Method for on-line calculation of boiler fuel efficiency with modified ash ratio and external heat

Abstract

The application discloses a boiler fuel efficiency online calculation method for correcting ash content and external heat, and belongs to the technical field of energy saving of power station boilers burning solid fuel. The method solves the problem of low feasibility and accuracy of real-time online testing of the boiler fuel efficiency of the power station boilers burning solid fuel in the prior art. The application improves the calculation accuracy of the external heat by correcting the conversion heat of dry flue gas and dry air at the reference temperature. The application introduces the water vapor density parameter under the standard state, thereby improving the accuracy of the test result of the boiler fuel efficiency. The application iteratively corrects the mass fraction of the ash content of the slag in the total ash content of the fuel into the furnace and the mass fraction of the ash content of the fly ash in the total ash content of the fuel into the furnace, thereby improving the accuracy of the test result of the boiler fuel efficiency. The application functions the related curves, thereby greatly improving the calculation efficiency and accuracy of the heat loss of the boiler, and realizing the real-time online calculation of the boiler fuel efficiency.

Description

Technical Field

[0001] This application relates to an online calculation method for boiler fuel efficiency, and more particularly to an online calculation method for boiler fuel efficiency that corrects the ash ratio and external heat input, belonging to the field of energy-saving technology for power plant boilers burning solid fuels. Background Technology

[0002] A power plant boiler is a pressure-bearing special equipment that converts the chemical energy of solid fuels (coal, biomass, municipal solid waste, etc.) into thermal energy through combustion. It is also the main energy consumer in a thermal power plant. Boiler fuel efficiency is the most direct indicator for evaluating the boiler's energy utilization level. As a crucial component of the integrated safety, energy conservation, and environmental protection of thermal power plants, routine online and accurate testing of boiler fuel efficiency will be the fundamental basis for future energy consumption assessment and energy conservation and efficiency improvement. By obtaining real-time online information on boiler fuel utilization, the economic operation of the boiler can be optimized, energy utilization efficiency improved, and total energy consumption reduced.

[0003] Currently, the main basis for testing the boiler fuel efficiency of power plant boilers in my country is the national standard GB / T 10184-2015 "Test Procedure for Performance of Power Plant Boilers". The following issues need to be optimized and resolved in the implementation of the routine online accurate testing of boiler fuel efficiency based on this standard.

[0004] Question 1: In the calculation of "heat loss from flue gas," only the heat difference between the actual flue gas temperature and the selected reference temperature is considered. The difference between the heat of the dry flue gas at the reference temperature and the heat of the dry air at the actual furnace inlet temperature is included in the calculation of "external heat." However, the calculation of "external heat" considers the heat difference between the dry air temperature and the actual furnace inlet temperature, assuming that the heat of the dry flue gas and dry air is the same at the reference temperature. In reality, due to differences in composition and volume before and after combustion, the heat of the dry flue gas and dry air at the same temperature will also have a certain difference.

[0005] Question 2: The calculation of "external heat" also includes "the heat carried by water vapor in the air entering the system". The commonly used calculation method currently overlooks the influence of water vapor density.

[0006] Question 3: "The mass fraction of ash content in slag as a percentage of the total ash content of the fuel fed into the furnace" and "The mass fraction of ash content in fly ash as a percentage of the total ash content of the fuel fed into the furnace" (i.e., the ash-slag ratio) are two important parameters required for boiler fuel efficiency testing. Usually, design values ​​or empirical values ​​are selected, but actual measurement is quite difficult.

[0007] Question 4: The two parameters involved in the calculation of "boiler heat loss" – "boiler heat loss at maximum output" and "boiler surface radiative power" – usually require manual lookup of the "radiative heat loss standard curve" and the "boiler emissivity map under different wind speeds and ambient temperature differences," which is not conducive to the implementation of routine online accurate testing of boiler fuel efficiency. Summary of the Invention

[0008] In view of this, this application provides an online calculation method for boiler fuel efficiency by correcting the ash ratio and external heat, in order to solve the problem of low feasibility and accuracy of real-time online testing of boiler fuel efficiency in power plant boilers burning solid fuels in the prior art.

[0009] The technical solution of this application is implemented as follows:

[0010] Online calculation methods for boiler fuel efficiency with corrected ash / slag ratio and external heat input include:

[0011] S1, based on the boiler fuel efficiency online calculation system, obtains the following heat losses: flue gas heat loss Q2, incomplete gas combustion heat loss Q3, incomplete solid combustion heat loss Q4, boiler heat dissipation loss Q5, ash and slag physical sensible heat loss Q6, and external heat loss Q. ex and input heat Q in ;

[0012] In S1, external heat Q is obtained. ex Specifically, it includes the following steps:

[0013] S16-1, Utilizing the inlet air temperature t of the air preheater a1 And the density of dry air under standard conditions ρ air To obtain the density ρ of the air entering the system boundary. p.a.d ;

[0014]

[0015] S16-2, Utilizing the inlet air temperature t of the air preheater a1 Obtain the instantaneous isobaric specific heat capacity c of the air entering the system boundary. p.a.d ;

[0016]

[0017] S16-3, Based on the reference temperature t re And the density of dry air under standard conditions ρ air To obtain the air density ρ at the reference temperature. p.a.re ;

[0018]

[0019] S16-4, Based on the reference temperature t re Obtain the instantaneous isobaric specific heat capacity c of air at the reference temperature. p.a.re ;

[0020]

[0021] S16-5, According to the revised theoretical dry air quantity V a.d.th.cr Corrected excess air coefficient α cr The density ρ of the air entering the system boundary p.a.d The instantaneous isobaric specific heat capacity c of the air entering the system boundary p.a.d The density ρ of air at the reference temperature p.a.re The instantaneous isobaric specific heat capacity of air at the reference temperature, c p.a.re Air preheater inlet air temperature t a1 Reference temperature t re And the density of dry air under standard conditions ρ air The heat Q carried by the dry air entering the system is obtained. a.d ;

[0022]

[0023] S16-6, Utilizing the inlet air temperature t of the air preheater a1 The instantaneous isobaric specific heat capacity c of the water vapor entering the system boundary is obtained. p.wv ;

[0024]

[0025] S16-7, According to the revised theoretical dry air quantity V a.d.th.cr Corrected excess air coefficient α cr The absolute humidity of the air (h) a.ab The instantaneous isobaric specific heat capacity c of water vapor entering the system boundary p.wv Air preheater inlet air temperature t a1 Reference temperature t re And the density of dry air under standard conditions ρ air The heat Q carried by water vapor in the air entering the system is obtained. wv ;

[0026]

[0027] Where, ρ wv It is the density of water vapor under standard conditions;

[0028] S16-8, Based on the N2 concentration C at the dry ground state flue gas outlet. N2 O2 concentration C at the dry ground state flue gas exhaust point O2CO2 concentration C at the dry ground state flue gas exhaust point CO2 CO concentration at the dry ground state flue gas exhaust point C CO and reference temperature t re Obtain the instantaneous isobaric specific heat capacity c of dry flue gas at the reference temperature. p.fg.re ;

[0029]

[0030] Where, c′ N2.re This represents the instantaneous isobaric specific heat capacity of nitrogen at the reference temperature.

[0031] c′ O2.re This is the instantaneous isobaric specific heat capacity of oxygen at a reference temperature;

[0032] c′ CO2.re This represents the instantaneous isobaric specific heat capacity of carbon dioxide at the reference temperature.

[0033] c′ CO.re This represents the instantaneous average isobaric specific heat capacity of carbon monoxide at the reference temperature.

[0034] S16-9, Based on the N2 concentration C at the dry ground state flue gas outlet. N2 O2 concentration C at the dry ground state flue gas exhaust point O2 CO2 concentration C at the dry ground state flue gas exhaust point CO2 CO concentration C at the dry ground state flue gas exhaust point CO Obtain the dry flue gas density ρ under standard conditions. p.fg.d ;

[0035]

[0036] Where, ρ N2 This represents the density of nitrogen gas under standard conditions.

[0037] ρ O2 The density of oxygen under standard conditions;

[0038] ρ CO2 The density of carbon dioxide under standard conditions;

[0039] ρ CO This represents the density of carbon monoxide under standard conditions.

[0040] S16-10, Based on the dry flue gas density ρ under standard conditions p.fg.d and reference temperature t re Obtain the dry flue gas density ρ at the reference temperature. p.fg.re ;

[0041]

[0042] S16-11, According to the revised theoretical dry air quantity V a.d.th.cr Corrected excess air coefficient α cr Actual dry flue gas volume V fg.d.AH.lv The density ρ of air at the reference temperature p.a.re The instantaneous isobaric specific heat capacity of air at the reference temperature, c p.a.re The instantaneous isobaric specific heat capacity of dry flue gas at the reference temperature, c p.fg.re Dry flue gas density ρ under standard conditions p.fg.d Dry flue gas density ρ at the reference temperature p.fg.re Reference temperature t re And the density of dry air under standard conditions ρ air To obtain the corrected heat of conversion Q of dry flue gas and dry air. xz.1 ;

[0043]

[0044] S16-12, Based on the heat Q carried by the dry air entering the system. a.d The heat Q carried by water vapor in the air entering the system. wv The heat of conversion between dry flue gas and dry air, and the modified heat of conversion Q. xz.1 , obtain external heat Q ex ;

[0045] Q ex =Q a.d +Q wv +Q xz.1 (Formula 56);

[0046] S2. Calculate the boiler fuel efficiency η′;

[0047]

[0048] S3. The boiler fuel efficiency η′ is corrected by an iterative algorithm to obtain the corrected boiler fuel efficiency η′, and finally the online calculation of boiler fuel efficiency is completed.

[0049] Furthermore, in step S1, obtaining the boiler heat loss Q5 specifically includes the following steps:

[0050] S15-1, Obtain the boiler heat loss Q under maximum output. 5.BMCR ;

[0051] When Q r When ≤40,

[0052] When 40 r When ≤1500, ​

[0053] Among them, Q r The rated output heat of the boiler (MW);

[0054] S15-2, Utilizing the average temperature t of the boiler's outer surface a2 and the ambient temperature t near the boiler body a3 The temperature difference t on the outer surface of the boiler is obtained. a4 ;

[0055] t a4 =t a2 -t a3 (Formula 28);

[0056] S15-3, Based on the temperature difference t on the outer surface of the boiler a4 To obtain different fixed wind speeds v i Boiler surface radiant power E i Where i = 0, 1, 2, 3, 4, 5, 6, 7, as detailed below:

[0057] When v0 = 0.0 m / s, E0 = 0 (Formula 29);

[0058] When v1 = 0.5 m / s,

[0059] When v2 = 1.5 m / s,

[0060] When v3 = 3.0 m / s,

[0061] When v4 = 4.5 m / s,

[0062] When v5 = 6.0 m / s,

[0063] When v6 = 7.5 m / s,

[0064] When v7 = 9.0 m / s,

[0065] S15-4. Based on the wind speed v near the boiler body and the eight fixed wind speeds involved in formulas 29 to 36, select the lower boundary fixed wind speed v. k And the fixed wind speed v at the upper boundary k+1 The requirements are as follows:

[0066] v k <v≤v k+1 (Formula 37);

[0067] k=0, 1, 2, 3, 4, 5, 6;

[0068] S15-5. Fix the wind speed v according to the selected lower boundary. k And the fixed wind speed v at the upper boundary k+1 Select the corresponding E from formulas 29 to 36 k and E k+1 E k It is the lower boundary boiler surface radiative power index, E k+1 It is the radiative power factor of the upper boundary boiler surface;

[0069] S15-6. Fix the wind speed v according to the selected lower boundary. k And the fixed wind speed v at the upper boundary k+1 The selected lower boundary boiler surface radiative power E k and the surface radiative power E of the upper boundary boiler k+1 The final surface radiative power factor E of the boiler is obtained by taking the wind speed v near the boiler body and the wind speed v near the boiler body.

[0070]

[0071] S15-7, Utilizing the boiler main feedwater mass flow rate D out Boiler main feedwater temperature t zgs Boiler main feedwater pressure p zgs Boiler main steam temperature t zzq and boiler main steam pressure p zzq To obtain the actual heat output Q of the boiler out ;

[0072] Q out =D out ×(h zzq -h zgs ) (Formula 39);

[0073] Among them, h zzq This refers to the main steam enthalpy of the boiler.

[0074] h zgs For the boiler main feedwater enthalpy;

[0075] S15-8, Based on the boiler heat loss Q under maximum output. 5.BMCR The final surface radiant power of the boiler, E, and the actual heat output of the boiler, Q. out and the rated output heat of the boiler Q r The boiler heat loss Q5 is obtained;

[0076]

[0077] Among them, Q BMCR It is the boiler's maximum continuous heat output.

[0078] Furthermore, the specific steps of S3 are as follows:

[0079] S31. Based on the actual dry flue gas volume V fg.d.AH.lv The carbon content (C) of the fuel received ar 1. Ash content of fuel received A ar CO2 concentration C at the dry ground state flue gas exhaust point CO2 CO concentration at the dry ground state flue gas exhaust point C CO Fly ash combustible content C as and the combustible content C of slag s The corrected ash content of the slag as a percentage of the total ash content of the fuel fed into the furnace, α, is obtained. s.xz.1 ;

[0080]

[0081] Among them, M C is the molar mass of carbon.

[0082] V mol Let be the molar volume of an ideal gas;

[0083] S32. Based on the corrected ash content of the slag as a percentage of the total ash content of the fuel fed into the furnace, α s.xz.1 The corrected fly ash content as a percentage of the total ash content of the fuel fed into the furnace, α, was obtained. as.xz.1 ;

[0084] α as.xz.1 =100-α s.xz.1 (Formula 59);

[0085] S33. Based on the corrected ash content of the slag as a percentage of the total ash content of the fuel fed into the furnace, α s.xz.1 The mass fraction α of fly ash content relative to the total ash content of fuel entering the furnace. as.xz.1 The average mass fraction of combustible matter in the ash residue was successively determined by ω. c.rs.m The actual mass fraction of carbon in the fuel fed into the furnace, ω c.b Corrected theoretical dry air quantity V a.d.th.cr and the corrected theoretical dry flue gas volume V fg.d.th.cr The update was performed, ultimately completing the calculation of the actual dry flue gas volume V. fg.d.AH.lv Update;

[0086] S34. The updated actual dry flue gas volume V fg.d.AH.lv Substitute this into step S31 to complete the adjustment of the mass fraction α of the corrected slag ash content relative to the total ash content of the fuel fed into the furnace. s.xz.1 Update;

[0087] S35. Determine the mass fraction α of slag ash content relative to the total ash content of fuel fed into the furnace in two consecutive revisions before and after the update. s.xz.1Is the absolute value of the difference less than 0.01%? If yes, proceed to step S37; if no, proceed to step S36.

[0088] S36. Repeat steps S32 to S35;

[0089] S37. The updated and corrected ash content of the slag as a percentage of the total ash content of the fuel fed into the furnace, α. s.xz.1 Substituting into Formula 59, the mass fraction α of the corrected fly ash content relative to the total ash content of the fuel fed into the furnace is calculated. as.xz.1 The system is updated to correct the boiler fuel efficiency η′.

[0090] The beneficial effects of this application are reflected in:

[0091] Compared to existing technologies, this application provides an online calculation method for boiler fuel efficiency that corrects the ash-slag ratio and external heat input. Specifically: 1. Addressing the issue that dry flue gas and dry air differ in composition and volume before and after combustion, resulting in variations in heat output at the same temperature, this application improves the accuracy of "external heat input" calculation by correcting the conversion heat of "dry flue gas and dry air" at the reference temperature, thereby enhancing the accuracy of boiler fuel efficiency test results. 2. The calculation of "external heat input" also includes "heat carried by water vapor in the air entering the system," but existing methods overlook the influence of water vapor density. This application introduces the parameter of "water vapor density under standard conditions," further improving the accuracy of boiler fuel efficiency test results. 3. Regarding the "mass fraction of ash content in slag relative to the total ash content of the fuel entering the furnace" and the "mass fraction of ash content in fly ash relative to the total ash content of the fuel entering the furnace," design or empirical values ​​are typically used, leading to significant difficulties in actual measurement. Based on empirical values, this application iteratively corrects two parameters—"mass fraction of ash content in slag relative to total ash content in fuel fed into the furnace" and "mass fraction of ash content in fly ash relative to total ash content in fuel fed into the furnace"—from the perspectives of ash balance and carbon balance, thereby improving the accuracy of boiler fuel efficiency test results. 4. Regarding the issue that the current methods for obtaining parameters such as "boiler heat loss at maximum output" and "boiler surface radiative power" are not conducive to the implementation of routine online and accurate testing of boiler fuel efficiency, this application functionalizes the relevant curves, greatly improving the calculation efficiency and accuracy of "boiler heat loss" and enabling real-time online calculation of boiler fuel efficiency. Furthermore, this application can obtain real-time online information on solid fuel utilization, thereby optimizing the economic operation of the boiler, improving energy utilization efficiency, and reducing total energy consumption. This aligns with the current management philosophy of strengthening the energy-saving responsibility of boiler users and is conducive to creating a new landscape for energy conservation work on high-energy-consuming special equipment. Attached Figure Description

[0092] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0093] Figure 1 This is a flowchart illustrating how the iterative algorithm of this application corrects the boiler fuel efficiency η′.

[0094] Figure 2 This is a framework diagram of an online boiler fuel efficiency calculation system according to an embodiment of this application. Detailed Implementation

[0095] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the relevant application and not intended to limit the application. Furthermore, it should be noted that, for ease of description, only the parts relevant to the application are shown in the accompanying drawings.

[0096] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0097] Specific Implementation Method 1: This application provides an online calculation method for boiler fuel efficiency based on corrected ash / slag ratio and external heat input. This method is implemented using an online boiler fuel efficiency calculation system, which includes a DCS data acquisition system 1, an online flue gas measurement and data recording system 2, an online fuel / ash / slag composition analysis system 3, an environmental parameter measurement system 4, and an online boiler fuel efficiency calculation platform 5. The calculation method includes the following steps:

[0098] S1. Data is collected from the boiler body system 6 using DCS data acquisition system 1, online flue gas measurement and data recording system 2, online fuel / ash / slag composition analysis system 3, and environmental parameter measurement system 4, and the collected data is sent to the boiler fuel efficiency online calculation platform 5.

[0099] The boiler fuel efficiency online calculation platform 5 uses the received data to obtain the following heat losses: flue gas heat loss Q2 (kJ / kg), incomplete gas combustion heat loss Q3 (kJ / kg), incomplete solid combustion heat loss Q4 (kJ / kg), boiler heat dissipation loss Q5 (%), ash and slag physical sensible heat loss Q6 (kJ / kg), and external heat loss Q. ex (kJ / kg) and input heat Q in (kJ / kg);

[0100] S2, Boiler fuel efficiency online calculation platform 5, Flue gas heat loss Q2, Incomplete gas combustion heat loss Q3, Incomplete solid combustion heat loss Q4, Boiler heat dissipation loss Q5, Physical sensible heat loss of ash and slag Q6, External heat Q ex and input heat Q in Perform calculations to determine the boiler fuel efficiency η′ (%); where,

[0101]

[0102] S3, the online boiler fuel efficiency calculation platform 5 corrects the boiler fuel efficiency η′ through an iterative algorithm, thereby obtaining the corrected boiler fuel efficiency η′, and finally completing the online calculation of boiler fuel efficiency.

[0103] This embodiment provides an online calculation method for boiler fuel efficiency by correcting the ash ratio and external heat. It can obtain the utilization status of solid fuel in real time, thereby optimizing the economic operation of the boiler, improving energy utilization efficiency, and reducing total energy consumption. This is in line with the current management concept of consolidating the energy-saving responsibility of boiler users and is conducive to creating a new situation for energy-saving work of high-energy-consuming special equipment.

[0104] The DCS data acquisition system 1, online flue gas measurement and data recording system 2, online fuel / ash / slag composition analysis system 3, and environmental parameter measurement system 4 can all be implemented using existing technologies.

[0105] In step S1, data is collected from the boiler body system 6 using the DCS data acquisition system 1, the online flue gas measurement and data recording system 2, the online fuel / ash / slag composition analysis system 3, and the environmental parameter measurement system 4. All collected data are as follows:

[0106] The data collected by DCS data acquisition system 1 includes D out t zgs p zgs t zzq p zzq ;

[0107] The data collected by the online flue gas measurement and data recording system 2 includes t ds C O2 C CO2 and C CO ;

[0108] The data collected by the online fuel / ash / slag composition analysis system 3 includes C ar H ar O ar S ar N ar A ar Mar Q net.v.ar C as and C s ;

[0109] The data collected by the environmental parameter measurement system 4 includes t a1 t a2 t a3 p at h a.re and v.

[0110] Among them, D out The main feedwater mass flow rate (kg / h) for the boiler is t. zgs p represents the main feedwater temperature of the boiler (°C). zgs The boiler main feedwater pressure (MPa), t zzq The main steam temperature of the boiler (°C), p zzq This refers to the main steam pressure of the boiler (MPa).

[0111] t ds C represents the exhaust gas temperature (°C). O2 The O2 concentration (%) at the dry ground state flue gas exhaust point, C CO2 The CO2 concentration (%) at the dry ground state flue gas exhaust point, C CO CO concentration (%) at the dry ground state flue gas exhaust point;

[0112] C ar H represents the carbon content (%) of the fuel received as a base. ar The percentage of hydrogen received by the fuel is O. ar S represents the oxygen content (%) of the fuel received. ar The sulfur content (%) of the fuel received, N ar For the nitrogen content (%) of the fuel received, A ar M represents the ash content (%) of the fuel received. ar Q represents the moisture content (%) of the fuel received. net.v.ar For the lower heating value (kJ / kg) of the fuel, C as C represents the combustible content (%) of fly ash. s The combustible content of the slag (%);

[0113] t a1 The air temperature at the inlet of the air preheater (°C), t a2 The average temperature of the boiler's outer surface (°C), t a3 The ambient temperature (°C) near the boiler body, p at h is the atmospheric pressure (Pa) near the boiler body. a.re v represents the relative humidity (%) of the air near the boiler body, and v represents the wind speed (m / s) near the boiler body.

[0114] In step S1, the boiler fuel efficiency online calculation platform 5 uses the received data to obtain the following heat losses: flue gas heat loss Q2, incomplete gas combustion heat loss Q3, incomplete solid combustion heat loss Q4, boiler heat dissipation loss Q5, ash and slag physical sensible heat loss Q6, and external heat loss Q7. ex and input heat Q in The implementation involves the following steps:

[0115] S11. Obtain the heat loss Q4 from incomplete combustion of solids, specifically including the following steps:

[0116] S11-1, Utilizing the collected combustible content C of the slag s and fly ash combustible content C as The average mass fraction of combustible material in ash was obtained ω. c.rs.m (%)

[0117]

[0118] Where, α s The ash content of the slag is the mass fraction (%) of the total ash content of the fuel fed into the furnace; α as The fly ash content is the mass fraction (%) of the total ash content of the fuel fed into the furnace.

[0119] In practical applications, α s Based on experience, 80%; α as Based on experience, 20%;

[0120] S11-2, Based on the average mass fraction ω of combustible matter in the ash obtained in step S11-1 c.rs.m And the content of ash content of the collected fuel received as a basis A ar The heat loss due to incomplete combustion of solids is Q4;

[0121]

[0122] Among them, Q C The calorific value of carbon upon complete combustion (kJ / kg);

[0123] In practical applications, Q C This is a fixed value, 33727 kJ / kg;

[0124] S12. Obtain the heat loss Q2 from the flue gas exhaust, which specifically includes the following steps:

[0125] S12-1, Based on the average mass fraction of combustible matter in the ash obtained in step S11-1, ω c.rs.m And the carbon content (C) of the collected fuel. ar And the content of ash content of fuel received as base A arTo obtain the actual carbon content (ω) of the fuel entering the furnace as a percentage of the total carbon content in the combustion process. c.b (%)

[0126]

[0127] S12-2, The mass fraction ω of carbon actually burned relative to the fuel fed into the furnace, obtained from step S12-1. c.b And the content of hydrogen H in the collected fuel. ar The oxygen content of the fuel received is O ar and the content of basic sulfur in fuel S ar To obtain the corrected theoretical dry air quantity V a.d.th.cr (m 3 / kg);

[0128]

[0129] in, The theoretical volume of air (m³) required for complete combustion of carbon 3 / kg); The theoretical air volume (m³) required for the complete combustion of sulfur 3 / kg); The theoretical volume of air (m³) required for the complete combustion of hydrogen 3 / kg); The theoretical air volume corresponding to oxygen (m³) 3 / kg);

[0130] In practical applications It is a fixed value, 8.889m 3 / kg; It is a fixed value, 3.333m 3 / kg; This is a fixed value, 26.667m 3 / kg, It is a fixed value, 3.333m 3 / kg;

[0131] S12-3, The mass fraction of carbon in the actual combusted fuel ω obtained from step S12-1. c.b The corrected theoretical dry air quantity V obtained in step S12-2 a.d.th.cr And the sulfur content S of the collected fuel ar and the nitrogen content of fuel ar To obtain the corrected theoretical dry flue gas volume V fg.d.th.cr (m 3 / kg);

[0132]

[0133] in, The volume of dry flue gas generated by the complete combustion of carbon (m³) 3 / kg); The volume of dry flue gas generated by the complete combustion of sulfur (m³) 3 / kg); The volume of dry flue gas generated by the complete combustion of nitrogen (m³) 3 / kg); The proportion of nitrogen in the air (dimensionless);

[0134] In practical applications It is a fixed value, 1.867m 3 / kg; It is a fixed value, 0.7m 3 / kg; It is a fixed value, 0.8m 3 / kg; It is a fixed value, 0.79;

[0135] S12-4. Utilizing the collected O2 concentration C at the dry ground state flue gas exhaust point O2 CO2 concentration C at the dry ground state flue gas exhaust point CO2 CO concentration C at the dry ground state flue gas exhaust point CO The N2 concentration C at the dry ground state flue gas exhaust point was obtained. N2 (%)

[0136] C N2 =100-C O2 -C CO2 -C CO (Formula 7);

[0137] S12-5, Based on the N2 concentration C at the dry ground state flue gas exhaust obtained in step S12-4 N2 And the collected dry ground state O2 concentration C at the flue gas exhaust point O2 The corrected excess air coefficient α is obtained. cr (dimensionless);

[0138]

[0139] S12-6, The corrected theoretical dry air quantity V obtained from step S12-2 a.d.th.cr The corrected theoretical dry flue gas quantity V obtained in step S12-3 fg.d.th.cr and the corrected excess air coefficient α obtained in step S12-5 cr To obtain the actual dry flue gas volume V fg.d.AH.lv (m 3 / kg);

[0140] V fg.d.AH.lv =V fg.d.th.cr +(αcr -1)×V a.d.th.cr (Formula 9);

[0141] S12-7, The actual dry flue gas volume V obtained from step S12-6 fg.d.AH.lv and the collected flue gas temperature t ds The heat Q carried away by the dry flue gas is obtained. 2.fg.d (kJ / kg);

[0142] Q 2.fg.d =V fg.d.AH.lv ×c′ p.fg.d ×(t ds -t re ) (Formula 10);

[0143] Among them, t re Reference temperature (°C);

[0144] In practical applications, t re The value is fixed at 25℃.

[0145] In formula 10,

[0146]

[0147] In formula 11,

[0148]

[0149]

[0150]

[0151]

[0152] Where, c′ p.fg.d The average isobaric specific heat capacity of dry flue gas from the reference temperature to the exhaust temperature (kJ / (m³)) 3 ·K));c′ N2 The average isobaric specific heat capacity of nitrogen from the reference temperature to the flue gas temperature (kJ / (m³)) 3 ·K));c′ O2 The average isobaric specific heat capacity of oxygen from the reference temperature to the flue gas temperature (kJ / (m³)) 3 ·K));c′ CO2 The average isobaric specific heat capacity of carbon dioxide from the reference temperature to the flue gas temperature (kJ / (m³)) 3 ·K));c′ CO The average isobaric specific heat capacity of carbon monoxide from the reference temperature to the flue gas temperature (kJ / (m³)) 3 ·K));

[0153] The applicable temperature range for formulas 12 to 15 is -18.15 to 726.85℃; since these are empirical formulas, the balancing of units on both sides of the equation is not considered.

[0154] S12-8. Utilizing the collected ambient temperature t near the boiler body a3 Obtain the water vapor saturation pressure p at ambient temperature. wv.sat (Pa);

[0155]

[0156] Formula 16 is applicable to a temperature range of 0 to 50℃; since it is an empirical formula, the balancing of units on both sides of the equation is not considered.

[0157] S12-9, The water vapor saturation pressure p at the ambient temperature obtained in step S12-8 wv.sat and the atmospheric pressure p near the boiler body collected. at The relative humidity of the air near the boiler body (h) a.re To obtain the absolute humidity h of the air a.ab (kg / kg);

[0158]

[0159] The absolute humidity of the air here is h a.ab It represents the kilogram mass of water vapor in one kilogram of dry air; Formula 17 is an empirical formula, so the balancing of units on both sides of the equation is not considered.

[0160] S12-10, The corrected theoretical dry air quantity V obtained from step S12-2 a.d.th.cr The absolute humidity h of the air obtained in step S12-9 a.ab The corrected excess air coefficient α obtained in step S12-5 cr And the content of hydrogen H in the collected fuel. ar And the moisture content M of the fuel received ar The volume V of water vapor in the flue gas is obtained. wv.fg.AH.lv (m 3 / kg);

[0161]

[0162] in, The volume of water vapor generated by the complete combustion of hydrogen (m³) 3 / kg); The volume of water vapor corresponding to pure water (m³) 3 / kg); ρ air The density of dry air under standard conditions (kg / m³) 3 );

[0163] In practical applications It is a fixed value, 11.2m 3 / kg; It is a fixed value, 1.244m 3 / kg; ρ air This is an empirical value, 1.293 kg / m³ 3 ;

[0164] S12-11, Based on the volume V of water vapor in the flue gas obtained in step S12-10 wv.fg.AH.lv and the collected flue gas temperature t ds The heat Q carried away by the water vapor in the flue gas is obtained. 2.wv.fg (kJ / kg);

[0165] Q 2.wv.fg =V wv.fg.AH.lv ×c′ p.wv ×(t ds -t re ) (Formula 19);

[0166] Where, c′ p.wv The average isobaric specific heat capacity of water vapor from the reference temperature to the flue gas temperature (kJ / (m³)) 3 ·K)), specifically

[0167]

[0168] The applicable temperature range of Formula 20 is -18.15 to 726.85℃; since it is an empirical formula, the balancing of units on both sides of the equation is not considered.

[0169] S12-12, The heat Q carried away by the dry flue gas obtained in step S12-7 2.fg.d The heat Q carried away by the water vapor in the flue gas obtained in step S12-11 2.wv.fg The heat loss from exhaust gas, Q2, is obtained.

[0170] Q2 = Q 2.fg.d +Q 2.wv.fg (Formula 21);

[0171] S13, The method for obtaining the heat loss Q3 due to incomplete combustion of gas is as follows:

[0172]

[0173] Among them, Q CO The calorific value of carbon monoxide upon complete combustion (kJ / m³) 3 );

[0174] In practical applications, Q COThis is a fixed value, 12636 kJ / m 3 ;

[0175] S14. The method for obtaining the physical sensible heat loss Q6 of ash slag is as follows:

[0176]

[0177] In formula 23,

[0178] c′ s =0.71 + 5.02 × 10 -4 ×t s (Formula 24);

[0179] c′ as =0.71 + 5.02 × 10 -4 ×t as (Formula 25);

[0180] Among them, t s Temperature of slag discharged from the combustion chamber (°C); t as The fly ash temperature (°C); c′ s Specific heat of slag (kJ / (kg·K)); c′ as The specific heat of fly ash (kJ / (kg·K));

[0181] In practical applications, t s This is an empirical value, 800℃; t as Equivalent to the collected flue gas temperature t ds ;

[0182] S15. Obtain the boiler heat loss Q5, which includes the following steps:

[0183] S15-1, Obtain the boiler heat loss Q under maximum output. 5.BMCR (%), as detailed below:

[0184] When Q r When ≤40,

[0185] When 40 r When ≤1500,

[0186] Among them, Q r The rated output heat of the boiler (MW);

[0187] Formulas 26 and 27 are empirical formulas, so balancing the units on both sides of the equation is not considered.

[0188] In practical applications, the boiler's rated output heat Q r ​This is a fixed preset value, determined by the boiler's manufacturer's specifications; based on the boiler's rated output heat Q. r For the size, choose formula 26 or 27;

[0189] S15-2, Using the collected average temperature t of the boiler's outer surface a2 and the ambient temperature t near the boiler body a3 The temperature difference t on the outer surface of the boiler is obtained. a4 (°C);

[0190] t a4 =t a2 -t a3 (Formula 28);

[0191] In practical applications, the average temperature t on the outer surface of the boiler a2 The temperature will be higher than the ambient temperature near the boiler body. a3 ;

[0192] S15-3, Based on the boiler outer surface temperature difference t obtained in step S15-2 a4 To obtain different fixed wind speeds v i Boiler surface radiant power E (m / s) i (kW / m 2 ), where i = 0, 1, 2, 3, 4, 5, 6, 7, as detailed below:

[0193] When v0 = 0.0 m / s, E0 = 0 (Formula 29);

[0194] When v1 = 0.5 m / s,

[0195] When v2 = 1.5 m / s,

[0196] When v3 = 3.0 m / s,

[0197] When v4 = 4.5 m / s,

[0198] When v5 = 6.0 m / s,

[0199] When v6 = 7.5 m / s,

[0200] When v7 = 9.0 m / s,

[0201] Formulas 29 to 36 apply to the boiler outer surface temperature difference t a4 The range is 0.1~165℃; Formulas 29 to 36 are empirical formulas, so the balancing of units on both sides of the equation is not considered.

[0202] S15-4. Based on the collected wind speed v near the boiler body and the eight fixed wind speeds involved in formulas 29 to 36, select the lower boundary fixed wind speed v. k (m / s) and the fixed wind speed v at the upper boundary k+1 (m / s), meeting the following requirements:

[0203] v k <v≤v k+1 (Formula 37);

[0204] Here, k = 0, 1, 2, 3, 4, 5, 6;

[0205] S15-5. Fixed wind speed v at the lower boundary selected according to step S15-4. k And the fixed wind speed v at the upper boundary k+1 Select the corresponding E from formulas 29 to 36 k and E k+1 E k It is the lower boundary boiler surface radiative power factor (kW / m²) 2 E k+1 It is the radiative power of the upper boundary boiler surface (kW / m²) 2 );

[0206] S15-6. Fixed wind speed v at the lower boundary selected according to step S15-4. k And the fixed wind speed v at the upper boundary k+1 Step S15-5: Select the lower boundary boiler surface radiative power index E k and the surface radiative power E of the upper boundary boiler k+1 The final surface radiative power E (kW / m²) of the boiler was obtained by collecting the wind speed v near the boiler body. 2 );

[0207]

[0208] S15-7. Utilizing the collected boiler main feedwater mass flow rate D out Boiler main feedwater temperature t zgs Boiler main feedwater pressure p zgs Boiler main steam temperature t zzq and boiler main steam pressure p zzq To obtain the actual heat output Q of the boiler out (kJ / h), specifically:

[0209] Q out =D out ×(h zzq -h zgs ) (Formula 39);

[0210] Among them, h zzq The enthalpy of the main steam in the boiler is (kJ / kg), and h zzq Through the main steam pressure p of the boiler zzq and boiler main steam temperature t zzq Find the enthalpy values ​​of water and water vapor in the table; h zgs The enthalpy of the boiler main feedwater (kJ / kg) and h zgs Through the boiler main feedwater pressure p zgs and boiler main feedwater temperature t zgs Find the enthalpy values ​​of water and water vapor in the table;

[0211] S15-8. Boiler heat loss Q under maximum output obtained in step S15-1 5.BMCR The final boiler surface radiant power E obtained in step S15-6, and the actual boiler output heat Q obtained in step S15-7. out and the rated output heat of the boiler Q r The boiler heat loss Q5 is obtained;

[0212]

[0213] Among them, Q BMCR This refers to the boiler's maximum continuous heat output (MW), i.e., the boiler's heat output under BMCR conditions; in practical applications, the boiler's maximum continuous heat output Q is... BMCR These are fixed preset values, determined by the boiler's factory specifications;

[0214] Formula 40 is an empirical formula, so balancing the units on both sides of the equation is not considered.

[0215] In practical applications, when the boiler's rated output heat Q r When the capacity is greater than 1500MW or the wind speed v near the boiler body is greater than 9m / s, according to Q r =1500 or v=9 for processing;

[0216] S16, Obtain external heat Q ex Specifically, it includes the following steps:

[0217] S16-1, Utilizing the collected air inlet temperature t of the air preheater a1 And the dry air density ρ under standard conditions air To obtain the density ρ of the air entering the system boundary. p.a.d (kg / m 3 );

[0218]

[0219] S16-2, Utilizing the collected air inlet temperature t of the air preheatera1 Obtain the instantaneous isobaric specific heat capacity c of the air entering the system boundary. p.a.d (kJ / (m 3 ·K));

[0220]

[0221] The applicable temperature range of Formula 42 is -18.15 to 726.85℃; since it is an empirical formula, the balancing of units on both sides of the equation is not considered.

[0222] S16-3, Based on the reference temperature t re And the dry air density ρ under standard conditions air To obtain the air density ρ at the reference temperature. p.a.re (kg / m 3 );

[0223]

[0224] S16-4, Based on the reference temperature t re Obtain the instantaneous isobaric specific heat capacity c of air at the reference temperature. p.a.re (kJ / (m 3 ·K));

[0225]

[0226] The applicable temperature range of Formula 44 is -18.15 to 726.85℃; since it is an empirical formula, the balancing of units on both sides of the equation is not considered.

[0227] S16-5, The corrected theoretical dry air quantity V obtained from step S12-2 a.d.th.cr The corrected excess air coefficient α obtained in step S12-5 cr The density ρ of the air entering the system boundary obtained in step S16-1 p.a.d Step S16-2: The instantaneous isobaric specific heat capacity c of the air entering the system boundary. p.a.d The density ρ of air at the reference temperature obtained in step S16-3 p.a.re The instantaneous isobaric specific heat capacity c of air at the reference temperature obtained in step S16-4 p.a.re and the collected air inlet temperature t of the air preheater a1 and reference temperature t re The density of dry air under standard conditions, ρ air The heat Q carried by the dry air entering the system is obtained. a.d (kJ / kg);

[0228]

[0229] S16-6, Utilizing the collected air inlet temperature t of the air preheater a1 The instantaneous isobaric specific heat capacity c of the water vapor entering the system boundary is obtained. p.wv (kJ / (m 3 ·K));

[0230]

[0231] The applicable temperature range of Formula 46 is -18.15 to 726.85℃; since it is an empirical formula, the balancing of units on both sides of the equation is not considered.

[0232] S16-7, The corrected theoretical dry air quantity V obtained from step S12-2 a.d.th.cr The corrected excess air coefficient α obtained in step S12-5 cr The absolute humidity h of the air obtained in step S12-9 a.ab The instantaneous isobaric specific heat capacity c of the water vapor entering the system boundary obtained in step S16-6 p.wv and the collected air inlet temperature t of the air preheater a1 and reference temperature t re The density of dry air under standard conditions, ρ air The heat Q carried by water vapor in the air entering the system is obtained. wv (kJ / kg);

[0233]

[0234] Where, ρ wv The density of water vapor under standard conditions (kg / m³) 3 );

[0235] In practical applications, ρ wv This is a fixed value, 0.80357 kg / m³. 3 ;

[0236] S16-8, The N2 concentration C at the dry ground state flue gas outlet obtained in step S12-4 N2 The collected dry ground state O2 concentration C at the flue gas exhaust point O2 CO2 concentration C at the dry ground state flue gas exhaust point CO2 CO concentration C at the dry ground state flue gas exhaust point CO and reference temperature t re Obtain the instantaneous isobaric specific heat capacity c of dry flue gas at the reference temperature. p.fg.re (kJ / (m 3 ·K));

[0237]

[0238] In formula 48,

[0239]

[0240]

[0241]

[0242]

[0243] Where, c′ N2.re The instantaneous isobaric specific heat capacity of nitrogen at the reference temperature (kJ / (m³)) 3 ·K));c′ O2.re The instantaneous isobaric specific heat capacity of oxygen at the reference temperature (kJ / (m³)) 3 ·K));c′ CO2.re The instantaneous isobaric specific heat capacity of carbon dioxide at the reference temperature (kJ / (m³)) 3 ·K));c′ CO.re The instantaneous average isobaric specific heat capacity of carbon monoxide at the reference temperature (kJ / (m³)) 3 ·K));

[0244] The applicable temperature range for formulas 49 to 52 is -18.15 to 726.85℃; since these are empirical formulas, the balancing of units on both sides of the equation is not considered.

[0245] S16-9, The N2 concentration C at the dry ground state flue gas exhaust point obtained in step S12-4 N2 The collected dry ground state O2 concentration C at the flue gas exhaust point O2 CO2 concentration C at the dry ground state flue gas exhaust point CO2 CO concentration C at the dry ground state flue gas exhaust point CO Obtain the dry flue gas density ρ under standard conditions. p.fg.d (kg / m 3 );

[0246]

[0247] Where, ρ N2 The density of nitrogen gas under standard conditions (kg / m³) 3 );ρ O2 The density of oxygen under standard conditions (kg / m³) 3 );ρ CO2 The density of carbon dioxide under standard conditions (kg / m³) 3 );ρ CO The density of carbon monoxide under standard conditions (kg / m³) 3 );

[0248] In practical applications, ρN2 This is a fixed value, 1.2501 kg / m³. 3 ;ρ O2 This is a fixed value, 1.4278 kg / m³. 3 ;ρ CO2 This is a fixed value, 1.9638 kg / m³. 3 ;ρ CO This is a fixed value, 1.2499 kg / m³. 3 ;

[0249] S16-10, The dry flue gas density ρ under standard conditions obtained according to step S16-9 p.fg.d and reference temperature t re Obtain the dry flue gas density ρ at the reference temperature. p.fg.re (kg / m 3 );

[0250]

[0251] S16-11, The corrected theoretical dry air quantity V obtained from step S12-2 a.d.th.cr The corrected excess air coefficient α obtained in step S12-5 cr The actual dry flue gas volume V obtained in step S12-6 fg.d.AH.lv The density ρ of air at the reference temperature obtained in step S16-3 p.a.re The instantaneous isobaric specific heat capacity c of air at the reference temperature obtained in step S16-4 p.a.re The instantaneous isobaric specific heat capacity c of dry flue gas at the reference temperature obtained in step S16-8 p.fg.re The dry flue gas density ρ under standard conditions obtained in step S16-9 p.fg.d The dry flue gas density ρ at the reference temperature obtained in step S16-10 p.fg.re and reference temperature t re And the density of dry air under standard conditions ρ air To obtain the corrected heat of conversion Q of dry flue gas and dry air. xz.1 (kJ / kg);

[0252]

[0253] S16-12, The heat Q carried by the dry air entering the system, obtained from step S16-5. a.d The heat Q carried by water vapor in the air entering the system, obtained in step S16-7. wv The corrected heat of conversion Q of dry flue gas and dry air obtained in step S16-11 xz.1 , obtain external heat Q ex ;

[0254] Q ex =Q a.d +Q wv +Q xz.1 (Formula 56);

[0255] S17. Utilize the collected fuel to obtain the lower heating value Q. net.v.ar Obtain the input heat Q in The details are as follows:

[0256] Q in =Q net.v.ar (Formula 57);

[0257] In this preferred embodiment, the following are provided: heat loss Q2 from flue gas, heat loss Q3 from incomplete combustion of gas, heat loss Q4 from incomplete combustion of solids, heat dissipation Q5 from boiler, heat loss Q6 from sensible physical heat of ash and slag, and external heat Q. ex and input heat Q in The specific implementation method relies on data collected by the DCS data acquisition system 1, the online flue gas measurement and data recording system 2, the online fuel / ash / slag composition analysis system 3, and the environmental parameter measurement system 4 to obtain the boiler fuel efficiency η′.

[0258] In step S3, the online boiler fuel efficiency calculation platform 5 corrects the boiler fuel efficiency η′ using an iterative algorithm to obtain the corrected boiler fuel efficiency η′. The final implementation of the online calculation of boiler fuel efficiency includes the following steps:

[0259] S31, The actual dry flue gas volume V obtained from step S12-6 fg.d.AH.lv The carbon content (C) of the collected fuel received. ar 1. Ash content of fuel received A ar CO2 concentration C at the dry ground state flue gas exhaust point CO2 CO concentration C at the dry ground state flue gas exhaust point CO Fly ash combustible content C as 1. Combustible content of slag C s The corrected ash content of the slag as a percentage of the total ash content of the fuel fed into the furnace, α, is obtained. s.xz.1 (%)

[0260]

[0261] Among them, M C is the molar mass of carbon (g / mol);

[0262] V mol The molar volume (L / mol) of an ideal gas;

[0263] In practical applications, MC A fixed value, 12 g / mol; V mol The value is fixed at 22.4 L / mol.

[0264] S32. The mass fraction α of the corrected ash content in the slag relative to the total ash content of the fuel fed into the furnace, obtained in step S31. s.xz.1 The corrected fly ash content as a percentage of the total ash content of the fuel fed into the furnace, α, was obtained. as.xz.1 (%)

[0265] α as.xz.1 =100-α s.xz.1 (Formula 59);

[0266] S33. The mass fraction α of the corrected ash content of the slag relative to the total ash content of the fuel fed into the furnace, obtained in step S31. s.xz.1 The corrected fly ash content as a percentage of the total ash content of the fuel entering the furnace, obtained in step S32. as.xz.1 The average combustible mass fraction ω of the ash obtained in step S11-1 is then processed sequentially. c.rs.m The actual carbon mass fraction ω of the fuel fed into the furnace obtained in step S12-1. c.b The corrected theoretical dry air quantity V obtained in step S12-2 a.d.th.cr The corrected theoretical dry flue gas quantity V obtained in step S12-3 fg.d.th.cr The process is updated to finally complete the update of the actual dry flue gas volume V obtained in step S12-6. fg.d.AH.lv Update;

[0267] S34. The updated actual dry flue gas volume V obtained in step S33 fg.d.AH.lv Substitute this into step S31 to complete the adjustment of the mass fraction α of the corrected slag ash content relative to the total ash content of the fuel fed into the furnace. s.xz.1 Update;

[0268] S35. Determine the mass fraction α of slag ash content relative to the total ash content of fuel fed into the furnace in two consecutive revisions before and after the update. s.xz.1 Is the absolute value of the difference less than 0.01%? If yes, proceed to step S37; if no, proceed to step S36.

[0269] S36. Repeat steps S32, S33, S34 and S35;

[0270] S37. The updated and corrected ash content of the slag as a percentage of the total ash content of the fuel fed into the furnace, α. s.xz.1 Substituting into formula 59, we can complete the calculation of the mass fraction α of fly ash content relative to the total ash content of the fuel entering the furnace. as.xz.1 The update was performed, and formulas 1 to 57 were updated to complete the correction of boiler fuel efficiency η′.

[0271] In this preferred embodiment, a specific implementation method for correcting the boiler fuel efficiency η′ is provided, thereby improving the accuracy of the corrected boiler fuel efficiency η′ obtained in real time online.

[0272] Specific Implementation Method Two: The difference between this implementation method and Specific Implementation Method One is that the data collected by the DCS data acquisition system 1, the online flue gas measurement and data recording system 2, the online fuel / ash / slag composition analysis system 3, and the environmental parameter measurement system 4 can be the average value of 2 hours, 4 hours, 8 hours, or 168 hours. The corresponding output boiler fuel efficiency η′ reflects the boiler fuel efficiency over the entire time period of 2 hours, 4 hours, 8 hours, or 168 hours.

[0273] The embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made based on the technical solution of this application should be included within the scope of protection of this application.

Claims

1. A method for on-line calculation of boiler fuel efficiency with correction of ash ratio and external heat, characterized in that, Comprise: S1, based on the boiler fuel efficiency online calculation system, obtain the flue gas loss heat Q2, the gas incomplete combustion loss heat Q3, the solid incomplete combustion loss heat Q4, the boiler heat loss Q5, the ash and slag physical sensible heat loss heat Q6, and the external heat Q ex and the input heat Q in ; In the S1, the external heat Q is obtained ex and specifically includes the following steps: S16-1, use the air preheater inlet air temperature t a1 and the standard state dry air density p air , obtain the density p p.a.d of the air entering the system boundary S16-2, using the air preheater inlet air temperature t a1 , obtaining the instantaneous constant-pressure specific heat capacity c p.a.d of the air entering the system boundary; S16-3, obtaining the density p of the air at the reference temperature t re and the density p of the dry air at the standard state air , obtaining the density p of the air at the reference temperature t p.a.re ; S16-4, obtaining the instantaneous specific heat capacity c of the air at the reference temperature t re p.a.re ;​ S16-5, the corrected theoretical dry air amount V a.d.th.cr , the corrected excess air factor a cr , the density p of air entering the system boundary p.a.d , the instantaneous specific heat capacity c of air entering the system boundary at constant pressure p.a.d , the density p of air at a reference temperature p.a.re , the instantaneous specific heat capacity c of air at a reference temperature at constant pressure p.a.re , the air preheater inlet air temperature t a1 , the reference temperature t re , and the dry air density p at a standard state air , the heat Q carried by dry air entering the system is obtained a.d ; S16-6, utilize the air preheater inlet air temperature t a1 , obtain the instantaneous constant-pressure specific heat capacity c p.wv of the water vapor entering the system boundary S16-7, corrected theoretical dry air amount V a.d.th.cr , corrected excess air factor a cr , absolute humidity of air h a.ab , instantaneous constant-pressure specific heat capacity c of water vapor entering the system boundary p.wv , air preheater inlet air temperature t a1 , reference temperature t re , and standard-state dry air density p air , obtain the heat Q carried by water vapor in the air entering the system wv ; wherein p wv is the density of water vapor at standard conditions; S16-8, N2 concentration C at the dry base state exhaust gas location N2 O2 concentration C at the dry base state exhaust gas location O2 CO2 concentration C at the dry base state exhaust gas location CO2 CO concentration C at the dry base state exhaust gas location CO and reference temperature t re obtaining the dry exhaust gas instantaneous constant-pressure specific heat capacity c at the reference temperature p.fg.re ; where c' is the instantaneous heat capacity at constant pressure of nitrogen at the reference temperature; and N2.re where c' is the instantaneous heat capacity at constant pressure of nitrogen at the reference temperature; and N2.re where c' is the instantaneous c′ O2.re Cp is the instantaneous specific heat capacity of oxygen at the reference temperature and pressure; c′ CO2.re Cp is the instantaneous constant pressure heat capacity of carbon dioxide at the reference temperature; c′ CO.re Cp is the instantaneous average specific heat capacity of carbon monoxide at the reference temperature; S16-9, N2 concentration C at the dry base state exhaust gas outlet N2 O2 concentration C at the dry base state exhaust gas outlet O2 CO2 concentration C at the dry base state exhaust gas outlet CO2 CO concentration C at the dry base state exhaust gas outlet CO obtaining the dry flue gas density p in the standard state p.fg.d ; where p N2 is the density of nitrogen at standard conditions; p O2 p is the density of oxygen at standard conditions; p CO2 p is the density of carbon dioxide at standard conditions; p CO p is the density of carbon monoxide at standard conditions; S16-10, the dry flue gas density p under the standard state p.fg.d and the reference temperature t re , the dry flue gas density p under the reference temperature t is obtained p.fg.re ; S16-11, the corrected theoretical dry air volume V a.d.th.cr , the corrected excess air factor α cr , the actual dry flue gas volume V fg.d.AH.lv , the density of air at a reference temperature ρ p.a.re , the instantaneous specific heat capacity of air at a reference temperature c p.a.re , the instantaneous specific heat capacity of dry flue gas at a reference temperature c p.fg.re , the dry flue gas density at a standard state ρ p.fg.d , the dry flue gas density at a reference temperature ρ p.fg.re , the reference temperature t re , and the dry air density at a standard state ρ air , the corrected dry flue gas and dry air conversion heat Q xz.1 ; S16-12, the heat Q carried by the dry air entering the system a.d , the heat Q carried by the water vapor in the air entering the system wv and the heat of transformation Q of the dry flue gas and dry air corrected xz.1 , the exogenous heat Q ex ; Q ex = Q a.d + Q wv + Q xz.1 (Formula 56); S2, obtaining the boiler fuel efficiency η'; S3, correcting the boiler fuel efficiency η' by iteration algorithm, thereby obtaining the corrected boiler fuel efficiency η', and finally completing the online calculation of the boiler fuel efficiency.

2. The method of claim 1, wherein the method is characterized by: In the S1, the boiler heat loss Q5 is obtained, specifically comprising the following steps: S15-1, obtain the boiler heat loss Q under the maximum output 5.BMCR ; When Q r ≤ 40, When 40 < Q r ≤ 1500, where Q r is the rated output of the boiler, MW; S15-2, utilize the average temperature t of the outer surface of the boiler a2 and the ambient temperature t near the boiler body a3 , obtain the temperature difference t of the outer surface of the boiler a4 ; t a4 = t a2 - t a3 (Formula 28); S15-3, Based on the temperature difference t on the outer surface of the boiler a4 To obtain different fixed wind speeds v i Boiler surface radiant power E i Where i = 0, 1, 2, 3, 4, 5, 6, 7, as detailed below: When v0=0.0 m / s, E0=0 (formula 29); when v1 = 0.5 m / s, when v2 = 1.5 m / s, when v3 = 3.0 m / s, when v4 = 4.5 m / s, when v5 = 6.0 m / s, when v6 = 7.5 m / s, when v7 = 9.0 m / s, S15-4. Selecting the lower boundary fixed wind speed v from the wind speed v near the boiler body and the eight fixed wind speeds involved in the formulas 29 to 36 k and the upper boundary fixed wind speed v k+1 , satisfying the requirements as follows: v k <v≤v k+1 (Equation 37); k＝0、1、2、3、4、5、6； S15-5, according to the selected lower boundary fixed wind speed v k and the upper boundary fixed wind speed v k+1 , in formulas 29 to 36, select the corresponding E k and E k+1 , where E k is the lower boundary boiler surface radiation rate, E k+1 is the upper boundary boiler surface radiation rate; S15-6, the lower boundary fixed wind speed v selected k and the upper boundary fixed wind speed v k+1 , the lower boundary boiler surface radiation rate E selected k and the upper boundary boiler surface radiation rate E k+1 , and the wind speed v near the boiler body, the final boiler surface radiation rate E is obtained; S15-7, using the boiler main feed water mass flow D out , the boiler main feed water temperature t zgs , the boiler main feed water pressure p zgs , the boiler main steam temperature t zzq , and the boiler main steam pressure p zzq , to obtain the actual boiler output heat Q out ; Q out = D out × (h zzq - h zgs ) (Equation 39); wherein h zzq is the enthalpy of the main steam of the boiler; h zgs h for the boiler main feed water enthalpy; S15-8, the boiler heat loss Q under the maximum output 5.BMCR , the final boiler surface radiation rate E, the actual boiler heat output Q out and the rated boiler heat output Q r , the boiler heat loss Q5 is obtained; where Q BMCR is the maximum continuous output of the boiler.

3. The method of claim 2, wherein the method is characterized by: The specific steps of the S3 are: S31, the actual dry flue gas volume V fg.d.AH.lv , the fuel received base carbon content C ar , the fuel received base ash content A ar , the dry base state exhaust gas CO2 concentration C CO2 , the dry base state exhaust gas CO concentration C CO , the fly ash combustible content C as , and the slag combustible content C s , the mass fraction α of the corrected slag ash content in the total ash content of the fuel into the furnace is obtained s.xz.1 ; wherein M C is the molar mass of the carbon element; V mol Molar volume of an ideal gas; S32, according to the corrected furnace slag ash content of the total ash content of the fuel mass fraction a s.xz.1 , the corrected fly ash ash content of the total ash content of the fuel mass fraction a as.xz.1 ; a as.xz.1 = 100 - a s.xz.1 (Formula 59); S33, according to the corrected furnace slag ash content of total ash content of fuel into the mass fraction α s.xz.1 and the corrected fly ash ash content of total ash content of fuel into the mass fraction α as.xz.1 , in turn, the average ash slag mass fraction ω c.rs.m , the actual carbon burned into the mass fraction of fuel ω c.b , the corrected theoretical dry air volume V a.d.th.cr and the corrected theoretical dry flue gas volume V fg.d.th.cr Update, eventually complete the actual dry flue gas volume V fg.d.AH.lv Update; S34, updating the actual dry flue gas volume V fg.d.AH.lv The step S31 is entered, and the updating of the corrected mass fraction a of the ash content of the slag in the total ash content of the fuel fed into the furnace is completed. s.xz.1 of the fuel fed into the furnace is completed. S35, judging whether the mass fraction of the ash content of the slag in the total ash content of the fuel into the furnace before and after the two adjacent corrections is α s.xz.1 whether the absolute value of the difference between the two adjacent corrections is less than 0.01%; if the result is yes, step S37 is executed; if the result is no, step S36 is executed; S36, repeating the steps S32 to S35; S37. The updated and corrected ash content of the slag as a percentage of the total ash content of the fuel fed into the furnace, α. s.xz.1 Substituting into Formula 59, the mass fraction α of the corrected fly ash content relative to the total ash content of the fuel fed into the furnace is calculated. as.xz.1 The system is updated to correct the boiler fuel efficiency η′.

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