US2030198A - Electrical dehydration of oils - Google Patents

Description

Feb. 11, 1936.

M. E. CERF ELECTRICAL DEHYDRATION 0F OILS Filled April s, 1955 MARCEL E. CERF lNl/EN TOR w f A ORNE) Patented Feb. 111, 1936 ELECTRICAL DEHYDRATION F OILS Marcel E. Cerf, San Francisco, Callfi, assignor to L. Blake Smith, San Francisco, Galif.

Application April 3, 1933, Serial No. 664,224. Claims. (01. 204-24) The object of my invention is to provide means for positively preventing the formation of water chains between the electrodes of an electrostatic emulsion-breaking system.

5 It is well known that petroleum emulsions of the water-in-oil type may be resolved into their constituents by bringing them,between spaced electrodes on which a relatively high electrical potential difierence is impressed. The emulsion being, relatively at least, a nonconductor of electricity, the charge imparted to the live electrode sets up an electrical field which (in a manner which is immaterial to my invention) acts to bring together into larger particles the microscopic water drops which constitute the disperse phase of the emulsion.

{is these aggregated water particles increase in size, they tend to subside more and more rapidly from the emulsion and thus to remove themselves from the field, but in many cases, as for instance where the water proportion is very large or the emulsion unusually viscous, the water particles do not subside with sufiicient rapidity to prevent the formation of a more or less'conductive medium between the electrodes, through which the static field is dissipated and by which the resolution is brought to an end.

H Thus, in its very nature, the method of demulsification which depends on the maintenance of an electrical field, necessarily tends to set up conditions which, if not resisted, result in the dissipation of the field by conduction and the consequent termination of the operation.

This tendency, though it may in any given case be insufiiciently powerful to actually interrupt body of emulsion undergoing electrical resolu-' tion, but only to that certain method of accomplishing that result which is about to be described.

My invention comprises, in combination with any static electrical demulsification of oil, the step of laying hold of water drops, as they are set free in the field, by attachment to granules of water-wettable solids, the solid grains being of such size and relative weight as to rapidly pass through the field. Strictly corollary steps, useful in practice, are to immerse the water-coated granules in a body of water, with the object of removing from the granules any adherent oil particles, to drain water from the granules while leaving them water-wet, and to return the wet granules to again pass through the electrical field in the emulsion body.

Both the manipulation and the theory of my invention may best be explained with reference 10 to the attached drawing which illustrates, in a highly diagrammatic manner, the operation'of an apparatus suitable for putting the invention into practice. In this drawing, Fig. 1 illustrates the apparatus in vertical cross section and par- 15 tial elevation, While Fig. 2 is an internal plan view of the distributor head J as on the line 2-2 of Fig. 1.

Referring to Fig. 1, A is a tank having a converging bottom B. C is a relatively wide tube 20 having walls parallel to the walls of the tank and supported therein by insulating media such as the spiders DD. E is a relatively narrow inner tube substantially concentric with tube C and supported therein by insulating media such 25 as the spiders F-F. The spiders D and F which are located beneath the body of oil in the lower part of the tank should have a narrow section and a sharp upper edge to avoid the accumula- I tion of conductive grains thereon. 30

G is a conveyer screw within the innertube, depending from and rotated by a distributor head J which, in turn, rotates on a bearing not shown in the bottom of an annular groove I formed at the upper end of the tube. The head J carries 35 a plurality of spouts W and the assembly comprising head, spouts, and screw is rotated on and within the fixed tube E by means of a pair of bevel gears K and L, driven by any source of power not shown.

The'construction and operation of the head J are shown in Fig. 2. The tube E, as described,

is stationary and both the head J and the screw G revolve in relation to it. Revolution of the screw in the proper direction lifts a column of 5 grains from the mass V accumulating in the bottom of the shell and these grains flow over the top'of the tube E onto the bottom plate JB of the head J. This bottom plate is divided into seg ments of equal width by ribs X, the equal spacing 50 of these ribs at the ends adjacent tube E ensuring that equal quantifies of grainswill be received by each segment. These segments are provided with spouts W which permit the grains to fall into the annular spaces T and Y in a slow- 55,

' tions.

Referring again to Fig. 1, M is a valve-controlled pipe for admitting emulsion, N is a similar pipe for withdrawing treated oil and O is a similar pipe for withdrawing water. The tank A is connected at P and the tube C is connected at Q to an alternating current transformer in the usual manner.-

As an electrical dehydrator the above apparatus functions in a purely conventional manner. An electrical field is set up in the annular space Y and a similar field in the space T, tube C acting as a live electrode while the wall of the tank and also tube E (which is grounded to the wall by immersion in the water body 'U) function as grounded electrodes. An upper liquid level being established, as for instance at S, emulsion admitted through pipe M fiows slowly downwardly through the annular space Y and upwardly through space T, and through the electrical fields. Proper conditions as to voltage and temperature being maintained, the emulsion is gradually resolved in its passage through the fields, water droplets separating from the emulsion mass and passing slowly downward to collect in the water body U. From this body collected water may be withdrawn through pipe 0 to maintain a constant Water level Z, while water-free, oil overflows through pipe N.

I do not describe suitable operating conditions for the electrical treatment because such conditions are well known and understood, because they are no part of my invention and because my invention applies to all operating conditions which will produce any degree whatever of electrical demulsification.

My invention consists in passing through that portion of the emulsion body which is in process of resolution by reason of being subjected to electrical stress, a more or less continuous stream or shower of solid granules which have at least a moderate superficial attraction for water and which, by reason of that attraction, lay hold of all liberated water drops with which they come into contact and carry such .drops out of the field, thus maintaining the dielectric constant of the emulsion and the integrity of the field.

The water droplets liberated by the electrical resolution of the emulsion are of extremely minute size and consequently present a relatively large surface as regards their mass. Further, the specific gravity difierence between the water and the oil is relatively small, as for example 1.02 for a moderately salty water vs. 0.90 for a 25 B. oil. The rate of unassisted sedimentation of the water droplets from the oil is therefore slow under the most favorable conditions, and under unfavorable conditions it may become extremely slow, as in the case of emulsions of very heavy oils, where the specific gravity difference is at its minimum and the viscosity of the oil extremely high.

so that the adhering water film may not be displaced in the rapid passage of the granule through the oil, and second, a solid materially heavier than water, grinding this solid to relatively large granules which will have a low relation of surface to mass.

As illustrative examples, I may select such materials as the harder'varieties of iron oxid (hematite, magnetite martite) coarse silica sand or crushed quartz, crushed flint glass, massive hornblende, alundum or other bodies of a similar nature.

These bodies have all a relatively high specific gravity and, other things being equal, are efiective in direct ratio to their weight. I do not limit myself to any particular specific weight for the granules though I prefer to use solids having a specific gravity not less than 2.5.

The mesh to which these solids should be ground is variable within limits and may be varied in relation to the specific gravity of the solid.

Coarser grains will settle out more rapidly, which is advantageous, while finer grains will expose more area per unit of volume, also an advantage. In a general way it may be said that for emulsions of average weight and viscosity the mesh should not be finer than will be retained on a 20- mesh screen if the specific gravity of the solid is of the order of 3.5, while if the weight of the solid is of the order of'2.5, the smallest granules should not be less than 10-mesh, the coarser in either case being perhaps 4-mesh. The granules should be clean and free from adherent fine material such as dust.

Solids which are preferentially wetted by water will lose the water coating and .become coated with oil it for a long time exposed to contact with oil. For this reason I prefer to immerse granules which are to be returned for further treatment of emuslion through a body of water, as indicated at U in Fig. 1.

It will be obvious that the apparatus described is subject to'numerous mechanical variations, particularly as to the provisions for raising and distributing the granules, and I desire to claim invention in apparatus as broadly as the state of the art will permit, within the limits of the attached claims.

As described in a copending application of Charles J. Robinson, Serial No. 612,855, filed May 21, 1932, the solids above enumerated as well as others will resolve emulsions when passed therethrough in a similar manner. The present invention, however, is not of the addition of an electrical dehydration step to the step described in the copending application, the benefit obtained by applying these two steps seriatum, in either order, or alternately, being of slight if any importance. I conceive my invention as being substantially a method for maintaining the integrity of the field in an electrical dehydration, thereby rendering the electrical method applicable to emulsions of high water percentage and extreme viscosity; permitting the use of very high voltages, and greatly reducing the amount of heatrequired for bringing heavy emulsions within treatable viscosity limits, the emulsion-resolving effect of the solids themselves, in the quantities in which they are required to be used, being altogether incidental.

I claim as my invention:

' 1. In-the resolution in a static electrical field of an emulsion in which water is the dispersed phase, the method of maintaining the dielectric value of said field which comprises: passing preferentially water-wettable, insoluble, solid granules through said field at a velocity materially exceeding that of the passage of emulsion therethrough; collecting said granules on one side of the body of emulsion in which said field is maintained, and returning said granules to the opposite side of said body to be again passed through said field.

2. In the resolution in a static electrical field of an emulsion in which water is the dispersed phase, said field being substantiallyhorizontally disposed, the method of maintaining the dielectric value 01 said field which comprises: downwardly passing through said field solid granules of a, preferentially water-wettable, insoluble, solid material, the specific weight of said material being not substantially less than 2.5 times that of water; collecting said granules at the lower side of the body of emulsion in which said field is maintained; removing excess water from said granules while maintaining them in a water-wet condition, and returning said water-wet granules to the upper side of said emulsion body to again pass downwardly therethrough.

3. In the resolution in a static electrical field of an emulsion in which water is the dispersed phase, said field being substantially horizontally disposed, the method of maintaining the dielectric value of said field which comprises: continuously downwardly passing through said field solid granules of a preferentially water-wettable, insoluble, solid material at a velocity materially exceeding that of the passage of emulsion through said field; maintaining a, body of water beneath the body of emulsion in which said field is maintained; passing through and collecting in said body of water the granules which have passed through said field; continuously removing a portion of said granules from said water body; continuously returning said portion of granules to again pass through said field, and withdrawing water from said water body.

4. Apparatus for the electrical resolution of water-in-oil emulsions, comprising: means for maintaining a body of said emulsion; means for maintaining a static electrical field within said body, said means including electrodes; means for showering solid heavy' granules over the upper surface of said body to pass through said field out of contact with said electrodes; means tor collecting said granules below said body, and means for returning said granules to a position above said body to be again showered thereover.

5. Apparatus for the continuous electrical resolution of water-in-oil emulsions, comprising: means for maintaining a flowing body of said emulsion; means for introducing untreated emulsion to said body; means for maintaining a static electrical field within said body, said means including electrodes; means for showering solid heavy granules over the upper surface of said body to pass through said field out of contact with said electrodes; means for retaining a body of water below said emulsion body and for accumulating therein granules which have passed through said emulsion body; means for withdrawing last said granules from said water body and for returning them to a position above said emulsion body, and means for separately withdrawing water and demulsified oil.

MARCEL E. CERF.

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