US2305464A

US2305464A - Process for purifying oil

Info

Publication number: US2305464A
Application number: US305479A
Authority: US
Inventors: Ashworth Daniel Irving
Original assignee: De Laval Separator Co
Current assignee: De Laval Separator Co
Priority date: 1939-11-21
Filing date: 1939-11-21
Publication date: 1942-12-15
Anticipated expiration: 1959-12-15

Description

Dec. 15, 1942.

D. l. ASHWORTH PROCESS FOR PURIFYING OIL Filed Nov. 21, 1939 2 Sheets-Sheet l COO R CO/VTAM/IVA 7' 17 OIL Dem. 15, 1942'. D. l. ASHWORTH 2,305,464

PROCESS FOR PURIFYING OIL Filed Nov. 21, 1939 I 2 Sheets-Shasta HEATER iflmweys 2,305,4tid

UCESS IFWR l? i i Daniel g- Ashwo appingers i i assignor to The De la Separator Comm. it i New York, N. Y a corporation of New .lersey application November 21, use, Serial No. starve (oi. aio-i'il Ill My invention relates to the art of purifying oil and particularly oil, whether new or used, containing carbon in finely divided form. The process is also emcacious for the removal, along with the carbon, of other impurities. It is applicable, for example, to the removal, from oil that has been used in internal combustion engines, of the finely divided carbon, such as colloidal carbon, which is the product of heat in such engine's. Quenching oils used in the tempering of steel and oils used for high temperature distribution of heat are also susceptible, if overheated, to formation therein of carbon, and my process is effective as applied thereto. The process is also of value in. the removal from oil of finely divided sediments and other impurities even though they may not benecessa'rily associated with finely divided carbon, such as; for instance, fine metallic particles and dissolved soaps from oils, such as, for example, palm oil, used in the manufacture-of tin plate and as a lubricant in cold rolling of metals. The process has been found eficacious for breaking oil-water emulsions.

While the invention is thus applicable to vari= ous oils containing various types of finely divided impurities, it is more particularly intended, and has probably its greatest value, for use in the reclamation of used oils containing finely divided carbon. The invention is characterized by the fact that it effects the removal of the major portion of the carbon or other impurities without requiring the addition'of substances which have deleterious effects on the oil, such as reduction of ease of separation from water or increase of ash content. Though other oils may require the use of aqueous solutions of acids, alkalies or salts, the practice of the process usually requires for used internal combustion oils the addition thereto of only water, which is preferably, but not necessarily, thoroughly mixed therewith, followed by heating to a temperature not lower than about 295 F. and under a superatmospheric pressure sufficiently high to prevent substantial vaporization at that temperature, followed by a subsidence separation, preferably, if not necessarily, centrifugal, of the wate'rand impurities from the oil. I have discovered that the high temperature-high pressure operation above described will so agglomerate the carbon that its separation, with the water, by centrifugal force, from the oil can be easily effected. The subsidence separation must be effected while maintainlng pressure and temperature conditions preventative of substantial evaporation. Centrifcentrifugeat atmospheric pressure. In such case the oil-water mixture, after heating at high temperature under high pressure as above described, is cooled, without reduction in pressure, to a temperature lower than the lowest temperature at which substantial vaporization will occur at atmospheric pressure and the pressure is then relieved and the mixture conducted, at atmos-' pheric pressure, to the centrifuge. In other words, so far as concerns the water constituent of the mixture, the temperature is reduced to below 212 F. So far as concerns the oil of the A mixture, if the boiling point of the lightest constituent is below 212 F. the temperature will be further reduced to'below the boiling point of such constituent. The temperature of 212 F. is specified on the assumption that the process is being conducted at sea level under average atmospheric temperature. In practical operation, the temperature in the cooling zone will be reduced to substantially, and not barely, below that required to prevent vaporization in the centrifugal separating step, in order to with certainty insure against any vaporization of water or light oil constituents in the passage of the mixture to, through, and out of the centrifuge.

Another characteristic feature of the process is that the reduction in ressure is efiected without atomization, homogenization or wire drawing, which is a condition precedent to subsequent satisfactory centrifugation.

Another characteristic feature of the process is that it is applied to a continuously flowing stream of oil. This feature. together with the described high temperature-high pressure operation and other features hereinafter set forth, effects the delivery-at the end of the stream of finished clean oil in less than ten minutesfrom the time it enters the stream as dirty oil, as contrasted with the 12 to 15 hours period required to complete a batch in the most emcient batch process known to me. While of course the quantity purified in ten minutes in my proces is not comparable with the quantity purified in 12 to 15 hours by the batch process, the comparatively great rapidity with which a given small quantity of oil is purified enables me to purify, in'the time required to treat the maximum quantity of oil that is practically capable of being treated in batch, a very much greater quantity of oil and to effect a higher degree of puriflcaflon'with greater emciency and economy.

The improved process is not dependent for its execution upon the use of any particular apparatus and I have disclosed two difierent constructions which are about equally well adapted for carrying out the process. Fig. 1 is a diagram of one apparatus. Fig. 2 is a diagram of another apparatus. with the supply tanks and pump omitted;

Referring to the apparatus of Fig. 1: The contaminated oil to be cleaned or purified is stored in a tank a, from which it flows, through a pipe b, to a pump 0. The water or other aqueous reagent to be added to the oil is taken from any convenient source of supply, a water storage tank 1) being shown in the drawings, the water being fed from this tank through a pipe q to pipe b ahead of the pump a. In pump the oil and water are thoroughly mixed, such thorough admixture being highl desirable but not absolutely necessary,

From pump 0 the mixture of oil and water flows through a regenerator or heat exchanger d, wherein it is preliminarily heated as hereinafter described. The preliminarily heated mixture flows, through a pipe 1', to and through a heating coil s in a heater e, and thence through a chamber h, containing a float 1i, and, by way of pipe t, through said heat exchanger d (thereby preliminarily heating the mixture as above stated) into a cooling coil u in a cooler i. Heater e may be heated by high pressure steam, hot oil or any other convenient means including exhaust gases from an engine or direct fire. A gas burner is shown in the drawings.

Pump 0 is operative to establish the desired pressure upon the oil-water mixture flowing through heat exchanger (2, heater e and cooler i. g is a pressure gauge. which may conveniently be applied to pipe t. The cooler i may be a water tank. Beyong cooling coil u is a pressure device including a liquid motor k with a brake wheel w on which presses a brake shoe w operated by float 7' through levers and links 7", 7' and i At device It the pressure is reduced to atmospheric and the mixture is discharged into a centrifuge 0 having a spout m for the discharge of the heavier constituents and a spout n for the discharge of the lighter constituents. v is a thermometer applied to cooler 12.

The process will be described as applied to Diesel engine crank case oil.

With pump a running at a speed to feed oil through the coils at the desired treating rate, valve 20 is opened to feed from tank p the proper quantity of water, which may be from less than 5% to over 50% of the volume of the oil. About 20 to 25% gives very good results. The oil and water are mixed in their passage through pump 0. In some cases the oil to be purified may contain water in suflicient proportion to dispense with the necessity of its addition. But where the oil contains a smaller proportion of water than about five per cent., it is desirable to add thereto enough additional water to bring its water content up to at least five per cent. and preferably much above that percentage.

Gas burner f is so adjusted that, in its passage through heater e, the oil-water mixture will be heated to a temperature of not less than 295 F. The pressure is always such that the pressure in the chamber It will be that corresponding to the highest pressure at which the lowest boiling point constituent of the mixture will vaporize at the temperature in that chamber. Such pressure at a temperature of 295 F. would be about 50- pounds (gauge pressure).

asoaect After being heated the oil-water mixture passes through regenerator d, where it gives up part of its heat to incoming oil and water, and then through coil u in water tank 2', where it is cooled to less than 212 F. or to less than the flash point of the oil. The mixture then escapes through pressure device It to centrifuge o, wherein the water and carbon are separated from the oil and are discharged from spout m, while the oil is discharged from spout n practically free of carbon and other impurities that may have been present in the original oil or have accumulated as a result of use. From the time that the mixture leaves the pump 0 until it reaches the pressure controlling device It, the pressure is, except for not substantial variations due to changes in elevation and a slight reduction due to pipe friction, perfectly uniform.

The pressure control acts as follows. If the pressure is above that for boiling at the existing temperature the vapors in the float chamber h will be condensed, allowing the liquid and the float 7' to rise therein. This, through levers and link 7", i and 9' will release the brake w and allow cooled liquid to escape at a higher rate of discharge, thereby reducing the pressure in the heating and cooling system. If the pressure is low enough to just permit boiling of some of the liquid in the chamber h, the partial change to vapor causes the liquid and the float 7' to fall and tighten the brake and resist the escape of liquid thereby slowing down the rate of discharge and increasing the pressure in the heating and cooling system. The pressure and rate of discharge will thereby be held at all times within a range so narrow as to be substantially constant, the pressure therefore being at all times substantially at that equivalent to the boiling pressure at the existing temperature.

While it may be possible to discharge some liquids from a zone of superatmospheric pressure to a zone of atmospheric pressure through a throttle valve, I have found that in such liquid mixtures as I have tested this causes such atomization, including homogenization or wire-drawing, as to make subsequent separation difiicult if not impossible. With the above described device, using an ordinary gear pump acting as a motor, this is entirely eliminated.

As for the oil above specified the process requires the addition of only water to the oil; no objectionable acids, alkalies or ash are added or formed.

Because the oil is completely enclosed during its time of heating there is no fire risk and as air is excluded there is no opportunity for air oxidation.

No minimum or maximum limit on the time during which the oil-water mixture should be heated can be specified. The shortest time (about five minutes) in which the oil-water mixture can be heated to cause a pressure of lbs. per square inch and then cooled back to atmospheric temperature has given good results.

While the temperature for optimum separation seems to be that corresponding to a pressure of between 100 and lbs. per square inch, the temperature may be that corresponding to a considerably higher pressure, or may be as low as that'corresponding to a pressure of about 50 pounds per square inch.

While the above described process will remove substantially all of the carbon and other sediment from the oil, it may still be dark colored and for some purposes it is desirable to remove acteristics of oils.

aeoaeca this color by percolation with some one of the orbent materials well known in the oil refining art. 1

While the process is particularly emcacious for the-removal of carbon from oils, it will at the same time remove, along with the agglomerated with an oil outflow pipe at leading to the centrifuge o. Tanks I3 and It are connected at the bottom with a valve chamber I6 having a circarbon (and in many caseswithout carbon if separate from the oil bygravity in time, but a much more complete, as well as a much more expeditious, separation can be immediately accomplished by centrifugal force.

It is most convenient and economical to efiect the separation in that most usual type of. centrifuge whose inlet and outlets are open to the atmosphere, and where separation is effected in such a separator the described reduction in temperature before separation must be efiected in order to avoid loss of oil constituents by-flashing or evaporation. If, however, the centrifuge is of the closed type, the separation may be efiected under the pressure in the system without cooling, or the separation may be efiected under a reduced but still superatmospheric pressure with cooling only sufficient to prevent substantial evaporation. In one case the cooling may be efiected, and in the other case partly effected, beyond the centrifuge. It is preferred, however,

in all cases, to cool to below 212 F. before discharging.

While for used oils from internal combustion engines water is usually the only material needed to remove impurities, I have found that for some other liquids other reagents are more emcacious, as, for instance, an aqueous solution of salt for removal of metallic soaps and alkalies for removal of excess acids, etc. Where the word water is used in the claims, I intend it to broadly include water alone or aqueous solutions of any acids, bases or salts that will give the best results with the liquid being treated.

In claiming the application of the process to "oil I intend to include not only mineral oils but animal and vegetable oils and such allied materials as fats and waxes which, under certain thermal conditions, have the physical char- While in certain of the claims I have specified that the oil which is treated by the process contains water, it will be understood that I mean to include oil which may contain water and to which no water need be added, and also oil to which water is added preparatory to being processed, it being only necessary to insure that water shall be mixed with the oil before the,

process starts.

It is possible, and may be desirable, to substitute, for the pressure device is, the means, shown in an application filed by me July 30, 1937, Serial No. 156,448, for transferring an emulsifiable cular valve seat for a tapered valve II, the stem of which is connected, by a bell crank lever It, with the connecting rod 9'. At the beginning of the operation, one of the tanks I3, It (say the tank I3) is full of water, while the other is nearly empty. With the valve in the position shown, oil flows from the coil u at the high pressure previously specified, through valve I0 and pipe II into container I3, displacing the water, which is forced through valve II into tank It. The

air in tank It escapes through pipe I2, valve Ill and pipe I5. When the tank I3 is nearly full of oil and the tank It nearly full of water, valve It is turned 90, whereupon oil from coil 1!. flows through pipe I2 into tank It, forcing water through valve I'l into tank It and thereby forcing oil in tank I3 through pipe II, valve I0 and pipe I5 into the centrifuge. It will be understood that in these tanks I3 and Hi there will be some separation of water from the entering oil-water mixture, but such separation. is incidental and incomplete and the oil-goes to the centrifuge admixed with some water.

Valve III may be operated manually. However,

it is preferred to operate it automatically by means of a float 20, which has a welght'intermediate between the weights of equal volumes of oil and water. stops 2| and 22 on a rod 23 connected, by a lever M, with the valve It. With the parts in the position shown, oil is flowing through coil u, valve Ill, pipe II, into tank It, forcing water through valve II into tank It and oil out of tank It, through pipe I2, valve It and pipe It, to the centrifuge. As the water rises it carries the float 20 with it until the float strikes the stop 2i, 'after which, in its continued upward movement,

. it lifts the rod 23 and, through lever 2t, turns the valve III until the connections are reversed; whereupon oil will then flow into tank It and out of tank i3 to the centrifuge. As the water level in tank I3 falls, the float falls with it until it strikes the stop 22, lowers the rod 23 and turns the lever M to return valve It to the position shown in Fig. 2.

The valve It may be replaced by an ordinary throttle valve unconnected with the float 9 as shown in the drawings, but in such case the rate of discharge from the coil u will not be controlled. It is distinctly preferred, however, to use the valve H and connect it with the float i, this arrangement permitting control of the rate of discharge of the oil. If the rate of discharge is so fast that the level of oil in chamber It falls, the float a will also fall and, by raising the tapered valve I'I, willdecrease the area of the flow passage, causing a reduction in the rate of discharge. If the rate of discharge is so slow that the oil level in chamber it rises, the float 1 will rise and lower the valve I! to increase the area of the flow passage.

Where, in the claims, reference is made to atomization, I mean to include emulsification and homogenation. I

While certain features of the process are novel regardless of whether it is practiced in batch or continuously, and while I do not want to be limited to continuous operation except in the claims expressly limited thereto, the continuous process is distinctly preferable. tinuous operation, however, involves the solution of problems, particularly discharge without The float slides freely between The most successful con-.

atomization and the maintenance of a substantially constant rate of discharge, which would not be encountered in a batch process, which problems are solved by the process herein described. While the process is not dependent for its execution upon any particular apparatus, it is believed, also, that the apparatus that I have designed for carrying out the process is novel as well as useful.

This application is a continuation in part of an application filed by me September 25, 1936, Serial No. 102,511.

What I claim and desire to protect by Letters Patent is:

l. The process of continuously removing from oil containing water other impurities contained therein, which comprises establishing a flowing stream of the oil-water mixture, heating said stream to a temperature adapted to coalesce the impurities and render them readily separable from the oil and not lower than about 295 F., maintaining the stream during the heating under a superatmospheric pressure, above 50 pounds to the square inch, not lower than that required to prevent substantial vaporization of water at the temperature specified, then cooling the stream to a temperature adapted to prevent substantial vaporization of water and below the flash point of the oil at the reduced pressure hereinafter specifled, maintaining on the stream during the cooling step substantially the same pressur as that applied in the heating step, and then substantially reducing the pressure on the cooled stream without atomization and at'such reduced pressure effecting separation of water and impurities from the oil.

2. The process set forth in claim 1 in which during the cooling step the temperature is reduced to a temperature below 212 F. and in which, after the cooling step, the pressure is reduced to about atmospheric.

3. The process of continuously removing from oil containing water other impurities contained therein, which comprises establishing a flowing stream of the oil-water mixture, heating said stream to a temperatureadapted to coalesce the impurities and render them readily separable from the oil and not lower than about 295 F., maintaining the stream during the heating under a superatmospheric pressure, above 50 pounds to the square inch, as close as possible to the minimum pressure required to prevent vaporization at accuses the oil and not lower than about 295 F., maintaining the stream during the heating under a superatmospheric pressure, above 50 pounds to the square inch, as close as possible to the minimum pressure required to prevent vaporization at said temperature of the lowest boiling constituent of the mixture, cooling the stream to a temperature adapted to prevent vaporization of water and below the flash point of the oil at the reduced pressure hereinafter specified, maintaining on the stream during the cooling step the same pressure as that applied in the heating step, then substantially reducing the pressure on the cooled stream without atomization and at such reduced pressure effecting separation of water and impurities from the oil, .owing the oil, after heating and before cooling, into, through and out of, a vapor collecting space, maintaining said pressure during said heating and cooling by controlling the rate of discharge of the mixture to the zone of reduced pressure by the level of liquid in the vapor-collecting space, said level of liquid and rate of discharge falling with any formation of vapors due to any reduction in pressure and said level of liquid and rate of discharge rising with any condensation of vapors due to any increase in pressure.

5. The process of removing from oil containing water other impurities contained therein, which comprises establishing a flowing stream of the oil-water mixture, heating said stream to a temperature not lower than 295 F., maintaining the stream during the heating under a superatmospheric pressure, above 50 pounds, approximately that at which water boils at said temperature, then cooling the stream, while mainsaid temperature of the lowest boiling constituent Y of the mixture, cooling the stream to a temperature adapted to prevent vaporization of water and below the flash point of the oil at the reduced pressure hereinafter specified, maintaining on the stream during the cooling step the same pressure as that applied in the heating step, then substantially reducing the pressure on the cooled stream without atomization 'and'at such reduced pressure effecting separation of water and impurities from the oil, and maintaining said pressure during said heating and cooling by slightly increasing the pressure when it falls below that required to wholly prevent vaporization and by slightly reducing the pressure when it rises to that effective to condense any vapors that may form.

4. The process of continuously removing from oil containing water other impurities contained therein, which comprises establishing a flowing stream of the oil-water mixture, heating said stream to a temperature adapted to coalesce the impurities and render them readily separable from Iii taining it at such superatmospheric pressure, to a temperature below the boiling point of water at atmospheric pressure, reducing, without atomization, the pressure of the cooled streamto atmospiilieric and separating the impurities from the o 6. The process of continuously removing from oil containing water other impurities contained therein, which comprises establishing a flowing stream of the oil-water mixture, heating said stream to a temperature adapted to coalesce the impurities and render them readily separable from the oil and not lower than about 295 F., maintaining the stream during the heating under a superatmospheric pressure, above 50 pounds to the square inch, as close as possible to the minimum pressure required to prevent vaporization at said temperature of the lowest boiling constituent of the mixture, cooling the stream to a temperature adapted to prevent vaporization of water and below the flash point of the oil at the reduced pressure hereinafter specified, maintaining on the stream during the cooling step the same pressure as that applied in the heating step, then substantially reducing the pressure on the cooled stream without atomization and at such reduced pressure effecting separation of water and impurities from the oil, flowingthe oil, after heating and before cooling, into, through and out of, a vapor collecting space, maintaining said pressure during said heating and cooling by establishing a resistance to flow of the mixture from the cooling step to the reduced pressur zone, controlling said resistance to flow by the level of the liquid in the vapor-collecting space, said level of liquid falling and said resistance to flow rising with any formation of vapors due to any reduction in pressure and said level of liquid rising and said reslstance to How falling with any condensation of vapors due to increase in pressure.

'7. Th process of removing from oil containing water other impurities contained therein, which comprises heating the mixture to a temperature adapted to coalesce the impurities and render them readily separable from the oil and not lower than 295 F., maintaining the mixture during the heating under a superatmospheric pressure, not lower than 50 pounds to the square inch and not lower than that required to prevent substantial vaporization of water at the temperature specifled, then cooling the mixture to a temperature below the flash point of the oil at the reduced pressure hereinafter specified, maintaining on the mixture during the cooling step substantially the same pressure as that applied in the heating step, then substantially reducing the pressure on the cooled mixture without atomization and at such reduced pressure effecting separation of water and impurities from the oil.

3. The process of removing from oil containing water other impurities contained therein, which comprises heating the mixture to a temperature adapted to coalesce the impurities and render them readily separable from the oil and not lower than 295 F., maintaining the liquid during the heating step under a superatmosphere pressure not lower than that required to prevent substantial vaporization at the existing tempera ture and reaching a minimum of not less than to pounds per square inch, then cooling the mixture to a temperature below that for vaporization at atmospheric pressure of any constituent thereof, maintaining on the mixture during the cooling step a pressure suflicient to prevent substantial vaporization thereof, reducing the presilB, without atomization, to atmospheric and at such reduced pressure effecting separation of water and impurities from the oil.

9. The process of removing carbon from used oil containing carbon in finely divided form which comprise-s adding water to the oil, establishing a flowing stream of the. oil-water mixture, heatin said stream to a temperature adapted to coalesce the impurities and render them readily separable from the oil and not lower than about 295 F., maintaining the stream during the heating under a superatmospheric pressure, above 50 pounds to the square inch, not lower than that required to prevent substantial vaporization of water at the temperature specified, then cooling the stream to a temperature adapted to prevent substantial vaporization of water and below the flash point of the oil at the reduced pressure hereinafter specified, maintaining on the stream during the cooIin" step substantially the same pressure as that applied in the heating ste and then substantially reducing the pressure on the cooled stream without atomization and at such reduced pressure effecting separation of water and carbon from the oil.

10. Th process set forth in claim 9 in which during the cooling step the temperature is reduced to a temperature below 212 F. and in which, after the cooling step, the pressure is reduced to about atmospheric. 1

DANIEL IRVING ASI-IWORTH.