US2042775A - Apparatus for dewaxing oil - Google Patents

Description

June 2, 1936. H, sH 2,042,775

APPARATUS FOR DEWAXING OIL Filed Sept. 18, 1933 INVENTOR Harmon F. Fisher ATTORNEY.

Fatented June 2, 1936 UNITED STATES APPARATUS FOR DEWAXING on.

Harmon F. Fisher, Los Angeles, Calif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California The present invention relates to the separation of wax from wax-bearing oils and more particularly it pertains to the separation ofa wax precipitate from a suspension thereof in oil.

In'view of the presence of parafiine or of wax in a number of lubricating oil fractions derived from parafline base crude oils, asphalt base crude oils or mixtures or blends thereof, and in view of the doubtful lubricating value of such paraifine or wax, it has become customary, in the produc-- tion of lubricating oils from petroleum fractions containing wax or parafline, to remove most or a substantial portion of the wax or paramne present in oil mainly for the purpose of lowering its pour point, and the temperature at which the oil congeals.

Recently a method has been developed for separating electrically the waxwhich has been precipitated from a wax-containing oil. According tothis method the wax-containing oil or a "fraction thereof is first diluted with a light hydrocarbon fraction, such as naphtha, liquid propane, etc., then chilled to the proper temperature at which the wax precipitation takes place, and finally the mixture of oil, diluent and precipitated wax is subjected to an electric field or electric current to aid the separation and deposition of the wax from this mixture. The treatment of the wax-oil-diluent mixture according to this process causes the wax to deposit on the electrodes. In the case of some waxes, i. e., waxes which are apparently charged negatively, the deposition occurs on the positive electrodes since the waxparticles subjected to an electric field appear to be drawn to the electrode having a polarity opposite to that of the particles themselves. Therefore,

if the wax is charged positively the above de-' scribed electric treatment causes it to deposit on the negative electrode. However, some wax precipitates are found to be charged-so that they deposit on-both the positive and the negative electrodes.

In operating according to the above described method it has been found that the potential gradient of the electric field must be comparatively high. Thus potential gradients of from 5,000 to 60,000 volts per inch of either continuous or interrupted direct current through the solution have been found to be effective in agglomeratihg and depositing the precipitated wax. Also, it has been discovered that time is an essential element. Thus, it is necessary to maintain the ers so that the electric field, i. e., the gap between the positive andnegative electrodes is comparatively short. With such small gaps it is obvious that the depositing of the wax on either or both electrodes will gradually diminish the space provided for the passage of the wax-containing mixture and finally completely close the gaps. Obviously, such gradual diminishing of the gap changes. the velocity of the mixture passing therethrough, thereby changing the above described time element and causing an insuflicient or incomplete depositing of the wax, so that the oil solution removed from such treaters may still contain considerable quantities of precipitated wax. The presence of such precipitated wax obviously raises the pour point of the final produce and decreases the lubricating value of the oil.

It is, therefore, one of the objects of the present invention to obviate the above described defects and to provide for passing the wax-containing chilled oil solution continuously through an electric field and for simultaneously and continuously removing and withdrawing from this field the wax depositing on the electrodes.

It is a still further object of the present invention to provide a structure wherein the rate of passage of the oil containing the wax precipitate through an electric field may be maintained constant.

The above and other objects may be attained by continuously removing the deposited wax from -the electrodes and allowing the thus removed wax tosettle out more rapidly to the bottom of the treater from whence it is removed. The scrapers may also act as bafiiing means to cause the wax and oil mixture to pass through the electric field and to prevent its passage through the treater in a manner as to avoid complete treatment.

Now, therefore, broadly stated the invention resides in passing the chilled mixture of oil and Wax through an electric field of a suificiently high intensity and at a proper rate to cause the wax contained therein to deposit on certain of the electrodes, and to remove the thus deposited wax continuously for the purpose of maintaining the electric gap constant, thus permitting a sufficient period of treatment for the oil being dewaxed. The invention further resides in a dewaxing structure wherein the electrodes are of the plate or disk type and are arranged to alternate in polarity to produce an electric field be- PATENT OFFICE tween each pair of electrodes, and wherein certain of the electrodes are rotated and are provided with scraping means to remove from these rotating circular or disk electrodes any wax deposit formed thereon' from the wax-bearing oil passing through the electric fields between said electrodes.

In its preferred form the invention comprises an electric treater, a plurality of stationary plate electrodes disposed therein, a plurality of circular electrodes of a polarity opposite to that of the stationary electrodes disposed within the treater, inter'spaced between the stationary electrodes and electrically insulated therefrom, means for rotating the circular electrodes, and scraping means to remove the wax depositing on the rotating electrodes by the .wax-bearing oil passing between the electrodes, the deposit being caused by an electric field impressed between each pair of electrodes. The scraping means may also act as a battle to force the oil and wax mixture to be treated to flow through the electric fields. The above described structure is also provided with an inlet for the introduction into the treater of the wax-bearing oil-solvent mixture, an outlet for the dewaxed oil-solvent mixture, and means, such as a screw pump, to remove from the treater the deposited wax which has been removed from the electrodes by the above described scraping means. I

Other objects, advantages and featuresof the invention will be evident hereafter, and more par'-' ticularly by' reference to the accompanying drawing wherein:

Fig. 1 shows diagrammatically a vertical section through one embodiment of the present invention; and

Fig. 2 is a section along line A-A of Fig. 1.

Referring to the drawing, the treating chamber ill is preferably cylindrical in form and is arranged so that its main axis is in the horizontal plane. End walls H and I 2 enclose the treater, the latter being also provided with an inlet pipe I3 and an outlet pipe i l. The treater is further provided at its upper end with a hollow projection i5 closed at its top by a cover l6, while at its bottom the treater is provided with a similar projection ll closed by plate l8 and provided at its side with a pipe Hi. This pipe i9 encloses a screw pump 20 set on shaft -2l. .Pipe i9 is closed at its outer end by a plate 22 through which the shaft 2! passes through a stuifing box 23. Pipe I9 is also equipped with-a wax discharge line 25.

Pipe l5 contains a supporting insulator. 26

held in place'by means of a plate 21 rigidly attached to and made integral with projection IS. The electrode 26 supports a plurality of stationary diaphragm electrodes 28 suspended therefrom within the treating chamber it). These elec-, trodes are in the form of segments-of a circle and are cut out-as at 29 for. the passage of a shaft 30 described hereinbelow. This shaft 30 is disposed along the main axis of the treating chamber l0 andpasses out through the respective walls II and I2 thereof through stuffing boxe's 3i and 32, respectively. The latter also act as bearings for said shaft. A plurality of circular plate electrodes 33 are attached rigidly to shaft 30 and are disposed thereon in a manner so that they pass through the spaces between. the stationary electrodes 28 and provide gaps or spaces 34 between said stationary and circular electrodes. An electric field of, the desired intensity is impressed across these gaps 34 by connecting the'stationary electrodes through the medium of wire 35 to a pipe I! and is removed therefrom through pipes sourceof an electric potential. This wire leads into the treating chamber l0 through an insulated inlet bushing 36. The circular plate elec-' L trodes 33 are grounded through shaft 30 and the body of the structure, and the return circuitto the electric potential source is completed through the ground. A plurality of scraping plates or diaphragms 31 are attached attheir lower ends to .plate l8. These plates project upwardly through pipe ll -and abut' vvith their edges 38 against the surfaces of the. circular plate electrodes 33. Alternatively, one slotted scraping plate may be. used, permitting passage of the plate electrodes 33.

In operation, the diluted waxy oil chilled to a temperature at which the desired wax has precipitated out of solution, is passed into. the treating chamber ill through inlet l3. Due to the positioning of the scraper diaphragm 31, which closes the space betwen the electrodes 33 below shaft 30, the 20 wax and oil mixture passes through the gapsor spaces 34 between the interspaced electrodes 28 and 33. Simultaneously with this introduction of V the oil, an electric field of the desired intensity is maintained across the gaps 34 by impressing an 5. electric. potential of the desired intensitybetween wire 35 and the ground. The action of the electric field on the oil-wax mixture passing-through the gaps 34 is such that the wax is deposited on the surfaces of certain of the-electrodes. The polarities of the electrodes must be selected so, that the wax is deposited on the circular plate electrodes 33 attached to the shaft'30. The thus: dewaxed oil solution" passes out of the treating chamber ill through outlet pipe l4.

As stated above the proper dewaxing of a waxbearing oil requires a certain potential gradient across the electric field through which the wax and oil mixture pass as well as a certain anddefinite period of time of treatment. Obviously 4&02 the deposition of the wax on the electrodes 33 decreases the gaps 34, thus increasing the velocity of the oil passing through the electric field and preventing a proper dewaxing of the oil. To obviate this disadvantage the circular electrodes 33 attached to shaft 30 are rotated by actuating said shaft. This rotation of the circular electrodes 33 causes the scraper diaphragms 31, abutting against the surfaces of these electrodes by means of their edges 38, to remove from these electrodes the wax deposited thereon. Such a removal ofthe deposited wax obviously permits the maintenance of constant gaps or spaces between the electrodes 28 and 33, thus allowing the 011- wax mixture (introduced into the treater at a predetermined and constant rate) the period of time necessary for a proper deposition of the wax. The wax scraped off the faces or surfaces of the electrodes 33 by the scrapers 31 falls down into l9 and 25 by the actuation of the screw 20 rotated by the shaft 2!.

The direction of rotation of the plate electrodes 33 may be such that it is either in the direction of new of the oil being dewaxed, or it may be countercurrent to such oilflow. However, a

countercurrent rotation is preferred. if, it is desired to provide the cleanest electrode surfaces to or at the finishing stages of the treatment.

It. is to be understood that the above discloe sures are not to be construed as limiting but merely as descriptive of the generic invention, since many variations may be made by those skilled in the art within the scope of the appended claims. 7

I claim:

1. An apparatus for dewaxing wax-bearing oil comprising a chamber, a stationary electrode disposed within said chamberIa movable plate electrode within said chamber adjacent; said stationary electrode but without contact therewith, means in engagement with said plate electrode adapted to move the same, means in communication with said chamber to pass wax-bearing 011 between said stationary and movable electrodes, means in electrical contact with said electrodes adapted to impress an electric field on the oil and to cause depositing of wax therefrom, and scraping means in engagement with said movable electrode to remove the wax deposited thereon, said scraping means being in the direction of flow of the incoming wax-bearing oil and serving as a baflie to deflect said oil to the treating space between said electrodes.

2. An apparatus as in claim 1 wherein said plate electrode is a rotatable disc electrode.

3. An apparatus for dewaxing wax-bearing oil comprising a chamber, stationary plate electrodes disposed within said chamber, movable plate electrodes within said chamber between each pair of said stationary electrodes but without contact therewith, means in engagement with said plate electrodes adapted to move the same, means in communication with said chamber to pass waxbearing oil between said stationary and movable electrodes, means in electrical contact with said electrodes adapted to impress an electric field on the oil and to cause depositing of wax therefrom, said means impressing an electric field including an insulated electric conductor attached to the stationary electrodes and adapted to convey thereto an electric current, and means to ground the movable electrodes and means in engagement with said movable electrodes to remove the wax deposited thereon.

4. An apparatus as in claim 1 in which the scraping means is a slotted scraper.

5. An apparatus for dewaxing wax-bearing oil comprising a chamber, a stationary electrode disposed within said chamber, said stationary electrode being in the formof a. segment of a circle, a movable plate electrode within said chamber adjacent said stationary electrode but without contact therewith, means in engagement with said plate electrode adapted to move the same, means in communication with said chamber to pass waxbearing oil between said stationary and movable electrodes, means in electrical contact with said electrodes adapted to impress an electric field on the oil and to cause depositing of wax therefrom, and scraping means in engagement with said movable electrode to remove the wax deposited thereon.

6. An apparatus as in claim 5 wherein said stationary electrode is substantially U-shaped.

' HARMON F. FISHER.

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