US2253006A - Apparatus for hydrocarbon oil conversion - Google Patents

Description

Aug. 19, l941. J. G. ALTHER 2,253,006

APPARATUS FOR HYDROCARBON OIL CONVERSION Original Filed April 17, 1929 &

J72 dzz for: Jsep)? flizker Patented Aug. 19, 1941 APPARATUS FOR HYDROCARBON OIL CONVERSION Joseph G. Alther, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware Application December 4, 1935, Serial No. 114,182,

which is a division of application Serial No. 355,704, April 17, 1929. Divided and this application February 15, 1938, Serial No. 190,634

4 Claims.

This is a division of my co-pending application Serial No. 114,182 filed December 4, 1936 which in turn is a division of SerialNo. 355,704 filed April 17, 1929, which has matured into Patent 2,091,261.

This invention relates to improvements in apparatus 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 loss.

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 apparatus means whereby it is possible to approach dry distillation. 7

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 throughthe stock. This is of particular importance in effecting the capacity and thermal efliciency of the process.

In one type of operation practised commercially on a large scale, the conditions o11 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 into the 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 operationit is possible to approach dry distillation,

accomplishing 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 ofi. One of 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 ofheat by the incoming oil to carry on this redueing or coking action.

As is well known, such type of operation proof 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 longtime onstream before shutting down. Some of the disadvantages are limited gasoline yield and largeamount 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 flashed residuum which is withdrawn from the flashing still resembles a productwhich is uncracked. I do not mean to indicate that this oil was not cracked but merely that it resembles an uncracked oil. This may be due to 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 different'a relatively lower percentage of the oil leaving the pressure drum leaves that drum through the vapor line in the form of 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 from 100 to 1009 pounds, more or less. 'sion takes place in the drum from which substantially all oil, vapor. and gas may be withdrawn through a single outlet being directed into a large flash drum where flashing takes place of operation, the conditions being so controlled 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.

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 apparatus the desirable features of the non-residuum and flashing types of operation, the conditions being so controlled in the flashing still as to produce either a good residue suitable for asphalt making StOCkl, or a substantially solid coke, as local conditions may dictate. V

Another purpose of the invention resides in the employment of means to increase the decomposition of both the vapors and liquid from the pressure expansion drum under controlled conditions designed to accomplish the best results. This feature 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. 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. 7

The pressures on theexpansion chamber may 7 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 operation of the apparatus of the present invention is as follows:

place, i. e., all the vapors from the flashing still are directed to a dephlegmator where the sumciently converted fractions are separated from the insufiiciently converted fractions or heavy ends (reflux) by the incoming cold raw oil or other cooling medium, said reflux being returned I to the the cracking coil for retreatment.

If the The charging stock plus reflux will be pumped 7 through a conventional furnacehaving a large heating surface from which the heated oil may be transferred to a drum. This drum is prefer ably 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 Expanby reduction 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 expansion drum may tion therein; or a combination of both methods may be employed.

From this point on the usual operation takes- 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 will be 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 coinplete 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 I of the apparatus of the invention.

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 coil 4, located in a conventional furnace 5. I

In heating coil l the oil is heated to a temperature within the crackingrange under a suitable pressure. The amount of oil passed 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 cracldng ob tained 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 It may take any desirable form and size in relation to the capacity of theapparatus. 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 main-,

. Proper control of the degree of heat furnished to chamber I0 may be obtained by regulation of suitable dampers shown 'at 15, spectively located in flue l4 and and I3.

While, for the treatment a most oils, it may l1 and I8 reby-passes I2 be desirable not to raise the temperature of the materials entering chamber II] to a temperature substantially higher than that prevailing at the discharge of the heating coil 4, this is not to be takenas a limitation, since charging stocks, particularly the lighter ones, may be heated in chamber Ill to a temperature above that prevailing at the discharge of coil 4. On the other hand, particularly for the heavier charging stocks and depending upon the limitations imposed upon the amount of coke and sludge to be formed or contained in the products, it may be desirable to maintain the materials in chamber l 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 H]. To this end chamber In may be unheated or the oil may be cooled in a manner hereinafter described.

The vapors pass out of chamber l0 through line |9 having valve 20 to dephlegmator 2|. As a feature of the invention I may subject all or part of the vapors removed from chamber ID to additional heating at elevated temperatures to effect a controlled degree of so-called vaporphase cracking whereby I am enabled to produce lighter valuable distillates having the characteristics of motor fuels or gasoline, possessing high anti-knock properties due to the presence of controlled proportions of aromatic and unsaturated hydrocarbons formed by said vapor cracking.

For this purpose a vapor coil 22 may be positioned in furnace and located therein in such a manner that the combustion gases pass over coil 22 before passing over coil 4. In this manner 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 l0 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 33, having valve 34. A portion of the distillate collected in receiver 30 may be returned to the dephlegmator to facilitate closer fractionation. To this end line 35, pump 36 and valve 31 are provided.

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 49 andvalve 42, and through which said reflux condensate may be directed to the main feed line I, 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 maybe diverted through line 45, having valve 46, then to line 41 which connects with the main feed line whereby all or a portion of the charging 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 l as heretofore described. If desired, the line 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 sludge-like 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 H), or by subjecting the heavier liquid products Withdrawn from chamber Hi to such additional treatment as will hereinafter be described, that a so-called dry distillation thereof is efiected, 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-oif lines and valves 50', through line 5|, having valves 52 and 53 interposed thereon, are directed to a flash chamber 54 to be subjected therein to flash distillation to any desired degree.

By means of reduction of pressure obtained by proper control of valves shown, a large portion of said unvaporized 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 suflicient 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 suflicient 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 i9 may thus be directed. through branches 55, having valves 55 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 suchproducts are subjected does not cause substantial additional cracking to take chamber H] in the shortest possible time.

valves lit.

6!, having valve 52 and by-pass t3 controlled by point that rapid heat transfer takes place, so that the amount of heat required may be transmitted to theheavier 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 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 to be fed therethrough and with the degree of heat transfer therein. To assist in the regulation of the heat transfer in heating coil l, vapor coil 22 and heavier liquid products coil 58 respectively, which may be'more or less independent of eachother, 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 theyare well known and would simply complicate the drawing.

By the proper control of the degree of reaction obtained in the zones 4 and land 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 outer coils shown as heretofore explained, any desired additional amount of heat may be given to the heavier, liquid products withdrawn from 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 effected in chamber 53 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 It is provided with bottom draw-off valves 54, 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 52 may be removed therefrom through top or bottom manholes in the usual manner.

One of the principal features of this invention 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 iii may be removed therefrom through line 66 having valve 6?, whereby they may be passed directly to condensing and collecting means and in part or in total removed from the process or returned to the heating zone for retreatment. Or, as shown inthe drawing, they may be passed first through a fractionating column 69, wherein they may be subjected to controlled condensation by introducing to dephlegmator 69 suitable cooling medium through line it, having valvell or raw oil to be charged to the process maybe diverted from line 53 through line 12, having valve i3 and introduced to column 69.

Vapors uncondensed in column 69 may be removed therefrom through upper draw-off line M, having valve 15, and passed to condenser '16, thence to'receiver 11, having usual gas release valve 18 and distillate release valve 19. The fractions of the flash vapors condensed in column 69 may be discharged from the bottom thereof through line 80, on which may be interposed pump 8i. 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 69 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 valves 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 directed 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 i, chamber 50 and vapor coil 22, by controlling the temperature, characteristics and quantity of 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 lil, liquid products or condensates from otherparts of the process. It may also be desirable to do the same thing for the vapors withdrawn from chamber H). 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 r from line 39 to branch Bl by suitable control of valve 42 in line 39 and valve 86 in line 8'1. In this manner this material may be injected into line 8 combining therein with the products passing from heating coil 4 to chamber Ill. In the same manner a portion of these materials maybe diverted from line 39 through line 88 by suitable control of valve 42 and valve 39 in line 38, and through line 88 this material may be injected into line 90 wherein it combines with vapors passing from chamber Hi 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 22 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 2d through which the vapors leavethe coil 22. Instead of inject ing' 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 l shown, but if such is used it is preferable to connnect it with a separating chamber, which may be unheated, such soaking coil (or digestion chamber) and separating chamber performing the functions of the chamber 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 products of 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 H are preferably maintained at a pressure substantially lower than the pressure maintained in chamber I0. 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 2lor reduced differential pressures may be maintained on condenser 29 and receiver 30.

The pressure maintained on the heating element 58 may be the same as that maintained on chamber H1, 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 In to permit a certain degree of' vaporization of the liquid products withdrawn from chamber Hi 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 II].

If desired, vacuum may be maintained on the flash chamber 54 and its associated parts 69, and 11. This may be effected by proper use of vacuum pumps (not shown), which would be connected to line 65 or to the draw-offs from condenser 16 or receiver 11. It may be preferable to use vacuum on this part 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 through heating coil 4 or chamber 10 or its equivalent as heretofore described, under equalized pressure, or the pressure maintained on chamber 10 may be lower than that maintained on heating 'coil 4 although still substantially above 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 of these parts providing that such alternative arrangements permit the operator to carry outthe process in the manner and for the purpose indicated with the results heretofore described.

For instance, each of the heating coils or v chambers 4, 22, 58 and I0, ifthe 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 drawing.

Or, the heated zones 4, I0, 22 and 58, or their equivalent, may be positioned in separate heating chambers wherein, in addition to, or independently of, the heat which may be produced 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 ll}, 22 and 58. Or, the spent combustion gases leaving the furnace Where heating coil 4 is positioned maybe utilized to help heat the furnace to 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 l0. 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 ofthe temperatures which maybe 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 II] at a temperature near, but relatively lower than said temperature. In chamber 10 the oil may be maintained at a temperature of, say 850 F. to 900 F. In this illustration chamber Ill may not be heated, dampers H being closed and damper l6 being open. The vapor leaving chamber I0 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 In 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 approxie mately 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 l 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 Mid- Continent topped crude having a gravity of approximately 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-called naphtha bottoms and gas oils, the balance being solid residue and gas.

While I have shown and describeda 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 noncondensable gas from receiver [1 may be returned to vapor line leaving reaction chamber I0 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 controlling valves 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 Land 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 vaporizationv in the flash chamber and decrease the amount of non-vaporous fractions therein.

In the second method of operation, vaporswill 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 H! into line I00 by proper regulation of valve lfll. 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 I2. That is, residual oil is withdrawn from chamber ll] before it has had sufficient time to form more than 5% of sludge or coke-like constituents.

I claim as my invention:

1. A cracking apparatus comprising a heating coil and a separating chamber communicating therewith, a second chamber connected to and adapted to receive residual liquid from the separating chamber, a fractionator, a final condenser and a receiver serially connected to said second chamber, means for heating vapors from the first-named chamber and gases from said receiver, and means for discharging the heated vapors and gases into said second chamber.

2. A cracking apparatus comprising a heating coil and a separating chamber communicating therewith, a second chamber connected to and adapted to receive residual liquid from the separating chamber, a fractionator, a final condenser and a receiver serially connected to said second chamber, vapor communicating means between said chambers and including a second heating coil, and means for supplying gases from said receiver to said second coil.

3. The apparatus as defined in claim 1 further characterized in the provision of a heater between the separating chamber and the second chamber for heating said residual liquid in transit from the former to the latter.

4. The apparatus as defined in claim 2 further characterized in the provision of a heater between the separating chamber and the second chamber for heating said residual liquid in transit from the former to the latter. I

JOSEPH G. AL'I'HER.

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