IT8222565A1 - PROCEDURE AND EQUIPMENT FOR THE RECOVERY OF SOLVENTS IN DRY CLEANING MACHINES - Google Patents

Description

Description of the invention entitled:

PROCEDURE AND EQUIPMENT FOR THE RECOVERY OF SOLVENTS IN DRY CLEANING MACHINES.

SUMMARY

Process for the recovery of the solvent of the vapor content air in dry cleaning machines, where the drying takes place in a closed circuit characterized by the fact that the vapor-air mixture of the solvent circulated is cooled in a predominantly isobaric way and that the solvent what so? it condenses is discharged from the circuit together with the water what is it? well it condenses, then made to expand in an isentropic way so that? the rich vapor-air mixture cools down further, the solvent and water condense and are discharged from the circuit, the resulting lean vapor-air mixture is heated isobaric in countercurrent to the isobaric cooling direction and enriched again of solvent and water vapors through the passage of the fabrics to be dried.

PROCEDURE AND EQUIPMENT FOR THE RECOVERY OF SOLVENTS IN DRY CLEANING MACHINES

The invention relates to a process and an apparatus for the recovery of solvents during the drying operations in dry cleaning machines, in a closed circuit, so? that is not more? it is necessary, at the end of the drying operations, the discharge of non-condensed vapors, as well as? to an apparatus for carrying out this procedure. Furthermore, the vapors that develop outside the machine can also be condensed as required, in which case clean air would be expelled. Ipfine refers to a modification and expansion of the possibility? of use of channel capacitors la-I

(annular) which can guarantee a perfect and rapid separation of the condensate of solvents and water vapors.

The solvent used in dry cleaning machines, in particular perchlorethylene (tetrachlorethylene), according to the current provisions of the law can? be contained only to the extent of 30 ppm in the stale air discharged from such machines.

Furthermore ? a specific MAK value is prescribed (MAK value = maximum concentration allowed in the workplace). Similar provisions also apply to other solvents where a slightly higher MAK value is allowed. high of fluorinated hydrocarbons. However, if the opinion about the qualities is confirmed? carcinogens of chlorinated and fluorinated hydrocarbons, greater severity is to be expected? of these provisions.

For this reason, a process is necessary which is capable of falling below the current MAK values relating to the solvents.

For the condensate of perchlorethylene there is currently a process according to which the vapor mixture flows in the following circuit:

the rich air-vapor stream is drawn in at about 50 ° C from the machine through a dust filter of a fan. This leads it to a water-cooled heat exchanger where, through an appropriate air supply, the condensate of solvent and water vapor is separated.

Subsequently, the now depleted air-steam current is conveyed to a thermal register, heated to about 60 ° C and sent to a drum for the new enrichment. These devices are placed along the path on the top of the drum; on the one hand to get short routes with resistance the pi? possible reduced due to the limited compression of the fans and on the other hand to obtain a total volume of the system as much? possible reduced due to the drawbacks that have yet to be described.

With the use of water as a cooling medium and the heat exchangers used, can? good cooling of the air-steam stream can only be achieved with relatively low cooling water temperatures and slight heating of the cooling water. As a rule, the? air-vapor current cools down to about 30 ° C. At this temperature, however, the saturation of the air with perchlorethylene reaches 240 g / m (about 355 ppm), so that this mixture of steam and air still requires treatment through the exhaust with the simultaneous supply of fresh air. Since? the quantity? of the discharged solvents depends on the volume of the mixture of vapor and air that is discharged, ci? explains the need ^ sit? described above to have a reduced total volume of the system.

This mixture of vapor and discharged air is usually currently conveyed to an activated carbon filter. Here also arises the difficulty? that such filters have a-capacity? limited reception. Consequently, regeneration or adsorption interventions of those filters are necessary at regular time intervals, which cause considerable consumption of time, energy and chilled water. If these interventions were not carried out regularly and in a workmanlike manner, the maintenance of sufficiently low exhaust air values would not be guaranteed. The purified air is discharged to the outside with this procedure. Due to the drawbacks reported by this process and the formation of fog, resulting after regeneration by water vapor in the drying of the activated carbon, on the discharge nozzle of the activated carbon filter, it is generally provided to let this air out through the roof. For all these reasons, a machine that is possibly "free from drains" is sought.

Plants are known for the recovery of exhaust solvents from dry cleaning machines in which the exhaust air of the machine is conveyed into a closed annular duct, in which there is a cooling equipment for the recovery of solvents by condensation. .

In this way the drain is passed through a finned cooler under which the condensate containing solvents and water is collected and divided into its components.

However ? been shown that in this way not? possible to obtain a cooling below 0? C since? the lamella cooler is blocked by the formation of ice resulting from the water vapor contained in the drain. The recovery process? therefore only possible at a temperature above 0 ° C. Thus for? in the drain is still such a quantity? of solvent 'that can not? guarantee the safety emission value of 30 ppm.

If the flow channels of this cooler were widened to take into account the congestion, would the degree of effectiveness drop again? would increase the gi? considerable need for cold.

Furthermore, some processes are known which aim at reducing the expenditure of the equipment and at the downsizing of the cold group through cold accumulators, such as, for example, mineral beds that are continuously cooled with compressed cooling groups in order to be able to withdraw a quantity of water. heat the most? possible eie vata during the unloading process (about 1/6 of the machine time).

It is also already? It is known how to be able to condense the vapors of the solvents with direct cooling with the same liquid solvents coming from the transport gas, during the recovery phase of the volatile solvents of the humid transport gases (DE-AS 10 51 247).

Also in the known procedure it is necessary for? remove the water vapor of the carrier gas by absorption with a solution with a hygroscopic effect. Subsequently, the water-free solvent vapor is washed off with the same fluid solvent. Since? the known procedure includes two steps, it? relatively expensive. Finally, a type of solvent recovery is also known by condensation with a cooled solvent equal to the solvent obtained with the recovery (US-PS 1 381 002).

THE

In DE-AS 27 01 938? also described a process which works with solvents in function of cold accumulators. The air-vapor mixture is compressed through the cooled solvent. Due to the low freezing point of the solvent, the problems associated with freezing the chiller can be avoided and it becomes possible to drop the temperature below 0 ° C.

All of these processes have a high cost in equipment; they always have two different circuits or streams of the air-vapor mixture. Either because of the low temperature of the chilled flow water, or because of the low temperature of the heat emitted by the compression cooling equipment, they cannot directly lead to the heat recovery process resulting from the production of the cold. . Why? however the quantities? of heat that must be discharged during the production of the cold are always considerably higher than the capacity? refrigeration, these processes show a very unfavorable energy balance. In DE-PS 2308 793? further described is a process by which the steam-water mixture is compressed and cooled and then made to expand by means of throttlingb. The patented process links the drying cycle to the cycle of a cold air machine according to the throttling process. With the throttling process, the need is eliminated. of the volume change work during expansion. The cooling takes place independently of the behavior of the perfect gas according to the J0ULE-TH0MS0N effect. Since? the achievable expansion work significantly improves the degree of performance of a cold air machine, a throttling process? considerably wasteful from an energy point of view. Finally, this procedure eliminates the need? of the cold, between mild counter-current, which on the one hand leads to a greater need for cold in the heat exchanger and on the other hand the minimum temperature? pi? high, since? in countercurrent, in the ideal case, the temperature drop can? quickly doubled (Dear Lindes process for gas fluidization).

It should also be noted that according to the known procedure, no? in practice, a machine free from drains can be obtained, why? Not ? a drop in temperature to below 0 ° C is possible. And this ? due to the fact that the Joule Thomson effect as a change in the behavior of the perfect gas in the temperature difference follows the isenic expansion, that is to say that the temperature drop? less than that which occurs with expansion by means of a turbine. It comes close only in the range of the large pressure differences of the isentropes. According to throttling experiments with real gases carried out by Thomson and Joule, the air at room temperature only cooled by approx. 1/4? C for atmospheric pressure drop (Plank, Handbuch der Kaltetechnik I, p. 14).

According to the explanations, the known procedure therefore also mainly uses the cooling of the compressed mixture, which? here well coolable due to the high pressure with a small volume, for the separation of condensate. There is also no mention of the attempt to reach temperatures below 0 ° C, which could not be achieved despite the high compression at 7 atm cited as an example due to the unfortunate trend of the Joule-Thomson effect. The possible temperature drop by throttling expansion would have been only a few? C.

In practice, such a procedure with compression greater than 2 atm is not? possible due to the heating of the vapor-air mixture beyond the decomposition temperature (separation of chlorine gas and hydrochloric acid) of the solvent, so in order to achieve the temperature drop? only possible expansion by means of a turbine with transfer of work to the outside. The pressure according to the patented process can not? therefore be conceived in order to reduce the temperature but? it must have another reason not deducible from the explanations.

According to the invention, the drying process in the circuit of a cold air machine? linked to the dynamic procedure or to the throttling procedure and - since no part of the cold is transferred to the outside - the quantity? of cold obtained with the Linde method of gas fluidization is used for the pre-cooling of the rich inlet vapor-air mixture.

The procedure relating to the invention? characterized above all by the fact that the vapor mixture of the solvent circulated during the drying is cooled in an isobaric way and the solvent which is so? it condenses is discharged from the circuit together with the water what cos? well it condenses, then made to expand in an isentropic way so that? the rich vapor-air mixture cools further, the solvent and water condense and are discharged from the circuit, the resulting lean vapor-air mixture is heated in an isobaric way, in countercurrent to the isobaric cooling direction and again enriched with solvent and water vapors through the passage of the fabrics to be dried.

It is useful in this regard that the isobaric cooled mixture is allowed to cool isentropically in a partial vacuum and subsequently heated to isobaric heat in a polytropic / adiabatic manner by means of compression from partial vacuum to atmospheric pressure or that the mixture is compressed isothermally / isentropically before isobaric cooling.

Characteristics of the apparatus relating to the invention for carrying out this process are mainly represented by the fact that the isentropic expansion is carried out through a choke and / or in a turbine, in which the volume variation work is used.

The equipment relating to the invention? an appliance with an annular duct connected to the cleaning drum in which the double counter-current heat exchanger? intended for cooling the rich vapor-air mixture ,, where? provided for an external conduction of the refrigerant for the lean vapor-air mixture and an internal conduction of the refrigerant for separate cooling, as well as? a heat exchanger equipped with condensate direction apparatus for water and solvent and at least one expansion apparatus for discharging the cooled vapor-air mixture and where further diversions for condensate are provided after or in the discharge equipment.

Furthermore, according to the invention,? provided a throttle valve and / or an expansion turbine as exhaust apparatus.

For the method variant without initial compression? further provided a vacuum pump in the unloading apparatus; for initial compression before counter-current heat exchanger? fixed a compressor to one or more? stages. The compressor? effectively cooled separately or in countercurrent; for this purpose? in some cases an intermediate cooler is provided.

The mechanically operated assemblies of the apparatus relating to the invention are effectively controlled simultaneously, i.e. the expansion turbine and the vacuum pump or the expansion turbine and the compressor have a cpmune drive shaft.

In this case it can? be a unit? similar, such as those known to the exhaust gas compressors of motor vehicles, however the power supply of the cyclic process is conveyed to the unit? compressor / turbine through an electric motor or other driving machine, that is to say that the unit? com pressor / turbine sometimes has a separate motor. A precise adaptation of the turbine to the foreseen conditions is therefore necessary. Relatively modest mass currents appear in dry cleaning machines, which must be subjected to an increase in pressure. In current machines this can? be achieved only with small diameters of the drive wheel and high number of revolutions, so that certain difficulties can be overcome. and needs with reference to the mechanisms to be used by electrically operating the unit? turbine / compressor.

The units turbine / compressor pi? small currently in series production are the PKW exhaust gas compressors which carry approx. 2 m of air / min at 70 ° C, where for a pressure difference of 0.5-1 bar there is a number of revolutions between 60,000 and 100,000 rpm-1.

With exhaust gas compressors there is a large difference in volumetric current between the starting part (turbine and exhaust gas) and the user (compressor) which? originated by the large temperature difference between the exhaust gas and the outlet air. This difference? even less in a cyclic process Joule cosicch? the fact of using unit? turbine / compressor of the exhaust gas type usually on the market must take into account the problems mentioned above in providing a separate engine.

The structure according to which the expanding turbine and the compressor are located on a common shaft, can according to the invention be further improved so that it? it can be inserted in a Joule cyclic process without a separate motor.

This, according to the invention, is carried out so that the unit? expansion turbine / compressor? without motor and the missing pressure energy on the compressor side is conveyed to a special directly driven compressor. There? involves the further advantage that the expansion turbine can? be adapted to the effects of a possibly high adiabatic effi-ciency since? it does not have to work at a number of revolutions forced by the separate control. In this way, according to the invention, also the usual agas exhaust compressors can be inserted.

Can you? advantageously to speak in terms of a second compressor directly driven of a volumetric compressor for air, in particular a rotary cylinder compressor, annular compressor for gas (side channel) or a radial compressor with multiple pumps. stages. The disadvantage of the bad degree of efficiency of the volumetric compressor can? be accepted due to the relatively modest performance in the presence of low volumetric current, since? the attempt to build a mechanism in this field of performance for a high number of revolutions would certainly be the best strategy? expensive.

One possibility? for the arrangement of the second compressor consists in connecting both compressors in series, so that the second directly driven compressor is put into operation as the second compression stage of the circuit.

The second possibility? of differential power supply consists in arranging the compressor which performs this function in the volumetric stream parallel to the compressor of the exhaust gas compressor. This compressor therefore does not produce the required differential pressure decrease after the first compression stage but instead? the global pressure drop, however only for a part of the total volumetric current.

Since? the bad degree of efficiency of the volumetric compressor mainly causes a strong increase in the compression temperature and therefore produces heat, which is then required in the process, even this energy is not lost; can you? likewise, control the final compression temperature with the use of a specific model. It is of primary importance for the good degree of efficiency of the cyclic process that the exhaust energy through the turbine is transformed into optimal temperature drops and that the work resulting from the expansion of the system remains unaltered with a good degree of efficiency. This ? the case in point; only the maximum temperature is transformed in the cyclic process into energy fed during the second compression stage which - if used - gives the process the same degree of efficiency of the arrangement with unit? driven compressor / turbine. In particular, for the solvent recovery process in dry cleaning machines, the arrangement relating to the invention appears, in the current state of the art, to be the most effective way. advantageous to achieve an optimal degree of efficiency.

For the compression of the mixture from partial vacuum to atmospheric pressure? provided is the second compressor operated separately preferably with a current parallel to the compressors coupled with the expansion turbine, which thus produces the overall pressure drop of a part of the volumetric current. There? ? particularly significant when the pressure increase in the compre- sor of the expansion turbine falls below 400 mbar, since? in this case a current machine has a bad degree of efficiency.

For compression of the mixture before isobaric cooling? preferably provided is the compressor coupled with the expansion turbine in the direction of flow of the mixture intended before the counter-current heat exchanger and the compressor operated separately after the counter-current heat exchanger; both compressors are cos? operated in series. In some cases it would also be possible to connect both compressors in series without intermediate cooling of the mixture; in this case for? a considerable increase in temperature must be taken into consideration, which certainly leads to the decomposition of the solvents (perchlorethylene decomposes starting from 150 ° C) and also weighs on the equipment.

Basically it is desired to bring the vapor-air mixture in the system to a constant saturation as high as possible, since? only with constant saturation? It is possible to avoid alterations in the temperature level with the heats of condensation that are released in a different way. A constant saturation? however, difficult to reach in chemical cleaning as even a second dryer-fan-dryer circuit would not be useful for reaching a pi? high degree of saturation for 11 final drying process.

On the contrary, the vapor concentration must go towards zero to satisfy government regulations and not to damage the fabrics.

Wouldn't it be very economical to equip the system for the condensation of the pi? high degree of saturation as it would also require a strong pressure drop and / or greater cooling and a higher heat exchanger? great. It would therefore be economical to choose a system for an average degree of saturation. There? however, it would be obtained without other measures at the beginning of the drying of the fully saturated vapor-air mixture in the system, the saturation of which could only be decreased but not eliminated. The vapors would then reach the turbine. This shouldn't happen in the machines n? current (turbines with centripetal movement) since? the transport of heavy vapors through compressor and turbine? linked to a greater expenditure of work and brings down the degree of efficiency of the turbine with centripetal movement since? the particles that condense due to the centrifugal force against the expansion current press outwards. There? can lead to erosion of the blades, particularly in the case of high rpm.

According to the invention, can you? also provide, with great advantages, a deviation line (by-pass) for the cleaning drum of the drying circuit where? provided for a reactor and which is opened at the beginning of the drying process so that a part of the lean steam mixture is not re-loaded into the drum but? is mixed with the rich steam * mixture coming from the drum to "dilute" it. A large part of the flow will flow? in this line due to the lower resistance in the short circuit line. By means of a bottleneck of this line can? the degree of saturation of the rich vapor-air stream can be adjusted. It can? in this way to adapt to the power of the cold air machine in view of condensation. this deviation line is continuously throttled up to the middle? about the drying process and then closed so that the degree of drying obtainable is not affected, the drying time can? be just a little bit? protracted. ; On the other hand, if at the end of the drying process they are already? few solvent vapors in the circulated air mixture? useful increase the quantity? In circulation. ; What? can According to the invention, a second deviation line with a restriction is also provided which acts as a bridge on the exhaust turbine, so that a part of the mixture no longer flows. in the exhaust turbine and in such a way that the flow rate of the compressor is increased. ; For the compression of the mixture prior to isobaric cooling and the accommodation of the second 'driven compressor' directly between the heat exchanger and the exhaust turbine (the exhaust gas compressor is provided before the heat exchanger), this second line of deviation goes from first ^ but to second? compressor and before re-entry into the heat exchanger and into that line? a pressure limiter is preferably provided. In the arrangement, in which the rich mixture is cooled in a partial vacuum without prestress, and? provided the second compressor operated separately in current parallel to the compressor coupled to the expansion turbine, this second deviation line goes from before the access of the expansion turbine to before the access of the separately driven compressor and? a suction limiter is preferably provided. ; The capacity of the second compressor operated separately is increased and thanks to the presence of the suction limiter this is opened so that the speed? flow rate through the second compressor increases with a relatively constant pressure ratio while the flow rate through the expansion turbine and the compressor coupled thereto and its pressure ratio remain relatively constant. ; By means of the greatest quantity? of air transported in virt? of the second deviation line, on the one hand, heavy and thick fabrics dry better and on the other hand the saturation of the air towards the end already? almost clean is raised again. ; The air that comes from the turbine can? cool the mpggior quantity in the counter-current heat exchanger of hot steam-air mixture at the same temperature, as the quantity? of heat discharged despite the greater amount? of air due to the lower heat of condensation for lower saturation / unit? of volume? considerably decreased. ; How already? remembered,? advantageous and useful to keep the turbine and the compressor the most? possible free from steam. For this reason and because of the pressure decrease that can be saved with counter-current, the degree of effectiveness of the counter-current heat exchanger is of great importance. It should be cleaned at the same time but economically and also easily. Also it should be built? as compact as possible due to the limited need for space. According to the invention, the counter-current heat exchanger is provided which consists of a corrugated screw tube as well as a counter-current heat exchanger. of an internal sliding sleeve and an external sliding overlay, both cylindrical and which are connected to the corrugations of the corrugated tube. From there? drift from time to time the cavity? spiral-shaped cylindrical outside and inside in which both means are conducted in countercurrent. The estate of both charities? spiraling occurs, for example, by means of two rubber rings which are crushed from time to time by screwing two metal rings. The gas stream is supplied and discharged with a tangential sleeve. ; It is useful to cover the sliding sleeve on the outside and the sliding overcoat inside with a solvent-resistant cover to prevent the gas stream from escaping and so that the the friction of the spiral caused by the expansion of heat in the sleeve does not lead to undesired wear. How advantageous is the heat exchanger according to the invention can be seen from the following example. ; average diameter of the spiral 450 mm. ; depth of the side 100 mm. ; pitch 40 mm. ;There? allows an average length of 1.42 m per circuit. ; You can? therefore achieve a counter-current length of 17.50 m over a total height of 500 mm. ; And this with a current cross section of 2,000 mm ^. ;In the end, ? still envisaged by the invention that this 3-wall heat exchanger is used, which is also insulated both externally and internally, for the acoustic insulation of the controlled units; in particular for the compressor operated separately but also for the compressor / expansion turbine. There? occurs as these units are mounted in the cylinder consisting of the internal sliding sleeve. ; Since the maximum degree of effectiveness for the temperature drop is recommended in the turbine? 85% and the two-stage compressor has a maximum degree of effectiveness of 65%. the remaining percentages of energy are transformed into heat. A part of this is discharged to the outside through the friction of the bearing and radiation losses, the remainder heats the circulating air. ; However, additional cooling is required to limit the temperature upwards, and additional cooling at the end of the process? advantageous on the one hand to bring down the temperature level and * therefore also the temperature pi? low and on the other side to take the cooled fabrics from the cleaning machine. Warm fabrics tend to wrinkle when they lie there for a long time.

It is known that the prices of chilled water rise considerably and that for this reason the developed regulators which make chilled water save iridium are technically predisposed. the

A cooling of the air would avoid this inconvenience, while normally the air has a higher temperature? high and more? oscillating with respect to water and for this reason not? up to now it has been used as a cooling medium in chemical cleaning machines. It was surprisingly discovered that the air? however, it can be well used for the simultaneous cooling of the air stream entering the machine drum and the air stream exiting the machine drum. There? takes place advantageously by means of two counter-current heat exchangers whose internal shaft can? be provided for extending the transmission surface to the outside with cooling fin. The refrigerated air is first conducted in counter-current to the pipe coming from the cleaning machine and then - due to the small temperature difference that is slightly heated - further conveyed in counter-current to the inlet pipe of the cleaning machine.

In summer, the heated air is sent outside; in winter it can? be used advantageously for space heating.

The invention? described below more? in detail with the aid of detailed examples based on the drawings, of which figures 1 and 2 show the diagram of the apparatus relating to the invention. Figures 3 and 4 show a sectional view of a side channel turbine with condensate department, Figure 5 shows a partially sectioned view of an appliance in which the mixture rich in steam and air is not pre-compressed before isobaric cooling.

Figure 1 shows an apparatus relating to the invention in which the water vapor / solution mixture is cooled isentropically in a partial vacuum without prior compression and is subsequently brought in a polytropic / adiabatic way to isobaric heat, after expansion, by compression. , from partial vacuum to atmospheric pressure.

The operation of the equipment shown in figure 1? the following: the rich vapor-air mixture is taken from the cleaning machine and conveyed, through the dust filter, to the heat exchanger where it is cooled outside, in counter-current, by the lean vapor stream coming from the expansion turbine and inside in countercurrent by water,

With us? a part of the condensate of water vapor and solvent vapor falls and is conveyed to the outside.

The rich vapor-air mixture now enters the expansion turbine significantly cooled into which more condensate falls and is separated either immediately afterwards or even in the turbine. Here the highest temperature is reached. high. The lean vapor-air mixture which is now in partial vacuum heats up by discharging the cold flow in counter-current to the rich vapor-air mixture coming from the drum before entering the vacuum pump where the lean vapor-air mixture heats up before entering the machine up to the desired temperature. Possible cooling if greater pressure differences threaten too high heating.

A one-stage vacuum pump with one-stage expansion turbine was shown. Can also be used vacuum pumps and expansion turbines at pi? stages in which a pair consisting of turbine and compressor can? be placed on a shaft without motor drive as in the case of an exhaust gas compressor. Can you? also think, optionally, of a series or parallel connection in the pr? yielding to pi? stages.

| In the process relating to the invention, the solvent concentration in the circulating air, according to the principle of a modified cold air machine in the dynamic process or by throttling by condensation of the solvent vapors by cooling to atmospheric pressure and further condensing by expansion to partial vacuum through a throttling device or an expansion turbine, or a combination of the two systems, is reduced to such a point that, without the need for additional equipment, the solvent concentration permitted by law in the working environment is not is exceeded. The disadvantages of the cold air machine turn out to be an advantage in the specific application case. The cold-air machines that produce cooling according to the dynamic process Are in some way more? economic how much more? the pressure ratio, and consequently also the temperature drop,? minor. What? for example the value of the power according to the dynamic procedure = -_ quantity? cold_

compression work - expansion work

in pressure ratios 1.5 1? of 8.125, while in the 6: 1 pressure ratios it amounts to only 1.497 (Plank manual for the cold technique vol. I, p. 1 (p) - The power values of the throttling process always remain considerably below of 1, since the quotients of the expansion work cannot be reduced.

On the other hand, small pressure differences force large and expensive compressors and multi-stage expansion turbines to reach a certain cooling capacity, while these are used for the purpose of producing cold only in special cases, mainly in the field of low temperatures.

The disadvantages are not particularly significant in the condensation process since? the quantity? of air circulated due to enrichment in the cleaning drum, can not? be increased indefinitely and on the other hand with the countercurrent process only temperature differences = pressure of 1: 1.8 max are necessary, which can still be produced economically or profitable. The utilization of the incoming heat which here falls within a usable temperature range as well as? the better use of chilled water further increase the economy.

Also on the basis of adjustability? of this system and the relative constructive premises of cooling the tank and sealing, is given the possibility? to include in the same type of machines, also low boiling point and highly volatile solvents such as R 11 (CC1? F) and R 113 (C2C1F 3), while until now very different types were needed for this purpose of machines. It is also possible, by correspondingly increasing the drying time in machines for perchlorethylene with cooling temperatures below 40 ° C, to obtain a total recovery of the solvents.

The process relating to the invention in the field of vacuum offers considerable advantages and represents a new process for the production of cold which? perfectly tuned to real needs.

Generally there is a compression to obtain a pressure / temperature gradient. This compression involves a considerable increase in the temperatures of the gases that must be cooled along the way, already? in the compression phase (labor saving of isothermal compression compared to adiabatic compression). Also the heating of the vapor-air mixture? limited upwards, as already? described.

On the other hand in the cooling circuit at the entrance to the cleaning drum? a tem perature of about 70 ° C is required (for perchlorethylene), since? with a temperature pi? high the absorption of the solvent by the air rises beyond the proportions. For this reason ? an ideal compressor design as a counterflow heat exchanger is required. However, the temperature drop that occurs between entering the cleaning drum at about 70 ° C and leaving it at about 50 ° C is missing. C with evaporation of the solvents (enrichment) and by heat fingers. From there? also the need? to install a heat register. Since? due to the counter current and the expansion by turbine according to this procedure the result is found for pressure differences such diff-

pressure differences can also be reached between depression and atmospheric pressure, for example

,

The main advantages of the process related to the invention without prestress are:

a) direct use of the heating-mixture of steam and lean air in the vacuum pump, as it is blown directly into the drum, so that? ? warming is desirable;

b) no heating of the vapor-air mixture between the exit from the drum and the entry into the expansion turbine;

c) the big advantage? the utilization of the pressure drop in condensation. Depending on the saturation and the temperature, the condensate produces a pressure drop of up to 0.4 bar. The above can? It can be used here as in steam turbines, in which, even by cooling the exhaust steam of the driving machine just before condensation, a greater pressure drop is available and thus a better degree of efficiency is achieved. This pressure drop leads, according to the method without initial compression, to an increase in vacuum or to a saving in driving power, whereas with the initial compression this pressure drop must be balanced with greater compression work. The expansion according to the second procedure with atmospheric pressure does not give? no possibility of using depression. The advantage of the procedure without initial compression can? correspond to the compression work for 0.4 - 0.6 bar of depression .;

d) total suppression of the thermal register. This method of drying laundry with air circulation is particularly advantageous where, due to the high temperatures, the partial pressure of the water vapor? particularly high and consequently d? an advantageous pressure difference. For example the pressure difference between saturated air of 90? C with cooling to 45? C? equal to 0.8 bar.

In Figure 2? an apparatus relating to the invention is illustrated in which the water vapor mixture of the solvent is compressed isothermally / isentropically before isobaric cooling. The operation of the equipment shown in figure 2? the following:

the rich vapor-air mixture is sucked in by the cleaning machine and sent to the compressor through the dust and flow filter. Such a com pressure? shown here in two stages with intermediate cooling. The rich vapor-air mixture passes from the compressor into a heat exchanger, which is cooled from the outside in counter-current with water. The rich vapor-air mixture is now cooled in counter-current at constant pressure for as long as and until the desired temperature is reached before the expansion turbine. This temperature can? be regulated with the use of cooling water that enters counter-current near the expansion turbine and exits in the compressors, where it can? heating up to approximately the boiling temperature of the water may be permitted. This results in full exploitation of the cooling potential of the water. In this counter-current chiller is condensation already? a large part of the vapors that are conveyed through the condensate derivation line. To take advantage of the volume change work, the vapor-air mixture is now brought into the turbine for expansion, where the condensate falls into the turbine and must be discharged. If there? does not occur, the turbine must be able to transport the condensate. The expanded steam-cold air mixture is now isolated in counter-current towards the outside and heated internally upon transfer of cooling capacity to the compressed-rich steam-air flow, so that the counter-current can also receive the heat resulting from the compression. . Before entering the cleaning machine again, the lean steam-air mixture is heated separately. The entity? of this heating depends on the degree of efficiency of the heat exchangers.

Compared to systems with refrigeration accumulators, this process has the advantage, in addition to the use of the exhaust heat and the relatively low cost of the appliances, of always being ready to operate, that is to say that, when the door is opened loading doors at the end of the drying process yes? found that the drying is not? finished due to a malfunction of the sensitive drying control device or due to the characteristics of the fabrics (blankets, curtains), you can? at any time proceed to complete drying, without having to wait a long time before the cold accumulator is ready to receive again.

The compressor can, if necessary, be cooled separately and / or in countercurrent.

With this process variant the solvent concentration in the circulating air is reduced in the dynamic process according to the cold air machine principle by condensation of the compressed cooling phase and further condensation in the expansion turbine so that, without additional devices, the solvent concentrations permitted by law are not exceeded.

In side channel compressors and turbines, the gas enters at the base of the impeller in the guide blade and is pushed outwards, from the guide blades to the annular channel, by centrifugal effect, where it is diverted to enter the base again. ? lia impeller in the guide vane.

The compression or expansion process is divided into a series of stages, among which the gas in the annular channel = deviation device is subjected to a large centrifugal acceleration and between which the heavy components of the gas can be discharged. It avoids cos? that, particularly in the event of condensation, the droplets fall into the drive wheel, thus creating? of the drawbacks.

The expansion for condensation also prevents the condensate that is formed from scaling and vaporizing again due to the friction on the drive wheel, which would also be a disadvantage you know, as a possibly large amount of condensate increases the degree of turbine efficiency by vacuum formation.

In DE-PS 1001 237 a method is described in which the condensate which forms in the guide body is discharged, during expansion to pi? stages in steam turbines, through an annular channel. This patent? been already? granted for another type of turbomachinery. For side channel compressors, the concept is that they have not been used up to now as a turbine due to the limited pressure differences they can produce and the relatively unsatisfactory degree of efficiency. Since? in the concrete case, the separation of substances takes precedence over the degree of efficiency of the turbine, a side channel turbine according to figs. 3 and 4? particularly suitable for the formation and conveyance of condensate.

Do you know, that in the lateral wall of the annular canal? an annular groove with corresponding openings for conveying the condensate is provided.

The drying device according to fig. 5 (cleaning drum not indicated)? consisting of a unit? compressor-turbine with turbine 1 and compressor 2. The energy supply takes place with a pressure gradient, generated by a volumetric air compressor 3, in this case a three-piston compressor, which is driven by an electric motor 4. Such appliances are mounted on a frame 5. Is the counter-current heat exchanger? placed on such a frame. It consists of a spiral or serpentine tube, the outer upper propulsion tube 7, the inner upper propulsion tube 8, elastic liners 9, sealing rings 10, two exhaust connections 11 and 2 inlet connections 12 The end bottom of the heat exchanger? formed as a solvent-water separator 13. From the lower part the solvent flows into a tank 14, while from the upper part the separated water flows into the conveyor 15. After the turbine the separated condensate collects in the lower part of the internal spiral 16 and, at the end of the drying process, it is discharged into the separator through a solenoid valve 17. The cold part of the appliance is separated from the heat with an insulating layer 18.

Line 19 of the cleaning drum? connected with line 20 to the cleaning drum through a first by-pass 21.

This by-pass has a throttle valve 22. The second by-pass 23 from "in front of the turbine" to "towards the compression stage 1" has a solenoid valve 24 and an intake limiter 25. The line to the drum and the line from the cleaning drum are equipped with noise dampers. 26.

The two lines are air-cooled with two double-tube counter-current heat exchangers 27 through a fan 28.

The upper connections of the value exchanger 29 are rigid, removable connections. The lower links 30 as well? the conveyors of the separator 31 are removable and flexible. The heat exchanger 32? externally and internally insulated, it rests on an insulated plate 33 and? closed with an insulated lid 34. Ventilation of the space of the assembly takes place by convection through slots in the base and on the lid.

How does this device work? the following: the rich vapor-air stream that comes from the machine drum enters the cooler in countercurrent at point A, exits cooled at point B and enters the external spiral of the heat exchanger with spiral tube, which leaves in point C. In this spiral the solvent and the water have almost completely separated, water in truth? as an icy layer, the boundary of which goes from top to bottom as the drying process progresses. The depleted vapor-air stream passes from C into the expansion turbine 1 into which and after which, depending on the graduation, other condensate or ice crystals falls, continues towards D and enters the heat exchanger again. The lean vapor-air stream heats up under the cooling capacity of the rich vapor-air stream and leaves the internal spiral of the heat exchanger at point E. It arrives in the compressor of the turbocharger 2, where it is compressed according to the performance of the turbine. In point F it comes out with a pressure pi? high and enters the second compression stage, in this case a three-piston fan, which compresses the lean vapor-air stream into near atmospheric pressure. The depleted steam-hot air mixture enters point G in the counter-current air cooler and leaves it at point H, where it is cooled to the maximum permissible inlet temperature to the drum and finally enters the inlet of the machine drum.

The behavior of the device described with reference to fig. 5 is obtained from the real temperatures and the real pressure differences found in the following 3 operating phases, which are indicated in the device for positions A to H .:

Exercise Phase 1: In the first half? of the drying process, however already? after reaching a temperature of 60? C in the cleaning drum. Line 1 of by-pass in operation. Air cooler in the stadium? .

Exercise Phase 2: In the second half? of the by-pass line 2 drying process in operation. Air cooler on stage 1.

Between F and G it mixes at 60? C with air 0 + C-of bypass 2, so that in point G and then in point H the temperature drops, which is fine, as it no longer comes? consumed cos? so much heat of evaporation to give 50? C at point A.

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

G 1.05 80

H 1.025 40

In the air cooler it is cooled to 35-40? C for increasing the quantity? of cold air. In the car there? pi? no reduction in temperature.

The process according to the invention can? also be used in the sense that it is used for washing the air with chemical or industrial processes, in which the air containing solvents is sucked in at the point of origin and is subjected to washing before being discharged to the atmosphere, in such a way that the circuit described is opened, so that instead of the drum outlet the intake opening is directed towards the atmosphere and instead of the drum inlet there is the discharge opening. Will it be possible? other s? provide an activated carbon filter as a final separator.

A disadvantage of the closed loop systems described above can? be constituted by the fact that residual vapors can remain in the drum, which pass through the dried material? d and enter the ambient air when the loading door is opened. In a device according to the invention this can? be avoided as when opening the drum the compre ^ sor or the vacuum pump runs and the cooling is activated. The washed air mixture does not fit for? back into the drum, but is conveyed outdoors through a valve - possibly through an activated carbon filter -, i.e. the circuit is opened.

For the same purpose, so that? no residual solvent vapors can enter the cleaning drum when the machine is stopped, the chemical cleaning systems, in particular the device according to the invention can be modified in such a way that the dust filter, the transport equipment, the refrigeration register and the heat register are arranged in such a way as to be at the same low level as the suction and return opening of the drum or in such a way that the aforementioned components are connected to the drum on a siphon.

Finally, you can? also provide for an aspiration of the solvent vapors that form in the immediate vicinity of the device, where the aspirated air is fed before the dust filter through a valve in the circuit.

The devices according to the invention can also be used advantageously in the so-called they

Claims (22)

1. Procedure for the recovery of the solvent from the air with vapor content in the turkey for dry cleaning, where the drying takes place in a closed circuit characterized by the fact that the vapor-air mixture of the solvent is circulated it is mainly cooled. isobaric and that the solvent what is it? condenses is discharged from the circuit together with the water what is it? it also condenses, then made to expand in an isentropic way so that? the rich vapor-air mixture cools further, the solvent and water condense and are discharged from the circuit, the resulting lean vapor-air mixture is heated in an isobaric way in counter flow to the isobaric cooling direction and enriched again of solvent and water vapors through the passage of the fabrics to be dried. 2. Procedure as per claim no. 1, characterized by the fact that the isobaric cooled mixture is isentropically cooled in partial vacuum and then heated to isobaric heat in a polytropic / adiabatic manner by means of compression, from partial vacuum to atmospheric pressure. 3. Procedure as per claim no. 1, distinguished by the fact that the mixture is understood in an isothermal / isentropic manner prior to isobaric cooling. Process according to one of claims 1 to 3, characterized in that the isentropic expansion is carried out through a constriction and / or in a turbine, in which the volume change work is used. 5. Apparatus for carrying out the process as per claim n. 1 with one of the annular pipes connected to the cleaning drum, in which a double counter-current heat exchanger? intended for cooling the rich vapor-air mixture, where? provided for an external conduction of the refrigerant for the vapor-air mixture and an internal conduction of the refrigerant for separate cooling as well as? a heat exchanger equipped with condensate management equipment for water and solvent and at least one expansion equipment for the discharge of the cooled vapor-air mixture, and where further diversions for the condensate are provided after or in the discharge equipment . 6. Equipment referred to in claim 5? distinguished by the fact that? provided a throttle valve and / or an expansion turbine as exhaust apparatus 7 It appears to be referred to in claim no. 6, distinguished by the fact that? a side channel turbine with a condensate department is envisaged as an expansion turbine. 8. Apparatus as per claim n. 5, distinguished by the fact that? a vacuum pump is also provided as an expansion apparatus. 9. Apparatus as per claim n. 5, distinguished by the fact that before the counter-current heat exchanger? fixed a coma one or more? stages. 10. Apparatus as per claim n. 9, distinguished by the fact that the compressor? counter-current or separately cooled; for this purpose? in some cases an intermediate cooler is provided. 11. Apparatus as claimed in claims 5 to 10, characterized in that? it is foreseen that the mechanically operated groups have a common command. 12. Equipment according to claims 5 to 10, characterized by the fact that the unit? expansion turbine / compressor? provided without separate motor as well as an additional separately driven compressor. 13. Apparatus as per claim n. 12, distinguished by the fact that the compressor operated separately? designed as an air compressor, especially as a rotary compressor. 14. Apparatus according to claims 12 and 13, characterized in that for the compression of the mixture from the partial vacuum to the pre? atmospheric sion? provided for the compressor operated separately in parallel current to the compressor coupled to the expansion turbine. 15. Apparatus according to claims 12 or 13, characterized in that for the compression of the mixture before isobaric cooling? foreseen the compressor coupled to the expansion turbine in the direction of flow of the mixture intended before the counter-current heat exchanger and the compressor operated separately after the counter-current heat exchanger. 16. Apparatus as per claims 12 to 15, characterized by the fact that in the drying circuit? provided for a by-pass duct for the deviation of the cleaning drum. 17. Apparatus as per claims 12 to 16, characterized by the fact that in the drying circuit? a by-pass duct is provided for the diversion of the expansion turbine. 18. Apparatus according to claims 12 to 17, characterized in that the heat exchanger in. countercurrent has the shape of an aj3 if helical with an internal and external cylindrical tube. 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. Apparatus according to claim 18 19, characterized in that the compressor is controlled separately, preferably together with the unit? exhaust turbine / compressor,? provided in the free internal space of the counter-current heat exchanger. 21. Apparatus according to one of claims 18 to 20 characterized in that the counter-current heat exchanger? placed in a vertical position and? equipped with at least one derivation for the condensate preferably in its lower section. 22. Apparatus according to one of claims 12-21, characterized in that? a counter-current air cooler is provided for the simultaneous cooling of the rich gas mixture coming from the cleaning drum and the clean return gas.