US1715670A - Dewaxing lubricants by double centrifuging - Google Patents

Description

I www@ June 4, l1929.

Filed Oct. 15, 1927 GVFOLSENv INVENTOR.

v MEDQE BY Maf/.@m

ATTORNEY l Patented June 4, 1929.`

GEORGE FREI-)RIC OLSE'N, OF LOS ANGELES, CALIFORNIA.

DEWAXING LUBRICANTS BY DOUBLE CENTRIFUGING.

Application led october 15, 1927. Serial No. 226,510.

AMy invention relates to the removal of par-.

atin wax from lubricating oils which have been diluted with petroleum naphtha and chilled for the precipitation of the wax. My

invention relates more particularly to a method in which thechilled solution is twice centrifuged at different temperatures and with different adjustments of the centrifuging machine.

The object of myinvention is to obtain a drier wax than hasheretofore been obtainable, thus reducing the loss of valuable oil entrained in the wax and to obtain a greater output per machine than has heretofore been possible. My invention is particularly applicable to such oils as contain a large quantity `of wax and must of necessity be twice centrifuged, but it is also advantageous when applied to oils containing smaller quantities of wax and which have heretofore been completely dewaxed in one stage.

Itis well known in the art that residual petroleum oils containing wax, and therefore having too high a cold test for commercial requirements, are often diluted with a suitable naphtha in order to separate the wax from the oil. The methods by which this solution of residual oils are chilled and centrifuged are also well known and understood. In general terms these methods comprise: chilling the oil to the requisite low temperature, (which is often as low as minus 20 F.) and passing it through a suitable type of centrifuge by which a finely crystalline or amorphous wax containing considerablev entrained oil is separated from the solution of residual oil. The latter is then deprived of the solvent by well known methods, and sometimes further treated with acid or adsorbent, or both, for the production of the desired color.

In cases where oils 'contain a very large proportion of wax it has heretofore been the practice to partially chill the oil for the'separation of a portion of the wax, to return the partially dewaxed solution to a second chiller by which it is brought to the final temperature,l and to centrifuge the second chilled solution for obtaining a second crop of wax and the required cold test.

In my improved method of dewaxing in two stages I follow any usual or preferred method of carrying out the chilling and cent-rifuging operations, my invention lying, first, in the rate at which the oil is chilled in the two stages, second, in the different time rates at which the oil is centrifuged in the two stages, and third in returningthe second stage wax to a new batch of unseparated oil for the recovery from said second stage wax of a substantial quantity of oil entrained therein. v

In detail, my method consists of the following steps: I first prepare the customary solution of oil in'naphtha or petroleum distillate, using the customary proportion of naphtha to oil, which may range from three parts of oil with two partsof naphtha to two parts of oil with three parts of naphtha. I then chill this solution, using any usual or preferred means, to a temperature ranging form 260 to 20 above zero F., atwhich temperature a material proportion of the wax `will be set free from solution. This first stage chilling should be' carried out at a rate of about 4 F. temperature drop per hour, in order to avoid gelatinization of the oil-wax solution. The chilled mixture is then centrifuged in the usual manner, but in this first centrifuging it is essential that the machine be set to a close adjustment and the driest possible wax obtained. This wax is segregated and directed to its ordinary uses, which are no 'part of my present invention.

The solution, still containing a small quantity of wax, is then further chilled to such temperature as is required to produce the required cold test yon the finished oil. This temperature can not -be stated in figures as it will depend on the nature of the oil, the degree of dilution and the predetermined cold test, but it may be said -that the temperature will be substantially higher than would be required if the wax were to be removed in the first stage, or even in a two stage operation as heretofore conducted. The twice chilled oil is then again centrifuged but, instead of using the usual adjustment of the machine, this is Set to a very slack adjustmentwhich will remove the wax rapidly and completely from the solution but will leave a materiallquantity of solution entrained in the wax. The-advantages of this slack adjustment are a much greater throughout capacity for the .Second .Stage machinathe more complete removal of wax, and a higher centrithe application ofthe usual method of two fuging temperature with a corresponding'restage chllhng and centrifuging, and will often duction in the. amount of refrigeration re-V be lnaterially greater than their outputA when quiredwhich is most expensive at such low operated single stage on oils which can be de- 5 temperatures as are required for the final waxed in a single operation. The iinalwax 70 chill'. will also carry lessoil, the operating loss will If this second stage wax were to be segrebe correspondingly reduced. and the refriggated and diverted to its usual uses the loss eration eHect required will also be materially of oil by entrainment in the wax would be a decreased.

' prohibitive bar to the application of this As an illustration of the manner in which 75 method. I therefore return this slack wax, my invention may be applied to the produc- Which consists of paralins having relatively tion of low cold test lubricating oils and withlow melting points, to another batch of fresh out in any way limiting the scope of such in- 'solution prior to the rst chilling. On the vention to the 'specific details comprised in addition of such wax to an unchilled solution such description, I submit the following: 80 the wax immediately dissolves and is in part I start with a crude petroleum of suitable reprecipitated in the first stage chilling of the quality. such for instance as the oil from the second batch, the harder and higher melting` pioneer field in Oklahoma. This oil I reduce point waxes carried by the original solution in a still to the. required viscosity and flash,

2o acting as points dappui for this smaller quantreat the residue orI still bottom with sulfuric 85 tity of soft wax arfdipreventing it from asacid` settle out the acid sludge thus formed,v suming the 'slimy consistency which makes it and neutralize and decolorize the acid treatdiiiicultand tedious to separate sharply from ed oil by heating it with a suitable adsorbent thesolution. clay. such for instance as'the well known Inasmuch as all the wax is inally removed, -Death Valley clay. at a temperature approxi- 90 in the 'rst stage centrifuging, it may appear mately 450 and 500 F..finallyfiltering out at first sight that the addition of a second the spent clay and permittitn'g the decolorized stage centrifuging is a useless loading of the oil to cool. This is .ordinary refinery pracmanipulation. This, however, is not the .tice which is well known and understood and case. In ordinary two` stage chilling it is the. is no part of my invention', the description be- 95 custom `to strip the oil from the wax as coming given solely-to` illustrate the manner in pletely as possible in both stages, and in sinwhich a raw stock suitablefor the application gle stage chilling it is absolutely necessary to .of my invention may be prepared. strip closely in the single centrifuging opera- -I then introduce any desired quantity of tion. When this close stripping in a single the prepared lubricating stock. which con- 100 stage is conducted atthe very lw temperature tains a considerable proportion of wax or` required toproducethe final cold test'. the paraffin, into one or the other of the dilution `separation becomes very slow because of the tanks A-B, (see Fig. 1). These tanks are material increase in viscosity of the 'solution at provided for the purpose of diluting the oil 40 such low-temperatures, which range from 20 and Chillina the SOIUD formed by such di- 105 to 30 or even 40 F. below zero-. If the chilllution. and may be identical in size and coning is conducted in two stages and the wax struction, the-tanksbeing most conveniently product from the second stage is segregated as used alternately. In the present example I- wax, as has heretofore been the custom; it is introduce the prepared lub1-icatitngstockinto necessary to strip very closely in the second-v tank A. through the pipe line C commu'nicat- 110 stage, and this is still more tedious because of ing with-.a -Source of supply of lubricatingthe soft consistency of the wax separated in 'stock not shown. Pipe C also communicates the second stage and the relatively slight with asource of supply not shown of -a suit# gravity dierence between this wax and the able diluting material. I Iprefer to usela 1 5o solution. The density of the solution inpetroleum naphtha having the general chaff 115 creases rapidly with diminishing tempera..n-ctciistics of gasoline. but a somewh nar-f' 'l ture while the density of the wax 2remains rowercutl.a fraction havingan initial peint'zbf substantially unchanged. If, however, the 200 F. and an end point of 400 F. being suitsecond stage wax be produced by a .Lslac'k able. This naphtha should be refined to a adjustment of the machine, so that it-will vwater white color and should be clean vand 1'20 entrain and carry away a material proporsweet. I woulduseabout onel and one-'half tion of solution into the slack waxf, which volumes of such naphtha to one volume of the is returned to an original solution for the -prepared lubricating stock and mix the two stripping of the oil from the wax, the second in tank A by any convenient agitating I'ne `ans stage operation also may be performed rapidnot shown. i125 ly and cheaply. The total output of a given The dilution tanks A; and';B should bepro- Y number of machines, when handled according vided with cooling coils through which co'ldl to my improved method as above set forth, brine may be passed for the `purpose of reduc will always be materially greater than the ing thetemperature of the contentsy of the 65 output which could be obtained from them by tank. Such brine is admitted through the 130 'means,' passing the vtank where it absorbs heat from the con,-

. a final dischar inuevo pipe I)y from any convenient refrigerating t ence through coils within tents yof the tank, and passing out through the pipe E to return to the refrigerating means. This brine may be cooled to about F., and

while brine is being passedthrough the coils the contents of thel tank should be vgently stirred to bring the cooling oil into contact with the' coils, but the stirring 4should not be suiciently vigorous to'break the crystals of wax as this will cause the formation of very line crystals, which are diicult to separate. In this first stage chilling I prefer to cool at a rate of approximately 4 F. temperature drop er hour and in this specific example I pre er to cool the solution to approximately 26 F.

When this temperaturehas been reached4 the contents of the dilutiontank are withdrawn through the pipe F and fed into the first stage centrifufga G. This centrifuge may be of any pre erred type'and there are available numerous machines adapted' to this particular purpose of. separating oilV from wax, the 'character and use of which is well known to those skilled in the art.

In this machine'the solution is se 'arated from the larger part but not Vall of t e wax. The machie should be set to avery close adjustment in order to obtain the driest possible waxas the wax is lessvaluable than the oil '4 andthe wax dischar from this machine .is

an .any oil content is irrecoverable. e wax leavesl the machine through the pipe or conduit H andis. dis-v charged as at the pointJ to a container from whic it may be withdrawn-forany use for which it may be suited.

The oil solution, from centrifugal G is carried through the pipe K to one orvthe other of a pair of cooling tanks L M, which may be similar to or identical with solution tanks A and B. In the 'present illustration I will assume that the oil is dischar ed throu h the pipe K into tank L, tank filled with solution resulting from a prior operation of the same character. These tanks `also are equipped with cooling coils supplied with cold brine throughthe pipe N from a refrigerating means not shown, the warmed brine returning through the pipe O 'to the refrigerating means. It -is obvious that b making suitable connections between pipe g and pipe lD the cooling brine escaping from' tanks L and M, which are maintained at a very low temperature, might be used for chilling the contents of tanks A and B, which are maintained at a materially higher temperature.

The contents of tanks L and M should be cooled to a temperature suitable for obtaining the desiredfiiash test on the finished oil,

in this casefsayg.v 4below 0 F. It will be understood that tanks are to be used present invention.

vThe Aoperation should being a readypairs -of ta ter than the 4 per hour towhich the first stage chilling is limited, as for instance at a rate of 10 to 15 F. per hour.

The second stagecentrifugal Q is set with a slack adjustment and is fed at such rate that,

while the wax is not completely deprived of solution, the solution is completely deprived of wax. The dewaxed solution is conveyed from the centrifugal through the pipe R and 'escapes as at S to a tank or receptacle from which it maybe withdrawn for the removal of the dilutingnaphtha, by which removal the lubricating oil is recovered as such. This removal of naphtha'by distilling and steaming is conventional practice and i-s no part of my The slack wax lfrom the second Stageucentrifugal Q. still contains a valuable Iquantity of solution. It is, therefore, conveyed from this centrifugal through the pipes T and C linto the first. stage dilution'tank B, Where itl is admixed with a new charge 'of oil, either before or after the dilution of such oil with naphtha, butprior to the chilling operation above described. The mixture, being diluted, isthen chilledas first described, to the aforesaid temperature of a proximately 26 F. e so conducted that by the time tank A is emptyztank B will have been filled and cooled to the proper temperature. At such time tank L will be filled-with partly Astripped oil and tank M should also e empty at this time, its contents having been fed'through the second stage centrifugal. At such time the valve connections to the tanks are reversed, the first stage centrifugal G be- -I ing fed from'tank B, the discharge from this centrifugal passing into tank M, the secondsta e centrifugal Q, beingl fed from tank L an the discharge from this centrifugalpassing backto tank A. By this means continuous operation .of the centrifuges may be maintained, the only requisite being that t-he feed to the two centrifugals beibalancedat substantiallljysthe same rates in order that the (A-L and B,---M)l may empty at substantially the same time. v`Where I speak of a centrifugal (itv or a centrifugal Q it will be understood that in practicev a plufor each stage, the capacity of each individual unit being small.

I call particular attention to 'the 4 1 in this method of operating, the final removal 1,30

las. rality of centrifugal units would be provided j I of Wax is solely from the first stage centrifugal; that the wax from the second stage centrifugal passes back to and through the first stage, and that the final separation of dewaxed oil is from' the second stage centrifugal only.

I claim as my invention:

l. The method of separating wax from lubricating oils by means of dilution, chilling and centrifuging, comprising the following steps in the order named: diluting the oil with naphtha; slowly chilling the solution to substantially 20 F.; centrifuging said solution with a close adjustment of the machine for sharp separation of solution from wax; diverting substantially oil-free wax from the system; again chilling said solution at a substantiallv faster rat-ey than in the first chilling, to such point as will bring the finished oil to the desired cold test; centrifuging the second chilled solution with a slack adjustment of the machine for the partial separation of solution from wax; diverting substantially wax-free oil from the system; returning the last said slack wax to another batch of diluted oil which has not `been chilled, and chilling said mixture of oil and wax and centrifuging the chilled mixture as first aforesaid.

2. The method of separating wax from lubricating oils by means of dilution, chilling and centrifuging, comprising the following vmi steps in the order named: diluting the oil with naphtha; slowly chilling the solution to a temperature of partial separation of the wax from said solution; diverting substantially oil-free wax from the system; centrifuging said solution with a close adjustment of the machine for sharp separation of solution from wax; again chilling said solution at a substantially faster rate than in the first chilling, to such point as will bring the finished oil to the desired cold test; centrifuging the second chilled solution with a slack adj ustment of the machine for the partial separation of solution from wax; diverting substantially wax-free oil from the system; returning the last said slack wax to another batch of diluted oil which has not been chilled, andjchilling said mixture of oil and wax and centrifuging the chilled mixture as first aforesaid. 3. The method of separating wax from lubricating oils by means of dilution, chilling and centrifuging, comprising the following steps in the order named: diluting the oil with naphtha; slowly chilling the solution to substantially 20 AF.; centrifuging said solution with a close adjustment of the machine for sharp separation of solution from wax; diverting substantially oil-free wax from the system; further chilling said solutionto such point as will bring the'finished oilto the desired cold test; centrifuging the second chilled solution with a slack adjustment of the machine f or the lpartial separation of solution from wax; diverting substantially wax-free oil from the system; returning thc last said slack wax to another batch of diluted oil which has not been chilled, and chilling said mixture of oil and wax and centrifuging the chilled mixture as first aforesaid.

y4. The method of separating wax from lubricating oils by means of dilution, chilling and'centrifuging, comprising the following steps in the order named: diluting the oil with naphtha; slowly chilling the solution to a temperature of partial separation of Wax from said solution; centrifugingsaid solution with a close adjustment lof the machine for sharp separation of solution from Wax; diverting substantially oil-free wax from the system; further chilling said solution to such point as will bring the finished oil to the dcsired cold test; centrifuging the second chilled solution with a slack adjustment of the machine for the partial separation of solution from wax; diverting substantially waxfree oil from the system; returning the last said slack wax to another batch of dilutedv oil which has not been chilled, and chilling said mixture of oil and wax and centrifuging the chilled mixture as first aforesaid.

5. The method of separating wax from lubricating oils by means of dilution, chilling and centrifuging, comprising the following steps in the order named: diluting the oil with naphtha; chilling the solution at a rate not exceeding 40 F. temperature drop per hour to substantially 20 F.; centrifuging said solution with a close adjustment ofthe machine for sharp separation of solution from wax; diverting substantially oil-free Wax from the system; again chilling said solution at a substantially faster rate than in the first chilling, to such a point as will bring the finished oil to the desired cold test; centrifuging the second chilled solution with a slack adjustment of the machine for the partial separation of solution from wax; diverting substantially wax-free oil from the system; returning the last said slack wax to another batch of diluted oil which has not been chilled, and chilling said mixture of oil and wax and centrifuging the chilled mixture as first aforesaid.

6. The method of separating wax from lul bricating oils .by meansof dilution, chilling with naphtha; chilling the solution at a rate g not exceeding 4? hour to a temperature of partial separation of the wax from said solution; centrifuging said solution with a close adjustment of the machine `for sharp from wax, diverting substantially oil-free wax from the system; again chilling said solution at a substantially faster rate than in F. temperature drop per separat-ion of solution i the erst chilling, t@ such point as win bring 1.3

, the finished oil to the desired cold test; centrifuging the second chilled solution with a slack adjustment of the machine for the narl,

chilled, and chilling said mixture of oil and Wax and centrifuging the chilled mixture as first aforesaid.

7. The method of separating wax from lubricating oilsI by means of dilution, chilling and centrifuging, comprisingithe following steps in the order named: diluting the oil With naphtha; chilling the solution at a rate not exceeding 4 F. temperature drop 4per hour to substantially F.; centrifuging said solution with a close adjustment of the machine for sharp separation of solution from Wax; diverting substantially oil-free wax from the system; further chilling said solution to such point as will bring the linished oil to the desired cold test; centrifuging the second chilled solution with a slack adj ustment of the machine for the partial separation of solution from wax; diverting substantially wax-free oil from the system; re-

. turning the last said slack wax to another batch of diluted oil which has not been chilled, and chilling said mixture of oil and October, 1927.

Wax and centrifuging the chilled mixture as first aforesaid.-

8. The method of separating Wax from 1ubricating oils by means of dilution chilling and centrifuging, comprising the ollowing steps in the ordernamed: diluting the oil With naphtha; chilling the solution at a rate not exceeding 4 F. temperature drop per -hour to a temperature of partial separation of wax from said solution; centrifuging said solution with a close adjustment of the machine for sharp separation of solution from Wax; diverting substantially oil-free Wax 'fromthe system;'further chilling said solu-y tion to such point as will bring the nished oil to the desired cold test; centrifugin the second chilled solution with a slack a j tion of solution from wax; diverting substantially Wax-free oil from the system; returning the last said slack wax to another batch of diluted oil which has not been chilled, and chilling said mixture of oil and Wax and centrifuging the chilled mixture as first aforesaid.

In 'Witness that I claim the foregoing I have hereunto subscribed my name this 6th day of GEORGE FREDRIC oLsEN.y

ust-4 ment of the machine for the partial separa-

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