Real-time online prediction method for influence on electric output of thermoelectric unit

Abstract

The invention discloses a real-time online prediction method for the influence on the output of a thermoelectric unit, which belongs to the technical field of performance monitoring and diagnosis of thermal equipment and comprises the steps of deriving a main steam flow calculation equation, deriving the change of the output of the thermoelectric unit, solving the change of the electric power of the unit and the like. According to the mass and energy conservation principle of the unit after the change of the excess air coefficient, a quantitative calculation equation of the influence of the generation power of the unit caused by the change of the excess air coefficient is obtained by combining a mathematical differential thought; operation data of a benchmark working condition of a unit DCS, unit design parameters, unit test data and unit excess air coefficient variation are input, and real-time online prediction and calculation of the main steam flow and the unit generation power of the thermoelectric unit can be achieved according to excess air coefficient variation in combination with a computer technology and an algorithm program. The problem that the existing boiler cannot quantitatively predict and calculate the power output of the thermoelectric unit according to the boundary condition change of the excess air coefficient is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal equipment performance monitoring and diagnosis, and specifically is a real-time online prediction method for the influence on the electric output of a thermal power unit. Background Art

[0002] At present, the load change of coal-fired power units has a great impact on the power generation of steam turbines, especially for thermal power units under peak load regulation, which need to determine the power output regulation capacity and range of the units. The power grid also often needs to dispatch the power generation load of the units in real time based on the thermal characteristics of the peak load thermal power units. In addition, coal-fired power companies also need to clarify the power output regulation characteristics of their peak load units as a basis for reporting the peak load of the units. Coal-fired power units need to provide the power output data of the units to the power grid dispatcher based on the power output regulation characteristics of their own peak load units for reference by the power grid dispatcher. Therefore, whether for the power grid dispatcher or for coal-fired power companies, effectively mastering the power output characteristics of their own power generation companies' peak load units affected by boiler boundary conditions is of great practical significance for maximizing their economic benefits.

[0003] However, there is currently no accurate calculation method for the quantitative impact of changes in the excess air coefficient of thermal power units on the main steam flow parameters and the unit's electrical output, and it is mainly determined by empirical methods. In addition, although the thermal calculation method of the variable operating condition of the boiler of the coal-fired power unit can determine the impact of changes in the excess air coefficient on the main steam flow parameters, it cannot determine the quantitative impact on the unit's electrical output. In addition, this method requires the structural parameters of the boiler and the steam turbine, and the calculation is not only labor-intensive, but also has poor speed and real-time performance. Moreover, this method is complex to calculate and is often not easy to be quickly mastered by the operating personnel of the power plant. Therefore, it is particularly important to seek a simple calculation method that can quickly analyze the quantitative impact of changes in the excess air coefficient on the main steam flow parameters and the unit's electrical output for the rapid prediction of the electrical output of thermal power units. Summary of the invention

[0004] In view of the above problems, the present invention proposes a real-time online prediction method for the effect of excess air coefficient change on the electrical output of thermal power units based on the principles of conservation of mass and energy and in combination with the differential method.

[0005] The technical solution of the present invention is as follows: a real-time online prediction method for the impact of thermal power unit power output, comprising:

[0006] Derivation of S1 main steam flow calculation equation;

[0007] Derivation of the variation of electrical output of S2 thermal power unit;

[0008] Solution for the electric power variation of S3 unit.

[0009] Furthermore, step S1 is specifically, from the energy balance equation of the boiler:

[0010] D gr (h gr -h fw )+D zr (h zr ″-h zr ′)=B j ×Q ar,net η b (1)

[0011] Where: D gr is the superheated steam flow rate, kg / s; h gr is the enthalpy of superheated steam, kJ / kg; h fw For boiler

[0012] ″′

[0013] Water enthalpy, kJ / kg; D zr is the reheat steam flow rate, kg / s; h zr is the outlet enthalpy of reheat steam, kJ / kg; h zr is the inlet enthalpy of reheat steam, kJ / kg; B j is the calculated fuel quantity of the boiler, kg / s; Q ar,net is the low calorific value of boiler coal, kJ / kg; η b is the boiler thermal efficiency, %;

[0014] The calculation equation of the main steam flow rate obtained by transforming equation (1) is:

[0015]

[0016] Assume that the heat absorption ratio of reheated steam and superheated steam remains unchanged under the same load, that is:

[0017]

[0018] Substituting equation (3) into equation (2) can be further transformed into:

[0019]

[0020] Under the same load, the calculated fuel quantity of the boiler can be expressed as:

[0021]

[0022] Where: q4 is the incomplete combustion heat loss of the boiler machinery, %.

[0023] Substituting equation (5) into equation (4), we can obtain:

[0024]

[0025] In equation (6), the change of excess air coefficient, that is, the change of air-to-coal ratio, will affect q4, η b and h gr , and ultimately causes the change of the main steam flow rate. Therefore, the change of the main steam flow rate caused by the change of the excess air coefficient can be expressed as:

[0026]

[0027] in,

[0028]

[0029] The change of incomplete combustion heat loss of boiler machinery with excess air coefficient can be expressed as:

[0030]

[0031] Among them, the mechanical incomplete combustion heat loss can be expressed as:

[0032]

[0033] Where: is the amount of unburned carbon in 1 kg of fuel in the furnace, m 3 / kg; 33727 is the calorific value per kilogram of pure carbon, kJ / kg;

[0034] Therefore, according to equation (12), we can get:

[0035]

[0036] In equation (11), Determined by experimental method;

[0037] The calculation equation for boiler thermal efficiency is:

[0038]

[0039] In the formula: q2 is the heat loss of boiler flue gas, %; q3 is the heat loss of boiler chemical incomplete combustion, %; q4 is the heat loss of boiler mechanical incomplete combustion, %; q5 is the heat loss of boiler heat dissipation, %; q6 is the physical heat loss of boiler ash, %;

[0040] The change in boiler thermal efficiency caused by boiler exhaust heat loss and boiler mechanical incomplete combustion heat loss can be expressed as:

[0041]

[0042] The heat loss of boiler chemical incomplete combustion can be expressed as:

[0043]

[0044] Where: v g is the total volume of dry flue gas, m 3 / kg; CO is the percentage of CO gas in dry flue gas, %.

[0045] Approximately, v g ≈αv 0 , v 0 is the theoretical air volume, and the following calculation equation can be obtained:

[0046]

[0047] Among them, the theoretical air volume can be expressed as:

[0048]

[0049] Where: κ is the correction coefficient representing the type of coal, and its approximate value is 2.63.

[0050] The exhaust heat loss of the boiler can be expressed as:

[0051]

[0052] Where: v y is the total volume of flue gas, m 3 / kg;c gp is the constant pressure specific heat of flue gas, kJ / kg·℃; θ py is the exhaust gas temperature, °C; t0 is the ambient temperature, °C;

[0053] The change of excess air coefficient causes the change of heat transfer characteristics in the furnace, and the change of boiler exhaust temperature is:

[0054]

[0055] Here we still approximately assume that v y ≈αv 0 , v 0 is the theoretical air volume, and the following calculation equation is obtained:

[0056]

[0057] The physical heat loss of ash can be expressed as:

[0058]

[0059] Combining equations (6)-(24), the calculation method for the effect of excess air coefficient change on boiler main steam flow is:

[0060]

[0061] By solving equation (25) based on the experimental data, we can obtain a real-time online prediction method for the effect of changes in the excess air coefficient on the electrical output of the thermal power unit.

[0062] Furthermore, step S2 is specifically that the energy equation of the steam turbine generator is:

[0063]

[0064] Where: P el is the power generated by the steam turbine, kW; γ is the heat recovery coefficient of the high-pressure cylinder, is the ideal enthalpy drop of the high-pressure cylinder of the steam turbine, kJ / kg; is the relative internal efficiency of the high-pressure cylinder of the steam turbine; δ is the heat recovery correction coefficient of the intermediate-pressure cylinder, is the relative internal efficiency of the intermediate pressure cylinder of the steam turbine, is the ideal enthalpy drop of the intermediate pressure cylinder of the steam turbine, kJ / kg; D dy is the steam inlet flow rate of the low-pressure cylinder, ψ is the heat recovery correction coefficient of the low-pressure cylinder, is the ideal enthalpy drop of the low-pressure cylinder of the steam turbine, kJ / kg; is the relative internal efficiency of the low-pressure cylinder of the steam turbine; η m is the mechanical efficiency of the steam turbine; η g is the electrical efficiency of the steam turbine;

[0065] Using the differential idea, we can get the change of turbine power as:

[0066]

[0067] In the formula: Calculation is performed using step S1; Take 1 / 40.

[0068] Furthermore, step S3 is specifically as follows:

[0069] S301 selects the changes of the reference parameters and the excess air coefficient, and uses equation (25) to calculate the change of the main steam flow, and then obtains the change of the unit electric power by equation (27), wherein the excess air coefficient is obtained by real-time calculation of the operating oxygen content, and the calculation equation is:

[0070]

[0071] Where: O2 is the oxygen content in dry flue gas, %;

[0072] S302 exhaust gas temperature, ambient temperature, superheated steam enthalpy, feed water enthalpy, main steam flow, reheated steam flow, flue gas CO content use the real-time operation data of DCS, among which the superheated steam enthalpy is calculated in real time by superheated steam pressure and temperature, and the feed water enthalpy is calculated in real time by feed water pressure and temperature. The fly ash specific heat is calculated by the real-time exhaust gas temperature, and the fitting formula of the fly ash specific heat changing with the flue gas temperature is:

[0073]

[0074] S303 mechanical incomplete combustion heat loss, boiler thermal efficiency, ideal enthalpy drop of turbine high pressure cylinder, ideal enthalpy drop of turbine intermediate pressure cylinder, ideal enthalpy drop of turbine low pressure cylinder, relative internal efficiency of turbine intermediate pressure cylinder, relative internal efficiency of turbine low pressure cylinder, relative internal efficiency of turbine high pressure cylinder can be approximated by test data. The received basic ash content, low calorific value of coal, theoretical air volume are parameters related to coal type. Over a period of time, coal type can be considered to have little change. Take test data, and the heat recovery correction coefficient of high pressure cylinder, heat recovery correction coefficient of intermediate pressure cylinder and heat recovery correction coefficient of low pressure cylinder adopt design data.

[0075] The beneficial effects of the present invention are:

[0076] The method of the present invention overcomes the defect that the change of the boiler excess air coefficient cannot accurately and quantitatively predict and calculate the main steam flow and electric output. The calculation method is simple, accurate and scientific, and can achieve the purpose of accurately calculating and diagnosing the change of the main steam flow and electric output of the coal-fired power unit caused by the change of the excess air coefficient in the furnace. It has important engineering significance for the real-time prediction of the electric power of the peak-shaving coal-fired power unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 This is a schematic diagram of the concept of the present invention.

[0078] Figure 2 This is a schematic diagram of the algorithm of the present invention.

[0079] Figure 3 This is a schematic diagram of real-time online prediction of the present invention. DETAILED DESCRIPTION

[0080] A real-time online prediction method for the effect of excess air coefficient change on the power output of a thermal power unit comprises the following steps:

[0081] (a) Derivation of the main steam flow calculation equation

[0082] When boiler blowdown is neglected, the energy balance equation of the boiler yields:

[0083] D gr (h gr -h fw)+D zr (h zr ″-h zr ′)=B j ×Q ar,net η b (1)

[0084] Where: D gr is the superheated steam flow rate, kg / s; h gr is the enthalpy of superheated steam, kJ / kg; h fw For boiler

[0085] ″′

[0086] Water enthalpy, kJ / kg; D zr is the reheat steam flow rate, kg / s; h zr is the outlet enthalpy of reheat steam, kJ / kg; h zr is the inlet enthalpy of reheat steam, kJ / kg; B j is the calculated fuel quantity of the boiler, kg / s; Q ar,net is the low calorific value of boiler coal, kJ / kg; η b is the boiler thermal efficiency, %.

[0087] The calculation equation of the main steam flow rate obtained by transforming equation (1) is:

[0088]

[0089] Assume that the heat absorption ratio of reheated steam and superheated steam remains unchanged under the same load, that is:

[0090]

[0091] Substituting equation (3) into equation (2) can be further transformed into:

[0092]

[0093] Under the same load, as long as the air-coal ratio, pulverizing system and combustion system remain unchanged, the carbon content of the generated fly ash and slag can be considered unchanged, that is, the mechanical incomplete combustion heat loss of the boiler remains unchanged. At this time, the calculated fuel amount of the boiler can be expressed as:

[0094]

[0095] Where: q4 is the incomplete combustion heat loss of the boiler machinery, %.

[0096] Substituting equation (5) into equation (4), we can obtain:

[0097]

[0098] In equation (6), the change of excess air coefficient, that is, the change of air-to-coal ratio, will affect q4, η b and h gr , and ultimately causes the change of main steam flow. Therefore, the change of main steam flow caused by the change of excess air coefficient can be expressed as:

[0099]

[0100] in,

[0101]

[0102] The change of incomplete combustion heat loss of boiler machinery with excess air coefficient can be expressed as:

[0103]

[0104] Among them, the mechanical incomplete combustion heat loss can be expressed as:

[0105]

[0106] Where: is the amount of unburned carbon in 1 kg of fuel in the furnace, m 3 / kg; 33727 is the calorific value per kilogram of pure carbon, kJ / kg.

[0107] Therefore, according to equation (12), we can get:

[0108]

[0109] In equation (11), Determined by experimental method.

[0110] The calculation equation for boiler thermal efficiency is:

[0111]

[0112] Wherein: q2 is the heat loss of boiler flue gas, %; q3 is the heat loss of boiler chemical incomplete combustion, %; q4 is the heat loss of boiler mechanical incomplete combustion, %; q5 is the heat loss of boiler heat dissipation, %; q6 is the physical heat loss of boiler ash, %. For large-capacity boilers, it can be considered that the change of boiler heat dissipation loss q5 is small, so the influence of the change of excess air coefficient on the main steam flow rate is not considered here.

[0113] The change in boiler thermal efficiency caused by boiler exhaust heat loss and boiler mechanical incomplete combustion heat loss can be expressed as:

[0114]

[0115] The heat loss of boiler chemical incomplete combustion can be expressed as:

[0116]

[0117] Where: v g is the total volume of dry flue gas, m 3 / kg; CO is the percentage of CO gas in dry flue gas, %. It is approximately assumed that v g ≈αv 0 , v 0 is the theoretical air volume, and the following calculation equation can be obtained:

[0118]

[0119] Among them, the theoretical air volume can be expressed as:

[0120]

[0121] Where: κ is the correction coefficient representing the type of coal, and its approximate value is 2.63.

[0122] The exhaust heat loss of the boiler can be expressed as:

[0123]

[0124] Where: v y is the total volume of flue gas, m 3 / kg;c gp is the constant pressure specific heat of flue gas, kJ / kg·℃; θ py is the exhaust temperature, ℃; t0 is the ambient temperature, ℃.

[0125] The change of excess air coefficient causes the change of heat transfer characteristics in the furnace, and the change of boiler exhaust temperature is:

[0126]

[0127] Here we still approximately assume that v y ≈αv 0 , v 0 is the theoretical air volume, and the following calculation equation can be obtained:

[0128]

[0129] In equation (22), the most important thing is to solve It can be obtained through test parameters.

[0130] Since the proportion of slag is small and can be ignored, the physical heat loss of ash slag can be expressed as:

[0131]

[0132] Combining equations (6)-(24), the calculation method for the effect of excess air coefficient change on boiler main steam flow is:

[0133]

[0134] By solving equation (25), we can obtain a real-time online prediction method for the effect of excess air coefficient change on the power output of thermal power units.

[0135] (b) Derivation of the change in the electrical output of thermal power units

[0136] According to the law of conservation of energy, the energy equation of the steam turbine generator is:

[0137]

[0138] Where: P el is the power generated by the steam turbine, kW; γ is the heat recovery coefficient of the high-pressure cylinder, is the ideal enthalpy drop of the high-pressure cylinder of the steam turbine, kJ / kg; is the relative internal efficiency of the high-pressure cylinder of the steam turbine; δ is the heat recovery correction coefficient of the intermediate-pressure cylinder, is the relative internal efficiency of the intermediate pressure cylinder of the steam turbine, is the ideal enthalpy drop of the intermediate pressure cylinder of the steam turbine, kJ / kg; D dy is the steam inlet flow rate of the low-pressure cylinder, ψ is the heat recovery correction coefficient of the low-pressure cylinder, is the ideal enthalpy drop of the low-pressure cylinder of the steam turbine, kJ / kg; is the relative internal efficiency of the low-pressure cylinder of the steam turbine; η m is the mechanical efficiency of the steam turbine; η g is the electrical efficiency of the steam turbine.

[0139] When the excess air coefficient of coal changes, it is believed that the main steam flow rate is greatly affected. After this flow is diverted to each reheat extraction port of the steam turbine, the change and its influence on the ideal enthalpy drop and reheat coefficient of the steam turbine can be ignored, but the relative internal efficiency of the low-pressure cylinder and the high-pressure cylinder is greatly affected. If the change of the relative internal efficiency of the intermediate-pressure cylinder is ignored, and the influence of mechanical efficiency and electrical efficiency is not considered, the change of the steam turbine power can be obtained by using the differential idea:

[0140]

[0141] In the formula: It can be approximately considered that The calculation can be done using step (a); Approximately 1 / 40 is acceptable.

[0142] (c) Solution to the change in unit power

[0143] 1) Select the change of the baseline parameters and the excess air coefficient, use equation (25) to calculate the change of the main steam flow, and then use equation (27) to obtain the change of the unit power. Table 1 shows the operating data of the required unit baseline conditions. Among them, the excess air coefficient is obtained by real-time calculation of the operating oxygen content, and the calculation equation is:

[0144]

[0145] Where: O2 is the oxygen content in dry flue gas, %.

[0146] 2) The exhaust gas temperature, ambient temperature, superheated steam enthalpy, feed water enthalpy, main steam flow, reheated steam flow, and flue gas CO content use the real-time operation data of DCS. The superheated steam enthalpy is calculated in real time based on the superheated steam pressure and temperature, and the feed water enthalpy is calculated in real time based on the feed water pressure and temperature. The fly ash specific heat is calculated using the real-time exhaust gas temperature.

[0147] The fitting formula of fly ash specific heat changing with flue gas temperature is:

[0148]

[0149] 3) Mechanical incomplete combustion heat loss, boiler thermal efficiency, ideal enthalpy drop of turbine high-pressure cylinder, ideal enthalpy drop of turbine intermediate-pressure cylinder, ideal enthalpy drop of turbine low-pressure cylinder, relative internal efficiency of turbine intermediate-pressure cylinder, relative internal efficiency of turbine low-pressure cylinder, and relative internal efficiency of turbine high-pressure cylinder can be approximated by test data. The received basic ash content, lower calorific value of coal, and theoretical air volume are parameters related to the type of coal. Over a period of time, the type of coal can be considered to have little change, and test data can be taken. The heat recovery correction coefficient of the high-pressure cylinder, the heat recovery correction coefficient of the intermediate-pressure cylinder, and the heat recovery correction coefficient of the low-pressure cylinder can use design data.

[0150] Table 1 Benchmark operating data

[0151] Operating oxygen Theoretical air volume Excess air coefficient change Exhaust temperature Mechanical incomplete combustion heat loss Ambient temperature Main steam pressure Main steam temperature Low calorific value of coal Feed water temperature Water supply pressure Main steam flow Boiler thermal efficiency Reheat steam flow Dry flue gas CO content Low pressure cylinder steam flow Received base ash Ideal enthalpy drop of steam turbine high pressure cylinder Specific heat of fly ash Ideal enthalpy drop of steam turbine intermediate pressure cylinder Flue gas specific heat Heat recovery correction factor of medium pressure cylinder Ideal enthalpy drop of low pressure cylinder of steam turbine Relative internal efficiency of the high pressure cylinder of the steam turbine High pressure cylinder heat recovery correction factor Relative internal efficiency of steam turbine intermediate pressure cylinder Heat recovery correction factor for low pressure cylinder Relative internal efficiency of the low pressure cylinder of the steam turbine

[0152] The present invention proposes a real-time online prediction method for the effect of excess air coefficient change on the power output of a thermal power unit, based on the following concepts:

[0153] On the one hand, the change of excess air coefficient will directly cause the change of steam flow rate. On the other hand, the change of excess air coefficient will cause the change of combustion conditions in the furnace, which will cause the change of heat loss of incomplete combustion of solids in the boiler, heat loss of incomplete combustion of gases and exhaust temperature of the boiler. These changes will also cause the change of boiler thermal efficiency, thus leading to the change of main steam flow rate. In addition, the change of excess air coefficient will also cause the change of main steam pressure and temperature, which will cause the change of main steam flow rate of the boiler when the main steam valve opening remains unchanged.

[0154] To simplify the calculation, the influence of the change of excess air coefficient on the operation state of the coal mill is not considered, so the influence of the temperature of the air-powder mixture at the coal mill outlet on the main steam flow is not considered. In addition, it can be assumed that the heat absorption ratio of reheated steam and superheated steam under the same load remains unchanged, so that the calculation of the main steam flow and the reheated steam flow can be separated.

[0155] The present invention is based on the above conception. According to the energy conservation equation, the functional relationship of the main steam flow rate change is obtained after the boiler excess air coefficient changes. Combined with the differential theory, the principle followed by the technical solution of the present invention is further proposed, namely:

[0156] 1. After the boiler excess air coefficient changes, it will cause the boiler incomplete combustion heat loss, gas incomplete combustion heat loss and boiler exhaust temperature changes, which will cause the boiler thermal efficiency to change;

[0157] 2. After the boiler excess air coefficient changes, it will cause the main steam pressure and temperature to change. If the main steam valve opening of the steam turbine remains unchanged, it will affect the change in the main steam flow rate.

[0158] 3. After the boiler excess air coefficient changes, the main steam flow changes slightly due to the use of the differential theory, so the change in boiler heat loss is ignored;

[0159] 4. The rate of change of boiler excess air coefficient relative to the main steam enthalpy value can be calculated by using the idea of ​​difference instead of differentiation, which can simplify the calculation steps.

[0160] The computer software program of the present invention is compiled based on automatic control and computer processing technology, which is a technology familiar to those skilled in the art.

[0161] Calculation example: Taking the data collected from a 600MW unit under 100BMCR operating conditions as the basic data, see Table 2, a real-time online prediction method for the impact of changes in excess air coefficient on the electrical output of a thermal power unit is now described as an example.

[0162] Table 2 Benchmark operating conditions data

[0163] Operating oxygen 3.5％ <![CDATA[Theoretical air volume 5.7m 3 / kg]]> Excess air coefficient change 0.1 Exhaust temperature 126℃ Mechanical incomplete combustion heat loss 0.8％ Ambient temperature 25℃ Main steam pressure 16.03Mpa Main steam temperature 542℃ Low calorific value of coal 21805kJ / kg Feed water temperature 286.1℃ Water supply pressure 19.37Mpa Main steam flow rate 531.39kg / s Boiler thermal efficiency 0.925 Reheat steam flow rate 438.89kg / s Dry flue gas CO content 0 Low pressure cylinder steam flow 339.82kg / s Received base ash 15％ The ideal enthalpy drop of the high pressure cylinder of the steam turbine is 425 kJ / kg Specific heat of fly ash 0.83kJ / (kg / k) The ideal enthalpy drop of the intermediate pressure cylinder of the steam turbine is 879 kJ / kg Flue gas specific heat 1.45kJ / (kg / k) The heat recovery correction coefficient of the medium pressure cylinder is 0.99 Ideal enthalpy drop of low pressure cylinder of steam turbine 357.1kJ / kg The relative internal efficiency of the high-pressure cylinder of the steam turbine is 87.69% High pressure cylinder heat recovery correction factor 0.98 The relative internal efficiency of the intermediate pressure cylinder of the steam turbine is 94.89% Heat recovery correction factor for low pressure cylinder 0.97 The relative internal efficiency of the low-pressure cylinder of the steam turbine is 90.31%

[0164] (a) Calculation of main steam flow

[0165] According to the main steam pressure of 16.03Mpa and the main steam temperature of 542℃, the main steam enthalpy under the corresponding working conditions can be calculated to be 3424.31kJ / kg according to the water vapor thermodynamic properties table.

[0166] According to the feed water pressure of 19.37Mpa and the feed water temperature of 286.1℃, the feed water enthalpy under the corresponding working conditions can be calculated according to the water vapor thermodynamic properties table to be 1238.12kJ / kg.

[0167] The effect of excess air coefficient change on boiler main steam flow can be obtained according to formula (25):

[0168]

[0169] In the formula, the test data

[0170] When the operating oxygen content is 3.5%, the corresponding excess air coefficient is:

[0171] When the flue gas temperature is 126℃, the corresponding fly ash specific heat is:

[0172]

[0173] Substituting the baseline operating data into the above formula, we get:

[0174]

[0175] Available

[0176] (b) Calculation of unit power generation

[0177]

[0178] In the formula: It can be approximately considered that Approximately 1 / 40.

[0179] Substituting the baseline operating data into the above formula, we get:

[0180] ΔP el =531.39×425×0.98×0.8769×0.98×0.98×0.5932+0.98×0.98×531.39×425×0.98×0.8769×(1 / 40)+438.89×0.99×879×0.9489×0.5932+0.97×339.82×357.1×0.9031×0.98×0.98×0.5932+0.97×339.82×0.9031×357.1×0.98×0.98×(1 / 40)

[0181] We can get ΔP el =439910.09kJ / s≈4.39MW.

[0182] It can be obtained that when the excess air coefficient changes by 0.1, the change in the unit's power generation capacity under the 100BMCR operating condition is 4.394.39MW.

[0183] The above is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any modification, equivalent replacement and improvement made by any person skilled in the art within the technical scope disclosed by the present invention and within the spirit and principle of the present invention shall be covered within the protection scope of the present invention. At the same time, the contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0184] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

Claims

1. A real-time online prediction method for the impact of thermal power unit power output, characterized in that: include: Derivation of S1 main steam flow calculation equation; Derivation of the variation of electrical output of S2 thermal power unit; Solution for the electric power variation of S3 unit.

2. A real-time online prediction method for the impact of thermal power generation unit power output according to claim 1, characterized in that: Step S1 is specifically, from the energy balance equation of the boiler: D gr (h gr -h fw )+D zr (h zr ″-h zr ′)=B j ×Q ar,net η b (1) Where: D gr is the superheated steam flow rate, kg / s; h gr is the enthalpy of superheated steam, kJ / kg; h fw is the boiler feed water enthalpy, kJ / kg; D zr is the reheat steam flow rate, kg / s; h zr is the outlet enthalpy of reheat steam, kJ / kg; h zr is the inlet enthalpy of reheat steam, kJ / kg; B j is the calculated fuel quantity of the boiler, kg / s; Q ar,net The low calorific value of boiler coal, kJ / kg; η b is the boiler thermal efficiency, %; The calculation equation of the main steam flow rate obtained by transforming equation (1) is: Assume that the heat absorption ratio of reheated steam and superheated steam remains unchanged under the same load, that is: Substituting equation (3) into equation (2) can be further transformed into: Under the same load, the calculated fuel quantity of the boiler can be expressed as: Where: q4 is the incomplete combustion heat loss of the boiler machinery, %. Substituting equation (5) into equation (4), we can obtain: In equation (6), the change of excess air coefficient, that is, the change of air-to-coal ratio, will affect q4, η b and h gr , and ultimately causes the change of the main steam flow rate. Therefore, the change of the main steam flow rate caused by the change of the excess air coefficient can be expressed as: in, The change of incomplete combustion heat loss of boiler machinery with excess air coefficient can be expressed as: Among them, the mechanical incomplete combustion heat loss can be expressed as: Where: is the amount of unburned carbon in 1 kg of fuel in the furnace, m 3 / kg; 33727 is the calorific value per kilogram of pure carbon, kJ / kg; Therefore, according to equation (12), we can get: In equation (11), Determined by experimental method; The calculation equation for boiler thermal efficiency is: In the formula: q2 is the heat loss of boiler flue gas, %; q3 is the heat loss of boiler chemical incomplete combustion, %; q4 is the heat loss of boiler mechanical incomplete combustion, %; q5 is the heat loss of boiler heat dissipation, %; q6 is the physical heat loss of boiler ash, %; The change in boiler thermal efficiency caused by boiler exhaust heat loss and boiler mechanical incomplete combustion heat loss can be expressed as: The heat loss of boiler chemical incomplete combustion can be expressed as: Where: v g is the total volume of dry flue gas, m 3 / kg; CO is the percentage of CO gas in dry flue gas, %. Approximately, v g ≈αv 0 , v 0 is the theoretical air volume, and the following calculation equation can be obtained: Among them, the theoretical air volume can be expressed as: Where: κ is the correction coefficient representing the type of coal, and its approximate value is 2.

63. The exhaust heat loss of the boiler can be expressed as: Where: v y is the total volume of flue gas, m 3 / kg;c gp is the constant pressure specific heat of flue gas, kJ / kg·℃; θ py is the exhaust gas temperature, °C; t0 is the ambient temperature, °C; The change of excess air coefficient causes the change of heat transfer characteristics in the furnace, and the change of boiler exhaust temperature is: Here we still approximately assume that v y ≈αv 0 , v 0 is the theoretical air volume, and the following calculation equation is obtained: The physical heat loss of ash can be expressed as: Combining equations (6)-(24), the calculation method for the effect of excess air coefficient change on boiler main steam flow is: By solving equation (25) based on the experimental data, we can obtain a real-time online prediction method for the effect of changes in the excess air coefficient on the electrical output of the thermal power unit.

3. A real-time online prediction method for the impact of thermal power generation unit power output according to claim 2, characterized in that: Specifically, step S2 is that the energy equation of the steam turbine generator is: Where: P el is the power generated by the steam turbine, kW; γ is the heat recovery coefficient of the high-pressure cylinder, is the ideal enthalpy drop of the high-pressure cylinder of the steam turbine, kJ / kg; is the relative internal efficiency of the high-pressure cylinder of the steam turbine; δ is the heat recovery correction coefficient of the medium pressure cylinder, is the relative internal efficiency of the intermediate pressure cylinder of the steam turbine, is the ideal enthalpy drop of the intermediate pressure cylinder of the steam turbine, kJ / kg; D dy is the steam inlet flow rate of the low-pressure cylinder, ψ is the heat recovery correction coefficient of the low-pressure cylinder, is the ideal enthalpy drop of the low-pressure cylinder of the steam turbine, kJ / kg; is the relative internal efficiency of the low-pressure cylinder of the steam turbine; η m is the mechanical efficiency of the steam turbine; η g is the electrical efficiency of the steam turbine; Using the differential idea, we can get the change of turbine power as: In the formula: Calculation is performed using step S1; Take 1 / 40.

4. A real-time online prediction method for the impact of thermal power unit power output according to claim 3, characterized in that: Step S3 is specifically as follows: S301 selects the changes of the reference parameters and the excess air coefficient, and uses equation (25) to calculate the change of the main steam flow, and then obtains the change of the unit electric power by equation (27), wherein the excess air coefficient is obtained by real-time calculation of the operating oxygen content, and the calculation equation is: Where: O2 is the oxygen content in dry flue gas, %; S302 exhaust gas temperature, ambient temperature, superheated steam enthalpy, feed water enthalpy, main steam flow, reheated steam flow, flue gas CO content use the real-time operation data of DCS, among which the superheated steam enthalpy is calculated in real time by superheated steam pressure and temperature, and the feed water enthalpy is calculated in real time by feed water pressure and temperature. The fly ash specific heat is calculated by the real-time exhaust gas temperature, and the fitting formula of the fly ash specific heat changing with the flue gas temperature is: S303 mechanical incomplete combustion heat loss, boiler thermal efficiency, ideal enthalpy drop of turbine high pressure cylinder, ideal enthalpy drop of turbine intermediate pressure cylinder, ideal enthalpy drop of turbine low pressure cylinder, relative internal efficiency of turbine intermediate pressure cylinder, relative internal efficiency of turbine low pressure cylinder, relative internal efficiency of turbine high pressure cylinder can be approximated by test data. The received basic ash content, low calorific value of coal, theoretical air volume are parameters related to coal type. Over a period of time, coal type can be considered to have little change. Take test data, and the heat recovery correction coefficient of high pressure cylinder, heat recovery correction coefficient of intermediate pressure cylinder and heat recovery correction coefficient of low pressure cylinder adopt design data.

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