Dehumidifiers for a drying system and drying systems with such dehumidifiers, as well as drying processes

Abstract

Dehumidifier for a drying system, characterized in that it is designed for alternative operation in two operating modes, wherein the first operating mode comprises a fresh air operation in which the exhaust air stream (10) coming from a dryer (20) of the drying system is fed to a first heat exchanger (4) and thermal energy is extracted from the exhaust air stream (10) there, and the exhaust air stream (10) is subsequently released into the environment, and a fresh air stream (11) drawn in from the environment is fed to a second heat exchanger (5), is dehumidified there if the drying process requires it and / or the moisture content of the fresh air stream (11) is above a defined limit value, and is then fed to the first heat exchanger (4), where it is heated with the thermal energy previously extracted from the exhaust air stream (10) and fed to the dryer (20), and the second operating mode comprises a recirculation operation.in which the exhaust air stream (10) coming from the dryer is fed to the first heat exchanger (4) and heat energy is extracted from the exhaust air stream (10) there, and the exhaust air stream (10) is subsequently fed to the second heat exchanger (5), where it is dehumidified if the drying process requires it and / or the moisture content of the exhaust air stream (10) is above a defined limit value, and is again fed to the first heat exchanger (4), where the air stream is heated with the heat energy previously extracted from the exhaust air stream (10) and fed to the dryer (20).

Description

[0001] The invention relates to a dehumidifier for a drying system, and to a drying system for drying objects or the like with such a dehumidifier, as well as to a drying method.

[0002] Drying systems are used in industry and in the trades and are used, for example, in the field of electroplating to dry the galvanized objects after the final rinsing process.

[0003] However, the application area of ​​such drying systems is not limited to electroplating technology and can include any other application areas.

[0004] Dryer systems typically consist of a dryer and a dehumidifier for dehumidifying the air inside the dryer. Condensation dehumidification is a common method. This is based on the heat pump principle. Air is cooled by an air cooler (direct evaporator in a refrigeration circuit) to such an extent that water vapor condenses and can be separated as water by falling below the dew point.

[0005] The previously cooled air is then heated to intake temperature by the refrigerant condenser using waste heat from the heat pump circuit.

[0006] Other methods of air dehumidification, so-called absorption dehumidification or adsorption dehumidification, use liquid or granular media that absorb the moisture contained in the air flowing through it.

[0007] Various drying systems for drying components or the like are known from the state of the art.

[0008] DE 20 2019 100 525 U1 discloses a drying system in which moist exhaust air is removed from the dryer and replaced by ambient air (hall air) as supply air.

[0009] A heat recovery system, through which the exhaust air flows, saves energy when heating the supply air. This system reaches its limits, especially in warmer months with high ambient temperatures and high humidity. Drying is then no longer reliable or insufficient.

[0010] In another well-known concept, the air in the dryer system is dehumidified using a cold trap in a closed system and the cooled air is then heated using a heat pump.

[0011] The system is expensive to purchase. Since the heat pump is constantly running, it consumes energy continuously, even when the air in the dryer is already dry.

[0012] DE 20 2019 100 525 U1 describes a dryer with a recirculation device for generating a recirculating air flow through the dryer chamber. Continuous fresh air operation is provided by a ventilation device that, in bypass mode, continuously supplies fresh air to the recirculating air flow in the dryer chamber and removes exhaust air.

[0013] US 2019 / 0 274 ​​316 A1 discloses a dehumidifier for an oven. Humid air from the oven is fed into the dehumidifier, passes through a heat exchanger for cooling, and then through an evaporator / condenser for dehumidification. The cool, dehumidified air is heated in the heat exchanger using the energy extracted from the air flow from the oven and fed back into the oven. Thus, the air in the oven is dehumidified in pure recirculation mode.

[0014] DE 969 260 B discloses a dryer which cannot be operated in a pure circulation mode, but operates according to claim 1 either in a fresh air or fresh air-recirculation mode, or according to claim 3 in a mixed air mode or according to claim 5 in a pure fresh air mode.

[0015] The object of the invention is to improve a dehumidifier and a drying system with such a dehumidifier with regard to application possibilities and energy efficiency, whereby optimal dehumidification with low energy consumption should be enabled depending on the situation and ambient conditions.

[0016] This object is achieved by a dehumidifier having the features of patent claim 1 and a drying system having the features of patent claim 5.

[0017] A drying process according to the invention is specified in claim 9.

[0018] Preferred embodiments of the invention and further advantageous features of the invention are specified in the subclaims.

[0019] According to the invention, the dehumidifier for the drying system is designed for operation in two operating modes.

[0020] In the first operating mode, fresh air operation takes place, in which an exhaust air stream coming from the dryer is fed to a first heat exchanger, heat energy is extracted from the exhaust air stream and the exhaust air stream is subsequently released into the environment.

[0021] A fresh air stream drawn in from the environment is fed to a second heat exchanger, dehumidified there if necessary and then fed to the first heat exchanger, where it is heated using the thermal energy previously extracted from the exhaust air stream and then fed to the dryer.

[0022] In a second operating mode, a recirculation operation takes place in which the exhaust air flow coming from the dryer is fed to the first heat exchanger and heat energy is extracted from the exhaust air flow there, and the exhaust air flow is subsequently fed to a second heat exchanger, dehumidified there if necessary and again fed to the first heat exchanger, where the air flow is heated with the heat energy previously extracted from the exhaust air flow and subsequently fed to the dryer.

[0023] This is a closed air circuit in the drying system.

[0024] Depending on the design of the invention, the first heat exchanger can be completely omitted in all operating modes or can only be put into operation when required.

[0025] The second heat exchanger is only put into operation when necessary.

[0026] The air in the dryer must be dehumidified, especially at the beginning of the drying process, as this is when the humidity in the dryer is at its highest.

[0027] Once the initial moisture has dried off the components to be dried and disappeared, the humidity in the dryer decreases.

[0028] The humidity in the dryer remains largely constant at a low level over a large period of the drying period.

[0029] During this period, you can avoid dehumidifying the air in the dryer and save energy by switching off the second heat exchanger or operating at a low power level.

[0030] The advantage of the invention is that the dehumidification can be adjusted by sensor control to the lowest energy requirement for the drying task and yet process reliability and fast drying operation are guaranteed.

[0031] In a preferred embodiment of the invention, the dehumidifier comprises a housing in which a first and a second fan, the first and the second heat exchanger and a first and a second flap are arranged.

[0032] The components are connected to each other via internal airways, with the airways being able to be partially opened and closed by the flaps.

[0033] Preferably, in the first operating mode, the first flap is in a first flap position in which an exhaust air outlet is open, through which the exhaust air flow coming from the dryer and laden with moisture can escape into the environment.

[0034] At the same time, the second flap is in a first flap position in which a fresh air inlet is opened and a connection is established between the outlet of the first heat exchanger and the inlet of the second heat exchanger, wherein a fresh air flow is sucked in from the environment via the fresh air inlet, fed to the second heat exchanger, dehumidified there if necessary, and subsequently fed to the first heat exchanger, heated there and then fed to the dryer.

[0035] In the second operating mode, the first flap is in a second flap position in which the exhaust air outlet is closed.

[0036] The second flap is in a second flap position in which the fresh air inlet is closed and a connection is established between the outlet of the first heat exchanger and the inlet of the second heat exchanger, so that the exhaust air flow coming from the first heat exchanger is fed to the second heat exchanger and dehumidified there if necessary, and then fed to the first heat exchanger and heated there, and subsequently fed to the dryer.

[0037] Advantageously, the second heat exchanger only needs to be switched on and the air dehumidified through it when the drying process requires it and / or the moisture content of the air flow is above a specified limit.

[0038] The invention also relates to a drying system for drying components, which comprises a dryer with a housing and a receiving space for the components to be dried, wherein the dryer is connected to a dehumidifier which removes moisture-laden exhaust air from the receiving space of the dryer and supplies less humid supply air, wherein a dehumidifier with the features described above is used.

[0039] The dryer system according to the invention can be designed such that the dryer and the dehumidifier form separate units that are connected to each other via air ducts, or can be designed such that the dryer and the dehumidifier form a common unit.

[0040] A further advantageous feature of the invention is that the drying system can be constructed flexibly and modularly, with dryers and dehumidifiers being available in various designs and types that can be combined with each other as required depending on the application.

[0041] According to a method according to the invention for drying components, the components to be dried are brought into a receiving space of a dryer and there surrounded by an air stream, wherein moisture-laden exhaust air is removed from the dryer by a dehumidifier and less humid supply air is supplied, wherein a dehumidifier according to the features described above is used.

[0042] In a dehumidifier, by switching between a first and a second operating mode, either the exhaust air flow coming from the dryer is dehumidified in a closed circuit through a heat exchanger and fed back to the dryer, or the exhaust air flow is released from the dryer into the environment and a fresh air flow is fed to the heat exchanger and dehumidified if necessary, whereby the heat exchanger is only used to dehumidify the air flow when the drying process requires it.

[0043] Optionally, a further heat exchanger can be provided which extracts thermal energy from the exhaust air stream coming from the dryer and uses this thermal energy to heat the dehumidified supply air stream fed to the dryer.

[0044] Preferred embodiments of the invention are explained in more detail below with reference to the drawings. Further features and advantages of the invention will become apparent from the drawings and the following description. Fig. 1 shows a schematic diagram of a drying system with a dryer and a dehumidifier. Fig. 2 shows a schematic section through a first embodiment of a dehumidifier in a first operating mode (fresh air mode) Fig. 3 shows a schematic section through a first embodiment of a dehumidifier in a second operating mode (circulation mode) Fig. 4 shows a schematic section through a second embodiment of a dehumidifier in a first operating mode (fresh air mode) Fig. 5 shows a schematic section through a second embodiment of a dehumidifier in a second operating mode (circulation mode)

[0045] The drying system 20 consists of a dryer 20 and a dehumidifier 30.

[0046] The dryer 20 has a closed dryer housing 21 which has a flap 22 on the top side, via which objects to be dried can be introduced into and removed from a receiving space of the dryer housing 21.

[0047] In the dryer housing 21, for example, recirculating air ducts and one or more fans are arranged, which generate a recirculating air flow in the receiving space, which flows around the components to be dried and absorbs the moisture adhering to the components.

[0048] Furthermore, heating elements are preferably provided in the dryer housing 21 to heat the air in the receiving space. Heated air can absorb more moisture, thus accelerating the drying process.

[0049] According to the invention, the drying system comprises a dehumidifier 30, which is preferably designed as an external unit and dehumidifies the process air in the dryer 20 to further accelerate the drying process. Alternatively, the dehumidifier 30 can be integrated into the housing of the dryer 20.

[0050] The dryer 20 is connected to the dehumidifier 30 via air ducts. Fig. 2 and Fig. 3 shows a first preferred embodiment of a dehumidifier 30 in section.

[0051] The dehumidifier 30 has a housing 31 in which the components of the dehumidifier are arranged and fluidically connected to one another via air ducts and connected chambers.

[0052] The housing 31 has several air inlets and air outlets, some of which can be opened or closed by means of flaps 6, 7.

[0053] In a first operating mode of the dehumidifier 30, according to Fig. 2, a moisture-laden exhaust air stream 10 is sucked from the dryer 20 via an air inlet by means of a fan 2 arranged in the housing 31 and enters the dehumidifier 30.

[0054] The exhaust air stream 10 is optionally filtered by a mechanical filter 3 to remove dirt and dust particles.

[0055] The exhaust air stream 10 is then passed through a heat exchanger 4, where heat energy is extracted from the exhaust air stream 10, which is then used to preheat the dehumidified air stream fed back to the dryer 20.

[0056] The heat exchanger 4 can be a cross-counterflow heat exchanger.

[0057] Downstream of the heat exchanger 4, a first flap 6 is arranged, which can assume a first position and a second position.

[0058] In the illustrated first position of the flap 6, a connection to the fan 2 is open, which, as described above, sucks in the exhaust air flow 10 from the dryer 20 and blows it out into the environment via an exhaust air outlet 13.

[0059] In the first position, the first flap 6 closes a connection between the outlet of the first heat exchanger 4 and the inlet of the second heat exchanger 5.

[0060] A second fan 1 draws in a fresh air stream 11 from the environment and passes through a fresh air inlet 9 into the dehumidifier 30.

[0061] A second flap 7 is arranged at the fresh air inlet 9, which is in the Fig. 2, the fresh air inlet 9 is released.

[0062] The fresh air stream 11 flows through a second heat exchanger 5, which extracts heat energy from the fresh air stream 11 so that the moisture contained therein condenses out.

[0063] The resulting condensate is drained away. The dehumidified fresh air stream 11 is passed through the first heat exchanger 4 described above, where it is preheated with the thermal energy extracted from the exhaust air stream 10. It is then blown into the dryer 20 via the air outlet 12 by the fan 1.

[0064] The second heat exchanger 5 only needs to be put into operation when the fresh air flow 11 has a moisture content that is above a predetermined limit.

[0065] Especially in winter at low temperatures and low humidity, the second heat exchanger 5 does not need to be put into operation, since the fresh air flow 11 does not need to be dehumidified under these conditions.

[0066] This saves considerable energy and increases the efficiency of the dehumidifier 30.

[0067] The first operating mode of the dehumidifier 30 described above is referred to as fresh air operation.

[0068] A second operating mode of the dehumidifier 30 is the circulation mode, which Fig. 3 is shown.

[0069] In the second operating mode, the first flap 6 is in a second flap position in which the connection between the heat exchanger 4 and the second fan 2 is closed and instead a connection between the outlet of the first heat exchanger 4 and the inlet of the second heat exchanger is open.

[0070] The second fan 2 is not needed.

[0071] The second flap 7 is closed and closes the fresh air inlet 9 and thus the connection to the environment.

[0072] By means of the first fan 1, the exhaust air flow 10 is sucked in from the dryer 20 and enters the dehumidifier 30 via the air inlet 8.

[0073] The exhaust air stream 10 is moisture-laden air from the dryer 20.

[0074] The exhaust air stream 10 is optionally filtered by a mechanical filter 3 to remove dirt and dust particles.

[0075] The exhaust air stream 10 is then passed through a first heat exchanger 4, where heat energy is extracted from the exhaust air stream 10, with which heat energy the dehumidified air stream fed to the dryer 20 is preheated.

[0076] The first flap 6 closes the connection to the second fan 2 so that the exhaust air flow 10 flows through the second heat exchanger 5, where heat energy is extracted from the exhaust air flow 10 so that the moisture contained therein condenses out.

[0077] The condensate is drained away.

[0078] The dehumidified exhaust air stream 10 is again passed from the second heat exchanger to the first heat exchanger 4, where it is preheated with the thermal energy previously extracted from the exhaust air stream 10, and is fed to the dryer 20 via the fan 1 and the air outlet 12 as a dehumidified and preheated air stream 10*.

[0079] Here, too, the second heat exchanger 5 only needs to be put into operation when the exhaust air stream 10 has a moisture content that is above a predetermined limit value.

[0080] The second embodiment of the dehumidifier, according to the Fig. 4 and Fig. 5, differs from the first embodiment of the dehumidifier, according to the Fig. 2 and Fig. 3, only by the arrangement of the first flap 6* and the air flow through the second fan 2.

[0081] The first flap 6* is not arranged at the inlet but at the outlet of the second fan 2 and can close the exhaust air outlet 13 towards the environment.

[0082] The arrangement of the second flap 7 remains unchanged.

[0083] In a second flap position, the second flap 7 establishes a connection between the outlet of the second fan 2 and the inlet of the second heat exchanger 5.

[0084] The first operating mode of the dehumidifier 30, according to Fig. 4, corresponds exactly to the first operating mode explained above, as used in conjunction with Fig. 2 was described.

[0085] The only difference is that the first flap 6* is arranged at the outlet of the fan 2 and is open in the first operating mode so that the exhaust air flow 10 from the dryer 20 can escape into the environment.

[0086] The second operating mode of the dehumidifier 30, the circulation mode, is in Fig. 5 shown.

[0087] In the second operating mode, the first flap 6* is in a second flap position and closes the exhaust air outlet 13 so that no air can escape into the environment via the second fan 2 and the exhaust air outlet 13.

[0088] The second flap 7 is in a second flap position and closes the fresh air inlet 9 so that no air can enter or escape via the fresh air inlet 9.

[0089] In a second flap position, the second flap 7 establishes a connection between the outlet of the second fan 2 and the inlet of the second heat exchanger 5.

[0090] The exhaust air flow 10 from the dryer 20 is sucked in by the second fan 2 and passed through the filter 3 and the first heat exchanger 4, where heat energy is extracted from the air flow 10, into the second heat exchanger 5 by the second fan.

[0091] In the second heat exchanger 5, the air stream 10 is cooled, causing the moisture contained in the air stream 10 to condense. The condensate is then removed.

[0092] By means of the first fan 1, the dehumidified air flow 10 is passed through the first heat exchanger 4 and preheated there with the thermal energy previously extracted from the exhaust air flow 10 and fed to the dryer 20 via the fan 1 and the air outlet 12 as a dehumidified and preheated air flow 10*.

[0093] The second heat exchanger 5 only needs to be put into operation when the exhaust air stream 10* has a moisture content that is above a predetermined limit. List of reference symbols 1 fan 2 fans 3 filters 4 heat exchangers 5 heat exchangers 6 flap 7 flap 8 Air inlet (exhaust air from the dryer) 9 Fresh air intake 10 Exhaust air flow (from the dryer) 11 Fresh air flow 12 Air outlet (to the dryer) 13 Exhaust air outlet 20 dryers 21 Dryer housing 22 flap 30 dehumidifiers 31 housings

Claims

[1] Dehumidifier for a drying system, characterized bythat it is designed for alternative operation in two operating modes, wherein the first operating mode comprises a fresh air mode in which the exhaust air stream (10) coming from a dryer (20) of the drying system is fed to a first heat exchanger (4) and thermal energy is extracted from the exhaust air stream (10) there, and the exhaust air stream (10) is subsequently released into the environment, and a fresh air stream (11) sucked in from the environment is fed to a second heat exchanger (5), dehumidified there if the drying process requires it and / or the moisture content of the fresh air stream (11) is above a predetermined limit, and then fed to the first heat exchanger (4), heated there with the thermal energy previously extracted from the exhaust air stream (10) and fed to the dryer (20), and the second operating mode comprises a recirculation mode,in which the exhaust air stream (10) coming from the dryer is fed to the first heat exchanger (4) and heat energy is extracted from the exhaust air stream (10) there, and the exhaust air stream (10) is subsequently fed to the second heat exchanger (5), dehumidified there if the drying process requires it and / or the moisture content of the exhaust air stream (10) is above a predetermined limit, and is again fed to the first heat exchanger (4), where the air stream is heated with the heat energy previously extracted from the exhaust air stream (10) and fed to the dryer (20). [2] Dehumidifier according to claim 1, characterized by in that it comprises a housing (31) in which a first and a second fan (1, 2), the first and the second heat exchanger (4, 5) and a first and a second flap (6, 6*, 7) are arranged. [3] Dehumidifier according to one of claims 1 or 2, characterized byin that in the first operating mode the first flap (6, 6*) is in a first flap position and releases an exhaust air outlet (13), but closes the connection between the outlet of the first heat exchanger (4) and the inlet of the second heat exchanger (5) so that the exhaust air flow (10) coming from the dryer (20) escapes into the environment via the exhaust air outlet (13), and the second flap (7) is in a first flap position and releases a fresh air inlet (9), wherein a fresh air flow (11) is sucked in from the environment via the fresh air inlet (9) and fed to the second heat exchanger (5) and dehumidified there if necessary, and subsequently fed to the first heat exchanger (4) and heated there and finally fed to the dryer (20). [4] Dehumidifier according to one of claims 1 to 3, characterized byin that in the second operating mode the first flap (6, 6*) is in a second flap position and closes the exhaust air outlet (13), and the second flap (7) is in a second flap position and closes the fresh air inlet (9) but opens the connection between the outlet of the first heat exchanger (4) and the inlet of the second heat exchanger (5), so that the exhaust air flow (10) coming from the first heat exchanger (4) is fed to the second heat exchanger (5), dehumidified there if necessary, then fed to the first heat exchanger (5), heated there and subsequently fed to the dryer (20). [5] Drying system for drying components, which comprises a dryer (20) with a housing (21) and a receiving space for the components to be dried, wherein the dryer (20) is connected to a dehumidifier (30) which removes a moisture-laden exhaust air flow (10) from the dryer (20) and supplies the dryer (20) with a less humid supply air flow (10*, 11), characterized by that a dehumidifier (30) according to one of claims 1 to 4 is used. [6] Drying system according to claim 5, characterized by that the dryer (20) and the dehumidifier (30) form separate units which are connected to each other via air ducts. [7] Drying system according to claim 5, characterized by that the dryer (20) and the dehumidifier (30) form a common unit. [8] Drying system according to one of claims 5 to 7, characterized bythat dryers (20) and dehumidifiers (30) are available in various designs and types, which can be combined with one another as required depending on the application. [9] Method for drying components with a drying system according to one of claims 5 to 8, wherein the components to be dried are brought into a receiving space of the dryer (20) and are surrounded there by an air stream, wherein a moisture-laden exhaust air stream (10) is withdrawn from the dryer (20), and a less humid supply air stream (10*, 11) is supplied to the dryer (20), characterized bythat in the dehumidifier (30) by switching between a first and a second operating mode either a circulation operation is carried out, in which the exhaust air flow (10) coming from the dryer (20) is dehumidified in a closed circuit through a heat exchanger (5) and fed back to the dryer (20), or a fresh air operation is carried out, in which the exhaust air flow from the dryer (20) is released into the environment and a fresh air flow (11) is fed to the heat exchanger (5) and dehumidified if the drying process requires it and / or the moisture content of the fresh air flow (11) is above a predetermined limit. [10] Method according to claim 9, characterized by the use of the dehumidifier (30) according to one of claims 1 to 4.

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