EP0767267B1 - Method and device for dry cleaning textiles - Google Patents

Description

The invention relates to a method for dry cleaning Textiles washed with solvents and with warm air be dried, the solvent after condensation is recovered.

The invention relates to such a device with washing and Dryer drum, condenser for the solvent, one Heating and a warm air supply for drying, washing and Drying in one and the same machine, but alternatively also in two separate machines.

Textile cleaning systems (dry cleaning systems) for Hydrocarbon solvent (KWL), i.e. as far as possible win aromatic-free solvents from the group of alkanes with the ban on CFCs and the drastically decreasing public acceptance of per (tetrachlorethylene) increasing Meaning. The flash point of these is above 55 ° C.

Textile cleaning systems work in a closed system and ensure in addition to the actual cleaning at the same time Drying of the goods with simultaneous recovery by Condensation and regeneration (distillation, adsorption) of the used solvent.

With the use of the combustible KWL with its low Steam pressures and high boiling ranges resulted in new ones Requirements regarding optimal conditions from the point of view of the Fire protection, drying times, energy use and Ecology to the drying process.

Drying in textile cleaning systems is done by a large Number of changing conditions influenced: these are the type of goods and quantity, as well as after spinning in the goods remaining amount of residual solvent, the physical Properties of the solvent used, the supplied Thermal energy, the volume flow of the circulating air. These conditions change from one batch to another.

• Übertrocknungen der Ware durch zu lange Trocknungszeiten mit der Folge möglicher Warenschädigungen, überhöhter Einergieverbräuche und verminderter Maschinenkapazität,
• unzureichernder Trockungseffekt durch zu kurze Trocknungszeiten mit der Folge, daß die Ware ungenügend getrocknet ist, die Restlösemittel zu zusätzlichen Emissionen und unter Umständen bei längeren Kontaktzeiten zu Hautreizungen führen. Diesem Problem kommt aus ökologischer und gesundheitlicher Sicht eine besondere Bedeutung zu, da in der Praxis durch fehlende Meßtechnik und aus wirtschaftlichen Gründen eher eine Unter- als eine Übertrocknung festgestellt werden kann.

Up to now, the drying process has been controlled in dry cleaning plants according to time and ambient air temperature using empirical specifications that the machine operator selects at his discretion. The consequences of this procedure are either

• Overdrying of the goods due to drying times that are too long, resulting in possible damage to the goods, excessive energy consumption and reduced machine capacity,
• Inadequate drying effect due to drying times that are too short, with the result that the goods are not sufficiently dried, the residual solvents lead to additional emissions and, under certain circumstances, lead to skin irritation with longer contact times. From an ecological and health point of view, this problem is of particular importance, since in practice a lack of over-drying rather than over-drying can be determined due to the lack of measuring technology and for economic reasons.

• Verringerung des O₂-Gehaltes in der Trocknerumluft auf deutlich unter 11 %, entweder durch Eindüsen eines Inertgases (z.B. N₂) oder durch Vakuumierung, oder
• Begrenzung der Trocknungstemperatur auf Werte deutlich unterhalb des Flammpunktes.

Furthermore, in the case of flammable solvents, depending on the random conditions, concentrations in the circulating air of the drying system are possible, which can be above the LEL (lower explosion limit). To prevent fires or explosions, primary protection measures of the following types are used:

• Reduction of the O ₂ content in the dryer air to well below 11%, either by injecting an inert gas (eg N ₂ ) or by vacuuming, or
• Limitation of the drying temperature to values well below the flash point.

In the first variant, considerable additional mechanical and energy expenditure is necessary. In the second variant, the drying process is delayed, ie the drying times are extended and the machine capacity is reduced. In both cases, however, the safety-relevant parameters can be measured easily (O ₂ content or temperature).

A third security variant is that the solvent concentration in all phases of the drying process is kept in an uncritical concentration range, ie below the LEL. This could circumvent the technical outlay for reducing the O ₂ content or the disadvantages of reducing the temperature. However, it is a prerequisite that the solvent concentration can be measured continuously and that it can be controlled under all process conditions.

Reliable metrological monitoring of the Solvent concentration at the given during drying However, conditions have so far failed for all those in question Measuring principles (FID, PID, IR, GC) on the partially occurring Condensation in the measuring systems caused by occurring dew point falls. With that, the ongoing processes are neither observed nor influenced - the drying process was necessarily controlled empirically.

In contrast, the invention has for its object to avoid the effort previously considered necessary, such as reducing the O ₂ content in the dryer air or delayed drying or on the other hand condensation in the measuring systems and to propose a particularly inexpensive method.

This is achieved according to the invention in a method of type mentioned in that the temperature of the circulating air before entering the drum and the solvent concentration on Place of highest concentration immediately after leaving the Drum and the temperature of the circulating air immediately after exiting measured from the drum at the highest temperature and the Values are processed in a computer and that the Concentration of the warm air supply, depending on the assignment of concentration as a conductance and temperature along one Characteristic, is controlled.

After a steep climb, according to the invention, a plateau is reached of concentration.

Heat is expediently intermittent in order to rise to to avoid high solvent concentrations.

It turned out to be particularly cheap, and therefore interference from condensation is also avoided if the Sensor is heated.

By switching to the next phase (cool-down phase) waited until the respective maximum concentration around falls below at least 90%.

It is useful to work with an infrared (IR) measuring device for the Concentration directly at the dryer drum exit and used this leads to a continuous, not yet achieved Concentration measurement and that until the end of drying.

A fuzzy logic controller has proven to be particularly useful for this.
This results in a conductivity-controlled drying, intended for KWL cleaning systems. A transfer to Per systems is of course possible, whereby the safety aspect (risk of explosion) and the related measures can be disregarded.

Reliable measurement technology has therefore been developed and developed solving case and has been adapted continuous concentration measurement throughout Drying process. The influencing factors on the Drying process are examined. The influence of Disruptive factors on drying are examined. Control variables for the drying process are determined. By the measure after the invention it was possible to use suitable software for procedural implementation of the measurement signals in control signals to develop. The measure according to the invention could Solvent concentrations below all scheduled and unscheduled procedural conditions in the range of maximum 75% LEL can be guaranteed.

At the drum exit, in the area of the highest concentration i.e. a measuring device in a modified version (modified e.g. through a heated measuring cell) installed, through the previous occurring condensation phenomena can be safely avoided. Thus, a continuous concentration measurement from the beginning possible until the end of drying. The measured value signals are fed to the machine's internal computer control (PLC). By Self-check functions are automatic Functional check of the IR measuring device. In the programmable logic controller (PLC) are the signals with the help of the determined process engineering Influencing factors processed, and control signals to the Given machine system (for example with regard to Steam supply, control of the blower motor, the drum drive and the door lock, the ventilation flaps, the Valve control of the refrigeration systems etc.).

In contrast to the conventional procedure, it takes over the computer control the optimal setting of the dry and Cool-down times depending on the concentration curve in the drum.

It is known (JP5285297) that when a temperature is exceeded, where the associated saturation concentration is one can reach critical value (exceeding the lower explosion limit), by opening a valve the closed one Air circuit is opened. There is air from the installation room sucked into the machine and after flowing through the drum via the air duct exit into the installation room or outside derived. This will lower the temperature and concentration achieved. However, since only in exceptional cases the saturation concentration is reached, the air cycle is usually also open at uncritical concentrations. With that the Environment polluted with solvent vapors, the drying time unnecessary extended and consumed additional heat and electrical energy.

• Die Konzentrationskurve verläuft deutlich flacher, dafür aber über ein Plateau.
• Bei Erreichen des vorgegebenen Grenzwertes von 70 % UEG wird sofort die Wärmezufuhr gestoppt. Als Folge sinkt die Konzentration wieder.
• Die Wärmezufuhr wird so lange aufrechterhalten, wie ein deutliches Absinken der Konzentration bis zu einem vorgegebenen Schwellenwert feststellbar ist.
• Unter Nutzung der im Trockner noch vorhandenen latenten Wärme erfolgt in der Cool-Down-Phase ein weiteres Absenken der Konzentration. Nach Unterschreiten der 10 % Grenze der UEG wird der Cool-Down beendet und der Ausblasprozeß eingeleitet.
• Trotz deutlicher Verringerung der Konzentrationsspitze verringert sich die Gesamtdauer des Trocknungsprozesses bis zu 25 %.

The following effects are achieved:

• The concentration curve is significantly flatter, but on a plateau.
• When the specified limit of 70% LEL is reached, the heat supply is stopped immediately. As a result, the concentration drops again.
• The heat supply is maintained as long as a significant drop in the concentration up to a predetermined threshold value can be determined.
• Using the latent heat still present in the dryer, the concentration is reduced further in the cool-down phase. After falling below the 10% limit of the LEL, the cool-down is ended and the blow-out process is initiated.
• Despite a significant reduction in the peak concentration, the overall duration of the drying process is reduced by up to 25%.

• Ein Wegfall der für die Sicherheit notwendigen Inertisierung bzw. Vakuumierung, damit Kosteneinsparung und Erhöhung der Zuverlässigkeit in der Anwendung.
• Eine optimale Trockenzeit unter den unterschiedlichsten Bedingungen. Damit kann im Durchschnitt die Trockenzeit um 20 % verringert werden. Die Kapazität der Textilreinigungsanlage erhöht sich dementsprechend um 20 %.
• Eine Vermeidung von Wärmeverlusten durch Übertrocknung. Aus der Summe der Trockenzeitverringerung, der Wärmeeinsparung und des Wegfalls der überwiegend angewandten Inertisierung resultiert eine Energieeinsparung von ca. 160 Wh/kg getrockneter Ware (ca. 40 %).
• Untertrocknungen der Ware und damit verbundene Lösemittelemissionen an die Umwelt sowie gesundheitliche Risiken werden sicher vermieden. Dieser Vorteil ist nicht qualifizierbar, hat aber aus ökologischen und gesundheitlichen Gründen eine besondere Bedeutung.

The result is:

• Eliminating the inerting or vacuuming required for safety, thus saving costs and increasing reliability in use.
• An optimal drying time under the most varied conditions. The average drying time can be reduced by 20%. The capacity of the textile cleaning system increases accordingly by 20%.
• Avoiding heat loss through overdrying. The sum of the drying time reduction, the heat saving and the elimination of the predominantly used inerting results in an energy saving of approx. 160 Wh / kg of dried goods (approx. 40%).
• Underdrying of the goods and the associated solvent emissions to the environment as well as health risks are safely avoided. This advantage cannot be qualified, but is of particular importance for ecological and health reasons.

In the European guidelines there are 350 ppm as a residual value allowed. According to the invention, this limit is increased by 99% undershot.

The transition from the cool-down phase to the blow-out phase takes place when the difference in the decrease in concentration over time after the plateau first flat and then very flat, one certain very low value reached.

With the fuzzy logic an ideal drying curve is determined, the computer with fuzzy logic then sets a temperature and Concentration comparison and controls you Concentration course over time, the influencing factors such as overloaded, underloaded drums, heavier textiles where the solvents are more difficult to escape, lighter textiles, where this is easier to do. After the control one has determined certain course of concentration is at this concentration curve has a certain conductance as Function of the concentration curve and the temperature calculated. The important thing here is that since it is non-polar media electrical measurements are not possible.

Fig. 1 ein Funktionsschema der Trocknung ohne die erfindungsgemäße Leitwertsteuerung zeigt;

Fig. 2 zeigt ein ähnliches Funktionsschema der Trocknung jedoch mit der erfindungsgemäßen Leitwertsteuerung.

For example, embodiments of the invention will now be explained in more detail with reference to the accompanying drawings, in which

1 shows a functional diagram of drying without the conductance control according to the invention;

2 shows a similar functional diagram of drying, however, with the conductance control according to the invention.

After completing the cleaning process, pumping out the free Liquor from the drum and the subsequent centrifugation the actual drying process begins (phase I). Depending on The type and sensitivity of goods becomes the permissible in the program Maximum temperature of the circulating air during drying, the drying time, the temperature of the cool-down phase (phase II) and the time for blowing out (phase III) deposited.

The preheated in the preheater 6 and in the heating register 7 on the Set temperature of heated air flows through the outside and Inner drum 1, 2 and takes solvent from it cleaned goods. Coming from the outer drum 1, the flows solvent-containing air first through a fluff filter 3, in which the fiber debris is filtered off, from there into the Solvent capacitor 5, in which the on cooled surfaces Solvents and water components are condensed out. The Solvent / water mixture runs through a water separator a solvent tank and stands again for cleaning to disposal. The cooled and discharged air takes in Condenser of the refrigerator, that is the preheater 6, one Part of the heat previously removed is again flowed through then the steam or electrically heated heating register 7 and gets into the drum again. Phase I is after The preselected time automatically ends and the phase II (cool down) initiated. It cannot be determined whether Phase I was too long or too short - the result only becomes apparent after the goods have been unloaded.

In the cool-down process, the goods are in the drum gradually cooled and residual amounts of solvent still present will be eliminated. This is done by supplying heat from the chiller (Preheater) and the steam supply to the heating register is closed. This phase ends when the preselected one Temperature (<50 ° C) is reached. After the cool down phase (Phase III) the blowing out is time-controlled (approx. 1 minute) the dryer. The closed air cycle open, i.e. room air is sucked in and after it has flowed through of the dryer led outside.

eine Temperaturmessung vor Eintritt in die Trommel;

weiterhin erfolgt eine Temperaturmessung nach Austritt aus der Trommel;

schließich gibt es noch eine Luftstromüberwachung nach dem Gebläse;

abhängig von den gemessenen Daten erfolgt eine Ansteuerung der Ausblas- und Frischluftklappe;

es erfolgt eine Ansteuerung des Heizregisters;

eine Ansteuerung der Kälteanlage wird vorgenommen und schließlich geht es noch um die Ansteuerung des Trommelantriebs.

So in the prior art

a temperature measurement before entering the drum;

furthermore a temperature measurement takes place after exiting the drum;

finally there is an air flow monitor after the fan;

depending on the measured data, the discharge and fresh air flap are activated;

the heating register is activated;

The refrigeration system is activated and finally the drum drive is activated.

In Fig. 2 are the essential changes according to the invention lead to the surprising result. Same Parts are identified by the same reference numerals. In both Is essentially the air circulation in the Drying phase specified. Are in the measure after the Invention emerging from the central processor unit Signal processing in the PLC (programmable logic controller Control) signals obtained significantly, so the Control of machine components and process design, especially when measuring, completely different.

A temperature measurement is made before entering the drum. A temperature measurement is made at 19 immediately after exiting the drum;
a concentration measurement 20 is carried out immediately after exiting the drum.
A self-check function of the concentration measuring device is switched on and there is an air flow monitoring after the blower. In order to avoid condensation phenomena that have so far been accepted, the concentration measuring device, in particular its measuring cuvette, is heated. The concentration measuring device arranged directly at the outlet of the drum 1/2 is to be installed in the area of the highest concentration and is designed as a modified infrared (IR) measuring device. For the first time, the concentration measuring device 20 enables continuous concentration measurement from the beginning to the end of drying. Its measured value signals are fed to the machine's internal computer control (PLC of the CPU). Self-check functions automatically check the function of the IR measuring device, thus ensuring safe control and possible shutdown under all conceivable process conditions. The signal processing of the recorded measured value signals takes place in the PLC (five input signals are shown). The control signals are sent to the machine system with the help of the determined process engineering influencing factors.

In contrast to the prior art according to FIG. 1, the Computer control (CPU / PLC) the optimal determination of the drying and cool-down times depending on the course of concentration in drum 1/2, over 20 in association with 19 (Temperature measurement) is determined before.

In the state of the art, it was so that empirically found values and depending on the ability of each Master drying was stopped and driven. Because of the The risk of overheating of the textiles was often accepted taken that there are also residual amounts of solvent in the tissues found.

Claims (21)

1. Method of dry cleaning textiles which are washed with a solvent and dried by hot air, the solvent being recovered after condensation, characterized in that the temperature of the environment air before entry into the drum and the solvent concentration continuously at the place of highest concentration immediately after leaving of the drum and the temperature of the environment immediately after leaving of the drum at the place of highest temperature is measured and the values are processed in a computer and that the concentration of the hot air feed, dependent on the allocation of concentration as a characteristic guide line value (Leitwert) and the temperature are controlled along a characteristic curve.
2. Method according to claim 1, characterized in that from the allocation of temperature and the increase in concentration per unit of time the control value is derived.
3. Method according to either of the preceding claims, characterized in that concentration is controlled in such a way that it remains restricted under all conditions to a maximum value of the LOWER EXPLOSIVE LIMIT, and in particular to a value equal to 75 % of the LOWER EXPLOSIVE LIMIT.
4. Method according to one of the preceding claims, characterized in that drying is conducted to a residual concentration level of 1-2 g/m³.
5. Method according to one of the preceding claims, characterized in that when a maximum is reached during an increase in concentration, the supply of heat is only permitted intermittently.
6. Method according to one of the preceding claims, characterized in that in measuring concentration for avoiding condensation, the measuring sensor is heated.
7. Method according to one of the preceding claims, characterized in that measurements are made directly in the flow of recirculated air.
8. Method according to one of the preceding claims, characterized in that the interaction of temperature and concentration is used to arrive at a point where it is no longer worthwile to introduce heat.
9. Method according to one of the preceding claims, characterized in that the factors which influence the drying process are determined for a given machine and a given solvent and are fed into the computer as known curves to form a reference.
10. Method according to one of the preceding claims, characterized in that a temperature, of 50°C for example, is preset for the cool-down following the drying and when the temperature drops below this level there is an automatic changeover to the venting phase, unless a given concentration level has still not been reached.
11. Method according to one of the preceding claims, characterized in that changeover from the heating phase to the cool-down phase is delayed until the concentration has dropped by at least 90 % below whatever is the figure of maximum concentration.
12. Method according to one of the preceding claims, characterized in that any disturbance in the operation of the concentration measuring technique is being used to interrupt the supply of heat.
13. Method according to one of the preceding claims, characterized in that stored-program signals are used to control the machine system (the supply of steam, the fan motor, the drum drive, the door lock, or ventilation flaps, the valve controls, the cooling systems, and so on) considering the influence values of the processing conditions.
14. Method according to one of the preceding claims, characterized in that the computerised control internal to the machine sets the optimum drying and cool-down times in dependency of the concentration curve in the drum.
15. Method according to one of the preceding claims, characterized in that by making use of the latent heat still present in the dryer, a further drop in concentration is brought about in the cool-down phase, cool-down being brought to an end and the venting process is initiated once concentration has dropped to below a preset limit, and in particular a limit represented by 10 %.
16. Apparatus for cleaning textiles with a chemical solvent, having a washing and drying drum (1; 2), a condenser (5) for the solvent, a heating system (7) and a supply of hot air to the dryer, washing and drying being possible in one and the same machine, characterized by a temperature measuring device in front of the entrance to the drum, an infrared (IR) device (20) immediately after exit from the drum (1/2) for continuously measuring concentration till the end of drying as well as a temperature measuring device (19) in the same region as well as a computer control (SPS) internal to the machine for feeding stored program signals to act as control signals for the supply of heat.
17. Apparatus according to claim 16, characterized in that the measuring container of the concentration measuring device (20) is being heated.
18. Apparatus according to claim 16 or 17, characterized in that the measuring container of the concentration measuring device (20) is directly arranged in the hot air stream at the exit of the drum (1/2).
19. Apparatus according to any of claims 16 to 18, characterized in that the control of drying is performed by a control of the fuzzy logic kind.
20. Apparatus according to any of claims 16 to 19, characterized by designing the IR measuring device (19) to have self-check functions to check its functions automatically.
21. Apparatus according to any of claims 16 to 20, characterized by a stored programmed control (SPS) for signal processing.

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