US1978072A - Converting hydrocarbon oils - Google Patents

Description

Oct. 23, 1934. o. BEHIMER I CONVERTING HYDROCARBON OILS Filed Aug. 6, 1920 5 Sheets-Sheet 3 GAI Patented Oct. 23, 1934 UNITED STATES Otto Behimer, Port Arthur, Tcx., .assignor, by mesnc assignments, to The Texas Company, New York, N. Y., a corporation of Delaware Application August 6, 1920, Serial No. 401,623

14 Claims.-

This invention relates to methods and apparatus for making condensable light. oils, such as gasolene and naphtha, and is closely related to and constitutes a modification of certain inventions patented in the following patents: Patent 1,883,850, issued on application Serial No. 630,242, filed April 6, 1923; Patent 1,840,012, issued on application Serial No. 615,850, filed January 30, 1923; Reissue Patent 16,877, being a reissue of Patent 1,585,496, issued on application Serial No. 49,962 filed August 13, 1925 which latter application was filed as a division of application Serial No. 630,242; said applications 630,242 and 615,850 being divisions of my pending application, Serial Number 263,562, filed November 21, 1918.

In accordance with my present invention theoil to be converted, which is first preheated, preferably by means of waste heat, is passed through a highly heated coil so that the oil will absorb a large quantity of heat and attain a sufficiently high temperature for cracking. The oil is then passed into a plurality of converters or cracking stills in which it is held at a cracking temperature for thetime necessary for decomposition, the necessary heat for maintaining a conversion ternperature being supplied by moderate heating of the stills, although loss of heat may be prevented by thoroughly insulating the stills.

The highly heated oil is charged from the heating coil directly into one or more of, the stills or converters and flows to the others in series. One or more of the cracking stills serve the purpose ofcarbon and residue collectors as well as converters and enable the removal of ,the residue.

including carbon and heavy polymerized products from the system in an effective manner. The operation is carried on with a positive flow of cracking oil through the successive convertersthus preventing the apparatus from being clogged with carbon and insuring the withdrawal of the residual products. The vapors and gases generated are passed to suitable separators whereby those of less volatility than desired are condensed and after being mixed with the oil charge are returned to the heating coil, the vapors of desired volatility being withdrawn and condensed as a desired final product.

By using two or more converters the large scale production of gasolene is facilitated with a high degree of economy and safety because the oil may be charged into one converter and the carbon may be effectively separated by drawing off the residue from another converter, where the bottom liquid is not disturbed by the admission of either the'oil charge or the backtrap. The

intermediate or heavy distillates formed, that is, those of higher boiling point than desired for the final product, such as for example the kerosene fractions, are separated out from the vapors generated and are returned continuously as formed tothe heating coil so that the ratio of charge to backtrap or returned condensate is substantially constant for a given mode of operation.

In order to more fully disclose my invention I have illustrated in the drawings a preferred form of apparatus adapted forcarrying out the invention and constituting an embodiment thereof.

In the drawings:

Figure 1 is a general diagram of a conversion Z apparatus arranged and constructed in accordance with my invention and adapted for practicingthe same.

Figure 2 is a partially diagrammatic elevation of the same apparatus including the converters,

the separators, the condenser, the receiver, and their connections' Figure 3 is a partially sectional elevation of the heating coil on the line 3-3 of Figure 4.

Figure 4 is a sectional elevation of the heating coil and its furnace, taken at right angles to Figure 3.

Figure 5 is a detail view of the separator drum drawn to a larger scale.

Figure 6 is a transverse sectional view of a 35 a cracking zone D, a separating device E, a con- 9 denser F and a collector G.

A pump 1 is connected to a suitable source of oil supply (not shown) and is adapted to force the oil to be converted to the heating coil C.

Preferably, however, the oil is not supplied directly to the heating coil C and, as illustrated, the exchanger A and the economizer B are interposed between the pump and the coil 0. The connection is established by a pipe 2, a coil 3 in the exchanger drum 4, a pipe 5, a preheating coil 6 of the economizer B, and a pipe 7 which discharges into the heating coil 8 of heater C. The coils 3 and 6 are preferably heated by means of waste heat in a manner hereinafter set forth.

The coil 8 is arranged to be subjected to a high degree of heat and the construction may conveniently take the form of that shown in Figures 3 and 4, in which 9 designates the furnace in which the coil 8 is supported. The furnace has a perforated baffle 8a to insure complete combustion and uniform distribution of the gases before they reach the tubes. The gases after giving up heat to the rapidly flowing oil in the tubes pass out through the flue 10.

The outlet 11 of the heating coil 8 extends to the converter 12 to which it is connected. The converter 12 of the cracking zone D is connected to a converter 13 and both represent a series of vertical stills. One of the converters may serve the function of a receiver still, being supplied with oil from the coil C at sufficient rate to keep its contents agitated and prevent much carbon deposit, and another may constitute a residue tom can be drawn off effectively. Any suitable number of stills may be used such as, for example, a battery of six, the number of receiver and residue collecting stills being proportioned as desired. For instance, the oil may be charged into three stills and withdrawn from the other three or the charge may be run into four and the residue collected in and drawn off from the other two. Ordinarily I prefer to draw off from as few stills as possible in order to increase the fiow of oil through the draw-off still or stills.

In the embodiment of the invention shown in the drawings the cracking zone D, for simplicity and convenience, consists of the two stills 12 and 13 which are intended to be illustrative of any suitable number.

The pipe 11 from the heating coil 8 has a valve 14, and is connected to still 12 near the bottom, while a connection is established from the still 12 to the still-13 by a liquid flow line 15 and a. vapor equalizing line 16.

The conversion of the oil takes place in the stills of the cracking zone D, although the heat necessary for decomposition is supplied to the oil largely while it flows through the highly heated coil 8. Therefore it is not necessary to apply such high furnace temperatures to the stills as have been considered essential in the past to the operation of cracking stills. In fact, the process may be conducted without supplying external heat to the stills (except at the start of a rim until decomposition sets in) provided the stills are insulated against loss of heat. However, I prefer to install the converters in a furnace and to supply only sufiicient heat to compensate for losses and to maintain the converters at a proper cracking temperature. If desired, the stills may be internally heated by electricity.

The stills 12 and 13 are disposed in a furnace 17, as shown in dotted lines in Figures 1 and 2, with their lower ends extending below the heating zone and thus shielded from the direct furnace heat, and their upper ends extending into a cool space above the brickwork. Each still is thus provided with a relatively cool bottom Where the carbon may collect without danger of burning out the walls of the still and a vapor space free from the direct furnace heat which would tend to produce large volumes of fixed gases and burn the still at the liquid level.

At even the comparatively low furnace temperatures applied to the stills in my process, there is a relatively slight tendency for carbon to deposit on the walls and, for this reason, it is best to pro vide each still with scraping mechanism to keep the interior metal surfaces free of carbon. As

shown in Figure 2, each still is preferably equipped with a shaft 18 which carries suitable brushes or scrapers 19 and is rotated by a power driven shaft 21 through the action of gears 20. The scraper shafts may be journaled in any suitable manner, but it is preferable to avoid a bearing at the bottom of the still where carbon or residue collects. Each shaft extends above the still at the top through a stufiing box 22 mounted on a pipe 23 which is of sufiicient length to prevent overheating and disruption of the stuffing box. The carbon removed from the heated walls is al lowed to gravitate out of the heating zone.

The converters are equipped with suitable means for withdrawing the residue and carbon from the system. Preferably a pair of draw-off lines are provided for each still so that in case one line should become choked up with carbon the remaining line will be available. Thus, the still 12 is equipped with the outlet pipes 24 and 25 having the valves 26 and 2'7 respectively, and the still 13 has the outlet pipes 28 and 29 controlled by the valves 30 and 31, respectively. The outlets terminate in the common residue line 32 which preferably extends to the exchanger drum 4 and thus heats the oil flowing through the coil 3. The exchanger drum 4 is provided with the valve controlled draw-off 33 by which the carbon and residue may be removed as desired. In any case, the residue is discharged entirely from the system and no part thereof is retreated in the heating or cracking zones. It is well to provide the converters with additional valve controlled outlets 34 located at the extreme bottom of the stills; for instance, they may be constructed in the manhole plates 35 and are available for drawing off any water which may collect in the stills at the beginning of a run due to moisture contained in the oil operated on, and also to expedite the draining of the stills at the end of a run.

To correctly indicate the liquid level in each still, a piping 37 is provided, having a U bend 38 and an inverted U bend 39, and a gage 40 is attached to the vertical portion of the piping, as illustrated. With this construction the U bend 33 forms a liquid seal of relatively cool oil and the bend 39 forms a comparatively cool gas pocket, thereby protecting the gage from the heat of the still and making possible a correct reading on the gage.

The gage mounting shown and described, is not claimed herein as it is set forth and claimed in a co-pending application, Serial No. 419,806, filed Oct. 27, 1920, by Otto Behimer and assigned to The Texas Company.

The vapor line 41 extends from the still 13 to a suitable separating device or reflux condenser E. The type of separating device shown comprises a primary separator 42 and a secondary separator 43. Additional sections may be employed, if desired. For example, I may provide a triplex arrangement in which the several sections may be referred to as the primary or heavy separator, the intermediate separator and the light separator. However, the principle involved is substantially the same regardless of the number of sections and will be clearly understood from the duplex form illustrated.

The heavy separator 42 consists of a lower drum or header 44, preferably of cylindrical form, and a similar upper drum 45, connected to each other by a series of vertically extending pipes or risers 46. The vapor line 41 may comprise pipes extending from the vapor space of the still 13,

arator 43, which is similar in construction to the primary separator, having an upper drum 49 and the pipes '50 connecting the upper and lower drums. The condensate pipe 51, which may have a valve 52, extends from the lower part of the drum 48 to the upper part of the drum 44 and thus serves to bring the condensate from the light separator into contact with the vapors entering the drum 44 from the vapor line 41. In order to more efficiently utilize the heat of the vapors. for redistilling the condensate the drum 44 is provided with a distilling pan 53 into which the reflux from the secondary condenser may be discharged. In the modified'form of apparatus shown in Figure 6 a pair of baiile plates 54 are provided upon which the backtrap flows. The condensate dropping in the pan 53 or flowing over the distilling plates 54 is revaporized bythe heat of the vapors entering the drum 44.

The primary function of the air condensers E, or any other type of separator which may be employed in connection with the herein described process, is to separate out from the mixed vapors passing out of the vapor line 41 those hydrocarbons which are less volatile than desired for the final product and to trap those constituents without substantial loss in heat and enable them to be returned in cyclic passage through the heating coil C and the converters D. To accomplish this I provide a backtrap return line 55 having a valve 73 which extends from the bottom of the primary separator to the heater C. A heat cycle is thus-generated which assists in the maintenance of the required heat in the converters and the kerosene and like constituents are ultimately decomposed into the volatile products desired. The backtrap may be admitted to the heating coil 8 in any suitable manner. As shown in Figure 1 the condensate is pumped by means of an oil pump 56 and positively forced into the rapidly flowing stream of charging oil and thence into the coil 8. As illustrated in Figure 4'the return condensate may be injected into the oil charge entering the heating coil by means of a suitable jet pump or other similar means 5'? controlled and operated by the oil charge itself. In this way the fractions of less volatility than desired, as, for example, the kerosene fractions which have been an inconvenience in the ordinary cracking processes are taken care of as they are formed and are utilized as an aid in carrying onthe process.

It sometimes happens, particularly at the beginning of a run, that water is condensed out in the separators E and for this reason it is well to provide facilities for draining off the water. Thus the line 55 having a valve 73 is provided with a branch line 74 connecting with a branch pipe '75 which extends downwardly from the condensate line 51. The pipe 74 has a valve '76 and the pipe '75 has a valve '77, the two pipes terminating in a draw-off line '78. By closing the valve '73 and opening either or both of the valves '76 and 77 liquid may be drawn off through either or both of the pipes 74 and 75.

The vapors uncondensed in the separating device E pass into the vapor line 58 which terminates in the coil 59 located in the condenser box 60 of the condenser F, the box being supplied with water or any suitable cooling medium. A control valve 61 may be placed in the line 58, as shown in Figure 1. However, it is generally more convenient to place the control valve in the condenser outlet 62 as shown in Figure 2 at 63. The line 62 terminates in suitable mechanism for collecting the distillate, as the receiver 64 which is equipped with a gas outlet 65, having the valve 66 and a condensate outlet 6'! having a valve 68. The distillate line 62 may be provided with a valved branch line 69 as it is sometimes conven- 'ient to draw off oil from the condenser without admitting it into the receiver 64.

I prefer to install the heating coil C and converters D in separate furnaces located as close together as practicable in order to make the connecting pipe 11 as short as possible and avoid loss of heat during the transmission of the oil from the heating coil to the converters. The waste heat from these two furnaces may be advantageously utilized to heat the economizer coil 6. Thus, as shown in Figure 1, the fiue 10 conducts furnace gases from the furnace 9 to the economizer BV and flue 80 conducts gases from the furnace 1'? to the economizer B.

It is understood that the apparatus described herein may be equipped with thermometers, or pyrometers, pressure gages and other well known accessories which need no explanation to those skilled in the art to which my invention pertains. However, in order to use my invention to the best advantage certain parts of the apparatus should be equipped with temperature recording devices, as the thermometer 70, in the connecting line 11, and the thermometers 72 in the separators.

My process is adapted for converting any higher boiling oil into lower boiling hydrocarbons. For example, crude oil, or the'residues thereof from which the lighter oils have been previously distilled, or distillates such as kerosene and gas oil,

may be treated by my process and converted into lower boiling hydrocarbons. I prefer, to use a distillate such as gas oil, or possibly a mixture of a distillate with a residuum, on account of the smaller proportions of carbon formed in cracking distillates than are produced in cracking residual oils. However, as a result of my method of utilizing the heavier distillates such as the kerosene fractions formed in the cracking operation for diluting the charge entering the heating coil, it is possible by means of my invention to successfully manufacture gasoline and similar light products from heavy residual oils.

The oil to be converted is heated in the coil C to the desired cracking temperature or higher and is then held at such cracking temperature in the stills D long enough to cause molecular decomposition and formation of light hydrocarbons, the oil being under a superatmospheric pressure of the grnerated vapors and gases. Ordinarily I do not employ pressures much lower than 100 pounds, due to the fact that the rate of decomposition is too slow under the lower pressures for the most efiicient method of operation. I prefer to use pressures around 200 pounds and while I may at times employ higher pressures, such as 400 pounds, I have found that it is not generally necessary to use the higher pressures, as good results can ordinarily be obtained at pressures ranging from 150 to 250 pounds.

lhe oil to be converted is forced by the pump 1 through the preheating coils 3 and 6 of the heat exchanger and the economizer. Sometimes it is not necessary to use both preheating coils and the charge may be by-passed around the one or the other. It is best, however, to preheat the oil before it enters the coil 8 so as to reduce as far as possible the large quantity of heat which must be applied to this coil. As the oil circulates through the coil 8 it absorbs heat and is elevated to the desired cracking temperature or even higher so that the incipient stages of decomposition may set in before it leaves the coil to enter the stills. It is to be noted that I do not gasify or vaporize the whole body of the oil in the coil, as I desire to avoid the disadvantages of the vapor phase processes which are always accompanied with a large production of fixed gases and carbon. The oil leaving the coil 8 is substantially in liquid form and at a cracking temperature, but since it does not actually reach a cracking temperature until it approaches the outlet 11, or at least until it reaches the last portion of the coil 8, it is not subjected to a cracking temperature in the coil long enough for any material decomposition.

As an example to illustrate the time element or factor necessary to cracking, I have discovered that in order to obtain a 30% conversion of paraffin base gas oil it is necessary to hold it at a temperature of 850 F., under a pressure exceeding 200 pounds for about 15 minutes. In the ordinary operation of my process the oil will be at a cracking temperature in the discharge end of coil 8 for a fraction of a minute only. As a result there is practically no carbon formed in the coil and consequently the coil will last almost indefinitely.

After the oil has absorbed the heat necessary for decomposition it is passed directly through the connecting pipe 11 to the converters D in which large bodies of oil are maintained, the liquid level being substantially as indicated in the drawings. Here the oil, while still under the same pressure to which it was subjected in the heating coil, is maintained at the desired cracking temperature for the time necessary for decomposition. Of course, there may be some eduction in pressure in the converters, possibly as much as 50 pounds, due to the fact that the friction of the pipe 8 will augment somewhat the pressure in the heating coil. The temperature in the converters is preferably held at that at which there is an efiicient rate of decomposition. By way of example, it may be stated that in converting paraflin base gas oil I have held the converters at a temperature of from '750-850 F. under a pressure around 200 pounds. When cracking a lower boiling hydrocarbon, such as the kerosene fractions, I have used substantially the same temperatures with a pressure around 300 pounds. In each case the temperature in the heating coil outlet was maintained at about 50 higher than that of the converters.

The highly heated oil is introduced into the bottom of still 12 and overflows through the 1: '16

15 into the still 13. The residual oil is drawn off through either or both of the lines 28 and 29 and there is consequently produced a positive flow of oil up through the converter 12 and down through converter 13. The outlets 24 and 25 are not ordinarily used except for an emergency or at the end of a run.

The stills are not required to stand the high furnace temperatures commonly sought to be applied to cracking stills because the oil enters the stills at such a high temperature and only a moderate heat is necessary to maintain the cracking temperature. Consequently, carbon is deposited on the still walls in less quantities and in a softer condition so that it may be removed readily by the scrapers 18 and the life of the stills is thus greatly prolonged. The heat contained in the oil entering the still 12 maintains the body of oil in the converters at the necessary temperature, loss of heat from decomposition and radiation being prevented by a moderate heating of the stills. Through my method of operation I have reduced the furnace temperatures necessasry for cracking stills by 200 to 600 F. Since no oil is introduced into the bot-- tom of the still 13 the settling out of the residual products containing most of the carbon formed 5 is facilitated, and they are continuously drawn off through the pipes 28 and 29.

The vapors and gases generated pass out through the vapor line 41 to the separator E. It is best that the vapor line be made of as short length as practicable and that it have little or no upward incline as I desire to avoid as far as possible the cooling effect upon the still 13 of the return thereto of any condensate through the vapor line. For safety purposes the pipe 41 may well have a slight incline, but in order to get the best results with my apparatus it is not desirable to permit any extensive backtrapping into the converters, as to do so will make necessary a higher temperature in the furnace 16.

The temperature in the separator E is so regulated that those hydrocarbons of less volatility than desired for the final product are condensed, while the volatile product desired is allowed to pass out through the line 58 in the form of vapor. To facilitate the description of the process I use the term kerosene as an example of the product condensable in the separator and the term gasoline as an example of the volatile product which leaves the separator in the form of vapor. Bearing in mind then that these terms are used by way of example, and not in a limiting sense, the kerosene is condensed in the primary separator, drops down from drum 45 through the pipes 46 and comes in contact with the heated vapors entering the drum 44 so that any gasoline entrapped in the condensate is revaporized while the kerosene falls into the back trap pipe 55.

The gasoline vapors passing through the line 47 to the light separator 43 will contain a greater or less amount of kerosene mixed with the vapors. These kerosene constituents are condensed out in the separator 43 and returned to the drum 44 where the heat of the incoming vapors is utllized to redistill the condensate nd revaporize any gasolene returned in solution in the back flowing condensate. In this manner the heat of vaporization is utilized to vaporize successive portions of entrapped liquid and thus insure that a maximum portion of the volatile product desired is utimately passed out through the vapor line 58 in the form of a homogeneous vapor, while at the same time the back flowing condensate is employed to cool the vapors.

The condensate such as kerosene is returned to the heating coil 8 through the line 55, being either pum ed into the coil by the pump 56 or injected into the oil charge through a suitable jet 5'7. In this Way the kerosene fractions which are produced so abundantly in the cracking operation are continuously returned to the heating coil 8,-a constant ratio of charge to backtrap being maintained and in this way the kerosene fractions are ultimately reduced to gasoline. The constant circulation through the system of the M5 easily vaporizable kerosene constituents creates a heat cycle which assists in maintaining th required degree of heat in the heating coil and converters and lessens the amount or external heat required to be applied thereto.

till

The vapors uncondensed in the separators E pass through the vapor line 58 to the condenser F where the gasoline, naphtha or other hydrocarbon product desired is condensed. The distillate is collected in the receiver 64 and is withdrawn, as desired, through the outlet 67. The permanent gases escape through the pipe 65. By controlling the escape of the permanent gases by means of the valve 66 and eifective control of the pressure in the system may be obtained.

- The following may be given as a specific example of the invention: An apparatus of the type described herein comprising a battery of two or more converters is used for the conversion of parafiin base gas oil. The oil after being preheated in the exchanger A and. economizer Bis charged into the heating coil Cat the rate of about 5070 barrels per hour. The temperature at the heating coil outlet is maintained constantly at about 850 F. which permits a constant temperature in the convertersof about 775 F. or higher. The oil is passed from the heating oil directly into the first still 12 (or into the first two if there are four in the series), and flows to the other still 13 (or to the remaining stills in succession). A constant oil level is maintained in the converters, as denoted by gages 40. Distillate is drawn ofi from the receiver 64 at the rate of about 25 barrels per hour and residue is drawn off from the last still 13 at the rate of about 35 barrels per hour. The charge into the converters is at the rate of approximately 25% of their liquid capacity per hour. The distillate is withdrawn at the rate of about 10% of the liquid capacity of the converters per hour and the residue at the rate of about 15% of the liquid capacity of the.

converters per hour. The kerosene fractions are taken care of as formed, being separated out in the separators E and forced back into the heating coil thus maintaining a constant ratio of backtrap to charge entering the heating coil C and forming a constant cycle of the kerosene fractions through the system. A pressure around 200 pounds is maintained throughout the apparatus. It is understood that I do not intend to limit the scope of my invention by the mention of the specific temperatures, rates of flow, etc., which are given in this instance of the use of my invention, and that this specific case is given merely as an example of the invention- I attribute the longevity of the tubes 8 to the fact that little or no cracking occurs therein. Another explanation of the remarkable length of life of the coils 8 employed in my system may reside in the fact that even if there is some decomposition therein it is a decomposition without carbon formation. My experiments tend to show that in the first stages of cracking there is little or no formation of hydrocarbons of the gasoline group'and practically no formation of carbon, but

rather a breaking down into more intermediate products, such as those of the kerosene group. At any rate, there is no substantial formation of either gasoline or carbon until the oil has been held at a cracking temperature and pressure for a considerable length of time in the converters.

In the ordinary operation of my process I prefer to convert oils from which the gasoline content has already been removed by fractional distillation and thus reserve the apparatus solely for the conversion process in which higher boiling hydrocarbons are actually decomposed into lower boiling ones. At times it is convenient, however, to convert an oil which may already contain certain proportions of the more volatile oils. For

example, a crude oil having the gasoline content in its natural state may be utilized. When operating upon a crude oil or other oil which contains ,a greater or less amount of gasoline or other volatile oils it is convenient to use the apparatus shown in Figure '7 which serves the function of a separator of the volatile products from the condensate and also as a preheater of the oil to be treated and as a means for distilling off the more volatile fractions. The vapor line 41 conducts the vapors from the converters to the primary separator 42. The vapors uncondensed in the primary separator pass through the pipe 47 to the secondary separator 43. Each separator is provided with a number of vbaiile plates or distilling pans 79 to collect the back flowing condensate and to enable the lighter constituents thereof to be vaporized by means of the heat of the vapors, the condensate line 51 bringing the liquid from the light separarator into contact with the vapors in the heavy separator. The crude oil or other oil to be treated is charged through the line 7 (with or without having been preheated in exchanger A or economizer B) into the upper part of the separator 42. The oil charge, as well as the returningcondensate, flowing down over the distilling pans is vaporized by the heat of the vapors and thus the charge is stripped of its lower boiling point constituents, after which it is passed together with the condensate into the line 55 and charged into the heater coil 8. In this way by a single continuous operation the oil is fractionally distilled to recover its more volatile contents and the residue is then converted into more volatile products through molecular decomposition of the hydrocarbons.

Obviously, many modifications in the apparatus and mode of operation may be made without departing from the spirit of the invention which is defined in its true scope in the appended claims.

What I claim is: v

Mil

1. In apparatus for the conversion of oils, a

heating coil connected to the first of a series of converters severally'having liquid and vapor spaces, means for charging fresh oil into the heating coil, means disposed at the liquid level for conveying the oil from the first to the last of the converters in succession and for maintaining,uniform liquid levels therein, vapor lines directly connecting the vapor spaces of the converters one with another, means for drawing off residue from the seriesof converters, means for conducting the vapors generated from the converters to a separator, means for returning the condensate from the separator to the heating coil, a vapor line from the separator terminating in a condenser and means for controlling pressure in the apparatus.

2. In apparatus for the conversion of oils, a

heating coil connected to the lower part of the first of a series of converters, means for conducting the oil to the upper parts of the other converters in succession, means for drawing ofi residuefrom the bottom of the last converter, a vapor line from the converters to a separator, means for returning the condensate from the separator to the heating coil, means for condensing the vapors leaving the separator, and means for controlling pressure in the apparatus.

3. In apparatus for the conversion of oils, the combination with means for subjecting a stream of oil under pressure --to a cracking temperature, a plurality of series connected conversion receptacles maintained under pressure and adapted for the accumulation of pools of oil, a furnace surrounding said converters intermediate their ends for supplying a relatively small amount of heat thereto, and means for delivering the highly heated stream of oil into the first of said series of conversion receptacles and causing it to pass successively through said conversion receptacles, said conversion receptacles being maintained at a cracking temperature largely by the heat of the stream of oil delivered thereto, of means for removing the evolved vapors from the vapor spaces of the conversion receptacles above the heating zone, means for separating out the heavier constituents of said vapors and means for positively forcing said heavier constituents into the stream of oil about to be passed through said heating means and said conversion receptacles.

4. In apparatus for the conversion of oils, the combination with an elongated vertical converter, means surrounding the converter intermediate its ends for supplying a limited amount of heat thereto, an elongated heating coil for raising a stream of oil to a crackii g temperature, means for delivering the highly heated stream of oil into the bottom of the converter below the heating zone and maintaining a cracking temperature therein largely by the heat of the oil so delivered thereto, means connected to the vapor space of the converter above the heating zone for receiving the evolved vapors and separating out the heavier constituents thereof, means for returning said heavier constituents and positively forcing them into the stream of oil about to pass through the elongated heating coil and means operated during the cracking operation for removing carbon deposited on the heated walls of the converter and permitting it to gravitate out of the heating zone.

5. In apparatus for the conversion of oils, the combination with an elongated vertical converter, means surrounding theconverter intermediate its ends for supplying a limited amount of heat thereto, an elongated heating coil for raising a stream of oil to a cracking temperature, means for delivering the highly heated stream of oilinto said converter below the heating zone, and maintaining a cracking temperature therein largely by the heat of the oil so delivered thereto, means for receiving the evolved vapors from the converter and separating out the heavier constituents thereof, means for returning the heavier constituents into the stream of oil about to pass through the elongated heating coil, stirring means within the converter operated during the cracking operation for agitating and mixing the oil therein, and means for withdrawing the mixed heavy residual products from the bottom of the converter below the heating zone.

6. In an apparatus for cracking hydrocarbon oil, the combination with a cracking coil through which oil is passed to be-heated to a cracking temperature, of an enlarged conversion receptacle adjacent said coil into which the heated oil is introduced, a second enlarged receptacle communicating with said first mentioned receptacle wherein oil undergoes conversion and heavier carbon containing residuum collects, means for passing the oil successively through said receptacles wherein pools of oil are maintained, a reflux condenser, means for delivering vapors generated from said oil in said receptacles to said reflux condenser, means for returning reflux condensate to the cracking coil for further treatment, means for withdrawing heavy carbon containing residuum from said last mentioned receptacle, a final condenser, means for passing uncondensed vapors from said reflux condenser to the final condenser, and means for maintaining the oil undergoing treatment up to and through the reflux condenser under a superatmospheric pressure.

' 7. In an apparatus for cracking hydrocarbon oil, the combination with a furnace, a continuous cracking coil therein, means for feeding a stream of oil to said cracking coil to pass therethrough and be heated to a cracking temperature, of communicating enlarged receptacles adjacent said cracking coil, means for passing heat ed oil while in a substantially liquid phase from said coil to one of said receptacles wherein the oil accumulates in a pool, means for passing oil overflowing from said first mentioned receptacle to the second receptacle in which a pool of oil collects and in both of which receptacles the oil undergoes conversion, reflux condensing means adjacent said receptacles, means for passing vapors generated in said receptacles to said reflux condensing means, means for withdrawing heavy residuum from the last receptacle in the series, means for returning reflux condensate from said reflux condenser to the inlet side of said cracking coil, and means for maintaining a superatmospheric pressure on the oil undergoing conversion in said system.

8. In an apparatus for cracking hydrocarbon oil, the combination with a furnace, a cracking coil therein, means for feeding a stream of oil to said coil to be heated to a cracking temperature, of an enlarged vertically disposed conversion receptacle adjacent said coil into which heated oil is introduced, a second enlarged vertically disposed receptacle communicating with the first mentioned receptacle wherein oil undergoes conversion and heavier carbon containing residue collects, means for passing oil successively through said receptacles in which oil pools are maintained, a reflux condenser, means for delivering vapors generated from said oil in said receptacles to said reflux condenser, means for returning reflux condensate to the cracking coil for further treatment, means for withdrawing heavy carbon containing residuum from the last mentioned receptacle, and means for maintaining the oil undergoing conversion in said system under a superatmospheric pressure.

9. In an apparatus for cracking hydrocarbon oil, the combination with a furnace, of a continuous cracking coil therein, means for feeding oil to said coil to pass therethrough and be heated to a cracking temperature, an enlarged receptacle adjacent said cracking coil, means for passing heated oil while in a substantially liquid phase to the lower portion of said receptacle in which oil accumulates in a pool and through which pool the incoming heated oil must pass, means for continuously passing the oil from said first mentioned receptacle to a second enlarged receptacle wherein a pool of oil collects and in both of which receptacles the oil undergoes conversion, reflux condensing means adjacent said receptacles, means for passing vapors generated in said receptacles to said reflux condensing means, means for withdrawing heavy carbon containing residuum from the last receptacle in the series, means for returning reflux condensate from said reflux condenser to the cracking coil, and means for maintaining a superatmospheric pressure on the oil undergoing conversion in the system.

10. A process for treating hydrocarbon oil, consisting in initially passing the charging oil in a restricted stream through that portion of a heating zone maintained at the lowest temperature, in then uniting with the charging oil reflux condensate formed in the process and in passing the commingled charging oil and reflux condensate in a restricted stream through that portion of the heating zone maintained at the highest temperature, in delivering the highly heated oil from said stream into an enlarged reaction zone from wnich no unvaporized oil is permitted to return to either of said streams, in passing vapors from .said enlarged zone to a dephlegmator wherein =passing the commingled charging oil and reflux condensate in a second restricted stream constituting a continuationof the first stream wherein said commingled charging oil and reflux condensate is raised to a cracking temperature, in delivering the highly heated commingled reflux condensate and charging oil to an enlarged reaction zone from which no unvaporized oil is'permitted to return to either of said streams, in fractionating the vapors evolved from the oil to separate therefrom the insufliciently cracked fractions which form said reflux condensate and in maintaining a superatmospheric pressure on the oil undergoing conversion.

12. A continuous process for converting heavier hydrocarbons into lighter hydrocarbons, consisting in initially advancing a charging oil in a restricted stream through a portion of a heating zone, in then introducing to the restricted stream of charging oil a stream of reflux condensate formed in the process and in then passing the commingled charging oil and reflux condensate in a restricted stream through a second portion of the heating zone wherein the commingled charging oil and reflux condensate are raised to a cracking temperature, in then introducing the highly heated commingled reflux condensate I d charging oil into an enlarged reaction zone wh rein conversion and substantial vaporization ocours, in passing the evolved vapors to a dephlegmator wherein the insuffioiently cracked fractions are condensed forming said reflux condensate, in taking off the uncondensedvapors from said dephlegmator for condensation and collection and in maintaining a self-generated vapor pressure on the oil undergoing conversion.

13. A process for cracking hydrocarbon oil, consisting in passing the oil in a restricted stream through a heating zone wherein it is raised to a cracking temperature, in delivering the highly heated oil from said stream to an enlarged reaction zone from which no unvaporized oil is permitted to return to said stream, in passing vapors .evolved from the oil to a dephlegmator, wherein the insufiiciently cracked fractions are condensed forming reflux eondensate, in introducing such reflux condensate to said stream of oil at a point intermediate its travel through said heating zone to again subject said reflux condensate to a cracking temperature, in taking off the uncondensed vapors from said dephlegmator for condensation and collection and in maintaining a self-generated superatmospheric vapor pressure on the oil undergoing conversion.

14. A process for cracking hydrocarbon oil, consisting in maintaining a body of oil under cracking conditions of temperature and pressure in an enlarged conversion zone where vaporization occurs, in removing the vapors from such zone and subjecting the same to reflux condensation to separate the sufliciently cracked from the insufficiently cracked vapors, in introducing charging oil to a heating coil at a point thereof to cause such charging oil to initially flow through a portion of the coil located in the part of a heating furnace subjected to the lowest furnace temperature, in simultaneously introducing a stream of reflux condensate formed in the process to the heating coil at a point to cause such reflux condensate to initially flow through that portion of the coil maintained at the highest temperature in the furnace, in passing the heated commingled charging oil and reflux condensate from the outlet of the coil tosaid enlarged conversion zone,

- in withdrawing unvaporized oil from the enlarged conversion zone without permitting the return of such withdrawn oil to the heating coil,v and in maintaining a superatmospheric pressure on the oil undergoing conversion.

o'rro BEHIlVIER.

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