Steam boiler

Abstract

To provide a steam pot capable of reducing a used amount of cooling water while protecting a pipe for returning the cooling water to a cooling water supply source.SOLUTION: A steam pot 1 of the present invention includes: an inner pot 2 in which a material to be processed is stored; a jacket 3 provided outside the inner pot 2; steam providing means 4 for providing steam to the jacket 3; and cooling water circulation means 7 for circulating the cooling water between the jacket 3 and a cooling water supply source 100. The cooling water circulation means 7 includes an outward water path 70, a return water path 80, a bypass path 90, and mixing means 84. The outward water path 70 is configured so as to supply cooling water from the cooling water supply source 100 to the jacket 3, and the return water path 80 is configured so as to return the return water from the jacket to the cooling water supply source 100. The bypass path 90 is configured so as to bypass the outward water path 70 and the return water path 80, and the mixing means 84 is configured so as to mix the return water circulating in the return water path 80 through the bypass path 90 with the cooling water from the cooling water supply source 100 to bring the temperature of the return water to be returned to the cooling water supply source 100 to a predetermined temperature T or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a steam kettle for heating an object to be processed with steam.

Background Art

[0002] Conventionally, there is a steam kettle provided with a jacket (steam chamber) outside an inner kettle that houses an object to be processed such as food. For example, the steam kettle disclosed in Patent Document 1 is a steam kettle capable of heating and cooling food by supplying steam and cooling water to the jacket.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the case of a configuration in which cooling water is supplied to the jacket in addition to steam, in order to reduce the amount of cooling water used, it is preferable to circulate the cooling water between the jacket and the cooling water supply source (chiller). However, since the condensed water from the jacket immediately after the start of cooling becomes high in temperature, if it is returned to the cooling water supply source as it is, there is a risk of problems occurring in the piping to the cooling water supply source where the flow of high-temperature water is not assumed. On the other hand, if the condensed water is drained until the temperature of the condensed water sufficiently drops, the amount of cooling water used can hardly be reduced.

[0005] The present invention has been made in view of such circumstances, and provides a steam kettle capable of reducing the amount of cooling water used while protecting the piping returned to the cooling water supply source.

Means for Solving the Problems

[0006] According to the present invention, a steam boiler is provided, comprising: an inner boiler containing a workpiece to be processed; a jacket provided on the outside of the inner boiler; a steam supply means for supplying steam to the jacket; and a cooling water circulation means for circulating the cooling water between the jacket and a cooling water supply source, wherein the cooling water circulation means comprises a supply channel, a condensate channel, a bypass channel, and a mixing means, the supply channel is configured to supply cooling water from the cooling water supply source to the jacket, the condensate channel is configured to return condensate from the jacket to the cooling water supply source, the bypass channel is configured to bypass the supply channel and the condensate channel, and the mixing means is configured to mix cooling water from the cooling water supply source with the condensate flowing through the condensate channel via the bypass channel, so that the temperature of the condensate returned to the cooling water supply source is below a predetermined temperature.

[0007] According to the present invention, by providing a mixing means in the condensate channel from the jacket to the cooling water supply source and mixing the cooling water supplied from the cooling water supply source via a bypass channel with the condensate flowing through the condensate channel, the condensate from the jacket is cooled even if it is at a high temperature, and the piping that returns the condensate to the cooling water supply source without draining it is protected.

[0008] The following are examples of various embodiments of the present invention. The embodiments shown below can be combined with each other.

[0009] Preferably, the condensate channel is provided with a drain switching valve, which is configured to switch between draining the condensate or returning it to the cooling water supply source.

[0010] Preferably, the mixing means is a mixing valve provided in the condensate.

[0011] Preferably, the first temperature sensor is provided at a position on the jacket side of the connection point between the condensate and the bypass passage in the condensate passage, and the bypass passage is provided with a bypass valve, which is opened and closed according to the temperature of the condensate detected by the first temperature sensor.

[0012] Preferably, the mixing means comprises the first temperature sensor and the bypass valve, wherein the bypass valve is an adjustable valve with an adjustable opening, and the mixing means is configured to lower the temperature of the condensate to a predetermined temperature or lower by adjusting the opening of the bypass valve according to the temperature of the condensate detected by the first temperature sensor.

[0013] Preferably, the second temperature sensor is located on the cooling water supply source side of the connection point between the condensate and the bypass. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram showing a steam kettle 1 according to one embodiment of the present invention. [Figure 2] Figure 1 is a flowchart showing the operation of the steam boiler 1. [Figure 3] Figure 1 shows the flow paths of steam and condensate in the heating process S1 of the steam kettle 1, indicated by thick lines. [Figure 4] Figure 1 shows the flow paths of compressed air in the first compressed air supply process S2 and the second compressed air supply process S5 of the steam boiler 1, indicated by thick lines. [Figure 5] Figure 1 shows the flow paths of the cooling water and condensate in the first cooling process S3 of the steam boiler 1, indicated by thick lines. [Figure 6] Figure 1 shows the flow paths of the cooling water and condensate in the first cooling step S3 of the steam boiler 1, when the condensate is not returned to the chiller 100, with the thick lines indicating the flow paths of the cooling water and condensate. [Figure 7] Figure 1 shows the flow paths of the cooling water and condensate in the second cooling process S4 of the steam boiler 1, indicated by thick lines. [Figure 8] This is a schematic diagram showing a modified steam kettle 1 according to the present invention. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described below. The various features shown in the embodiments below can be combined with each other. Furthermore, each feature constitutes an independent invention.

[0016] 1. Configuration of the steam kettle 1 FIG. 1 is a schematic diagram showing a steam kettle 1 according to an embodiment of the present invention. The steam kettle 1 of the present embodiment is a kettle capable of heating and cooling food as the object to be processed.

[0017] As shown in FIG. 1, the steam kettle 1 of the present embodiment includes an inner kettle 2, a jacket 3, a steam supply means 4, a drain discharge means 5, a compressed air supply means 6, a cooling water circulation means 7, and a control means 10. Further, in the present embodiment, the cooling water circulation means 7 is connected to a chiller 100 as a cooling water supply source. The chiller 100 may be a component outside the steam kettle 1 or may be included as a component of the steam kettle 1. Hereinafter, each configuration will be specifically described.

[0018] The inner kettle 2 is a bottomed hollow container that opens upward, and food is accommodated therein. The inner kettle 2 may have a stirring device (not shown) for stirring food inside, regardless of its shape.

[0019] The jacket 3 is provided outside the inner kettle 2. For example, in the illustrated example, the jacket 3 is provided so as to cover the lower region of the inner kettle 2. Steam, compressed air or cooling water is switched and supplied into the jacket 3.

[0020] The steam supply means 4 supplies steam from a boiler (boiler connection port) into the jacket 3. Specifically, the steam supply means 4 includes a steam supply path 40 that connects the boiler (boiler connection port) and the jacket 3. A steam supply valve 41 is provided in the steam supply path 40.

[0021] The drain discharge means 5 discharges the condensed water (drain) of the steam supplied into the jacket 3. Specifically, the drain discharge means 5 includes a drain discharge path 50, and a steam trap 51 and a drain valve 52 are provided in the drain discharge path 50 in order from the upstream side. The downstream side of the drain discharge path 50 is connected to an exhaust and drain path 54 via a drain switching valve 53, and a check valve 55 is provided in the exhaust and drain path 54.

[0022] The compressed air supply means 6 supplies compressed air from the compressed air source (compressor connection port) into the jacket 3. Specifically, the compressed air supply means 6 includes a compressed air supply passage 60, and the compressed air supply passage 60 is provided with a compressed air supply valve 61 and a check valve 62 in order from the upstream side.

[0023] The cooling water circulation means 7 is configured to supply cooling water from the chiller 100, which serves as the cooling water supply source, into the jacket 3, and to discharge the cooling water from within the jacket 3 and return it to the chiller 100. Specifically, the cooling water circulation means 7 comprises a supply water channel 70, a return water channel 80, and a bypass channel 90.

[0024] The supply water channel 70 connects the chiller 100 and the jacket 3, and is configured to supply cooling water from the chiller 100 to the jacket 3. A cooling water supply valve 71 is provided in the supply water channel 70. In this embodiment, the steam supply channel 40 downstream of the steam supply valve 41, the compressed air supply channel 60 downstream of the check valve 62, and the supply water channel 70 downstream of the cooling water supply valve 71 are connected to the jacket 3 as a common pipeline.

[0025] The condensate channel 80 connects the jacket 3 and the chiller 100 and is configured to return condensate from the jacket 3 to the chiller 100. The condensate channel 80 is equipped with, in order from the upstream side, a cooling water outlet valve 81, a drain switching valve 53, a check valve 82, a first temperature sensor 83, a mixing valve 84 as a mixing means, and a second temperature sensor 85. Here, the drain switching valve 53 is a three-way valve and is configured to switch between draining water (drain water or condensate) from the drain discharge channel 50 of the drain discharge means 5 or the condensate channel 80 through the exhaust drain channel 54 or returning it to the chiller 100 via the condensate channel 80. However, the drain switching valve 53 can be configured in any way as long as it can switch between draining and condensing. For example, the drain switching valve 53 may be replaced with a three-way valve and configured with a combination of two valves.

[0026] In this embodiment, the drain discharge channel 50 is connected to the condensate channel 80 at a position between the drain valve 52 and the drain switching valve 53, and the drain discharge channel 50 and the condensate channel 80 are a common pipeline from this connection point to the drain switching valve 53.

[0027] The bypass channel 90 is configured to bypass the supply channel 70 and the condensate channel 80. The bypass channel 90 is provided with a bypass valve 91. Specifically, one end of the bypass channel 90 is connected to the supply channel 70 at a position between the chiller 100 and the cooling water supply valve 71, and the other end is connected to the mixing valve 84. The mixing valve 84 mixes the condensate flowing through the condensate channel 80 with the cooling water from the chiller 100 and returns it to the chiller 100.

[0028] Furthermore, the mixing valve 84 in this embodiment is equipped with a thermo-element inside its body, and is configured to allow adjustment of the mixing ratio between the condensate flowing through the condensate passage 80 and the cooling water flowing through the bypass passage 90. Therefore, the mixing valve 84 is capable of returning the condensate flowing through the condensate passage 80 to the chiller 100 as water at a predetermined temperature T (for example, 30°C).

[0029] Since the mixing valve 84 is positioned as described above, in this embodiment, the first temperature sensor 83 is positioned on the jacket 3 side of the mixing valve 84, i.e., the connection point with the bypass passage 90 in the condensate 80. The second temperature sensor 85 is positioned on the chiller 100 side of the mixing valve 84 (the connection point with the bypass passage 90 in the condensate 80).

[0030] The control means 10 controls the various valves mentioned above based on detection signals from the first temperature sensor 83 and the second temperature sensor 85, as well as the elapsed time. Specifically, the control means 10 controls the steam supply valve 41, drain valve 52, drain switching valve 53, compressed air supply valve 61, cooling water supply valve 71, cooling water outlet valve 81, mixing valve 84, bypass valve 91, etc. As will be described later, the control means 10 performs the heating of food in the inner pot 2 and the subsequent cooling process according to a predetermined procedure (program).

[0031] The control means 10 described above can be specifically configured as an information processing device equipped with a CPU, memory (e.g., flash memory), an input unit, and an output unit. The processing performed by each of the above-mentioned components of the control means 10 configured by the information processing device is carried out by the CPU reading and executing a program stored in memory. Examples of information processing devices include personal computers, PLCs (programmable logic controllers), or microcontrollers. However, some functions of the control means 10 may be configured to be executed on a cloud connected by any communication means.

[0032] The chiller 100 comprises a refrigerator 101, a heat exchanger 102, and a chilled water tank 103. The chiller 100 cools the water in the chilled water tank 103 by circulating a refrigerant (not shown) between the refrigerator 101 and the heat exchanger 102 using a pump (not shown), and by circulating water (not shown) between the chilled water tank 103 and the heat exchanger 102 using a pump. The cooled water is supplied to the outside as cooling water via a cooling water outlet passage 105 by a cooling water pump 104. The condensate (circulated water) used for cooling is returned to the chilled water tank 103 via a condensate inlet passage 106. The configuration of the chiller 100 is not limited to the above; any chiller capable of supplying cooling water can be used.

[0033] 2. Operation of steam boiler 1 Next, the operation of the steam boiler 1 by the control means 10 will be described. The control means 10 controls various valves, etc., according to a predetermined procedure (program) to heat and then cool the food in the inner boiler 2. Before starting operation, that is, before each of these processes is executed, at least the steam supply valve 41, the compressed air supply valve 61, and the cooling water supply valve 71 are closed. When the start of operation is instructed, such as by pressing a predetermined start button, the control means 10, with the food contained in the inner boiler 2, sequentially executes the following, as shown in Figure 2: a heating process S1 to heat the food, a first compressed air supply process S2 to supply compressed air into the jacket 3, a first cooling process S3 and a second cooling process S4 to cool the food, and a second compressed air supply process S5 to supply compressed air into the jacket 3. Each process will be described in more detail below.

[0034] <Heating process S1> In heating step S1, the control means 10 supplies steam into the jacket 3 via the steam supply means 4 to heat the food in the inner pot 2. Specifically, the control means 10 opens the steam supply valve 41 with the compressed air supply valve 61 and the cooling water supply valve 71 closed, thereby supplying steam from the boiler (boiler connection port) into the jacket 3 via the steam supply passage 40. The control means 10 also opens the drain valve 52 and sets the drain switching valve 53 to the drain side. As a result, the condensed water (drain) from the steam supplied into the jacket 3 is discharged from the exhaust drain passage 54 via the drain discharge passage 50, which is equipped with a steam trap 51 (see Figure 3).

[0035] Then, after bringing the inside of the jacket 3 to the set heating pressure (set heating temperature), the food in the inner pot 2 is heated by maintaining that state. For example, the control means 10 adjusts the opening or closing of the steam supply valve 41 so as to maintain the pressure detected by the pressure sensor (not shown) installed in the jacket 3 at the set heating pressure. When predetermined termination conditions such as heating time are met, the control means 10 stops the supply to the inside of the jacket 3 by closing the steam supply valve 41 and moves on to the next process.

[0036] <First compressed air supply process S2> In the first compressed air supply step S2, the control means 10 supplies compressed air into the jacket 3 via the compressed air supply means 6. Specifically, the control means 10 opens the compressed air supply valve 61 while the steam supply valve 41 and the cooling water supply valve 71 are closed, thereby supplying compressed air from the compressed air source into the jacket 3 via the compressed air supply passage 60. Also, similar to the heating step S1, the control means 10 opens the drain valve 52, closes the cooling water outlet valve 81, and sets the drain switching valve 53 to the drain side. As a result, the compressed air supplied into the jacket 3 is discharged from the exhaust drain passage 54 via the drain discharge passage 50 (see Figure 4).

[0037] The first compressed air supply process S2 allows for the discharge of residual steam from the jacket 3 and also cools the jacket 3 and the inner boiler 2. After executing the first compressed air supply process S2 for a predetermined time, the control means 10 closes the compressed air supply valve 61 to proceed to the next process.

[0038] <First cooling process S3> In the first cooling process S3, the control means 10 supplies cooling water into the jacket 3 via the cooling water circulation means 7 to cool the food in the inner pot 2. Specifically, the control means 10 opens the cooling water supply valve 71 with the steam supply valve 41 and compressed air supply valve 61 closed, thereby supplying cooling water from the chiller 100 into the jacket 3 via the supply water passage 70. The control means 10 also closes the drain valve 52, opens the cooling water outlet valve 81, and sets the drain switching valve 53 to return to the chiller 100. As a result, the cooling water supplied into the jacket 3 is returned to the chilled water tank 103 of the chiller 100 via the condensate passage 80. This causes the cooling water to circulate between the chilled water tank 103 of the chiller 100 and the jacket 3.

[0039] In addition, during the first cooling process S3, the control means 10 controls the bypass valve 91 of the bypass passage 90 to open. As a result, a portion of the cooling water flowing through the supply passage 70 flows through the bypass passage 90 to the mixing valve 84 provided in the condensate passage 80. The mixing valve 84 then mixes the cooling water with the condensate, which has become hot after flowing through the heated jacket 3, and returns it to the chilled water tank 103 of the chiller 100 as water at a predetermined temperature T (see Figure 5).

[0040] Furthermore, if, immediately after the start of the first cooling process S3, it is determined that the temperature of the condensate returned to the chiller 100 will not reach a predetermined temperature T (or lower) even if the mixing ratio of the cooling water by the mixing valve 84 is set to the drain side for a predetermined time until the temperature of the inner casing 2 drops to a certain extent (see Figure 6). In this case, the control means 10 keeps the bypass valve 91 of the bypass passage 90 closed. This prevents the condensate from being returned to the chiller 100 at a high temperature, thereby protecting the condensate passage 80 and the condensate inlet passage 106 of the chiller 100.

[0041] The control means 10 continues the first cooling process S3 as long as the temperature of the condensate detected by the first temperature sensor 83, which is located on the jacket 3 side of the mixing valve 84, exceeds a predetermined temperature T, and proceeds to the next process when the temperature of the condensate falls below the predetermined temperature T.

[0042] <Second cooling process S4> In the second cooling step S4, the control means 10 supplies cooling water into the jacket 3 via the cooling water circulation means 7, similar to the first cooling step S3, to cool the food in the inner pot 2. However, in the second cooling step S4, the control means 10 closes the bypass valve 91 to prevent cooling water from flowing through the bypass passage 90. As a result, all the cooling water from the chiller 100 is supplied into the jacket 3 (see Figure 7).

[0043] During the first cooling process S3 and the second cooling process S4, the control means 10 constantly monitors whether the temperature of the condensate returned to the chiller 100, as detected by the second temperature sensor 85, has reached a predetermined temperature T. If the control means 10 determines that condensate at a temperature exceeding the predetermined temperature T is being returned to the chiller 100, it sets the drain switching valve 53 to the drain side to drain the condensate, stops the cooling process, or issues a warning. With this configuration, even if a malfunction occurs in the mixing valve 84 or the like, it is possible to prevent high-temperature water from flowing to the chiller 100, thereby protecting the piping such as the condensate inlet passage 106 of the chiller 100.

[0044] <Second compressed air supply process S5> In the second compressed air supply step S5, similar to the first compressed air supply step S2, the control means 10 supplies compressed air into the jacket 3 via the compressed air supply means 6. Specifically, the control means 10 opens the compressed air supply valve 61 with the steam supply valve 41 and the cooling water supply valve 71 closed, thereby supplying compressed air from the compressed air source into the jacket 3 via the compressed air supply passage 60. The control means 10 also opens the drain valve 52, closes the cooling water outlet valve 81, and sets the drain switching valve 53 to the drain side. As a result, the compressed air supplied into the jacket 3 is discharged from the exhaust drain passage 54 via the drain discharge passage 50 (see Figure 4).

[0045] The second compressed air supply step S5 allows residual water in the jacket 3 to be discharged, preventing water hammer from occurring in the next heating step S1. After the second compressed air supply step S5 has been performed for a predetermined time, the control means 10 closes at least the compressed air supply valve 61. This completes the series of heating and cooling steps performed by the steam kettle 1.

[0046] 3. Effects As described above, the steam boiler 1 of this embodiment is configured such that the cooling water circulation means 7 is equipped with a bypass passage 90 that bypasses the supply passage 70 and the condensate passage 80, and the cooling water from the chiller 100 flowing through the bypass passage 90 via the mixing valve 84 can be mixed with the condensate flowing through the condensate passage 80 (first cooling step S3). By adjusting the mixing ratio of the cooling water and condensate using the mixing valve 84, the temperature of the condensate returned to the chiller 100 (chiller 100's chilled water tank 103) can be set to a predetermined temperature (or lower). Because the steam boiler 1 of this embodiment is configured in this way, even if the condensate from the jacket 3 is at a high temperature, the condensate is cooled by the cooling water, making it possible to protect the piping that returns the condensate to the cooling water supply source without draining it. Such a configuration is particularly effective when the benefit of reducing the amount of chiller water used is greater than the benefit of rapidly cooling food.

[0047] Furthermore, in this embodiment, the steam boiler 1 is configured to supply all the cooling water to the jacket 3 during the second cooling step S4, which is performed when the condensate temperature has decreased. This makes it possible to increase the cooling rate in the second cooling step S4 compared to the first cooling step S3.

[0048] 4. Variations Furthermore, the present invention can also be implemented in the following embodiments.

[0049] In the above embodiment, the mixing means for mixing cooling water with condensate and keeping the condensate temperature below a predetermined temperature was a mixing valve 84. However, the mixing means for keeping the condensate temperature below a predetermined temperature is not limited to a mixing valve 84. For example, as shown in Figure 8, the mixing means according to the present invention can also be composed of a first temperature sensor 83 located on the jacket 3 side of the connection point with the bypass passage 90 in the condensate passage 80, and a bypass valve 91 provided in the bypass passage 90 as an adjustable valve. Specifically, the control means 10 according to this modified example provides feedback control of the opening degree of the bypass valve 91 based on the temperature of the first temperature sensor 83. This makes it possible to adjust the mixing ratio of cooling water to the condensate returned to the chiller 100 and maintain the temperature of the condensate returned to the chiller 100 at a predetermined temperature (or below a predetermined temperature).

[0050] In the above embodiment, the operation of various valves was controlled by the control means 10, but the operation of some or all of the valves may be performed manually.

[0051] In the above embodiment, the inner pot 2 was heated with its top open. However, the present invention can also be used in a vacuum pot in which a lid is provided on the inner pot 2 and the inside of the inner pot 2 is heated under reduced pressure.

[0052] In the above embodiment, when the temperature of the condensate detected by the second temperature sensor 85 was above a predetermined temperature T, the drain switching valve 53 was set to the drain side and all the condensate was drained. However, it is also effective to make the drain switching valve 53 an adjustable valve so that some of the condensate is drained and some of the condensate is returned to the chiller 100 according to the temperature of the condensate detected by the second temperature sensor 85. [Explanation of Symbols]

[0053] 1: Steam boiler 2: Inner pot 3: Jacket 4: Steam supply means 5: Drain discharge means 6: Compressed air supply means 7: Cooling water circulation means 10: Control means 40:Steam supply path 41:Steam supply valve 50: Drain discharge channel 51: Steam trap 52: Drain valve 53: Drain switching valve 54: Exhaust and drainage channel 55: Check valve 60: Compressed air supply path 61: Compressed air supply valve 62: Check valve 70:Outgoing waterway 71: Cooling water supply valve 80: Return channel 81: Cooling water outlet valve 82: Check valve 83: First temperature sensor 84: Mixing valve (mixing means) 85: Second temperature sensor 90: Bypass Road 91: Bypass valve 100: Chiller (cooling water supply source) 101: Refrigeration unit 102:Heat exchanger 103: Cold water tank 104: Cooling water pump 105: Cooling water outlet path 106: Fushui Inlet Road S1: Heating process S2: First compressed air supply process S3: 1st cooling process S4: 2nd cooling process S5: Second compressed air supply process T: Predetermined temperature

Claims

1. A steam boiler comprising an inner boiler containing a material to be processed, a jacket provided on the outside of the inner boiler, a steam supply means for supplying steam to the jacket, and a cooling water circulation means for circulating the cooling water between the jacket and a cooling water supply source, The cooling water circulation means comprises a supply channel, a return channel, a bypass channel, and a mixing means. The aforementioned supply channel is configured to supply cooling water from the cooling water supply source to the jacket, The condensate channel is configured to return condensate from the jacket to the cooling water supply source. The bypass road is configured to bypass the supply channel and the return channel, The mixing means is configured to mix cooling water from the cooling water supply source with the condensate flowing through the condensate channel via the bypass channel, so that the temperature of the condensate returned to the cooling water supply source is below a predetermined temperature.

2. A steam kettle according to claim 1, The aforementioned condensate channel is provided with a drain switching valve. The drain switching valve is configured to switch between draining the condensate or returning it to the cooling water supply source, depending on the temperature of the condensate, in a steam boiler.

3. A steam boiler according to claim 1 or claim 2, The mixing means is a steam boiler, which is a mixing valve provided in the condensate.

4. A steam kettle according to any one of claims 1 to 3, A steam boiler is provided with a first temperature sensor located on the jacket side of the connection point between the condensate and the bypass, and a bypass valve in the bypass.

5. A steam kettle according to claim 4, The bypass valve is opened and closed according to the temperature of the condensate detected by the first temperature sensor in the steam boiler.

6. A steam kettle according to claim 5, The mixing means consists of the first temperature sensor and the bypass valve. The bypass valve is a control valve whose opening degree can be adjusted. The mixing means is configured to adjust the opening of the bypass valve according to the temperature of the condensate detected by the first temperature sensor, thereby keeping the temperature of the condensate below a predetermined temperature, in a steam boiler.

7. A steam kettle according to any one of claims 1 to 6, A steam boiler is provided with a second temperature sensor located on the cooling water supply source side of the connection point between the condensate and the bypass.

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