US2168143A - Oil dewaxing - Google Patents

Description

1, 1939-- Y AVH. SCHUTTE 2,158,143

OIL DEWAXING Filed May 19, 1938 2 Sheets-Sheet 2 Warm Wash G'lzz'l Refrigerant Mixer Wax Refrigerant; jalpeizt 5'1 Hq'g/z [Melting Wax Intermediate Melting Wax cold Wash 75' f iVar/n Wash Wax low Infer- Non-Solvent Z011; Pour 01' Ref/Ligamnt Low [Mehfirgg We ut: 1v VENTOR I Patented Aug. 1,1939

UNITED STATES.

1 OFFICE August Henry Schutte, Westfleld, 1;

This invention relates to improvements in the art of dewaxing oils such as petroleum oils. It

. is an improvement on my, prior invention disclosed in application Serial No.c192,534, filed February 25 1938.

One of the principal objects of the present invention is to continuously remove wax from oils, particularly petroleum lubricating oils with a relatively low cost of utilities and added matinuously treat the wax as it is removed from' the oil so that it is possible to, simultaneously separate the wax fractions of difierent melting points without the necessity o'f a sweating 25 operation.

' Further objects and advantages of this invention will appear from the following descrip--' tion of preferred forms of embodiment thereof taken in connection with the attached drawings in which:

Figure l is a diagrammatic layout of apparatus for the removal of wax from oil; and

Figure 2 is a diagram of modified'apparatus for the treatment of wax bearing oil.

35 I have heretofore discovered that it is possible to remove wax from petroleum oils by the intimate mixture therewith of an immiscible liquid such as water, after which the mixture is chilled and filtered. Not only is the filtra- 40 tion entirely satisfactory, but the economy of .the process is superior tov thatof heretofore imown methods for this purpose y In accordance with the present invention, I find that added economies can be obtained on 5 certain classes of oils which contain substantial amounts of crystalline wax due to the fact that a crystalline formation of the non-solvent is not essential to the free filtration of .the immiscible liquid and oil. As the heat of fusion of the non- 50 solvent need not be removed, this materiallyreduces the refrigeration load. Further, no heat need be supplied to separate the non-solvent from v the oil by evaporation or distillation, since the' separation is eifectively obtained by gravity set- 55 tling. More specifically, therefore, this inven-' Application May 19, weasel-iii no. acac a s (flaims. (01. 196-18 tion relates to the treatment of neutral oils having a preponderance ofcrystalline wax and a relatively low viscosity. Among such oils, Diesel engine oil is a typical one but not an exclusive example. I can materially reduce the cold test 5 of such oil by the following disclosed process.

Viscous waxy oils containing commercially valuable waxes but having 'an oil component of poor lubricating quality may be processed cheaply forjthe separation ofthe wax by chilling only to a sumciently low temperature to obtain the full yield 'of high melting point waxes;

The. waxy oil charge which is introduced at 'II is first passed through a'chiller 'l I,the tem-' perature of which is preferably regulated by the 1 temperature control 12, inter-connected in the chilled oil line II. The cold non-solvent material which'is of any suitable type which does not react with the oil and which does not freeze at the desired refrigerating temperature, is preferably a solution of a chemical salt such as calcium chlo'ride'brine. It is added either at ll before chilling-or at I! after chilling as may be desired; and depending upon its temperature.

The'mixtu're of cold oil and non-solvent is then passed through a suitable mixing device Ii which forms an intimate mixture between the particles of waxy oil and the non-solvent. While this mixture is in the nature of an emulsion, it is not necessarily a technical emulsion. It is merely necessary that the materials be effectively comingled so that there is a fine mechanical mixture entering the chiller IS. The oil, wax and non-solvent emulsion is preferably made at about the pour point of the oil.-'- At this temperature the oilis sufiiciently viscous to produce a stable mixture.

'Ihe'chiiler -ll may be of any suitable type, preferably cooled by circulating a refrigerant through the walls thereof, such refrigerant en- 40 tering at I! andcirculating through the receiver 2. from which'the vapors are discharged at 2| for-further compression. Ifdesired, a temperature control 22 maybe used interconnected with the'discharge 23 so that uniform temperature conditions are obtained and so that the chilled mixture of non-solvent and waxy oil discharged at 23 will beat the desired temperature.

The discharged chilled waxy oil and non-sol- 5o vent mixture is then passed on to a suitable filter generally indicated at 24 which may be of the "Fourdrinier type or of any other suitable type of centrifugal, suction or pressure, disc or leaf filter with the filtrate drawn through the filter 55.

medium as by a vacuum applied in the suction box 25 and with the filtrate removed at 26. The filtrate is the dewaxed oil and non-solvent which is drawn into the decanting tank 21 and from which the non-solvent is removed from the bottom at 28, with the aid of pump 29, for further use. The decanting tank 21 is operated under suitable vacuum maintained by the vacuum pump 30 and the dewaxed oil is removed at 3| from the upper part of the tank.

It is found that the emulsion of wax, oil and non-solvent is readily filtered even at the low temperature to which the mass must be subjected. No diluent or solvents are necessary which accounts for the very small spread between pour point and dewaxing temperature. The non-solvent, however, is very useful in assisting filtration. In the non-solvent emulsion the waxy oil is in finely divided particles which cannot agglomerate, due to the presence of the non-oily material. The formation of a dense wax crystal structure is prevented and the filtration of the oil is thus greatly accelerated. Since each particle has been originally surrounded by non-solvent, the subsequent washing with non-solvent may be carried out 'at high filtration rates and with the displacement of further quantities of low pour oil. The filter cake appears as a porous easily filterable mass.

The filter cake removed from the filter 24 is discharged into the hopper 35 which may be effectively provided with a steam coil 36 so that the melted wax can be introduced into the wax settling tank 31 through the line 38. The wax product is removed from the top layer at 39 and the non-solvent, which may be carried from the filter with the wax crystals, is removed at 40 from the bottom of the settling tank 31.

During the filtration, the filter cake may be suitably washed with the non-solvent at the desired temperature, such non-solvent being provided by the line 42 from the original non-solvent supply supplemented by the non-solvent removed from the line 40, and such non-solvent is passed through a cooler 43 so that the wash temperature can be under the desired control. The wash nozzle is indicated at 44 in a suitable location' on the filter: If it is found that there is an excess of non-solvent, it may be removed from the line 45, or if make-up non solvent is desired, it can be added through the line 46. It has been found that in certain cases, the wash at 44 may be maintained at a temperature substantially higher than the chilling temperature in chiller l8 without an adverse effect on the pour of the dewaxed oil. This is of advantage since it decreases the viscosity of the filtrate during the washing step and thus increases the filtration rate. The refrigeration requirement is also thereby decreased.

The modified flow diagram as shown in Figure 2 is more particularly adapted for a higherviscosity oil containing waxes which have melting points making them commercially valuable. The oil charged at 50. is thus given a multiple step treatment to remove the wax, it being first cooled at 5|, and mixed with the suitable non-solvent such as the brine heretofore described. This nonsolvent in the line 52 may be added'either prior to or after the cooling. The mixture is then preferably emulsified at 53 and the emulsion is then further chilled in the chiller 54 with the chilled mixture discharging at 55 onto the filter 56.

In this case, the filter 56 is provided with a plurality of suction boxes 51 and 58, each of which is adapted to receive a broad cut of filtrate and wash liquid from wash nozzles 59 and 60. The filtrate is then removed from the respective boxes 51 and 58 through the line GI and 62. The filter the oil is removed for further dewaxing at 68.-

The dewaxing steps include further chilling at 69, and mixing with additional non-solvent at or II. This mixture is then emulsified at 12 and further chilled in the chiller I3 and discharged at 14 onto the second filter 15. In this second filter, the filtrate removed at 16 from the first suction box includes low pour point oil and non-solvent. These are separated out in the knock-out drum 11 which is under vacuum. The low pour point oil is removed at 18 and the non-solvent is removed in the line I9.

In the first filter 56, the filtrate removed from the second suction box 58 is drawn into knockout drum 82 under vacuum provided in the line 83. After settling, the bottoms product is wash liquid which is drawn off at 84 and cooled in the chiller 85 for cold wash. Some of the wash liquid may be used as warm wash and by control of the valve 86, the desired temperature can be obtained by blending the warm and cold wash for the desired temperature at the nozzles 59 and 69.

The upper layer of liquid in the knock-out drum 82 is an intermediate melting point wax removed in the line 88. This material may be returned in part in line 89 to the original charge as a recycle to increase the yield.

The filtrate removed in the line 90 from the second suction box in the filter l5 is'drawn into I a knock-out drum 9-2. The wash liquid recovered at 93 as a bottoms product may be used as the wash liquid for the second filter and, as in the first case, part passes through a chiller 94 with the portions so blended that the desired wash temperatures are obtained.

A low melting point wax is removed at 95 as another end product. If desired, a part of this may be recycled through line 98 to increase the yield v I i It is thus possible to obtain not only the substantially wax free oil at 19, the high melting point wax at 63a, and a low melting point wax at 95, but it is also possible to obtain two intermediate cuts' of wax at 88 and 91, the latter being the filter cake from the second filter. Recycling of the low melting point wax and intermediate melting point waxes is also provided for. The wax treating process is carried out in a within the scope and spirit of the description herein and of the claims appended hereinafter.

I claim:

1. The method of separating wax from mineral oils whichcomprises mixing said oil with brine to iorm an emulsion therewith, chilling said emulsion to precipitate-the wax in finelydispersed condition, filtering out the wax as precipitate from the chilled emulsion and removing the dewaxed oil from thebrine.

2. The method of removing crystalline wax from oil which comprises emulsifying the oil with a non-freezing non-solvent liquid, chilling said emulsion to precipitate the wax, filtering the chilled emulsion and removing the wax as a filter cake.

3. The method of removing crystalline wax from oil which comprises emulsifying the oil with a non-freezing non-solvent liquid, chilling said emulsion to precipitate the wax, filtering the chilled emulsion, removing the wax as a filter cake, removing the filtrate, and separating the non-solvent from the dewaxedoil in said filtrate.

4. The method of separating narrow melting point cuts of crystalline wax from oil which comprises the steps of mixing a non-solvent liquid with said oil chilling said mixture, filtering said mixture'to obtain a partially dewaxed oil filtrate, mixing said dewaxed oil filtrate with additional non-solvent liquid, chilling said mixture to a lower temperature, again filtering said mixture, and obtaining a dewaxed oil as the filtrate.

5. The method of separating crystalline wax from oil which comprises the steps of intimately dispersing said oil in brine, chilling said.mixture, filtering said mixture to obtain a partially dewaxed oil filtrate and a high melting point wax filter cake, mixing said dewaxed oil filtrate with additional brine, chilling said mixture to a lower temperature, again filtering said mixture and obtaining a dewaxed oil, as the filtrate.

6. The method of separating crystalline wax from oil which comprises the steps of emulsifying a non-solvent with said oil, chilling said emulsion, filtering said emulsion to obtain a partially dewaxed oil filtrate and a high melting point wax filter cake, emulsifying said dewaxed oil filtrate with additional non-solvent, chilling said emulsion to a lower temperature, again filtering said mixture and obtaining a dewaxed oil as the filtrate, and an intermediate melting point wax as the filter cake.

'7. The method of reducing the cold test of. l ght neutral oils of Diesel grade by the removal of crystalline wax therefrom which comprises the steps of adding to said oils a cold brine solution having a freezing point materially lower than the desired cold test, intimately mixing said brine and oil to form a partially stable emulsion, chilling said emulsion below the desired cold test of theoil to crystallize the wax, filtering the liquid from the solid constituents of the emulsified mixture and settling the brine from the removed liquids to provide the dewaxed oil.

8. The method of reducing the cold test of light neutral oils of Diesel grade by the removal of crystalline wax therefrom which comprises the steps of adding to said oils a cold calcium chloride brine solution having a freezing point materially lower than the desired cold test, intimately mixing said brine and oil to form a partially stable emulsion, chilling said emulsion below the desired cold test of the oil to crystallize the wax, filtering the liquid from the solid constituents of the emulsified mixture and settling the brine from the removed liquids to provide the dewaxed oil.

AUGUST HENRY SCHUTTE.

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