Drying system

Abstract

To provide a drying system capable of restraining a refrigerator for supplying a refrigerant to a cold trap from stopping a cooling function of the refrigerant during drying processing.SOLUTION: A drying system 1 for drying a frozen object F by sublimating a solidified liquid component contained in the frozen object F obtained by freezing a treated material includes a vessel body 21 for storing the frozen object F, a jacket 23 which covers an outer periphery of the vessel body 21 and in which a heat medium flows, a heat medium cooler 35 for cooling the heat medium, a cold trap 5 for solidifying and collecting the steam generated by sublimating the liquid component in the vessel body 21, and a common refrigerator 6 for supplying a refrigerant to both of the heat medium cooler 35 and the cold trap 5.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a drying system that dries a frozen object by freezing an object to be processed and sublimating a solidified liquid component contained in the frozen object. [Background technology]

[0002] Vacuum freeze-drying technology is known, which freezes materials (hereinafter referred to as the object to be processed) used in foods, cosmetics, medical products, raw materials for electronic components, chemical products, paints, etc., to produce a frozen product, and then sublimates the solidified liquid components contained in the frozen product to obtain a dried product. A typical system using this vacuum freeze-drying technology is a shelf-type drying system. In a shelf-type drying system, shelves are provided in a drying container for placing frozen products, and the temperature of the shelves is adjusted to an appropriate temperature under reduced pressure to dry the frozen product while it is still frozen to obtain a dried product. In the shelf-type drying system, a cold trap is provided in the exhaust path between the drying container and the vacuum pump to prevent the liquid components that have become vaporized by sublimation from reaching the vacuum pump. The inside of this cold trap is cooled by circulating a refrigerant cooled by a refrigerator. The liquid components that have become vaporized in the drying container freeze to solidify as they pass through the cold trap, and are collected by the cold trap.

[0003] In a shelf-type drying system, a tray containing the object to be processed is placed on a shelf and frozen to obtain a frozen product. After that, the pressure inside the drying container is reduced to sublimate the solidified liquid components contained in the frozen product. At that time, the shelf on which the tray is placed is heated to supply heat to the frozen product to promote drying. However, if the product is heated too much, the solidified liquid components contained in the frozen product melt and lumps (aggregations of the object to be processed) form in the dried product, which reduces the quality, so the amount of heat supplied to the frozen product by heating is set to a level that compensates for the heat taken away by sublimation. In addition, when the dried product is dispersed in a liquid, the dried product is required to have good restorability (water reconstitution) so that it can return to the same state as before drying. However, if lumps form, the restorability (water reconstitution) is impaired. In a shelf-type drying system, the frozen product in the tray basically receives heat only from the bottom side where the shelf is located, so the part of the frozen product that receives heat is always the same part, and that part is prone to melting. Even if only the bottom side of the frozen product melts, a small amount of lumps will be mixed into the dried product, which reduces the quality of the dried product. For this reason, in a shelf-type drying system, it is necessary to heat the material while significantly suppressing the amount of heat supplied (heating temperature) to prevent lumps from forming, so it takes a long time to dry the material. The shelf-type drying system described here can be said to be a static drying system in which the frozen material does not move.

[0004] On the other hand, a drying system has been proposed in which the material to be processed is frozen to obtain a frozen material consisting of a number of blocks of material, and the frozen material is dried while being moved (see, for example, Patent Document 1). The drying in this drying system can be said to be dynamic drying. In the drying system of Patent Document 1, the frozen material stored in a drying container is dried while being moved in the drying container, so that heat can be applied uniformly to the surface of the frozen material, and therefore a larger amount of heat can be supplied to the frozen material (higher heating temperature) compared to a shelf-type drying system, and the drying time is shortened. In addition, frictional heat is generated between the frozen materials by moving the frozen material, so that the frozen material is heated in areas other than those where heat from the outside is transmitted, and the drying time is further shortened. Even in a dynamic drying system such as Patent Document 1, liquid components that have become vapor are collected by a cold trap installed in the exhaust path between the drying container and the vacuum pump. In addition, whether the drying system is static or dynamic, it is confirmed that the drying is completed and the frozen material has become the desired dried material by the disappearance of pressure fluctuations in the drying container and the exhaust path and temperature fluctuations of the frozen material. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2022-72411 Summary of the Invention [Problem to be solved by the invention]

[0006] As the drying process nears the end, the amount of liquid components that turn into vapor decreases, and so does the amount of vapor captured by the cold trap. As the refrigerant circulating between the refrigerator and the cold trap is no longer heated by the cold trap, the refrigerator that cools the cold trap goes into a low-pressure cut state, and the refrigerant's cooling function may stop. After the low-pressure cut state is reached, the pressure of the refrigerant increases over time, and when the refrigerant pressure increases, the refrigerator's function is released, so the refrigerator repeatedly stops and restarts its function. This causes the temperature and pressure of the cold trap to fluctuate, which in turn causes the pressure and temperature in the exhaust path and drying container connected to the cold trap to fluctuate, making it difficult to determine whether the drying is complete in conventional drying systems.

[0007] In addition, at the end of the drying process, the liquid content of the frozen material is reduced, so the risk of the frozen material melting is reduced. For this reason, in dynamic drying systems, there is a demand to shorten the drying time by increasing the speed and frequency at which the frozen material is moved. However, as described above, the pressure and temperature in the drying container and the exhaust path fluctuate depending on the operation of the refrigerator, so in conventional drying systems, it is difficult to determine whether the drying process is at the end from the pressure and temperature measurement results.

[0008] In view of the above circumstances, an object of the present invention is to provide a drying system that prevents a refrigerator that supplies a refrigerant to a cold trap from stopping its cooling function of the refrigerant during a drying process. [Means for solving the problem]

[0009] The drying system of the present invention which solves the above problems includes: A drying system that dries a frozen object by sublimating a solidified liquid component contained in the frozen object obtained by freezing the object to be processed, comprising: A container body for storing the frozen food; a jacket covering the outer periphery of the container body and through which a heat transfer medium flows; a heat medium cooler that cools the heat medium; a cold trap that converts the vapor generated by sublimation of the liquid component in the container body into a solid and collects the solid; The present invention is characterized in that it includes a common refrigerator that supplies refrigerant to both the heat medium cooler and the cold trap.

[0010] According to this drying system, even if the amount of vapor captured in the cold trap decreases, the temperature of the refrigerant can be increased in the heat medium cooler, thereby preventing the common refrigerator from stopping its cooling function of the refrigerant during the drying process.

[0011] Here, the common refrigerator may cool the refrigerant recovered and mixed from the heat medium cooler and the cold trap, and supply the refrigerant to both the heat medium cooler and the cold trap. That is, the common refrigerator may circulate a refrigerant shared by both the heat medium cooler and the cold trap. The drying system may include a heat medium heater that heats the heat medium. The heat medium may supply heat to the frozen material stored in the container body when flowing through the jacket.

[0012] In this drying system, a monitoring means for monitoring a state of collection of the solid in the cold trap; The heat transfer medium cooler may further include a control unit that adjusts a flow rate of the heat transfer medium passing through the heat transfer medium cooler in accordance with the collection status.

[0013] The collection state coincides with the state of temperature rise of the refrigerant in the cold trap. Therefore, by adjusting the flow rate of the heat medium in accordance with the collection state to raise the temperature of the refrigerant in the heat medium cooler, it is possible to prevent the common refrigerator from stopping during the drying process.

[0014] Here, the monitoring means may monitor a change in mass of the solid, may monitor a change in thickness of the solid adhering to a cooling tube in the cold trap, or may monitor a change in shape of the solid adhering to a cooling tube in the cold trap.

[0015] In addition, in this drying system, A refrigerant pressure gauge for measuring the pressure of the refrigerant; The cooling system may further include a control unit that adjusts a flow rate of the heat medium passing through the heat medium cooler in accordance with the pressure measured by the refrigerant pressure gauge.

[0016] By adjusting the flow rate of the heat medium in accordance with the pressure of the refrigerant to raise the temperature of the refrigerant in the heat medium cooler, it is possible to prevent the common refrigerator from stopping during the drying process.

[0017] Here, the refrigerant pressure gauge may measure a pressure of the refrigerant on a low pressure side of the common refrigerator. The control means may adjust an amount of heat transferred per unit time from the heat medium to the refrigerant in the heat medium cooler.

[0018] In addition, in this drying system, A pressure reducing device for reducing the pressure inside the container body; an exhaust path connecting the container body and the pressure reducing device and through which gas in the container body passes; a pressure regulating valve that adjusts an opening degree to keep the pressure reduced by the pressure reducing device within a predetermined range, thereby allowing an amount of outside air to flow into the exhaust path according to the opening degree, The cooling fan may further include a control unit that adjusts a flow rate of the heat medium passing through the heat medium cooler in accordance with the opening degree.

[0019] By adjusting the flow rate of the heat medium in accordance with the opening degree to raise the temperature of the refrigerant in the heat medium cooler, it is possible to prevent the common refrigerator from stopping during the drying process.

[0020] Here, the pressure regulating valve may regulate the amount of outside air flowing into the exhaust path downstream of the cold trap. The pressure reducing device may constantly reduce the pressure in the container body with a constant capacity. The control means may regulate the opening of the pressure regulating valve based on the pressure measured upstream of the cold trap in the exhaust path.

[0021] Furthermore, in this drying system, The common refrigerator cools the refrigerant using cooling water circulating between the common refrigerator and a first heat exchanger, The present invention may also be an aspect further comprising a second heat exchanger that is disposed in a circulation path of the cooling water and performs heat exchange between the cooling water heated by the common refrigerator and the heat medium cooled by the heat medium cooler.

[0022] In this embodiment, since the cooling water is cooled in the second heat exchanger, it is possible to obtain even colder cooling water in the first heat exchanger. Also, since the heat medium is not cooled too much, less energy is required for heating the heat medium when it is necessary to heat it. Effect of the Invention

[0023] According to the present invention, it is possible to provide a drying system that prevents a refrigerator that supplies a refrigerant to a cold trap from stopping its cooling function of the refrigerant during a drying process. [Brief description of the drawings]

[0024] [Figure 1] 1 is a system diagram of a drying system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing a control configuration of the drying system shown in FIG. [Diagram 3] 2 is a flowchart showing control in a drying process of the drying system shown in FIG. 1. [Figure 4] FIG. 11 is a diagram showing a heat medium temperature regulator in a drying system according to a first modified example. [Diagram 5] FIG. 11 is a diagram showing a heat medium temperature adjuster in a drying system according to a second modified example. [Figure 6] 13(a) is a flowchart showing the control associated with the drying process of the drying system of the third modified example, and FIG. 13(b) is a flowchart showing the control associated with the drying process of the drying system of the fourth modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A drying system according to an embodiment of the present invention will now be described in detail with reference to the drawings. The drying system described below is a system for freezing a processing object and drying the frozen object.

[0026] FIG. 1 is a system diagram of a drying system 1 according to one embodiment of the present invention. In the upper right part of FIG. 1, a table is shown showing the correspondence between symbols of the elements constituting the drying system 1, such as valves and instruments, and the names of the components indicated by the symbols. Since the components indicated by these symbols and their functions are well known, some of them will not be described in the description of this embodiment. Furthermore, the measurement results of the components indicated by these symbols that belong to the instruments are appropriately transmitted to control means 10 (see FIG. 2). In addition, the opening and closing and the opening degree of the motor-operated valves, among the components indicated by these symbols, are controlled by control means 10.

[0027] 1 includes a drying container 2, a heat medium temperature adjusting section 3, a vacuum pump 4, a cold trap 5, a common refrigerator 6, and a first heat exchanger 7. An example of the first heat exchanger 7 is a cooling tower.

[0028] The drying container 2 has a container body 21, a stirring means 22, and a jacket 23. In Fig. 1, the container body 21 is shown in a schematic vertical cross section so that the inside can be seen. In Fig. 1, the frozen material F in the container body 21 is shown by a dot pattern.

[0029] The container body 21 is supported by a support pillar (not shown). The container body 21 is composed of a cylindrical upper portion, an inverted cone-shaped portion that gradually reduces in diameter as it moves away from the upper portion, and an upper lid that covers the upper end. The container body 21 is also provided with a container thermometer 211 that measures the temperature of the stored items such as the brine liquid and frozen items F stored inside, and a brine liquid outlet 212. The container thermometer 211 constantly measures the temperature of the stored items. The lower end of the container body 21 is provided with an outlet 213 for discharging the stored items. The outlet 213 is closed by an outlet lid 214 that can be opened and closed except when discharging the stored items.

[0030] The upper lid of the container body 21 is provided with an inlet 215, an exhaust port 216, and a vortex breaker 217. For example, a dispersion liquid in which the material to be treated is dispersed in a liquid is introduced into the container body 21 through the inlet 215. Then, the dispersion liquid is frozen while being stirred in the container body 21, and a frozen material F consisting of a number of processed material chunks is generated. Note that a brine liquid is stored in the container body 21 before the dispersion liquid is introduced, and the dispersion liquid is frozen in the brine liquid, and then only the brine liquid is drained from the brine liquid outlet 212, so that the frozen processed material chunks remain in the container body 21. However, the frozen material F may be prepared using a dispersion liquid in another device, and the frozen material F may be directly introduced into the empty container body 21 through the inlet 215 and stored in the container body 21. Also, the material to be treated containing a liquid component may be directly frozen in the container body 21 without using a dispersion liquid to produce the frozen material F. Furthermore, the object to be processed containing a liquid component may be directly frozen in another device without using a dispersion liquid to prepare a frozen object F, which may then be introduced into the empty container body 21 through the introduction port 215 and stored in the container body 21. In this embodiment, ethanol is used as the brine liquid, but instead of ethanol, organic compounds such as paraffins, alicyclic hydrocarbons, alcohols, and ethers having a melting point of −30° C. or lower and a boiling point of less than 100° C. may be used.

[0031] The exhaust port 216 is for discharging gas such as air in the container body 21 and steam generated in the container body 21. The exhaust port 216 is connected to an upstream exhaust path 511 via an exhaust filter (not shown). Gas that has passed through the exhaust filter enters the upstream exhaust path 511. A cold trap 5 is connected downstream of the upstream exhaust path 511. A vacuum pump 4 is installed downstream of the cold trap 5 via a downstream exhaust path 512. The upstream exhaust path 511, the cold trap 5, and the downstream exhaust path 512 form an exhaust path. The upstream exhaust path 511 is provided with an exhaust path pressure gauge 513, which is a vacuum gauge that measures the pressure in the upstream exhaust path 511. The pressure in the upstream exhaust path 511 measured by the exhaust path pressure gauge 513 is constantly transmitted to the control means 10 (see FIG. 2). Note that instead of or in addition to the exhaust line pressure gauge 513, a pressure gauge may be installed to measure the pressure inside the vessel body 21, the pressure inside the cold trap 5, or the pressure of the downstream exhaust line 512. Note that the pressure inside the vessel body 21, the pressure inside the upstream exhaust line 511, the pressure inside the cold trap 5, and the pressure inside the downstream exhaust line 512 are all gas pressures.

[0032] The vortex current breaker 217 is attached to the lower end of a shaft hanging down from the upper lid of the container body 21. The vortex current breaker 217 is disposed at a position facing the cylindrical upper part of the container body 21 with a gap therebetween, and is composed of an arc-shaped plate that follows the cylindrical shape of the upper part. The vortex current breaker 217 guides the frozen material F that has reached the top of the container body 21 downward.

[0033] The stirring means 22 has a rotating spiral ribbon 221, a stirring drive shaft 222, and a stirring drive device 223. This stirring means 22 corresponds to an example of a frozen material operating unit. The spiral ribbon 221 is made entirely of metal, is supported by a plurality of rod-shaped support members protruding radially from the stirring drive shaft 222, and travels around the inner surface of the container body 21 in the vicinity of the inner surface of the container body 21. The spiral ribbon 221 may be made of a resin such as engineering plastic or fiber-reinforced plastic. The spiral ribbon 221 has a spiral shape that tapers downward. This spiral ribbon 221 rotates as the stirring drive shaft 222 rotates around its axis. The stirring drive shaft 222 penetrates the upper lid of the container body 21, and the penetration portion is sealed. The stirring drive device 223 is a motor that rotates the stirring drive shaft 222. The agitation drive shaft 222 rotates around its axis by driving the agitation drive device 223, thereby rotating the spiral ribbon 221. The rotation of the spiral ribbon 221 generates a circulatory flow of the frozen material F stored in the container body 21. That is, the rotation of the spiral ribbon 221 causes the frozen material F located near the inner surface of the container body 21 to be lifted upward, and the frozen material F located in the center part in a plan view of the container body 21 to move downward. This causes the frozen material F stored in the container body 21 to be agitated. By increasing the rotation speed of the spiral ribbon 221, that is, the agitation rotation speed of the frozen material F, the frozen material F is lifted further upward, and the flow speed in the circulatory flow of the frozen material F increases, so that the frozen material F is moved more at a faster speed.

[0034] The jacket 23 covers the outer periphery of the container body 21. A heat medium supply path 231 and a heat medium recovery path 232 are connected to the jacket 23. The heat medium supply path 231 has a leading end connected to the lower part of the jacket 23 and a rear end connected to the heat medium temperature adjustment unit 3. On the other hand, the heat medium recovery path 232 has a leading end connected to the heat medium temperature adjustment unit 3 and a rear end connected to the upper part of the jacket 23. The heat medium supplied to the jacket 23 through the heat medium supply path 231 flows inside the jacket 23 and is discharged to the heat medium recovery path 232. The outside of the jacket 23 is covered with a heat insulating member (not shown) so that the temperature of the heat medium in the jacket 23 does not change depending on the installation environment of the drying container 2.

[0035] The heat medium temperature adjustment unit 3 includes a heat medium pump 31, a cooling flow rate adjustment valve 33, a constant flow rate valve 34, a heat medium cooler 35, a heat medium heater 36, a heat medium tank 37, and a second heat exchanger 38. In FIG. 1, the heat medium temperature adjustment unit 3 is surrounded by a two-dot chain line. This heat medium temperature adjustment unit 3 corresponds to an example of a supply heat amount adjustment unit. In addition, in FIG. 1, the heat medium cooler 35 and the heat medium heater 36 are shown in a schematic cross section cut vertically so that the inside can be seen. The heat medium pump 31 delivers the liquid heat medium at an arbitrary flow rate. The heat medium is ethanol, which is the same as the above-mentioned brine liquid. Of course, the heat medium may be other than ethanol, and may be different from the brine liquid. The delivered heat medium is divided into the heat medium cooler 35 and the heat medium heater 36 at the divided flow rates set by the cooling flow rate adjustment valve 33 and the constant flow rate valve 34, respectively. The constant flow valve 34 is a valve that allows the heat medium to flow at a set flow rate.

[0036] The cooling flow rate control valve 33 is an electric valve that changes the flow rate of the heat medium passing therethrough under the control of the control means 10 (see FIG. 2), which will be described later. The cooling flow rate control valve 33 can be closed to set the flow rate to zero, and by setting it to zero, the heat medium flows only to the heat medium heater 36. The control means 10 adjusts the flow rate sent out by the heat medium pump 31 according to the opening degree of the cooling flow rate control valve 33 so that the flow rate of the heat medium toward the heat medium heater 36 is always constant. Under the control of the control means 10, a constant amount of the heat medium always flows to the heat medium heater 36, and a flow rate according to the opening degree of the cooling flow rate control valve 33 flows to the heat medium cooler 35. The heat medium that has passed through the heat medium heater 36 is supplied to the jacket 23 through the heat medium supply path 231, so that a constant amount of the heat medium always circulates between the jacket 23 and the heat medium temperature adjustment unit 3. The flow rate toward the heat medium heater 36 may be changed by adjusting the flow rate sent out by the heat medium pump 31 and the opening degree of the cooling flow rate control valve 33. Alternatively, instead of or in addition to the constant flow valve 34, an electric valve may be disposed in the flow path toward the heat medium heater 36, thereby making it possible to form a flow of the heat medium toward only the heat medium cooler 35.

[0037] The heat medium cooler 35 cools the heat medium passing through it. The heat medium cooled by passing through this heat medium cooler 35 passes through the second heat exchanger 38 and flows toward the heat medium tank 37. A refrigerant circulates between the heat medium cooler 35 and the common refrigerator 6. The refrigerant cooled by the common refrigerator 6 is sent to the heat medium cooler 35, where it is heated by the heat medium and returned to the common refrigerator 6. That is, in the heat medium cooler 35, the heat medium is cooled and the refrigerant is heated. A cooler expansion valve 351 is provided immediately before the heat medium cooler 35 in the refrigerant flow. The high-pressure refrigerant cooled by the common refrigerator 6 is decompressed by this cooler expansion valve 351 to a state where it is easy to evaporate, and the amount set by the cooler expansion valve 351 flows to the heat medium cooler 35. The flow of this refrigerant will be described later. The outside of the heat medium cooler 35 is covered with a heat-insulating member. In FIG. 1, the heat retaining member is shown by cross-hatching.

[0038] The heat medium heater 36 heats the heat medium passing through it. However, the heat medium heater 36 can also pass the heat medium as it is without heating it. The heat medium that has passed through the heat medium heater 36 flows toward the jacket 23 through the heat medium supply path 231. The heat medium heater 36 is provided with a heating thermometer 361 that measures the heating temperature at which the heat medium is heated. In addition, a heat medium thermometer 362 that measures the temperature of the heat medium that has passed through the heat medium heater 36 is provided downstream of the heat medium heater 36 in the flow of the heat medium. The measured values ​​of these thermometers are constantly transmitted to the control means 10 (see FIG. 2). The control means 10 controls the heating temperature of the heat medium by the heat medium heater 36 based on these measured values ​​so that the heat medium flowing from the heat medium heater 36 toward the jacket 23 has a desired temperature. The heat medium heater 36 is covered on the outside with a heat retaining member. In FIG. 1, the heat retaining member is indicated by cross-hatching.

[0039] The heat medium tank 37 stores the heat medium returned from the jacket 23 through the heat medium recovery path 232 and the heat medium that has passed through the heat medium cooler 35. The heat medium stored in the heat medium tank 37 is extracted at a desired flow rate by the heat medium pump 31 and sent out from the heat medium pump 31. The heat medium sent out from the heat medium pump 31 flows toward the branch section 32 that branches into the heat medium cooler 35 and the heat medium heater 36.

[0040] The second heat exchanger 38 exchanges heat between the cooling water flowing from the common refrigerator 6 toward the first heat exchanger 7 and the heat medium flowing from the heat medium cooler 35 toward the heat medium tank 37. A waste heat supply valve 381, which is an electric valve that adjusts the flow rate of the cooling water toward the second heat exchanger 38, is provided in the front stage (upstream side) of the second heat exchanger 38 in the flow of the cooling water. The opening degree of the waste heat supply valve 381 is controlled by the control means 10 (see FIG. 2). In addition, a bypass path that connects the front stage (upstream side) and the rear stage (downstream side) of the second heat exchanger 38 in the flow of the cooling water is formed in the vicinity of the second heat exchanger 38. The bypass path is provided with a waste heat bypass valve 382, ​​which is an electric valve. The opening degree of the waste heat bypass valve 382 is also controlled by the control means 10. When heat exchange is not required, the waste heat supply valve 381 is closed and the waste heat bypass valve 382 is opened, so that the cooling water flows toward the first heat exchanger 7 without passing through the second heat exchanger 38. Conversely, when heat exchange is required, the waste heat supply valve 381 is opened and the waste heat bypass valve 382 is closed, so that the cooling water flows toward the first heat exchanger 7 after passing through the second heat exchanger 38. When only a portion of the cooling water is to be heat exchanged, the ratio of the flow rate of the cooling water that is heat exchanged in the second heat exchanger 38 to the flow rate of the cooling water that is not heat exchanged can be set arbitrarily by adjusting the opening degree of each of the waste heat supply valve 381 and the waste heat bypass valve 382.

[0041] The heat medium temperature adjustment unit 3 circulates the heat medium, the temperature of which is adjusted to a set temperature mainly by the heat medium cooler 35 and the heat medium heater 36, between the jacket 23 and the heat medium temperature adjustment unit 3. That is, the temperature-adjusted heat medium is repeatedly circulated, such as being supplied to the jacket 23 through the heat medium supply path 231, and then being returned from the jacket 23 to the heat medium temperature adjustment unit 3 through the heat medium recovery path 232. By circulating and supplying the heat medium to the jacket 23, the temperature of the container body 21 can be adjusted from the outside, and the temperature inside the container body 21 can be adjusted to a desired temperature. That is, the heat medium temperature adjustment unit 3 adjusts the amount of heat supplied to the frozen object F from the heat medium flowing between the jacket 23 and the heat medium temperature adjustment unit 3. The heat medium temperature adjustment unit 3 can adjust both the temperature and flow rate of the heat medium, and can adjust the amount of heat supplied to the frozen object F in the container body 21 by either of these. However, in this embodiment, an example will be described in which the flow rate of the heat medium supplied to the jacket 23 is controlled to be constant, and the amount of heat supplied to the frozen object F in the container body 21 is adjusted by adjusting the temperature of the heat medium. Although the heat medium temperature adjusting unit 3 mainly supplies heat to the frozen object F, it can also be used to cool the brine liquid in the container body 21, which will be described later in detail.

[0042] The vacuum pump 4 reduces the pressure in the container body 21, the upstream exhaust path 511, the cold trap 5, and the downstream exhaust path 512. Hereinafter, the container body 21, the upstream exhaust path 511, the cold trap 5, and the downstream exhaust path 512 may be collectively referred to as the container body 21. The vacuum pump 4 is provided at the downstream end of the flow of gas that has passed through the exhaust port 216 of the container body 21. The vacuum pump 4, the heat medium temperature adjustment unit 3, and the stirring means 22 correspond to an example of a drying means. By driving the vacuum pump 4, the solidified liquid component contained in the frozen material F in the container body 21 sublimes and becomes vapor. In addition, the solidified liquid component contained in the frozen material F sublimes and becomes vapor when the frozen material F is heated by the heat medium whose temperature is adjusted by the heat medium temperature adjustment unit 3, or when the frozen material F is heated by frictional heat generated by the rotation of the spiral ribbon 221. The steam generated in the container body 21 and gases such as air that were in the container body 21 are drawn toward the vacuum pump 4. Then, the gases that reach the vacuum pump 4 are exhausted to the outside of the vacuum pump 4. However, liquid components contained in the gases are collected by the cold trap 5 before they reach the vacuum pump 4.

[0043] By driving the vacuum pump 4, the pressure inside the container body 21 and the like is reduced to about 13 Pa or more and 120 Pa or less. In order to prevent this pressure from dropping too much, the downstream exhaust path 512 is connected to the intake path 41, which draws in outside air. The intake path 41 is provided with a pressure regulating valve 42, which is an electric valve. If the pressure inside the upstream exhaust path 511 measured by the exhaust path pressure gauge 513 is too low, the control means 10 (see FIG. 2) adjusts the opening of the pressure regulating valve 42 according to the pressure. As a result, outside air according to the opening of the pressure regulating valve 42 passes through the intake path 41 and enters the downstream exhaust path 512, so that the pressure inside the container body 21 and the like is maintained at 13 Pa or more and 120 Pa or less. An intake filter 43 for reducing intake noise and foreign matter contamination is attached to the end of the intake path 41 opposite to the end connected to the downstream exhaust path 512.

[0044] The downstream exhaust passage 512 is provided with an oxygen concentration meter 44 for measuring the oxygen concentration in the downstream exhaust passage 512. Since the steam generated in the container body 21 is almost oxygen-free, the oxygen concentration in the downstream exhaust passage 512 changes mainly depending on the amount of outside air sucked through the intake passage 41. At the beginning and middle of the drying process, the amount of steam generated from the frozen object F is large, so the pressure inside the container body 21 and the like is increased by the pressure increase action of the steam generated in the container body 21 and the pressure reduction action of the vacuum pump 4 are in balance, and the amount of outside air sucked through the intake passage 41 is zero or very small. On the other hand, at the end of the drying process, the liquid component contained in the frozen object F is reduced, so the steam generated in the container body 21 is greatly reduced. As a result, at the end of the drying process, the amount of outside air sucked through the intake passage 41 increases, and the oxygen concentration in the downstream exhaust passage 512 increases.

[0045] The cold trap 5 is for freezing and collecting the received vapor. In FIG. 1, the cold trap 5 is shown in a schematic vertical cross section so that the inside can be seen. Basically, vapor freezes by sublimation (solidification) in the cold trap 5, but a very small amount of vapor may condense (liquefy) and then solidify (freeze) to become a solid. A refrigerant circulates between the cold trap 5 and the common refrigerator 6. This refrigerant is a refrigerant that is used in common with the refrigerant circulating between the heat medium cooler 35 and the common refrigerator 6. A part of the refrigerant cooled in the common refrigerator 6 is sent to the cold trap 5, passes through the cooling pipe 51 that is folded back multiple times in the cold trap 5, and then returns to the common refrigerator 6. A trap expansion valve 55 is provided immediately before the cold trap 5 in the refrigerant flow. The high-pressure refrigerant cooled in the common refrigerator 6 is decompressed by the trap expansion valve 55 to a state that is easy to evaporate, and the amount set by the trap expansion valve 55 flows into the cooling pipe 51. The steam passing through the cold trap 5 is cooled and frozen in the cooling tube 51, and adheres to the surface of the cooling tube 51, and the thickness of the adhesion gradually increases from the surface of the cooling tube 51. The outside of the cold trap 5 is covered with a heat-insulating material. In Fig. 1, the heat-insulating material is indicated by cross-hatching.

[0046] The cold trap 5 is provided with a trap thermometer 53 for measuring the temperature inside the cold trap 5. The cold trap 5 is also provided with a load cell 56 for measuring the mass of the vapor generated by the sublimation of the liquid component of the frozen object F and collected by the cold trap 5. In order to measure the mass with the load cell 56, a flexible hose 54 is installed in the vicinity of the cold trap 5 of each pipe connected to the cold trap 5. The load cell 56 measures the mass of the part located closer to the cold trap 5 than the flexible hose 54, and constantly transmits the measurement result to the control means 10 (FIG. 2). The load cell 56 and the control means 10 correspond to an example of a monitoring means. In this embodiment, the load cell 56 measures the total mass of the part located closer to the cold trap 5 than the flexible hose 54 and the collected vapor, and transmits it to the control means 10, and the control means 10 calculates the mass of the collected vapor. However, the mass of the collected vapor may be directly measured by the cold trap 5 and transmitted to the control means 10 by setting the mass of the vapor before collection to zero in the load cell 56 .

[0047] The common refrigerator 6 supplies refrigerant to both the heat medium cooler 35 and the cold trap 5. The common refrigerator 6 has a refrigerant compression cooling section 61 and a refrigerant pressure gauge 62. The refrigerant returning from the heat medium cooler 35 and the refrigerant returning from the cold trap 5 join in a refrigerant recovery passage 64 to become a mixed refrigerant. The refrigerant compression cooling section 61 compresses the mixed refrigerant to a high pressure, and cools the refrigerant that has become hot by compression with cooling water to condense it and send it to the refrigerant supply passage 63. The refrigerant supply passage 63 branches into a cooler refrigerant supply passage 631 leading to the heat medium cooler 35 and a trap refrigerant supply passage 632 leading to the cold trap 5. The cooler refrigerant supply passage 631 is provided with a cooling refrigerant supply valve 633. The cooling refrigerant supply valve 633 is operated under the control of the control means 10 (see FIG. 2), and is a valve that opens when the supply of refrigerant to the heat medium cooler 35 starts and closes when the supply is stopped. The cooler expansion valve 351 described above is disposed between the cooling refrigerant supply valve 633 and the heat medium cooler 35. The refrigerant, which has expanded in the cooler expansion valve 351 to become a low-pressure liquid, evaporates into gas by cooling the heat medium in the heat medium cooler 35, and is then returned to the common refrigerator 6 through the refrigerant recovery path 64. Note that if the heat medium does not pass through the heat medium cooler 35, if the amount of heat medium passing through the heat medium cooler 35 is small, or if the heat medium passing through the heat medium cooler 35 is sufficiently cooled, some or all of the refrigerant may return to the common refrigerator 6 from the heat medium cooler 35 in liquid form.

[0048] Further, the trap refrigerant supply passage 632 is provided with a trap refrigerant supply valve 634. This trap refrigerant supply valve 634 is operated under the control of the control means 10 (see FIG. 2), and is a valve that opens when the supply of refrigerant to the cold trap 5 is started and closed when the supply is stopped. The above-mentioned trap expansion valve 55 is disposed between the trap refrigerant supply valve 634 and the cold trap 5. The refrigerant that has expanded to a low-pressure liquid by the trap expansion valve 55 flows into the cooling pipe 51 in the cold trap 5, freezes the vapor, and evaporates to a gas, and is then returned to the common refrigerator 6 through the refrigerant recovery passage 64. Note that when the amount of vapor received by the cold trap 5 decreases, a part or all of the refrigerant may return from the cold trap 5 to the common refrigerator 6 in a liquid state.

[0049] The refrigerant recovery path 64 is a refrigerant flow path formed by joining a cooler refrigerant recovery path 641 connected to the heat medium cooler 35 and a trap refrigerant recovery path 642 connected to the cold trap 5. The refrigerant that joins in the refrigerant recovery path 64 flows into the refrigerant compression and cooling section 61. The refrigerant pressure gauge 62 measures the pressure of the refrigerant after the refrigerant recovery path 64 joins and before the refrigerant flows into the refrigerant compression and cooling section 61. That is, the refrigerant pressure gauge 62 measures the pressure of the low-pressure side of the refrigerant.

[0050] As the drying process approaches the end, the liquid component contained in the frozen material F decreases, and the vapor generated in the container body 21 also decreases. As a result, the amount of vapor collected in the cold trap 5 decreases, and the refrigerant circulating between the cold trap 5 and the common refrigerator 6 is no longer heated in the cold trap 5. As the drying process progresses further, the temperature of the refrigerant hardly increases in the cold trap 5, and the pressure of the refrigerant measured by the refrigerant pressure gauge 62 decreases. When the pressure of the refrigerant measured by the refrigerant pressure gauge 62 falls below a predetermined pressure, the low pressure cut state is entered and the common refrigerator 6 stops the operations of refrigerant compression, refrigerant cooling, and refrigerant circulation. In contrast, in this embodiment, the refrigerant used in common by the heat medium cooler 35 and the cold trap 5 is controlled to be warmed in the heat medium cooler 35, so that the operation of the common refrigerator 6 is not stopped. The details of this control will be described later.

[0051] The first heat exchanger 7 is for cooling the cooling water circulating between the common chiller 6 and the first heat exchanger 7. The first heat exchanger 7 is provided with a chemical injection device 71 that injects a chemical to keep the water in the first heat exchanger 7 in an optimal state. As described above, the cooling water selectively passes through the second heat exchanger 38 on the way from the common chiller 6 to the first heat exchanger 7, and flows toward the common chiller 6 after being cooled by the first heat exchanger 7. This flow is formed by the cooling water pump 72 located on the way from the first heat exchanger 7 to the common chiller 6.

[0052] FIG. 2 is a block diagram showing a control configuration of the drying system 1 shown in FIG.

[0053] As shown in FIG. 2, the control means 10 includes a control unit 101 and a storage unit 102. The control means 10 is a PLC (Programmable Logic Controller). Note that other computers may be used as the control means 10 instead of or in addition to the PLC. Measurement results of various instruments such as the load cell 56, the refrigerant pressure gauge 62, the container thermometer 211, the heat medium thermometer 362, and the exhaust passage pressure gauge 513 are transmitted to the control means 10. The control means 10 controls each of the controlled object configurations such as the heat medium pump 31, the cooling flow rate control valve 33, the heat medium heater 36, the pressure control valve 42, and the agitation drive device 223 provided in the drying system 1 in response to the measurement results by the control unit 101. The control means 10 also performs calculations based on the measurement results of the various instruments as necessary. The storage unit 102 is composed of a volatile memory and a non-volatile memory. The storage unit 102 stores programs and the like that describe the control operations of each controlled object configuration by the control unit 101.

[0054] Next, a description will be given of a drying method for obtaining a dried material by drying the frozen material F using the drying system 1 shown in Fig. 1. The processing in this drying method is executed by the control means 10 controlling each controlled object configuration.

[0055] In this drying system 1, a frozen material F is produced as a preparation step before starting the drying process. In the production of the frozen material F, a brine liquid is supplied from the inlet 215 of the container body 21 to the container body 21, the inside of which is empty. Then, when the container body 21 is sealed, the control means 10 is made to start the preparation step. The control means 10 opens the cooling refrigerant supply valve 633 and operates the common refrigerator 6 and the cooling water pump 72. The control means 10 also controls the heat medium temperature adjustment unit 3 to open the cooling flow rate adjustment valve 33 to start driving the heat medium pump 31, close the waste heat supply valve 381, and open the waste heat bypass valve 382. Thereafter, the heat medium is cooled by the heat medium temperature adjustment unit 3 to a desired cooling temperature (for example, -30°C) that is equal to or lower than the freezing point of the dispersion liquid, while measuring the temperature of the brine liquid by the container thermometer 211. The control means 10 controls the heat medium heater 36 not to heat the heat medium until the cooling temperature is reached.

[0056] When the brine reaches a desired cooling temperature, the dispersion is poured into the container body 21 and rapidly frozen by immersion in the brine, thereby producing a frozen product F in which the dispersion is frozen. In this embodiment, an example is described in which a dispersion using water as a liquid component is used, but a dispersion using a liquid component other than water may be used. In addition, the dispersion is pre-frozen in advance and crushed to a degree that allows it to pass through the inlet 215, and a plurality of processed material chunks may be used as the frozen product F. When cooling the brine, the control means 10 also starts driving the stirring means 22 to rotate the spiral ribbon 221. This stirs the brine and the entire brine is cooled evenly. Then, the dispersion dropped into the brine is divided by the rotation of the spiral ribbon 221 to become a frozen product F consisting of a number of processed material chunks. When the frozen product F is obtained, only the brine is discharged from the brine outlet 212 provided in the container body 21. As a result, the frozen product F remains in the container body 21. Thereafter, the control means 10 opens the trap refrigerant supply valve 634 to circulate the refrigerant between the cold trap 5 and the common refrigerator 6 to lower the temperature of the cold trap 5 to -40°C. In addition, the control means 10 closes the cooling flow rate control valve 33 to start heating by the heat medium heater 36 to adjust the heating temperature and control the temperature of the heat medium to -20°C, which is a temperature below the eutectic point of the frozen object F. Furthermore, the control means 10 controls the spiral ribbon 221 to rotate at 10 rotations per minute. In the case where the basic minimum rotation speed of the spiral ribbon 221 is 10 rotations per minute, it is preferable that the maximum rotation speed that can be adjusted depending on the situation is 15 rotations per minute. The rotation speed set in this preparation process becomes the minimum rotation speed of the spiral ribbon 221 in the drying process. Then, the control means 10 adjusts the rotation of the spiral ribbon 221 to the minimum rotation speed or a higher rotation speed depending on the progress of the drying process. Instead of changing the rotation speed, intermittent stirring may be performed by repeatedly rotating and stopping the spiral ribbon 221. In this case, the control means 10 controls the time allocation between the driving time and the driving stop time of the stirring means 22 instead of the rotation speed.The temperature of the heat medium, the number of revolutions of the spiral ribbon 221, or the intermittent time distribution of the spiral ribbon 221 in the case of intermittent stirring, are set by the operator selecting a value that does not reliably melt the frozen material F according to the type of the object to be processed, the type of liquid component of the dispersion, or the proportions of the container body 21, and inputting it into the control means 10, and can be changed appropriately by the operator. In addition, by using a means that can automatically recognize the input conditions, it is possible to perform the preparation process in an automatic operation. By executing the above preparation process, preparation for starting the drying process is completed. Note that the method of generating the frozen material F using a brine solution is only one example, and there are various other preliminary freezing methods, such as a freezing method in which the dispersion liquid is sprayed under vacuum, and a freezing method in which the jacket 23 is heated to around 0°C to make the inside of the container body 21 less than 600 PaA and self-freeze it, and any of these methods may be used to generate the frozen material F.

[0057] FIG. 3 is a flowchart showing control in the drying process of the drying system 1 shown in FIG.

[0058] When the drying process is started, the control means 10 drives the vacuum pump 4 while maintaining the temperature of the heat medium, the temperature in the cold trap 5, and the rotation speed of the spiral ribbon 221 at the values ​​set in the preparation process. The pressure in the container body 21 is reduced to about 13 Pa or more and 120 Pa or less by driving the vacuum pump 4. During the drying process, the control means 10 controls the opening of the pressure regulating valve 42, so that the pressure in the container body 21 and the like is maintained at about 13 Pa or more and 120 Pa or less. When the pressure in the container body 21 decreases to 13 Pa or more and 120 Pa or less, for example, about 110 Pa, and further receives frictional heat from the spiral ribbon 221 and the container body 21 or heat from the heat medium in the jacket 23, moisture, which is a liquid component of the frozen object F that has been solidified, sublimes and begins to generate steam. Most of the steam generated during this drying process is frozen by the cold trap 5 on the way to the vacuum pump 4 and collected as ice (solid). The process in which this drying process is performed corresponds to an example of a collection process. In addition, there may be a small amount of brine liquid remaining in the container body 21 that was not completely drained during the preparation process. In such a case, the gas generated in the container body 21 may contain evaporated brine liquid, but this is an extremely small amount and usually does not pose a problem.

[0059] The control means 10 periodically repeats the processing of steps S11 to S26 shown in FIG. 3 at a predetermined time interval (for example, every 10 minutes) until the drying process is completed. Hereinafter, each of these periodically repeated processes may be referred to as a periodic process. The control means 10 obtains temperature data of the frozen object F at the start of each periodic process from the container thermometer 211, and determines whether the temperature of the frozen object F is equal to or lower than a reference temperature (step S11). The reference temperature is the temperature (eutectic point) at which the frozen object F begins to melt under the pressure inside the container body 21, or a temperature slightly lower than that temperature. For example, this reference temperature is −15° C. at the beginning of the drying process, and is gradually increased (raised) according to the elapsed time from the start of the drying process to finally reach 20° C.

[0060] If the temperature of the frozen object F is equal to or lower than the reference temperature (YES in step S11), the control means 10 judges whether the mass measured by the load cell 56 has changed from the previous mass stored in the memory unit 102 (step S12). This change in mass is a change caused by the steam collected as ice by freezing in the cold trap 5 during the period from the start of the previous regular processing to the start of the current regular processing, and is an increasing change. Therefore, the changed mass corresponds to the mass of the steam collected in the most recent regular processing, and is calculated by subtracting the previous mass stored in the memory unit 102 from the mass measured this time by the load cell 56. Hereinafter, this changed mass may be referred to as the collected mass. The existence of the collected mass indicates that the moisture contained in the frozen object F has sublimated and the drying process has progressed smoothly. That is, the control means 10 of this embodiment monitors the ice collection status by monitoring the change in the mass of ice measured by the load cell 56. By monitoring this collection status, the drying status of the frozen object F can be grasped. This step S12 corresponds to an example of a monitoring step. Note that in the first regular process, the previous mass information is not stored in the storage unit 102, so this step S12 becomes NO.

[0061] If there is a change in the mass of ice collected in the cold trap 5 (YES in step S12), the control means 10 judges whether the temperature of the heat medium supplied to the jacket 23 is less than the maximum temperature (step S13). This maximum temperature is, for example, 20°C. The maximum temperature is set by an operator selecting and inputting into the control means 10 a value according to the type of material to be treated and the type of liquid component of the dispersion, and can be changed as appropriate by the operator. On the other hand, if there is no change in the mass of ice collected in the cold trap 5 (NO in step S12), the process proceeds to step S24.

[0062] If the temperature of the heat medium supplied to the jacket 23 is less than the maximum temperature (YES in step S13), the temperature of the heat medium supplied to the jacket 23 is increased by 3° C. (step S14). That is, when the control means 10 judges in step S12 that the drying of the frozen object F is proceeding smoothly and in step S13 that there is still room for increasing the temperature of the heat medium, the temperature of the heat medium is increased to increase the amount of heat supplied to the frozen object F, thereby increasing the drying speed. The temperature to be increased to in step S14 is set by the operator by selecting and inputting it into the control means 10, and can be changed as appropriate by the operator, but is preferably 3° C. or more and 10° C. or less. Note that if an increase of 3° C. would cause the temperature of the heat medium to exceed the maximum temperature, the temperature of the heat medium is increased only to the maximum temperature.

[0063] When the process of increasing the temperature of the heat medium in step S14 is completed or the temperature of the heat medium supplied to the jacket 23 is equal to or higher than the maximum temperature (NO in step S13), the control means 10 judges whether the rotation speed of the spiral ribbon 221 is less than the maximum rotation speed (step S15). If the rotation speed of the spiral ribbon 221 is less than the maximum rotation speed (YES in step S15), the rotation speed of the spiral ribbon 221 is increased by 4 rotations / min (step S16). That is, when it is judged in step S12 that the drying of the frozen object F is proceeding smoothly and in step S15 that there is still room for increasing the rotation speed of the spiral ribbon 221, the rotation speed of the spiral ribbon 221 is increased to move the frozen object F more, thereby increasing the drying speed. The rotation speed to be increased in step S15 is set by the operator selecting and inputting it into the control means 10, and can be appropriately changed by the operator. Note that, if the maximum rotation speed is exceeded by increasing the rotation speed by 4 rotations / min, the increase in the rotation speed is limited to the maximum rotation speed. This maximum rotation speed is set by the operator to about 4 to 10 times the minimum rotation speed (10 rotations / min). In this embodiment, the maximum rotation speed of the spiral ribbon 221 is set to 86 rotations / min. By increasing the rotation speed of the spiral ribbon 221, the frozen object F is lifted higher.

[0064] When the process of increasing the number of rotations of the spiral ribbon 221 in step S16 is completed or the number of rotations of the spiral ribbon 221 is equal to or greater than the maximum number of rotations (NO in step S15), the control means 10 judges whether the collected mass, which is the amount of change between the currently measured mass and the previous mass stored in the memory unit 102, is equal to or less than a first predetermined amount (step S17). The first predetermined amount is a value set by an operator selecting and inputting into the control means 10 according to the amount of dispersion liquid or the amount of frozen material F put into the container body 21. This first predetermined amount is set to the mass of steam generated from the frozen material F at the time interval of the regular processing when the drying process is at the end and most of the moisture contained in the frozen material F has disappeared. By setting in this manner, it is possible to judge whether the drying process is at the end when most of the moisture contained in the frozen material F has disappeared.

[0065] If the rotation speed of the spiral ribbon 221 is increased in the beginning or middle of the drying process, the frozen object F is likely to melt due to frictional heat between the spiral ribbon 221 and the frozen object F, frictional heat between the frozen object F and the inner surface of the container body 21, and frictional heat between the frozen objects F themselves. However, since the moisture content is reduced at the end of the drying process, the risk of melting is reduced even if the rotation speed of the spiral ribbon 221 is increased. For this reason, it is preferable to shorten the drying time by increasing the rotation speed of the spiral ribbon 221 at the end of the drying process. By shortening the drying time, not only can the production efficiency be improved, but also the energy required for drying can be reduced. Furthermore, since the rotation speed of the spiral ribbon 221 is increased, the frozen object F is raised to a higher position, so that the frozen object F comes into contact with the inner surface of the container body 21 even in the upper part of the container body 21, and the heat of the heat medium can be efficiently transferred to the frozen object F. Therefore, if the amount of change between the currently measured mass and the previous mass is equal to or less than the first predetermined amount (YES in step S17), the rotation speed of the spiral ribbon 221 is increased to the maximum rotation speed to increase the drying speed (step S18). On the other hand, if the amount of change between the currently measured mass and the previous mass exceeds the first predetermined amount (NO in step S17), the drying process is still in the early or middle stage, so the process proceeds to step S24 without executing step S18 and step S19 described later so as not to melt the frozen object F.

[0066] Furthermore, if the amount of change between the currently measured mass and the previous mass is equal to or less than the first predetermined amount (YES in step S17), the amount of vapor received by the cold trap 5 is extremely small, so the refrigerant passing through the cooling pipe 51 returns to the common refrigerator 6 without being heated. This makes it easy for the common refrigerator 6 to enter a low-pressure cut state. When the common refrigerator 6 enters a low-pressure cut state, the cooling function of the refrigerant in the common refrigerator 6 is temporarily stopped, and the pressure and temperature in the cold trap 5 increase, and when the cooling function of the common refrigerator 6 is resumed, the pressure and temperature in the cold trap 5 decrease. This is repeated. Depending on the pressure and temperature in the cold trap 5, the pressure and temperature in the container body 21, the upstream exhaust path 511, and the downstream exhaust path 512 also fluctuate, so it becomes difficult to judge the drying state and whether or not drying is completed based on these pressures and temperatures. In contrast, in this embodiment, step S19 is executed depending on the ice collection state in the cold trap 5 to warm the refrigerant in the heat medium cooler 35, thereby controlling the common refrigerator 6 not to enter a low pressure cut state.

[0067] Specifically, in step S19, the control means 10 controls the heat medium temperature adjustment unit 3 to open the cooling flow rate adjustment valve 33, open the waste heat supply valve 381, and close the waste heat bypass valve 382. As a result, the heat medium that flowed only to the heat medium heater 36 also flows to the heat medium cooler 35, and the heat medium is cooled by the heat medium cooler 35. On the other hand, the refrigerant is heated in the heat medium cooler 35 and expands or evaporates, increasing its pressure and flowing to the common refrigerator 6, so that the pressure of the refrigerant measured by the refrigerant pressure gauge 62 increases, and the low-pressure cut state can be avoided. In other words, by raising the temperature of the refrigerant in the heat medium cooler 35, the load on the common refrigerator 6 is increased, and the low-pressure cut state can be avoided. The control means 10 fully opens the cooling flow rate adjustment valve 33 in step S19, but may also control the cooling flow rate adjustment valve 33 to be opened slightly when the collected mass becomes smaller than a predetermined amount in step S12, and then to increase the opening of the cooling flow rate adjustment valve 33 as the collected mass decreases.

[0068] Furthermore, by opening the waste heat supply valve 381 and closing the waste heat bypass valve 382, ​​the heat medium cooled in the heat medium cooler 35 and the cooling water heated in the common refrigerator 6 are heat exchanged in the second heat exchanger 38. As a result, the heat medium is heated, and less energy is required to heat the heat medium to a set temperature in the heat medium heater 36. Furthermore, as the cooling water is cooled in the second heat exchanger 38, even colder cooling water can be obtained in the first heat exchanger 7. As a result, the energy consumed in the drying system 1 can be reduced. After the above step S19 is completed, proceed to step S24.

[0069] If the temperature of the frozen material F exceeds the reference temperature in step S11 described above (NO in step S11), there is a risk that the frozen material F will melt if left as is. Therefore, the control means 10 sets the temperature of the heat medium supplied to the jacket 23 to a lowering temperature that is equal to or lower than the eutectic point of the frozen material F (step S21). This reduces the drying speed of the frozen material F, and suppresses melting of the frozen material F. This lowering temperature is, for example, -5°C. The lowering temperature is set by the operator selecting it according to the type of the material to be treated and the type of liquid component of the dispersion liquid, and inputting it into the control means 10, and can be changed as appropriate by the operator.

[0070] Following the start of the temperature change of the heat medium in step S21, the control means 10 judges whether the rotation speed of the spiral ribbon 221 exceeds a predetermined rotation speed (step S22). This predetermined rotation speed is set to 10 rotations / min, which is the minimum rotation speed. However, this predetermined rotation speed can be changed appropriately by the operator. If the rotation speed of the spiral ribbon 221 exceeds the predetermined rotation speed (YES in step S22), the control means 10 reduces the rotation speed of the spiral ribbon 221 to the minimum rotation speed (step S23). This reduces the drying speed of the frozen object F, and further suppresses the melting of the frozen object F. When the process of step S23 is completed or the rotation speed of the spiral ribbon 221 does not exceed the predetermined rotation speed (NO in step S22), the process proceeds to step S24.

[0071] In step S24, the mass information obtained from the load cell 56 in the current periodic process is stored in the storage unit 102. Here, when step S24 is executed via steps S21 to S23, there is no mass information in the current periodic process, so the previous mass information is stored in the storage unit 102 as the current mass information. When step S24 is executed via steps S21 to S23, mass information may be obtained from the load cell 56 in step S24 and stored in the storage unit 102. The mass data stored in the storage unit 102 may be overwritten for each drying process, but it is preferable to leave all data during the drying process or data for multiple periodic processes as history data in the storage unit 102 together with data measured by each instrument. These data can be used when verifying the setting values ​​set by the operator in the drying process. After storing the mass information, the control means 10 judges whether a predetermined time has elapsed since the start of the current periodic process (step S25). Then, it waits until the predetermined time has elapsed (NO in step S25). This predetermined time is 10 minutes, which is the time interval for regular processing. Note that the predetermined time in step S25 can be changed as appropriate by an operator, and by changing this predetermined time, the time interval for regular processing can be changed arbitrarily.

[0072] When a predetermined time has elapsed (YES in step S25), the control means 10 judges whether the collected mass is zero, the temperature of the frozen material F measured by the container thermometer 211 is the same as the temperature of the heat medium measured by the heat medium thermometer 362, and the temperature of the frozen material F has not changed for the past 10 minutes (step S26). If the collected mass is zero and the temperature of the frozen material F is the same as the heat medium and has not changed (YES in step S26), the drying is complete and the drying process is terminated. On the other hand, if there is a collected mass, if the temperature of the frozen material F is different from the temperature of the heat medium or if the temperature of the frozen material F has changed (NO in step S26), the process returns to step S11 and starts the next periodic process.

[0073] According to the drying system 1 of this embodiment, since the common refrigerator 6 that supplies refrigerant to both the heat medium cooler 35 and the cold trap 5 is provided, when the temperature of the refrigerant is no longer increased in the cold trap 5, the heat medium cooler 35 can instead increase the temperature of the refrigerant. This prevents the pressure of the refrigerant recovered in the common refrigerator 6 from decreasing too much, and suppresses the common refrigerator 6 from going into a low pressure cut state during the drying process and temporarily stopping its cooling function of the refrigerant. In addition, since the heat medium cooler 35 and the cold trap 5 are cooled by the common refrigerator 6, the drying system 1 can be configured at a lower cost than when a dedicated refrigerator is provided for each.

[0074] In this embodiment, the trapping status in the cold trap 5 is monitored based on the change in the mass of the trapped ice, and when the trapped mass becomes equal to or less than a first predetermined amount, the cooling flow rate control valve 33 is opened to send the heat medium to the heat medium cooler 35 to raise the temperature of the refrigerant. That is, since a decrease in the trapped mass in the cold trap 5 indicates that the temperature of the refrigerant in the cold trap 5 is only slightly raised, the flow rate of the heat medium passing through the heat medium cooler 35 is adjusted from zero to the maximum amount in response to the decrease in the trapped mass to equal to or less than the first predetermined amount, thereby raising the temperature of the refrigerant in the heat medium cooler 35. Alternatively, the trapping status in the cold trap 5 is monitored, and when the trapped mass becomes smaller than a predetermined amount, the heat medium starts to pass through the heat medium cooler 35, and the flow rate of the heat medium passing through the heat medium cooler 35 is increased as the trapped mass decreases, gradually increasing the degree of raising the temperature of the refrigerant passing through the heat medium cooler 35. Either of these methods can prevent the common refrigerator 6 from temporarily stopping the refrigerant cooling function during the drying process. Since the common refrigerator 6 no longer temporarily stops the cooling function of the refrigerant, the pressure and temperature inside the container body 21 become stable, and the quality of the dried product obtained by drying the frozen material F becomes stable. In addition, the temperature of the cold trap 5 also becomes stable, so that it is possible to prevent the vapor from reaching the vacuum pump 4 without being captured by the cold trap 5 and damaging the vacuum pump 4.

[0075] According to the drying system 1 and the drying method of this embodiment, the ice collection state in the cold trap 5 is basically equal to the steam generation state in the container body 21, so the drying state of the frozen object F can be grasped by monitoring the collection state. That is, the drying state of the frozen object F is determined by the amount of liquid components contained in the frozen object F, and when the amount of the liquid components decreases, the total amount of ice collected in the cold trap 5 increases accordingly, so that the amount of liquid components contained in the frozen object F and the total amount of ice collected in the cold trap 5 are inversely proportional to each other. On the other hand, when the amount of liquid components contained in the frozen object F decreases, the amount of steam generated decreases, so that the collected mass, which is the increase in ice per unit time in the cold trap 5, also decreases, so that they are in a proportional relationship. In this embodiment, the collection state is monitored by judging the presence or absence of a change in the mass of ice and the collected mass, and the progress of drying, the end of the drying process, and the completion of the drying process are grasped from the collection state. The control means 10 appropriately adjusts the amount of heat supplied from the heat medium to the frozen material F according to the ice collection state in the cold trap 5, so that the drying time of the frozen material F can be shortened. And by shortening the drying time, the energy required for drying can be reduced. Furthermore, the speed at which the frozen material F is moved is increased toward the end of the drying process, so that the drying time of the frozen material F can also be shortened and the energy required for drying can be reduced.

[0076] Next, a modified example of this embodiment will be described. In the following description, components having the same names as components described above will be assigned the same reference numerals as those used above, and duplicate descriptions will be omitted.

[0077] FIG. 4 is a diagram showing the heat medium temperature adjusting section 3 in the drying system 1 of the first modified example.

[0078] As shown in FIG. 4, the heat medium temperature adjustment unit 3 of the drying system 1 of the first modification is different from the previous embodiment in that the heat medium that has passed through the heat medium cooler 35 is supplied to the jacket 23 (see FIG. 1) through the heat medium supply path 231 without returning to the heat medium tank 37. In the drying system 1 of the first modification, when it is desired to cool the heat medium or to heat the refrigerant, the cooling flow rate adjustment valve 33 is opened to pass the heat medium cooler 35. The heat medium that is diverted at the diverter 32 and passes through the heat medium heater 36 is sent to the heat medium supply path 231 without heating if it is desired to cool the heat medium, and when it is desired to heat the refrigerant, the heat medium is heated by the heat medium heater 36 as necessary to adjust the temperature to a desired value and sent to the heat medium supply path 231. When neither cooling nor heating of the heat medium nor heating of the refrigerant is required, the cooling flow rate adjustment valve 33 is closed, and the heat medium is passed through the heat medium heater 36 without being heated and sent to the heat medium supply path 231.

[0079] The drying system 1 of the first modified example described above also provides the same effects as those of the previous embodiment.

[0080] FIG. 5 is a diagram showing a heat medium temperature adjusting section 3 in a drying system 1 of the second modified example.

[0081] As shown in Fig. 5, the heat medium temperature adjustment unit 3 of the drying system 1 of the second modified example is different from the previous embodiment in that the heat medium that has passed through the heat medium cooler 35 flows toward the heat medium heater 36, and that a first flow rate adjustment valve 341, which is an electric valve, is provided in the heat medium flow path from the heat medium pump 31 toward the heat medium heater 36 instead of the constant flow rate valve 34. Also, it is different from the previous embodiment in that a detour 363 through which the heat medium flows is formed to bypass the heat medium heater 36, a second flow rate adjustment valve 342, which is an electric valve, is provided in the detour 363, and a third flow rate adjustment valve 343, which is an electric valve, is provided between the branch point to the detour 363 and the heat medium heater 36. The openings of the first flow rate adjustment valve 341, the second flow rate adjustment valve 342, and the third flow rate adjustment valve 343 are controlled by the control means 10 (see Fig. 2). The first flow rate control valve 341, the second flow rate control valve 342, and the third flow rate control valve 343 can be closed to set the flow rate to zero. The heat medium thermometer 362 is disposed downstream of the junction where the flow path of the heat medium passing through the heat medium heater 36 and the bypass 363 join. This allows the heat medium thermometer 362 to measure the temperature of the heat medium that has passed through the heat medium heater 36, the temperature of the heat medium that has passed through the bypass 363, and the temperature of the heat medium that is a mixture of these.

[0082] In the drying system 1 of the second modified example, when it is desired to cool the heat medium, the cooling flow rate control valve 33 and the second flow rate control valve 342 are opened, and the first flow rate control valve 341 and the third flow rate control valve 343 are closed. As a result, the heat medium passes through the heat medium cooler 35 and is cooled, and passes through the bypass 363 without passing through the heat medium heater 36. When it is desired to raise the temperature of the refrigerant, the cooling flow rate control valve 33 and the third flow rate control valve 343 are opened, and the first flow rate control valve 341 and the second flow rate control valve 342 are closed. As a result, the heat medium passes through the heat medium cooler 35 and the heat medium heater 36, has its temperature adjusted, and is sent out to the heat medium supply path 231. When it is desired to heat the heat medium, the cooling flow rate control valve 33 and the second flow rate control valve 342 are closed, and the first flow rate control valve 341 and the third flow rate control valve 343 are opened. As a result, the heat medium is heated in the heat medium heater 36 without passing through the heat medium cooler 35. The openings of the cooling flow rate control valve 33, the first flow rate control valve 341, the second flow rate control valve 342, and the third flow rate control valve 343 may be adjusted to mix the heated heat medium and the cooled heat medium and send it to the heat medium supply path 231. When neither cooling nor heating of the heat medium nor heating of the refrigerant is required, the cooling flow rate control valve 33 and the third flow rate control valve 343 are closed, and the first flow rate control valve 341 and the second flow rate control valve 342 are opened to send the heat medium to the heat medium supply path 231 without cooling or heating.

[0083] Furthermore, the heat medium temperature adjustment unit 3 in the drying system 1 of the second modified example is different from the previous embodiment in that a heat medium pressure gauge 311, a tank heat medium thermometer 312, a first bypass passage 391, a fourth flow rate control valve 392, a fifth flow rate control valve 393, a second bypass passage 395, a sixth flow rate control valve 396, and a seventh flow rate control valve 397 are provided. The heat medium pressure gauge 311 is disposed between the branch section 32 and the heat medium pump 31. The heat medium pressure gauge 311 is a pressure gauge that measures the pressure of the heat medium sent out from the heat medium pump 31. The tank heat medium thermometer 312 is a thermometer that measures the temperature of the heat medium moving from the heat medium tank 37 toward the heat medium pump 31. The pressure of the heat medium measured by the heat medium pressure gauge 311 and the temperature of the heat medium measured by the tank heat medium thermometer 312 are constantly transmitted to the control means 10 (see FIG. 2).

[0084] The first bypass path 391 is a heat medium flow path through which the heat medium diverted toward the heat medium cooler 35 at the diverting section 32 returns directly to the heat medium tank 37. The fourth flow control valve 392 is provided on this first bypass path 391. The fifth flow control valve 393 is an electric valve arranged between a diverting section 394 to the first bypass path 391 and the heat medium cooler 35. The opening degrees of these fourth flow control valve 392 and fifth flow control valve 393 are controlled by the control means 10 (see FIG. 2). The fourth flow control valve 392 and fifth flow control valve 393 can also be closed to set the respective flow rates to zero.

[0085] The second bypass passage 395 is a heat medium flow path through which the heat medium that has passed through the heat medium cooler 35 flows, bypassing the second heat exchanger 38. The sixth flow rate control valve 396 is provided in this second bypass passage 395. The seventh flow rate control valve 397 is an electric valve that is disposed between a branch portion 398 to the second bypass passage 395 and the second heat exchanger 38. The opening degrees of these sixth flow rate control valve 396 and seventh flow rate control valve 397 are controlled by the control means 10 (see FIG. 2). Note that the sixth flow rate control valve 396 and seventh flow rate control valve 397 can also be closed to set the respective flow rates to zero.

[0086] The heat medium pump 31 generates heat when driven, and the temperature of the heat medium discharged from the heat medium pump 31 increases due to this heat. If the output of the heat medium pump 31 is increased, the temperature of the heat medium that increases in the heat medium pump 31 increases in proportion to the output. The output here refers to the rotation speed of the heat medium pump 31. In addition, by increasing the output of the heat medium pump 31, the flow rate of the heat medium being pumped increases, but since the valve opening of the cooling flow rate control valve 33 and the first flow rate control valve 341 in the subsequent stage is narrowed to achieve a desired flow rate, the kinetic energy of the heat medium is converted into thermal energy, and the temperature of the heat medium further increases. Therefore, in the drying system 1 of the second modified example, when the temperature of the heat medium measured by the tank heat medium thermometer 312 is too low and it is expected that the effect of increasing the temperature of the refrigerant in the heat medium cooler 35 is insufficient, the output of the heat medium pump 31 is increased to increase the temperature of the heat medium in the heat medium pump 31 and send it to the heat medium cooler 35. At that time, the cooling flow rate adjustment valve 33 and the first flow rate adjustment valve 341 are also controlled by the control means 10 (see FIG. 2) in accordance with the pressure of the heat medium measured by the heat medium pressure gauge 311 so that the heat medium flows at a desired flow rate.

[0087] The drying system 1 of the second modified example described above also has the same effects as those of the previous embodiment. In addition, the control means 10 controls the opening degree of each valve provided in the heat medium temperature adjustment unit 3, thereby achieving the effect that the temperatures of the heat medium and the refrigerant can be adjusted in a wide adjustment range in the heat medium temperature adjustment unit 3.

[0088] Fig. 6(a) is a flow chart showing control associated with the drying process of the drying system 1 of the third modified example. The process shown in Fig. 6(a) is executed during the drying process under the control of the control means 10, and ends simultaneously with the end of the drying process. Note that the cooling flow rate adjustment valve 33 is closed at the time when the preparation process for starting the drying process is completed.

[0089] The drying system 1 of the third modified example differs from the previous embodiment in that a parallel process shown in FIG. 6(a) is executed instead of step S19 shown in FIG. 3. As shown in FIG. 6(a), in this parallel process, it is determined whether the pressure of the collected refrigerant is equal to or lower than a first reference value based on the measurement result of the refrigerant pressure gauge 62 (step S31). The first reference value is set to a pressure higher than the threshold pressure at which the system transitions to a low-pressure cut state. This first reference value is set by the manufacturer of the drying system 1 and stored in the storage unit 102, but is a value that can be rewritten by a predetermined procedure.

[0090] If the pressure of the refrigerant is equal to or lower than the first reference value (YES in step S31), the control means 10 half-opens the cooling flow rate control valve 33 to allow a certain amount of heat medium to flow to the heat medium cooler 35 and pass through the heat medium cooler 35 (step S32). In the heat medium cooler 35, the heat medium is cooled while the refrigerant is heated, so the refrigerant that has passed through the heat medium cooler 35 expands or evaporates, increasing its pressure and flowing to the common refrigerator 6. If the pressure of the refrigerant exceeds the first reference value (NO in step S31), the control means 10 closes the cooling flow rate control valve 33 to block the flow of the heat medium to the heat medium cooler 35 (step S35). As described above, the heat medium pump 31 is controlled so that a constant flow rate of the heat medium flows to the heat medium heater 36 and the jacket 23 regardless of whether the cooling flow rate control valve 33 is open or closed.

[0091] When step S32 is completed, the control means 10 judges whether the pressure of the collected refrigerant is equal to or lower than the second reference value based on the measurement result of the refrigerant pressure gauge 62 (step S33). The second reference value is set to a pressure higher than the threshold pressure when transitioning to the low pressure cut state and lower than the first reference value. This second reference value is set by the manufacturer of the drying system 1 and stored in the storage unit 102, but is a value that can be rewritten by a predetermined procedure. If the pressure of the refrigerant is equal to or lower than the second reference value (YES in step S33), the control means 10 opens all the cooling flow rate adjustment valves 33 to allow the maximum amount of heat medium to flow to the heat medium cooler 35 and pass through the heat medium cooler 35 (step S34). As a result, a large amount of heat medium is cooled while the amount of heat of the refrigerant per unit time is maximized, so that the refrigerant that has passed through the heat medium cooler 35 flows into the common refrigerator 6 with an increased pressure.

[0092] If the refrigerant pressure exceeds the second reference value (NO in step S33), if step S34 is completed, or if step S35 is completed, the control means 10 determines whether or not the parallel processing time has elapsed since the start of the processing in step S31 (step S36). If the parallel processing time has not elapsed, the control means 10 waits until the parallel processing time has elapsed (NO in step S36). This parallel processing time is, for example, 1 second. Note that the parallel processing time is set by the manufacturer of the drying system 1, but can be changed in a predetermined procedure. Once the parallel processing time has elapsed (YES in step S36), the control means 10 returns to step S31 and starts the next parallel processing.

[0093] The drying system 1 of the third modified example described above also has the same effects as those of the previous embodiment. In addition, the measurement result of the refrigerant pressure gauge 62, which is performing the measurement for determining whether or not to transition to the low-pressure cut state, is compared with a reference value to control the opening and closing of the cooling flow rate control valve 33, so that the low-pressure cut state can be reliably prevented. In the drying system 1 of the third modified example, the opening degree of the cooling flow rate control valve 33 is adjusted in two stages, but three or more reference refrigerant pressure values ​​may be set, and the opening degree of the cooling flow rate control valve 33 may be adjusted more finely according to the refrigerant pressure values. In addition, steps S31 and S32 may be omitted and the opening and closing of the cooling flow rate control valve 33 may be set in one stage. In addition, if steps S31 and S32 are omitted, when step S33 is NO, step S35 may be executed and then the process may proceed to step S36.

[0094] Fig. 6(b) is a flowchart showing control associated with the drying process of the drying system 1 of the fourth modified example. The process shown in Fig. 6(b) is also executed during the drying process under the control of the control means 10, and ends simultaneously with the end of the drying process.

[0095] The drying system 1 of the fourth modified example differs from the previous embodiment in that a parallel process shown in Fig. 6(b) is executed instead of step S19 shown in Fig. 3. As shown in Fig. 6(b), in this parallel process, it is determined whether the pressure regulating valve 42 is open (step S41). If the pressure regulating valve 42 is open even a little, step S41 becomes YES.

[0096] If the pressure regulating valve 42 is open (YES in step S41), the control means 10 opens the cooling flow rate regulating valve 33 to the same opening as the pressure regulating valve 42 (step S42). As a result, the heat medium flows into the heat medium cooler 35 according to the opening of the cooling flow rate regulating valve 33, and the refrigerant is heated by an amount of heating according to the flow rate of the heat medium, and expands or evaporates, increasing the pressure. If the pressure regulating valve 42 is closed (NO in step S41), the control means 10 closes the cooling flow rate regulating valve 33 to block the heat medium to the heat medium cooler 35 (step S43).

[0097] When step S42 or step S43 is completed, the control means 10 judges whether or not the parallel processing time has elapsed since the start of the process of step S41 (step S44). If the parallel processing time has not elapsed, the control means 10 waits until the parallel processing time has elapsed (NO in step S44). If the parallel processing time has elapsed (YES in step S44), the control means 10 returns to step S41 and starts the next parallel processing.

[0098] As described above, when the amount of steam generated in the container body 21 is significantly reduced toward the end of the drying process, the opening degree of the pressure regulating valve 42 increases, so the drying system 1 of this fourth modified example, in which the opening degree of the cooling flow rate regulating valve 33 is set to the same as the opening degree of the pressure regulating valve 42, also achieves the same effect as the previous embodiment.

[0099] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims. For example, in the above-described embodiment, the ice collection status in the cold trap 5 is monitored based on the change in mass of ice or the collected mass, but it may be monitored based on the change in thickness or thickness of ice attached to the cooling tube 51, or based on the change in shape of ice attached to the cooling tube 51. In addition, a configuration may be adopted in which a plurality of cold traps 5 are provided and switched in sequence to receive steam, and the collection status in the cold trap 5 immediately after the cold trap 5 has finished receiving steam and is switched may be monitored.

[0100] In addition, the drying speed of the frozen material F was adjusted by adjusting the temperature of the heat medium supplied to the jacket 23 and the rotation speed of the spiral ribbon 221, but only one of these may be adjusted and the other may be kept constant. In addition, the spiral ribbon 221 was always rotating, but it may be configured to rotate and stop repeatedly, and the frequency of moving the frozen material F, which is the ratio of the driving time and the driving stop time of the stirring means 22, may be adjusted instead of the rotation speed of the spiral ribbon 221, or both the rotation speed of the spiral ribbon 221 and the frequency of moving the frozen material F may be adjusted. Furthermore, instead of adjusting the temperature of the heat medium supplied to the jacket 23, or in addition to adjusting the temperature of the heat medium, the flow rate of the heat medium supplied to the jacket 23 may be adjusted. Furthermore, instead of the spiral ribbon 221, a stirring blade consisting of a blade-shaped paddle member having a flat surface in the vertical direction at the tip of a metal arm radially protruding from the stirring drive shaft 222 may be provided in the container body 21 to move the frozen material F.

[0101] In addition, instead of the stirring means 22, the entire container body 21 may be supported by a tubular shaft so that it can rotate or swing freely, and the container body 21 may be rotated or swinged by a motor, so that the frozen object F is moved within the container body 21. In such a configuration, the shaft supporting the container body 21, the container body 21, and the motor rotating or swinging the container body 21 correspond to an example of a frozen object operating unit. In that case, instead of adjusting the number of rotations of the spiral ribbon 221, it is preferable to adjust the frequency of rotation or swing of the container body 21. However, the number of rotations or swing of the container body 21 may be adjusted by controlling the container body 21 to always rotate or swing.

[0102] In addition, even if a constituent element is included only in the description of the embodiment and each modified example described above, that constituent element may be applied to the embodiment and each modified example. [Explanation of symbols]

[0103] 1 Drying System 5. Cold Trap 6 Common refrigerator 10. Control Means 21 Container body 23 Jacket F Frozen material

Claims

1. A drying system that dries a frozen object by sublimating a solidified liquid component contained in the frozen object obtained by freezing the object to be processed, comprising: A container body for storing the frozen food; a jacket covering the outer periphery of the container body and through which a heat transfer medium flows; a heat medium cooler that cools the heat medium; a cold trap that converts the vapor generated by sublimation of the liquid component in the container body into a solid and collects the solid; a common refrigerator for supplying a refrigerant to both the heat medium cooler and the cold trap.

2. a monitoring means for monitoring a state of collection of the solid in the cold trap; 2. The drying system according to claim 1, further comprising a control means for adjusting a flow rate of the heat medium passing through the heat medium cooler in accordance with the collection status.

3. A refrigerant pressure gauge for measuring the pressure of the refrigerant; 2. The drying system according to claim 1, further comprising: a control means for adjusting a flow rate of the heat medium passing through the heat medium cooler in response to the pressure measured by the refrigerant pressure gauge.

4. A pressure reducing device for reducing the pressure inside the container body; an exhaust path connecting the container body and the pressure reducing device and through which gas in the container body passes; a pressure regulating valve that adjusts its opening to keep the pressure reduced by the pressure reducing device within a predetermined range, thereby allowing an amount of outside air to flow into the exhaust path according to the opening; 2. The drying system according to claim 1, further comprising a control means for adjusting a flow rate of the heat medium passing through the heat medium cooler in accordance with the opening degree.

5. The common refrigerator cools the refrigerant using cooling water circulating between the common refrigerator and a first heat exchanger, 5. The drying system according to claim 1, further comprising a second heat exchanger that is disposed in a circulation path of the cooling water and performs heat exchange between the cooling water heated by the common refrigerator and the heat medium cooled by the heat medium cooler.

Images