EP0360866B1 - Method and installation for cleaning parts - Google Patents

Abstract

PCT No. PCT/SU88/00075 Sec. 371 Date Dec. 4, 1989 Sec. 102(e) Date Dec. 4, 1989 PCT Filed Mar. 29, 1988 PCT Pub. No. WO89/09099 PCT Pub. Date Oct. 5, 1989.The proposed method resides in that the surface of a workpiece is treated with a molten solvent which at first is crystallized at the surface of the workpiece and then is melted to result in a used solution which is cooled and settled to form two layers, viz., an upper layer containing petroleum products, light mechanical impurities and a quantity of the solvent, and a lower layer containing the solvent, heafy mechanical impurities and a quantity of petroleum products, after which petroleum products are separated from the upper layer, whereas, the crystals of the solvent are melted and added to the lower layer from which the solvent is separated and conveyed for cleaning the workpieces. An apparatus for carrying out the method comprises a system (12) for regenerating the used solution connected to a system (20) for separating constituents of the upper layer (18), and a system (21) for separating constituents of the lower layer (19).

Description

Field of the invention

The invention relates to the field of cleaning articles by ridding them of technological impurities, and more specifically, it relates to a method of cleaning articles by ridding them of petroleum products and mechanical impurities, as well as an installation for realization of this process.

The invention can be applied with the greatest effect to the cleaning of the surface of articles fouled with mineral, vegetable oils and animal fats, with pastes, preservatives, cutting fluids and other technological impurities, referred to more far petroleum products and mechanical impurities.

State of the art

In modern production technology, a large number of auxiliary materials are involved. You can bring in mineral oils, vegetable and animal fats, pasta, preservatives, cutting fluids, etc. They remain on the surface of the articles and necessitate cleaning before assembly or application of a protective coating. In the cleaning operations of the articles, hydrocarbon solvents, chlorinated and / or fluorinated hydrocarbon solvents, aqueous solutions of electrolytes, surface-active substances and complex mixtures based on these are used. After the cleaning operation of the articles, they are, with the impurities, all discharged into the environment in the form of industrial spills, vapors, incineration products of the residues of distillation, of mud to be buried. The cost of irrecoverable loss of chemicals and the damage caused by environmental pollution are immense.

There is a known process for cleaning articles (SU-A-1093732) . This method involves treating the surface of the articles with aqueous solutions containing surfactants and process activators, for example, ammonium persulfate, mono-ethanolamine phosphate, sulfamic acid, acid oxalic, naphthalene sulfonates and water. The regeneration of used solutions is carried out by decantation, elimination of petroleum products emerged on the surface of the solution and by filtering mechanical impurities.

In this process, the regeneration of the spent solution consists only in decanting and filtering inhomogeneous systems. The spent solvent, polluted with soluble impurities, is in no way regenerated. Thus, aqueous solutions, and organic solvents and petroleum products are released to the environment.

A method of cleaning the surface of articles is known by ridding them of petroleum products and mechanical impurities (SU-A-541857) consisting in that the article to be cleaned is previously heated to 60 ° C., is treated with a detergent containing white spirit, hydroxylated alkylphenols or fatty alcohol, water, sodium alkylsulphonate and gas oil. With this, the article is kept 10 to 15 min at a temperature of 50 to 60 ° C and the article is washed with an aqueous solution heated to 60 ° C and containing 0.1 to 0.3% of tripolyphosphate and 0 , 1 to 1% of hydroxyethylphenol. The used solution is regenerated by heating it to a temperature of 80 to 90 ° C., then the supernatant petroleum product is eliminated, while the detergent aqueous solution is reused several times for cleaning.

However, during the article cleaning operation, the solvent partially reacts with the impurities removed by washing. Petroleum products, greases and solid mechanical impurities, periodically removed from the process, contain solvent, products of its chemical reaction with impurities and must therefore be buried.

The aqueous phase, after saturation with soluble components of petroleum products, must also be buried.

A method is known for descaling hard surfaces of articles using compositions of organic substances US Pat. No. 3,957,672 . The process consists in treating hard surfaces with polyfluorinated ethers or chlorinated and / or fluorinated alkanes with additions of perfluoro-alcohols, perfluoro-ethers, perfluoro-acids in an amount of 0.02 to 1% by mass. Volatile solvents distribute the dissolved substance over the surface and, rapidly volatilizing, reject (disperse) the film of petroleum products from the surface. The consumption of the composition is equal to a few cm³ per 100 p. surface squares. In the known process, the problem of separating the used solutions into initial constituents has not been resolved for use in recycling and the consumption of detergents is quite high, while the volatile base, the fluorocarbon liquids, evaporating in the destroy the ozone layer in the atmosphere.

A method of cleaning the surface of articles is also known (GB-A-2104104) . According to this process, the surface of the articles is cleaned by a circulating solvent, composed of a liquid chlorinated hydrocarbon and a surfactant whose constituents are selected so that they do not mix and do not react with technological impurities. The used solution is regenerated by evaporation of the liquid chlorinated hydrocarbon. After condensation, the surfactant is added to the purified solvent and returned for repeated cleaning of the article. The impurities removed by washing, after evaporation of the solvent, must be separated from the surfactant to be able to be reused. In the process, this operation is not carried out while the process itself is only applied in a limited field: cleaning of the surface of articles after application of protective coatings, but then, there may be decomposition of the chlorinated solvent in the presence of water and metal chlorides with the formation of very toxic substances.

To carry out the known processes, it is possible to use the installation for cleaning the surface of articles of the carousel type, which is composed of standard assemblies corresponding to the type of the detergent solution or to the prescriptions of the technological operation (D-tor V Kampschulte et al., RFA, Somingen, "Ultrasonic and ultrasonic cleaning and degreasing installation"). The installation includes a cleaning chamber provided with a mechanical and ultrasonic activation device, a cleaning device, a distillation device, a device for separating solid mechanical impurities, condensers for trapping and condensing the vapors. solvent. This installation is characterized by a low factor of use of the solvent because of the decomposition and the reaction of the solvent with the mechanical impurities removed by washing and water and the burial of distillation residues containing a significant amount of solvent. Solvent losses in installations of this type make from 0.1 to 0.5 kg per m² of surface cleaned of the articles.

There is a known method of cleaning articles by ridding them of petroleum products and mechanical impurities described in document SU-A-1,189,515 having served as a basis for the preamble of the main claim, carried out in an installation and comprising the cleaning of the surface of the articles with a circulating solvent, drying of the cleaned articles, regeneration of the spent solution and separation of the impurities removed by washing. According to this process, the articles are heated to a required temperature and are treated with the circulating solvent. After cleaning, the article is dried under vacuum. The dried items are cooled and taken out of the facility. The solvent vapors formed during drying are condensed and returned to the surface cleaning cycle of the articles. The spent solvent is regenerated by distillation. A distillate and a distillation residue are then formed which contain non-volatilized solvent, petroleum products and mechanical impurities removed by washing. The distillate is returned to the cleaning cycle and the liquid components of the distillation residue are filtered and reused.

This process is also characterized by large losses of solvent, caused by its high volatility, by its evacuation with the distillation residue and also due to its chemical reaction with the impurities removed by washing and water.

The installation for carrying out this process described in the document (SU-A-1 189 515) which served as the basis for claim 8 comprises a conveyor for moving the articles and, aligned, an inlet chamber, neutral chambers, a cleaning chamber provided with a solvent circulation system, a drying chamber connected to a vacuum system, a condenser for trapping the solvent vapors, a distiller, a distillate accumulator, a collector of petroleum products and a filter to separate mechanical impurities. All the rooms of the installation are hermetically closed using valves.

Statement of the invention

The invention aims to create a method of cleaning articles consisting in ridding them of petroleum products and mechanical impurities and an installation for its realization which would make it possible to change the state of aggregation of the cleaning medium from solid to gaseous, to regulate the reciprocal solubility in the system "technological pollution - cleaning medium" and thanks to this, to increase the efficiency of cleaning of the articles, to reduce the losses of the cleaning medium as well as the quantity of impurities eliminated by washing diffusing in the environment.

To this end, the present invention relates to a method of cleaning articles consisting in ridding them of petroleum products and mechanical impurities comprising the treatment of the surface of the articles with a circulating solvent, the drying of the articles cleaned, the regeneration of the used solution, the capture of the solvent vapors from the air-vapor mixture and the separation of petroleum products and mechanical impurities, this process being characterized in that the treatment of the cold surface of the articles is carried out using molten solvent which crystallizes on the cold surface of the articles, then heating of the articles is carried out, causing the melting of the crystallized solvent, the used solution is cooled to a temperature close to but 1 to 10 ° C. higher than that of the solvent melting, leading to the settling of the cooled solution with the formation of two layers: an upper layer containing the products petroleum, light mechanical impurities and part of the solvent, and a lower layer, containing the solvent, heavy mechanical impurities and part of the petroleum products, then the upper layer is cooled until the solvent completely crystallizes it contains, petroleum products are separated therefrom, then the solvent crystals are melted separated from the light mechanical impurities, and united in the lower layer from which the solvent is then separated from the heavy mechanical impurities, the solvent being returned to the cleaning of the articles, while light mechanical impurities from the upper layer and heavy mechanical impurities from the neck The lower che are dried to separate the solvent which is reused after condensation to clean the articles.

Thus, the method makes it possible to increase the cleaning efficiency (the residual pollution of the surface of the articles after cleaning makes up 0.01 to 0.05 mg / cm²), to achieve a regeneration of the used solutions with the recycling of the solvent. , exclude losses of petroleum products, separate petroleum products and mechanical impurities and reduce their release into the environment.

According to a particular embodiment, the solvents used are organic substances, solid under normal conditions, fluorinated and / or chlorinated, chemically inert, insoluble in petroleum products and unable to dissolve the latter at temperatures below the melting point of the solvent.

The application of such solvents makes it possible to reduce their loss thanks to the absence of a chemical reaction between them and the impurities removed by washing, to their low solubility in petroleum products and also thanks to the low values of the vapor pressure at above the solid solvent. In addition, the use of such solvents makes it possible to separate the impurities without changing the chemical composition or the properties of the solvents. In this way, an almost completely waste-free process is achieved. For example, the solvent losses according to the proposed process do not exceed 4 g per m² of surface of the article treated and at least 94% of the initial petroleum products introduced into the cleaning operation on the articles are extracted from used solutions. dirty.

It is preferable to subject a portion of the spent solvent to distillation, then to send the distillate formed for rinsing the articles and after this rinsing to direct the distillate again for distillation, while the distillation residue, containing the products tankers and a significant amount of solvent, must be combined with the spent solution.

The application of these operations makes it possible to increase the cleaning efficiency and also to reduce the losses of solvent and petroleum products. Residual fouling, after rinsing the surface of the articles with the solvent distillate, represents 0.01 to 0.001 mg / cm².

The problem of preventing the rejection of solvent vapors into the atmosphere can be solved in that the air and the vapors of chlorinated and / or fluorinated organic substances, after drying of the articles, are cooled until complete crystallization solvent and then the solvent crystals are separated from the air.

It is preferable that the solvent crystals, separated from the air, be melted and used to rinse the items. This operation increases the rate of use of the solvent.

According to a particular embodiment, the petroleum products are separated from the upper layer of the spent solution by filtering. Filtering is sufficiently effective when there is an insignificant amount of mechanical impurities in the upper layer and the solvent crystals are sufficiently large.

According to an alternative embodiment, the petroleum products are separated from the upper layer by centrifugation. Centrifugation is preferable to separate petroleum products from finely dispersed crystals and mechanical impurities.

The present invention also relates to an installation for carrying out the process comprising an article cleaning chamber connected to a system for regenerating the spent solution, comprising a distiller and an accumulator of the distillate communicating with the latter, an article drying chamber , a means for moving the articles through the chambers, a vacuum system and a system for capturing solvent vapors, this installation being characterized in that it also comprises a chamber for rinsing the articles, connected via of a pump to the distillate accumulator and in that the regeneration system of the spent solution is provided with a cooler of the spent solution, connected to a decanter used to separate the spent solution into two layers: an upper layer and a lower layer, said decanter is connected to a system for separating the components of the upper layer e t to a system for separating the components of the lower layer, that the system for separating the constituents of the upper layer comprises, in series, a crystallizer and a device for separating petroleum products, which has an outlet connected to a collector of petroleum products, as well as an outlet connected to a collector of solvent, comprising a heater and having a lower outlet which, via a pump, is connected to the inlet of the spent solution cooler, while the system for separating the components of the lower layer comprises, in series , a pump, a siphon washer and an evaporator with a built-in heater, an upper outlet of the washer siphon being connected, via a heater, to the cleaning chamber, and a lower outlet, to the evaporator one of whose outputs is connected to the decanter and another to the solvent collector.

To achieve an even better cleaning of the articles, to obtain a distillate free from petroleum products and to reduce the losses of solvent and petroleum products, it is rational that the distiller has three pipes, one of which is connected, via from a pump, at the inlet of the cooler, another, at the upper outlet of the washing siphon and at a lower outlet of the article rinsing chamber, and the third, to the distillate accumulator.

It is useful that the solvent vapor capture system is connected to the drying chamber and includes, in series, a refrigerator-crystallizer, a siphon and a filter connected to the vacuum system, which prevents the release of solvent vapors in the atmosphere and which ensures residue-free technology.

It is recommended that the lower parts of the fridge-crystallizer, the siphon and the filter are heated using a heater and are connected to the distillate accumulator. This increases the rate of use of the solvent.

According to a particular embodiment, the device for separating petroleum products from the upper layer comprises a container with a filtering element, a mechanism for the evacuation of solvent crystals and light mechanical impurities and pipes: inlet for the heterogeneous mixture , outlet of petroleum products, outlet of solvent crystals and light mechanical impurities and outlet connected to the vacuum system. This practically ensures complete separation of petroleum products from solvent crystals and mechanical impurities. Petroleum products then contain no more than 0.2% (by mass) of solvent and can be used again for different purposes.

According to an alternative embodiment, the device for separating petroleum products from the upper layer is designed in the form of a centrifuge provided with pipes for inlet of the heterogeneous mixture, outlet for petroleum products and outlet for solvent crystals and mechanical impurities.

Brief description of the drawings

• La figure 1 représente la vue générale d'une installation pour réaliser le procédé de nettoyage des articles consistant à les débarrasser des produits pétroliers et des impuretés mécaniques, selon l'invention;
• La figure 2 est un dispositif de séparation des produits pétroliers, selon l'invention;
• La figure 3 est un dispositif de séparation des produits pétroliers par centrifugeage, selon l'invention.

The present invention is clarified by the detailed description below of a concrete example of its embodiment with reference to the attached drawings in which:

• FIG. 1 represents the general view of an installation for carrying out the method of cleaning articles consisting in ridding them of products petroleum and mechanical impurities, according to the invention;
• Figure 2 is a device for separating petroleum products, according to the invention;
• Figure 3 is a product separation device tankers by centrifugation, according to the invention.

Best Mode for Carrying Out the Invention

The articles, clogged with petroleum products and with mechanical particles, having the temperature of the production room, are treated using a circulating molten solvent. At the initial stage of treatment, the solvent, falling on the cold surface of the article, crystallizes by changing volume and displaces the solid mechanical impurities stuck on the surface of the article, thus reducing their adhesion to the surface. . During the subsequent treatment of the articles with molten solvent, the articles are heated, the solvent is melted and the petroleum products and mechanical impurities removed from the surface. The residual fouling at this stage amounts to 0.01 to 0.05 mg / cm².

Then, the spent solution, representing a mixture of solvent, petroleum products, heavy and light mechanical impurities, is cooled to a temperature higher than that of the melting of the solvent from 1 to 10 ° C. then reduction of the solubility in the solvent-petroleum product system and two layers are formed: an upper layer, containing petroleum products, light mechanical impurities and solvent partially dissolved in petroleum products, and a lower layer containing solvent, heavy mechanical impurities and petroleum products partially dissolved in the solvent.

The top layer is poured and cooled to room temperature. As a result, the solvent crystallizes. Petroleum products are separated from solvent crystals and light mechanical impurities by filtration or by centrifugation. Then, the solvent is melted, it is separated from the light mechanical impurities and it is added to the lower layer. The heavy mechanical impurities are separated from the bottom layer, while the solvent is returned to the articles for cleaning. The light mechanical impurities of the upper layer and the heavy mechanical impurities of the lower layer are combined and dried so as to separate the solvent which is evaporated. The solvent is then condensed and used again to clean the items. Thus, the cleaning efficiency of the articles is increased thanks to the reduction of the adhesion of mechanical particles to the surface during the crystallization of the solvent on the surface of the articles and a residue-free production is ensured due to the cooling of the layer. superior, crystallization of the solvent as well as thanks to the separation of petroleum products from the solvent which is returned for a new cleaning operation.

As the solvent for treating the articles, chlorinated and / or fluorinated organic materials are used, solid under normal conditions, chemically inert and reciprocally insoluble with petroleum products at a temperature below that of the melting of the solvent. They must be explosion-proof and flammable, non-toxic and allow, by using phase transformations during the temperature variation, to easily separate petroleum products and mechanical impurities. In addition, low vapor pressures above the solid solvent at room temperature make it possible to reduce the losses of solvent by discharges into the atmosphere.

To increase cleaning efficiency and reduce residual surface pollution, items are rinsed with solvent distillate. To this end, a part of solvent, taken from the lower layer and free of heavy mechanical impurities, is subjected to distillation and the distillate is sent to rinse the articles. At the end of this step, the residual pollution of the surface of the articles amounts to 0.01 to 0.001 mg / cm². After rinsing the articles, the solution contains the solvent and an insignificant amount of petroleum products dissolved in it. The solvent is again sent to distillation, while the residue, formed as a result of the distillation of the solution and representing a mixture of petroleum products (95 to 70% by mass) and solvent (5 to 30% of the mass), is combined in the used solution and is then regenerated.

Thus, high cleaning efficiency of the articles is achieved, solvent losses are reduced by regenerating the residue from the distillation operation, and the efficiency of the distillation is also increased.

After rinsing, the articles are dried at a temperature higher than that of the solvent, under vacuum or with hot air.

The air and vapors, formed during the drying of the articles, of chlorinated and / or fluorinated organic solvent are cooled to a normal temperature. The crystallization of the solvent then occurs.

The solvent crystals are filtered from the air, melted and used to rinse the items. Thus, the solvent vapors are efficiently recovered by a simple technique and are again used during the cleaning operation of the articles.

The total losses of the solvent during the realization of the process described above do not exceed 0.004 kg per square meter of surface cleaned of articles, at least 94% of petroleum products are extracted during the process.

The proposed installation, carrying out the method for cleaning the surface of the articles, comprises a chamber 1 for cleaning the articles 2, a rinsing chamber 3 where there are injectors 4 and sources of ultrasound 5, a drying chamber 6 articles 2, provided with heating elements 7, which is connected to a system 8 for capturing the solvent vapors and to a vacuum system 9. The chambers 1, 3 and 6 are separated from each other and from the outside environment by valves 10. The installation comprises a means 11 for moving the articles in chambers 1, 3 and 6.

The article cleaning chamber 1 is connected to the system 12 for regenerating the used solution, comprising a distiller 13, connected to an accumulator 14 of the distillate, a cooler 15 of the used solution connected to a decanter 16 provided with a heater 17 incorporated. The decanter 16 is used to separate the spent solution into two layers: upper 18 and lower 19, and is connected to a system 20 for separating the components (petroleum products, solvent dissolved in small quantities in petroleum products, light mechanical impurities) from the upper layer 18, and to a system 21 for separating the components (solvent, petroleum products dissolved in small quantities in the solvent, heavy mechanical impurities) of the lower layer 19. The system 20 for separating the components of the upper layer 18 comprises, connected in series, a crystallizer 22 and a device 23 for separating petroleum products, an outlet 24 of the device 23 for separating petroleum products which is connected to a collector 25 for the products tankers, an outlet 26 connected to a solvent manifold 27 provided with an incorporated heater 28. The lower outlet 29 of the manifold 27, by means of a pump 30, is connected to the inlet 31 of the cooler 15 of the used solution. The system 21 for separating the components of the lower layer 19 comprises, connected in series, a pump 32, a siphon washer 33 and an evaporator 34 provided with a heater incorporates 35, an upper outlet 36 of the siphon washer 33, is connected by via a solvent heater 37 at the nozzles 4 of the cleaning chamber 1 while a lower outlet 38 is connected to the evaporator 34. An outlet 39 from the evaporator 34 is connected to the decanter 16 and an outlet 40, to the collector 27 of the solvent.

The system 12 for regenerating the used solution comprises the still 13 which includes a heater 41 for a load 42, a refrigerator 43 and three pipes 44, 45, 46 one of which, 44, located at the bottom, is connected, by means of a pump 47, at the inlet 31 of the cooler 15. The tubing 45 is connected to the accumulator 14 of the distillate, and the tubing 46 is connected to a lower outlet 48 of the chamber 3 for rinsing the articles 2 and at the upper outlet 36 of the siphon washer 33.

The article drying chamber 6 is connected to the rinsing chamber 3 and to the solvent vapor capture system 8 which comprises, connected in series with one another, a refrigerator-crystallizer 49, a siphon 50 and a filter 51. The chamber 6 and the solvent vapor capture system 8 are connected to the vacuum system 9. It is not only possible, but technologically recommended, to connect the drying chamber 6 and the solvent vapor capture system 8 to each other. help an air line 52.

The lower parts 53, 54, 55 of the refrigerator-crystallizer 49, the siphon 50 and the filter 51 are provided with heaters 56 and are connected to the accumulator 14 of the distillate, which, by means of a pump 57, is connected to the nozzles 4 of the rinsing chamber 3.

According to one of the versions, represented in FIG. 2, the device 23 for separating petroleum products from the upper layer 18 consists of a container 58 provided with a filter element 59, with an unloading mechanism 60 solvent crystals and light mechanical impurities, and inlet pipes 61 for heterogeneous mixing, from the outlet of petroleum products 24, connected to the collector of petroleum products 25, from outlet 26 of the solvent crystals and mechanical impurities light, itself connected to the solvent collector 27, as well as an outlet 62 connected to the vacuum system 9.

In the version shown in FIG. 3, the device 23 for separating petroleum products from the upper layer 18 consists of a centrifuge 63 which is provided with an inlet pipe 64 for the admission of the heterogeneous mixture, connected to the crystallizer 48, as well as two outlet pipes 24 and 26, connected respectively to the collector of petroleum products 25 and to the solvent collector 27.

The installation for cleaning articles, which consists in removing petroleum products and mechanical impurities, operates as follows.

Before starting to clean the articles, the installation is put into operation. For that, we connects the heaters 7, 17, 37, 41 and the coolant is admitted into the cooler 15, the refrigerator-crystallizer 49 and the refrigerator 43. After having reached the required temperatures, it is advanced inside the chamber cleaning 1, using the displacement means 11, the articles 2. By moving successively through the chambers 1, 3, 6, the articles 2 undergo the cleaning and rinsing operation with heated solvent sprayed by the nozzles 4, and the ultrasonic treatment carried out by the ultrasonic sources 5 to obtain drying with hot air and under vacuum.

By drying the surface of the articles 2, the air becomes saturated with solvent vapors and passes into the solvent vapor capture system 8. The chambers 1, 3, 6 are sealed against each other and in relation to the environment, using the valves 10.

The used solution, consisting of a mixture of solvent, petroleum products and light and heavy mechanical impurities, passes through the cleaning chamber 1 to the cooler 15 of the regeneration system 12 of the used solvent where it is cooled to a temperature close to that of the solvent melting and then the reciprocal solubility of the solvent and of the petroleum products is reduced and an emulsion is formed; then, the emulsion passes through the decanter 16 where it settles and separates into two layers: on the one hand the upper layer 18 containing petroleum products, a small amount of dissolved solvent and light mechanical impurities, and on the other hand the lower layer 19 containing solvent, a small amount of petroleum products dissolved therein and heavy mechanical impurities. The upper layer 18 is poured into the separation system 20 of the components of the upper layer 18 where, passing through the crystallizer 22, the solvent crystallizes at a temperature below that of its melting: then, the heterogeneous mixture formed is directed to the device 23 for separation of petroleum products where the solvent crystals and the light mechanical impurities are separated from the petroleum products liquids by filtration or by centrifugation. The separated petroleum products arrive at the collector 25 of the petroleum products via the outlet 24 and the solvent crystals with the light mechanical impurities arrive at the solvent collector 27 where the solvent crystals are melted using the heater 28. By the lower outlet 29 of the collector 27, the molten solvent, using the pump 30, feeds the inlet 31 of the cooler 15 of the spent solution.

The lower layer 19 is sent using the pump 32, from the decanter 16, to the system 21 for separating the components of the lower layer 19 where, in the washing siphon 33, the solvent is separated from the heavy mechanical impurities. Then, the solvent arrives at the heater 37 via the outlet 36 of the washing siphon 33, is heated to the required temperature and is sent via the injectors 4, to the chamber 1 for cleaning the articles, while the mechanical impurities heavy, through the outlet 38 of the washing siphon 33, pass through the evaporator 34. The light impurities from the collector 27 arrive at the evaporator through the outlet 40.

In the evaporator 34, the impurities are heated by the heater 35 to a temperature higher than that of the melting of the solvent, the solvent is then evaporated and its vapors are sent through the outlet 39 to the settling tank 16. The residues solid, light and heavy mechanical impurities are discharged from the evaporator 34 and used.

The solvent, after rinsing the articles, containing a small quantity of petroleum products, passes through the lower outlet 48 of the rinsing chamber 3 to the tube 46 of the distiller 13 and then into the charge 42. Right here, through the outlet upper 36 of the siphon washer 33, the solvent-free portion of the solvent is brought in. The solvent is brought to boiling point and is evaporated on the heated charge 42. The solvent vapors are condensed on the refrigerator 43 to form the distillate. Through the tube 45, the distillate is directed to the accumulator 14 of the distillate. The distillation residue, essentially containing petroleum products and solvent, is sent, via the lower pipe 44 and by means of the pump 47, to the inlet 31 of the cooler 15 of the system 12 of regeneration of the spent solution.

The solvent vapor capture system 8 is connected to the article drying chamber 6, which is moreover recommended to be supplied with hot air by the air line 52 for effective drying of the articles. The solvent vapors as well as the air after drying of the articles, pass successively through the refrigerator-crystallizer 49, the siphon 50 and the filter 51, are cooled, the solvent vapors crystallize and are captured by the siphon 50 and on the filter 51. The system 8 is connected to the vacuum system 9 to create the vacuum.

The solvent crystals captured in the apparatuses 49, 50 and 51 fall respectively in the lower parts 53, 54 and 55 thereof and, as the accumulation takes place, the crystals are melted by the heaters 56, and then are drained by the lower parts 53, 54 and 55 in the accumulator 14 of the distillate from which the distillate is brought to injectors 4 of the rinsing chamber 3 using the pump 57.

According to one version (Figure 2), the heterogeneous mixture, consisting of liquid petroleum products, solid solvent crystals and light mechanical impurities, passes from the crystallizer 22, to the filter 59 located in the container 58 by the inlet pipe 61. Once the mixture is in the container 58 and using the vacuum system 9 connected to the pipe 62, a vacuum is created so as to separate the petroleum products therefrom.

The petroleum products arrive at the collector 25 through the outlet pipe 24 and the solid residue, composed of solvent crystals and light mechanical impurities, is discharged from the filter 58 by means of the mechanism 60 through the outlet pipe 26 into the collector 27.

According to another version (FIG. 3), the heterogeneous mixture passes from the crystallizer 22 to the tubing 64 of the centrifuge 63 where the separation of liquid petroleum products from solid solvent crystals and mechanical impurities takes place. The separated petroleum products arrive via the tubing 24 at the manifold 25 and the mechanical mixture is discharged through the tubing 26 into the manifold 27.

This ensures a high quality of cleaning and a reduction in discharges into the environment thanks to the operations of crystallization of the solvent on the surface of the articles being cleaned, the more complete regeneration of the solvent and the separation of the impurities in a closed technological circuit.

To have a more complete notion of the advantages of the invention, we refer to a concrete example application thereof.

Articles with a total surface area of 1 m², polluted by industrial oils from various destinations, by metal filings and dust, are placed in the cleaning chamber where they are treated for 5 minutes with a jet of molten solvent (T 120 ° C) circulating. At the start of treatment, the molten solvent which falls on the cold surface of the article crystallizes, changes its volume, displaces the solid particles adhered to the surface of the article and thus reduces their adhesion to this surface. The treatment after spraying with the molten solvent is a heating operation of the article which results in the melting of the solvent and the removal of impurities from the surface of the article. A fluorinated organic substance comprising eleven carbon atoms, having a melting temperature close to 90 ° C., which is insoluble in industrial oil below its melting temperature as well as chemically inert in contact with washed items and impurities.

The cleaned article is transferred to the rinsing chamber and is rinsed with the molten distillate of fluorinated organic substance. After rinsing, the residual pollution of the surface amounts to 0.001 mg / cm². Then, the article is conveyed to the drying chamber and is dried with hot air at a temperature of 120 to 125 ° C for 5 min.

The solvent vapors which evaporate from the surface of the article are recovered. For this purpose, an air-vapor mixture is directed to the refrigerator-crystallizer and is cooled to a temperature of 15 to 20 ° C. Then, the vapors crystallize and partially deposit on the bottom of the refrigerator-crystallizer. The mixture formed, composed of crystals of solvent and air, is sent to the siphon for an additional extraction of the crystals from the air, then to the bag filter where the complete separation of the solvent crystals and the air takes place. A filter membrane is used in the filter, for example, of felt.

The solvent crystals recovered from the air-vapor mixture in the refrigerator-crystallizer, inside the siphon and in the filter, are melted and incorporated into the solvent distillate.

After cleaning the article, the spent solution is regenerated as follows. It is cooled to the melting temperature. Then, the reciprocal solubility in the fluorinated solvent - industrial oil system is reduced and an industrial oil emulsion is formed in the solvent. This emulsion is decanted and two layers are formed: the upper layer containing mainly industrial oil, solvent (2 to 3% of the mass) dissolved in it and light mechanical impurities, and the lower layer mainly containing solvent, industrial oil (0.2 to 0.3% by mass) dissolved therein and heavy mechanical impurities.

The upper layer is drained and slowly cooled to a temperature of 15 to 20 ° C. Then, the solubility of the solvent in the oil suddenly reduces and a suspension of large solvent crystals is formed. The industrial oil is filtered off from the suspension formed. A filter is then used, the pore size of the filter membrane of which is 100 μm. The separated industrial oil is collected in a collector while it does not contain more than 0.2% of its mass in solvent. The solvent crystals are removed from the filter membrane, melted and the impurities are separated.

After cleaning the article, the solvent is reintegrated into the used solution, while the light impurities are directed to the evaporator and the solvent is separated therefrom. The evaporated solvent is condensed and is mixed with the spent solution, while the impurities are discharged from the evaporator and are then reused.

These heavy mechanical impurities which are sent to the evaporator are separated in the washing siphon the lower layer, while the solvent is again used for cleaning the articles. A specific part of the solvent is distilled to obtain an industrial oil-free solvent and is then used to rinse the articles. After rinsing, the solvent is again returned to distillation. The distillation residue, which represents a mixture of 95 to 70% of the mass in industrial oil with 5 to 30% of the mass in solvent, is added to the spent solution and regenerated according to the scheme described above. The solvent, discharged with the distillation residue, is renewed by distillation of a portion of solvent free from mechanical impurities, taken from the lower layer.

The main characteristics of the process using, for cleaning the surface of the articles, the solvent described and others, are given in the table.

Thus, the application of the method and of the installation for cleaning the surface of the articles makes it possible to achieve high cleaning efficiency, to avoid discharges of solvent and washed petroleum products into the environment.

Industrial applicability

The invention can be used, with the greatest success in mechanical engineering, in the construction of control and measuring apparatus and in other technical fields, for cleaning articles before assembly and application of coatings protectors.

Claims (13)

1. Methods of cleaning articles consisting in ridding them of the petroleum products and of the mechanical impurities comprising the treatment of the surface of the articles with a solvent being in circulation, the drying of the cleaned articles, the regeneration of the waste solution, the catching of the solvent vapours from the air-vapour mixure and the separation of the petroleum products and of the mechanical impurities, characterized in that one effects the treatment of the cold surface of the articles with the assistance of the molten solvent which crystallizes on the cold surface of the articles and then one effects a heating of the articles entailing the fusion of the crystallized solvent, one cools the waste solution down to a temperature close to but higher by 1 to 10° C than that of fusion of the solvent entailing the decantation of the cooled solution with the formation of two layers : of one upper layer containing the petroleum products, the light mechanical impurities and one part of the solvent, and of a lower layer containing the solvent, the heavy mechanical impurities and one part of the petroleum products and then one cools the upper layer down to complete crystallization of the solvent it contains, one separates the petroleum products therefrom and then the solvent crystals are molten, separated from the light mechanical impurities and gathered within the lower layer of which one then separates the solvent from the heavy mechanical impurities, the solvent being returned to the cleaning of the articles whereas the light mechanical impurities of the upper layer and the heavy mechanical impurities of the lower layer are dried to separate therefrom the solvent which is used again after condensation for cleaning the articles.
2. Method according to claim 1, characterized in that one uses a solvent quality such as chlorinated and/or fluorinated organic substances solid under normal conditions, chemically inert, insoluble in the petroleum products and not capable of dissolving the latter at a temperature lower than the melting temperature of the solvent.
3. Method according to claim 1, characterized in that one subjects one part of the waste solvent to the distillation, one carries the formed distillate to the rinsing of the articles and after the rinsing of the articles one again carries the distillate to the distillation while adding the distillation residue formed during the distillation to the waste solution.
4. Method according to claim 2, characterized in that after the drying of the articles, one cools the air and the vapours of chlorinated and/or fluorinated organic substances down to the complete crystallization of the solvent and then the solvent crystals are separated from the air.
5. Method according to claim 4, characterized in that one causes the solvent crystals separated from the air to melt by using the molten solvent for rinsing the articles.
6. Method according to claim 1, characterized in that one separates the petroleum products from the upper layer by filtration.
7. Method according to claim 1, characterized in that one separates the petroleum products from the upper layer by centrifugation.
8. Installation for carrying out the method according to claim 1, comprising a chamber (1) for the cleaning of the articles (2), connected to a system (12) for the regeneration of the waste solution, comprising a distillator (13) and a distillate accumulator (14) communicating with the latter, a chamber (6) for drying articles, a means (11) for the displacement of the articles through the chambers (1, 3 and 6), a vaccum system (9) and a system (8) for catching the solvent vapours, characterized in that it moreover comprises a chamber (3) for the rinsing of the articles, connected through the medium of a pump (57) to the distillate accumultor (14) and in that the system (12) for the regeneration of the waste solution is provided with a cooler (15) for the waste solution connected to a decanter (16) serving to separate the waste solution into two layers : an upper one and a lower one, which is connected to a system (20) for the separation of the components of the upper layer (18) and to a system (21) for the separation of the components of the lower layer (19), in that the system (20) for the separation of the components of the upper layer (18) comprises connected in series a crystallizer (22) and a device (23) for the separation of the petroleum products which has an outlet (24) connected to a collector (25) of the petroleum products as well as an outlet (26) connected to a collector (27) of the solvent, provided with a reheater (28) and having a lower outlet (29) which through the medium of a pump (30) is connected to the inlet (31) of the cooler (15) of the waste solution and the system (21) for the separation of the components of the lower layer (19) comprises connected in series a pump (32), a washing siphon (33) and an evaporator (34) provided with an incorporated reheater (35), an upper outlet (36) of the washing siphon (33) being connected through the medium of a reheater (37) to the cleaning chamber (1) and a lower outlet (38) of this siphon being connected to the evaporator (34) which has an outlet (39) connected to the decanter (16) and another outlet (40) connected to the collector (27) of the solvent.
9. Installation according to claim 1, characterized in that the distillator (13) is provided with three necks (44, 45, 46) one of which is connected through the medium of a pump (47) to the inlet (31) of the cooler (15), another one (46) is connected to the upper outlet (36) of the washing siphon (33) and to a lower outlet (48) of the chamber (3) for the rinsing of the articles (2), the third neck (45) being connected to the distillate accumulator (14).
10. Installation according to claim 8, characterized in that the system (8) for catching solvent vapours is connected to the drying chamber (6) and comprises connected in series a refrigerator-crystallizer (49), a siphon (50) and a filter (51) connected to the vacuum system (9).
11. Installation according to claim 10, characterized in that the lower parts (53, 54, 55) of the refrigerator-crystallizer (49), of the siphon (50) and of the filter (51) are provided to be heated with the assistance of a reheater (56) and are connected to the distillate accumulator (14).
12. Installation according to claim 8, characterized in that the device (23) for the separation of the petroleum products from the upper layer (18) comprises a vessel (58) provided with a filtering element (59), a mechanism (60) for the discharge of the solvent crystals and of the light mechanical impurities and necks (24, 26, 61, 62) : for the ingress (61) of the heterogeneous mixture, for the egress (24) of the petroleum products, for the egress (26) of the solvent crystals and of the light mechanical impurities and for the egress (62) connected to the vacuum system (9).
13. Installation according to claim 8, characterized in that the device (23) for the separation of the petroleum products from the upper layer (18) is designed in the shape of a centrifuge (63) provided with necks (24, 26 and 64) : for the ingress (64) of the heterogeneous mixture, for the egress (24) of the petroleum products and for the egress (26) of the solvent crystals and of the mechanical impurities.

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