A method and system for monitoring performance changes in a vacuum system based on characteristic parameters

Abstract

The application discloses a kind of vacuum system performance change monitoring method and system based on characteristic parameter, belong to the technical field of energy saving and consumption reduction of coal-fired unit, method includes: the total pressure parameter and temperature parameter of the steam-air mixture at the suction inlet of vacuum pump are collected;Under the premise of assuming that steam is in saturated state in steam-air mixture, the saturated water vapor pressure parameter under corresponding working condition is determined by inquiring water vapor table;Based on the total pressure parameter and saturated water vapor pressure parameter of steam-air mixture, the air partial pressure proportion parameter in steam-air mixture is calculated;The air partial pressure proportion parameter is compared with the numerical value of reference air partial pressure proportion parameter, and the cause type of coal-fired unit vacuum system performance change is identified;Corresponding vacuum system troubleshooting and disposal instruction is generated.The application can relatively accurately distinguish the cause of performance deterioration, has abnormal early warning capability, can narrow the scope of investigation, quickly restore vacuum system performance and reduce unit energy consumption, improve efficiency and stability.

Description

Technical Field

[0001] This invention belongs to the field of cold-end optimization technology for thermal power plants, specifically relating to a method and system for monitoring performance changes in a vacuum system based on characteristic parameters. Background Technology

[0002] The performance of the vacuum system of a coal-fired power unit directly determines the heat exchange efficiency of the condenser and the power generation energy consumption of the unit. There are two main factors that affect the performance of the vacuum system: one is the increased air flow into the condenser (vacuum system); the other is the decreased suction capacity of the vacuum pump.

[0003] Currently, relying solely on vacuum tightness tests as a routine monitoring method for vacuum system performance makes it difficult to determine the extent of air's impact on condenser performance. This is because, when the unit's vacuum tightness is poor (vacuum drop rate 500~600 Pa / min), if the vacuum pump's suction capacity is strong, air is less likely to accumulate in the condenser, thus having a smaller impact on the vacuum system's performance. In this case, relying solely on the unit's vacuum tightness test results can lead to incorrect judgments. Similarly, even with good unit vacuum tightness, if the vacuum pump's suction performance deteriorates, air will accumulate in the condenser, affecting its performance. Judging solely based on vacuum tightness tests would lead to the conclusion that air has no or negligible impact on condenser performance, again resulting in misjudgments.

[0004] Therefore, vacuum tightness tests only reflect the sealing status of the vacuum system and cannot distinguish whether performance degradation is caused by increased air leakage into the condenser or a decrease in the vacuum pump's suction capacity. When vacuum tightness is poor, if the vacuum pump's suction capacity is strong, leaked air is unlikely to accumulate in the condenser, resulting in a small impact on the vacuum system's performance. In this case, the test results are prone to misjudging the extent of the air's influence. When vacuum tightness is good, if the vacuum pump's suction capacity declines, air will continuously accumulate in the condenser and degrade its performance. In this case, the test results are prone to ignoring the actual negative impact of air on the condenser's performance. In summary, current vacuum system performance monitoring makes it difficult to distinguish whether performance degradation is due to air leakage or a decrease in vacuum pump capacity; poor tightness easily leads to misjudgment, while good tightness easily leads to ignoring the actual impact of air on system performance. Summary of the Invention

[0005] This invention provides a method and system for monitoring changes in the performance of a vacuum system based on characteristic parameters. The purpose is to solve the problems in current vacuum system performance monitoring, such as difficulty in distinguishing whether the deterioration of vacuum system performance is due to air leakage or a decrease in vacuum pump capacity, easy misjudgment when the tightness is poor, and easy to ignore the actual impact of air on system performance when it is good.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for monitoring performance changes in a vacuum system based on characteristic parameters, comprising the following steps: S1. In the starting section of the condenser air extraction pipeline of the vacuum system in the coal-fired unit, the total pressure and temperature parameters of the gas-air mixture at the vacuum pump inlet are collected in real time. S2. Based on the temperature parameters of the steam-gas mixture; assuming that the steam in the steam-gas mixture is saturated, the saturated steam pressure parameters under the corresponding operating conditions are determined by consulting the steam table. S3. Using the obtained total pressure parameters of the steam-gas mixture and the saturated water vapor pressure parameters as the basis for calculation, calculate the air partial pressure ratio parameter in the steam-gas mixture. S4. Pre-select the baseline air partial pressure ratio parameter, compare the real-time calculated air partial pressure ratio parameter with the baseline air partial pressure ratio parameter, and identify the cause type of change in the performance of the vacuum system of the coal-fired unit. S5. Based on the identified causes of changes in the performance of the vacuum system of the coal-fired unit, generate corresponding instructions for investigation and handling of the vacuum system.

[0007] In some implementations, in S1, pressure and temperature measuring points are configured at the starting section of the condenser air extraction pipeline of the vacuum system in the coal-fired unit to collect total pressure and temperature parameters, respectively.

[0008] In some implementations, in S2, the steam meter is a standard data table that records the relationship between saturated steam temperature and pressure.

[0009] In some implementations, in S3, the air partial pressure ratio parameter is calculated using the following formula: ; in, This is a parameter representing the proportion of air partial pressure. This represents the total pressure parameter of the gas-vapor mixture. This refers to the saturated water vapor pressure parameter.

[0010] In some implementations, in S4, the reference air partial pressure ratio parameter includes: the air partial pressure ratio parameter calculated under the operating conditions of the coal-fired unit being above the rated load, the vacuum tightness meeting the standard, and the temperature of the working fluid of the vacuum pump being lower than the first preset temperature.

[0011] Furthermore, in S4, when the real-time air partial pressure ratio parameter is greater than the reference air partial pressure ratio parameter, a vacuum tightness test of the coal-fired unit is performed; if the vacuum drop rate measured by the vacuum tightness test is within the preset qualified range, the cause of the change in vacuum system performance is determined to be a decrease in the vacuum pump's suction capacity.

[0012] Furthermore, in S4, when the real-time air partial pressure ratio parameter is greater than the preset percentage value, it is determined that the vacuum tightness check of the coal-fired unit and the vacuum pump working fluid inlet temperature check can be carried out.

[0013] In some implementations, in S5, when the cause is a decrease in the vacuum pump's suction capacity, the handling operation is to check the inlet temperature of the vacuum pump's working fluid; if the inlet temperature of the vacuum pump's working fluid exceeds a second preset temperature, it is determined that a cooling operation can be performed.

[0014] In some implementations, in S5, when the cause is an increase in the condenser air leakage flow, the handling operation includes turning on the preset standby vacuum pump. If the vacuum rise of the coal-fired unit reaches 0.4kPa-0.5kPa, it is determined that vacuum leak detection can be carried out.

[0015] This invention also provides a vacuum system performance change monitoring system based on characteristic parameters, to implement the aforementioned vacuum system performance change monitoring method based on characteristic parameters, including a pressure and temperature parameter acquisition module, a saturated water vapor pressure parameter acquisition module, an air partial pressure ratio calculation module, a cause type identification module, and a troubleshooting and handling instruction generation module; wherein: The pressure and temperature parameter acquisition module is used to: collect the total pressure and temperature parameters of the gas-steam mixture at the inlet of the vacuum pump in the starting section of the condenser air extraction pipeline of the vacuum system in a coal-fired unit in real time. The saturated steam pressure parameter acquisition module is used to: determine the saturated steam pressure parameter under the corresponding operating condition by querying the steam table, based on the temperature parameter of the steam-gas mixture and assuming that the steam in the steam-gas mixture is in a saturated state. The air partial pressure ratio calculation module is used to: calculate the air partial pressure ratio parameter in the steam-gas mixture based on the obtained total pressure parameter of the steam-gas mixture and the saturated water vapor pressure parameter. The cause type identification module is used to: pre-select a reference air partial pressure ratio parameter, compare the real-time calculated air partial pressure ratio parameter with the reference air partial pressure ratio parameter, and identify the cause type of the change in the performance of the vacuum system of the coal-fired unit. The investigation and handling instruction generation module is used to generate corresponding vacuum system investigation and handling instructions based on the identified causes of changes in the performance of the vacuum system of the coal-fired unit.

[0016] Compared with existing technologies, the present invention provides a method and system for monitoring performance changes in a vacuum system based on characteristic parameters, which has the following advantages: This invention collects the total pressure and temperature parameters of the steam-air mixture at the vacuum pump inlet in real time at the starting section of the condenser air extraction pipeline in the vacuum system of a coal-fired power unit. Based on the temperature parameter, and assuming steam saturation, it queries the steam meter to determine the saturated steam pressure parameter. The air pressure ratio parameter is obtained through calculation. The real-time parameters are compared with the baseline parameters to identify the causes of changes in vacuum system performance and generate handling instructions. This invention improves upon the limitation of current vacuum tightness tests, which can only reflect the sealing status. It can relatively accurately distinguish whether the deterioration of vacuum system performance is due to condenser leakage or a decrease in vacuum pump suction capacity. It also improves the shortcomings of current tests that make positive misjudgments when the tightness is poor and negative misjudgments when the tightness is good. To a certain extent, it can ensure the efficiency and stability of the operation of the vacuum system of a coal-fired power unit. Attached Figure Description

[0017] The accompanying drawings are provided to further understand the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0018] Figure 1 This is a schematic diagram of the relationship between the partial pressure of air and the pressure of condenser under 300M load of Unit A in an embodiment of the vacuum system performance change monitoring method based on characteristic parameters of the present invention. Figure 2 This is a schematic diagram of the relationship between the partial pressure of air and the condenser terminal differential pressure of Unit A under 300M load in an embodiment of the vacuum system performance change monitoring method based on characteristic parameters of the present invention. Figure 3 This is a schematic diagram of the relationship between the partial pressure of air and the pressure of condenser under 240M load of Unit A in an embodiment of the vacuum system performance change monitoring method based on characteristic parameters of the present invention. Figure 4 This is a schematic diagram of the relationship between the partial pressure of air and the condenser terminal differential pressure under 240M load of Unit A in an embodiment of the vacuum system performance change monitoring method based on characteristic parameters of the present invention. Figure 5 This is a schematic diagram of the relationship between the partial pressure of air and the pressure of condenser under 300M load for Unit B in an embodiment of the vacuum system performance change monitoring method based on characteristic parameters of the present invention. Figure 6 This is a schematic diagram of the relationship between the partial pressure of air and the condenser terminal differential pressure of Unit B under 300M load in an embodiment of the vacuum system performance change monitoring method based on characteristic parameters of the present invention. Figure 7 This is a schematic diagram illustrating the relationship between air partial pressure and working fluid inlet temperature at a 300MW load for a 300MW unit in a certain plant, as an embodiment of a vacuum system performance change monitoring method based on characteristic parameters according to the present invention. Figure 8 This is a schematic diagram of the vacuum system framework in an embodiment of a vacuum system performance change monitoring method based on characteristic parameters according to the present invention.

[0019] Among them, 1. Steam turbine, 2. Condenser, 3. Pumping pressure gauge, 4. Platinum resistance temperature measuring point, 5. Vacuum pump, 6. Vacuum pump working fluid system. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0022] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0023] It should be noted that the apparatus and methods disclosed in the embodiments herein can also be implemented in other ways. The apparatus embodiments described above are merely illustrative; for example, the flowcharts and block diagrams in the accompanying drawings show the architecture, functionality, and operation of possible implementations of apparatus, methods, and computer program products according to various embodiments herein. In this regard, each block in a flowchart or block diagram may represent a module, program, or part of code containing one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram and / or flowchart, and combinations of blocks in block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system to perform the specified function or action, or can be implemented using a combination of dedicated hardware and computer instructions.

[0024] In addition, the functional modules in the various embodiments of this article can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0025] This invention provides a method for monitoring performance changes in a vacuum system based on characteristic parameters, comprising the following steps: S1. In the starting section of the condenser air extraction pipeline of the vacuum system in the coal-fired unit, the total pressure and temperature parameters of the gas-air mixture at the vacuum pump inlet are collected in real time. S2. Based on the temperature parameters of the steam-gas mixture; assuming that the steam in the steam-gas mixture is saturated, the saturated steam pressure parameters under the corresponding operating conditions are determined by consulting the steam table. S3. Using the obtained total pressure parameters of the steam-gas mixture and the saturated water vapor pressure parameters as the basis for calculation, calculate the air partial pressure ratio parameter in the steam-gas mixture. S4. Pre-select the baseline air partial pressure ratio parameter, compare the real-time calculated air partial pressure ratio parameter with the baseline air partial pressure ratio parameter, and identify the cause type of change in the performance of the vacuum system of the coal-fired unit. S5. Based on the identified causes of changes in the performance of the vacuum system of the coal-fired unit, generate corresponding instructions for investigation and handling of the vacuum system.

[0026] This invention monitors the pressure and temperature of the gas-vapor mixture at the vacuum pump inlet, enabling a relatively accurate assessment of the impact of air on the performance of the vacuum system. It distinguishes whether the change in vacuum system performance is caused by an increase in the leakage air flow or a deterioration in the working performance of the vacuum pump, thus allowing for timely implementation of appropriate improvement measures for different causes, and has certain engineering applicability.

[0027] like Figure 8 As shown, this invention relates to a vacuum system in a coal-fired power unit. The vacuum system includes a steam turbine 1, a condenser 2, and a vacuum pump 5. An air extraction pressure gauge 3 and a platinum resistance temperature measuring point 4 are installed at the beginning of the condenser air extraction pipeline of the vacuum system in the coal-fired power unit. The vacuum pump 5 has a vacuum pump working fluid system 6. Based on this, the pressure and temperature data of the steam-gas mixture at the vacuum pump inlet can be collected in real time, providing basic parameters for calculating the partial pressure of air.

[0028] Specifically, the vacuum pump 5 of this invention extracts the air accumulated in the air-cooled zone of the condenser 2 through the air extraction pipe of the condenser 2. Based on the continuous flow theory of fluid mechanics, neglecting steam condensation in the pipe, flow losses of the steam-gas mixture in the pipe, and insulation between the pipe and the external environment, the performance (pressure, temperature, mixture composition, and flow rate) of the steam-gas mixture at any cross-section in the air extraction pipe is the same. The air extraction pipe is connected to the air-cooled zone of the condenser 2, and the performance of the steam-gas mixture in the air extraction pipe is the same as at the end of the air-cooled zone. By monitoring the change in the relative content of air in the steam-gas mixture in the air extraction pipe, the change in the relative content of air at the end of the air-cooled zone of the condenser 2 can be obtained, and thus the change in the relative content of air in the condenser 2 can be determined.

[0029] This invention assumes that the steam in the steam-air mixture in the air extraction pipe of condenser 2 is in a saturated state. Therefore, the corresponding saturation pressure can be obtained by consulting a steam meter based on the monitored temperature of the steam-air mixture. The saturation pressure is approximately equal to the partial pressure of the steam in the mixture. Using a steam meter ensures the consistency of the relationship between saturated steam temperature and pressure. Subtracting the steam partial pressure from the measured total pressure of the mixture yields the partial pressure of the air in the mixture. According to Dalton's law of partial pressures, the ratio of the partial pressure of air in the mixture to the total pressure is equal to the ratio of the volume of air in the mixture to the total volume. Thus, the percentage of air partial pressure reflects the relative percentage of air content in the mixture. Testing the pressure and temperature at the beginning of the air extraction pipe of condenser 2 effectively avoids the influence of steam condensation and heat exchange with the outside environment on the percentage of air partial pressure.

[0030] Furthermore, this invention monitors the pressure and temperature of the gas-vapor mixture at the vacuum pump inlet in real time to obtain the total pressure of the gas-vapor mixture. and temperature .according to Find the corresponding steam saturation pressure Calculate the percentage of partial pressure of air. Then, the percentage of air partial pressure at different times is compared and judged (note the same unit load). Percentage of air partial pressure in the air extraction pipeline. for: ; in, This is a parameter representing the proportion of air partial pressure. This represents the total pressure parameter of the gas-vapor mixture. This refers to the saturated water vapor pressure parameter. By directly quantifying the relative air content using the ratio of the difference between the total pressure and the saturated water vapor pressure, relatively accurate quantitative results can be output relatively quickly, providing relatively reliable data support for parameter comparison and cause identification.

[0031] Furthermore, the vacuum tightness of coal-fired power units is better at high loads above the rated load than at low loads. Therefore, the air partial pressure percentage is generally selected when the unit load is above the rated load, the vacuum tightness is at a good level, and the vacuum pump is operating normally (here, the first preset temperature; in some operating conditions, the first preset temperature is below 20°C of the working fluid temperature). This serves as a benchmark value. Establishing a benchmark value avoids distorted comparison results due to improper benchmark operating conditions, improving the accuracy of cause identification. At any stage of unit operation, as long as the unit load is above the rated load, the actual air partial pressure percentage can be compared. Monitor and calculate, and compare with benchmark values. Comparison. When > When the vacuum drop rate is low, it indicates a decrease in the unit's vacuum tightness or a deterioration in the vacuum pump's operating characteristics. At this point, a vacuum tightness test of the coal-fired unit is performed. If the vacuum drop rate does not increase or increases only slightly (within the acceptable range), it indicates that the operating characteristics of vacuum pump 5 have deteriorated. This effectively narrows down the troubleshooting scope, avoids ineffective maintenance work, and improves problem location efficiency. At this time, it is possible to check whether the inlet temperature of the vacuum pump working fluid system 6 exceeds the second preset temperature (in some operating conditions, the second preset temperature is 35℃) or other faults.

[0032] For large thermal power units, when When the air concentration exceeds a preset percentage (which can be 35% in some operating conditions), it indicates a significant amount of air accumulating in condenser 2. Immediately check the unit's vacuum tightness and whether the vacuum pump's working fluid temperature is excessively high, and take appropriate technical measures to improve the unit's vacuum tightness and reduce the vacuum pump's working fluid inlet temperature. This allows for early warning and proactive intervention in abnormal conditions, preventing excessive air accumulation from degrading the heat exchange performance of condenser 2 and reducing unnecessary energy losses in the unit.

[0033] The above describes the monitoring of the partial pressure of air in the air extraction pipe of condenser 2. By monitoring the percentage of air volume in the air extraction pipe, and since the percentage of air volume in the air extraction pipe is approximately equal to the percentage of air volume in the steam-gas mixture at the end of the air-cooled zone of condenser 2, the degree of influence of air on the performance of condenser 2 can be determined relatively accurately, without being affected by vacuum tightness or the working performance of the vacuum pump.

[0034] When a significant decrease in the unit's vacuum tightness is not solely due to air leakage (with a large air leakage rate), this can be determined by activating the standby vacuum pump and observing the vacuum changes in the coal-fired unit. If the vacuum of the coal-fired unit rises significantly after activating the standby vacuum pump (the rise exceeds 0.4~0.5 kPa), it indicates a severe air leakage rate, and vacuum leak detection should be initiated. This invention verifies the severity of air leakage by activating the standby vacuum pump and determines the timing of leak detection based on the vacuum rise rate. This approach can relatively avoid blindly conducting leak detection operations, efficiently locate the leak point, and ensure the long-term stable operation of the vacuum system.

[0035] This invention also provides a vacuum system performance change monitoring system based on characteristic parameters, including a pressure and temperature parameter acquisition module, a saturated water vapor pressure parameter acquisition module, an air partial pressure ratio calculation module, a cause type identification module, and a troubleshooting and handling instruction generation module; wherein: The pressure and temperature parameter acquisition module is used to: collect the total pressure and temperature parameters of the gas-steam mixture at the inlet of the vacuum pump in the starting section of the condenser air extraction pipeline of the vacuum system in a coal-fired unit in real time. The saturated steam pressure parameter acquisition module is used to: determine the saturated steam pressure parameter under the corresponding operating condition by querying the steam table, based on the temperature parameter of the steam-gas mixture and assuming that the steam in the steam-gas mixture is in a saturated state. The air partial pressure ratio calculation module is used to: calculate the air partial pressure ratio parameter in the steam-gas mixture based on the obtained total pressure parameter of the steam-gas mixture and the saturated water vapor pressure parameter. The cause type identification module is used to: pre-select a reference air partial pressure ratio parameter, compare the real-time calculated air partial pressure ratio parameter with the reference air partial pressure ratio parameter, and identify the cause type of the change in the performance of the vacuum system of the coal-fired unit. The investigation and handling instruction generation module is used to generate corresponding vacuum system investigation and handling instructions based on the identified causes of changes in the performance of the vacuum system of the coal-fired unit.

[0036] The present invention will be further described in detail below through specific embodiments.

[0037] like Figures 1-6As shown, taking the monitoring of air partial pressure in the condensers of two 300MW units in a power plant as an example, the relationship between changes in air partial pressure and changes in condenser performance is analyzed.

[0038] By introducing air at different flow rates into condenser 2, the percentage of air partial pressure was varied, and the performance changes of condenser 2 were observed. The relationship curves between the condenser performance and air partial pressure of two 300MW units in a power plant are shown below. Figures 1-6 .from Figures 1-6 As can be seen from the data, for a 300MW unit at a 300MW load, when the percentage of air partial pressure exceeds about 30%, the air accumulated in condenser 2 begins to significantly affect the terminal differential and pressure of condenser 2. If the air partial pressure further increases, the terminal differential and pressure of condenser 2 will increase rapidly.

[0039] like Figure 7 As shown, if the unit's vacuum tightness is up to standard, but the working characteristics of the air extraction equipment deteriorate, this can also be detected by monitoring the percentage of air partial pressure in the air extraction pipe. Figure 7 For a 300MW unit in a power plant with a 300MW load and a vacuum tightness of 260Pa / min, the increased temperature of the working fluid in the vacuum pump leads to a deterioration in the pump's operating characteristics, resulting in increased condenser pressure. The paper describes how the percentage of air partial pressure in the condenser's extraction pipe changes with the working fluid temperature. Figure 7 As can be seen, when the inlet temperature of the working fluid of the vacuum pump exceeds about 38°C, the percentage of air partial pressure reaches more than 30%; when the working fluid temperature is 41°C, the percentage of air partial pressure reaches more than 35%, at which point the condenser pressure in the vacuum system rises by about 0.5 kPa.

[0040] In summary, this invention can relatively accurately distinguish whether the performance degradation is caused by condenser air leakage or a decrease in vacuum pump suction capacity. It has anomaly early warning capabilities, and the handling instructions are relatively targeted, which can narrow down the scope of investigation, quickly restore the performance of the vacuum system, reduce unit energy consumption, and improve the operation and maintenance efficiency and operational stability of the vacuum system.

[0041] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Anyone skilled in the art can readily implement the present invention according to the description and above. Any modifications, alterations, or equivalent variations made using the technical content disclosed above are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A method for monitoring performance changes in a vacuum system based on characteristic parameters, characterized in that, The steps include the following: S1. In the starting section of the condenser air extraction pipeline of the vacuum system in the coal-fired unit, the total pressure and temperature parameters of the gas-air mixture at the vacuum pump inlet are collected in real time. S2. Based on the temperature parameters of the steam-gas mixture; assuming that the steam in the steam-gas mixture is saturated, the saturated steam pressure parameters under the corresponding operating conditions are determined by consulting the steam table. S3. Using the obtained total pressure parameters of the steam-gas mixture and the saturated water vapor pressure parameters as the basis for calculation, calculate the air partial pressure ratio parameter in the steam-gas mixture. S4. Pre-select the baseline air partial pressure ratio parameter, compare the real-time calculated air partial pressure ratio parameter with the baseline air partial pressure ratio parameter, and identify the cause type of change in the performance of the vacuum system of the coal-fired unit. S5. Based on the identified causes of changes in the performance of the vacuum system of the coal-fired unit, generate corresponding instructions for investigation and handling of the vacuum system.

2. The method for monitoring performance changes of a vacuum system based on characteristic parameters according to claim 1, characterized in that, In S1, pressure and temperature measuring points are configured at the starting section of the condenser air extraction pipeline of the vacuum system in the coal-fired unit to collect total pressure and temperature parameters, respectively.

3. The method for monitoring performance changes of a vacuum system based on characteristic parameters according to claim 1, characterized in that, In S2, the steam meter is a standard data table that records the relationship between saturated steam temperature and pressure.

4. The method for monitoring performance changes of a vacuum system based on characteristic parameters according to claim 1, characterized in that, In S3, the air partial pressure ratio parameter is calculated using the following formula: ； in, This is a parameter representing the proportion of air partial pressure. This represents the total pressure parameter of the gas-vapor mixture. This refers to the saturated water vapor pressure parameter.

5. The method for monitoring performance changes of a vacuum system based on characteristic parameters according to claim 1, characterized in that, In S4, the reference air partial pressure ratio parameter includes: the air partial pressure ratio parameter calculated under the operating conditions of the coal-fired unit being above the rated load, the vacuum tightness meeting the standard, and the temperature of the working fluid of the vacuum pump being lower than the first preset temperature.

6. The method for monitoring performance changes of a vacuum system based on characteristic parameters according to claim 5, characterized in that, In S4, when the real-time air partial pressure ratio parameter is greater than the reference air partial pressure ratio parameter, a vacuum tightness test of the coal-fired unit is performed; if the vacuum drop rate measured by the vacuum tightness test is within the preset qualified range, the cause of the change in vacuum system performance is determined to be a decrease in the vacuum pump's suction capacity.

7. The method for monitoring performance changes of a vacuum system based on characteristic parameters according to claim 5, characterized in that, In S4, when the real-time air partial pressure ratio parameter is greater than the preset percentage value, it is determined that the vacuum tightness check of the coal-fired unit and the vacuum pump working fluid inlet temperature check can be carried out.

8. The method for monitoring performance changes of a vacuum system based on characteristic parameters according to claim 1, characterized in that, In S5, when the cause is a decrease in the vacuum pump's suction capacity, the handling operation is to check the inlet temperature of the vacuum pump's working fluid; if the inlet temperature of the vacuum pump's working fluid exceeds the second preset temperature, it is determined that a cooling operation can be performed.

9. The method for monitoring performance changes of a vacuum system based on characteristic parameters according to claim 1, characterized in that, In S5, when the cause is an increase in the air flow rate leaking into the condenser, the handling operation includes turning on the preset standby vacuum pump. If the vacuum rise of the coal-fired unit reaches 0.4kPa-0.5kPa, it is determined that vacuum leak detection can be carried out.

10. A vacuum system performance change monitoring system based on characteristic parameters, used to implement the vacuum system performance change monitoring method based on characteristic parameters as described in any one of claims 1-9, characterized in that, This includes a pressure and temperature parameter acquisition module, a saturated water vapor pressure parameter acquisition module, an air partial pressure ratio calculation module, a cause type identification module, and an investigation and handling instruction generation module; among which: The pressure and temperature parameter acquisition module is used to: collect the total pressure and temperature parameters of the gas-steam mixture at the inlet of the vacuum pump in the starting section of the condenser air extraction pipeline of the vacuum system in a coal-fired unit in real time. The saturated steam pressure parameter acquisition module is used to: determine the saturated steam pressure parameter under the corresponding operating condition by querying the steam table, based on the temperature parameter of the steam-gas mixture and assuming that the steam in the steam-gas mixture is in a saturated state. The air partial pressure ratio calculation module is used to: calculate the air partial pressure ratio parameter in the steam-gas mixture based on the obtained total pressure parameter of the steam-gas mixture and the saturated water vapor pressure parameter. The cause type identification module is used to: pre-select a reference air partial pressure ratio parameter, compare the real-time calculated air partial pressure ratio parameter with the reference air partial pressure ratio parameter, and identify the cause type of the change in the performance of the vacuum system of the coal-fired unit. The investigation and handling instruction generation module is used to generate corresponding vacuum system investigation and handling instructions based on the identified causes of changes in the performance of the vacuum system of the coal-fired unit.

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