US2027616A - Method and apparatus for electrical dehydration - Google Patents

Description

jana- M, 936 P. w. PRUTZMAN ND APPARATUS FOR ELECTRICAL DEHYDRATION METHOD A Filed Oct. 10, 1933 EMULSION Patented Jan. 14, 1936 PATENT OFFICE METHOD AND APPARATUS FOR ELEC- TRICAL DEHYDRATION Paul W. Prutzman, Los Angeles, Calif., assignor to Socony-Vacuum Corporation, New York, N. IL, a corporation of New York Application October 10, 1933, Serial No. 692,980

11 Claims.

tension electrical field was disclosed by Cottrell and others as early as 1911 (see U. S. Patent 987,115), is very well known and understood and needs but the briefest description.

In general terms, the emulsion is passed between opposite charged electrodes on which a high potential is impressed. This potential produces a static electrical field between the electrodes and, under the influence of this field, electrical charges are imparted to the suspended water particles. These charges cause the particles to approach each other and to coalesce to larger particles and droplets which finally attain such dimensions as to settle out of the oil.

This is purely a static effect and ceases if any material leakage or conduction between the electrodes occurs. The tendency of the liberated water particles is to arrange themselves along the lines of force at such minute intervals as to form conductive chains by breaking down the dielectric oil layer between them. When this occurs, the static field is dissipated by conduction and the resolving efiect ceases until the field is reestablished.

In order to maintain the integrity of the field and thecontinued functioning of its resolving effect, it is necessary to maintain a dielectric barrier between the electrodes at all times. To this end several methods have been proposed. Cottrell (Patent 987,115) dilutes the emulsified oil with relatively dry oil, by which step the distance between the water particles and the thickness of the dielectric oil barrier between them is increased. Fisher (Patent 1,838,928) interposes a barrier layer of relatively dry oil between one of the electrodes and a layer or stream of emulsion which is in contact with the opposite elec-- trode. Peek (Patent 1,170,184) interposes a solid dielectric barrier such as glass between one of the electrodes and a layer of emulsion which is in contact with the opposite electrode. McKibben (Patent 1,276,386) sweeps the water particles out 'of the field as fast as they are formed, thus maintaining in the field a constantly renewed supply of emulsion which, prior to resolution, has usually a high dielectric value.

The method of the instant application adopts the last named alternative and is directed to a specific method and means for directing a constantly renewed supply of emulsion alternately into and out of a longitudinally extended single field of high intensity and for separating and detouring free water separated in each passage through the field.

The objects and advantages of the invention may best be understood with reference to the attached drawing, in which Fig. 1 is a vertical section and internal elevation of a preferred form of apparatus which may be used to illustrate the method employed and Fig. 2 is an internal plan view as on the line 2-2 of Fig. 1.

Referring to the drawing, in is a substantially closed shell which may be of any preferred dimensions. In this shell is suspended a conical electrode ll, of sheet metal, both ends of this truncated cone being closed and the lower end being sufiiciently weighted to overcome its buoyancy when submerged. This cone is rigidly attached to an electrode rod I 2 which passes to the exterior of the vessel through an insulator is. It is desirable to provide this rod with threads M and a hand nut 15 by means of which it may be 5 raised and lowered.

Spaced from the conical electrode and so formed and supported as to be substantially parallel to its inclined surface is a grounded electrode I 6 formed of metallic screen, which may be of perforated or slotted sheet metal but is preferably formed of woven wire mesh, as for example of 8 to 12 gauge wire woven to to 1" mesh. This screen is supported by tacking to the inner edges of circular openings in a plurality of plates Ila and Nb, the plates themselves being attached as by welding to the inner surface of the shell.

For the plates, two alternative forms are proposed, the form shown on the left side of Fig. 1 differing somewhat from that shown at the right side of the drawing. In the form shown on the left side the edge of the opening is upturned to form a shallow flange l9. The plates numbered Ila, being every alternate plate, are provided with downspouts 28 sealing in cups 2| formed on the upper face of the next lower plate. The plates numbered llb are provided with openings I8 adjacent the wall of the shell.

In the form shown on the right side of Fig. 1 the downspouts and sealing cups are omitted, the plates being otherwise as above described.

The bottom plate He is recessed at one or more points along its edge and provided with a downturned flange 2i at such points to form a channel or channels 18b. It is also provided around the central opening with a downward looking flange or ring 22 defining a central passage 23 which is of substantially the diameter of the lower end of screen electrode IS.

The plate "a being secured to the wall of the shell, these walls together with the down turned flanges 2| and 22 define a zone 24 of substantially complete quiescence in the lower portion of the shell. Oil is withdrawn from the upper side of this zone through a pipe 25 which branches at 26 to permit the separation of any gas emerging from this zone. Water is drained from the bottom of the shell through a siphon 28, and gas evolved in the upper portion of the shell or carried into it with the entering emulsion is vented through a pipe II. The gas vents may be individual or may be collected into a header and a single vent as shown. Emulsion or wet oil is introduced into the upper portion of the shell, at any point above the upper plate [1a, through a pipe 29.

A step-up transformer 30 has its primary winding 3| connected to any source of supply of alternating current. One terminal of the secondary winding 32 is grounded as at 33, the other terminal is connected by a cable 34 to electrode rod l5. The shell is grounded as indicated at 35.

The above described apparatus functions in the following manner. Emulsion introduced into the top of the shell fills it to a level at least slightly above the lower end of insulator iii, the level of the oil outlet pipe 25 being adjusted with that end in view.

Passing downwardly, the emulsion flows through the annular space 36 between the cone and the screen electrode. Any desired potential, as of the order of 5,000 to 12,000 volts, being impressed on the electrodes, a high intensity static field is set up in the annular space, this field being most concentrated in the immediate vicinity of the wires of which screen I6 is composed. In passing through this field this emulsion is progressively resolved into its constituents, clean oil and suspended water, in the well known manner.

In flowing downwardly, however, a portion of the emulsion passes through the meshes of the screen, which are too far spaced to offer any appreciable resistance to such fiow, into the space between a plate l'la and a plate l'lb, to pass down through opening l8 and to return to the main current over plate llb. These plates being alternated, the movement of emulsion is simultaneously as indicated by the arrows A and B. In this slow movement through the space between the plates opportunity is afforded for all free water to subside from the oil onto the plate next below. On plate l'la as shown on the left side of the drawing this water flows through downspout 20 which seals in cup 2|, while on these plates as shown at the right of the drawing the water fiows down the screen to the plate next below. In either showing, the water settling on plate l'lb is carried with the oil through opening l8 to the next lower plate.

On finally emerging from the field the mixture of resolution products passes into the space 31 in the lower end of the shell, in which'free water separates from the oil, to be withdrawn through pipe 28. The separated oil rises slowly into the quiescent zone 24 in which it is afforded opportunity to sediment its last traces of free water, completely treated and settled oil being delivered from the upper side of this zone through pipe 25.

The apparatus above described is pa icularly adapted to the dehydration of viscous emulsions at low temperatures, the areas of the passes being such that there is substantially no pressure drop through the field. While it will not cut so closely as the forms in which the emulsion is positively directed through a succession of fields it can be made to cut to commercial requirements by proper regulation of the-rate of flow, and produces superior results on many emulsions which are handled only with difliculty in treaters of types heretofore disclosed.

I claim as my invention:

1. An electrical dehydrator, comprising: a vertically arranged and substantially closed shell; a live electrode in the form of an electrically conductive cone, at least one end of said cone being closed; means insulated from said shell for supporting said cone in substantially the center of said shell with the smaller end of said cone directed downwardly; a grounded electrode in the form of a wire screen surrounding, spaced from and parallel to said live electrode; a plura'lity of horizontally disposed and vertically spaced plates projected from the vertical walls of said shell to contact and support said screen, every alternate plate being provided with an opening adjacent said shell wall; means for impressing an electrical potential on said electrodes; means for introducing a flow of emulsion into said shell above said live electrode, and means for withdrawing water and oil from said shell below the lowermost of said plates.

2. Apparatus substantially as and for the purpose set forth in claim 1, in which each of said plates is provided with an upwardly directed flange adjacent and surrounding said screen and in which each plate not provided with an opening adjacent said wall is provided with a downwardly directed drain pipe adjacent said flange, said drain pipe cooperating with sealing means to prevent the fiow of emulsion through said pipe.

3. Apparatus substantially as and for the purpose set forth in claim 1, in which the lowermost of said plates is provided with an opening adjacent the wall of said shell, a downwardly directed wall surrounding said opening and a downwardly directed nozzle, said wall, plate, and nozzle defining a zone of quiescencebeneath said plate, the means for withdrawing water communicating with said shell below said zone and the means for withdrawing oil communi eating with the upper portion of said zone.

4. In an electrical dehydrator; a substantially vertical, impermeable electrode; a screen wire electrode arranged parallel thereto and spaced therefrom; means for maintaining a static electrical field 'or fields between said electrodes; a shell divided into chambers extending from said screen electrode to the wall of said shell; means for causing a flow of emulsion through the space between said electrodes, and means for causing a portion of said flow to pass from said space through said screen into one of said chambers and to return to said space through another of said chambers and said screen.

5. Apparatus substantially as and for the purpose set forth in claim 4, in which said chambers are horizontally disposed and vertically arranged.

6. Apparatus substantially as and for the purpose set forth in claim 4, in which said chambers are superposed, including means for draining water separating in each said chamber into the chamber next below.

7, Apparatus substantially as and for the purpose set forth in claim 4, in which said chambers are superposed, including means for draining water separating in each chamber into the chamber next below, said drainage being effected out of contact with emulsion in said chambers.

8. The method of resolving petroleum emulsion in which water is the dispersed phase, which comprises: downwardly passing a flow of emulsion through an elongated static electrical field substantially vertically arranged; laterally diverting a portion of said flow from said field into a zone of quiescence; separating water in said zone; returning said diverted emulsion into another portion of said field below the point of diversion, and finally vin'thdrawing water and dehydrated oil from the lowermost end of said field.

9. The method of resolving petroleum emulsions in which water is the dispersed phase, which comprises: downwardly passing a flow of emulsion through an elongated static electrical field substantially vertically arranged; laterally diverting portions of said flow from said fields into superposed zones of quiescence; separating water in said zones; returning each said diverted portion of emulsion into a portion of said field below the respective point of diversion, and finally withdrawing water and dehydrated oil from the lowermost end of said field.

10. A method substantially as and for the purpose set forth in claim 9, including the steps of draining water separated in each said zone into a lower zone, and withdrawing water from the lowermost of said zones.

11. A method substantially as and for the purpose set forth in claim 9, including the steps of draining water separated in each zone into a lower zone, said drainage being efiected out of contact with emulsion in said zone, and with drawing water from the lowermost of said zones.

PAUL W. PRUTZMAN.

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