Centrifugal vapor compression system and control method thereof

Abstract

The invention discloses a centrifugal steam compression system and a control method thereof, the system comprises a flash tank and a centrifugal steam compressor, an air outlet of the centrifugal steam compressor is communicated with an air outlet main path and a backflow branch, and the air outlet of the centrifugal steam compressor is communicated with the flash tank through the backflow branch. Compared with the prior art, the backflow branch is arranged at the air outlet of the centrifugal steam compressor, when the centrifugal steam compressor enters the low-load working condition, redundant steam output by the compressor can flow back into the flash tank through the backflow branch, water for steam generation of the flash tank is heated, and the steam generation efficiency of the flash tank is improved. And therefore, energy consumed by water for heating steam generation is reduced, the low-load operation range of the centrifugal steam compressor is widened, meanwhile, redundant heat recovery is achieved, and the economical efficiency of the system is improved.

Description

Technical Field

[0001] The present application belongs to the field of steam heating technology, and in particular relates to a centrifugal steam compression system and a control method thereof. Background Art

[0002] Steam is widely used for heating in industrial applications, and one source of steam is an open-loop steam heat pump. This type of system typically consists of a water purification and deaeration system, a water pump, a heat pump (optional when the heat source temperature is too low), a steam generator, a steam compressor, a steam cooler, and supporting piping, valves, and a power supply. After being filtered through the water purification and deaeration system, tap water is fed into the steam generator for heat exchange with the heat source. The water absorbs heat and evaporates, converting it into low-pressure steam. This steam is then compressed by the steam compressor into high-temperature, high-pressure steam for industrial use.

[0003] Centrifugal steam compressors play a vital role in steam heating due to their large capacity and high efficiency, but they also have significant drawbacks: a narrow capacity adjustment range, typically between 80% and 100%. Centrifugal compressors are speed-type compressors, and to ensure a sufficient compression ratio, the speed must be maintained at a high level. However, if the suction flow rate decreases too much at high speeds, the impeller loses its force and surges, resulting in a loss of force applied to the impeller. Therefore, centrifugal compressor capacity cannot be adjusted over a wide range. Positive displacement compressors, such as screw and piston compressors, compress gas by changing the volume of the compression chamber. The rotor speed has little effect on the pressure ratio, allowing for wide capacity adjustment without changing the pressure ratio. The capacity adjustment range is generally between 30% and 100%.

[0004] To expand the operating range of centrifugal steam compressors, the industry currently uses a recirculation method. This involves reducing the temperature and pressure of a portion of the high-pressure exhaust gas before re-introducing it into the intake, allowing only a portion of the steam to exit the compression system for air supply. While this method expands the compressor's operating range, it also results in significant energy waste and negatively impacts the unit's overall efficiency. Summary of the Invention

[0005] In view of this, an embodiment of the present application provides a centrifugal steam compression system and a control method thereof to solve at least one of the above technical problems.

[0006] A first embodiment of the present application provides a centrifugal steam compression system, comprising:

[0007] A flash tank and a centrifugal steam compressor, wherein the gas outlet of the centrifugal steam compressor is connected to a gas outlet main path and a return branch path respectively, and the gas outlet of the centrifugal steam compressor and the flash tank are connected via the return branch path;

[0008] The flash tank is used to flash the steam generating water heated to a specified flash temperature into low-pressure steam under negative pressure conditions in the tank;

[0009] The centrifugal steam compressor is used to compress the low-pressure steam into superheated steam whose saturation pressure is the target condensing pressure.

[0010] The centrifugal steam compression system of the first embodiment of the present application is provided with a reflux branch at the outlet of the centrifugal steam compressor. When the centrifugal steam compressor enters a low-load operating condition, excess steam output by the compressor can flow back into the flash tank through the reflux branch to heat the water used for steam generation in the flash tank. This reduces the energy consumed in heating the water used for steam generation, expands the low-load operating range of the centrifugal steam compressor, and simultaneously recovers excess heat, thereby improving the economic efficiency of the system.

[0011] In one possible implementation, the system further includes: a first control valve and a second control valve;

[0012] The first control valve is used to control the amount of steam output from the main gas outlet;

[0013] The second control valve is used to control the flow of the reflux branch.

[0014] In one possible implementation, the system further includes:

[0015] The heat pump is used to extract waste heat from the heat source and release it into the water used for steam generation, thereby raising the temperature of the water used for steam generation to the specified flash temperature.

[0016] In one possible implementation, the heat pump includes a heat pump evaporator, a heat pump compressor, a heat pump condenser, and a heat pump throttle valve;

[0017] The heat pump evaporator extracts waste heat from the heat source, and the heat pump condenser releases the waste heat from the heat source into the water inlet pipe of the flash tank to heat the water for steam generation in the water inlet pipe of the flash tank.

[0018] In a possible implementation, the flash tank is provided with an air return port, and the air outlet of the centrifugal steam compressor and the air return port of the flash tank are connected via the reflux branch.

[0019] In a possible implementation, the air outlet of the centrifugal steam compressor and the water inlet pipe of the flash tank are connected via the reflux branch.

[0020] In a possible implementation, the position where the reflux branch is connected to the water inlet pipe of the flash tank is located on the pipeline through which the water used for steam generation flows after being heated.

[0021] In a possible implementation, the position where the reflux branch is connected to the water inlet pipe of the flash tank is located on the pipeline through which the water used for steam generation flows before being heated.

[0022] A control method for a centrifugal steam compression system according to a second aspect of the present application includes:

[0023] Determine whether the set value of the system's steam output is less than or equal to the system's normal minimum steam output threshold;

[0024] According to the set value being less than or equal to the system's normal minimum air output threshold, controlling the centrifugal steam compression system to enter or maintain an air return control mode;

[0025] The return air control mode includes:

[0026] Opening the second control valve to open the reflux branch; controlling the first control valve and the second control valve so that the output steam volume of the centrifugal steam compression system reaches the set value;

[0027] According to the water temperature in the flash tank exceeding the set temperature range, the operating frequency of the heat pump is adjusted until the water temperature in the flash tank is within the set temperature range.

[0028] In a second embodiment of the present application, a control method for a centrifugal steam compression system is provided with a return branch at the outlet of the centrifugal steam compressor. When the centrifugal steam compressor enters a low-load operating condition, excess steam output by the compressor can flow back into the flash tank through the return branch to heat the water used for steam generation in the flash tank. This reduces the energy consumed in heating the water used for steam generation, expands the low-load operating range of the centrifugal steam compressor, and simultaneously recovers excess heat, thereby improving the economic efficiency of the system.

[0029] In one possible implementation, adjusting the operating frequency of the heat pump according to the water temperature in the flash tank exceeding a set temperature range includes:

[0030] According to the water temperature in the flash tank being higher than the upper limit of the set temperature range, the heat pump is controlled to reduce the operating frequency;

[0031] When the water temperature in the flash tank is lower than the lower limit of the set temperature range, the heat pump is controlled to increase the operating frequency.

[0032] In one possible implementation, controlling the heat pump to reduce the operating frequency includes: controlling the heat pump to reduce the operating frequency to half of the current frequency;

[0033] The controlling the heat pump to increase the operating frequency includes: controlling the heat pump to increase the operating frequency to twice the current frequency.

[0034] In a possible implementation, the method further includes:

[0035] According to the set value being greater than the normal minimum gas output threshold of the system, controlling the centrifugal steam compression system to enter or maintain a normal control mode;

[0036] The conventional control mode includes: detecting and closing the second control valve, and fully opening the first control valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0038] Attachment Figure 1 A schematic structural diagram of a centrifugal steam compression system provided by the present application is shown;

[0039] Attachment Figure 2 A flow chart showing a specific control method for a centrifugal vapor compression system provided in the present application is shown.

[0040] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0042] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0043] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referenced. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this disclosure, "plurality" means at least two, such as two or three, unless otherwise specifically defined.

[0044] In the present invention, unless otherwise specified or limited, the terms "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can mean fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will be able to understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0045] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0046] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0047] Figure 1 Schematic diagram of a centrifugal steam compression system provided in an embodiment of the present application. Figure 1 As shown, the system includes: a heat pump (11-14), a flash tank 26, and a centrifugal steam compressor 31. The air outlet of the centrifugal steam compressor 31 is connected to the main air outlet and the return branch respectively, and the air outlet of the centrifugal steam compressor 31 and the flash tank 26 are connected through the return branch.

[0048] Figure 1 In the figure, A1 is the heat source water inlet, A2 is the heat source water outlet, B1 is the steam generation water inlet, B2 is the flash tank drain outlet, and C1 is the system steam outlet.

[0049] The heat pump is used to extract waste heat from the heat source and release it into the water used for steam generation, so that the temperature of the water used for steam generation is increased to a specified flash temperature.

[0050] Specifically, such as Figure 1 As shown, the heat pump is a system consisting of a heat pump evaporator 11, a heat pump compressor 12, a heat pump condenser 13 and a heat pump throttle valve 14. Its operating principle is the same as that of the refrigeration system and will not be repeated here.

[0051] The heat source can be industrial waste heat, such as Figure 1 As shown, the heat source flows in from the pipe A1 port and flows out from the A2 port, passes through the heat pump evaporator 11, and the heat pump evaporator 11 extracts the waste heat in the heat source. The heat pump condenser 13 releases the waste heat in the heat source into the water inlet pipe of the flash tank 26 to heat the water for steam generation in the water inlet pipe of the flash tank 26.

[0052] like Figure 1 As shown, the inlet of the water inlet pipe of the flash tank 26 is B1, and the flow rate is controlled by the third control valve 21. The water is connected to the flash tank 26 via the first water pump 22 and can be used to pump out the water stored in the flash tank 26. After passing through the heat pump condenser 13, the steam generation water heated by the heat pump condenser 13 is pumped into the flash tank 26 by the second water pump 23. The pumping method and flow rate are controlled by the fourth control valve 24 and the fifth control valve 25.

[0053] Flash tank 26 is used to flash the heated water for steam generation into low-pressure steam under the negative pressure inside the tank. Flash tank 26 is a steam generator and can be replaced with other types of heat exchangers, such as a shell-and-tube heat exchanger. Steam is also introduced into the tank (shell side) to heat the water. It should be noted that various methods can be used to preheat the water for steam generation, including but not limited to heat pumps.

[0054] The centrifugal steam compressor 31 is used to draw low-pressure steam from the flash tank 26 and compress it into superheated steam with a saturation pressure equal to the target condensing pressure. This steam is then output through port C1 of the main outlet. The superheated steam is then cooled to saturation by water spraying and then fed into the heat-using process. The water in the flash tank absorbs heat during flash evaporation under negative pressure. The flash temperature is typically between 70°C and 90°C, with a flash temperature difference of approximately 10°C. After compression by the centrifugal steam compressor, the low-pressure steam can achieve a single-stage temperature rise of over 20°C, ensuring a sufficient temperature difference between the low-pressure steam and the water used for steam generation.

[0055] like Figure 1 As shown, the centrifugal steam compression system further includes: a first control valve 35 and a second control valve 34 .

[0056] like Figure 1 As shown, the first control valve 35 is used to control the steam output from the main outlet port C1. A pipeline is also connected between the centrifugal steam compressor 31 and the flash tank 26, and a third water pump 33 and a sixth control valve 32 are installed on the pipeline.

[0057] The flow rate of the return branch provided between the outlet of the centrifugal steam compressor 31 and the flash tank 26 can be controlled by a second control valve 34. Specifically, the second control valve 34 is a flow regulating valve that controls the flow rate of the return branch by controlling its own opening. Thus, it can coordinate with the first control valve 35 to control the flow rates of the main outlet and the return branch, achieving more precise and sensitive flow control.

[0058] In practical applications, the centrifugal steam compressor 31 can be a single centrifugal compressor, or a plurality of centrifugal compressors connected in series or a single-unit multi-stage centrifugal compressor, so as to improve the system pressure ratio.

[0059] One end of the reflux branch is set at the outlet of the centrifugal steam compressor 31, and the position of the other end can be implemented in the following ways:

[0060] In the first embodiment, if Figure 1 As shown, the flash tank 26 is provided with an air return port, and the air outlet of the centrifugal steam compressor 31 and the air return port of the flash tank 26 are connected through the reflux branch.

[0061] In the second embodiment, the air outlet of the centrifugal steam compressor 31 and the water inlet pipe of the flash tank 26 are connected via the reflux branch to achieve heating of the water used for steam generation.

[0062] Specifically, the position where the reflux branch is connected to the water inlet pipe of the flash tank 26 is located on the pipeline through which the water for steam generation flows after being heated, that is, on the pipeline between the heat pump condenser 13 and the flash tank 26; the position where the reflux branch is connected to the water inlet pipe of the flash tank 26 can also be located on the pipeline through which the water for steam generation flows before being heated, that is, on the pipeline between the heat pump condenser 13 and the pipeline inlet B1.

[0063] Therefore, the steam reflux can flow back to the water inlet pipe of the flash tank (branch of the fifth control valve 25) or directly enter the steam generation water inlet (B1) side to achieve heating of the steam generation water.

[0064] Based on the above centrifugal steam compression system, the present application also provides a control method for the centrifugal steam compression system, comprising the following steps:

[0065] 101. Determine whether the set value of the system steam output volume is less than or equal to the system's normal minimum steam output volume threshold;

[0066] 102. Controlling the centrifugal steam compression system to enter or maintain a return air control mode according to the set value being less than or equal to a normal minimum air output threshold of the system;

[0067] 103. According to the set value being greater than the normal minimum gas output threshold of the system, control the centrifugal steam compression system to enter or maintain a normal control mode.

[0068] The return air control mode includes:

[0069] Opening the second control valve to open the reflux branch; controlling the first control valve and the second control valve so that the output steam volume of the centrifugal steam compression system reaches the set value;

[0070] According to the water temperature in the flash tank exceeding the set temperature range, the operating frequency of the heat pump is adjusted until the water temperature in the flash tank is within the set temperature range.

[0071] The conventional control mode includes: detecting and closing the second control valve, and fully opening the first control valve.

[0072] Specifically, since the centrifugal steam compressor 31 has an exhaust volume adjustment range, the lower limit of the range is the minimum exhaust volume limit of the compressor. The minimum exhaust volume limit of the compressor is set to the system's conventional minimum exhaust volume threshold A. The user can set the system's output steam volume according to demand. In the above step 101, first determine whether the set value S of the system's output steam volume is less than or equal to the system's conventional minimum exhaust volume threshold A. If the set value S ≤ the system's conventional minimum exhaust volume threshold A, the excess steam output by the centrifugal steam compressor 31 needs to be returned to the flash tank. At this time, the control system enters the return air control mode. If the system is in the return air control mode, the return air control mode is maintained.

[0073] like Figure 1 As shown, in the return air control mode, the system first checks whether the second control valve 34 is closed. If the system has just entered the return air operation state from the normal operation state, the second control valve 34 is opened, and the first control valve 35 is controlled to ensure that the output steam volume reaches the set value S. When the second control valve 34 is open, steam will flow from the outlet of the centrifugal steam compressor 31 through the return branch into the flash tank 26 to heat the water stored in the flash tank. If the output power of the preheat pump remains unchanged, the water temperature will inevitably rise. At this time, it is necessary to determine whether the water temperature in the flash tank is within the set temperature range (Tf1-Tf2), which is determined by the set output steam temperature. If the water temperature in the flash tank is within the set temperature range, the heat pump is controlled to maintain the current operating frequency. If the water temperature in the flash tank exceeds the set temperature range, the heat pump operating frequency needs to be adjusted until the water temperature in the flash tank is within the set temperature range.

[0074] Specifically, if the temperature of the water in the flash tank exceeds the upper limit of the set temperature range, Tf2, the heat pump is controlled to reduce its operating frequency to lower the temperature of the water for steam generation entering the flash tank. This brings the water temperature back within the set temperature range and rebalances the heat within the flash tank. In practical applications, the heat pump can be controlled to reduce its operating frequency to half of its current frequency.

[0075] Specifically, if the set steam output increases, the flash tank's flash volume increases, and the water temperature drops, if the water temperature in the flash tank falls below the lower limit of the set temperature range, Tf1, the heat pump is controlled to increase its operating frequency to raise the temperature of the water input to the flash tank for steam generation. This brings the water temperature back within the set temperature range and rebalances the heat within the flash tank. In practical applications, the heat pump can be controlled to reduce its operating frequency to twice its current frequency.

[0076] For ease of understanding, this application provides Figure 2A flow chart of a specific control method for a centrifugal vapor compression system is shown.

[0077] The control method for a centrifugal steam compression system according to an embodiment of the present application provides a return branch at the outlet of the centrifugal steam compressor, which is controlled by a second control valve. When the centrifugal steam compressor enters a low-load operating condition, excess steam output by the compressor can flow back into the flash tank through the return branch, heating the water used for steam generation in the flash tank, thereby reducing the output power of the heat pump, thereby extending the low-load operating range of the centrifugal steam compressor and realizing excess heat recovery, thereby improving the economic efficiency of the system.

[0078] It should be noted that:

[0079] In the description provided herein, a large number of specific details are described. However, it is understood that the embodiments of the present application can be practiced without these specific details. In some instances, well-known methods, structures, and techniques are not shown in detail so as not to obscure the understanding of this description.

[0080] Similarly, it should be understood that in order to streamline the present application and aid in understanding one or more of the various inventive aspects, in the above description of the exemplary embodiments of the present application, various features of the present application are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting an intention that the claimed application requires more features than are expressly recited in each claim. Rather, as reflected in the claims below, inventive aspects lie in fewer than all the features of the individual embodiments disclosed above. Accordingly, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim itself serving as a separate embodiment of the present application.

[0081] Those skilled in the art will appreciate that the modules in the devices in the embodiments may be adaptively changed and arranged in one or more devices different from the embodiments. The modules or units or components in the embodiments may be combined into one module or unit or component, and in addition may be divided into multiple submodules or subunits or subcomponents. All features disclosed in this specification (including the accompanying claims, abstracts and drawings) and all processes or units of any method or device disclosed herein may be combined in any combination, except that at least some of such features and / or processes or units are mutually exclusive. Unless expressly stated otherwise, each feature disclosed in this specification (including the accompanying claims, abstracts and drawings) may be replaced by an alternative feature providing the same, equivalent or similar purpose.

[0082] Furthermore, those skilled in the art will appreciate that although some embodiments described herein include certain features included in other embodiments but not other features, combinations of features from different embodiments are intended to be within the scope of this application and to form different embodiments. For example, in the claims below, any of the claimed embodiments may be used in any combination.

[0083] The various component embodiments of the present application can be implemented in hardware, or implemented in a software module running on one or more processors, or implemented in a combination thereof. Those skilled in the art will appreciate that a microprocessor or digital signal processor (DSP) can be used in practice to implement some or all of the functions of some or all of the components in the creation device of the virtual machine according to an embodiment of the present application. The application can also be implemented as a part or all of the equipment or device program (for example, computer program and computer program product) for performing the method described herein. Such a program realizing the present application can be stored on a computer-readable medium, or can have the form of one or more signals. Such a signal can be downloaded from an Internet website, or provided on a carrier signal, or provided in any other form.

[0084] It should be noted that the above embodiments illustrate rather than limit the present application, and that a person skilled in the art may devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbols placed between brackets should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present application may be implemented by means of hardware comprising several different elements and by means of appropriately programmed computers. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third etc. does not indicate any order. These words may be interpreted as names.

[0085] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention description and drawings under the concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A centrifugal steam compression system, characterized in that: include: A flash tank and a centrifugal steam compressor, wherein the gas outlet of the centrifugal steam compressor is connected to a gas outlet main path and a return branch path respectively, and the gas outlet of the centrifugal steam compressor and the flash tank are connected via the return branch path; The flash tank is used to flash the steam generating water heated to a specified flash temperature into low-pressure steam under negative pressure conditions in the tank; The centrifugal steam compressor is used to compress the low-pressure steam into superheated steam whose saturation pressure is the target condensing pressure.

2. The centrifugal vapor compression system according to claim 1, wherein: The system further comprises: a first control valve and a second control valve; The first control valve is used to control the amount of steam output from the main gas outlet; The second control valve is used to control the flow of the reflux branch.

3. The centrifugal steam compression system according to claim 1 or 2, characterized in that The flash tank is provided with an air return port, and the air outlet of the centrifugal steam compressor and the air return port of the flash tank are communicated with each other through the reflux branch.

4. The centrifugal vapor compression system according to claim 2, wherein: The air outlet of the centrifugal steam compressor and the water inlet pipe of the flash tank are communicated with each other through the reflux branch.

5. The centrifugal vapor compression system according to claim 4, wherein: The position where the reflux branch is connected to the water inlet pipe of the flash tank is located on the pipeline through which the steam generation water flows after being heated.

6. The centrifugal vapor compression system according to claim 4, wherein: The position where the reflux branch is connected to the water inlet pipe of the flash tank is located on the pipeline through which the steam generation water flows before being heated.

7. The centrifugal vapor compression system according to claim 1, wherein: The system further comprises: The heat pump is used to extract waste heat from the heat source and release it into the water used for steam generation, thereby raising the temperature of the water used for steam generation to the specified flash temperature.

8. The centrifugal vapor compression system according to claim 7, wherein: The heat pump comprises a heat pump evaporator, a heat pump compressor, a heat pump condenser and a heat pump throttle valve; The heat pump evaporator extracts waste heat from the heat source, and the heat pump condenser releases the waste heat from the heat source into the water inlet pipe of the flash tank to heat the water for steam generation in the water inlet pipe of the flash tank.

9. A control method for a centrifugal steam compression system according to any one of claims 2 to 8, characterized in that: include: Determine whether the set value of the system's steam output is less than or equal to the system's normal minimum steam output threshold; According to the set value being less than or equal to the system's normal minimum air output threshold, controlling the centrifugal steam compression system to enter or maintain an air return control mode; The return air control mode includes: Opening the second control valve to open the reflux branch; controlling the first control valve and the second control valve so that the output steam volume of the centrifugal steam compression system reaches the set value; According to the water temperature in the flash tank exceeding the set temperature range, the operating frequency of the heat pump is adjusted until the water temperature in the flash tank is within the set temperature range.

10. The control method according to claim 9, characterized in that: The method of adjusting the operating frequency of the heat pump according to the water temperature in the flash tank exceeding the set temperature range includes: According to the water temperature in the flash tank being higher than the upper limit of the set temperature range, the heat pump is controlled to reduce the operating frequency; When the water temperature in the flash tank is lower than the lower limit of the set temperature range, the heat pump is controlled to increase the operating frequency.

11. The control method according to claim 10, characterized in that: The controlling the heat pump to reduce the operating frequency includes: controlling the heat pump to reduce the operating frequency to half of the current frequency; The controlling the heat pump to increase the operating frequency includes: controlling the heat pump to increase the operating frequency to twice the current frequency.

12. The control method according to claim 9, characterized in that: The method further comprises: According to the set value being greater than the normal minimum gas output threshold of the system, controlling the centrifugal steam compression system to enter or maintain a normal control mode; The conventional control mode includes: detecting and closing the second control valve, and fully opening the first control valve.

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