US3538615A - Drycleaning machine with adsorber - Google Patents

Description

NOV. 10, 1970 [J ETAL I 3,538,615

DRYCLEANING MACHINE WITH ADSORBER Filed March 25, 1968 Heinrich FUTIRING Johannes Helmut SIEBER INVENTORS Attorney United States Patent DRYCLEANING MACHINE WITH ABSORBER Heinrich Fiihring, Augsburg, and Johannes Helmut Sieber, Aystetten, Germany, assignors to Bowe Bohler & Weber KG, Augsburg, Germany, a corporation of Germany Filed Mar. 25, 1968, Ser. No. 715,648 Claims priority, application Austria, Mar. 23, 1967, A 2,806/ 67 Int. Cl. F26!) 21/06 US. C]. 34-74 7 Claims ABSTRACT OF THE DISCLOSURE To control the moisture content in the atmosphere of a drycleaning drum during a solvent-extraction phase, air circulated through the drum in a closed path is passed first through an adsorber for the solvent, then through a condenser for the separation of excess moisture, and finally through a heater wherein the air cooled in the condenser is reheated before reentering the drum.

The invention relates to a method of and to apparatus for the recovery of solvent gases from an air current issuing from the cleaning drum of a drycleaning machine, the air current being passed through a device by which the gases to be recovered are adsorbed and then recirculated to the drum.

In commonly owned German patent application No. B 62,503 it has been proposed to use for the recovery of the solvent an adsorber, particularly for low-boiling solvents, instead of the condenser otherwise used in drycleaning machines as the goods are dried. The efficiency of the adsorber is reduced when a solvent of high concentration is used; for this reason, a condenser is provided at the inlet of the adsorber so that the yield of solvent may be slightly increased. Upon regeneration of the adsorber in the opposite direction of flow, the condenser could be used simultaneously for the condensation of the mixture of water vapor and solvent. It has, however, been .found that the increase in yield thus obtained is very limited since the adsorption capacity of the adsorber is reduced by the increased relative humidity of the air being cooled by the condenser. A decisive disadvantage resulting from the use of adsorbers of this kind in a solvent-recovering circulation system consists primarily in the fact that air passing through the adsorber during the recovery phase absorbs moisture as the solvent is adsorbed and entrains it to the drum, this moisture having been retained in the adsorber during the preceding regeneration by means of water vapor or steam. Upon recirculation, the air absorbs further moisture whenever it passes through the adsorber. The moisture thus accumulating in the air deposits on the goods as it passes through the drum, so that the goods absorb excessive moisture with resultant creasing and clamminess thereof. Even when an air heater is used, the continual, ever increasing concentration of moisture in the air and the precipitation thereof on the goods cannot be prevented inasmuch as only limited air heating is permissible for the sake of preservation of the goods. For these reasons, the use of adsorber for the recovery of solvents in drycleaning machines has not succeeded.

It is the principal object of the invention to eliminate by simple means the aforementioned disadvantages resulting from the use of an adsorber for the recovery of the solvent in air-circulation systems of drycleaning machines, and to prevent an undesired creasing of the goods. It is a further object of the invention to ensure uniform conditioning of the goods to be treated, so that a predetermined, desired state of moisture may be produced in the finished goods. Here and in the following the term moisture" applies to the water content.

In accordance with the invention, all of the moisture, except for a desired residual quantity, is withdrawn from the air stream by cooling as it circulates through the adsorber, after it has issued therefrom, and before its readmission to the cleaning drum. It is thus ensured that aqueous moisture entrained from the adsorber by the air current is largely eliminated therefrom before it can spoil the goods, only a predetermined quantity of moisture which may be controlled by the degree of cooling being retained in the air admitted to the drum.

In accordance with the invention, the air is advantageously reheated to a desired temperature immediately after the cooling process in order to ensure that the process of evaporation in the drum should not be too slow. In the recovery of the solvent by means of a condenser it is known to heat the air after it has left the condenser and before it is admitted to the drum. We have found, however, that, in connection with the cooling of the air issuing from the adsorber, a subsequent heating affords particular advantages since a predetermined, desired concentration of water vapor in the air present in the drum, i.e., a certain relative humidity may be produced simply by adjusting the cooling and the heating to corresponding values. The cooling and heating of the air are used for the elimination of "water and for controlling the air moisture rather than for the recovery of the solvent, as has been the case in conventional plants.

The use of adsorbers in the air-circulation system of drycleaning machines affords particular advantages when a low-boiling solvent, for example a fiuorinated chlorinated hydrocarbon, is used since then a condensation plant of high cooling power would have to be provided, or else a correspondingly high loss of solvent would have to be accepted.

In accordance with the invention, apparatus for carrying out the aforedescribed method comprises a drycleaning machine provided with a cleaning drum mounted, for example, in a housing and provided with peripheral openings for the passage of air and solvent, these openings being connected by conduits to the inlet and to the outlet of an adsorber to form a recirculation system between the drum and the adsorber. The chamber of any other type of drying plant, in which the goods to be dried are to be protected against being moistened by water, may be substituted for the cleaning drum of a drycleaning machine.

In apparatus according to the invention, in which the movement of the air may be produced by a fan or the like, an indirectly cooled condenser is provided in the zone of the recirculation system between the outlet of the adsorber, i.e., the location where the recirculated air .issues from the adsorber, and the inlet of the drum. The

air issuing from the adsorber is cooled by the condenser until it contains only a desired quantity of residual moisture.

In one advantageous construction of apparatus according to the invention, the condenser is provided with adjustable cooling means, as by making the supply of coolant adjustable. A desired rate of cooling, corresponding to a predetermined moisture content in the air admitted to the drum, may thus be selected by simple means. Thus, for example, the cooling of the condenser may be controlled by means of a suitable sensing device in dependence upon the temperature of the coolant issuing from the condenser. It is thus ensured that the air issuing from the condenser and readmitted to the drum contains a quantity of moisture not exceeding a predetermined maximum.

In one embodiment of the invention, an air heater of conventional construction is provided downstream of the condenser and upstream of the inlet of the drum, in order to establish a predetermined relative humidity in the drum atmosphere. In accordance with the invention, the output of the heater may be controlled so that various degrees of relative humidity, or an air moisture content not exceeding a predetermined maximum, may be produced thereby in the drum with correspondingly adjusted precooling to selected temperatures. The use of an air heater in connection with a cooling of the condenser in drycleaning machines is known; this technique, however, has heretofore been used only for the purpose of recovering the solvent and not for controlling and proportioning the moisture content in the drum atmosphere in connection with an adsorber provided in a closed aircirculation system.

A further feature of our invention is the provision of means for regulating the thermal output of the heater, as by controlling the steam supplied thereto or the heating voltage or heating current with the aid of, for example, a temperature sensing element, according to the temperature of the air issuing from the heater. In accordance with another feature of the invention, the cooling of the condenser, for example the supply of cooling water, may also be controlled, e.g., by a hydrometer, in dependence upon the relative humidity of the air issuing from the heater. The invention thus also enables automatic adjustment and maintenance of the desired air moisture in the drum of a drycleaning machine.

The invention is diagrammatically illustrated by way of example in the sole figure of the accompanying drawing in which the cleaning drum, or the housing enclosing it, is denoted by the reference numeral 1. The drum is loaded and unloaded through a hatch 2. A conduit 3, which may contain a lint filter 4, is connected to the drum 1 or to the housing enclosing it. In the illustrated construction, the conduit 3 extends to a blower 6 driven by a motor 5.

The blower 6 draws the solvent-containing air present in the drum 1 through the conduit 3 and then passes it under pressure into an adjoining adsorber 7 filled, for example, with activated carbon. The adsorber 7 withdraws solvent from the air flowing through it. As illustrated in the drawing, a filter 8 retaining particles of carbon and the like, entrained by the air current from the adsorber 7, may be provided at the outlet thereof. The filter 8 is followed by a condenser 9 for cooling the air issuing from the adsorber 7. A conduit 10 extends from the condenser Q back to the drum 1. The condensate recovered in the condenser 9 and collected in a drain trough 11 may be fed through a conduit 12 to a collecting device 13 advantageously constructed as a water separator. The direction of flow of the circulating air is indicated by arrows. Other valves, flaps, terminals, and the like, which have no direct connection with the invention, have been omitted from the drawing for the sake of clarity.

The water in vapor form entrained from the adsorber and originating from the preceding regeneration process is withdrawn from the air by the condenser 9 by corresponding adjustment of the cooling. The residual quantity of moisture entrained by the air issuing from the condenser 9 varies in accordance with the adjusted cooling power of the condenser 9 and can thus be controlled as desired.

A device for controlling the quantity supplied may be provided, for example in the supply line 14 for the cooling water, so that the cooling rate of the condenser 9 may be adjusted to a desired value. The control device 15 may be operated preferably by a device 16 for measuring the temperature of the coolant issuing from the condenser. The adjustment of the control device 15 by the measuring device 16 is diagrammatically indicated by a broken line 17.

In the illustrated embodiment of our invention, a heater 18 of conventional construction is provided upstream of the inlet of the drum 1 in the branch conduit 10- between the condenser 9 and the drum 1, so that a desired relative humidity may be established in the drum atmosphere, and particularly so that the quantity of water absorbed or given off by the goods from or to the air may be adjusted; a predetermined desired conditioning of the goods may thus be obtained. Thus, with a given rate of cooling in the condenser 9, a predetermined relative humidity may be produced by adjusting the heater 18; similarly, with a given permanent adjustment of the heater 18, this may be achieved by corresponding variation of the cooling action of the condenser 9. A device 19 for adjusting the heater 18 by controlling the supply of energy thereto is provided in the energy-supply line 19 (the heater may .be operated either with steam or With electrical energy). In one specific construction, the adjustment of the control device 19 is carrier out by a device 20 which measures the temperature of the air at the outlet of the heater. In the drawing, the control of the adjusting device 19 by the measuring device 20 is diagrammatically indicated by a broken line 21.

The supply of coolant to the condenser 9 may also be controlled directly by operating the control device 15, even when the heater 18 has a permanently adjusted output, by having the measuring device 20 sense the relative humidity of the air issuing from the heater instead of measuring the temperature thereof. This further means of control is indicated diagrammatically in the drawing by a dash-and-dot line 22.

In accordance with the invention, an absorber which has been found particularly advantageous for the recovery of low-boiling solvents may be used for the recovery of the solvent by recirculation, the hitherto existing danger of excessive moisture passing from the adsorber to the goods being no longer present. Over and beyond this, the invention afifords the advantage that an excessive drying of the goods in the drum is prevented and the realtive humidity of the drum atmosphere may be controlled by simple means even at realtively low drying temperatures, so that the goods may be conditioned as desired. The goods are subjected to substantially less strain than in conventional cleaning machines, since the heater may be operated at a low temperature.

The construction and disposition of an adsorber in drycleaning machines, in which the condenser is provided downstream of the adsorber as viewed in the direction of flow of the circulating air, may be realized in various ways, so that the invention is not limited to the illustrated construction. It will be readily understood that the invention may also be applied to systems, operating exclusively as drying plants, in which similar problems exist.

We claim:

1. A method of controlling the moisture content of the atmosphere of a drycleaning vessel during extraction of residual solvent from goods in said vessel, comprising the steps of recirculating an air stream through said vessel in a closed path including an adsorber for removing entrained solvent therefrom, said adsorber having been previously regenerated by flushing with an aqueous medium leaving a residue of moisture therein, separating excess moisture from said air stream by cooling same at a first location downstream of said adsorber and reheating said air stream at a second location between said first location and said vessel.

2. A method as defined in claim 1 wherein the cooling rate of said air stream at said first location is controlled in dependence upon the moisture content of the air stream between said second location and its point of reentry into said vessel.

3. In a drycleaning plant including a vessel for the treatment of goods with a solvent, the combination therewith of conduit means forming a closed path for the pas sage of an air stream through said vessel during a solvent-extraction phase, blower means in said path for recirculating said air stream, adsorber means in said path for removing entrained solvent from said air stream after passage thereof through said vessel, said adsorber means being regeneratable by an aqueous medium leaving a residue of moisture therein, condenser means in said path downstream of said adsorber means for separating excess moisture from said air stream by cooling same, and heater means in said path between said condenser means and said vessel for reheating said air stream before its reentry into said vessel.

4. The combination defined in claim 3, further comprising filter means in said path between said absorber means and said condenser means for removing entrained particles of adsorber material from said air stream.

5. The combination defined in claim 4, further comprising additional filter means in said path ahead of said adsorber means, said blower means being disposed between said additional filter means and said adsorber means.

6. The combination defined in claim 3, further comprising control means for varying the cooling eifect of said condenser means.

7. The combination defined in claim 6, further comprising moisture-sensing means in said path between said heater means and said vessel, said control means being responsive to said moisture-sensing means for maintaining a predetermined humiditydevel in said vessel.

References Cited UNITED STATES PATENTS FREDERICK L. MATTERN, JR., Primary Examiner 20 H. B. RAMEY, Assistant Examiner US. Cl. X.R.

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