US3252884A - Apparatus for treating emulsions - Google Patents

Description

y 1966 R. E. MARTIN ETAL 3,252,884

APPARATUS FOR TREATING EMULSIONS 2 Sheets-Sheet 1 Filed June 13, 1962 FIG] FIG. 2

INVENTORSI RALPH E. MARTIN JAMES ELAUBACH JACK C, SCOTT THOMAS R. RUDD ATTIYS May 24, 196 R. E. MARTIN ETAL 3,252,834

APPARATUS FOR TREATING EMULSIONS Filed June 1:5, 1962 2 Sheets-Sheet 2 FIGB FIG. '7 F168 INVENTORSI RALPH E.MARTIN JAMES E. LAUBACH JACK C. SCOT THOMAS R RUDD I 23 25 WW United States Patent 3,252,884 APPARATUS FGR TREATING EMULSIGNS Ralph E. Martin, Tyler, James E. Laubach, Lake Jackson, and Jack C. Scott and Thomas R. Rudd, Tyler, Tenn, assignors to Howe Baker Engineers, Inc., Tyler, Tex

a corporation of Texas Filed June 13, 1962, Ser. No. 202,248 Claims. (6i. 204302) This invention relates to an apparatus and method for the electrical treatment of emulsions of the oil-continuous type, and more specifically to a new apparatus and method by which the amount of residual dispersed-phase in the treated oil is reduced to a much lower value in smaller equipment than is possible with older commercial processes.

It has previously been proposed to treat an oil continuous emulsion (US. Patent 987,115), by subjecting the emulsion to a high voltage electric field. The dis persed droplets are coalesced and then gravitationally separated from the oil phase. This process has gained wide commercial acceptance and is widely used to desalt and dehydrate crude oil. This process removes the bulk of the dispersed phase, but it is not possible to reduce the dispersed phase to below about one-tenth of one percent, even when treating easily treated crude oils.

It has also been proposed to treat an oil continuous emulsion (US. Patent 1,931,725) by subjecting the emulsion to the action of an electric field of greater voltage gradient toward the negative electrode than toward the positive electrode, said field being produced by a unidirectional electric current. The dispersed phase is moved by cataphoresis and collects on one of the electrodes and drains off by gravity. While this process is technically feasible with some emulsions, it has not found commercial acceptance.

It has also been proposed (US. Patent 2,855,356) to treat an oil continuous emulsion by subjecting it to a unidirectional electrical field in laminar flow between parallel vertical plates. In this system every effort was made to keep the electric field as uniform as possible.

Objects of this invention are to provide a new and novel method and apparatus for treating an oil continuous emulsion; to provide an electric field which is highly non-uniform in the vertical and horizontal planes in the lower few inches of the electric field and which is nonuniform in the horizontal plane and uniform in the vertical plane throughout the majority of the electric field; to provide the oil continuous emulsion flowing vertically through the electric field, to control the process so that the treated oil will contain much less of the dispersed phase than was possible with other commercial processes, and to reduce the dispersed phase in the treated oil to a very low value in much smaller equipment than was possible with prior electric treaters.

A further object of the invention is to create the electric field with an electrode system which is vertical, economical to build, and can be easily installed in either new or used pressure vessels.

Further objects and advantages of the invention will be evident to those skilled in the art from the following description in conjunction with the accompanying drawings in which:

FIGURE 1 is a cross sectional view of an electric treater employing the principle and mode of operation of the invention;

FIGURE 2 is a sectional view taken along the line 22 of FIGURE 1;

FIGURE 3 is a view with parts broken away of an insulator, insulator housing, power bushing, bushing housing, and the unidirectional potential power supply;

FIGURE 4 is a detail of a tube electrode;

3,252,834 Patented May 24, I966 FIGURE 5 is a detail of a plate electrode;

FIGURE 6 is a detail of a mesh electrode;

FIGURE 7 is a detail of a suspension bushing;

FIGURE 8 is a detail of a bushing; and

FIGURE 9 is a detail of a power unit bushing.

In accordance with the invention an electric treater and a new and improved method for treating oil continuous emulsions are provided. An essential feature of the in vention embodies the use of planar electrodes, for example, plates, alternately arranged with respect to rows of non-planar electrodes which are preferably substantially round in cross section, such as, for example, rods or tubes. The electric treater as a whole preferably comprises a container, a set of electrodes consisting of alternate vertically substantially parallel plate electrodes, rows of vertical electrodes of substantially round cross section, the plate electrodes being from two to fourteen inches apart, the substantially round electrodes being substantially equidistant from adjacent plate electrodes, the spacing between the substantially round electrodes being approximately equal tothe distance between the substantially round electrodes and the plate electrodes, at source of unidirectional potential, means connecting said source of unidirectional potential to said electrodes, an emulsion inlet header located below said electrodes, an oil outlet header located above said electrodes through which the treated oil is withdrawn, preferably continuously, and means for withdrawing the coalesced discontinuous phase, preferably continuously. In this type of apparatus, the plate electrodes can be replaced by wire mesh electrodes.

In a typical apparatus of the type described the housing or container is a cylindrical structure disposed horizontally and provided at the bottom with inlet means for the emulsion to be treated and separate outlet means for the coalesced discontinuous phase. At the top of the container an outlet means is provided for removing the treated oil. The container is otherwise closed and the treated oil normally fills the container during operation.

The planar electrodes which preferably consist of plates or wire mesh, are suspended from opposite sides of the container in a vertical position and are spaced apart in a substantially parallel relationship. The rod or tubular electrode are suspended in rows between the plate electrodes and preferably terminate above or below the bottom of the plate electrodes. In a typical construction good results have been obtained by using plate or wire mesh electrodes which are arranged six inches apart and rod or tube electrodes approximately three-quarters inch in diameter spaced three inches from center to center in rows equidistant from the plate or wire mesh electrodes. A suitable arrangement of such planar and non-planar electrodes, for example, consists of twenty-five vertical plate or screen electrodes and twenty-three rows of vertical rod or tube electrodes, each row containing twentythree rods or tubes. In this arrangement, it is preferable to have a vertical distance of about thirty-six inches in which the rods or tubes, on the one hand, and the plates or wire mesh, on the other, are opposite one another or, in other words, in the same field. As previously indicated, the vertical rods or tubes preferably either extend below the plate electrodes or terminate short of the bottoms of the plate electrodes. In this way the lower part of the field is non-uniform, both vertically and horizontally.

The invention is not limited to any specific sizes or lengths of rods or tubes employed as vertical non-planar electrodes but, as a practical matter, it is desirable to use rods or tubes from twelve to sixty inches long. The planar electrode spacing, as previously indicated, is preferably from two to fourteen inchesapart. Since the non-planar electrodes are substantially equidistant from the planar electrodes, the spacing of the non-planar electrodes from the planar electrodes varies from about one to seven inches.

The undirectional potential is infinitely variable up to about 40,000 volts. Excellent results have been obtained by using about 5,000 volts per inch of electrode spacing. A general range is 3,500 volts per inch of electrode spacing to 15,000 or more volts per inch of electrode spacing. In this type of operation the current or amperage is kept at a minimum and preferably does not exceed 85 milliamperes.

In constructing the apparatus it is usually preferable to ground the plates or planar electrodes to the side of a steel container and to insulate the electrical conductors for the non-planar electrodes from the container. Thus, the rods, tubes or other non-planar electrodes are connected to a positive source'of unidirectional potential and the planar electrodes are negative. While this is a preferred arrangement it can be reversed.

The ratio of the surface area of the planar electrodes to the non-planar electrodes is subject to variation but is preferably within the range of 4:1 to 1:1. A good operating ratio involves the use of a plate surface area to rod or tube surface area of about 2.5:1.

Where the rods or tubes extend below the plates or other planar electrodes they are preferably rounded.

In the apparatus shown in the drawings the container or vessel 1 is generally cylindrical in structure as shown in FIGURES 1 and 2 and is closed at opposite end by manholes 2 and 3. An inlet pipe or conduit 4 is provided at the bottom of the container 1 to introduce a material which is to be treated. The inlet conduit 4 is connected to a horizontal distributing pipe 5 which is provided with spaced openings 6 on opposite sides thereof adapted to uniformly distribute or spray the material to be treated into the container 1 as shown in FIGURE 2. The electrodes consist of rows of rods 7 substantially equally spaced from vertically extending plates 8, thereby providing vertical passageways between the rods and the plates for the material to be treated as this material flows upwardly toward an outlet 9.

The rods 7 are supported in rows by a plurality of channel members 10 constructed of steel or other suitable conducting material. The channel members 10 are bolted, welded or otherwise attached to a pair of cross channel members 11 and 12 (see FIGURE 2). The cross channel members in turn are welded, bolted or riveted to steel or other electrically conducting channel member 13 and 14 and the latter in turn are supported by tubular or rod-like supporting members 15 and 16. The supporting member 15 is connected to another supporting member 17 which in turn is electrically connected to a unidirectional power supply through a bushing housing 18 as hereinafter described. The supporting member 16 is connected to another supporting member 19 which in turn is connected to a suspension bushing 20 (see FIGURES 3 and 7) supported in an insulating housing 21 as hereinafter described. Iii connecting the supporting member 19 to the suspension bushing 20 it is preferable to attach a hook 22 to the upper part of the supporting member 19 which engages with a ring 23 secured to the lower part of the suspension bushing 20 as shown on the left hand side of FIGURE 3. Similarly, the supporting member 17 is provided at the upper end with a hook 24 which engages a ring 25 disposed in an eyelet 26 fastened to a bushing 27 in the bushing housing 18.

A source of unidirectional power 28 is connected through a power unit bushing 29 to an electrical conductor 30 which in turn is connected through the bushing 27 to the rod 17 and from the rod 17 through the rod 15 to the supporting members for the vertical rod electrodes. The members 20, 27 and 29 which are referred to as bushings can also be described as insulators and the insulating portions are preferably fabricated from a polymer such as polypropylene or a polymer of tetrafluorethylene (Teflon). With insulator of this type it is not necessary to inject a non-conducting purge stream around the insulating surfaces to prevent the formation of conductive paths across the surface of the insulators as was previously necessary with older commercial electric treaters.

The vertical plate electrodes 8 are supported from the sides of the container 1 by angle bars 31 and 32 which are Welded or otherwise secured to the interior surface of the container 1. As shown in FIGURE 2, the angle bar 31 is Welded to a projecting member 33 and the angle bar 32 is welded to a projecting bar 34. The opposite side of each electrode 8 is supported from .angle bars 35 and 36 which in turn are welded or otherwisesecured to the interior surface of the container 1 by supporting members 37 and 38. Each of the angle bars 31, 32, 35 and 36 is provided with holes or openings adapted to receive J-bar hooks which are threaded at one end and inserted through the openings where they areheld in place by nuts. The I-bar hooks are designated by numbers 39, 40, 41 and 42 and the hook end is inserted through openings 43, 44, 45 and 46 in the plate electrodes. The plate electrodes are reinforced at the ends by laminated metal strips 47 and 48.

In the alternative type of plate electrode shown in FIGURE 6 the effective electrode area consists of electrically conducting metal screen or mesh 49 and the openings from which the electrode is supported are designated by numbers 50, 51, 52 and 53. Metal strips 54 and 55 are provided on opposite ends of each of the screen electrodes 49 for reinforcement.

In FIGURES 1 and 2 the electrodes 7 are solid rods. An alternative type of electrode which may be substituted for the rods is illustrated in FIGURE 4. This consists of a tubular member 56 having a hollow space 57 therein and preferably closed at the ends 58 and 59. The end 58 is preferably rounded as shown in FIGURE 4, especially if this end projects below the plate electrodes. The end 59 may be provided with threads adapted to receive a cap and the electrode can be held in place by inserting it through openings in the supporting elements 10 and then applying a cap to the threaded end.

A plate bafile 60 which is welded or otherwise secured to the interior of the container 1 directs the liquid issuing through the openings 6 so that it must pass between the electrodes rather than around them. The end plate electrodes 8 are welded or otherwise secured to the baffle 60.

At the bottom of the container 1 an outlet 61 is provided for the removal'of the coalesced discontinuous phase.

Referring to FIGURE 3 it will be seen that the bushing 27 is provided with a flange 62 which seats on a partition 63 in the housing for the bushing. The partition 63 prevents liquid from the space 64 from passing into the compartment 65. The upper end of the element 27 is provided with a metal member 66 which is electrically connected to a metal member 26 through the insulating portion of the bushing. The member 66 is also connected to the electrical conductor 30 which in turn is connected to a unidirectional potential power supply through the power unit bushing 29.

As shown in FIGURE 9 the power unit bushing 29 has a flange portion 67 which seats against an annular member 68 and is secured to said member 68 in any suitable manner thereby preventing the passage of liquid from the undirectional power supply 28 to compartment 65. A small hole or capillary 69 is provided to remove small amounts of liquid which might form or be present in compartment 65. The conductor 30 is connected at one end to a metal conductor 70 by means of a bolt and washer assembly generally indicated at 71. The other end 72 of the conductor 70 is connected to the unidirectional potential power supply in any suit-' able manner.

The suspension bushing shown in FIGURE 7 is provided at one end with a threaded nut 73 adapted to receive a threaded rod 74 (FIGURE 3) which extends through a cross member 75 supported and secured to the upper part of the inside of the housing 21. In this manner the bushing 20 is suspended in the housing 21 and the rod 19 is centrally positioned and spaced from the inside of the housing as it passes into container 1. The insulating portion of the bushing 20 insulates it and the rod 19 from the housing 21 and hence from the container 1. Similarly, the rod 17 is centrally positioned in the housing 18 and is insulated from the housing 18 and from the container 1 by the insulating portions of the bushing 27. At the same time, the undirectional potential from the power supply passes through the interior of the bushing 27 to the rod 17 and thence to the suspended rod-like or tubular electrodes 7.

In the apparatus described, suitable valves, not shown, are provided to control the flow through the pipe 4 of the liquid to be treated and the flow through the pipe 9 of the treated liquid. A suitable valve, not shown, is also provided in order to control the flow through pipe 61 of the coalesced liquid from the discontinuous phase at the bottom of the container 1. Ordinarily the discontinuous phase occupies a vertical depth of about twelve to eighteen inches in the bottom of the container.

The invention is useful for treating a wide variety of hydrocarbon oils, such as petroleum oils, shale oils and extracts and distillates derived therefrom, especially Where such oils, extracts and distillates have been chemically refined with an acid or alkaline treatment, so that they contain a disperse or discontinuous phase which is either acid or alkaline and which must be removed from the oil in order to improve its quality. Examples of treatments which produce such disperse or discontinuous phases are sulfuric acid treatments, sodium hypochlorite treatments, caustic alkali treatments, treatments with doctor solution andany treatments which introduce an aqueous discontinuous phase into the oil.

The bulk of the dispersed or discontinuous phase is coalesced in the first few inches of the highly non-uniform field at the bottom of the electrodes. The non-uniform field causes rapid random motion of the dispersed particles which promotes a large number of collisions and subsequent coalescence.

A variety of coalescing actions take place in the bulk of the field. A great deal of coalescence takes place in situ in the emulsion because of the forces the individual droplets exert on each other in the presence of the electric field.

The non-uniformity of the field in the vertical plane causes the particle to move by cataphoresis to one of the electrodes where they coalesce on the electrodes. Part of the dispersed phase drains from the bottom of the electrodes. Other portions of the dispersed phase are repelled from the electrode at right angles to the flow. These droplets fall lower and lower in the electric field as they move from one electrode to the other. motion between the electrodes makes it almost impossible for a dispersed particle to pass through the electric field without colliding with another particle.

When a particle reaches sufiicient size to fall by gravity, it settles downward against the upward flowing emulsion and increases in size by coalescence with the dispersed particles in the rising emulsion.

It is a necessary part of this invention that the flow be vertical. It is most advantageously employed when the applied unidirectional potential can be varied. The efiiciency of this inventionis very dependent upon the optimum voltage being applied. This optimum voltage will vary with the emulsion being treated.

As an illustration of the practical operation of the invention the following example is given:

The large number of these particles in rapid Example A light cycle oil was mixed with 3 volume percent of 30 B. aqueous caustic solution and passed through an electrical treater of the general type previously described at a temperature of 76 F. The treater contained rod electrodes inch in diameter, 5 inches long, spaced apart one inch, center to center, and disposed in rows equidistant between plate electrodes 10 inches wide and 4 inches deep spaced 2 inches apart. The plates projected about one inch below the rod electrodes and there was a vertical distance of about 3 inches where the rods and plate electrodes formed a common field. 'A unidirectional potential of 5,000 volts per inch was applied with a maximum amperage not exceeding 85 milliamperes. The volume of flow was 600 cc. per minute. The coalesence of the caustic soda solution present in the dispersed phase of the oil took place in a very short period of time as the oil fiowed continuously through the treating apparatus and the coalesced caustic soda solution was removed through the outlet 61. The treated oil was removed through the outlet header 9 and was found to contain 0.0014 volume percent caustic soda solution.

A comparative test made under identical conditions with the same voltage gradient in an electrical treater which was the same except that parallel vertical plates were substituted for the rows of rod electrodes gave a treated oil containing 50% more caustic soda solution by volume. Thus the invention gave a 50% improvement over the results obtained by using an apparatus in which both sets of electrodes consisted of plates.

No explanation can be offered for this improvement except that the use of rows of rods or tubes between plates provides an unusual electrical field due to the arrangement of the planar surfaces of the plate electrodes and the non-planar surfaces of the rows of rods or tube electrodes. This field evidently produces exceptional nonunity in all directions and enhances the coalescence of the discontinuous phase of the liquid being treated.

The residence time of the liquid to be treated in the treating apparatus will vary depending upon the type of emulsion, the size of the treating unit, the particular electrical potential employed, and the temperature used. In general, the residence time will vary from five to forty minutes and this is controlled by controlling the flow rate of the liquid introduced into the treating'apparatus.

The temperature is usually subject to variation but ordinarily will be within the range of 40 F. to approximately F. and this will vary depending upon the particular emulsion to be treated.

The predetermined electrical potential may be supplied in any convenient manner normally used to produce a direct current. It is generally preferable to provide a direct current by employing a three-phase system wherein the deviation of the maximum voltage from the average voltage, generally known as the ripple factor, is reduced so as to effect a reduction in pulsation. However, a single phase system can also be used. A single phase system pulses constantly with the ripple factor being approximately 52%. In a three-phase system the ripple factor is reduced to about 4%. Other forms of unidirectional potential can be employed such as are derived, for example, by superimposing an alternating current on a direct current to produce a pulsating direct current which is unidirectional.

The coalesced discontinuous phase which settles in the bottom of the treating vessel may be removed intermittently or continuously. It is usually preferable to provide a level control, not shown, which operates a valve,

not shown, connected to the outlet 61 when the coalesced discontinuous phase reaches a predetermined level.

The invention is especially useful in treating oils in which the dispersed or discontinuous phase does not exceed about 3% by volume of the oil to be treated.

In general, however, the invention is useful in treating any oil continuous emulsions, some of which can contain as high as 40% by volume of the discontinuous phase.

The invention is hereby claimed as follows:

1. An electric treater for treating oil continuous emulsions, said treater comprising a container, a set of spaced, vertically disposed, substantially parallel planar electrodes, rows of non-planar electrodes extending vertically in the spaces between said planar electrodes substantially equidistant from each other and from said planar electrodes, a source of unidirectional potential connected to said electrodes, an inlet for said oil continuous emulsion below said electrodes, an outlet for the treated oil above said electrodes, and means for withdrawing a coalesced discontinuous phase from said container.

2. An electric treater for treating an oil continuous emulsion, said treater comprising a container, a set of electrodes in said container consisting of alternate vertical plate electrodes, rows of vertical electrodes of substantially round cross section, the plate electrodes being from 2 to 14 inches apart, the substantially round electrodes being substantially equidistant from adjacent plate electrodes, the spacing between the substantially round electrodes being approximately equal to the distance between the substantially round electrodes and the plate electrodes, a source of unidirectional potential, means connecting said source of unidirectional potential to said electrodes, an emulsion inlet header located below said electrodes, an oil outlet header located above said electrodes through which the treated oil is withdrawn, and means for withdrawing the coalesced discontinuous phase.

3. An electric treater as claimed in claim 2 in which the vertical plate electrodes are replaced by Wire mesh.

4. An electric treater as claimed in claim 1 in which the source of unidirectional potential is infinitely variable up to 40,000 volts.

5. An electric treater for treating an oil continuous emulsion, said treater comprising a container, a set of electroda in said container consisting of alternate vertical plates spaced about 6 inches apart, rows of vertical substantially round electrodes approximately A1 inch in diameter positioned equidistant from said plates and spaced about 3 inches apart, center to center, in said rows, means connecting a source of unidirectional potential to said electrodes, an emulsion inlet header located below said electrodes, a treated oil outlet header located above said electrodes, and means for withdrawing a coalesced discontinuous phase from the lower part of said container.

6. An electric treater as claimed in claim 2 in which said vertical electrodes of substantially round cross section are solid cylindrical rods.

7. An electric treater as claimed in claim 2 in which said vertical electrodes of substantially round cross section are cylindrical tubes.

8. An electric treater as claimed in claim 5 in which the lower ends of said vertical electrodes of substantially round cross section extend below the lower-ends of said vertical plates.

9. An electric treater as claimed in claim 1 in which the ratio of the planar surface area of the planar electrodes to the non-planar surface area of the non-planar electrodes is Within the range of 4:1 to 1:1.

10. An electric treater as claimed in claim 5 in which the ratio of the electrode plate area to the total area of the electrodes of substantially round cross section is approximately 2.5 :1.

References Cited by the Examiner UNITED STATES PATENTS 1,414,079 4/ 1922 Giebner 204305 2,033,567 3/1936 Worthington 204305 2,588,111 3/1952 Hanneman 204302 2,681,311 6/1954 De Wit 204302 2,855,356 10/1958 Stenzel 204302 2,884,375 4/1959 Seelig et al. 20428 2,976,228 3/1961 Waterman et al 204302 FOREIGN PATENTS 88,004 4/ 1958 Netherlands.

OTHER REFERENCES Ser No. 340,856, Barbier (A.P.C.), published May 18, 1943.

JOHN H. MACK, Primary Examiner.

MURRAY TILLMAN, Examiner.

Claims (1)

1. 2. AN ELECTRIC TREATER FOR TREATING AN OIL CONTINUOUS EMULSION, SAID TREATER COMPRISING A CONTAINER, A SET OF ELECTRODES IN SAID CONTAINER CONSISTING OF ALTERNATE VERTICAL PLATE ELECTRODES, ROWS OF VERTICAL ELECTRODES OF SUBSTANTIALLY ROUND CROSS SECTION, THE PLATE ELECTRODES BEING FROM 2 TO 14 INCHES APART, THE SUBSTANTIALLYROUND ELECTRODES BEING SUBSTANTIALLY EQUIDISTANT FROM ADJACENT PLATE ELECTRODES, THE SPACING BETWEEN THE SUBSTANTIALLY ROUND ELECTRODES BEING APPROXIMATELY EQUAL TO THE DISTANCE BETWEEN THE SUBSTANTIALLY ROUND ELECTRODES AND THE PLATE ELECTRODES, A SOURCE OF UNIDIRECTIONAL POTENTIAL, MEANS CONNECTING SAID SOURCE OF UNIDIRECTIONAL POTENTIAL TO SAID ELECTRODES, AN EMULSION INLET HEADER LOCATED BELOW SAID ELECTRODES, AN OIL OUTLET HEADER LOCATED ABOVE SAID ELECTRODES THROUGH WHICH THE TREATED OIL IS WITHDRAWN, AND MEANS FOR WITHDRAWING THE COALESCED DISCONTINUOUS PHASE.

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