US1909600A - Method for distilling hydrocarbon oils - Google Patents

Description

METHOD FOR DISTILLING HYDROCARBON OILS File May 28, 1930 s Sheets-Sheet 1 INVENTOR y 16, 1933- s. c. YEATON 1,909,600

METHOD FOR DISTILLING HYDROCARBON OILS Filed May 2 1930 5 Sheets-Sheet 2 INVENTOR y 16, 1933- s. c. YEATON 1,909,600

METHOD FOR DISTILLING HYDROCARBON OILS Filed May 28, 1930 5 Sheets-Sheet 3 23 24 1T1; J36 W 57 INVENTOR May 16, 1933. s. c. YEATON 1,909,600

METHOD FOR DISTILLING HYDROCARBON OILS Filed May 1930 5 Sheets-Sheet 4 INVENTOR May 16, 1933. s. c. YEATON 1,909,600

METHOD FOR DISTILLING HYDROCARBON OILS File May 1930 5 Sheets-Sheet 5 FIG-.5:

Patented May 16, 1933 PTATET OFFICE SAMUEL G. YEA'ION, OF BAYSIDE, NEW YORK METHOD FOR DISTILLING HYDROCARIBON OILS Application filed May 28,

This invention relates to improvements in means and methods for distilling hydrocarbon oils, and more particularly for refining such oils involving What is commonly termed the cracking thereof.

In distilling hydrocarbon oils by a cracking process, a considerable amount of carbon is developed, depending more or less upon the nature of the stock treated, Which, if not taken care of, gives much trouble and materially curtails the run in such modern methods as are commonly termed continuous, all of Which is Well known in the gasolene and allied manufacturing industries. It has been discovered that by releasing, during the run, a portion of the oil charge from the still containing this objectionable carbon, the length of the run may be materially increased. It is to such apparatus and methods of manufacture of gasolene and the like involving a relieving of the charge of a part of its carbon-contained oil during the cracking process that the present invention is directed.

A common type of such set-up for carrying out the method includes a heating element Where the charge of oil is heated to a cracking temperature; means for relieving the element of carbon-contained oil; a receiver for receiving a portion of theoil discharged from the charge Within the element after a cracking treatment; means for supplying oil to the charge Within the element from the receiver; and means for feeding fresh oil to the charge. In set-ups of this type it has been the common practice to relieve the charge of the desired portion of carbon-contained oil While oil is being supplied to the charge from the receiver, in a manner to permit this supply to commingle with the portion of the charge therein that is being released.

The principal object of this invention is to provide for an intermittent releasing of r a porton of the carbon-contained oil from the charge, and to provide means, during this period, to prevent such commingling of the oil supplied to the charge fi'om the receiver.

This improvement is particularly advanthe carbon-contained oil.

1930. Serial No. 456,361.

tageous in such methods and types of apparatus provide for discharging the oil from the charge to the receiver in vapor form, after Which a portion of the discharge is condensed in the receiver and supplied in liquid form therefrom to the charge. This vapor discharge from the element has, previous to its discharge, as is obvious, been submitted to a cracking temperature in the heating element, and therefore presents a much purer stock than the carbon-contained charge in the element. As it is only necessary, in clearing the system, to remove the heavy carbon-contained oil, it can be readily seen that this relatively pure discharged stock should not be supplied to the element to commingle With the heavier stock therein that is being carried out of the system by the relieving means. In short, this relatively pure discharged stock is supplied to the charge in the heating element for the sole purpose of being recracked and thereafter to again be discharged to the receiver. Therefore it is obvious that to prevent this commingling of the relatively pure oil With the carbon-contained stock that is being released, efi'ects an economy in the method of manufacture.

While the invention contemplates broadly the prevention of this undesirable commingling, in the preferred embodiment the supply from the receiver to the element takes place intermittently, the supplying of such oil being alternately With the releasing of It has beenfound advantageous for several Well-known reasons to maintain a substantially constant charge in the heating element, and as such intermittency of feed would temporarily interrupt this constancy, the invention further contemplates, if desired, feeding a fresh stock to the charge in the heating element during the releasing period, to maintain the charge substantially constant. The fresh stock may be permitted to commingle or not, with the portion being released for it Will not be particularly di advantageous to so handle it especially Where the fresh stock represents crude oil that has not been previously subjected to a cracking or distilling treatment. The pres ent invention further contemplates either permitting or preventing the commingling of the fresh stock with the stock being released as may be desired.

A further object of the invention is to provide a new type of receiver for receiving the discharged oil from the charge in the heating element in vapor form, the receiver serving as a condenser for a portion of the discharge by indirect heat transfer between the discharge in the receiver and the fresh charge of oil to be supplied to the element. The receiver preferably but not necessarily comprises means for directly feeding fresh oil thereto. The two feeding means are supplied with valves whereby they may operate intermittently, conjointly or alternately as desired in a manner as will more fully be hereafter described.

While the heating element may be of any well-known or preferred type, the invention further contemplates, when desired, a heating element wherein the charge of oil is heated to the required temperature by subjecting it to the action of a heated fluid brought into indirect heat exchange relation with the charge.

Other objects of the invention will appear from the following description.

In the accompanying drawings: Figure 1 is a side elevation of an apparatus involving the present invention shown diagrammatically; Fig. 2, a view similar to Fig. 1, show: ing a feed for the heating element passing through the receiver in indirect heat exchange relation; Fig. 3, a view similar to Fig. 1, showing a valve or gate for separating the charge in the heating element; Fig. 4, a view, similar to Fig. 2, showing the charge separating valve or gate of Fig. 3; Fig. 5, a side elevation partly in section of a portion of the apparatus showing a heating element where the charge of oil to be heated is brought into indirect heat exchange relation with a heated fluid; and, Fig. 6, a transverse section, taken on the line 66 of Fig. 5.

Referring to Figs. 1 to 4 inclusive, the heating element indicated generally by the reference A, while it may be of any suitable type, is shown as of a type resembling the Babcock 8a Wilcox boiler comprising a horizontal longitudinal drum 10, front trans verse drum 11, rear transverse drum 12, connecting tubes 13, front sluice way 14, rear sluice way 15, a fire box 16, oil burner 17, safety valves 18, and propeller and electric motor for driving same, generally indicated by the numeral 19, same being employed in a usual way for increasing the travel of the oil charge through the still in the direction indicated by the arrows.

While the invention is not confined to any r u o q n part1cular means for rel1eving the charge 1n the heating element of a portion of the carbon-contained oil, in the present instance, except for the employment of a control valve, a well-known means is shown which romprises vaporizer 20, pipe 21, leading from the heating element to the evaporator through which the carbon-contained oil release is carried, said pipe being shown in Figs. 1 and 2 as leading from the front transverse drum 11, control valve 22, to 3rovide for intermittent release of the carboncontained oil from the heater to the evaporator, pressure reducing valve 22, safety valve 23, vapor take-oil pipe 24, and residuum take-off pipe 25, leading from the evaporator.

The receiver, indicated generally by the reference B, for receiving the discharge from the charge of oil may be of any suitable type of reflux tower or dephlegmator, modified as will appear presently. In the present in stance, it comprises vertical drum 26, pro vided with horizontal baffles 27, vapor takeoff pipe 28, and safety valve 29. The discharge of oil vapor is conveyed through a pipe 30, leading from the drum 10, to the receiver drum 26, and oil is supplied through a pipe 31, leading from the receiver to the heating element, which pipe, in Figs. 1, 2 and 4, is provided with a control valve 32, for intermittently supplying such oil to the charge in the heating element alternately with the release of the carbon-contained oil through the pipe 21, as will hereafter more fully appear. The receiver, or reflux tower is provided with a coil trim, 33, to which a cooling fluid is lead through the pipe 34, the fluid after passing through the trim being discharged through pipe 35, in the usual manner.

Fresh oil is fed to the receiver through pipe 36, provided with control valve 37. Fresh oil is fed to the heating element, which in the present instance, as shown in Fig. 1, is accomplished by feeding it through a pipe 38, provided with a control valve 39, said pipe 38, for convenience, leading from pipe 36 to pipe 31 below the valve 32. The take-off pipe 40 provided with control valve 41 leads from pipe 31 above valve 32.

In Fig. 2 the feed pipe for feeding fresh oil to the receiver is provided with a control valve 42, near the upper end thereof, and the feeding of fresh oil directly to the heating element is accomplished through a pipe 43, provided with a control valve 44, lead ing to the heating element and connected at its upper end to a heat exchanger element disposed in the receiver and indicated diagrammatically by the winding pipe 45, passing back'and forth between the bailies 27. This heat exchanger is connected at its upper end to a pipe 46, leading from pipe 36, below the valve 42.

Fig. 3 shows a form of apparatus somewhat similar to Fig. 1, except no direct feed of fresh oil is provided for the heating element, and no take-off pipe from the receiver is employed. In this form of apparatus, the drum 10, is divided in two parts at a suitable point in the length thereof, as actual practice willdictate, with a separating valve or gate, which is shown in the present instance as a butter-fly type of valve 47, mounted on a horizontal transverse shaft which extends through the drum. The shaft is provided with a handle, 48, for opening and closing the valve, flanges 4L9, being provided on the inner walls of the drum for seating the valve when in closed position. The normal level of oil charge in the drum is shown by the line w,.which may be at any suitable height. The valve may divide the drum transversely throughout its entire height in which case a second discharge pipe similar to pipe 30 would be required at the opposite end of the drum leading to the receiver at substantially the same point as does the discharge pipe 80. In the form shown, however, the valve 47 is shown as not entirely dividing the upper or vapor space of the drum 10. Therefore, the vapor space on both sides of the valve when closed being in communication, a single discharge pipe 30 is all that is necessary. In this form of apparatus the release pipe 21 leads from the drum 10 at a point conveniently near the surface of the oil charge therein, but sufiiciently below such surface to be still covered by the oil charge at the termination of the release period, it being desired in this form of apparatus to release the carbon-contained oil from the charge during the re leasing period without removing any appreciable amount of the newly supplied oil that might circulate from the supply end of the drum to the release end through the bank of tubes 13. To further safeguard against this the supply from pipe 81, in this form of apparatus preferably enters the heating element at or above the surface of the charge of oil.

Fig. 4c shows a form of apparatus similar to that of Fig. 3 with the exception that the direct feed to the heating element and the take-off pipe from the receiver, shown in Fig. 2, are provided.

l/Vhile the heating element has been thus described as of the Babcock & Wilcox type of boiler, a. modified type of heating element is shown in Figs. 5 and 6. This type of heating element is patterned after the steam boiler shown in United States patent to Hartmann, No. 1,663,910, and reference may be there had for a more complete understanding of such a type of boiler. In the present instance, it comprises briefly, a horizontal drum 50, provided with an oil feed pipe 51, a discharge pipe 52, and a release pipe 53, for the carbon-contained oil. The

heat is supplied to the drum 50 by the indi rect fluid-contained heat-exchanger, indicated generally by the reference C, and as shown comprising a fire box, D, receptacles, E, E extending longitudinally at each side of the fire box, and longitudinally extending drums F, F disposed above the receptacles E, E. Each receptacle is connected to a drum above it by a series of tubes 54:, and to a drum on the opposite side by a series of tubes 54. The large. drum 50 is separated from direct contact with the heat of the fire box by the separating walls 55.

Two series of heat exchanger units are shown. Each unit of one series comprises a bank of tubes 56, disposed in the drum 50 each tube being bent back and forth upon itself and connected at its ends to headers as shown. The upper header of each unit is connected to a pipe 57, leading to the drum F, and the lower header is connected to a pipe 58 leading to the receptacle E, passing thereto on the outside of theheater. The other series of units is likewise disposed in the drum 50. Each unit comprises asimilar bank of bent tubes 56, having its upper header connected to a pipe 57 leading to the drum F and its lower header connected to a pipe 58 leading to the receptacle E passing thereto on the outside of the boiler.

These heat exchange units, as is obvious, form, taken collectively, a closed system for fluid which may be water, oil, or other heat transferring medium that can be heated to the required temperature, and such medium should be of a purity, as for instance distilled water, pure oil, etc., that may be continuously used in the closed system without producing any appreciable precipitate or incrustations on the conveying tubes of the system, all in the usual manner in such apparatus. While no feed is shown for this exchanger, a relatively small feed may be necessary to take care of leakages etc., as more fully set forth in the above mentioned Hartmann Patent No. 1,663,910.

A number of power driven rotatable cylindrical brushes indicated at G may, when desired, be employed in the drum 50, similar to those shown in the patent to Smith No. 1,324,07 5, for producing a circulation of oil through the drum.

This type of heater as shown is appropriate for use in the forms of set up shown in Figs. 1 and 2 but it is obvious that it may i be modified to include the valve 47 of Figs. 3 and 4 and be made to operate similarly thereto.

In continuous cracking stills in common use where carbon is produced during cracking of the oil, even in the most favorable circumstances, and with the best precautionary measures, carbon will, to some extent, precipitate and form a crust on the metal surfaces, and the system Will, in time, be-

come sufficiently clogged with the carbon and other residuums to require shutting down and complete cleaning out. The incrustations are found largely on the tubes that come in direct contact with the heat of the furnace, such for instance as the tubes 13 of the Babcock & Wilcox type of boiler shown in Figs. 1 to 1. In Figs. 5 and 6, all such trouble is avoided by the indirect fluid heat exchanger employed.

The operation of the apparatus, refer ing first more particularly to Fig. 1, is as follows:

When the still is under normal cracking operation the valves 22, 39 and 41 are closed, all other valves being open, the propeller 19 being driven in the usual way to increase the circulation of the charge in the still, as indicated by the arrows. During this period of operation fresh oil is fed through the pipe 36 to the receiver drum 26, and a supply of oil is fed from the receiver drum 26 through pipe 31 to the heating element, A. The oil fed through pipe 36 may come from any desired source, as the usual make up tank, and may be of any desired grade, crude petroleum, pretreated stock, etc., and may contain other ingredients as is usual in make up stock.

The pipe 36 entersthe receiver at a point near the top from where the oil descends in a zig-zag path through the system of bailies 27, forming a direct heat exchanger for the vapors of the discharge from the heating element A, which enter the receiver, from the pipe 30, near the bottom thereof, and ascend therethrough. Part of this discharge is thus condensed and passes, with the fresh feed or" liquid, through the pipe 31 to the heating element. The part of the discharge in the receiver uncondensed passes out through the pipe 28 as vapor in the usual manner.

When it is desired to relieve the charge of part of the carbon-contained oil, the valves 22, 39 and 4-1 are opened, and the valve 32 closed. This permits the desired carboncontained oil to be released from the heating element, A (due to the pressure of the charge); a take-off of the oil from the receiver through the pipe 40; and a feeding of the fresh oil to the heatingelernent A through the pipe 38. When suiiicient carbon-contained oil has been released, the valves are then set in their normal cracking positions as first described. The released carbon-contained liquid, in the present embodiment, passes through a reducing vaive, 22', and enters the vaporizer 20, where it is partially vaporized, the vapor passing off through the pipe 24, the residuum PESSQS off through the pipe 25 in a well known manner.

It will be noted that during the reiief period, the fresh oil is being fed to the receiver through the pipe 36, and, with the condensate portion of the discharge, is taken off through the pipe 40, thereby in no way interrupting the action of the dephlegmator or reflux tower, B, during this relief period when the contents of the receiver B is shut off from the heating element by the closing of the valve 32. Likewise the valve 39 being open, fresh oil is fed, during this period of relief, to the heating element, thereby making it possible to maintain a constant volume of charge therein.

The operation of the apparatus of Fig. 2 varies slightly from that of F 1. When the still is under normal cracking operation the valves 22, i1 and i i are closed. The apparatus then operates in a manner similar to that of Fig. 1, during this period. Then it is desired to relieve the charge of carboncontained oil, the valves 22, 1-1 and are opened and the valves 32 and [L2 closed. This permits the feed of fresh oil to the heating element during this period of release to pass through the receiver in indirect heat exchange relation with the discharge therein, thereby avoiding the necessity during this period of feeding fresh oil directly to the receiver through the pipe 36. This receiver thus operates, during this period, as a de phlegmator or reflux tower without the necessity of passing a direct feed th. :ethrough, and then taking it off with the discharge through the pipe 40, which would be in some instances a useless operation and wasteful of heat. While in Fig. 2, a direct feed through the pipe 36 to the receiver is shown, this may be omitted, and the feed to the heating element through the heat exchanger 45 solely relied upon as a feed to the heating element, and a heat exchanger for the condensation of the vapors to be condensed in the reflux tower, in which case the valve 44 would be continuously open. And as another alternative, where the direct feed to the receiver through pipe 36 is employed, both this feed and the feed through the pipe 43 may be employed during the normal cracking operation, the respective valves governing these feeds being suitably adjusted to provide for the proper amount of feed. In this case, the feed from the pipe 43 to the heating element will be continuous, but regulated to maintain a substantial constancy of the charge during the release period when the feed froa. the re ceiver to the heating element is discontinned.

When the still of the form shown in Fig. 3 is in normal cracking operation, the valve 22 is closed, and the valve or 47 open. During this period, the apparatus operates in a manner similar to other well known types of apparatus, except that no release of carbon-contained oil is being effected during this period. Fresh .oil is continuously fed to the receiver and the supply therefrom to the heating element is likewise continuous. When it is desired to relieve the charge of carbon-contained oil, the valve 22 is open and the valve, 47, closed. Also during this period, the propeller 19 may be slowed down or stopped entirely, as desired, relying upon the thermal circulation in the boiler. During this period of relief it will be observed that the liquid charge in the drum 10, is divided by the dividing wall formed by the closed valve 47, but that theupper vapor portions at each end of the drum are in communication over the top of this valve, so that a free discharge of vapor may be effected from the entire vapor contained portion of the drum through the pipe 30. If, however, the valve 47 be made to entirely separate the two ends of the drum 10, so that while the valve 47 is closed, two steam spaces are provided, a duplicate pipe similar to the pipe 30 should be led from the opposite end of the drum 10 to the receiver. During this re lease period there is no opportunity for the charge of oil to circulate through the drum 10 on account of the closed position of the valve 47. Therefore the supply of oil from the receiver to the rear end of the drum 10 and the release of carbon-contained oil from the front end of the drum 10 should be relatively apportioned to permit a suflicient circulation of the liquid through the tubes 13 to prevent overheating of the .oil therein. In his form of apparatus, the release pipe 21 extends below the surface of the oil in the drum 10, and this should be to a suflicient extent only, to permit the desired amount of carbon-contained oil to be removed, which removal should preferably be at or near the surface of the charge of oil in order that the relatively pure oil being fed to the drum 10, (which by thermal circulation will travel over to the forward end of the drum via the tubes 13) will not have reached the release pipe 21 until the desired amount of carbon-contained oil has been released and the valve 22 closed.

Fig. 4 shows a form of apparatus involving the valve 47 and rellef pipe 21 similar to that shown in Fig. 3, but otherwise the construction is similar to that shown in Fig. 2 and the operation is similar to that described in connection with Fig. 2 except that when the release of carbon-contained oil is taking place, the valve 47 is closed, as in Fig. 3. The feed of fresh oil through pipe 43 during this period is prevented from commingling with the carbon-contained oil being released in like manner as the supply from the receiver to the heating element was prevented from commingling in the form shown in Fig. 3.

It will be apparent from the foregoing that the instant invention provides a new and improved process which comprises the following steps :heating a charge of hydrocarbons to cracking temperatures; separating the vapors produced thereby from the unvaporized hydrocarbons; subjecting the unvaporized hydrocarbons to further heating to cracking temperatures; passing the vapors in heat exchange with hydrocarbons introduced into the charge (the cracking system) for further charging; partially condensing the vapors in the heat exchange operation to form a reflux condensate; delivering the reflux condensate for re-cracking; removing the uncondensed vapors from the charge as the product of the process; and the novel steps which include intermittently removing unvaporized carbon-containing hydrocarbons from the charge (or system), while at the same time diverting the reflux condensate while the carbon-containin hydrocarbons are being withdrawn and c arging hydrocarbons are being introduced.

It will also be apparent that the aforedescribed process may be varied. In one instance, vapors may be passed in direct heat exchange with the hydrocarbons being introduced for charging, and the reflux condensate resulting from the partial condensation of these vapors may be mixed with the charging hydrocarbons and the mixture delivered to be cracked. Here the mixture isdiverted from the charge (the cracking system) whlle unvaporlzed carbon-containing hydrocarbons are being discharged from the of the several instances will be apparent from the foregoing description, or will be apparent to those skilled in the art, and it will be understood that all and any such changes and modifications as fall within the scope of the appended claims are contemplated as a part of the present invention.

While the invention is primarily directed to the manufacture of gasolene and the like, it is not so limited, but may be used in the cracking of hydro-carbon oils generally for the production of any product obtainable therefrom, and while the term fresh oil and the like has been used throughout the description it will be understood that this is intended to include any make-up oil whether crude petroleum or any product obtained therefrom, or combinations thereof,

and any other ingredients that may be mixed therewith, all of which is well known.

From the foregoing it will be seen that during both the normal cracking period and the relieving period, provision is made for maintaining the charge of oil in the heating element substantially constant. This obviously is desirable in order to maintain a uniform discharge from the heating element to the receiver and uniform maximum utilization of the heat from the furnace. Ordinarily there is considerable apparatus in a complete set-up, beyond that shown in the drawings, which involve various heat exchangers, and therefore to maintain normal operation of these, it is important that the discharge to the receiver be uniform in order that the vapor take-off going to certain heat exchangers from the take-off pipe, 28, may be maintained constant. Also in set-ups where the fresh oil entering the feed pipe 36, has previously passed through heat exchangers, it may be desirable that the flow through this pipe be maintained constant, and provision is made in the present invention to accomplish this if and when desired, as has been described. Furthermore, the periodic take-off of heated oil from the receiver through the pipe 40, may be conveyed through heat exchangers for utilizing the heat thereof, and oil therefrom passed to a tank for future use as make-up stock, or for such other use as desired. The invention contemplates the continued use of the reflux tower 26, as such, and the heat exchanger 4-5, disposed therein performs the triple office of serving as a feed of fresh oil for the charge in the heating element, of being preheated in its passage through the receiver or reflux tower 26, and of serving as a condenser for the vapors to be condensed in the receiver. It will be further understood that the intermittent periods of normal cracking and or relief may be timed as to duration to maintain a continuous carrying on of the method, and a suitable removal of the required quantity of carbon-contained liquid to insure a suflicient length of run before shut down and cleaning is necessary to render the method commercially profitable. In this regard the size of the various pipes leading to and from the heating element will be apportioned to feed and remove respectively the desired quantities of material during the periods alloted therefor, and of course the release will begin before too great an amount of carbon has been liberated in the heating element. For instance, in the forms of apparatus shown in Figs. 3 and 4, it may be found desirable to decrease the period of relief and increase the rate of relief in order to minimize the likelihood of the fresh stock reaching the relief pipe 21 during this relief period. In methods in common use, it has been found advantageous to maintain frequent inspection of the apparatus and therefore hand operated control valves have been comonly used where the attendants are always on duty to regulate them in accord ance with a predetermined schedule, the attendants thus being able to maintain a careful watch as to the way the apparatus is functioning, and the method of procedure. Therefore in the present invention, hand controlled valves have been shown, but it is obvious that these may be replaced by power controlled valves operated from a central station if desired or by timed automatic valves, which are employed to some extent in modern apparatus.

The invention claimed and desired to be secured by Letters Patent is:

1. In a process for cracking hydrocarbon oil, wherein the hydrocarbons are heated to cracking temperatures, vapors produced thereby are separated from the unvaporized hydrocarbons, the unvaporized hydrocarbons are subjected to further heating to cracking temperatures, the vapors are passed in heat exchange with charging oil for the system, a part of the vapors being condensed thereby to form a reflux condensate, the reflux condensate is returned for re-cracking, and the uncondensed vapors are removed as the product of the process, the improvement which comprises intermittently removing unvaporized carbon-containing hydrocarbons from the system while diverting the reflux condensate from the system during said removal of the carbon-containing hydrocarbons, and continuously supplying charging oil to the system.

2. In a process for cracking hydrocarbon oil, wherein the hydrocarbons are heated to cracking temperatures, vapors produced thereby are separated from unvaporized hydrocarbons, the unvaporized hydrocarbons are subjected to further heating to cracking temperatures, the vapors are passed in indirect heat exchange with charging oil for the system, a part of the vapors being condensed thereby to form a reflux condensate, the reflux condensate is returned for recracking, and the uncondensed vapors are removed as the product of the process, the improvement which comprises intermittently removing unvaporized carbon-containing hydrocarbons from the system and diverting the reflux condensate from the system while directly supplying the system with said indirect-heat-exchanging charging oil during said removal of the unvaporized carbon-containing hydrocarbons.

3. In a process for cracking hydrocarbon oil, wherein the hydrocarbons are heated to cracking temperatures, vapors produced thereby are separated from the unvaporized hydrocarbons, the unvaporized hydrocarbons are subjected to further heating to cracking temperatures, the vapors are normally passed in direct heat exchange with charging oil for the system, a part of the vapors being condensed thereby to form a reflux condensate, the heat exchange mixture of condensate and charging oil is delivered for cracking, and the uncondensed vapors are removed as the product of the process, the improvement which comprises intermittently removing unvaporized carbon-containing hydrocarbons from the system While diverting said mixture from the system, and during said Withdrawal successively passing charging oil in indirect heat exchange with said vapors and directly supplying the system with said last mentioned charging oil.

4:. In a process for cracking hydrocarbon oil, wherein the hydrocarbons are heated to cracking temperatures, vapors produced thereby are separated from the unvaporized hydrocarbons, the unvaporized hydrocarbons are subjected to further heating to cracking temperatures, the vapors are passed in heat exchange with charging oil for the system, a part of the vapors being condensed thereby to form a reflux condensate, the reflux condensate is normally mixed With charging oil passed in direct heat exchange therewith and the mixture delivered for cracking, and the uncondensed vapors are removed as the product 01"- the process, the improvement which comprises intermittently Withdrawing unvaporized carbon-containing hydrocarbons from the system and discontinuing direct heat exchange of the charging oil and vapors, and diverting the reflux condensate from the system during said withdrawal While successively passing charging oil in indirect heat exchange With said vapors and directly supplying the system With said last-mentioned oil.

5. In a process for cracking hydrocarbon oil, wherein a charge of the hydrocarbon oil is heated to cracking temperatures, vapors produced thereby are separated from unvaporized hydrocarbons of the charge, the unvaporized hydrocarbons are subjected to further heating to cracking temperatures, the vapors are passed in heat exchange with charging oil for the charge, a part of the vapors being condensed thereby to form a reflux condensate, the reflux condensate is returned to the charge for re-cracking, and the uncondensed vapors are removed as the product or" the process, the improvement which comprises intermittently removing unvaporized carbon-containing hydrocarbons directly from the charge, While diverting the reflux condensate from the charge during said removal of the carbon-containing hydrocarbons, and during said diverting adding oil to the charge.

SAMUEL C. YEATON.

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