US1818513A - Process of cracking oil vapors into vapor phase - Google Patents

Description

Patented Aug. '11, 1931 I UNITED STATES PATENT OFFICE JOSEPH B. WEAVER AND CARY It. WAGNER, OF CHICAGO, ILLINOIS, ASSIGNORS TO THE GYRO PROCESS COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN PROCESS OF CRACKING OIL VfAPOI S INTO VAPOR PHASE Application filed February 17, 1928. Serial No. 255,142.

This invention relates .to processes of converting high boiling hydrocarbons into hydrocarbons of low boiling point, and has particular reference to high temperature proo- 5. esses wherein the oil while undergoing con version is maintainedin the vapor phase by the heating'thereof to temperatures usually in excess of 1000 Fah.

In the vapor phase method of converting oil the temperatures employed ordinarily are considerably higher than those which obtain in the so called liquid phase method. Also, the pressures maintained on the ,oil during conversion are considerably difier- 15. ent in that the vapor phase methods utilize low pressures, which generally do not exceed thirty pounds per square inch, whereas the liquid phase methods employ pressures which are much higher and wherein pressures of several hundred pounds to the square inch are common. Further, there is aconsiderable difference ip the combustion properties of the products produced by the two methods, particularly with respect to the motor fuel products or fractions thereof. The motor fuel fractions produced by vapor phase methods are highly non-detonating when carburet ted and burned in the cylinders of an internal combustion engine and, in fact, theanti-detonating value of such fractions issufliciently high to permit the latter to be blended with fractions produced by liquid phase methods so that a composite fuel may be provided which possesses the requisite anti-knock value'suitable for present day internal combustion motors. These attributes of a vapor phase motorfuel products, among others equally important and advantageous, are well recognized in the 40 industry, but owing to difficulties in design and operations vapor phase methods of cracking hydrocarbons have not been widely used heretofore by the petroleum industry, liquid phase methods having been generally employed because of greater convenience in control and a more complete recovery of the products sought. It is, therefore, an object of the present invention to provide a vapor phase method of cracking oil and in efiecting the separation and operation and products resulting1 refining of the several fractions thereof by readily controlled and through the operation of which a motor fuel product is obtainable characterized by its stability, color, absence of gum forming compounds when the product is left standing, of improved anti-knock value, volatility and other properties here-.

inafter more fully explained.

The present invention is directed further to a vapor phase process of producing motor fuels, and other less valuable fractions,

wherein the hydrocarbons during conversion, and while admixed with steam, are heated to reactlon temperatures nexcess of 1000 Fah., and wherein upon the comple-. -tion of the conversion process reactions are sharply checked by suddenly and rapidly cooling the vapors to a sub-conversion temperature less than 600 Fah, and wherein the vapor present following the cooling operation is separated from the heavier products and passed through. a bed of fullers earth or other-equivalent material for the purpose of filtering the vapors and minimizing the presence of objectionable compounds which tend to undesirably color the oil, produce gum forming compounds, reduce the volatility and anti-knock value of the motor fuel product and to detract in other ways from the essential value of the product.

More specifically, the present invention resides in a vapor phase process of oil conversion wherein steam and oil vapors present following conversion are passed through a body of fullers earth contained in a' closed tower for the purpose of removing objectionable compounds of polymers'to produce a final product of improved value as a motor fuel, the use of the steam present in the oil vapor serving to facilitate and improve the from the passing of the vapors through e filtering or contact'material. v

For a further understanding of the invention reference is to be had to the following description and the accompanying drawing. wherein:

The figure is a diagrammatic view of a vapor phase cracking stemv designed to operate in accordance Wlth the features of the present invention.

Referring more particularly to the drawing the numeral 1 designates a heater or converter which consists of a furnace setting divided internally by a. bridge wall 2 so as to define burner and tube chambers. An oil or gas burner 3 is arranged within the burner chamber and is employed to heat the interior of the converter to the desired temerature. Arranged within the tube chamher of the converter is a coil 4, through which is circulated oil vapor admixed with steam. When entering the coil 4 the vapors may be at a temperature of 750 Fah., but this temperature is immediately raised to a point in excess of l000 Fah. by exposure of the entrance portion of the coil to the radiant heat developed in .the burner compartment of the converter. The oil vapors travel at high velocity, usually between 4000 to 8000 feet per minute through the coil 4 so that any given body of oil vapor will travel through the entire coilor converter in a period of time less than two seconds. Low pressures obtain on the oil while the latter is travelling through the converter, such pressures usually not exceeding 30 pounds per squareinch. The coils 4 preferably contain a core of ferrous oxide, since experience has demonstrated that improved results are obtainable when this catalytic or contact material is em loyed in the several passes of the coil 4. travel of the oil vapors through the coil 4 that the conversion reactions take place, the vapors leaving the coil at a temperature of approximately 1150 Fah. These conversion temperatures may valiy in range between 1000 F. and 1250 In the operation of this system it is necessary to instantly check the conversion reactions immediately upon discharge of the vapors from the converter unit 1. This is done in order to minimize the formation of non-condensable gases and the formation or liberation of free carbon, which tends to accumulate rapidly in the tubes or passages of a vapor phase process when the vapors are allowed to expand and cool slowly following the stage of conversion.

To effect this rapid cooling of the highly heated and reactiveivapors leaving-the converter, the discharge end of the coil 4 terminates in a restricted conduit'5 which enters a cooler 6. Also. situated within the cooler 6 is a spra nozzle 7 through which is forced the cold char 'ing stock which is supplied to the systemy way of the pipe line 8. The charging stock issues from the nozzle 7 in the form of a finely divided mist of cold liquid particles and is brought into intimate contact over an extended surface with the hot vapors discharged from the,

t is during the rapidconverter. This mixture takes place initial- If; within the restricted conduit 5 wherein t e velocity of travel of the oil vapors is comparable .with that which obtains in the coil 4. This intimate contact between the cold spray and the hot va ors results in an instantaneous lowering 0 the temperature of such vapors from a point in excess of 1000 Fah. to a sub-conversion temperature of below approximately 600 Fah. The oils thus cooled may vary in temperature from 450 to 600 F. At this latter temperature the vapors are no longer reactive with the result that carbon deposition is practically eliminated, as set forth in U. S patent to Weaver Reissue Patent No. 17,681, dated May 27 1930.

liquid form in the bottom of the cooler and are drawn of]? b way of a pipe line 9 to a hot oil tank 10. The liquid which collects in the bottom of the cooler 6 comprises the heavier ends of the charging stock which enters by way of the pipe llne '8 and also the liquefied portion of the vapors which have issued from the converter 1. These liquefied fractions are then, pumped by way of the pipe line 11 to a preheater 12 wherein the temperature of the chargin stock is raised from approximately 400 ah. to approximately 750 Fah. The temperature in the preheater, however, is such as to preclude any appreciable conversion on the part of the oil vapors. In the preheater 12 the oil is partially reduced to a state of V9. or and at a temperature of roughly 750 l ah. the

and enters an evaporator 13. In a vance of the evaporated superheated steam introduced by a line 1! is admixed with the oil and vapor and passes overhead with the vapor from the evaporator into the upper or first pass of the coil 4. The heavy bottoms which accumulates in the evaporator are removed from the system by way of a line 15in theform of fuel oil. The steam and oil vapors then circulate through'the converter wherein the conversion reactions take place as reviously specified.

The lig ter fractions of the charging stock which are heated and vaporized in the cooler 6 and the vaporized fractions of the cracked stock discharged from the converter, pass overhead from the cooler by way of the pipe line 16 and enter a fractionating column or tower 17. Within this tower there takes place, as usual, aseparation of the hydrocarbon. fractions of different boilinfg point, the heavier or higher boiling point ractions accumulating as a liquid in the bottom of said tower and are then led back to the hot oil tank .for'recirculation through the system by means of the pipe line 18. The lighter or unvaporized fractions ass overhead of a clay tower 19. Arranged within this tower is a bed of filtering material, preferably fullers earth, which is designated by the numeral 20. The steam laden oil vapors penetrate through this body of material for the purpose of removing from the vapors objectionable properties which, if present, would diminish the value of the final product. In this respect we have found that the presence of steam in the oil vapors when the latter are filtering through the fullers earth results in greatly improving the final prod not and that the system operates to much better advantage than it does when the steam is omitted. The filtering material, namely fullers earth or its equivalent, removes highly colored compounds, eliminates the 7 use of acid treatment and the necessity of re-running the distillates obtained, removes gum forming compounds and produces a d1stillate of clear color. After filtering through the bed of fullers earth the vapors are then passed to a second fractionating tower 21, the final vapors passing overhead from this tower to a condenser 22 and then to a storage tank 23. The liquid which accumulates 1n the bottom of the second fractionating tower 21 is transferred to the hot Oll tank by way of the pipe lme 24, where it may be recirculated through the system. A typical test run made in accordance with the above described steps is glven 1n the table immedlately following: Barrels gas oil charged Barrels motor fuel produced Barrels fuel oil produced Cubic feet dry gas produced Gus consumed as fuel, cubic feet Average temperature of cracking Average temperature vapors ex arrester Temperature vapors to fullers earth tower..- Temperature vapors ex tullers earth Pressure on.oil to arrester sprays Pressure on oil to economizer Pressure on evaporator' Pressure at converter inlet Pressure at converter outlet Pressure entering fullers earth tower 3. 9 lbs. 2. 3 lbs.

The gas oil charged had an average A. P. I. gravity of 39.69, flash point of 235 F. and a fire point of 255 F. The motor fuel produced tested 59.7 gravity, initial 88,

20% 184, 50% 248, 90% 372 and end point 421.

The color of the finished product was +20 Saybolt. I

We are aware of the fact that it has been proposed heretofore to pass hydrocarbons in a state of vapor through a filtering material, such as fullers earth, for the purpose of removing objectionable unsaturated compounds in certain desired motor fuel prod ucts. Prior to our invention, however, we are not aware of any analogous system employing the principle of mixing steam with the oil vapors to procure greater efiiciency on the part of the filtering operation wherein fullers earth is employed. Typical of many tests made to determine the comparative merits of such systems operating with and without the use of steam are the results shown in the following table:

Amount No steam With steam 415 Fah. 1.2511).

The above table represents merely average conditions and discloses that with the use of steam loss of the charging stock was reduced by 3.3%; reductionjn polymers in recovered product 3I55%'*"again of 4.7 in the total amount of gasoline recovered; an increase of 4.5% in the unsaturated compounds present in the finished gasoline. At this point it might be stated that the process does not aim to minimize or eliminate the presence of unsaturated compounds, as in previous processes but operates to retain a greater percent of the unsaturated compounds which are not objectionable in the finished product. These objectionable compounds constitute but a small fraction of the total unsa'turates present, the undesired proportions tending to discolor the oil and to produce the gum forming compounds. These, however, are effectively removed by the aid of fullers earth -with the steam present. It will be understood that it is desirable to retain in the final product a high content in unsaturated compounds,

since these unsaturates possess or impart to 1b the fuel a high anti-knockvalue. The motor fuel distillate upon standing does not reproduce gum forming constituents nor does it lose its color. The fullers earth thus serves the double purpose of removing through polymerization the undesired constituents and at the same time stabilizes its color without any additional treatment.

It will thus be observed that in carrying out the invention a mixture of gasoline and steam, together with fixed gases, is passed through the fullers earth bed wherein the latter is maintained at a temperature materially below the boiling point of the heaviest hydrocarbons present. At this time the cliolefines and gum forming compounds present in the mixture are converted into heavy hydrocarbons which can bev readily removed by fractional distillation. Also, some of the-normally gaseous olefines are converted into valuable gasoline fractions and the desirable aromatic content is very appreciably increased The steam present serves the. purpose of lowering the temperature of the exothermic polymerization reactions so that desirable olefines are not destro ed and provides for better regulation of t e pol merization reaction temperatures and con itions.

What is claimed is: The method of treating cracked low boiling petroleum oils containing high per ccntages of unsaturated compounds to remove therefrom only excessive undesirable unsaturated compounds which produce gums and discoloration on standing, the

steps which comprise: introducing va ors of such cracked oils admixed with steam mto a confined polymerizing zone, bringing the mixture of oil and water vapor during the passage thereof through said zone into intimate contact with a finely divided solid adsorbent catalyst, the steam bein present in such proportion as to cause p0 ymerization of approximately one-fourth of the total unsaturates which would be polymerized without the presence of steam, the remaining unsaturates being unpolymerized and thus present in desirable increased amount over that originally present in the oil vapors charged to the polymerizing zone, removing" the material from the pol erizing zone, and separating the treate oil .as vapors from the high boilin oils produced in the polymerizing zone an containing the aforesaid undesirable compounds.

In testimony whereof we aflix our signatures.

JOSEPH B. WEAVER. CARY R, WAGNER.

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