DE3227558A1 - Process and apparatus for recovery of the solvent in dry-cleaning machines - Google Patents

Abstract

In dry-cleaning machines having a closed circulation for the drying, recovery of the solvent from steam-containing air is initially carried out in a first step in that the solvent/steam/air mixture circulated in the drying is essentially isobarically cooled and the solvent condensing during this, with the likewise condensing water, is led off from the circulation. In a subsequent second step, the mixture is isentropically expanded, in order to further cool the rich steam/air mixture and again to condense solvent and water, which are then likewise led off from the circulation. The lean steam/air mixture obtained is then heated isobarically and further passed through the fabrics to be dried. The apparatus used therefor is provided with a circulation pipe connected to the cleaning drum, in which circulation pipe is arranged a double countercurrent heat exchanger for cooling the rich steam/air mixture and at least one expansion apparatus for expanding the cooled steam/air mixture. Condensate discharges are provided both on the heat exchanger and on the expansion apparatus.

Description

The invention relates to a method and a pre

direction for the recovery of the solvent during the drying process in dry cleaning machines in a closed circuit such that blowing out non-condensed vapors are no longer necessary at the end of the drying process is, as well as a device for performing this method. Furthermore Optionally, vapors that arise outside the machine can also be condensed the cleaned air is then blown out. Furthermore to an amendment and expansion of the use of side (ring) channel compressors, a reliable and quick elimination of solvent and water vapor condensate to ensure.

The solvent used in dry cleaning machines, in particular Perchlorethylene (tetrachlorethylene) may due to legal provisions in the Exhaust air escaping from such machines into the open only in a large amount of 30 ppm. In addition, a certain MAK value is prescribed (MAK Value = maximum permissible workplace concentration). The same applies to others Solvent, with a higher MAK value for fluorinated hydrocarbons is allowed. Should there be any suspicion of carcinogenic properties of the chlorinated hydrocarbons and fluorocarbons harden, however, so is with a further aggravation of these provisions to be expected. Therefore a procedure is needed that is able to go below the previous MAK for solvents.

For the condensation of perchlorethylene is so far after a process proceeded in which the steam mixture goes through the following cycle: The rich Steam airflow is at around 500C from the machine via dust filters from a conveying fan sucked in. This brings him to a water-cooled heat exchanger, whereby through suitable air ducting, solvent and water vapor condensate is eliminated.

The now poorer steam-air flow is then passed over a heating register guided, heated to about 60 ° and directed into the drum for renewed enrichment. These devices are consistently placed on top of the drum, on the one hand around Due to the low pressure of the fans, short distances with as little resistance as possible to achieve, on the other hand because of the shortcomings to be described as possible to achieve a low overall volume of the system.

With water as the coolant and the short heat exchangers used is a good cooling of the air-vapor flow only with relatively low cooling water temperatures and to achieve a low heating of the cooling water. Usually cools down the steam-air flow drops to approx. 300C.

At this temperature the air is saturated with perchlorethylene but still 240 g / m3 (approx. 355 ppm), which is why this steam-air mixture still requires treatment by blowing out with the simultaneous supply of fresh air. Since the amount of solvent blown out depends on the volume of the steam-air mixture, that is blown depends, there is a need for the little one described above Total volume in the system.

This blown out steam-air mixture is currently usually over Activated charcoal filter out. However, there is the difficulty that such filters have only a limited capacity. There are therefore at regular intervals Measures for the regeneration or desorption of such filters are necessary cause considerable expenditure of time, energy and cooling water. Will such If measures are not carried out regularly and conscientiously, compliance is sufficient lower exhaust air values are not guaranteed.

In this process, the cleaned air is released into the open. Because the identified shortcomings of this process and after regeneration using steam When the activated carbon is dried, the formation of mist at the outlet connection of the activated carbon filter a discharge of this air via the roof is usually prescribed.

For all these reasons, a "blowout-free" Machine wanted.

There are recovery systems for the solvent from the exhaust air of dry cleaning machines become known, in which the exhaust air of the machine is guided via a closed ring line, in which a cooling device for Recovery of the solvent by condensation is arranged. It will the exhaust air is passed through a finned cooler, below which the solvent and water-containing condensate collected and separated according to its components will. It has been shown, however, that cooling below OOC is not possible with this is because the finned cooler by the formation of ice from the in the exhaust air Water vapor become clogged. The recovery process is therefore only one Temperature range above OOC feasible. But then there is still so much solvent contained in the exhaust air that the immission protection value of 30 ppm is not guaranteed can be.

If the through channels of this coolness are expanded, there is an icing on the surface However, if you accept it, the efficiency drops again and it increases anyway already considerable cooling demand.

Furthermore, methods are known which are used to reduce the apparatus Work with cold accumulators to reduce the size of the refrigeration units, E.g. with stone beds, which are continuously cooled by compression refrigeration units during the blow-out process (approx. 1/6 of the machine time) as much as possible to be able to absorb large amounts of heat.

It is also useful in the recovery of volatile solvents Already known from moist carrier gases, the solvent vapors through direct To condense cooling with the same liquid solvent from the carrier gas (DE-AS 10 51 247). For this, however, the water vapor must first be used in the known method removed from the carrier gas by absorption with a hygroscopic solution will. Subsequently, the anhydrous solvent vapor with the same, So washed out liquid solvent. Because the known process has two stages includes, it is relatively expensive. Finally, there is also a solvent recovery by condensation with a cooled solvent of the same type as that to be recovered Solvents known (US-PS 1,381,002).

Furthermore, DE-AS 27 01 938 describes a method that works with solvents as cold storage. The air-vapor mixture is thereby through the cooled solvent pressed. Because of the low freezing point of the solvents problems with icing in the cooler can be avoided and it will be avoided a temperature reduction below OOC is possible.

All of these processes have a high outlay in terms of equipment always two different circuits or streams of the air-steam mixture. You can the heat generated when the cold is generated, both because of the low temperature of the draining cooling water, as well as the low temperature of the waste heat from compression refrigeration units, not return directly to the recovery process. Here but always the amount of heat that has to be dissipated when generating cold are significantly above the cooling capacity, these methods are very unfavorable Energy balance.

Furthermore, a method is described in DE-PS 2 308 793, at which compresses and cools the steam-air mixture and then uses a throttle is relaxed. The patented process ties the drying cycle into the Circuit of a cold air machine according to the throttle process. With the throttling process the use of room change work during expansion is dispensed with. The cooling off takes place differently from the behavior of the ideal gas according to the JOULE - THOMSON effect instead of. Because the work of expansion that can be gained increases the efficiency of a cold air machine significantly improved, a throttling process is extremely energy-intensive. In the end this process also dispenses with the use of cold by countercurrent, what on the one hand leads to a higher cooling requirement in the heat exchanger and on the other hand the lowest temperature is higher, because in the ideal case the temperature gradient is in countercurrent can almost be doubled (Carl Linde's process for gas liquefaction).

It should be noted that, according to the known method, a blow-out fres Machine is practically impossible to reach, as a temperature decrease to below OOC is not possible with it. This is because the Joule Thomsen effect as a deviation on the behavior of the ideal gas in the temperature difference not the isentropic Expansion follows, i.e. the temperature decrease is less than with expansion above Turbine. It only approaches the isentropes in the area of large pressure differences.

Cooled according to throttle tests with real gases from Thomsen and Joule For example, air from room temperature only changes by around 1/4 0C per atmosphere pressure drop from (Plank, Handbuch der Kältetechnik I, p. 14).

The known method is therefore mainly used, according to the explanations the cooling of the compressed mixture, which here because of the high pressure with a small volume can be cooled well to separate the condensate. Also won't talked about trying to reach temperatures below OOC, which is exemplary despite the cited high compression of 7 atm because of the unfavorable course of the Joule-Thomson Effect would also not be achievable. The possible temperature drop through expansion above throttle would be only a few ° C.

Such a process with compression above 2 atm is practical the heating of the steam-air mixture above the decomposition temperature (splitting off chlorine gas and hydrochloric acid) the solvent is not possible, which is why for the purpose the Temperaturabeltng only the expansion over the turbine when releasing external work is possible. Compaction using the patented process is therefore not possible be intended for the purpose of lowering the temperature, but must be one others, however, have no apparent reason from the explanations.

According to the invention, the drying process is carried out in the circuit of a cold air machine dynamic process or throttle process involved and - since no cold after is released outside - the amount of cold achieved according to Linde's type of gas liquefaction used to pre-cool the incoming rich Dam # f air mixture.

The method according to the invention is primarily characterized in that that the solvent / steam / air mixture circulated during the drying process is essentially Isobarically cooled and the thereby condensing solvent with the also condensing Water removed from the circuit, then expands isentropically, whereby the rich steam-air mixture cools down further, solvent and water condense and derived from the circuit, the poor steam-air mixture obtained in the Countercurrent to the isobaric cooling direction isobarically heated and by flowing through the textiles to be dried again with solvent vapors and water vapor is enriched.

The isobarically cooled mixture is advantageously isentropic in one Partial vacuum cooled and then to isobaric heating by compression Polytropically to adiabatically heated from the partial vacuum to atmospheric pressure, or that Mixture isothermally to isentropically diluted before isobaric cooling.

Characteristics of the device according to the invention for performing this Process are mainly that the isentropic expansion by throttling and / or # in a turbine, in which the space change work is used, is carried out.

The device according to the invention is a device with one of the Cleaning drum connected ring line in which a double countercurrent heat exchanger is arranged for cooling the rich steam-air mixture, with an external cooling medium duct for the poor steam-air mixture and an internal cooling medium duct for external cooling is provided, as well as the heat exchanger with condensate drainage device for water and solvent is provided, and with at least one expansion device for Relaxation of the cooled steam-air mixture, after or in the relaxation devices further condensate drains are provided.

According to the invention, a throttle valve is used as the expansion device and / or an expansion turbine provided, for the process variant without an initial Compression, a vacuum pump is provided after the expansion device, at the initial compression there is a one or more upstream of the countercurrent heat exchanger multi-stage compressor arranged. The compressor is advantageously externally or countercurrently cooled, an intercooler may be provided.

The mechanically driven units of the invention contraption are advantageously driven together, i.e.

the expansion turbine and the vacuum pump or the expansion turbine and the compressor have a common drive shaft.

These units can be similar to those used by the Exhaust gas turbocharging in motor vehicles is known, however, the compressor turbine unit the energy to be supplied to the cycle by means of an electric motor or other prime mover supplied, i.e. the compressor / turbine unit each has an external drive. A precise adaptation of the turbine construction to the given conditions is required. Relatively small mass flows occur in dry cleaning machines that are to be subjected to a pressure increase. This is the case with turbo machines but only achievable with small impeller diameters and high speeds, so that certain difficulties and requirements related to the gears to be used can occur with the electric drive of the turbine / compressor unit.

The smallest turbine / compressor units currently built in series are passenger car exhaust gas turbochargers that deliver around 2 m3 of air / min at 700C, whereby for a Pressure difference of 0.5 - 1 bar, speeds between 60,000 and 100,000 rev / min -l appear.

In exhaust gas turbochargers, there is a high volume flow difference between Drive side (exhaust gas turbine) and consumer (turbocharger) assumed that from the high Temperature difference between exhaust gas and outlet air results.

This difference is much smaller in a Joule cycle, so that when using conventional turbine compressor units of the exhaust gas turbocharger construction an external drive with the problems mentioned above must be accepted.

The construction of the expansion turbine and compressor together Sitting on a shaft can be improved according to the invention in that it can be used for a Joule cycle without an external drive.

This is achieved according to the invention in that the expansion turbine / compressor unit Provided without drive and the lack of pressure energy on the compressor side is supplied via a separate, directly driven compressor. this has furthermore the advantage that the expansion turbine with respect to the highest possible adiabatic efficiency can be tuned as they are not at by a External drive must run at forced speeds. In this way, conventional Exhaust gas turbochargers are used according to the invention.

Air displacement compressors are advantageous as directly driven second compressors for use, such as in particular rotary piston seal, gas ring (side channel) -Compressor or multistage centrifugal compressor in question. The disadvantage of the bad The efficiency of the air displacer can be due to the relatively low performance Small volume flows are accepted, since the attempt gearboxes in this power range To build for high speeds would certainly be the much more expensive way.

There is one possibility of arranging the second compressor to connect the two compressors in series, preferably the second, Directly driven compressors are used as a second compressor stage in the circuit will.

The second possibility of supplying the differential energy is therein, the compressor, which takes care of this, in the volume flow parallel to the compressor to arrange the turbocharger.

This compressor then does not generate the necessary differential pressure gradient after the first compression stage, but the entire pressure gradient, however only for part of the total volume flow.

Since the poor efficiency of air displacers is primarily reflected in a a greater increase in the compression temperature, i.e. generates heat that is then needed in the process, this energy is not lost, you can even Deliberately control the compression end temperature by using a certain type. For the good efficiency of the cycle it is primarily important that the relaxation energy is optimally converted into temperature gradient via the turbine and the extracted Work from expansion the system is preserved with good efficiency.

This is the case here; it changes in a circular process only the highest temperature due to more energy supplied in the second compressor stage, which - if it can be used - gives the process the same degree of efficiency, like an arrangement with a driven compressor turbine unit. Especially for the process for recovering the solvent in dry cleaning machines the arrangement according to the invention appears, given the prior art, as the most advantageous way to achieve optimal efficiency.

When compressing the mixture from partial vacuum to around atmospheric pressure the second, externally driven compressor is preferably in parallel flow to the with The compressor coupled to the expansion turbine is provided, which means the entire pressure drop generated for part of the volume flow. This is particularly important then if the pressure increase in the compressor of the expansion turbine falls below 400 mbar, because then a turbo machine has a poor efficiency.

If the mixture is compressed before isobaric cooling, it is preferred the compressor coupled to the expansion turbine in the direction of flow of the mixture seen in front of the counterflow heat exchanger and the externally driven compressor after the counterflow heat exchanger is provided, the two compressors thus connected in series. If necessary, it would also be possible to use the two compressors without intermediate cooling to switch the mixture in series; however, there is a very large increase in temperature in Purchase, which may lead to solvent decomposition (perchlorethylene decomposes from 1500C) and is also more stressful on the device.

In principle, it would be desirable to use the steam-air mixture as possible high constant saturation into the system, because only through constant saturation changes in the temperature level can be seen by differently released Avoid condensation heat. However, a constant saturation is with dry cleaning not to be reached, which is why a second cycle dryer - fan - dryer not to achieve a high degree of saturation for finite drying processes would be beneficial.

In the case at hand, the vapor concentration must approach zero, in order to comply with official regulations and to keep the textiles free from odors to keep.

It would not be very economical to use the system for condensation to set up the highest degree of saturation, because this would require a large pressure gradient and / or more cooling and a larger heat exchanger required. Would be economical in other words, to choose a system for a medium degree of saturation. It would be without further measures, however, at the beginning of the drying process, fully saturated steam-air mixture get into the system, its saturation only decreased, but not eliminated could be. So vapors would get into the turbine. That should be the case with turbomachines (Centripetal turbines) don't happen because the heavy vapors are transported through compressor and turbine is associated with increased workload and reduces the efficiency of the centripetal turbine, because condensing particles force outwards against the expansion flow by centrifugal force. That can lead to erosion of the blades, especially at high speeds.

According to the invention, a bypass line can therefore also advantageously be used be provided for the cleaning drum in the drying circuit, in which a throttle is provided and which is opened at the beginning of the drying process, so that a Do not reload part of the poor steam mixture in the drum, but rather to "Dilution" of the rich steam mixture leaving the drum is added to it will. Because of the lower resistance in this short-circuit line, in large part of the current flow through this line. So it can be done by throttling this line the saturation state of the rich steam-air flow can be regulated. He can thereby the efficiency of the cold air machine in terms of condensation adjust. This by-pass line is about halfway through the drying process continuously throttled and then closed, so that the achievable degree of dryness is not influenced by this, it can only extend the drying time somewhat.

If on the other side towards the end of the drying process already there are very few solvent vapors in the circulating air mixture, it is beneficial to to increase the circulation rate.

According to the invention, this can also be done in that one second throttled bypass line is provided, which the expansion turbine bridged so that part of the mixture no longer passes through the expansion turbine flows and thus the flow rate of a compressor is increased.

When compressing the mixture before isobaric cooling and arrangement of the second directly driven compressor between the heat exchanger and the expansion turbine (the turbo compressor is provided in front of the heat exchanger) this second bypass goes Line from upstream of the second compressor to upstream of the re-entry into the heat exchanger and a pressure limiter is preferably provided in this line.

In the arrangement in which the rich mixture without pre-compression is cooled in a partial vacuum and the externally driven second compressor in parallel flow is provided to the compressor coupled to the expansion turbine, this goes second by-pass line from before the expansion turbine inlet to before the inlet of the externally driven compressor and preferably is a suction power limiter for this provided.

The delivery rate of the second, externally driven compressor is increased and in the presence of a Saugleistungsbe limiter this is opened so that the throughput speed through the second compressor increases by approximately constant pressure ratio, while the throughput through expansion turbine and with this coupled compressor and its pressure ratio also approximate same stay.

Due to the higher volume of air conveyed as a result of the second by-pass line On the one hand, heavy, thick fabrics dry better and, on the other hand, they become saturated which towards the end increases the air again, which is almost pure. The one emerging from the turbine In the countercurrent heat exchanger, air can remove the increased amount of poor air-steam mixture nevertheless cool to the same temperature, as the amount of heat to be dissipated is despite Increased air volume due to the lower heat of condensation with lower saturation per unit volume has decreased sharply. As mentioned earlier, it is beneficial and necessary to keep the turbine and the compressor as free of vapors as possible. Because of this, and because of the pressure drop that can be saved by countercurrent flow, the efficiency factor comes into play of the counterflow heat exchanger is of great importance. It should be cheap at the same time and also easy to clean.

It should also be as compact as possible because of the limited space it takes up be built.

According to the invention, a countercurrent heat exchanger is provided which consists of a central corrugated screw tube as well as an inner slide-in tube and an outer one Overtube is made, both of which are cylindrical and attached to the shafts of the corrugated pipe issue. This creates an outer and an inner cylindrical spiral cavity, in which the two media are conducted in countercurrent. The sealing of the two Spiral spaces are created e.g. by two rubber rings, each by two metal rings be squeezed over screws.

The gas streams are supplied and discharged as tangential as possible Support.

It is advantageous to have the push-in tube on the outside and the push-on tube on the inside to be coated with a solvent-resistant elastic pad To prevent overflow of the gas streams and thus that caused by thermal expansion Chafing of the spiral on the extension tubes does not lead to unnecessary wear. How advantageous the heat exchanger according to the invention is can be seen from the following Example.

Average spiral pipe diameter 450 mm, flank depth 100 mm pitch 40 mm This results in an average length of 1.42 m per cycle.

With a total height of 500 mm, a countercurrent length of 17.50 can be achieved m achieve. Finally, this with a flow cross-section of 2,000 mm. is still provided according to the invention, this 3-walled heat exchanger, which also still is insulated outside and inside, as sound insulation for the driven units, especially for the externally driven compressor, but preferably both for this as well as for the expansion turbines / compressors. This is done so that these units are mounted in the cylinder, which is formed by the inner tube will.

Because with the proposed turbines the maximum efficiency for the temperature drop is 85 and the two-stage compression ensures maximum efficiency of 65%, the remaining percent of the energy is converted into heat. Of that a part is discharged to the outside through bearing friction and radiation losses, the rest, however, heats the circulating air. It must therefore be additionally cooled to limit the temperature upwards. Furthermore, stronger cooling has come to an end of the process, on the one hand, to reduce the temperature level and thus also lowering the lowest temperature and, on the other hand, cooling textiles from the To be taken from the cleaning machine. If they are left lying down for a long time, warm textiles tend to to increased creasing.

It is known that the prices for cooling water rise sharply and the For this reason, cooling water-saving control devices developed technically vulnerable are. Air cooling would avoid these disadvantages, but the air in the Usually has a much higher and more fluctuating temperature than water and therefore has so far could not be used as a coolant in dry cleaning machines. It Surprisingly, it was found that air can be used for the simultaneous Cooling of the air flow leading to the machine drum and that of the machine drum coming air flow. This is advantageously done with two double-tube counterflow heat exchangers, their inner tubes to enlarge the transfer area outside with cooling fins can be provided. The cooling air is first in countercurrent to that of the cleaning machine coming line led and then - because of the small temperature difference only slightly heated - further in countercurrent to that leading into the cleaning machine Line led.

In summer the heated air is led outside; in winter can they can be used advantageously for space heating.

The invention is described below on the basis of exemplary embodiments described in more detail with reference to the drawing, in which FIGS. 1 and 2 according to the invention Show devices in the scheme. 3 and 4 show a side channel turbine with condensate drainage in the cutout, Fig. 5 shows a partially sectioned view a device in which the rich vapor-air mixture prior to isobaric cooling is not pre-compressed.

Fig. 1 shows a device according to the invention in which the solvent / steam mixture isentropically cooled to a partial vacuum without prior compression and then cooled the isobaric heating after expansion by compression from the partial vacuum polytropically to adiabatically heated to atmospheric pressure.

The function of the device according to FIG. 1 is as follows: The rich The steam-air mixture is sucked in from the cleaning machine and passed through a dust filter fed to the heat exchanger, where it is outside in countercurrent from the expansion turbine coming poor steam-air flow is cooled and inside counter-current by water is cooled.

Part of the water vapor and solvent vapor condensate falls that is directed to the outside.

The rich steam-air mixture now enters, already considerably cooled the expansion turbine in which more condensate arises, and either afterwards or is already eliminated in the turbine. This is where the lowest temperature is reached.

The poor steam-air mixture, which is now partially under vacuum heats up while releasing cooling power in countercurrent to that coming out of the drum enough steam-air mixture before it enters the vacuum pump in which the poor steam-air mixture to the desired temperature before entering the machine warmed up. Possible cooling if there is too much heating at higher pressure differences threatens.

A single-stage vacuum pump with a single-stage expansion turbine is shown here. Multi-stage vacuum pumps and expansion turbines can also be used, a pair consisting of a turbine and a compressor on a shaft without a motor drive can be arranged in the manner of an exhaust gas turbocharger. There is also the option of parallel or series connection is conceivable for multi-stage processes.

In the method according to the invention, the solvent concentration is thus in the circulating air according to the principle of a modified cold air machine in the dynamic or throttling process by condensation of the solvent vapors by means of cooling at atmospheric pressure and further condensation by expansion into a partial vacuum via a throttle device or a Expansion turbine or in a Combination of both systems reduced to such an extent that without additional devices the legally permissible workplace concentration of solvents is not exceeded will.

The disadvantages of the cold air machine turn out to be for the special one Use case as an advantage. Cold air machines for cold generation according to the dynamic Processes are all the more economical, the lower the pressure ratio and thus also the temperature drop is. For example, the performance figure for the dynamic Procedure = amount of cold with pressure ratio compression work - expansion work 1.5: 1 is still 8.125, while at a pressure ratio of 6: 1 it is only 1.497 (Plank Handbook for Refrigeration Technology, Vol. I, p. Lo). The performance figures of the throttling process always lie - since the expansion work cannot be deducted in the quotient considerably below 1.

On the other hand, require small pressure differences to achieve a large, expensive multi-stage compressors and expansion turbines for certain cooling capacities, which is why they are used for cooling purposes only for special tasks, mostly in areas lowest temperatures, find application.

The disadvantages are not important for the condensation process, because the amount of air moved anyway because of the accumulation in the cleaning drum must be considerable and on the other hand only very small with the countercurrent process Temperature = pressure differences of a maximum of 1: 1.8 are necessary, the still can be produced or recovered economically.

The use of the heat to be dissipated here in a usable temperature range accrues, as well as the better use of the cooling water, increase this economic efficiency.

In addition, due to the controllability of this system and the the tank cooling and tightness the possibility of corresponding structural requirements given, in the same machine type also low-boiling and highly volatile solvents like R 11 (CCl3F) and R 113 (C2C13F3) to be used, while so far completely different Machine types were necessary. It is also possible with an appropriate extension the drying time in machines for perchlorethylene with drying temperatures below 40 ° C to achieve complete recovery of the solvent.

The inventive method in the vacuum range offers considerable Advantages and represents a new process for refrigeration, which is based on the given Requirements is precisely matched.

In general, compression is used to achieve a pressure-temperature gradient. This compression leads to considerable increases in temperature of the gases, which is possible already during the compression (labor saving of the isothermal compared to the adiabatic Compression) have to be cooled down. There is also the heating of the steam-air mixture - as already described - limited upwards.

On the other hand, in the drying cycle when entering the cleaning drum a temperature of approx. 700C (for per chloroethylene) required, as it is at a higher temperature the solvent uptake of the air increases disproportionately. That is why it is an ideal The compressor must be designed as a heat exchanger for the counterflow. Nevertheless the temperature drop that occurs between entry into the cleaning drum is missing approx. 700C and exit from it with approx. 500C due to the evaporation of the solvent (Enrichment) and heat loss occurs. Hence the need for a heating register to install. Because of the countercurrent and the expansion via turbine after this Process with pressure differences EL p 1.2 1 8 that is sufficient These 1 1 pressure differences can also be achieved between negative pressure and atmospheric pressure, e.g. 1 = 1.43 0.7 = 300 mbar vacuum = achieve pressure, e.g. 0.7 1 30% vacuum.

The main advantages of the method according to the invention without precompaction are a) direct use of the heating of the poor steam-air mixture in the vacuum pump, since it is blown directly into the drum, so that heating is desired; b) none The steam-air mixture is heated between the exit from the drum and the entry into the expansion turbine; c) the greatest advantage is the use of the pressure drop with condensation. Depending on the degree of saturation and temperature, condensation occurs a pressure drop of up to 0.4 bar.

This can be done here as with steam turbines, where you can also use cooling The exhaust steam from the engine, which is just before condensation, has a higher pressure gradient makes available and thus a better degree of efficiency can be used. This pressure drop leads to a gain in the process without initial compression of the vacuum or saving of drive power, while at the initial compression this pressure drop must be compensated for by higher compression work. the Expansion according to the latter process to atmospheric pressure is not possible the use of the negative pressure. The advantage of the procedure without initial compaction the compression work can correspond to 0.4-0.6 bar overpressure.

d) Complete elimination of the heating register. Seems to be particularly advantageous this process for tumble dryers in the circulating air process, where because of the high temperatures the partial pressure of the water vapor is particularly high and a correspondingly favorable one Pressure difference results.

For example, the pressure difference between saturated air is from 900C when cooling to 450C = 0.8 bar.

In Fig. 2, a device according to the invention is shown in which the Solvent / steam mixture before isobaric cooling isothermal to isentropic is compressed. The function of the device according to Fig. 2 is as follows: That A rich mixture of steam and air is sucked in from the cleaning machine and and lint filter fed to the compressor. This compression is in two stages here shown with intercooling. The rich vapor-air mixture comes from the compressor in a heat exchanger which is cooled from the outside in countercurrent by water. The rich steam-air mixture is now strong for so long and so at constant pressure cooled in countercurrent until the desired temperature is reached in front of the expansion turbine will. This temperature can be controlled through the use of cooling water in the Enters the counterflow near the expansion tuxline and exits at the compressors, heating up to approximately the boiling temperature of the water can be permitted. This fully utilizes the cooling potential of the water. In this counterflow cooler Most of the vapors that are discharged via steam traps are already condensing will. The steam-air mixture is now used in the The turbine is brought to expansion, with the condensate already accumulating in the turbine and must be derived. If this does not happen, the turbine must be able to to convey the condensate. The expanded cold steam-air mixture is now in the Countercurrent insulated to the outside, inside with delivery of cooling capacity to the compressed rich steam-air stream is heated, so that the countercurrent is also the case Compression can absorb the heat generated by the casing. Before re-entering the cleaning machine will the poor steam-air mixture is still externally heated. The amount of this warming depends on the Efficiency of the heat exchanger.

Compared to cold storage systems, this process has in addition to waste heat recovery and the low expenditure on equipment the advantage of being always ready for use, i.e. it should turn out when opening the loading door after the drying process has ended, that the drying process e.g. due to the failure of the mostly sensitive dryness control device or incomplete due to the nature of the textiles (quilts, curtains) can be re-dried at any time without having to wait a long time for the cold store is capable of receiving again.

The compressor can be externally and / or countercurrently cooled as required be.

In this process variant, the solvent concentration is thus in the circulating air according to the principle of the cold air machine in the dynamic process Condensation in the compressed cooling phase and further condensation in the subsequent expansion turbine reduced so far that without additional devices the legally permissible workplace concentrations of the solvents are not exceeded will.

In side channel compressors and turbines, the gas enters the foot of the impeller enters the guide vane and is outwards due to the centrifugal effect the guide vanes pressed into the annular channel, where it is deflected and at the foot of the Impeller re-enters the guide vane.

The compression or expansion process is divided into one Variety of stages between which the gas in the ring channel = deflection device a is subject to large centrifugal acceleration and discharges heavy gas components can be. This prevents condensation, especially in the event of condensation Droplets enter the impeller / and cause malfunctions there. When expanding for the purpose The condensation is also prevented from forming condensate due to friction heated again on the impeller and evaporated, which would also be disadvantageous because a the largest possible proportion of condensate by creating a vacuum the efficiency of the Turbine increased.

In DE-PS 1 001 237 a method is described in which in multi-stage Expansion in steam turbines through an annular channel in the guide body that forms condensate is derived. However, this patent was for a different type of turbomachine granted. For side channel blowers, it is true that they have not been used as a turbine so far because of the small pressure differences they can handle and the relative poor efficiency. Since in the present case, the separation of substances has priority has before the efficiency as a turbine, is a side channel turbine according to Fig. 3 and 4 in the present case particularly well suited for the formation and drainage of condensate.

It can be seen that there is an annular groove in the side wall of the annular channel with corresponding condensate drainage openings are provided.

The drying device according to Fig. 5 (the cleaning drum is not shown) consists of a turbo compressor unit with turbine 1 and compressor 2. The energy is supplied via a pressure gradient generated by an air displacer 3, here a rotary piston compressor which is driven by an electric motor 4. These devices are mounted on a frame structure 5. Via this frame structure the counterflow heat exchanger is turned upside down.

It consists of the spiral tube 6, the outer tube 7, the inner tube 8, the elastic coatings 9, the sealing rings 10 and two outlet ports 11 and two inlet ports 12. The lower end of the heat exchanger is designed as a solvent and water separator 13. the end In the lower part, the solvent flows into a tank 14, from the upper part the separated water flows into the drain 15. After the turbine the discharged water Condensate collects in the lower part of the inner spiral 16 and is after termination of the drying process is drained into the separator via a solenoid valve 17. Of the The cold part of the apparatus is separated from the warm part by an insulating layer 18. the The line from the cleaning drum 19 is connected to the line to the cleaning drum 20 connected by a first by-pass 21. This by-pass has a throttle valve 22. The second by-pass 23 from "before turbine" to "after compression stage 1" has a magnetic valve 24 and a suction limiter 25. The line to the cleaning drum and the line silencers 26 are provided from the cleaning drum. Both lines will air-cooled with two double-tube countercurrent heat exchangers 27 via a conveying fan 28.

The upper connections of the heat exchanger 29 are releasable, rigid connections. The lower connections 30 and the drains of the separator 31 are detachable and flexible. The heat exchanger is insulated 32 on the outside and inside, it sits on an insulated Platform 33 and is closed with an insulated cover 34. The ventilation the unit room is carried out by convection through slots in the base and cover.

The function of this device is as follows: The one from the machine central station incoming rich steam airflow enters the counterflow air cooler at A, exits which it exits cooled at B and into the outer spiral of the spiral tube heat exchanger which he leaves at C. Solvent and water are in this spiral Almost completely separated, the water partly as a layer of ice, the limit of which increases with increasing The drying process moves from bottom to top. From C the now poorer arrives Steam air flow in the expansion turbine 1 in and after, depending on the degree further condensate or ice crystals accumulate after D and re-enter the heat exchanger a. Now the poor steam-air flow warms up at the richest with cooling capacity Steam-air flow and leaves the inner coil of the heat exchanger at E. It arrives into the compressor of the turbo loaders 2 where he's of work performance the turbine is compressed accordingly. At F it exits with higher pressure and in the second compression stage, here a rotary piston blower, the poor Steam-air flow compressed to around atmospheric pressure. The warm, poor steam-air mixture enters the countercurrent air cooler at G and leaves it at H, which affects the maximum permissible drum inlet temperature has cooled down and then reaches it again to the inlet of the machine drum.

The operating behavior of the described with reference to FIG Apparatus results from those obtained in the following three operating phases real temperatures and real pressure differences for positions A to H the device specifies: Operating phase 1: In the first half of the drying process, however, after reaching a temperature of 600C in the cleaning drum. By-pass line 1 in operation.

Air cooler on level 1.

0 position pressure bar temperature OC A 0.965 + 50 B 0.97 + 40 C 0.95 0 D 0.61 - 5 E 0.6 + 35 F 0.75 + 60 G 1.05 +100 H 1.025 + 70 Operating phase 2: In the second half of the drying process by-pass line 2 in operation. Air cooler at level 1.

Position pressure bar temperature OC A 0.965 + 50 B 0.97 + 40 C 0.95 0 D 0.61 - 5 E 0.6 + 35 F 0.75 + 60 G 1.05 + 85 H 1.025 + 60 Between F and G mixes 600 with OOC air from by-pass 2, so that at G and in the sequence at H the temperature drops, which is desirable because there is no longer so much heat of evaporation is consumed to give 500C at A.

Operating phase 3: In the cooling and air cleaning phase shortly before End of the drying process. By-pass line 2 in operation, air cooler on stage 2.

Position pressure bar temperature OC A 0.965 + 40 B 0.97 + 35 C 0.95 - 5 D 0.61 - 10 E 0.6 + 30 F 0.75 + 55 G 1.05 + 80 H 1.025 + 40 in the air cooler is cooled by increasing the amount of cooling air to 35 or 400. A temperature drop no longer takes place in the machine.

The inventive method can also be applied so that it is used for air purification in chemical or industrial processes in which solvent-based Air is sucked off at the point of origin and one before blowing out into the open air Is subjected to cleaning, such that the described cycle is opened so that the drum outlet, the suction opening and the drum inlet the exhaust opening enters the open air. An activated carbon filter can be used as a final separator be provided.

A disadvantage of the closed loop systems described above is in itself the fact that residual vapors may remain in the drum, such as the dried ones Put it through well and get into the air when the loading door is opened. This can be prevented in a device according to the invention that upon opening the drum, the compressor or the vacuum pump starts up and the cooling is activated will. The cleaned air mixture does not get back into the drum, Instead, it is released into the open through a valve - possibly via an activated carbon filter diverted, i.e. the circuit is opened.

For the same purpose, namely that the remaining when the machine is at a standstill Solvent vapors cannot get into the cleaning drum, dry cleaning systems, in particular the device according to the invention, are modified so that the dust filter, the conveying device, the cooling register and the heating register are either at a lower level are arranged as the suction opening and return opening of the drum, or else that said components are connected to the drum via a siphon.

Finally, a suction system can be installed in the immediate vicinity of the device Occurring solvent vapors be provided, with the extracted air in front the dust filter is fed into the circuit via a valve.

The devices according to the invention can also advantageously be used in so-called condensation tumble dryers.

Method and device for recovering the solvent in Dry cleaning machines priority of the Austrian note A 3280/81 of July 24, 1981 and the Austrian note A 342/82 of January 29, 1982 List of Reference Numbers 1 - Turbine 2 - Compressor 3 - Air displacer 4 - Electric motor 5 - Frame construction 6 - Spiral tube 7 - outer sleeve 8 - inner sleeve 9 - coatings 10 - sealing rings 11 - Outlet Connections 12 - Inlet Connections 13 - Solvent and Water Traps 14 - tank 15 - drain 16 - inner spiral 17 - solenoid valve 18 - insulating layer 19, 20 - cleaning drum 21 - by-pass 22 - throttle valve 23 - by-pass 24 - solenoid valve 25 - suction limiter 26 - silencer 27 - double pipe counterflow heat exchanger 28 - conveyor fan 29, 30 - connections 31 - separator 32 - insulation inside and outside 33 - platform 34 - cover

Claims (22)

Method and device for recovering the solvent in Dry cleaning machines priority of the Austrian note A 3280/81 of July 24, 1981 and the Austrian registration A 342/82 of January 29, 1982 patent claims 1.) Process for the recovery of the solvent from air containing water vapor in dry cleaning machines, in which the drying takes place in a closed circuit, characterized in that, that the solvent-steam-air mixture circulated during the drying process is essentially Isobarically cooled and the thereby condensing solvent with the also condensing Water removed from the circuit, then expands isentropically, whereby the rich steam-air mixture cools further, solvent and water condense and derived from the circuit, the poor steam-air mixture obtained in the Countercurrent to the isobaric cooling direction isobarically heated and through flow of the textiles to be dried again Solvent fumes and water vapors is enriched. 2.) The method according to claim 1, characterized in that the isobaric cooled mixture isentropically cooled in a partial vacuum and then to the Isobaric heating by compression from the partial vacuum to atmospheric pressure is polytropic until it is heated adiabatically. 3.) The method according to claim 1, characterized in that the mixture before isobaric cooling is isothermal to isentropic compression. 4.) Method according to one of claims 1 to 3, characterized in that that the isentropic expansion by throttling and / or in a turbine in which the Room change work is used. 5.) Device for performing the method according to claim 1 with a ring line connected to the cleaning drum, in which a double countercurrent heat exchanger is arranged for cooling the rich steam-air mixture, with an external cooling medium duct for the poor steam-air mixture and an internal cooling medium duct for external cooling is provided, as well as the heat exchanger with condensate drainage device for water and solution is provided means, and with at least one expansion device for Relaxation of the cooled Steam-air mixture, after or Further condensate drains are provided in the expansion devices. 6.) Device according to claim 5, characterized in that as Expansion device provided a throttle valve and / or an expansion turbine is. 7.) Device according to claim 6, characterized in that the expansion turbine a side channel turbine with condensate drainage is provided. 8.) Device according to claim 5, characterized in that then a vacuum pump is provided on the expansion device. 9.) Device according to claim 5, characterized in that before A single or multi-stage compressor is arranged next to the counterflow heat exchanger is. 10.) Device according to claim 9, characterized in that the Compressor is provided externally and / or countercurrently cooled, where appropriate an intercooler is provided. 11.) Device according to one of claims 5 to 10, characterized in that that a common drive is provided for the mechanically driven units is. 12.) Device according to one of claims 5 to 10, characterized in that that the expansion turbine / compressor unit without external drive and at least one further externally driven compressor is provided. 13.) Device according to claim 12, characterized in that the externally driven compressors as air displacers, in particular rotary piston compressors, is trained. 14.) Device according to claim 12 or 13, characterized in that that when the mixture is compressed from the partial vacuum to about atmospheric pressure, the externally driven Compressor in parallel flow to the compressor coupled to the expansion turbine is provided. 15.) Device according to claim 12 or 13, characterized in that that when the mixture is compressed before the isobaric cooling with the expansion turbine Coupled compressors, seen in the direction of flow aszGemisches, upstream of the counterflow heat exchanger and the externally driven compressor is provided after the counterflow heat exchanger. 16.) Device according to one of claims 12 to 15, characterized in that that in the drying circuit a by-pass line to bypass the machine drum is provided. 17.) Device according to one of claims 12 to 16, characterized in that that in the drying circuit a by-pass line to bypass the expansion turbine is provided. 18.) Device according to one of claims 12 to 17, characterized in that that the counterflow heat exchanger in the form of a screw corrugated pipe with inside and outside arranged cylinder tube is formed. 19.) Apparatus according to claim 18, characterized in that the Outer surface of the cylindrical inner tube and the inner surface of the cylindrical outer tube are provided with an elastic coating. 20.) Device according to claim 18 or 19, characterized in that that the externally driven compressor, preferably together with the expansion turbine / compressor unit, is provided in the free interior of the counterflow heat exchanger. 21.) Device according to one of claims 18 to 20, characterized in that that the countercurrent heat exchanger is arranged upright and preferably in its lower section is provided at least one condensate drain. 22.) Device according to one of claims 12 to 21, characterized in that that for simultaneous cooling of the rich gas mixture coming from the cleaning drum and a countercurrent air cooler is provided for the recycled, purified gas.