WO1998026031A1

WO1998026031A1 - High performance method and plant for regenerating lubricating waste oil

Info

Publication number: WO1998026031A1
Application number: PCT/FR1997/002224
Authority: WO
Inventors: Med Ali Boufahja; Abdelhafidh Jaafar; Salah Meziou; Achour Ouazzane; Mohamed Dhaouadi
Original assignee: Societe Tunisienne De Lubrifiants - Sotulub
Priority date: 1996-12-13
Filing date: 1997-12-05
Publication date: 1998-06-18
Also published as: EP0944696B1; CZ300297B6; PT944696E; BG64486B1; DE69704500T2; CZ211899A3; ES2156008T3; BG103577A; OA11060A; HU222544B1; MA24424A1; HK1022928A1; RU2187544C2; GR3036074T3; CA2274831A1; AR010353A1; DE69704500D1; FR2757175A1; PL186318B1; TNSN97189A1

Abstract

The invention concerns a method and a plant for regenerating lubricating waste oil with low content of fuel, fatty acids and chloric products. The lubricating waste oil is subjected to the following steps successively: adding strong bases in aqueous solution at the rate of 0.5 to 3 % of pure bases by mass of waste oil; dehydrating and extracting the light hydrocarbons, extracting and recuperating the gas oil (stripping); extracting the impurities. The invention is characterised in that a complementary addition of a strong base in aqueous solution at the rate of 0.1 to 1 % by mass of waste oil is carried out following the dehydrating and extracting of light hydrocarbons. The treated lubricating waste oil are rid of their impurities by distillation.

Description

METHOD AND PLANT FOR THE REGENERATION OF HIGH PERFORMANCE LUBRICATING OILS

The present invention relates to a process and an installation for regenerating high-performance used lubricating oils.

Such regeneration processes are already known and, in particular, advantageously refer to that described in patent application O-94/21761. This prior document describes a process for regenerating used lubricating oils in which they are subjected to the following successive treatment steps: a) preheating in which the oils to be regenerated are brought to a temperature between 120 and

250 ° C; b) adding a strong base in aqueous solution at a rate of 1 to 3% by mass of pure bases; c) extraction of impurities. This prior document also describes various preferred embodiments of this method which are generally satisfactory. However, attempts have been made to obtain regenerated oils of even improved quality. The object of the invention is therefore to propose such a method and the corresponding installation.

To this end, the invention relates to a process for regenerating used lubricating oils having a low content of fuel oil, fatty acids and chlorinated products, in which the used lubricating oils are subjected to the following successive treatment steps in order: ) selection of used oils suitable for treatment; b) adding a first quantity of a strong base in aqueous solution; c) heating the mixture to a temperature between 120 and 250 ° C; d) adding a second quantity of the strong base in aqueous solution, the first and the second quantity of strong base in aqueous solution representing together from 0.5 to 3% of pure bases by mass of used lubricating oils; e) dehydration and extraction of light hydrocarbons; f) extraction and recovery of gas oil (stripping); g) extraction of impurities. According to the invention, a complementary addition of a strong base in aqueous solution due to 0.1 to 1% of pure bases by mass of lubricating oils is carried out after step e).

In different embodiments, the invention can also have the characteristics below considered in isolation or in all their technically possible combinations:

- the additional addition of strong bases is carried out during the diesel extraction and recovery stage,

- the additional addition of strong bases is carried out after the diesel extraction and recovery stage,

- after the dehydration stage, extraction of light hydrocarbons and stripping of the diesel oil, the stripped oil is freed of its impurities (residues) in a vacuum column provided with a reboiling system, then subjected to a stage oxidation before the additional addition of strong bases, then fractionated, - The elimination of impurities is obtained by vacuum distillation ensuring the separation into lubricating base oils on the one hand, and in a residue concentrating all the impurities on the other hand. During the first addition, the amount of strong bases in aqueous solution provided may be between 0.5 to 3% of pure bases by mass of used lubricating oils. This addition can be made totally or partially cold or hot. The heating temperature of the used oils to be regenerated between 120 and 250 ° C. is a temperature at which the addition of the hot base is carried out in whole or in part.

The invention will be described in detail with reference to the accompanying drawings in which:

- Figure 1 is a schematic representation of a process and an installation for regenerating used lubricating oils of the prior art;

- Figure 2 is a schematic representation of a process and a regeneration system of used lubricating oils in a first embodiment of invention 1 ^•;

- Figure 3 is a schematic representation of a process and an installation for regenerating used lubricating oils according to a second embodiment of the invention;

- Figure 4 is a schematic representation of a process and an installation for regenerating used lubricating oils according to a third embodiment of the invention.

The used oils collected can have various origins. It can be, for example, engine oil, gear oil, hydraulic oil, turbine oil, etc. When these oils arrive in the regeneration unit, their suitability for processing is checked.

Indeed, the regeneration process of the invention aims to eliminate light components, such as petrol, diesel and water, it also allows the elimination of degradation products from oil and additives, but does not make it possible to eliminate certain components as heavy as the oils themselves and having different physical properties. It could be, for example, fuel whose elimination or treatment could only be obtained by a complete refining process.

Excessive chlorine content in the mixtures could cause premature wear of the system.

Collected oils therefore containing too high a percentage of fuel oil, fatty acids or chlorine are eliminated. These are, in general, oils that do not pass the regenerability tests. In order to evaluate the concentrations of these various compounds, the regeneration tests well known in themselves used in the field are practiced.

The regenerability tests are as follows: - The "Chlor test" makes it possible to detect the presence of chlorides. A copper wire dipped in used oil is presented to the flame. A greenish flame indicates the presence of chlorides.

- The "Drop test" detects the presence of fuel. A drop of oil is deposited on a chromatographic paper. A concentric spot with a yellowish halo indicates the presence of fuel.

- The "Fat test" detects the presence of fatty acids in oils. 2 ml of used oil is heated in the presence of a soda tablet: when the oil freezes, after cooling, this means that fatty acids are present.

- Determination of the concentration of PCB (polychlorinated biphenyl). This test is performed and its limits are set according to the regulations in force.

The waste oils collected 1 having successfully undergone all of the tests are combined in a tank 2. They are then mixed, either inside the tank 2, or during their extraction by conventional means not shown in the Figures .

A base or a mixture of bases stored elsewhere in a tank 4a is provided and mixed by means 5a with the used oils at room temperature between 10 and 40 ° C.

Heating means 3 bring the oils taken from the tank 2 and optionally mixed with the base, to a temperature between 120 and 250 ° C and preferably between 140 and 160 ° C.

A base or a mixture of bases stored elsewhere in a tank 4b is supplied and mixed by means 5b with the heated waste oils.

Preferably, an amount of pure bases of between 0.5 and 3% by mass is added to the used oils.

This rate, as well as its distribution between the two cold and hot injection points, can be advantageously specified depending on the quality of the used oils and the nature of the base used.

The base used is a strong base, preferably sodium or potassium hydroxide. One can also consider using a mixture of these bases.

Waste oils, brought to a high temperature, added with strong base, feed a unit 6 for extraction of water and light hydrocarbons by expansion (flash). In such a unit 6, the evaporation of water is produced by the sudden expansion of the mixture in a balloon. Water and light hydrocarbons are extracted and discharged to outlet 7. The remaining mixture is directed to a unit 8 for extracting gas oil (stripping). This elimination is carried out by distillation in a column. The gas oil 9 is then evacuated and the remaining mixture is led to a distillation column 10 allowing the fractionation of the mixture into sections of lubricating base oils 11, 12 and the separation of the residue 15 where all the impurities are concentrated. Base oils can be separated at different levels depending on the number of cuts desired. Good results have been obtained by separating, on the one hand, a base oil of 150 Neutral 11 and, on the other hand, a base oil of 400 to 500 Neutral 12. The distillation column 10 is a traditional column under vacuum which allows the dissociation and extraction of the residues which are directed to an accumulation tank 14.

The residues 15 are then removed and are capable of being used, for example, as tar or bitumen for the construction of roads. They can also be used as fuel.

The vacuum distillation column 10 is preferably associated with a column bottom exhaustion evaporator 13 making it possible to improve its efficiency. Part of the energy required to raise the temperature of the used oils before the flash preferably comes from the energy recovery carried out on the sections of lubricating base oils 11, 12 from the column outlet 10. The used oils are advantageously filtered during their recovery and when they leave the storage tank 2, so as to remove the solid particles which they may contain. Different pumps, not shown, ensure the circulation of the mixture and of the products extracted through the installation described.

An addition of additional base solution is made in lower proportions than the initial additions, before the flash, the additional addition being in proportions of the order of 0.1 to 1% by mass of pure bases relative to the used lubricating oils. It can be carried out at different points of the installation corresponding in each case to an embodiment.

This additional addition gives the process flexibility that allows it to adapt to the different physico-chemical requirements of regenerated base oils, that is to say to provide oils whose quality is adapted to the desired results.

This process makes it possible to ensure better stability of the regenerated base oils and to fluidize the impurities, which allows easier operation of the process.

In a first embodiment shown in Figure 2, this additional addition is made after the dehydration and extraction of light hydrocarbons. A base stored in a tank 16 is supplied and mixed by means 17 with the waste oils to the portion of the recirculated stripped oil.

The oil temperature is then advantageously between 270 and 310 ° C. In another embodiment shown in FIG. 3, the addition of complementary base is carried out under the same concentration and temperature conditions as in the first embodiment, but after the gas oil extraction operation (stripping ). A base stored in a tank 18 is supplied and mixed by means 19 with the heated stripped oil directed towards the fractionation column. In the third embodiment shown in FIG. 4, following the stripping operation of gas oil, an evaporator 13, preferably with thin layers, coupled to a vacuum column 10, makes it possible to eliminate most of the impurities. The oil obtained is then subjected to accelerated oxidation in a tank 22, before an additional quantity of pure bases is added to it. To this end, a base stored in a reservoir 23b is supplied and mixed with the oil by mixing means 24.

The oil is then fractionated in the distillation column 20.

The temperature of the oil during the addition of the base is advantageously between 200 and 300 ° C for an injection from the reservoir 23b just before column 20 and is between 120 and 200 ° C for an addition from of a reservoir 23a directly in the oxidation tank 22.

The evaporator 13 is advantageously a thin film evaporator. It is also possible to use several evaporators successively.

The residues 21 of column 20 are, depending on the efficiency of this column and the requirements imposed on the regenerated oils, either recirculated and injected at the inlet of column 10, or conveyed to the storage of the residues such as the residues 15 coming from the distillation column 10 and 1 • evaporator 13.

This choice is a function of the concentration of residues 21 in lubricating oil. It is done regularly according to the requirements imposed on regenerated oils.

The color stability of the regenerated base oil 150N is shown in the table in annex No. 1 below. Sample 2 was obtained by a process according to the invention implemented according to one of Figures 2 and 3. Sample 3 was obtained by a process according to 1 invention implemented according to Figure 4 These samples are compared to sample 1 obtained with a single basic injection according to the prior art.

Similarly, for the regenerated base oil 400-500 N, samples 5 and 6 obtained according to the invention are to be compared with sample 4 obtained according to the prior art.

The color stability and the appearance of the cuts obtained by this process are better and reflect a higher quality of the oil obtained compared to that obtained by the previous processes. The reference signs inserted after the technical characteristics mentioned in the claims, have the sole purpose of facilitating the understanding of the latter, and in no way limit their scope. APPENDIX 1

OXIDATION TEST ACCORDING TO IP 306/79 STANDARD

Original specifications at the date of production

Characteristics before the oxidation test and after an industrial storage of 6 (six) months

Oxidation test according to standard IP 306/79

S = Total Sluge

TOP = Total Oxidation Products

Sample N ° = 1: Section 1 50 N regenerated obtained at the regeneration unit according to the prior art in accordance with Figure 1

Sample N ° = 2 Section 150 N regenerated obtained at the regeneration unit according to the invention in accordance with Figures 2 or 3 Sample N ° = 3 Section 1 50 N regenerated obtained at the regeneration unit according to the invention in accordance with Figures 2 or 3 Figure 4 Sample N ° = 4 Section 400-500 N regenerated obtained at the regeneration unit according to the prior art in accordance with Figure 1 Sample N ° = 5 Section 400-500 N regenerated obtained at the regeneration unit according to l invention according to Figures 2 or 3 Sample No = 6 Section 400-500 N regenerated obtained at the regeneration unit according to the invention according to Figure 4

Note: The higher the S / TOP ratio, the more unstable the oil.

Claims

1. Method for regenerating used lubricating oils having a low content of fuel oil, fatty acids and chlorinated products, in which the used lubricating oils are subjected to the following successive treatment steps in 1 ^" order: a) selection of used oils suitable for treatment satisfying the regenerability tests; b) adding a first quantity of a strong base in aqueous solution; c) heating the waste oils to be regenerated at a temperature between 120 and 250 ° C; d) adding a second quantity of the strong base in aqueous solution, the first and the second quantity of strong base in aqueous solution representing together from 0.5 to 3% of pure bases by mass of used lubricating oils; e) dehydration and extraction of light hydrocarbons; f) extraction and recovery of gas oil (stripping); g) extraction of impurities, characterized in that a complementary addition of a strong base in aqueous solution due to 0.1 to 1% of pure bases by mass of used oils is carried out after step e).

2. Regeneration method according to claim 1, characterized in that the additional addition of strong bases is carried out during the step of extraction and recovery of diesel.

3. Regeneration method according to claim 1, characterized in that the additional addition of strong bases is carried out after the stage of extraction and recovery of diesel.

4. Regeneration method according to claim 1, characterized in that, after the dehydration step, extraction of light hydrocarbons and stripping of diesel, the stripped oil is freed of its impurities in a vacuum column provided with '' a reboiling system, then subjected to an oxidation step before the additional addition of strong bases, then fractionated.

5. Method for regenerating used lubricating oils according to any one of claims 1 to

4, characterized in that the elimination of impurities is obtained by vacuum distillation ensuring the separation into oils of lubricating bases, on the one hand, and into a residue concentrating all the impurities, on the other hand.

6. Used oil regeneration installation comprising:

- a tank (2) for storing used oils,

- heating means (3) for used oils, - storage means (4) for a strong base,

means for mixing (5) the strong base in a proportion determined with the used oils,

- means for removing impurities (10, 13, 14), means for mixing (5) the strong base with used oils and means for removing impurities (10, 13, 14), a unit for water extraction by expansion (6) (flash) and a gas oil extraction unit (8) (stripping) and the impurity extraction means (10, 13, 14) include a vacuum distillation unit ( 10) associated with an evaporator (13) at the bottom of the column, characterized in that it comprises means for complementary addition of a strong base after the means (5) for mixing the strong base.

7. Installation according to claim 6, characterized in that it comprises an evaporator (13) at least placed after the diesel extraction unit.

8. Installation according to claim 7, characterized in that 1 • evaporator (13) is thin layers.