WO2012005164A1 - Drying system of dry exhaust gas circulation type equipped with heat pump unit - Google Patents

Abstract

[Problem] To develop a drying system of a dry exhaust gas circulation type equipped with a novel heat pump unit, wherein cyclic use of dry exhaust gas is enabled, and energetic efficiency in the whole drying system is improved and furthermore cost reduction is realized. [Solution] The drying system is characterized in that an evaporator in the heat pump unit is cyclically supplied with acting water as a heat source medium, and a scrubber device for cleaning the dry exhaust gas exhausted from a dryer is provided such that the cleaned dry exhaust gas (gas which has been cleaned) is partially or entirely sent again to the heat pump unit, warmed there and thereafter supplied to the dryer as drying gas.

Description

Dry exhaust gas circulation drying system with heat pump unit

The present invention relates to a hot-air drying apparatus such as a fluidized bed dryer or a rotary drum dryer, and particularly relates to a dry exhaust gas circulation drying system including a heat pump unit that can circulate and use dry exhaust gas as a dry gas. It is.

In recent years, environmental conservation efforts have become active, and from the viewpoint of energy saving (so-called energy saving), it has been attempted to apply a heat pump unit as a heat source in a drying apparatus.
Specifically, an apparatus in which a heat pump unit using a chlorofluorocarbon refrigerant is applied to a so-called band dryer has been developed (see, for example, Patent Document 1).

By the way, the band dryer is provided with a plurality of stages of net conveyors in which drying is performed in contact with a dry gas when an object to be processed moves on a track such as a net conveyor disposed in a drying chamber. Thus, processing for a long time can be performed.
On the other hand, in a hot air drying apparatus such as a fluidized bed dryer or a rotary drum dryer that performs processing in a relatively short time, it is not practical to apply a heat pump unit to the heat source.

Specifically, in fluidized bed dryers, etc., the residence time (processing time) of the object to be processed in the dryer is short, and a high temperature dry gas is required at the initial stage of drying. In the heat pump using the above refrigerant, the temperature of the hot air obtained is about 50 ° C., and the temperature necessary for drying in a short time cannot be obtained. Therefore, it is necessary to cope with such as increasing the size of the dryer. Therefore, it is impossible to operate efficiently, which leads to an increase in cost.

Therefore, the present applicant makes it possible to apply a heat pump unit as a device for supplying a high-temperature drying gas to a hot-air drying apparatus, and has high energy efficiency as a whole drying system, and further high energy efficiency. A drying system comprising a new heat pump unit and a temperature raising device capable of performing stable operation has been developed and has already been filed for a patent (see Patent Document 2).
The present applicant has continued research and development of a drying system including this type of heat pump unit, and has paid particular attention to circulating and using dry exhaust gas as a dry gas. This means that when exhausted dry exhaust gas is discharged to the outside, a device for removing odorous components and volatile organic compounds is indispensable, and it is possible to reduce costs by reducing the operating rate of these devices and making them smaller. It is expected to become. Further, it is expected that further cost reduction can be achieved by effectively utilizing the heat contained in the dry exhaust gas.

And in order to implement | achieve the circulation use of the above dry exhaust gas, the following subjects exist.
First, it is inevitable that fine powder is mixed in the dry exhaust gas during the drying process of the object to be treated. Therefore, in order to circulate and use the dry exhaust gas, it is necessary to remove the fine powder with high efficiency.
In addition, since odorous components and volatile organic compounds are vaporized from the object to be treated and are contained in the dry exhaust gas, if these odorous components and volatile organic compounds are present in the circulating gas, the odorous components are Or volatile organic compounds can adversely affect the condenser of the heat pump.
Furthermore, in the case of a heat pump unit using carbon dioxide as a refrigerant, when the temperature of the dry exhaust gas exhausted from the dryer is as high as 50 ° C. or higher, supply the dry exhaust gas directly to the condenser in the heat pump unit. Is less advantageous when the efficiency of the entire drying system is taken into account.
Therefore, in the case of a drying system in which the temperature of the drying gas supplied to the dryer is required to be around 100 ° C., a heat pump unit that uses carbon dioxide as a refrigerant is used, and dry exhaust gas is circulated as a drying gas. In order to do this, it is necessary to remove odorous components and volatile organic compounds from the dried exhaust gas and further cool them.

Japanese Patent No. 3957665 Japanese Patent Application No. 2009-40699

The present invention has been made from such a background, and in a drying system to which a heat pump unit is applied as a device for supplying a high-temperature dry gas to a hot air drying device, a deodorizing device is provided by including a scrubber. A new exhaust gas that can be recycled while reducing the amount of exhaust gas treated with exhaust gas treatment equipment, etc., and the energy efficiency of the entire drying system is high, further reducing costs. The development of a dry exhaust gas circulation drying system equipped with a heat pump unit is a technical issue.

That is, a dry exhaust gas circulation type drying system comprising the heat pump unit according to claim 1 is a drying system comprising a dryer and an air supply mechanism for supplying a drying gas to the dryer. Is a hot air dryer, and the air supply mechanism is provided with a heat pump unit.
The evaporator in the heat pump unit is circulated and supplied with working water as a heat source medium,
In addition, a scrubber device for cleaning the dry exhaust gas exhausted from the dryer is provided, and a part or all of the cleaned dry exhaust gas is sent again to the heat pump unit and heated, and then the dryer is used as a dry gas. It is comprised so that it may be supplied to.

In addition to the above requirements, the dry exhaust gas circulation drying system comprising the heat pump unit according to claim 2 further includes a heat for transferring heat transferred from the dry exhaust gas to the scrubber water to the working water. It is characterized in that an exchange mechanism is provided.

Furthermore, the dry exhaust gas circulation type drying system comprising the heat pump unit according to claim 3 is characterized in that, in addition to the above requirements, the scrubber device comprises a plurality of machines.

Furthermore, the dry exhaust gas circulation type drying system comprising the heat pump unit according to claim 4 is provided with a heat exchanger for transferring the heat of the dry exhaust gas to the working water at the subsequent stage of the scrubber device in addition to the above requirements. It is characterized by being.

In addition to the above requirements, the dry exhaust gas circulation type drying system including the heat pump unit according to claim 5 is characterized in that the working water is used as cleaning water located in the scrubber device.
The above problems can be solved by using the configuration of the invention described in each of the claims as a means.

First, according to the invention described in claim 1, since the dry exhaust gas is washed by the scrubber device, it is possible to remove odor components and volatile organic compounds, and it can be reused as dry gas. As a result, the amount of dry exhaust gas discharged to the outside can be remarkably reduced, exhaust gas treatment equipment such as a deodorizing device can be reduced in size, and simplification of the equipment can be realized.

According to the invention described in claim 2, the fine powder in the dry exhaust gas avoids heat transfer inhibition caused by adhering to the heat transfer surface of the heat exchanger, and the heat of the dry exhaust gas is transferred to the working water with high efficiency. Can be made.
Further, since the odor component and the volatile organic compound are removed from the dry exhaust gas by the scrubber device, the exhaust gas treatment facility such as the deodorization device can be completed with a small scale.
Furthermore, the energy efficiency of the entire drying system is improved, and operation at a low running cost becomes possible.

Furthermore, according to the third aspect of the present invention, the dry exhaust gas is more reliably cleaned, the amount of heat in the dry exhaust gas is more reliably recovered, and the absolute humidity of the dry exhaust gas that has passed through a plurality of scrubber devices is further reduced. Since it can be set to a smaller value, the dried exhaust gas can be brought into a more preferable state as a circulating gas to the drying system.

Furthermore, according to the invention described in claim 4, the heat that could not be transferred to the scrubber water in the scrubber device can be transferred to the working water, and the energy efficiency of the entire drying system can be improved. It becomes possible to drive at.

Furthermore, according to the invention described in claim 5, in the scrubber device, the heat of the dry exhaust gas is directly transferred to the working water, so that the configuration of the exhaust heat recovery can be simplified.
In addition, the energy efficiency of the entire drying system is improved, and operation at a low running cost is possible.

It is a block diagram which shows the drying system of this invention comprised so that one scrubber apparatus might be provided. It is a block diagram which shows the drying system of this invention comprised so that two scrubber apparatuses might be provided. It is a block diagram which shows the drying system of this invention comprised so that a scrubber apparatus and a heat exchanger might be provided. It is a block diagram which shows the drying system of this invention comprised so that scrubber water might function as working water.

S Drying System 1 Dryer 10 Housing 10a Duct 11 Ventilation Plate 11a Dam Plate 12 Air Supply Port 12A Air Supply Port 12B Air Supply Port 13 Input Port 14 Exhaust Port 15 Exhaust Port 16A Blow Fan 16B Blow Fan 17 Cyclone 18 Exhaust Fan 19 Exhaust fan 2 Heat pump unit 2A Heat pump unit 2B Heat pump unit 21 Condenser 22 Expansion valve 23 Evaporator 24 Compressor 3 Working water tank 31 Pump 32 Pump 33 Filter 5 Scrubber device 5A Scrubber device 5B Scrubber device 50 Housing 51 Heat transfer tube 52 Scrubber Water 55 Heat exchanger 56 Heat transfer tube 57 Housing 6 Deodorizing device D0 Washed gas D Dry gas D1 Dry gas D2 Dry gas D3 Dry exhaust gas D4 Washed gas H Processed object M Working water T1 Temperature sensor T2 Temperature sensor T3 Temperature sensor V1 damper V2 damper V3 Three-way valve V4 damper

The form of the dry exhaust gas circulation type drying system provided with the heat pump unit of the present invention is as shown in the following examples, but these examples may be appropriately modified within the scope of the technical idea of the present invention. Is possible.

A dry exhaust gas circulation drying system S (hereinafter referred to as a drying system S) provided with a heat pump unit of the present invention includes a dryer 1 and an air supply mechanism for supplying the drying gas D to the dryer 1. It is made up of. Specifically, as shown in FIG. 1, as an example, a dryer 1, a heat pump unit 2 and a scrubber device 5 constituting an air supply mechanism are provided as main elements, and further, as a heat source for the heat pump unit 2. A working water tank 3 for supplying the working water M is provided and configured.
In the drying system S of the present invention, a hot air dryer is applied as the dryer 1, and the residence time (processing time) of the workpiece H in the dryer 1 is short, and further at the initial stage of drying. The drying process by the continuous dryer 1 that requires the high-temperature drying gases D1 and D2 can be performed in a more stable state with high energy efficiency while using the heat pump unit 2. .
Hereinafter, the components of the drying system S will be described in detail, and then the operation mode of the drying system S will be described.

First, the dryer 1 is a fluidized bed dryer which is an example of a hot air dryer. The dryer 1 serves as a processing space for drying the inside of the housing 10, and dry gas D (D 1, D 2) is generated from below a vent plate 11 provided so as to divide the processing space vertically. The drying is performed while forming a fluidized bed on the workpiece H that is supplied and located on the ventilation plate 11.
For this reason, an air inlet 12 is formed at the lower part of the casing 10, an inlet 13 is formed at the upper front (left side in FIG. 1), and an exhaust outlet at the upper rear (right side in FIG. 1). 14 is formed, and a discharge port 15 is formed with respect to the duct 10a connected further to the rear and above the vent plate 11.
Further, the peripheral device of the dryer 1 includes a blower fan 16A, a blower fan 16B, a cyclone 17 and an exhaust fan 18, and the connection state thereof will be described in detail later.

In this embodiment, a configuration is adopted in which a dam plate 11a is provided in the middle of the ventilation plate 11, and the workpiece H that has been dried to some extent passes over the dam plate 11a and moves to the next drying stage. For this reason, the lower space of the ventilation plate 11 is also divided below the barrier plate 11a, and the air supply ports 12A and 12B are formed in the respective spaces. In addition, although illustration is abbreviate | omitted, it is set as the structure which can lift the said dam plate 11a upwards, and you may make it move the to-be-processed object H by releasing at an appropriate time interval.
Further, in this embodiment, a fluidized bed dryer is adopted as the dryer 1, but other hot air dryers such as a fluidized bed granulator dryer, a band dryer or an air dryer can also be adopted.

Next, the heat pump unit 2 will be described. The heat pump unit 2 includes a condenser 21, an expansion valve 22, an evaporator 23, and a compressor 24 to form a heat pump cycle. As an example, carbon dioxide is used. A refrigerant is used. In addition, the temperature of the dry gas D1 heated by the heat pump unit 2 can be increased by employing carbon dioxide as the refrigerant. Incidentally, at present, the heat pump unit 2 using carbon dioxide as a refrigerant has been put into practical use as being capable of raising the temperature of the dry gas D1 to around 150 ° C., but in the future, an equivalent using other refrigerants will be used. When the heat pump unit 2 having performance is put into practical use, it can be adopted.

Next, the scrubber device 5 sends the dry exhaust gas D3 sent from the dryer 1 into the scrubber water 52 filled in the casing 50, and is mixed into the dry exhaust gas D3 during the drying process of the workpiece H. The scrubber water 52 captures fine powder, odor components, and volatile organic compounds, and performs cleaning.
Further, a heat transfer tube 51 is provided in the housing 50, and a heat exchange mechanism is configured to move the heat transferred from the dry exhaust gas D3 to the scrubber water 52 to the fluid moving in the heat transfer tube 51. The scrubber device 5 may be a spray-type device that sprays the scrubber water 52 from the top of the device or a cooling tower type device filled with a saddle or the like.

And as shown in FIG. 1, the drying system S is comprised combining the said dryer 1, the heat pump unit 2, the working water tank 3, and the scrubber apparatus 5. As shown in FIG.
In addition, in this Example, the structure by which the dry gas D1 and D2 from which temperature differs with respect to the dryer 1 is each supplied with respect to air supply port 12A, 12B is taken. For this reason, the blower fan 16A is connected to the input side of the condenser 21 in the heat pump unit 2 by a pipe, and the pipe connected to the output side of the condenser 21 is branched to connect to the air inlets 12A and 12B, respectively. Is done. Further, the pipe connected to the air supply port 12B is connected to a pipe provided with the blower fan 16B, so that the outside gas is mixed into the dry gas D1 to form the dry gas D2 having a lowered temperature. It is configured to be able to.

The input side of the evaporator 23 in the heat pump unit 2 is connected to the working water tank 3 by a pipe line, and the working water tank 3 is further connected to the heat transfer pipe 51 in the scrubber device 5. The output side of the evaporator 23 is also connected to the heat transfer tube 51 in the scrubber device 5. A pump 31 is provided in a pipe line between the input side of the evaporator 23 and the working water tank 3, thereby forming a working water M flow path that continues from the working water tank 3, the evaporator 23, and the heat transfer pipe 51. The
The working water tank 3 is provided with a temperature sensor T1 for measuring the temperature of the working water M accommodated therein.
Furthermore, a valve body of a three-way valve V3 is connected to a pipe line between the output side of the evaporator 23 and the scrubber device 5, and the remaining valve body is a pipe between the working water tank 3 and the scrubber device 5. Connected to the road.
By adopting such a configuration, when there is no need to recover heat from the dry exhaust gas D3 to the working water M, the working water M evaporates from the working water tank 3 without passing through the scrubber device 5. It is possible to flow between the containers 23.

Further, a temperature sensor T2 for measuring the temperature of the dry gas D1 is provided in the pipe line between the heat pump unit 2 and the air supply port 12A, and an appropriate value is determined based on the detection value of the temperature sensor T2. The operating state of the compressor 24 is adjusted by the control device, and is automatically controlled so that the temperature of the dry gas D1 detected by the temperature sensor T2 becomes a predetermined value (for example, 100 ° C.).

Further, a temperature sensor T3 is provided in a pipe line between the air supply port 12B and the blower fan 16B, and an operation state of the blower fan 16B is adjusted by an appropriate control device based on a detected value of the temperature sensor T3. Then, the temperature of the dry gas D2 detected by the temperature sensor T3 is automatically controlled so as to become a predetermined value (90 ° C. as an example).

Further, a cyclone 17 and an exhaust fan 18 are provided for a pipe line connecting the exhaust port 14 and the scrubber device 5 in the dryer 1.
Further, a pipe line is connected to an upper portion of the casing 50 in the scrubber device 5, and this pipe line is branched, and one branch path is connected to the deodorizing device 6 through a damper V1. The other branch path is connected to the blower fan 16A via a damper V2.
By adopting such a configuration, the amount of the cleaned gas D0 flowing out from the scrubber device 5 is distributed by adjusting the balance of the opening degree of the damper V1 and the damper V2.
Then, the cleaned gas D0 sent to the deodorizing device 6 is discharged to the outside by the exhaust fan 19. On the other hand, the cleaned gas D0 sent to the blowing fan 16A side is mixed with an appropriate amount of outside air corresponding to the opening degree of the damper V4 and sent to the condenser 21.

Although illustration is omitted, the working water tank 3 may be configured to have a configuration capable of recovering surplus heat from warm waste water discharged from the peripheral equipment of the drying system S. Here, the peripheral equipment includes not only the peripheral equipment of the drying system S, but also, for example, equipment constituting other production equipment installed in the same factory, and equipment installed in another factory. It shall be.

Moreover, although the drying system S described above is configured to include one heat pump unit 2, by providing two heat pump units 2, the drying gas is individually supplied to each of the air supply ports 12A and 12B. D1 and D2 may be supplied.

The drying system S of the present invention is configured as described above as an example, and the operation mode thereof will be described below.
(1) Flow of dry gas First, the flow of dry gas D will be described. First, the cleaned gas D0 (outside air or gas located in the pipeline in the initial operation state) is sent to the heat pump unit 2 by the blower fan 16A, where it is heated in the condenser 21 to become the dry gas D1 (as an example) 100 ° C). A part of the dry gas D1 is directly sent to the air supply port 12A of the dryer 1, and the remaining dry gas D1 is mixed with outside air to become a dry gas D2 (90 ° C. as an example), which is supplied to the air supply port 12B. Sent.
The dry gases D1 and D2 that act on the object to be processed H in the casing 10 become dry exhaust gas D3 (66 ° C. as an example) whose temperature is reduced by evaporating volatile components such as moisture from the object to be processed H. The air is exhausted from the exhaust port 14 to the outside of the dryer 1 by the fan 18.
Next, the dry exhaust gas D3 is supplied into the scrubber water 52 located in the scrubber device 5 after the dry powder and the like of the workpiece H is removed by the cyclone 17. In the process in which the dry exhaust gas D3 passes through the scrubber water 52, heat, fine powder, odor components, volatile organic compounds, and the like contained in the dry exhaust gas D3 are taken into the scrubber water 52.
In this way, the dried exhaust gas D3 is circulated and used as the cleaned gas D0 in which the fine powder and the like are removed and the temperature is lowered (for example, 30 ° C.), and is sucked by the blower fan 16A and heat pump unit 2 Is supplied to the condenser 21.

In the heat pump unit 2, the COP varies according to the temperature of the cleaned gas D0 supplied to the condenser 21, and in this embodiment, when the temperature of the cleaned gas D0 is 30 ° C., the COP is Since it becomes 3.4 as an example, by operating the heat pump unit 2 in such a state, an efficient operation is possible, and the energy efficiency of the entire drying system S is improved.
When the temperature of the cleaned gas D0 is 50 ° C. or higher, there are few merits when the efficiency of the entire drying system S is taken into consideration.

At this time, the hot water is supplied to the working water tank 3 according to the detected value of the temperature sensor T1 so that the temperature of the working water M in the working water tank 3 is always a constant water temperature (30 ° C. as an example). The
The heat pump 2 has an optimum operating temperature range for efficient operation, and the temperature of the working water M is set to be close to this optimum operating temperature (30 ° C. as an example), whereby the heat pump unit 2 Will be operated efficiently. For this reason, the energy efficiency of the whole drying system S improves.
When all the cleaned gas D0 is discharged to the outside, the damper V1 is opened and the damper V2 is fully closed and sent to the deodorizing device 6, where the deodorizing process is performed and then discharged to the outside.
When all the cleaned gas D0 is circulated, the cleaned gas D0 is sent to the condenser 21 by fully closing the damper V1 while keeping the damper V2 open.

(2) Operation of Heat Pump Unit and Flow of Working Water Next, the operation of the heat pump unit 2 and the flow of working water M will be described.
In the heat pump unit 2, the external heat is taken into the refrigerant (carbon dioxide or the like) in the evaporator 23, and further heated by the compressor 24, and then the heat is transferred to the cleaned gas D 0 in the condenser 21. Temperature is done. And as the external heat source in such an evaporator 23, the working water M supplied from the working water tank 3 is provided, and the working water M supplied to the evaporator 23 is a refrigerant (carbon dioxide or the like). ) Is exhausted from the evaporator 23 in a state where the temperature is lowered due to the loss of energy.
And although the temperature of the working water M will fall, in order to use this working water M again as a heat source in the heat pump unit 2, it is necessary to raise the temperature to around 30 ° C.
For this reason, in this invention, the working water M (25 degreeC as an example) discharged | emitted from the evaporator 23 is sent to the heat exchanger tube 51 in the scrubber apparatus 5, Here, the scrubber water 51 is contained in the working water M. The heat moves and the temperature rises (as an example, 30 ° C.).
At this time, heat transfer inhibition due to the fine powder in the dry exhaust gas D3 adhering to the heat transfer surface of the heat transfer tube 51 is avoided, and the heat of the dry exhaust gas D3 can be transferred to the working water M with high efficiency.
In this way, the working water M heated by the heat of the dry exhaust gas D3 (mediated by the scrubber water 51) is sent again to the heat pump unit 2 via the working water tank 3 to increase the cleaned gas D0. Since the temperature is provided, the energy efficiency of the entire drying system S is improved, and operation at a low running cost is possible.

(3) Drying of the object to be processed In the object to be processed H such as food raw material supplied to the dryer 1, a fluidized bed is first formed by the dry gas D1 (100 ° C.) blown from the air inlet 12A. At the same time, volatile components such as moisture are removed.
Eventually, the workpiece H becomes lighter in weight as the drying progresses, gets over the barrier plate 11a, enters the working area of the dry gas D2 (60 ° C.) blown from the air supply port 12B, and further proceeds to the desired drying state. It becomes a dry state and is discharged | emitted from the discharge port 15 outside.

[Other Examples]
Although the present invention is based on the above-described embodiment, the present invention can take the following forms based on the technical idea of the present invention.

[Embodiment configured to include two scrubber devices]
First, the drying system S shown in FIG. 2 is provided with two scrubber devices 50, and is configured by arranging scrubber devices 5B in series at the subsequent stage of the scrubber device 5A.
Specifically, the heat transfer tube 51 of the scrubber device 5A and the heat transfer tube 51 of the scrubber device 5B are connected, and the upper portion of the casing 50 of the scrubber device 5A and the lower portion of the casing 50 of the scrubber device 5B are connected by a pipe line. To do.
When such a configuration is adopted, the dry exhaust gas D3 is cleaned by the scrubber water 52 in the scrubber device 5B next to the scrubber device 5A, so that it is possible to more reliably remove fine powder and the like. . Further, since the dry exhaust gas D3 moves heat to the scrubber water 52 in the scrubber device 5A and the scrubber water 52 in the scrubber device 5B, the temperature of the cleaned gas D0 can be further reduced.
For example, if the temperature (water temperature) of the scrubber water 52 in the scrubber device 5B is maintained below the dew point temperature of the outside air, the temperature of the cleaned gas D0 can be lowered below the dew point temperature of the outside air, and the absolute humidity of the cleaned gas D0 Can be lowered below the absolute humidity of the dry exhaust gas D3.
Three or more scrubber devices 5 may be provided in the drying system S, and a plurality of scrubber devices 5 may be arranged in parallel.

[Embodiment configured to include a scrubber device and a heat exchanger]
Further, the drying system S shown in FIG. 3 includes a heat exchanger 55 for transferring the heat of the cleaned gas D4 to the working water M at the subsequent stage of the scrubber device 5.
In the heat exchanger 55, a heat transfer tube 56 is arranged in a housing 57, and heat exchange is performed between the cleaned gas D 4 that passes through the housing 57 and the working water M that passes through the heat transfer tube 56. Is configured to be performed.
When such a configuration is adopted, the heat that could not be transferred to the scrubber water 52 in the scrubber device 5 can be transferred to the working water M, and the energy efficiency of the entire drying system S can be improved to further reduce the running. Operation at cost is possible.

[Example in which scrubber water functions as working water]
Furthermore, the drying system S shown in FIG. 4 uses the working water M as the scrubber water 52 located in the scrubber device 5. A pump 32 is provided in a pipe line between the three-way valve V3 and the evaporator 23.
The scrubber device 5 is configured without the heat transfer tube 51 in the casing 50. In this case, the dry exhaust gas D3 is in direct contact with the scrubber water 52 (working water M). Therefore, the heat of the dry exhaust gas D3 is directly transferred to the scrubber water 52 (working water M), so that the efficiency of exhaust heat recovery can be enhanced and the configuration for exhaust heat recovery can be simplified.
In this embodiment, it is assumed that the dry exhaust gas D3 does not contain fine powder or components that adversely affect the evaporator 23 or the like. However, fine powder or the like is present in the working water M (scrubber water 52). If mixing is unavoidable, a filter 33 may be provided in a pipe line connecting the scrubber device 5 and the working water tank 73 in the circulation path of the working water M so as to remove fine powder and the like.

[Other modifications]
In the above-described embodiments, the scrubber device 5 and the heat exchanger 55 are disposed between the exhaust fan 18 and the damper V1, and all of the exhaust gas D3 discharged from the dryer 1 is supplied to the scrubber device 5. However, the scrubber device 5 and the heat exchanger 55 are arranged between the damper V2 and the blower fan 16A, and only the dry exhaust gas D3 that is diverted for circulation is supplied to the scrubber device 5. You may comprise as follows.

Claims (5)

A drying system comprising a dryer and an air supply mechanism for supplying dry gas to the dryer, wherein the dryer is a hot air dryer, and the air supply mechanism is provided with a heat pump unit. In the drying system, the evaporator in the heat pump unit is circulated and supplied with working water as a heat source medium, and further includes a scrubber device for cleaning dry exhaust gas exhausted from the dryer. A part of or all of the dry exhaust gas after cleaning is again sent to the heat pump unit and heated, and then supplied to the dryer as a dry gas. Dry exhaust gas circulation drying system. 2. The dry exhaust gas with a heat pump unit according to claim 1, wherein the scrubber device is provided with a heat exchange mechanism for transferring heat transferred from the dry exhaust gas to the scrubber water to the working water. Circulating drying system. 3. A dry exhaust gas circulation drying system comprising a heat pump unit according to claim 1, wherein the scrubber device comprises a plurality of machines. A dry exhaust gas circulation type equipped with a heat pump unit according to claim 1, 2 or 3, further comprising a heat exchanger for transferring the heat of the dry exhaust gas to the working water after the scrubber device. Drying system. The dry exhaust gas circulation type drying system comprising the heat pump unit according to claim 1, 2, 3, or 4, wherein the working water is used as washing water located in the scrubber device.

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