon oil which comprises passing a clean distillate oil through a cracking Zone wherein said oil is raised to a cracking temperature and subjected to conversion, introducing the resulting cracked products into a low point in an evaporating zone wherein vapors separate from liquid residue, passing resulting vapors upwardly through said evaporating zone and successively through a first fractionating Zone and a second fractionating zone wherein fractional condensation thereof occurs, removing the fractionated vapors from said second fractionating zone and condensing them as a desired product, utilizing the reflux condensate from said second fractionating zone as a source of said clean distillate oil rst mentioned, removing liquid residue from said evaporating zone, and introducing it into a separate flashing Zone wherein vaporization of lighter fractions thereof occurs, contacting fresh relatively heavy charging stock with resulting flashed Vapors to cause partial vaporization thereof, collecting unvaporized portions of said fresh charging stock and condensed heavier fractions of the flashed vapors and introducing the resulting mixture, Without intermediate passage through a cracking zone, into a higher point in said evaporating zone alcove the liquid level therein in countercurrent contact with the vapors rising therethrough so that said mixture is subjected to partial vaporization before any portion thereof contacts directly with the hot cracked products at the point of introduction thereof into said evaporating Zone, withdrawing reflux condensate from said first fractionating Zone and introducing it into said evaporating zone at a still higher point therein as a refluxing medium which serves to wash from the rising vapors undesirably heavy constituents.

CHARLES W. NOFSINGER. PERCY C. KEITH, JR.

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