A system and method for calculating the exhaust characteristics of low-pressure cylinders

Abstract

This invention discloses a system and method for calculating the exhaust characteristics of a low-pressure cylinder, comprising a boiler, a regenerative system, a feedwater pump turbine, a condensate pump, a condensate flow measurement device, a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder. The regenerative system includes a high-pressure heater system and a low-pressure heater system. This invention eliminates the need for extending the expansion line. Using condensate flow as a reference, by installing drain flow measurement devices for low-pressure heaters 7 and 8, the drain flow rates entering low-pressure heater 8 and the condenser are measured. The difference between these two flow rates is the extraction steam flow rate of low-pressure heater 8. Combined with heat balance calculations for low-pressure heaters 5 and 6, the extraction steam flow rate of low-pressure heater 7 can be obtained. This allows for convenient and accurate calculation of the low-pressure cylinder exhaust flow rate and enthalpy, among other characteristic parameters.

Description

Technical Field

[0001] This invention relates to the field of thermal power generation technology, specifically to a system and method for calculating the exhaust characteristics of low-pressure cylinders. Background Technology

[0002] The condenser exhaust flow rate can be used to accurately calculate the condenser heat transfer coefficient, and the condenser heat transfer coefficient can be used to monitor the condenser heat transfer in real time, determine whether the condenser performance has deteriorated, and perform quantitative analysis of the deterioration.

[0003] The existing technology calculates the condenser exhaust flow rate according to the steam turbine thermodynamic test procedure, which is very complicated. The calculation uses all performance monitoring points on the steam turbine side. Furthermore, since the steam turbine's 7th stage extraction, 8th stage extraction, and low-pressure cylinder exhaust are all in the humid steam region, the enthalpy value cannot be directly obtained from pressure and temperature. The computer needs to perform iterative calculations of the thermal balance of the entire steam turbine thermodynamic system. Due to the large number of thermodynamic measuring points involved, the measurement uncertainty is increased, making it inconvenient to accurately and in real-time monitor the condenser exhaust flow rate. Summary of the Invention

[0004] The purpose of this invention is to provide a system and method for calculating the exhaust characteristics of the low-pressure cylinder, thereby solving the problem of difficulty in measuring and calculating the condenser exhaust flow rate mentioned in the background art. Current technology uses a method of determining the expansion line from the steam inlet point of the intermediate-pressure cylinder and the extraction point of the final stage, extending the expansion line to the exhaust pressure to determine the enthalpy ELEP at the end of the expansion line. This invention, however, does not require extending the expansion line. Using the condensate flow rate as a reference, by installing drain flow devices for low-pressure heaters 7 and 8, the drain flow rates entering low-pressure heater 8 and the condenser are measured. The difference between these two is the extraction steam flow rate of low-pressure heater 8. Combined with the heat balance calculations of low-pressure heaters 5 and 6, the extraction steam flow rate of low-pressure heater 7 can be obtained, thus enabling convenient and accurate calculation of the low-pressure cylinder exhaust flow rate and enthalpy, among other characteristic parameters.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a system for calculating the exhaust characteristics of a low-pressure cylinder, comprising a boiler, a regenerative system, a feedwater pump turbine, a condensate pump, a condensate flow measurement device, a high-pressure cylinder, an intermediate-pressure cylinder, and a low-pressure cylinder.

[0006] The regenerative system includes a high-pressure heater system and a low-pressure heater system;

[0007] The high-pressure heater system consists of high-pressure heater No. 1, high-pressure heater No. 2, and high-pressure heater No. 3 connected in sequence.

[0008] The low-pressure heater system has a secondary end condensate flow rate measuring device and an end condensate flow rate measuring device installed on the condensate pipes of the two-stage low-pressure heaters near the condenser. The secondary end condensate flow rate measuring device is used to measure the condensate flow rate of the secondary end stage low-pressure heater in the low-pressure cylinder, and the end condensate flow rate measuring device is used to measure the condensate flow rate from the final stage low-pressure heater in the low-pressure cylinder to the condenser, which is used for calculating the extraction enthalpy of the final stage low-pressure heater.

[0009] The low-pressure heater system consists of a deaerator, No. 5 low-pressure heater, No. 6 low-pressure heater, No. 7 low-pressure heater, No. 8 low-pressure heater, shaft seal heater, and condenser connected in sequence, and a condensate flow measurement device is installed between the deaerator and No. 5 low-pressure heater.

[0010] The secondary terminal condensate flow measurement device is installed on the condensate pipe between low-pressure heater No. 7 and low-pressure heater No. 8; the terminal condensate flow measurement device is installed on the condensate pipe between low-pressure heater No. 8 and condenser.

[0011] Preferably, the high-pressure cylinder, medium-pressure cylinder, and low-pressure cylinder are all connected to the boiler via drainage pipes.

[0012] Preferably, the condenser is connected to the condensate pump and the shaft seal heater via a drain pipe.

[0013] Preferably, the deaerator is connected to the feedwater pump turbine via a drainage pipe.

[0014] A method for calculating the exhaust characteristics of a low-pressure cylinder, based on the condensate flow rate measured by the secondary end condensate flow rate measuring device, calculates the inlet steam flow rate of low-pressure heater No. 8, and combines this with the heat balance calculation of low-pressure heaters No. 5 and No. 6 to obtain the inlet steam flow rate of low-pressure heater No. 7, thus obtaining the exhaust characteristic parameters; including the following:

[0015] S1, Calculation of steam and water flow rate in the high and medium pressure section;

[0016] S2, Calculation of steam and water flow rate in the low-pressure section;

[0017] S3, Heater flow balance calculation.

[0018] Preferably, step S1 includes the following steps:

[0019] S10. Based on the condensate flow rate at the deaerator inlet, the steam flow rate entering each high-pressure heater is obtained through iterative calculation of the feedwater flow rate and thermal balance calculation of the high-pressure heater.

[0020] S11. Combine the measurement or calculation of auxiliary flow rate to obtain the overall steam and water flow rate of the high and medium pressure section, including the main steam flow rate, the high pressure cylinder exhaust flow rate, the intermediate pressure cylinder inlet steam flow rate, and the intermediate pressure cylinder exhaust flow rate.

[0021] Preferably, step S2 includes the following steps:

[0022] S20. Based on the condensate flow rate entering the deaerator obtained from the existing measuring points on site, starting from the low-pressure heater with the highest pressure, calculate the steam inlet flow rate of each heater step by step until the heater that extracts wet steam. The steam inlet flow rate and condensate flow rate of each heater can be calculated directly.

[0023] S21. After measuring the total condensate flow of the final stage low heater through the terminal condensate flow measuring device, the extraction steam rate of the final stage low heater can be obtained by subtracting the condensate flow of the second and final stages from this flow rate.

[0024] S22. Based on the calculation results of the steam extraction rate of each heater in the low-pressure cylinder and the auxiliary flow measurement or calculation, the exhaust flow rate of the low-pressure cylinder is obtained.

[0025] Preferably, in step S3, the heater flow balance calculation model includes the following:

[0026] a. Thermal balance of high-pressure heater No. 1: ;

[0027] b. Thermal balance of high-pressure heater No. 2:

[0028] c. Thermal balance of high-pressure heater No. 3: ;

[0029] d. Deaerator thermal balance: ;

[0030] e. Thermal balance of low-pressure heater No. 5: ;

[0031] f. Thermal balance of low-pressure heater No. 6: ;

[0032] in, —Feed flow rate [t / h] through the high-pressure heater;

[0033] —Heater inlet steam flow rate [t / h];

[0034] , —Heater inlet and outlet water flow rates [t / h];

[0035] , —Inlet and outlet water enthalpy of heater [kJ / kg];

[0036] , —Inlet steam and condensate enthalpy of heater [kJ / kg];

[0037] The subscripts 1, 2, 3, 4, 5, and 6 represent high-pressure heaters 1 to 3, deaerators, and low-pressure heaters 5 to 6, respectively.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] 1. In this invention, the complex iteration of the enthalpy of the steam extraction from the final stage, the second final stage, and the low-pressure cylinder is no longer required when calculating the condenser exhaust flow rate, which greatly reduces the amount of calculation work.

[0040] 2. In this invention, the calculation process eliminates the need for input and output energy balance calculations for the entire machine, greatly reducing the steam and water parameters required for calculation and effectively avoiding deviations in condenser exhaust flow calculations caused by individual measurement errors. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the structure of a system for calculating the exhaust characteristics of a low-pressure cylinder according to the present invention.

[0042] In the picture:

[0043] 1. High-pressure heater No. 1; 2. High-pressure heater No. 2; 3. High-pressure heater No. 3; 4. Deaerator; 5. Low-pressure heater No. 5; 6. Low-pressure heater No. 6; 7. Low-pressure heater No. 7; 8. Low-pressure heater No. 8; 9. High-pressure cylinder; 10. Intermediate-pressure cylinder; 11. Low-pressure cylinder; 12. Boiler; 13. Generator; 14. Condenser; 15. Condensate pump; 16. Shaft seal heater; 17. Secondary terminal condensate flow measurement device; 18. Terminal condensate flow measurement device; 19. Feedwater pump turbine; 20. Condensate flow measurement device. Detailed Implementation

[0044] 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. 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. Example

[0045] Reference Figure 1As shown: A system for calculating the exhaust characteristics of a low-pressure cylinder includes a boiler 12, a regenerative system, a feedwater pump turbine 19, a condensate pump 15, a condensate flow measurement device 20, a high-pressure cylinder 9, an intermediate-pressure cylinder 10, and a low-pressure cylinder 11; the high-pressure cylinder 9, the intermediate-pressure cylinder 10, and the low-pressure cylinder 11 are all connected to the boiler 12 through drain pipes; the condenser 14 is connected to the condensate pump 15 and the shaft seal heater 16 through drain pipes; the deaerator 4 is connected to the feedwater pump turbine 19 through drain pipes.

[0046] The regenerative system includes a high-pressure heater system and a low-pressure heater system.

[0047] The high-pressure heater system consists of high-pressure heater 1, high-pressure heater 2, and high-pressure heater 3 connected in sequence.

[0048] The two-stage low-pressure heaters near the condenser 14 of the low-pressure heater system are equipped with a secondary-end condensate flow measurement device 17 and an end condensate flow measurement device 18. The secondary-end condensate flow measurement device 17 is used to measure the condensate flow of the secondary-end low-pressure heater of the low-pressure cylinder 11, and the end condensate flow measurement device 18 is used to measure the condensate flow from the final stage low-pressure heater of the low-pressure cylinder 11 to the condenser, which is used for calculating the extraction enthalpy of the final stage low-pressure heater.

[0049] The low-pressure heater system consists of deaerator 4, low-pressure heaters 5 and 6, low-pressure heaters 7 and 8, shaft seal heater 16, and condenser 14 connected in sequence. A condensate flow measurement device 17 is installed on the condensate drain pipe between low-pressure heater 7 and low-pressure heater 8; a condensate flow measurement device 18 is installed on the condensate drain pipe between low-pressure heater 8 and condenser 14.

[0050] In this embodiment, the secondary-end condensate flow measurement device 17 and the terminal condensate flow measurement device 18 are installed on the condensate pipes between low-pressure heater 7 (No. 7) and low-pressure heater 8 (No. 8), and between low-pressure heater 8 (No. 8) and condenser 14. By measuring the condensate flow and combining it with the heat balance calculations of low-pressure heaters 5 and 6, the steam inlet flow of low-pressure heaters 7 and 8 can be obtained without iteration. The condensate flow of the low-pressure heaters is measured by the condensate flow measurement device 20 entering the deaerator 4 from low-pressure heater 5. The steam inlet flow of low-pressure heaters 5 and 6 is calculated based on the condensate flow and the steam-side and water-side parameters of the heaters. Example

[0051] A method for calculating the exhaust characteristics of a low-pressure cylinder, based on the condensate flow rate measured by the secondary end condensate flow rate measuring device 17, calculates the inlet steam flow rate of low-pressure heater 8 (No. 8), and combines this with the heat balance calculation of low-pressure heaters 5 (No. 5) and 6 (No. 6) to obtain the inlet steam flow rate of low-pressure heater 7 (No. 7), thus obtaining the exhaust characteristic parameters; including the following:

[0052] 1. Calculation of steam and water flow rate in the high and medium pressure section: Based on the condensate flow rate at the inlet of deaerator 4, the steam flow rate entering each high pressure heater is obtained through iterative calculation of feedwater flow rate and heat balance calculation of high pressure heater; combined with the measurement or calculation of auxiliary flow rate, the overall steam and water flow rate of the high and medium pressure section is obtained, including the main steam flow rate, the high pressure cylinder exhaust flow rate, the intermediate pressure cylinder inlet steam flow rate and the intermediate pressure cylinder exhaust flow rate.

[0053] 2. Calculation of steam and water flow rate in the low-pressure section: Based on the condensate flow rate entering the deaerator 4 obtained from the existing measuring points on site, starting from the low-pressure heater with the highest pressure, calculate the steam inlet flow rate of each heater step by step until the heater that extracts wet steam. The steam inlet flow rate and condensate flow rate of each heater can be directly calculated. After measuring the total condensate flow rate of the final stage low-pressure heater through the terminal condensate flow rate measuring device 18, the extraction steam flow rate of the final stage low-pressure heater can be obtained by subtracting the condensate flow rate of the second-to-last stage from this flow rate. Based on the calculation results of the extraction steam flow rate of each heater in the low-pressure cylinder and the auxiliary flow rate measurement or calculation, the exhaust steam flow rate of the low-pressure cylinder is obtained.

[0054] 3. Heater flow balance calculation model:

[0055] ① Thermal balance of high-pressure heater No. 1:

[0056] ;

[0057] ② Thermal balance of high-pressure heater No. 2: ;

[0058] ③ Heat balance of high-pressure heater No. 3: ;

[0059] ④ Deaerator 4 heat balance: ;

[0060] ⑤ Heat balance of low-pressure heater No. 5: ;

[0061] ⑥ Thermal balance of low-pressure heater No. 6: ;

[0062] in, —Feed flow rate [t / h] through the high-pressure heater;

[0063] —Heater inlet steam flow rate [t / h];

[0064] , —Heater inlet and outlet water flow rates [t / h];

[0065] , —Inlet and outlet water enthalpy of heater [kJ / kg];

[0066] , —Inlet steam and condensate enthalpy of heater [kJ / kg];

[0067] The subscripts 1, 2, 3, 4, 5, and 6 represent high-pressure heaters 1 to 3, deaerators, and low-pressure heaters 5 to 6, respectively.

[0068] The calculation method in this embodiment eliminates the need for complex iterations of the enthalpy of the final stage, the secondary final stage low-pressure heater extraction, and the low-pressure cylinder exhaust when calculating the condenser exhaust flow rate, significantly reducing the computational workload. Furthermore, since the calculation process eliminates the need for input and output energy balance calculations for the entire unit, it greatly reduces the required steam and water parameters, effectively avoiding deviations in condenser exhaust flow rate calculations caused by individual measurement errors.

[0069] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A system for calculating low-pressure cylinder exhaust characteristics, characterized by, The system comprises a boiler (12), a regenerative system, a feed water pump turbine (19), a condensate pump (15), a condensate flow measuring device (20), a high-pressure cylinder (9), a medium-pressure cylinder (10), and a low-pressure cylinder (11). The regenerative system comprises a high-pressure heater system and a low-pressure heater system. The high-pressure heater system is sequentially connected by a No. 1 high-pressure heater (1), a No. 2 high-pressure heater (2), and a No. 3 high-pressure heater (3). The low-pressure heater system is provided with a penultimate end drain flow measuring device (17) and an end drain flow measuring device (18) on the drain pipeline of the two-stage low-pressure heater close to the condenser (14), the penultimate end drain flow measuring device (17) is used for measuring the drain flow of the penultimate stage low-pressure heater of the low-pressure cylinder (11), and the end drain flow measuring device (18) is used for measuring the drain flow from the end stage low-pressure heater of the low-pressure cylinder (11) to the condenser, and is used for calculating the extraction enthalpy of the end stage low-pressure heater. The low-pressure heater system is sequentially connected by a deaerator (4), a No. 5 low-pressure heater (5), a No. 6 low-pressure heater (6), a No. 7 low-pressure heater (7), a No. 8 low-pressure heater (8), a shaft seal heater (16), and a condenser (14), and the condensate flow measuring device (20) is installed between the deaerator (4) and the No. 5 low-pressure heater (5). The penultimate end drain flow measuring device (17) is arranged on the drain pipeline between the No. 7 low-pressure heater (7) and the No. 8 low-pressure heater (8), and the end drain flow measuring device (18) is arranged on the drain pipeline between the No. 8 low-pressure heater (8) and the condenser (14).

2. The system for calculating low-pressure cylinder exhaust characteristics according to claim 1, characterized by: The high-pressure cylinder (9), the medium-pressure cylinder (10), and the low-pressure cylinder (11) are all connected with the boiler (12) through drain pipelines.

3. The system for calculating low-pressure cylinder exhaust characteristics according to claim 1, characterized by: The condenser (14) is connected with the condensate pump (15) and the shaft seal heater (16) through drain pipelines.

4. The system and method of computing low-pressure cylinder steam exhaust characteristics of claim 1, wherein: The deaerator (4) is connected with the feed water pump turbine (19) through a drain pipeline.

5. A method of calculating low-pressure cylinder exhaust characteristics, characterized by, The system for calculating the exhaust steam characteristics of the low-pressure cylinder according to any one of claims 1-4 is used to calculate the steam flow of the No. 8 low-pressure heater (8) based on the drain flow measured by the penultimate end drain flow measuring device (17), to obtain the steam flow of the No. 7 low-pressure heater (7) by combining the heat balance calculation of the No. 5 low-pressure heater (5) and the No. 6 low-pressure heater (6), and to obtain the exhaust steam characteristic parameters. The system comprises the following contents: S1, calculation of the steam and water flow of the high and medium pressure part; S2, calculation of the steam and water flow of the low pressure part; S3, calculation of the heater flow balance.

6. The method of calculating low-pressure cylinder exhaust characteristics according to claim 5, characterized by, In step S1, the following steps are included: S10, taking the condensate flow at the inlet of the deaerator (4) as a reference, the steam flow into each high-pressure heater is obtained by iterative calculation of the feed water flow and heat balance calculation of the high-pressure heater; S11, the steam and water flow of the high and medium pressure part is obtained by combining the measurement or calculation of the auxiliary flow, including the main steam flow, the high-pressure cylinder exhaust steam flow, the medium-pressure cylinder steam flow, and the medium-pressure cylinder exhaust steam flow.

7. The method of calculating low-pressure cylinder exhaust characteristics according to claim 5, characterized by, In step S2, the following steps are included: S20, the condensate flow into the deaerator (4) is obtained according to the existing measuring points on site, the steam intake of each heater is calculated from the low-pressure heater with the highest pressure to the rear, until the heater before which the steam is wet steam, the steam intake and the drain of each heater can be directly calculated; S21, after the total drain flow of the last-stage low-pressure heater is measured by the end drain flow measuring device (18), the steam intake of the last-stage low-pressure heater is obtained by subtracting the second-to-last-stage drain flow from the total drain flow; S22, the exhaust flow of the low-pressure cylinder is obtained according to the calculation results of the steam intake of each heater of the low-pressure cylinder and the auxiliary flow measurement or calculation.

8. The method of calculating low-pressure cylinder exhaust characteristics according to claim 5, characterized by, In step S3, the heater flow balance calculation model includes the following contents: a, 1# high-pressure heater (1) heat balance: ； b, 2# high-pressure heater (2) heat balance: ； c, 3# high-pressure heater (3) heat balance: ； d, deaerator (4) heat balance: ； e, 5# low-pressure heater (5) heat balance: ； f, 6# low-pressure heater (6) heat balance: ； wherein, feed water flow through high pressure heater [t / h] - heater steam flow [t / h] , - heater in, out water flow [t / h] , - heater inlet and outlet water enthalpy [kJ / kg] , - Enthalpy of heater steam, drain [kJ / kg] The subscripts 1, 2, 3, 4, 5, and 6 respectively represent 1-3# high-pressure heaters, a deaerator, and 5-6# low-pressure heaters.

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