Title:
Method and apparatus for electrically treating fluids
United States Patent 2364118


Abstract:
This invention relates to electrical treatment of fluids and, more particularly, to a method and apparatus for electrically resolving emulsions of water and oil into their constituent phases. The treatment of water-in-oil emulsions by high-tension alternating fields has found wide industrial...



Inventors:
Halley, Wolfe
Application Number:
US26608939A
Publication Date:
12/05/1944
Filing Date:
04/05/1939
Assignee:
PETROLITE CORP
Primary Class:
Other Classes:
204/671, 204/672
International Classes:
B01D17/06; C10G33/02
View Patent Images:



Description:

This invention relates to electrical treatment of fluids and, more particularly, to a method and apparatus for electrically resolving emulsions of water and oil into their constituent phases.

The treatment of water-in-oil emulsions by high-tension alternating fields has found wide industrial application, particularly in connection with the dehydration of crude oil emulsions and the like. Such treatment ordinarily comprises the passage of the emulsion between surfaceuninsulated energized electrodes, the action of the electric field causing coalescence of the dispersed droplets to masses large enough to respond to gravitational settling. Other effects conducive to settling may also be attributed to the field. In general, however, the field effects depend upon the gradients which are established through the oil.

With the usual type of treater in which the bare electrodes are immersed in or are contacted by the emulsion, the voltage gradient that can be applied is Influenced by the fact that chains of water particles are formed between the electrodes, thus decreasing the effective length of insulating oil in the gap and resulting in dielectric breakdown short-circuiting, and consequent high currents. An occasional breakdown can be tolerated but, if the occurrence becomes too frequent, the power 'consumed becomes excessive, and, what is worse from the standpoint of treatment, the average voltage between the electrodes usually drops due to regulation in the transformer-choke coil combination.

It is an object of the present invention to provide a method and apparatus for the electric treatment of water-in-oil emulsions in which the desired potential gradient is substantially maihtained throughout all parts of the oil, irrespective of the condition of the emulsion or the variation of effective length of the dielectric oil in the inter-electrode gap due to local formation of conducting chains and the like. It is, furthermore, an object of the invention to provide treatment of the kind described in which high gradients may be maintained in the oil without dielectric breakdown, short-circuiting, excessive current consumption, and the like, by providing electrode or bounding surfaces which are not necessarily equipotential surfaces.

In accordance with this invention, a dielectric is interposed between the electrodes, constraining the emulsion as a layer of limited thickness in the field, whereby, with due reference to the respective thicknesses, specific resistances and specific capacitive reactances of the dielectric and emulsion, and the frequency of the imposed potential, the major portion of the voltage drop between the electrodes is taken up by the interposed dielectric, and only a minor portion thereof is imposed across the emulsion. By this means, major variations in the effective insulating thickness of the oil, such as may be caused by the formation of conducting chains, produce only relatively minor variations in the gradient in said oil. In effect, the potential difference across the emulsion layer at any given point is maintained substantially proportional to the effective dielectric thickness of the oil included in the emulsion at that point and, hence, the desired optimum gradient can be maintained in all other parts of the oil without dielectric breakdown, the dielectric surface bounding one side of the emulsion layer being non-conducting and, hence, not necessarily equipotential.

It is, accordingly, an object of the present invention to provide for the treatment of an emulsion as a layer in an inter-electrode space in series with an inter-electrode dielectric layer, the dielectric layer being arranged to take up a major portion of the potential difference between the electrodes.

It is, furthermore, an object of the invention to provide a method and apparatus for the application of a potential difference across a layer of emulsion which varies locally according to the local dielectric thickness of the layer, the layer being bounded on one side by a non-equipotential surface.

By a non-equipotential surface I have reference to a surface of high surface resistivity, which may or may not be equipotential under ideal conditions in which the emulsion is everywhere uniform, but which becomes a non-equipotential surface under conditions of local electric breakdown of the emulsion, the variations in the potential of the surface arising from such a local breakdown being restricted to that area of the surface in the immediate vicinity of the breakdown.

46 In accordance with my invention, I prefer to use alternating fields of high frequency such that the capacitive reactance of the emulsion layer becomes small with respect to its resistance, whereby the relative voltage drops across the interposed dielectric and the emulsion layer ap-' portion themselves according to the respective capacitive reactances, and whereby the dielectric may be suitably chosen on the basis of its specific inductive capacity.

It is, accordingly, an object of the present in2 3,5* ventlon to treat an emulsion layer with alternating fields of such frequency that the capacitive reactance of the emulsion layer is small with respect tb its resistance. It is, furthermore, an object to impress such a field across a space containing a dielectric layer whose capacitive reactance is at least equal to that of the emulsion layer, whereby the major portion of the voltage drop Is taken up by the dielectric layer and only a minor portion of the voltage drop is Impressed across the emulsion layer.

In accordance with my invention, I may also provide that the electrode in contact with the emulsion layer has a water surface, i. e., the electrode may be formed of a conducting body of water, or a water-wet septum, or similar wet material, such that the droplets of water in the emulsion being treated may coalesce directly with said body of water, as well as with each other, or such that the partially coalesced masses of water in the oil may be removed directly from the oil without necessity for the usual settling process.

Further objects and aspects of the invention will be apparent from the following discussion of the drawing, in which: Fig. 1 is illustrative of conditions present between the electrodes in conventional electrical treating practice.

Fig. 2 is illustrative of conditions present in emulsions being treated according to my invention.

Fig. 3 is a section of an apparatus embodying my invention.

Fig. 4 is a plan view of the same apparatus.

Fig. 5 Is a section of another apparatus embodying my invention.

Fig. 8 is a section of another apparatus embodying my invention.

Fig. 1 is intended to be illustrative of the formation of conducting chains of water dropleti such as give rise to dielectric breakdown anc short-circuiting in the usual type of treater Conducting electrodes 10 and II form equipoten. tial surfaces separated by a space containine the emulsion undergoing treatment. Disperse( throughout the oil are the emulsified water drop lets which are represented by the greatly mag. ninfed spheres 12. A normal path for the elec trostatic lines of force is shown by the dotte line ii. A chain of water droplets and of larger partially coalesced masses of water is shown b. the dotted line 14. In each instance, the patl is taken through the drops in order to penetrat the minimum possible thickness of oil and repre sents the path along which electric breakdow2 with high current flow would occur if the im pressed voltage becomes too high. It is seen tha the thickness of the oil along the path 14 is ver much less than the thickness of the oil along th path 13 and, for purposes of argument, the rati may be taken as 1:10. When the impresse voltage is such that the oil along the path 14 at incipient breakdown, the oil along the pat, 13 will be stressed to only one-tenth of its break down value. As a result, far less than the opti mum treating is obtained along the path 13. I other words, to prevent the breakdown of to many paths, such as 14, the voltage gradient ani hence the coalescing forces in the main body emulsion must be maintained far below tU theoretically allowable value. In practice, I ha\ found that it is rarely possible to impose o such a system a gradient more than one-third ( the theoretically allowable value without obtair ing undesirable short-circuiting and power coi sumption.

94,118 Fig. 2 illustrates the conditions obtaining in a system embodying my invention. I5 and II are energized electrodes and interposed therebetween is a dielectric layer I7, leaving a layer I1 which may be filled with the emulsion, as illustrated. It is assumed that a high frequency potential is employed such that the impedance of the system is largely dependent on the capacitive reactances of the dielectric and the emulsion. The dielectric constant of the dielectric may be assumed to be about equal to the dielectric constant of the oil or emulsion so that the voltage gradient is the same in both, and the dielectric layer II may be taken of such thickness that it is ten times the thickness of the layer space I8, whereby about 90% of the voltage drop across the electrodes is taken up by the dielectric layer 17, and only about 10% is impressed across the emulsion layer. Assuming that the layer IS Is filled with a dry oil corresponding to the continuous phase of the emulsion which is to be treated, and assuming that this dry oil has a dielectric strength of about 25,000 volts per inch, a total voltage may then be impressed across the electrodes such that the gradient in the oil is about 22,000 volts per inch, and manifestly no breakdown will result. Now, let a cluster or chain of water particles, such as illustrated along the dotted line 19, be formed in the oil layer, as will happen when the dry oil is replaced with 3 emulsion. The effective dielectric thickness of the oil along the path 19 may correspond to only one-tenth of the thickness of the layer 18. However, the reactance between the electrodes in this S$ vicinity will have only dropped to 91% of its former value since the oil at niost can contribute but 10% of the total reactance, the remainder being afforded by the dielectric 17. With the same impressed voltage on the electrodes, the S0 gradient through this region in the vicinity of I the path 19 will have risen only to 22,000 divided by 0.91, or 24,200 volts, which is still well below . the breakdown gradient for the oil concerned.

g namely, 25,000 volts. It will thus be seen that S4 the gradient maintained in the oil is substantially . constant irrespective of the condition of the S emulsion or the formation or length of conductS ing chains. In effect, the potential difference d across the layer t1 is at any given point auto. o matically dropped to about the same degree that y the thickness of the oil is reduced whenever h chains or other conducting systems are set up in o the emulsion. Thus, the potential difference impressed across the layer of the emulsion varies n 55 locally according to the local impedance of the . emulsion and is always substantially proportional ,t to the thickness of the oil included within the y emulsion layer at thatha point.e Hence, no matter what the water content may o be of the emulsion in the treating space, the oil d phase thereof will not be stressed beyond the is breakdown point. Furthermore, even though a h chain broke down and became conducting, a high S current could not flow because no connection - would thereby be established to the electrode II, n the dielectric I7 still remaining a substantial 0o barrier. Furthermore, the voltage gradient on i. the rest of the emulsion would be unaffected beof cause the surface of the dielectric in contact with e 0 the emulsion is laterally non-conducting and re may exist as a non-equipotential surface. Hence, In full voltage may always be maintained across the )f electrodes and the desired treating gradient ali- ways maintained in the emulsion whereby opti1- mum treating may be obtained under all condi76 tions. Also, the power consumed by this system remains negligible under the varying conditions.

In the above explanation, certain simplifying assumptions have been made for clarifying the exposition, but it is not intended to limit the invention to such simplified conditions. For example, the ratio of the thickness of the dielectric layer to the emulsion layer need not be 10:1, and may be any value dependent upon the electrical characteristics of the two layers such that the impedance of the dielectric layer is greater than the impedance of the emulsion layer. Furthermore, it is unnecessary for the dielectric constant of the dielectric to be the same as the dielectric constant of the oil for, while it is convenient for purposes of illustration to assume approximately the same voltage gradient in the dielectric and in the oil, it is not essential that they be the same. Also, the voltage gradient in the oil films between the water droplets of a cluster would be somewhat higher than that calculated because of convergence of the lines of force, but this does not introduce substantial error into the argument.

At relatively high frequency, for example 100,000 to 200,000 cycles per second, the reactance between the electrode plates will be much lower than the resistivity of the oil or the dielectric and, hence, the voltage gradients in these two media will be inversely proportional to their respective dielectric constants, and the potential difference across each layer will be equal to the product of the gradient in the layer times the thickness of the layer. While, theoretically, the dielectric may be sufficiently characterized by its dielectric constant, practically, it should also be chosen to have a dielectric strength such that no breakdown of the dielectric will occur even though the emulsion becomes short-circuiting, and its resistivity should be sufficiently high that it may be effectively regarded as an insulator or non-conductor.

Another advantage resident in my invention resides in the fact that water particles of any substantial size are removed directly from the relatively thin layer of emulsion by electrical attraction to the electrode 'without the necessity of settling. When a conducting particle comes near a charged plate, it becomes inductively charged, the charge being so distributed that there is a net attractive force. Hence, the larger water particles, as they are formed in the space 18 of Fig. 2, will be drawn downwardly out of the oil and, thus, the settling process will be accelerated by the electrostatic attraction which, in many instances, will be several times as large as the gravitational forces. By making the electrodes 16 consist of a surface of a conducting body of water or a water-wet septum, the particles thus separated are immediately coalesced therewith and removed from the treating space (8. f FJgs. 3 and 4 show sectional and plan views of an apparatus embodying my invention. 30 is a tank containing a body of water 31 and having a water overflow pipe 32. The tank 30 is provided with a shoulder 33 near its upper extrem- fi ity in which the dielectric slab 34 is hermetically sealed by a gasket 35. Attached to the dielectric slab 34 by means of screws 36 is a separating gasket 37 which also serves to define the horizontal extension of the treating space, a water-wet sep- 7 tur 38. for example, a layer of water-wet canvas, and a perforate support 39 for the septum, suitably a perforated metallic plate. There is thus defined a layer or zone of the treating space 40 between the central portion of the dielectric 7 Sslab 34 and the water-wet septum 38. Emulsion is introduced into one end of the treating space 40 by means of a pipe 41, and dry oil is removed from the other end of the space 40 by means of a pipe 42. A conducting electrode 43 is carried on top of the central portion of the dielectric slab 34. The plan view of the electrode 43 is shown clearly in Fig. 4, and also the lateral extensions of the treating space 40, as defined by the separating gasket 37, this gasket being shown in dotted lines in Fig. 4. The electrode 43 is energized by high potential, high frequency current from a high frequency generator 44. The companion electrode is formed by the water-wet septum 38 and may conveniently be grounded by grounding tank 30. The septum 38, being water-wet, comprises a water surface bounding the electric field.

The inter-electrode space is thus constituted by the treating layer 40 and the dielectric layer 34, and the relative thickness of these two layers is so adjusted that a sufficiently large proportion of the voltage drop across the electrodes is taken up in the dielectric so that variation in the impedance of the emulsion in the layer 40 will have relatively little effect on the gradient in the oil phase in the layer.40.

When the emulsion is introduced through the pipe 41 by means of a pump or other suitable device, it spreads out as a layer in the treating space 40. This oil-continuous layer will not pass through the water-wet septum because of the repellent character of the latter for the oil and, furthermore, any hydrostatic head tending to force the oil through the septum may be counterbalanced by suitably adjusting the back pressure in the water overflow pipe 32. The emulsion thus traverses the treating space 40 and is subJected to the treating action of the electric field.

Very high gradients may be maintained in the emulsion' in the layer 40, as hereinbefore explained, and the emulsion is thereby quickly and effectively treated, the small droplets coalescing into larger ones. These larger droplets settle, or are electrostatically attracted or otherwise migrate, to the water-wet septum and are there coalesced into the water-continuous phase represented by the body of water 31. The dry oil substantially free from water particles is removed through the pipe 42, and water equivalent in volume to the separated water is removed through the water overflow pipe 32.

While the maintenance of suitable impedance ratios between the dielectric layer and the emulsion layer is the essence of my invention, this ration can be varied over rather wide'limits according to the character of the emulsion treated the potentials employed, and the like. If it is desired to work with gradients in the oil- which are near the dielectric breakdown value of the 1o oil, then a dielectric having a substantially greater impedance than that of the oil should be employed so that the gradient in the oil may be very substantially stabilized so that no danger of breakdown will be present. On the other 15 hand, if the emulsion is readily treated at gradients somewhat below the maximum allowable gradient, the impedance of the dielectric may be made equal to that of the emulsion layer, and there will still be obtained a substantial'. lessened 0 sensitivity of the gradient in the oil layer to local changes in the impedance thereof, such as occasioned by the formation of conducting chains and the like. -As a rule, excessive ratios of dielectric impedance to emulsion impedance 5 are not practical because they will require the application of unduly high voltages across the electrodes in order to obtain the desired potential across the emulsion, or will require working with very thin layers of emulsion such that a small potential thereacross will set up the desired gradient.

While substantially lessened sensitivity of the gradient through the oil may be obtained when the ratio of dielectric impedance to emulsion impedance is as low as one, I find that, in practice, 1 best results are obtained when working in the ratio range of 3 to 8, although, in some Instances, it may be desirable to go to ratios of 10 or 20, or even higher. As a rule, I find that excellent treating is obtained when the thickness of the i emulsion layer is adjusted to give a gradient therein from 60 to 80% of the dielectric strength of the dry oil, although, in some instances, higher and lower gradients than correspond to this range may be advantageously employed to secure 2 effective treating.

If desired, the electrode 43 of Fig. 3 may be covered by a layer 45 of transformer oil or other oil suitable for reducing corona effects.

In Fig. 5, an alternative embodiment of my 2 invention is illustrated. Here, the energized electrode 50 is placed inside and adjacent the bottom of a dielectric cup 51. The bottom of the dielectric cup provides the inter-electrode dielectric layer of my invention. This cup is suitably positioned in a container 52 filled with water up to the level 53. Emulsion is introduced by means of a pipe 54 and discharged at a point centrally under the electrode 50. The emulsion rises until in contact with the bottom of the cup 51 and then spreads itself as a thin film 55, the thickness of which is determined by the thickness of a dam ring 56, preferably constructed of material which is preferentially wetted by oil, e. g., rubber. Treatment takes place in the film 55 substantially as described hereinbefore, the water at the level immediately below the film 55 forming a water surface bounding the field. The dry oil flows under the dam 56 and passes upwardly to accumulate as a body of oil 51, suitably restrained by a cylindrical barrier 58. Treated oil is removed from the body of oil 57 by means of a pipe 59, and the separated water is removed from the container 52 by means of a pipe 59a. The apparatus shown in Fig. 5 is particularly adapted for use with high frequency current such that the relativevoltage drops across the dielectric barrier and across the emulsion film 55 are adjustable according to the thickness and specific inductive capacities of the layers concerned to give the desired ratio of potential drops. The dielectric cup should have sufficient dielectric strength to receive the entire applied potential, however, without being over-stressed.

In Fig. 5, the top of the electrode 50 may be suitably protected against corona effect by covering it with an oil having good dielectric properties, such as transformer oil.

Fig. 6 shows a vessel 10 having an emulsion inlet pipe 71, oil withdrawal pipe 12, and water withdrawal pipe 73, the upper or treating portion of which vessel is filled with a battery of electrodes 74 in dielectric cups. With regard to the dielectric cups and electrodes there illustrated, the chief difference with regard to the cup and electrode assembly shown in Fig. 5 lies in the upturned edges of the electrodes 14 in Fig. 6. Alternate electrode assemblies are charged to opposite polarities by a source of high potential 7I, and fields are thus set up between the upturned edges of neighboring electrodes which are effective in further treating the oil layer therebetween, the lower level of the oil layer being preferably maintained below the electrodes '14.

I find that the apparatus and construction Illustrated in Fig. 6, as well as that in Fig. 5, is advantageously employed in electrically treating 0 emulsions generally, irrespective of the adjustment of relative voltage drops in dielectric and emulsion. It is, therefore, a further object of the invention to provide such novel arrangement of apparatus for electrically treating emuls sions and, in particular, to provide a treating space containing a plurality of dielectric cups containing electrodes of alternately opposite polarity.

It is to be understood that the above examples o0 of methods and apparatus embodying my Invention are illustrative rather than limiting, and that various other modifications may be employed which embody my invention without departing from the scope of the appended claims.

> I claim as my invention: 1. A process of treating emulsions of the water-in-oil type with an electric field, comprising: impressing a high tension high frequency alternating-current potential across a field space de10 fined by two electrodes; maintaining a layer of solid dielectric medium in one portion of said inter-electrode field space adjacent one electrode, said layer cooperating with the other of said electrodes in defining, a treating space 85 comprising a zone of the inter-electrode space unoccupied by said layer of dielectric; and passing the emulsion to be treated through said treating space as a layer bridging said zone, said dielectric layer being characterized by such capacitive reactance at the frequency employed, relative to the capacitive reactance of the emulsion layer at the frequency employed, that the portion of the impressed voltage absorbed by said dielectric layer is at least three times the portion absorbed by the emulsion layer, whereby the potential gradient in the oil of said emulsion is rendered substantially non-sensitive to changes in impedance of said emulsion, said potential being of sufficiently high frequency that the capacitive reactance of the emulsion layer is small relative to its resistance.

2. A process as in claim 1 in which the capacitive reactance of the dielectric layer is not greater than 20 times the capacitive reactance of the emulsion layer.

3. A process of treating oil-continuous emulsions, comprising: subjecting a layer of emulsion in series with a layer of solid dielectric having a non-conducting surface contacting said layer so of emulsion to the action of a high potential high frequency alternating-current field, said dielectric layer being characterized by a capacitive reactance at said high frequency which is at least three times and not greater than twenty times the capacitive reactance of said emulsion layer, whereby the voltage drop across said emulsion layer varies locally according to the local capacitive reactance of the emulsion layer and is greater than three and not more than twenty times the voltage drop across the emulsion layer.

4. A process as in claim 3, in which the frequency of the alternating field is maintained greater than 100,000 cycles per second.

5. A process of treating water-in-oil emulsions, comprising: flowing the emulsion as a thin layer in a space defined by a solid dielectric and a conducting electrode, said dielectric being positioned between said conducting electrode and a second electrode; and maintaining a high tension high frequency alternating-current field across said emulsion and dielectric by energization of said electrodes, said dielectric being of such dimension and of such capacitive reactance at said high frequency as to absorb a portion of the potential drop in said field which is at least three times the portion absorbed by said emulsion layer.

6. A process as in claim 5 in which the conducting electrode is an electrode having a water surface bounding said space.

7. In combination in an apparatus for electrically treating water-in-oil emulsions: two electrodes defining an inter-electrode field space; a solid dielectric layer positioned to extend along said field space adjacent one electrode and defining with the other electrode boundary surfaces of an inter-electrode treating space, the boundary surface of said dielectric being characterized by a high surface resistivity; means for introducing. emulsion into said treating space; discharge means from said treating space for conducting electrically-treated emulsion constituents therefrom; and means for energizing said electrodes with high potential high frequency alternating current, said dielectric layer being characterized by such capacitive reactance at the high frequency employed relative to the capacitive reactance of the emulsion between said boundary surfaces at the frequency employed that the voltage drop across the dielectric layer is at least three times the voltage across the emulsion in said treating space whereby a substantially constant gradient is maintained in the oil irrespective of variations in electric impedance of the emulsion and a minor fraction of the voltage drop is impressed across said emulsion, said minor fraction being sufficient to set up effective treating gradients in the oil of said emulsion.

8. In apparatus for treating emulsions of water in oil, the combination of: two spaced electrodes; means for impressing upon said electrodes an alternating electromotive force, whereby an alternating electric field is set up and an alternating current is caused to flow between said electrodes, the frequency of said electromotive force being sufficiently high to result in the capacitive reactance of a given body of said emulsion being small compared to the resistance of said body of emulsion; means to pass the emulsion to be treated between said electrodes in a stream of limited thickness; and a solid dielectric medium interposed in series with said emulsion stream between said electrodes, the thickness and specific inductive capacity of said solid dielectric medium at said frequency being such that the capacitive reactance of said solid dielectric medium encountered by said alternating current is at least three times the capacitive reactance of said emulsion stream.

9. A process for the separation of water from an emulsion of the water-in-oil type by use of an electrode means having a water surface, which process includes the steps of: establishing a high-frequency alternating-current electric field to said water surface; disposing in said field a layer of solid dielectric material separated from said water surface by a small treating space containing a layer of the emulsion immediately adjacent said water surface, said layer of solid dielectric material having such capacitive reactance at the frequency employed, relative to the capacitive reactance of the emulsion layer at the frequency employed, that the portion of 6 the impressed voltage absorbed by said layer of solid dielectric material is at least three times the portion absorbed by the emulsion layer whereby said field acts to coalesce the water droplets of said emulsion and electrically attract those adjacent said water surface to bring the coalesced water droplets directly to said surface; and maintaining the water surface in substantially constant spacial relationship to the dielectric barrier.

10. In combination in an apparatus for treating emulsions of the water-in-oil type by use of an electrode means having a horizontally disposed Water surface: a substantially horizontal electrode disposed above said water surface; a source of high-potential, high-frequency, alternating-current connected between said electrode and said water surface; a layer of solid dielectric material below said electrode and providing a lower surface substantially parallel to said water surface but spaced therefrom to define a shallow treating space containing the emulsion to be treated, said layer of solid dielectric material being characterized by such capacitive reactance at the frequency employed, relative to $0 the capacitive reactance of the emulsion layer at the frequency employed, that the portion of the voltage impressed between said electrode and said water surface which is absorbed by said layer of solid dielectric material is at least three g5 times the portion absorbed by the emulsion being treated, whereby the potential gradient in the oil of said emulsion is rendered substantially non-sensitive to changes in impedance of said emulsion, said electric field acting to coalesce the water droplets of said emulsion and electrically attract those adjacent said water surface to bring the coalesced water droplets into coalescing contact with said water surface; and means for withdrawing.the thus-collected water from a zone below said water surface.

11. In combination in an apparatus for treating emulsions of the water-in-oil type: an upper electrode extending substantially horizontally; a lower electrode comprising a water-wet septum providing a water-wet surface extending substantially horizontally; alternating potential means for energizing said electrodes to establish a field therebetween terminating at said waterwet surface; a layer of solid dielectric material B5 in said field below said upper electrode and providing a lower surface, spaced from said waterwet surface of said septum to define an emulsion-treating space; means for delivering emulsion to said treating space to fill the zone between said lower surface of said dielectric layer and said water-wet surface whereby said oil contacts said lower surface of said layer of solid dielectric material to prevent water-wetting thereof and to maintain a high surface resistiv05 ity, said electric field acting to coalesce the water droplets of said emulsion and electrically attract those adjacent said water-wet surface to bring the coalesced water directly to said surface for movement through said water-wet septum said layer of solid dielectric material having sufficient dielectric strength to withstand without electrical breakdown the entire potential applied between said electrodes by said alternating potential means and being of such carT pacitive reactance with respect to the capacitive reactance of said emulsion as to absorb a portion of the potential between the electrodes which is at least three time the portion absorbed by said emulsion; and means for removing water from a position below said septum.

12. In combination in an apparatus for treating emulsions of the water-in-oil type: a body of solid dielectric material providing upper and lower surfaces and disposed substantially horizontally; a first electrode adjacent said upper surface; a body of water providing a surface below said lower surface and cooperating therewith to form a treating space; means for introducing emulsion in an upward direction into the central portion of said treating space, whereby said emulsion spreads outward and moves through said treating space; and means for maintaining an alternating potential difference between said electrode and said body of water of sufficient intensity to coalesce the dispersed water droplets of said emulsion, said body of solid dielectric material providing sufficient dielectric strength to withstand without electrical breakdown the entire potential applied by said last-named means between said electrode and said body of water and being of. such capacitive reactance with respect to the capacitive reactance of said emulsion as to absorb a portion of the potestial difference between the electrodes which is at least three times the portion absorbed by said emulsion.

13. In combination in an apparatus for treating emulsions of the water-in-oil type: a body of solid dielectric material providing upper and lower surfaces and disposed substantially horizontally; a first electrode adjacent said upper surface; a body of water below said lower surface; an annular dam extending downward from said lower surface to a position beneath the surface of said body of water to bound a treating space; means for introducing emulsion into said treating space to flow toward said dam between said lower surface and said surface of said body of water; means for establishing an alternating potential difference between said electrode and said body of water of sufficient intensity to coalesce the dispersed water droplets of said emulsion, the coalesced droplets joining said body of water, the treated oil moving downward beneath said dam, said body of solid dielectric material providing sufficient dielectric strength to withstand without electrical breakdown the entire potential applied by said lastnamed means between said electrode and said body of water and being of such capacitive reactance with respect to the capacitive reactance of said emulsion as to absorb a portion of the potential difference between the electrodes which is at least three times the portion absorbed by said emulsion; and means for collecting the treated oil.

14. A combination as defined in claim 7, in which the ratio of the capacitive reactance of said dielectric medium to the capacitive reactance of said emulsion is from 3 to about 8.

15. A combination as defined in claim 8, in which the thickness of said stream of emulsion and the electromotive force impressed thereacross is such as to give a gradient therein from about 60-80% of the dielectric strength of the oil of said emulsion.

EALLEY WOIPE.