US2039797A - Hydrocarbon oil conversion - Google Patents

Description

May 5, 1936. L. c. HUFF HYDROCARBON OIL CONVERSION Filed Jan. 14, 1933 n Om Patented May 5,- 1936 PATENT OFFICE HYDROCARBON OIL CONVERSION Lyman C. Hull, Chicago, vIll., sal'Oil Products Company,

poration of Delaware Application January 14, `1933, serial No. 651,741

(ol. 19e-'48) 6 Claims.

This invention particularly refers to an improved process and apparatus for the simultaneous conversion of different hydrocarbon -oil chargingstocks wherein the different charging stocks and diiferent selected intermediate conversion products of the process are each sub-V jected to independently controlled conversion conditions of elevated temperature and superatmospheric pressure regulated to secure the production of high yields of desirable light hydrocarbons such as motor fuel of high fantiknock value.

A specific embodiment of the present invention may comprise subjecting a relatively` low boiling hydrocarbon oil ,charging stock to conversion temperature at superatmospheric pres. sure in a heating coil, introducing the heated oil into an enlarged reaction chamber, also maintained at superatmospheric pressure, withdrawing both vaporous and liquid conversion products from the reaction chamber to a reduced pressure vaporizing chamber wherein further vaporization of liquid conversion products rand separation of the residual liquid from the vaporous products of the process is accomplished, withdrawing residual Aliquid from the vaporizing chamber and returning a regulated portion thereof to commingle with and assist cooling of the products passing from the reaction chambf-r to the vaporizing chambenwithdrawing vaporous conversion products from the vaporizing chamber and subjecting them to indirect contact and heat exchange with cooler oil from within the' system whereby a portion of their high-boiling components are condensed, subjecting the remaining vaporous conversion products to fractionation, supplying condensate resulting from said heat exchange in regulated amounts either to the vaporizing chamber and/or to the frac-l tionator and/or to the reaction chamber, arbitrarily separating the reflux condensate formed by fractionation of the vaporous conversion products into low boiling and high boiling fractions, simultaneously supplying to the fractionator, preferably in preheated state, another hydrocarbon oil charging stock of different characteristics than the first mentioned charging stock whereby it is subjected to the same separation in the fractionator as that afforded the vaporous conversion products of the process, subjecting fractionated vapors of the desired end-boiling point to condensation, collecting the resulting distillate and gas, returning said lowboiling fraction of the reflux condensate, together with any components of the second menof the process.

assignor to Univerv Chicago, Ill., a corinto the reaction chamber.

The first mentioned charging stock, which may, for the sake of convenience, be termed primary charging stock, preferably comprises a hydrocarbon oil distillate such as light gas oil, kerosene distillate, naphtha, pressure distillate bottoms, straight-run gasoline or other motor fuel of inferior anti-knock value or fractions or mixtures of such materials. The last mentioned or secondary charging stock, which is supplied to the fractionator of the system, may comprise any desired hydrocarbon oil ranging from naphtha or other light distillates through the various crude oil fractions to residual or fuel oil and specifically including oils such as crude petroleum, topped crudes and/the like, as well as pressure distillate, pressure distillate bottoms or other final or intermediate products of conversion. Any material boiling within the range of the desired nal light product of the process contained within the secondary charging stock are vaporized within the fractionator and recovered with the motor fuel conversion product Any materials contained within the secondary charging stock boiling within the range or having cracking characteristics similar to the primary charging stock are preferably withdrawn from the fractionator, together with selected low-boiling fractions of the reux condensate of corresponding boiling range and subjected to conversion, together withv the primary charging stock. Any components of the secondary charging stock of higher `boiling nature than the material returned from the fractionator to conversion with the pri- .mary charging stock collect with the high-boiling fractions of the refiux condensate and are subjected therewith to independently controlled conversion conditions in a separate heating coil. Thus, it will be apparent that the process of the present invention possesses a wide flexibility with respect to the type of oil which may be employed as secondary charging stock, inherently providing for (optimum treatment of the various fractions of virtually any type of oil. y

' The accompanying diagrammatic drawing illustrates one specic form of cracking apparatus embodying the features of the present invention and the cooperative nature of its various features will be more apparent with reference to the following description of the drawing which includes a more detailed description of the operation of the processas it may be practised in the apparatus shown.

Primary charging stock for the cracking operation which may comprise, for example, straightrun gasoline or other motor fuel of low-anti-knock value, naphtha, kerosene distillate, pressure distillate bottoms, gas oil, light gravity crude or similar hydrocarbon oil is supplied through line I and valve 2 to pump 3 by means of which it is fed through line 4 and valve 5 to heating coil 6. The charging stock may, of course, be preheated in any well known manner (not shown) priorI to its introduction into the heating coil.

The oil supplied to heating coil 8 is subjected therein to the desired conversion temperature, preferably at substantial superatmospheric pressure, by means of heat supplied from a furnace 'I of any suitable form. The heated oil is discharged from the heating coil through line 8 and valve 9 into Vreaction chamber Ill.

Chamber III is also preferably maintained at a substantial superatmospheric pressure and, although not illustrated in the drawing, is preferably well insulated to prevent the excessive loss of heat therefrom by radiation so that conversion of the products introduced into the reaction chamber, and particularly their vaporous components, may continue in` this zone. In the case here illustrated, both vaporous and liquid conversion products are withdrawnin commingled state from the lower portion of the reaction chamber, passing through line I I and valve I2 into vaporizing chamber I3. When desired, in order to prevent segregation of vapors and gases in chamber III and the formation of a gas pocket in the upper part of the chamber a portion of the vaporous conversion products may be separately withdrawn from the! upper portion of this zone passing through line 42 and valve 43 into chamber I3.

Chamber I3 is preferably maintained at a. substantially reduced pressure relative to that employed in chamber I0, by means of which further vaporization of the liquid conversion products introduced into this zone is accomplished. The vaporous and residual conversion products of the process are separated in chamber I3 and the residual liquid remaining unvaporlzed in this zone is withdrawn therefrom through line I4 and may pass, all or in part, to storage or to any desired further treatment through line I5 and valve I6.

When desired, in order to cool the products passing from chamber I0 through line I I to chamber I3 further than the cooling accomplished by the pressure reductionin passing through valve I2, so as to prevent the formation and deposition of coke or heavy pitch-like material in this line fed through line I9 and valve 20 and through cool-l er 2I from which it passes through line 22 and valve 23 into line II. When desired, all or any portion of the residual oil thus recirculated to line I I may by-pass cooler 2| by means of line 24, controlled by valve 25.

Vaporous products of the process are withdrawn from chamber I3 through line 26 and valve 21 and may pass throughheat exchangers 28 and 29, a connecting vapor line 30 being interposed between the heat exchangers, passing therefrom through line 3| and Valve 32 to fractionation in fractionator 33.

The vaporous conversion products of the process 4are partially cooled in heat exchangers V28 and 29 by indirect contact with a suitable cooling medium, preferably comprising raw oil charging stock or intermediate conversion products of the process or mixtures of such materials, whereby the heat extracted from the vapors is recovered for a useful purpose and certain high-boiling fractions of the vapors, undesirable as recycled stock, are condensed therefrom. Condensate formed in heat exchangers 28 and 29 is withdrawn therefrom through line 34 and valves 35, respectively, con'- trolled by the respective valves 36 and 31, passing into line 38 from which all or a portion of this material may be returned through valve 39 in this line into vaporizing chamber I3 or through valve 40, in line 38, into fractionator 33. A valve 4I, in line 38, between the junction of this line with lines 34 and 35 permits separation of the condensates from heat exchangers 28 and 29 so that the somewhat heavier material from the first heat exchanger 28, may be turned to chamber I3, as described, while the somewhat lighter condensate from the second heat exchanger 29, passes to chamber 33. In this manner when substantially all of the objectionable heavy components of the vapors are condensed therefrom in heat exchanger 28, additional heat may be extracted from the vapors in heat exchanger 29, prior to their fractionation for the preheating, for example, of raw oil or recycled stock without decreasing the desirable recycled stock which, in this case, is returned from heat exchanger 29 to fractionator I33. It will be understood that itis within the scope of the invention to employ a single heat exchanger or any number of a plurality of such zones, dividing the condensate therefrom, when desired, into any number of separate streams of somewhat different boiling characteristics for treatment in the manners indicated.

Ordinarily, rough fractionating means such'as suitable baffles (not shown) are located in the upper lportion of vaporizing chamber ,I3 for the purpose of preventing heavy oil particles entrained in the vapors from passing to further treatment therewith. In such cases the condensate returned from heat exchanger 28 or from heat exchangers 28 and 29 to chamber I3 will serve as a refluxing medium, being introduced above the fractionating means and flowing downward thereover to assist cooling of the vapors and extraction of the entrained heavy oil particles.

The vaporous conversion products of the process supplied to fractionator 33, as described, are subjected to fractionation in this zone by well known means whereby their insufficiently converted components, boiling above the range of thel desired ilnal lightv distillate product of the process, are condensed as reflux condensate.

Fractionated vapors of the desired end-boiling point, representing the nal light distillate product of the process and preferably of substantially motor fuel boiling range, are withdrawn, together with uncondensable gas, from the upper portion of fractionator 33 through line 58 and valve 5I to be subjected to condensation and cooling in condenser 52, from which the resulting distillate and gas passes-through line 53 and-va1ve 54 to collection and separation in receiver 55. Uncondensable gas may be released from the receiver through line 56 and valve 51. The distillate may be withdrawn from receiver 55 through line 58 and valve 59 to storage or to any desired further treatment. When desired, a'portion of the distillate collected in receiver 55 may be recirculated, by well known means (not shown) to the upper portion of fractionator 33 to assist fractionation of the vaporsin this zone and to maintain the desired vapor outlet temper- Y' ature from the fractionator..

As a special feature of the invention the reflux f condensate formed in fractionator 33 is arbitrarily separated into low-boiling and high-boiling fractions. The low-boilingA fractions of the reflux condensate are withdrawn as a `side-stream from one or a plurality vof suitable .points in the fractionator, for example, through lines 44, controlled by valves 45, passing through line 46 to pump 41 by means of whichv this relatively .low`

boiling oil, preferably within the boiling range or otherwise corresponding in cracking characteristics to the primary charging stock, is fed through line 48 and valve 49 into line 4, commingling therein. with the primary charging stock` and passing therewith to conversion in heating coil 6. It will be understood that well known means (not shown) may be provided,I when desired, for subjecting the side-stream from fractionator 33 to reboiling, whereby it may be substantially freed of desirable light products within the boiling range of the overhead product from the fractionator.

Heavy fractions of the reflux condensate formed in fractionator 33, boiling above the desired end-boilingpoint of the selected fractions returned to heating coil 6 as described, collect within the lower portion of the fractionator, from which they are withdrawn through line 68 andv valve 6I to pump 6.2,by means of which they are returned through line 63, valve 64, heat exchanger 29, line 65, heat exchanger 28, line 66 and valve 61 to heating coil 68 for further conversion. -It will be understood that, when desired, all or any portion of this material may be diverted from either or both of the heat exchangers, by well known means (not shown).

The oil supplied to heating coil 68 is subjected therein to independently controlled conversion conditions of elevated temperature and superatmospheric pressure by means of heat supplied from a furnace 69 of any suitable form and the heated oil is discharged through line 18 and valve 1 I 'into' reaction chamber I8, commingling therein or prior to its introduction thereto with the heated oil from heating coil 6, and being subjected thereafter to the same treatment, in chamber I8 and in subsequent portions of the system, as that already described in connection with the heated oil from heating coil 6.

As another special feature of the invention a suitable oilor mixture of oils, preferably from within the system, may be introduced, at one or a plurality of desirable points, into reaction chamber I8, particularly for the purpose of cooling and/or diluting and increasing the volume of liquid traversing or withdrawn from this zone. Such an oil, introduced, for example, into the upaosavsv shown).

described comprises a portion of the high-boiling 2 per portion of chamber I8 through line 12 and valve 13, may be sprayed against the inner surfacevof the walls of the reaction chamber by any suitable spray device (not shown), to dilute, cool and increase the volume of liquid passing downward over the walls of the chamber in order to hasten its passage through and removal from this zone, thereby assisting in preventing the formation of coke on the walls of the chamber. In a similar manner oil introduced into the lower portion of the chamber through line 14 and valve 15 may commingle with the vaporous and liquid conversion products withdrawn through line Il,

\ thereby increasing the volume of liquidpassing rial in line I I. i (The drawing illustrates a method and means of employing two specific intermediate products of the operation as'cooling oil in chamber I8. One suitable material for this purpose comprises all or' a portion of the condensate from heat exchangerv 28 or from heat exchangers 28 and 29 which iswithdrawn from line 38 through line 16 and valve 11 to pump 18 by means of which it is fed through line 19, valve 88 and cooler 8|, passing therefrom, after being cooled to any desired degree, through line 82, valve 83 and line 84 into chamber I8, entering this zone either through line 12 or through line 14,I as previously described, or at any other desired point vin the chamber (not Another suitable oil for the purpose fractions of the reflux condensate withdrawn from the lower portion of fractionator 33 including in some cases, as will be later more fully described, secondary charging stock or high-boiling fractions thereof supplied to fractionator 33. This oil may be diverted from line 68 through line 86 and valve 81 and through line 16 to pump 18 to be fed therefrom, either alone or together with condensate from line 38, to chamber I8, as previously described. When desired, a portion or all of the oil thus recirculated to chamber I8 may by-pass cooler 8| by means of valve 85, in line 84.

Simultaneous with the operation already described, a secondary charging stock comprising any desired oil, ranging, as already ind'cated, from into fractionator 33, entering this zone at any desired point. Heat exchanger 93 offers a means of preheating the secondary charging stock by means of heat recoveredfrom the fractionated vaporous products of the process, prior to their introduction into condenser 52. and prior to the introduction of the secondary charging stock into the fractionator. It will be understood that the secondary charging stock may, when desired, be supplied to the fractionator without preheating or that it may be preheated to any desired degree in any well known manner (not shown). The secondary charging stock thus supplied to fractionator 33 is subjected to vaporization in this zone by direct contact and heat exchange'with the vaporous conversion products of the process unare vaporized within the fractionator, withdrawn therefrom, subjected to condensation and collected together with the distillate resulting from conversion. Higher boiling fractions of the secl ond-ary charging stock corresponding in boiling range to the low-boiling fractions of the reflux condensate, returned, as described, to heating coil 6, are collected therewith and subjected to the same treatment. When the secondary charging stock contains any appreciable fractions of higher boiling point than the side-stream supplied to heating coil 6 they collect, together with the high boiling fractions of the reflux condensate, in the lower portion of fractionating column 33 and are returned therewith to further conversion in heating coil 68.

The primary charging stock and selected lowboiling side stream from the yfractionator are preferably subjected to a temperature ranging from 950 to 1050 F., at a superatmospheric pressure of from 300 to 800 pounds, or thereabouts, per square inch, measured at the outlet from the heating coil to which they are supplied. The high-boiling fractions of the intermediate conversion products, together with any corresponding fractions of the secondary charging stock, are preferably subjected to a temperature within the range of 850 to 975 F., at a superatmospheric pressure of from 100 to 500 pounds, or more, per square inch, measured at the outlet from the separate heating coil to which this material is supplied. A The pressure employed in the reaction chamber may range, for example, from 100 to 500 pounds, or thereabouts per square inch, and preferably is substantially equalized with the pressure at the outlet from the heating coil employing the lowest pressure, in case different pressures are employed in the two heating coils. A reduced pressure ranging, for example, from 100 pounds, or thereabouts, per square inch, down to substantially atmospheric pressure is preferred in the vaporizing chamber and the pressures employed in the succeeding fractionating, condensing and collecting portions of the system may be substantially equalized "with or somewhat reduced relative to the pressure employed in they vaporizing chamber.

ble operations of the process of the present inventon, the primary charging stock, which amounts to about 56% of the total oil subjected to conversion in the process, is a 45 A. P. I. gravity naphtha having a boiling range of approximately 265 to 470 F., with an octane num-v ber of approximately 35, a sulphur content of about 0.41% and containing about 77% of material boiling up to 400 F. with an octane number of approximately 43. The secondary charging stock is pressure distillate derived from other cracking operations containing about 75% of 400"y end-point motor fuel having an octane number of approximately 73 and a sulfur content of about 0.25%. The 25% or thereabouts of material in the secondary charging stock, boiling above 400 F. comprises about 44% of the total oil subjected to conversion in the system, the motor fuel components of the secondary charging stock being recovered, Without conversion, together with the motor fuel product of the process, as an overhead stream from the fractionator. Components of the secondary charging stock and intermediate conversion products of the process having an end-boiling point of approximately 650 F. are withdrawn as a side stream from the fractionator and subjected to conversion, together with the As a specific example of one of the many possli ancona? primary charging stock, at a temperature of from 970 to 980 F. measured at the. outlet from the heating coil. The higher boiling components of the reflux condensate are subjected in a separate heating coil to a conversion temperature of 930 to 935 F. Pressures in excess of 1,000 pounds per square inch are maintained at the vinlet to both heating coils and a pressure of approximately .400 pounds per square inch is maintained in the reaction chamber.v The pressure is reduced in .the vaporizing chamber to about 85 pounds per square inch and is substantially equalized in the succeeding fractionating, condensing and collecting portions of the system. 'I'his operation may yield, per barrel of total charging stock, neglecting the 75% or thereabouts of motor fuel inthe secondary charging stock which is not subjected.

to conversion, about 77% of 400 F. end-point motor fuel having an octane number of about 'l2 and a sulphur content of approximately 0.23%,

the additional products of the process being about of low gravity residual oil having a velocity of about 12 seconds Saybolt Furol at 122 F. and

containing about 0.5% B. S. and W. and about 430 due, passing such separated vapors to a fractionating zone and fractionatng the same therein in direct contact with the heavier charging oil thereby commingling the latter with the reflux condensate formed by the fractionation, separating the commingled charging oil and reux during the fractionation into relatively light and heavy liquid fractions, passing such heavy liquid fraction through a heating zone maintained at cracking temperature and thence dischargmgthe same into the reaction zone, at least a portion of said A*heavy liquid fraction supplied t0 said heating zone `being passed in indirect heat exchange with the vapors being supplied from said separating zone to the fractionating zone and resultant condensate being introduced to the separating zone, combinmg said light liquid fraction with the lighter charging oil, passing the resultant mixture through a second dheating zone maintained at higher cracking temperature than the first-mentioned heating zone and thence introducing the same to the reaction zone, and finally condensing the vapors uncondensed in the fractionatl-ng zone.

2. A process for the simultaneous cracking of relatively light and heavy charging oils which comprises maintaining hydrocarbon oil under cracking conditions of temperature and pressure in a reaction zone, removing vapors and unvaporized oil as a mixture from said zone, lowering the pressure on said mixture and separating the same in a separating zone into vapors and residue, passing such separated vapors to a fractionating zone and fractionating the same therein in direct contact with the heavier charging oil thereby commingling the latter with the reflux condensate formed by the fractionation, separating the commingled charging oil and reflux during the fractionation into relatively light and heavy liquid fractions, passing such heavy liquid fraction through a heating zone maintained at cracking temperature and thence discharging the same into the reaction zone, at least a portion of said heavy liquid fraction supplied to said heating zone being passed in indirect heat exchange with the vapors being supplied from said separating zone to the fractionating zone and resultant condensate being introduced to the .reaction zone, combining said light liquid` fraction'with the lighter. charging oil, passing the resultant'mixture through a second heating zone maintained at higher cracking Atemperature than the firstmentioned heating zone and thence introducing the same to the reaction zone, and nally condensing the vapors uncondensed in the fractionating zone. f

3. A conversion process which comprises subjecting hydrocarbon oil to cracking conditions of temperature and pressure in a cracking zone, removing vapors and unvaporized oil as a mixture from said zone, lowering the pressure on said mixture and separating the same in a separating zone into vapors and residue, passing such separated vapors to a fractionating zone and fractionating the same therein in direct contact with charging oil for the process, passing admixed charging oil and reiiux condensate from the fractionating zone in indirect heat exchange relationfwith the vapors being supplied from the separating zone to the fractionating zone and then introducing the same to the cracking zone, introducing condensate formed by said heat exchange to the separating zone, and finally condensing the fractionated vapors.

4. A conversion process which comprises subjecting hydrocarbon oil to cracking conditions of temperature and pressure in a heating coil and reaction zone, removing vapors and unvaporized oil as a mixture from said zone, lowering the pressure on said mixture and separating the same in a separating zone into vapors and residue1 passing such separated vapors'to a fractionating zone and fractionating the same therein in direct contact with charging oil for the process, passing admixed charging oil and reiiuxcondensate from the fractionating zone in indirect heat exchange y relation with the vapors being supplied from the separating zoner to the frationating zone and then introducing the same' to the heating coil,

introducing condensate formed by said heat ex-` change to the separating zone, and nally condensing the fractionated vapors.

5. The process-as defined in claim 4 further k characterized in that condensate formed by said heat exchange is also introduced to the reaction zone.

6. A conversion process which comprises subjecting hydrocarbon oil to 'cracking conditions of temperature and pressure in a heating coil and reaction zone, removing vapors and unvaporized oil as a mixture from said zone, lowering the pressure on said mixture and separating the same in a separating zone into vapors and residue, passing such separated vapors to a fractional-,ing zone and fractionating the same therein in direct contact with charging oil for the process, passing admixed charging oil and reux condensate from the fractionating zone in indirect heat exchange relation with the vapors being supplied from the separating zone to the fractionating zone 'and then introducing the same to the heating coil, introducing condensate formed by said heat exchange to the reaction zone, and nally condensing the fractionated vapors.

4L YMAN C. HUFF.

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