Desulfurizing tower with embedded phase change heat storage device and dynamic control method for heat storage and desulfurization process

Abstract

The invention discloses a desulfurization tower with an embedded phase change heat storage device and a dynamic control method for heat storage and desulfurization processes. The desulfurization tower comprises a desulfurization tower body, a flue gas inlet is formed in the side bottom of the desulfurization tower body, and a flue gas outlet is formed in the top of the desulfurization tower body; a desulfurization slurry inlet is formed in the side top of the desulfurization tower body, and a desulfurization slurry outlet is formed in the bottom; a heat storage pipe assembly layer is arranged on the inner wall of the desulfurization tower body, the heat storage pipe assembly layer is non-uniformly distributed on the inner wall of the desulfurization tower body, the heat storage pipe assembly layer is filled with a phase change material, and the heat storage pipe assembly layer absorbs heat in the flue gas desulfurization process and stores the heat; a heat exchange strengthening structure is arranged on the outer surface of the heat storage pipe assembly layer and used for heat exchange in the flue gas desulfurization process; a temperature control valve is arranged outside the desulfurizing tower body, is connected with the heat storage pipe assembly layer, is externally connected with a heating system, and controls heat storage and heat release of the heat storage pipe assembly layer to the heating system.

Description

Technical Field

[0001] This application belongs to the technical field of flue gas desulfurization and waste heat recovery, and specifically refers to a desulfurization tower embedded with a phase change heat storage device and a dynamic control method for heat storage and desulfurization processes. Background Art

[0002] In conventional flue gas desulfurization technologies, most use the limestone-gypsum method to desulfurize high-temperature flue gas. This method directly discharges the high-temperature flue gas after absorbing its heat with limestone-gypsum slurry. In this method, the waste heat utilization rate of high-temperature flue gas is less than 20%, resulting in waste of heat.

[0003] Moreover, using this traditional method, the temperature of the limestone-gypsum slurry will fluctuate around 50 - 80 °C, leading to a decrease in desulfurization efficiency. Therefore, additional temperature control equipment is required to maintain the stable temperature of the limestone-gypsum slurry, which will increase energy consumption. And the traditional heat storage system needs an external heat storage tank and heat exchanger, and the pipeline heat loss is more than 15%, resulting in waste of heat. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, this application provides a desulfurization tower embedded with a phase change heat storage device and a dynamic control method for heat storage and desulfurization processes. The phase change heat storage device integrated inside directly absorbs the waste heat of the desulfurization slurry and releases it to the heating system, improving the heat absorption efficiency.

[0005] The present invention provides a desulfurization tower embedded with a phase change heat storage device, including: a desulfurization tower body. The side bottom of the desulfurization tower body is provided with a flue gas inlet, and the top is provided with a flue gas outlet. The side top of the desulfurization tower body is provided with a desulfurization slurry inlet, and the bottom is provided with a desulfurization slurry outlet;

[0006] A layer of heat storage pipe assembly layer is arranged on the inner wall of the desulfurization tower body. The heat storage pipe assembly layer is non-uniformly distributed on the inner wall of the desulfurization tower body. The heat storage pipe assembly layer is filled with a phase change material inside, and the heat storage pipe assembly layer absorbs and stores the heat during the flue gas desulfurization process;

[0007] The outer surface of the heat storage pipe assembly layer is provided with a heat transfer enhancement structure for heat exchange during the flue gas desulfurization process;

[0008] A temperature control valve is arranged outside the desulfurization tower body. The temperature control valve is connected to the heat storage pipe assembly layer. The temperature control valve is externally connected to the heating system, and the temperature control valve controls the heat storage and heat release of the heat storage pipe assembly layer to the heating system.

[0009] Further, for the desulfurization tower with the embedded phase change heat storage device provided by the present application, the heat storage tube assembly layer includes heat storage tubes arranged in a spiral trajectory, and the pitch of the spiral arrangement of the heat storage tubes is 1.2 - 1.5 times the tube diameter.

[0010] Further, for the desulfurization tower with the embedded phase change heat storage device provided by the present application, the inner surface of the heat storage tube is a stainless steel tube wall surface or a silicon carbide ceramic wall surface, the outer surface of the heat storage tube is a polytetrafluoroethylene anti-corrosion layer, and the inside of the heat storage tube is a phase change material filling layer and an expansion buffer layer, and the expansion buffer layer is arranged at intervals between the material filling layers.

[0011] Further, for the desulfurization tower with the embedded phase change heat storage device provided by the present application, the phase change material in the phase change material filling layer includes a paraffin wax and expanded graphite composite, and the mass ratio of the paraffin wax to the expanded graphite composite is 9:1.

[0012] Further, for the desulfurization tower with the embedded phase change heat storage device provided by the present application, the phase change material filling layer further contains pre-mixed nano-thermal conductive particles with an addition amount of 5 wt% of aluminum oxide material, and the phase change temperature of the phase change material filling layer is 50 - 80 °C.

[0013] Further, for the desulfurization tower with the embedded phase change heat storage device provided by the present application, a desulfurization slurry spraying layer is arranged inside the desulfurization tower body, the desulfurization slurry spraying layer is connected to the desulfurization slurry inlet, and the desulfurization slurry spraying layer includes a plurality of slurry spraying nozzles.

[0014] Further, for the desulfurization tower with the embedded phase change heat storage device provided by the present application, the outer surface of the heat transfer enhancement structure is in a corrugated shape or a fin shape.

[0015] Further, for the desulfurization tower with the embedded phase change heat storage device provided by the present application, a temperature sensor is further arranged at the bottom of the desulfurization tower body, the temperature sensor is connected to the temperature control valve, and the temperature control valve is linked with the desulfurization slurry outlet through the temperature sensor to control the release of heat.

[0016] Further, for the desulfurization tower with the embedded phase change heat storage device provided by the present application, the response time of the opening and closing valve of the temperature control valve ≤ 30 seconds.

[0017] The present application also provides a dynamic control method for heat storage and desulfurization processes of a desulfurization tower with the embedded phase change heat storage device described in the present application, including:

[0018] Setting according to time into a day mode and a night mode, where 8:00 - 18:00 is set as the day mode, and 18:00 - 8:00 is set as the night mode;

[0019] In the daytime mode, when the temperature of the desulfurization slurry is greater than 75°C, the temperature control valve is closed for desulfurization and heat storage; wherein, the temperature at which the temperature control valve closes can be set according to requirements;

[0020] In the nighttime mode, when the temperature of the desulfurization slurry is less than 55°C, the temperature control valve is opened to release the heat of the heat storage pipe assembly layer to the external heating system; wherein, the temperature at which the temperature control valve opens can be set according to requirements.

[0021] The beneficial effects of the present invention are as follows: The present application provides a desulfurization tower with an embedded phase change heat storage device and a dynamic control method for heat storage and desulfurization processes. By embedding a phase change heat storage unit inside the desulfurization tower to absorb and store the heat during the flue gas desulfurization process, the external heat storage device is eliminated. By directly absorbing the waste heat of the desulfurization slurry and releasing it to the heating system, the cascade utilization of energy and the optimization of desulfurization efficiency are realized. And by stabilizing the temperature fluctuation of the slurry during the heat storage / heat release process, the stability of the desulfurization reaction is improved. The dynamic control method for heat storage and desulfurization processes, through the temperature control valve, ensures the efficiency of flue gas desulfurization and the dynamic coordination of heat storage and desulfurization processes, matches the nighttime heat release period with the peak heating demand, and improves the utilization rate of flue gas heat. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The following, in conjunction with the drawings, through a detailed description of the specific embodiments of the present application, will make the technical solutions and other beneficial effects of the present application obvious.

[0023] Figure 1 It is a schematic structural diagram of a desulfurization tower with an embedded phase change heat storage device provided by an embodiment of the present application.

[0024] Figure 2 It is a cross-sectional schematic diagram of the heat storage pipe structure provided by this embodiment.

[0025] Figure 3 It is a schematic flow diagram of a dynamic control method for heat storage and desulfurization processes of a desulfurization tower with an embedded phase change heat storage device provided based on this embodiment

[0026] The reference numerals of each component in the figure are as follows: desulfurization tower body 1, desulfurization slurry spraying layer 2, heat storage pipe assembly layer 3, heat transfer enhancement structure 4, temperature control valve 5, temperature sensor 6, inner surface a of the heat storage pipe, polytetrafluoroethylene anti-corrosion layer b, phase change material filling layer c, expansion buffer layer d. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present application.

[0028] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present application. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the described features. In the description of the present application, "a plurality" means two or more, unless otherwise specifically defined.

[0029] The following disclosure provides many different embodiments or examples for implementing different structures of the present application. To simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are only examples and are not intended to limit the present application. In addition, the present application may repeat reference numerals and / or reference letters in different examples. Such repetition is for the purpose of simplification and clarity and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0030] The embodiments of the present application will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0031] Figure 1 It is a schematic structural diagram of a desulfurization tower of an embedded phase change heat storage device provided for the embodiments of the present application.

[0032] As Figure 1As shown in the figure, this embodiment provides a desulfurization tower with an embedded phase change heat storage device, which includes a desulfurization tower body 1. A flue gas inlet is provided at the side bottom of the desulfurization tower body 1, and a flue gas outlet is provided at the top. A desulfurization slurry inlet is provided at the side top of the desulfurization tower body 1, and a desulfurization slurry outlet is provided at the bottom. The high-temperature flue gas is arranged to enter from the bottom and exit from the top, and the desulfurization slurry is arranged to enter from the top and exit from the bottom, which can increase the contact time between the flue gas and the desulfurization slurry and improve the desulfurization efficiency of the high-temperature flue gas. A layer of heat storage pipe assembly layer 3 is provided on the inner wall of the desulfurization tower body 1. The heat storage pipe assembly layer 3 is unevenly distributed on the inner wall of the desulfurization tower body 1. The heat storage pipe assembly layer 3 is filled with a phase change material, and the heat storage pipe assembly layer 3 absorbs and stores the heat during the flue gas desulfurization process. By directly embedding the phase change heat storage unit in the desulfurization tower body 1, the external energy storage device can be omitted, greatly improving the heat storage efficiency and reducing the heat loss. A heat transfer enhancement structure 4 is provided on the outer surface of the heat storage pipe assembly layer 3 for heat exchange during the flue gas desulfurization process. The heat transfer enhancement structure 4 exchanges heat with the high-temperature flue gas and absorbs the heat of the high-temperature flue gas. A temperature control valve 5 is provided outside the desulfurization tower body 1. The temperature control valve 5 is connected to the heat storage pipe assembly layer 3. The temperature control valve 5 is externally connected to a heating system, and the temperature control valve 5 controls the heat storage and heat release of the heat storage pipe assembly layer 3 to the heating system.

[0033] Specifically, in this embodiment, the high-temperature sulfur-containing flue gas enters the desulfurization tower through the flue gas inlet provided at the side bottom of the desulfurization tower body 1, and the desulfurization slurry is poured into the desulfurization slurry inlet provided at the side top of the desulfurization tower body 1. Inside the desulfurization tower, the high-temperature sulfur-containing flue gas reacts with the desulfurization slurry for desulfurization and exchanges heat through the heat transfer enhancement structure 4. The heat storage pipe assembly layer 3 stores the exchanged heat. Heat exchange or heat storage through the heat storage pipe assembly layer 3 and the heat transfer enhancement structure 4 can maintain and stabilize the temperature of the desulfurization slurry within a small range during the flue gas desulfurization process, so that the temperature of the flue gas desulfurization is always at an appropriate temperature. At the same time, the heat stored in the heat storage pipe assembly layer 3 can be delivered to the externally connected heating system through the temperature control valve 5, greatly improving the utilization efficiency of the waste heat during the flue gas desulfurization process.

[0034] Such as Figure 1As shown, the heat storage pipe assembly layer 3 includes heat storage pipes arranged in a spiral trajectory, and the pitch of the spiral of the heat storage pipes is 1.2 - 1.5 times the pipe diameter. Specifically, in this embodiment, an annular bracket is welded on the inner wall of the desulfurization tower body 1, and the heat storage pipes are arranged on the annular bracket according to the spiral trajectory. The spirally arranged heat storage pipes increase the contact area and contact time between the heat storage pipes and the high-temperature flue gas, which can effectively improve the heat storage efficiency of the heat storage pipes. In this embodiment, the pipe diameter of the heat storage pipes is set to 80 mm, and the spiral pitch is 100 mm. The pipe diameter and spiral pitch of the heat storage pipes can be adjusted according to actual needs.

[0035] Figure 2 It is a cross-sectional schematic diagram of the heat storage pipe structure provided in this embodiment.

[0036] As Figure 2 shown, the heat storage pipes are embedded in the inner wall of the desulfurization tower, and the inner surface a of the heat storage pipes is made of stainless steel or silicon carbide ceramic material. Among them, the stainless steel material can be 316L type stainless steel.

[0037] The outer surface of the heat storage pipes is a polytetrafluoroethylene anti-corrosion layer b, and the thickness of the polytetrafluoroethylene anti-corrosion layer b coated on the outer wall of the heat storage pipes is 0.2 mm - 0.5 mm, and this polytetrafluoroethylene anti-corrosion layer b can withstand a corrosion environment with pH = 4 - 6. In this embodiment, the curing process of the polytetrafluoroethylene anti-corrosion layer b uses baking at 150 °C for 2 hours; the thickness tolerance of the polytetrafluoroethylene anti-corrosion layer b is ±0.05 mm.

[0038] Inside the heat storage pipes are a phase change material filling layer c and an expansion buffer layer d, and the expansion buffer layer d is arranged at intervals between the material filling layers. The phase change material of the phase change material filling layer c includes a paraffin and expanded graphite composite, and the mass ratio of the paraffin to the expanded graphite composite is 9:1. The phase change material filling layer c also contains pre-mixed nano-thermal conductive particles with an addition amount of 5 wt% of aluminum trioxide material, and the phase change temperature of the phase change material filling layer c is 50 - 80 °C. The expansion buffer layer d reserves a 12% volume expansion space. Among them, the phase change material of the phase change material filling layer c can also be other combined materials that meet the needs, which will not be elaborated here.

[0039] As Figure 1As shown, a desulfurization slurry spraying layer 2 is provided inside the desulfurization tower body 1. The desulfurization slurry spraying layer 2 is connected to the desulfurization slurry inlet, and the desulfurization slurry spraying layer 2 includes a plurality of slurry spraying nozzles. Specifically, the liquid inlet pipe of the desulfurization slurry spraying layer 2 is connected to the desulfurization slurry inlet, and a plurality of slurry spraying nozzles are arranged below the desulfurization slurry spraying pipe. The desulfurization slurry is sprayed out from the slurry spraying nozzles to carry out a desulfurization reaction with the high-temperature flue gas inside the desulfurization tower. The arrangement of the plurality of slurry spraying nozzles can increase the contact area between the desulfurization slurry and the high-temperature flue gas, and improve the desulfurization reaction efficiency of the desulfurization slurry and the high-temperature flue gas.

[0040] In this embodiment, the outer surface of the heat transfer enhancement structure 4 is in a corrugated shape or a fin shape. The heat transfer enhancement structure 4 in a corrugated shape or a fin shape can increase the contact area with the high-temperature flue gas, and its contact area is increased by more than 40%, improving the heat transfer efficiency.

[0041] A temperature sensor 6 is further arranged at the bottom of the desulfurization tower body 1. The temperature sensor 6 is connected to the temperature control valve 5, and the temperature control valve 5 is linked with the desulfurization slurry outlet through the temperature sensor 6 to control the release of heat. Among them, the response time of the temperature control valve 5 to open and close the valve ≤ 30 seconds. In this embodiment, through the linkage control of the temperature sensor 6 and the temperature control valve 5, the temperature of the desulfurization slurry can be maintained and stabilized within a small range during the flue gas desulfurization process, so that the temperature of the flue gas desulfurization is always at an appropriate temperature. And the waste heat is delivered to the external heating system on the premise of meeting the desulfurization reaction, which not only gives priority to ensuring the heat storage / heat release logic of the desulfurization efficiency, but also greatly improves the utilization efficiency of the waste heat during the flue gas desulfurization process.

[0042] Figure 3 It is a schematic flow chart of the heat storage and desulfurization process dynamic control method of the desulfurization tower with an embedded phase change heat storage device provided based on this embodiment.

[0043] As Figure 3 shown, the control method includes:

[0044] Set to a daytime mode and a nighttime mode according to time, where 8:00 - 18:00 is set to the daytime mode, and 18:00 - 8:00 is set to the nighttime mode;

[0045] In the daytime mode, if the temperature of the desulfurization slurry is greater than 75 °C, the temperature control valve 5 is closed for desulfurization and heat storage; among them, the temperature at which the temperature control valve 5 is closed can be set according to requirements;

[0046] In the nighttime mode, if the temperature of the desulfurization slurry is less than 55 °C, the temperature control valve 5 is opened to release the heat of the heat storage pipe assembly layer 3 to the external heating system; among them, the temperature at which the temperature control valve 5 is opened can be set according to requirements.

[0047] In this embodiment, an innovative control is carried out on the heat storage and desulfurization processes of the desulfurization tower, dynamically coordinating the heat storage and desulfurization processes. The matching of the heat release period at night with the peak heating demand improves the utilization rate of the flue gas heat.

[0048] This application provides a desulfurization tower embedded with a phase change heat storage device and a dynamic control method for heat storage and desulfurization processes. By embedding a phase change heat storage unit inside the desulfurization tower to absorb and store the heat during the flue gas desulfurization process, the external heat storage device is omitted. By directly absorbing the waste heat of the desulfurization slurry and releasing it to the heating system, the cascade utilization of energy and the optimization of desulfurization efficiency are realized. And by suppressing the temperature fluctuation of the slurry during the heat storage / release process, the stability of the desulfurization reaction is improved. The dynamic control method for heat storage and desulfurization processes ensures the efficiency of flue gas desulfurization and the dynamic coordination of heat storage and desulfurization processes through the temperature control valve 5, matches the heat release period at night with the peak heating demand, and improves the utilization rate of the flue gas heat.

[0049] Although the preferred embodiments of the embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they know the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the present invention. Finally, it should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or terminal device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or terminal device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the existence of additional identical elements in the process, method, article or terminal device comprising the element.

[0050] The above has introduced in detail a desulfurization tower embedded with a phase change heat storage device and a dynamic control method for heat storage and desulfurization processes provided by the embodiments of this application. Specific examples are used in this article to elaborate on the principle and implementation manner of this application. The description of the above embodiments is only used to help understand the technical solution and its core idea of this application; those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A desulfurization tower with a built-in phase change heat storage device, characterized in that: include: A desulfurization tower body, wherein the bottom of the desulfurization tower body is provided with a flue gas inlet, the top of the desulfurization tower body is provided with a flue gas outlet, the top of the desulfurization tower body is provided with a desulfurization slurry inlet, and the bottom of the desulfurization tower body is provided with a desulfurization slurry outlet; A heat storage tube assembly layer is arranged on the inner wall of the desulfurization tower body, the heat storage tube assembly layer is unevenly distributed on the inner wall of the desulfurization tower body, the heat storage tube assembly layer is filled with phase change material, and the heat storage tube assembly layer absorbs and stores heat in the flue gas desulfurization process; The outer surface of the heat storage tube assembly layer is provided with a heat exchange enhancement structure to perform heat exchange during the flue gas desulfurization process; A temperature control valve is provided on the outside of the desulfurization tower body, the temperature control valve is connected to the heat storage tube assembly layer, the temperature control valve is externally connected to a heating system, and the temperature control valve controls the heat storage of the heat storage tube assembly layer and the heat release to the heating system.

2. The desulfurization tower with a built-in phase change heat storage device according to claim 1, characterized in that: The heat storage tube assembly layer includes heat storage tubes arranged along a spiral trajectory, and the spiral pitch of the spirally arranged heat storage tubes is 1.2-1.5 times the tube diameter.

3. The desulfurization tower with a built-in phase change heat storage device according to claim 2, characterized in that: The inner surface of the heat storage tube is a stainless steel tube wall or a silicon carbide ceramic wall, the outer surface of the heat storage tube is a polytetrafluoroethylene anti-corrosion layer, the interior of the heat contact tube is a phase change material filling layer and an expansion buffer layer, and the expansion buffer layer is arranged between the material filling layers.

4. The desulfurization tower with a built-in phase change heat storage device according to claim 3, characterized in that: The phase change material of the phase change material filling layer includes a composite of paraffin wax and expanded graphite, and the mass ratio of the paraffin wax to the expanded graphite composite is 9:

1.

5. The desulfurization tower with a built-in phase change heat storage device according to claim 4, characterized in that: The phase change material filling layer further comprises premixed nano thermal conductive particles of aluminum oxide material with an addition amount of 5 wt %. The phase change temperature of the phase change material filling layer is 50-80° C.

6. The desulfurization tower with a built-in phase change heat storage device according to claim 1, characterized in that: A desulfurization slurry spraying layer is arranged inside the desulfurization tower body, the desulfurization slurry spraying layer is connected to the desulfurization slurry inlet, and the desulfurization slurry spraying layer includes a plurality of slurry spraying ports.

7. The desulfurization tower with a built-in phase change heat storage device according to claim 1, characterized in that: The outer surface of the heat exchange enhancement structure is in a corrugated shape or a fin shape.

8. The desulfurization tower with a built-in phase change heat storage device according to claim 1, characterized in that: A temperature sensor is also provided at the bottom of the desulfurization tower body. The temperature sensor is connected to the temperature control valve. The temperature control valve controls the release of heat through the linkage between the temperature sensor and the desulfurization slurry outlet.

9. The desulfurization tower with a built-in phase change heat storage device according to claim 8, characterized in that: The response time of opening and closing the temperature control valve is ≤30 seconds.

10. A method for dynamically controlling heat storage and desulfurization process of a desulfurization tower with an embedded phase change heat storage device according to any one of claims 1 to 9, characterized in that: include: Set to day mode and night mode according to the time, 8:00-18:00 is set to day mode, 18:00-8:00 is set to night mode; In the daytime mode, if the temperature of the desulfurized slurry is greater than 75°C, the temperature control valve is closed to perform desulfurization and heat storage. The temperature at which the temperature control valve is closed can be set according to demand. In night mode, if the temperature of the desulfurization slurry is less than 55°C, the temperature control valve is opened to release the heat of the heat storage pipe assembly layer to the external heating system; the temperature at which the temperature control valve opens can be set according to demand.

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