US1980071A - Separation of wax from hydrocarbon oils - Google Patents

Description

Nov. 6, 1934.. R. E. MANLr-:Y

SEPARATION OF WAX FROM HYDROCARBON OILS Filed April 20, 1931 NNI Q Km. RN.

/NVENTOR ,Ll/5 A TTORNEY Patented Nov.- 6, 1934 UNITED STATES PATENT oFFIcE SEPARATION OF WAX FROM HYDROCARBON OILS Robert E. Manley, Port Arthur, Tex., assignor to The Texas Company, New York, N. Y., a corporation of Delaware Application April 20, 1931, Serial No. 531,648

l Claim.

This invention relates to the separation or extraction of `paraiiin wax from hydrocarbon oils, and more 'particularly to an improved4 properties ofA dissolving all the hydrocarbonsA contained therein atielevated temperature and having a selective solvent action between the liquid hydrocarbons and solid hydrocarbons at relatively low temperatures, chilling the liquid solution to a point where the solid hydrocarbons separate out, then filtering the chilled solution to remove-the liquid hydrocarbons in solution from the separated solid hydrocarbons and washing the resulting filter cake of separated solid hydrocarbons, in situ, with` cold solvent liquid to remove entrained or adhering oil.

In my prior application, Serial No. 233,565, Afiled November 16, 1927, I have describeda process' for dewaxing hydrocarbon oils by ltration of a chilled mixture of solvent and oil in the presence of a filter-aid material and wherein the resulting cake of solid hydrocarbons and lter-aid material is subjected to,washing by forcing an oil solvent through the material deposited on the lter atk such temperature that no substantial quantity of the waxy constituents may be dissolved therein, whereby a substantially complete separation of voil from .the waxy F5 constitutents isfobtaineli. y

-My present invention comprises an improvement to the method of dewaxing oils disclosed in the aforesaid application, and has particularreference to the treatment of the slack wax 40 cake to eiect complete removal of the adhering and retained oil, and also produce substantially oil-free slack wax which is entirely satisfactory for sweating for the production of high melting -point wax. The invention has particular reference to the so-called solvent type of dewaxing process wherein, for example, the wax-bearing oil is mixed withlacetone and benzol in such a. ratio to each other and to the said fraction that the acetone and benzol together at temperatures of approximately 100 F. have substantially complete solventaction on the waxbearing oil and at temperatures of 5 F. and below, have substantially complete solvent action on the liquid hydrocarbons but substantially no solvent action on the -solid hydrocarbons in said fraction, and upon removal of the solid hydrocarbons and the acetone and benzol, such oil has a cold test substantially the same as the temperature of the mixture at the time of the removal of the solid`hydrocarbons, and following which the mixture is cooled to a temperature at which substantially all of the solid hydrocarbons are precipitatedand the cooled mixture then subjected to ltration toI separate the solid hydrocarbons so precipitated. E

The iilter cake of slack Wax or petrolatum formed in the filtration methods of dewaxing Wax-bearing hydrocarbon oils usually contains substantial proportions of 'liquid hydrocarbons which are not -only valuable as lubricating oil but also whenallowed to remain even in fairly small amounts in the Wax cake inhibit and pre- `vent the satisfactory sweating of the wax cake.

The complete removalof this adhering oil, particularly in the case of wax filter cakes formed in the dewaxing of hydrocarbon oils by means of a selective solvent such as acetone and ben'zol,

and wherethe resulting cake does not contain lter aid material, has never been realized heretofore.L As is usual in filtering operations of this type when a lter cake of desired thickness hasbeen built upion the ltering surfaces, it is customary to stop the iiow \of liquid into the filter and displace the contents of the lter shell, either-by draining out or by blowingback with gas or air and then subjecting the cake to washing with asuitable-washing liquids However, during the draining of the lter or blowing back of the-lter shell contents, and which includes the body oiliquid immediately adjacent the cake, substantial portions of the cakemay fall completely away from the iiltering surface, or the :cake may develop cracks so that during the subsequent cake washing step the'` washing liquid short circuits through the cracks in the cake 'y or through those portions of the-filtering ,sur-

li'aces vfrom which the cake has fallen; thus militating against the uniform'andeiiective washing.

of the filter cake.

thesolvent and dissolved oil while depositing the solid hydrocarbonson thev ltering surface in the form of a cake.

As soon' 'as a lter cake of desired thickness has been obtained the intro- I stopped and .the introduction to the filter of a solvent wash liquid is immediately started without a cessation of 'flow of liquid through the filter cake Yand filtering surfaces. 'I'he change in liquid ow from solvent and dissolved hydrocarbon liquid to pure solvent washing liquid is effected in such a manner as to maintain a continual plus liquid pressure on the filter cake during the final stages of filtration as well as throughout the washing period. In this way there is a body of liquid continually in contact with the entire surface of. the cake exerting a positive pressure thereover to facilitate its complete adherence to the filtering surfaceso that it does not become partially dislodged therefrom prior to or develop cracks during thefinitial stages of the washing period and, consequently, sinceshort circuiting of the solvent wash liquid is thus prevented, the filter cake is subjected to a complete and effective washing action, thereby resulting in the obtaining of a substantially oilefree wax cake.

Reference may be'made to the accompanying drawing which illustrates apparatus suitable for practicing the method of my invention.

This apparatus may comprise a charging tank 1 from which the dilute wax-bearing mixture is introduced to a chiller 2 wherein it may be chilled to a temperature of around 0 F. or below. From the chiller, the oil is conducted' through a pipe 3 having a valve 4 into the interior' of a filter 5. if'

The filter 5 is advantageously of the rotating leaf type and adapted for pressure filtration. It comprises an insulated shell containing a filtering element comprising a series of hollow leaves 6 supported on, vand integral with, a hollow rotating shaft '7.' In operation, the solids are deposited* on the exterior 4surfaces of the hollow leaves`while the filtrate passes therethrough into the interior of the leaves. Fromi the interior of eachleaf, the filtrate flows into the hollow shaft 'l from which it is discharged through a filter valve 8. l

From the valve 8, the filtrate is discharged through a pipe' 9 having a valve 10..

Solvent "liquid for washing the cake is con-j ducted from a tank 11 through a pipe 12, having a valve 13, into the interior of the filter 5. This wash solvent, together with the oil displacedfrom the filter and filter cakes, is 'removed from the filter through the hollow shaft rI in a manner similar tothat of the filtrate already described.v However, the wash liquidfmay be removed from the valve. 8 through a separate pipe v 14 having a valve 15.

4`lDuring filtration the filter shell is maintained -tance to flow of fluid through the cake, the pressure within the filter shell, asindicated on- 'a pressure gauge 16, alsoincreases, reaching a given maximum point when a cake of desired thickness has been formed.

At this point, the valve 4 is gradually closed l while -the valve 13 is' simultaneously open so as to maintain a substantially constant inflow of fluid tothe interior of the filter shell and thus continually maintain a plus-pressure therewithin.

The inflowing wash solvent liquid mingles with the liquid contents of the filter shell, and is displaced through the lter cakes into the hollow shaft 7, from which it is discharged from the filter. The flow of wash solvent into the filter is, continued until all the oil remaining in the filter shell and adhering to the 'cakes is displaced. Thereupon, the valve 13 is closed, and cold gas introduced to the lter through a valve 17 for the purpose of displacing the bulk of the remaining liquid contents of the ltery through the leaves and into the hollow shaft 7. The remaining portion of the liquid contents of the filter shell may be drawn off from the lter shell through a drain valve 18. Following this, the filter cake is removed from the filter leaves inthe usual manner by applying to the interior of the leaves a reverse flow gas pressure. The wax cake which thus aceumulates in the bottom ofthe shell is discharged therefrom through a valve 19.

As an' example for, the purpose of illustrating one mode of operation, I dissolve 1,000 gallons of wax bearing mineral-oil at a temperature of 90 `F. in a mixture of 1,110 gallons of acetone and 1,890 gallons. of benzoland cool the solution 1n vthe chiller 2 to ,-10* F. to effect precipitation of f the solid hydrocarbons. The cooled mixture ofV dissolved oil and solid matter suspended gtherein is introduced to filter press 5, advantageously of the rotating leaf type, wherein the solvent and dissolvedv liquid hydrocarbons are removed and a filter cake of slack wax of desired thickcake and filtering surfaces while the filtering element is kept in drotation, thus displacing the filtering mixture of solvent, dissolved oil and solid hydrocarbons from the filtery and also displacing the liquid hydrocarbons fromthe cake itself. The Ywashing is-kept up until a sample of the solvent wash liquid Aexhibits a compara.'- tive absence "of dissolved liquid hydrocarbons, indicating that the retained oil has been substantially completely removed from the filter i cake. The introduction of solvent wash is then( stopped whereupon a cool gas is admitted through the valve 17 to the filter to displace the greater portion of the solvent liquid retained in the filter cake and after which the filter cake is ,removed fr om the lter.

The washed cake may then be transferred to a still wherein the solvent is removed by evap'ofration and recovered for further use and the. solvent free wax is run to sweat pans wherein it y be sweated in the usual manner to a desired melting point or to produce wax fractions of different melting points.

All or a portion ofthe wash solvent liquor accumulated during the washing of the filter cake may be used as the original solvent for mixing with fresh wax bearing oil which is to undergo treatment. On the other hand, all or a portion of it may be run in with the filtrate and subjected to distillation therewith to remove the solventliquid andfurnish additional low cold test oil since the ,wash liquid may contain substantial amounts of such oil dissolved therein.

The portion of the wash liquor diverted back to the filtrate is dependent upon the quantity of oil or liquid hydrocarbon dissolved therein, the wash liquor or solvent initially passing through the press, particularly during the oil displacement period, being quite rich inA dissolved oil and becoming progressively leaner as washing continues, nally reaching a point where it contains substantially no dissolved oil, and at which point it 'may advantageously be I diverted Without further treatment for use in the dissolving of fresh Wax bearing oil.

While in the above example I have described a dewaxing operation wherein the wax-bearing mineral oil has been mixed with a selective solvent consisting of suitable proportions of acetone and benzol, it is contemplated that the invention is equally applicable to` dewaxing operations wherein other solvents, suchas petroleum naphtha, for example,y may be employed.

'Ihe invention is not limited to the treatment of a mineral oil such as given in the example herein, but is adapted to the treatment of other wax containing fractions of precipitates obtained from crude oils and may, for example, embrace the treatment of solid yhydrocarbons contained in a slack Wax produced in the manufacture of low cold test lubricating oils, and which material is an equivalent of the stock referred to in the example. Thus, while the example describedl advantageously `sets forth one modeof operation, the invention is not restricted to any particular set of operating conditions such as that of temperature, etc., as therein described and it'is, therefore, contemplated that many modications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claim.

I claim:

In the process of manufacturing lubricating oil from wax-bearing mineral oil comprising mixing the oil with a solvent comprising acetone and benzol mixed in substantial proportions, chilling the resulting mixture to a temperature of 0 F. or lower to eiIect precipitation of solid hydrocarbons and introducing the chilled mixture to, pressure lteringmeans to remove the solvent and liquid hydrocarbons and form a illter cake of solid hydrocarbons, the steps comprising introducing acetone and benzol mixed in substantially the same proportions and chilled to a temperature of 0 F. or below to the filtering means simultaneously with the cessation of flow of filtering mixture thereto, whereby Ithe lter is maintained full of liquid and a plus liquid pressure is continuously maintained upon the lter cake throughout filtration and the subsequent cake washing step, thereby preventing fracturing or dislodgment of the cake, continuing the ilow of said solvent through the cake, in situ, to remove adhering and entrained liquid hydrocarbons therefrom, and while uninterruptedly continuing the positive pressure within the filter forcing a cool gas through the washed cake to remove retained solvent liquid.

ROBERT E. MANLEY.

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