JP2004116846A - Drying system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce initial cost and running cost of a drying system. <P>SOLUTION: This drying system has a drier 1 having a pressure-proof sealed structure shape, a tank 22 for temporarily storing moisture from the drier 1, a steam exhaust passage 9 for communicating the drier 1 with the tank 22, a heat pump 19, a waste heat recovery unit 11 for exchanging heat between a part of the steam exhaust passage 9 and the cold heat side of the heat pump 19, a first valve 23 arranged in the steam exhaust passage 9 between the tanks 22 from the waste heat recovery unit 11, a second valve 24 for discharging liquid outside in a lower part of the tank 22, a decompressing means 25, a branch pipe for piping the decompressing means 25 by branching off from between the first valve 23 and the second valve 24 and a third valve 26 arranged in the branch pipe. A part of the hot heat side of the heat pump 19 is arranged so as to tranfer heat to the drier 1. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hydrate drying system.
[0002]
[Prior art]
As a conventional drying system, there is a combination of a dryer and a heat pump (for example, see Patent Document 1).
[0003]
Hereinafter, the conventional drying system will be described with reference to the drawings.
[0004]
As shown in FIG. 8, the conventional drying system includes a dryer 1 and a heat pump chiller unit 2 configured in a pressure-resistant closed container shape. The dryer 1 is provided with an inlet 3 for charging the object to be dried and an outlet 4 for extracting the material to be dried, and is equipped with a stirrer 5 and an auxiliary heating device 6 for stirring the object to be dried to promote drying. ing.
[0005]
The stirrer 5 includes a screw 7 and a motor 8 for driving the screw 7 to rotate. The screw 7 lifts the material to be dried downward so as to drop it along the inner peripheral surface of the side wall of the dryer 1. The peripheral edge has a slight distance from the inner peripheral surface of the side wall of the dryer 1 and is formed such that the distance gradually increases as it extends upward. The auxiliary heating device 6 will be described later.
[0006]
In the dryer 1, the water vapor discharge passage 9 is taken out from the upper part, and a water jacket 10 is provided on a side wall part. The terminal of the steam discharge passage 9 is open to the atmosphere, and a waste heat recovery unit 11 and a water ring vacuum pump 12 are provided in the middle.
[0007]
The water jacket 10 is connected to a heat medium circulation path 14 in which a first circulation pump 13 is interposed. Therefore, the heat medium for circulating and flowing through the water jacket 10 exchanges heat with the dryer 1 to heat the dryer 1, thereby constituting a dryer heating heat exchanger. The heating medium is hot water.
[0008]
The waste heat recovery unit 11 is provided in the steam discharge passage 9 between the dryer 1 and the water-sealed vacuum pump 12, passes through the steam discharge passage 9 in a meandering shape, and has a second circulation pump 15 interposed therebetween. The refrigerant circulation path 16 is connected.
[0009]
The water-sealed vacuum pump 12 has a conventionally well-known structure in which a main body is constituted by a circular casing and an impeller mounted eccentrically in the casing, and an appropriate amount of water is filled in the casing. When the car is rotated, the water creates a circular water film concentric with the casing due to the centrifugal force, which creates a space enclosed by the water film and the adjacent blades and blades, and the space increases as the impeller rotates. By changing the volume, suction, compression and discharge are continuously performed.
[0010]
On the other hand, the heat pump type chiller unit 2 condenses the heat between the compressor 17 and the capillary tube 18 in the flow direction of the refrigerant in the heat pump 19 in which the compressor 17 and the capillary tube 18 are interposed in a closed circulation pipe filled with a refrigerant such as Freon. An evaporator 21 is provided between the condenser 20, the capillary tube 18 and the compressor 17, and the heat medium circulation path 14 is provided in the condenser 20, and the refrigerant circulation path 16 is provided in the evaporator 21.
[0011]
In the vacuum drying apparatus, for example, an object to be dried such as garbage is put in the dryer 1 and hermetically closed, and the water ring vacuum pump 12 is driven to drive the inside of the dryer 1 to the boiling point of water. When the compressor 17 of the heat pump 19 is driven by reducing the pressure until the temperature becomes equal to the outside temperature, the heat pump 19 becomes high pressure between the compressor 17 and the capillary tube 18 due to the passage resistance of the capillary tube 18, and the refrigerant condenses. As a result, the temperature rises, and the pressure between the capillary tube 18 and the compressor 17 becomes low, so that the refrigerant evaporates and the temperature decreases.
[0012]
The heat generated by the heat pump 19 is exchanged with the water circulating through the refrigerant circuit 16 in the evaporator 21 of the chiller unit 2 to absorb the heat of the water and cool the water. The condenser 20 heats the hot water by exchanging heat with the hot water circulating in the heat medium circulation path 14.
[0013]
The hot water heated by the condenser 20 of the chiller unit 2 flows to the heat exchanger 10 for heating the dryer, heats the dryer 1, and heats the material to be dried inside the dryer 1 by the heating energy to evaporate the water. Let it.
[0014]
Thereby, the steam pressure in the dryer 1 is increased, and the steam in the dryer 1 is sucked into the steam discharge passage 9 together with the operation of the water ring vacuum pump 12.
[0015]
On the other hand, the cold water cooled by the evaporator 21 of the chiller unit 2 flows to the waste heat recovery unit 11, and recovers and condenses waste heat from the steam flowing through the steam discharge passage 9.
[0016]
As a result, the steam is reduced in volume and discharged as drain water via the water ring vacuum pump 12. Therefore, evaporation occurs continuously inside the dryer 1 to dry the object to be dried.
[0017]
In this apparatus, the dryer 1 indirectly uses the heat of the heat pump 19 by exchanging heat with water for heating, and the waste heat recovery unit 11 uses a heat pump for recovering and condensing waste heat of steam. The cold energy of 19 is exchanged with water for indirect use. That is, the heat energy consumed for evaporation inside the dryer 1 is recovered by the waste heat recovery unit 11, returned to the original dryer 1 by the heat pump 19, and recycled.
[0018]
In the final stage of drying, when it is necessary to dry the object to be dried, the auxiliary heating device 6 is used.
[0019]
The auxiliary heating device 6 is a tube-type gas burner that generates far-infrared rays. In addition to the case where the object to be dried needs to be dried quickly, the temperature of the cold water is too low in the early stage of operation in winter, and the operation becomes impossible. It may be used temporarily to prevent this.
[0020]
When the auxiliary heating device 6 is used in combination, the balance of the thermal energy sent to the dryer 1 and the waste heat recovery device 11 is lost, so an auxiliary radiator (not shown) including a fan or the like is provided in the heat medium circulation path 14 to Release heat.
[0021]
As described above, when the garbage is dried using the conventional drying system, as a general vacuum drying effect, it can be easily recovered immediately after the drying is completed by low-temperature drying, and the weight can be reduced by drastically reducing the amount of water. It is sanitary due to the elimination of specific species of bacteria in a vacuum. No chemicals are used, so the collected garbage can be reused as fertilizer and feed, and can be easily incinerated. Since it is water, there is an effect that there is no fear of water pollution even if it is discharged as it is.
[0022]
Furthermore, in addition to the above-mentioned effects, energy is dissipated into the atmosphere, so that it is very economical without wasteful consumption. Water vapor evaporated from the material to be dried is condensed by the waste heat recovery unit to reduce the volume. Therefore, the discharge efficiency of the water ring vacuum pump is increased, and a small-sized and small-capacity pump can be used. In addition to reducing the size and cost of the entire apparatus, the aim is to reduce running costs such as power consumption. It is a thing.
[0023]
[Patent Document 1]
Japanese Patent Publication No. 7-35946
[0024]
[Problems to be solved by the invention]
However, in the above-mentioned conventional drying system, since there is no condensed water in front of the water ring vacuum pump 12 in the water vapor exhaust passage 9 in the initial stage of use, the exhaust capacity of the water ring vacuum pump 12 is reduced, and a predetermined vacuum is reached. Takes time to do. Alternatively, in the worst case, the drying time is not reduced at the temperature in the dryer 1 heated by the heat medium in the heat medium circulation path 14 to the evaporation pressure at which the moisture of the material to be dried in the dryer 1 evaporates. Extremely slow.
[0025]
When the pressure is not reduced to the predetermined pressure as described above, the evaporation temperature of the moisture of the object to be dried becomes higher than the temperature of the heat medium in the heat medium circulation path 14, so that the latent heat of evaporation during the evaporation of the water of the object to be dried is given. Therefore, the heat medium in the heat medium circulation path 14 returns to the condenser 20 of the heat pump 19 without depriving a large amount of heat.
[0026]
As a result, the ability of the condenser 20 to remove the latent heat of condensation of the refrigerant in the heat pump 19 is reduced, and the efficiency of the heat pump 19 is reduced. It is needless to say that, if such an ability is designed in the early stage of use, the ability is insufficient at normal times.
[0027]
Further, assuming that a system that satisfies both is constructed, in order to sufficiently transfer heat to the object to be dried in the initial stage of use when the capacity of the heat medium becomes excessive, the heat exchange area between the dryer 1 and the heat medium circulation path 14 is required. It is necessary to take a large amount, and it becomes very large, and is usually wasted.
[0028]
Further, the water ring vacuum pump 12 is more expensive than the oil diffusion vacuum pump and the dry vacuum pump, and in addition, the water ring pump 12 is continuously operated during the drying process, so that the water ring type vacuum pump 12 is worn out and has a long life. Be shorter.
[0029]
Although the conventional example does not particularly describe the refrigerant in the heat pump 19, it is common to use chlorofluorocarbon. In this case, the condensation temperature of the condenser 20 is about 50 ° C. In order to evaporate the moisture of the object to be dried in the dryer 1, a large heat exchange area between the dryer 1 and the heat medium circulation path 14 is required, and the pressure in the dryer 1 is reduced to about 10 kPa, or Alternatively, the pressure in the dryer 1 is further reduced from 10 kPa, and the heat exchange area between the dryer 1 and the heat medium circulation path 14 is increased by the temperature difference between the evaporation temperature of water and the heat medium corresponding to the reduced pressure. In the former case, the cost increases due to an increase in the heat exchange area between the dryer 1 and the heat medium circulation path 14 and the heat exchange area between the heat medium circulation path 14 and the condenser 20. There is a problem that the size of the equipment and equipment will increase In the latter with a required high capacity vacuum pumps, vacuum is the portions such as the dryer 1 and the steam discharge passage 9 is expensive and requires a strong pressure-resistant structure.
[0030]
From this, it is possible to shorten the drying process time by early decompression in the early stage of operation, reduce the initial cost by using an inexpensive vacuum pump, save energy and extend the life of the vacuum pump operation time, and reduce the running time by efficient operation of the heat pump. There was a problem that cost reduction was required.
[0031]
The present invention has been made in view of the above-described conventional problems, and has as its object to provide a drying system that reduces drying time with low running costs and low initial costs, in addition to the effects of general vacuum drying and the effects of the conventional example. .
[0032]
[Means for Solving the Problems]
In order to achieve the above object, an invention of a drying system according to claim 1 of the present invention comprises a drier having a pressure-tight structure, a tank arranged so as to store moisture evaporated from the drier, and the drier And a steam discharge passage communicating the tank, a heat pump, a waste heat recovery unit for exchanging heat between a part or all of the steam discharge passage and the cold heat generation side of the heat pump; and A first valve installed in the middle of a steam discharge passage located between the second valve and a second valve installed in the middle of a drainage path located below the tank and communicating the inside and outside of the tank; A branch pipe that branches from the pipe or tank between the first valve or the first valve and the second valve and pipes the pressure reducing unit, and a third valve that is installed in the middle of the branch pipe. The heat pon Some of the heat generating side is one that is arranged to heat transfer to the drier.
[0033]
In the above configuration, the first valve and the third valve are opened at the beginning of use, and the pressure reducing means is operated with the second valve closed. Then, the pressure inside the dryer is reduced to a predetermined pressure equal to or lower than the evaporation pressure at which water evaporates at a temperature not higher than the temperature on the warm side when the heat pump is operated, and then the heat pump is operated. Thereafter, the heat of the heat pump is transferred to the dryer, and the heat evaporates the moisture of the object to be dried. Then, the evaporated water vapor is cooled and condensed in the waste heat recovery device by the cold heat on the cold side of the heat pump.
[0034]
In the present invention, the pressure is reduced to a predetermined pressure in the early stage of operation, and then the heat pump is operated to use the heat source of the condenser of the heat pump as a heat source for generating steam during drying and to use the cold source as a heat source for condensing steam. Maintain pressure.
[0035]
As a result, in the initial stage of use and operation, the air inside the dryer is saturated air or unsaturated air at a low temperature equivalent to the outside air temperature, so that an oil diffusion vacuum pump and many other types of vacuum pumps can be used as the pressure reducing means. Thus, the initial cost can be reduced and the drying time can be shortened because the pressure can be reduced to the predetermined pressure at an early stage. Furthermore, since the heat pump is operated after the pressure has been reduced to a predetermined pressure, the heat pump can be operated at an efficient point, thereby saving energy and reducing running costs.
[0036]
In the drying system according to the second aspect of the present invention, the steam discharge passage of the waste heat recovery unit in the first aspect of the invention is configured such that the downstream side is always located below the upstream side, and the tank is provided with the waste heat recovery unit. It is installed below.
[0037]
In the above configuration, the water vapor evaporated from the dryer is cooled and condensed from the waste heat recovery unit inlet portion of the water vapor discharge passage, and the condensed water together with the uncondensed water vapor is supplied to the downstream side of the water vapor discharge passage which is the waste heat recovery unit outlet side. Flows. Most of the steam becomes condensed water at the outlet of the waste heat recovery unit in the steam discharge passage, and is dropped and temporarily stored in the tank. Then, after the material to be dried is dried and the operation is completed, the water stored in the tank is discharged to the outside.
[0038]
In the present invention, the amount of residual water after the previous operation is completed is reduced in the exhaust path of the pressure reducing means such as the steam discharge passage, and the amount of water suctioned into the pressure reducing means at the time of operation of the pressure reducing means in the initial operation is reduced. Need not be used, in which case the maintenance period is extended.
[0039]
As a result, an oil diffusion vacuum pump or many other types of vacuum pumps can be used as the decompression means, resulting in a low initial cost and a drying time can be reduced because the pressure can be reduced to a predetermined pressure at an early stage of the operation. In this case, the heat pump operation is performed after the pressure is reduced to a predetermined pressure, so that the heat pump can be operated at an efficient point, thereby saving energy and reducing running costs. In addition, the amount of residual water after the previous operation is completed is reduced in the exhaust path of the pressure reducing means such as a steam discharge passage, and the amount of water intake to the pressure reducing means at the time of operation of the pressure reducing means in the initial operation is reduced, so that strong water resistance is provided. Even if the pump does not have a pump, the maintenance period is extended and the running cost is further reduced.
[0040]
Further, the invention of the drying system according to the third aspect is the invention according to the first or second aspect, wherein the first valve and the third valve are opened and the second valve is closed to operate the pressure reducing means. A first step of reducing the pressure of the dryer, the steam discharge passage, and the tank below the atmospheric pressure, and a second step of operating the heat pump when the first valve is open and the second and third valves are closed. A third step of draining liquid in the tank when the first valve is closed and the second valve is open and the third valve is closed or open; and the first valve and the second valve are closed. The third valve comprises a fourth step of opening the tank to reduce the pressure in the tank to a predetermined pressure by operating the pressure reducing means when the valve is opened. The first to fourth steps are sequentially performed in the initial stage of the operation, and then the second step is performed. At least one drying cycle in which the steps from the fourth step are sequentially performed is performed.
[0041]
In the above configuration, in the first step, the pressure in the dryer is reduced to a predetermined pressure equal to or lower than an evaporation pressure at which water evaporates at a temperature equal to or lower than the heating side temperature when the heat pump is operated, and then the first step is completed. Then enter the second step. In the second step, the water vapor evaporated from the dryer by the heat of the heat pump is cooled and condensed by the waste heat recovery device by the cold heat on the cold side of the heat pump. The condensed water is temporarily stored in a tank. After a lapse of a predetermined time, the process enters the third step from the second step, in which the water stored in the tank is drained to the outside, and the outside air flows into the tank to reach atmospheric pressure. Then, when the drainage of the water in the tank is completed and the inside of the tank is filled with the outside air, the process proceeds from the third step to the fourth step. In the fourth step, the pressure in the tank is reduced to the same pressure or less as that in the dryer, and the process proceeds to the second step. Thereafter, the cycle in which the second step to the fourth step are sequentially performed is performed one or more times, so that the water in the tank is periodically discharged to the outside while suppressing the pressure increase in the dryer.
[0042]
As a result, an oil diffusion vacuum pump or many other types of vacuum pumps can be used as the decompression means, resulting in a low initial cost and a drying time can be reduced because the pressure can be reduced to a predetermined pressure at an early stage of the operation. Since the heating is performed after the pressure is reduced to a predetermined pressure, the heat pump can be operated at an efficient point, thereby saving energy and reducing running cost. In addition, by periodically discharging condensed water to the outside, the tank can be made smaller, further lowering initial costs and saving space.In addition, since the decompression means operates intermittently, it saves energy and extends its life. Further lower running costs.
[0043]
Further, in the invention of a drying system according to claim 4, in the invention of claim 1, the heat pump has a compressor, a condenser, an expansion mechanism, and an evaporator, which are functionally annularly piped, and a carbon dioxide refrigerant is sealed therein. It is a cooling cycle.
[0044]
In the above configuration, as the pressure reducing means, an oil diffusion vacuum pump or many other types of vacuum pumps can be used, resulting in a low initial cost, and a reduced drying time because the pressure can be reduced to a predetermined pressure early in the initial operation, and the heat pump is reduced. Since the operation is performed after the pressure has been reduced to a predetermined pressure, the heat pump can be operated at an efficient point, saving energy and reducing running costs. In addition, if the refrigerant in the heat pump leaks, the environmental load is extremely small and the risk of ignition can be reduced. Furthermore, in recent years, a heat pump for hot water supply using a carbon dioxide refrigerant has been commercialized, and the temperature on the heating side is up to 90 ° C. Therefore, when applied to the present drying system, the pressure inside the dryer is the same as the conventional vacuum degree. If this is the case, the difference between the evaporation temperature of the object to be dried under reduced pressure and the temperature between the condenser and the condenser increases, so that the heat transfer area between the condenser and the dryer can be reduced, saving space, or evaporating the condenser and the object to be dried. If the temperature is designed to be the same as the temperature difference, the internal pressure of the dryer can be increased, so that the capacity of the pressure reducing means can be reduced and the initial cost can be reduced.
[0045]
According to a fifth aspect of the present invention, there is provided a drying system having a pressure tight structure, a steam discharge passage communicating the dryer with the outside, and a fourth valve provided in the middle of the steam discharge passage. Pressure reducing means for reducing the pressure in the dryer, a heat pump, and waste heat recovery in which a part or all of the steam discharge passage located closer to the dryer than the fourth valve exchanges heat with the evaporator of the heat pump. Unit, the heat pump comprises a compressor, at least two or more condensers of a capacity adjusting condenser capable of varying the condensation capacity and a heating condenser of the dryer, an expansion mechanism, and an evaporator. It is a pipe which is functionally arranged in an annular shape, and is a pipe in which a steam discharge passage located on the dryer side with respect to the fourth valve and a pressure reducing means are provided.
[0046]
In the above configuration, the dryer is controlled by controlling the heat pump so that the capacity of the condenser of the heat pump becomes equal to the capacity of the steamer at the time of operating the heat pump after the pressure is reduced to the predetermined pressure by the pressure reducing means in the initial stage with less moisture. The amount of heat given to the water evaporation of the material to be dried and the amount of heat condensing the evaporated water vapor become equal, and the predetermined pressure in the dryer can be maintained for a long time without operating the pressure reducing means.
[0047]
As a result, in the initial stage of use and operation, the air inside the dryer is saturated air or unsaturated air at a low temperature equivalent to the outside air temperature, so that an oil diffusion vacuum pump and many other types of vacuum pumps can be used as the pressure reducing means. Thus, the initial cost can be reduced and the drying time can be shortened because the pressure can be reduced to the predetermined pressure at an early stage. Further, since the heat pump is operated after the pressure has been reduced to a predetermined pressure, the heat pump can be operated at an efficient point, thereby saving energy and reducing running costs. In addition, since the operation time of the decompression means is extremely shortened, the decompression means is energy saving, has a longer life, and further lowers running costs.
[0048]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the drying system of the present invention will be described with reference to FIGS. In addition, about the same structure as a conventional one, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.
[0049]
(Embodiment 1)
Embodiment 1 of the present invention will be described with reference to the drawings.
[0050]
FIG. 1 is a schematic configuration diagram of a drying system according to Embodiment 1 of the present invention.
[0051]
As shown in FIG. 1, the drying system according to the present embodiment includes a tank 22, a first valve 23, a second valve 24, a pressure reducing unit 25, a third valve 26, an expansion mechanism 27 constituting a heat pump 19, A first pressure sensor 28 for detecting the pressure in the dryer 1, a water level sensor 29 installed at a position where the lowest part can be measured when there is no water in the tank 22 and detecting the level of water stored in the tank 22. And a temperature sensor 30 installed at a position where the temperature of the object to be dried put into the dryer 1 can be measured.
[0052]
The drying system according to the present embodiment includes a drier 1 having a pressure-resistant hermetic structure, a tank 22 arranged to store moisture evaporated from the drier 1, and a steam discharge communicating the drier 1 and the tank 22. A waste heat recovery unit 11 for exchanging heat between the passage 9, the heat pump 19, and a part or all of the water vapor discharge passage 9 and the cold heat generation side of the heat pump 19, and a water vapor positioned between the waste heat recovery unit 11 and the tank 22. A first valve 23 installed in the middle of the discharge passage 9, a second valve 22 installed in the middle of a drainage path located below the tank 22 and communicating between the inside and the outside of the tank 22, and a pressure reducing unit 25. And a third valve 26 installed in the middle of the branch pipe, the condenser being a part of the heat pump 19 on the heat generation side. 20 is the dryer 1 In which are arranged to heat transfer.
[0053]
The operation of the drying system configured as described above will be described below.
[0054]
An object to be dried (not shown) is put into the dryer 1 by opening a cover (not shown) of the inlet 3. After the charging, the lid of the charging port 3 is closed, so that the charging port 3 is in a closed state. When the user presses a drying start button on an operation panel (not shown), the second valve 24, which has been closed, is opened, the first valve 23 is kept open, and the third valve 26 is opened. The state changes from the closed state to the open state, and after a lapse of a predetermined time, the first valve 23 and the third valve 26 are maintained in the open state, the second valve 24 is closed, and at the same time, the pressure reducing means 25 operates.
[0055]
Then, the air in the dryer 1, the steam discharge passage 9, and the tank 22 is discharged to the outside to reduce the pressure. When the pressure in the dryer 1 becomes 3 kPa by the first pressure sensor 28, the third valve 26 is closed. At the same time as the decompression means 25 is stopped, the compressor 17 is driven to compress the refrigerant inside the heat pump 19 by the compressor 17 and to flow through the condenser 20, the expansion mechanism 27, and the evaporator 21 to perform a general vapor compression type cooling. Activate the cycle.
[0056]
By the operation of the heat pump 19, the temperature of the condenser 20 becomes high, and the temperature of the evaporator 21 becomes low. Then, the condenser 20 heats the inside of the dryer 1 at a temperature exceeding 24 ° C., and the moisture of the material to be dried evaporates at an evaporating temperature of 3 kPa or higher at 24 ° C. or higher. The evaporated water vapor passes through the water vapor discharge passage 9 and is condensed by the cooling of the evaporator 21 of the heat pump 19 at the portion of the waste heat recovery device 11 to be converted into water and stored in the tank 22.
[0057]
When the temperature rising speed of the object to be dried reaches a predetermined value or more by the temperature sensor 30, the compressor 17 is stopped to stop the heat pump 19, and the second valve 24 is opened to discharge the stored water in the tank 22 to the outside. Drain to finish drying. Then, the second valve 24 is closed after a certain time when the water in the tank 22 finishes draining.
[0058]
At this time, the inner diameter of the pipe and the diameter of the second valve 24 are larger than a predetermined value so that drainage is performed smoothly, and the maximum water level of the tank 22 is lower than the connection position of the pressure reducing means 25 with the tank 22. Needless to say, the position is set.
[0059]
If the inside diameter of the drain pipe for the tank 22 or the second valve 24 cannot be made large, a separate pipe for communicating the tank 22 with the outside and an on-off valve in the middle of the pipe are provided for smooth drainage. The valve may be opened when the tank 22 is drained.
[0060]
As described above, since the decompression means 25 discharges the air in the early stage of the drying operation, the amount of sucking the water is significantly reduced as compared with the conventional one, and the vacuum pump which could not be used conventionally can be used. The maintenance period of the vacuum pump, which can be used but the maintenance period becomes extremely short, can be significantly extended.
[0061]
Therefore, when the pressure reducing means 25 is selected, a wide range of methods can be selected, so that an inexpensive one can be selected. Also, the number of maintenance operations is reduced. In addition, since the heat pump 19 is operated after the pressure is reduced, the heat pump 19 operates in an efficient cycle to save energy.
[0062]
As described above, the inexpensive decompression unit 25 can be used, and the initial cost can be reduced, and the running cost can be reduced by extending the maintenance period of the decompression unit 25 and operating the efficient heat pump 19.
[0063]
In the drying of an object to be dried, such as garbage, which may give off a bad odor, the second valve 24 is kept in a closed state during stoppage, so that the bad odor does not flow out to the outside and during the processing, Also, the odor is reduced by shortening the drying time.
[0064]
Further, although the third valve 26 is used to prevent the backflow of the pressure reducing means 25, a three-way valve having a necessary function may be used by being integrated with the first valve 23.
[0065]
The expansion mechanism 27 of the heat pump 19 according to the embodiment of the present invention can use a capillary, an expansion valve, or the like. When the expansion valve is used, the amount of the material to be dried or the temperature of the condenser 20 when the input is changed. It becomes easy to cope with the load fluctuation. That is, the condensing temperature can be set to a predetermined temperature by changing the condensing pressure of the refrigerant by changing the throttle amount of the expansion valve, and even when the load of the condenser 20 or the cycle of the heat pump 19 fluctuates, the condensing temperature is always kept constant. And the heat exchange becomes smooth.
[0066]
(Embodiment 2)
Next, a second embodiment of the present invention will be described with reference to the drawings. The same components as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0067]
FIG. 2 is a schematic configuration diagram of a drying system according to Embodiment 2 of the present invention.
[0068]
As shown in FIG. 2, the steam discharge passage 9 which is located downstream of the waste heat recovery unit 11 and includes the waste heat recovery unit 11 is provided so as to be located downstream, that is, the lower the tank 22 side. Further, the tank 22 is installed below the waste heat recovery unit 11, and a drainage path of the tank 22, that is, a piping path in which the second valve 24 is installed and communicates with the outside of the tank 22 is attached below the tank 22. I have.
[0069]
In the present embodiment, in the configuration of the drying system according to the first embodiment shown in FIG. 1, the steam discharge passage 9 of the waste heat recovery unit 11 is configured such that the downstream side is always located below the upstream side, and the tank 22 is eliminated. It is installed below the heat recovery unit 11.
[0070]
The operation of the drying system configured as described above will be described below.
[0071]
When the heat pump 19 is operated, the dryer 1 is heated by the condenser 20, the moisture of the material to be dried in the dryer 1 evaporates as steam, and the evaporated water vapor passes through the steam discharge passage 9 to collect the waste heat At the eleventh portion, water is condensed by cooling of the evaporator 21 to become water.
[0072]
Then, the condensed water flows to the downstream pipe located below. As the steam proceeds to the downstream side of the waste heat recovery unit 11, the ratio of the water vapor decreases and the ratio of the condensed water increases. It flows and is stored.
[0073]
Then, when the drying of the object to be dried is completed, the water in the tank 22 is drained, and the second valve 24 is closed after a lapse of a predetermined time when the drainage is almost completed. At this time, the third valve 26 remains closed.
[0074]
Here, most of the water in the steam discharge passage 9 is drained when the tank 22 is drained. Further, during the stop after the termination, an extremely small amount of water remaining in the steam discharge passage 9 is dropped and stored in the tank 22. Then, after stopping the drying for an arbitrary time, the second valve 24 is opened after the material to be dried is introduced, and the water stored in the tank 22 during the stop is drained to the outside.
[0075]
Then, after draining, the second valve 24 is closed, the first valve 23 and the third valve 26 are opened, and the pressure reducing means 25 operates. By operating the pressure reducing means 25, the air in the dryer 1, the water vapor discharge passage 9, and the tank 22 and a very small amount of moisture are exhausted to reduce the pressure. When the pressure is reduced to a predetermined pressure, the heat pump 19 is operated to dry the object to be dried. Is
[0076]
As described above, in addition to the first embodiment in which the inexpensive decompression unit 25 can be used and the initial cost is reduced, the maintenance period of the decompression unit 25 is extended, and the running cost is reduced by the efficient operation of the heat pump 19, the initial operation is reduced. In this case, the amount of water suctioned into the pressure reducing means 25 when the pressure reducing means 25 is operated is further reduced, so that even if the pressure reducing means 25 does not have strong water resistance, the maintenance period is extended and the running cost is further reduced.
[0077]
(Embodiment 3)
Embodiment 3 of the present invention will be described with reference to the drawings. In addition, about the same structure as Embodiment 1 and 2, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.
[0078]
FIG. 3 is a schematic configuration diagram of a drying system according to the third embodiment of the present invention, and FIG. 4 is a flowchart illustrating an operation of the drying system according to the third embodiment.
[0079]
As shown in FIG. 3, the second pressure sensor 31 detects the pressure in the tank 22. The water level detecting means 29 indicates 0 mm when there is no stored water in the tank 22.
[0080]
In FIG. 4, an initial drainage time counted by a timer counter (not shown) is H, a pressure value in the dryer as an output value of the first pressure sensor 28 is P1, and a tank detected by the water level detecting means 29. The water level is L, the tank maximum water level less than the junction height of the tank 22 in the piping path connecting the pressure reducing means 25 and the tank 22 is A, the drying object temperature detected by the temperature sensor 30 is T, The pressure in the tank detected by the pressure sensor 31 is represented by P2.
[0081]
In STEP 1, the state in which the pressure reducing means 25 is OFF (stopped), the first valve 23 is open, the second valve 24 and the third valve 26 are open, and the heat pump 19 is OFF is counted by a timer counter (not shown). The initial drainage time H1, which is a fixed time, is maintained.
[0082]
In STEP 2, the first valve 23 and the third valve 26 are opened, the second valve 24 is closed, the heat pump 19 is turned off, and the pressure reducing unit 25 is turned on (operating). Maintain until the pressure is reduced to below.
[0083]
In STEP3, the first valve 23 is opened, the second valve 24 and the third valve 26 are closed, the pressure reducing means 25 is OFF, and the heat pump 19 is ON, the tank water level L exceeds Amm, or The internal pressure P1 of the dryer exceeds 3 kPa, or the internal pressure P1 of the dryer is 3 kPa or less, and the temperature T of the material to be dried is maintained at 30 ° C. or less.
[0084]
In STEP 4, the state where the pressure reducing means 25 is OFF, the first valve 23 and the third valve 26 are closed, the second valve 24 is open, and the heat pump 19 is OFF is maintained until the tank water level L becomes less than 1 mm. .
[0085]
In STEP5, the pressure reducing means 25 is turned on, the first valve 23 and the second valve 24 are closed, the third valve 26 is opened, and the heat pump 19 is turned off until the tank pressure P2 is reduced to less than 3 kPa. maintain.
[0086]
In STEP 6, the state where the pressure reducing means 25 is OFF, the first valve 23 and the third valve 26 are closed, the second valve 24 is open, and the heat pump 19 is OFF is maintained until the tank water level L becomes less than 1 mm. .
[0087]
In STEP 7, the pressure reducing means 25 is OFF, the first valve 23 is open, the second valve 24 and the third valve 26 are closed, and the heat pump 19 is OFF.
[0088]
The operation of the drying system configured as described above will be described below.
[0089]
First, when the first valve 23 is open, the second valve 24 and the third valve 26 are closed, and the devices such as the pressure reducing means 25 and the heat pump 19 are stopped, the material to be dried is put into the inlet of the dryer 1. 3 and closed by closing a lid (not shown).
[0090]
Then, when a drying start button on an operation panel (not shown) is pressed, the drying process is started, and the flow goes to STEP 1, and a small amount of water stored while the drying process is stopped is drained to the outside through the second valve 24. Then, after the elapse of the initial drainage time H, the process proceeds to STEP 2 to depressurize the dryer 1, the steam discharge passage 9, and the tank 22.
[0091]
When the pressure P1 in the dryer becomes less than 3 kPa, the process proceeds to STEP3, where the dryer 1 is heated by the condenser 20 of the heat pump 19, and the material to be dried has an evaporating temperature of 24 ° C. to evaporate moisture. The evaporated water vapor is cooled in the evaporator 21 of the heat pump 19 in the waste heat recovery unit 11, condensed, stored in the tank 22, and dried by moving the moisture of the material to be dried to the tank 22.
[0092]
When the tank water level L exceeds the maximum water level Amm, the process proceeds to STEP 4 in order to prevent water from flowing into the pipe to the pressure reducing means 25. To prevent the amount of heat transfer from decreasing due to a rise in temperature and a temperature difference from the condenser 20 being not taken, thereby preventing moisture drying, that is, by keeping the evaporation temperature of the material to be dried at 24 ° C. If the pressure P1 in the temperature difference dryer exceeds 3 kPa so as to enable evaporation by the heat of the condenser 20, the process proceeds to STEP4.
[0093]
Also, since the water evaporation temperature is 24 ° C. or less at 3 kPa or less, when it is determined that the water evaporation of the material to be dried is completed under the condition that the pressure P1 in the dryer is 3 kPa or less and the temperature T of the material to be dried is 30 ° C. Move to STEP6. That is, when the tank water level L is Amm or less, the dryer internal pressure P1 is 3 kPa or less, and the temperature T of the object to be dried of the temperature sensor 30 exceeds 30 ° C., the process proceeds to STEP6.
[0094]
When the process proceeds to STEP4, the water stored in the tank is drained to the outside, and when most of the water in the tank 22 is drained, the tank water level L becomes less than 1 mm, and the process proceeds to STEP5.
[0095]
In STEP 5, in order to prevent the air from flowing into the dryer 1, that is, to maintain the pressure P 1 in the dryer at 3 kPa or less, the pressure in the tank 22 is reduced before the first valve 23 is opened. When P2 is reduced to 3 kPa or less, the process returns to STEP3, and the same operation is repeated.
[0096]
Further, when the process proceeds to STEP 6, the water in the tank 22 is drained. When the tank water level L becomes less than 1 mm, it is determined that the drainage is completed, and the process proceeds to STEP 7.
[0097]
In STEP 7, the second valve 24 and the third valve 26 that may communicate with the outside such that there is no convection between the air and gas in the dryer 1 and the steam discharge passage 9 and the tank 22 and the outside air are closed. Then, the first valve 23 is kept open so that a small amount of residual water in the steam discharge passage 9 is stored in the tank 22 until the next drying starts, and the entire drying process is completed.
[0098]
As described above, an oil diffusion vacuum pump and many other types of vacuum pumps can be used as the decompression means 25, so that the initial cost can be reduced. In addition, since the pressure can be reduced to a predetermined pressure early, the drying time can be reduced, and the operation of the heat pump 25 can be reduced. In this case, the heat pump 19 is operated after reducing the pressure to a predetermined pressure, so that the heat pump 19 can be operated at an efficient point, thereby saving energy and reducing running costs. The tank 22 can be miniaturized, further lowering initial costs and saving space. In addition, since the operation of the decompression means 25 is intermittent operation, energy is saved and the life is prolonged, so that the running cost is further reduced.
[0099]
(Embodiment 4)
Embodiment 4 of the present invention will be described with reference to the drawings. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.
[0100]
FIG. 5 is a schematic configuration diagram of a drying system according to Embodiment 4 of the present invention.
[0101]
In FIG. 5, carbon dioxide is sealed as a refrigerant in the heat pump 19. The heat exchange surface between the dryer 1 and the condenser 20 is downsized.
[0102]
The operation of the drying system configured as described above will be described below.
[0103]
During the operation of the heat pump 19, the average temperature of the inlet and outlet of the carbon dioxide refrigerant in the condenser 20 is about 70 ° C., and the pressure in the dryer 1 is 3 kPa. Therefore, the drying is performed in a state where the temperature difference between the condenser 20 and the temperature of the object to be dried is large.
[0104]
Thereby, if the drying time is the same, the heat exchange area between the dryer 1 and the condenser 20 can be reduced, so that the cost can be reduced and the size can be reduced. If the heat exchange area is the same, the drying time can be shortened. .
[0105]
In the present embodiment, the internal pressure of the dryer is 3 kPa and the moisture evaporation temperature of the object to be dried is 24 ° C., for example, when the heat exchange area is the same as the conventional one, When the temperature difference between the inside of the dryer 20 and the inside of the dryer 1 is the same as the conventional one, the condensing temperature when the conventional Freon refrigerant or HC refrigerant is used is about 50 ° C. or less. The temperature difference between the inside of the dryer 1 is about 26 ° C., whereas the average temperature of the condenser 20 is 75 ° C. in the heat pump 19 of the carbon dioxide refrigerant. Will be good.
[0106]
That is, the pressure in the dryer 1 may be about 13 kPa, which simplifies the pressure-resistant vacuum structure and lowers the capacity of the decompression means. Furthermore, when the water vapor evaporating from the material to be dried of the dryer 1 is insulated in the water vapor discharge passage 9 leading to the waste heat recovery unit 11, the temperature when entering the waste heat recovery unit 11 is about 50 ° C. Since the temperature is higher than the conventional temperature of 24 ° C., the temperature difference between the evaporator 21 and the evaporator 21 increases, and the heat exchange area between the evaporator 21 of the waste heat recovery unit 11 and the steam discharge passage 9 corresponding to the temperature difference is reduced. it can.
[0107]
As described above, an oil diffusion vacuum pump or many other types of vacuum pumps can be used as the decompression means 25, resulting in a low initial cost, and since the pressure can be reduced to a predetermined pressure at an early stage, the drying time is reduced, and the heat pump is used. Since the operation of the heat pump 19 is performed after the pressure has been reduced to a predetermined pressure, the heat pump 19 can be operated at an efficient point, thereby saving energy and reducing running costs. In addition, the refrigerant in the heat pump 19 leaks. In this case, the environmental load is extremely small, and the risk of ignition can be reduced.
[0108]
Further, if the pressure in the dryer 1 is the same degree of vacuum as the conventional one, the heat transfer area between the condenser 20 and the dryer 1 can be reduced to save space, and the evaporation temperature of the condenser 20 and the object to be dried is the same. If the temperature difference is designed, the initial cost is reduced by applying the low-pressure decompression means 25.
[0109]
(Embodiment 5)
Embodiment 5 of the present invention will be described with reference to the drawings. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.
[0110]
FIG. 6 is a schematic configuration diagram of a drying system according to Embodiment 5 of the present invention, and FIG. 7 is a Ph diagram of a heat pump when an HFC or HC system is used as a refrigerant.
[0111]
As shown in FIG. 6, the fourth valve 32 is provided on the open-air side of the waste heat recovery unit 37 of the steam discharge passage 9, and the fifth valve 33 is located above the fourth valve 32 and the dryer 1. It is provided in the middle of the pipe that connects the 9 side steam discharge passage 9 and the pressure reducing means 25. Further, the waste heat recovery unit passes through the compressor 17, the condenser 34 for adjusting the capacity to be cooled by the fan 35 capable of changing the air volume, the condenser 36 for heating the dryer 1, the expansion mechanism 27, and the steam discharge passage 9. The heat pump 19 is configured by sequentially and annularly connecting the evaporator 21 for cooling the water vapor flowing into the 37.
[0112]
In FIG. 7, the compression work obtained by subtracting the enthalpy of the suction portion of the compressor 17 (enthalpy at the outlet of the evaporator 21) from the enthalpy of the compressor 17 after compression by the compressor 17 is represented by h1, and the amount of heat condensed by the refrigerant in the condenser 34 for capacity adjustment. The first heat of condensation is represented by h2, the second heat of condensation being the heat of condensation of the refrigerant in the heating condenser 36 is represented by h3, and the enthalpy at the inlet of the expansion mechanism 27 is subtracted from the enthalpy after compression by the compressor 17. The heat of condensation (equal to the sum of the first heat of condensation h2 and the second heat of condensation h3) is represented by h4, and the enthalpy at the inlet of the expansion mechanism 27 is represented by h5. The enthalpy h5 at the inlet of the expansion mechanism 27 is the refrigeration obtained by subtracting the enthalpy at the inlet of the compressor 17 which is also the enthalpy at the outlet of the evaporator 21 from the enthalpy at the inlet of the evaporator 21 which is also the enthalpy at the outlet of the expansion mechanism 27. The effect is.
[0113]
The operation of the drying system configured as described above will be described below.
[0114]
When the drying operation is started, the fourth valve 32 and the fifth valve 33 are both opened, and after maintaining for a certain period of time, the fourth valve 32 is closed and the pressure reducing means 25 operates. Then, after reducing the pressure in the dryer 1 and a part of the inside of the steam discharge passage 9 to less than 3 kPa, for example, 2.5 kPa, the pressure reducing means is stopped and the fifth valve 33 is closed.
[0115]
Then, the heat pump 19 starts functioning by the operation of the compressor 17, and in the early stage of the operation of the heat pump 19, the fan 35 is operated to operate the condenser 34 for capacity adjustment so that the second heat of condensation h3 becomes smaller than the refrigeration effect h5. The first heat of condensation h2 is controlled.
[0116]
Then, the air volume of the fan 35 is reduced by the first pressure sensor 28 as the pressure detecting means in the dryer 1 until the pressure in the dryer 1 exceeds 2.5 kPa. The air volume of the fan 35 is maintained at a pressure exceeding 2.5 kPa, for example, 3 kPa. At this time, the second heat of condensation h3 becomes equal to the refrigeration effect h5, and the pressure in the dryer 1 is maintained at 3 kPa. In other words, the water evaporated from the object to be dried by the second heat of condensation h3 of the heating condenser 36 is all condensed by the evaporator 21.
[0117]
If the pressure in the dryer 1 exceeds a predetermined value of 3 kPa for some reason such as a change in the outside air temperature, the air pressure of the fan 35 is detected by the first pressure sensor 28 and the first heat of condensation h2 is detected. Increase. That is, the pressure in the dryer 1 is temporarily reduced to less than 3 kPa by increasing the first heat of condensation h2 such that the second heat of condensation h3 is smaller than the refrigeration effect h5, and then the fan 35 When the air volume of the fan 35 is reduced to a predetermined pressure, the air volume of the fan 35 is stopped from decreasing, and the predetermined pressure is maintained by maintaining the air volume.
[0118]
On the other hand, when the outside air temperature decreases, the pressure in the dryer 1 may be reduced, so that the pressure in the dryer 1 is maintained at a predetermined value of about 3 kPa by reducing the air volume of the fan 35. .
[0119]
As described above, since the decompression means 25 is operated only when the air containing almost no water is discharged at the beginning of the operation, it is not necessary to use a strong water-resistant one. Since it can be used for a period, an inexpensive one can be used, and the operating time is shortened, resulting in a long life.
[0120]
As described above, in the initial stage of use and the initial stage of operation, the air in the dryer 1 is saturated air or unsaturated air at a low temperature corresponding to the outside air temperature, so that the decompression means 25 is an oil diffusion vacuum pump or many other types. A vacuum pump is available, which reduces initial costs and reduces drying time because the pressure can be reduced to a predetermined pressure at an early stage. Furthermore, since the heat pump 19 is operated after the pressure is reduced to a predetermined pressure, the heat pump 19 can be operated at an efficient point, thereby saving energy and reducing running costs.
[0121]
In addition, since the operation time of the decompression means is extremely shortened, the decompression means 25 saves energy, extends its life, and further reduces running costs.
[0122]
In the embodiment of the present invention, the only condensers are the condenser 34 for adjusting the capacity and the condenser 36 for heating. However, the condenser for supercooling and stabilizing which exchanges heat with the outside air temperature between the condenser 36 for heating and the expansion mechanism 27 is provided. When the evaporating temperature of the material to be dried rises due to a rise in the pressure in the dryer 1, a fluctuation in the degree of supercooling at the inlet of the expansion mechanism 27 is suppressed, and the degree of supercooling at a constant temperature equivalent to the outside temperature is always maintained. You may do so.
[0123]
【The invention's effect】
As described above, according to the invention of the drying system according to claim 1 of the present invention, the pressure is reduced to a predetermined pressure in the initial stage of operation, and then the heat pump is operated to change the heat source of the condenser of the heat pump to generate steam during drying. Since a predetermined pressure is maintained by using the heat source as a heat source and using a cold heat source as a heat source for water vapor condensation, an oil diffusion vacuum pump and many other types of vacuum pumps can be used as the pressure reducing means, and the initial cost is reduced. In addition, since the pressure can be reduced to a predetermined pressure at an early stage, the drying time can be shortened. Furthermore, since the heat pump is operated after the pressure has been reduced to a predetermined pressure, the heat pump can be operated at an efficient point, saving energy and reducing running costs.
[0124]
According to the second aspect of the present invention, since the downstream side of the steam discharge passage of the waste heat recovery unit is always located below the upstream side, the pressure reducing means having strong water resistance is used. There is no need to carry out such an operation, and even if the pump does not have strong water resistance, there is an effect that the maintenance period is extended and the running cost is further reduced.
[0125]
Further, according to the invention of the drying system according to the third aspect, the tank can be downsized by periodically discharging the condensed water to the outside, which further reduces the initial cost and saves space. In addition to the effects described above, the decompression means operates intermittently, thereby conserving energy and extending the life, so that the running cost is further reduced.
[0126]
Further, according to the invention of the drying system according to claim 4, the heat pump is a cooling cycle in which a compressor, a condenser, an expansion mechanism, and an evaporator are functionally piped annularly and a carbon dioxide refrigerant is sealed therein. Therefore, in the event that the refrigerant in the heat pump leaks, the environmental load is extremely small and the danger of ignition can be reduced. Also, if the pressure inside the dryer is the same degree of vacuum as before, the heat transfer area between the condenser and the dryer can be reduced, saving space.If the evaporation temperature of the condenser and the object to be dried is designed to have the same temperature difference, For example, there is an effect that the use of a low-capacity pressure reducing means results in a low initial cost.
[0127]
According to the drying system of the fifth aspect, the operating time of the decompression means is extremely shortened, so that the decompression means has the effect of saving energy, prolonging the life and further reducing the running cost.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a drying system according to a first embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of a drying system according to a second embodiment of the present invention.
FIG. 3 is a schematic configuration diagram of a drying system according to a third embodiment of the present invention.
FIG. 4 is a flowchart showing the operation of the drying system according to the embodiment;
FIG. 5 is a schematic configuration diagram of a drying system according to a fourth embodiment of the present invention.
FIG. 6 is a schematic configuration diagram of a drying system according to a fifth embodiment of the present invention.
FIG. 7 is a Ph diagram of the heat pump in the embodiment.
FIG. 8 is a schematic configuration diagram of a conventional drying system.
[Explanation of symbols]
1 dryer
9 Water vapor discharge passage
11 Waste heat recovery unit
17 Compressor
19 heat pump
20 condenser
21 Evaporator
22 tank
23 1st valve
24 Second valve
25 Decompression means
26 Third valve
27 Expansion mechanism
32 4th valve
34 Condenser for capacity adjustment
36 Heating condenser
37 Waste heat recovery section

Claims (5)

A drier having a pressure-resistant hermetic structure, a tank arranged to store moisture evaporated from the drier, a steam discharge passage communicating the drier with the tank, a heat pump, and a part of the steam discharge passage. Or a waste heat recovery unit for exchanging heat between the whole and the heat generation side of the heat pump; a first valve installed in the middle of a steam discharge passage located between the waste heat recovery unit and the tank; , A second valve disposed in the middle of a drainage path communicating between the inside and the outside of the tank, a pressure reducing means, and a pipe or tank between the first valve or the first and second valves A branch pipe, which is further branched and provided with the decompression means, and a third valve installed in the middle of the branch pipe, and a part of the heat pump on the heat generation side transfers heat to the dryer. Drying system located in . The drying system according to claim 1, wherein the downstream side of the steam discharge passage of the waste heat recovery unit is always located below the upstream side, and the tank is installed below the waste heat recovery unit. A first step of operating the pressure reducing means when the first and third valves are opened and the second valve is closed to reduce the pressure of the dryer, the steam discharge passage, and the tank to below atmospheric pressure; A second step of activating the heat pump when the second valve and the third valve are closed and the first valve is closed and the third valve is closed or open; A third step of draining the liquid in the tank, and a first valve and a second valve are closed and the third valve is opened to operate the pressure reducing means to reduce the pressure in the tank to a predetermined pressure. The drying according to claim 1 or 2, wherein the first step to the fourth step are sequentially performed in the initial stage of the operation, and then at least one cycle of sequentially performing the second step to the fourth step is performed. system. The drying system according to claim 1, wherein the heat pump is a cooling cycle in which a compressor, a condenser, an expansion mechanism, and an evaporator are functionally piped in a ring shape and a carbon dioxide refrigerant is sealed therein. A drier having a pressure tight structure, a steam discharge passage communicating the drier with the outside, a fourth valve provided in the middle of the steam discharge passage, a decompression means for decompressing the drier, and a heat pump And a waste heat recovery unit for exchanging heat between part or all of the steam discharge passage located closer to the dryer than the fourth valve and the evaporator of the heat pump, wherein the heat pump has a compressor and a condensing capacity. Wherein at least two condensers, a condenser for adjusting the capacity and a condenser for heating the dryer, which are variable, an expansion mechanism, and an evaporator are piped functionally in a ring shape, A drying system in which a steam discharge passage located on the dryer side from the valve 4 and a pressure reducing means are provided.

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