US2211999A - Process for hydrocarbon oil conversion - Google Patents

Description

Aug. 20, 1940. J. G. ALTHER PROCESS FOR HYDROCARBON OIL CONVERSION Filed NOV. 30, 1936 Patented Aug. 20, 1940 UNITED STATES PROCESS FOR HYDROCARBON OIL CONVERSION Joseph G. Alther, Chicago, -I1l., assignor to Univ `versal Oil Products Company, corporation of Delaware Chicago, Ill., a

Application November 30, 1936, Serial No. 113,427

3 Claims.

This is a continuation-impart of my copending application Serial No. 355,704 led AApril 17, 1929, now Patent No. 2,091,261.

' This invention relates to improvements in process for hydrocarbon oil conversion, and refers more particularly to improvements designed for the eicient cracking of hydrocarbon. oils to-.conl vert and produce there-from 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 ci the invention is to subject hydrocarbon oil to such conditions of 1153 temperature and p-ressure as` to produce maxi- 3`O' stantially solid coke-like residue.

mum 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 process and apparatus steps and means whereby it is possible to approach dry distillation.

In one type of ope-ration practised commercially on a large scale, the conditions. of operation are so controlled as to mainly produce a gasolinelike product suitable for use asl motor fuel, which is the desired product of conversion, and a sub- Such operation .is described, as; a...nonresiduum type of operation, the expression resduum in such instance meaning liquid. Theop'eration'is carried. out in atube and drum. type of apparatus wherein the oil is heated in the tubeand dis-l charged 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-residuuni type of operation it is possible to approach dryrdistillation, accomplishing same in the drum, wherein practically all volatile matter is distilled oii, leaving a,

substantially solid, coke-like residue. lOne of the reasons why this is possible in the non-'residuum type of operation is the large amount of cracking time given to the heavy material in the pressure drum whereby it is reduced to a coke solid. Obviously this could not be done except for the fact that a large amount of heat is constantly supplied to the drum by the incoming oil to carry onthis reducing or coking action.

As-is Well known, such type of operation produces a maximum amount of coke, due to cracking and polymerization of the cracked materials in the pressure drum, thereby decreasing the actual onstream time eiciency of the system. To eliminate the objectionably large coke production, it has become commonpractce, in many cases, 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 an un. heatedy 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 a somewhat reduced gasolineyield as' compared -to 'nonresiduum operations and large amounts of liquid residue or fuel oil which may be unmarketable in some instances becauseof high viscosity and/or other objectionable characteristics. Asa

matter of fact the nal liquid residue or flashed residuum which iswithdrawn fromk the flashing still resembles a product which is'uncracked. I do not mean to indicate that this oil is 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 to cracking as compared with a non-residuum type of operation. Or, the high viscosity/of the final flashed residue may alsobe due to other causes which need not be here analyzed.

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 pressurev drum through the vapor line and what remains in the chamber isv 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. A greater proportion of the oil is withdrawn from the bottom of the pressure drum and flashed into the reduced pressure dashing still Where, due to the pressure reduction, latent heat contained in the oil is liberatedv and utilized to carry on the vdistillation of this oil.

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

The purpose of the present invention is to desirable features of both the non-residuum and ilashing types of operation, the conditions being Cil so controlled in the flashing still as to produce either a good liquid or semi-liquid residue suitable for example as` fuel oil or asphalt making stock, or coke of controlled volatility, aa local conditions may dictate.

The charging stock plus reflux will be pumped through a conventional furnace having a relatively large heating surface or tubular cracking coil from which the heated oil may be transferred to a drum or high pressure reaction chamber. This drum may lbe 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 withdrawn through a single outlet being directed into a large flash drum where ash distillation takes place by reduction in pressure. In certain operations where insui'cient heat is contained in the residual oil leaving the high pressure drum, additional heat may be supplied to the oil either prior or subsequent to its introduction into the flash chamber, or both.

Vapors from the flashing still are directed to a dephlegmator where the low boiling, sufficiently converted fractions are separated from the higher boiling, insufciently converted fractions, the latter being condensed as reflux condensate by the incoming cold raw oil or other cooling medium, and said refiux being returned to the cracking coil for retreatment.

A feature of the invention is to have the oil which is undergoing treatment in cracking stage at such temperature and pressure that, when the oil is released in the flashing still, there will be sufficient heat to give rapid and substantially complete distillation to dryness, that is, separation of substantially all of the vaporizable constituents from the oil, removal of the same from the flashing zone and accumulation of substantially solid residue in the latter.

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 conducting the process of the invention.

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

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 and valve 46 to line il which connects with the main feed line I, whereby all or any desired portion of the charging stock may be fed directly to the heating tubes, preferably mixing before entering therein with reflux condensate supplied to line 4l', as hereinafter described.

In heating coil 4 the oil is heated to a temperature within the cracking range 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 cracking obtained in the heating coil is preferably short of that at which formation of coke and sludge-like matter occurs, or exceeds a predetermined unobjectionable amount.

Chamber Ill to which the heated products from coil 4 are supplied through line E and valve 1 may take any desired form and size in relation to the capacity of the apparatus. It may be unheated and insulated against loss of heat by radiation. 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 chamber I0. drawn from chamber lll before it has had sufficient time to form more than five percent or thereabouts of sludge or coke-like constituents.

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 five percent and preferably less than 2 percent, of sludgelike or coke-like materials, as may be determined by so-called benzol centrifuge method, said heavier liquid products contain a substantial proportion of vaporizable fractions, which, when separated from such solids or sludge-like materials under proper conditions, may be subjected advantageously to additional cracking for the formation of substantial additional yields of motor fuel, This maybe effected by regulating the conditions in coil 4 and chamber I0, or by subjecting the heavy liquid products withdrawn from chamber l! to such additional treatment, as will hereinafter be described, that a so-called dry distillation thereof is eiected, leaving in the zone of distillation a substantially solid residue, the remaining fractions having been vaporized to produce a material which may be advantageously subjected to additional cracking.

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 lll, and passed through valve 52, wherein the pressure is reduced, to flash chamber 54. The advantage of this procedure, especially with non-residuum operations, will be that an appreciable partial pressure effect will be exerted by the vapors, tending to increase the amount of vaporization in the flash chamber and decrease the amount of unvaporized fractions remaining therein. In the second method of operation, vapors will be separated and withdrawn through vapor line I9, while the residual oil will be withdrawn from the bottom of the chamber through line 5l.

As a feature of the invention I may subject all or part of the vapors removed from chamber l 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 and possessing high anti-knock properties due to the presence of fairly large proportions of aromatic and unsaturated hydrocarbons formed by said vapor cracking.

For this purpose 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 the combustion gases passing over coil 22 may be higher in temperature than when they pass over coil 4 and a greater degree of radiant heat may be utilized in coil 22 than in coil 4. Coil 22 may be connected to vapor line I9 through branches 23 and 24, respectively, controlled by valves 25 and 26. By proper regulation of valves 20, 25 and 26, any desired portion or all of vapors separated in chamber I0 may be passed through the vapor heating coil 22.

That is, residual oil is with-V i.Povisionis niade to permit'bleeding off of a regulated quantity of vapors from line I9 into line |00 by proper regulation of valve I 0I. By controlling the point of entry by means of valves 51, these vapors may enter flash chamber 54 either above or below the liquid level maintained the percentage of unvaporized oil.

Provision is also made for diverting, when desired, a regulated portion .or all of the vapors withdrawn from chamber I0 from line I9 through line IDU' and valve IDI to separate fractionating,

condensing and collecting equipment, of any well known form, not illustrated. v

By means of thereduction in pressure obtained by proper control of valves shown, a large portion of said unvaporized liquid products maybe vaporized in chamber 54. Depending upon the conditions under which the operation is conducted and upon the characteristics of the charging stock employed, such reduction in pressure may be Sufcient to distill or vaporize said heavier liquid products substantially to dryness by means of the self-contained heatin the heavy oil removed from chamber I9. However, I have found that generally this self-contained heat is not sufficient to induce satisfactory coking of the oil and in a majority of cases it is necessary to supply additional vheat to the heavy liquid products withdrawn from the reaction zone either before subjecting them to ash distillation or during flash distillation thereof in order to vaporize substantially all of their volatile constituents and reduce the oil to coke.

One of the principal features of this invention resides in depositing the bulk of the carbon or coke outside the zone of high pressure. This permits the use of much cheaper equipment and minimizes the danger of explosion.

As a means of facilitating the operation for the production of substantially dry coke, a portion of the non-condensable gas from receiver 11 may be returned to vapor line I9 leaving reaction chamber Ill bymeans of valve 92 and pump 94 in line 93. This gas will pass through coil 22, either alone or together with the vapors from the reaction chamber, or m-ay Icy-pass coil 22 through valve 20, depending upon the operation desired. In either event, by controlling valves 51 on ash chamber 54 the uncondensed gas, either alone or together with the vapors may be introduced at any one or more of several points therein either in highly heated state or otherwise, as desired. Inl 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 the coking operation.

It may be desirable to regulate the heating of the heavy liquid products supplied from chamber I 9 to chamber 22 in such a manner that, while they receive the necessary additional heat to cause their substantially further vaporization by accompanying o-r subsequent reduction of pressure, the additional heat is not sumcient to cause substantial additional cracking to take place in the low pressure zone thereby decreasing the formation of the sludge and coke-like constituents.

Chamber 54 is provided with bottom draw-01T line 6I, having valve 62, whereby liquid or semiliquid products may beremofved therefrom. Coke formed in the'operation of the process and deposited in chamber 54 may be removed therefrom through top or bottom manholes inv the' usual manner.

Vapors separated by flash distillation in chamber 54 may be removed therefrom through line 66 having valve 61, and maybe passed directly,

to condensing and collecting means, not shown, wherefrom the resultant products may be removed, all or in part, from the process or returned,. in part, to the heating zone for retreatment. Or, as shown in the drawing, they may be passed r'st through a fractionating column 69, wherein they` are subjected to controlled partial condensation for the formation' of reflux condensate by introducing a suitable cooling and reiiuxing medium to dephlegmator 69 through line 10, having valve 1I; or raw oil charged to the process may be diverted from line 43 through line 12, having valve 13 and introduced to column B9 to serve as a cooling and refluxing medium.

Vapors remaining uncondensed in column 69 may be removed therefromv through upper drawoff line 14,` having valve 15, and passed through condenser 16 to receiver 11 which has the usual gas releasevalve 18 and distillate release valve 19. The fractions of the vapors condensed in column 59, comprising reflux condensate, maybe discharged from the bottom thereof through line 89, Yin which may be interposed pump BI, from which this material may be passed through line 84 and valve 85 to feed line 41, whereby said fractions may be returned directly to heating coil 4.

While I have indicated a specic form of apparatus, in a diagrammatic manner, for the various parts of the system, it is to be understood that many other forms of apparatus andtypes of construction may be employed providing that the substituted equipment perform substantially the same functionand obtain the desired results. For instance, avapor 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 IIJbut if such is used it is preferably connected with a separating chamber, which'may be unheated, such soaking coil (or digestion chamber) and the separating chamber performing the functions of the chamber I0 as 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 cracking and/0r polymerization formed by theI vapor cracking zone, may be separated from the vapors.

While I have described a particular arrangement of the various heating coils and a particular construction of the furnace 5, it is within theA scope of the invention to use other relative arrangements of these parts providing that such alternative arrangement permits the operatorto conduct the process in the manner and for the purpose indicated. For instance, each of the heating coils4 and 22 may be positioned in separate furnaces, or coils 4 and 22 or their equivalents may be positioned in separate heatingchambers zone wherein heating coill 4 may be positioned,-

may be utilized to help heat coil I0. Any other combination may be employed to best utilize the heat of the process without departing from` the scope of the invention so long as the desired relative temperatures, pressures and rates of heating may be obtained in the various steps of the process.

The operating conditions employed to accomplish the objects of the invention in an apparatus such as illustrated and above described may be approximately as follows: The first mentioned heating coil may utilize a conversion temperature ranging, for example, from 850 to 975 F., preferably with a superatmospheric pressure, measured at the outlet therefrom, of from 100 to 500 pounds, or more, per sq. in. Substantially the same or a somewhat lower superatmospheric pressure may be maintained in the succeeding reaction chamber. The second mentioned heating coil, to which vaporous products from the reaction chamber or uncondensed gaseous products of the process, or both, may be supplied, preferably employs a substantially higher temperature than that of the residual liquid products withdrawn from the reaction chamber ranging, for example, from 850 to 1l00 F., and the pressure employed in this zone may range from substantially the same as that maintained in the reaction chamber down to substantially atmospheric pressure. The pressure employed in the Vaporizing or coking chamber may range from substantially the same as that employed at the outlet from the second mentioned heating coil down to substantially atmospheric pressure and this zone is preferably operated at a substantially reduced pressure relative to that employed in the reaction chamber. The fractionating condensing and collecting equipment to which vaporous products from the vaporizing or coking chamber are supplied may utilize substantially the same o1' somewhat lower pressures than that maintained in the vaporizing or coking chamber.

As an example of one specific operation of the process, which may be conducted in accordance `with the provisions of the invention and in an apparatus such as illustrated and above described, the charging stock, which is a mixed base topped crude of approximately 26 A. P. I. gravity, is subjected, together with reflux condensate from l the fractionator, to a temperature measured at the outlet from the iirst heating coil of approximately 940 F. at a superatmospheric pressure of approximately 350 pounds per sq. in. Substantially the same pressure is maintained in the reaction chamber from which vaporous and liquid products are withdrawn in commingled state and supplied to the coking chamber which is maintained at a superatmospheric pressure of approximately 50 pounds per sq. in. The liquid products are reduced in this zone to substantially dry coke by the introduction, into direct contact therewith, of a portion of the uncondensed gaseous products of the process, heated in the second heating coil to a temperature of approximately 970 F. at a superatmospheric pressure of about 100 pounds per sq. in. This operation will produce, per barrel, of charging stock, approximately percent of 400 F. end-point gasoline having an octane number of approximately 67 and about '75 pounds of good quality low volatile coke, the remainder being chargeable, principally, to uncondensable gas.

As a modication of the operation above described wherein vaporous and liquid conversion products are separately withdrawn from the reaction chamber, the latter supplied to the coking chamber and the vaporous products subjected in the second heating coil to an outlet conversion temperature of approximately 960 F. at a superatmospheric pressure of approximately 500 pounds per sq. in., the pressure being reduced, as before, to approximately 50 pounds in the coking chamber to which the heated vaporous products are supplied, a slightly lower yield of gasoline having an octane number of approximately '72 is produced with an increased yield ofkgas and approximately the same amount of co e.

The process of this application is disclosed in my companion application, Serial No. 114,182, wherein the process is claimed without limitation to the use of reheated uncondensed gases to assist coking. Apparatus suitable for practicing the process is shown and claimed in my application, Serial No. 190,634.

I claim as my invention:

1. In a process for the pyrolytic conversion of hydrocarbon oils wherein an oil is subjected to an initial cracking operation under suicient pressure to maintain a substantial portion there of in liquid phase, the resulting vaporous and residual liquid products separated and the latter subjected to appreciable further vaporization in a zone of substantially reduced pressure relative to that in which they are formed, the improvement which comprises heating regulated quantities of said vaporous conversion products to a higher temperature in a separate cracking Zone, whereby to materially improve the antiknock characteristics of their gasoline-like components, introducing resultant highly heated vaporous products into direct contact with the residual liquids undergoing said further vaporization, whereby to effect reduction of the latter to substantially dry coke, separating the resultant vapors into gasoline-like fractions of the desired characteristics, higher boiling components and normally gaseous products and returning a portion of the latter to further treatment in said separate cracking zone.

2. A process for the conversion of hydrocarbon oils which comprises subjecting an oil to cracking temperature at superatmospheric pressure n a heating coil and communicating enlarged re action chamber, separately removing resultant vaporous and liquid conversion products from the reaction chamber, introducing the'latter into a zone of substantially reduced pressure, heating vaporous products separately removed from the reaction chamber to an appreciably higher cracking temperature in a separate heating coil, commingling the highly heated products with said residual liquid products supplied to the reduced pressure zone, reducing said residual liquid products in the latter Zone to substantially dry coke, subjecting vaporous products from the reduced pressure zone to fractionation for the formation of reiiux condensate, returning reflux condensate formed by said fractionation to further cracking in the iirst mentioned heating coil, subjecting fractionated vapors of the desired end-boiling point to condensation, collecting and separating the resulting distillate and uncondensed gases and returning a portion of the latter to further treat ment in said separate heating coil.

3. A conversion process which comprises fractionating a mixture of cracked vapors and gases and then subjecting the same to final condensation, separating the final condensate from the uncondensed gases, simultaneously cracking hydrocarbon oil in a cracking zone under .suicient pressure to maintain a substantial portion thereof in liquid phase, rseparately removing vapors and.A

unvaporized oil from the cracking zone and distilling the latter to coke in a coking zone, heating vapors Withdrawn from the cracking zone and a portion of said uncondensed gases to at least the coking temperature of said unvaporized oil, introducing such heated vapors and gases into Contact with the unvaporized oil in the coking zone to assist the coking operation, and supply admixed vapors and gases from the coking zone to the aforesaid fractionating step.

JOSEPH Gr. ALTI-IER.

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