US20080070816A1

US20080070816A1 - Process for recovering used lubricating oils using clay and centrifugation

Info

Publication number: US20080070816A1
Application number: US11/856,813
Authority: US
Inventors: Pablo Martin de Julian; Leonardo Ramon Padrino Torres; Pedro Adolfo Torres Fonseca
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-09-18
Filing date: 2007-09-18
Publication date: 2008-03-20
Also published as: ES2338207A1; BRPI0718458B1; WO2008036696A2; ES2338207B2; ES2338207B8; BRPI0718458A2; WO2008036696A3

Abstract

A process for recovering used lubricating oils, and oils recovered using the process. In a first embodiment (for used industrial oils), the used lubricating oil is mixed with clay in a reactor. The mixture is preferably heated to between 80 and 200 degrees Celsius. The temperature should not be too great, to avoid “cracking” the oil (i.e., breaking molecular chains in the oil). After a certain period of time, the mixture is pumped through filters. Cakes of clay and contaminants remain in the filters, while the oil emerges without the contaminants. A second embodiment (for removing ash or soot, very fine carbon particles and other organic compounds from used motor oils) is the same as the first embodiment, except that before the mixture is passed through the filters, a centrifuge is used to remove most of the clay contaminated with soot, so that it will not block the filters.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to the removal of contaminants from industrial used lubricating oils and used motor oils by treatment of the used oil with clay at high temperatures, but at lower temperatures than that of “cracking”, and later removing the contaminated clay by filtration and centrifugation.
2. Description of the Prior Art
The recycling of used lubricating oils coming from industrial processes, car motors, transmissions and other sources is an important process, because it avoids contamination by lubricating oils, and allows the recovery of lubricating base oils, which are a scarce product. The oils form a monomolecular layer on the surface of the water, which it means that a small quantity of oil can contaminate a great volume of water.
The recovered lubricating oil bases have all the properties of the first refining, and they can be used to produce new oils. The recycling process can be done several times.
The contaminants in industrial oils, besides water, are usually iron, chromium, cadmium, nickel, copper, calcium, barium, zinc, aluminum, and phosphorus. Motor oils also have soot, contaminants due to degraded additives, and other contaminants coming from the gasoline, and for that reason they are more difficult to be re-refined.
Several techniques have been used to re-refine used oils, mainly by distillation and treatment with chemical reactives to precipitate the coagulants (principally sulfuric acid and other solvents, which are also contaminants that produce environmental problems).
The treatments with clays at very high temperature have the problem that the later separation becomes difficult because the pores of the felt (cloths, cellulose, synthetic materials or others) of the filter press become plugged, mainly due to soot, colloidal coal, and organic compounds.
The distillation systems require large investments, and the re-refining cost is usually expensive. This is also the case of the other used treatments with sulfuric acid, sulfates, phosphates and other chemicals, which are difficult to extract later on. For example in the separation of sulfuric acid with clays there is the inconvenience of the great production of sludge, besides the large volumes of corrosive acids and the great lost of used original oils. It is necessary to take into account that the pre-heating of the mixtures must not be higher than 250° C. to 300° C., if one wants to avoid the “cracking” of the lubricating oils. (Excessive heat causes hydrocarbon chains in the oil to “crack” and break into smaller chains, which are not suitable for lubricating oil, though they may be suitable for fuel oil.) Other more economic systems use inorganic catalysts mixed with clays in continuous feeding systems.
The present invention has important advantages with respect to these processes.
U.S. Pat. No. 3,625,881, issued on Dec. 7, 1971, to John M. Chambers and Herbert A. Hadley, discloses a process for reclaiming lubricating oils, including flash vaporization to remove water, mixing the used oil with a hydrocarbon oil, using a centrifuge to remove solid precipate, and two fractional distillations. The instant invention is distinguishable, in that in it the used oil is mixed with clay rather than another oil.
U.S. Pat. No. 3,639,229, issued on Feb. 1, 1972, to Darrell W. Brownawell and Remi H. Renard, discloses a process of refining used lubricating oils, in which the used oil is mixed with aliphatic alcohol. There may be a final clay treating step (see claim 9). The instant invention is distinguishable, in that it does not require the use of alcohol.
U.S. Pat. No. 3,819,508, issued on Jun. 25, 1974, to Morton Fainman and Charles Stouse McCauley, discloses a method of purifying lubricating oils, in which the oil is mixed with a predominantly hydrocarbon liquid diluent, then with an alcohol and water mixture, and centrifuging is used to remove sludge and metal compounds. The instant invention is distinguishable, in that in it the used oil is mixed with clay.
U.S. Pat. No. 3,919,076, issued on Nov. 11, 1975, to Louis E. Cutler, discloses a process for re-refining used automotive lubricating oil, including treatment with a saturated hydrocarbon solution, followed by vacuum distillation, followed by catalytic hydrogenation, which are not required in the instant invention.
U.S. Pat. No. 3,930,988, issued on Jan. 6, 1976, to Marvin M. Johnson, discloses a process for reclaiming used motor oil using an aqueous solution of ammonium sulfate or bisulfate, which is not required in the instant invention.
U.S. Pat. No. 4,033,859, issued on Jul. 5, 1977, to Donald Douglas Davidson and Bjorn I. Engesvik, discloses thermal treatment of used petroleum oils under pressure at temperatures to above about 400 to 800 degrees Fahrenheit (or 190 to 412 degrees Celsius). Although there is a small overlap in the temperature range, the instant invention does not require pressure during its heating step.
U.S. Pat. No. 4,383,915, issued on May 17, 1983, to Conrad B. Johnson, discloses a clay contacting process for removing contaminants from waste lubricating oil, in which the oil is contacted with decolorizing clay at a temperature in the range of 650 to 725 degrees Fahrenheit (or 329 to 370 degrees Celsius). The instant invention is distinguishable, in that it uses a lower temperature range, and a different type of clay (see column 3, lines 21 to 31).
U.S. Pat. No. 5,112,479, issued on May 12, 1992, to Vichai Srimongkolkul, discloses an oil purification unit with a cyclonic (centrifuge) reservoir section and a filtration section. The second embodiment of the instant invention is distinguishable, in that in it the oil is first mixed with clay before being centrifuged.
U.S. Pat. No. 5,759,385, issued on Jun. 2, 1998, to Marcel Aussillous et al., discloses a process and plant for purifying spent oil, including vacuum distillation, which is not required by the instant invention.
U.S. Patent Application Publication No. 2006/0000787, published on Jan. 5, 2006, to Louis Galasso III et al., discloses purification of impure oil by centrifugation, without first mixing the oil with clay as in the instant invention.
French Patent No. 2 690 924, published on Nov. 12, 1993, to Virgulino Antonio Digilo, discloses a method of re-cycling of used or contaminated lubricating oils, including adding clay to the oil in a reactor, and also adding water containing a dissolved sulphur based catalyst and filtration aid. The instant invention is distinguishable, in that it does not require adding water with a catalyst.
Japanese Patent No. 2-4898, published on Jan. 9, 1990, to Kyoho Seisakusho and Toyota Jidosha, discloses a process of reclaiming lubricating waste oil, including a thermal reaction treatment in which an aqueous solution of caustic alkali is added to the oil, a centrifugation process after diatomaceous earth and activated clay are added to the oil, and a filtration process. The instant invention is distinguishable, in that it does not require that the addition of a solution of caustic alkali to the oil.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.

SUMMARY OF THE INVENTION

In our search for a process for the recovery of used lubricating oils that was economic and did not require high investments, a fact to be considered appeared immediately. It was necessary to separate the treatment of industrial oils, with mainly watery and metallic contaminants, from those with organic contaminants and soot, such as those coming from the internal combustion motors. For this reason, the present invention has two preferred embodiments: the first for recovery of used industrial lubricating oils, and the second for recovery of oils coming from internal combustion motors (including used lubricants oils of explosion and diesel motors, automatic transmissions, and in general, every kind of oils coming from filling and service stations for cars).
The first preferred embodiment of the present invention is suitable for used industrial oils, and it includes the steps of: (a) Mixing the used lubricating oils with clay in a reactor, and heating the mixture to temperatures from 80° C. to 200° C., in a batch type system. The temperatures are low enough that the cracking of the lubricating oils in the mixture does not take place or at least is minimized. (b) Keeping the mixture of clay and used lubricating oil for a certain residence time in the reactor. (c) Filtration by a system of filter presses, wherein the clay sticks to the filtering cloths, and the filtered oil goes through free of impurities. This system is shown in FIG. 1, which corresponds to the first preferred embodiment.
An important observation in this process is that, if this is performed in a continuous way, with feeding of used oil and preheated clay through the bottom of the reactor and gathering of recovered oil from the upper side, then the oil still contains a large amount of contaminants, and is not suitable for future use. In continuous systems in the prior art, they use catalysts or chemical reactives to obtain suitable results, which complicate and increase the cost of the process.
On the other hand, it is important also to point out that the amount of water contained in some oils is high, and in these cases before adding the clay it is convenient to eliminate the water with a “flash” distillation process from 80° C. to 100° C., prior to treatment with the clay.
The second preferred embodiment of the invention is designed for the removal of metallic contaminants, soot and organic contaminants from the used lubricating oils coming from automotive market. It includes the steps of: (a) Mixing the used lubricating oils with clay in a reactor, and heating the mixture to temperatures from 80° C. to 200° C. Again, the temperatures are low enough that the cracking of the lubricating oils in the mixture does not take place or at least is minimized. (b) Keeping the mixture of clay and used lubricating oil is for a certain residence time in the reactor. (c) Using a centrifuge to separate a large part of the oils to be recovered from the clay containing organic and metallic contaminants. (c) Filtration of the oils coming from the centrifuge, by passing them through a filter press as described above for the industrial used oils. The second preferred embodiment is illustrated in FIG. 2.
For both embodiments, the heating system which was found most economic for the process of the present invention, consists of a boiler heated with gas and a transference fluid (e.g., hydraulic oil), which carries the heat from the boiler to a heating jacket in the reactor containing the used oil and clay. The heating is done by conduction. The used lubricating oils are loaded in the reactor with movable and diaphragm electric pumps, or by gravity. Before the used oils are placed into the reactor, they may be passed through a gross filter (for instance, 200 mesh) to remove large particles. After passing them through the gross filter, there can also be a flash distillation from 80° C. to 120° C. to remove excessive quantities of water. Next, the right amount of clay is added, and after some residence time determined by the type of oil and laboratory analysis, the mixture in the reactor is discharged. During the residence time the clay reacts with the contaminants, creating chemical bonds between them. For this, it is necessary to have good control of the temperature (in order to avoid cracking the oils) and of the amount of clay and the residence time in the reactor. All these conditions are previously determined by the laboratory analysis. After that the filtering process is performed.
Accordingly, it is a principal object of the invention to provide an improved process for recycling industrial lubricating oils.
It is another object of the invention to provide an improved process for recycling automotive lubricating oils.
It is a further object of the invention to reduce pollution to the environment from discarded used lubricating oils.
Still another object of the invention is to reduce the depletion of nonrenewable resources used in making lubricating oils.
It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.
These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the first preferred embodiment of the invention.

FIG. 2 is a schematic diagram of the second preferred embodiment of the invention.

Similar reference characters denote corresponding features consistently throughout the attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention an improved process for recycling used lubricating oils, having two preferred embodiments.
The FIG. 1 depicts the first preferred embodiment of the process of the invention, which is its simplest form. The concept discussed is a “batch” or “semi-batch” type process, wherein the used contaminated lubricating oil 10, which may be filtered before going to the reactor 12, is mixed with activated clay 14 to high temperature, obtained by means of a heating jacket 16 in the reactor. To maintain the temperature of the heating jacket, hot hydraulic oil can be used as a heat transference fluid, which is heated in a boiler (not shown in the drawings). The operation of mixing oil with clay and heating can be done in a continuous way, but the best results are obtained with the “batch” or “semi-batch” non-continuous system. The reactor, where the interaction between the clays and the oil to be recovered is taken place, usually has stirring rods 18, which allow a faster process and decrease the residence time. The residence time can be from several minutes to several hours, depending on the type of oil and contaminants. Before loading the reactor, it may be desirable to perform a flash distillation, to eliminate the water that is coming with the used oils, as well as a pre-filtration to eliminate contaminants of large size. From the reactor, the heated oil-clay mixture is pumped using pump 20 through a filter press 22 where the clay and trapped contaminants are separated from the oil. The clay is left in the filters 24 as a “cake”, and the recovered oil without contaminants is carried out to a pipe system 26, which retake the filtered oil from the filter press. After loosening the filtered frame with its filters, the clay cake sticks to the filters, but is separated from them, in order to recover the filters, leaving the clay as waste material 28. The recovered oil, now without contaminants, can be used as lubricating base oil.
In FIG. 2, showing the second preferred embodiment of the invention, the process is similar to that depicted in FIG. 1, but now there is an industrial centrifuge 30 between the reactor 12 and the filter press 22. The reason for this centrifugal system is that for the used oils coming from explosion motors, an important contaminant is the soot, which comprises very small particles of carbon and other organic compounds, such as the additives of the lubricants. The problem with these contaminants is that when they are taken directly to the filter press, they plug the pores of the filter felts (cloths, cellulose, synthetic, etc.), stopping or decreasing very strongly the filtered flow. It is for this reason that a centrifugal operation is needed prior to filtration, in order to remove most of the clay contaminated with soot 32, in order to allow a filtered operation later without problems.
The system described in FIG. 1 is suitable for the recovery of industrial oils with low or no contamination with soot or organic products, and the system described in FIG. 2 is mainly appropriate for used oils coming from cars and motor vehicles, where there is a high percentage of soot contamination. However, this more complete second system can be also used for industrial oils or any kinds of used oils, e.g., oil used in internal combustion motors, or in industrial or other motors.
Once the recovered bases are obtained, the corresponding analysis has to be performed in order to determine that the amount of contaminants is below the wanted level, as well as to determine the characteristics of the recovered base lubricating oils, such as their viscosity, total basic number (TBN), flash point, etc.
The following examples are given for illustration:

Example 1

A treatment of 1,800 liters of used oil of industrial origin was performed, to show the effectiveness of the present invention.

Process of Recovery of Used Industrial Oils (Example Industrial Plant)

Materials.—

1,800 liters of lubricating oils for industrial gears coming from Carbonorca Enterprise C.A.

Initial Characteristics of the used Oils.—

1. Color: Opaque brown, non-translucent.

2. Presence of free water and/or in emulsion: (10-50% v/v).

3. Presence of solid suspended particles (>1000 mg/Kg, 0-30% v/v)

4. pH: >7

5. Aromatics: <1 mg/Kg.

6. Solvents: 0-10% v/v.

System of Absorbent/Adsorbent.—

Activated clays, hybrid type of hormite and smectite, with acid characteristic, with pH (5% solids diluted in H₂O) equal to 2.5-3.0, density of 336-416 g/l, and particle size, by sieve analysis (Tyler Standard), particles with sizes less than 150 μm: 100%, and particles with sizes less than 45 μm: of 73-76%.

Procedure Description.—

- 1) Pre-filtration: The used industrial oil goes through mobile filtering equipment to eliminate big particles that could be present in the oils. Polyester sleeve filters with holes of 10-100 microns were used.
- 2) Reactor load: Mobile pumps were used for the process of loading the 1,800 liter batch.
- 3) Distillation flash: The oil was heated with a system of thermal oil recirculation coming from a boiler, with the aim of eliminating the water and the residual part of the solvents. The temperature reached oscillates between 105-115° C., measured and controlled with instruments installed in the reactor (i.e., thermocouples and flow control valves). Time of heating averaged two hours. In this stage the oil is recirculated and there is a continuous mechanical stirring. Once the distillation temperature is reached and the water eliminated, a crackling test (ECC001) is performed to be sure that there is no water remaining.
- 4) Absorption/Adsorption Process: Once the crackling test is performed, the absorbent/adsorbent elements, namely the clays, are added in the reactor. The amount to be used is determined previously by the laboratory tests. The addition of these different elements varies between 0.5-2% v/v for a batch of 1800 liters. (By “v/v” is meant the volume of clay divided by the total volume of the mixture in the reactor.) For lower loads of this amount and/or more contaminants the clays added could be in the range of 2-5% v/v. There is stirring during the addition of the clays, and once they are added, the stirring continues simultaneously with the recirculation to get an optimums contact between the oil and clay. This process lasts for a period of five to fifteen minutes. (Note that absorption means drawing into the interior of the clay particles, adsorption means attachment to the surface of the clay particles, and absorption and adsorption are collectively referred to as “sorption”.)
- 5) Filtration Process: Once the period of clay-oil mixture is finished, the filtration process is started. This is performed with a filter press of vertical plates provided with a series of 100% cotton cloths with openings between 10-40 microns and a 100% cellulose filter of 8-20 microns holes. The operation pressures are 30-100 psi at the entrance of the filter and 10-15 psi at the exit. The amount of solid particles in the filtration process is analyzed to guarantee that the final oil does not contain any solids.
  Once the removal of contaminants is finished the procedure is:
- 1) Passing the recovered lubricating base oil to the observation tank (checking previously that there are not solid particles). The observation tank has a preventive function, since it enables the determination of the location of any possible contamination with solid particles or high levels of metals, if the removal process becomes inefficient for any reason.
- 2) There is a metallic characterization by the method of atomic absorption to determine if the product is good to be used to produce lubricants.
- 3) Once the two preceding steps are done, viscosity and viscosity index are determined with the aim of storing in lubricating plant tanks, to decide which kind of use will be assigned. There is a pumping system connected to a series of pipes and valves, wherein the recovered lubricating base oils go through post-filters, to insure that there is not any type of residue or solid particle.
  Table 1 shows the analysis of properties of industrial used oil:

TABLE 1

Initial Properties of Used Oil Before the Process

Parameter	Unit*	Value	Method

Cadmium and composites	mg/Kg	<0.10	ASTM D 5185
Chromium and composites	mg/Kg	14.4	ASTM D 5185
Soluble copper composites	mg/Kg	22.1	ASTM D 5185
(salts and acids)
Nickel and composites	mg/Kg	3.51	ASTM D 5185
(salts and acids)
Lead and composites	mg/Kg	534.9	ASTM D 5185
(salts and oxides)
Vanadium and composites	mg/Kg	8.9	ASTM D 5185
(salts and oxides)
PCBs	ppm	<0.10	HGPC
Sediments	ml/L	<0.10	ASTM D 473
R²—Cl**	ppm	800	9077
Cinematic Viscosity to	cSt	18.6
100° C.
Density	g/cm³		ASTM D 1298
Flash Point	° C.	195	NVC 372
H₂O by distillation	% p/v	0.00	ASTM D95
Total Sulfur	% p/p	0.60	ASTM D 1552

*1 mg/Kg = 1 ppm
**R²—C1 = Organic Radical

Table 2 presents the properties of the recovered lubricating base oils obtained through this process:

TABLE 2

Final Properties of Recovered Oil (Lubricating Bases)
After the Process

			Obtained
Parameter	Unit	Specification	value	Method

FlashPoint	° C.	210-260	219	Covenin 372
Method of open cup
Cinematic Viscosity to	cSt	15-19	17.4	Covenin 424
100° C.
Viscosity Index		90		Covenin 889
Calcium	ppm	<0.01	0.005	Covenin 2044
Magnesium	ppm	<0.014	0.009	Covenin 2044
Zinc	ppm	<0.1	0.02	Covenin 2044
Crepitating, crackle		S/N	Negative	Covenin
Specific Gravity to	g/ml	0.8685	0.8703	Covenin
15.6° C.
Amount of clay		S/N	Negative	Method EC-
				B05

Example 2

A laboratory experiment was performed, with a sample of used motor oil. The following is a description of the details of the experiment:

Materials:

800 ml of used oil, coming from a Fiat “Ritmo” car, 1987 model, 1600 ml motor, with 45 days of running, and a total of 55,000 km passed over. The original oil was PDV (Petroleum of Venezuela) brand, 20W-50W multigrade (Experiment No. 1). There was also used 800 ml of a mixture of used oils coming from an workshop for oil change, located in Maracay, Aragua State-Venezuela (Experiment No. 2).

System of Absorbent:

Activated clays, hybrid type of hormite and smectite, with acid characteristic.

Experimental Process and Preparation of Samples for Analysis:

A sample of 800 grams of used motor oil was put in a glass beaker, with a magnetic stirrer inside, and was placed on an electric heating plate with continuous magnetic stirring.
The heating of the sample was between 100-120° C. during 30 minutes, in order to eliminate the water, until the crepitating or crackling test was negative. The amount of clay was prepared in approximately 20% m/m of used oil. (By “m/m” is meant the mass of the clay divided by mass of the used oil.) The oil was added with stirring of 800 to 1200 rpm, during one hour, and reaching temperatures of 180° C.
The mixture oil-clay was passed through a filtration process at vacuum with a Buchnner funnel, using two cycles of filtering: first with 35 mesh, and second with Watman No. 5 cellulose. In this way, the contaminants retained with the clay are separated from the filtered oil.
Tables 3 and 4 show the results obtained, giving the characteristics of the used oils in the experiments, and the recovered lubricating base oils after applying the experimental procedure.

TABLE 3

Initial Properties of the Used Motor Oil

	Flash
Exp.	point	Density	μ (cSt)	Metals (ppm)

Number	(° C.)	(gr/ml)	100° C.	Ca	Mg	Zn	Fe	Cu	Al	Color	Odor

1	203	0.81	13.2	1768	112	841	98	3	17	Dark	Burned oil
										brown
2	183	0.83	14.9	1826	129	972	96	5	12	Dark	Burned oil
										black

TABLE 4

Final Properties of the Recovered Motor Oil After the Process

	Flash
Exp.	point	μ (cSt)	Metals (ppm)

Number	(° C.)	100° C.	Ca	Mg	Zn	Color	Odor

1	196	11.2	50.2	3.1	12.4	Light	Lubricating
						brown to	base oil
						yellow
2	180	12.8	45.6	4.1	23.2	Reddish	Lubricating
						chestnut	base oil

CONCLUSION

The laboratory tests have shown that with the process described, a removal takes place of metallic and organic contaminants of used industrial lubricating oils and those oils coming from internal combustion motors. The level of removal is such that the recovered lubricating oil bases can be used again with confidence in motor oils, automatic transmissions and other required uses. Our system is simple and economic compared to other systems, and the quality of the recovered oils is similar.
It is clear that the process and the product of the present invention will find wide use in the recovery and recycling of used industrial oils as well as those oils coming as wastes from internal combustion motors and transmissions. The foregoing describes only some embodiments of the present invention and obvious modifications to those skilled in the art can be made thereto without departing from the scope of the invention. It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.

Claims

1. A process for recovering used lubricating oil, comprising the steps of:

a) placing used lubricating oil and clay in a container where they are put together in contact to form a mixture;

b) heating the mixture to a suitable temperature for good sorption, with low effect of cracking; and

c) removing and separating the lubricating oil from waste products containing the clay and contaminants of the used lubricating oil.

2. The process for recovering used lubricating oil according to claim 1, wherein a filter press system is used to separate the lubricating oil from the clay and contaminants, to form a clay cake that is discarded, obtaining oil essentially free from contaminants.

3. The process for recovering used lubricating oil according to claim 1, wherein the clay and contaminants are separated from the used lubricating oil using a centrifuge.

4. The process for recovering used lubricating oil according to claim 3, wherein a filter press system is used to separate the lubricating oils from the clays and contaminants, to form a clay cake that is discarded, obtaining oil essentially free from contaminants.

5. The process for recovering used lubricating oil according to claim 4, wherein the centrifuge is an industrial centrifugal machine.

6. The process for recovering used lubricating oil according to claim 5, wherein the centrifuge has a rotating screw, which allows it to separate most of the clay from the lubricating oil to be recovered.

7. The process for recovering used lubricating oil according to claim 2, wherein the used lubricating oil is pre-filtered before forming the mixture with the clay.

8. The process recovering used lubricating oil according to claim 7, wherein the used lubricating oil is pre-treated with a flash type distillation, to separate a water residue from the used lubricating oil.

9. The process for recovering used lubricating oil according to claim 8, wherein the mixture is heated with a system including a heating jacket, wherein hot hydraulic fluid circulates to transfer heat.

10. The process for recovering used lubricating oil according to claim 9, wherein the clay is acid-activated.

11. The process for recovering used lubricating oil according to claims 10, wherein the clay is a hybrid of hormite and smectite.

12. The process for recovering used lubricating oil according to claim 11, wherein the container is a reactor, the hydraulic oil comes from a boiler, and a residence time in which the mixture remains in the reactor varies according the type of used lubricating oil.

13. The process for recovering used lubricating oil according to claim 12, wherein the mixture is heated to temperatures lower than 300 degrees Celsius.

14. The process for recovering used lubricating oil according to claim 13, wherein the mixture is heated to temperatures from 80 degrees Celsius to 200 degrees Celsius.

15. The process for recovering used lubricating oil according to claim 14, wherein after the residence time in the reactor, the mixture is poured out, and treated by a separation process.

16. The process for recovering used lubricating oil according to claims 15, wherein stirring rods are used to decrease the residence time of the mixture in the reactor.

17. The process for recovering of used lubricating oil according to claim 16, wherein the volume of the clay is lower than 60% of the volume of the used lubricating oil.

18. The process for recovering used lubricating oil according to claim 17, wherein the volume of clay is from 2% to 25% of the volume of the used lubricating oil.

19. The process for recovering used lubricating oil according to claim 18, wherein gases coming from the reactor are treated with trapdoors and filters to avoid atmospheric pollution.

20. Recovered used lubricating oil produced by a process comprising the steps of:

c) removing and separating recovered lubricating oil from waste products containing the clay and contaminants of the used lubricating oil.