A method for online calculation and correction of working medium-fuel ratio of a thermal power system

Abstract

The application discloses a kind of online calculation and correction methods of thermal power system working medium fuel ratio, by collecting the historical data of each thermodynamic parameter of boiler system and steam turbine system, by the method of data preprocessing, these original data are washed, the thermodynamic parameter of each working medium of boiler and steam turbine is calculated, and the steam turbine low-pressure cylinder exhaust enthalpy, extraction enthalpy and unit working medium work amount are calculated, obtain the feed water flow and unit working medium heat absorption, finally obtain the working medium fuel ratio of thermal power system under the load. Working medium fuel ratio as the important parameter of thermal power system variable condition process control, master working medium fuel ratio function curve about thermal power system load has important significance to the flexibility of thermal power system quick variable load, can be used for the optimization of thermal power system flexible and efficient operation control strategy.

Description

Technical Field

[0001] This invention belongs to the field of thermal power system control optimization, specifically relating to an online calculation and correction method for the working fluid-fuel ratio of a thermal power system. Background Technology

[0002] Since the beginning of the 21st century, the world's energy structure has been continuously transforming towards a cleaner, lower-carbon, more efficient, and diversified direction. However, due to the strong time-varying characteristics of renewable energy sources such as wind and solar power, my country faces difficulties in absorbing renewable energy power generation, resulting in serious problems of wind and solar curtailment. Improving the operational flexibility of conventional thermal power systems to provide absorption services for renewable energy power generation is an important technological direction. Taking coal-fired power generation as an example, coal-fired power generation will shift from a primary energy source to a basic energy source, and the load variation range and frequency of coal-fired power generating units will gradually increase. Therefore, thermal power systems will be in a transient operating condition with frequent load variations for a long time.

[0003] To achieve "energy conservation first," the thermal power system must possess high energy utilization efficiency while operating flexibly. The matching of the working fluid and fuel quantity of a thermal power unit directly determines the unit's operating quality under different load conditions and is a core parameter for optimizing the control of the unit during load changes. Therefore, determining the working fluid-fuel ratio and reasonable feedwater and coal quantities under different load conditions is an important task for optimizing the control of the thermal power system of a thermal power unit and improving its flexibility during load changes.

[0004] In order to determine the reasonable coal feed rate, water feed rate and working fluid-fuel ratio of a thermal power system under different load conditions, this invention proposes an online calculation and correction method for the working fluid-fuel ratio of a thermal power system. Summary of the Invention

[0005] In order to overcome the problems existing in the prior art, the purpose of this invention is to provide an online calculation and correction method for the working fluid-fuel ratio of a thermal power system. The working fluid-fuel ratio is an important parameter for optimizing the control of a thermal power system and further realizing flexible operation. This invention can conveniently, quickly and accurately calculate the working fluid-fuel ratio of a thermal power system under different load conditions.

[0006] The present invention adopts the following technical solution:

[0007] A method for online calculation and correction of the working fluid-fuel ratio in a thermal power system. The thermal power system consists of a boiler system and a turbine system, which are connected by m working fluid inlets and outlets. One working fluid is converted from feedwater into fresh steam through heat absorption. The feedwater flows out from the highest-stage regenerative heater and enters the boiler, while the fresh steam flows out from the high-temperature superheater and reaches the fresh steam inlet of the turbine. The remaining m-1 streams are reheated steam, which flows out from a stage extraction port of the turbine and enters the boiler reheater, and then enters the turbine reheat steam inlet after reheating. The turbine system includes a turbine, a z-stage regenerative heater, and a condenser. The z-stage regenerative heater is connected by a pipe... The system connects to the turbine extraction port. Following the extraction pressure from high to low, the first to k-1 stages of the regenerative heater are high-pressure heaters, the k-th stage is a deaerator, and the k+1 to z-th stages are low-pressure heaters. Finally, the turbine exhaust steam enters the condenser. There are two connection methods between the water and steam sides. For the indirect-flow regenerative heater, water flows inside the tubes, and steam flows outside. Heat is transferred from the steam side to the water side through the tube walls, heating the feedwater or condensate. The extracted steam releases heat and becomes condensate, flowing by gravity to the next stage of the regenerative heater. For the combined heater, water and steam are fully mixed and exchange heat within the heater, merging into a single working fluid that continues to flow along the water side.

[0008] The online calculation and correction method for the working fluid-fuel ratio of the thermal power system includes the following steps:

[0009] Step 1: Data Collection

[0010] Collect m working fluid inlet and outlet thermal parameters between the boiler system and the turbine system, including the temperature and pressure T of the m working fluids entering the boiler. in,i P in,i The temperature and pressure T of the working fluid leaving the boiler out,i P out,i Where i = 1 - m;

[0011] Collect the thermodynamic parameters of the Z-stage regenerative heater, including the temperature T before and after each stage of the regenerative heater on the feedwater side. w,in,i T w,out,i Temperature T of each stage of extraction steam on the extraction side s,i P s,i Temperature T of the condensate drain of each stage of the regenerator d,i , where i = 1 - z;

[0012] Collects the power generation W of the thermal power system e And the exhaust pressure P of the low-pressure cylinder of the steam turbine c condensate pump pressure P cp Deaerator pressure P dea Water supply pressure P after the water pump fp Economizer inlet feedwater pressure P eco,in ;

[0013] Step 2: Data Preprocessing

[0014] The collected parameter data will be cleaned.

[0015] Step 3: Calculate the enthalpy of the working fluid at each point.

[0016] (1) Using temperature and pressure data, the enthalpy of the working fluid at each point is calculated through thermophysical property calculations, including the enthalpy h of the m working fluids flowing into and out of the boiler. in,i and h out,i Where i = 1 - m; the enthalpy h of the inlet water of each stage of the regenerator on the feedwater side. w,in,i and the enthalpy h of the outlet water w,out,i ; enthalpy h of each stage of extraction steam on the extraction side s,i ; enthalpy h of each level of hydrophobicity d,i , where i = 1 - z;

[0017] First, determine whether all extracted steam is superheated steam or wet steam. For superheated steam, use thermophysical property calculation methods to obtain the enthalpy values ​​at each point:

[0018] h = f TP (P,T)

[0019] In the formula, f TP It is a thermal property function;

[0020] (2) Since the exhaust steam from the low-pressure cylinder and the partial extraction steam from the low-pressure cylinder are in the wet steam zone during the operation of the thermal power system, the enthalpy value cannot be obtained simply by using the thermophysical property calculation method. The following pressure ratio efficiency fitting method should be used for calculation:

[0021] Select the low-pressure cylinder exhaust pressure P c and the extraction pressure P of stage a s,a The ratio P of the exhaust pressure to the extraction pressure of stage a is used. c / P s,a The internal efficiency data η of this section of the steam turbine a-c By fitting the data, the functional relationship between the pressure ratio and the internal efficiency is obtained;

[0022] Then, based on the pressure ratio P before and after this section under a certain load condition during the actual operation of the thermal power system... c / P s,a To obtain the relative internal efficiency η of this segment under this working condition. a-c Therefore, the exhaust enthalpy is obtained through the following formula:

[0023] h c =h s,a -η a-c (h s,a -h cs )

[0024] Where: h c The enthalpy of exhaust steam from the low-pressure cylinder of the steam turbine, kJ / kg; h s,a The enthalpy of the steam extracted from stage a of the steam turbine, kJ / kg; η a-c The efficiency of the extraction and exhaust section of the a-stage steam in the low-pressure cylinder of the steam turbine; h cs The ideal exhaust enthalpy of the low-pressure cylinder of the steam turbine, kJ / kg;

[0025] Meanwhile, the enthalpy of the steam extracted from the first-stage low-pressure cylinder in the wet steam zone is also calculated using the above method; the relationship curve between the ratio of the first-stage extraction pressure to the higher a-stage extraction pressure and the efficiency of this section from the a-stage extraction port to the first-stage extraction port is fitted; and then, based on the pressure ratio P before and after this section under a certain load condition during the actual operation of the thermal power system... s,l / P s,a To obtain the relative internal efficiency η of this segment under this working condition. a-l Therefore, the enthalpy of the first stage extraction is obtained by the following formula:

[0026] h s,l =h s,a -η a-l (h s,a -h s,ls )

[0027] Where: h s,l The enthalpy of the first stage extraction steam of the steam turbine, kJ / kg; h s,a The enthalpy of the steam extracted from stage a of the steam turbine, kJ / kg; η a-l The efficiency of steam extraction from stage a to stage l in the low-pressure cylinder of the steam turbine; h s,ls The enthalpy of the ideal extraction steam for the first stage of the steam turbine is given in kJ / kg.

[0028] Step 4: Calculate the work done per unit of working fluid, H.

[0029]

[0030] Where: h in,1 σ is the enthalpy of the main steam in the boiler, kJ / kg; j The heat absorbed by a unit mass of reheat steam in each reheat cycle of the boiler, expressed in kJ / kg; h. c The enthalpy of exhaust steam from the low-pressure cylinder of the steam turbine, kJ / kg; τ r The feedwater enthalpy rise of the r-th stage heater, kJ / kg; H r The equivalent heat drop of the extraction steam at stage r is kJ / kg; q r ∑Π represents the heat release per unit mass of steam extracted by the r-th stage heater, in kJ / kg; ∑Π represents the decrease in work done per unit working fluid due to various losses, in kJ / kg.

[0031] The calculation method for the equivalent heat drop of each stage of steam extraction is as follows:

[0032] 1) The equivalent heat reduction of all extracted steam after reheating is:

[0033]

[0034] 2) Equivalent heat drop of the regenerator before the final reheat:

[0035]

[0036] In the formula, γ r The heat released by the hydrophobic condenser in the r-th stage heater is expressed in kJ / kg; mixi represents the nearest concentrator heater whose extraction pressure is lower than that of the i-th stage extraction; rhi represents the most recent reheat after the i-th stage extraction.

[0037] Where, τ r q r γ r The calculation method is as follows:

[0038] 1) For condensate drain type heaters:

[0039] τ r =h w,out,r -h gs,in,r

[0040] q r =h s,r -h d,r

[0041] γ r =h d,r-1 -h d,r

[0042] 2) For centralized heaters:

[0043] τ r =h w,out,r -h w,in,r

[0044] q r =h s,r -h w,in,r

[0045] γ r =h d,r-1 -h w,in,i

[0046] Step 5: Calculate the main steam flow rate D 水

[0047] Based on the relationship between the working fluid flow rate and the power of the thermal power system, and using the work done per unit working fluid H calculated in step four, the main feedwater flow rate D of the thermal power system is calculated. 水 ;

[0048]

[0049]

[0050] In the formula: W e The power generation capacity of a thermal power system is expressed in MW or W. t For turbine power, MW; η m For mechanical efficiency; η g For generator efficiency;

[0051] Step 6: Calculate the total heat absorption Q of the working fluid in the boiler.

[0052] The total heat absorption Q of a unit working fluid in the boiler is obtained by calculating the heat absorption of different working fluid flows in the boiler.

[0053]

[0054]

[0055] In the formula: α i The proportion of the working fluid stream entering the boiler as a percentage of the main feedwater; h out,i The enthalpy of the i-th working fluid outlet is given in kJ / kg; h in,i Let be the inlet enthalpy of the i-th working fluid stream, in kJ / kg.

[0056] Step 7: Calculate the working fluid-to-fuel ratio λ of the thermal power system.

[0057] By changing the formula for calculating the working fluid-fuel ratio, the relationship between the working fluid-fuel ratio and the heat absorbed per unit working fluid is obtained, and finally the working fluid-fuel ratio λ under this load condition is calculated.

[0058]

[0059] In the formula: D 煤 η is the flow rate of coal, kg / s; b For boiler efficiency; q net The lower heating value of coal is expressed in kJ / kg.

[0060] Step 8:

[0061] Calculate the working fluid-to-fuel ratio λ and feedwater flow rate D for multiple power generation capacities in a thermal power system. 水 A working fluid-to-fuel ratio λ is fitted as a function of the thermal power system power W. e The curve;

[0062] λ=f(W e )

[0063] In the formula: λ is the working fluid-fuel ratio;

[0064] When the working fluid-fuel ratio of the thermal power system in actual operation is λ w When the deviation of the working fluid-fuel ratio λ corresponding to the comparison curve exceeds 5%, the working fluid-fuel ratio curve needs to be corrected.

[0065] Combined with water supply D 水 This allows us to determine the corresponding water and coal feed rates for the thermal power system under that load, which is of great significance for improving the flexibility of the thermal power system and optimizing the control strategy.

[0066] Preferably, the specific methods for data cleaning in step two include:

[0067] (1) Data denoising methods include mean filtering, median filtering, wavelet transform, connected graph method, support vector machine and Kalman filtering to denoise the original running data;

[0068] (2) Fill in missing data values, correct outlier data values, and remove erroneous data values;

[0069] (3) Combining the change patterns and physical mechanisms in the actual operation of the thermal power system, analyze the magnitude and trend of the essential basic parameters that are indispensable in the thermal power system, select more accurate measurement points for data from multiple measurement points, correct or discard data points that contradict the changes in the basic data of the thermal power system, and finally complete the data cleaning work of the entire operating database.

[0070] Preferably, the specific processing method used in step three for calculating the low-pressure cylinder exhaust enthalpy and the extraction enthalpy in the wet steam zone using the pressure ratio efficiency fitting method is as follows:

[0071] The low-pressure cylinder exhaust pressure P from the thermal power system test data is used. c With the extraction pressure P of stage a s,a The ratio P c / P s,a The internal efficiency η of the section from the a-th stage extraction port to the low-pressure cylinder exhaust is... a-c The above data are fitted to obtain the relationship curve between the two, and then the pressure ratio P from the actual operating data is used. c / P s,a The corresponding internal efficiency η is calculated. a-c There are various methods for data fitting and interpolation, including: least squares fitting, stepwise regression, multinomial fitting, logarithmic fitting, cubic spline interpolation, or using signal domain, gradient descent learning, and swarm intelligence optimization algorithms.

[0072] Preferably, in step three, the hydrophobic enthalpy values ​​h at each level are calculated using thermophysical properties. d,iThe necessary but unmeasurable condensate pressure P of each stage of the heater d,i According to the extraction steam pressure P at each level s,i Calculate using 95%, that is

[0073] P d,i =0.95P s,i

[0074] In step three, the enthalpy h of the inlet water of each stage of the regenerator on the feedwater side is calculated using thermophysical properties. w,in,i and the enthalpy h of the outlet water w,out,i The necessary but unmeasurable pressure P of the inlet water of each stage of the regenerative heater w,in,i and the pressure P of the outlet water w,out,i Where i = 1 - z, then the pressure P after the condensate pump is used. cp Deaerator pressure P dea Water supply pressure P after the water pump fp Economizer inlet feedwater pressure P eco,in To calculate and obtain, that is

[0075] When the heater is a low-pressure heater

[0076]

[0077]

[0078] Where i = k+1 - z;

[0079] When the heater is a high-pressure heater

[0080]

[0081]

[0082] Where i = 1 - k - 1;

[0083] Step four involves calculating the steam consumption α of the feedwater pump turbine required to produce the work H per unit of working fluid, but without a measurement point. bfpt This is calculated using the relationship between the enthalpy rise of the feedwater pump, the actual enthalpy drop of the feedwater pump turbine extraction steam, and steam consumption.

[0084]

[0085] In the formula, h w,in,k-1 Enthalpy of the heater inlet water after the feedwater pump; h w,out,k h is the enthalpy of the water at the heater outlet before the feedwater pump. s,k h is the enthalpy of the steam extracted from the feedwater pump turbine. c,bfpt For the exhaust steam enthalpy of the feedwater pump turbine;

[0086] If other missing parameters cannot be obtained through calculation, they are replaced by interpolation based on the power of the thermal power system under the design conditions and the actual operating power of the thermal power system.

[0087] Preferably, in step eight, the fitting method used is least squares fitting, polynomial fitting, logarithmic fitting, stepwise regression, or neural network method.

[0088] The beneficial effects of this invention are as follows: Based on the energy balance principle of thermal power systems, this invention collects thermodynamic parameters such as temperature and pressure of the working fluid entering and exiting the boiler, turbine, and regenerator of the thermal power system, and performs data preprocessing to calculate the enthalpy of each working fluid entering and exiting each device. For the enthalpy of exhaust steam and extraction steam, etc., in the wet steam zone, the enthalpy is obtained through pressure ratio efficiency fitting. The equivalent heat drop principle is applied to calculate the work done per unit mass of working fluid, and combined with power, the total feedwater flow rate of the thermal power system is obtained. By calculating the proportion of each heat exchange working fluid and its heat absorption in the boiler, the total heat absorption per unit mass of working fluid in the boiler is obtained. Subsequently, by deriving the working fluid-fuel ratio formula, the corresponding working fluid-fuel ratio under this load condition is calculated, and a function curve of the working fluid-fuel ratio versus the load of the thermal power system is fitted using the calculated data. The calculated feedwater flow rate and working fluid-fuel ratio can provide basic information for the matching control of fuel quantity and working fluid quantity in thermal power systems under varying loads. At the same time, the working fluid-fuel ratio, as the core parameter for the optimized control of thermal power systems in thermal power units, is the key to ensuring the control effect of thermal power systems.

[0089] Advantages of the present invention

[0090] 1) This invention provides a method for calculating exhaust steam enthalpy and the enthalpy of the last few stages of extraction steam in the wet steam zone, namely the pressure ratio efficiency fitting method. Compared with the method of directly using pressure and temperature to calculate the enthalpy value through thermophysical property calculation, it greatly improves the accuracy of the calculated enthalpy value, and compared with the traditional curve extrapolation method to obtain the enthalpy of the last few stages of extraction steam and exhaust steam, it also greatly improves the reliability of the obtained results.

[0091] 2) This invention uses the equivalent heat drop theory to calculate the equivalent heat drop of new steam, and uses the power of the thermal power system to determine the values ​​of feedwater flow rate and coal feed rate, and further obtains the working fluid fuel ratio corresponding to different loads of the thermal power system; it uses the equivalent heat drop method to obtain the work done per unit working fluid, and accurately calculates the actual feedwater flow rate of the thermal power system. Compared with the feedwater flow rate measured by measuring points, it greatly improves the accuracy, and at the same time greatly improves the accuracy of subsequent calculation of the working fluid fuel ratio.

[0092] 3) This invention can obtain the relationship curve between the working fluid-fuel ratio and the load of a thermal power system, so as to ensure the optimized control effect of the thermal power system and improve the control quality. Attached Figure Description

[0093] Figure 1 This is a schematic diagram of a thermal power system.

[0094] Figure 2 The flowchart for online calculation of the working fluid-fuel ratio in a thermal power system (taking the last two stages of an eight-stage extraction steam regeneration system as an example, where the steam may be wet in the last two stages);

[0095] Figure 3 This is a thermal system diagram of a 1000MW ultra-supercritical single reheat unit. Detailed Implementation

[0096] To make the objectives, technical solutions, and advantages of this invention clearer, the method of this invention is further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0097] This invention provides an online calculation and correction method for the working fluid-fuel ratio in a thermal power system, such as... Figure 1 As shown, the thermal power system consists of a boiler system and a turbine system. The boiler system and turbine system are connected by m working fluid inlets and outlets. One working fluid is converted from feedwater into fresh steam through heat absorption. The feedwater flows out from the highest-level regenerative heater and enters the boiler, while the fresh steam flows out from the high-temperature superheater and reaches the turbine's fresh steam inlet. The remaining m-1 streams are reheat steam, flowing out from a certain stage extraction port of the turbine and into the boiler reheater, and then into the turbine's reheat steam inlet after reheating. The turbine system includes a turbine, a z-stage regenerative heater, and a condenser. The z-stage regenerative heater is connected to the turbine extraction port via a pipeline, and the extraction pressure is adjusted accordingly. The pressure decreases from high to low. Stages 1 to k-1 are high-pressure heaters, stage k is a deaerator, and stages k+1 to z are low-pressure heaters. Finally, turbine exhaust steam enters the condenser. There are two connection methods for the water and steam sides. For a wall-type regenerative heater, water flows inside the tubes, and steam flows outside. Heat is transferred from the steam side to the water side through the tube walls, heating the feedwater or condensate. Extracted steam releases heat and becomes condensate, flowing by gravity to the next stage of the regenerative heater. For a combined heater, water and steam are fully mixed and exchange heat within the heater, merging into a single working fluid that continues to flow along the water side. In this example, the thermal power system is as follows: Figure 3 As shown, an 8-stage regenerative heater is used. Figure 2 In the diagram, 1 represents the high-pressure cylinder of the steam turbine, 2 represents the intermediate-pressure cylinder of the steam turbine, 3 represents the low-pressure cylinder of the steam turbine, 4 represents the small steam turbine, and 5 represents the boiler.

[0098] The specific thermal power system configuration characteristics used in the calculation case are as follows:

[0099] 1) This thermal power unit is a 1000MW ultra-supercritical once-through reheat condensing turbine unit;

[0100] 2) The rated water supply temperature is 294.7℃;

[0101] 3) The rated main steam temperature is 600℃, the rated main steam pressure is 25MPa, the rated reheat steam temperature is 600℃, and the rated reheat steam pressure is 4.366MPa;

[0102] 4) Reheat steam is taken from the exhaust steam of the high-pressure cylinder, heated by the boiler, and then enters the inlet of the intermediate-pressure cylinder;

[0103] 5) The thermal system diagram of this unit is attached. Figure 3 As shown;

[0104] like Figure 2 As shown, the online calculation and correction method for the working fluid-fuel ratio of the thermal power system in this embodiment includes the following steps:

[0105] Step 1: Data Collection

[0106] Collect the inlet and outlet thermal parameters of the two working fluids between the boiler system and the turbine system, including the temperature and pressure T of the two working fluids entering the boiler. in,i P in,i The temperature and pressure T of the working fluid leaving the boiler out,i P out,I where i = 1, 2;

[0107] Collect the thermodynamic parameters of the 8-stage regenerative heaters, including the temperature T before and after each stage of the regenerative heater on the feedwater side. w,in,i T w,out,i Temperature T of each stage of extraction steam on the extraction side s,i P s,i Temperature T of the condensate drain of each stage of the regenerator d,i Where i = 1-8;

[0108] Collects the power generation W of the thermal power system e And the exhaust pressure P of the low-pressure cylinder of the steam turbine c condensate pump pressure P cp Deaerator pressure P dea Water supply pressure P after the water pump fp Economizer inlet feedwater pressure P eco,in ;

[0109] Step 2: Data Preprocessing

[0110] The collected parameter data will be cleaned.

[0111] Step 3: Calculate the enthalpy of the working fluid at each point.

[0112] (1) Using temperature and pressure data, the enthalpy of the working fluid at each point is calculated through thermophysical property calculations, including the enthalpy h of the two working fluids flowing into and out of the boiler.in,i and h out,i Where i = 1, 2; the enthalpy h of the inlet water of each stage of the regenerator on the feedwater side. w,in,i and the enthalpy h of the outlet water w,out,i ; enthalpy h of each stage of extraction steam on the extraction side s,i ; enthalpy h of each level of hydrophobicity d,i Where i = 1-8;

[0113] First, determine whether all extracted steam is superheated steam or wet steam. For superheated steam, use thermophysical property calculation methods to obtain the enthalpy values ​​at each point:

[0114] h = f TP (P,T)

[0115] In the formula, f TP It is a thermal property function;

[0116] (2) Since the exhaust steam from the low-pressure cylinder and the partial extraction steam from the low-pressure cylinder are in the wet steam zone during the operation of the thermal power system, the enthalpy value cannot be obtained simply by using the thermophysical property calculation method. The following pressure ratio efficiency fitting method should be used for calculation:

[0117] Select the low-pressure cylinder exhaust pressure P c and the sixth stage extraction pressure P s,6 The ratio P of the exhaust pressure to the sixth-stage extraction pressure is used. c / P s,6 The internal efficiency data η of this section of the steam turbine 6-c By fitting the data, the functional relationship between the pressure ratio and the internal efficiency is obtained;

[0118] Then, based on the pressure ratio P before and after this section under a certain load condition during the actual operation of the thermal power system... c / P s,6 To obtain the relative internal efficiency η of this segment under this working condition. 6-c Therefore, the exhaust enthalpy is obtained through the following formula:

[0119] h c =h s,6 -η 6-c (h s,6 -h cs )

[0120] Where: h c The enthalpy of exhaust steam from the low-pressure cylinder of the steam turbine, kJ / kg; h s,6 The enthalpy of the sixth stage extraction steam of the steam turbine, kJ / kg; η 6-c The efficiency of the sixth stage extraction steam to the exhaust section of the low-pressure cylinder of the steam turbine; h cs The ideal exhaust enthalpy of the low-pressure cylinder of the steam turbine, kJ / kg;

[0121] Meanwhile, the enthalpy of the steam extracted from the first-stage low-pressure cylinder in the wet steam zone is also calculated using the above method; the relationship curve between the ratio of the first-stage extraction pressure to the higher sixth-stage extraction pressure and the efficiency of this section from the sixth-stage extraction port to the first-stage extraction port is fitted; and then, based on the pressure ratio P before and after this section under a certain load condition during the actual operation of the thermal power system, the efficiency of this section is calculated. s,l / P s,6 To obtain the relative internal efficiency η of this segment under this working condition. 6-l Therefore, the enthalpy of the first stage extraction is obtained by the following formula:

[0122] h s,l =h s,6 -η 6-l (h s,6 -h s,ls )

[0123] Where: h s,l The enthalpy of the first stage extraction steam of the steam turbine, kJ / kg; h s,a The enthalpy of the sixth stage extraction steam of the steam turbine, kJ / kg; η 6-l The efficiency of steam extraction from the 6th stage to the 1st stage of the low-pressure cylinder of the steam turbine; h s,ls The ideal extraction steam enthalpy of the l-th stage of the steam turbine is kJ / kg, where l = 7, 8;

[0124] The accuracy of calculating exhaust enthalpy and extraction enthalpy in the low-pressure cylinder in the wet steam zone by using the pressure ratio efficiency fitting method is greatly improved compared with the calculation of exhaust enthalpy and extraction enthalpy by directly using the curve extrapolation method. This greatly improves the accuracy of subsequent calculation of the work done by a unit working fluid, H.

[0125] Step 4: Calculate the work done per unit of working fluid, H.

[0126]

[0127] Where: h in,1 σ is the enthalpy of the main steam in the boiler, kJ / kg; σ is the heat absorbed per unit mass of reheat steam in the boiler reheater, kJ / kg; h c The enthalpy of exhaust steam from the low-pressure cylinder of the steam turbine, kJ / kg; τ r The feedwater enthalpy rise of the r-th stage heater, kJ / kg; H r The equivalent heat drop of the extraction steam at stage r is kJ / kg; q r ∑Π represents the heat release per unit extraction of steam in the r-th stage heater, in kJ / kg; ∑Π represents the decrease in work done per unit working fluid due to various losses, in kJ / kg.

[0128] The calculation method for the equivalent heat drop of each stage of steam extraction is as follows:

[0129] 1) The equivalent heat reduction of the extracted steam after reheating is:

[0130] Where i = 3;

[0131] Where i = 5-8;

[0132] 2) Equivalent heat drop of the regenerator before reheating:

[0133] Where i = 1, 2;

[0134] In the formula, γ r The heat released by the hydrophobic material in the r-th stage heater is expressed in kJ / kg.

[0135] Where, τ r q r γ r The calculation method is as follows:

[0136] 1) For condensate drain type heaters:

[0137] τ r =h w,out,r -h gs,in,r

[0138] q r =h s,r -h d,r

[0139] γ r =h d,r-1 -h d,r

[0140] 2) For centralized heaters:

[0141] τ r =h w,out,r -h w,in,r

[0142] q r =h s,r -h w,in,r

[0143] γ r =h d,r-1 -h w,in,i

[0144] Step 5: Calculate the main steam flow rate D 水

[0145] Based on the relationship between the working fluid flow rate and the power of the thermal power system, and using the work done per unit working fluid H calculated in step four, the main feedwater flow rate D of the thermal power system is calculated. 水 ;

[0146]

[0147]

[0148] In the formula: W e The power generation capacity of a thermal power system is expressed in MW or W. t For turbine power, MW; η m For mechanical efficiency; η g For generator efficiency;

[0149] The actual water flow rate D is obtained by calculating the work done by a unit of working fluid, H, using the power calculation of the thermal power system. 水 Compared to measuring points, the accuracy of the data is greatly improved, which is of great significance for improving the accuracy of subsequent calculations of the working fluid-fuel ratio of thermal power systems.

[0150] Step 6: Calculate the total heat absorption Q of the working fluid in the boiler.

[0151] The total heat absorption Q of a unit working fluid in the boiler is obtained by calculating the heat absorption of different working fluid flows in the boiler.

[0152]

[0153] Q=(h out,1 -h in,1 )+α2·(h out,2 -h in,2 )

[0154] In the formula: α2 is the proportion of reheat steam flow rate to main feedwater flow rate; h out,1 and h out,2 The enthalpy of the main steam and the enthalpy of the reheat steam are respectively, in kJ / kg; h in,1 and h in,2 These are the enthalpy of feedwater and the enthalpy of exhaust steam from the high-pressure cylinder, respectively, in kJ / kg.

[0155] Step 7: Calculate the working fluid-to-fuel ratio λ of the thermal power system.

[0156] By changing the formula for calculating the working fluid-fuel ratio, the relationship between the working fluid-fuel ratio and the heat absorbed per unit working fluid is obtained, and finally the working fluid-fuel ratio λ under this load condition is calculated.

[0157]

[0158] In the formula: D 煤 η is the flow rate of coal, kg / s; b For boiler efficiency; q net The lower heating value of coal is expressed in kJ / kg.

[0159] Step 8:

[0160] Calculate the working fluid-to-fuel ratio λ and feedwater flow rate D for multiple power generation capacities in a thermal power system. 水 A working fluid-to-fuel ratio λ is fitted as a function of the thermal power system power W. e The curve;

[0161] λ=f(W e )

[0162] In the formula: λ is the working fluid-fuel ratio;

[0163] When the working fluid-fuel ratio of the thermal power system in actual operation is λ w When the deviation of the working fluid-fuel ratio λ corresponding to the comparison curve exceeds 5%, the working fluid-fuel ratio curve needs to be corrected.

[0164] Combined with water supply D 水 This allows us to determine the corresponding water and coal feed rates for the thermal power system under that load, which is of great significance for improving the flexibility of the thermal power system and optimizing the control strategy.

[0165] Preferably, the specific methods for data cleaning in step two include:

[0166] (1) Data denoising methods include mean filtering, median filtering, wavelet transform, connected graph method, support vector machine and Kalman filtering to denoise the original running data;

[0167] (2) Fill in missing data values, correct outlier data values, and remove erroneous data values;

[0168] (3) Combining the change patterns and physical mechanisms in the actual operation of the thermal power system, analyze the magnitude and trend of the essential basic parameters that are indispensable in the thermal power system, select more accurate measurement points for data from multiple measurement points, correct or discard data points that contradict the changes in the basic data of the thermal power system, and finally complete the data cleaning work of the entire operating database.

[0169] Preferably, the specific processing method used in step three for calculating the low-pressure cylinder exhaust enthalpy and the extraction enthalpy in the wet steam zone using the pressure ratio efficiency fitting method is as follows:

[0170] The low-pressure cylinder exhaust pressure P from the thermal power system test data is used. c With the sixth stage extraction steam pressure P s,6 The ratio P c / P s,6 The internal efficiency η of the section from the sixth-stage extraction port to the low-pressure cylinder exhaust is... 6-c The above data are fitted to obtain the relationship curve between the two, and then the pressure ratio P from the actual operating data is used. c / P s,6The corresponding internal efficiency η is calculated. 6-c There are various methods for data fitting and interpolation, including: least squares fitting, stepwise regression, multinomial fitting, logarithmic fitting, cubic spline interpolation, or using signal domain, gradient descent learning, and swarm intelligence optimization algorithms.

[0171] Preferably, in step three, the hydrophobic enthalpy values ​​h at each level are calculated using thermophysical properties. d,i The necessary but unmeasurable condensate pressure P of each stage of the heater d,i According to the extraction steam pressure P at each level s,i Calculate using 95%, that is

[0172] P d,i =0.95P s,i , where i = 1-3, 5-8;

[0173] In step three, the enthalpy h of the inlet water of each stage of the regenerator on the feedwater side is calculated using thermophysical properties. w,in,i and the enthalpy h of the outlet water w,out,i The necessary but unmeasurable pressure P of the inlet water of each stage of the regenerative heater w,in,i and the pressure P of the outlet water w,out,I Where i = 1-8, then the pressure P after using the condensate pump is... cp Deaerator pressure P dea Water supply pressure P after the water pump fp Economizer inlet feedwater pressure P eco,in To calculate and obtain, that is

[0174] When the heater is a low-pressure heater

[0175]

[0176]

[0177] Where i = 5-8;

[0178] When the heater is a high-pressure heater

[0179]

[0180]

[0181] Where i = 1-3;

[0182] Step four involves calculating the steam consumption α of the feedwater pump turbine required to produce the work H per unit of working fluid, but without a measurement point. bfpt This is calculated using the relationship between the enthalpy rise of the feedwater pump, the actual enthalpy drop of the feedwater pump turbine extraction steam, and steam consumption.

[0183]

[0184] In the formula, h w,in,3 Enthalpy of the inlet water for the third-stage heater; h w,out,4 Enthalpy of deaerator outlet water; h s,4 h is the enthalpy of the steam extracted from the feedwater pump turbine. c,bfpt For the exhaust steam enthalpy of the feedwater pump turbine;

[0185] If other missing parameters cannot be obtained through calculation, they are replaced by interpolation based on the power of the thermal power system under the design conditions and the actual operating power of the thermal power system.

[0186] Preferably, in step eight, the fitting method used is least squares fitting, polynomial fitting, logarithmic fitting, stepwise regression, or neural network method.

[0187] This invention employs a pressure ratio efficiency fitting method to obtain the enthalpy values ​​of extraction steam and low-pressure cylinder exhaust steam in the wet steam zone. It then uses the equivalent heat drop theory to calculate the equivalent heat drop of the new steam, i.e., the work done per unit working fluid, and finally uses the working fluid-fuel ratio calculation formula to obtain the working fluid-fuel ratio curves for different loads in the thermal power system. This invention can provide a benchmark for optimizing the control logic of thermal power systems during load changes and provides a guarantee for further improving the flexibility of thermal power systems.

[0188] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent transformations, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for online calculation and correction of the working fluid-fuel ratio in a thermal power system, characterized in that: The thermal power system consists of a boiler system and a steam turbine system, which are connected by a... m The working fluid inlet and outlet are connected. One stream of working fluid is converted from feedwater into fresh steam through heat absorption. The feedwater flows out of the highest-stage regenerative heater and enters the boiler, while the fresh steam flows out of the high-temperature superheater and reaches the fresh steam inlet of the turbine. The remaining... m -1 is reheat steam, flowing out from a certain stage extraction port of the steam turbine and entering the boiler reheater. After reheating, it enters the steam turbine reheat steam inlet. The steam turbine system includes the steam turbine, z Stage regenerative heater and condenser, z The first-stage regenerative heaters are connected to the turbine extraction port via pipelines, arranged from high to low extraction pressure, from stage 1 to stage 2. k The -1 stage regenerative heater is a high-pressure heater. k The first stage is a deaerator, the second stage is a deaerator. k +1 to the z The first stage is a low-pressure heater, and the final turbine exhaust steam enters the condenser. There are two types of water-side and steam-side connection methods. For the indirect-flow regenerative heater, water flows inside the tubes and steam flows outside the tubes. Heat is transferred from the steam side to the water side through the tube wall, heating the feedwater or condensate. The extracted steam releases heat and becomes condensate, flowing by gravity to the next stage of the regenerative heater. For the combined heater, water and steam are fully mixed and exchange heat inside the heater, and then flow together as a working fluid along the water side. The online calculation and correction method for the working fluid-fuel ratio of the thermal power system includes the following steps: Step 1: Data Collection Data collection between the boiler system and the steam turbine system m The inlet and outlet thermal parameters of the working fluid include m The temperature and pressure of the working fluid entering the boiler T in,i , P in,i Temperature and pressure of the working fluid leaving the boiler T out,i , P out,i ,in i= 1— m ; collection z Thermodynamic parameters of the stage regenerative heaters, including the temperatures before and after each stage of the regenerative heaters on the feedwater side. T w,in,i , T w,out,i Temperature of each stage of extraction steam on the extraction side T s,i 、P s,i Temperature of the drain condensate from each stage of the regenerator T d,i ,in i= 1— z ; Collect the power generation of thermal power systems W e And the exhaust pressure of the low-pressure cylinder of the steam turbine P c , Condensate pump pressure P cp Deaerator pressure P dea Water supply pressure after the water pump P fp Economizer inlet feedwater pressure P eco,in ; Step 2: Data Preprocessing The collected parameter data will be cleaned. Step 3: Calculate the enthalpy of the working fluid at each point. (1) Using temperature and pressure data, the enthalpy of the working fluid at each point is calculated through thermophysical property calculations, including the boiler. m Enthalpy values ​​of the working fluid flowing in and out h in,i and h out,i ,in i= 1— m ; enthalpy of inlet water for each stage of the regenerator on the feedwater side h w,in,i and the enthalpy of the effluent h w,out,i ; enthalpy values ​​of each stage of extraction steam on the extraction side h s,i ; enthalpy values ​​of drainage at each level h d,i ,in i= 1— z ; First, determine whether all extracted steam is superheated steam or wet steam. For superheated steam, use thermophysical property calculation methods to obtain the enthalpy values ​​at each point: In the formula, It is a thermal property function; (2) Since the exhaust steam from the low-pressure cylinder and the partial extraction steam from the low-pressure cylinder are in the wet steam zone during the operation of the thermal power system, the enthalpy value cannot be obtained simply by using the thermophysical property calculation method. The following pressure ratio efficiency fitting method should be used for calculation: Select low-pressure cylinder exhaust pressure P c and the a Stage extraction steam pressure P s,a Using exhaust pressure and the first a The ratio of stage extraction steam pressure P c / P s,a Internal efficiency data of this section of the steam turbine By fitting the data, the functional relationship between the pressure ratio and the internal efficiency is obtained; Then, based on the pressure ratio before and after this section under a certain load condition during actual operation of the thermal power system... P c / P s,a To obtain the relative internal efficiency of this segment under this working condition. Therefore, the exhaust enthalpy is obtained through the following formula: In the formula: h c The enthalpy of exhaust steam from the low-pressure cylinder of the steam turbine, kJ / kg; h s,a For steam turbine a Enthalpy of extraction steam, kJ / kg; For the low-pressure cylinder of the steam turbine a The efficiency of the extraction steam to the exhaust section; h cs The ideal exhaust enthalpy of the low-pressure cylinder of the steam turbine, kJ / kg; Meanwhile, for the first in the wet steam zone l The enthalpy of the steam extracted from the first-stage low-pressure cylinder is also calculated using the above method; the fitting result is... l Stage extraction pressure and higher first a The ratio of extraction steam pressure at stage 1 to that from stage 2 a The first stage of steam extraction port to the first l The efficiency curve of this section at the extraction steam inlet; and then, based on the pressure ratio before and after this section under a certain load condition during actual operation of the thermal power system. P s,l / P s,a To obtain the relative internal efficiency of this segment under this working condition. Therefore, the first l The enthalpy of the extraction vapor stage is obtained by the following formula: In the formula: h s,l For steam turbine l Enthalpy of extraction steam, kJ / kg; h s,a For steam turbine a Enthalpy of extraction steam, kJ / kg; For the low-pressure cylinder of the steam turbine a Level extraction steam to the first l The efficiency of staged steam extraction; h s,ls For steam turbine l Ideal extraction enthalpy, kJ / kg; Step 4: Calculate the work done per unit of working fluid H In the formula: h in,1 Enthalpy of the main steam in the boiler, kJ / kg; The heat absorbed by a unit mass of reheat steam in each reheat cycle of the boiler, expressed in kJ / kg. h c The enthalpy of exhaust steam from the low-pressure cylinder of the steam turbine, kJ / kg; For the first r Enthalpy rise of feedwater in stage heater, kJ / kg; H r For the first r The equivalent heat drop of the extraction steam at the stage, kJ / kg; q r For the first r Heat release per unit mass of steam extracted by the stage heater, kJ / kg; The decrease in work done per unit working fluid due to various losses, in kJ / kg; The calculation method for the equivalent heat drop of each stage of steam extraction is as follows: 1) The equivalent heat reduction of all extracted steam after reheating is: 2) Equivalent heat drop of the regenerator before the final reheat: In the formula, For hydrophobicity in the first r The heat release in the stage heater, kJ / kg; mixi This indicates that the extraction steam pressure is lower than the first i The nearest centralized heater for stage extraction steam; rhi Representing the i The most recent reheat after stage extraction; in, , , The calculation method is as follows: 1) For condensate drain type heaters: 2) For centralized heaters: Step 5: Calculate the main steam flow rate D 水 Based on the relationship between the working fluid flow rate and the power of the thermal power system, the work done per unit working fluid calculated in step four is used. H Calculate the main feedwater flow rate of the thermal power system. D 水 ; In the formula: W e The power generation capacity of a thermal power system is expressed in MW. W t The turbine power is expressed in MW. For mechanical efficiency; For generator efficiency; Step Six: Calculate the total heat absorption per unit working fluid in the boiler. Q The total heat absorption per unit working fluid in the boiler is obtained by calculating the heat absorption of different working fluid flows in the boiler. Q ; In the formula: For the first i The proportion of the working fluid entering the boiler to the main feedwater; For the first i Enthalpy of working mass at outlet, kJ / kg; For the first i Inlet enthalpy of mass flow, kJ / kg; Step 7: Calculate the working fluid-fuel ratio of the thermal power system By transforming the formula for calculating the working fluid-fuel ratio, the relationship between the working fluid-fuel ratio and the heat absorption per unit working fluid is obtained, and finally, the working fluid-fuel ratio under this load condition is calculated. ; In the formula: D 煤 The flow rate of coal is expressed in kg / s. η b For boiler efficiency; q net The lower heating value of coal is expressed in kJ / kg. Step 8: Calculate the working fluid-fuel ratio for multiple power generation levels in a thermal power system. and water supply flow D 水 A working fluid-fuel ratio was fitted. Regarding the load of the thermal power system W e The curve; In the formula: The working fluid to fuel ratio; When the working fluid ratio of the thermal power system in actual operation is... Compare the working fluid-fuel ratios corresponding to the curves When the deviation exceeds 5%, the working fluid-fuel ratio curve needs to be corrected. Combined with water supply D 水 This allows us to determine the water and coal feed rates for the thermal power system under that load.

2. The calculation and correction method according to claim 1, characterized in that: The specific methods for data cleaning in step two include: (1) Data denoising methods include mean filtering, median filtering, wavelet transform, connected graph method, support vector machine and Kalman filtering to denoise the original running data; (2) Fill in missing data values, correct outliers, and remove erroneous data values; (3) Based on the change law and physical mechanism of the actual operation of the thermal power system, analyze the magnitude and change trend of the essential basic parameters that are indispensable in the thermal power system, select more accurate measurement points for the data of multiple measurement points, correct or discard data points that contradict the changes of the basic data of the thermal power system, and finally complete the data cleaning work of the entire operation database.

3. The calculation and correction method according to claim 1, characterized in that: The specific processing method used in step three for calculating the low-pressure cylinder exhaust enthalpy and the extraction enthalpy in the wet steam zone using the pressure ratio efficiency fitting method is as follows: Low-pressure cylinder exhaust pressure from thermal power system test data P c With the a Stage extraction steam pressure P s,a ratio P c / P s,a , and the a The internal efficiency of the section from the extraction port to the low-pressure cylinder exhaust. The above data is fitted to obtain the relationship curve between the two, and then the pressure ratio from the actual operating data is used. P c / P s,a The corresponding internal efficiency was calculated. There are various methods for data fitting and interpolation, including: least squares fitting, stepwise regression, multinomial fitting, logarithmic fitting, cubic spline interpolation, or trust region, gradient descent learning, and swarm intelligence optimization algorithms.

4. The calculation and correction method according to claim 1, characterized in that: In step three, the enthalpy values ​​of hydrophobicity at each stage are calculated using thermophysical properties. h d,i The necessary but unmeasurable condensate pressure of each stage of the heater P d,i According to the extraction pressure at each level P s,i Calculated using 95%, that is In step three, the enthalpy of the inlet water of each stage of the regenerator on the feedwater side is calculated using thermophysical properties. h w,in,i and the enthalpy of the effluent h w,out,i The pressure of the inlet water of each stage of the regenerative heater, which is necessary but has no measuring point. P w,in,i and the pressure of the outlet water P w,out,i ,in i =1— z Then the pressure after the condensate pump is used. P cp Deaerator pressure P dea Water supply pressure after the water pump P fp Economizer inlet feedwater pressure P eco,in To calculate and obtain, that is When the heater is a low-pressure heater in, i = k +1— z ; When the heater is a high-pressure heater in, i =1— k -1; Step four involves calculating the work done per unit of working fluid. H Steam consumption of the feedwater pump turbine that is required but has no measuring points This is calculated using the relationship between the enthalpy rise of the feedwater pump, the actual enthalpy drop of the feedwater pump turbine extraction steam, and steam consumption. In the formula, h w,in,k-1 Enthalpy of the water inlet to the heater after the water supply pump; h w,out,k The enthalpy value of the water outlet from the heater before the feedwater pump; h s,k The enthalpy of the steam extracted from the feedwater pump turbine; h c,bfpt For the exhaust steam enthalpy of the feedwater pump turbine; If other missing parameters cannot be obtained through calculation, they are replaced by interpolation based on the power of the thermal power system under the design conditions and the actual operating power of the thermal power system.

5. The calculation and correction method according to claim 1, characterized in that: In step eight, the fitting method used includes least squares fitting, polynomial fitting, logarithmic fitting, stepwise regression, or neural network methods.

Images