Calculation Method and System for Heat Loss of Working Medium Discharged from Boiler of Supercritical Thermal Power Unit

Abstract

The present invention relates to a calculation method and system for the heat loss of the working medium discharged from the boiler of a supercritical thermal power unit. By measuring the desuperheating water flow of the superheater with instruments and meters, the feed water flow and the main steam flow are calculated, and finally the flow of the working medium discharged from the boiler is calculated. The pressure of the steam-water separator is measured, and the enthalpy value of saturated water at the corresponding pressure can be obtained by referring to the enthalpy-entropy diagram. Given the flow and enthalpy value of the discharged working medium, the heat carried by the discharged working medium can be calculated. Thus, the technical problem in the prior art that the heat loss data caused by the discharged working medium when the boiler transitions from the once-through operation mode to the wet operation mode cannot be obtained is solved. The heat loss carried away by the working medium discharged from the boiler after the supercritical thermal power unit is peak-shaved to the wet operation mode can be accurately calculated. The detection process is rigorous and standardized, and the conclusion obtained is relatively reliable, providing data support for subsequent relevant energy conservation and consumption reduction work.

Description

Technical Field

[0001] The present invention relates to the technical field of supercritical thermal power units, and particularly to a calculation method and system for heat loss of the working medium discharged from the boiler of a supercritical thermal power unit. Background Art

[0002] The current energy situation in China requires the transformation of thermal power units into system regulating power sources for peak shaving and frequency modulation, giving full play to the emergency peak shaving capacity of existing thermal power units. In some areas, policies encourage thermal power units to have the ability to continuously and stably operate at a load condition with peak shaving down to below 30%. However, when a supercritical thermal power generating unit is deeply peak-shaved to a lower load condition, its economy drops rapidly and energy consumption increases sharply. The reason is that during the load reduction process of a supercritical unit, between the unit load of 30%-25% THA, the boiler changes from a once-through operation mode to a wet operation mode. For the currently put-into-production supercritical units, due to the large initial investment, most of them are not equipped with a furnace water circulation pump. When the boiler operates in the wet state, the high-temperature and high-pressure working medium separated by the steam-water separator enters the storage tank and then is discharged, resulting in the loss of working medium and heat; moreover, these discharged working media are not metered, and the temperature of the working medium in the pipeline is relatively high. At high temperatures, conventional ultrasonic flowmeters will fail and cannot accurately measure the discharged flow rate, thus making it impossible to quantitatively analyze its impact on the economy of the unit and carry out energy conservation and emission reduction work based on relevant data. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defects in the prior art, so as to provide a calculation method and system for heat loss of the working medium discharged from the boiler of a supercritical thermal power unit.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A calculation method for heat loss of the working medium discharged from the boiler of a supercritical thermal power unit includes the following steps:

[0006] Step 1: The unit includes a steam turbine, a boiler, and a deaerator. The boiler has a discharge pipeline. A main steam pipeline is connected between the steam turbine and the boiler, and a feed water pipeline and a desuperheater spray water pipeline are connected between the deaerator and the boiler;

[0007] Taking the boiler as a whole, determine the inlet flow rate and the outlet flow rate. The inlet flow rate includes the feed water flow rate F fw and the desuperheater spray water flow rate F gr , and the outlet flow rate includes the main steam flow rate F ms and the boiler discharge flow rate F wp . The inlet flow rate is balanced with the outlet flow rate, that is, F fw +F gr =F ms +F wp . From the feed water flow rate Ffw , Superheater desuperheating water flow F gr and main steam flow F ms Determine the boiler exhaust flow F wp ;

[0008] Step 2: Connect a flow meter to the superheater cooling water pipeline to detect the superheater cooling water flow rate F gr ;

[0009] Step 3: Several high-pressure heaters are connected to the feed water pipeline. The condensate flow rate entering the deaerator is used as the calculation basis. The heat balance and flow balance calculation of the deaerator and several high-pressure heaters are used to calculate the steam inlet volume of the deaerator and each high-pressure heater. fw Unknown, solve the heat balance and flow balance equations of the high-pressure heater and deaerator, and calculate the feed water flow F fw ;

[0010] Step 4: A pressure measuring instrument is connected to the main steam pipeline to detect the regulating stage pressure of the steam turbine, and then calculate the steam inlet flow rate of the steam turbine, that is, the main steam flow rate F ms ;

[0011] Step 5: Determine the boiler discharge flow F from the above steps wp , determine the enthalpy value corresponding to the discharged working fluid. The heat carried by the discharged working fluid is the boiler discharge flow multiplied by the corresponding enthalpy value.

[0012] Preferably, in step 3, the number of high-pressure heaters is 3, and a feed water pump sealing water inlet, a feed water pump sealing water outlet and a reheater desuperheating water outlet are provided on the feed water pipeline between the deaerator and the high-pressure heater. Based on this,

[0013] Heat balance calculation equation for No. 1 high-pressure heater:

[0014] F fw (h f0 -h f1 )=F1(h1-h d1 )

[0015] Where: F fw is the water flow rate, t / h; h f0 is the outlet enthalpy of the No. 1 high-pressure heater, kJ / kg; h f1 is the water inlet enthalpy of No. 1 high-pressure heater, kJ / kg; F1 is the steam inlet volume of No. 1 high-pressure heater, t / h; h1 is the steam inlet enthalpy of No. 1 high-pressure heater, kJ / kg; h d1 is the hydrophobic enthalpy of No. 1 high-pressure heater, kJ / kg;

[0016] Heat balance calculation equation for No. 2 high-pressure heater:

[0017] F fw (h f1 -h f2 ) = F2(h2 - h d2 ) + F1(h d1 -h d2 )

[0018] Where: F2 is the steam inlet flow rate of the No. 2 high-pressure heater, t / h; h2 is the steam inlet enthalpy of the No. 2 high-pressure heater, kJ / kg; h d2 is the drain enthalpy of the No. 2 high-pressure heater, kJ / kg; h f2 is the feed water enthalpy of the No. 2 high-pressure heater, kJ / kg;

[0019] Thermal balance calculation equation for the No. 3 high-pressure heater:

[0020] F fw (h f2 -h f3 ) = F3(h3 - h d3 ) + (F1 + F2)(h d2 -h d3 )

[0021] Where: F3 is the steam inlet flow rate of the No. 3 high-pressure heater, t / h; h3 is the steam inlet enthalpy of the No. 3 high-pressure heater, kJ / kg; h d3 is the drain enthalpy of the No. 3 high-pressure heater, kJ / kg; h f3 is the feed water enthalpy of the No. 3 high-pressure heater, kJ / kg;

[0022] Thermal balance calculation equation for the deaerator:

[0023] F ot4 h ot4 = F4h4 + F in h in4 + (F1 + F2 + F3)h d3 ;

[0024] Where: F ot4 is the outlet water flow rate of the deaerator, t / h; h ot4 is the outlet water enthalpy of the deaerator, kJ / kg; F4 is the steam inlet flow rate of the deaerator, t / h; h4 is the steam inlet enthalpy of the deaerator, kJ / kg; F in is the measured condensate water flow rate at the inlet of the deaerator, t / h; h in4 is the feed water enthalpy of the deaerator, kJ / kg;

[0025] Flow balance calculation for the deaerator:

[0026] F ot4 = F1 + F2 + F3 + F4 + F in ;

[0027] Feed water flow rate F fw Calculation equation:

[0028] F fw = F ot4 + F mfin - F mfot - F gr - F zr ;

[0029] Wherein: F mfin is the inlet flow rate of the feed pump seal water obtained by measurement, t / h; F mfot is the outlet flow rate of the feed pump seal water obtained by measurement, t / h; F gr is the desuperheating water flow rate of the superheater obtained by measurement, t / h; F zr is the desuperheating water flow rate of the reheater obtained by measurement, t / h;

[0030] The above equations form a five - element linear equation system. Using the iterative method, first assume an initial value of the feed water flow rate, calculate the corresponding calculated value of the feed water flow rate, correct the initial value with the deviation between the two, and then substitute it into the calculation and iterate cyclically until the deviation between the assumed feed water flow rate and the calculated feed water flow rate meets the accuracy requirements, then the accurate feed water flow rate F fw .

[0031] Preferably, in step four, the main steam flow rate F ms The calculation formula is F ms = cP1 + k, where: F ms is the main steam flow rate, t / h; P1 is the regulating stage pressure of the steam turbine obtained by measurement, MPa; c is a constant, the thermal characteristic data provided by the manufacturer; k is a constant, the thermal characteristic data provided by the manufacturer.

[0032] Preferably, in step five, the boiler includes a steam - water separator, and the working medium discharged from the boiler is the saturated water separated by the steam - water separator. The corresponding enthalpy value can be obtained by checking the enthalpy - entropy diagram according to the pressure of the steam - water separator;

[0033] The boiler external discharge flow rate F wp is F wp = F fw + F gr - F ms ;

[0034] The heat loss Q of the working medium discharged from the boiler wp is Q wp = F wp h wp , where h wp is the saturated water enthalpy corresponding to the pressure of the boiler steam - water separator, kJ / kg.

[0035] To achieve the above object, the present invention also adopts the following technical solutions:

[0036] A calculation system for the heat loss of the working medium discharged from the boiler of a supercritical thermal power unit, adopting the above calculation method, includes a data acquisition module and a calculation module. The data acquisition module is used to collect data of the boiler and the deaerator. The data includes the desuperheated water flow rate F of the superheater gr , the regulating stage pressure of the steam turbine, the pressure of the steam-water separator, the outlet pressure and temperature, the inlet pressure and temperature, the inlet steam pressure and temperature, and the drain pressure and temperature of each high-pressure heater, the inlet condensate flow rate of the deaerator, the flow rate at the inlet of the feed pump seal water, and the flow rate at the outlet of the feed pump seal water, as well as the desuperheated water flow rate of the reheater. The calculation module is used to respectively calculate the inlet steam flow rate of each high-pressure heater, the inlet steam flow rate of the deaerator, the feed water flow rate F fw and the main steam flow rate F ms , and calculate the boiler external discharge flow rate F wp , then determine the enthalpy value corresponding to the discharged working medium, and calculate the heat carried by the discharged working medium.

[0037] Preferably, the data acquisition module includes a first orifice flowmeter located in the desuperheating water pipeline of the superheater, a first pressure measuring instrument located on the main steam pipeline for detecting the regulating stage pressure of the steam turbine, a first ultrasonic flowmeter arranged at the inlet of the seal water of the feed water pump, a second ultrasonic flowmeter arranged at the outlet of the seal water of the feed water pump, a second orifice flowmeter arranged at the outlet of the desuperheating water of the reheater, a third orifice flowmeter for measuring the condensate water flow at the inlet of the deaerator, a second pressure measuring instrument for measuring the pressure of the steam-water separator, a third pressure measuring instrument for measuring the outlet water pressure of the No. 1 high-pressure heater, a fourth pressure measuring instrument for measuring the inlet water pressure of the No. 1 high-pressure heater, a fifth pressure measuring instrument for measuring the inlet steam pressure of the No. 1 high-pressure heater, a sixth pressure measuring instrument for the drain pressure of the No. 1 high-pressure heater, a seventh pressure measuring instrument for measuring the outlet water pressure of the No. 2 high-pressure heater, an eighth pressure measuring instrument for measuring the inlet water pressure of the No. 2 high-pressure heater, a ninth pressure measuring instrument for measuring the inlet steam pressure of the No. 2 high-pressure heater, a tenth pressure measuring instrument for the drain pressure of the No. 2 high-pressure heater, an eleventh pressure measuring instrument for measuring the outlet water pressure of the No. 3 high-pressure heater, a twelfth pressure measuring instrument for measuring the inlet water pressure of the No. 3 high-pressure heater, a thirteenth pressure measuring instrument for measuring the inlet steam pressure of the No. 3 high-pressure heater, a fourteenth pressure measuring instrument for the drain pressure of the No. 3 high-pressure heater, a fifteenth pressure measuring instrument for measuring the outlet water pressure of the deaerator, a sixteenth pressure measuring instrument for measuring the inlet water pressure of the deaerator, a seventeenth pressure measuring instrument for measuring the inlet steam pressure of the deaerator, a first temperature measuring instrument for measuring the outlet water temperature of the No. 1 high-pressure heater, a second temperature measuring instrument for measuring the inlet water temperature of the No. 1 high-pressure heater, a third temperature measuring instrument for measuring the inlet steam temperature of the No. 1 high-pressure heater, a fourth temperature measuring instrument for measuring the drain temperature of the No. 1 high-pressure heater, a fifth temperature measuring instrument for measuring the outlet water temperature of the No. 2 high-pressure heater, a sixth temperature measuring instrument for measuring the inlet water temperature of the No. 2 high-pressure heater, a seventh temperature measuring instrument for measuring the inlet steam temperature of the No. 2 high-pressure heater, an eighth temperature measuring instrument for measuring the drain temperature of the No. 2 high-pressure heater, a ninth temperature measuring instrument for measuring the outlet water temperature of the No. 3 high-pressure heater, a tenth temperature measuring instrument for measuring the inlet water temperature of the No. 3 high-pressure heater, an eleventh temperature measuring instrument for measuring the inlet steam temperature of the No. 3 high-pressure heater, a twelfth temperature measuring instrument for measuring the drain temperature of the No. 3 high-pressure heater, a thirteenth temperature measuring instrument for measuring the outlet water temperature of the deaerator, a fourteenth temperature measuring instrument for measuring the inlet water temperature of the deaerator, and a fifteenth temperature measuring instrument for measuring the inlet steam temperature of the deaerator.

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

[0039] In the calculation method and system provided in the above technical solution, through measurement and calculation, quantitative analysis is carried out on the working medium discharged outside the boiler of a supercritical thermal power unit in the wet operating state to determine its impact on the economy of the unit, and relevant data can be provided as support for energy conservation and emission reduction work. The detection process is rigorous and standardized, and the conclusions drawn are relatively reliable. In the current situation where high-parameter and large-capacity supercritical units frequently participate in peak shaving and frequency modulation, it is beneficial to explore the optimization space of thermal power units under peak shaving operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0041] Figure 1 It is a system framework diagram of a boiler, a deaerator and a connected feed water system in a supercritical thermal power unit according to an embodiment of the present invention.

[0042] Figure 2 It is a characteristic curve of the relationship between the typical main steam flow rate and the pressure after the governing stage.

[0043] Description of the reference numerals:

[0044] 1. Boiler; 11. Discharge pipeline; 12. Main steam pipeline; 13. Steam-water separator; 14. Storage tank; 2. Deaerator; 21. Feed water pipeline; 22. Desuperheater spray water pipeline; 23. No. 3 high-pressure heater; 24. No. 2 high-pressure heater; 25. No. 1 high-pressure heater; 26. Feed pump seal water inlet; 27. Reheater desuperheater outlet; 28. Feed pump seal water outlet. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0046] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0047] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected to" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0048] In the prior art, during the load reduction process of a supercritical thermal power unit, between the unit load of 30%-25% THA working conditions, the boiler changes from a once-through operation mode to a wet operation mode. For the currently put into production supercritical thermal power units, due to the relatively large initial investment, most of them are not equipped with a boiler water circulation pump. As shown in the attached Figure 1 figure, when the boiler 1 is in wet operation, the saturated water separated by the steam-water separator 13 enters the water storage tank. The water storage tank 14 has two drain outlets. One is drained to the boiler drain expansion vessel, and the other is drained to the condenser hot well. When the steam-water quality of the boiler is unqualified and cannot be recycled, the drain water is drained to the boiler drain expansion vessel. When the steam-water quality is qualified and needs to be recycled, it is drained to the condenser hot well. To ensure the safety of the unit, the water level of the water storage tank is controlled to be normal by two parallel 361 valves. The saturated water separated by the boiler steam-water separator is finally drained to the boiler drain expansion vessel or the condenser hot well through the water storage tank, resulting in heat loss of the high-temperature and high-pressure working medium. In the prior art, since traditional orifice plate flow meters and long-neck nozzle flow meters are generally not installed in the external discharge pipeline, and due to the relatively high temperature of the working medium in the pipeline, conventional ultrasonic flow meters have failed at high temperatures and cannot accurately measure the external discharge flow rate. The external discharge of these working media is not metered, and there is no data statistics on the heat loss caused by this part of the external discharge working medium, and it is impossible to determine its impact on the economy of the unit.

[0049] Based on this, as shown in the attached Figure 1 figure, the embodiment of the present invention provides a calculation method for the heat loss of the external discharge working medium of a supercritical thermal power unit boiler, including the following steps:

[0050] Step 1: The unit includes a steam turbine (not shown), a boiler 1, and a deaerator 2. The boiler 1 has an external discharge pipe 11. A main steam pipe 12 is connected between the steam turbine and the boiler 1. A feed water pipe 21 and a desuperheated steam water pipe 22 are connected between the deaerator 2 and the boiler.

[0051] Regarding the boiler as a whole, determine the inlet flow rate and the outlet flow rate. The inlet flow rate includes the feed water flow rate F fw and the desuperheated steam water flow rate F gr . The outlet flow rate includes the main steam flow rate F ms and the boiler external discharge flow rate F wp . The inlet flow rate is balanced with the outlet flow rate, that is, F fw +F gr =F ms +F wp . Determine the boiler external discharge flow rate F fw from the feed water flow rate F gr , the desuperheated steam water flow rate F ms , and the main steam flow rate F wp .

[0052] Specifically, it is known that the heat carried by the working fluid is the flow rate of the working fluid multiplied by the corresponding enthalpy value. In this embodiment, the external discharge working fluid of the boiler is the saturated water separated by the steam-water separator 13, and its corresponding enthalpy value can be obtained by referring to the enthalpy-entropy diagram according to the pressure of the steam-water separator 13. Therefore, the key to calculating the heat carried by the external discharge working fluid of the boiler lies in how to obtain the flow rate of the external discharge working fluid of the boiler, that is, the boiler external discharge flow rate F wp . Regarding the boiler as a whole, there is an inlet of feed water flow rate and desuperheated steam water flow rate, and an outlet of main steam flow rate and boiler external discharge flow rate. That is, knowing the feed water flow rate, desuperheated steam water flow rate, and main steam flow rate, the boiler external discharge flow rate F wp can be obtained. Therefore, the boiler external discharge flow rate F wp is obtained in the subsequent steps.

[0053] Step 2: A flow meter is connected to the desuperheated steam water pipe 22 to detect the desuperheated steam water flow rate F gr . Since the temperature of the desuperheated steam water is not high, a flow meter can be directly installed in the desuperheated steam water pipe 22. The flow meter is specifically a first orifice flow meter, which is used to detect the desuperheated steam water flow rate F gr , and then the detected data is transmitted to the calculation module.

[0054] Step 3: A number of high-pressure heaters are connected to the feed water pipe 21. Based on the condensate water flow rate entering the deaerator 2 as a calculation reference, through the heat balance and flow balance calculations of the deaerator 2 and a number of high-pressure heaters, the steam inlet amounts of the deaerator 2 and each high-pressure heater are obtained. Since the feed water flow rate F fwUnknown, solve the heat balance and flow balance equations of the high-pressure heater and the deaerator 2 simultaneously to calculate the feedwater flow rate F fw 。

[0055] Specifically, as shown in the appendix Figure 1 The number of high-pressure heaters in this embodiment is 3. On the feedwater pipe 21 between the deaerator 2 and the high-pressure heaters, there are a feed pump seal water inlet 26, a feed pump seal water outlet 28, and a reheater desuperheating water outlet 27. Taking the condensate flow rate entering the deaerator 2 as the calculation basis, through the heat balance and flow balance calculations of the deaerator 2 and the high-pressure heater system, the steam inlet flow rates of the deaerator 2 and each high-pressure heater are obtained. Since the feedwater flow rate is unknown, solve the heat balance and flow balance equations of the heater and the deaerator 2 simultaneously. Specifically, the heat balance calculation equation of the No. 1 high-pressure heater 25 is

[0056] F fw (h f0 -h f1 )=F1(h1 - h d1 )

[0057] In the formula: F fw is the feedwater flow rate, t / h; h f0 is the outlet enthalpy of the No. 1 high-pressure heater 25, kJ / kg; h f1 is the inlet enthalpy of the No. 1 high-pressure heater 25, kJ / kg; F1 is the steam inlet flow rate of the No. 1 high-pressure heater 25, t / h; h1 is the steam inlet enthalpy of the No. 1 high-pressure heater 25, kJ / kg; h d1 is the drain enthalpy of the No. 1 high-pressure heater 25, kJ / kg. The above parameters are all measured. Specifically, the outlet enthalpy, inlet enthalpy, steam inlet enthalpy, and drain enthalpy of the No. 1 high-pressure heater 25 can be obtained from the temperature and pressure of the working fluid at each position. The pressure and temperature of the working fluid at each position are respectively measured by a third pressure measuring instrument for measuring the outlet pressure of the No. 1 high-pressure heater 25, a first temperature measuring instrument for measuring the outlet temperature of the No. 1 high-pressure heater 25, a fourth pressure measuring instrument for measuring the inlet pressure of the No. 1 high-pressure heater 25, a second temperature measuring instrument for measuring the inlet temperature of the No. 1 high-pressure heater 25, a fifth pressure measuring instrument for measuring the steam inlet pressure of the No. 1 high-pressure heater 25, a third temperature measuring instrument for measuring the steam inlet temperature of the No. 1 high-pressure heater 25, a sixth pressure measuring instrument for the drain pressure of the No. 1 high-pressure heater 25, a fourth temperature measuring instrument for measuring the drain temperature of the No. 1 high-pressure heater 25 and other measuring instruments. Then, the outlet enthalpy, inlet enthalpy, steam inlet enthalpy, and drain enthalpy of the No. 1 high-pressure heater 25 are obtained by corresponding calculations of the calculation module or by querying the enthalpy-entropy diagram. The measuring point positions, measuring methods, and corresponding calculation methods of each measuring instrument are prior arts.

[0058] The heat balance calculation equation of the No. 2 high-pressure heater 24 is

[0059] F fw (h f1 -h f2 ) = F2(h2 - h d2 ) + F1(h d1 -h d2 )

[0060] Where: F2 is the steam inlet flow rate of the No. 2 high-pressure heater 24, t / h; h2 is the steam inlet enthalpy of the No. 2 high-pressure heater 24, kJ / kg; h d2 is the drain enthalpy of the No. 2 high-pressure heater 24, kJ / kg; h f2 is the feed water enthalpy of the No. 2 high-pressure heater 24, kJ / kg, and the above parameters are all obtained by measurement; specifically, the outlet enthalpy, feed water enthalpy, steam inlet enthalpy and drain enthalpy of the No. 2 high-pressure heater 24 can be obtained from the temperature and pressure of the working fluid at each position. The pressure and temperature of the working fluid at each position are respectively measured by the seventh pressure measuring instrument for measuring the outlet pressure of the No. 2 high-pressure heater 24, the fifth temperature measuring instrument for measuring the outlet temperature of the No. 2 high-pressure heater 24, the eighth pressure measuring instrument for measuring the feed water pressure of the No. 2 high-pressure heater 24, the sixth temperature measuring instrument for measuring the feed water temperature of the No. 2 high-pressure heater 24, the ninth pressure measuring instrument for measuring the steam inlet pressure of the No. 2 high-pressure heater 24, the seventh temperature measuring instrument for measuring the steam inlet temperature of the No. 2 high-pressure heater 24, the tenth pressure measuring instrument for the drain pressure of the No. 2 high-pressure heater 24, the eighth temperature measuring instrument for measuring the drain temperature of the No. 2 high-pressure heater 24 and other measuring instruments. Then, the outlet enthalpy, feed water enthalpy, steam inlet enthalpy and drain enthalpy of the No. 2 high-pressure heater 24 are obtained by corresponding calculation of the calculation module or querying the enthalpy-entropy diagram. The measuring point positions, measuring methods and corresponding calculation methods of each measuring instrument are prior arts.

[0061] The heat balance calculation equation of the No. 3 high-pressure heater 23:

[0062] F fw (h f2 -h f3 ) = F3(h3 - h d3 ) + (F1 + F2)(h d2 -h d3 )

[0063] Where: F3 is the steam inlet flow rate of the No. 3 high-pressure heater 23, t / h; h3 is the steam inlet enthalpy of the No. 3 high-pressure heater 23, kJ / kg; h d3 is the drain enthalpy of the No. 3 high-pressure heater 23, kJ / kg; h f3is the inlet enthalpy of the No. 3 high-pressure heater 23, in kJ / kg, and the above parameters are all obtained by measurement. Specifically, the outlet enthalpy, inlet enthalpy, steam inlet enthalpy, and drain enthalpy of the No. 3 high-pressure heater 23 can be obtained from the temperature and pressure of the working medium at each position. The pressure and temperature of the working medium at each position are respectively measured by the eleventh pressure measuring instrument for measuring the outlet pressure of the No. 3 high-pressure heater 23, the ninth temperature measuring instrument for measuring the outlet temperature of the No. 3 high-pressure heater 23, the twelfth pressure measuring instrument for measuring the inlet pressure of the No. 3 high-pressure heater 23, the tenth temperature measuring instrument for measuring the inlet temperature of the No. 3 high-pressure heater 23, the thirteenth pressure measuring instrument for measuring the steam inlet pressure of the No. 3 high-pressure heater 23, the eleventh temperature measuring instrument for measuring the steam inlet temperature of the No. 3 high-pressure heater 23, the fourteenth pressure measuring instrument for the drain pressure of the No. 3 high-pressure heater 23, and the twelfth temperature measuring instrument for measuring the drain temperature of the No. 3 high-pressure heater 23 and other measuring instruments. Then, the outlet enthalpy, inlet enthalpy, steam inlet enthalpy, and drain enthalpy of the No. 3 high-pressure heater 23 are obtained by corresponding calculation of the calculation module or querying the enthalpy-entropy diagram. The measuring point positions, measuring methods, and corresponding calculation methods of each measuring instrument are prior arts.

[0064] Thermal balance calculation equation of the deaerator 2:

[0065] F ot4 h ot4 = F4h4 + F in h in4 +(F1 + F2 + F3)h d3 ;

[0066] In the formula: F ot4 is the outlet flow rate of the deaerator 2, in t / h; F in is the measured inlet condensate flow rate of the deaerator 2. There is a third orifice flowmeter for measuring the inlet condensate flow rate of the deaerator 2 at the condensate inlet of the deaerator 2, and F in is obtained therefrom. F4 is the steam inlet flow rate of the deaerator 2, in t / h;

[0067] h ot4 is the outlet enthalpy of the deaerator 2, in kJ / kg; h in4$h_0$ is the enthalpy of the inlet water to the deaerator 2, in kJ / kg; $h_4$ is the enthalpy of the inlet steam to the deaerator 2, in kJ / kg; the above parameters are all obtained by measurement; specifically, the enthalpy of the outlet water, the enthalpy of the inlet water, and the enthalpy of the inlet steam of the deaerator 2 can be obtained from the temperature and pressure of the working fluid at each position. The pressure and temperature of the working fluid at each position are respectively measured by the fifteenth pressure measuring instrument for measuring the outlet pressure of the deaerator 2, the thirteenth temperature measuring instrument for measuring the outlet temperature of the deaerator 2, the sixteenth pressure measuring instrument for measuring the inlet pressure of the deaerator 2, the fourteenth temperature measuring instrument for measuring the inlet temperature of the deaerator 2, the seventeenth pressure measuring instrument for measuring the inlet steam pressure of the deaerator 2, the fifteenth temperature measuring instrument for measuring the inlet steam temperature of the deaerator 2 and other measuring instruments. Then, the enthalpy of the outlet water, the enthalpy of the inlet water, and the enthalpy of the inlet steam of the deaerator 2 are obtained by corresponding calculation by the calculation module or querying the enthalpy-entropy diagram. The measuring point positions, measuring methods, and corresponding calculation methods of each measuring instrument are prior arts.

[0068] Material balance calculation of the deaerator 2:

[0069] F ot4 = F1 + F2 + F3 + F4 + F in ;

[0070] Calculation equation for the feed water flow rate F fw :

[0071] F fw = F ot4 + F mfin - F mfot - F gr - F zr ;

[0072] In the formula: F mfin is the measured inlet flow rate of the seal water of the feed water pump, in t / h. Specifically, it is measured by the first ultrasonic flowmeter installed at the inlet 26 of the seal water of the feed water pump; F mfot is the measured outlet flow rate of the seal water of the feed water pump, in t / h. Specifically, it is measured by the second ultrasonic flowmeter installed at the outlet 28 of the seal water of the feed water pump; F gr is the measured desuperheated steam spray water flow rate, in t / h. Specifically, it is measured by the first orifice flowmeter located in the desuperheated steam spray water pipeline 22; F zr is the measured reheater spray water flow rate, in t / h. Specifically, it is measured by the second orifice flowmeter installed at the outlet 27 of the reheater spray water;

[0073] The above equations form a five - variable linear equation system with a total of 5 unknowns, namely the steam inlet flow of the No. 1 high - pressure heater 25, the steam inlet flow of the No. 2 high - pressure heater 24, the steam inlet flow of the No. 3 high - pressure heater 23, the steam inlet flow of the deaerator 2, and the feed - water flow. Then, the iterative method is adopted. First, an initial value of the feed - water flow is assumed. The corresponding calculated value of the feed - water flow is obtained through calculation. The deviation between the two is used to correct the initial value, and then it is substituted into the calculation and iterated cyclically until the deviation between the assumed feed - water flow and the calculated feed - water flow meets the accuracy requirements, and then the accurate feed - water flow F can be obtained. fw The iterative method adopted in this embodiment is an existing algorithm and will not be described in detail here.

[0074] Step Four: A pressure - measuring instrument is connected to the main steam pipeline 12 to detect the regulating - stage pressure of the steam turbine, and then the new - steam inlet flow of the steam turbine, that is, the main - steam flow F, is calculated. ms Specifically, the main - steam flow F ms The calculation formula is F ms = cP1 + k, where: F ms is the main - steam flow, t / h; P1 is the measured regulating - stage pressure of the steam turbine, MPa, which is specifically measured by the first pressure - measuring instrument for detecting the regulating - stage pressure of the steam turbine located on the main steam pipeline 12; c is a constant, the thermal - characteristic data provided by the manufacturer; k is a constant, the thermal - characteristic data provided by the manufacturer, and both are known parameters. As shown in the appendix Figure 2 is a typical characteristic curve of the main - steam flow and the pressure after the regulating stage.

[0075] Step Five: After the above steps, the desuperheating - water flow F gr is measured by the instrument, the feed - water flow F wp and the main - steam flow F ms are calculated. Thus, the boiler external - discharge flow F wp can be determined, and the enthalpy value corresponding to the discharged working medium is determined. The heat carried by the discharged working medium is the boiler external - discharge flow multiplied by the corresponding enthalpy value. Specifically, the boiler includes a steam - water separator 13. The working medium discharged from the boiler is used as the saturated water separated by the steam - water separator 13. The corresponding enthalpy value can be obtained by referring to the enthalpy - entropy diagram according to the pressure of the steam - water separator 13. The pressure of the steam - water separator 13 can be measured by a pressure - measuring device; therefore, the formula for the boiler external - discharge flow F wp is F wp = F fw + F gr - F ms ; the formula for the heat loss Q wp of the boiler - discharged working medium is Q wp = F wp h wp , where h wpis the enthalpy of saturated water corresponding to the pressure of the boiler steam-water separator 13, in kJ / kg. By the above steps, the external discharge working medium flow rate and the corresponding enthalpy value of the boiler are determined, and then the heat of the external discharge working medium of the boiler can be calculated, the heat loss corresponding to the unit can be determined, and the heat loss carried away by the external discharge working medium of the boiler after the supercritical thermal power unit is adjusted to the wet state operation can be accurately calculated. Under the current situation that high-parameter and large-capacity supercritical units frequently participate in peak shaving and frequency modulation, explore the optimization space of thermal power units under peak shaving operation, and provide data support for subsequent energy conservation and consumption reduction work.

[0076] This embodiment also provides a calculation system for the heat loss of the external discharge working medium of a supercritical thermal power unit boiler, including a data acquisition module and a calculation module. The data acquisition module is used to collect data of the boiler and the deaerator 2, and the data includes the superheater desuperheating water flow rate F gr, the regulating stage pressure of the steam turbine, the pressure of the steam-water separator 13, the outlet pressure and temperature, inlet pressure and temperature, inlet steam pressure and temperature, and drain pressure and temperature of each high-pressure heater, the outlet pressure and temperature, inlet pressure and temperature, inlet steam pressure and temperature, and inlet condensate flow rate of the deaerator 2, the flow rate of the feed pump seal water inlet 26 and the flow rate of the feed pump seal water outlet 28, and the flow rate of the desuperheating water outlet 27 of the reheater. Specifically, the data acquisition module includes a first orifice flowmeter located in the desuperheating water pipeline of the superheater, a first pressure measuring instrument located on the main steam pipeline for detecting the regulating stage pressure of the steam turbine, a first ultrasonic flowmeter installed at the feed pump seal water inlet, a second ultrasonic flowmeter installed at the feed pump seal water outlet, a second orifice flowmeter installed at the desuperheating water outlet of the reheater, a third orifice flowmeter for measuring the inlet condensate flow rate of the deaerator, a second pressure measuring instrument for measuring the pressure of the steam-water separator, a third pressure measuring instrument for measuring the outlet pressure of the No. 1 high-pressure heater, a fourth pressure measuring instrument for measuring the inlet pressure of the No. 1 high-pressure heater, a fifth pressure measuring instrument for measuring the inlet steam pressure of the No. 1 high-pressure heater, a sixth pressure measuring instrument for measuring the drain pressure of the No. 1 high-pressure heater, a seventh pressure measuring instrument for measuring the outlet pressure of the No. 2 high-pressure heater, an eighth pressure measuring instrument for measuring the inlet pressure of the No. 2 high-pressure heater, a ninth pressure measuring instrument for measuring the inlet steam pressure of the No. 2 high-pressure heater, a tenth pressure measuring instrument for measuring the drain pressure of the No. 2 high-pressure heater, an eleventh pressure measuring instrument for measuring the outlet pressure of the No. 3 high-pressure heater, a twelfth pressure measuring instrument for measuring the inlet pressure of the No. 3 high-pressure heater, a thirteenth pressure measuring instrument for measuring the inlet steam pressure of the No. 3 high-pressure heater, a fourteenth pressure measuring instrument for measuring the drain pressure of the No. 3 high-pressure heater, a fifteenth pressure measuring instrument for measuring the outlet pressure of the deaerator, a sixteenth pressure measuring instrument for measuring the inlet pressure of the deaerator, a seventeenth pressure measuring instrument for measuring the inlet steam pressure of the deaerator, a first temperature measuring instrument for measuring the outlet temperature of the No. 1 high-pressure heater, a second temperature measuring instrument for measuring the inlet temperature of the No. 1 high-pressure heater, a third temperature measuring instrument for measuring the inlet steam temperature of the No. 1 high-pressure heater, a fourth temperature measuring instrument for measuring the drain temperature of the No. 1 high-pressure heater, a fifth temperature measuring instrument for measuring the outlet temperature of the No. 2 high-pressure heater, a sixth temperature measuring instrument for measuring the inlet temperature of the No. 2 high-pressure heater, a seventh temperature measuring instrument for measuring the inlet steam temperature of the No. 2 high-pressure heater, an eighth temperature measuring instrument for measuring the drain temperature of the No. 2 high-pressure heater, a ninth temperature measuring instrument for measuring the outlet temperature of the No. 3 high-pressure heater, a tenth temperature measuring instrument for measuring the inlet temperature of the No. 3 high-pressure heater, an eleventh temperature measuring instrument for measuring the inlet steam temperature of the No. 3 high-pressure heater, a twelfth temperature measuring instrument for measuring the drain temperature of the No. 3 high-pressure heater, a thirteenth temperature measuring instrument for measuring the outlet temperature of the deaerator,The fourteenth temperature measuring instrument for measuring the inlet water temperature of the deaerator and the fifteenth temperature measuring instrument for measuring the inlet steam temperature of the deaerator. The above-mentioned measuring instruments are not shown in the drawings, but the measuring positions and measuring methods of each measuring instrument are prior art and will not be elaborated here.

[0077] The data acquisition module and the calculation module are communicatively connected for data transmission. The calculation module is used to respectively calculate the feed water flow rate F fw and the main steam flow rate F ms , and calculate the boiler external discharge flow rate F wp . Then, calculate the heat carried by the externally discharged working medium. The calculation module adopts the calculation method of the above-mentioned embodiment.

[0078] Specifically, the calculation system of the present invention includes a processor and a memory. The memory is used to store program codes and transmit the program codes to the processor. The calculation module is located on the processor and is used to execute the calculation method of the heat loss of the externally discharged working medium of the supercritical thermal power unit in the above method embodiment according to the instructions in the program codes.

[0079] The above-mentioned implementation manners are only the preferred implementation manners of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantive changes and substitutions made by those skilled in the art on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A calculation method for the heat loss of the working medium discharged outside the boiler of a supercritical thermal power unit, characterized in that, The method includes the following steps: Step 1: The unit includes a steam turbine, a boiler, and a deaerator. The boiler has an external discharge pipeline. A main steam pipeline is connected between the steam turbine and the boiler. A feed water pipeline and a desuperheating water pipeline for the reheater are connected between the deaerator and the boiler; Taking the boiler as a whole, determine the inlet flow rate and the outlet flow rate. The inlet flow rate includes the feed water flow rate F fw and the desuperheating water flow rate F gr for the superheater. The outlet flow rate includes the main steam flow rate F ms and the boiler blowdown flow rate F wp . The inlet flow rate is balanced with the outlet flow rate, that is, F fw +F gr =F ms +F wp . Determine the boiler blowdown flow rate F fw from the feed water flow rate F gr , the desuperheating water flow rate F ms for the superheater, and the main steam flow rate F wp ; Step 2: Connect a flow meter to the attemperating water pipe of the superheater to detect the attemperating water flow rate F of the superheater gr ; Step 3: Several high-pressure heaters are connected to the feed water pipeline. The condensate flow rate entering the deaerator is used as the calculation basis. The heat balance and flow balance calculation of the deaerator and several high-pressure heaters are used to calculate the steam inlet volume of the deaerator and each high-pressure heater. fw Unknown, solve the heat balance and flow balance equations of the high-pressure heater and deaerator, and calculate the feed water flow F fw ; Step 4: A pressure measuring instrument is connected to the main steam pipeline to detect the regulating stage pressure of the steam turbine, and then the new steam inlet flow rate of the steam turbine, i.e., the main steam flow rate F, is calculated. ms ; Step 5. Determine the boiler external discharge flow rate F from the above steps wp , determine the enthalpy value corresponding to the externally discharged working medium, and the heat carried by the externally discharged working medium is the product of the boiler external discharge flow rate and the corresponding enthalpy value; In step 4, the main steam flow rate F ms is calculated by the formula , where: F ms is the main steam flow rate, t / h; P1 is the regulated stage pressure of the steam turbine measured, MPa; c is a constant, the thermal characteristic data provided by the manufacturer; k is a constant, the thermal characteristic data provided by the manufacturer; In Step 5, the boiler includes a steam-water separator. The working medium discharged from the boiler is the saturated water separated by the steam-water separator. The corresponding enthalpy value can be obtained by referring to the enthalpy-entropy diagram according to the pressure of the steam-water separator; The external discharge flow rate F of the boiler wp is ; Heat loss Q of the working medium discharged from the boiler wp is , where h wp is the enthalpy of saturated water corresponding to the pressure of the boiler steam-water separator, kJ / kg.

2. The calculation method according to claim 1, wherein In Step 3, the number of high-pressure heaters is 3. On the feed water pipeline between the deaerator and the high-pressure heaters, there are a feed pump seal water inlet, a feed pump seal water outlet, and a desuperheating water outlet for the reheater. Based on this, The heat balance calculation equation of the No. 1 high-pressure heater: Where: F fw is the feed water flow rate, t / h; h f0 is the enthalpy of the outlet water of the No. 1 high-pressure heater, kJ / kg; h f1 is the enthalpy of the inlet water of the No. 1 high-pressure heater, kJ / kg; F1 is the steam inlet flow rate of the No. 1 high-pressure heater, t / h; h1 is the enthalpy of the inlet steam of the No. 1 high-pressure heater, kJ / kg; h d1 is the enthalpy of the drain water of the No. 1 high-pressure heater, kJ / kg; The heat balance calculation equation of the No. 2 high-pressure heater: Where: F2 is the steam inlet flow rate of the No. 2 high-pressure heater, t / h; h2 is the steam inlet enthalpy of the No. 2 high-pressure heater, kJ / kg; h d2 is the drain enthalpy of the No. 2 high-pressure heater, kJ / kg; h f2 is the feed water enthalpy of the No. 2 high-pressure heater, kJ / kg; The heat balance calculation equation of the No. 3 high-pressure heater: Where: F3 is the steam inlet flow rate of the No. 3 high-pressure heater, t / h; h3 is the steam inlet enthalpy of the No. 3 high-pressure heater, kJ / kg; h d3 is the drain enthalpy of the No. 3 high-pressure heater, kJ / kg; h f3 is the inlet water enthalpy of the No. 3 high-pressure heater, kJ / kg; The heat balance calculation equation of the deaerator: ； Where: F ot4 is the outlet flow rate of the deaerator, t / h; h ot4 is the enthalpy of the outlet water of the deaerator, kJ / kg; F4 is the inlet steam flow rate of the deaerator, t / h; h4 is the enthalpy of the inlet steam of the deaerator, kJ / kg; F in is the measured inlet condensate flow rate of the deaerator, t / h; h in4 is the enthalpy of the inlet water of the deaerator, kJ / kg; The flow balance calculation of the deaerator: ； Feed water flow rate F fw Calculation equation: ； Where: F mfin is the measured inlet flow rate of the feed pump sealing water, t / h; F mfot is the measured outlet flow rate of the feed pump sealing water, t / h; F gr is the measured desuperheating water flow rate of the superheater, t / h; F zr is the measured desuperheating water flow rate of the reheater, t / h; The above equations form a five - variable linear equation system. Using the iterative method, first assume an initial value of the feed water flow rate. Calculate the corresponding calculated value of the feed water flow rate. Use the deviation between the two to correct the initial value, then substitute it into the calculation and iterate cyclically until the deviation between the assumed feed water flow rate and the calculated feed water flow rate meets the accuracy requirements, and then the accurate feed water flow rate F can be obtained. fw 。 3. A calculation system for the heat loss of the working medium discharged from the boiler of a supercritical thermal power unit, characterized in that, The calculation method described in claim 1 or 2 is adopted, which includes a data acquisition module and a calculation module. The data acquisition module is used to collect data of the boiler and the deaerator, and the data includes the desuperheated water flow rate F of the superheater gr , the regulating stage pressure of the steam turbine, the pressure of the steam-water separator, the outlet pressure and temperature, the inlet pressure and temperature, the inlet steam pressure and temperature, and the drain pressure and temperature of each high-pressure heater, the inlet condensate flow rate of the deaerator, the flow rate at the inlet of the feed pump seal water, and the flow rate at the outlet of the feed pump seal water, as well as the desuperheated water flow rate of the reheater. The calculation module is used to respectively calculate the inlet steam flow rate of each high-pressure heater, the inlet steam flow rate of the deaerator, the feed water flow rate F fw and the main steam flow rate F ms , and calculate the boiler external discharge flow rate F wp , then determine the enthalpy value corresponding to the discharged working medium, and calculate the heat carried by the discharged working medium.

4. The computing system according to claim 3, wherein The data acquisition module includes a first orifice flowmeter located in the attemperating water pipeline of the superheater, a first pressure measuring instrument located on the main steam pipeline for detecting the regulating stage pressure of the steam turbine, a first ultrasonic flowmeter arranged at the inlet of the feed pump seal water, a second ultrasonic flowmeter arranged at the outlet of the feed pump seal water, a second orifice flowmeter arranged at the outlet of the attemperating water of the reheater, a third orifice flowmeter for measuring the condensate flow rate at the inlet of the deaerator, a second pressure measuring instrument for measuring the deaerator inlet pressure, a third pressure measuring instrument for measuring the outlet pressure of the No. 1 high-pressure heater, a fourth pressure measuring instrument for measuring the inlet pressure of the No. 1 high-pressure heater, a fifth pressure measuring instrument for measuring the inlet steam pressure of the No. 1 high-pressure heater, a sixth pressure measuring instrument for measuring the drain pressure of the No. 1 high-pressure heater, a seventh pressure measuring instrument for measuring the outlet pressure of the No. 2 high-pressure heater, an eighth pressure measuring instrument for measuring the inlet pressure of the No. 2 high-pressure heater, a ninth pressure measuring instrument for measuring the inlet steam pressure of the No. 2 high-pressure heater, a tenth pressure measuring instrument for measuring the drain pressure of the No. 2 high-pressure heater, an eleventh pressure measuring instrument for measuring the outlet pressure of the No. 3 high-pressure heater, a twelfth pressure measuring instrument for measuring the inlet pressure of the No. 3 high-pressure heater, a thirteenth pressure measuring instrument for measuring the inlet steam pressure of the No. 3 high-pressure heater, a fourteenth pressure measuring instrument for measuring the drain pressure of the No. 3 high-pressure heater, a fifteenth pressure measuring instrument for measuring the outlet pressure of the deaerator, a sixteenth pressure measuring instrument for measuring the inlet pressure of the deaerator, a seventeenth pressure measuring instrument for measuring the inlet steam pressure of the deaerator, a first temperature measuring instrument for measuring the outlet temperature of the No. 1 high-pressure heater, a second temperature measuring instrument for measuring the inlet temperature of the No. 1 high-pressure heater, a third temperature measuring instrument for measuring the inlet steam temperature of the No. 1 high-pressure heater, a fourth temperature measuring instrument for measuring the drain temperature of the No. 1 high-pressure heater, a fifth temperature measuring instrument for measuring the outlet temperature of the No. 2 high-pressure heater, a sixth temperature measuring instrument for measuring the inlet temperature of the No. 2 high-pressure heater, a seventh temperature measuring instrument for measuring the inlet steam temperature of the No. 2 high-pressure heater, an eighth temperature measuring instrument for measuring the drain temperature of the No. 2 high-pressure heater, a ninth temperature measuring instrument for measuring the outlet temperature of the No. 3 high-pressure heater, a tenth temperature measuring instrument for measuring the inlet temperature of the No. 3 high-pressure heater, an eleventh temperature measuring instrument for measuring the inlet steam temperature of the No. 3 high-pressure heater, a twelfth temperature measuring instrument for measuring the drain temperature of the No. 3 high-pressure heater, a thirteenth temperature measuring instrument for measuring the outlet temperature of the deaerator, a fourteenth temperature measuring instrument for measuring the inlet temperature of the deaerator, and a fifteenth temperature measuring instrument for measuring the inlet steam temperature of the deaerator.

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