A METHOD AND APPARATUS FOR INCREASING THE YIELD OF AN AIR-DRYING PROCESS

Abstract: A method for increasing the yield of an air-drying process with the aid of a dehumidifier (2) and a condenser/heat-exchanger (3) comprises delivering wet regenerating air exiting from the dehumidifier (2) to one side of the condenser/heat-exchanger so as to deliver energy to the process air entering the other side thereof. Condensation deriving from the regenerating air is collected and carried away, and the heated, dried process air (21) is delivered to the dehumidifier (2) in which moisture is extracted from the air and the air further dried. The departing wet regenerating air may after its delivery process be led for instance to the room, atmosphere or the flow of process air. The invention also relates to system for carrying out the method.

Description: A Method and Apparatus for Increasing the Yield of an Air-Drvinα Process Field of Invention The present invention relates to a method of increasing the yield of an air-drying process in which fan-driven process air delivered to a dehumidifier is dehumidified and dried during a heat-exchange process with hot regen- erating air. The invention also relates to apparatus for carrying out the method. One problem with methods and apparatus of this kind is that the moisture present in the wet air flow must be extracted and led away. This can normally be achieved by passing the wet air-flow to a room or to the surround¬ ings, for example with the aid of a hose. There are cases, however, when this known technique can only be applied with difficulty and at relatively high costs, for instance when cellar air or the air in a bank vault shall be dehumidified and dried. This problem is normally solved by connecting a condenser to a dehumidifier. In principle, a condenser is a heat-exchanger in which wet air is brought into heat-exchange contact with cold air, therewith extracting and collecting the moisture in the wet air while heating the cold air delivered to the heat exchanger. In practice, the wet air that exits from the dehumidifier may have a temperature of about 35°C and may also contain a large amount of moisture. The cold air used is air at room temperature, e.g. 20°C, which causes the moisture in the wet, warm regenerating air delivered to the heat- exchanger to condense on the other side of the heat- exchanger. The dehumidified air is then passed back to the dehumi¬ difier, in which it is heated and used to regenerate the wet rotor. State of the Art In known methods and apparatus of this kind, the con¬ denser/heat-exchanger unit is completely separate from the dehumidifier. The condenser/heat-exchanger unit may thus have a separate cold-air fan and also a separate electric plug or like connector, etc. These two units are relatively bulky and heavy to handle, even when having a relatively limited capacity. The cost of one such condenser together with associated conduits is also high, and a system of relatively limited capacity will, today, cost at least SEK 10,000. One example of the present standpoint of techniques is described in SE,B,335.323 (Munters) . According to the teachings of this publication, the energy is not deliv¬ ered to the air to be dried, but to a separate cooling fluid. Another method and apparatus herefor are described in GB,B,1.400.255 (British Titan). This method utilizes, among other things, first and second columns, a condens¬ er, a fan, and a heater in a drying process. As in the former case, energy is not delivered from the wet air to the process air to be dried. Object of the Invention The object of the present invention is to provide a method and apparatus by means of which an increase in the yield of the energy delivered to the process can be achieved and which will also facilitate handling of the apparatus components. Another object is to provide process-air drying apparatus which has fewer components than known apparatus intended for the same purpose, and which has a simpler and more compact construction than previously known apparatus of this kind. Another object of the invention is to provide an air- drying method and air-drying apparatus in which regene¬ ration air departing from a dehumidifier is used more economically than is the case in earlier known methods and apparatus of the aforesaid kind. Summary of the Invention These and other objects are fulfilled by an inventive method having generally the characteristic features set forth in Claim 1. Thus, in accordance with the invention, the process air to be dried is heated with the aid of energy delivered from the wet regenerating air. Consequently, the dry air that exits from the dehumidifier will have a relative moisture content that is substantially lower than the moisture content of air dried by a conventional drying method. The inventive method is also much more economical than the known methods, partly because of the improved heat economy, but also because the inventive drying process can be performed in apparatus which comprise fewer compo¬ nents than known apparatus of this kind. Thus, in practice, the two main apparatus parts, namely the dehumidifier and the condenser/heat-exchanger are comprised of two separate, relatively lightweight units (together weighing about 28 kg as against a normal weight of about 50 kg) which can be readily carried to a user site and assembled together to form a complete system, using only a few simple manual manipulations. A condenser of this kind coupled to a dehumidifier, e.g. according to SE,C,8804281-7 (Corroventa) with an air 3 throughflow volume of about 300 m /h, and a regenerating battery of 1,500 w, has a water extraction capacity of about 15 kg/day (twenty-four hours) at 20°C and a 50% relative humidity. The warm, dry air has a drying capac¬ ity which is about 80% better than the capacity of the same dehumidifier which has no condenser/heat-exchanger, which, in turn, almost halves the drying time. Thus, it is preferred in practice that the wet regene¬ rating air is drawn into the condenser/heat-exchanger by means of the same fan as that which draws the process air into the dehumidifier. This obviates the need for one fan and its associated electric cables and other components. The regenerating air exiting from the condenser/heat- exchanger can be led away or recovered and processed in different ways, according to prevailing requirements and needs. For example, the regenerating air may be subjected to a heat-emitting and water-condensing process and then delivered to the room in which air shall be dried. Alternatively, the regenerating air can be subjected to a heat-emitting and water-condensing process and then either passed to a ventilation system or conducted to a location, e.g. atmosphere, outside the room in which the air has been dried. Another alternative is to deliver regenerating air to the flow of process air, subsequent to condensing the moisture in the regenerating air. Still another alternative is to deliver exiting wet air to incoming regenerating air by means of a separate fan. In this case, however, the system requires the provision of an additional fan in comparison with what is required in other, normal cases. Brief Description of the Drawings The invention will now be described in more detail with reference to some exemplifying embodiments thereof and also with reference to the accompanying drawings, in which Figure 1 is a partly cut-away, perspective view of an air-dehumidifier included in the inventive system; Figure 2 is a perspective view of a condenser/heat- exchanger for connection to the air-dehumidifier illus¬ trated in Figure 1; Figure 3 is a perspective view of an air-dehumidifier shown in Figure 1, wherein arrows show the various air flows delivered to and exiting from the dehumidifier; Figure 4 is a perspective view of the inventive system in use; Figure 5 is a view from the inside of a first embodiment of a condenser/heat-exchanger of the system illustrated in Figures 1-4; and Figure 6 is a view corresponding to the view of Figure 5, showing an alternative embodiment of the condenser/ heat-exchanger. Best Mode of Carrying Out the Invention The air-drying system 1 illustrated in Figures 1-4 com¬ prises an air-dehumidifier 2 and a condenser/heat- exchanger 3. The air-dehumidifier 2 is of a more or less conventional kind and comprises a housing or casing 4 provided with a process-air inlet 5 and a dry-air outlet 6. The dehumidifier also includes an outlet 7 for wet regenerating air. Journalled for rotation within the housing 4 is a rotor 8 which is provided with channels 8a which contain moisture adsorbing means, for instance silica gel crystals. Although not shown, the housing 4 houses an electric motor for driving the rotor 8 and a concentrically mounted impeller 10, which is driven by an electric motor 9. The fan 10 functions to pressurize process air delivered through the inlet 5, so that the air will flow through at least a part of the rotor 8 and, subsequent to being dehumidified, depart through the outlet 6. The housing 4 also houses heating means which heat rege¬ nerating air that passes through another part of the rotor. The illustrated embodiment may also include separate capturing devices (not shown) , for instance comprising a hood (not shown) positioned closely adjacent the rotor 8 on its low-pressure side and provided with heat-emitting devices (not shown) which deliver radiant heat in an axial direction and directly onto the moisture-adsorbing means present in the rotor channels 8a. Alternatively, the regenerating air can be delivered to the housing 5 through a separate inlet (not shown) and heated within the housing 4 in some suitable manner. The condenser/heat-exchanger 3 illustrated in Figure 2 comprises a generally four-cornered box 12 in which lamellar 32 are arranged between which heat-exchange is effected between wet regenerating air, delivered from the outlet 7 of the air-dehumidifier through a hose or pipe 14 and process air delivered centrally to the condenser/ heat-exchanger. The condenser/heat-exchanger is provided with an inlet 15 and an outlet 16. The condenser/heat- exchanger can be fitted removably to the air-dehumidifier 2 and secured thereto with the aid of wing nuts 18 which coact with screws 19 on the front side of the dehumidi¬ fier 2, i.e. in the same manner as that now proposed in the case of filter flaps which are replaced with con¬ denser/heat-exchanger. Thus, wet regenerating air exiting from the outlet 7 of the dehumidifier 2 is delivered to the inlet 15 of the condenser/heat-exchanger, via the hose 14, for the pur¬ pose of delivering energy to the process air, which is delivered to the front side of the unit, as shown by the arrow 21. The process air is therewith used for cooling purposes and will be slightly heated as it takes up energy from the wet regenerating air, the liquid contained thereby condensating and collecting on the bottom of the con¬ denser/heat-exchanger 3 from where it can be removed through a pipe 25. The slightly heated and dried process air then enters the dehumidifier 2, in which the air is dehumidified and further dried during its passage through the rotor channels 8a. In order to make the condenser more effective, a number of cells can be coupled sequentially so that the effi¬ ciency of the condenser will correspond to a contraflow heat-exchanger, despite each cell operating in cross- flow. The efficiency is greatly improved even when only two cells are coupled. The wet regenerating air is drawn into the condenser/ heat-exchanger by means of the same fan 10 as that which draws the process air into the dehumidifier. Figures 5 and 6 illustrate different ways of conducting away the wet regenerating air subsequent to its delivery of heat in the condenser/heat-exchanger 3. In the Figure 5 illustration, the regenerating air exit- ing from the outlet 16 is delivered to the room, or space, in which air is dried by means of the inventive system. Figure 6 illustrates a modified embodiment in which, subsequent to condensation, the regenerating air is delivered to the flow of process air through the slot or gap 28. If two cells are provided, this air flow can be delivered to the flow of process air between the two cells, sub- sequent to passage through the condenser and condensing of the moisture present in said air flow. Although not shown, the regenerating air may alterna- tively be delivered to a ventilation system or, for instance, to atmosphere outside the dried room, through a pipe or hose intended therefor. According to a further alternative, the departing wet regenerating air may be delivered to incoming regenerat¬ ing air through the medium of a separate fan. Although this arrangement provides the best heat yield, it also requires the provision of two fans, in order to function in the manner intended. The prevailing air flows are shown in the various Figures of the drawings by appropriate arrows. As before men¬ tioned, the arrow 21 indicates process air drawn into the system. The arrow 28 indicates dry air exiting from the air-dehumidifier, while the arrow 29 indicates wet air regenerating air exiting from the dehumidifier. In Figure 4, the arrow 30 indicates the delivery of regenerating air to the room concerned or to the surroundings, sub¬ sequent to heat exchange with the process air. Other modifications are conceivable within the scope of the inventive concept, as defined in the following Claims.

Claims: Claims 1. A method of increasing the yield of an air-drying process in which fan-driven process air is delivered to a dehumidifier and there dehumidified and dried during heat-exchange with heated regenerating air, c h r ¬ a c t e r i z e d by delivering wet regenerating air exiting from the dehumi- difier to one side of a condenser or heat-exchanger so as to deliver energy to the process air delivered to the other side of said condenser or heat-exchanger for cool¬ ing purposes; collecting and/or carrying away condensation obtained from the regenerating air; and delivering the process air heated and dried in the pre¬ ceding step to the dehumidifier so as to extract moisture from the process air and further dry said process air. 2. A method according to Claim 1, c h a r a c ¬ t e r i z e d by drawing the wet regenerating air into the condenser/heat-exchanger with the aid of the same fan as that used to draw process air into the dehumidifier. 3. A method according to Claim 1 or 2, c h a r a c ¬ t e r i z e d by delivering the regenerating air to the room in which air is to be dried, subsequent to subject¬ ing the regenerating air to a heat-exchange and moisture- condensating process. 4. A method according to Claim 1 or 2, c h a r a c ¬ t e r i z e d by delivering regenerating air, subsequent to a heat-exchange and moisture-condensating process, to a ventilation system or conducting said air to a location externally of the room whose air is dried. 5. A method according to Claim 1 or 2, c h a r a c ¬ t e r i z e d by subjecting the regenerating air to a condensing process and then delivering said air to the flow of process air. 6. A method according to Claim 1, c h a r a c t e ¬ r i z e d by delivering exiting wet air to incoming regenerating air with the aid of a separate fan. 7. An air-drying system comprising an air-dehumidifier and including a) a housing (4) provided with an inlet (5) and an outlet (6) ; b) a rotor (8) journelled in the housing (4) and pro- vided with channels (8a) or beds containing moisture absorbent means, such as silica gel crystals; c) a motor for driving the rotor (8) , preferably conti¬ nuously; d) a fan (10) for pressurizing air entering through the inlet (5) , so that said air will flow through at least one part of the rotor and, subsequent to being dehumidi¬ fied, depart through the outlet (6) ; e) means for heating regenerating air which passes through another part of the rotor; and f) a wet regenerating-air outlet (7) ; c h a r a c t e r i z e d in that the system also in¬ cludes g) a condenser/heat-exchanger having lamellar (32) for effecting an exchange of heat between wet regenerating air (29) and process air (21) , each being delivered through a respective inlet; h) an outlet for process air exiting from the con¬ denser/heat-exchanger, said outlet being connected or connectable to the inlet of the air-dehumidifier; i) means, such as a hose or pipe (14) , for connecting the wet regenerating air-inlet (15) of the condenser/ heat-exchanger to the corresponding outlet (7) of the air-dehumidifier (2) ; j) an outlet for regenerating air which has been sub¬ jected to a heat-exchange with process air; k) means (18, 19) for connecting, either fixedly or removably, the condenser/heat-exchanger (3) to the air- dehumidifier (2) ; and 1) means for collecting and/or carrying away condensa¬ tion from the condenser/heat- xchanger. 8. A system according to Claim 7, c h a r a c ¬ t e r i z e d in that the air-dehumidifier fan (10) is intended to draw process air (21) through the condenser/ heat-exchanger. 9. A system according to Claim 7 or 8, c h a r a c ¬ t e r i z e d in that the outlet (16) through which generating air exits from the condenser/heat-exchanger is intended to open into the room, to atmosphere or into the process air. 10. A system according to Claim 7, c h a r a c t e ¬ r i z e d in that a wet-air outlet on the condenser/ heat-exchanger (3) functions to deliver said wet air to regenerating air entering the dehumidifier (2) , by means of a separate fan.

Inventors: CLAESSON KNUT, CLAESSON, KNUT
Applicants: CORROVENTA AVFUKTNING AB
Application year: 1992
Main classification: B01D53
IPC codes: B01D53, F24F3