US2042776A - Apparatus for dewaxing oil - Google Patents

Description

June 2, 1936. H. F. FISHER 2,042,776

APPARATUS FOR DEWAXING OIL Filed Sept. 18, 1953 INVENTOR Harmon F Firs/292" ATTORNEY.

Patented June 2, 1936 UNITED STATES PATENT OFFICE APPARATUS FOR DEWAXING 01L Application September 18, 1933, Serial No. 689,985

7 Claims.

This invention relates to apparatus for the separation of wax from wax-bearing oil. The

invention relates more particularly to apparatus for the separation of precipitated wax from suspension in oil.

Many crude oils from which lubricating oil is produced contain parafiin or wax. It is found associated with lubricating oil fractions of paraffin base crude oil, asphalt base crude oil and the mixtures or blends of lubricating oil fractions of both paraflin and asphalt base crude oils. The wax is of limited lubricating value and also limits the minimum temperature at which lubricating oils containing it can be used, by congealing at low temperatures. Therefore, in the production of lubricating oil from petroleum fractions containing wax and paraffin it is necessary to remove a large proportion of the wax and paraffin present in the oil in order to lower its pour point and the temperature at which it congeals. In the separation of wax from wax-bearing oils by electrical processes the wax-bearing oils are mixed with suitable diluents, the solution of oil and diluent chilled to a temperature at which the wax precipitates from solution and the resulting mixture of wax-bearing oil', diluent and the suspension of precipitated wax subjected to an electric field between electrodes submerged .in'v said solution. A major portion of the precipitated wax suspension under the influence of the electric field is separated from the mixture in the form of a deposit upon the electrodes between which the said treating field is maintained. The diluent may be recovered by distillation subsequent to the electrical separation of the wax from the solution.

After a short period of electrical treating to remove precipitated wax from the chilled waxbearing oil, the electrodes upon which the wax is deposited become thickly coated with the deposited wax and it is necessary that this wax be removed from time to time in order to maintain the apparatus in operative condition. If the wax is allowed to accumulate to an appreciable thickness on the electrodes it decreases the effectiveness of the electrical precipitating and depositing action and reduces the cross sectional area of the passage between theelectrodes through which the oil undergoing treatment flows. This reduction in cross sectional area of treating space results in an increase in velocity of the wax-bearing oil undergoing treatment and a consequent decrease in time during which the oil remains in the treating field, and thus the capacity of the treater is either reduced or the thoroughness of the treating 55 impaired by allowing an accumulation of wax on fil the electrodes. Furthermore, the wax may in time accumulate to the extent that the entire treating space between the electrodes is filled with it and the wax-bearing oil forced to channel its way through the wax and by-pass the treating field.

It has been found that apparatus for the electrical deposition of precipitated wax from oil may be constructed to operate over long periods of time without attention, by providing said apparatus with a large area of electrode surfaces and suitable mechanical means for maintaining these surfaces reasonably free from deposited wax.

Objects of this invention therefore are to provide an apparatus for dewaxing oil which will be efficient, of high capacity and capable of operating for long periods of time without attention. Other objects are to provide an electric treater for dewaxing oil in which the completeness of the separation of precipitated wax from the waxbearing oil will be a maximum and in which the electric treating zone will be continuously maintained in operative condition by mechanical removal therefrom of accumulated wax.

In general these objects are attained according to the invention by providing an electrical treater structure incorporating a large electrode surface area and suitable mechanical scraper means for periodically or continuously freeing said electrode surfaces from accumulated deposit of wax. These objects are also attained according to the invention by providing suitable mechanical means for moving certain of the electrode surfaces through suitable scraper means for removing said accumulated wax, and by providing means for ejecting the wax from the treater.

The apparatus adapted to operate, as hereinbefore described, for the continuous deposition of precipitated wax from wax-bearing oil comprises in brief a tank, through which the wax-bearing oil flows, containing a number of parallel interspaced plate electrodes constructed of thin metal sheets. The electrodes are arranged and suitably insulated so that alternate plates may be charged to opposite electrical potentials to provide electric treating fields between the spaces of adjacent plates. Vertical supporting guiding members are provided within the treater tank between the thin plate electrodes to serve as spacers and to impart lateral rigidity to the otherwise flexible metallic sheet electrodes. These said members are not attached to the electrodes but merely make contact along the surfaces thereof and suflicientfreedom is provided between said plate electrodes and bearing oil comprising a plurality of flat plate.

electrodes, the adjacent plates being adapted to be oppositely electrically charged and mechanical means for removing accumulated wax from the surfaces of said plate electrodes.

The invention more specifically resides in anparatus comprising a tank to contain the oil undergoing treatment, a-plurality of interleaved flat plate electrodes adjacent ones of which are electrically insulated from one another, a means of supporting alternate electrode plates so that they may be moved or shifted in a body longitudinally through suitable supporting and spacing means whereby said spacing means also serve as scrap ing means for removing accumulated deposited wax from said electrode plate surfaces, means for supporting stationary plate electrodes in an interspaced position between said movable electrode plates, means for electrically insulating said stationary plates and said movableplates from one another, means to charge said plates to a high 1 electric potential relative to one another, means for flowing the wax-bearing oil through the treating spaces between the said plate electrodes and means for removing wax and oil from the treater.

Other objects, advantages and features of the invention will be evident hereinafter.

The accompanying drawing illustrates one em.- bodiment of the invention in which Fig. 1 is a sectional elevation of the treater assembly. Fig. 2 is a plan section through the treater unit taken on line AA. Fig. 3 is a plan section taken through the treater unit on line BB. Fig. 4 is a vertical section taken through the electrodes along line 4-4.

The treater unit shown in cross sectional elevation in Fig. 1 is enclosed in a cylindrical shell having an inverted conical bottom 2 and a bumped head top 3. A wax-bearing oil inlet pipe 4 is provided in the bottom section of the treater shell and a dewaxed oil outlet pipe 5 is provided near the top thereof. Also a wax pump is provided at the apex of the inverted conical bottom for the discharge of wax settlings through .discharge pipe 8. A high voltage lead-in insulator bushing I0 is provided through the bumped head top of the treater for the purpose of making electrical connections from the high voltage supply to the electrodesinside of the unit.

I A plurality of spaced rectangular plate electrodes El-E6 are centrally positioned and vertically supported in the treater shell at the top by means of supporting insulators l1 and I8 which are in turn supported from the treater shell by two cross members l9 and 20." Thesaid plate electrodes are maintained in proper spaced relationship to one another by means of requisite spacers at the top and bottom ends thereof which are held in position by bolts as shown at l5 and I6. Said plate electrodes E1Es are electrically insulated from the ground by means of insulators l1 and I8 and electrical connection is made to I the outside of the treater through lead-in insulator bushing l0 and electrical connection 9.

A plurality of plate electrodes E7E13 extend through and are inter-spaced between, stationary .electrodes E1-Ea as shown in Fig. 2 and are movably supported on supporting diaphragm 2| which extends across the lower middlesection of the treater. A number of vertically positioned channels C1Cs and 07 -013 are rigidly attached at their lower ends to the supporting diaphragm 2| on either side of the edges of stationary electrodes E1Ee. vSaid vertically positioned channels extend upward through and between the movable plate electrodes and serve as guides for the movement of these electrodes as well as to impart rigidity to the plates and to the whole electrode assembly. In addition to this the channels making a close fit against the flat plate electrodes act as scrapers so that when the movable electrodes E7E13 are moved longitudinally through the spaces between the stationary electrodes and between the said channels, any deposited material thereon will be removed, These channel spacers and scrapers may be urged against the electrode surfaces by means of springs or othersuitable mechanical means if desired.

But it-hasbeen found that they may be rigidly attached to the supporting diaphragm with space between them sufiicient to give the movable plate 0 electrodes a reasonable clearance for movement chanically joined and spaced at the ends by suitable tie bars as shown at 23 and 25 and the-weight of the whole movable electrode assembly is supported by the lower edges of the movable electrodes on diaphragm 2| which is in turn supported by angle iron ring 22.

Diaphragm 2| extends across the treater and divides the treater into upper and lower sections communicating through a central openingin the diaphragm around stationary electrodes E1--Ee which opening is outlined by movable electrode" -plates E7 and E13 and channels C1-Cs and 01-013. Thus oil flowing from the lower portion of the treater to the upper portion is forced by diaphragm 2| to flow between the plates of the movable electrodes. and the stationary electrodes and is confined to this path by channels C1-C12.

The movable electrodes Ev-Em are slowly reciprocated from left to right through the stationary electrodes and through the channel guides or scrapers. The maximum right hand position of the movable electrode group is shown by dotted lines in Fig. 2. Reciprocating motion is imparted to the movable electrodes by means of a rod'26 which passes through a stufiing box 21 through the treater shell I, and this rod is in turn moved with a reciprocating motion by suitable crank mechanism 28 and 30 driven by an electric motor 3| on the outside of the treater unit.

- The operation is as follows: Chilled wax-bearing. oil containing precipitated wax in suspension enters the treater through inlet pipe 4 and passes upward through the opening in diaphragm 2| into the space between the stationary electrodes E1E6 and the movable electrodes E7--E1a where it is subjected to an intense electric field therebetween. The intense electric field is established and maintained between the' stationary and movable electrodes by a suitable high voltage source, such as a generator |2 electrically connected through electrical connection Ii, high voltage lead-in insulator it and electrical conductor 9. The return circuit to the generator is completedthrough the ground and ground connection l3. The wax precipitate in the wax- -bearing oil under the influence of the electric field is deposited on the active surfaces of the movable electrodes. The dewaxed oil having thus had the precipitated wax removed moves upward out of the treating zone between the electrodes into the upper portion of the treater from where, after a period-of relative quiescence and settling, it is withdrawn through outlet as the a deposition or layer of wax of appreciable thickness will appear on the active surfaces of the movable electrodes. If this deposit is allowed to accumulate it will in time grow to a thickness where the action of the treater is impaired and the cross sectional area of the treating space is materially reduced. Thus, it is necessary to periodically or continuously remove this deposited layer of wax from the electrode surfaces and this is accomplished byperiodic movement or reciprocation of the movable electrode longitudinally through the spacer and scraper channels C1--C12, described hercinbefore. Wax thus scraped from the movable electrode surfaces will settle counter-currently through the wax-bearing oil stream and pass through the central opening of diaphragm 2i into the inverted conical bottom portion of the treater. Wax thus accumulated in the conical bottom of the treater is removed and ejected therefrom through line B by means of wax pump ll.

posited wax.

taining the electrodes suiiiciently clear. of de- It has been found that the wax particles in most colloidal suspensions of precipitated wax resulting from chilling of wax-bearing oil, is negatively charged, therefore, by providing for a positive polarity on the movable electrodes, deposition of a major-portion of the wax on the movable electrode is insured-and it is unnecessary to provide mechanical means for cleaning the negative stationary electrodes.

Where the charges on the precipitated wax are found to differ from this the polarities of the electrodes may obviously be reversed as required to cause the deposition to take place on the electrode which is provided with means for wax removal.

The apparatus is not to be limited to the treatment of oils for the removal of wax but is applicable to the treatment of similar substances or for the removal of asphalt, asphaltines, petrolatum, sludges and other substances and impurities both solid and plastic.

The foregoing is merely. illustrative of one apparatus and invention and is not limited thereby but may include any apparatus which accomplishes the same within the scope of the invention.

I claim: 1. Apparatus for electrically treating warbearing oil comprising a; tank to contain the oil to be treated, an electrode in said tank, means contacting said electrode to remove wax from said electrode, means to impart a relative reciprocating motion between said electrode and 5 said wax removing means, means to withdraw treated oil from said tank and means to withdraw wax from said tank.

2. Apparatus for electrically treating waxbearing oil comprising a tank to contain the oil to be treated, an electrode in said tank, a scraper making contact with a surface of said electrode means to impart a relative reciprocating motion between said electrode and said scraper, means to withdraw treated oilfrom a point in said tank 15 above said electrode and means to withdraw wax from'said tank at a. point below said electrode.

3. Apparatus for electrically treating waxbearing oil comprising a tank to contain the oil to be treated, a plurality of movable electrodes in said tank, a plurality of stationary scraper means in said tank in contact with the surfaces of said electrodes means to reciprocate said electrodes, means to withdraw treated oil from a point in said tank above said electrodes and means to withdraw wax from said tank at a point below said electrodes.

4. Apparatus for electrically treating waxbearing oil comprising a tank to contain the oil to be treated, a stationary electrode in said tank, a movable electrode in said tank in spaced relationship with said stationary electrode, a scraper in contact with the surface of said movable electrode means to impart reciprocating motion to said movable electrode relative to said scraper and said stationary electrode, means to withdraw treated oil from a point in said tank above said electrodes and means to withdraw wax from said tank at a point below said electrodes.

' 5. Apparatus for electrically treating wax- 40 hearing oil comprising a tank to contain the oil to be treated, aplurality of stationary electrodes in said tank, a plurality of interspaced movable electrodes insaid tank, scraper means in contact with surfaces of said movable electrodes means 45 to reciprocate said movable electrodes whereby motion is imparted to said electrodes relative to saidscraper means, means to withdraw treated oil from a point in said tank'above said electrodes and means to withdraw wax from said tank at a 50 point below said electrodes.

6. Apparatus for electrically treating waxbearing oil comprising a tank to contain the oil to be treated, a plurality of parallel spaced, vertically disposed supporting members in said tank, 55 a plurality of plate electrodes freely extending between and vertically supported by said supporting means whereby said plate electrodes are free to move horizontally in their extended planes. I

I. Apparatus for electrically treating waxbearing oil comprising a tank to contain the oil to be treated, a diaphragm having a central opening dividing the tank into upper and lower portions, a plurality ofplate electrodes vertically 65 positioned and supported by said diaphragm over said opening, means to flow oil to be treated from EAR-HON 1". FISHER. 75

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