US1575031A

US1575031A - Method and apparatus for cracking oils under pressure

Info

Publication number: US1575031A
Application number: US703339A
Authority: US
Inventors: John E Bell
Original assignee: Sinclair Refining Co
Current assignee: Sinclair Refining Co
Priority date: 1924-04-01
Filing date: 1924-04-01
Publication date: 1926-03-02
Anticipated expiration: 1943-03-02

Description

March Z 1926. 1,575,031

J. E. BELL METHOD AND APPARATUS FOR CRACKING OILS UNDER PRESSURE Filed April l, 1924 4 Sheets-Sheet l (ONDE/v50? REC/VER @D j I f? u a H E ki H u: E @j u E o kp i r INVENTOR M A TTORNE Y 5 March 2 1926. 1,575,031

J. E. BELL METHOD AND APPARATUS FOR CRACKING OILS UNDER PRESSURE Filed April l, 1924 4 Sheets-Sheet 2 INVENTOR jm@ M A TTORNEY-S March 2 1926. 1,575,031

J. E. BELL METHOD AND APPARATUS FOR CRACKING OILS UNDER PRESSURE 4 Sheets-Sheet 5 Filed April 1 1924 INVENTOR ATTORNEY.`

Mrch 2 1926..

J. E. BELL METHOD AND APPARATUS EUR CRACKING OILS UNDER PRESSURE Filed April 1, 1924 4 Sheets-Sheet 4 ATTORNEY Patented Mar. 2, 1926.

UNITED STATES PATENT OFFICE.

JOHN E. BELL, OIBROOKLYN, NEW YORK, ABSIGNOB 'TO SINCLAIRABEFINING COH- PANY, OI CHICAGO, ILLINOIS. A CORPORATION OF MAINE.

IETHOD AND APPARATUS FOB CBACKING OILS 'UNDER PBmSURE.

Application 1011 April 1, 1924 Seal No. 705,339.

T o all whom it may concern.'

Be it known that I, JOHN E. BELL, a citizen of the United States, residing atBrooklyn, in thel county' of Kings, State of New York, have invented certain new andx useful Improvements in Methods and Apparatus for Cracking Oils Under Pressure; and I do hereby declare the following to be a full, clear, and exact description of the invention,

ksuch a's will enable others skilled in the art to which it appertains to make and Ause the same. v

This invention relates to improvements in the construction and operation of pressure stills for cracking heavier hydrocarbon oils for the production of lighter hydrocarbon oils therefrom.

In the cracking of heavier hydrocarbon oils in pressure stills,the pressure is controlled eitherv by release of fixed gas at a point beyond the condenser or by means of a pressure regulating and reducing valve interposed between the pressure still and the condenser. The regulation of the pressure in either of these ways requires the attendance of an operator and the adjustment of valves to maintain a Substantially uniform pressure under varying conditions of operation. The present invention provides a new and improved method and means for controlling and regulating the pressure of pressure stills. According to the present invention, the pressure still is provided with a fixed orifice from which the vapors and gases can escape at a. substantially constant rate, and the vapors from the pressure still, before reaching such discharge orifice, are subjected to partial condensation, and this partial condensation is regulated and variedv to take care of fluctuations of operation and to maintain approximately constant pressure in the still.

The pressure stills themselves. with which the invention is combined, or in which the method of the invention is carried out, may vary in their construction. -It may be a pressure still of the shell type, or it may be a tubular pressure still. 'In case of a tubular still, the still may be one in which the oil is circulated from a large supply tank or. drum through heating tubes and back to the main supply tank, or it may be a still in which the oil is passed through the heating tubes in a single pass. The invention isof more or less general application in so far as the construction of the pressure still is concerned.

Pressure stills are commonly provided with a reflux tower so connected and arranged as to subject the vapors from the pressure still to a refluxing operation so as to condense and return the heavier vapors. The present invention is of special application and advantage in connection with pressure stills which are provided with such refiux towers, although the invention, in its broader and more general applications, is not limited to the use of a reflux tower or to the return of the reflux or condensed vapors to the pressure still.

In ressure stills where a reflux tower is provi ed, I also provide one or more additional towers which are adapted to be maintained at still pressure, and I provide such additional tower or towers with a fixed orifiee outlet and with variable condensing means so that a regulated amount of the vapers can be condensed therein. By regulating the condensation in this way, a regulated flow of vapors is provided which is approximately constant in amount through the fixed outlet.

The present invention accordingly involves a partial and regulated condensation of the vapors while they are main-tained under the same pressure as that in the pressure still, or in the vaporizing chamber of such still, and a subsequent condensation of the remaining vapors under a lower pressure, which may be atmospheric or a predetermined pressure higher than atmospheric.

The fixed orifice, or orifices, in case more than one is used, may vary somewhat in their construction but in general they should be so constructed as to permit a substantially constant outflow of vapors therethrough and to offer a suicient reslstance to such fiow to maintain the desired pressure in the pressure still. The orifice may be one which is adjustable` and which, when once adjusted can be left without further adjustment or regulation during the pressure still run.

Vith such a fixed orifice as the means of escape of the high pressure vapors from the pressure still, is it evident that increase in pressure in the still will bring about a corresponding outflow of vapors. According to the present invention, however, if the pressure increases in the still, the condensing effect upon the vapors is increased, so that an increased amount of the vapors is condensed, and the pressureythereby reduced. The operation of the pressure still is thus regulated and controlled without regulation and control of the outlet from the still; and a substantially constant rate of outflow through a fixed orifice outlet is obtained while regulating the pressure within the still by a variable condensation ofthe vapors before they escape through -the fixed outlet.

The regulations of the condensation of the vapors, acrording to the present invention, can be e'tcted in various ways. For example, one advantageous method of regulation is to provide a second tower 1n addition to the usral reflux tower and to circulate through this second tower a regula-ted amount of' a cooling fluid. By regulating the amount of the cooling fluid so circulated, the cooling and condensing effect can be regulated. The cooling fluid may advantageously be cold oil whichlis to be fed into the pressure still as charging stock or a part'only of the still feed may be employed as the cooling fluid.l Instead of employing oil, cold vater or other liquid can be employed and can be circulated in regulated amount through the tower for regulating the condensation of the vapors.

ln the practical carrying out of the invention, the regulation of the condensation can be controlled automatically by a pressure regulator acting upon the cooling fluid circulated in heat interchanging relation with the vapors. As the pressure in the still increases, such a regulator will cause an' increased amount of the cooling liquid to flow through the tower and a correspondingly increased condensation of such vapor; while if the pressure in the still decreases, the flow of cooling liquid will be reduced and the amount of vapors condensed will be correspondingly reduced.

The condenser construction for subjecting the vapors to the condensing action of the cooling liquid can be varied, but in general,

the construction should be such as to present a relatively large surface of heat interchanged between the vapors and the cooling l1 uid.

(ll'he condenser may be of tubular construction with the cooling liquid flowing through tubes or it may be of multi-whirl construction with the vapors in the shell space coming in at the Lottom and going out at the top, and the .cooling liquid circulating through small cooling pipes entering at the top and fl( wing out at the bottom. A tower in which the vapors are directly contacted Vwith the tooling medium, for example, a tower in which cool oil is introduced into the vapors may be employed.

Where the pressure still is provided with a reflux tower, the condensate from` the variable condenser will be of intermediate character, fighter than the reflux from the reflux tower and heavier than the final condensate. 'Ihis intermediate fraction or cut may be returned to the pressure still or it may be separately drawn out and treated in a separate. pressure still or it may be used for some other purpose.

AWhere gas oil is the charging stock in a pressure still and gasolene or pressure distillate is the product desired in the final condenser the intermediate fraction or cut from the variable condenser will be of a kerosene-like character and can be used where an oil of such intermediate composition is desired.

The improved regulation of the present invention (an accordingly be embodied and combined in a pressure still and in the operation of such a still in such a way as to give a fractional condensation of the vapors from the still, with the obtaining of one or more intermediate fractions in addition to the final gasolene or pressure distillate fraction. The heavier vvapors may be thus be returned directly to the pressure still from the reflux lower while the lighter vapors, including the lighter gas oil and kerosene constituent as well as the gasolene constituents can be fractionally condensed and re covered as fractions, for example, by separating the kerosene fraction in the variable condenser and the gasolene fraction in the final condenser at a lower pressure. By operating in this way, only heavier oil is present in the pressure still, the light constituents being carried over to the variable condenser and separately condensed.

l'Vher'e the cooling of the variable condenser is effected by cold oil, the oil will be preheated, and this oil inay advantageously be that which is supplied as charging stock to the still, so that the heat absorbed in the condenser will' be made available to assist 1n the cracking operation. This preheated oil may advantageously be supplied, or part of it supplied to the top of the reflux tower and permitted to intermingle with the vapors 1n such tower to promote the refluxing operation. The lighter constituents of such feed will lie vaporized and will pass over with the vapors from the pressure still to the variable condenser, and the heavier vapors will be condensed in the variable condenser. while the lighter vapors will pass through the rcd orifice to the filial condenser. The introduction of the feed in this way not onli' preheats the feed but also fractionates it and separates it into a heavier charging stock for the pressure still and lighter constituents which are separately condensed elther in the variable condenser as intermediate oil or in the final condenser as gasolene or pressuiedistillate. Gasolene and kerosene constituentsof the charging stock can .thus be driven off and separately recovered without introducing. them into the crackin still proper.

' IVhere 'the same ,oil is circulatedy first through the variable condenser and then Into tbe to'p of the reflux tower, any increase in the amount of -oilcrculating through the variablecondenser will likewise increase the amount of `oil fed into the reflux tower. This will resuit in an' increased condensing action in the variable condenser and an increased cooling action in the reflux tower as well 'as`an increase in the amount of oil fed to the still proper.

In the preferredpractice of the invention, the pressure still is provided with a reflux tower .through which the vapors from the still are first passed, and the still is also provided with a second tower which will 'act' as a variable condenser, in which `the vvapors will be subjected to a regulated condensation and from which the uncondensed vapors will escape at a substantially constant `rate through a fixed orifice or nozzle outlet.

In such a still` the pressure will be regu- 'latedv by regulating the condensation in the variable condenser, for example, by circulating a cooling fluid through a cooling coil yat a controlled rate, increasing the flow with pressure increase and decreasing the flow with pressure decrease. The flow of feed oil `may' be controlled by hand orautomaticallyby a pressure regulating valve acting upon the supply of cooling fluid.

\ The invention will be further described in connection with the accompanying draw- Vyings 'which illustrate, in a somewhat conventional and diagrammatic manner, four pressure still constructions embodying the invention and adapted `for the practice of the process of the invention. It will be understood, however, that the modifications so illustrated and described, are illustrative of the invention, and that the invention is not limited thereto.

In thel accompanying drawings Figs. 1,2, 3 and. 4 illustrate diagrammatically and partly in section three embodiments of the invention.

In the vdrawings the pressure still illustrated is of the general type and construction set forth in U. S. Letters Patent No.

1,285,200, granted November 19, 1918, to the Sinclair Refining Company upon an application fof Edward W. Isom, but it will be understood that the `invention is appplicable to other pressure stills and may be combined therewith in a similar way and with the same or similar advantages.

In the accompanying'drawings the same or corresponding parts are indicated by the same reference characters.

The pressure 'still illustrated comprises heating tubes 6 locate 1n the heating flue of the furnace 7 the pi connections 8, 9 and 10 connecting thebu supply tank with the top andbottom headers or manifolds, respectively, of the vertical heating tubes and t e pump 11 for circulating the oil from the bulk sup ly tank through the heating tubes and bac to the bulk supply tank.

Located above the pressure still is a reflux tower 13 connected with the vapor dome 12 of the bulk supply tank by a vapor line and having a return pipe 14 for returning the refluxto the bulk supply tank. The reflux tower is shown as ofcommon baille construction. Thebulk su ply tank 5 is shown with an outlet .15 for t e withdrawal of tar.

The vapor outlet 16 from the top of the reflux tower passes to the bottom of a variable condenser 2O having a cooling coil therein whereby a regulated amount of the vapors can be condensed. The variable condenser 20 has a fixed orifice outlet 21, conventionally` shown, but of a construction such that a sufficient resistance will be provided tothe escape of vapors therethrough to maintain the necessary or desired pressure in the pressure still. A valve controlled bypass 31 is provided around the fixed orifice to permit the free escape of vapors and gases in the event of excessive rise of pressure'in 4the pressure still. This emergency bypass may be automatic in its action, acting upon a predetermined increase in pressure above that normally maintained in the still, or it may be hand controlled.

The vapors and fixedL gas escaping through the fixed orifice 21 pass through the vapor line 22 to the condenser shown conventionally at 23. The condensed vapors and uncondensed gas are collected in the receiver 24 from which the condensate.,ordaressure distillate is drawn off through the valifecontrolled pipe 25 and the fixed gas and uncondensed vapors through the valve controlled outlet pipe 26. The pressure maintained onA the condenser and receiver may be approximately atmospheric or may be a predetermined pressure between still pressure and atmospheric- In the construction illustrated in Fig. 1 the cooling coil 30 located in the variable condenser 2O is supplied with feed oil of the character which is charged into the pressure still. This feed oil is sup-plied through', the feed pipe 60 and a regulated amount circulated through theeoil 30, the amount being regulated by the valve 32. In place of regulating the flow of oil by valve 32 by reference to the pressure gage 32, the flow of oil may be regulated by the pressure-actuated valve 321. -After flowing through the coil and being preheated therein, the oil then passes to the top of the reflux tower L(the

valves

33, 36 and 37 being open and the valve 38 closed) and. enters the reflux tower at the top through the pipe 35; or by ening the

valves

33 and 39, and closing tlie valve 36, the preheated oil will be discharged through the pipe 34 into the circulating stream of oil in the pipe 10. By opening the

valves

38 and 37 and closing the valve 36, the feed oil can be fed without preheating into the top of the reflux tower 13. A supplemental feed line 60 permits the introduction of additional feed either to the top ofthe tower or to the circulating stream i of oil. This line 60a also permits the escape of oil after it has circulated ,through the variable condenser Without introducing it into the pressure still, the valve 33 and the valve in the pipe 60 being open, and the valves 36 and 39 being closed.

It will thus be seen that the construction illustrated in- Fig. 1 provides for various methods of operation. The cold feed oil can be circulated through the coil 30 without entering the pressure still, or this preheated oil can be in part or in whole introduced into the pressure still either through the reflux tower or through the circulating line or in part through each. In addition, the feed oill can be independently supplied to the sti l.

In the operation of the apparatus illustrated in Fig. 1 the oil in the still will be rapidly circulated from the bulksupply tank 5 through the heating tubes and back to the bulk supply tank and the oil will thus be heated to a cracking temperature, while the pressure will be raised to that corresponding to the temperature ofcracking. T hev vapors given off from the pressure still will be subjected to a refluxing operation in the tower 13 where they Will-come in contact with the feed oil introduced either cold or in a preheated state. The heavier constituents of the vapors from the still and the heavier portions ofthe feed will .be returned to the pressure still. The uncondensed vapors from the still and the vaporized portions of the feed will pass over through the pipe 16 into the variable condenser 20 where they will be subjected to a regulated condensing operation. The contents from this variable condenser can 'be drawn out through the line 27 to'a place of storage orof further use. The uncondensed vapors from the variable condenser will escape with reduction of pressure through the orifice 21 and the expanded vapors will then pass to the main condenser Where the condensation of the gasolenc or pressure distillate willtake place.

The orifice 21 is designed'to permit the escape of vapors at a fixed rate. In operation, this rate of escape through the orifice is constant at any given pressure and does not vary greatly with the variations in pressure which take place within the pressure still. The regulation ofl the pressure is effected by regulation of the rate of condensation in the variable condenser 20. With increase in pressure, the rate of flow of the cooling fluid is increased so that the Yrate of condensation is increased, with resulting decrease in the pressure and decrease in the amount of vapors and gases which must escape from the still to maintain the desired pressure. When the pressure is thus reduced to the predetermined or desired pressure, the rate of flow of the cooling liquid will be regulated to maintain this rate of condensation.

Regulation of the 'condensation in this way, increasing it with increase in pressure in the still and vice versa, the operation is continued with substantially constant outflow of vapors through the fixed orifice and with control of operation by increase and decrease of flow of cooling liquid, and corresponding increase and decrease in the amount of vapors condensed, as the pressure increases or decreases inA the still. It will be evident that this method of pressure control is independent of the manipulation of valves in the distillation system, and

that the vapors escape unregulated and in Y approximately constant amount through the fixed orifice, the regulation being preliminarily effected by regulated condensation under the pressure maintained in the still itself.

As an example of the operation of the apparatus, the orifice may be designed to permit the passage of 75% of the amount of vapors and gases normally produced by the pressure still under the usual conditions of operation. If we take the total production of' vapors as 100 units, then 75 units would pass through the orifice, and the desired equilibrium would be maintained by con- (lensing 25 units in the variable condenser 9.0. If the rate of formation of vapors increased inthe still to say 125 units, there would still be about 75 units passing through increase to 75 units while 75 units wouldstill escape through the fixed orifice. If, on the other hand, the still production decreased to 7 5 units, this total production would pass through the fixed orifice and no condensation would be required in the variable condenser 20. It will be evident that the amount of vapors fiowing from the reflux tower to the variable condenser is equal to the amount of vapor passing throu h the orifice 21 plus the amount condensed 1n the variable condenser.

With the pressure still of the construction illustrated and using ordinary gas oil charging stock, the heavier vapors will be refluxed aan ' the main through to have a relatively to the still while a fraction or cut Asimilar to ker'osene can be drawn ofi from thevariable condenser 27 and a final gasolene distillate or kerosene distillate can e recovered from the final condenser. Whi e the intermediate or kerosene distillate may be returned to the pressure still, it is more advantageously subjected to a separate cracking operation by circulating it through a separate cracking coil maintained under a Sullicient pressure and at an appropriate temperature for such lighter charging stock. This intermediate kerosene distillate may, for example, be treated with advantage 1n accordance with the vapor phase cracking process set forth in application, Serial No. 584711 of Edward W. Isom, filed August 28, 1922, and the products of such va or phase cracking operation maybe returne to ressure still.

The fina condensation of the vapors passing the fixed orifice can be effected in condensers of various t pes. The fixed nozzle or orifice will cause t e vapors assing thereigh velocity. 'lhis velocityT may be taken advantage of in a condenser in which the vapors are discharged as a jet into a body of condensate, for example, as described in U. S. applications Serial No. 470,790, filed May 19, 1921, Serial No. 472,990, filed May 27, 1921, Serial No. 479,796, filed June 23, 1921, Serial No. 657,177, filed kAugust 13, 1923, Ser. No. 661,750, filed Sept. 10, 1923 which described apparatus and methods .for the condensation of hydrocarbon vapors by injecting them into cooled bodies of liquid condensate. ln the drawings, a conventional form of condenser is illustrated.

The fixed orifice illustrated in the drawing is shown as a restriction in the outlet pipe but, as above noted, this orifice may be adjustable so that, for example, if the still A is to be operated with an increased rate of vapor formation, a fixed orifice of increased size may be rovided by suitable adjustment, and the stillpthen o erated with a regulated fixed orifice adapte to the conditions ofoperation. When the fixed orifice has once been adjusted, the pressure control then becomes independent of any further adjustment of valves, connected with the pressure still, but the regulation is accomplished entirely by variable condensation of the vapors in the manner previously described, and a substantially constant pressure is maintained by varying the feed or cooling liquid :n thevariable condenser.

In the apparatus in Fig. 1, the feed or cooling oil for regulating the cooling and condensing action is accomplished by hand operated valves, but, as already pointed out, the regulation may be automatic in character. Figs. 2 and 3 show two types of apparatus with automatic control.

In Fig. 2 the variable condenser 20 is provided with a cooling coil 40 conventionally shown, and through which oil or other liquid is circulated. This cooling coil has inlet and

outlet valves

42 and 43, but the primary control of the cooling liquid therethrough is by me'ans of: a pressure actuated valve conventionally shown at 44. InA practice, this pressure control valve should belone which will withstand the pressure of the pressure still on one side of the diaphragm or other actuating means and it should be sensitive to Within a narrow pressure range above and below that which it is desired to maintain in the pressure still so that it will increase the flow of cooling fluid through the coil with increase of pressure and decrease the flow with decrease of pressure. The connecting pipe is shown as connecting the pressure regulating valve 44 with the interior of the variable condenser 20 but by closing the valve in the pipe 45 and using the hand operated

valvesy

42 and 43 the flow of oil or water or other cooling liquid can be manually controlled.

In the operation of the pressure still illustrated in Fig. 2 the feed may be introduced through the feed line and the pipe 35 into the top of the reflux tower and a partial regulation of the operation of the still can be effected by regulating the amount of the feed so introduced. The vapors from the reflux tower and while still under same pressure will then be subjected to a regulated condensation in the variable condenser 20. The uncondensed vapors will escape through the fixed orifice 21 and the vvariable condenser will be regulated, either manually or automatically, to condense the excess amount of vapors, in excess of the constant amount flowing through the fixed orifice. The intermediate condensate escaping at 27, may be subjected to any desired further treatment. The vapors escaping from the fixed orifice pass through the pipe 22 to anyy suitable condenser (not shown).

In the apparatus illustrated in Fig. 3 a regulated closed circulation of the cooling fluid is provided for regulating the condensation in the variable condenser. The closed cycle of circulation is shown which includes the cooling coil 50 located inthe variable condenser 20, a coil 51 immersed in a cooling liquid contained in a tank 52 and a pump 53 for circulating the liquid through the coils. The cooler 52 may be maintained at a low temperature to abstract the heat absorbed in the coil 50. The cooling effect in the coil 50 and hence the rate of con densation in the variable condenser 20 will vary with the rate of circulation, and hence the rate of condensation can be effected by regulation of the pump speed.

In Fig. 3 the pump 53 is shown as driven by a variable speed motor 56, the speed of which is regulated by a pressure actuated control 54 operated by a pressure regulator shown conventionally at 55, and connected through the pipe 57 with the vapor space in the pressure still. The pressure regulator and variable speed motor and control are conventionally shown but they should be so constructed and related to the cooling liquid and construction of the cooling coil that the increase in pressure in the pressure still will increase the speed in the motor and the rate of circulation of the cooling liquid so as to maintain an approximately con-` stant pressure in the system and variable condensation of vapors with variation in the amiunt of vapors produced in the pressure sti In the construction illustrated in Fig. 4 the variable condenser is a baflie tower, conventionally shown, through which cool o il is introduced directly into the vapo-rs therein. This cool oil is supplied to the top of the tower 70 through pipe 71, either from the feed pipe 60 or through pipe 72, and the flow of cooling oil is regulated by the

valves

74 or 74a and' 75, The condensate and revaporized cooling oil, after passing over the baffles in the tower and effecting partial and regulated condensation of the vapors therein, leaves the tower through pipe 73, and may be discharged through the valve controlled pipe 76 (the Vvalve 77 being closed) or may be discharged into the circulating stream of oil in the pipe 10 through pipe 34 (the

valves

39 and 77 eing open andthe valve 76 closed). A supplemental valve controlled connection 78 ermits the introductionof additional feed into the circulating stream of oil.

In the operation of the pressure still illustrated in Fig. 4, the feed may be introduced through the feed line 6() and the pipe 35 into the top of the reflux tower 13 and a partial regulation of the operation of the still can be effected by regulating the amount of feed so introduced by valve 37. The vapors from the reflux tower` still under the same pressure, will then be subjected to a regulated condensation in the variable condenser 70. The uncondensed vapors will escape through the fixed orifice 2l and the variable condenser will be regulated, by regulation of the oil introduced through pipe 7l, to condense the excess amount of vapors, in excess of the constant amount flowing through the fixed orifice. The intermediate condensate escaping at 73 may be returned to the pressure still, or it may be treated in a separate pressure still, or subjected to any desired further treatment. The vapors escaping through the fixed orifice pass through the pipe 22 to the condenser and receiver.

Feed oil from the line 60 may be introduced into the variable condenser to effect the regulated condensation therein, or a separa-te fraction, such as a part of the condenser distillate collecting in the receiver 24, may be returned through pipe 72 for this purpose. l/Vhere all or a part of the feed oil to the pressure still is introduced through the variable condenser, the unvaporized feed oil and condensate may be returned to the circulating line of the still, or it may be introduced into the top of the redux tower on the still by means of a pump through suitable connections (not shown). Where a part of the condensed pressure distillate is employed to effect the regulated condensation in the variable condenser, the condensate therein comprises a fraction corresponding tothe heavy ends of the pressure distillate.

It will thus be seen that the invention provides for a partial but regulated condensation of the vapors from the pressure still before the vapors escape to a lower ressure, and that the escape of the vapors 1s at a constant rate such that regula-tion thereof is not required. The pressure still can 'accordingly be operated without the usual pressure control means for regulating the drawing off of vapors or liquid. The regulation is nevertheless effected in a novel and advantageous way within the system itself by variably condensing vapors within the system, and subsequently condensing the fixed amount of vapors that escape from the system.

It will further be seen that, where the 1100 pressure still is provided with a redux tower, the head temperature of the redux tower can be regulated by the feed so introduced, this regulation being in addition to the regulation effected in the v variable con- 105 denser. The vapors escaping at the desired head tem rature from the to of the redux tower wil be in part con ensed in the -variable condenser and a fixed amount will 'operating normally with but small variations in 'tshe amount of vapor formed, a fairly constant amount of condensation will be obtained in the variable condenser, but as the' pressure still departs from such normal operation, and the vapors increase or decrease with resulting increase or decrease of pressure, the cooling effect applied to the variable condenser can be correspondingly varied and an approximately constant pressure maintained. y

The invention thus provides a novel method of construction and operation whereby the regulation of thepressure by manipulation of gas or vapor control valves is avo-id' ed and whereby the' pressure still may be operated with a substantially constant out.- flow of vapors therefrom,r and whereby variations in pressure are taken care of and a substantially uniform pressure obtained by a regulated condensation of vapors within the pressure still system itself and at the sane pressure maintained in the presure stil The pressure maintained in the ressure still can be varied. With heavier c arging stockssuch as gas oil, the pressure may be around 90 to 125 pounds, while with lighter charging stocks of the nature of kerosene or light gas oil, considerably higher pressures may be used, e. g. around 300 to 325 pounds, or even much higher. The charging stock for the pressure still may also vary, although the invention is of special advantage in conjunction with pressure stills using heavier charging stock such as gas oil, and where an intermediate cut of the nature of kerosene is to be separated and separately treated. In such a pressure still operating with a heavy charging stock, any lighter constituents introduced with the charging stock can be recovered along with the lighter vapors from the cracking operation, while the introduction of the fresh feed into the top of the reflux tower permits the control of the head temperature of the still independently of the pressure control so that all of the lighter vapors passing over at the regulated head temperature will be obtained in two or more separate fractionsA due to the fractional condensation, partly under still pressure and partly at lower pressure, to which the vapors are' subjected.

Where the charging stock for the pressure still is introduced into the top of the reflux tower, it may contain a considerable amount of light constituents which will be vaporized in the reflux tower and which will pass off from Vthe top of the reflux tower in admi'xture with the lighter vapors from the crackin operation.` These llighter constituents o the' feed, in vaporizing in the reflux tower, will add to the refluxing ac A tion without increasing the amount of heavier oil entering the still 'through the reflux tower.

The lighter vapors passing from the top of the reflux tower will be subjected to partial condensation in the variable condenser and the intermediate condensate therefrom will be of a composite character, being made u in 'part of the constituents produced by it e cracking operation and 1u part of constituents vaporized from the additional feed o'il. -Where the feed oil also contains gasoline or similar light constituents, such constituents will pass to the final condenser with the lighter vapors from the cracking operation so that the pressure distillate recovered will also be of a composite character, containing crackedV distillate admixed with the lighterdistillate from the feed. The' present invention accordingly provides for the recovery of lighter constituents from the feed stock in admixture with the pressure distillate and intermediate distillate or distillates from the cracking operation. The lighter constituents of the feed stock will thus be vaporized in the reflux tower, where they will exert a desirable cooling action, and they will then be fractionally condensed in admixture with the condensates from the pressuer still operation. l

The present invention enables regulating valves in the vapor lines of pressure stills to be avoided and enables the pressure to be controlled independently of such valves, or, if such valves are used to furnish the fixed orifice, they do not require adjustment during` the normal operation of the still. The

invention nevertheless p'ermits the final condensation to take place at a lower pressure than that maintained in the still itself. Should execessive pressures develop in the system which the method of centro! will not take care of, the emergency bypass 31, if of automatic construction, will automatically-release the pressure upon a predetermined increase, or, if a hand operated valve isprovided, the operator may release the excessive pressure by manipulation of such bypass valve.

I claim:

1. The process of cracking heavier hydro-V carbons under pressure, which comprises subjecting the hydrocarbons to a cracking temperature under pressure, subjecting the resulting vapors to a regulated condensation while under pressure, .permitting uncondensed vapors to escape through a fixed orifice, and increasing and decreasing the condensation in the said kregulated condensation with increase and decrease, rc spectively, of the pressure.`

2. The process of cracking heavier hydrocarbons under pressure, which comprises subjecting the hydrocarbons to a cracking temperature under pressure, subjecting the resulting vapors to a regulated condensation while under pressure, permitting uncondensed vapors to escape through a fixed orifice, and increasing and decreasing the condensation in the said regulated condensation with increase and decrease, respectively, of the rate at which vapors escape through the said orifice.

3. The process of cracking heavier hydrocarbons under pressure, which comprises subjecting the hydrocarbons to a cracking vtemperature under pressure, subjecting the i densed vapors at a substantially uniform j rate, and increasing and decreasing the condensation in the said regulated condensation with increase and decrease, respectively, of the pressure.

4. The process of cracking heavier hydro carbons under pressure, which Acomprises subjecting the hydrocarbons to a cracking tem erature under pressure, subjecting the resu ting vapors to aregulated condensation while under pressure, permitting uncondensed vapors to escape through a fixed orifice, and regulating the pressure solely by regulating the said condensation.

5. The process of cracking heavier hydrocarbons under pressure, which comprises subjecting the hydrocarbons to a cracking temperature under pressure, subjecting the resulting vapors to a regulated condensation While under pressure, returning condensate therefrom to the cracking operation, permitting uncondensed vapors to escape through a fixed orifice, and increasing and decreasing the condensation in the said regulated condensation with increase and decrease, respectively, of the pressure.

6. The process of cracking heavier hydro carbons under pressure, which comprises subjecting the hydrocarbons to a cracking temperature under pressure, subjecting the resulting vapors to a refluxing operation from which reflux is returned to the cracking operation and then to a regulated condensation froln which condensate is returned to the cracking operation While under pressure, permitting uncondensed vapors to escape through a fixed orifice. and increasing and decreasing the condensation in the said regulated condensation with increase and decrease, respectively, of the pressure.

7. The process of cracking heavier hydrocarbons under pressure, which comprises subjecting the hydrocarbons to a cracking temperature under pressure, subjecting the resulting vapors to a refluxing operation from which refiux is returned to the cracking operation and then to a regulated condensation while under pressure, permitting uncondensed vapors to escapeV through a fixed orifice, and increasing and decreasing the condensation inthe said regulated condensation with increase and decrease, respectively, of the pressure.

8. The process of cracking heavier hydrocarbons under pressure, which comprises. subjecting the hydrocarbons to -a cracking temperature under pressure, subjecting the resulting vapors to a regulated condensation while under pressure by` heat interchange with feed oil, permitting uncondensed vaamener pors to escape through a fixed orifice, and mcreasing and decreasing the rate of supply of feed oil with increase and decrease, respectively of the pressure.

9. The process of cracking heavier hydrocarbon oils under pressure, which comprises heating the loils to a cracking temperature, passing the resulting vapors while still under pressure through a condenser, withdrawing vapors and gases from said condenser at a substantially constant rate, passing -feed oil in heat-interchanging relation with the vapors in said condenser before introducing it into the pressure still, and increasing and decreasing the rate of flow of the feed oil with increase and decrease. in pressure in the system.

10. The process of cracking heavier hydrocarbons under pressure, which comprises subjecting the hydrocarbons to a cracking temperature under pressure, subjecting the resulting' vapors Ato a, regulated condensation while under pressure, permitting uncondensed vapors to escape through a fixed orifice, increasing and decreasing the condensation in the said regulated condensation with increase and decrease, respectively, of the pressure,and withdrawing the condensate as a liquid.

11. The process of cracking heavier hydrocarbons under pressure, which comprises subjecting the hydrocarbons to a cracking temperature under pressure, subjecting the resulting vapors to a regulated condensation while under pressure by direct contact with feed oil, permitting uncondensed vapors to escape through a fixed orifice, and increasing and decreasing the supply of feed oil to said condensation with increase and decrease, respectively, of the pressure.

12. Apparatus for the cracking of heavier hydrocarbons under pressure, comprising a pressure still, a condenser communicating with the vapor space of said still, means for withdrawing vapors and gases from the condenser at a substantially constant rate, and means for subjecting the vapors in said condenser to a regulated condensation, said means being automatically actuated by the pressure in said system.

13. Apparatus for the cracking of heavier hydrocarbons under pressure, comprising a pressure still, a reflux tower, and a condenser, all adapted to be maintained under the same pressure, said condenser having a fixed orifice for the discharge therefrom of vapors and gases at a substantially constant rate, means for subjecting the vapors in said condenser to a regulated condensation, and automatic regulating means for regulating the condensation adapted to maintain a substantially constant pressure in the system.

14. Apparatus for the cracking of heavier hydrocarbons under pressure, comprising a pressure still, a reflux tower, and a condenser, all adapted to be maintained under the samepressure, said condenser having a fixedprifice for the discharge therefrom of vapors and gases at a substantially constant l rate, means for subjecting the vapors in said condenser .to a regulated condensation, and automatic. regulating means for regulating the condensation to maintain a substantially constant pressure in the system, said automatic regulating means being controlled by the pressure in the system.

15. Apparatus for the cracking of heavier hydrocarbons under pressure, comprising a pressure' still, a reflux tower,' and a condenser, all adapted to be maintained under the same pressure, said condenser having a fixed l`orifice for the discharge therefrom of vapors and gases at a substantially constant rate, means for. subjectingthe vapors in said condenser to a re ulate condensation, and

`automatic means or regulating the condensationin said condenser, said automatic meansbeing actuated by the pressure in the system.

, 16. Apparatus for the cracking of heavier hydrocarbons under pressure, comprising a pressure still, a condenser communicating with the vapor space of said still, means for flowing feed oil to the still in heat interchange with vapors in the-said condenser, means for withdrawing vaEorsmand gases from the condenser at a vsu stantially constant rate, and means actuated by the res'- sure in said system for increasing an decreasing the flow of feed 011 with increase and decrease, respectively, of the pressure.

17. Apparatus for the cracking of heavier hydrocarbons under pressure, comprising a pressure still, a 'condenser communicating with the vapor space of said still, means for withdrawing vapors and gases from the condenser at a substantially constant rate, means for introducing feed oil into direct contact with vapors in the condenser, and means actuated by the pressure in the system for increasing and decreasing the supplycf feed oil with increase and decrease, respectively, of the pressure.

18. Apparatus for the cracking of heavier hydrocarbons, comprising a system adapted to be maintained under pressure including means for heating the hydrocarbons to a cracking temperature therein, a condenser communicating with said system and adapted to beV maintained under substantially the same pressure, means for withdrawing vapors and gases from the condenser at a substantially constant rate, and means actuated bythe pressure in the system for increasing and decreasing condensation in the condenser with increase and decrease, respectively, `ot the pressure. p

19. Apparatus for the cracking of heavier hydrocarbons, comprising a system adapted to be maintained under pressure including means for heating the hydrocarbons to a cracking temperature therein, a condenser communicating with said system and adapted to be maintained under substantially the same pressure, means for withdrawing vapors and gases from the condenser at a substantially constant rate, means for flowing feed oil to the system in heat exchange with vapors in the condenser, and means actuated by the pressure in the system Ifor increasing and decreasing the flow of feed oil with increase and decrease, respectively, of the pressure.

In testimony whereof I aftix my si ature.

JOHN E. B LL.