US2001301A - Method for converting hydrocarbon oils - Google Patents

Description

y 1935. 1.. DE FLOREZ 2,001,301

METHOD FOR CONVERTING HYDROCARBON OILS Filed Aug. 31, 1932 2 Sheets-Sheet 1 T "W e) I ,Cwnja N M U INVENTOR 00 K AL BYlQ z \fi 7 ATTORNEY May 14, 1935. DE FLOREZ METHOD FOR CONVERTING HYDROCARBON OILS Filed Aug. 31, 1932 2 Sheets-Sheet 2 INVENTOR. LU/S 0'6 FLOREZ ATTORNEY Patented May 14, 1935 PATENT OFFICE 2,001,301 .METHOD FOR convex-mac. mmno- CARBON OILS Luis de Florez, Pomfret, Conn., asslgnor to The Texas Company, New York, N. Y., a corporation of Delaware Application August 31, 1932, Serial No. 631,224

9 Claims.

This invention relates broadly to the treatment of petroleum hydrocarbon oils in acyclic system and more particularly to a method and apparatus in which a cycle condensate stock may be selected and controlled continuously during operation.

In a cracking system, the hydrocarbon oil to be cracked is subjected to an elevated temperature for a period of time during which reaction takes place. During this reaction, the hydrocarbon tends to deposit carbon and other solids, if present, in the apparatus causing interruption in the operations.

It has been found that if the cycle stock is properly selected as to cleanliness and character, the tendency for it to form deposits is virtually eliminated permitting the process to function for indefinitely long periods of time, which is commercially highly desirable. My invention deals, as one of its main features, with the control and selection of the cleanliness and character of the cycle condensate to accomplish these ends.

By a clean cycle condensate is meant one which is substantially free from carbon and/or sediment and potentially high carbon forming constituents and may be safetly returned to the heating element in the heating zone for the particular operation being carried out without excessive deposition of carbon in the heating element or other parts of the system. The color of the cycle stock produced in a cracking operation will vary depending upon the particular type of charging stock being treated. It has been discovered that although the color may vary for different cycle stocks, a given cycle stock having a color satisfactory to be returned will not yield an excessive amount of carbon. This invention comprehends broadly the continuous detection and control of the cleanliness and character of a cycle condensate formed in any cracking operation without being limited to the particular hydrocarbon oil being treated.

It is an object of this invention to provide a process in which the cleanliness and character of the cycle stock is continuously detected and controlled.

Another object of this invention is to provide an apparatus for carrying out the process.

With these and other objects in view, which may be incident to my improvements, the invention consists in the several method steps and the parts and combinations to be hereinafter set forth and claimed, with the understanding that the procedure of the several necessary elements may be varied without departing from the spirit and scope of the appended claims.

In accordance with my invention, the cleanliness of the cycle condensate, which may be determined by the color thereof, may be used as an indication of the manner in which the sys-. tem is operating. The quantity of cycle condensate in the base of a fractionating column may be ordinarily so great that the color changes very gradually and consequently considerabl con- 10 tamination with the resultant excessive deposition of carbon may have taken place before being discovered by an operator. Excessive contamination or a color change has been found to bee good criterion of determining whether adequate cracking and separation of the oil is being effected and further whether priming of the preceding vessel is taking place.

Figure 1 illustrates diagrammatically a form of apparatus capable of carrying out the invention.

Figure 2 illustrates a modified form of apparatus for carrying out the invention.

Referring to Figure 1 of the drawings, any suitable form of cracking system may be employed, although I have illustrated a. simple system of the type commonly termed coil and drum.", In the system illustrated, super-atmospheric pressure is maintained throughout, although lower pressures may be employed for parts of a cracking system capable of carrying out the invention, as will be referred to hereinafter.

In accordance with the cracking system illustrated for carrying out the invention, a suitable charging stock may, for example, be introduced into a heating coil 1 by means of a charging pump 2. The heating coil I may be enclosed in a furnace setting 3 and the oil passing through the heating coil may be highly heated by means of a burner 4. While only one burner has been illustrated, obviously more than one may be used if desired. Other types of furnaces may be used, such for example, as that shown in Patent No. 1,717,334 issued on June 11, 1929 to me. The highly heated oil in leaving the heating coil I may be conducted through a pipe 5 to a still or chamber 6 which comprises a conversion zone. Any number of chambers may be employed as a conversion zone, only one being shown for simplicity.

The hydrocarbons undergoing treatment may be subjected to conversion conditions in the chamber 6. A portion of the oil under these conditions whichconsists mainly of the products of conversion may bevaporized while another por- 55 tion, being mainly the residual components, remains unvaporized and collects in the bottom of the chamber 6.

The unvaporized portion of the oil may be conducted through a pipe 1 controlled by a valve 8 to storage for any desired use or, as contemplated in one method of operation, may be introduced into a system of reduced pressure wherein a flashing operation is carried out." A still further method of treating the unvaporized portion of the oil in the bottom of the still 6 is to permit it to remain in the bottom thereof to decompose to coke.

The vaporized portion of the oil in the still 6 may pass overhead through a vapor line 9, connected to a lower part of a fractionator or dephlegmator l0, wherein the vapors are subjected to fractionation. The vapors entering the fractionator l pass upwardly and portions thereof become condensed and form a liquid body in the bottom of the fractionator. The components that remain in the vaporized state pass upwardly through the fractionating column where additional vapors are condensed and drop to the body of liquid in the bottom of the fractionator.

A reflux condenser, not shown, may be employed and the remaining vaporized products passing therethrough have a portion thereof condensed and knocked back to the body of liquid in the bottom of the fractionator. While a reflux condenser has been mentioned, any suitable cooling means may be used for the fractionator III. For instance, the fresh charge may be passed in indirect heat exchange with the vaporized components passing through the upper part of the fractionator or, if a reflux condenser is used, the fresh charge "may be passed in indirect heat exchange with the vapors passing through the reflux condenser.

It is to be understood that any desired method of fractionation may be employed. Suitable refluxing material may, for instance, be introduced directly into the top of the fractionating column.

The final vapor fraction passing upwardly through the fractionator i0 emerges through a pipe II and is passed through a condensing coil 12 to form an ultimate distillate which may be collected in an accumulator drum IS. The ultimate distillate may be delivered to any suitable storage by means of a valved controlled pipe i4 and the fixed gas constituent may be delivered to any suitable storage or use by means of a valved control pipe IS.

The body of liquid in the bottom of the fractionator III which may be of the nature of a light gas oil and suitable as a cycle condensate. may be withdrawn through a pipe I6 controlled by means of a valve IT. The cycle condensate may be withdrawn by means of a pump i8 and returned to the heating coil I for further treatment. While I have shown the cycle condensate being returned to the inlet of the heating coil, it is to be understood that this recycle stock may be returned to an intermediate point of the heating coil.

In accordance with my invention the color of the cycle condensate is determined prior to its return to the conversion zone. Broadly this is accomplished by withdrawing a sample of the vapors passing to the fractionating zone, condensing this portion and comparing it with a cycle condensate or other standard whose color makes it satisfactory to be returned to the heating coil, or by comparing it with a sample of the cycle condensate in the bottom of the fractionator being run through a sight glass on the control board to determine whether a gradual color change, which indicates contamination, is taking place in the body of liquid in the bottom of the fractionator.

As illustrated in the drawing, a sample line l9, controlled by a valve 20, may be branched from the vapor line 9, preferably at the lowest part, to permit withdrawing condensates as well as vapors. The sample line IQ for this purpose may be a small pipe which conducts the withdrawn vapors to a condenser 2 I, which may be air cooled or otherwise, in which the withdrawn vapors are condensed. This condensate may then be passed through a sight glass 22 positioned on a control board, not shown, andeither of the observations above mentioned carried out.

If it is desired to pass a sample of the cycle condensate formed in the bottom of a fractionator to the control board, a simple mean for carrying this out is shown. As illustrated, a sample line 23, controlled by a valve 24, may be branched of! of the line i6 which conducts the cycle condensate to the heating coil I. Obviously this line may be branched off from the line It at any point or may be suitably inserted into the bottom of the fractionator Ill. The line 23 may be a small pipe as it is only necessary to conduct a relatively small portion of the cycle condensate to the control board. A sight glass 25 may be positioned adjacent the sight glass 22 in order s that the colors of the condensates passing through the sight glasses may be compared. It is also to be understood that the color of the cycle condensate may be compared with that of the standardcolor. The condensate passing through the sight glass 25 may, of course, be returned by a suitable pipe to the line I 6, or to the bottom of the fractionator.

A modification contemplated by my invention is to introduce the charging stock directly into the upper portion of the chamber 6. As illustrated, a pump 26 may be employed for this purpose, the charging stock passing through a suitable pipe 21. When practicing the invention in accordance with this modification; only the clean cycle condensate from the bottom of the fractionator i0 is passed through the heating coil l, the pump 2 being blocked oif by a suitable valve 28.

With the fresh charge introduced into the upper portion of the chamber 6 to reflux the vapors, excellent control of the color of the cycle condensate may be obtained. If the color of the cycle condensate is gradually becoming too dark, more cooling may be effected in the upper portion of the chamber 6 either by reflux from any suitable source or by more charging stock, thereby knocking back heavy ends and entrainment from the vapors passing into the vapor line 9. The upper portion of the chamber 6 under these conditions of operation functions as a primary fractionator. In lieu of introducing the charge into the chamber 6, an additional fractionating column may be used to receive the vapors from the chamber 6, with the fresh charge being introduced thereinto. In this manner, there are provided two separate fractionating columns, the primary of which removes entrainment and heavy ends by the refluxing action of the fresh charge and the secondary of which collects a clean cycle condensate for return to the cracking system. The liquid collected in the bottom of the primary fractionating column may, if desired, be passed into the cracking zone of chamber 6 or otherwise utilized.

Figure 2 shows the modified form of apparatus just described. Referring to this figure, there is shown a furnace setting having a heating coil 3| positioned therein. Oil passing through the heating coil 3! is heated to the desired cracking temperature and passed through a line 32 to a conversion chamber 33 wherein liquid and vaporous products may be separated. The thus separated liquid products may be withdrawn through a line 34 and the vaporous constituents conducted through a line 35 to a primary fractionating column 36. The vaporous constituents passing through the fractionating column 36 are therein fractionated to remove heavy condensible fractions therefrom, which may be withdrawn through a line 31 and passed to the conversion chamber 33 by means of a pump 38.

Charging stock for the system may be introduced into the upper part of the fractionating column 36 through a line 39 by means of a pump 4|. The fresh charging oil is thus heated by the vaporous constituents and if more cooling of the vaporous constituents is desired, reflux from any suitable source may be introduced.

The vaporous constituents from the primary fractionating column are conducted through a line 42 to a secondary fractionating column 43 wherein an overhead vapor fraction and a clean cycle condensate are formed. The overhead vapor fraction may be conducted through a line 44 to a condenser 45 from which the condensed fraction is passed to a distillate receiver 46.

The cycle condensate formed in the fractionating column 43 collects in the bottom thereof and may be withdrawn through a pipe 41 and forced by means of a pump 48 to the inlet of the heating coil 3! to constitute the charge oil therefor.

In practicing this invention in accordance with Figure 2, a sample line 49 controlled by a valve 5| may be branched off of the vapor line 42 for withdrawing a sample of the vapors passing therethrough. The withdrawn vapors are passed through a condenser 52 and then conducted through a sight glass 53 from which the color of the condensed sample may be observed and the process adjusted to correct for any variations in the color thereof.

If desired, a pressure reduction valve 54 may be positioned in the line 35 in order to maintain the apparatus beyond this valve at a pressure lower than that maintained on the other part of the apparatus. By this arrangement, the column 36 acts as a combined evaporator and fractionating column and a sample of the vaporous constituents may be withdrawn in accordance with this invention in the manner described. Obviously, a separate evaporator may be positioned between the chamber 33 and the column 36, the separate evaporator being maintained at a lower pressure than the apparatus preceding it.

While my invention is adapted generally for cracking processes within any of the ranges of temperature employed, it is particularly well adapted to the cracking of hydrocarbons at higher temperatures, say in the order of 900 and 1000 F. or higher.

By practicing this invention, it is possible to determine whether more or less cracking is required or whether the level of the oil in the bottom of the fractionator should be altered. Moreover the extent of priming and also whether adequate separation between vaporous and liquid constituents inthe chamber 6 is taking place can be determined by the color of the sample passing through the sight glass 22.

If the color of the cycle condensate is unsatisfactory to be returned to the heating zone, it is possible in accordance with my invention to control its,cleanliness by various adjustments. This control may be effected by varying the amount of reflux, if used, being introduced into the top of the fractionators, changing the level of the condensate in the bottom of the chamber 6 and also verying the temperature at this point. It is to be understood that either of the above adjustments, or any combination thereof may be employed to control the color of the cycle condensate in the bottom of the fractionator.

The above adjustments to the cracking system' can be made while in operation. The sight glasses 22 and 25 may have samples of the condensates continuously passing therethrough andan operator can at all times determine whether the cycle condensate is becoming contaminated by gradually going oiT color.

One way of practicing the invention when the cracking system is in continuous operation is to place a sample of a cycle condensate, which can be safely returned to the heating coil, or any other standard, at a convenient point on the control board. The particular sample, will, of course, be a clean cycle condensate or its equivalent standard suitable to be returned to the heating coil for the particular oil being treated. The condensed vapor fraction passing through the sight glass 22 may be compared with this standard cycle condensate and any change in color or the presence ofcontaminating entrainment detected. If the color of the condensed vapor fraction does not compare favorably with the standard color, either or any combination of the adjustments above described may be made to restore a satisfactory color to the condensed vaporfraction and the cycle condensate being formed and collected in the fractionating zone.

In order to determine whether the cycle condensate in the bottom of the fractionator is gradually going ofi color, a sample of the condensate passing through the sight glass 25 can be observed. The color of the sample from the bottom of the fractionator can be compared with the color. of the condensed vapor portion passing through the sight glass 22. If this observation indicates that the cycle condensate in the bottom of the fractionator is gradually going offcolor, adjustments of the operating conditions of the cracking system can be made, as described, to minimize the return of a dirty cycle condensate to the heating coil.

The condensed vapor fraction passing through the sight glass 22 of Figure 1 may be withdrawn therefrom through a line 22' and that passing through the sight glass 53 of Figure 2 may be withdrawn therefrom through a line 53'. Similarly, the sample of the cycle condensate passing through the sight glass 25 of Figure 1 may be withdrawn therefrom through a line 25. The oil withdrawn through the lines 22 and 25' may be used in any well known manner;

This invention is also applicable to either the so-called liquid or vapor phase processes. It may also be satisfactorily used in the so-called low liquid level operation where the liquid is withdrawn at a rate adequate to prevent the accumulation of much liquid in the cracking vessels.

In operation, the color of the cycle condensate will vary, depending upon the. particular hydrocarbon oil being treated. I have discovered that a straw colored cycle condensate is generally danger of having coke troubles.

satisfactory and particularly one having a green cast. These colors are merely examples and not limitations of my invention.

The color examples as above given are within a group that may be termed lightcolors. When the color of the cycle condensate becomes darker, such as having a brown cast, there is a great If this condition exists, adjustments may be carried out as above described to obtain a satisfactory colored recycle condensate.

In my various experiments with color of the cycle condensate, I have found out that fifteen color on a half-inch cell, using a conventional Saybolt colorimeter, and a carbon content of .02 as determined by the Conradson tests, is quite satisfactory for the cycle condensate. Generally the color will vary somewhat depending upon the nature of the charging stock. A-satisfactory color for each charging stock may be determined and generaliy the carbon contentfor each should not exceed approximately .02 as determined by the Conradson tests. Obviously my invention is not limited to any particular number color nor to a particular carbon content, as it broadly comprehends detecting and controlling the color of a cycle condensate so that it may be satisfactorily returned to the heating zone.

While I have shown and described a suitable apparatus for carrying out my invention, I wish it to be understood that I do not confine myself to the precise details of construction herein-set forth by way of illustration as it is apparent that many changes and variations may be made by those skilled in the art, without departing from the spirit of invention, or exceeding the scope of the appended claims;

I claim:

1. In a cracking system for hydrocarbon fluids wherein the fluid is passed through a heating zone and therein raised to a conversion temperature, the thus heated fluidbeing thereafter separated into vaporous and liquid constituents and the vaporous constituents passed through a fractionating zone to form a cycle condensate for the cracking system, the improvement that comprises withdrawing a sample of the vaporous constituents prior to entering said fractionating zone, condensing said withdrawn sample, utilizing the color of the sample of condensed vaporous constituents as a criterion of the cleanliness of the cycle condensate, determining variations in the color thereof from that desired and controlling operating conditions of the cracking system in response to variations in the color of the condensed sample to thereby form cycle condensate of the desired color in said fractionating zone for return to the heating zone.

2. In a cracking system for hydrocarbon fluids wherein the fluid is passed through a heating zone and therein raised to a conversion temperature, the thus heated fluid being thereafter separated into vaporous and liquid constituents and the vaporous constituents passed through a fractionating zone to form a cycle condensate for the cracking system, the improvement that comprises withdrawing a sample of the .vaporous constituents prior to entering said fractionating zone, condensing said withdrawn sample, passing said condensed sample through a sight glass to observe the color thereof, withdrawing a sample of the cycle condensate formed in said fractionating zone and passing it through another sight glass to observe the color thereof, utilizing the color of the samples passing through a sight glass as a criterion of their cleanliness and comparing them to determine whether the cycle condensate is going off color and controlling the operating conditions of the cracking system in response to variations in the colors of said samples .to thereby form cycle condensate of the desired color in the fractionating zone for return to the heating zone.

3. In a cracking system for hydrocarbon fluids wherein the fluid is passed througha heating zone and therein raised to a conversiorrtemperature, the thus heated fluid being thereafter separated into vaporous and liquid constituents and the vaporous constituents passed through a fractionating zone toform a cycle condensate for the cracking system, the improvement that comprises'withdrawing a sample of the vaporous constituents prior to entering said fractionating zone, condensing said withdrawn sample, utilizing the color of the sample of condensed vaporous constituents as a criterion of the cleanliness of the cycle condensate, comparing the color of said sample of condensed vaporous constituents with that of a standard andcontrolling the operating conditions of the cracking system in response to variations in the color' of the condensed sample to thereby form cycle condensate of the desired color in the fractionating zone for return to the heating zone.

4. In a cracking system for hydrocarbon fluids wherein the fluid is passed through a heating zone and therein raised to a cracking temperature to form a vapor fraction and the vapor fraction subjected to primary and secondary fractionation to form a cycle condensate in the secondary fractionating zone for further cracking, the improvement that comprises withdrawing a sample of the vapor fraction prior to entering the secondary fractionating zone, condensing said withdrawn sample, utilizing the color of the sample of condensed vaporous constituents as a criterion of the cleanliness of the cycle condensate, determining variations in colorthereof from that desiredand controlling operating conditions of the cracking system in response to variations in the color of the cycle condensate to thereby prevent objectionable carbon formation therefrom when subjected to cracking.

5. In a cracking system for hydrocarbon fluids wherein the fluid is passed through a heating zone and therein raised to a cracking temperature to form a vapor fraction and the vapor fraction subjected to primary and secondary fractionation to form a cycle condensate in the secondary fractionating zone for further cracking, the improvement that comprises withdrawing a sample of the vapor fraction prior to entering the secondary fractionating zone, condensing said withdrawn sample, utilizing the color of the sample of condensed vaporous constituents as a criterion of the cleanliness of the cycle condensate, determining variations in color thereof from that desired and controlling the extent of fractionation in the primary fractionating zone in response to variations in the color of the con densed sample to thereby remove carbon forming constituents from the vapor fraction in the primary fractionating zone and form a cycle condensate in the secondary fractionating zone substantially free of objectionable carbon forming constituents when subjected to cracking.

6. In a cracking system for hydrocarbon fluids wherein the fluid is passed through a heating zone and therein raised to a cracking temperature to form a vapor fraction and the vapor fracill tion subjected to primary and secondary fractionation to form a cycle condensate in the secondary fractionating zone for the cracking system, the improvement that comprises withdrawing a sample of the vapor fraction prior to entering the secondary fractionating zone, condensing said withdrawn sample, utilizing the color of the sample of condensed vaporous constituents as a criterion of the cleanliness of the cycle condensate, determining variations in the color thereof from that desired and controlling the extent of fractionation in the primary fractionating zone in response to variations in the color of the condensed sample to thereby remove carbon forming constituents from the vapor fraction in the primary fractionating zone and form a cycle condensate in the secondary fractionating zone substantially free of objectionable carbon forming constituents for return to the heating zone.

7. In a cracking system for hydrocarbon fluids wherein the fluid is passed through a heating zone and therein raised to a conversion temperature, the thus heated fluid being thereafter separated into vaporous and liquid constituents and the vaporous constituents passed through a fractionating zone to form a cycle condensate for the cracking system, the improvement that comprises condensing a portion of the vaporous constituents passing to the fractionating zone todetermine the color of said condensed portion prior to entrance into the fractionating zone, utilizing the color of said condensed portion as a criterion of the cleanliness of the cycle condensate formed in the fractionating zone and controlling operating conditions of the cracking system in response to variations in color to thereby prevent objectionable carbon formation in the heating zone.

8. In a cracking system for hydrocarbon fluids wherein the fluid is passed through a heating zone and therein raised to a cracking temperature to form a vapor fraction and the vapor fraction subjected to primary and secondary fractionation to form a cycle condensate in the secondary fractionating zone for further cracking, the improvement that comprises condensing a portion of the vaporous constituents passing to the secondary fractionating zone to determine the color of said condensed portion prior to entrance into the secondary fractionating zone, utilizing the color of said condensed portion as a criterion of the cleanliness of the cycle condensate formed in the secondary fractionating zone and controlling operating conditions of the cracking system in response to variations in color to thereby prevent objectionable carbon formation in the heating zone.

9. In a cracking system for hydrocarbon fluids wherein the fluid is passed through a heating zone and therein raised to a conversion temperature, the thus heated fluid being thereafter separated into vaporous and liquid constituents and the vaporous constituents passed through a fractionating zone to form a cycle condensate for the cracking system, the improvement that comprises condensing a portion of the vaporous constituents to determine the color of said condensed portion prior to the collection of the cycle condensate in the fractionating zone, utilizing the color of said condensed portion as a criterion of the cleanliness of the cycle condensate collected in the fractionating zone and controlling operating conditions of the cracking system in responseto variations in color to thereby prevent objectionable carbon formation in the heating zone.

LUIS 1m FLOREZ.

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