US2031214A - Process and apparatus for dewaxing oil - Google Patents

Description

Fel). 18, 1936. I F FlsHER 2,031,214

PnocEss AND APPARATUS Fon DEwAxING ou.

Filed oct. 9. 193s INVENTOR .Harmon Ffslz er' A ATTORNEY.

Patented Feb. 18, 1936 :PATENT OFFICE Y y n.214 n raocsss sun mmm ron nsw AXI'NG Harmon F. Fisher, Los

OIL

Calif., assignor to Angeles. Union Oil Company of California. Los Angeles. Oalif., a corporation of California Appuumoeuber a. 193s, sen-m No. mais 1o clam. (ci. .n4-ww The present invention relates to the separation of wax from waxfbearing oils, and more particularlypertains to the separation of wax precipitate from a suspension thereof in oil. A

In view. of the presence of paraiiin or of wax in a number of lubricating oil fractions derived from pantin-base crude oils. asphalt-base crude oils, ormixtures or blends thereof, and since the lubricating value of such paraiiin or wax is highly 3 doubtful, in the production of lubricating oils from such petroleum fractions containing paramn or wax. it has become lcustomary to remove most or a substantial portion ofthis parafiin or wax from the oil. Such a removal of the wax and/or 5 paramn is mainly for the purpose o! lowering its pour poin and the temperature at which the oil congeals.

A method has recently been developed for -separating the wax which has -been precipitated from o a wax-containing oil, thismethod employing electricity for such wax separation. According in this method the wax-containing oil, or any fraction thereof, is first diluted with a light hydrocarbon fraction, suchas naphthaliquid propane,

5 butano, etc.. then chilled to the proper temperature at which the wax precipitation takes and finally the mixture of oil, diluent and precipitated wax is subjected to an electric field or electric potential to aid the agglomeration and deposition of the wax from this mixture. The

treatment of the wax-oil-dlluentmixture according to this process causes the wax to deposit on the electrodes. It has been found that the wax particles suspended in an oil and subjected to an il electric field appeal' to be drawn to the electrode having a polarity opposite to that of the particles themselves. Thus, if the wax particles arecharged negatively, the deposition occurs on the positive electrodes, while, if the wax is positively n charged the electric treatment causes it to deposit on the negative electrodes. However, some waxbcaringoils seemtocontainwaxparticlesofboth polar-ities, in which case the above-described electric treatment causes these waxparticles to depodt on both the positive and negative electrodes. In operating according tp the above-described method it .has been found that the potential gradient of the electric field must be comparatively high. Thus, voltages oi from 5,000 to 60,000

so volts per inch passed through the oil-wax-diluent solution have been found to be eiIective in agglomerating and depositing the precipitated wax. alsmithasbeenfoundthattimeisanessential factor'in the proper treatment of wax-bearing oIII.i.e.it isn tomaintainsuchoilwithin the electric field for a predetermined and constant period of time` to 'obtain the deposition .and agglomeration of the wax particles.

In view of the above-described requirement of using electric fields of high intensity it is necestrodes in a comparatively small and inexpensive treating chamber.

vIt is another object of the invention to provide electrodes which take up the minimum of space thereby permitting a larger through-put of oil to be treated. y

The depositing of the wax on either or both electrodes of a treating chamber gradually diminishes the space provided for the of the mixture of wax and diluted oil. and this space or gap may be nally completely closed by depositing wax. Naturally, such a gradual diminishing so of the gap, a constant rate of input of oil to be treated, changes the velocity of the rnix- :ture passing therethrough. 'Ihis change in velocity modifies the above-described time element andcausesaninsuiilcientdepositingofthewax so that the oil solution removed from such treating chambers still contains considerable quantities of precipitated wax. Thepresence of such precipitated wax obviously raises the pour point of the final product and decreases the lubricat- 40 ing value of the oil.

It is therefore another object of the presmt invention to provide for the removal of the wax deposid on the electrodes and thus maintain the gaps between the positive and negative electrodes constant.

The above and other objects may be attained by providing a treating chamber equipped with a plurality of interspaced and alternately live and grounded flat plate electrodes. and by providing some ofsaid electrodes with means for heating them and for melting oi! any wax deposited thereon. Theheating means may'bein theform of an electric heating coil and may itself act as the grounded electrode. 6a

izallicV surfaces thereof.

- so flut they are alternately live and grounded electrodes The invention further resides in providing certain of the electrodes with means for heating the surfaces of these electrodes, and means for passing periodically a current through said heating` means toheat the surfaces of the electrodes. thus mdting any wax depositing thereon.

Home speciiically stated, the invention resides in a structure for removing wax from a waxcontaining oil, which structure comprises a chamber. a pluralityof thin, flat plateelectrodes within said chamber and spaced away from each to provide gaps therebetween, a pipe leadinto the chamber to introduce thereinto a oiltobetreatedbailiingmeanswithinthe chamber to cause the thus introduced oil to pass through the above gaps between the electrodes,

m certain of said electrodes, a pipe leading out from the chamber and adapted to withdraw therefrom the dewaxed oil, and means associated with the electrodes on which the wax deposition taks place for heating the surfaces of these elec' trodes periodically to melt and remove therefrom In its preferred form the chamber may be provided with a conical bottom which opens into a dhchargelllpecquippedwith apump. such asa gear pump. to remove' the wax thus deposited in the lowerportlon oi the chamber.

'nie means for the periodical heating of the surfaces of certain of the electrodes may preferably consist of a resistance coil wound around the plate electrode but without contact with the me- However, the heating means themselves may be u sed asthe electrodes on which the wax is caused to deposit. 'lhere-V fue, the invention' may further reside in an electrode structure comprising an insulating frame,

a metallicV band wolmd on said frame, means for said metallic band or for connecting it to me pole of a source of electric potential, and electric means associated with said band and adapted to heat the same. 'lhe heating meansv includes a pair ot electric conductors connecting the opposite ends of the metallic band with the opposite poles of a source oi! electric current.

'nie invention still further resides in providing the electrodes withtensional means to prevent than from buckling. Ihese tensionai means may consistoftensionspringsatthe corners of the plates. or may consist of insulating spacers or plus placed within the aforementioned gaps and agaimt the surfaces of adjacent plate electrodes. other objects, advantages and features oi the pracht invention will be more evident especially by reference to the accompanying drawing. wherein:

Flgurel is a 1 :m tic, sectional elevation taken along the axis of a preferred embodiment of the treater;

, Figure 2 is a section through the theater, and along line 2-2 of Figure 1:

'. Figure 3 is an enlarged view of a part of an -line 'I- l of Figure 6.

In the form of the invention shown in the drawing, and particularly in Figures l and 2, the

treater includes an outer shell It closed at the top with a cover Il, and provided at its lower end with a conical bottom I2, opening into a waxdischarge pipe I2, equipped with a pump Il, such as a gear pump. to remove from the treater the aggiomerated wax settling in the bottom I2. Chamber It is provided with a pipe II leading thereinto and provided within the chamber with a plurality of openings I1. 'Ihis pipe introduces the waxy oil to be treated. means associated with the electrodes and adapted to generate an electric neid or potential across, said gaps and to cause the wax particles to deposit The space within chamber I and above the pipe Il is divided into two compartments by a baille plate Il welded or otherwise rigidly attached to the inner walls oi' the chamber ill. A rectangular opening I9 is provided in the center of baille-plate Il, the inner edgesof which are equipped with vertically aligned walls 20. It is thus obvious that the oil to be treated in chamber Il, and entering thereinto through pipe It, passes upwardly through the rectangular opening Il. This space I9 enclosed by the walls 2li is provided with a plurality of vertically disposed ilat plate electrodes 22, 23, which are arranged and installed so that they provide gaps or spaces between each pair of electrodes. The electrodes are also arranged so that adjoining electrodes are of opposite polarity. For this purpose electrodes 22 are attached at their upper ends to bars 25 and 2O. 'Ihese bars are equipped with bosses 2l and 2l, respectively. by means of which they lare attached to insulators 29 and It. These latter. are in turn attached to the inner walls of chamber il. Electrodes 22 are connected to one pole of a source of high potential by means of a conductor'wire 32 entering into chamber Il through aninsulator Il. 'I'he electrodes 23 placed between the electrodes 22 and without y contact therewith are held in place by means of bars I attached at their ends to the inner walls of chamber Il. These electrodes 22 are grounded through chamber It and the ground It.

these resistance coils being connected to conductors 2l and Il. These conductors pass out of the treating chamber Il through insulators I2 and Il respectively installed in the sides of the' chamber. 'Ihe conductors 39. and 40 are connectible to the opposite poles of a source of electric current not shown in the drawing. As will be described further below, it is necessary to prea,osi,214

vent the contact of the resistance coils Il with 'the electrodes 33. For this purpose the upper and lower edges of the electrodes 23 are provided with outwardly projecting insulating strips il over which the coils` I8 are wolmd, thm keeping said coils away from the faces of the electrodes 23, and preventing any short-circuiting when a current is through the coils.

A pipe perforated at l1 leads from the upper part oi' chamber Il, and is adapted to withdraw therefrom the dewaxed oil.

In operation, the waxy oil to be treated, with or without a preliminary dilution by a diluent auch as a liquefied but normally gaseous hydrocarbon, is first chilled to a temperature at which the waxprecipitates out of solution. 'lhe thus chilledmixtureoi'oilendwaxisthenpassed through pipe Il and perforations Il thereof into the interior of chamber Il. After illling the lower portion of the trear the mixture passes through the space enclosed by the walls 2. and containing the electrodes 22 and 2l. Simultaneously. an electric potential is induced through the gaps separating these electrodes, this potential being produced by connecting conductor n to a' proper source of electricity. As stated above, the electric potential thus induced through the gaps. through which the waxy oil must pass in its upward movement vthrough the treater. acts on the wax particles in suspension 'and causes them to be withdrawn and deposited on the electrodes having the potential opposite to that of these particles. 'Ihe polarity of the electrodes 22 and 23 is therefore selected so that the waxy particles deposit on the grounded electrodes 2l. The reason for this will be described below. The thus devmxed oil, or oil and solvent mixture. then rises into the space above the electrodes and is discharged through pipe I6, after entering thereinto through the perforations I1 in said pipe II. 'Ihe rate of introduction of the waxy oil through pipe Ii, as well as the rate of discharge of dewaxed oil through pipe 46, are

auch' that there occurs a complete depositing of the waxy particles on the electrodes 23.

As stated above, it is essential to keep the waxy oil to be treated in the treating eld for a predetermined period of time to cause the desired deposition of the waxy particles. On the other hand,thedepositionofthiswaxontheelec trades changes the gap between the electrodes. Thlsnaturallychangestherateofeofthe wan oil through the electric ileld, assuming a constant rate oi.' introduction thereof into the treater. Buch an increased rate of travel of the waxyoilobviouslyresultsinasmallerdegreeof de'waxing thus producing an oil of a lesser value. To eliminate this disadvantage it is n to remove periodically the wax depositing on the electrodes. For this purpose, an electric currentispassedthroughthecoils wound on theelectrodes 23 carrylngthe depodted wax on their surfaces. Ihis electric current heats the resistance coils and melts the deposited wax, the position of the resistance coils with respect to the surfaces of the electrodes 2l and the period of e of the heating current through these reaistancecoilsbelngsuchthatthewaxis melted only substantially at the surface of the electrodes. Obviously, such a melting reduces the coefllcient of friction of the wax and permits 'the agglomerated and deposited wax to fall down into the conical bottom I2 of the treating chamber from where it is withdrawn through pipe I3 bymeansoi'thc gearpump il. Itisobviousthat the provision of insulating strips 44 on the upper and lower edges of the electrodes 23 prevents short-circuiting when the current is passed through conductors 39 and 40 to the resistance coils 38. It is also obvious that such heating of the wax deposited on the electrodes 23 must be made periodically and each time-only for .a period just suillcient to reduce the coeiiicient of friction to cause the wax to fall down into the conical bottom i2 and not enough to materially heat the liquid.

In view of the fact that it is essential to make the treaters so that they are not too bulky, and since the intensity of the electric eld, i. e. itl potential, must be comparatively high, it has been found preferable to make the electrodes of comparatively thin dat plates and to space them quite close to each other. Obviously, these thin plate electrodes tend to buckle. Such buckling is undesirable not only because of the change in the gap space between the electrodes, but also in view of the dangers which may be caused by short-circuiting as when two adjoining electrodes come in contact with each other. For this purpose, it may be preferable to place the electrodes in tension, such an arrangement being shown in Figure 5. In this gure the electrode 22', simllar to the electrodes 22, is provided at its four comers with arms 50 attached to the inner walls of chamber I0 by means of insulators 5I and tension springs 53, which latter tend to prevent the buckling of the electrodes. Obviously, similar tensioning means may also be provided at intermediate points. Also, instead of using these tensioning means, the buckling may be prevented by the use of insulating spacers or plugs placed between adjoining electrodes.

Instead of using va metallic electrode and a separate heating means such as a resistance coil Y wound thereon, as shown in particular in Figures 3 and 4, it is also possible to use an electrode structure which is constructed so that the coil wound thereon acts both as the electrode for the depositing of the wax particles, and as the heating means or resistance coil for the removal of the thus agglomerated and deposited wax. Such va structure is shown in Figures 6 and 7. In these figures an insulating frame, generally indicated by numeral 60 is held in position within the treater by means of a rod 62 similar to rod 35 of Figures 1-3. This frame carries. a metallic coil 63 wound thereon, and held in tension by means of strips 64 and 65 made of an insulating material, and springs 66 and 6l. Coil 63 is preferably in the form of a band or a thin metallic ribbon and is grounded so as to act as one of the electrodes, i. e. an electrode similar to electrode 23. 'Ihe opposite ends of this coil 63 are also connected, as this is shown in Figure l in conjunction with resistance coil 38, to the opposite ends of a source of electric current. Obviously, the band acts as an electrode for the deposition of wax thereon when an electric potential is imposed across the gaps between adjacent coll systems acting as the electrodes. The coil 63 also acts as the heating means for the removal of the agglomerated and deposited wax when the opposite ends thereof are connected to a source of electric current.

Instead of passing the oil to be treated upwardly through the treater andvbetween the electrodes, it is obviously possible, and sometimes preferable, to introduce the oil to be treated through pipe Iii and remove the treated oil through pipe I6.

The heating oi the 'electrode surfaces during the periodic removal ot the wax deposited on the surfaces o! these electrodes is undesirable becauseoi' the fact that such heating raises the temperature and causes a part of the wax to go back into solution in the oil. To obviate this disadvantage it may be preferable to reverse momentarily the now of the oil through the treater, thus cooling the electrode surfaces with the dewaxed treated oil, rather than with the oil still containing the wax precipitate.

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

I claim: v

l. A process for dewaxing oil which comprises generating an electric field between electrodes of opposite polarity, passing a wax-containing oil through said ileld whereby wax is Vdeposited on certain of said electrodes and periodically heating said electrodes upon which wax has been deposited to remove the deposited wax from said electrodes while maintaining a body of wax-containing oil in contact with said electrodes.

2. A process asin claim l in which the heating of said electrodes upon which wax has been deposited is sufiiclent to melt the wax but is insumcient to appreciably heat the body of waxcontaining oil.

3. In an apparatus for electrically dewaxing oils, a chamber, a plurality of electrodes disposed within said chamber, means to ow the waxbearing oil between said electrodes, means `to impress an electric potential between adjacent pairs of said electrodes to deposit the wax on certain of said electrodes, and means associated with said electrodes and adapted to heat and remove therefrom the deposited wax.

4. In an apparatus for electrically dewaxing oils, a chamber, a plurality of plate electrodes disposed within said chamber, means to ow the wax-bearing oil between said electrodes, means to impress an electric potential between adjacent pairs of said plate electrodes to deposit the wax on certain of said electrodes, and means assoc'ated with said certain electrodes and adapted to heat and remove therefrom the deposited wax.

5. In an apparatus for electrically dewaxing Y oils, a chamber, a plurality of plate electrodes positioned within said chamber, means to flow the wax-bearing oil through the chamber and be tween said electrode plates, means to impress an electric potential between adjacent pairs of said plate electrodes to deposit the wax on certain of said electrodes, and electrical means associated with said certain electrodes and adapted to remove perlodically therefrom the wax deposited thereon.

6. A structure according to claim 5, wherein the electrical means for removing the wax depositlng on some of the electrodes, includes a resistance coil wound around the electrode and without contact therewith.

7. An apparatus for electrically treating waxbearing oils comprising a chamber. a baille plate within said chamber, having an opening therethrough and dividing the chamber into al plurality of compartments, means to flow the oil to be treated through said opening from one compartment to another, a plurality of plate electrodes positioned in the path of said oil and arranged so as to cause the oil to pass through the gaps therebetween, means to impress an electric potential between adjacent pairs of said plate electrodes and to cause the deposition of wax on certain of said electrodes, and heating means to remove the deposits from the surfaces of said certain electrodes.

8. A structure according to claim '7, wherein the heating means comprises a resistance coil actuated by electricity to heat the surfaces of the electrode to remove the wax deposited thereon. 9. In combination, a flat plate electrode adapted for the deposition of wax thereon, projecting insulating strips on said plate electrodes, and a heating coil wound over said strips and electrodes and out of contact with the latter.

10. In a dewaxing structure for wax-bearing oils, an electrode structure adapted for the deposition of wax thereon, comprising an insulating frame. a metallic band coil wound on said frame, means for connecting the coil to a source of electric potential, and means for passing periodically a heat-producing electric current through said coil.

' HARMON F. FISHER.

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