US2158840A

US2158840A - Conversion of hydrocarbon oils

Info

Publication number: US2158840A
Application number: US125799A
Authority: US
Inventors: Swartwood Kenneth
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1937-02-15
Filing date: 1937-02-15
Publication date: 1939-05-16
Anticipated expiration: 1956-05-16

Description

y 1939. K. SWARTWOOD CONVERSION OF HYDROCARBON OILS Filed Feb. 15, 1957 CONDENSER FRACTIONATOR VAPORIZING AND SEPARATING CHAMBER FURNACE 39,

82 RECEIVER INVENTOR KENNETH SWART WOOD CONDENSEF FURNACE 7,

ATTORNEY Patented May 16, 1939 UNITED STATES PATENT OFFIQE CONVERSION OF HYDROCARBON OILS Kenneth Swartwood, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware Application February 15, 1937, Serial No. 125,799

7 Claims.

or the separation of products resulting from the ditions.

relatively mild cracking of such oil, accompanied by the selective cracking of said relatively lowboiling and high-boiling componentsunder independently controlled cracking conditions, reduction of residual liquid conversion products of the process to coke and further cracking of the intermediate liquid conversion products of the process together with said relatively high-boiling components of the charging stock.

One of the features of the invention is the flexibility cf the process which it provides with respect to the variety and range of materials which may be produced. The operating conditions may be varied to suit the type of oil undergoing treatment and to suit varying economic con- For example, the process may be oper ated to produce one, two or three grades of gasoline and the residual product of the process may comprise either coke or liquid residue, or both, and various grades of liquid residue, such as asphaltic material, lubricating stock, and various grades of fuel oilmay be produced.

In the initial step of the process to which charging stock of relatively wide boiling range, such as crude petroleum, topped crude, or the like, is supplied, the charging stock may be heated either to below cracking temperature, for the purpose of efiecting its separation into the desired components by fractional distillation without appreciable cracking, or relatively mild cracking conditions may be employed and the resultant products separated into the desired components by fractional distillation. Any desired low-boiling materials, such as gasoline, and any desired high-boiling materials such as heavy fuel oil, asphaltic residue, lubricating stock, or the like, may be separated from each other and from materials of intermediate boiling characteristics in the initial relatively mild cracking or fractional distilling step of the process, and either or both of said relatively low-boiling and relatively highboiling material may, when desired, be recovered as final products of the process, or subjected to further treatment in subsequent portions of the system. Intermediate components of the charging stock, or the products resulting from relatively mild cracking of the charging stock, are separated into relatively low-boiling and high-boiling materials. The latter are cracked under independently controlled conversion conditions, the resultant vapors and liquid conversion products separated, said vaporous products subjected to fractionation to form a reflux condensate, which is returned to the same cracking step for further treatment, while fractionated vapors of the desired end-boiling point from this stage of the process are subjected to condensation and the resulting distillate and gaseous products collected and separated. The low-boiling fractions of said intermediate components of the charging stock, or

the products resulting from relatively mild crack- -ing of the charging stock, are subjected to cracking in an independently controlled cracking zone and the resultant hot conversion products are introduced into a separate zone to which unvaporized residual liquid from one or both of the other cracking stages of the system are supplied and wherein they may, when desired, be reduced to coke. Vaporous products from said vaporizing zone are subjected to fractionation and the resulting reflux condensate is returned for further cracking to the same cracking zone to which the aforementioned reflux condensate is returned, while fractionated vapors of the desired endboiling point from the last mentioned fractionating step are subjected to condensation and the re sultant distillate and gaseous products collected and separated.

The accompanying diagrammatic drawing illustrates one specific form of apparatus in which the process of the invention may be conducted, and the operation of the process will be more fully described in conjunction with the following description of the drawing.

Relatively wide boiling range charging stock of the character above mentioned may be supplied from any suitable source through line i and valve 2 to pump 3, wherefrom it is fed through line it and valve 5 into heating coil 6.

Heating coil 6 is disposed in a suitable furnace 1 and the charging stock passing through this zone may be heated either to a relatively mild cracking temperature, or heated under non-cracking conditions to a temperature sufiicient to eiiect its subsequent separation into the desired components. The heated products are discharged from heating coil 6 through line 8 and valve 9 into column If] which functions as a vaporizing, separating and fractionating zone and which, depending upon the type of operation desired, be maintained under cracking, or non-cracking conditions. Preferably, however,' no substantial cracking is allowed to occur in column IE! and vaporization of the heating product supplied to this zone from coil 6 is assisted by substantially reducing the pressure imposed thereon as they pass through valve 9 in line 8, although when noncracking conditions are employed in heating coil 6, both the heating coil and column l9 may, when desired, be maintained at substantially atmospheric or relatively low superatmospheric pressure.

In case fractional distillation of the charging stock without appreciable cracking is desired in the above described initial step of the process, heating coil 6 may be eliminated when desired, in which case the charging stock may be heated sufficiently to effect its fractional distillation by indirect heat exchange with various relatively hot intermediate and/or final products of the process, although provisions for accomplishing this are not illustrated in the drawing. It is, of course, also within the scope of the invention to preheat the charging stock to any desired temperature, preferably below the cracking range, by any well known means, not shown, prior to its introduction into heating coil 6, regardless of whether or not it is heated to cracking temperature in coil 6.

In the particular case here illustrated, the charging stock is separated in column l0 into four selected fractions of different boiling characteristics, although its separation into any desired number of selected components is entirely within the scope of the invention. The highest boiling components of the charging stock, or of the products resulting from its relatively mild conversion in coil 6, as the case may be, are withdrawn as non-vaporous residual liquid from the lower portion of column I 0 and directed through line H and valve l2 to cooling and storage, or to any desired further treatment. This product may comprise such materials as asphaltic residue, fuel oil, lubricating stock, or the like, depending upon the nature of the charging stock, and the conditions of treatment to which it is subjected in coil 6. The lowest boiling components of the charging stock, or of the conversion products, comprising, for example, gasoline, naphtha and/or any other desired light distillates, are withdrawn, together with any normal gaseous materials, from the upper portion of column I0 and directed through line l3 and valve M to condensation and cooling in condenser Hi. The resulting distillate and normally gaseous products are directed through line l6 and valve l! to collection and separation in receiver I8. Uncondensed gases may be released from the receiver l9 and valve 20. A portion or all of the distillate collected in receiver l8 may, when desired, be withdrawn therefrom through line 2| and valve 22 to storage, or to any desired further treatment. When desired, regulated quantities of the distillate collected in receiver l8 may be recirculated, by well known means not illustrated, to the upper portion of column Hi to serve as a cooling and refluxing medium in this zone.

The invention also contemplates subjecting a regulated portion or all of the distillate collected in receiver 8 to cracking or reforming in a separate stage of the system, in which event distillate may be directed from receiver I8 through line 23 and valve 24 to pump 25, by means of which it is fed through line 26 and valve 21 to heating coil 28 for conversion therein in the manner to be later described.

The intermediate components of the materials supplied to column H] are separated by fractionation in this zone into relatively low-boiling and high-boiling fractions, which are withdrawn from suitable intermediate points in column In through the

respective lines

29 and 31 and directed through the

respective valves

30 and 32 to pump 25 and pump 33 respectively. The lowboiling fractions which may comprise, for example, such materials as high-boiling motor fuel fractions, naphtha, kerosene, or kerosene distillate, pressure distillate bottoms, light gas oil, etc., are directed from pump 25 through line 26 and valve 21 to cracking or reforming in heating coil 28.

The high-boiling fractions of the condensate from column l0, supplied to pump 33 as described, are directed therefrom through line 34 and valve 35 into line 36, wherefrom they are supplied through line 37 to heating coil 38.

A furnace 39 of suitable form supplies the required heat to the oil passing through heating coil 38 to bring the same to the desired cracking temperature, preferably at substantially superatmospheric pressure and the heated products are discharged from coil 38 through line 40 and valve 4! into reaction chamber 42.

Chamber 42 is also preferably maintained at a substantial superatmospheric pressure and, although not here indicated, this zone is preferably well insulated, to conserve heat, so that the hot conversion products supplied thereto undergo appreciable continued cracking therein. Both vaporous and liquid conversion products are withdrawn from the lower portion of cham ber 42 and directed through line 43 and valve 44 into vaporizing and separating chamber 45.

Chamber 45 is preferably maintained at a substantially reduced pressure, relative to that employed in the reaction chamber, by control of valve 44 in line 43, whereby the conversion products supplied to this zone in liquid state are subjected to appreciable further vaporization. The liquid residue remaining unvaporized in chamber 45 is withdrawn from the lower portion of this zone through line 46 and may be directed, all or in part, through line 41 and valve 48 to cooling and storage or elsewhere as desired, or a portion or all of this material may be supplied to another portion of the system for further treatment, as will be later described. Vaporous products are directed from the upper portion of chamber 45 through line 49 and valve 50 to fractionation in fractionator 5|.

Components of the vaporous products supplied to fractionator 5i, which boil above the range of the desired final light distillate product of this stage of the process, are condensed in this zone as reflux condensate which is directed from the lower portion of the fractionator through line 52 and valve 53 to pump 54, wherefrom the reflux condensate is supplied through line 3'! and valve 55 to further cracking in the heating coil 38.

Fractionated vapors of the desired end-boiling point and normally gaseous products are directed from the upper portion of fractionator 5| through line 56 and valve 5? to condensation and cooling in condenser 58, the resultant distillate and uncondensed gases passing through line 59 and valve 68 to collection and separation in receiver 6|. The uncondensed gases may be released from receiver 6! through line 62 and valve 53 and the distillate recovered in this zone may be directed therefrom through line 64 and valve 65 to storage or to any desired further treatment. When desired, regulated quantities of the distillate collected in receiver 6| may be recirculated, by well known means, not illustrated, to the upper portion of fractionator 5! to serve as a cooling and refluxing medium in this zone.

The relatively low-boiling oils supplied as previously described to heating coil 28 are heated during their passage through this zone to the desired cracking temperature, preferably at sub stantial superatmospheric pressure, by means of heat supplied to the heating coil from furnace 6B. When materials within the boiling range of gasoline are supplied to heating coil 28, the conversion conditions maintained in this zone are regulated to effect a substantial improvement in the quality of the gasoline, particularly with respect to its antiknock value, without excessively altering its boiling range. narily termed reforming and, since conditions within the reforming range are also suitable for cracking light distillates boiling above the range of gasoline (such for example, naphtha, kerosene, kerosene distillate and the like) to produce high yields of good quality gasoline therefrom, the invention specifically contemplates supplying a mixture of light distillates from the initial step of the process to treatment in heating coil 28, a portion of the mixture comprising materials within the boiling range of gasoline and the remainder comprising materials, of the nature above mentioned, boiling above the range of gasoline. However, in case it is desired to recover the gasoline product separated from the charging stock and/or produced in the initial step of the process, the material supplied to heating coil 28 may comprise only distillates boiling above the range of gasoline from column Ii), in which case the cracking conditions employed in heating coil 2% may be somewhat milder than those which may be utilized for reforming gasoline, or for cracking a mixture of gasoline and higher boiling distillates. In case the charging stock does not contain an appreciable quantity of gasoline or gasoline fractions and no appreciable quantity of such materials is produced in the initial step of the process, the invention, of course, contemplates supplying only higher-boiling distillates to heating coil 28.

Heated products are discharged from heating coil 28 through line 6? and valve 88 into chamber 69 which is operated as a vaporizing and separating zone and wherein the high-boiling co1nponents of the materials supplied to this zone may, when desired, be reduced to substantially dry coke. Chamber 59 is preferably maintained at a substantially reduced pressure, relative to that employed at the outlet from heating coil 28, in order to retard or arrest cracking in this zone and assist vaporization, although chamber 6%) may, when desired, be operated at a substantially superatmospheric pressure, suflicient to allow a controlled degree of continued cracking therein.

Preferably, at least a portion of the nonvaporous residual liquid withdrawn, as previously described, from chamber 45 is directed through valve ill in line 46 to pump H by means of which it is supplied through line 12 and valve 73 into chamber 69, wherein it is subjected to further vaporization by virtue of the additional heat supplied thereto from the more highly heated products in chamber 69 and/or by virtue of a reduced pressure in chamber 69 relative to that employed in chamber 45. It is also within the scope of the invention, when desired, to commingle at least a portion of the non-vaporous residual liquid from chamber ie with the nonconversion products passing from heating coil 28 Such treatment is ordiinto chamber Bil, by introducing same into line 61', although well known means for accomplishing this are not shown in the drawing. It will, of course, be understood that in case chamber 69 is operated at a substantially lower pressure than chamber 45, pump H will not be required and may be by-passed by well known means not illustrated.

When chamber 69 is operated as a coking zone, the coke produced may be allowed to accumulate therein until the chamber is substantially filled, or until its operation has been completed for any other reason, following which the accumulated coke may be removed in any well known manner, not illustrated, and the chamber cleaned and prepared for further operation. A plurality of coking chambers similar to chamber 69 may, of course, be employed, although only one is shown in the drawing, and in such cases the chambers may be operated simultaneously or, preferably, are alternately operated, cleaned and prepared for further operation. When liquid or semilicuid residue is produced in chamber 69, it may be withdrawn therefrom through line H and valve 15 to cooling and storage or elsewhere as desired. This line may also serve as a means of introducing steam, water, or any other suitable cooling medium into the chamber after its operation has been completed and, preferably, after it has been isolated from the rest of the system, in order to hasten cooling and facilitate removal of the coke.

Vaporous products are directed from the upper portion of chamber 69 through line 16 and valve Ti to fractionator 15, wherein their components boiling above the range of the desired final light distillate product of this state of the system are condensed as reflux condensate. This reflux condensate is directed from the lower portion of fractionator it through line .9 and valve to pump 8| by means of which it is supplied through lins 82, valve 83, line 36 and line 31 to further cracking in heating coil 38.

Fractionated vapors of the desired end-boiling point and normally gaseous products are directed from the upper portion of fractionator 18 through line 8 and valve to condensation and cooling in condenser 35-, the resulting distillate and uncondensed gases pass through line 8'! and valve 88 to collection and separation in receiver 89. Uncondensed gases may be released from receiver 83 through line 90 and valve 9|. Distillate collected in receiver 89 may be directed therefrom through line 92 and valve 93 to storage, or to any desired further treatment. When desired, regulated quantities of the distillate collected in receiver 89 may be recirculated, by well known means not illustrated, to the upper portion of fractionator T8 to serve as a cooling and refluxing medium in this zone.

The preferred range of operating conditions which may be employed to attain the desired results, in an apparatus such as illustrated and above described, may be approximately as follows: The charging stock may be heated in the initial cracking or fractional distilling step to a temperature ranging for example, from 600 to 800 F. or thereabouts. A superatmospheric pressure of from to 500 pounds or more per square inch is preferred in the heating stage of this step when temperatures within the cracking range are employed, and substantially atmospheric or relatively lower superatmospheric pressure are preferred when the temperature employed is below the cracking range. The presthe vaporizing and separating chamber.

sure employed in this first heating step may be substantially equalized or reduced in the succeeding vaporizing, separating and fractionating equipment. The cracking coil to which the rela tively high-boiling oils are supplied may employ an outlet conversion temperature ranging for example, from 800 to 950 F., preferably with a superatmospheric pressure at the point in the system of from 100 to 500 pounds, or thereabouts, per square inch. The succeeding reaction chamber is also preferably maintained at a substantially superatmospheric pressure, which may be substantially the same or somewhat lower than that employed at the outlet from the communieating heating coil. The vaporizing and separating chamber of this stage of the system is preferably operated at a substantially reduced pressure, relative to that employed in the reaction chamber, ranging for example, from substantially atmospheric pressure up to 150 pounds, or thereabouts, per square inch. The fractionating, condensing and collecting portions of this stage of the system may employ pressure substantially the same or somewhat lower than that employed in The relatively light oil cracking coil may utilize an outlet conversion temperature of the order of 900 to 1050 F. or more, preferably with a superatmospheric pressure at this point in the system of from 250 to 1000 pounds, or thereabouts, per square inch. The succeeding chamber to which heated products from the light oil cracking coil and residual liquid from the vaporizing and separating chamber are supplied, may employ any desired pressure ranging from substantially atmospheric to a superatmospheric pressure of 150 pounds, or thereabouts, per square inch, although this zone is preferably operated at substantially lower pressure than that employed in the vaporizing and separating chamber. When operated as a coking zone, the temperature maintained in this chamber is preferably of the order of 800 to 900 or more. The succeeding fractionating, condensing and collecting equipment may utilize pressure substantially the same or somewhat lower than that employed in the last mentioned chamber.

As an example of one specific operation of the process, conducted in an apparatus such as illustrated and above described; the charging stock is a light Smackover crude of about 26.6 A. P. I. gravity, containing slightly more than 18% of 437 F. end-point gasoline. The charging stock is mildly cracked in the first heating coil of the system at a temperature of approximately 800 F. and a superatmospheric pressure of about 250 pounds per square inch. This pressure is reduced in the succeeding vaporizing, separating, and fractionating zone to approximately 100 pounds per square inch and the products supplied thereto are separated into a heavy residual fraction, which is supplied to the coking chamber of the system, a light overhead fraction hav ing an end-boiling point of approximately 275 F., which is recovered, and two intermediate fractions, the relatively light intermediate fraction has an initial boiling point of approximately 240 F. and an end-boiling point of approximately 550 F. This material is supplied to the light oil cracking coil of the system, wherein it is heated to outlet conversion temperature of approximately 980 F. at a superatmospheric pressure of about 800 pounds per square inch, the resultant products being discharged therefrom into the coking chamber. The relatively heavy intermediate fraction, which has a boiling range of approximately 500 to 690 F. is supplied to the heavy oil cracking coil, wherein it is heated to outlet conversion temperature of approximately 950 F. at a superatmospheric pressure of about 350 pounds per square inch. The resultant heated products are introduced into the reaction chamber which is maintained at substantially the same pressure and both vaporous and liquid products are supplied from the reaction chamber to the reduced pressure vaporizing and separating chamber. The latter zone is operated at a superatmosph ric pressure of approximately 60 pounds per square inch and a portion of the residual liquid remaining unvaporized in this -zone is recovered as a final product of the process, the remainder being supplied to the coking zone. Vaporous products from the vaporizing and separating chamber and vaporous products from. the coking zone are separately subjected to fractionation for the formation of reflux condensates and the recovery of overhead products comprising gasoline of about 400 F. end-boiling point. Reflux condensates from both fractionating zones are returned to the heavy oil cracking coil for further treatment.

The above operation will produce, per barrel of charging stock, a total of approximately 65% of 400 F. end-point gasoline (this figure includes the low-end point gasoline recovered from the initial relatively mild cracking step) having an antiknock value of approximately '70. In addition, about 6% of good quality liquid residue, suitable for sale as premium fuel oil, and about 55 pounds of low volital petroleum coke are removed per barrel of charging stock. The remainder is chargeable principally to normally gaseous products and loss.

I claim as my invention:

1. In the process for the pyrolytic conversion of hydrocarbon oils wherein reflux condensate, formed as hereinafter described, is cracked in a heating coil and communicating enlarged reaction chamber maintained at substantial pressure, the resultant vaporous and liquid conversion products separated, and the latter subjected to appreciable further vaporization at substantially reduced pressure, the vaporous products, including those resulting from said further vaporization, subjected to fractionation for the formation of said reflux condensate which is supplied to said heating coil, fractionated vapors of the desired end-boiling point subjected to condensation and the resultant distillate recovered, the

improvement which comprises simultaneously heating charging stock for the process, comprising an oil of relatively wide-boiling range, to a lower cracking temperature than that employed in said coil and sufiicient to eiiect its substantial vaporization, separating the resulting heated materials into unvaporized oil and a plurality of distillate fractions, supplying one of said distillate fractions of said charging stock to said heating coil, wherein it is cracked with said reflux condensate, supplying another of said distillate fractions, of lower boiling point than the first mentioned distillate fraction, to a separate heating coil, wherein it is heated to a higher cracking temperature, supplying conversion products from said separate heating coil to a separate enlarged chamber and introducing to the latter chamber at least a portion of said unvaporized oil and non-vaporous residual liquid resulting from said further vaporization of said liquid conversion products, separating the com- 1 mingled materials in said separate enlarged chamber into vaporous and non-vaporous components, recovering the latter, subjecting said vaporous components to fractionation for the formation of reflux condensate, returning reflux condensate from the last mentioned fractionating step to the first mentioned heating coil for further cracking, subjecting fractionated vapors of the desired end-boiling point from the last mentioned fractionating step to condensation, and recovering the resulting distillate.

2. A process such as defined in claim 1, wherein the oil supplied to said separate heating coil contains a substantial quantity of fractions boiling within the range of gasoline and the cracking conditions employed in said separate heating coil are controlled to effect a substantial improvement in the antiknock value of said gasoline fractions.

3. A process such as defined in claim 1, wherein a distillate of lower initial-boiling point than the oil supplied to said separate heating coil is separated from the materials resulting from said heating of the charging stock and recovered as a final product of the process.

4. A process such as defined in claim 1, wherein non-vaporous components of the materials supplied to said separating chamber are reduced therein to coke.

5. A process such as defined in claim 1, wherein a regulated portion of the non-vaporous residual liquid resulting from said further vaporization of the liquid conversion products of the first mentioned cracking step is recovered as a final product of the process and the remainder supplied to said separate chamber, wherein it is reduced to coke.

6. A process such as defined in claim 1, wherein liquid residue of higher boiling characteristics than the oil supplied to the first mentioned heating coil is separated from the products resulting from said heating of the charging stock and is recovered as a final product of the process.

'7. A hydrocarbon oil conversion process which comprises heating a charging oil of relatively wide boiling range to cracking temperature and separating the same into vapors and unvaporized oil fractionally condensing the vapors to form a plurality of condensates, heating one of said condensates under pressure to higher cracking temperature than said charging oil in a heating coil and separating the same into vaporous and liquid conversion products in a separating zone, simultaneously subjecting another of said condensates, of lower boiling point than the firstmentioned condensate, to higher cracking temperature under pressure in a second heating coil and subsequently discharging the same into a reduced pressure chamber, removing liquid conversion products from said separating zone and introducing the same to said reduced pressure chamber, also introducing to said chamber at least a portion of said unvaporized oil, further distilling said liquid products and unvaporized oil in the chamber, and fractionating and condensing the vaporous products from the separating zone and from said chamber.

. KENNETH SWAR'I'WOOD.