Simplified method for peak-shaving variable-working-condition performance analysis of coal power unit

Abstract

The invention discloses a simplified method for peak-shaving variable-working-condition performance analysis of a coal power unit, and mainly relates to the field of performance state monitoring, analysis and diagnosis of thermal equipment. Comprising the steps of S1, determining boiler heat efficiency; s2, calculating the variable quantity of the main steam quantity of the boiler; s3, determining unit power generation standard coal consumption rate change parameters; the method is based on a boiler counter-balance method and is combined with concepts of an empirical equation and a differential idea, a relational expression of boiler thermal efficiency is further obtained, a relational expression of change of boiler main steam flow and change of power generation standard coal consumption rate is deduced through the relational expression of the boiler thermal efficiency, and a simplified method of variable working condition performance analysis is achieved. The problems that structural parameters of a boiler and a steam turbine need to be known in an existing variable working condition analysis method of the boiler and the steam turbine, the calculation workload is large, the calculation time is long, the calculation method is complex, and it is inconvenient for operators to rapidly master the operation characteristics of a coal power unit are solved.

Description

Technical Field

[0001] The present invention relates to the field of monitoring, analysis and diagnosis of the performance state of thermal equipment, and specifically to a simplified method for analyzing the performance of a coal-fired power unit under peak load regulation and variable operating conditions. Background Art

[0002] At present, the operation of coal-fired power units under peak load regulation and variable operating conditions has become the norm. During the variable operating conditions of the units, the coal type, load and excess air coefficient, as the boundary operating conditions of coal-fired power units, frequently change, seriously affecting the safe and economic operation of the units. Therefore, carrying out research on the performance analysis model of units under variable operating conditions has important practical significance for ensuring the safe and economic operation of peak load regulation units.

[0003] However, the existing performance analysis methods for coal-fired power units often rely on analysis software for performance analysis. The analysis software requires more boundary conditions to be input, and the calculation is relatively complex. In addition, the internal program of the analysis software is often a black box and is not publicly available, which is not conducive to the operating personnel to change the initial conditions and boundary conditions of the program according to the operating conditions of the unit. Moreover, the calculation process of the existing analysis software is complicated and the calculation time is long, which is not convenient for the operating personnel to quickly analyze the performance changes of the peak load regulation unit before and after variable operating conditions. In addition to using analysis software for the performance analysis of coal-fired power units, the variable operating condition performance analysis of coal-fired power units can also adopt the variable operating condition analysis methods of boilers and steam turbines. However, the variable operating condition analysis methods of boilers and steam turbines require knowledge of the structural parameters of boilers and steam turbines, which not only involve a large amount of calculation work, long calculation time, but also extremely complex calculation methods, and are not convenient for the operating personnel to quickly master the operating characteristics of coal-fired power units.

[0004] Therefore, in order to effectively improve the management level of the performance of coal-fired power units under peak load regulation and variable operating conditions and clarify the influence of changes in boundary conditions on the operating characteristics of the units. It has a great promoting effect on the power plant to strengthen the control of the safe and economic operation of the units. Therefore, it is necessary to propose a simplified method for analyzing the performance of coal-fired power units under peak load regulation and variable operating conditions, which is convenient for operating personnel to quickly understand and master the performance analysis of coal-fired power units under variable operating conditions. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems existing in the prior art. Aiming at the technical problem that it is not convenient for operating personnel to analyze the performance of coal-fired power units in power plants under peak load regulation and variable operating conditions at present, the present invention provides a simplified method for analyzing the performance of coal-fired power units under peak load regulation and variable operating conditions based on the boiler inverse balance method and combined with the concepts of empirical equations and differential thinking, and solves the problems that the existing variable operating condition analysis methods of boilers and steam turbines require knowledge of the structural parameters of boilers and steam turbines, involve a large amount of calculation work, long calculation time, and complex calculation methods, and are not convenient for operating personnel to quickly master the operating characteristics of coal-fired power units.

[0006] To achieve the above object, the present invention is realized through the following technical solutions:

[0007] A simplified method for analyzing the peak shaving and off-design performance of a coal-fired power unit, including the steps:

[0008] S1. Determine the boiler thermal efficiency. The expression for the boiler thermal efficiency is:

[0009]

[0010] where η Boiler is the boiler thermal efficiency; Q Input is the heat input to the boiler; Q Flue.G is the heat loss due to boiler flue gas; Q Unburned.G is the heat loss due to incomplete combustion of gas; Q Unburned.S is the heat loss due to incomplete combustion of solid; Q Heat is the heat loss due to boiler heat dissipation; Q Ash is the heat loss due to the physical heat of ash and slag;

[0011] S2. Calculate the change in the main steam flow rate of the boiler. The change in the main steam flow rate of the boiler is expressed as:

[0012]

[0013] where B Fuel is the boiler fuel quantity; D Main is the main steam flow rate of the boiler; h Main is the enthalpy of the main steam of the boiler; h fw is the enthalpy of the feed water of the boiler; D zr is the reheated steam flow rate; h″ zr is the enthalpy of the reheated steam outlet of the boiler; h′ zr is the enthalpy of the reheated steam inlet of the boiler;

[0014] S3. Determine the change parameters of the standard coal consumption rate of the unit power generation. The change parameters of the standard coal consumption rate of the unit power generation include the change in the power generation of the unit, the change in the heat consumption rate of the steam turbine generator set, and the change in the standard coal consumption rate of the unit power generation;

[0015] The change in the power generation of the unit is expressed as:

[0016]

[0017] where P Power is the power generation of the coal-fired power unit; η oi is the relative internal efficiency of the steam turbine;

[0018] The change in the heat consumption rate of the steam turbine generator set is:

[0019]

[0020] The change in the standard coal consumption rate for unit power generation is:

[0021]

[0022] Among them, is the standard coal consumption rate for unit power generation.

[0023] Preferably, in step S1, the technical process of the boiler thermal efficiency includes the steps:

[0024] S11. Construct an inverse balance calculation model for the boiler thermal efficiency:

[0025] Q Input = Q Effective + Q Flue.G + Q Unburned.G + Q Unburned.S + Q Heat + Q Ash ;

[0026] Q Input ≈ Q ar,net ;

[0027] Among them, Q Input is the heat input to the boiler; Q Effective is the effectively utilized heat of the boiler; Q Flue.G is the heat loss due to boiler flue gas; Q Unburned.G is the heat loss due to incomplete combustion of gas; Q Unburned.S is the heat loss due to incomplete combustion of solids; Q Heat is the heat loss due to boiler heat dissipation; Q Ash is the physical heat loss of ash and slag; Q ar,net is the lower calorific value of the fuel as received;

[0028] S12. Calculate the heat loss of the boiler flue gas through the flue gas temperature and the ambient temperature. Q Flue.G is expressed as:

[0029]

[0030] Among them, V Flue.G is the dry flue gas generated by burning 1 kg of coal; is the flue gas temperature of the boiler; t Ambient.T is the ambient temperature; c Flue.G is the average constant pressure specific heat capacity of dry flue gas at ; M Received is the moisture content of the coal as received; α Air outlet is the excess air coefficient at the outlet of the air preheater; k Flue.G is the coal quality coefficient in the flue gas volume; k Air is the coal quality coefficient in the air volume;

[0031] S13. Calculate the flue gas temperature of the boiler using the following empirical equation

[0032]

[0033] where α Rating is the excess air coefficient at rated load; D Rating is the rated load of the boiler; D Actuality is the actual load of the boiler; is the flue gas temperature at rated load; t Design is the design value of the ambient temperature;

[0034] S14. After determining the excess air coefficient of the boiler, the following calculation equation can be used to determine the operating oxygen content at the outlet of the air preheater of the unit, that is:

[0035]

[0036] where O Oxygen is the volume percentage content of oxygen;

[0037] S15. After neglecting the trace combustible gases in the flue gas, express Q Unburned.G as:

[0038]

[0039] where CO is the percentage of the gas volume in the dry flue gas volume;

[0040] The concentration of CO is calculated using the following empirical equation:

[0041]

[0042] S16. Calculate the heat loss due to unburned solids. The heat loss due to incomplete combustion of solids is related to the unburned carbon contained in the ash, that is, the heat loss due to unburned solids Q Unburned.S can be expressed by the following empirical formula:

[0043]

[0044] where A1, y0, t1, x0 are empirical coefficients;

[0045] S17. Calculate the heat loss due to heat dissipation. The heat loss due to heat dissipation Q Heat is expressed under non-rated evaporation as:

[0046]

[0047] S18. Calculate the heat loss due to the physical heat of ash and slag. The heat loss due to the physical heat of ash and slag Q Ash is expressed as:

[0048]

[0049] Among them, A Received is the percentage of ash in the coal quality; c Fly ash is the average constant-pressure specific heat capacity of fly ash from t Ambient.T to ; c Slag is the average constant-pressure specific heat capacity of slag from t Ambient.T to θ Slag ; a Fly ash , a Slag are the shares of the ash content in fly ash and slag in the total ash content of the fuel; θ Slag is the slag temperature.

[0050] Preferably, in step S2, let

[0051] The calculation equation for the main steam flow rate can be obtained as follows:

[0052] Under the condition that the fuel quantity, coal quality, and steam parameters are approximately unchanged, the calculation equation for the main steam flow rate can be obtained by using the differential idea:

[0053]

[0054] Among them, D Main is the main steam flow rate.

[0055] Preferably, in step S3, when determining the change in the generating power of the unit, first establish the conversion equation of the thermal functional energy of the coal-fired power unit:

[0056] P Power = BQ ar.net η boiler η Pipeline η Circle η oi η m η g

[0057] Among them, P Power is the generating power of the coal-fired power unit, kW; η Pipeline is the pipeline efficiency of the boiler; η Circle is the ideal cycle thermal efficiency of the steam turbine; η oi is the relative internal efficiency of the steam turbine; η m is the mechanical efficiency of the steam turbine generator set; η g is the electrical efficiency of the generator;

[0058] Since the generating power of the unit depends only on the boiler efficiency η Boiler and the relative internal efficiency of the steam turbine η oiIt is related. By adopting the differential idea, the change amount of the generating power of the unit can be obtained.

[0059] Preferably, in step S3, when determining the heat consumption rate of the steam turbine generator unit, first establish the heat consumption rate equation of the steam turbine generator unit:

[0060]

[0061] Among them, q Heat is the heat consumption rate of the steam turbine generator unit;

[0062] Since the steam parameters of the steam turbine do not change, the heat consumption rate of the steam turbine generator unit is only affected by the boiler efficiency. Therefore, by adopting the differential idea, the change amount of the heat consumption rate of the steam turbine generator unit can be obtained:

[0063]

[0064] Preferably, in step S3, when determining the change amount of the standard coal consumption rate of unit power generation, first establish the standard coal consumption rate equation of unit power generation:

[0065]

[0066] Among them, is the standard coal consumption rate of unit power generation; According to the standard coal consumption rate equation of unit power generation, the change amount of the standard coal consumption rate of unit power generation can be obtained.

[0067] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0068] A simplified method for analyzing the peak shaving and off-design performance of a coal-fired power generation unit of the present invention overcomes the defect that the performance of a peak shaving unit cannot be accurately calculated and the performance analysis and diagnosis cannot be carried out under large off-design conditions. The calculation method is simple, accurate and scientific, and can accurately calculate and diagnose the quantitative impact of changes in boiler boundary conditions on the performance of coal-fired power generation units. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 is a schematic diagram of peak shaving and off-design performance analysis of a coal-fired power generation unit;

[0070] Figure 2 is a schematic diagram of the algorithm principle of peak shaving and off-design performance analysis of a coal-fired power generation unit;

[0071] Figure 3 is a schematic diagram of the calculation process of peak shaving and off-design performance analysis of a coal-fired power generation unit. DETAILED DESCRIPTION OF THE INVENTION

[0072] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by this application.

[0073] Embodiment: As shown in the appendix Figures 1-3 , the present invention relates to a simplified method for analyzing the peak shaving and off-design performance of a coal-fired power unit. The present invention is proposed based on the following concept:

[0074] 1. The heat efficiency of the boiler is determined by the boiler indirect method. By means of the unit energy balance equation and the heat-work conversion principle, the calculation equations for the unit power generation, the heat consumption rate of the steam turbine, and the standard coal consumption rate of the unit power generation can be obtained.

[0075] 2. When the boiler fuel quantity and coal quality remain unchanged, the change in the boiler heat efficiency mainly affects the main steam flow of the boiler. When the main steam flow of the boiler changes, the relative internal efficiency of the steam turbine changes. On the basis of ignoring the boiler pipeline efficiency, mechanical efficiency, ideal cycle heat efficiency, and generator electrical efficiency, the unit power generation, the heat consumption rate of the steam turbine, and the standard coal consumption rate of the unit power generation can be further calculated.

[0076] Based on the above concept, according to the boiler energy balance equation and the differential deviation theory, the present invention can further propose the principle followed by the technical solution of the present invention, that is:

[0077] 1. The boiler flue gas temperature is approximately regarded as a function of the boiler load and the boiler excess air coefficient. The empirical equation is used to determine the flue gas temperature of the boiler after the change of the boiler boundary conditions. The operating oxygen content can be jointly determined by the heat loss due to incomplete combustion of solids and the excess air coefficient.

[0078] 2. The boiler flue gas volume can be expressed as a function of the fuel calorific value, moisture, coal type correction coefficient, and excess air coefficient. At the same time, it is considered that the CO content in the flue gas is only related to the boiler load and the excess air coefficient. After obtaining the flue gas volume and the CO content in the flue gas by the empirical equation, the heat loss due to incomplete combustion of gas can be calculated.

[0079] 3. In the construction of the simplified model, it can be considered that the heat loss due to incomplete combustion of solids is related to the fuel ash content and the operating oxygen content. The heat loss due to incomplete combustion of solids at different loads can be obtained through the empirical fitting equation.

[0080] 4. The physical heat loss of ash slag is determined by the ash content and the unburned carbon content. The boiler heat dissipation loss is only related to the boiler load. Thus, the physical heat loss of ash slag and the boiler heat dissipation loss can be calculated.

[0081] 5. When the boiler fuel quantity and coal quality remain unchanged, the change in the boiler thermal efficiency mainly affects the main steam flow of the boiler. The change in the main steam flow of the boiler will in turn cause a change in the relative internal efficiency of the steam turbine. On the basis of neglecting the boiler pipeline efficiency, mechanical efficiency, ideal cycle thermal efficiency, and generator electrical efficiency, the generating power of the unit, the heat consumption rate of the steam turbine, and the standard coal consumption rate of the unit can be further calculated and obtained.

[0082] The specific implementation steps of the present invention are as follows:

[0083] (a) Determination link of boiler thermal efficiency change

[0084] Assuming that the coal quality composition remains unchanged, an inverse balance calculation model of the boiler thermal efficiency can be constructed. According to the principle of the energy balance equation in the boiler, we have:

[0085] Q Input = Q Effective + Q Flue.G + Q Unburned.G + Q Unburned.S + Q Heat + Q Ash (1)

[0086] In the formula: Q Input is the heat input to the boiler, kJ / kg; Q Effective is the effectively utilized heat of the boiler, kJ / kg; Q Flue.G is the heat loss due to boiler flue gas, kJ / kg; Q Unburned.G is the heat loss due to incomplete combustion of gas, kJ / kg; Q Unburned.S is the heat loss due to incomplete combustion of solid, kJ / kg; Q Heat is the heat loss due to boiler heat dissipation, kJ / kg; Q Ash is the heat loss due to physical heat of ash and slag, kJ / kg.

[0087] If the heat brought into the boiler by air and fuel heating steam is not taken into account, the heat input to the boiler can only consider the heat brought into the boiler by the low calorific value of coal, that is:

[0088] Q Input ≈ Q ar,net (2)

[0089] In the formula: Q ar,net is the received-base low calorific value of the fuel, kJ / kg.

[0090] Among them, the heat loss due to boiler flue gas is the largest heat loss item of the boiler, which can be calculated through the flue gas temperature and the ambient temperature. The heat loss due to boiler flue gas Q Flue.G can be expressed as:

[0091]

[0092] Where: V Flue.G is the dry flue gas generated by the combustion of 1 kg of coal, m 3 / kg; is the flue gas temperature of the boiler, °C; t Ambient.T is the ambient temperature, °C; c Flue.G The average specific heat capacity at constant pressure of dry flue gas at is kJ / (m 3 ·°C); M Received is the moisture content of the coal as received, %; α Air outlet is the excess air coefficient at the outlet of the air preheater; k Flue.G is the coal quality coefficient in the flue gas volume. For lean coal and anthracite, k Flue.G = 0.0162; for bituminous coal and lignite, k Flue.G = -0.006; k Air is the coal quality coefficient in the air volume. For lean coal and anthracite, k Air = 0.083; for bituminous coal and lignite, k Air = 0.23.

[0093] For the convenience of simplified calculation, when the coal type is certain, it can be considered that the flue gas temperature of the boiler is only related to the boiler load and the excess air coefficient of the boiler. Therefore, the flue gas temperature can be approximately calculated using the following empirical equation, that is:

[0094]

[0095] Where: α Rating is the excess air coefficient at rated load, which can be determined by interpolation method. The value of α Air outlet is shown in Table 1; D Rating , D Actuality are the rated load and actual load of the boiler, t / h; is the flue gas temperature at rated load, °C; t Design is the design value of the ambient temperature, °C.

[0096] Table 1 Empirical parameter value table

[0097]

[0098] After the excess air coefficient of the boiler is determined, the following calculation equation can be used to determine the operating oxygen content at the outlet of the air preheater of the unit, that is:

[0099]

[0100] Where: O Oxygen is the volume content percentage of oxygen, %.

[0101] The heat loss due to unburned gas is mainly caused by combustible gases in the flue gas. Ignoring trace combustible gases such as H2 and C in the flue gas, Q m H n etc., can be expressed as: Unburned.G In the formula: CO is the percentage of the gas volume in the dry flue gas volume, %.

[0102]

[0103] In the equation (6), the prediction calculation of the CO concentration is the key to determining the heat loss due to incomplete combustion of the gas. During operation, it can be considered that CO is mainly generated by volatile matter, and it is approximately considered that the CO concentration is mainly a function of the boiler load and the operating oxygen content. Therefore, the CO concentration can be expressed by an empirical equation as:

[0104] In the construction of the simplified model, it can be considered that the heat loss due to incomplete combustion of solids is related to the unburned carbon contained in the ash, that is, the heat loss due to unburned solids Q

[0105]

[0106] can be expressed by the following empirical formula: Unburned.S In the formula: A1, y0, t1, x0 are the empirical coefficients of formula (8), as shown in Table 2,

[0107]

[0108] Table 2 Empirical coefficient table of formula (8)

[0109] When the boiler operates at a non - rated evaporation capacity, since the temperature change on the outer surface of the boiler is not significant, the total heat dissipation of the boiler also changes little. It can be approximately considered that the heat dissipation loss is inversely proportional to the boiler operating load, that is, the heat dissipation loss Q

[0110]

[0111] can be expressed as: Heat In addition, the heat carried out when the boiler slag is discharged out of the furnace forms the physical heat loss of the ash slag. The physical heat loss of the ash slag Q

[0112]

[0113] can be expressed as: Ash In the formula: A

[0114]

[0115] is the percentage of ash in the coal quality, %; c Received is the fly ash t Fly ash to Ambient.T to The average constant pressure specific heat capacity, kJ / (kg·℃), can be determined by interpolation, see Table 3; c Slag For slag from t Ambient.T to θ Slag Average specific heat capacity at constant pressure, kJ / (kg·℃); a Fly ash 、a Slag is the proportion of fly ash and slag ash in the total ash of fuel, and a is Fly ash =0.9, a Slag =0.1;θ Slag is the slag temperature, ℃, and is 600℃.

[0116] Table 3. Constant pressure specific heat value of fly ash at different temperatures in formula (10)

[0117]

[0118] Combining the above equations (1) to (10), we can get the boiler thermal efficiency η Boiler The expression is:

[0119]

[0120] Where: η Boiler is the boiler thermal efficiency, %.

[0121] (b) Determination of boiler main steam flow rate changes

[0122] In the simplified calculation of the model, when the boiler fuel quantity and coal quality remain unchanged, it can be considered that the change of boiler efficiency will affect the main steam flow of the boiler. Therefore, according to the energy balance equation of the boiler, the change of the main steam flow of the boiler can be expressed as:

[0123]

[0124] Where: B Fuel is the boiler fuel quantity, kg / s; D Main is the main steam flow rate of the boiler, kg / s; h Main is the main steam enthalpy of the boiler, 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 reheat steam outlet enthalpy of the boiler, kJ / kg; h' zr is the reheat steam inlet enthalpy of the boiler, kJ / kg.

[0125] Can be ordered

[0126]

[0127] Therefore, from Equation (12), the calculation equation for the main steam flow rate can be obtained as follows:

[0128]

[0129] As can be seen from Equation (13), when the fuel quantity, coal quality, and steam parameters are approximately constant, the calculation equation for the main steam flow rate can be obtained by using the differential concept as follows:

[0130]

[0131] In the formula: D Main is the main steam flow rate, kg / s.

[0132] (c) Determination link for the change in the standard coal consumption rate of unit power generation

[0133] The conversion equation for the thermal energy of a coal-fired power unit can be expressed as:

[0134] P Power = BQ ar.net η boiler η Pipeline η Circle η oi η m η g (16)

[0135] In the formula: P Power is the power generation of the coal-fired power unit, kW; η Pipeline is the pipeline efficiency of the boiler; η Circle is the ideal cycle thermal efficiency of the steam turbine; η oi is the relative internal efficiency of the steam turbine; η m is the mechanical efficiency of the steam turbine generator set; η g is the electrical efficiency of the generator;

[0136] When the steam parameters of the boiler unit remain unchanged, it can be considered that the ideal cycle thermal efficiency of the steam turbine does not change. In addition, ignoring the influence of changes in the pipeline efficiency, mechanical efficiency, and electrical efficiency from the boiler to the steam turbine, the power generation of the unit only depends on the boiler efficiency η Boiler and the relative internal efficiency η oi of the steam turbine. Using the differential concept, the change in the power generation of the unit can be expressed as:

[0137]

[0138] According to the steam turbine principle, the relative internal efficiency of the main body is affected by changes in boundary parameters, and it can be approximately taken as 1 / 50.

[0139] From Equation (12) and Equation (15), the heat consumption rate of the steam turbine generator set can be obtained as:

[0140]

[0141] Where: q Heat is the heat consumption rate of the steam turbine generator set, kJ / (kW·h).

[0142] Since the steam parameters of the steam turbine do not change, the heat consumption rate of the steam turbine generator set is only affected by the boiler efficiency. Therefore, using the differential concept, the change in the heat consumption rate of the steam turbine generator set can be obtained as follows:

[0143]

[0144] Therefore, the change in the heat consumption rate of the steam turbine generator set can be expressed as:

[0145]

[0146] Where: q Heat is the heat consumption rate of the steam turbine generator set, kJ / (kW·h).

[0147] From equation (15), the calculation equation for the standard coal consumption rate for power generation can be obtained as:

[0148]

[0149] Where: is the standard coal consumption rate for power generation of the unit, g / (kW·h).

[0150] With the changes in the boiler thermal efficiency and the relative internal efficiency of the steam turbine, the heat consumption rate of the steam turbine and the power generation change, and ultimately lead to a change in the standard coal consumption rate for power generation of the unit. The change in the standard coal consumption rate for power generation of the unit can be expressed as:

[0151]

[0152] Where: is the standard coal consumption rate for power generation of the unit, g / (kW·h).

[0153] The computer software program of the present invention is compiled based on automation control and computer processing technologies, and is a technology familiar to those skilled in the art.

[0154] Based on the boiler inverse balance method of the present invention, combined with the concepts of empirical equations and differential thinking, the relationship of the boiler thermal efficiency is further obtained, and then the relationships of the change in the main steam flow rate of the boiler and the change in the standard coal consumption rate for power generation are derived through the relationship of the boiler thermal efficiency, achieving a simplified method for off-design performance analysis. It solves the problems that the current off-design analysis methods for boilers and steam turbines require knowledge of the structural parameters of boilers and steam turbines, with large calculation workload, long calculation time, complex calculation methods, and inconvenience for operators to quickly master the operating characteristics of coal-fired power units.

[0155] Calculation example: Taking a 600 MW supercritical coal-fired power unit as an example, based on the coal quality and the data collected during the unit operation, as shown in Table 4, a calculation and diagnosis case is presented to illustrate the impact of coal quality changes in the boiler on the economic performance of the coal-fired power unit.

[0156] Table 4 Operating parameter table of boundary conditions collected by the unit

[0157]

[0158] (a) Boiler thermal efficiency determination section

[0159] Flue gas temperature of the boiler

[0160]

[0161] Flue gas heat loss Q of the boiler Flue.G :

[0162]

[0163] Operating oxygen content O at the outlet of the unit air preheater Oxygen :

[0164]

[0165] Concentration of CO:

[0166]

[0167] Heat loss Q of unburned gas Unburned.G :

[0168]

[0169] Heat loss Q of unburned solids Unburned.S :

[0170]

[0171] Heat dissipation loss Q Heat :

[0172]

[0173] Heat loss Q of physical heat of ash and slag Ash :

[0174]

[0175] Boiler thermal efficiency η Boiler :

[0176]

[0177] (b) Determination link for the change in the main steam flow rate of the boiler

[0178] Change in the main steam flow rate

[0179]

[0180] (c) Determination link for the change in the standard coal consumption rate for unit power generation

[0181] Unit power generation

[0182]

[0183] Heat consumption rate of the steam turbine generator set

[0184]

[0185] Standard coal consumption rate for power generation

[0186]

[0187] That is, after the calorific value of the unit coal type changes, the change in the standard coal consumption rate for power generation is:

[0188]

Claims

1. A simplified method for analyzing the peak shaving and off-design performance of a coal-fired power unit, characterized in that, Including the steps: S1. Determine the boiler thermal efficiency, and the expression of the boiler thermal efficiency is: Among them, η Boiler is the boiler thermal efficiency; Q Input is the heat input to the boiler; Q Flue.G is the heat loss due to flue gas of the boiler; Q Unburned.G is the heat loss due to incomplete combustion of gas; Q Unburned.S is the heat loss due to incomplete combustion of solid; Q Heat is the heat loss due to heat dissipation of the boiler; Q Ash is the heat loss due to physical heat of ash and slag; S2. Calculate the change in the main steam flow rate of the boiler, and the change in the main steam flow rate of the boiler is expressed as: Among them, B Fuel is the boiler fuel quantity; D Main is the main steam flow rate of the boiler; h Main is the main steam enthalpy of the boiler; h fw is the feed water enthalpy of the boiler; D zr is the reheated steam flow rate; h' z ' r is the reheated steam outlet enthalpy of the boiler; h' zr is the reheated steam inlet enthalpy of the boiler; S3. Determine the change parameters of the standard coal consumption rate for unit power generation. The change parameters of the standard coal consumption rate for unit power generation include the change in the unit power generation, the change in the heat consumption rate of the steam turbine generator set, and the change in the standard coal consumption rate for unit power generation; The change in the unit power generation is expressed as: Among them, P Power is the power generation of the coal-fired power unit; η oi is the relative internal efficiency of the steam turbine; The change in the heat consumption rate of the steam turbine generator set is: The change in the standard coal consumption rate for unit power generation is: Among them, is the standard coal consumption rate for the unit to generate electricity.

2. The simplified method for analyzing the peak shaving and off-design performance of a coal-fired power unit according to claim 1, wherein In step S1, the technical process of the boiler thermal efficiency includes the steps: S11. Construct an inverse balance calculation model for the boiler thermal efficiency: Q Input = Q Effective + Q Flue.G + Q Unburned.G + Q Unburned.S + Q Heat + Q Ash ; Q Input ≈Q ar,net ; Among them, Q Input is the heat input to the boiler; Q Effective is the effectively utilized heat of the boiler; Q Flue.G is the heat loss due to flue gas of the boiler; Q Unburned.G is the heat loss due to incomplete combustion of gas; Q Unburned.S is the heat loss due to incomplete combustion of solid; Q Heat is the heat loss due to heat dissipation of the boiler; Q Ash is the physical heat loss of ash and slag; Q ar,net is the lower calorific value of the as-received fuel; S12. Calculate the heat loss due to flue gas of the boiler through the flue gas temperature and the ambient temperature, Q Flue.G It is expressed as: Among them, V Flue.G is the dry flue gas generated by the combustion of 1 kg of coal; is the flue gas discharge temperature of the boiler; t Ambient.T is the ambient temperature; c Flue.G The average constant pressure specific heat capacity of the dry flue gas at ; M Received is the moisture content of the coal as received; α Air outlet is the excess air coefficient at the outlet of the air preheater; k Flue.G is the coal quality coefficient in the flue gas volume; k Air is the coal quality coefficient in the air volume; S13. Calculate the flue gas temperature of the boiler using the following empirical equation Among them, α Rating is the excess air coefficient under the rated load; D Rating is the rated load of the boiler; D Actuality is the actual load of the boiler; is the flue gas temperature under the rated load; t Design is the designed value of the ambient temperature; S14. After the excess air coefficient of the boiler is determined, the following calculation equation can be used to determine the operating oxygen content at the outlet of the unit air preheater, that is: where O Oxygen is the volume percentage of oxygen; S15. After ignoring the trace combustible gases in the flue gas, represent Q Unburned.G as follows: where CO is the percentage of the gas volume in the dry flue gas volume; The concentration of CO is calculated using the following empirical equation: S16. Calculate the heat loss due to unburned solids. The amount of heat loss due to incomplete combustion of solids is related to the unburned carbon contained in the ash, that is, the heat loss due to unburned solids Q Unburned.S It can be expressed by the following empirical formula: where A1, y0, t1, and x0 are empirical coefficients; S17. Calculate the heat dissipation loss, and the heat dissipation loss is Q Heat It is expressed as follows under non-rated evaporation capacity: S18. Calculate the physical heat loss of ash residue. The physical heat loss of ash residue Q Ash is expressed as: Among them, A Received is the percentage of ash in the coal quality; c Flyash is the average specific heat capacity at constant pressure of fly ash from t Ambient.T to ; c Slag is the average specific heat capacity at constant pressure of slag from t Ambient.T to θ Slag ; a Flyash , a Slag are the shares of ash in fly ash and slag in the total ash of the fuel; θ Slag is the slag temperature.

3. A simplified method for analyzing the peak shaving and off-design performance of a coal-fired power unit, characterized in that, In step S2, let The calculation equation for the main steam flow rate can be obtained as follows: Under the condition that the fuel quantity, coal quality, and steam parameters are approximately unchanged, the calculation equation for the main steam flow rate can be obtained using the differential concept as: Among them, D Main is the main steam flow rate.

4. A simplified method for analyzing the peak shaving and off-design performance of a coal-fired power unit, as described in claim 1, wherein, In step S3, when determining the change in the unit power generation, first establish the conversion equation of the thermal functional energy of the coal-fired power unit: P Power = BQ ar.net η boiler η Pipeline η Circle η oi η m η g Among them, P Power is the power generation power of the coal-fired power unit, kW; η Pipeline is the pipeline efficiency of the boiler; η Circle is the ideal cycle thermal efficiency of the steam turbine; η oi is the relative internal efficiency of the steam turbine; η m is the mechanical efficiency of the steam turbine generator set; η g is the electrical efficiency of the generator; Since the generating power of the unit is only related to the boiler efficiency η Boiler and the relative internal efficiency η oi of the steam turbine, by adopting the differential idea, the change in the generating power of the unit can be obtained.

5. The simplified method for analyzing the peak shaving and off-design performance of a coal-fired power unit according to claim 1, wherein In step S3, when determining the heat consumption rate of the steam turbine generator set, first establish the heat consumption rate equation of the steam turbine generator set: where q Heat is the heat rate of the steam turbine generator set; Since the steam parameters of the steam turbine have not changed, the heat consumption rate of the steam turbine generator set is only affected by the boiler efficiency. Therefore, using the differential concept, the change in the heat consumption rate of the steam turbine generator set can be obtained:

6. The simplified method for analyzing the peak shaving and off-design performance of a coal-fired power unit according to claim 1, wherein In step S3, when determining the change in the standard coal consumption rate for unit power generation, first establish the standard coal consumption rate equation for unit power generation: Among them, is the standard coal consumption rate for unit power generation; the change in the standard coal consumption rate for unit power generation can be obtained according to the unit power generation standard coal consumption rate equation.

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