WO2001000756A1

WO2001000756A1 - Method for decontaminating waste semi-synthetic or synthetic mineral oils

Info

Publication number: WO2001000756A1
Application number: PCT/FR2000/001705
Authority: WO
Inventors: Richard Deutsch
Original assignee: Richard Deutsch
Priority date: 1999-06-23
Filing date: 2000-06-21
Publication date: 2001-01-04
Also published as: AU6450200A; FR2795421B1; FR2795421A1; EP1190023A1

Abstract

The invention concerns a method for decontaminating waste lubricating oils which consists in: a) pouring the oils to be treated in a container, adding thereto 1-2 wt. % of glycol, heating at 60 °C, stirring and allowing to cool and decanting; b) drawing the aqueous phase, adding to the oily phase a chelating agent, in sodium solution with a pH ∫ 7, preferably pH 6, bringing to 60-80 °C, stirring for at least one hour, then centrifuging; c) adding to the oily phase a coagulating agent; d) adding to the oily phase barium hydroxide in water to precipitate the sulphate and phosphate ions in the form of barium sulphate and phosphate which is separated; e) performing a fractionated distillation to recuperate the basic constituents of the oils, and optionally carrying out a discoloration of the resulting products.

Description

PROCESS FOR DECONTAMINATION OF USED SEMI-SYNTHETIC AND SYNTHETIC MINERAL OILS

The present invention relates to a method for decontaminating modern lubricating oils by the extraction of heavy metals, sulfur compounds and phosphate compounds.

Lubricating oils have undergone a very strong development in the last fifteen years. This development is mainly due to the increase in performance of thermal engines put into service in recent years.

A few decades ago, the lubrication was done by a base oil simply extracted by distillation of crude oil in a refinery.

Very quickly the lubricating performances were increased by additives. A further increase in performance has been obtained by the addition of new additives, in particular polymers which have the function of thickening the oil at high temperature.

Another performance increase was obtained by adding synthetic oils of the polyalphaolefin type. These synthetic oils can significantly lower the freezing point of lubricating oils (down to -50 ° C, if necessary).

Modern lubricating oils are currently composed:

- mineral oil called base oil,

- mineral oils which have undergone a hydrogenation treatment, which makes them oils with a high viscosity index,

- polyalphaolefin type synthetic oils, - additives.

After use, the lubricating performance of the oils is very degraded, which necessitates the change of these oils.

Used lubricating oils come mainly from the draining process of automobile engines. These used oils are extremely toxic and a law imposes their collection and disposal in approved centers throughout Europe and the North American countries.

Used oil, also known as engine drain oil, consists of the above ingredients, to which is added the soiling due to the operation of the engines at operating temperatures (more than

300 ° C). In fact, this oil contains volatile constituents (water, petrol, diesel), oil-soluble compounds formed by oxidation (resins, metallic soaps, additives of viscosity index, organometallic compounds), compounds insoluble in the oils

(carbon particles, atmospheric dust, metals, metal oxides, lead oxides kept in suspension by detergents added to oils), additives containing a metal, dispersing additives, ashless additives, antioxidant and anti-corrosive additives, metals from pipes or fittings (iron, copper, lead), bearings (silver, cadmium), or fuels

(tetraethyl lead, among others).

The list of products mentioned is not exhaustive but given as an example. The descriptions are given by way of illustration but not limitation.

The oil deteriorates and becomes colored by oxidizing action in engines, by the formation of colored varnishes and by the action of sulfur. The regeneration and recycling of these oils was a flourishing industry until the early 1990s, which deteriorated due to the presence in the drain oils of polymers which made redistillation very complex. Indeed, during the redistillation operation of these waste oils. the incorporation of the oily phase leaves the polymers alone at the bottom of the distillation column

As long as these polymers are in the distillation column at a temperature above 150 ° C, they remain in the liquid phase, but as soon as they leave the distillation column and enter a heat exchanger, they solidify and , at a temperature below 100 ° C, they block the whole distillation process.

This phenomenon of solidification of polymers in heat exchangers led to the closure or the cessation of operation of most of the plants for the regeneration of waste oils in the world.

Another phenomenon has hit the regeneration industry hard

In ettet. the elimination of heavy metals, metalloids, complex products, tars, colloidal residues and other content in used engine oils is currently carried out by the combined action of heat, sulfuric acid, bleaching earth , filtration of centπfugation, distillation

This sulfuπque acid technique is starting to become illegal in several European countries (Spain, Benelux, Great Britain, etc.), which means that the regeneration units using this technique are stopped.

In addition, this technique using sulfuπque acid in combination with very high distillation temperatures led to the production of Polynuclear aromatic products considered to be carcinogenic, the regulatory authorities imposing their strict limitation.

All these facts produce the following paradoxical situation: the oils of idange which are composed of more and more expensive products, and which could allow by their recovery of the interesting profits, are currently directed towards the incineration in cement factory instead to be recycled.

In addition, the mineral and synthetic oils contained in the drain oils keep good specific qualities after their use, because they are very thermally stable.

In addition, the current regeneration technique using high distillation temperatures (above 350 ° C.) generates cracking phenomena giving a strong odor to the regenerated oil.

This strong odor leads to a significant reduction in the sale price of the regenerated oil. These cracking phenomena also generate a coloration of the oils imposing an extensive bleaching treatment on bleaching earths, causing a significant additional cost of production.

This significant additional cost is due to the need to reprocess and eliminate the bleaching earth (activated clay type) used. Finally, landfilling after reprocessing is increasingly problematic.

Given the investments involved, it is important to implement a process allowing better recovery of recycling.

The invention solves this technical and economic problem by a process for decontaminating lubricating oils, containing mineral oils and semi-synthetic and synthetic oils, used, called drain oils, characterized by the following steps: a) the oils to be treated are placed in a container, 1 to 2% by weight of glycol is added to them, the mixture is heated to 60 ° C., the mixture is stirred and then allowed to cool and decant, so that an aqueous phase containing the glycol and the phenolic products extracted from the oily phase as well as the suspended matter and the residues of silicone oil possibly present as anti-foaming additive, b) the aqueous phase is drawn off, a chelating agent. in a stoichiometric amount or slightly greater than the stoichiometric amount relative to the compounds to be eliminated in the step, in soda solution at a pH not exceeding 7, preferably at pH 6. the temperature is brought to 60 ° -80 ° C., the mixture is stirred for at least one hour and then centrifuged to separate the sodium solution containing the chelated heavy metals extracted from the oils from the oily phase,

c) a coagulant is added to the oily phase obtained after centrifugation, in a stoichiometric amount or slightly greater than the stoichiometric amount relative to the compounds to be eliminated in the step, in an acidic aqueous medium to extract the iron, and the aqueous phase is separated obtained

d) barium hydroxide in suspension or in solution is added to the oily phase, in a stoichiometric amount or slightly greater than the stoichiometric amount relative to the compounds to be eliminated in the step, in water to precipitate the sulfate and phosphate ions in the form of barium sulfate and phosphate which are separated by decantation or by centrifugation, e) a fractional distillation is carried out to recover the basic constituents of the oils, and optionally a discoloration of the products thus obtained, steps b and c and c and d can be reversed provided that step d is carried out after l 'step b.

Advantageously, step b is repeated after step c. Preferably, the discoloration of step e is carried out with a clay.

Advantageously, the coagulating agent of step c is chosen from the group comprising hydroxides of trivalent metals, amines and polyamines. and the acid used to bring the pH to an acid value is an organic acid or a strong inorganic acid.

When the drain oils come only from motor vehicles, that is to say when they have not been mixed - for transport problems - with other used oils of industrial origin, it is possible to simultaneously carrying out steps b and c, that is to say simultaneously carrying out the addition of the chelating agent and the coagulant.

The problem with decontaminating used oils is as follows: metals, heavy metals, part or all of the sulfur compounds, phosphate compounds, chlorine, chlorine compounds and phenolic compounds must be removed.

In an industrial process for recycling drain oils, said oils arrive in a collection truck, of the tanker type, and drain (or used) oils are then transferred to a storage tank. When collected, these oils are generally mixed with water (around 4 to 5%). From this tank, the decontamination process consists of: pumping the waste oils into a cylindrical tank with a conical base, equipped with a heating coil and a means of agitation such as a counter-rotating propeller or compressed air. The used oil is mixed with 1 to 2% glycol to remove the phenolic compounds. The whole is brought to a temperature of at least 60 ° C. stirred, then allowed to stand to obtain separation of the phases by decantation.

The aqueous phase is positioned at the bottom of the tank, that is to say in the conical part, provided with a withdrawal tap; this aqueous phase contains the glycols mixed with the phenolic products and all the particles in suspension (iron, carbon, sand, etc.) which will have deposited, as well as the residual silicone oil (anti-foaming additive). This aqueous phase mixed with these components is drawn off in order to leave only the oily phase in the tank.

We then proceed to the injection of chelating agents in aqueous sodium solution and at a pH of 6 or slightly higher.

The whole is brought to a temperature between 60 ° C and 80 ° C and stirred for at least one hour to complex the heavy metals (including zinc) with the chelating agents.

At the end of this step, the whole is centrifuged in order to separate the oil from the complexed heavy metals which are in the aqueous solution.

This operation extracts between 80 and 90% of the heavy metals while the sodium neutralizes the chlorine. After centrifugation, the oily phase is directed into another tank of the conical bottom type. A coagulant is then added in small quantities in an acid medium which allows the extraction of iron.

The coagulant is chosen, for example, from the group comprising hydroxides of trivalent metals, amines and polyamines and the acid used to bring the pH to an acid value is an organic acid or a strong inorganic acid.

In the next step, barium hydroxide suspended in water is added, this hydroxide precipitates the phosphate and sulfate ions. It should be noted that the use of this barium hydroxide allows the use of sulfur chelating agents, because its action makes it possible to control the level of residual sulfur in the oils, according to the wishes of the end customer, who may require levels residual sulfur in the oil variable, but not exceeding a threshold generally between 3000 and 3500 ppm.

The whole is then decanted or centrifuged, which makes it possible to obtain a decontaminated oil which can be distilled by fractionation.

Decontamination due to the elimination of zinc and its derivatives allows distillation all the easier to conduct when the fouling phenomena due to the recombination of zinc with the products at the bottom of the column are eliminated. If a higher degree of purity of the oil is required, a phase can optionally be repeated with a mixture of chelating agents, if necessary.

Depending on the composition of the oils treated or the specifications of the desired final product, the phases of the treatment may be modified, for example the treatment with barium hydroxide may precede the phase of elimination of heavy metals. Another advantage of this decontamination treatment is that it makes it possible to replace, in the final treatment, bleaching earth activated by a simple clay (bentonite and derivatives). The cost advantage is considerable, a bleaching earth worth 6 to 8 times the price of a clay.

All of these operations are necessary to bring the oils to the specifications desired by the market.

In addition, this decontamination carried out in the initial phase before distillation, unlike the methods applied hitherto, makes it possible to preserve the distillation unit and to conduct it at very low temperature, which will not induce cracking phenomenon polymers and therefore to separate them from the oil much more easily and to obtain a fractionation which is much easier to conduct.

Claims

1. Method for decontaminating lubricating oils, containing mineral oils and semi-synthetic and synthetic oils, used, called drain oils, characterized by the following steps: a) the oils to be treated are placed in a container, and added to them from 1 to 2% by weight of glycol, the mixture is heated to 60 ° C., the mixture is stirred and then allowed to cool and decant, so that an aqueous phase containing the glycol and the phenolic products extracted from the oily phase is formed, as well as the materials suspension and the residues of silicone oil which may be present as an anti-foaming additive, b) the aqueous phase is drawn off, a chelating agent is added to the oily phase in a stoichiometric amount or slightly greater than the stoichiometric amount relative to the compounds to be eliminated in the step, in sodium solution at a pH not exceeding 7, preferably at pH 6, the temperature is brought to 60 ° -80 ° C., the mixture is stirred for at at least one hour, then centrifuged to separate the soda solution containing the chelated heavy metals extracted from the oils from the oily phase. c) a coagulant is added to the oily phase obtained after centrifugation, in a stoichiometric amount or slightly greater than the stoichiometric amount relative to the compounds to be eliminated in the step. in an acidic aqueous medium to extract the iron, and the aqueous phase is separated obtained. d) barium hydroxide in suspension or in solution is added to the oily phase in a stoichiometric amount or slightly greater than the stoichiometric amount relative to the compounds to eliminate in the step, in water to precipitate the sulfate and phosphate ions in the form of barium sulfate and phosphate which are separated by decantation or by centrifugation, e) a fractional distillation is carried out to recover the constituents base oils, and optionally discoloration of the products thus obtained, steps b and c and c and d can be reversed on condition that step d is carried out after step b.

2. Method according to claim 1, characterized in that, if necessary, step b is repeated after step c.

3. Method according to claim 1, characterized in that step b and step c are carried out simultaneously.

4. Method according to one of claims 1 to 3, characterized in that the discoloration of step e is carried out with a clay.

5. Method according to one of claims 1 to 4, characterized in that the coagulating agent of step c is chosen from the group comprising the hydroxides of trivalent metals, the amines and the polyamines, and the acid used for bringing the pH to an acid value is an organic acid or a strong inorganic acid.