US2091261A - Process for hydrocarbon oil conversion - Google Patents

Description

Aug. 31, 1937. J ALTHER 2,091,261 PROCESS FOR HYDROCARBON OIL CONVERSION Filed April 17,, 1929 ENSER RAW OIL FLA 5 H DEPHLEG HATOR H CHAMBER PR! MA R Y DEPHLEG MATOR SECONDARY PRI MARY i loss.

Patented Aug. 31, 1937 UNITED STATES PATENT OFFICE PROCESS FOR HYDROCARBON oIL CON- VERSION Application April 17, 1929, Serial No. 355,704

3 Claims.

This invention relates to improvements in proo ess for hydrocarbon oil conversion, and refers more particularly to improvements designed for the eflicient cracking of hydrocarbon oils to convert and produce therefrom products having higher.commercial value.

The utility of the invention as well as many objects and advantages thereof will be brought out in the following description.

' The principal object of the invention is to subject hydrocarbon oil to such conditions of temperature and pressure as to produce maximum yields of lighter gravity products suitable for use as motor fuel with a minimum coke and gas Another object is to carry out the operation in such manner as to cause the non-vaporous residue to accumulate in a low pressure zone.

Another object is to provide in a cracking process and. apparatus steps and means whereby it is possible to approach dry distillation.

Another object is to provide for lowering the reflux ratio by making it possible to convert a greater proportion of the higher boiling point hydrocarbons per pass through the stock. This is of particular importance in effecting the'capacity and thermal efiiciency of the process.

In one type of operation practised commercially on a large scale, theconditions of operation are so controlled as to mainly produce a gasoline-like product suitable for use as motor fuel, which is the desired product of conversion, and a substantially solid coke-like residue. Such operation is described as a non-residuum type of operation, the expression residuum" in such instance meaning liquid. The operation is carried out in a tube and drum type of apparatus wherein the oil is heated in the tube and discharged intothe drum where separation takes place between the lighter and heavier products of conversion, both the tube and drum being maintained under substantially superatmospheric pressure.

In a conventional non-residuum type of operation it is possible to approach dry distillation, accompli'shing same in the drum, for the reason that there is a separation in the drum to dryness, which is the coke-like residue, practically all volatile matter having been distilled oil. One of the reasons why it is possible to do this on nonresiduum runs is the large amount of time given to the heavy material in the drum to be reduced to a coke solid. It is not believed that this could be done if it were not for the fact that there is constantly supplied to the drum a large amount of heat by the incoming oil to carry on this reducing 'or coking action.

As is well known, such type of operation produces a maximum amount of coke, decreasing the actual onstream time efficiency. To eliminate the objection to this large coke production, it has recently been proposed to remove the liquid residue from the pressure drum, reduce or release its pressure and discharge same into what is termed a flashing still, which in reality takes the form of a drum or still operating under little or no pressure. A flashing operation has advantages as well as disadvantages, one of the advantages being a long time onstream before shutting down. Some of the disadvantages are limited gasoline yield and large amount of liquid residue or fuel oil which may be unmarketable in some instances because of high viscosity. As a matter of fact the final liquid residue or flashedresiduum which is withdrawn from the flashing still resembles a product which is uncracked. I do not means to indicate that this oil was not cracked but merely that it resembles an uncracked oil. This may be due to a polymerization, or it may be the direct result of decreasing the time to which residue is normally subjected in a non-residuum type of operation. Or, the high viscosity of the final flashed residue may also be due to lack of heat while flashing.

It has been determined that, in a non-residuum type of operation; there is practically a complete distillation, that is, all or substantially all of the volatile matter is removed from the drum through the vapor line and what remains in the chamber is substantially a solid. The flashing operation is dififerenta relativelylower percentage of the oil leaving the pressure drum leaves that drum through the vapor line in the form or vapors.- The bulk of the oil is withdrawn from the bottom of the pressure drum and flashed into the reduced pressure flashing still where, due to the pressure reduction, full benefit of the heat contained in the oil is obtained to carry on the distillation or separation of this oil.

From the foregoing it will be apparent that there is a pressure distillation or separation in the pressure drum and a second distillation or separation in the reduced pressure flashing still.

The purpose of the present invention is to embody in an efficient process and apparatus the desirable features of the non-residuum and flashing type of operation, the conditions being so con- 3 trolled in the flashing still as to produce either a good. residue suitable for asphalt making stock,

or a substantially solid coke, as local conditions may dictate.

Another purpose of the invention resides in the employment of means to increase the decom- 5 position of both the vapors and liquid from the pressure expansion drum under controlled conditions designed to accomplish the best results. Thisfeature not only has an effect in increasing the yields of lighter hydrocarbons contained from the operation but also in improving their quality, especially for use as a motor fuel, in that they will consist more largely of higher anti-knock compounds.

It will be understood that the expansion drum may be operated at or near the same temperature as the coil outlet but may vary either above or below, depending upon the nature of the stock being treated and the results desired. If the temperature is maintained at or slightly above that of the coil outlet, an advantage will accrue in that said drum may be of much smaller size than if a material temperature drop is allowed to prevail, as in the case where the chamber obtains no heat from external sources.

The pressures on the expansion chamber may be substantially that of the coil outlet or lower, but in the preferable operation this pressure should be as high as possible in order to increase the capacity of the unit and raise the thermal efliciency of the process.

Briefly, the process of the present invention is as follows:

The charging stock plus reflux will be pumped through a conventional furnace having a large heating surface from which the heated oil may be transferred to a drum. This drum is preferably heated by placing it in a heating zone to permit temperature control, or it may be unheated but lagged against excessive radiation losses. The oil in the coil and the drum is maintained under superatmospheric pressure ranging from 100 to 1000 pounds, more or less. Expansion takes place in the drum from which substantially all oil, vapor and gas may be with- 5 drawn through a single outlet being directed into a large flash drum where flashing takes place byreduction in pressure; or vapors may be withdrawn separately from the pressure drum, passing to a dephlegmator, or preferably through a vapor heating coil to provide further conversion and then into a zone of lower pressure into which the residual oil from the expansiondrum may also be directed. In certain operations where insuflicient heat is available from residual oil leaving the expansion drum, additional heat may be supplied thereto during passage to the flash drum or the latter may be heated to facilitate vaporization therein; or a combination of both methods may be employed.

From this point on the usual operation takes place, i. e., all the vapors from the flashing still are directed to a dephlegmator where the sufficiently converted fractions are separated from the insufliciently converted fractions or heavy ends (reflux) by the incoming cold raw oil or other cooling medium, said reflux being returned to the cracking coil for retreatment.

The, main feature of the invention is to have the oil which is undergoing treatment in the tubes and in the pressure drum at such temperature and pressure that, when the oil is released in the flashing still there willbe sufficient latent heat to give practically an instantaneous dry distillation, that is, separation of all liquid in vapor form which leaves the flash still at the top and the accumulation of substantially solid residue in the bottom.

If it is found in some instances that this complete separation or dry distillation is not accomplished, then resort can be had to the use of a heating medium to impart additional heat to the flashing still to dry the carbon by driving ofl. all volatile matter.

From the foregoing it will be appreciated that one of the fundamentals of the invention requires that coke or carbon formed in producing a maximum yield of gasoline is formed outside of the pressure zone.

From the foregoing it will also be seen that I am sacrificing time factor in the pressuredrum, but that I am making up for it by the additional heat which will be absorbed by the oil and vapors for the reason'that the pressure drum will be in a heated zone. I believe it is of importance that the pressure drum be small so that I can secure good heat transfer and moderate velocity to prevent coke accumulation in the pressure drum.

In order to more clearly understand the invention, I have shown the accompanying drawing, which is a diagrammatic view, but not to scale, of an apparatus suitable for carrying out the invention. 7

Referring to the drawing and to the operation of the invention, the oil to be treated is directed through line I and branch 2, having valve 3 into a heating coll 4, located in a conventional furnace 5.

In heating coil 4 the oil is heated to a temperature within the cracking range under a suitable pressure. The amount of oiLpassed through the coil per unit time, and the size of the apparatus are so correlated that under the temperatures and pressures used the degree of cracking obtained in the heating coil is preferably short of that degree of reaction at which formation of coke and sludge-like matter occurs, or exceeds a predetermined desired degree.

Chamber l0 may take any desirable form and size in relation to the capacity of the apparatus. It may be unheated and insulated against loss of heat by radiation; or, as shown in the drawing, it may be heated for the purpose of maintaining the material in chamber ID at the proper temperature, preferably not substantially higher than the temperature at which the oil is discharged from the heating coil 4. To illustrate, it may be positioned in a heating chamber ll interposed in fiue by,-passes l2 and I3 connected to flue 14, through which the combustion gases leaving the furnace 5 are directed to stack l5. Proper control of the degree of heat furnished to chambar 0 may be obtained by regulation of suitable dampers shown at l6, l1 and I8, respectively located in flue I4 and by-passes l2 and I 3.

While, for the treatment of most oils, it may be desirable not to raise the temperature of the materials entering chamber ill to a temperature substantially higher than that prevailing at the discharge of the heating coil 4, this is not to be taken as a limitation, since charging stocks, particularly the lighter ones, may be heated in chamber l0 to a temperature above that prevailing at the discharge of coil 4. On the other hand, particularlyfor the heavier charging stocks and depending upon the limitations imposed upon the amount of coke and sludge to beformed or contained in the products, it may be desirable to maintain the materials in chamber Ill at a temperature lower than that reached at the discharge of heating coil 4 to decrease the rate at which the reaction proceeds in chamber I 0. To

this end chamber l may be unheated or the oil may be cooled in a manner hereinafter described.

The vapors pass out of'chamber l0 through line l9 having valve to dephlegmator 2|. As

a feature of the infention I may subject all or For this purpose a vapor coil 22 may be posi-' tioned in furnace 5 and located therein in such a manner that the combustion gases pass over coil 22 before passing over coil 4. In this man- 20 ner and because the combustion gases passing over coil 22 are at a higher temperature than when they pass over coil 4, a greater degree of radiant heat may be utilized in coil 22 than in coil 4. Coil 22 may be connected to vapor line l9-through branches 23 and 24, respectively, controlled by valves 25 and 26. By proper regulation of valves 20, 25 and 26, any" desired amount of vapors separated in chamber l9 may be passed through the vapor heating coil 22.

Referring now to the dephlegmator 2|, the vapors remaining uncondensed therein leave the upper part thereof through line 21, having valve 28, through condenser 29 and thence to receiver 30. Receiver 30 is provided with the usual gas release line 3|, having valve 32, and distillate release line 33, having valve 34. A-portion of the distillate collected in receiver 39 may be returned to the dephlegmator to facilitate closer fractionation. To this end line 35, pump 35 and valve 31 40 are provided. l a a The reflux condensate formed in dephlegmator 2| may -.be withdrawn from the bottom thereof through leg 38 and through line 39, in which may be interposed a hot oil pump 40 and valve 42, and through which said reflux condensate may be directed to the main feed line whereby it may be returned for retreatment to the heating tubes 4 with a supply of fresh charging stock.

Raw oil to be treated in the process may be drawn from suitable storage tanks (not shown) through line 43 and pump 44. From line 43 and by suitable control of the valves shown, all or a portion of the raw oil to be treated in the process may be diverted through line 45, having valve 46, then to line 41 which connects with the main feed line I, whereby all or a portion of the charg ing stock may be fed directly to the heating tubes, mixing before entering therein with reflux condensate, directed through line 39. Or, all or a portion of the raw oil may be diverted from line 43 through branch 48, having valve 49, and then through line 50 from which it may be directed to the dephlegmator 2| to help fractionate the vapors therein. Raw oil fed to dephlegmator 2| is thereby preheated and mixed with reflux condensate and the mixture may be directed to the heating coil 4, through lines 38, 39 and I as heretofore described. If desired, the line 50 may terminate in a closed coil (not shown) connected to the feed lines 39 or 4'! instead of mixing directly with the vapors.

I have discovered that when the degree of conversion obtained in the cracking zone, such as heating coil' 4 and chamber i0, is so controlled that the heavier liquid products separated therein do not contain more than generally 5% and preferably less than 2%,of sludge-like or cokelike materials, as may be determined by so-called benzol centrifuge, said heavier liquid products comprise a substantial proportion of fractions, which, when separated from such solids or sludgelike materials under proper conditions, may be subjected advantageously to additional conversion, with the formation of substantial additional yields of motor fuel. This may be effected by regulating the conditions in coil 4 and chamber III, or by subjecting the heavier liquid products withdrawn from chamber ii) to such additional treatment as will hereinafter be described, that a so-called dry distillation thereof is effected, leaving in the zone of distillation a substantially solid residue, the remaining fractions having been vaporized to produce a material which may be subjected advantageously to additional cracking.

The heavier liquid products are separated and withdrawn from chamber I0, preferably from the bottom thereof or at various low levels as provided for by a plurality of draw-off lines and valves 50', through line 5|, having valves 52 and 53 interposed thereon, are directed to a flash chamber 54 tobe subjected therein to flash distillation to any desired degree.

By means of reductionof pressure obtained by proper control of valves shown, a large portion of said unvaporlzed liquid products may be vaporized in chamber 54. Depending upon the conditions under which the operation is carried out and upon the charging stock used, such reduction in pressure may be sufficient to distill or vaporize said heavier liquid products substantially to dryness by means of the self-contained heat. However, I have found that generally this self-contained heat is not sufficient and in a majority of cases it is necessary to give additional heat to the heavier liquid products withdrawn from the .reaction zone before subjecting them to flash distillation in order to obtain during flash distillation a vaporization substantially to dryness.

According to one of the features of the invention any desired proportion of, or all, the heavier liquid products withdrawn from the reaction zone l0 may thus be directed "through branches 55, having valves 56 interposed thereon, through a heating coil 58 located in furnace .5.

It may be desirable to regulate the heating of the heavier liquid products of reaction in such a manner that, while they receive the necessary additional heat to cause substantially dry distillation by accompanying or subsequent reduction of pressure, at the same time the additional heat to which such products are subjected does not cause substantial additional "cracking to take place, which would otherwise cause a material increase of the sludge or coke-like constituents.

Therefore, the heating coil 58, through which the heavier products of reaction receive additional heat, may be located in furnace 5, at such a point that rapid heat transfer takes place, so that the amount of heat required may be transmitted to the heavier liquid products of reaction in'the shortest possible time. In this manner I materially decrease the additional cracking to which such products would be subjected, if they were heated to the required temperature with a slower rate of heat transfer. For this purpose I have shown, in the drawing, the heating coil 58 positioned near the hottest part of furnace 5, whereby, with the help of intense radiant heat and high heating gas temperatures the non-vaporized turned to the heating-zone for retreatment.

products withdrawn from chamber It may be. raised rapidly to the required temperature.

The sizes of heating coil 58 must be carefully proportioned relative to the amount of materials 5 to be fed therethrough and with the degree of heat transfer therein. To assist in the regulation of the heat transfer in heating coil 4, vapor coil 22 and heavier liquid products coil 58 respectively, which may be more or less independent of each other, I may provide furnace 5 with such means as are well known to regulate the temperature and the amount of combustion gases therein. Such means are, for instance, flue gas recirculation, superheated steam injection and additional burners properly located in furnace 5. Such additional means have not been shown on the attached drawing, as I believe they are well known and would simply complicate the drawing. By the proper control of the degree of reaction obtained in the zones 4 and I0 and by proper control of valves 52 and 56 as well as by the control of the heat transfer to coil 58, more or less independently of the heat transfer to the other coils shown as heretofore explained, any desired additional amount of heat may be given to the heavier liquid products withdrawn from chamber l0 in the shortest possible time. In this manner and coupled with proper control of the degree of reduction of pressure to which said heavier liquid products may be subjected by means of either valves 52, 56 or 53, substantially dry distillation of said heavier liquid products is efiected in chamber 54 without materially increasing the comparative amount of coke formation in the process.

Or, chamber 54 may be provided with suitable heating means, such as coil 59 controlled by valves 60. 7 It is provided with bottom draw-off 6|, having valve 82 and by-pass 63 controlled by valves 64, on which may be interposed pump 65, whereby liquid or semi-solid products may be removed therefrom. Solid matters formed in the operation of the process and deposited in chamber 54 may be removed therefrom through top or bottom manholes in the usual manner.

One of the principal features of thisinvention is having the bulk of the carbon or coke deposition outside the zone of high pressure. This permits the use of much cheaper equipment as well as minimizing the danger of explosion.

Vapors separated by flash distillation in chamber 54 may be removed therefrom through line 66 having valve 61, whereby they may be passed directly to condensing and collecting means and in part or in total removed from the process or re- Or, as shown in the drawing, they may be passed first through a fractlonatin'g column 69, wherein they may be subjected to controlled condensation by introducing to dephlegmator 69 suitable cool- 50 ing medium through line 10, having valve H; or

raw oil to be charged to the process may be diverted from line 43 through line 12, having valve 13 and introduced to column 69.

Vapors uncondensed in column 69 may be removed therefrom through upper draw-off line 14, having valve 15, and passed to condenser 16, thence to receiver 11, having usual gas release valve I8 and distillate release valve 19. The fractions of the flash vapors condensed in column 69 70 may be discharged from the bottom thereof through line 80, on which may be interposed pump 8|. Thence, they may be diverted through branch 82 having valve 83, which connects with line 50 whereby said fractions may be returned to the process through dephlegmator 2 I. Or. the

fractions condensed in tower 89 may be passed through branch 84, having valve 85, connected with feed line 41, whereby said fractions may be returned directly to heating coil 4.

It will be apparent from the drawing that by suitable control of valve 13, 49, 46, 85 and 83, any desired proportion of fresh raw oil or of materials withdrawn from the bottom of tower 69, independently of each other, or together, may be di rected to dephlegmator 2| or to the heating part of the process.

It may be desirable to control the degrees of reaction respectively taking place in heating coil 4, chamber Ill and vapor coil 22, by controlling the temperature, characteristics and quantityof the material passing respectively through these zones. For instance, it may be desirable to introduce into the oil transferred from the heating coil' 4 to chamber l0, liquid products or condensates from other parts of the process. It may also be desirable to do the same thing for the vapors withdrawn from chamber 10. To this eifect a portion of the reflux condensate or combined feed passing through line 39 and being directed to the heating coil 4 may be diverted from line 39 to branch 81 by suitable control of valve 42 in line 39 and valve 86 in line 81. In this manner this material may be injected into line 8 combining therein with the products passing from heating coil 4 to chamber II]. In the same manner a portion of these materials may be diverted from line 39 through line 88 by suitable control of valve 42 and valve 89 in line 88, and through line 88 this material may be injected into line 90 wherein it combines with vapors passing from chamber ID to the vapor cracking coil 22.

In addition it may be desirable to cool the vapors immediately after they have been subjected to vapor phase cracking in coil 42 and for this purpose suitable lines and valves (not shown) may be provided whereby material passing through line 41 or through line 39 may be diverted and injected into line 24 through which the vapors leave the coil 22. Instead of injecting into the various parts of the system as heretofore described, liquid products or condensate, it may be desirable to introduce thereto gases whether produced by the process or from extraneous sources and which may have either a catalytic, hydrogenating or oxidizing action.

While I have indicated in a diagrammatic manner, for the various parts of the apparatus a type of construction, it is to be understood that other types of construction may be used for such parts, providing that the substituted parts permit of accomplishing the same function and obtain the same results as such parts of the construction shown diagrammatically on the attached drawing. For instance, a vapor phase cracking chamber suitably heated, may be substituted for the vapor heating coil 22. A so-called soaking coil, or digestion chamber, may be substituted for the chamber 10 shown, but if such is used it is preferable to connect it with a separating chamber, which may be unheated, such soaking coil (or digestion chamber) and separating chamber performing the functions of the chamber l0 herein shown and described. As another modification it may be desirable to interpose in line 24, connected with the discharge of the vapor coil 22 or its equivalent, a separator whereby heavy productsof polymerization formed by the vapor phase cracking effected in coil 22 or its equivalent, may be separated from the vapors before passing the latter to dephlegmator 2|.

The valves and pumps shown permit the operator to maintain suitable pressures on the various. parts of the apparatus. The flash chamber 54 and its connected parts such as dephlegmator 69, condenser 16 and receiver 11 are preferably maintained at a pressure substantially lower than the pressure maintained in chamber H). Dephlegmator 2| may be maintained at any desired pressure equal to or lower than the pressure maintained on vapor coil 22. The same pressure as that on dephlegmator 2| or reduced differential pressures-may be maintained on condenser 29 and receiver 30.

The pressure maintained on the heating ele- 15 ment 58 may be same as that maintained on chamber III, or the same as that maintained on flash chamber 54 or an intermediate pressure. A

proper control of the pressure maintained on heating element 58 helps to control the heat transfer and the velocity in said coil by proper regulation of vaporization therein; for instance,

, it may be advantageous to maintain element 58 at a pressure lower than the pressure maintained in chamber I 0 to permit a certain degree of vaporization of the liquid products withdrawn from chamber ill to take place therein, the balance of the vaporization being effected in flash chamber 54 under further reduced pressure, as heretofore described.

Any suitable pressure may be maintained on vapor cracking coil 22 in relation to the pressure maintained in chamber ill.

If desired, vacuum may be maintained on the flash chamber 54 and its associated parts B9, 16 and "II. This may be effected by proper use of vacuum pumps (not shown) which would be connected to line 66 or to the draw-offs from condenser 16 or receiver Tl. It may be preferable to use vacuum on thispart of the process when the conditions of operation are such that, should the pressure be reduced on flash chamber 54 down to atmospheric pressure, dry distillation of the heavier liquid products drawn off from chamber I0 could not be effected without such additional heating in heating element 58, that objectionable reaction and excessive formation of coke and sludge proceeds, even with the use of rapid heat transfer as contemplated by my process. The use of vacuum would thus reduce the additional amount of heat required to cause dry distillation of the heavier liquid products of reaction, and would thus obviate the difficulty and disadvantages just mentioned.

In addition, the conversion may be effected 55 through heating coil 4 or chamber In or its equiv alent as heretofore described, under equalized pressure; or the pressure maintained on chamber l0 may be lower than that maintained on heating coil 4 although still substantially above 60 atmospheric pressure.

When vacuum is used, parts of the apparatus, such as vapor lines and condensers, may be enlarged in proportion to their dimensions when used under pressure.

While I have described a particular arrangement of the various heating zones of my process and a particular construction of the furnace 5 and heating chamber II, it is within the scope of the invention to use other relative arrangements 70 of these parts providing that such alternative arrangements permit the operator to carri out the process in the manner and for the purpose indicated with the results heretofore described.

For instance, each of the heating coils or cham- 75 here 4, 22, 5a and l0, 1: the latter is to be heated,

may be positioned in separate furnaces or heating chambers independently heated. In this alternative the furnaces or heating means in which vapor cracking coil 22 or its equivalent and element 58 are located, may preferably be of such type'as will permit the use of rapid heat transfer such as caused by intense radiant heat, in the manner and for the purpose heretofore described in connection with the device shown in the draw- Or, the heated zones 4, i0, 22 and 58, or their equivalent, may be positioned in separate heating chambers wherein, in additionto, or independently of, the heat which may beproduced by burners, the products of combustion which leave heating zones at relatively higher temperatures may be utilized in part or in total to help heat the parts maintained at lower temperatures. For instance, the spent combustion gases leaving the furnace wherein heating coil 4 may be positioned, may be utilized to help heat either one or more of the associated heated zones I0, 22 and 58. Or, the spent combustion gases leaving the furnace where heating coil 4 is positioned may be utilized to help heat the furnace in which coil 58 may be positioned and the spent combustion gases leaving the furnace in which vapor coil 22 or its equivalent may be positioned, may be utilized to help heat chamber I 0. Any other combination may be used to utilize best the heat of the process without departing from the scope of the invention so long as such alternative arrangement permits the operator to reach in the various heating zones described, the relative temperatures desired and to obtain therein the relative amount and rate of heat transfer which the process requires.

As an illustration of the temperatures which may be maintained in an operation carried out in accordance with the invention, the oil may be heated in heating coil 4 to a temperature of, say 920 F. to 960 F., said oil entering chamber In at a. temperature near, but relatively lower than said temperature. In chamber III the oil may be maintained at a temperature of, say 850 F. to 900F. In this illustration chamber I0 may not be heated, dampers l1 beingclosed and damper l6 being open. The vapor leaving chamber in may be heated in vapor coil 22 to a temperature of approximately 975 F. to 1100 F. and the heavier liquid products removed from chamber [0 may be .passed through coil 58 and heated therein to a temperature between 950 F. and 1000 F. and then directed to flash chamber 54. In this illustration a pressure of approximately 450 pounds may be maintained on heating coil 4 and chamber In. The pressure maintained on heating coil 58 may be approximately 250 pounds, and this pressure may be reduced on flash chamber 54 down to approximately 25 pounds. The vapors leaving chamber I0 may be passed through vapor coil 22 under a pressure of approximately 100 pounds, more or less.

While it will be apparent that the modifications referred to in the foregoing description refer mainly to the disposition of the heating zone as well as to the arrangement of the conversion zone and parts directly connected therewith, it is to be understood that other modifications may be made to the same or other parts of the apparatus used to carry out the invention without departing from the spirit of the process described herein.

While I have described in the apparatus shown in the drawing such relative arrangement of parts wherein heating element 58 is positioned in a hotter zone of the furnace than that in which vapor coil 22 is shown to be located, I may reverse the location of these two heating elements.

Under these conditions and treating a midcontinent topped crude having a gravity of approximatey 28 B., a yield of about 60% of 437 F. end point gasoline may be produced, with the accompanying production of approximately 20% to 25% of so-calle'd naphtha bottoms and gas 10 oils, the balance being solid residue and gas.

While I have shown and described a single dephlegmator, it is to be understood that the invention may be used in connection with a cracking apparatus and method wherein two or more dephlegmators in series or parallel are used and particularly to such types of apparatus and method where the vapors from the first dephlegmator are subjected to additional fractionation through a secondary dephlegmator, which may be of any suitable type.

As a means of facilitating the operation for the production of dry residue, a portion of the non-condensable gas from receiver 17 may be returned to vapor line leaving reaction chamber II] by means of valve 92 in line 93. This gas will pass through coil 22 together with the vapors from the reaction chamber or be by-passed through valve 20 depending upon the operation desired. In either event, by controllingvalves 51 on flash chamber 54 the uncondensed gas and vapors may be introduced at any one or more of several points therein. In the event the liquid level in chamber 54 is above any one of these points the hot gas and vapors will act as a partial pressure agent to facilitate vaporization and promote distillation to dryness.

Two methods of operation are contemplated. In the first method, both the vaporous and unvaporized oil will be withdrawn through line 5| from the bottom of chamber l0, and passed to flash chamber 54 after reduction in pressure. 'The advantage of this procedure, especially with non-residuum operations, will be that material partial pressure efiect will be exerted by the vapors, tending to increase the amount of vaporization in the flash chamber and decrease the amount of non-vaporous fractions therein.

In the second method of operation, vapors will be separated and withdrawn through vapor line 23, while the residual oil will be withdrawn from the bottom of the chamber through line 5|. Provision is made to permit bleeding off of a regulated quantity of vapors from line l9 into line I 00 by proper regulation of valve In I. By controlling the point of entry by means of valves 51, the vapors may enter flash chamber 54 either above or below the liquid level maintained therein. If full advantage of partial pressure effect of these vapors is to be taken, they should enter in the lowest point in chamber 54 in order to increase vaporization and facilitate reduction of'the percentage of unvaporized oil.

It is to be understood that the preferred method of operation is of the low level type, wherein a minimum quantity of residual oil is maintained in the pressure drum In. That is, residual oil is withdrawn from chamber 10 before it has had suflicient time to form more than 5% of sludge or coke-like constituents.

I claim as my invention:

1. A process of converting hydrocarbon oil into gasoline-like hydrocarbons, coke, and gas, comprising the steps of heating hydrocarbon oil to vaporizing temperature, flashing the heated oil into vapors and unvaporized oil, withdrawing the vapors and heating them to temperatures in excess of 1000 F. to convert the same into low boiling hydrocarbons, separately withdrawing the unvaporized oil and contacting it with the highly heated vapors in a coking zone so that the heat of the vapors will convert the oil into vapors and coke, withdrawing the vapors from thecoking zone, cooling the withdrawn vapors by contacting the same with the fresh oil being charged to the process, fractionating the vapors in a fractionating zone, withdrawing the reflux condensate from the fractionating zone and recycling the same, withdrawing the vapors from the fractionating zone and condensing the same to obtaingasolinelike hydrocarbons, and removing the coke from the coking zone.

2. In a hydrocarbon oil cracking process which comprises heating a flowing stream of the oil to cracking temperature under pressure in a heating zone, discharging the hot oil stream into a vapor separating zone, and separately removing vapors and unvaporized oil from said zone; the improvement which comprises passing thevapors to a vapor phase cracking zone and heating the same therein to cracking temperature, subjecting said unvaporized oil to flash distillation by lowering the pressure thereon, and introducing at least a portion of the constituents removed from said unvaporized oil by flashing to said vapor phase cracking zone for subjection therein to cracking temperature with the first mentioned vapors, and introducing heated vapors from said vapor phase cracking zone into the unvaporized oil being flash distilled.

3. A process for cracking hydrocarbon oil comprising passing oil through a coil wherein it is raised to a cracking temperature, delivering the oil thence to the reaction chamber, separately removing vapors and liquid from said reaction chamber, passing the vapors through a vapor phase cracking coil, passing the liquid to a low pressure flash distilling. zone, introducing the vapor phase cracked vapors from. said vapor phase cracking coil to said low pressure flash distilling zone, taking off vapors from said low pressure flash distilling zone, subjecting the same to fractionation, and returning constituents from said fractionating step to both the first mentioned heatin coil and the vapor phase cracking coil.

JOSEPH G. AL'I'I-IER.

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