US2920036A - Process and apparatus for breaking foam when treating petroleum or derivatives thereof with alkaline material - Google Patents

Description

s 2,920,036 I I PROCESS AND APPARATUS FOR BREAKING FOAM WHEN TREATING PETROLEUM R DE- RIVATIVES THEREOF: WITH ALKALINE MA- a:

William A. Gallup, Media, and Hugh L. Myers, Springfield, Pa., assignors to Sun OilCornpany, Philadelphia,

122., acorporation of New Jerseyl i.

Application April 1s, 1956, Serial b. 519,021 6 Claims. or. 208-284) This invention relates to processa-n'd apparatus for treating petroleum or derivatives thereof with alkaline material, and more particularly to process and apparatus for avoiding detrimental effects of foaming insuch treating. v t It is known in the art to treat various petroleum materials with alkaline materials such asaqueous caustic soda in order to refine the petroleum material. In 'one type of process, to' whichthe present invention is particrefining" zone, either periodically or continuously, in

order to maintain the desired alkalinity.

A serious problem which is frequently encountered in refining processes as described above is the formation of objectionable deposits on metal surfaces in'the refining zone; such deposits frequently result in excessive pres- Unit W8 sure drop of vapors in passing through the refining zone,

interference with flow of liquid alkaline material through the refining zone, etc. Another serious problem is the entrainment of liquid alkaline material by rising vapors, such entrainment often resulting in contamination of distillate products with alkaline material.

It has been found that a factor contributing to these detrimental efiects is the formation of foam in the refining zone, as a result of theintroduction ofw'ate'r thereinto with the fresh alkaline material which is'added in order to maintain alkalinity. The refining operation is generally conducted at a'temperature substantially above the boiling point of water, so that' the :water introduced with the alkaline materialis flashed uponentry into the refining zone. The use of anhydrous alkaline materials to overcome -this problem is not a satisfactory solution, since anhydrous caustic sodaforexample requires" an expensive and difficult fusion operation and is also difficult'=to convey satisfactorily inthe molten condition.

The present invention provides a novel manner of handling alkaline material containing water or other volatile materials, while avoiding the detrimental effects which characterize the prior art operation. According; to the present invention, as applied to the system previously given by way of example, the fresh aqueous alkaline material is introduced into the liquid alkaline material previously in the system, at a location which is external to the refining zone, the introduction being performed under condition which result in the production offoam. The

resulting mixture is passed through a foam-breaking constriction in order to shear the foam, andthen is introduced through an elongated conduit, which functions as 'to 10 pounds per square inch.

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a defoaming sectionfinto the refining "zone. Operation in this manner is capable of eliminating foam from the refining zone itself, with the result'that the deposits and entrainment encountered in conventional operation are 're ducedor eliminated. l r t The foam-breaking constriction which is employed according to the invention can be of anyjsuitable construc tion to give a pressure drop across the constriction;within the approximate range from 2 to 30poun'ds per square inch; Pressure drops within th is range arefirequired for satisfactory shearing of foam. Pr'eferred pressure drops are those within the approximate range from 5 to-15 pounds per square inch. .A preferred construction for the fo'a'm breakingconstriction is an orifice plate consisting of a thin transverse" plate in the conduit for conveyance of alkaline material, the plate containing a circular orifice having suitable proportions to provide thejdesired pressure drop; Inthe light of the present specification, a person skilled in the art can choose the proper'propoiftions for a given operation, in order to provide the desired pressure drop. I H I In one embodiment of theinvention, fresh' alkaline material is introducedinto liquid alkaline material previ ously in the system withthe assistance of suitablefrnixing means,such as an"orificejust'downstreain from the point at which the 'fresh 'alkaline material is introduced into the alkaline material previously in the system. "Pre ferred pressure drop for such mixing orifice, in order toprovide efficient mixing, is within the approximate range'jfrom '5 The portion of the apparatus between the' locus of vaporization of volatile matter and the ,foam;breaking orifice constitutes a foaming section, wherein 'yolatile matter vaporized fronrthe fresh I alkaline'r'naterial pro duces a foam 'with the" relatively non-volatile liquid alkaline material} The residence time 'of the liquid alkaline material in passing throughthis foaming section 'is preferably within the 'appr'oximaterange from 001 to '10 seconds, more preferably 004 to 1.0 second. Longerresidence times, can be employed. if desired, but are gerierally unnecessary. The residence time should; be at least 0.01 'seco'nd however, in order to provide satisfactory operation. I j V 1 i v f The ratio 1 of length to cross-sectional 'area in the foaming section is preferably such as to be equivalent to a ratio of length to diameter within the approximate range from '8 to 100. Longer foaming sections can'beemployed if desired, but are. generallyv unnecessary; Preferred ratios of length to diameter are those in the approximate range from 30 to 60. The ratio should be at least 8. for satisfactory operation.

The foaming section preferably has larger cross-sectional area than the cross-sectional area in the portion of the apparatus. which is directly upstream therefrom. The use of relatively larger cross-sectional area in the foaming section avoids, the hammering which may otherwise -occur as a result of foaming in the conduit. v

The portion'of theapparatus between the foambreak .ing orifice and the receivingzone. into which thealkaline material is ultimately introduced constitutes a defoaming section in which the suppression of foam initiated by the foam-breaking orifice is completed. [The-residence time'of alkaline material inthe'defoaming section. should be'at least 0.01 second, in order that the defoaming can be satisfactorily completed beforeiintroduction of the f the conduit. Generally, it will not be necessary or desirable to employ a conduit whose length is more than 100 times its diameter; however, such longer conduits can be employed if desired. Preferred ratios of length to diameter are those within the approximate range from 18m 40. In a conduit having other than circular cross section, the ratios of length to cross-sectional area should .be such as to provide a ratio equivalent to those set forth above for a conduit having circular cross-sectional area.

In typical operation according to one embodiment of the invention, the liquid alkaline material previously in the system is sufficiently hot at the time of mixing with the fresh alkaline material to vaporize volatile matter from the latter and form foam. The temperature of the 7 liquid alkaline material may for example be within the approximate range from 500 to 750 F. In such cases, it is not necessary to supply heat to the mixture of liquid alkaline material and fresh alkaline material, though such heating can be performed in cases where it is necessary in order to vaporize the volatile matter and form foam. In some cases, volatile matter can be vaporized from liquid alkaline material entirely by indirect heating without admixture with hot alkaline material or other direct heating medium.

In operation according to one embodiment of the invention, the refining zone is commonly maintained at a pressure below atmospheric, for example less than 10 p.s;i.a., and often less than p.s.i.a. However, the process and apparatus according to the invention are also applicable in systems operating at atmospheric pressure or above.

The invention will be further described with reference to the attached drawing, wherein Figure 1 is a schematic diagram of a system according to the invention, and Figure 2. illustrates in more detail a portion of the apparatus represented in Figure 1.

Referring to Figure 1, a Vacuum distillation tower 10, a mixing orifice 11,.and a foam-breaking orifice 12 are illustrated therein, together with appropriate piping for conveyance of the alkaline materials. In operation, by way of example, reduced crude petroleum containing naphthenic acids is introduced through line 13 into vacuum tower 10. Vapors of a portion of the reduced crude pass upwardly through a refining section in tower containing liquid alkaline material introduced through line 14. The naphthenic acids in the vapors react with the alkaline material to produce alkali metal naphthenates which become incorporated in the liquid alkaline material. The vapors from which naphthenic acids have been removed pass into an upper fractionating section of tower 10 and are fractionated in conventional manner to obtain distillate s, which are removed as generally indicated by line "15. Residue is removed from the tower 10 through line '16.

The liquid alkaline material passes downwardly from tray to tray within the refining zone and is continuously removed from'the tower through line 17 by means of pump 24. The material removed contains liquid oil which has been condensed from the vapors during passage of the latter through the refining zone, and also contains alkali metal vnaphthenates and fresh alkali metal hydroxide. Typical proportions of materials in the liquid alkaline material removed through line 17 are: liquid oil, 8 3.5%; alkali metal naphthenates, 15%; and alkali metal hydroxide, 1.5%.

' A portion of the liquid alkaline material withdrawn through line 17 is passed through line 18 to suitable means for recovering naphthenic acids from the liquid alkaline material. The remainder is passed through control valve 19 and then through mixing orifice 11. The purpose of 'valve 19 is to regulate the flow rate of liquid alkaline ma- ,terial through line 17 and the other conduits through which liquid alkaline material passes before re-introduc- 91 to Wa 1 Fresh queous caust c soda s in roduced through line of the alkaline material through foam-breaking orifice 12, and the defoaming is completed during passage of the alkaline material through line 22 which constitutes a defoaming section. Valve 23 in conduit 22 is an emergency valve which in ordinary operation is fully open.

The length and volume of foaming section 21 and of defoaming section 22 should be sufliciently great, as previously specified, to provide satisfactory operation with regard to formation of foam and subsequent suppression thereof. If the foaming section does not provide sulficient residence time, the foam is not fully formed when it reaches the foam-breaking orifice, and the effectiveness of the latter is substantially impaired, with the result that foam may be formed after passage through the orifice 12, and introduced into tower v10 with detrimental results. If the defoaming section is not sufiiciently long, in relation to the cross-sectional area thereof, the defoaming initiated by orifice '12 is not completed before introduction of alkaline material into tower 10, and foaming in the latter results. I

Referring to Figure 2, the conduit 17, the conduit 20 and the orifice plate 11 are illustrated in somewhat greater detail. As shown therein, the outlet of conduit 20 is positioned quite close to the orifice 24, in orifice plate ,11, the distance being for example about one inch, in the casewhere a 1.5 inch diameter orifice, a line 17 having diameter of 4 to 6 inches, and a line 20 having diameter of one inch are employed. With this construction, highly efiicient mixing of caustic soda introduced through line 20 with liquid alkaline material previously in the system, passing through line 17, is obtained.

The following examples illustrate the invention:

Example I Operation conforming generally to that illustrated in the drawing was carried out, liquid alkaline material at a temperature in excess of 500 F. being withdrawn through line 17 having diameter of /2 inch, at a rate of 2700 cc. per minute. The mixing orifice had a diameter of /8 inch. Aqueous caustic soda (50 B.) was introduced through line 20 at a rate of 38 cc. per minute. The foaming section consisted of 8.5 inches of /2 inch pipe followed by 17 inches of 1 inch pipe, thus being 34 nominal pipe diameters long, and providing a residence time of about 0.038 second as subsequently shown. The foambreaking orifice had a diameter of inch. The temperature near the foam-breaking orifice was 550 F., and the pressure just upstream from the foam-breaking orifice was 25 inches of mercury vacuum (about 5 inches of mercury absolute). The defoaming section consisted of 1 inch pipe and had a length of 18 inches. The defoaming section discharged the liquid alkaline material into a receiving vessel which was maintained under nearly com plete vacuum. In operation as described above, the foam produced in the foaming section was completely suppressed during passage of the alkaline material through the defoaming section, and no foaming occurred in the receiving vessel.

By way of comparison, similar operation carried out in the absence of the foam-breaking orifice results in severe foaming in the receiving vessel.

The manner of calculation of residence time is given elow for the foaming section in this example, in order to illustrate the calculation: The volume of the foaming section was about 17.24 cubic inches, since it contained 8.5 inches of Vzinch pipe having cross-sectional area of 0.304 square inch and 17 inches of 1 inch pipe having cross-sectional area of 0.862 square inch. The caustic soda rate was 38 cc. per minute or about 58 grams'per inin'ute sincethe specific gravity of 50 B. caustic soda is about 1.53; the rate of introduction of water was thus about 29 grams per minute since 50 B. caustic soda contains about 50 percent water. Assuming complete vaporization of water at 550 F. and 25 inches of mercury vacuum, the volumetric water vapor rate (the number of moles of water multiplied by 22,400 and correction factors for temperature and pressure) was about 441,000

cc. per minute. The volumetric rate of water vapor (441,000) and liquid alkaline material (2700) was thus about 444,000 cc. per minute, or 450 cubic inches per second. Division of the foaming section volume by 450 gives a residence time of about 0.038 second.

Comparison Example I Operation generally similar to that carried out in Example I, but with the foam-breaking orifice located nearer the receiving vessel, so that the length of the defoaming section was only four times the diameter thereof, was performed. The conditions were the same as those in Example I with the following exceptions: caustic rate, 40 cc. per minute, temperature and pressure near the foam-breaking orifice, 545 F. and 12 p.s.i.g. respectively, residence time in foaming section, about 0.7 second. The caustic was added to the other alkaline material in a mixing valve, rather than an orifice as in Example I. In this operation, severe foaming occurred in the receiving vessel. Comparison of these results with those obtained in Example I is given in the following table:

Ratio of Length to Diameter in Defoaming Section Result Severe foam. No foam.

In this example, the residence time in the defoaming section was about 0.0073 second, calculated as follows: volume of defoaming section, about 3.45 cubic inches; rate of introduction of Water in caustic soda, about 30.5 grams per minute; volumetric water rate at 545 F. and about 5 inches of mercury absolute pressure (this being the average pressure in the defoaming section), about 465,000 cc. per minute; volumetric rate of water vapor and liquid alkaline material, about 468,000 cc. per minute, or about 475 cubic inches per second; quotient of 3.45 divided by 475, about 0.0073. Thisresidence time was less than that in the defoaming section of Example I and was insufiicient for satisfactory defoaming.

This example shows that ratio of length to diameter and residence time are important characteristics of the defoaming section and the operation thereof.

Comparison Example 11 Operation generally similar to that in Example I, but employing in the foaming section a residence time of only about 0.007 second, was performed; the defoaming section had ratio of length to diameter of 52. The conditions were the same as in Example I with the following exceptions: caustic rate cc. per minute, temperature and pressure near the foam-breaking orifice, 560 F. and 28 inches of mercury vacuum (about 2 inches of mercury absolute). Caustic addition was as in Comparison Example 1. Severe foaming occurred in the receiving vessel. The following table shows a comparison of these results with those obtained in Example I.

Result Residence Time in Seconds in Foaming Section N o foam. Severe foam.

These examples showthat' the. residence time in the foamingsection is a critical factor for obtaining satisfactory results according. to the invention..

In the process according to the invention,.the pressure drop across the foam-breaking constriction is maintained at a substantially constant level within the approximate range from 2 to 30 pounds per square inch. 'Some fluctuation of pressure drop is of course permissible, but it is not feasible to use the foam-breaking constriction as 'a control valve, since the presence of the foam would interfere with such function. Preferably, the foambreaking constriction is provided by an orifice plate which is not adapted to function as a valve.

Although the invention has been described previously with regard to introduction of aqueous caustic soda into a process for treatment of petroleum vapors with liquid alkaline material, it is also applicable to other treatments of petroleum or derivatives. Thus, for example, caustic soda containing sodium sulfide produced in refining petroleum containing H 8 can be admixed with oil-inso1uble sulfonic acids produced in sulfonation of petroleum; upon such mixing, the sulfonic acids are neutralized by caustic soda, and concurrently, sodium sulfide reacts with acidic materials to release H 8 to produce a foam. According to the invention, the mixture is passed through a foaming section, a foam-breaking orifice, and a defoaming section beforeintroduction into a receiving vessel, foaming in the latter thus being avoided.

The invention claimed is:

1. In a petroleum refining process wherein liquid alkaline material is contacted with hydrocarbons in a refining zone, the liquid alkaline material is subsequently removed from the refining zone, an aqueous alkaline material is admixed with the removed liquid alkaline material, the latter being at a temperature suflicient to flash vaporize water from the aqueous alkaline material thereby to form foam, and the resulting mixture is reintroduced into the refining zone, the improvement which comprises, prior to the reintroduction, passing the resulting mixture through a foaming zone, the residence time in which is at least 0.01 second, subsequently passing the mixture through a constriction across which the pressure drop is maintained at a substantially constant level within the approximate range from 2 to 30 pounds per square inch, subsequently passing the mixture through a defoaming zone having ratio of length to cross-sectional area equivalent to a ratio of length to diameter of at least 8, the residence time in which defoaming zone is at least 0.01 second, and introducing the mixture from the defoaming zone into the refining zone.

2. Process according to claim 1 wherein the refining zone is maintained at a pressure less than 10 p.s.i.a.

3. Process according to claim 1 wherein said temperature is in the approximate range from 500 to 750 F.

4. In apparatus for refining petroleum which comprises a refining vessel, means for introducing petroleum into the refining vessel, means for removing refined petroleum from the refining vessel, a conduit communicating with the refining vessel and adapted to remove liquid alkaline material therefrom, and means for introducing aqueous alkaline material into the conduit, the improvement which comprises means providing a constricted passageway having fixed cross-sectional area adapted to produce a pressure drop within the approximate range from 2 to 30 pounds per square inch, a second conduitfor conveying the alkaline material to said constricted passageway from the point of introduction of aqueous alkaline material, and a third conduit for conveying alkaline material from said constricted passageway to said refining vessel, the second and third conduits each having a ratio of length to cross-sectional area equivalent to a ratio of length to diameter of at least 8.

5. Apparatus according to claim 4 wherein said constricted passageway is proyided by an orifice plate.

6. Apparatus according to claim 5, and additionally comprising a second orifice plate adjacent anddownstream from said means for introducing aqueous alkaline material.

References Cited in'the file of this patent UNITED STATES PATENTS McCorquodale et all Feb. 11, 1941 Hoover Nov. 3, 1953 Trusty et a1. Oct. 23, 1956 Blatz Dec. 11, 1956

Claims (2)

1. IN A PETROLEUM REFINING PROCESS WHEREIN LIQUID ALKALINE MATERIAL IS CONTACTED WITH HYDROCARBONS IN A REFINING ZONE, THE LIQUID ALKALINE MATERIAL IS SUBSEQUENTLY REMOVED FROM THE REFINING ZONE, AN AQUEOUS ALKALINE MATERIAL IS ADMIXED WITH THE REMOVED LIQUID ALKALINE MATERIAL, THE LATTER BEING AT A TEMPERATURE SUFFICIENT TO FLASH VAPORIZE WATER FROM THE AQUEOUS ALKALINE MATERIAL THEREBY TO FORM FOAM, AND THE RESULTING MIXTURE IS REINTRODUCED INTO THE REFINING ZONE, THE IMPROVEMENT WHICH COMPRISES, PRIOR TO THE REINTRODUCTION, PASSING THE RESULTING MIXTURE THROUGH A FOAMING ZONE, THE RESIDENCE TIME IN WHICH IS AT LEAST 0.01 SECOND, SUBSEQUENTLY PASSING THE MIXTURE THROUGH A CONSTRICTION ACROSS WHICH THE PRESSURE DROP IS MAINTAINED AT A SUBSTANTIALLY CONSTANT LEVEL WITHIN THE APPROXIMATE RANGE FROM 2 TO 30 POUNDS PER SQUARE INCH, SUBSQUENTLY PASSING THE MIXTURE THROUGH A DEFOAMING ZONE HAVING RATIO OF LENGTH TO CROSS-SECTIONAL AREA EQUIVALENT TO A RATIO OF LENGTH TO DIAMETER OF AT LEAST 8, THE RESIDENCE TIME IN WHICH DEFOAMING ZONE IS AT LEAST 0.01 SECOND, AND INTRODUCING THE MIXTURE FROM THE DEFOAMING ZONE INTO THE REFINING ZONE.

4. IN APPARATUS FOR REFINING PETROLEUM WHICH COMPRISES A REFINING VESSEL, MEANS FOR INTRODUCING PETROLEUM INTO THE REFINING VESSEL, MEANS FOR REMOVING REFINED PETROLEUM FROM THE REFINING VESSEL, A CONDUIT COMMUNICATING WIHT THE REFINING VESSEL AND ADAPTED TO REMOVE LIQUID ALKALINE MATERIAL THEREFROM, AND MEANS FOR INTRODUCING AQUEOUS ALKALINE MATERIAL INTO THE CONDUIT, THE IMPROVEMENT WHICH COMPRISES MEANS PROVIDING A CONSTRICTED PASSAGEWAY HAVING FIXED CROSS-SECTIONAL AREA ADPATED TO PRODUCE A PRESURE DROP WITHIN THE APPROXIMATE RANGE FROM 2 TO 30 POUNDS PER SQUARE INCH, A SECOND CONDUIT FOR CONVEYING THE ALKALINE MATERIAL TO SAID CONSTRICTED PASSAGEWAY FROM THE POINT OF INTRODUCTION OF AQUEOUS ALKALINE MATERIAL, AND A THIRD CONDUIT FOR CONVEYING ALKALINE MATERIAL FROM SAID CONSTRICTED PASSAGEWAY TO SAID REFINING VESSEL, THE SECOND AND THIRD CONDUITS EACH HAVING A RATIO OF LENGTH TO CROSS-SECTIONAL AREA EQUIVALENT TO A RATIO OF LENGTH TO DIAMETER OF AT LEAST 8.

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