Calculation method for boiler thermal efficiency variable quantity under variable working conditions and storage medium

Abstract

The invention discloses a calculation method of boiler thermal efficiency variation under variable working conditions and a storage medium, and belongs to the technical field of thermal equipment performance diagnosis. According to the calculation method for the boiler thermal efficiency variable quantity under the variable working condition, the heat loss variable quantity expression of the boiler and the variable quantity expression of the boiler thermal efficiency are established based on the influence of the variable working condition on the boiler thermal efficiency, and the calculation method is not limited to a theoretical model under a steady-state working condition any more; the actual performance of the boiler under the dynamic working condition can be reflected more accurately; the variable quantity of the thermal efficiency of the boiler is calculated by combining the rated operating parameters and the actual operating parameters of the boiler, so that the operating efficiency of the boiler can be evaluated and optimized more accurately, the energy utilization efficiency is effectively improved, energy consumption is reduced by reducing unnecessary energy loss, and the energy utilization rate is improved. And the trend of energy structure optimization in China and the sustainable development requirement of the power industry are met.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal equipment performance diagnosis, and particularly relates to a calculation method and a storage medium for the change amount of boiler thermal efficiency under variable working conditions. Background Art

[0002] With the continuous optimization of China's energy structure and the sustainable development requirements of the power industry, coal-fired power units still play an important role in power production. However, in the face of the operating requirements under different load conditions, how to improve the thermal efficiency of boilers, reduce energy consumption, and reduce environmental pollution has become a key issue in the development of modern coal-fired power unit technology.

[0003] During the actual operation process, the boiler thermal efficiency is affected by various factors, and the variable working condition phenomenon is particularly common. For example, load fluctuations, external environmental temperature changes, etc. These changes directly affect the boiler thermal efficiency, and thus affect the economy and environmental protection of the entire power plant. Currently, the calculation methods for the boiler thermal efficiency of coal-fired power units are mainly based on theoretical models under steady-state working conditions. Although this method can provide a relatively accurate efficiency assessment under steady-state conditions, under variable working conditions, especially in the face of dynamic working conditions such as load regulation, fuel property fluctuations, and steam temperature changes, the traditional boiler thermal efficiency calculation methods have obvious limitations and cannot accurately reflect the actual performance of the boiler under dynamic working conditions.

[0004] Therefore, developing a method that can accurately calculate the boiler thermal efficiency under variable working conditions is of great significance for improving the operating efficiency of coal-fired power units, reducing energy consumption, and reducing environmental pollution. Summary of the Invention

[0005] The purpose of the present invention is to provide a calculation method and a storage medium for the change amount of boiler thermal efficiency under variable working conditions, aiming to solve the limitations of the existing boiler thermal efficiency calculation method based on steady-state working conditions in dealing with dynamic changing environments, so as to more accurately capture and reflect the actual performance of the boiler under complex and variable working conditions, and overcome the problem that the traditional method cannot accurately evaluate the boiler thermal efficiency under variable working conditions.

[0006] The present invention solves the above technical problems through the following technical solutions: A calculation method for the change amount of boiler thermal efficiency under variable working conditions includes the following steps: S1. Establish an expression for the heat loss of the boiler, and differentiate the expression for the heat loss of the boiler to obtain an expression for the change amount of the heat loss of the boiler; S2. Based on the boiler indirect balance method, establish an expression for the boiler thermal efficiency under non-variable working conditions; differentiate the expression for the boiler thermal efficiency to obtain an expression for the change amount of the boiler thermal efficiency; S3. Obtain the rated operating parameters and actual operating parameters of the boiler, and calculate the change in boiler thermal efficiency by combining the expression for the change in boiler heat loss and the expression for the change in boiler thermal efficiency.

[0007] A further improvement of the present invention is that: the boiler heat loss expression specifically includes an expression for heat loss due to flue gas discharge, an expression for heat loss due to incomplete combustion of gas, an expression for heat loss due to incomplete combustion of solid, an expression for heat dissipation loss, and an expression for physical heat loss of ash; the change in boiler heat loss specifically includes a change in heat loss due to flue gas discharge, a change in heat loss due to incomplete combustion of gas, a change in heat loss due to incomplete combustion of solid, a change in heat dissipation loss, and a change in physical heat loss of ash.

[0008] A further improvement of the present invention is that: establishing the expression for heat loss due to flue gas discharge of the boiler specifically includes the following steps: S11. Based on the condition of variable operating conditions with the same coal type, the boiler flue gas discharge temperature is a function related to the excess air coefficient and the boiler load, and establish the boiler flue gas discharge temperature expression, specifically:

[0009] Wherein, is the boiler flue gas discharge temperature under the actual load; is the boiler flue gas discharge temperature under the rated load; is the ambient temperature under the rated load; t is the ambient temperature under the actual load; is the excess air coefficient under the rated load; is the excess air coefficient under the actual load; is the boiler rated load; is the boiler actual load; S12. Differentiate the boiler flue gas discharge temperature expression to obtain the expression for the change in boiler flue gas discharge temperature, specifically:

[0010] Wherein, is the change in boiler flue gas discharge temperature; is the change in excess air coefficient; is the change in boiler load; is the change in ambient temperature; S13. Based on the relationship between the boiler flue gas heat loss and the flue gas volume and specific heat generated by fuel combustion, obtain the flue gas heat loss expression, specifically:

[0011] Wherein, is the flue gas volume generated per kilogram of fuel; is the specific heat of flue gas; is the proportionality coefficient; S14. Differentiate the expression for the heat loss due to flue gas discharge to obtain the expression for the change in the heat loss due to flue gas discharge, specifically:

[0012] where, is the change in the heat loss due to flue gas discharge.

[0013] A further improvement of the present invention lies in: establishing the expression for the heat loss due to incomplete combustion of gas in the boiler, which specifically includes the following steps: S21. Based on the relationship between the carbon monoxide content in the dry flue gas, the oxygen content during boiler operation, and the boiler load adjustment parameter, establish the expression for the carbon monoxide content in the dry flue gas, specifically:

[0014] where, is the carbon monoxide content in the dry flue gas; is the boiler load adjustment parameter, ; is the oxygen content during boiler operation; S22. Differentiate the expression for the carbon monoxide content in the dry flue gas to obtain the expression for the change in the carbon monoxide content in the dry flue gas, specifically:

[0015] where, is the change in the carbon monoxide content in the dry flue gas, is the change in the oxygen content during boiler operation; S23. Based on the relationship between the dry flue gas volume, the excess air coefficient 、 and the theoretical air volume, establish the expression for the dry flue gas volume generated per kilogram of fuel, specifically:

[0016] where, is the dry flue gas volume generated per kilogram of fuel; α is the excess air coefficient; is the theoretical air volume; is the lower calorific value; S24. Differentiate the expression for the dry flue gas volume generated per kilogram of fuel to obtain the expression for the change in the dry flue gas volume generated per kilogram of fuel, specifically:

[0017] where, is the change in the dry flue gas volume generated per kilogram of fuel; α is the change in the excess air coefficient; is the change in the lower calorific value; S25. Based on the relationship between the heat loss due to incomplete combustion of gas, the volume of dry flue gas generated by the fuel, and the carbon monoxide content in the dry flue gas, establish an expression for the heat loss due to incomplete combustion of gas, specifically:

[0018] where, is the heat loss due to incomplete combustion of gas; S25. Differentiate the expression for the heat loss due to incomplete combustion of gas to obtain an expression for the change in the heat loss due to incomplete combustion of gas, specifically:

[0019] where, is the change in the heat loss due to incomplete combustion of gas.

[0020] A further improvement of the present invention lies in: establishing an expression for the heat loss due to incomplete combustion of solids in the boiler, which specifically includes the following steps: S31. Based on the combustion characteristics of solid combustibles, establish an expression for the heat loss due to incomplete combustion of solids, specifically:

[0021] where, is the heat loss due to incomplete combustion of solids; is the unburned carbon content per kilogram of fuel; 33727 is the calorific value of pure carbon; S32. Differentiate the expression for the heat loss due to incomplete combustion of solids to obtain an expression for the change in the heat loss due to incomplete combustion of solids, specifically:

[0022] where, is the change in the heat loss due to incomplete combustion of solids; is the unburned carbon content per kilogram of fuel; is the change in the unburned carbon content per kilogram of fuel.

[0023] A further improvement of the present invention lies in: establishing an expression for the heat loss due to heat dissipation of the boiler, which specifically includes the following steps: S41. Fit the heat loss due to heat dissipation of the boiler under different operating conditions to obtain an expression for the heat loss due to heat dissipation, specifically:

[0024] S42. Differentiate the expression for the heat loss due to heat dissipation to obtain an expression for the change in the heat loss due to heat dissipation, specifically:

[0025] Among them, is the change in heat loss due to heat dissipation.

[0026] A further improvement of the present invention lies in: establishing an expression for the physical heat loss of boiler ash slag specifically includes the following steps: S51. Based on the characteristics of the heat carried away by the ash slag discharged from the boiler, establish an expression for the physical heat loss of the ash slag, specifically:

[0027] Among them, is the ash content of the coal type; is the fly ash fraction; is the specific heat capacity of the fly ash; is the slag fraction; is the specific heat capacity of the ash slag; is the ash slag temperature; S52. Differentiate the expression for the physical heat loss of the ash slag to obtain an expression for the change in the physical heat loss of the ash slag, specifically:

[0028] Among them, is the change in the physical heat loss of the ash slag; is the heat generated by the slag; is the slag temperature; is the change in the ash content of the coal type.

[0029] A further improvement of the present invention lies in: the expression for the boiler thermal efficiency under non-variable operating conditions is specifically:

[0030] Among them, is the boiler thermal efficiency.

[0031] A further improvement of the present invention lies in: the expression for the change in the boiler thermal efficiency:

[0032] Among them, is the change in the boiler thermal efficiency.

[0033] The present invention also provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the method for calculating the boiler thermal efficiency under variable operating conditions as described above are implemented.

[0034] Compared with the prior art, the positive and progressive effects of the present invention are: The calculation method for the change in boiler thermal efficiency under variable operating conditions provided by the present invention, based on the influence of variable operating conditions on boiler thermal efficiency, respectively establishes an expression for the change in boiler heat loss and an expression for the change in boiler thermal efficiency, no longer limited to the theoretical model under steady-state conditions, and can more accurately reflect the actual performance of the boiler under dynamic conditions; by combining the rated operating parameters and actual operating parameters of the boiler, calculating the change in boiler thermal efficiency can more precisely evaluate and optimize the operating efficiency of the boiler, thereby effectively improving energy utilization efficiency. By reducing unnecessary energy losses, it helps to reduce energy consumption, meeting the trend of optimizing China's energy structure and the sustainable development needs of the power industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings in the specification are used to provide a further understanding of the present invention and form a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0036] Figure 1 It is a schematic flow chart of a calculation method for the change in boiler thermal efficiency under variable operating conditions of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The following further describes the present invention in detail with reference to the accompanying drawings and specific embodiments, which is an explanation rather than a limitation of the present invention.

[0038] See Figure 1 , a calculation method for the change in boiler thermal efficiency under variable operating conditions, comprising the following steps: S1. Establish an expression for boiler heat loss, and differentiate the expression for boiler heat loss to obtain an expression for the change in boiler heat loss; S2. Based on the boiler inverse balance method, establish an expression for boiler thermal efficiency under non-variable operating conditions; differentiate the expression for boiler thermal efficiency to obtain an expression for the change in boiler thermal efficiency; S3. Obtain the rated operating parameters and actual operating parameters of the boiler, and combine the expression for the change in boiler heat loss and the expression for the change in boiler thermal efficiency to calculate the change in boiler thermal efficiency.

[0039] The calculation method for the change in boiler thermal efficiency under variable operating conditions provided by the present invention, based on the impact of variable operating conditions on boiler thermal efficiency, respectively establishes an expression for the change in boiler heat loss and an expression for the change in boiler thermal efficiency. It is no longer limited to the theoretical model under steady-state conditions and can more accurately reflect the actual performance of the boiler under dynamic conditions. By combining the rated operating parameters and actual operating parameters of the boiler to calculate the change in boiler thermal efficiency, it can more precisely evaluate and optimize the operating efficiency of the boiler, thereby effectively improving energy utilization efficiency. By reducing unnecessary energy losses, it helps to reduce energy consumption and meets the trends of optimizing China's energy structure and the sustainable development needs of the power industry.

[0040] Specifically, the boiler heat loss expression specifically includes an expression for heat loss due to flue gas discharge, an expression for heat loss due to incomplete combustion of gas, an expression for heat loss due to incomplete combustion of solid, an expression for heat dissipation loss, and an expression for physical heat loss of ash and slag; the change in boiler heat loss specifically includes the change in heat loss due to flue gas discharge, the change in heat loss due to incomplete combustion of gas, the change in heat loss due to incomplete combustion of solid, the change in heat dissipation loss, and the change in physical heat loss of ash and slag.

[0041] Specifically, establishing the expression for heat loss due to flue gas discharge of the boiler specifically includes the following steps: S11. Based on the variable operating conditions of the same coal type, the boiler flue gas discharge temperature is a function related to the excess air coefficient and the boiler load, and an expression for the boiler flue gas discharge temperature is established, specifically:

[0042] Among them, is the boiler flue gas discharge temperature under the actual load; is the boiler flue gas discharge temperature under the rated load; is the ambient temperature under the rated load; t is the ambient temperature under the actual load; is the excess air coefficient under the rated load; is the excess air coefficient under the actual load; is the boiler rated load; is the boiler actual load; S12. Differentiate the expression for the boiler flue gas discharge temperature to obtain an expression for the change in the boiler flue gas discharge temperature, specifically:

[0043] Among them, is the change in the boiler flue gas discharge temperature; is the change in the excess air coefficient; is the change in the boiler load; is the change in the ambient temperature; S13. Based on the relationship between the heat loss due to boiler flue gas and the volume and specific heat of the flue gas generated by fuel combustion, the expression for heat loss due to flue gas is obtained, specifically as follows:

[0044] Among them, is the volume of flue gas generated per kilogram of fuel; is the specific heat of the flue gas; is the proportionality coefficient; S14. Differentiate the expression for heat loss due to flue gas to obtain the expression for the change in heat loss due to flue gas, specifically as follows:

[0045] Among them, is the change in heat loss due to flue gas.

[0046] Specifically, establishing the expression for heat loss due to incomplete combustion of gas in the boiler specifically includes the following steps: S21. Based on the relationship between the carbon monoxide content in dry flue gas, the oxygen content during boiler operation, and the boiler load adjustment parameter, establish the expression for the carbon monoxide content in dry flue gas, specifically as follows:

[0047] Among them, is the carbon monoxide content in dry flue gas; is the boiler load adjustment parameter, ; is the oxygen content during boiler operation; S22. Differentiate the expression for the carbon monoxide content in dry flue gas to obtain the expression for the change in the carbon monoxide content in dry flue gas, specifically as follows:

[0048] Among them, is the change in the carbon monoxide content in dry flue gas, is the change in the oxygen content during boiler operation; S23. Based on the relationship between the volume of dry flue gas, the excess air coefficient 、 and the theoretical air volume, establish the expression for the volume of dry flue gas that can be generated per kilogram of fuel, specifically as follows:

[0049] Among them, is the volume of dry flue gas that can be generated per kilogram of fuel; α is the excess air coefficient; is the theoretical air volume; is the lower calorific value; S24. Differentiate the expression for the dry flue gas volume per kilogram of fuel to obtain the expression for the change in the dry flue gas volume per kilogram of fuel, specifically:

[0050] where, is the change in the dry flue gas volume per kilogram of fuel; α is the change in the excess air coefficient; is the change in the lower calorific value; S25. Based on the relationship between the heat loss due to incomplete combustion of gas and the volume of dry flue gas generated by the fuel and the carbon monoxide content in the dry flue gas, establish the expression for the heat loss due to incomplete combustion of gas, specifically:

[0051] where, is the heat loss due to incomplete combustion of gas; S25. Differentiate the expression for the heat loss due to incomplete combustion of gas to obtain the expression for the change in the heat loss due to incomplete combustion of gas, specifically:

[0052] where, is the change in the heat loss due to incomplete combustion of gas.

[0053] Specifically, establishing the expression for the heat loss due to incomplete combustion of solids in the boiler specifically includes the following steps: S31. Based on the combustion characteristics of solid combustibles, establish the expression for the heat loss due to incomplete combustion of solids, specifically:

[0054] where, is the heat loss due to incomplete combustion of solids; is the unburned carbon content per kilogram of fuel; 33727 is the calorific value of pure carbon; S32. Differentiate the expression for the heat loss due to incomplete combustion of solids to obtain the expression for the change in the heat loss due to incomplete combustion of solids, specifically:

[0055] where, is the change in the heat loss due to incomplete combustion of solids; is the unburned carbon content per kilogram of fuel; is the change in the unburned carbon content per kilogram of fuel.

[0056] Specifically, establishing the expression for the heat loss due to heat dissipation of the boiler specifically includes the following steps: S41. Fit the heat loss of the boiler under different working conditions to obtain the heat loss expression, specifically:

[0057] S42. Differentiate the heat loss expression to obtain the expression for the change in heat loss, specifically:

[0058] Among them, is the change in heat loss.

[0059] Specifically, establishing the expression for the physical heat loss of boiler ash residues specifically includes the following steps: S51. Based on the characteristics of the heat carried away by the boiler ash residues, establish the expression for the physical heat loss of boiler ash residues, specifically:

[0060] Among them, is the ash content of the coal type; is the fly ash fraction; is the specific heat capacity of fly ash; is the slag fraction; is the specific heat capacity of ash residues; is the ash residue temperature; S52. Differentiate the expression for the physical heat loss of boiler ash residues to obtain the expression for the change in the physical heat loss of boiler ash residues, specifically:

[0061] Among them, is the change in the physical heat loss of boiler ash residues; is the heat generated by slag; is the slag temperature; is the change in the ash content of the coal type.

[0062] Specifically, the expression for the boiler thermal efficiency under non-variable working conditions is specifically:

[0063] Among them, is the boiler thermal efficiency.

[0064] Specifically, the expression for the change in boiler thermal efficiency:

[0065] Among them, is the change in boiler thermal efficiency.

[0066] Based on the same inventive concept, the present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the boiler thermal efficiency calculation method under the above variable operating conditions are implemented.

[0067] Embodiment 1 When the operating conditions change, under the same coal type, it can be considered that the boiler flue gas temperature is only related to the excess air coefficient and the boiler load. That is, the boiler flue gas temperature can be considered as a function related to the excess air coefficient and the boiler load. Thus, the boiler flue gas temperature is:

[0068] Where: is the boiler flue gas temperature under the actual load, °C; is the boiler flue gas temperature under the rated load, °C; is the ambient temperature under the rated load, °C; t is the ambient temperature under the actual load, °C; is the excess air coefficient under the rated load; is the excess air coefficient under the actual load; is the boiler rated load, t / h; is the boiler actual load, t / h; Differentiating the above formula, the change in the flue gas temperature under the change of the boiler load can be obtained as:

[0069] Where: is the change in the boiler flue gas temperature, °C; is the change in the excess air coefficient; is the change in the boiler load, t / h; is the change in the ambient temperature, °C; The boiler flue gas heat loss is mainly related to the flue gas volume and the specific heat of the flue gas Therefore, the boiler flue gas heat loss can be expressed as:

[0070] Where: is the flue gas heat loss, kJ / kg; is the flue gas volume generated per kilogram of fuel, m 3 / kg; is the specific heat of the flue gas, kJ / (kg·K); is the proportionality coefficient; Differentiating the above formula, the change in the boiler flue gas heat loss is obtained as:

[0071] Wherein: is the change in heat loss due to flue gas discharge, kJ / kg; is the change in flue gas discharge temperature under the rated load of the boiler, °C.

[0072] Since the content in dry flue gas is related to the content during boiler operation and the boiler load adjustment parameter during boiler operation, the content can be expressed as:

[0073] Wherein: is the load adjustment parameter, ; is the oxygen content during boiler operation, %; Differentiating the above formula, the change in the content in dry flue gas can be obtained as:

[0074] Wherein: is the change in the content in dry flue gas, is the change in the oxygen content during boiler operation, %; Among them, the dry flue gas volume is mainly related to the excess air coefficient α and the theoretical air volume and is approximately considered to have a certain theoretical relationship with the theoretical air volume and the coal type, that is, the dry flue gas volume produced per kilogram of fuel can be expressed as:

[0075] Wherein: is the theoretical air volume, m 3 / kg; is the lower calorific value, kJ / kg; Differentiating the above formula, the change in the dry flue gas volume produced per kilogram of fuel can be expressed as:

[0076] Wherein: is the change in the dry flue gas volume produced per kilogram of fuel, mainly related to the coal type and the excess air coefficient, kJ / kg; Also, the heat loss due to incomplete combustion of gas is related to the dry flue gas volume produced by the fuel and the concentration in the dry flue gas and can be expressed as:

[0077] Among them: is the volume of dry flue gas generated per kilogram of fuel, m 3 / kg; is the content of carbon monoxide in the dry flue gas; 12636 is the volumetric calorific value per cubic meter of gas, kJ / m 3 ; Differentiating the above formula, The change in is mainly related to the change in the content of in the dry flue gas, that is:

[0078] Among them: is the change in the heat loss due to incomplete combustion of gas, kJ / kg.

[0079] The unburned carbon content in the boiler is related to the boiler heat load, coal type characteristics, operating oxygen content, burner operation mode, and pulverized coal fineness. The influence relationship is relatively complex. Therefore, the unburned carbon content per kilogram of fuel can be expressed as:

[0080] Among them: is the coal type characteristic; is the burner operation mode; is the pulverized coal fineness; Therefore, the change in the unburned carbon content per unit mass of fuel can be expressed as:

[0081] Among them: is the change in the coal type characteristic; is the change in the burner operation mode; is the change in the pulverized coal fineness; The change in the unburned carbon content per unit mass of fuel; is and The solution of can be obtained based on the neural network model; Solid incomplete combustion heat loss is the heat loss caused by the incomplete combustion of solid combustibles in the fuel, resulting in part of the heat not being effectively utilized. It is mainly related to the unburned carbon content in the fuel and can be expressed as follows:

[0082] Among them: 33727 is the calorific value of pure carbon, kJ / kg; is the unburned carbon content per kilogram of fuel, kg / kg; Differentiating the above equation, it can be obtained that the change in the carbon content of unburned carbon per kilogram of fuel is the main reason for the change in the heat loss due to incomplete solid combustion. Therefore, the change in the heat loss due to incomplete solid combustion is as follows:

[0083] Where: is the change in the heat loss due to incomplete solid combustion, kJ / kg.

[0084] Heat loss due to boiler heat dissipation Using the empirical calculation formula fitted under different working conditions, it can be expressed as:

[0085] Where: is the heat loss due to boiler heat dissipation, kJ / kg; From the above equation, it can be seen that the heat loss due to boiler heat dissipation is a function of boiler load and coal type. Differentiating the above equation, the change in the heat loss due to boiler heat dissipation can be obtained as:

[0086] Where: is the change in the heat loss due to boiler heat dissipation, kJ / kg; is the change in the lower calorific value, kJ / kg.

[0087] Heat loss due to physical heat of ash and slag It is the loss caused by the fact that the ash and slag discharged from the boiler have a very high temperature and take away a part of the heat when discharged, and this part of the heat has not been utilized on the boiler. It can be expressed as:

[0088] Where: is the ash content of the coal type, %; is the fly ash fraction, and its value is taken as 0.9; is the specific heat capacity of fly ash, kJ / (kg·K); is the slag fraction, and its value is taken as 0.1; is the specific heat capacity of ash and slag, kJ / (kg·K); is the ash and slag temperature, °C; Differentiating the above equation, the change in the physical heat loss of ash and slag can be obtained as:

[0089] Where: is the change in the physical heat loss of ash and slag, kJ / kg; is the heat generated by slag, kJ / kg; is the slag temperature, °C; is the change in the ash content of the coal type, %. The heat balance of a boiler refers to the balance between the input heat and the output heat of the boiler. The input heat mainly comes from the heat released by fuel combustion. Due to various reasons, the fuel entering the furnace cannot be completely burned, and the heat released by the fuel cannot be fully and effectively utilized. Inevitably, a part of the loss will occur. Therefore, the boiler thermal efficiency is introduced to reflect the economic operation of the boiler. Using the inverse balance boiler calculation method, the boiler thermal efficiency can be expressed as:

[0090] Where: is the boiler thermal efficiency, %; is the heat loss due to flue gas, kJ / kg; is the heat loss due to incomplete combustion of gas, kJ / kg; is the heat loss due to incomplete combustion of solid, kJ / kg; is the heat loss due to heat dissipation, kJ / kg; is the physical heat loss of ash and slag, kJ / kg; is the lower calorific value, kJ / kg; When the operating conditions on the boiler side change, assuming remains unchanged, , , , , will all change, that is, the change amount of the heat loss due to flue gas , the change amount of the heat loss due to incomplete combustion of gas , the change amount of the heat loss due to incomplete combustion of solid , the change amount of the heat loss due to heat dissipation and the change amount of the physical heat loss of ash and slag . To sum up, when the operating conditions on the boiler side change, the change amount of the boiler thermal efficiency is related to , , , , are all related. Differentiating the above formula, the change amount of the boiler thermal efficiency is: Where: is the change amount of the boiler thermal efficiency.

[0091] Obtain the rated operating parameters and actual operating parameters of the boiler. Taking the operating parameters of a power plant boiler as an example, the rated operating parameters and actual operating parameters of the boiler are collected as shown in Table 1.

[0092] Table 1 Rated operating parameters and actual operating parameters of the boiler

[0093] The exhaust gas temperature of the boiler is:

[0094] The change in the exhaust gas temperature after the boiler load changes is: = 14.566266 °C The heat loss due to exhaust gas of the boiler is:

[0095] The change in the heat loss due to exhaust gas after the boiler load changes is: = -1323.0126 kJ / kg The volume of dry flue gas that can be produced per kilogram of fuel is:

[0096] During the operation of the boiler The content is:

[0097] In the dry flue gas The change in content is: = 20.186769 The heat loss due to incomplete combustion of gas after the boiler load changes is:

[0098] The change in the heat loss due to incomplete combustion of gas after the boiler load changes is: = 7.380272 kJ / kg The heat loss due to incomplete combustion of solids after the boiler load changes is:

[0099] The change in the heat loss due to incomplete combustion of solids after the boiler load changes is: = 33.727 kJ / kg The heat loss due to heat dissipation after the boiler load changes is:

[0100] The change in the heat loss due to heat dissipation after the boiler load changes is: = -62.7816 kJ / kg The heat loss due to the physical heat of ash and slag after the boiler load changes is:

[0101] The change in the heat loss due to the physical heat of ash and slag after the boiler load changes is: =2.601396 kJ / kg The change in the boiler thermal efficiency after the boiler load changes is as follows:

[0102] The calculation method for the change in the boiler thermal efficiency under variable operating conditions proposed by the present invention is based on the following conceptions: 1. The boiler inverse balance method is a simplified thermal efficiency calculation method based on the principle of energy conservation. Its core idea is to indirectly calculate the actual thermal efficiency by analyzing various energy losses in the boiler system. Different from the traditional direct balance method, which calculates the thermal efficiency by calculating the ratio of the heat input and heat output energy of the boiler, the inverse balance method focuses on the inevitable energy losses during the operation of the boiler, and then calculates the actually effectively utilized heat energy of the boiler by subtracting these loss parts.

[0103] 2. In the inverse balance method, the heat losses of the boiler can be divided into multiple aspects, mainly including flue gas loss, heat loss due to incomplete combustion of gas, heat loss due to incomplete combustion of solid, heat dissipation loss, and physical heat loss of ash residue, etc. These losses will directly affect the overall efficiency of the boiler. Therefore, the inverse balance method obtains the actual thermal efficiency of the boiler through accurate estimation of these losses.

[0104] Based on the above conceptions, the present invention further proposes the principle followed by the technical solution of the present invention according to the characteristics of the boiler mass balance and energy balance, that is: 1. The flue gas temperature of the boiler is approximately regarded as a function of the boiler load and the boiler excess air coefficient. An empirical equation is used to determine the flue gas temperature of the boiler after the boiler boundary conditions change, and the operating oxygen content can be jointly determined by the heat loss due to incomplete combustion of solid and the excess air coefficient; 2. 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 using an empirical equation, the heat loss due to incomplete combustion of gas can be calculated; 3. The physical heat loss of ash residue is determined by using the ash content and the unburned carbon content, and the boiler heat dissipation loss is only related to the boiler load. Thus, the physical heat loss of ash residue and the boiler heat dissipation loss can be calculated. The method of the present invention overcomes the technical defect of the cumbersome calculation process of the boiler thermal efficiency during variable operating condition analysis. The calculation method of the present invention is simple, accurate and scientific. By calculating various heat losses of the boiler and using the boiler inverse balance method, the change in the boiler thermal efficiency after variable operating conditions can be calculated.

[0105] Based on the same inventive concept, embodiments of the present application provide a computer-readable storage medium. The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the optimization method for supercapacitor energy storage frequency modulation are implemented. Specifically, the computer-readable storage medium includes, but is not limited to, for example, volatile memory and / or non-volatile memory. The volatile memory may include RAM (Random Access Memory) and / or cache, etc. The non-volatile memory may include ROM (Read-Only Memory), hard disk, flash memory, optical disc, magnetic disk, etc.

[0106] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications that fall within the scope of the present invention.

[0107] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these changes and modifications.

Claims

1. A method for calculating the change in boiler thermal efficiency under variable operating conditions, characterized in that: The following steps are involved: S1. Establish a heat loss expression for the boiler, differentiate the heat loss expression for the boiler, and obtain an expression for the change in heat loss of the boiler; S2. Based on the boiler counter-balance method, establish the boiler thermal efficiency expression under non-variable operating conditions; Differentiate the boiler thermal efficiency expression to obtain the boiler thermal efficiency change expression; S3. Obtain the rated operating parameters and actual operating parameters of the boiler, and calculate the change in the boiler thermal efficiency by combining the expression for the change in the heat loss of the boiler and the expression for the change in the thermal efficiency of the boiler.

2. The method for calculating boiler thermal efficiency under variable operating conditions according to claim 1, characterized in that: The heat loss expression of the boiler specifically includes the heat loss expression of flue gas, the heat loss expression of incomplete combustion of gas, the heat loss expression of incomplete combustion of solid, the heat loss expression of heat dissipation and the physical heat loss expression of ash; the heat loss change of the boiler specifically includes the change of heat loss of flue gas, the heat loss change of incomplete combustion of gas, the heat loss change of incomplete combustion of solid, the heat loss change of heat dissipation and the physical heat loss change of ash.

3. The method for calculating boiler thermal efficiency under variable operating conditions according to claim 2, characterized in that: The establishment of the boiler exhaust heat loss expression specifically includes the following steps: S11. Based on the fact that the boiler exhaust temperature is a function related to the excess air coefficient and boiler load under the same coal type and variable operating conditions, an expression for the boiler exhaust temperature is established, specifically: in, is the boiler exhaust temperature under actual load; is the exhaust gas temperature of the boiler under rated load; is the ambient temperature under rated load; t is the ambient temperature under actual load; is the excess air coefficient under rated load; is the excess air coefficient under actual load; is the rated load of the boiler; is the actual load of the boiler; S12. Differentiate the boiler exhaust temperature expression to obtain the boiler exhaust temperature change expression, which is: in, is the change in boiler exhaust temperature; is the change of excess air coefficient; is the change in boiler load; is the change in ambient temperature; S13. Based on the relationship between the heat loss of boiler flue gas and the flue gas volume and specific heat of the flue gas generated by fuel combustion, the heat loss expression of flue gas is obtained, which is: in, is the volume of smoke produced per kilogram of fuel; is the specific heat of flue gas; is the proportionality coefficient; S14. Differentiate the exhaust heat loss expression to obtain the variation expression of the exhaust heat loss, which is: in, is the change in exhaust heat loss.

4. The method for calculating boiler thermal efficiency under variable operating conditions according to claim 3, characterized in that: The establishment of the boiler gas incomplete combustion heat loss expression specifically includes the following steps: S21. Based on the relationship between the carbon monoxide content in dry flue gas and the oxygen content of boiler operation and boiler load adjustment parameters, an expression for the carbon monoxide content in dry flue gas is established, specifically: in, is the carbon monoxide content in dry flue gas; For boiler load adjustment parameters, ; Oxygen content for boiler operation; S22. Differentiate the expression of carbon monoxide content in dry flue gas to obtain the expression of the change of carbon monoxide content in dry flue gas, which is specifically: in, is the change in carbon monoxide content in dry flue gas, is the change in oxygen content during boiler operation; S23, based on dry flue gas volume and excess air coefficient 、 The relationship between the theoretical air volume and the dry flue gas volume that can be produced per kilogram of fuel is established, specifically: in, It is the volume of dry flue gas that can be produced per kilogram of fuel; α is the excess air coefficient; is the theoretical air volume; It is low heat; S24. Differentiate the expression of the dry flue gas volume that can be generated per kilogram of fuel to obtain the expression of the change in the dry flue gas volume generated per kilogram of fuel, which is specifically: in, It is the change in dry flue gas volume produced per kilogram of fuel; α is the change of excess air coefficient; is the change in low-level calorific value; S25. Based on the relationship between the heat loss of incomplete combustion of gas, the volume of dry flue gas generated by the fuel, and the carbon monoxide content in the dry flue gas, an expression for the heat loss of incomplete combustion of gas is established, specifically: in, Heat loss due to incomplete combustion of gas; S25. Differentiate the expression for heat loss from incomplete combustion of gas to obtain the expression for the change in heat loss from incomplete combustion of gas, which is specifically: in, is the change in heat loss due to incomplete combustion of gas.

5. The method for calculating boiler thermal efficiency under variable operating conditions according to claim 4, characterized in that: The establishment of the boiler solid incomplete combustion heat loss expression specifically includes the following steps: S31. Based on the combustion characteristics of solid combustibles, an expression for heat loss from incomplete combustion of solids is established, specifically: in, Heat loss due to incomplete combustion of solids; is the unburned carbon content per kilogram of fuel; 33727 is the calorific value of pure carbon; S32. Differentiate the solid incomplete combustion heat loss expression to obtain the change expression of the solid incomplete combustion heat loss, which is specifically: in, is the change in heat loss from incomplete combustion of solids; is the unburned carbon content per kilogram of fuel; It is the change in unburned carbon content per kilogram of fuel.

6. The method for calculating boiler thermal efficiency under variable operating conditions according to claim 5, characterized in that: The establishment of the heat loss expression of the boiler includes the following steps: S41. Fit the heat dissipation loss of the boiler under different working conditions to obtain the heat dissipation loss expression, which is specifically: S42. Differentiate the heat dissipation loss expression to obtain the change expression of the heat dissipation loss, which is specifically: in, is the change in heat loss.

7. The method for calculating boiler thermal efficiency under variable operating conditions according to claim 6, characterized in that: The establishment of the boiler ash physical heat loss expression specifically includes the following steps: S51. Based on the characteristics of boiler ash taking away heat, an expression for ash physical heat loss is established, which is: in, Ash content of coal; is the fly ash share; is the specific heat capacity of fly ash; is the slag share; is the specific heat capacity of ash; is the ash temperature; S52. Differentiate the expression of ash physical heat loss to obtain the expression of the change of ash physical heat loss, which is specifically: in, is the change in physical heat loss of ash; The heat generated by the slag; is the slag temperature; is the change in ash content of coal type.

8. The method for calculating boiler thermal efficiency under variable operating conditions according to claim 7, characterized in that: The boiler thermal efficiency expression under non-variable operating conditions is as follows: in, is the boiler thermal efficiency.

9. The method for calculating boiler thermal efficiency under variable operating conditions according to claim 8, characterized in that: The expression of the change of boiler thermal efficiency is: in, is the change in boiler thermal efficiency.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for calculating the thermal efficiency of a boiler under variable operating conditions described in any one of claims 1 to 9 are implemented.

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