JP2000171151A - Vacuum drier and operating method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote the evaporation of moisture from a matter to be dried with a saved energy without heating the same forcibly by a heater or the like by a method wherein an air-tight tank is equipped therein with a constant temperature retaining device for retaining the matter to be dried. SOLUTION: A vacuum drier is provided with a structure wherein a matter to be dried 4 is retained on a net made of copper and all of the net as well as supporting pillars for supporting the net are made of copper so as to have prominent thermal conduction in order to retain the matter to be dried 4 at a constant temperature under the vacuum condition of a constant temperature retaining device 1. Further, the surface of the supporting pillars is roughened so as to increase the surface area of contacting part when the pillars are contacted thermally with the air-tight tank. According to this method, the reduction of the temperature of the matter to be dried due to the depriving the same of evaporating heat upon evaporating moisture from the matter to be dried can be restrained by the heat conduction from the constant temperature retaining device to the matter to be dried and the effect of radiation. Accordingly, the evaporation of moisture from the matter to be dried can be promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum dryer for drying clothes, foods, dishes, and silicon wafers, and a method of driving the vacuum dryer.

[0002]

2. Description of the Related Art In life and industry, drying an object is an act that has been practiced for a long time. It is common to dry sun-dried clothes in the open air in order to dry clothes washed in ordinary households in Japan. The temperature of clothing exposed to sunlight rises and water evaporation becomes active, and the moisture around the clothing increased by the moisture evaporated from clothing diffuses into the outside air to promote moisture evaporation from clothing. Dry complementary. In northern Europe with a cold climate, clothes are generally dried by a heating device such as a boiler. Dryers equipped with a heating device are also commercially available in Japan. As for foods, there are many examples of drying by sun drying such as "dried persimmons" and "kiri dried radish." Freeze drying technology called freeze drying has also been developed. Generally, tableware is dried in a kitchen after wiping it with a cloth, and then naturally drying in a kitchen. However, a tableware dryer equipped with a heating device is gradually becoming popular. 2. Description of the Related Art In the semiconductor industry, a spin drier for rotating a cleaned silicon wafer at a high speed to blow off liquid droplets has become widespread. Examples of conventional vacuum dryers include JP-A-8-280994 and JP-A-7-280994.
208885, JP-A-8-299698, JP-A-6-2
No. 21754 has been filed.

[0003]

The conventional sun-drying had a problem that the quality of drying was greatly affected by natural phenomena. It is not unusual for clothing that has been dried on the veranda to get wet due to unexpected sudden rain. It is often troublesome that laundry does not dry out due to heavy rain. In areas with cold and short sunshine hours, such as in Northern Europe, sun drying can be very difficult for long periods of time. A drying method using a heating device such as a boiler has an advantage that it is not affected by natural phenomena, but has a problem of using a large amount of energy. When considering finite earth resources, energy waste cannot be neglected. When a heating device is used, there is a risk of fire due to overheating. Further, there is a concern that even if a fire does not occur, the material to be dried is overheated to a limit temperature or higher, thereby deteriorating the quality. In the case of a spin dryer, there is a problem that the material to be dried which can be dried by this drying method is limited. It is limited to those that can rotate at high speed and have good water separation. The silicon wafer can be spin-dried because the liquid does not penetrate into the solid and the surface is hydrophobic.
During the spin drying, an accident has occurred in which the silicon wafer loses its balance and rotates abnormally and is damaged. In some cases, a delicate structure formed by finely processing a silicon wafer is destroyed during a rotational movement.

[0004]

The vacuum dryer of the present invention comprises:
An airtight tank for storing the object to be dried 4 and allowing the inside to be airtight;
In addition to having an exhaust device for exhausting the inside of the airtight tank, the airtight tank is provided with a constant temperature holding device 1 for holding the object to be dried in the airtight tank, or the constant temperature holding device 1 is further provided. An airtight tank that is made up of an antifreeze liquid return pipe 2 and a metal net 3, or that refluxes gas into the antifreeze liquid return pipe, or that stores an object to be dried 4 and makes the inside airtight; In addition to having an exhaust device for exhausting the inside of the airtight tank, and having the constant temperature holding device 1 for holding the object to be dried in the airtight tank, a gas connected to the airtight tank by a pipe with a valve is provided. It is provided with a drying device 6, or it is provided with an airtight tank that stores the object 4 to be dried and makes the inside airtight, and an exhaust device that exhausts the inside of the airtight tank. For holding dry matter In addition to the provision of the temperature maintaining device 1 and the provision of the gas drying device 6 connected to the hermetic tank by a pipe with a valve, the antifreeze that has passed through the antifreeze recirculation pipe 2 is a cooling fluid provided by the gas drying device. An airtight tank that is capable of flowing into the supply pipe 12 or housing the object to be dried 4 and allowing the inside thereof to be airtight; and an exhaust device that exhausts the inside of the airtight tank. In addition to having the constant temperature holding device 1 for holding an object, a heat pipe that conducts heat generated by a vacuum pump that exhausts the airtight tank to the constant temperature holding device 1 is provided, The method for driving a vacuum dryer according to the present invention is a method for driving a vacuum dryer, comprising: an airtight tank that stores the object to be dried 4 and hermetically seals the inside; and an exhaust device that exhausts the inside of the airtight tank. Inside the airtight tank 600Torr
The above high pressure state and the low pressure state of less than 600 Torr
It is characterized in that this cycle is repeated a plurality of times.

[0005]

According to the present invention, in addition to having an airtight tank for accommodating the object to be dried and allowing the inside thereof to be airtight, and an exhaust device for exhausting the inside of the airtight tank, the object to be dried is held in the airtight tank. Is provided with a constant-temperature holding device 1 for removing the heat of vaporization when water evaporates from the material to be dried. And radiation effects. In addition, when the constant temperature holding device 1 is composed of the antifreeze reflux pipe 2 and the metal net 3, the temperature of the constant temperature holding device is forcibly fixed even when the material to be dried is extremely cooled by the heat of vaporization. The cooling effect can be enhanced. When the gas is recirculated into the antifreeze recirculation tube, the temperature of the constant temperature holding device can be forcibly set to a constant temperature without freezing and clogging of the recirculation tube. When the ambient air is used as a gas in the surrounding environment at room temperature, that is, the air which is higher in temperature than the object to be dried which tends to be cooled by the heat of vaporization, the abundant high temperature air is consumed one after another, and the forced constant temperature can be realized. It has an airtight tank for storing the object to be dried 4 and allowing the inside to be airtight, and an exhaust device for exhausting the inside of the airtight tank, and a constant temperature holding device 1 for holding the object to be dried in the airtight tank. In addition to the above, when a gas drying device 6 connected to the airtight tank by a pipe with a valve is provided, it is possible to partially remove the moisture of the wet exhaust gas discharged from the airtight tank. As a result, the degree of wetting of the wetting gas is reduced, and it is possible to prevent the outside of the exhaust pump and the vicinity of the exhaust port from being adversely affected by moisture. Having an airtight tank that stores the object to be dried 4 and makes the inside airtight, and an exhaust device that exhausts the inside of the airtight tank;
In addition to having a constant temperature holding device 1 for holding the object to be dried in the airtight tank, and having a gas drying device 6 connected to the airtight tank by a pipe with a valve, the antifreeze liquid reflux pipe When the antifreeze passed through 2 flows into the cooling liquid supply pipe 12 provided in the gas drying apparatus, the gas drying apparatus uses the antifreeze in the antifreeze reflux pipe cooled by the heat of vaporization taken from the material to be dried. 6 can be used as a cooling liquid introduced into the interior of the apparatus. It has an airtight tank for storing the object to be dried 4 and allowing the inside to be airtight, and an exhaust device for exhausting the inside of the airtight tank, and a constant temperature holding device 1 for holding the object to be dried in the airtight tank. In addition to the above, when a heat pipe that conducts heat generated by a vacuum pump that exhausts the airtight tank to the constant temperature holding device 1 is provided, the amount of heat generated at the time of exhaustion is reduced It can be effectively used to control the temperature. In a method for driving a vacuum drier having an airtight tank for storing an object to be dried 4 and allowing the inside to be airtight, and an exhaust device for exhausting the inside of the airtight tank, the inside of the airtight tank is maintained at a high pressure of 600 Torr or more and 600T.
When this cycle is repeated a plurality of times with a low pressure state of less than orr being one cycle, the effect of promoting the evaporation of water from the material to be dried at a low pressure state of less than 600 Torr and 600 Torr
By efficiently combining the effect of increasing the temperature of the object to be dried under a high pressure of r or more, evaporation of water from the object to be dried can be promoted.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment corresponding to claim 1 of the present invention will be described with reference to FIG. FIG. 1 shows a constant temperature holding device 1 housed in an airtight tank of a vacuum dryer. This is a structure in which the object to be dried 4 is held on a copper net. This constant temperature holding device is designed to have good heat conduction in order to keep the object to be dried at a constant temperature in a vacuum state. Specifically, the net and the pillars that support the net are all made of copper. Copper is a material having good heat conductivity. Furthermore, the strut is roughened so that the surface area of the contact part is large so as to make thermal contact with the airtight tank (the figure shows a bribe).

FIG. 2 shows an embodiment corresponding to claim 2 of the present invention. A constant temperature holding device 1 housed inside an airtight tank of a vacuum dryer is illustrated. As in FIG. 1, the metal net on which the object to be dried 4 is placed is a copper net, and the pillar is hollow. An antifreeze, which does not freeze even at a temperature of -10 ° C., is circulating inside the hollow support. This hollow support will be referred to as an antifreeze liquid reflux pipe 2. The antifreeze passes through the antifreeze reflux tube,
It is circulated to the outside of the airtight tank. The antifreeze circulated to the outside is warmed by the outside air temperature (although it may be cooled in some cases), and returns to the inside of the antifreeze reflux pipe shown in FIG. 2 again. As a result, the antifreeze reflux pipe and the metal net are maintained at substantially the same temperature as the outside air temperature. In FIG. 2, the object to be dried 4 is sandwiched between two copper nets. By sandwiching the object to be dried from above and below, the thermal contact is strengthened, and the temperatures of the copper net and the object to be dried can be brought close to each other.

An embodiment according to the third aspect of the present invention will be described. In FIG. 2, the atmosphere is recirculated inside the antifreeze recirculation pipe. In this embodiment, both ends of the antifreeze reflux tube are open. Atmosphere is taken in from one end, passes through a constant temperature holding device, and is discharged into the atmosphere through a diaphragm pump attached to the other end. This structure has a point that it is difficult to call it a reflux tube in the point that both ends are open, but considering it as a single reflux system including the surrounding environment,
It can be called a reflux system. That is, it is a reflux system that takes in the atmosphere, passes through the inside of the pipe, and returns the gas to the atmosphere again. Therefore,
The name of the reflux tube will be used as it is. The air intake port is located close to the heat release port of home appliances (TVs, etc.) that generate a lot of heat, and takes in gas at a slightly higher temperature. The gas outlet should be directed to the living room in summer. This is expected to have the effect of cooling the room. In some cases, the gas discharge port is brought close to an unnecessary heat-generating part inside a house, such as a heat sink of a refrigerator. In some cases, the intake port is disposed near an exhaust pump provided in a vacuum dryer.

An embodiment corresponding to claim 4 of the present invention is shown in FIGS. FIG. 3 shows a gas dryer 6 provided in a vacuum dryer.
FIG. The gas drying apparatus is provided with a wet gas inlet 7, a pressure recovery inlet 8, a gas outlet 9, and a liquid outlet 10 in an airtight tank. Each port is provided with a valve (V1 to V4). Inside the gas drying device 6, a cold trap 11 is held insulated from the wall surface of the drying device. The cold trap may be a metal net such as copper, or may be an aluminum foil. A coolant supply pipe 12 and a coolant recovery pipe 13 are arranged so as to be in thermal contact with the cold trap. Copper pipes that conduct heat well between the supply and recovery pipes made of heat insulating stainless steel. The coolant circulates through the supply pipe, copper pipe, and recovery pipe without leaking.

FIG. 3 shows an initial state in which a gas from an airtight tank containing an object to be dried is sent to a gas drying apparatus. V1 is open, V2 is closed, V3 is open, V4
Is in the closed state. The moisture evaporated from the material to be dried in the airtight tank is taken into the gas drying device via the V1 valve. This gas is exhausted to the outside via the V3 valve, during which some of the moisture is captured by a cold trap. After maintaining V1 open, V3 open and other valves closed for a certain period of time, close all valves including V1 and V3 valves, and immediately thereafter open V2 valve to send dry air to the gas drying device. And a water drop adheres to the cold trap and it drips.

FIG. 4 shows a state in which water has dropped. The accumulated water 14 is discharged to the outside by opening V4. After the discharge, the supply of the cooling liquid to the cold trap is stopped, and the temperature of the cold trap is returned (heated). V2 and V4 are closed and V3 is opened to evacuate the gas drying apparatus. After the evacuation, the supply of the cooling liquid to the cold trap is restarted. After the cold trap is sufficiently cooled, V1 is opened to take in gas from the airtight tank.

By repeating the series of operations described above, V
Part of the moisture of the gas taken in from 1 can be separated and drained as water via V4.

FIG. 5 shows an embodiment corresponding to claim 5 of the present invention. FIG. 5 is a configuration diagram of the vacuum dryer. The dry air that has been dried and reheated by the outside air intake gas drying device 16 and the outside air intake gas reheating device 17 is introduced into the airtight tank 15 in which the constant temperature holding device 1 is housed through the outside air intake valve 18. Configuration. The gas that has passed through the outside air intake gas reheating device is also introduced into the first gas drying device 20 via the dry air first intake valve 19. Although not shown, dry air is introduced into the second gas drying device in the same manner as in the first gas drying device. The dry air is also discharged to the exhaust pump 25 via the dry air discharge valve 21.

A plurality of systems for exhausting gas from the hermetic tank 15 are provided. The first system includes a first gas drying device 20 and a first gas drying device.
The second system is a system that is evacuated to the exhaust pump 25 via the second gas drying device 23 and the second gas reheating device 24. is there. The first and second systems are alternately used for exhaust. FIG.
In the method of using the gas drying apparatus described with reference to FIG. 4 and FIG. 4, gas is taken in from the airtight tank for a certain period in a series of use cycles, and the gas drying is stopped for the rest of the period. Explaining what to spend on drying. The first and second exhaust systems complement the period of the gas intake and the suspension of the intake, and alternately perform the exhaust.

In FIG. 5, the antifreeze that has passed through the antifreeze reflux pipe 2 flows into a coolant supply pipe 12 provided in the gas drying device. This will be described. The laundry to be dried is initially in a wet state with water. In this state, when the inside of the airtight tank is evacuated and decompressed, the water in the liquid state changes to vapor in the gas state, that is, evaporates according to the vapor pressure curve (FIG. 6) if the temperature of the object to be dried is constant. How to read FIG. 6 will be briefly described. It is 760 Torr for water to evaporate at 100 ° C in general lifestyle
Then, it is actually observing that it has a vapor pressure of 100 ° C. When rice is cooked on a high mountain, the rice becomes raw because it is observed that if the air pressure is low, water (hot water) evaporates at a temperature lower than 100 ° C. and the rice is not baked due to insufficient temperature. It can be observed that cooking in a pressure cooker in a short time can be boiled quickly because the temperature of the hot water exceeds 100 ° C. in an environment where the pressure is higher than the atmospheric pressure. When the inside of the airtight tank is evacuated, moisture evaporates rapidly from the object to be dried kept at a constant temperature, and the object to be dried dries.

If the material to be dried is kept at a constant temperature, the evaporation of water will continue as it is. However, when the water becomes steam, the heat of vaporization is removed from the object to be dried, and the object to be dried is cooled. As the object to be dried is kept in an adiabatic state, the temperature of the object to be dried becomes 0 ° C. or lower, and the water is frozen (solidified) to become ice. When the temperature of the material to be dried is reduced, the vapor pressure is also reduced, and the phenomenon that evaporation is suppressed occurs simultaneously. On the other hand, if the heat of the antifreeze in the antifreeze liquid reflux pipe is continuously transmitted to the object to be dried by a copper net or the like in consideration of keeping the object to be dried at a constant temperature, the object to be dried is maintained at a substantially constant temperature and evaporation is continued. Will be. When the structure for applying the heat of the antifreeze to the object to be dried is adopted, the temperature of the antifreeze at the time of exiting from the airtight tank is lower than before the airtight tank is introduced. The cooled antifreeze is introduced for cooling the cold trap of the first gas drying device or the second gas drying device. This provides a self-supporting device that can supply the cooling liquid necessary for the cold trap from the airtight tank. Note that the supply of the coolant to the second exhaust system is omitted in the figure.

Although a part of the moisture is removed from the wet gas by the first and second gas drying devices, the exhaust gas reaching the exhaust pump 25 is still a wet gas containing a large amount of moisture. The characteristic of the exhaust pump deteriorates due to the moisture, and the humidity near the exhaust port increases to deteriorate the environment. In order to suppress this, a configuration is adopted in which dry air can be supplied to the exhaust pump via a valve indicated by reference numeral 21. Dry air is supplied via 21 valves according to the condition of the exhaust pump and the exhaust port.

An embodiment corresponding to claim 6 of the present invention will be described with reference to FIG. This embodiment is an example of a vacuum dryer having a function of transmitting the amount of heat generated by the exhaust pump 25 to the constant temperature holding device 1. The object to be dried 4 is held in the constant temperature holding device 1 built in the airtight tank 15. The heat sink 27 is disposed so as to penetrate the pressure reducing side and the atmospheric side of the airtight tank. At the decompression side end, it is in thermal contact with the constant temperature holding device, and at the atmosphere side, it is in thermal contact with the flexible metal 28. The flexible metal is made of a copper mesh, and is wound around the exhaust pump 25 to remove heat from the pump. With this configuration, the heat generated by the pump motor and the exhaust piston can be efficiently transmitted to the constant temperature holding device. A vent valve 26 for introducing air into the airtight tank is arranged.

A method of driving a vacuum dryer according to claim 7 of the present invention will be described with reference to FIGS. FIG. 8 shows a vacuum dryer substantially the same as FIG. The difference is that there is no heat sink and no flexible metal. FIG. 9 shows an exhaust state of the apparatus shown in FIG. The upper graph shows the time change of the degree of vacuum. The exhaust pump and the vent valve are periodically operated to obtain the degree of vacuum change shown in this graph. The middle graph shows the change in the temperature of the material to be dried, and the lower graph shows the change in the water content. In the process of drawing a vacuum, the evaporation of water from the material to be dried proceeds rapidly, and the temperature decreases due to heat of vaporization. As the temperature is restored by introducing the room temperature atmosphere, the evaporation of water progresses little by little as shown in FIG. Since the moisture content of the material to be dried is reduced by repeating the depressurization and the re-pressurization, the lowering of the temperature due to the heat of vaporization at the time of depressurization is reduced, and the efficiency of water evaporation is also increased. Considering the correlation with the vapor pressure curve, the boundary between the pressure reduction and the pressure recovery is preferably set to 600 Torr.

[0020]

By using the vacuum dryer of the present invention, it is possible to promote the evaporation of water from the object to be dried with energy saving without forcibly heating the object to be dried by a heater or the like. The cooling water required for drying can be supplied by itself, resulting in an energy-saving dryer with low energy consumption. The effect of not heating enabled the drying of heat-sensitive materials. Since drying at room temperature or lower is also possible, drying of heat-sensitive chemicals and organic matter samples becomes possible. Even if there is a danger of explosion due to temperature rise, even if the temperature may drop in principle, the drying is performed in a manner that does not raise the temperature. Vacuum drying has the advantage that if the material to be dried is kept at a constant temperature, drying will occur uniformly from all sides. When the apparatus of the present invention is used, the temperature of the object to be dried can be kept constant, so that uneven drying is less likely to occur.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment corresponding to claim 1 of the present invention.

FIG. 2 is a perspective view of an embodiment corresponding to claim 2 of the present invention.

FIG. 3 is a first sectional view for explaining claim 4 of the present invention.

FIG. 4 is a second sectional view for explaining claim 4 of the present invention.

FIG. 5 is a configuration diagram of an embodiment corresponding to claim 5 of the present invention.

FIG. 6 is a graph showing a vapor pressure curve of water.

FIG. 7 is a block diagram for explaining claim 6 of the present invention.

FIG. 8 is a block diagram for explaining claim 7 of the present invention.

FIG. 9 shows a driving method according to claim 7 of the present invention and measurement results obtained by this driving.

[Explanation of symbols]

1 is a constant temperature holding device, 2 is an antifreeze reflux tube, 3 is a metal net, 4 is a material to be dried, 6 is a gas drying device, 7 is a wet gas intake, 8 is a recompression intake, 9 is a gas exhaust, 10
Is a liquid discharge port, 11 is a cold trap, 12 is a coolant supply pipe, 13 is a coolant recovery pipe, 14 is water, 15 is an airtight tank, 16 is a gas drying device for taking in outside air, and 17 is a gas reheating device for taking in outside air. Device, 18 is an outside air intake valve, 1
9 is a dry air first intake valve, 20 is a first gas drying device, 21 is a dry air discharge valve, 22 is a first gas reheating device, 23 is a second gas drying device, 24 is a second gas reheating device, 25 is an exhaust pump, 26 is a vent valve, 27 is a heat sink, and 28 is a flexible metal.

Claims (7)

[Claims] 1. A vacuum drier having an airtight tank for storing an object to be dried and allowing the inside thereof to be airtight, and an exhaust device for exhausting the inside of the airtight tank, wherein the object to be dried is stored in the airtight tank. A vacuum dryer comprising a constant temperature holding device 1 for holding. 2. A vacuum dryer according to claim 1, wherein said constant-temperature holding device comprises an antifreeze reflux tube and a metal net. 3. The vacuum dryer according to claim 2, wherein a gas is circulated inside the antifreeze reflux tube. 4. A gas dryer according to claim 1, wherein said gas dryer is connected to said airtight tank by a pipe with a valve.
A vacuum dryer comprising: 5. The vacuum drier according to claim 3, wherein the antifreeze passed through the antifreeze reflux pipe flows into a cooling liquid supply pipe provided in the gas drying device. 6. A vacuum dryer according to claim 1, further comprising a heat pipe for conducting heat generated by a vacuum pump for exhausting said airtight tank to said constant temperature holding device. . 7. A method for driving a vacuum dryer, comprising: a hermetic tank containing a material to be dried 4 for hermetically sealing the inside; and an exhaust device for exhausting the inside of the hermetic tank.
A driving method for a vacuum dryer, wherein a high-pressure state of Torr or more and a low-pressure state of less than 600 Torr are defined as one cycle and the cycle is repeated a plurality of times.