JPH1194461A - Dryer and drying method for water containing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method for drying a water containing material by reusing the condensation latent heat of steam in which the essential compression ratio of a compressor is stabilized while preventing abnormal temperature rise by minimizing the mixing ratio of air in the steam sucked by the compressor. SOLUTION: A water containing material is placed in a pressure reducing container A comprising an enclosed container 2 and heated to generate steam which is then introduced to a condenser 6 and liquefied and the condensation latent heat is used for heating and drying the water containing material in the pressure reducing container A. A condensate re-evaporator equipped with a condensate tank 25 being introduced with condensate from the condenser 6 heats up water in the condensate tank 25 to generate saturated steam which is introduced to a steam compressor 4. Water is then injected from a fresh water line 11 into an injection water spray 23 and saturated in the compressor 4 to produce heating steam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for drying hydrates, and more particularly to a method and an apparatus for recycling latent heat of condensation of recovered steam for drying hydrates.

[0002]

2. Description of the Related Art As a method for drying a hydrated product, a flash drying method in which high-temperature hot air is brought into direct contact with a hydrated product to dry the hydrated product,
As another method, a general method is to put a water-containing substance in a container, heat the water-containing substance by a boiler heating method, evaporate water, and perform a drying treatment. However, this method
The huge heat of water vapor is dumped into the atmosphere, which is inefficient.

Therefore, in recent years, a drying method has been proposed in which latent heat of condensation of water vapor is recovered and reused for drying water-containing substances, thereby improving energy efficiency.

[0004] However, the proposed method is a theoretically possible method, but technically, it is generated from a high technology of suction and compression of high-temperature steam having a complicated volume change and a dried product. At present, no satisfactory equipment has been completed because it is necessary to deal with chemical and physical changes due to vapor gas other than water vapor, fine powder (size 10 to 100 microns) and mixed air, etc. Not implemented.

[0005] The theory of the above-mentioned proposed drying method and the mode of its use in the present invention will be described by taking as an example the drying of okara, which is a slag of water and soybeans.

[0006] In FIG. 6, okara when supplied into the closed vessel 2 at the boiling point T ₁ (80% moisture) at a pressure P ₁ (° C.), the pressure generated in the sealed container 2 P ₁ (kg / cm
The saturated steam of ² abs = ata) is adiabatically compressed to the pressure P ₂ (ata) by the compressor 4 via the line 3, rises to the temperature T ₂ (° C.), and passes through the line 5 in the closed vessel 2. It is led to the jacket 6 as a heat source for okara. At this time, the drive motor 8 is required as a power source for adiabatically compressing the saturated steam of P ₁ and T ₁ to P ₂ and T ₂ . In FIG. 6, reference numeral 12 denotes an outlet for dried okara, and reference numeral 26 denotes a condensed water line.

Referring to FIG. 7, a description will be given of the compression work amount and the enthalpy change using a water vapor entropy diagram. The state of the saturated steam generated at the pressure P _{1 in} the closed vessel is a point A where the saturation line and the isobar P ₁ intersect. The temperature at this point is T ₁ from the isotherm, and the enthalpy i ₁ (Kcal
/ Kg) and entropy S ₁ (Kcal / kg).
If the compressor performs a reversible adiabatic compression of the saturated steam in this state, the compression work becomes an isentropic change and the pressure P ₁
Is compressed to a pressure P ₂ to give point B.

At this time, the enthalpy i ₂ (Kcal / k
g), the temperature becomes T ₂ , but there is heat loss and mechanical loss in the actual compressor, and irreversible adiabatic compression is performed, so that the entropy changes in the increasing direction to point C. At this point the pressure P
₂ , temperature T ₃ and enthalpy i ₃ .

The adiabatic compression efficiency of the compressor is η =
(I ₂ −i ₁ ) / (i ₃ −i ₁ ) i ₂ −i ₁ = ideal adiabatic compression work, i ₃ −i ₁ = adiabatic compression work actually required, η is generally 50% to It is 80%. In addition, the heating temperature difference ΔT in the closed vessel
Is given by ΔT = T ₄ −T ₁ (° C.). Note that T ₄
Is a saturation temperature at the pressure P _2.

From the above, Δi = i ₃ −i
By giving the enthalpy difference of ₁ , heated steam of enthalpy i ₃ having a temperature difference of ΔT in the heating jacket (steam condenser) of the closed vessel is obtained. Therefore, it is possible to newly heated without supplying a heating steam from the outside, the okara in the closed container to a maximum temperature T _4.

[0011]

In the above-mentioned method and apparatus for drying a hydrate, air other than the okara component is present in the reduced-pressure drying chamber, and air is also brought in when the okara is supplied and supplied.

The air in the drying chamber is mixed with evaporated steam of okara water and is sucked into the compressor. The change in the mixing ratio of air and water vapor causes a change in volume due to thermal expansion in the compressor due to the difference in unit mass, impeding the stability of the original compression ratio of the compressor and causing the compressor to overheat. The high temperature phenomenon causes the minute clearance between the fixed blade and the high-speed rotating blade in the compressor to be lost, resulting in a loss of balance, causing vibration and causing damage to the compressor.

[0013] In addition, the incorporation of air into the high-temperature steam discharged from the compressor deteriorates heat exchange in the condenser, reduces the work of the compressor, and increases the energy cost of the dryer.

The present invention has been made mainly to solve the above problems in a method and an apparatus for drying a hydrated material.
Minimize the ratio of the amount of mixed air in the suction steam of the compressor, and make the inside of the compressor into saturated steam, maintain the equilibrium between pressure and temperature, stabilize the compressor's original compression ratio,
To prevent abnormal temperature rise. further. An object of the present invention is to provide a method and an apparatus for drying a hydrate containing low energy costs by improving the heat transfer efficiency, increasing the work efficiency, shortening the drying time.

[0015]

According to the present invention, a water-containing substance is placed in a reduced-pressure drying chamber composed of a closed vessel and heated, the generated steam is compressed by a compressor, and the compressed steam is introduced into a condenser. When heating and drying the hydrated material in the vacuum drying chamber with the latent heat of condensation generated at that time, a condensed water re-evaporator having a condensed water tank into which condensed water is introduced from the condenser is provided. The water in the condensed water tank is heated to generate saturated steam, and the saturated steam is introduced into a steam compressor to obtain steam for heating.

Further, the hydrated substance is placed in a reduced-pressure drying chamber comprising a closed container and heated, and the generated steam is compressed by a compressor.
In the method for drying a hydrated material, in which the compressed water vapor is introduced into a condenser to liquefy the water, and the hydrated material in the reduced-pressure drying chamber is heated and dried with latent heat of condensation generated at the time, water is supplied to the suction side of the compressor. Water is sprayed to obtain steam for heating from the outlet of the compressor.

Further, a steam ejector which operates with steam from the outlet of the steam compressor is provided, and the steam ejector sucks air and steam mixed in the decompression drying chamber, thereby promoting the decompression state in the drying chamber, and promoting the moisture content of the water-containing substance. Evaporation is promoted to increase drying efficiency, and drying time is shortened to reduce energy costs.

A rotary valve having a function of maintaining airtightness is provided so that a water-containing substance can be charged into the reduced-pressure drying chamber at any time by using the rotary valve, and a stirrer having a discharge function is provided when discharging the dried substance. Then, the heat transfer efficiency is increased by the stirring, and the work efficiency is improved by the discharge function.

Further, two reduced-pressure drying chambers each composed of a closed container for containing a hydrated substance are installed, one steam compressor and one condensed water re-evaporator are provided, and one of the reduced-pressure drying chambers is provided with a steam compressor and condensed water. The re-evaporator is connected to heat and dry the hydrated material in the reduced-pressure drying chamber, and at this time, the hydrated material is supplied to the other reduced-pressure drying chamber, thereby facilitating continuous drying operation with high working efficiency.

The condensed water re-evaporation steam containing almost no air is sent to the suction side of the compressor, and the ratio of the amount of mixed air in the suction steam of the compressor is minimized by injecting the low-temperature water. A temperature stabilization phenomenon is caused by the saturated steam conversion of the injection water, thereby stabilizing the original compression ratio of the compressor and preventing abnormal temperature rise.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a drying operation of okara according to a first embodiment of the present invention.

The apparatus is roughly divided into an okara separator and an okara conveying conveyor, a vacuum drying chamber, a steam compressor and a condensed water re-evaporation apparatus.

The okara separator 13 is driven by a drive motor 14, into which boiled broth (95-98 ° C.) is introduced through an inlet 13a, discharged from the outlet 13b and added with a coagulant to obtain tofu. Okara K (90 to 95 ° C.) is conveyed by the belt conveyor 15 and is supplied from the rotary valve 1 to the reduced-pressure drying chamber A including the closed container 2.

The closed container 2 constituting the reduced-pressure drying chamber A includes:
A stirrer 9 for improving the function of discharging dried okara and heat transfer efficiency, an opening / closing hatch 16 for charging a large amount of hydrate, and a sampling cylinder 17 for measuring moisture during drying are provided. Also,
An opening / closing hatch 18 provided with a screen is provided at the drying okara discharge port 12, and the drying okara is discharged as the agitator 9 rotates. Further, a filter 19 is provided above the reduced-pressure drying chamber A to remove fine powder mixed in the vapor gas.

A pressure gauge 20 and a thermometer 21 are provided at an outflow portion of steam in the reduced-pressure drying chamber A (an upper portion of the reduced-pressure drying chamber A). The generated steam has a pressure of 530 to 540 mmH.
g and a temperature of 85 to 90 ° C. The pressure in the reduced-pressure drying chamber A is about 0.7 atm.

The steam in the reduced-pressure drying chamber A is supplied to the steam compressor 4
A drying chamber water vapor suction damper 22 is provided in the line 3 leading to. Further, a water injection sprayer 23 is provided at a connection part of the line 11 leading to the steam compressor 4 with the line 3, and is supplied with 0 to 400 ml / min of fresh water.
A flow meter 24 is provided on the line 11.

In the condensed water tank 25 of the condensed water re-evaporator,
Condensed water (95 ° C.) is introduced from a condenser (steam jacket) 6 via a line 26. The line 26 includes an initial operation blow valve 27, a strainer 28, and a steam trap 2.
9 are provided.

The condensed water tank 25 has a sheathed heater (4
KW) 30 is provided and used only at the start of operation. It is unnecessary if there is 90 ° C warm water. The temperature of the hot water is detected by a temperature detector 31. Water is supplied to the condensed water tank 25 from a water supply port 32.

The condensed water tank 25 has an upper limit level meter 3
3. A lower limit level meter 34 is provided. Further, a pressure gauge 35 and a thermometer 36 are provided, and the reevaporated steam has a pressure of 550 to 560 mmHg and a temperature of 90 to 92 ° C.

The re-evaporated steam from the condensed water tank 25 is
It is led to the steam compressor 4 by the re-evaporation steam suction line 37. The re-evaporated water vapor suction line 37 is provided with a flow rate adjustment damper 38 for adjusting the amount of re-evaporated water vapor to be sucked. A drain pump 40 is provided below the condensed water tank 25 via an electromagnetic valve 39, and discharges condensed water of the dried and evaporated moisture of the hydrate.

The compressed steam at the outlet side of the compressor 4 (1.1 to
Steam ejector 41 through which 1.2 kg / cm ² G) flows
Is provided, and the air and steam (530 to 540 mmH) in the drying chamber A through the line 42 by the ejector action are provided.
g, 85-90 ° C). The suction steam and the drive steam discharged from the ejector 41 are condensed in the cooling water tank 43 to further enhance the suction action. The compressed steam line 5 is provided with a pressure gauge 47, and each line is provided with a valve as required.

In operation, the water in the condensed water tank 25
0 liter is heated to 90 ° C. by a sheath heater 30. The degree of opening of the damper 22 of the suction line 3 of the vacuum drying chamber A is set to 50%.
Then, the compressor 4 is operated.

The damper 38 of the re-evaporation steam line 37 is opened, and saturated steam is sucked into the compressor 4 to obtain heating steam having a pressure of 1.2 kg / cm ² G and a temperature of 115 to 120 ° C. from the outlet of the compressor 4. This steam is led to the steam jacket 6 as a condenser to raise the temperature of the drying chamber A.

The low-temperature condensed water that has come out of the outlet of the jacket 6 in the early stage of the operation is discharged to the outside of the system by opening the blow valve 27.
The condensed water raised to a high temperature (for example, 90 ° C.) is collected in the tank 25 and the re-evaporated steam is circulated to warm up the apparatus.

After the heating medium circulation operation is performed for about 15 minutes to heat the closed container 2 in the drying chamber, the closed container 2 is heated.
Okara is charged, and the opening of the damper 22 of the drying chamber suction line 3 and the opening of the damper 38 of the condensed water re-evaporation line 37 are adjusted to dry the okara.

At this time, the okara is charged at 85 to 95 ° C.
Is preferable, but may be a low temperature, for example, 20 ° C.

The degree of drying of okara is determined by the water content of 45 to 50.
The operating data and the amount of water injected into the compressor at% are shown in the table in FIG.

According to the table of FIG. 3, the amount of water injected from the outside is 150 to maintain the stable operation of the compressor based on the operation state of the compressor.
２００200 ml / min is optimal.

The data 25 minutes after the start of operation is shown in the table of FIG.

During the drying of okara, the amount of water vapor generated in the reduced-pressure drying chamber A decreases as the water content decreases. That is, the drying speed becomes slow.

However, in order to maintain the operation of the compressor 4, re-evaporated steam and water injection are required at the compressor inlet side. Such supply to the compressor inlet also hinders the original suction of the reduced-pressure drying chamber A, thereby lowering the drying efficiency and, on the other hand, increasing the amount of water vapor at the compressor outlet.

By utilizing the excess steam to help the steam ejector 41 to suck in the air and steam in the reduced-pressure drying chamber A, the reduced-pressure state in the drying chamber A is advanced, and the evaporation of water from the okara is assisted. A drop in boiling point occurs, compensating for a decrease in drying efficiency resulting from a decrease in the amount of steam generated from the middle stage of the drying process. Alternatively, the amount of air entering the compressor 4 is reduced at the same time, and the operation of the compressor 4 is facilitated.

The operation method 1 in the table of FIG. 4 is data when the steam ejector 41 is not used.
Is data when the steam ejector 41 is used from the time when the moisture content during the drying of okara reaches 50%. Based on this data, the time required for the dry finish can be reduced from 52 minutes to 4 minutes by using the steam ejector 41.
It could be reduced in 5 minutes.

In the reduced-pressure drying chamber A, air is present in addition to the okara component, and air is brought in even when the okara is supplied and supplied.

The air in the reduced-pressure drying chamber A is mixed with the evaporated steam of okara water and is sucked into the compressor 4. The change in the mixing ratio of air and water vapor causes a change in volume due to thermal expansion in the compressor 4 due to the difference in the unit mass, hindering the stability of the compression ratio of the compressor body, causing an abnormal rise in the temperature of the compressor, and causing the operation to fail. Make it difficult.

In addition, the incorporation of air into the high-temperature steam discharged from the compressor 4 deteriorates the heat exchange in the condenser 6, reduces the work of the compressor 4 and increases the energy cost of the drying device. Let it.

Therefore, in order to minimize the ratio of the amount of mixed air in the suction steam of the compressor 4, condensed water reevaporation steam containing almost no air is sent to the suction side of the compressor 4 as described above. By injecting low-temperature water, it becomes saturated steam of 100 ° C. or more in the compressor 4, the balance between pressure and temperature is maintained, the compression ratio is stabilized, and abnormal temperature rise is prevented.

As the drying of the okara in the reduced-pressure drying chamber A progresses and the water content decreases, the amount of generated steam also gradually decreases. At this time, if the compressor 4 maintains a predetermined capacity and can obtain a sufficient heat supply from the steam jacket 6 as a condenser, even if the amount of steam generated from the okara is reduced, the okara is in a dry state. Will be maintained. In order to compensate for the decrease in the amount of steam generated from okara, it is necessary to feed in condensed water re-evaporated steam and inject low-temperature water.

In the present drying method, since the drying is performed in a relatively low temperature range under reduced pressure, the dried product is dried while maintaining the temperature at 90 ° C. or less, so that there is no cooking flavor such as burning smell. It does not impair the flavor and has little change in contained components, and is suitable for producing high-quality dried products.

By utilizing this feature, it is possible to dry the juice residue of various vegetables in the vegetable juice production process. For example, ginseng juice residue is dried and reused as a raw material for extracting residual carotene, fiber, and the like. Vegetable juice squeezed residue and processed residue of fresh food are difficult to reuse because they tend to deteriorate in freshness and spoil. However, if there is a drying device that can be directly connected to the production line by an inexpensive drying method without causing deterioration in quality, the drying process can be performed without causing deterioration in freshness or decay.

The drying of ginseng juice residue will be described as an example. Ginseng raw material → sorting → washing → crushing → pressing →
In the manufacturing process of sieving → juice sterilization, in the sieving process, ginseng juice residue is generated, and 20 ginseng juice residue is generated.
After 0 kg was put into the drying chamber A under reduced pressure and the apparatus was warmed up for 15 minutes by operating the condensed water re-evaporation line, test measurement was performed. The table in FIG. 5 shows data 25 minutes after the start of operation. Use a steam ejector from the beginning of operation.

FIG. 2 shows a continuous drying process according to a second embodiment of the present invention. In this case, two vacuum drying chambers A-
1, A-2 is installed, and the raw material is continuously supplied by using a raw material supply device having an airtight maintaining function such as a rotary valve 1, and two vacuum drying chambers A-1 and A-2 are provided. By alternately switching to be continuous, the drying process can be directly connected to the manufacturing process.

In this case, the compressor 4 and the condensed water tank 25
, Etc., only one condensed water re-evaporation device is provided, and only two reduced-pressure drying chambers A-1 and A-2 need to be provided.

When the No. 1 vacuum drying chamber A-1 is full, the rotary valve 1 of the No. 2 vacuum drying chamber A-2 is started, and the rotation direction of the screw conveyor 44 driven by the motor 45 is reversed. The charged raw material is moved in the direction of the No. 2 vacuum drying chamber A-2, and the raw material is charged into the No. 2 vacuum drying chamber A-2 from the outlet 44b.

At this time, the operation of the rotary valve 1 of the No. 1 vacuum drying chamber A-1 is stopped to maintain airtightness, and the drying chamber A-
Drying is performed until the raw material in 1 reaches a predetermined dry moisture region, and after the drying is completed, the dried raw material is discharged from the lower hatch 18 of the No. 1 vacuum drying chamber A-1 according to the rotation of the stirrer 9, Standby operation is performed until the No. 2 vacuum drying chamber A-2 is full. During this time, a small amount of steam is introduced into the steam jacket 6 to warm up.

[0056]

According to the present invention, condensed water re-evaporation steam containing almost no air is sent to the suction side of the compressor in order to minimize the ratio of the amount of mixed air in the suction steam of the compressor. By injecting low-temperature water, saturated steam is generated in the compressor to maintain the equilibrium between pressure and temperature, thereby stabilizing the compression ratio and preventing abnormal temperature rise.

At this time, by using the excess steam to assist the suction of the steam in the reduced-pressure drying chamber by the steam ejector, it is possible to reduce the time required for finishing the drying, to reduce the inflow of air into the compressor, and to reduce the compression. Facilitates the operation of the machine.

Further, by installing a rotary valve, it is possible to feed a water-containing substance into the reduced-pressure drying chamber while maintaining airtightness, thereby facilitating continuous operation. Further, by attaching a stirrer having a discharge function, discharge after the drying process is simplified, and there is an effect of increasing heat transfer efficiency during drying.

In the present drying method, drying is performed in a relatively low temperature range under reduced pressure.
Since it is dried while maintaining the following conditions, it has no cooking flavor such as burning smell, does not impair the flavor, and has little change in contained components.It is also suitable for making high quality dried products. I have.

[Brief description of the drawings]

FIG. 1 is a diagram showing a drying apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a drying apparatus according to a second embodiment of the present invention.

FIG. 3 is a table showing operation data when the degree of drying of okara is 45 to 50% of water content.

FIG. 4 is a view showing data 25 minutes after the start of the Okara drying operation.

FIG. 5 is a view showing data 25 minutes after the start of the operation of ginseng juice residue drying.

FIG. 6 is a configuration diagram of an apparatus for explaining the theory of a drying method.

FIG. 7 is a steam entropy diagram illustrating a drying method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rotary valve 2 ... Closed container 3 ... Steam line in a heating and drying room 4 ... Steam compressor 5 ... Compressed steam line 6 ... Condenser 7 ... Rotary valve motor 8 ... Motor of steam compressor 9 ... Agitating blade 10 ... Motor of agitating blade 11 ... Shimizu line 12 ... Dried okara outlet 13 ... Okara separator 14 ... O From the separator 15 ··· Belt conveyor 16 ··· Opening and closing hatch for introducing a large amount of hydrated substances 17 ··· Sampling cylinder 18 ··· Opening and closing hatch with screen 19 ··· Filter 20 ··· Pressure Total 21 21 Thermometer 22 Drying room steam suction damper 23 Water injection sprayer 24 Flow meter 25 Condensed water tank 26 Condensed water line 27 Blow valve 28・ ・Trainer 29 ・ ・ ・ Steam trap 30 ・ ・ ・ Sheds heater 31 ・ ・ ・ Temperature detector 32 ・ ・ ・ Suction port 33 ・ ・ ・ Upper limit level meter 34 ・ ・ ・ Lower level meter 35 ・ ・ ・ Pressure gauge 36 ・ ・ ・Thermometer 37: Re-evaporation steam suction line 38: Flow control damper 39: Solenoid valve 40: Drain pump 41: Steam ejector 42: Drying room steam suction line 43: Drain Tank 44: Screw conveyor 45: Screw conveyor motor 46: Rotating screw 47: Pressure gauge

Claims (8)

[Claims] 1. A hydrated substance is placed in a reduced-pressure drying chamber comprising a closed vessel and heated. The generated steam is compressed by a compressor, and the compressed steam is introduced into a condenser to be liquefied. In a method for drying a hydrated substance, wherein the hydrated substance is dried by heating the hydrated substance in the vacuum drying chamber with latent heat, a condensed water re-evaporator having a condensed water tank into which condensed water is introduced from the condenser is provided. A method for drying a hydrated material, comprising heating saturated water to generate saturated steam and introducing the saturated steam into the steam compressor to obtain steam for heating. 2. A hydrated substance is placed in a reduced-pressure drying chamber comprising a closed vessel and heated, and the generated steam is compressed by a compressor. The compressed steam is introduced into a condenser to be liquefied, and the condensation generated at that time A method for drying a hydrated product by heating and drying a hydrated product in the reduced-pressure drying chamber with latent heat, wherein water is injected and sprayed on the suction side of the compressor to obtain steam for heating from an outlet of the compressor. Drying method of hydrated material. 3. A reduced-pressure drying chamber consisting of a closed container for containing a hydrated substance, two units equipped with a rotary valve having a function of maintaining airtightness and a stirrer having a discharge function, and a steam compressor and a condensate. One re-evaporator is installed, and a steam compressor and a condensed water re-evaporator are connected to one or both of the reduced-pressure drying chambers to heat and dry the hydrated material in the reduced-pressure drying chamber. The method for drying a hydrate according to claim 1 or 2, wherein the hydrate is supplied into the room. 4. The method for drying a water-containing substance according to claim 1, wherein the steam in the reduced-pressure drying chamber is sucked by a steam ejector acting with steam from an outlet of the steam compressor. 5. A hydrated substance is placed in a reduced-pressure drying chamber comprising a closed vessel and heated, and the generated steam is compressed by a compressor. The compressed steam is introduced into a condenser to be liquefied, and the condensate generated at that time is condensed. A condensate re-evaporator having a condensed water tank into which condensed water is introduced from the condenser is provided, wherein the condensed water re-evaporator is provided. An apparatus for drying a hydrate, wherein saturated steam generated in an evaporator is introduced into the steam compressor. 6. The apparatus for drying a hydrated product according to claim 5, wherein a water injection sprayer is provided on the suction side of the steam compressor. 7. A reduced-pressure drying chamber comprising a closed container for containing a hydrate is provided with two facilities provided with a rotary valve having a function of maintaining airtightness and a stirrer having a discharge function. 7. The apparatus for drying a hydrate according to claim 5, further comprising one steam compressor and one condensed water re-evaporator alternately or simultaneously connected to one unit. 8. An apparatus for drying a water-containing substance according to claim 5, further comprising a steam ejector for flowing steam from an outlet of the steam compressor and for sucking steam in the reduced-pressure drying chamber. .