JP2007093163A - Wet vapor manufacturing device and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wet vapor manufacturing device for solving the problems that larger equipment is required and a drying degree of wet vapor is not uniform resulting from the mixture of drain in the wet vapor when manufacturing the wet vapor. <P>SOLUTION: The wet vapor manufacturing device comprises a first liquid adding means 4 for adding first liquid to dry vapor supplied from the upstream side, a drain removing means 5 located on the downstream side of the first liquid adding means 4 for removing drain from the vapor, and a second liquid adding means 8 located on the downstream side of the drain removing means 5 for adding second liquid to the drain removed vapor obtained by the drain removing means 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a wet steam manufacturing apparatus and a manufacturing method thereof.

  Saturated steam is mainly used for heating with steam. In particular, when it is desired to increase the temperature while maintaining the humidity of the object to be heated, such as heating food, wet steam further containing moisture is used from saturated steam. On the other hand, in the supply of steam, from the viewpoint of thermal efficiency, the saturated steam is further supplied in a dry steam state. Therefore, in a place where steam is used, dry steam is reduced in temperature to be wet steam. This temperature reduction is performed by a method such as cooling with a heat exchanger or addition of a liquid to the vapor (see, for example, Patent Documents 1 and 2).

FIG. 2 shows the relationship between the pressure P and the volume V in the process of generating saturated steam. A point w in the figure is a saturated liquid having a pressure P1, and its volume is v ₁ '. Point S represents saturated steam under pressure P ₁ and its volume is v ₁ ″. If the trajectories of w and S when the pressure P is now changed are drawn, v′v ″ curves are obtained. That is, the v ′ line is called a saturated liquid line, and the v ″ line is called a saturated vapor line. As the pressure increases, both curves approach and meet at a point k at pressure P _k . That is, the volume of the saturated liquid and the saturated vapor coincide with each other at the pressure _Pk . In addition, the steam indicated by the point m written in the central region surrounded by the v ′ line and the v ″ line in the figure is called wet steam under the pressure P ₁ , and the point S The steam belonging to the region on the right side of the figure is called dry steam. Further, the dryness x can be obtained as follows for the point m in the figure.

Japanese Patent Publication No. 5-55762 Japanese Patent No. 2873640 Japanese Utility Model Publication No.59-17581

  However, the conventional technique has the following problems. That is, in the temperature reduction using the heat exchanger, there is a problem that the surface of the heat exchanger pipe is cooled by the refrigerant flowing in the pipe of the heat exchanger, and a part of the steam is drained on the pipe surface. In addition, when liquid is added to dry steam to reduce the temperature, the liquid is vaporized to obtain wet steam, but a long pipe length is required to vaporize the added liquid. When the length is short, the added liquid is not completely vaporized and becomes drained. Further, if the pipe length is increased, a part of the steam is drained on the inner wall surface of the pipe for heat dissipation. As described above, in the conventional technique, since the drain is mixed with the wet steam, it is difficult to produce the wet steam having a uniform dryness.

  Concerning the problem of drainage, a measure to install a drain separator, which is a drain removal means, can be considered, but by installing the drain separator, not only the drain but also the moisture content of the wet steam is removed, and after passing through the drain separator This steam becomes saturated steam, making it difficult to produce wet steam.

  The wet steam production apparatus of the present invention employs the following means in order to solve the above problems. That is, in the wet steam production apparatus, the first liquid addition means for adding the first liquid to the dry steam supplied from the upstream side, and the downstream of the first liquid addition means, A drain removing unit that removes the drain, and a second liquid adding unit that is located downstream of the drain removing unit and adds the second liquid to the drain-removed vapor obtained by the drain removing unit. An apparatus for producing wet steam is provided.

  Moreover, according to the preferable form of this invention, the said 1st liquid addition means and said 2nd liquid addition means are spray nozzles, The wet steam manufacturing apparatus characterized by the above-mentioned is provided.

  Further, according to a preferred embodiment of the present invention, the second liquid addition means has an average particle diameter of the liquid added by the second liquid addition means, which is an average of the liquid added by the first liquid addition. An apparatus for producing wet steam is provided that is configured to be smaller than the particle size.

  According to a preferred aspect of the present invention, there is provided a wet steam producing apparatus, wherein the second liquid adding means is a liquid adding means for adding a liquid having an average particle diameter of 10 μm or more and 50 μm or less. Is done.

  Further, according to a preferred embodiment of the present invention, the dryness measuring means for measuring the dryness of the flowing down steam, and the dryness adjusting means for adjusting the dryness of the steam, located downstream of the second liquid adding means. There is provided an apparatus for producing wet steam.

  According to a preferred aspect of the present invention, there is provided a wet steam producing apparatus, wherein the dryness adjusting means also serves as the second liquid adding means.

  Further, according to another aspect of the present invention, after the first liquid is added to the dry steam supplied from the upstream side to form supersaturated steam, the drain in the supersaturated steam is removed downstream to remove the drain. There is provided a wet steam producing apparatus, characterized in that the steam is further converted into wet steam by adding a second liquid to the drain-removed steam downstream.

  According to a preferred embodiment of the present invention, the wet steam is produced by measuring the dryness of the wet steam and adjusting the amount of liquid added to the drain-removed steam based on the measured value. An apparatus is provided.

In the present invention, “saturated steam” refers to steam in a state on a saturated steam line. In other words, when a liquid is heated under a certain pressure, a phase change starts from a liquid to a gas at a saturation temperature and goes through a gas-liquid mixed state and then changes to a 100% gas. Steam in a state of being 100% gas is “saturated steam”.
In the present invention, “wet steam” refers to steam in a state corresponding to containing saturated liquid in saturated steam. Also called “supersaturated steam”. Moreover, a saturated liquid means the liquid in a saturated state.

  In the present invention, “dry steam” refers to steam having a higher calorific value than saturated steam at the same pressure, and can be generated by adding more heat to the saturated steam or expanding the saturated steam.

  In the present invention, “dryness” is considered to be divided into saturated steam xkg of 1 kg of steam and saturated liquid (1-x), and the ratio x of saturated steam to the total mass of 1 kg is called dryness of this steam. .

For measuring the dryness, a squeeze dryness meter or the like is used. The squeezing dryness meter obtains the original dryness by measuring the state by changing the wet steam into the dry steam by squeezing the wet steam in the heat insulating container. If the enthalpy of the dry steam after squeezing is h ₂ , the squeezing process is an isoenthalpy process, so the following equation holds.

Therefore, when h ′, γ, and h ₂ are obtained from the steam table from the temperature and pressure before and after throttling, the dryness x is obtained. Here, h ′ is the enthalpy of saturated steam and γ is the latent heat of evaporation.

  In the present invention, the “liquid adding means” refers to a pump or a nozzle used for adding a liquid to the vapor flowing through a pipe.

  In the present invention, “drain” means that a part of the vapor passing through the pipe is liquefied.

  In the present invention, “drain removal means” refers to means for reducing drainage in steam. It is preferable to use a separator that separates steam and drain using centrifugal force, or a drain separator that separates steam and drain mixed liquid by colliding with the collision plate and dripping the drain along the collision plate. . An example of the structure of the drain separator is shown in FIG. It enters the drain separator in a state 13 where steam and drain are mixed. Within the drain separator is a filter element 17. At this time, the steam passes through the filter element 17 toward the outlet 16 of the drain separator. On the other hand, the drain is captured by the filter element 17 and the drain 14 accumulates at the bottom of the drain separator. The drain 14 accumulated at the drain separator bottom is discharged outside the drain separator by removing the drain cock 15.

  In the present invention, “addition of liquid” is preferably spraying droplets rather than spraying.

  In the present invention, the “spray nozzle” refers to a nozzle that sprays a liquid in a spray form. A liquid jet that collides with a liquid jet in the nozzle and atomized by adding a liquid to a gas jet created in the nozzle and mixes it is preferably used.

  In the present invention, the “dryness measuring means” means means for measuring the dryness of steam. A squeeze dryness meter that calculates the dryness of steam using a squeeze mechanism is used.

  In the present invention, “dryness adjusting means” refers to means for adjusting the amount of liquid added to obtain the desired dryness based on the dryness measured by the dryness measuring means.

  As the “pump” used in the present invention, since the amount of liquid to be added is determined by the amount of dry steam supplied from upstream, a centrifugal pump or the like having a wide discharge amount range and being continuously uniform is preferably used.

  In the present invention, alcohol, industrial water, pure water or the like is preferably used as the “liquid” used for the first and second liquid additions.

  According to the wet steam production apparatus of the present invention, it is possible to produce homogeneous wet steam, and it is possible to reduce the size of the equipment. That is, it is not necessary to vaporize the added liquid by the drain separator installed downstream of the first liquid adding means, and equipment having a shorter pipe length than before can be used. Further, the addition of the liquid is divided into two stages, and a uniform wet steam with little drain can be produced by adding the minimum necessary moisture to the stable saturated steam that has passed through the drain separator.

Hereinafter, an example of the best mode of the present invention will be described with reference to FIG. FIG. 1 is a flowchart of a wet steam production apparatus.

  The wet steam production apparatus includes a dry steam inlet 1, a first liquid adding means 4 for adding a liquid to cool the dry steam, a first stage pump 2 and a first stage spray nozzle 3, and after the addition of the liquid The second stage pump 6 and the second stage spray nozzle are the drain separator 5 for separating the steam and the drain of the second stage, and the second liquid addition means 8 used to give the moisture to the saturated steam after passing through the drain separator. 7, a wet steam supply port 9, a squeeze dryness meter 10 for measuring the dryness of the produced wet steam, and the liquid in the second liquid addition means 8 based on the measured value of the squeeze dryness meter. It comprises dryness control means 11 for adjusting the addition amount and a flow rate adjustment valve 12.

  Next, operation | movement of this wet steam manufacturing apparatus is demonstrated.

The liquid is added by the first liquid adding means 4 to the dry steam supplied from the steam inlet 1. At this time, the amount of the liquid used for the first liquid addition may be a liquid amount that sufficiently exceeds the temperature of the supplied dry steam and exceeds the saturated steam to become supersaturated steam. The liquid amount M _PW1 (m ³ / hr) used for the first liquid addition can be calculated by the following equation. However, the constant-pressure specific heat of dry steam is C _p (Kcal / ° C kg), the dry steam mass flow rate M _MS (kg / hr), the temperature T _MS (° C) increased by overheating, and the specific heat C _{PW of} the liquid to be added (Kcal / ° C kg) and the liquid temperature T _PW1 (° C) increased by heating.

As a result, the dry steam can be cooled to the saturation temperature regardless of the steam flow rate by adjusting the amount of liquid added according to the steam flow rate.

  Normal temperature reduction using latent heat requires time until the added liquid evaporates, and thus requires a long pipe length, but as shown in the above formula, the present invention uses a sensible heat reduction. Therefore, saturated vapor can be obtained in a short time by adding a liquid having a sufficient flow rate. Therefore, the piping length can be shortened. However, when the vapor is cooled using a large amount of liquid, most of the liquid becomes drain. Therefore, the steam and drain are separated using the drain separator 5 next. The drain separator 5 uses only the specific gravity difference between the liquid and the gas to pass only the gas, and the steam immediately after passing the mixture of the saturated steam and the saturated water through the drain separator 5 is generally saturated steam.

Next, the second liquid addition means 8 adds the amount of liquid necessary for wetness. Here, the liquid added by the second liquid adding means 8 is preferably added with an average particle diameter smaller than the average particle diameter of the liquid droplets added by the first liquid adding means. The first liquid addition requires a flow rate sufficient to cool the vapor, and the average particle size of the droplets does not need to be reduced. On the other hand, in the second liquid addition, it is necessary to efficiently give a moisture component to the vapor. Therefore, it is preferable that the average particle diameter of the added droplets is small. For example, the average particle size of the first droplet is preferably about 2 to 20 times the average particle size of the second droplet.
In addition, since the pipe length necessary for vaporizing the added water is proportional to the square of the particle size average radius of the water droplets to be sprayed, the smaller the particle size average radius is more efficient in the second liquid addition. Can be moistened. Specifically, a size of 50 μm or less is preferable, and a droplet of 30 μm or less is more preferable. In addition, since it is not easy to efficiently produce droplets having an average particle size of 10 μm or less, the particle size of the droplets is preferably 10 μm or more. By adding minute droplets in this way, the steam can be efficiently moistened, and the amount of generated drain can be reduced as compared with the prior art, producing a homogeneous wet steam with less drain. be able to.

  Moreover, the wet steam production apparatus of the present invention is more preferably used when the steam flow rate is 500 kg / hr or more. In other words, as the steam flow rate increases, the amount of liquid added necessary for cooling also increases, and the flow rate becomes insufficient with a nozzle that sprays fine droplets. Therefore, a sufficient amount of liquid is added by the first liquid addition, the steam is cooled to saturated steam, and then wetness is imparted by fine spraying in the second liquid addition.

  Further, in order to control the dryness of the wet steam to be manufactured, the dryness measuring means 10 for measuring the dryness of the wet steam is installed downstream of the second liquid adding means 8, and the measured value of the dryness measuring means is measured. Based on the above, the control means 11 adjusts the flow rate adjustment valve 12 to adjust the liquid addition amount in the second liquid addition means 8 to control the dryness of the wet steam. In addition, it is the second liquid addition that provides moisture to the steam. That is, in order to adjust the dryness, it is efficient to directly adjust the second liquid addition amount. Therefore, it is preferable that the dryness adjusting means also serves as the second liquid adding means.

Example 1
Since the wet steam was manufactured using the wet steam manufacturing apparatus shown in FIG. 1, an example is shown below. In addition, the dryness of the wet steam to be manufactured was set to 0.985. Various conditions for producing wet steam are as follows.

  Dry steam has an inflow rate of 1000 kg / hr and a temperature of 175 ° C. The pipe diameter is 27.2mm (20A), the pipe material is stainless steel SUS304, the pipe length is 0.5m from the dry steam inlet to the first water addition means, the first water addition means to drain separator 0.5m from the drain separator to the second water addition means, 0.5m from the second water addition means to the dryness meter, and 0.1m from the dryness meter to the wet steam supply port And Moreover, a polyethylene foam is used for the heat insulating material which wraps piping. A squeeze dryness meter is used as the dryness meter. A drain separator with a capacity of 300 kg / hr is used.

As shown in FIG. 5, the spray nozzle was installed vertically on the bottom side of the pipe with respect to the main pipe through which dry steam flows, and the protruding length of the nozzle was 5 mm. Water was added continuously with the first and second water additions, and the water was added in the direction perpendicular to the main pipe in the same manner as the nozzle. As the liquid added to the vapor, pure water having an electric conductivity of about 50 μS / cm is used for both the first and second additions, and the temperature of the added water is 25 ° C. and the drain temperature is 100 ° C. The steam after the first water addition is controlled at 160 ° C. and the pressure at 0.55 MPa. The first water addition uses a spray nozzle with an average particle size of water droplets of 100 μm during spraying, and the second water addition uses a spray nozzle with an average particle size of water droplets of 50 μm during spraying. Yes (Manufacturer: Fog House, Model Number: 1 / 4MKB 80 063 S303-RW
). In addition, there are a liquid immersion method and a laser method for measuring the average particle diameter of the added water droplets. The liquid immersion method is a method in which fog is received on a plate glass coated with a thick silicone oil, an enlarged photograph is taken, and the number of particles is counted for each size from the finished photograph. The average particle diameter of the water droplets was a value calculated by the Sauter average that is generally used for calculating the average particle diameter of the droplets. The Sauter average is an equation for determining the ratio of the total volume of the measured droplets to the total surface area. Therefore, the Sauter average diameter is also called the body area average and is expressed by the following formula.

Note that n _i and d _i indicate the number of droplets and the droplet diameter in group i when the droplet sizes are grouped. If n _i = 1, individual droplets are handled without grouping.

  This time, by measuring the average particle size of the water droplets when spraying with the spray nozzle used for the first and second water addition by the immersion method, and calculating the average value of the Sauter, it was confirmed that they were 100 μm and 50 μm, respectively. did.

First, water is spray-added to the dry steam supplied from the dry steam inlet 1 by the first liquid adding means 4. The first water addition amount this time is 110 kg / hr. After the first water addition, the steam immediately after passing through the drain separator 5 becomes saturated steam. At this time, about 110 kg / hr of drain is discharged from the drain separator 5. The second water is then added to the saturated steam. This time, 10kg / hr of water is added by spraying to give moisture to saturated steam. Thereby, the dryness of the wet steam produced becomes 0.983 to 0.987. In addition, in the second water addition, when the water addition amount is 6 kg / hr, the dryness is 0.988 to 0.993. Thus, the dryness can be controlled by adjusting the second water addition amount. Moreover, in order to control the dryness of the wet steam to manufacture, the squeeze dryness meter 10 is installed after 2nd water addition, and the dryness of the manufactured wet steam is measured. By controlling the second water addition amount based on the measurement value of the squeeze dryness meter, it is possible to produce wet steam having a target dryness.
(Example 2)
Under the same conditions as in Example 1, in the second water addition means, wet steam was produced using a spray nozzle having an average particle size of the added water droplets of 150 μm. The target dryness was 0.985. When the average particle size of the water droplets to be added was larger than that in Example 1, it was not completely vaporized, and when the second water addition amount was 10 kg / hr, the measurement result of the dryness meter was 0.990. Therefore, when wet steam was produced by setting the pipe length from the second water addition means to the dryness meter to 4.5 m, wet steam having a dryness of 0.978 to 0.993 was obtained.
(Comparative Example 1)
Under the same conditions as in Example 1, no drain separator was installed, no second water was added, only the first water was added, and the amount of water added was 120 kg / hr to produce wet steam. . The target dryness was 0.985. However, the added water was not completely vaporized and the dryness was 1. Accordingly, when the production of wet steam was performed 10 times with the pipe length from the first stage water addition means to the dryness meter being 5.5 m, the dryness obtained varied in the range of 0.96-1.
(Comparative Example 2)
Production of wet steam under the same conditions as in Example 1, with the same pipe length as in Example 1, without adding the second water, only adding the first water, and adding the water to 120 kg / hr Went. The target dryness was 0.985. However, the added water was discharged from the drain separator, and the dryness of the resulting wet steam was 1. Then, when the production of wet steam was performed 10 times with the removal amount of the drain separator being 300 kg / hr as the first water addition amount of 310 kg / hr, the dryness varied in the range of 0.96-1.

  Table 1 shows the reproducibility of the dryness of the wet steam obtained in Example 1, Example 2, Comparative Example 1 and Comparative Example 2. For each example, wet steam was produced 10 times, and the average value and standard deviation of the dryness obtained were shown.

  From Table 1, the wet steam obtained by Example 1 is the most homogeneous.

In the production of wet steam by only the conventional one-stage addition of Comparative Example 1, the average value is almost the same as in Example 1, but the obtained dryness is in the range of 0.96 to 1, and the standard deviation is 0.00. Steam with a large variation of 014 was obtained. This is because, in Comparative Example 1, no drain separator was installed downstream of the water addition means, so out of the added water, 110 kg / hr of water used to reduce the temperature of the dry steam remained in the pipe, resulting in excess steam. This is because the state of steam is not stable because it becomes a wet part or accumulates as drainage in the pipe.
In Comparative Example 2, since the drain separator drains the water added in the first stage, the moisture content cannot be imparted to the dry steam. Therefore, in order to produce wet steam, it is necessary to add an amount of water that exceeds the removal capability of the drain separator, and the amount of water to be added increases. In addition, since the moisture content of the wet steam is the amount of water overflowing the drain separator, the amount of water that becomes the moisture content is not stable. As a result, although the average value was almost the same as in Example 1, the dryness of the produced wet steam varied with a standard deviation of 0.013.

  On the other hand, in the case of Example 1, it is possible to obtain steam with a small variation with a dryness of 0.983 to 0.987 and a standard deviation of 0.001. Most of the water added by the first water addition for use in reducing the temperature of dry steam is discharged out of the pipe by the drain separator. Therefore, the amount of drain remaining in the pipe immediately after passing through the drain separator is about 0.5 kg / hr, and it is less likely to become excessive moisture of steam, and the amount of drain accumulated in the pipe can be significantly reduced than before. It becomes. Moreover, since the minimum amount of water necessary for obtaining the desired dryness is added by the second water addition, a stable wet steam can be obtained.

  In addition, in the production of wet steam with only one-stage addition of Comparative Example 1, Comparative Example 1 requires a pipe length of 6.0 m from the water addition means to the dryness meter so that all of the added water 120 kg / hr is vaporized. is necessary. On the other hand, in the case of Example 1, since the drain separator was installed downstream of the first water addition means, 110 kg / hr of water added in the first stage need not be vaporized. The pipe length to the drain separator is 0.5 m, which is the required pipe length for reducing the temperature of the steam. Moreover, even if the pipe length of 0.5 m from the drain separator to the second water addition means and the pipe length of 0.5 m necessary for water vaporization by the second stage water addition are added, the first water addition means The pipe length to the dryness meter is 1.5 m, and the distance from the first water addition means to the dryness meter is 1.5 m.

  In Example 1, in the first addition of water, the water droplets to be sprayed are sprayed with an average particle diameter of 100 μm. This is because the role of the first water addition is to reduce the temperature of dry steam, and it is not necessary to vaporize the added water, so that it is not necessary to reduce the average particle diameter of the added water droplets.

  On the other hand, for the second water addition, since the added water needs to be vaporized, the average particle diameter of the added water droplets is important. FIG. 3 shows the relationship between the average particle size of the added water droplets and the pipe length necessary for the added water to vaporize. In Example 1, when the average particle diameter of the water droplets added by the second water addition means is 150 μm, the pipe length after the second water addition is 4.5 m from FIG. That is, the pipe length becomes 4 m longer than that in Example 1 when the average particle diameter of the water droplets added by the second water addition means is 50 μm. When the length of the pipe becomes long, the moisture that has been vaporized once drains, and the dryness of the wet steam becomes unstable. Therefore, the variation in dryness obtained in comparison with Example 1 increases, and the uniform wet steam. Will not be obtained.

  The present invention is not limited to being used to increase the temperature while maintaining the humidity of the object to be heated, such as heating of food, and can also be applied to the case where uniform wet steam is obtained from dry steam in a production line. However, the application range is not limited to these.

It is a flowchart of the wet steam supply apparatus in one Embodiment of this invention. It is a figure which shows the relationship between P and V in the generation | occurrence | production process of saturated steam. It is a figure which shows the relationship between the average particle diameter of the water droplet to add, and the piping length required in order for the added water droplet to vaporize. It is a figure which shows the structure of the drain separator in one Embodiment of this invention. It is a figure which shows the installation position of the nozzle in one Embodiment of this invention.

Explanation of symbols

1: Dry steam inlet 2: First stage pump 3: First stage spray nozzle 4: First liquid addition means 5: Drain separator 6: Second stage pump 7: Second stage spray nozzle 8: Second liquid addition Means 9: Wet steam supply port 10: Squeeze dryness meter
11: Dryness control means 12: Flow control valve 13: Saturated steam and drain 14: Drain 15: Drain cock 16: Drain separator outlet 17: Filter element 18: Main pipe 19: Saturated steam 20: Spray nozzle 21: Droplet 22: Projection length of spray nozzle P: Pressure V: Volume v ′: Saturated liquid line v ″: Saturated vapor line k: Critical point w: Saturated liquid v ₁ ′ at pressure P1 S: Volume of saturated liquid w S: Pressure P1 Saturated steam v ₁ ″: Volume m of saturated steam S: Wet steam v _{m1 at} pressure P ₁ : Volume of wet steam m

Claims (8)

In the wet steam production apparatus, the first liquid addition means for adding the first liquid to the dry steam supplied from the upstream side, and the downstream of the first liquid addition means, the drain in the steam A drain removing means for removing, and a second liquid adding means located downstream of the drain removing means for adding the second liquid to the drain-removed vapor obtained by the drain removing means. Wet steam production equipment. The apparatus for producing wet steam according to claim 1, wherein the first liquid adding means and the second liquid adding means are spray nozzles. The second liquid addition means is configured such that the average particle diameter of the liquid added by the second liquid addition means is smaller than the average particle diameter of the liquid added by the first liquid addition means. The apparatus for producing wet steam according to claim 1, wherein the apparatus is a wet steam. The apparatus for producing wet steam according to any one of claims 1 to 3, wherein the second liquid addition means is a liquid addition means for adding a liquid having an average particle diameter of 10 µm to 50 µm. The dryness measuring means for measuring the dryness of the flowing down steam and the dryness adjusting means for adjusting the dryness of the steam are provided downstream of the second liquid adding means. Item 5. The apparatus for producing wet steam according to any one of Items 1 to 4. 6. The apparatus for producing wet steam according to claim 5, wherein the dryness adjusting means also serves as the second liquid adding means. After adding the first liquid to the dry steam supplied from the upstream side to form supersaturated steam, the drain in the supersaturated steam is removed downstream to form drained steam, and further to the drain removed steam downstream. A method for producing wet steam, comprising adding a second liquid to obtain wet steam. The method for producing wet steam according to claim 7, wherein the dryness of the wet steam is measured, and the amount of liquid added to the drain-removed steam is adjusted based on the measured value.

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