EP0775225B1 - Method for cleaning in a liquid medium fabrics or clothes, and plant for implementing such method - Google Patents

Abstract

PCT No. PCT/FR95/00976 Sec. 371 Date Jan. 24, 1997 Sec. 102(e) Date Jan. 24, 1997 PCT Filed Jul. 20, 1995 PCT Pub. No. WO96/05352 PCT Pub. Date Feb. 22, 1996A method and apparatus are described for cleaning fabrics and clothes in a liquid medium wherein a vacuum drying step is effected at a pressure ranging from 1.5x103 Pa to 15x103 Pa in the presence of steam which is injected into the drying process at a pressure between 0.8x104 to 8x104 Pa and which is used as a carrier for removing the cleaning liquid.

Description

The invention relates to a method for cleaning in a liquid medium pieces of cloth or clothing and an installation for its implementation.

In the liquid cleaning techniques currently used, washing is carried out first by bringing the parts to be cleaned in contact with the liquid, constantly purified, by stirring inside a rotating drum, or by spraying the liquid on the moving parts.

In a second phase, we mechanically extract a proportion higher or lower liquid, by various techniques of wringing or pressing.

Finally, the rest of the liquid must be extracted from the parts during a so-called drying operation.

This must be pushed until the total elimination of the liquid, especially when it comes to organic solvents of an often toxic nature, even at very low doses.

Most solvent cleaning machines use a air circulation closed circuit drying process.

The heat necessary for the evaporation of the solvent remaining after spinning mechanics is provided by the circulating air. The entrained solvent is then condensed in the cold part of the circuit.

The heating and cooling needs are all the more close to the equivalent as evaporation and cooling temperatures are neighbors.

In fact, modern cleaning machines are equipped with a heat pump system that recovers about 50% of the energy thermal required.

We also know methods of cleaning clothes by solvents in which the drying step is carried out under vacuum. It is in particular the case of the processes described in patent FR-A-1338 398 and its certificate of addition FR-E-88 834. According to the process described in the certificate of addition, it is recommended to send before and / or during the application of the vacuum, vapors heated or superheated, especially solvent vapors, to transfer heat to the residual solvent and spray it. However, this document does not suggest in no way to send, throughout the drying stage, steam produced under low pressure, especially superheated steam.

However, the tests carried out by the inventor of the present application have clearly shown that the use of superheated steam from the vacuum contributes greatly to the acceleration of the heat exchanges necessary for drying.

French patent FR-2,696,480 also describes a method of vacuum drying by extraction, called "azeotropic" with water vapor relaxed.

This process has a number of advantages over the processes classics: speed of drying, complete removal of solvent, quality of cleaning, absence of electrostatic charges.

In the current state of the art, the machines used are quite good suitable for the use of solvents such as perchlorethylene.

However, this solvent has a level of toxicity which would condemn it in the medium term if it were not possible to effectively reduce emissions in the near zero, which conventional air drying machines do not allow not really.

These result moreover from a compromise with regard to specific processing capacities.

In these machines, you need twice as much capacity "container" for drying than for washing. Drum capacity adopted therefore results from a compromise between these two values.

On the other hand, the use as a solvent of hydrocarbons such as undecane, in conventional machines, poses safety problems that overcomes by operating under inert gas produced by a fairly expensive nitrogen generator.

In addition, due to the low volatility of the solvent, the drying time is practically doubled (compared to the chlorinated solvent).

Furthermore, with the use of low volatile solvents, from the family of hydrocarbons, currently envisaged, the processes implementing a step of vacuum drying, like the other more traditional ones, consume a lot of energy.

The new process and the means of its implementation, object of the present invention provide a response to the shortcomings and imperfections of current techniques as well as the needs expressed by users.

Thus, more specifically, the method of the invention, comprising a vacuum drying step carried out under a pressure of between 1.5 × 10 ³ and 15 × 10 ³ Pa in the presence of water vapor intended to serve as a vector for the elimination of said liquid and injected into the drying chamber is characterized in that said water vapor is injected as soon as the vacuum reaches a value between 1.5 and 15.10 ³ Pa from a pressure source between 0.8.10 ⁴ and 8.10 ⁴ Pa.

Injection of low pressure water vapor, in particular steam low pressure superheated water, as soon as the drying chamber is evacuated allows the air contained in the machine to be completely expelled. The operation of drying carried out according to the invention implements an extraction process not azeotropic, i.e. it is possible to vary the flow rate of the vapor injection for a given result, because the system is bi-variant, whereas in a azeotropic process, mono-variant by nature, the ratio of the quantities of vapor water and solvent is determined according to the pressure.

The advantage of the method of the invention which makes it possible to produce a system non-azeotropic solvent extraction is further increased during use undecane type hydrocarbon solvents, because the use of such a solvent would lead to much higher consumption of water vapor in the case of an azeotropic system: indeed, it would require 5 kg of vapor for 1 kg of solvent in such a system while the process of the invention makes it possible to limit the steam consumption not more than 1.1 kg per 1 kg of solvent, i.e. five times less.

Another advantage of the process according to the invention is that it makes it possible to lower the vaporization temperature of the solvent. Thus, under a pressure of 3.10 ³ Pa, with perchlorethylene, it is only 14 ° C, while it is approximately 28 ° C in the methods described in the patent FR-E-88 834 cited above .

As a result, in the process according to the invention, the evaporation gradient, i.e. the difference between the temperature of the clothing environment inside the machine basket and the solvent basket in the clothes is practically doubled, which considerably increases the drying efficiency.

Furthermore, when considering the use of hydrocarbon solvents which are called upon to replace chlorinated solvents, eliminating air by sweeping a second particularly important advantage of the steaming process the invention since it avoids the use of an inert gas generator such that it is used in particular currently in conventional machines and which represents an additional cost of installation of at least 20%.

Another advantage of using superheated steam when vacuum is that it also contributes to the acceleration of trade necessary for drying.

Indeed, the efficiency of this heat vector is much higher than that air or solvents used in the process described, in particular in the patent FR-E-88 834 cited above.

The invention also relates to an installation for implementing the above method, comprising a sealed drying enclosure comprising a rotary drum and means making it possible to create a vacuum of between 1.5 × 10 ³ and 15 × 10 ³ Pa in said enclosure during the drying step, as well as means for supplying and injecting steam into said enclosure, characterized by means for supplying and injecting water vapor from a pressure source of between 0.8.10 ⁴ and 8.10 ⁴ Pa.

The following description, given in particular with reference to Figures 1 to 3, clearly illustrates the advantages of the process of the invention.

• figure 1 : le diagramme de MOLLIER donnant l'enthalpie (H) du système en fonction de son entropie (S),
• figure 2 : une installation perfectionnée permettant la mise en oeuvre du procédé de l'invention,
• figure 3 : une autre installation pour la mise en oeuvre du procédé de l'invention.

The figures represent respectively:

• FIG. 1: the MOLLIER diagram giving the enthalpy (H) of the system as a function of its entropy (S),
• FIG. 2: an improved installation allowing the implementation of the method of the invention,
• Figure 3: another installation for implementing the method of the invention.

According to a first aspect, the invention relates to a new method of vacuum drying.

The invention relates to a method of cleaning in a liquid medium pieces of fabric or clothing comprising a vacuum step carried out under a pressure of between 1.5 × 10 ³ and 15 × 10 ³ Pa in the presence of water vapor intended to serve as a vector. for the elimination of said liquid and injected from a source at a pressure between 0.8.10 ⁴ and 8.10 ⁴ Pa, preferably between 4 and 6.10 ⁴ Pa.

This drying step is advantageously carried out at a temperature between 30 and 55 ° C, and preferably between 35 and 45 ° C.

This temperature is advantageously ensured by carrying the wall of the enclosure where drying takes place at a temperature between 40 and 75 ° C, thus ensuring direct heat transfer.

The water vapor is preferably superheated to a temperature between 80 and 150 ° C before injection.

Water vapor is introduced at the start of the drying phase and for the duration of this stage. It is therefore introduced as soon as the vacuum reaches a value between 1.5 and 15.10 ³ Pa.

The temperature and pressure conditions of the injected vapor allow to realize, unlike the system realized in the patent FR-2 696 480, an essentially non-azeotropic system for extracting solvent. It is a bi-variant system which optimizes the conditions solvent extraction.

According to a particularly advantageous variant, the method of the invention further implements a high performance heat pump system obtained thanks to the small difference in temperatures of the hot and cold parts which can be between 50 and 60 ° C. The practical coefficient of performance is thus close to 3.

This device provides all of the heat and cooling.

Thus, a heat generator provides low pressure steam, at a pressure between 0.8.10 ⁴ and 8.10 ⁴ Pa and at the same time heating water at a temperature of the order of 40 to 75 ° C, advantageously from 40 to 55 ° C., as required.

1) Par un gradient d'extraction élevé, accélérant le processus, en particulier quand il s'agit de solvants dits "lourds" tels que, par exemple l'undécane.

2) L'utilisation de vapeur d'eau à basse pression pour le balayage, évite les inconvénients inhérents à l'emploi de vapeur à 3 à 5.10⁵ Pa fournie par les générateurs classiques, vapeur dont la détente à l'intérieur de la machine n'est pas exempte de risques de condensation comme le montre le diagramme de MOLLIER, donné sur la figure 1 et bien connu de l'homme du métier. Ce diagramme montre que, dans les conditions de la présente invention, la vapeur de balayage évolue très au-dessus de la courbe de saturation, ce qui n'est pas le cas lorsqu'on détend la vapeur à 3 à 5.10⁵ Pa à l'intérieur de la machine.

3) Une consommation d'énergie réduite même par rapport à celle des machines classiques avec pompe à chaleur, le gain étant d'au moins 30 %.

4) Pas de consommation d'eau.

5) Une émission résiduelle de solvant extrêmement basse. La concentration de solvant dans la machine à l'ouverture, est inférieure à 25 ppm alors que les meilleures machines, respectant d'ailleurs les normes actuelles, présentent des concentrations au moins 10 fois plus importantes.

The above characteristics are reflected:

1) By a high extraction gradient, accelerating the process, in particular when it is a question of so-called "heavy" solvents such as, for example undecane.

2) The use of steam at low pressure for sweeping avoids the drawbacks inherent in the use of steam at 3 to 5.10 ⁵ Pa supplied by conventional generators, steam whose expansion inside the machine is not free from the risk of condensation as shown in the MOLLIER diagram, given in FIG. 1 and well known to those skilled in the art. This diagram shows that, under the conditions of the present invention, the sweeping vapor evolves well above the saturation curve, which is not the case when the steam is expanded to 3 to 5.10 ⁵ Pa at l inside the machine.

3) Reduced energy consumption even compared to that of conventional machines with heat pump, the gain being at least 30%.

4) No water consumption.

5) An extremely low residual solvent emission. The concentration of solvent in the opening machine is less than 25 ppm while the best machines, meeting current standards, have concentrations at least 10 times higher.

The MOLLIER diagram shown in Figure 1 highlights the advantage of injecting water vapor from a steam source superheated, for example at 150 ° C, under reduced pressure, represented by hatched area D of the graph. The relaxation resulting from the introduction of this vapor in a lower pressure enclosure occurs according to arrow F. The risk of condensation, materialized by the diagram area, located below the saturation curve (I) is practically zero.

On the other hand, the expansion of a vapor, at the same temperature of 150 ° C, but from a pressure of 5.10 ⁵ Pa, presents great risks of condensation. Such expansion takes place along paths located between an isentropic expansion materialized by the vertical BA ₆ and an isenthalpic expansion along the horizontal BA ₀ . Depending on the importance of the work provided by the steam during its expansion, the path is more or less inclined between BA ₆ and BA ₀ .

By way of examples, these intermediate detents are shown in FIG. 1 represented by the curves BA ₂ , BA ₃ , BA ₄ and BA ₅ . Only the trigger according to BA ₁ , practically without "outside" work, is free of condensation.

Another advantage of this drying process according to the invention is that, if it is perfectly suitable in the case of cleaning processes in a liquid medium using, as is most often the case today, solvents organic and more particularly chlorinated solvents, in particular perchlorethylene, it can also be used with hydrocarbon type solvents, in particular saturated or unsaturated C ₈ to C ₁₂ hydrocarbons, for example undecane, or derivatives of these hydrocarbons of ester or alcohol type possibly mixed with water and capable of being suitable for cleaning.

This represents a particular advantage of the invention since it is not excluded that this type of solvents will be led in the future to replace solvents chlorinated widely used at present.

The installation comprises a sealed drying enclosure comprising a rotary drum and means making it possible to create a vacuum of between 1.5 × 10 ³ and 15 × 10 ³ Pa in said enclosure losing the drying step, as well as means for supplying and injection of water vapor into said enclosure.

The means for establishing said vacuum are advantageously constituted a vacuum pump and an air ejector placed on the suction device of said vacuum pump.

In fact, the 2-stage liquid ring vacuum pumps used up to now do not allow the obtaining of voids of less than 4.10 ³ Pa and, this provided, moreover, that the liquid ring is cooled to at least 15 ° C. . In addition, in the vicinity of this pressure, it is difficult to avoid cavitation due to vaporization of the water inside the pump, damaging the latter quickly.

Thus, according to the invention, a pump is advantageously used. liquid ring. However, an air ejector device is placed at the suction of the vacuum pump, it is supplied with air at atmospheric pressure taken from the pump discharge, there is recycling, and it is the ejector which extracts directly on the capacity and makes it possible to obtain a vacuum advantageously of the order of 1,300 Pa, inaccessible with the pump alone. The result is spectacular because the diet solvent extraction is then at a clearly distinct temperature level inferior. The use of this new vacuum device makes it possible to extract the solvent vapors at an equilibrium temperature of around 15 ° C instead of 30 ° C at least with the pump alone. The temperature gradient, governing the vaporization of the solvent, is practically multiplied by 2, passing from 15 ° C to 30 ° C.

Another advantage is to avoid any risk of cavitation of the vacuum pump.

Thus in the installation of the present invention as in that described in patent FR-2 696 480, the liquid ring pump operates in closed circuit but the vacuum level can be significantly improved thanks to the addition an air ejector placed on the suction circuit of this vacuum pump.

However, in low capacity machines, the vacuum pump could be replaced by a device comprising a water pump.

According to an advantageous variant of the invention, the installation comprises also means for heating the rotary drum.

These means can be constituted by heating means direct or indirect from the drum. Preferably direct heating will be chosen.

This direct heating can in particular be achieved by means of a hot water circuit at 40 to 75 ° C, constituting the cylindrical surface of the drum, in using, for example, a coil in stainless steel tube 20 mm in diameter, by example with turns spaced 3 mm apart. With such a device, or any other equivalent, the heat transfer is much more efficient and the efficiency thermal is multiplied by three.

Low pressure water vapor is usually superheated before its injection into the drying chamber.

The installation for implementing the method of the invention also includes heating and cooling means providing uses quantities of heat all the more similar as the process is carried out lower pressure.

This is how a heat pump device is applied here in exceptional efficiency conditions.

It is indeed possible to operate between temperatures of 60 and 5 ° C. he The result is a theoretical coefficient of performance of 333/55 = 6.05.

We can therefore hope for a practical coefficient of 3, that is to say that with a 6 kW compressor, you can generate as much steam as a boiler 18 kW.

But, in addition, this system also provides cooling power equivalent around 4 to 12 ° C, preferably 5 to 8 ° C.

The process and the installation of the invention are illustrated by the description below of a particular embodiment of the invention made in look at Figure 2 which corresponds to a particularly interesting variant of the invention, implementing a heat pump system. We will describe also further on, with reference to FIG. 3, a simplified installation does not not presenting the improvement which constitutes the heat pump.

Figure 2 is a diagram of an installation for the implementation of the invention, incorporating a heat pump system.

Certain parts concerning materials common to all cleaning machines, in particular solvent tanks, cleaning equipment regulation, are not shown, for the purpose of simplification.

• La machine proprement dite, comprenant une enceinte étanche 1 munie d'une porte de chargement et un tambour rotatif 2 pourvu d'un dispositif de chauffage. Cette partie constitue la partie chaude du dispositif.

The installation shown in Figure 2 includes the following equipment:

• The machine itself, comprising a sealed enclosure 1 provided with a loading door and a rotary drum 2 provided with a heating device. This part constitutes the hot part of the device.

• un filtre à liquide 5 pour l'élimination des particules solides (épingles, boutons, etc...),
• un filtre des gaz et vapeurs 6,
• un condenseur des vapeurs 7,
• les condensats sont recueillis dans un réceptacle 8.

Following the liquid and gaseous effluents, we successively find:

• a liquid filter 5 for removing solid particles (pins, buttons, etc.),
• a gas and vapor filter 6,
• a vapor condenser 7,
• the condensates are collected in a receptacle 8.

• les vapeurs non condensées et les gaz sont extraits par un dispositif de vide comprenant :
  • une pompe à vide 10,
  • un éjecteur à gaz 11,
  • un séparateur/refroidisseur 17.

The components 7 and 8 of the installation constitute the cold part of the device.

• uncondensed vapors and gases are extracted by a vacuum device comprising:
  • a vacuum pump 10,
  • a gas ejector 11,
  • a separator / cooler 17.

The liquids collected are treated in a decantation container 14.

A heat pump system supplies the installation with the heat and cold.

• un compresseur à fréon 18,
• un générateur de chaleur 15 fournissant de la vapeur à basse pression : 0,8 à 8.10⁴ Pa injectée dans la machine, pratiquement sans détente, en passant par le réchauffeur 3,
• de l'eau chaude à 40 à 75°C, mise en circulation par la pompe 20 et introduite au tambour rotatif par l'arbre central de transmission,
• les besoins en refroidissement sont fournis séparément au séparateur 12 et au condenseur 7 par les évaporateurs 17 et 19 respectivement, munis chacun de leur détendeur, reliés à la capacité de réserve 16.

It basically includes:

• a freon compressor 18,
• a heat generator 15 supplying steam at low pressure: 0.8 to 8.10 ⁴ Pa injected into the machine, practically without expansion, passing through the heater 3,
• hot water at 40 to 75 ° C, circulated by pump 20 and introduced into the rotary drum by the central transmission shaft,
• the cooling requirements are supplied separately to the separator 12 and to the condenser 7 by the evaporators 17 and 19 respectively, each provided with their expansion valve, connected to the reserve capacity 16.

The installation allows the recycling of condensates, thus the water condensate collected in 14 and 12 can be used as feed water of the steam generator 15. This generator is supplied with water by the condensates products during the drying stage, with an optional external addition, such so that there is no discharge of liquid effluent to the outside.

According to another variant, the two evaporators 17 and 19 by a single evaporator to cool the water which then circulates to cool the condenser 7 and the separator 12.

Non-condensable gases pass through a carbon adsorber active 13.

They are sent in variable volume capacity 4 and are reintroduced into the machine, at the end of the cycle, to restore atmospheric pressure and allow the door to open.

The previous description of the main equipment of the installation represented on the diagram of figure 2 is supplemented below by that of operation of the same installation, with reference to the diagram in Figure 2.

The washing phase is carried out by circulation of solvent, introduced in jet directly into the drum 2 in alternating rotation, from the front face of 1.

The solvent flows through the filter 5 and the valve 22. It is taken up by a circulation pump and passes through a purifying filter, not shown, before being recycled.

Washing is often supplemented by a rinsing operation with the solvent which has just been distilled.

The mechanical extraction of a greater or lesser proportion of the solvent retained by clothing is carried out by wringing. The drum is set rapid rotation at a speed which can be adjusted, depending on the nature of the parts to be treat, thanks to a drive device by motor with electronic variator of speed.

The final drying phase implements the simultaneous means of its realization inside the drum, whose speed has been reduced to about that of washing.

Shortly before the end of the spin cycle, the heat pump system is switched on works to quickly meet heat and cold needs.

The vacuum device, essentially the pump 10, is also put working. It is then necessary to isolate the capacity 1 from the outside, which requires the closing of the valves 21, 22, 24. On the other hand, the valve 26 is closed while the valves 25, 27 and 28 are open.

The vacuum is quickly established in the equipment upstream of the pump 10, i.e. parts 1, 5, 6, 7 and 8 of the assembly.

Under the simultaneous action of the vacuum and the addition of heat, directly to the surface of the drum 2, the solvent contained in the clothing begins to vaporize. This phenomenon is then accelerated by the triggering of the steam injection controlled by the automatic valve 29, and introduced into the machine through the heater 3. The triggering of the steam injection is adjusted for a pressure which can be between 1.5 and 15.10 ³ Pa, depending on the case, the flow rate can be adjusted by a calibrated orifice, or any other equivalent device.

The acceleration of the extraction thus obtained results from the modification the vapor equilibrium regime, and mechanical effects accompanied by overheating thermal margins of azeotropy.

Most of the vapors from 1 and 2 are stopped (about 90%) in condenser 7. The cooling temperature is a function adjusting the regulator 31 supplying the evaporator 19.

The condensate reception capacity 8 is provided with a control to monitor the drying process.

In the device shown, the pump 10 is a ring pump liquid operating in a closed circuit, provided with a fluid separator 12 of the type cyclone cooled by the evaporator 17 supplied from the regulator 32.

A certain amount of solvent is stopped in the separator 12 and will be evacuated at the end of the operation to the decanter 14.

The solvent will ultimately be returned to the storage tanks of machine, not shown here.

The end of drying, visible on observation of the control light of 8, is also recorded at this point and can command the stopping of the injection of steam, then the vacuum pump.

Variable volume capacity 4 was filled during the drying, with the air extracted from 1 in particular, the excess gas from the leaks, for example, can escape through valve 32.

The drying being finished, the opening of the valve 21 between 4 and 1 allows restore atmospheric pressure in the machine and its opening for unloading of clothes, marking the end of the cycle

The sequence of operations which have just been described illustrates a implementation of the process.

Many variants can be used in the context of process.

These operations can be controlled by a programmer allowing different settings according to the specific needs of the user.

A small amount of solvent, less than 100 g per cycle, is retained by the activated carbon adsorber 13. The elimination of the solvent contained in the adsorber can be carried out either at each cycle or only after at least at least 20 cycles following techniques and procedures known to man of the trade and not requiring a specific description.

The process and its implementation which have just been described apply without significant change in the use of different solvents: organic solvents chlorinated, hydrocarbons and their derivatives and possibly aqueous mixtures, which constitutes a considerable advantage of the process of the invention which can function under satisfactory conditions with other solvents of the "hydrocarbon" type, such as undecane, which may well replace chlorinated solvents in the future.

With these solvents, little volatile, it is necessary to deviate from the regime azeotropic to avoid too much vapor consumption, which constitutes another very particular advantage in favor of the process of the present invention.

Of course, the embodiment of the invention as shown in Figure 2 can be modified and be the subject of a number of variants.

As examples of such variants, it is possible, for example, to modify the arrangement of the primary condenser which can, for example, be separated from the filter group, the filter groups can for example be associated and separated from the primary condenser. Such an arrangement is used in the context of the installation shown schematically in Figure 3.

The flexible tank 4 intended for the installation described to be received the gases may be omitted from the installation, insofar as the previous purification of the vapors emitted was sufficient.

Furthermore, although the heat pump device has a significant interest, it is possible that in some cases it is not requested for reasons of simplicity or investment cost.

Thus, FIG. 3 schematically represents an installation for the implementation of a method of the invention which does not incorporate the flexible tank 4 of the installation shown in Figure 2 but which could well be completed on if necessary by such a device, but which, above all, for reasons of economy investment, works without heat pump.

Thus, the machine shown in Figure 3 stands out essentially that of FIG. 2, by the fact that the heat pump has been replaced by a low pressure steam generator (15) and a water cooling (33) which operate independently.

Thus, on the device of FIG. 3, the low pressure steam generator (15) can be heated electrically or by a heating coil supplied by a conventional steam generator operating at a pressure between 4.10 ⁵ Pa and 8.10 ⁵ Pa and preferably from 5 to 6.10 ⁵ Pa.

This low pressure generator can deliver steam directly of superheated water at a temperature between 80 and 150 ° C. Overheating can also be performed independently.

The low pressure generator can also supply the necessary hot water heating the machine to a temperature between 40 and 75 ° C, or this can be heated independently.

The low pressure steam generator supplies superheated steam at a pressure between 0.8.10 ⁴ Pa and 8.10 ⁴ Pa, and preferably at a pressure of the order of 5.10 ⁴ Pa.

The water cooling (33) is a conventional device comprising a refrigeration unit capable of supplying cooling water to a temperature between 4 and 12 ° C for example.

Figure 3, representative of such a machine, differs essentially of that shown in Figure 2, comprising a heat pump in that the latter is replaced by the low pressure steam generator (15) and the water cooler (33) which operate independently. This is why same reference numbers have been given there to represent the same devices.

EXAMPLE

We used a machine as shown in Figure 3 equipped a rotary drum with a capacity of 400 liters to clean 20 kg of clothes with a commercial solvent, based on undecane, sold by the company Shell under the ACTEL brand, with the following results:

The clothes were first cleaned in a washing phase simple with a circulating solvent, constantly filtered. Duration of the operation: 11 minutes.

The washing was followed by a mechanical spin at 450 rpm for 4 minutes, leaving between 4.2 and 4.5 kg of solvent in the clothes.

Then the drying operation was started by simultaneously putting running the vacuum pump (10), heating the machine from the boiler (15) and the water cooling device (33, 17 and 19).

The steam injection was triggered when the residual pressure in the machine was below 1.5.10 ⁴ Pa.

After 14 minutes, the drying operation was complete and the atmospheric pressure restored inside the machine, allowing opening from the door and removing the load of clothing.

The solvent concentration inside the machine, at the opening, was well below current standards, currently 300 ppm in Germany and the United States in particular.

These particular conditions of operation, evacuation and sweeping by water vapor, ensuring total safety conditions. Indeed, the atmosphere of the machine is constantly outside the ignition and explosion limits.

The total duration of the cleaning cycle was around 30 minutes.

A similar cleaning operation, with conventional machines using the same solvent, requires a preliminary gas-firing phase inert and the total cycle time is around 50 minutes.

Claims (16)

1. Method of cleaning in a liquid medium fabrics or clothes, comprising a vacuum drying step carried out at a pressure between 1.5x10³ and 15x10³ Pa in the presence of steam adapted to serve as a carrier for elimination of said liquid and injected into the drying enclosure, characterized in that said steam is injected as soon as the vacuum reaches a value between 1.5 and 15x10³ Pa from a source at a pressure between 0.8x10⁴ and 8x10⁴ Pa.
2. Method according to claim 1 characterised in that said drying step is carried out at a temperature between 30 and 55°C.
3. Method according to claim 1 or claim 2 characterised in that the wall of the enclosure in which the drying is carried out is heated to a temperature between 40 and 75°C during this drying step.
4. Method according to any one of claims 1 to 3 characterised in that said steam is superheated to a temperature between 80 and 150°C before it is injected.
5. Method according to any one of claims 1 to 4 characterised in that it uses a temperature difference of between 50 and 60°C between the hot parts and the cold parts of the complete cleaning plant.
6. Method according to any one of claims 1 to 5 characterised in that the drying step is carried out in a bivariant system enabling for a given pressure the choice of the temperature and the proportion of steam injected during said drying step.
7. Method according to any one of claims 1 to 6 characterised in that said liquid medium is an organic solvent.
8. Method according to claim 7 characterised in that said organic solvent is a chlorinated solvent, preferably perchlorethylene.
9. Method according to claim 7 characterised in that said solvent is a hydrocarbon, for example a C₈ through C₁₂ saturated or unsaturated hydrocarbon, such as undecane, or a derivative of such hydrocarbons such as an ester or an alcohol, mixed or not with water and adapted to be used for cleaning.
10. Plant for implementing the method claimed in any one of claims 1 to 9 including a sealed drying enclosure (1) comprising a rotary drum (2) and means for establishing a vacuum of between 1.5x10³ and 15x10³ Pa in said enclosure during the drying step and means for supplying and injecting steam into said enclosure, characterised by means for supplying and injecting steam from a source at a pressure between 0.8x10⁴ and 8x10⁴ Pa as soon as the vacuum reaches a value between 1.5 and 15x10³ Pa.
11. Plant according to claim 10 characterised in that said means for establishing said vacuum comprise a water ring vacuum pump (10) operating in a closed circuit and an air injector (11) disposed on the suction device of said vacuum pump.
12. Plant according to claim 10 or claim 11 characterised in that said rotary drum (2) is provided with a heating device.
13. Plant according to any one of claims 10 to 12 characterised in that it comprises means (3) for superheating low-pressure steam before it is introduced into the drum.
14. Plant according to any one of claims 10 to 13 characterised in that the heating and cooling means are provided by a heat pump system.
15. Plant according to claim 14 characterised in that the heat pump system comprises :

    a compressor (18),

    a heat generator (15), and

    cooling devices (17, 19).
16. Plant according to claim 15 characterised in that said heat generator (15) supplies :

    low-pressure steam that is heated by the heater (3) before it is injected into the machine (1) and,

    hot water circulated by the pump (20) in a circuit for heating the surface of the drum (2).

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