Real-time on-line measuring system and method for circulating water flow rate of thermal power plant

Abstract

The application discloses a circulating water flow real-time online measurement system and method for a thermal power plant. The system comprises a circulating water pump, a condenser and a controller, and the circulating water pump is connected with the condenser through a pipeline. A condenser backwater pipeline and a condenser circulating water backwater temperature measuring element are arranged at the outlet of the condenser. The system further comprises an open water pipeline connected with the pipeline and the condenser backwater pipeline at two ends. A flowmeter and a backwater temperature measuring element are arranged on the open water pipeline. A circulating water temperature measuring element is arranged on the condenser backwater pipeline, and the circulating water temperature measuring element is located downstream of the connection position of the open water pipeline and the condenser backwater pipeline. The method comprises the following steps: measuring the backwater temperature of the open water, the condenser circulating water backwater temperature and the circulating water temperature; calculating the water enthalpy values corresponding to the temperatures; and calculating the circulating water flow. The application has the advantages of simple structure, convenient operation, real-time online measurement of the circulating water flow of the thermal power plant and high measurement precision.

Description

Technical Field

[0001] This invention relates to the field of steam turbine technology, specifically to a real-time online measurement system and method for circulating water flow in thermal power plants. Background Technology

[0002] In thermal power plants, circulating water flow rate is a crucial parameter for condenser and cooling tower performance diagnosis and cold-end operation optimization. However, in actual production, both direct and indirect soft measurement of circulating water flow rate present significant challenges. The main reasons are:

[0003] I. For direct measurement: (1) The circulating water pipes of large steam turbine generator sets are too large (pipe diameter more than 1 meter) and the circulating water flow is huge (more than 30,000 tons per hour), which means that there is currently no precision instrument that can accurately measure the circulating water flow in real time. (2) The circulating water pipes of most power plants are buried deep underground, and the straight pipe sections exposed on the surface are short, which does not meet the measurement requirements of some measuring instruments (such as ultrasonic measuring instruments), making it difficult for measuring instruments to perform measurements conveniently. (3) The circulating water flow of the unit is greatly affected by the unit's operating mode and equipment status. For example, the circulating water flow is different when one circulating water pump is running versus when two circulating water pumps are running, and the flow is different when a low-speed circulating water pump is running versus a high-speed circulating water pump. When the condenser heat exchange tube bundle is scaled or blocked, or when the circulating water pump efficiency is low, the circulating water flow will change. These effects mean that actual production requires real-time monitoring of the unit's circulating water flow.

[0004] II. For indirect measurement: Currently, there is another online soft measurement method for circulating water flow, such as Chinese invention patent application CN109408978A, which discloses an online soft measurement method for circulating water flow in a steam turbine generator set, used to measure the circulating water flow through the condenser heat exchange tube bundle. It obtains the current unit operating heat rate by collecting real-time operating data from the unit's DCS system, then calculates the current condenser heat load, and finally calculates the circulating water flow based on the condenser heat load. However, this method has the following problems: It calculates the circulating water flow through the condenser, excluding the open cooling water flow used for cooling closed-loop cooling water, making it unsuitable for situations requiring the full circulating water flow (such as circulating water pump performance tests, cooling tower tests, etc.). This method requires high stability of the turbine unit's operating parameters, making online measurement of circulating water flow difficult; the condenser heat balance equation used in this method includes some simplified empirical coefficients, resulting in low accuracy in calculating the circulating water flow. Summary of the Invention

[0005] The technical problem to be solved by this invention is:

[0006] Existing technologies cannot perform real-time online measurement of circulating water flow in thermal power plants, and the measurement accuracy is not high.

[0007] The present invention solves the above-mentioned technical problems through the following technical means:

[0008] A real-time online measurement system for circulating water flow in a thermal power plant includes a circulating water pump and a condenser, wherein the circulating water pump and the condenser are connected by a pipeline;

[0009] The condenser outlet is provided with a condenser return water pipe and a condenser circulating water return water temperature measuring element, and also includes an open water pipe with both ends connected to the pipe and the condenser return water pipe respectively. The open water pipe is provided with a flow meter and a return water temperature measuring element, and the condenser return water pipe is provided with a circulating water temperature measuring element. The circulating water temperature measuring element is located downstream of the connection between the open water pipe and the condenser return water pipe.

[0010] The condenser circulating water return water temperature measuring element, the return water temperature measuring element, and the circulating water temperature measuring element are each provided in a plurality of units; the plurality of condenser circulating water return water temperature measuring elements are arranged radially and uniformly in the condenser return water pipe at the condenser outlet; the plurality of return water temperature measuring elements are arranged radially and uniformly in the open water pipe; the plurality of circulating water temperature measuring elements are arranged radially and uniformly in the condenser return water pipe.

[0011] It also includes a controller. The condenser circulating water return water temperature measuring element, flow meter, return water temperature measuring element, and circulating water temperature measuring element are respectively connected to the controller. The controller can calculate the corresponding water enthalpy value based on the temperature detected by the condenser circulating water return water temperature measuring element, return water temperature measuring element, and circulating water temperature measuring element, and calculate the circulating water flow rate through the circulating water pump based on the water enthalpy value and the flow rate detected by the flow meter.

[0012] In practical application, the real-time online measurement system for circulating water flow in thermal power plants of this invention first measures the flow rate Q1 of the open-loop water using a flow meter, and the return water temperature t1 using a return water temperature sensing element. Then, it measures the condenser circulating water return water temperature t2 using a condenser circulating water return water temperature sensing element, and the temperature t3 of the circulating water after the condenser return water and open-loop water are mixed using a circulating water temperature sensing element. The controller calculates the enthalpy values ​​h1, h2, and h3 corresponding to the three temperatures t1, t2, and t3 using the internationally recognized IAPWS-IF97 formula for water and steam properties. Finally, based on the obtained data, the controller calculates the total circulating water flow rate Q2 flowing through the circulating water pump. Compared to existing technologies, this measurement system has a simple structure, is easy to operate, and allows for real-time online measurement of circulating water flow in thermal power plants with high accuracy.

[0013] In an optimized configuration, the condenser circulating water return water temperature measuring element, the return water temperature measuring element, and the circulating water temperature measuring element all adopt resistance temperature detectors (RTDs).

[0014] In the optimized configuration, five temperature measuring elements are respectively set for the condenser circulating water return water, the return water, and the circulating water.

[0015] The optimized flow meter is an orifice plate flow meter.

[0016] In an optimized configuration, the circulating water temperature sensing element is located at least 10 meters away from the connection point between the open water pipe and the condenser return water pipe.

[0017] Setting the circulating water temperature sensing element at a distance of more than 10 meters from the connection point between the open water pipe and the condenser return water pipe ensures sufficient mixing and results in more accurate and reliable measurements.

[0018] In an optimized configuration, a water-to-water heat exchanger is also installed on the open water pipe.

[0019] In an optimized configuration, the water-to-water heat exchanger, flow meter, and return water temperature measuring element are arranged sequentially along the open water pipeline.

[0020] The present invention also discloses a measurement method using the real-time online measurement system for circulating water flow in a thermal power plant as described in any of the above claims, comprising the following steps:

[0021] Step 1:

[0022] The flow rate Q1 of the open water is measured by a flow meter, and the return water temperature t1 of the open water is measured by a return water temperature measuring element.

[0023] Step Two:

[0024] The condenser circulating water return temperature t2 is measured by the condenser circulating water return temperature measuring element, and the circulating water temperature t3 after the condenser return water and open water are mixed is measured by the circulating water temperature measuring element.

[0025] Step 3:

[0026] Using the internationally recognized IAPWS-IF97 formula for the properties of water and water vapor, calculate the water enthalpy values ​​h1, h2, and h3 corresponding to the above three temperatures t1, t2, and t3;

[0027] Step Four:

[0028] Based on the data obtained from steps one to three, calculate the total circulating water flow rate Q2 that flows through the circulating water pump.

[0029] In the optimized step four, the formula for calculating the total circulating water flow rate Q2 through the circulating water pump is:

[0030]

[0031] The meanings of each letter code are as follows: Q1 represents the flow rate of open water; h1 represents the enthalpy of the return water of the open cooling water system; h2 represents the enthalpy of the circulating water at the condenser outlet; and h3 represents the enthalpy of the circulating water return.

[0032] The measurement method of this invention can accurately measure and calculate the total flow rate of circulating water flowing through the circulating water pump. The measurement and calculation are simple and the measurement accuracy is high.

[0033] The advantages of this invention are:

[0034] 1. In practical application, the real-time online measurement system for circulating water flow in thermal power plants according to this invention first measures the flow rate Q1 of the open-loop water using a flow meter, and the return water temperature t1 using a return water temperature sensing element; then, it measures the condenser circulating water return water temperature t2 using a condenser circulating water return water temperature sensing element, and finally, it measures the temperature t3 of the circulating water after the condenser return water and open-loop water are mixed using a circulating water temperature sensing element. The controller calculates the enthalpy values ​​h1, h2, and h3 corresponding to the three temperatures t1, t2, and t3 using the internationally recognized IAPWS-IF97 formula for water and steam properties. Then, based on the obtained data, the controller calculates the total circulating water flow rate Q2 flowing through the circulating water pump. Compared to existing technologies, this measurement system has a simple structure, is easy to operate, and can perform real-time online measurement of circulating water flow in thermal power plants with high accuracy.

[0035] 2. Placing the circulating water temperature sensing element at a distance of more than 10 meters from the connection point between the open water pipe and the condenser return water pipe ensures sufficient mixing, resulting in more accurate and reliable measurement results.

[0036] 3. The measurement method in this invention can accurately measure and calculate the total flow rate of circulating water flowing through the circulating water pump. The measurement and calculation are simple and the measurement accuracy is high. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the real-time online measurement system for circulating water flow in a thermal power plant according to Embodiment 1 of the present invention; wherein,

[0038] Circulating water pump-1; Condenser-2; Pipeline-3; Condenser return water pipeline-4; Condenser circulating water return water temperature measuring element-5; Open water pipeline-6; Flow meter-7; Return water temperature measuring element-8; Circulating water temperature measuring element-9; Water-to-water heat exchanger-10. Detailed Implementation

[0039] 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 in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1:

[0041] like Figure 1 As shown, a real-time online measurement system for circulating water flow in a thermal power plant includes a circulating water pump 1, a condenser 2, a pipeline 3, a condenser return water pipeline 4, a condenser circulating water return water temperature measuring element 5, an open water pipeline 6, a flow meter 7, a return water temperature measuring element 8, a circulating water temperature measuring element 9, a water-to-water heat exchanger 10, and a controller.

[0042] like Figure 1 As shown, the circulating water pump 1 is connected to the condenser 2 via a pipe 3; the outlet of the condenser 2 is equipped with a condenser return water pipe 4 and a condenser circulating water return water temperature measuring element 5.

[0043] like Figure 1 As shown, the two ends of the open water pipe 6 are connected to pipe 3 and condenser return water pipe 4, respectively. The open water pipe 6 of the unit is equipped with a water-to-water heat exchanger 10, a flow meter 7, and a return water temperature measuring element 8 in sequence. The flow meter 7 is a high-precision orifice plate flow meter. The orifice plate flow meter is installed on the return water header after the open water flows through all users and is installed on a straight pipe section with sufficient distance before and after.

[0044] like Figure 1 As shown, a circulating water temperature measuring element 9 is installed on the condenser return water pipe 4. The circulating water temperature measuring element 9 is located downstream of the connection between the open water pipe 6 and the condenser return water pipe 4. The installation position is on the circulating water return main pipe after the open water and circulating water return water are mixed, and the circulating water temperature measuring element 9 is more than 10 meters away from the connection between the open water pipe 6 and the condenser return water pipe 4.

[0045] In this embodiment, the condenser circulating water return water temperature measuring element 5, the return water temperature measuring element 8, and the circulating water temperature measuring element 9 are all high-precision thermal resistors.

[0046] Several condenser circulating water return water temperature measuring elements 5, 8, and 9 are respectively provided, and in this embodiment, 5 of each are provided.

[0047] Five condenser circulating water return temperature sensing elements 5 are evenly arranged radially in the condenser return water pipe 4 at the outlet of condenser 2, with equal distances between adjacent condenser circulating water return temperature sensing elements 5. The middle condenser circulating water return temperature sensing element 5 is positioned on the axis of the condenser return water pipe 4.

[0048] Five return water temperature sensing elements 8 are evenly arranged radially in the open water pipe 6, with equal distances between adjacent return water temperature sensing elements 8. The return water temperature sensing elements 8 are installed on the main pipe before the open water and circulating water return water are mixed. The middle return water temperature sensing element 8 is located on the axis of the open water pipe 6.

[0049] Five circulating water temperature sensing elements 9 are evenly arranged radially in the condenser return water pipe 4, with equal distances between adjacent circulating water temperature sensing elements 9. The middle circulating water temperature sensing element 9 is positioned on the axis of the condenser return water pipe 4.

[0050] The condenser circulating water return water temperature measuring element 5, flow meter 7, return water temperature measuring element 8, and circulating water temperature measuring element 9 are respectively connected to the controller. The condenser circulating water return water temperature measuring element 5, flow meter 7, return water temperature measuring element 8, and circulating water temperature measuring element 9 can transmit the detected data to the controller. The controller is existing technology and can receive the detected data and perform calculations based on the received data. For example, it can calculate the water enthalpy value corresponding to each temperature based on the detected return water temperature, condenser circulating water return water temperature, and circulating water temperature, calculate the total circulating water flow rate through the circulating water pump 1 based on the water enthalpy value and the flow rate of the open water, and output the calculation results.

[0051] In practical application, the real-time online measurement system for circulating water flow in thermal power plants of this invention first measures the flow rate Q1 of the open-loop water using flow meter 7, and the return water temperature t1 using return water temperature sensing element 8; then, it measures the condenser circulating water return water temperature t2 using condenser circulating water return water temperature sensing element 5, and the temperature t3 of the circulating water after the mixture of condenser return water and open-loop water using circulating water temperature sensing element 9. The controller calculates the enthalpy values ​​h1, h2, and h3 corresponding to the three temperatures t1, t2, and t3 using the internationally recognized IAPWS-IF97 formula for water and steam properties. Then, based on the obtained data, the controller calculates the total circulating water flow rate Q2 flowing through the circulating water pump 1. Compared to existing technologies, this measurement system has a simple structure, is easy to operate, and allows for real-time online measurement of circulating water flow in thermal power plants with high accuracy.

[0052] Setting the circulating water temperature measuring element 9 at a distance of more than 10 meters from the connection point between the open water pipe 6 and the condenser return water pipe 4 ensures sufficient mixing and makes the measurement results more accurate and reliable.

[0053] Example 2:

[0054] This invention also discloses a measurement method using the above-mentioned real-time online measurement system for circulating water flow in thermal power plants, used to measure the total circulating water flow through the circulating water pump (cooling tower) in a steam turbine generator set, comprising the following steps:

[0055] Step 1:

[0056] A flow meter 7 and a return water temperature measuring element 8 are installed on the open water pipe 6 of the unit. The flow rate Q1 of the open water is measured by the flow meter 7, and the return water temperature t1 of the open water is measured by the return water temperature measuring element 8. Here, t1 is the average value of the measurement results of each return water temperature measuring element 8, and the return water temperature t1 is calculated by the controller.

[0057] Step Two:

[0058] The condenser circulating water return temperature t2 is measured by the condenser circulating water return temperature measuring element 5, and the circulating water temperature t3 after the condenser return water and open water are mixed is measured by the circulating water temperature measuring element 9. Here, t2 is the average value of the measurement results of each condenser circulating water return temperature measuring element 5, and t3 is the average value of the measurement results of each circulating water temperature measuring element 9. The above-mentioned condenser circulating water return temperature t2 and circulating water temperature t3 are calculated by the controller.

[0059] Step 3:

[0060] The controller calculates the water enthalpy values ​​h1, h2, and h3 corresponding to the three temperatures t1, t2, and t3 using the internationally recognized IAPWS-IF97 formula for the properties of water and water vapor. The IAPWS-IF97 formula for the properties of water and water vapor is a well-known prior art.

[0061] Step Four:

[0062] Based on the data obtained from steps one to three, the controller calculates the total circulating water flow rate Q2 flowing through the circulating water pump 1. The formula for calculating the total circulating water flow rate Q2 flowing through the circulating water pump 1 is:

[0063]

[0064] The meanings of each letter code are as follows: Q1 represents the flow rate of open water, that is, the return water flow rate of the open cooling water system (before mixing with the circulating water return header); h1 represents the enthalpy of the return water of the open cooling water system; h2 represents the enthalpy of the circulating water at the condenser outlet; h3 represents the enthalpy of the circulating water return (after being fully mixed with the open cooling water).

[0065] The measurement method of this invention can accurately measure and calculate the total flow rate of circulating water flowing through the circulating water pump 1. The measurement and calculation are simple and the measurement accuracy is high.

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A real-time online measurement system for circulating water flow in a thermal power plant, characterized in that: It includes a circulating water pump (1) and a condenser (2), and the circulating water pump (1) and the condenser (2) are connected by a pipe (3); The condenser (2) is provided with a condenser return water pipe (4) and a condenser circulating water return water temperature measuring element (5) at its outlet. It also includes an open water pipe (6) that is connected to the pipe (3) and the condenser return water pipe (4) at both ends respectively. The open water pipe (6) is provided with a flow meter (7) and a return water temperature measuring element (8). The condenser return water pipe (4) is provided with a circulating water temperature measuring element (9). The circulating water temperature measuring element (9) is located downstream of the connection between the open water pipe (6) and the condenser return water pipe (4). Several condenser circulating water return water temperature measuring elements (5), return water temperature measuring elements (8), and circulating water temperature measuring elements (9) are respectively provided; several condenser circulating water return water temperature measuring elements (5) are evenly arranged radially in the condenser return water pipe (4) at the outlet of the condenser (2); several return water temperature measuring elements (8) are evenly arranged radially in the open water pipe (6); several circulating water temperature measuring elements (9) are evenly arranged radially in the condenser return water pipe (4); It also includes a controller. The condenser circulating water return water temperature measuring element (5), flow meter (7), return water temperature measuring element (8), and circulating water temperature measuring element (9) are respectively connected to the controller. The controller can calculate the corresponding water enthalpy value based on the temperature detected by the condenser circulating water return water temperature measuring element (5), return water temperature measuring element (8), and circulating water temperature measuring element (9), and calculate the circulating water flow rate through the circulating water pump (1) based on the water enthalpy value and the flow rate detected by the flow meter (7).

2. The real-time online measurement system for circulating water flow in thermal power plants according to claim 1, characterized in that: The condenser circulating water return water temperature measuring element (5), return water temperature measuring element (8), and circulating water temperature measuring element (9) are all thermal resistors.

3. The real-time online measurement system for circulating water flow in thermal power plants according to claim 1, characterized in that: Five condenser circulating water return water temperature measuring elements (5), five return water temperature measuring elements (8), and five circulating water temperature measuring elements (9) are respectively provided.

4. The real-time online measurement system for circulating water flow in thermal power plants according to claim 1, characterized in that: The flow meter (7) is an orifice plate flow meter.

5. The real-time online measurement system for circulating water flow in thermal power plants according to claim 1, characterized in that: The circulating water temperature measuring element (9) is located more than 10 meters away from the connection point between the open water pipe (6) and the condenser return water pipe (4).

6. The real-time online measurement system for circulating water flow in thermal power plants according to claim 1, characterized in that: A water-to-water heat exchanger (10) is also installed on the open water pipe (6).

7. The real-time online measurement system for circulating water flow in thermal power plants according to claim 6, characterized in that: The water-to-water heat exchanger (10), flow meter (7), and return water temperature measuring element (8) are arranged sequentially along the direction of the open water pipe (6).

8. A measurement method using the real-time online measurement system for circulating water flow in a thermal power plant as described in any one of claims 1-7, characterized in that: Includes the following steps: Step 1: The flow rate Q1 of the open water is measured by the flow meter (7), and the return water temperature t1 of the open water is measured by the return water temperature measuring element (8). Step Two: The condenser circulating water return water temperature t2 is measured by the condenser circulating water return water temperature measuring element (5), and the circulating water temperature t3 after the condenser return water and open water are mixed is measured by the circulating water temperature measuring element (9). Step 3: Using the internationally recognized IAPWS-IF97 formula for the properties of water and water vapor, calculate the water enthalpy values ​​h1, h2, and h3 corresponding to the above three temperatures t1, t2, and t3; Step Four: Based on the data obtained from steps one to three, calculate the total circulating water flow rate Q2 through the circulating water pump (1).

9. The measurement method according to claim 8, characterized in that: In step four, the formula for calculating the total circulating water flow rate Q2 through the circulating water pump (1) is as follows: The meanings of each letter code are as follows: Q1 represents the flow rate of open water; h1 represents the enthalpy of the return water of the open cooling water system; h2 represents the enthalpy of the circulating water at the condenser outlet; and h3 represents the enthalpy of the circulating water return.

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