US2004196A - Process for treating petroleum oil - Google Patents

Description

Jime 11, 1935. c p DUBBs PROCESS FOR TREATING PETROLEUM OIL Original Filed July 31, 1922 Patented June 11, 1935 UNITED STATES Application .July 31, 1922, Serial No.

Renewed July11,1934

4 Claims. (C1.:196-48):

This invention relates to a process and apparatus for treating petroleum oil and refers-more particularly to a continuous cracking process in which the oil is converted from relatively high boiling point products to lower boiling point oils.

Among the salient objects of the invention are to' provide a process whereby the volume ofoil being treated remains constant while the amount of raw oil, the cracking of the oil, theamount temperature necessary to crack it is very thin and of gasoline, and the amount of pressure distillate can be varied. I

Thenecessity of cracking petroleum of high boiling points into low boiling points such. as gasoline is becoming more acute owing to the demand for gasoline rapidly increasing. In cracking high boiling point products into the low boiling point products there is necessarily produced carbon in more or lessproportion to the amount of the high boiling point petroleum cracked.

Where the cracking of petroleum is carried on in a shell still, the carbon produced progressively increases as the cracklng proceeds, such carbon being retained in the still, While the amount of oil in the still is progressively decreased.

In the normal operation of cracking oil in a shell still the low boiling point products produced known as gasoline are contained in what is commonly designated as a pressure distillate. This pressure distillate isthat distillate from the still charge which contains what is known as gasoline, kerosene, and certain additional heavier. ends. For illustration, the pressure distillate produced contains. of gasoline distilling between 100 and 437 F. and 50% consisting of kerosene and oils'having higher boiling points. The pressure distillate represents of the total oil charged into the still, and the residuum representing 40 percent of the charging stock. It will be understood that these percentages both as to total percent distillate, its gasoline content, etc; will vary considerably from this according to the character of the oil.

In the operation of a shell still the oilis pro gressively heated throughout the process while maintained under the desired pressure. Therefore, the first one per cent of pressure distillate distilled oiirepresents one per cent of the total charge; the second per cent of the original charge distilled over represents 1.01% of the oil remaining while the third per cent distilled ofi of the original charge represents 1.02% of the oil remaining in the still and the process is progressive in this respect, showing that the conditions are not constant, but progressively change, and as the carbonfrom all these per cents distilled off isaccumulated in the still and is contained in the progressivelydecreasing amount of oil remaining in the still; it is evident that this process involves a condition that is-constantly progress ingftowards conditions detrimental to the continued carrying on of the process and its operation, therefore; is limited.

It is evident that the oil; maintained at the This condition applies to any apparatus whether thejexternal heat is applied to the still proper or to tubes through which the oil circulates whenthe total residuum is retained in the crackingunit. It also applies to cases where additional raw oil is fed to the cracking unit.

When attempts are made to withdraw part of the residuum from the unit it is found that the oil so withdrawn frequently contains a great- PATENT OFFICE er per cent of low boiling point products than the original charging stock;

One object of my invention is to overcome the foregoing objections by providing a process whereby the volume of hydrocarbon material treated remains constant :while the amount of raw oil fed into the system,'the amount. of pres- 35 sure distillate produced and the amount of gasoline produced can be varied.

The single figure is a diagrammatic side elevational view of the apparatus.

The raw oil is drawn from any suitable source 40 not shown and by means of a pump isforced through line I through valve 2, valve 3 being closed, through line 4 into the cracking coil 5. As the oil passes through this cracking coil it from the furnace 6 through the ports I into the top, part of the chamber containing the cracking tubes and passes downward around the tubes to a flue not shown. The oil passing through the coils is raised to a conversion temperature and. then passes through line 8 into expansion chamber 9. t

The process is not confined to any particular kind of apparatus and while the oil is shown is heated by the furnace 6. The heat passes 45 as entering the side of the expansion chamber 55 mator.

near the bottom and discharges near the top as shown, it may enter at any convenient point of said expansion chamber.

The vapors from the expansion chamber pass through line lil into the bottom of the dephleg- The dephlegmator contains pans or any other suitable arrangement for accomplishing the result which is later described. More or less of the vapors while ascending through the dephlegmator are condensed and are dropped backv ratus at which time the valve 2 is closed and the valve Sopened and the raw oil'ied through line ll into the dephlegmator through line I 8. Attention is called to the fact that this line 18 extendspart of the way down into the dephlegmator and this is one of the essential parts of my invention which I will describe later. a When the apparatus is brought to the pressure. it is desired to operate at then the surplus in .condensable gas is taken on through line l9, either continuously or intermittently, beingcontrolled by valve 26. This may be a hand control 'valve or an automatically operated valve.

The pressure distillate flowing .into the pressure istillate tank {6 is drawn off through line 2| controlled by valve 22 to any suitable storage. The amount of liquid in the receiving tank l6 is ascertained through a gauge glass or any other convenient means well known to the art. The raw oil, asTwillbe noted, is discharged into the ephlegm'ator at a point which will bring the vapor'sin contact with'this raw oil so as to obtain the highest efficiency of transfer of heat from sai'dfvapor's to said raw oil feed, also allowthe superheat to'be extracted from the said vapors/by said raw oil at the earliest possible moment, thus causing condensation of the higher "boiling point vapors as" quickly as possible and thereby decreasing the velocity of the vapors through the dephlegmator and overcoming the tendency 16f these vapors to mechanically carry over "withthe remaining vapors an excessive amount of'high boiling point ends.

"The Too'ndensed highboilin'g point vapors and the unvapdnzed portion of the raw oil feed contin'uou'sly pass down through dephlegmator leg liflthrough line l2, through cracking coils 5, through line 8 into expansion chamber 9. The dephlegmator may be elevated to a sufficient height 'toiurnish head pressure to force the 'oil'through the cracking tubes, or this oil may be "forced through the cracking tubes by interposing a suitable force pump of well known design in'line l2.

. The expansion chamber is properly insulated so that :the amount of. heat radiated therefrom can be controlled but it is preferred to insulate the expansion chamber in such manner that the temperature in the same may be controlled. A portion of the oil in the form of vapors continuously passes through line ll! into the bottom of the'dephlegmator and is subjected to the action of the raw oil being fed thereto with the result as already ydescribed. The remaining vapors 'ately.

pass beyond the discharge of the raw oil for further cooling with the further result that more ii's'drawn out through lines 2? and 28, through line 29, through cooler at and carried through line iii to any suitable storage or reducing still, the

flow being regulated by valves 32 and 33. The usual practice is to use line 21 until the accumulation of carbon in the expansion chamber interferes and then line '28 is used. Additional lines may be provided for drawing off this oil at higher elevations on the expansion chamber.

The manhead 34 is for cleaning the carbon out of the expansion chamber, while manhead 35 is for ventilation andfor allowing a man to probe 7 the carbon out of the retort without entering it.

By this process at least 95% of the carbon remaining in the apparatus and produced from cracking the oil will be contained in the expansion chamber and not more than 5% will-be contained in the cracking tubes 5, which is of great advantage. 7

In treating crude oil containing a certain percentage of natural gasoline such natural gasoline contained therein will be vaporized in the dephlegmator and drawn ofi from the system with the pressure distillate, thusavoiding such'gasoline passing through the cracking tubes, hence will allow the cracking tubes to be used for cracking nothing but oil containing no gasoline and of course'avoidingtaking from the cracking tubes a part of their capacity 'by passing gasoline through them. V v

7 Should the crude oil being treated contain sufiicient quantity of natural gasoline, or other products desired as to use more heat to vaporize such gasoline or other desired productsthan is desired to extract from the vapors in the dephlegmator, then such oil may be preheated to such temperature not in excess of that extracted from thempors in the dephlegrnator. This method may be variedif desired, by by-passing some of the raw oil directly to the cracking coils through line 4 by partly opening valve 2, but in doing this the capacity oi the plant is decreased proportion- Should the ,oil being treated contain water when fed vover the top such water content willbe converted into steam in the dephlegmatorby the heat of the vapors in said dephlegmator and such steam passes'w'ith the remainingoil vapors over into the pressure distillate tank [6 vand may'be withdrawn. Should the content of w'at'er'be such as to take too much heat from the vapors in the dephlegmator then'the oil may be preheated in any suitable means before being fed into thejdephlegmator, such preheating being sufiicien't so that the temperature of the oil'will besuchas not to extract too much'heat from-the vapors-in the dephlegmator. Should it be desired, instead of preheating the oil, sufiicient of theoil-may be fed direct to cracking coils 5 by regulating the opening of valve 2 and the remaining portion-of 011 being fed directly into the dephlegmator, the oil going into the dephlegmatornot being in excess of amount regulated to take only the. desired 7 amount of heatfrom the vapors in the dephleg mator.

J This operation also applieswhen treatingan 'oil containing both water and natural gasoline, that isfit may be'preheated to the proper-degree, orsuch portion of it 'p'assed throughyalve Z and line 4 to the cracking tubes asis found necessary as above described to keep the desired temperature in the dephlegmator. V f

' In the treatment of oil containing 'water if the temperature of the'vapor in the top of the "dephlegmator be maintained too low for th pressure held on' the apparatus, thesteam generated from this water-will be condensed in the dephlegmatorand be' refluxed back to the cracking tubes and result in the apparatus beingwater vapor bound For illustratiomthe boiling point ofwater is aboutf327 F when maintained at' 100' lbs. Temperature; thereforeyat the top 1 of" the dcphlegmator hQl1l1dj be maintainedfsufficiently high to prevent any 'substantial condensation of the waterin the top of the dephlegmator. Avery important fe'aturein the operation of this process with oils containing various amounts of water is that there are no sudden variations of pressure.

To give an illustrative run using a gas oil made from mid-continent crude oil and having a gravity of 33 B. at 60 F. 500 barrels per day of this raw charging stock is fed into the apparatus through line i, through valve 3, through line I! in the dephlegmator through line I 8. The vapors entering the bottom of the dephlegmator are approximately 790 F., while the raw oil fed into said dephlegmator is approximately 70 F. The vapors condensed with the raw gas oil and returned pressure distillate fed into the dephlegmator reach a temperature of about 700 to 780 F., and pass down dephlegmator leg ll through line l2, through coils 5 in which such oil is heated to about 814 F., and are discharged through line 8 into expansion chamber. 200 bar rels of residuum are drawn from expansion chamber through lines 21 and 28. The temperature of the vapors at the top of the dephlegmator is about 550 F. and 300 barrels of pressure distillate are taken out through receiving tank l6. This pressure distillate is about 50 B. gravity at 60 F. and contains approximately 50% of gasoline boiling point between 100 and 437 F.

For each barrel of raw material fed into the apparatus there are two barrels of reflux condensate condensed from the vapors in the dephlegmator and refluxed back to the cracking tubes for further treatment with the raw oil fed into dephlegmator. Therefore, in the operation there are substantially 500 barrels of raw oil being fed to the apparatus per day, 300 barrels of pressure distillate and 200 barrels of residuum taken therefrom per day, but there are 1,500 barrels of combined raw oil and reflux being passed through the cracking tubes per day. Therefore, there is only 10% of the oil passed through the cracking coils which is converted to gasoline representing 30% of the raw oil being fed in. The pressure distillate produced represents of the total oil passed through the cracking coils and represents 60% of the raw oil being fed in a day. a

An important feature of my process isthat it is possible to vary the amount of gasoline, pressure distillate and the residuum withdrawn from thesystem without substantially increasing or decreasing the total combined volume of reflux and.

raw oil passing through the cracking tubes in a day, or changing the percentage of such total volume that is converted into gasoline. Thisis accomplished by controlling the temperature in the dephlegmator through the fi'ow thereto or returned pressuredistillate. A pressure distillate jmay beproduced that'is rich in gasolin'eby re ducing J the "quantity of raw oil' and simultane ouslyincreasingthe how of returned pressure 1 distillate fed to the dephlegmator, or a larger volumepf pressure distillate may he -produced by increasingthe ra w'oil and decreasing the returned' pressure distillate" fed to the dephlegmator. In each instance the temperature 'of the dephlegmator so "controlledby the 'flo'w of returned pressure distillate, a large percentage of which vaporizes therein, that the volume o freflux condensate' plus the' raw oil charge returned to the heating coil" is-mai'ntaind const nt: 1 -I claim as my inven'tion: l I; A continuous process for cracking hydro? carbon oil' c'onsist'ing in passlngla constant vol ume"of combined charging oil and reflux com densfate through a heating" zone 'whereirr it' is raised to a cracking temperature, in "delivering the-heated' 1 oil from 5 said h'eat'ing" zone to a reaction zone wherein conversion occurs and from g which no'unvaporized oil is permitted to return to the heating zone, in passing evolved vapors to a dephlegmating zone wherein they are subjected to reflux condensation by passage in heat interchange relation with the incoming charging oil, in reducing the proportion of charging oil and increasing the proportion of reflux condensate in said constant volume of oil introduced to the heating zone by decreasing the amount of charging oil introduced to the dephlegmating zone and simultaneously returning to the dephlegmating zone an amount of the pressure distillate produced by the process sulficient to compensate for the decreased condensing elfect due to the decrease in the amount of charging oil introduced to the dephlegmating zone.

2. Aprocess for treating hydrocarbon oil con sisting in continuously introducing a constant volume of combined raw oil and reflux condensate to a heating zone wherein the oil is subjected to cracking conditions of temperature and pressure, in subjecting the evolved vapors to reflux condensation in a dephlegmating zone to supply the reflux condensate in said constant volume of oil, in introducing the charging oil to the dephlegmating zone to flow therethrough in heat interchange relation with the vapors'and commingle with the reflux condensate, in lowering the proportion of charging oil to reflux condensate in said constant volume of oil by decreasing the amount of charging oil introduced to said dephlegmating zone and in simultaneously introducing to said dephlegmating zone an amount of the pressure distillate produced by the process suflicient to compensate for the decreased condensing effect due to the decrease in the amount of charging oil introduced to the dephlegmating zone.

3. A conversion process which comprises continuously passing a mixture of charging oil and reflux condensate in a restricted stream through a heating zone and heating'the same therein to cracking temperature under pressure, subsequently separating the heated mixture into vapors and residue, fractionating the vapors in a fractionating zone in contact with fresh charging oil for the process to form said mixture for passage through the heating zone, finally condensing the fractionated vapors and introducing resultant final condensate into contact with the vapors undergoing fractionation, and, throughout the normaloperation of the process, so correlating the aammntmifinalrcundensate th finals-mutingtzone with thexamountm char in oil to the tractionatin czone aste e ubstantiailly constant the yolwne cf the mixture nf ycha-lyging oi1 rflild --reflux condensate which is in :the ifractipnatin g zone and massed thetlaztter to the heating zone, wombined-mooling.zaction-of thet'cha lg n 011 andzfinal condensate introduced [to the fracitionating "zone .sufimient ltqz-gmmintafm in said mixtures uantity 10f reflux condensate lat teastftmicezthat ofthe charg ingtnil.

V the .-\crac ing of hydrocarbon .oils, "the method which comprises trfnactionating the cracked waporstin a, iractionating zone in contact with a, first stream of charging oil forlthe pnoc ess .tO condense: msuflicientlyfcnacked fractions thereaortas .zre'fiux condensate, then combining :this chargingnil and the nefluxlcondensate withl'aflsec.

--ond stream 10f ,charg-ingeoiL-passing the resultant ,mimuiziegof charging-ail and reflux condensate through a vheating mne and heating the -same ttheneintto creams-immat e :pmssu e, .sepamti athe ehea-ted mixture into 1mm. residue summing the iormer :150 th Imotio s ms -zone a @sa d crat cd ,m o "finally =ccnd nsing =the fract onat d "vapors wind intro .duqmg a, portion. .Qf-

resultant final-c ndensat into contact with the vapors initheegfractionating zone, th amountm chatging' ikand finese edensate -=intt9du ced to thetiractionatiqg zone-he.-

r u ficient tgx form in ;the latter a. volume at treflux eqndensate :at :least twice :the combined volumecf said fiIStzflIldr-SGGQDdQStEQQXHS 10f charging m1, :'a nd .thmughcut the enqrmal gpensticn of the process so.-corr lati11g the amount 01 final condensat introduced into t e ins ticnating zone with ,thetamQu nt of charging "ail imsaid first and sec ndstrpams asto maintainst1 8ntia y mm fistant the volume tor ,saidtmixtuiielof char in 01,1 and-reflux gcondensate massed through the heating-zone.

. amour. Dumas,

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