Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B7/00—Cleaning by methods not provided for in a single other subclass or a single group in this subclass
  • B08B7/0021—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by liquid gases or supercritical fluids
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
  • B08B3/02—Cleaning by the force of jets or sprays
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
  • B08B3/04—Cleaning involving contact with liquid
  • B08B3/045—Cleaning involving contact with liquid using perforated containers, e.g. baskets, or racks immersed and agitated in a liquid bath
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
  • B08B3/04—Cleaning involving contact with liquid
  • B08B3/10—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
  • B08B3/04—Cleaning involving contact with liquid
  • B08B3/10—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration
  • B08B3/12—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration by sonic or ultrasonic vibrations

Definitions

• the present invention relates to a method of cleaning contaminated, polluted, soiled parts, by a dense fluid under pressure, in particular by a supercritical fluid, such as carbon dioxide C0 2 supercritical.
• the invention also relates to a device and an installation for cleaning contaminated parts, by a dense fluid under pressure, in particular by a supercritical fluid.
• the technical field of the invention can, in general, be defined as that of cleaning soiled, contaminated, polluted parts.
• the cleaning of materials and parts is a fundamental step in the making and development of intermediate or final products in a very large number of diverse and varied industries encompassing sectors, such as the automotive industry, fine mechanics, electronics, watchmaking, connectors, IT, aeronautics, medical equipment, packaging, which use multiple alloys, such as steels, stainless steels, aluminum and copper, and sectors, such as optics and armament, which can use, in addition to these alloys, composite materials, such as polycarbonates and borosilicate glasses, etc.
• the cleaning of parts and materials is in particular a necessity, before or during the machining, manufacturing, assembly, assembly, bonding, application of paint, varnish, coating; surface treatment, chromating, physical vapor deposition.
• successive cleaning steps are required and require the use of chemicals for degreasing, for example in the case of alloys, preparing a surface or debinding, for example example in the case of composite materials.
• the cleaning techniques hitherto commonly used, consist in using organic solvents, or detergents or surfactants in aqueous solutions by soaking, spraying or wiping.
• the solvents used differ in particular, depending on the nature of the pollutant, contaminant, to be dispersed.
• organic solvents are: hydrocarbons; halogenated alkanes, alkenes and alkynes (chlorinated and / or fluorinated), such as trichlorethylene, dichloromethane and other CFCs and HCFCs; alcohols and ethylene glycol.
• the cost of these solvents can be relatively high, while they do not always make it possible to reach the so-called “ultra clean” states required for certain materials, in particular in the aerospace industry.
• the cleaning operations with these solvents generate large volumes of effluents and there is generally an obligation for the user to provide for recycling of the solvents, as well as aqueous solutions, detergents, or a treatment facility for these, so as to comply with the regulations concerning discharges.
• the Montreal Protocol implemented by most industrial countries, aims to limit the release of VOCs or Volatile Organic Compounds, responsible for the destruction of the ozone layer.
• the objective is to achieve zero rejection of these VOCs in 2015, whether for old installations in service or for new installations under construction.
• the Montreal and Rio protocols also provide for a total ban by 2015 for certain solvents, which requires that they be replaced. This is the reason why, in order to remedy the drawbacks of the cleaning processes and products described above, and to meet the legal and regulatory, the use of fluids in the dense state under pressure, gas, liquid or supercritical, for cleaning parts, has been considered and studied. Indeed, these fluids have solvent properties allowing them to replace many common solvents used in cleaning techniques.
• Cleaning by supercritical fluid can be carried out by simple soaking, immersion in the supercritical fluid, possibly agitated by blades, or else the parts to be cleaned can be subjected to the action of jets of the supercritical fluid .
• US-A-5 412 958 relate to a dry cleaning installation, using a supercritical fluid, such as C0 2 , in which the parts to be cleaned are placed in a drum or basket rotating inside a autoclave.
• a supercritical fluid such as C0 2
• the rotating drum or basket is supported by two sets of rollers and is magnetically coupled to a motor, preferably an electric motor. It is indicated, in general, that other drive means are possible, but they are not described.
• the autoclave does not include a filter or spraying device.
• the object of the present invention is to provide a method and a device for cleaning with a dense fluid under pressure, which meets, inter alia, the needs mentioned above.
• the object of the present invention is also to provide a method and a device for cleaning with a pressurized fluid, which does not have the drawbacks, limitations, defects and disadvantages of the methods and devices of the prior art and which solves the problems of prior art.
• the parts to be cleaned are placed in a drum or basket inside a pressure enclosure containing the dense fluid under pressure, said drum or basket being set in motion by a shaft in direct contact with drive means located outside the enclosure; the parts are also subjected, simultaneously, to the action of a high speed jet of the dense fluid; the solid and / or liquid particles, insoluble in the dense fluid, essentially generated by cleaning are, simultaneously, continuously separated from the dense fluid by separation means provided inside the enclosure.
• the method according to the invention associates several mechanical effects with the simple contacting, or simple soaking, of the polluted, contaminated parts, with the dense fluid under pressure, these mechanical effects are, respectively, the stirring effect, stirring due to the movement of the basket or the drum in which the parts are located and, on the other hand, the pickling effect due to the impact of the jets of dense fluid at high speed on the parts.
• This high-speed jet allows perfect cleaning and eliminates any residual contamination of the parts.
• the basket or drum set in motion by a shaft in direct engagement with drive means there is no limitation on the quantity and weight of the parts which can be cleaned, as is the case. case when the basket, generally rotating, is actuated by a magnetic system, for example.
• the fact that the shaft is in direct contact with the drive means makes it possible to ensure an almost torque unlimited, which only depends on the power of the drive means, such as an electric motor, ensuring the generally rotational movements.
• the method according to the invention removes all the torque limitations which one finds oneself in the methods where the agitation is ensured by blades, by magnetic drive or by a system based on reaction forces due to jets of fluid.
• the continuous, simultaneous separation, during cleaning, of solid and / or liquid particles insoluble in the dense fluid by separation means provided inside the pressure vessel itself makes it possible to trap the contaminants and / or pollutants extracted, generated by cleaning, the stirring action, and the effect of high speed jets and to avoid redeposition of contaminants and / or pollutants on the parts being cleaned and already clean.
• the drum or basket can be rotated; the direction of rotation possibly being periodically reversed.
• the revolving drum or basket can also be moved in a pendulum motion.
• the rotational speed is generally 5 to 500 revolutions per minute.
• the fluid in the dense state under pressure is preferably brought into contact with the parts to be cleaned at a pressure of 100 to 300 bars and at a temperature of 15 to 80 ° C, preferably 40 at 60 ° C.
• the treatment conditions are much less severe than those of the processes of the prior art using dense fluids under pressure, which results in a considerable energy gain for the process of the invention.
• the milder conditions namely low temperatures, low pressures and short treatment time of the process of the invention, are precisely due to the combination, according to the invention, of the agitation caused by the moving drum or basket, the action of the high speed jet of dense fluid, and of the continuous separation of solid and / or liquid particles insoluble in the fluid, of the dense fluid under pressure.
• the implementation, according to the invention, of such “soft” conditions is particularly advantageous for the treatment of mechanically and / or thermally fragile parts, such as parts made of polymers or -alloy / polymer composites whose cleaning was not or hardly possible by the methods of the prior art.
• the method according to the invention has, of course, all the inherent advantages associated with the use for cleaning a dense fluid under pressure, instead of a conventional solvent, in particular of the halogenated hydrocarbon type.
• said dense fluid under pressure is a fluid in the liquid and / or supercritical state, that is to say that the dense fluid is under pressure and at a temperature, such that the fluid is in the state liquid and / or supercritical, more preferably the fluid is in the supercritical state.
• a gaseous compound is used, for example, under normal conditions of temperature and pressure, and its density is increased by increasing its pressure.
• temperature we will thus place our in the domain where the fluid is in the dense state and under pressure, preferably in its liquid and / or supercritical state.
• the extractive properties of the fluid can be varied, in a controlled manner, by acting on the two parameters of temperature and pressure, while remaining in the dense range and under pressure, preferably, the liquid and / or supercritical of the fluid in question: thus, the increase in pressure and temperature increases the solubilization capacity, while the decreasing the pressure decreases the viscosity and increases the diffusivity.
• compression / decompression cycles preferably very rapid, with, for example, an amplitude of the pressure variation of 10 to 100 bars, and time intervals. from 10 seconds to a few minutes, for example, 10 minutes, all for example, for one to a few hours, for example, 10 hours.
• the fluid used can be chosen, for example, from carbon dioxide, sulfur hexafluoride, nitrous oxide, nitrous oxide, light alkanes having, for example, from 1 to 5 carbon atoms, such as methane, ethane, propane, butane, isobutane, pentane, alkenes, such as ethylene and propylene, as well as certain organic liquids, such as methanol and ethanol, etc.
• Carbon dioxide is preferred because it has the advantage of a relatively easy implementation: it is inexpensive, non-toxic, non-flammable and has easily accessible critical conditions (critical pressure: Pc of 7.3 Mpa and critical temperature Te of 31.1 ° C).
• critical pressure Pc of 7.3 Mpa and critical temperature Te of 31.1 ° C.
• C0 2 in the dense state under pressure, liquid or supercritical, solubilizes most organic compounds with molar masses less than or equal to 2000 g / mole. It is therefore an excellent solvent, in particular vis-à-vis organic compounds, called “undesirable", forming most of the contaminants and pollutants.
• the two pressure and temperature characteristics make it possible to control a fluid whose solvent power is flexible in terms of solubilization, in particular of contaminating, polluting, undesirable compounds, parts and extraction kinetics.
• Treatment in a C0 2 atmosphere can avoid the risk of oxidation and improve the final surface condition of the part.
• a compound called "cosolvent”
• cosolvent is added to the dense fluid, under pressure.
• the addition of the cosolvent ensures a selective extraction, elimination, of undesirable organic compounds, while sparing the constituent components of the parts.
• said cosolvent is chosen, for example, from water, aqueous solutions, alcohols, for example, aliphatic alcohols of 1 to 5 C, such as ethanol, methanol, butanol, ketones, such as acetone, and mixtures thereof.
• alcohols for example, aliphatic alcohols of 1 to 5 C, such as ethanol, methanol, butanol, ketones, such as acetone, and mixtures thereof.
• aqueous solutions there may be mentioned solutions of detergents such as anionic and / or cationic surfactants, solutions of complexing agents, chelating agents, buffer solutions, for example of phosphate and / or hydrogen phosphate, etc. ; antioxidant solutions, such as ascorbic acid, to stabilize the material.
• said cosolvent is added to the dense fluid, under pressure, in an amount of 0.01 to 10% by weight, preferably from 0.02 to 1% by weight, more preferably from 0.02 to 0, 1% by weight.
• the cosolvent if it is water, can be partly already present in the parts to be cleaned, and we will not add in the fluid supercritical than the amount necessary to give the concentrations mentioned above.
• the dense fluid, under pressure, located in the pressure vessel, and added with a cosolvent, preferably in the proportions mentioned above, is also subjected to the action of ultrasonic waves.
• the dense fluid under pressure is C0 2 and the co-solvent is water or an aqueous solution.
• the frequency of said ultrasonic waves preferably varies from 20 kHz to 100 MHz, more preferably from 20 to 1000 kHz or from 1 to 100 MHz, such ultrasonic waves are also qualified, respectively, as ultrasound or megaons. .
• the duration during which the fluid is subjected to the action of ultrasonic waves is generally from 1 to 60 minutes.
• ultrasound was used on liquid C0 2 alone, at a temperature of 20 ° C and at a pressure of 50 bars.
• the ultrasound is multifrequency ultrasound from 20 to 1000 kHz or multifrequency megaons from 1 to 100 MHz, such ultrasound or megaons are produced either by probes whose emission covers several frequencies, or by the association of single frequency probes whose resulting emission covers several frequencies.
• sonotrodes there are several models of sonotrodes, some not very specific allow the emission of a “bouquet” of frequencies from 20 to 100 kHz, like the one we used for the tests described in example 8 below. There are also sonotrodes whose spectrum is narrower, for example from 20 to 25 kHz.
• any type of part can be treated by the method of the invention.
• the material (s) of these parts can (wind) be organic (s), mineral or other.
• the parts can be parts composites comprising the combination of several materials.
• the method of the invention knows no limitation as to the size and / or weight of the parts to be treated, in particular, thanks to the specific drive mode chosen.
• the materials, which can be cleaned by the process of the invention are generally solid materials, such as metals, metal alloys, possibly coated, such as aluminum, titanium, steel, stainless steel, copper, brass, and any other alloy, or plated metal.
• the parts made of these materials will therefore be, for example, aeronautical, automobile parts, timepieces and micromechanics, electrical and electronic connectors, microelectronic silicon components, such as wafers, medical tools. , etc.
• cleaning is generally meant the elimination, the extraction of polluting compounds, undesirable contaminants, which are not normally part of the material of which the parts are made.
• polluting compounds, contaminants, to be extracted can also be found on the surface of the part, but they can also be inside the material of the part, within, for example, its porosity.
• the method according to the invention makes it possible to clean the parts of any polluting, contaminating inorganic and organic compound found in or on the part.
• the inorganic and / or organic compounds can be products present accidentally or naturally on the parts, but they can also be, in particular, products introduced into and / or applied to the parts, during previous operations, entering their process. manufacturing and / or assembly.
• these may in particular be oils used in working with metals, such as cutting, machining, quenching and dyeing oils.
• the extracted inorganic compounds eliminated by the cleaning process according to the invention are, for example, free metals or metalloids or compounds of metals or metalloids.
• the method according to the invention is therefore particularly advantageous in the context of the decontamination of materials contaminated by radioactive products, for example, organic compounds, contaminated by radioelements such as strontium, cesium, iodine, americium, plutonium, uranium, thorium , tritiated organic compounds, etc.
• radioactive products for example, organic compounds, contaminated by radioelements such as strontium, cesium, iodine, americium, plutonium, uranium, thorium , tritiated organic compounds, etc.
• the organic compounds which can also be eliminated by the process according to the invention, are all the organic compounds liable to be found in or on the material of the parts accidentally, naturally or for other purposes, for example, during incoming treatments in their manufacturing and / or assembly process.
• These organic compounds include the low viscosity lubricants oil type cuts as Mobil Mobilube ®, Mobil DTE 24 ®, Castrol Variocut B27 + ®, paraffin oils such as Shell Neatcut XF15 ®, machining oils of water-soluble or in emulsion such as Castrol Alusol B ® (mineral), Peralube 7000 ® , Century oils Trancent LM2 ® (mineral), Cimstar 560 ® , Ardrox 970-P25E ® , Renoform MBO 2728 ® , anticorrosion films such as Shell Ensis Fluid ® SDC E or G, Brent Ardrox 3961 ® , Tectyl 800D ® , BP thermacote ®
• the temperature and pressure ranges used during the cleaning operation may vary, provided that the fluid always remains a dense fluid under pressure, preferably in a liquid and / or supercritical state, similarly, as indicated above, compression / decompression cycles can be carried out.
• the temperature and pressure ranges depend, in particular, on the nature of the fluid used.
• Such conditions can be maintained throughout the duration of the process, or else only at the start of the cleaning or treatment process, where such conditions correspond to a high density and to a high temperature - the predominant phenomenon being solubilization - allow 25
• the duration of the cleaning treatment is 1 or a few minutes, per example, 10 minutes, one or a few hours, for example, 5 hours, depending on the flow rate of the fluid and the quantity of materials to be treated.
• this duration is short compared to the duration of the processes comprising neither agitation in the drum or rotating basket, nor action of a jet of fluid at high speed, nor continuous separation.
• the extraction efficiencies of removing contaminants, pollutants and cleaning are, in all cases, very high, whatever the pollutants or contaminants.
• the level of solvent used i.e. the weight of dense fluid - solvent, preferably liquid and / or supercritical, implemented with respect to the surface of the part (s) to be cleaned, can vary from 0 to 100 kg of fluid / cm 2 of part (s). According to an additional advantage of the invention, the level of solvent used is significantly lower, thanks to the effects of agitation, and of the fluid jets, than that of the prior art.
• the method according to the invention comprises, after cleaning, recycling of the fluid, after one or more physico-chemical separation steps making it possible to separate the fluid from the extracts, and the fluid in gaseous form is recycled, reconditioned to the cleaning step, towards the pressure vessel.
• the separation steps should not be confused with the separation of solid and / or liquid particles insoluble in the fluid, generated by cleaning, which takes place continuously during the cleaning operation itself, and inside even from the pressure vessel. These separation steps relate to fractions soluble in the fluid.
• the first separation steps consist of a reduction in the density of the fluid by a series of expansion and successive reheating, in order to approach the gaseous state.
• the method according to the invention for cleaning parts makes it possible to physically recover at the end of treatment, on the one hand, the cleaned parts, on the other hand, undesirable products, including the handling, treatment or elimination can be done in a specific manner and therefore easily controlled, while the gas or fluid can advantageously be recycled, in order to carry out a new extraction or cleaning.
• the process can include, among other things, a stage of distillation of the dense fluid allowing an almost total purification, in accordance with the document FR 85 13246 of 06/03/1985 which describes a process and a device for the extraction of constituents by a supercritical fluid.
• the cleaning or extraction process can be carried out in a closed circuit or in a loop, which advantageously means that thanks to an initial and constant charge of fluid, such as C0 2 , it is possible to gradually eliminate parts, contaminating compounds, undesirable pollutants.
• the process according to the invention advantageously comprises one or more steps, for example up to 3 physicochemical separation steps, in which the density of the fluid is reduced, by example by a series of detents and successive reheating, preferably 1 to 3, in order to approach the gaseous state.
• the conditions prevailing in these successive stages will be, for example, the following: 90 bars and 50 ° C, 70 bars and 40 ° C and 50 bars and 40 ° C.
• These extracts are in the form of more or less fluid concentrated liquids, and can be specifically treated and, generally, they are destroyed.
• the gas obtained at the end of the separation is preferably recycled to the cleaning, extraction stage, where it is reconditioned, in order to put it back under temperature and pressure conditions so that it is in in a supercritical state, the gas can thus be first cooled to atmospheric pressure, stored in liquid form, then reheated and compressed before being sent to the cleaning or extraction process proper.
• the fluid is preferably purified by one or more stages of adsorption and / or liquefaction and / or distillation.
• the adsorption can be carried out, for example, with activated charcoal or other adsorbent, such as zeolite ® and the (re) distillation is preferably carried out using the specific device described in the document FR 85 131 246
• This purification carried out by adsorption for example, by passage over activated carbon and / or by distillation and / or by liquefaction makes it possible to remove the traces of organic products. volatile and / or insoluble in C0 2 and mechanically entrained by it during the previous separation steps.
• the dense fluid under pressure (initial fluid) is replaced by another weaker and chemically inert enthalpy fluid.
• this other fluid, chemically inert may be chosen from nitrogen, helium, neon and dry air, etc.
• a regulation can take place between the temperature of the wall (using a probe) and the percentage of opening of the expansion valve.
• an extension of the relaxation time to avoid this problem can harm the advantage of the process insofar as the treatment time is extended by a time as long for the relaxation.
• an expansion or depressurization time of more than 15 minutes would bring the overall processing time of the process since loading. until the pieces are unloaded in the autoclave at around one hour or more, which can be detrimental for rhythms generally admitted into an assembly line from the parts thus cleaned.
• the invention also relates to a device for cleaning contaminated parts with a dense fluid under pressure, comprising:
• the invention further relates to a cleaning installation comprising the device.
• FIG. 1 schematically represents a side view in section of an example of a device for implementing the method of the invention
• Figure 2 shows, schematically, a side sectional view of an example of an installation for implementing the method of one invention.
• FIG. 1 An example of a device according to the invention is described in FIG. 1.
• the device comprises, first of all, a sealed sealed enclosure (1), more commonly called an autoclave, capable of being pressurized and therefore able to withstand the working pressures, implemented according to the invention.
• a sealed sealed enclosure (1) more commonly called an autoclave, capable of being pressurized and therefore able to withstand the working pressures, implemented according to the invention.
• the enclosure or autoclave (1) will therefore be designed to withstand pressures, generally equal to or greater than 120 bars.
• the material used to manufacture the autoclave is preferably a material compatible with contact with a dense fluid under pressure, thus the enclosure will generally be made of stainless steel.
• the enclosure or the autoclave generally has, as shown in FIG. 1, a shape of a straight cylinder, with a diameter, preferably, from 1 to a few tens of centimeters, for example 10 cm up to 1 to several meters , for example 20 m; and of a length of a few tens of cm, for example 20 cm to several m, for example, 20 m.
• the volume of the autoclave is variable according to the parts to be cleaned and will be, for example, from 1 1 to 10 m 3 , but does not, in principle, have any limitation, in accordance with the invention.
• the autoclave or cylindrical enclosure is preferably placed so that its main axis and its generatrices are horizontal. This arrangement allows easy loading of the parts to be cleaned.
• one of the circular bases of the cylinder preferably opposite the drive means, forms a loading-unloading door (2), preferably provided with a rapid opening-closing system, allowing rapid and frontal loading and unloading of the parts.
• the autoclave can be positioned vertically, while retaining all of the quick closing opening devices.
• the autoclave or enclosure is generally provided with a double envelope (not shown) supplied with heat transfer fluid making it possible to adjust the temperature inside the enclosure within the required temperature ranges, in particular supercritical.
• a moving basket or drum (3) in which the parts to be treated are placed.
• this drum or basket (3) is a rotating drum or basket, that is to say that it is rotated.
• the rotational speed can range, for example, from 5 to 500 revolutions per minute, the rotational movement can be periodically reversed.
• the movement can also be pendulum.
• This revolving drum or basket is, like the autoclave, generally in the form of a straight, horizontal cylinder, the main axis (of rotation) preferably merges with the main axis of the autoclave. .
• the autoclave and the basket therefore appear as two straight horizontal cylinders with a common horizontal main axis, the cylinder forming the autoclave containing the smaller cylinder forming the basket or drum.
• the rotating drum or basket has a diameter of 1 to a few tens of cm, for example 10 cm up to several meters, for example, 5 m; and a length of a few tens of cm, for example 20 cm to several meters, for example, 20 m.
• This drum or basket is perforated, with openings of variable shapes, it can be, for example, made of a trellis or a grid and thus defines a "squirrel cage", with more or less loose meshes.
• This drum or basket is made of a material supporting the conditions prevailing in the enclosure and contact with a dense fluid, under pressure, this material is generally analogous to the material constituting the autoclave.
• the part or parts are arranged inside the drum or basket rotating on or in supports, such as tongs, claws, “racks” or racks, fixed or mobile, for example animated by a translational, rotational or other movement.
• the movement of the support (s) can be printed by a shaft in direct or indirect engagement with the drive means, for example, with the rotor of the electric motor, preferably this shaft is also the drive shaft of the drum.
• the basket or drum is generally rotated about its horizontal axis, by means of a horizontal shaft (4) located in the extension of the horizontal axis of the cylindrical basket or drum, and fixed to the circular base (5 ) of the drum, on the side opposite to the loading-unloading door (2) of the autoclave (1).
• This shaft passes through the wall (s) of the autoclave, namely the circular base of the cylinder (6) opposite the base forming a door (2) or loading opening, in the center thereof.
• the tightness at the crossing of the wall of the enclosure or autoclave is ensured by a rotary joint (7) pressure-tight, up to a pressure which can range, for example up to 350 bars.
• This shaft or axis (7) which can be defined as a transmission axis or shaft is preferably a hollow shaft or axis, which thus conveniently provides power (8) for the enclosure and the drum in dense fluid under pressure, such as C0 2 , as well as its evacuation (9).
• the shaft is in direct engagement by means of a coupling block (10) with drive means, such as an electric motor (11) of adequate power, located outside the enclosure.
• drive means such as an electric motor (11) of adequate power
• the loading / unloading door of the autoclave can itself be provided with an orifice connected by a flexible cord, resistant to pressure and not impeding its movement, which allows the evacuation and / or the supply of the autoclave in dense fluid under pressure.
• the device according to the invention further comprises means for subjecting the parts, simultaneously with their contact with the fluid or their immersion in the dense fluid under pressure, to the action of a high speed jet of the dense fluid under pressure.
• These means consist of one or more nozzle (s) or nozzle (s) for spraying fluid at very high speed, which allow mechanical stripping of the surfaces.
• This second mechanical effect is added to the first mechanical effect due to the rotating basket and to the solvent effect due to the dense fluid under pressure in contact with the parts. It has, in fact, been shown that during the expansion of the fluid through a restrictor, the fluid, such as C0 2 , does not instantly lose its density. This decreases rapidly, but gradually in the jet leaving the restrictor.
• the supply pressure of the dense fluid under pressure arriving at the nozzle (s) is generally from 10 to 500 bars.
• a pressure differential generally 500 to 10 bars, can be achieved between the upstream part and the downstream part of the restrictor device (s) or nozzles.
• the nozzle (s) can (wind) be fixed (s) or mobile (s) and this or these nozzle (s) can (wind), likewise, be placed (s) on one or more support (s) fixed (s) and / or mobile (s).
• This or these support (s) can (wind) be, for example, in the form of arms, ramps, crowns or other, fixed or driven by a movement of rotation, translation, for example, back and forth type , or others.
• the nozzles could be fixed on an arm or rotating crown.
• Each of the supports can carry from 1 to 100 nozzles, depending on the size of the autoclave and depending on the geometry of the parts to be cleaned.
• Each nozzle (13) can generate one or more jets (14) of conical or flat shape, thus sweeping the entire basket and the parts to be cleaned. If the nozzle (s) and / or their support is (are) in motion, the latter is printed by a shaft in direct or indirect engagement with the drive means, for example, with the rotor of the electric motor.
• the movement of the nozzle (s) and / or their support (s) can be associated, in addition to the movement of the basket or drum, with the movement of the support of the parts, which makes it possible to expose the assembly different faces to be cleaned, for the effect of the jet (s) from one or more angles: this is particularly interesting in the case of cleaning complex parts.
• the nozzle (s) can be supplied with dense fluid under pressure, such as C0 2 , either by the main circuit, that is to say by the same circuit which allows the filling of the autoclave by the shaft.
• dense fluid under pressure such as C0 2
• the main circuit that is to say by the same circuit which allows the filling of the autoclave by the shaft.
• hollow (see description of the installation, below) and its compression pump either by a secondary circuit, in which all or part of the fluid, such as C0 2 , is recycled by an annex recirculation pump.
• the device according to the invention also comprises means for continuously separating, inside the closed enclosure, the solid and / or liquid particles from the dense fluid under pressure.
• the purpose of these separation means is to trap the insoluble solid and / or liquid particles of contaminants or other, extracted, entrained, so as to avoid recontamination of the clean cleaned parts, by redeposition of these particles.
• These means are generally constituted by filtration means, possibly combined with absorption means.
• the filtration means will take the form of a filter, known as an “anti-redeposition filter” (15) or a “pollution trap”. It is generally a filter of specific shape, preferably removable, and metallic. This filter could thus have a semi-cylindrical shape (see FIG.
• the windows or slots must be oriented according to the direction of rotation.
• the solid particles or “chips” are eliminated in part by the centrifugal force due to the rotation of the basket, depending on whether the basket rotates clockwise or vice versa, and these slots must be rotated so to capture particles that escape from the basket and cleaning parts towards the filter without letting them escape and return to the basket to recontaminate the parts.
• the filter could, in other words, be presented as a filter, for example, metallic in the shape of a semicircle perforated by windows of particular shapes, which take account of the direction of rotation, in which an absorbent material, such as absorbent paper or cloth, can be placed if necessary and which makes it possible to collect and trap liquid particles coming from the fraction insoluble in the fluid, such as C0 2 , set in motion by circular agitation and / or the mechanical effects induced by the ramp (s) of nozzle (s), as well as the solid particles, “chips” and “microchips” of metal and other, of totally random shapes, produced during the machining of the parts, in particular metallic, being the object of an operation of cleaning.
• These particles are "peeled off” and set in motion by the agitation and the effect of the jets, in the lower part or the upper part or both parts of the enclosure.
• the device according to the invention can comprise means (not shown) for subjecting the dense fluid under pressure located inside the enclosure, to the action of ultrasonic waves.
• These means generally include one or more devices, more sonotrode frequency generators, for generating sound waves, ultrasound and / or megaons, for example a mono or multifrequency frequency generator and from one to ten sonotrodes.
• sonotrodes are generally placed at regularly spaced points inside the enclosure, for example in the longitudinal axis of the autoclave (a sonotrode) or in the radial axis of the autoclave (from one to ten sonotrodes spaced a few centimeters (5 cm) to a few tens of centimeters (20 cm) depending on the size of the enclosure. Only the sonotrode can be placed in the enclosure, thanks to a pressure-tight passage which nevertheless allows its vibration. Alternatively, the sonotrode plus the transducer can be placed in the enclosure, which then requires only a sealed passage for the electrical supply cable from the sonotrode to the frequency generator.
• the sonotrode (s) is (are) only one block with the transducer part and is (are) connected (s) to the frequency generator by a coaxial cable for the generation of sound waves of adequate frequency (s) (s), etc.
• Figure 2 shows, schematically, a side sectional view of the installation according to the invention.
• FIG. 2 shows the autoclave, schematically.
• the installation according to the invention is substantially analogous to a conventional installation for the treatment or cleaning of parts by a dense fluid under pressure, for example supercritical, except that it uses instead of autoclaves conventional, a specific autoclave or extractor, as described in Figure 1.
• the installation according to the invention therefore has all the advantages inherent in the device and method according to the invention, as already indicated.
• the autoclave Inside the enclosure, the autoclave, is a basket or rotating drum (22) driven by a shaft (23) in direct contact with the drive means, such as an electric motor (24) .
• the drive means such as an electric motor (24) .
• the autoclave can also be driven by a movement, for example, of rotation, preferably, being driven by the same shaft or axis as the basket or rotating drum.
• the autoclave is capable of withstanding the pressure used in the process of the invention and it is also provided with heating and temperature regulation means in the form, for example, of a thermostated double jacket (not shown ), in which a suitable heat transfer fluid circulates.
• the volume of the autoclave is variable, it depends in particular on the volume of the parts to be treated, it can be easily determined by a person skilled in the art.
• the extractor or autoclave receives the parts to be cleaned (25), which are preferably placed on one or more support (s) or grid (s), inside the basket or rotating drum (22).
• the installation shown has only one extractor or autoclave (21), it is obvious that the installation can include several extractors, for example, from 2 to 10, arranged, for example, in series.
• the installation also includes means for bringing a fluid, such as C0 2 in the dense state and under pressure, for example in the supercritical state.
• the fluid for example, from C0 2 , coming from a recycling pipe (26), and / or possibly from a storage and make-up tank, for example, from C0 2 (27) does it enter, by means of a valve (28) in a liquefaction tank (29) provided with temperature regulation means in the form of a thermostated double jacket (210), in which circulates a suitable heat transfer fluid (211, 212).
• Said fluid such as C0 2 , is thus liquefied and circulates through a flow meter (213), then is pumped and compressed by means of a pump (214), for example, a compression pump of the type diaphragm or piston or, for example, from a compressor to the autoclave (21).
• the fluid for example, the pumped C0 2
• an exchanger 216
• supercritical exchanger in which it is heated to be in conditions where it is in the form of a dense fluid and under pressure, in particular, a dense supercritical fluid.
• the fluid is, in this exchanger heated above its critical temperature which is, for example, 31.1 ° C, in the case of C0 2 .
• the fluid is (see Figure 1) preferably introduced into the autoclave, via the basket drive shaft or rotating drum, which is hollow.
• the same circuit also supplies the nozzles or spray nozzles provided in the autoclave.
• FIG. 2 also shows means for injecting a co-solvent in the form of a high pressure pump (217) supplied by a co-solvent tank (218), which allows the gradual supply of a quantity known cosolvent in the compressed fluid, via a line (219) connected to the fluid supply line of the extractor (21), upstream of the exchanger (216) and downstream of the compression pump (214).
• the fluid or, optionally, the fluid and cosolvent mixture comes into contact with the parts and cleans them in the enclosure of the extractor (21), while this same fluid is projected at high speed onto the parts . Unwanted polluting contaminant compounds are thus extracted.
• the supercritical fluid will, for example, be a homogeneous solution of fluid, such as C0 2 alone or C0 2 with cosolvent.
• the stream of fluid such as C0 2 in which the polluting compounds, contaminants, extracts eliminated from the parts are dissolved, is then preferably sent by the same hollow shaft used for feeding, or by an orifice located at side on the same side or placed opposite to the door allowing the opening of the autoclave for loading - unloading of the parts, towards separation means connected to the extractor or autoclave (21) and comprising, for example , three cyclone type separators (220, 221, 222) connected in series, each of them being preceded by an automatic expansion valve (23, 24, 25).
• separation means connected to the extractor or autoclave (21) and comprising, for example , three cyclone type separators (220, 221, 222) connected in series, each of them being preceded by an automatic expansion valve (23, 24, 25).
• the expansion to which the fluid is subjected takes place at constant temperature.
• each of the separators separation or demixing takes place, on the one hand, of the extracted organic compounds which are in the form of liquid and, on the other hand, of a gas, for example, C0 2 .
• the compounds extracted from the parts are drawn off (226, 227, 228), for example, at the base of the separators, and recovered, then possibly subjected to new operations of separation, extraction or purification, for example, centrifugation, decantation or liquid / liquid extraction, or destroyed.
• the gas resulting from the separation, such as C0 2 is purified, then sent to the means for recycling the fluid, which essentially comprise a pipe (26) and a “cold” exchanger (229) or liquefier, for example, in the form of a thermostatically controlled enclosure, to be directed towards the liquid reserve (29) at low temperature, maintained by means of a cooling bath which cools and liquefies the fluid (211, 212), such as C0 2 .
• the purification means (230) have been represented in FIG. 1 by a reflux column or an activated carbon column (230) placed on the means for recycling the fluid.
• the dense fluid under pressure can be made to recirculate continuously, during cleaning, using a recirculation pump (231). Continuously, during the entire cleaning operation, the insoluble particles are trapped on the filter inside the autoclave (not shown). The particles trapped on the filter are generally recovered at the end of the cleaning operation, when the autoclave is opened and eliminated as solid waste or recovered for the purpose of recycling.
• the device may further comprise means for introducing another enthalpy fluid weaker than the dense fluid under pressure, inside of the pressure vessel, and replace all or part of it during a final expansion step.
• the introduction of the weakest and chemically inert enthalpy fluid takes place from the top or from the bottom of the autoclave according to the respective densities of the weakest and chemically inert enthalpy fluid and of the dense fluid under pressure to be eliminated.
• the installation comprises regulation means (not shown), in particular of the pressure, in the various parts of the process, which include a regulation chain composed of pressure sensors, regulators and pneumatically controlled needle valves.
• regulation may take place between the temperature of the wall (using a probe) and the percentage of opening of the expansion valve.
• the method is implemented in the installation of FIG. 2, according to a succession of steps, which is generally the following:
• a specific extractor in the form of a rotating basket autoclave with a volume of 10 liters and a maximum pressure of 300 bars, fitted with a double jacket, a device for nozzles for spraying and a metal filter system allowing in particular to trap the solid particles and the oily fractions not dissolved by the solvent CO 2 ;
• the samples to be cleaned are test tubes and / or parts of complex aluminum shapes, previously contaminated with various oils used in metalworking, such as a water-soluble machining oil, a cutting oil, a dyeing oil as respectively oils available commercially under the names CIMSTAR 560 ®, Mobile Mobilube ®, Drawsol 2345 N ®.
• oils used in metalworking such as a water-soluble machining oil, a cutting oil, a dyeing oil as respectively oils available commercially under the names CIMSTAR 560 ®, Mobile Mobilube ®, Drawsol 2345 N ®.
• the test piece is placed more than 5 cm from the nozzle outlet.
• the surface mass of the contaminant is determined by weighing before and after cleaning with C0 2 .
• the cleaning efficiency in percentage is obtained by the following formula: areal mass of contaminant after cleaning
• Efficiency% x 100 areal mass of contaminant before cleaning
• Table 1 presents this comparison, with the nature of the contaminant, the surface contamination and the operating conditions.
• This example shows an improvement in the cleaning efficiency induced by the mechanical effects brought about by the use of C0 2 sprayed at high speed.
• the very higher level of cleaning achieved it can also be seen that the treatment time and the working pressure are significantly reduced, namely 1 hour instead of 2 hours and 100 bars instead of 300 bars.
• the nature of the contaminant is modified, which in this case is a relatively viscous cutting mineral oil.
• Example 2 The procedure for the experiment is the same as in Example 1.
• cleaning is carried out by simple contact, soaking, of identical test pieces coated with the contaminant.
• the procedure being identical to the previous examples, the nature of the contaminant is again modified.
• This time it consists of a fluid of high viscosity, used during dyeing operations (inking) on metals ("drawing oil").
• This fluid has the particularity of being difficult to clean, including by conventional methods using solvents and detergents.
• cleaning is also carried out by simple contact, soaking, of identical test pieces coated with the same contaminant. Table 3 shows the conditions and the results of this comparison.
• This example consists in coating contaminants with real aluminum parts and complex shapes comprising several faces, as well as one or more holes for drilling.
• the overall size of these pieces does not exceed 10 cm in length and 6 cm in height.
• the evaluation of the effectiveness is carried out by weighing the tare and the contaminant before and after cleaning and the effectiveness is determined by the formula given above.
• the overall mass of contaminant is used in this formula and not the surface mass, as in the previous examples, the surface of an actual part being difficult to obtain precisely.
• the contaminants chosen are those of the previous examples: 20% water-soluble machining oil (from Example 1), cutting oil (from Example 2) and dyeing / inking oil (from Example 3).
• This example 4 constitutes the reference for a cleaning operation by supercritical C0 2 , without any mechanical effect and based on the sole power of dissolution, with respect to the contaminants studied and indicated in Table 4 below.
• This example consists in treating parts of complex shapes contaminated with different oils identical to example 4.
• the parts, 15 in number per test are treated in the rotating autoclave, but not equipped with the jetting device and the anti-redeposition filter, that is to say that the parts are subjected to agitation due to the only rotary movement of the basket or drum.
• Table 5 shows the contaminants, their masses, the treatment conditions and the efficiencies obtained.
• the efficiency remains optimal at 100%, with a clear saving in the time of treatment, which goes from 1 h, for example 4, to h, for example 5.
• the gain turns out to be essentially of an energy order, thanks to a reduction in treatment time, therefore in the rate of solvent C0 2 .
• the efficiency reaches 94, with stirring, in approximately 1 h, against 90% of effectiveness in 2 h of treatment (for example 4 for reference). In this case, therefore, the efficiency is improved while reducing the treatment time.
• a nozzle ramp making it possible to spray C0 2 , at very high speed, was implemented, as well as an openwork metal filter provided with absorbent paper, all to allow to trap the insoluble particles of the contaminant detached from the surface of the parts by the jet of C0 2 and the rotary movement of the basket.
• Table 6 shows all the conditions, as well as the efficiencies obtained.
• a depressurization of the C0 2 is carried out from 230/250 bars to approximately 100/135 bars, then an introduction of nitrogen is carried out to expel the C0 2 still present for times varying from 2 to 5 minutes , followed by expansion to atmospheric pressure.
• the temperature is monitored using a thermocouple placed inside the enclosure.
• Test n ° l shows that during an expansion deemed rapid at 8'15 '', the final temperature at decompression reaches -50 ° C, with the formation of 2/32593
• test No. 2 shows that a final temperature of the fluid in the autoclave is obtained of 17 ° C for a total depressurization time of 11' 30.
• the difference obtained between the two tests is +67 ° C for only 4 '15' 'more relaxation time.
• Test n ° 3 comparable to tests n ° 1 and n ° 2, shows that by reducing the relaxation time from 11 '30 to 10', the final temperature of the enclosure remains positive, at 2 ° C.
• Table 8 below gives the operating conditions for the various tests carried out.
• test 8 - 2 carried out under the same conditions as test 8 - 1, but in the presence of co-solvent, it is found that the screening of the sample is more important and results in the appearance of a hole in aluminum foil several centimeters in diameter (4 cm). In this case, the phenomenon is confirmed by a very significant increase in the audible sound level during the test. This proves that the presence of the cosolvent in the dense CO 2 under pressure reveals the ultrasonic phenomenon by amplifying it.
• the sheet is very weakly screened when acting in the presence of C0 2 , alone, in the supercritical state.
• the effects of ultrasound appear qualitatively weaker than those observed in liquid C0 2 , alone. This clearly reflects the fact that cavitation is more difficult to obtain when the C0 2 is supercritical.
• Tests 8 - 4 and 8 - 6, respectively identical to tests 8 - 3 and 8 - 5, but carried out in the presence of a co-solvent shows that the sheets aluminum are more strongly screened with the appearance of holes a few centimeters in diameter (1 to 1.5 cm), as well as a very high noise level outside the pressure vessel, tangible testimony of '' a phenomenon of propagation and / or increased cavitation. This demonstrates that it is the presence of the cosolvent which acts as a developer and an amplifier of ultrasonic phenomena in supercritical CO 2 . Finally, it is found that the screening is more important with liquid C0 2 with cosolvent, compared to the other supercritical tests.

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• 2000
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