Condenser inlet steam dryness detection device and control method thereof

Abstract

This invention discloses a condenser inlet steam dryness detection device and its control method. It adopts an integrated "sampling-conversion-measurement-calculation" design. A corrosion-resistant diaphragm-type air pump precisely extracts a wet steam sample, which is then compressed by the pump to spontaneously condense into liquid water. Coriolis mass flow meters, absolute pressure transmitters, and turbine volumetric flow meters are used to simultaneously collect relevant parameters. Combined with a temperature compensation module and fitting equations, the steam dryness is derived, achieving real-time, accurate, and continuous measurement of low-pressure wet steam dryness. The device features a compact structure, energy saving, convenient maintenance, and high reliability. The relative measurement error is ≤±1%, and the core component service life is ≥5 years. It can achieve unattended operation and remote data transmission. It is also suitable for low-pressure steam dryness measurement in industries such as chemical and metallurgy, providing reliable data support for unit operation control, fault diagnosis, and energy efficiency optimization, and has broad application value.

Description

Technical Field

[0001] This invention relates to the field of condenser inlet steam dryness detection device and its control method. Background Technology

[0002] In the operation of a thermal power generation system, the condenser, as a core auxiliary equipment of the generator unit, directly determines the turbine exhaust efficiency, condenser heat exchange effect, and overall power generation efficiency of the unit by the dryness index of its inlet steam. It also provides important reference value for early diagnosis of equipment faults. The condenser inlet steam is wet steam, and its dryness fluctuates dynamically with multiple factors such as condenser back pressure, turbine inlet steam parameters, circulating water temperature, and unit load. Too low a dryness will lead to increased turbine exhaust humidity, exacerbating blade erosion and wear, and reducing unit output; too high a dryness will affect condenser heat exchange efficiency and increase unit energy consumption. Therefore, achieving accurate and real-time measurement of the condenser inlet steam dryness is of great significance for ensuring the safe, efficient, and economical operation of the unit.

[0003] Currently, most power plants in China still lack specialized equipment for measuring the dryness of condenser inlet steam that can operate stably on-site. Existing measurement methods are mostly indirect estimations or borrowing general-purpose steam dryness measuring equipment, which suffer from problems such as low measurement accuracy, poor adaptability, high maintenance costs, and inability to operate continuously, making it difficult to meet the needs of power plants for refined control.

[0004] Current mainstream steam dryness measurement technologies mainly include throttling measurement method, heating measurement method, condensation measurement method, and optical measurement method. Each method has obvious technical defects, as detailed below: Throttling measurement method: The core principle of this method is to utilize the expansion effect of steam at the throttling element and calculate the steam dryness by measuring the pressure and temperature changes before and after throttling. However, it relies on high pressure differential conditions (usually requiring a pressure difference of not less than 0.5 MPa before and after throttling) to achieve effective expansion throttling. However, the condenser inlet steam pressure is usually below 0.1 MPa, which is a typical low-pressure, low-velocity condition. Using this method, an effective throttling effect cannot be formed, the measurement error is extremely large, and even effective measurement data cannot be obtained. It is completely unsuitable for the measurement requirements of condenser inlet steam.

[0005] Heating and condensation measurement methods: The heating method requires heating the wet steam to a superheated state and calculating the dryness fraction by measuring the parameters of the superheated steam. The condensation method requires completely condensing the wet steam into liquid water and calculating the dryness fraction by measuring the mass of the condensate and the volume of the steam. Both methods require large heating furnaces, condensers, constant temperature control systems, and complex piping systems. This results in large equipment footprints (a single unit typically occupies more than 15 square meters), cumbersome piping layouts, and significant additional consumption of electricity and water resources, contradicting the energy conservation and consumption reduction requirements of power plants and their compact plant space. Furthermore, the installation and commissioning cycle for this type of equipment is as long as 1-2 weeks, requiring on-site calibration by professional technicians, making practical application extremely difficult. Frequent maintenance of the heating and condensation components during operation also leads to high maintenance costs.

[0006] Optical measurement method: This method utilizes the scattering and refraction characteristics of light by liquid water droplets in wet steam, and uses an optical probe to capture the light change signal to calculate the steam dryness. However, there is a large amount of dust and water vapor at the condenser inlet, and the optical probe is prone to condensation and dust accumulation, which obstructs light transmission and rapidly reduces measurement accuracy. At the same time, this method is sensitive to fluctuations in temperature and humidity and light interference, has poor measurement stability, and requires frequent disassembly of the probe for cleaning and maintenance (usually 1-2 times per week). It cannot meet the measurement requirements of power plants operating continuously for 24 hours, and the cost of optical components is high, and the replacement cost after damage is also high.

[0007] Furthermore, some existing measuring devices lack effective protective structures, making them susceptible to problems such as external air infiltration and medium backflow in the low-pressure vacuum environment of the condenser. This not only affects measurement accuracy but may also disrupt the condenser vacuum environment, threatening the stable operation of the generator unit. Simultaneously, most devices lack medium recovery functions, resulting in the direct discharge of condensate generated during measurement, wasting water resources and potentially posing safety hazards to on-site equipment and personnel. Therefore, developing a compact, low-pressure-condition-adaptable, accurate, and easily maintained condenser inlet steam dryness detection device that meets the energy-saving requirements of power plants has become a pressing technical challenge for those skilled in the art. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a condenser inlet steam dryness detection device and its control method.

[0009] To address the problems of existing technologies, this invention discloses a condenser inlet steam dryness detection device, comprising: a sampling port, a measuring pipeline, a vacuum pump, a guide pipeline, a water tank, a PLC controller, and a data processing unit; One end of the sampling port is connected to the condenser inlet, and the other end is connected to the air pump through a measuring pipeline. The measuring pipeline is equipped with an absolute pressure transmitter, a volumetric flow meter, and a one-way check valve. The air pump is connected to the water tank through a guide pipe, and the guide pipe is equipped with a mass flow meter and an electric shut-off valve; The PLC controller is used to start the electric shut-off valve and the vacuum pump. The vacuum pump draws a wet steam sample from the condenser inlet through the sampling port. The absolute pressure transmitter collects the absolute pressure of the wet steam in real time, and the volumetric flow meter records the volumetric flow rate of the wet steam in real time. The vacuum pump compresses the drawn wet steam sample, and the wet steam spontaneously condenses into liquid water. The mass flow rate of the condensed liquid water is measured by the mass flow meter. The mass flow rate of the condensed liquid water is consistent with the mass flow rate of the original drawn wet steam sample. The measured liquid water flows into the water tank through the guide pipe. The data processing unit is used to calculate the condenser inlet steam dryness based on the absolute pressure and volumetric flow rate of the wet steam and the mass flow rate of the condensed liquid water.

[0010] Furthermore, the sampling port is made of 304 stainless steel and has a 100-mesh stainless steel filter in front.

[0011] Furthermore, the air pump is a corrosion-resistant diaphragm air pump with an air pumping power adjustment range of 0.3-1.0kW and an air pumping volume adjustment range of 0.01-0.1m³ / s.

[0012] Furthermore, the air pump uses a polytetrafluoroethylene diaphragm.

[0013] Furthermore, the mass flow meter is a Coriolis mass flow meter.

[0014] Furthermore, the one-way check valve is a stainless steel spring-loaded structure with an opening pressure of 0.005 MPa and a leakage rate of ≤0.01 L / min. It is used to prevent outside air from seeping into the condenser and to maintain the vacuum environment of the condenser.

[0015] Furthermore, the electric shut-off valve seals are made of fluororubber, achieving a sealing rating of IP67.

[0016] Furthermore, it also includes temperature sensors, which are installed in the measuring pipeline and the flow guiding pipeline respectively, for real-time acquisition of steam and condensate temperatures.

[0017] Furthermore, the control method of the condenser inlet steam dryness detection device is as follows: the PLC controller starts the electric shut-off valve, and after a 10-second delay, starts the air pump. The air pump extracts wet steam samples from the condenser inlet through the sampling port. The absolute pressure transmitter collects the absolute pressure p of the wet steam in real time, and the volumetric flow meter records the volumetric flow rate v of the wet steam in real time. Both are collected synchronously through the same data acquisition module at a frequency of 10Hz. The vacuum pump compresses the extracted wet steam sample, raising the outlet pressure to 0.1-0.12 MPa. Under this pressure, the wet steam spontaneously condenses into room-temperature liquid water. The condensed liquid water passes through a mass flow meter. According to the law of conservation of mass, the mass flow rate of the condensed liquid water is consistent with the mass flow rate of the original extracted wet steam sample. The measured liquid water flows into a water tank through a guide pipe, completing the recovery of the medium.

[0018] Furthermore, the control method for the condenser inlet steam dryness detection device: The data processing unit refers to the IF-97 international steam properties standard, combined with the steam pressure collected by the absolute pressure transmitter. p The saturated vapor density at the corresponding pressure and temperature is obtained by fitting the temperature t collected by the temperature sensor. r The condenser inlet pressure was obtained by fitting experimental data. p With saturated vapor density r The fitting equation is: r =-0.00002 p ²+0.007 p +0.0011, the goodness of fit of the equation. R ²≥0.999; Condensate flow rate measured by mass flow meter m The wet steam volumetric flow rate v measured by the volumetric flow meter is calculated using the density formula. r 1= m / v Calculate the actual density of the wet steam. r 1; The mass of liquid water per unit volume of steam is approximately equal to the measured density of wet steam. r 1 and corresponding pressure p Lower saturated vapor density r The difference; based on the definition of wet steam dryness, that is, the mass ratio of dry steam in a unit mass of wet steam, the formula for calculating dryness is derived as follows: x = r / r 1.

[0019] The beneficial effects of this invention are as follows: Highly adaptable and precisely suited for low-pressure condenser conditions: This device is designed for low-pressure conditions where the condenser inlet steam pressure is below 0.1 MPa. It employs a dedicated corrosion-resistant diaphragm pump to stably extract steam samples, overcoming the technical bottleneck of traditional throttling measurement methods that cannot adapt to low-pressure conditions. At the same time, the sampling structure is optimized to ensure sample representativeness. Combined with a temperature compensation module, it effectively reduces the impact of pressure and temperature fluctuations on measurement accuracy. The relative error of the measurement data is controlled within ±1%, which is far superior to existing measurement equipment (existing equipment errors are usually above ±3%).

[0020] Compact structure, energy saving, and convenient installation and commissioning: Compared with traditional heating and condensing measuring equipment, this device does not require additional heating units, large condensing mechanisms, or constant temperature control systems. It achieves vapor-liquid conversion solely through natural condensation at the outlet pressure of the extraction pump. The overall equipment occupies only 5 square meters, with a simple pipeline layout, reducing space requirements by more than 70% compared to traditional equipment. It can be directly installed in an unused area next to the condenser, without occupying a large amount of plant space. The installation and commissioning cycle is shortened to within 24 hours, requiring only 2-3 professional technicians to complete the installation, commissioning, and calibration work, significantly reducing the layout cost and installation difficulty within the power plant. Furthermore, the equipment consumes no additional energy or water during operation; only the extraction pump consumes a small amount of electricity (0.3-1.0 kW), meeting the energy-saving and consumption-reducing operational needs of power plants, saving the plant significant energy and water costs annually.

[0021] Stable operation, convenient maintenance, and long service life: Compared to optical measurement methods, this device adopts a mechanical measurement principle, eliminating the need for light transmission. It is more resistant to environmental interference factors such as dust content and temperature / humidity fluctuations. The core measuring components (air pump, mass flow meter, pressure transmitter) have a service life of over 5 years. Routine maintenance only requires monthly checks of pipeline sealing, valve status, and pre-filter cleanliness, and calibration of the measuring components every 6 months. This maintenance frequency is significantly lower than that of optical measuring equipment (1-2 times per week), reducing maintenance costs by over 60%. It meets the measurement needs of power plants operating continuously for 24 hours, significantly improving operational stability.

[0022] Safe and reliable with media recovery function: This device is equipped with protective structures such as one-way check valves and electric shut-off valves to effectively prevent outside air from seeping into the condenser, prevent media backflow, and ensure the stable operation of the condenser vacuum environment and generator set. The pipeline adopts welded seals, with an extremely low leakage rate, avoiding safety hazards to on-site equipment and personnel caused by steam leakage. At the same time, it is equipped with a sealed water storage tank and return pipeline to realize the recycling and reuse of condensate. Compared with the direct discharge method of traditional measuring equipment, it can reduce water waste, reduce power plant operating costs, and avoid on-site pollution caused by water vapor leakage.

[0023] Highly integrated and capable of unattended operation: This device is equipped with a PLC controller, data acquisition module, and remote communication function, allowing seamless integration with the power plant's DCS automated operation system. It enables automatic start / stop of the measurement process, data acquisition, calculation, storage, transmission, and anomaly alarms. This allows for automated measurement operations under unattended conditions, reducing operator workload and improving the power plant's automation control level. Measurement data can be uploaded to the power plant monitoring platform in real time, facilitating remote monitoring by operators. Alarms are triggered promptly in case of abnormalities, ensuring stable equipment operation.

[0024] With a wide range of applications and strong versatility, this device is not only suitable for measuring the dryness of condenser inlet steam in 300MW and above thermal power generating units and gas-steam combined cycle units, but also for measuring the dryness of low-pressure steam (pressure 0.01-0.1MPa) in industries such as chemical, metallurgy, and papermaking. At the same time, parameters such as the power of the extraction pump and the flow metering range can be flexibly adjusted according to the actual application scenario. It has strong versatility and has broad application value. Attached Figure Description

[0025] Figure 1 This is a graph showing the relationship between the absolute pressure of steam and the density of saturated steam in the condenser inlet steam dryness detection device. Figure 2 This is a schematic diagram of the overall structure of the condenser inlet steam dryness detection device of the present invention. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention. Example 1

[0027] like Figure 2 As shown, this embodiment provides a condenser inlet steam dryness detection device, including: a sampling port, a measuring pipeline, a vacuum pump, a guide pipeline, a water tank, a PLC controller, and a data processing unit; One end of the sampling port is connected to the condenser inlet, and the other end is connected to the air pump through a measuring pipeline. The measuring pipeline is equipped with an absolute pressure transmitter 1, a volume flow meter 2, and a one-way check valve 3. The air pump is connected to the water tank through a guide pipe, which is equipped with a mass flow meter 4 and an electric shut-off valve 5.

[0028] The sampling port is made of 304 stainless steel and embedded flush with the inner wall of the condenser inlet pipe. This avoids disturbance to the steam flow caused by a protruding sampling port, ensuring that the extracted sample has the same flow pattern, humidity, and pressure as the steam in the pipe, thus guaranteeing the representativeness of the sample. A real-time pressure value of the extracted steam is acquired by an integrated absolute pressure transmitter 1, while the steam volumetric flow rate per unit time is recorded by a turbine-type volumetric flow meter 2. Both are synchronously triggered using the same data acquisition module, with an acquisition frequency set to 10Hz and a sampling delay of no more than 0.1s, ensuring the temporal consistency of pressure and volumetric flow rate data and providing accurate basic parameters for subsequent dryness calculations. The absolute pressure transmitter has a measurement range of 0-0.2MPa, an accuracy class of 0.05, and a resolution of 0.0001MPa, accurately capturing pressure fluctuations under low-pressure environments. The turbine-type volumetric flow meter has a measurement range of 0.01-0.1m³ / s, an accuracy of ±0.5%, and features strong anti-interference capabilities and fast response speed, making it suitable for measuring the volumetric flow rate of low-pressure steam.

[0029] Mass flow meter 4 is installed at the outlet end of the air pump, with straight pipe sections of no less than 5 times the pipe diameter reserved before and after it to ensure stable flow of liquid medium and avoid flow disturbance caused by pipe bends, valves and other components, which may affect measurement accuracy.

[0030] The one-way check valve 3 adopts a spring-loaded structure, featuring fast response, excellent sealing performance, and a leakage rate not exceeding 0.01 L / min. An electric shut-off valve is installed at the pipeline outlet, which is linked to the air pump for control. It remains normally closed when the measuring equipment is stopped, preventing backflow of liquid water from the storage tank and preventing external dust and impurities from entering the pipeline and causing blockage or corrosion. The valve seal is made of fluororubber, suitable for long-term use in humid environments, achieving an IP67 sealing performance rating. It is waterproof, dustproof, corrosion-resistant, and has a service life of over 3 years. All connecting pipelines are made of 304 stainless steel with an outer diameter of 25 mm, a wall thickness of 3 mm, and a compressive strength of not less than 1.6 MPa, capable of withstanding the low-pressure environment of condenser inlet steam and the corrosion of condensate. The pipeline interfaces use welded seals, achieved through argon arc welding. The welds are smooth, free of porosity and cracks, with a leakage rate not exceeding 1×10⁻⁻⁻⁶. 6 Pa·m³ / s, to avoid steam leakage affecting measurement accuracy and on-site safety.

[0031] The PLC controller adopts the Siemens S7-1200 series, possessing powerful logic control and data processing capabilities. It enables automatic start / stop of the measurement process, parameter acquisition, data calculation, anomaly alarms, and remote communication. The data acquisition module has a built-in high-speed data processing unit, capable of real-time conversion of pressure, volumetric flow rate, and mass flow rate, as well as dryness calculation. The storage capacity for sampled data is no less than 1 million records. It supports data export (via USB interface to a USB flash drive) and remote transmission, and supports the RS485 communication protocol, allowing measurement data to be uploaded in real-time to the power plant's DCS automation system and monitoring platform, facilitating remote monitoring of the measurement status by operators. Simultaneously, the system features an anomaly alarm function. When measurement data exceeds a set threshold (e.g., flow rate exceeding range, excessive pressure fluctuations, pipeline leaks, etc.), an audible and visual alarm is triggered. The alarm sound intensity is no less than 80dB, and the alarm indicator light is solid red. The alarm threshold can be manually set via the power plant monitoring platform or local control panel, allowing operators to promptly detect and handle abnormal situations.

[0032] The extraction pump is a specialized corrosion-resistant diaphragm pump adapted to the low-pressure working environment of the condenser. Its extraction power is flexibly adjustable within the range of 0.3-1.0 kW, and its extraction rate is adjustable within the range of 0.01-0.1 m³ / s, ensuring that the extracted steam sample flow rate is within the precise range of the subsequent volumetric flow meter and mass flow meter. It also meets the requirement of stably extracting steam samples from the low-pressure environment inside the condenser (pressure below 0.1 MPa). The extraction pump uses a polytetrafluoroethylene diaphragm, which is corrosion-resistant, wear-resistant, and has a service life of over 5 years. Its operating noise does not exceed 60 dB, making it suitable for noise control requirements at power plant sites.

[0033] The mass flow meter 4 is a high-precision liquid mass flow meter, specifically a Coriolis mass flow meter, which can be adapted to the measurement needs of condensed liquid media under normal temperature (20-30℃) and normal pressure (0.1-0.12MPa) conditions. The measurement accuracy error is controlled within ±0.5%, the repeatability error does not exceed ±0.2%, the response time does not exceed 0.5s, and it has a self-calibration function. The calibration program can be remotely started through the power plant monitoring platform without disassembling the equipment, thus reducing maintenance costs.

[0034] The electric shut-off valve 5 features remote control switching functionality, allowing seamless integration with the power plant's DCS automation system. Through a PLC controller, it enables automatic start / stop of the measurement process, data acquisition, and anomaly alarms, facilitating automated measurement operations under unattended conditions. The electric shut-off valve has a rated voltage of AC220V, a rated current of 1A, and a switching time not exceeding 5 seconds. It also features a manual emergency switch function; in the event of remote control failure, the valve can be manually opened or closed to ensure normal equipment operation.

[0035] Both the measuring pipeline and the flow guiding pipeline are made of 304 stainless steel, with an outer diameter of 25mm and a wall thickness of 3mm. The pipeline bends are made of arc elbows with a bending radius of not less than 5 times the pipe diameter to avoid excessive pipeline resistance that could cause steam flow disturbance. The pipeline is wrapped with an insulation layer made of rock wool with a thickness of 50mm, which can effectively prevent condensation from forming prematurely in the pipeline and affecting the measurement accuracy.

[0036] The data processing unit employs a 32-bit high-speed microcontroller with a processing speed of at least 100MHz. It can perform real-time numerical conversions of pressure, volumetric flow rate, and mass flow rate, as well as dryness calculations, with an accuracy of at least 0.1%. It also features data storage, export, and remote transmission capabilities, supporting the RS485 communication protocol with an adjustable communication rate within the range of 9600-19200bps. Measurement data can be uploaded to the power plant monitoring platform. Abnormal data (such as flow exceeding the range, excessive pressure fluctuations, abnormal liquid levels, and pipeline leaks) can trigger audible and visual alarms. Alarm thresholds can be manually set via the platform, and alarm information can be synchronously uploaded to the power plant's DCS system for timely handling by operators. The data acquisition module also has power-off protection; data can be retained for at least one year after a power outage to prevent data loss.

[0037] The water tank is equipped with vents and a filter at the top. The vents balance the pressure inside the tank, preventing damage from excessive pressure. The filter uses an activated carbon screen to block dust and impurities from entering the tank, ensuring clean recycled water and preventing blockage of the return pipe. A drain valve, a ball valve with a 15mm diameter, is located at the bottom of the tank for periodic removal of sediment. A monthly drain cycle is recommended. The inner wall of the tank is treated with an epoxy resin coating of 0.1mm thickness to prevent condensation from corroding the tank and extend its lifespan.

[0038] A pre-filter device with a 100-mesh stainless steel screen is added to the sampling port. The screen is removable and washable for regular cleaning, preventing dust and impurities in the steam from entering the measuring pipeline and causing blockage or damage to the measuring elements. The connection between the sampling port and the condenser inlet pipe is welded, with the weld seam flush with the inner wall of the pipe to avoid steam flow disturbance and ensure the representativeness of the sample.

[0039] The device is also equipped with a temperature compensation module. The temperature sensor uses a PT100 platinum resistance thermometer with a measurement range of 0-100℃ and an accuracy of ±0.1℃. It can collect temperature data of steam and condensate in the measurement pipeline in real time. The data processing unit performs temperature compensation on the pressure, volumetric flow rate and mass flow rate data to further improve the measurement accuracy and avoid the influence of temperature fluctuations on the measurement results. Example 2

[0040] This embodiment provides a control method for a condenser inlet steam dryness detection device. Based on the law of conservation of mass and the density characteristics of wet steam, it achieves accurate detection of condenser inlet steam dryness through four steps: sampling, conversion, measurement, and calculation. The core principle is as follows. Simultaneously, a robust protective structure ensures the accuracy of the sampling and measurement process, making it suitable for the low-pressure, space-constrained operating conditions of power plants. Sampling and Basic Parameter Acquisition: First, the electric shut-off valve is activated via the PLC controller. After a 10-second delay, the corrosion-resistant diaphragm-type vacuum pump is started to prevent damage to components from no-load operation. The vacuum pump precisely extracts wet steam samples from the condenser inlet section through the sampling port. The pre-filter at the sampling port filters out dust and impurities in the steam, ensuring sample purity. Simultaneously, absolute pressure transmitter 1 acquires the absolute pressure p (unit: kPa) of the inlet steam in real time, and turbine volumetric flow meter 2 records the volumetric flow rate v (unit: m³ / s) of the wet steam in real time. Both are synchronously acquired through the same data acquisition module at a frequency of 10Hz to ensure the time synchronization of pressure and volumetric flow rate data, providing accurate basic data for subsequent calculations. The temperature compensation module synchronously acquires the steam temperature t (unit: °C) in the pipeline for temperature compensation of subsequent data.

[0041] Vapor-Liquid Conversion and Mass Flow Measurement: The vacuum pump compresses the extracted wet steam sample, raising the outlet pressure to 0.1-0.12 MPa (close to atmospheric pressure). Under this pressure, the wet steam spontaneously condenses into room-temperature liquid water without additional heating or condensation, achieving efficient and energy-saving vapor-liquid conversion. The condensed liquid water is then accurately measured by horizontally arranged mass flow meters 4, with the mass flow rate m (unit: kg / s) precisely measured. Based on the law of conservation of mass, the mass flow rate of the condensed liquid water is completely consistent with the original mass flow rate of the extracted wet steam sample, with no media loss, ensuring the accuracy of the mass flow rate measurement. The measured liquid water flows into a sealed storage tank through a guide pipe, completing the media recovery.

[0042] Density calculation and dryness fraction derivation: Refer to the IF-97 International Standard for Steam Properties, such as... Figure 1 As shown, the steam pressure is collected by an absolute pressure transmitter. p The temperature t collected by the temperature compensation module is used to fit the saturated vapor density at the corresponding pressure and temperature. r (Unit: kg / m³). The condenser inlet pressure was obtained by fitting experimental data. p (0-0.2MPa) and saturated vapor density r The fitting equation is: r =-0.00002 p ²+0.007 p +0.0011, the goodness of fit of the equation. RA value ≥ 0.999 accurately reflects the relationship between pressure and saturated vapor density. This is combined with the actual measured mass flow rate of the liquid medium using a mass flow measurement element. m The wet steam volumetric flow rate v measured by the volumetric flow meter is calculated using the density formula. r 1= m / v Calculate the actual density of the wet steam. r 1 (Unit: kg / m³). Given that the volume fraction of liquid water in wet steam is extremely small (usually less than 5%), it can be ignored. The mass of liquid water per unit volume of wet steam can be approximately equivalent to the measured density of wet steam. r 1 and corresponding pressure p Lower saturated vapor density r The difference. Based on the definition of wet steam dryness (i.e., the mass ratio of dry steam to wet steam per unit mass of wet steam), the formula for calculating dryness is derived as follows: x = r / r 1. The data processing unit completes the above calculations in real time and outputs the final steam dryness value. x (Range 0-1) Data is uploaded in real time to the power plant monitoring platform and local control panel for easy viewing by operators.

[0043] Safety and Media Recovery: During measurement, the one-way check valve effectively prevents outside air from seeping into the condenser, ensuring a stable vacuum environment. The electric shut-off valve is linked to the vacuum pump, closing the valve when the unit stops to prevent liquid water backflow and impurities from entering the pipeline. The liquid level sensor in the water storage tank monitors the liquid level in real time. When the liquid level reaches the set upper limit, the return pump automatically starts, guiding the recovered condensate back to the condenser circulating water system, realizing water resource recycling. Impurities at the bottom of the water tank are periodically discharged through the drain valve to ensure the cleanliness of the recovered water. Example 3

[0044] This embodiment provides a calibration and maintenance method for a condenser inlet steam dryness detection device: After installation, this device requires no-load commissioning, full-scale calibration, and on-site comparison testing to ensure that the measurement accuracy meets the requirements. No-load commissioning: Start the equipment without taking steam samples, check the operating status of each component and the sealing of the pipeline, and ensure that there are no leaks or abnormal noises, and that the air pump, valves, sensors and controllers are operating normally, and that data acquisition and transmission are normal.

[0045] Full-scale calibration: Mass flow meter 4 is calibrated using the standard weight method. A standard weight (accuracy ±0.01g) is connected to the calibration loop, and the measured value is compared with the standard value. The calibration parameters are adjusted to ensure that the measurement accuracy error is controlled within ±0.5%. Absolute pressure transmitter 1 is calibrated using a standard pressure source (accuracy class 0.01). The output parameters of the pressure transmitter are adjusted to ensure that the pressure measurement accuracy meets the requirements. Volumetric flow meter is calibrated using a standard volumetric tube to ensure that the volumetric flow measurement accuracy meets the requirements.

[0046] On-site comparison test: The dryness of the condenser inlet steam was measured simultaneously with the laboratory standard measuring equipment (accuracy ±0.1%) for 24 hours. Two sets of measurement data were recorded, and the measurement error was calculated to ensure that the error was within ±1% to meet the measurement requirements of the power plant.

[0047] Routine maintenance cycle and contents: Check the pipeline sealing, valve status, pre-filter cleanliness, and water tank level monthly; clean the pre-filter and drain impurities from the bottom of the water tank; calibrate all measuring elements (pressure transmitter, volumetric flow meter, mass flow meter) every 6 months to ensure measurement accuracy; disassemble and maintain the air pump annually, replace the diaphragm and vulnerable parts, and check the operation status of the return pump; regularly check the integrity of the insulation layer, and repair any damage promptly to prevent premature condensation of the medium in the pipeline.

[0048] Furthermore, it should be noted that in the specific embodiments described in this specification, parameter names, component models, and measurement range specifications can be flexibly adjusted according to actual application scenarios. For example, a 0.5kW air pump and a corresponding small-range flow meter can be selected for small units, and a pre-filter can be added at the sampling port for high dust conditions. The above content is only an exemplary explanation of the present invention. All equivalent transformations or simple substitutions made based on the concept of this invention and its technical features and principles, such as replacing the turbine volumetric flow meter with an electromagnetic volumetric flow meter, or replacing the PLC controller with a single-chip microcomputer controller, are all within the protection scope of this invention. Those skilled in the art can make various modifications and additions to the specific embodiments, or use similar technical means to replace them. At the same time, this device can also be adapted to low-pressure steam dryness measurement scenarios in industries such as chemical and metallurgical processing. As long as it does not deviate from the core measurement principle of the present invention and exceed the protection scope defined by the claims, it is within the protection scope of the present invention. In addition, after installation, this device requires no-load commissioning, full-scale calibration, and on-site comparison testing. No-load commissioning requires checking the operating status and sealing of each component to ensure no leakage or abnormal noise. Full-scale calibration uses the standard weight method to calibrate the mass flow meter and a standard pressure source to calibrate the pressure detection device. On-site comparison testing can be performed synchronously with standard laboratory measuring equipment to ensure that the measurement error is within the allowable range. The calibration cycle is recommended to be once every 6 months to ensure long-term measurement accuracy.

[0049] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, 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. Additionally, in the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, in the accompanying drawings of this invention, the fill patterns are only for distinguishing layers and do not constitute any other limitation.

[0050] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A device for detecting the dryness of condenser inlet steam, characterized in that, include: Sampling port, measuring pipeline, air pump, diversion pipeline, water tank, PLC controller and data processing unit; One end of the sampling port is connected to the condenser inlet, and the other end is connected to the air pump through a measuring pipeline. The measuring pipeline is equipped with an absolute pressure transmitter, a volumetric flow meter, and a one-way check valve. The air pump is connected to the water tank through a guide pipe, and the guide pipe is equipped with a mass flow meter and an electric shut-off valve; The PLC controller is used to start the electric shut-off valve and the vacuum pump. The vacuum pump draws a wet steam sample from the condenser inlet through the sampling port. The absolute pressure transmitter collects the absolute pressure of the wet steam in real time, and the volumetric flow meter records the volumetric flow rate of the wet steam in real time. The vacuum pump compresses the drawn wet steam sample, and the wet steam spontaneously condenses into liquid water. The mass flow rate of the condensed liquid water is measured by the mass flow meter. The mass flow rate of the condensed liquid water is consistent with the mass flow rate of the original drawn wet steam sample. The measured liquid water flows into the water tank through the guide pipe. The data processing unit is used to calculate the condenser inlet steam dryness based on the absolute pressure and volumetric flow rate of the wet steam and the mass flow rate of the condensed liquid water.

2. The condenser inlet steam dryness detection device according to claim 1, characterized in that, The sampling port is made of 304 stainless steel and has a 100-mesh stainless steel filter in front.

3. The condenser inlet steam dryness detection device according to claim 1, characterized in that, The air pump is a corrosion-resistant diaphragm air pump with an air pumping power adjustment range of 0.3-1.0kW and an air pumping volume adjustment range of 0.01-0.1m³ / s.

4. The condenser inlet steam dryness detection device according to claim 3, characterized in that, The air pump uses a polytetrafluoroethylene diaphragm.

5. The condenser inlet steam dryness detection device according to claim 1, characterized in that, The mass flow meter is a Coriolis mass flow meter.

6. The condenser inlet steam dryness detection device according to claim 1, characterized in that, The one-way check valve is a stainless steel spring-loaded structure with an opening pressure of 0.005 MPa and a leakage rate of ≤0.01 L / min. It is used to prevent outside air from seeping into the condenser and to maintain the vacuum environment of the condenser.

7. The condenser inlet steam dryness detection device according to claim 1, characterized in that, The sealing components of the electric shut-off valve are made of fluororubber, with a sealing rating of IP67.

8. The condenser inlet steam dryness detection device according to claim 1, characterized in that, It also includes temperature sensors, which are installed in the measuring pipeline and the flow guiding pipeline respectively, for real-time acquisition of steam and condensate temperatures.

9. The control method for the condenser inlet steam dryness detection device according to claim 1, characterized in that: The PLC controller starts the electric shut-off valve, and after a 10-second delay, it starts the vacuum pump. The vacuum pump extracts wet steam samples from the condenser inlet through the sampling port. The absolute pressure transmitter collects the absolute pressure p of the wet steam in real time, and the volumetric flow meter records the volumetric flow rate v of the wet steam in real time. Both are collected synchronously through the same data acquisition module at a frequency of 10Hz. The vacuum pump compresses the extracted wet steam sample, raising the outlet pressure to 0.1-0.12 MPa. Under this pressure, the wet steam spontaneously condenses into room-temperature liquid water. The condensed liquid water passes through a mass flow meter. According to the law of conservation of mass, the mass flow rate of the condensed liquid water is consistent with the mass flow rate of the original extracted wet steam sample. The measured liquid water flows into a water tank through a guide pipe, completing the recovery of the medium.

10. The control method for the condenser inlet steam dryness detection device according to claim 8, characterized in that: The data processing unit refers to the IF-97 international steam properties standard and combines the steam pressure collected by the absolute pressure transmitter. p The saturated vapor density at the corresponding pressure and temperature is obtained by fitting the temperature t collected by the temperature sensor. ρ The condenser inlet pressure was obtained by fitting experimental data. p With saturated vapor density ρ The fitting equation is: ρ =-0.00002 p ²+0.007 p +0.0011, the goodness of fit of the equation. R ²≥0.999; Condensate flow rate measured by mass flow meter m The wet steam volumetric flow rate v measured by the volumetric flow meter is calculated according to the density formula. ρ 1= m / v Calculate the actual density of the wet steam. ρ 1; The mass of liquid water per unit volume of steam is approximately equal to the measured density of wet steam. ρ 1 and corresponding pressure p Lower saturated vapor density ρ The difference; based on the definition of wet steam dryness, that is, the mass ratio of dry steam in a unit mass of wet steam, the formula for calculating dryness is derived as follows: x = ρ / ρ 1.

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