Quantitative calculation method for influence of steam pressure change of once-through boiler on thermal efficiency of boiler and related device

Abstract

The invention belongs to the technical field of thermal equipment performance state monitoring and diagnosis, and discloses a quantitative calculation method for the influence of steam pressure change of a once-through boiler on boiler thermal efficiency and a related device. Wherein the quantitative calculation of the influence of the steam pressure change of the once-through boiler on the heat efficiency of the boiler comprises the steps of performing differential processing on a heat balance equation, deducing the influence of the fuel quantity change on the enthalpy value of a main steam working medium, and then calculating the heat efficiency of the boiler by combining a converted temperature empirical equation of the main steam working medium temperature and a steam turbine critical working condition flow approximate calculation equation. Calculating the specific influence of the boiler vapor pressure change on the boiler thermal efficiency, and finally further obtaining and optimizing a calculation model by correcting the variable quantity of the boiler thermal efficiency; according to the method, the defect that the boiler thermal efficiency cannot be accurately calculated and quantitatively analyzed due to the steam pressure change of the boiler can be overcome, the variable quantity delta eta of the boiler thermal efficiency can be quickly, conveniently and accurately calculated only according to the parameters in the reference working condition operation data, the calculation steps are greatly simplified, and the boiler operation efficiency is optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of performance state monitoring and diagnosis of thermal equipment, and particularly relates to a quantitative calculation method for the influence of the steam pressure change of a once-through boiler on the boiler thermal efficiency and related devices. Background Art

[0002] It is very difficult for the operating units and thermal systems to work completely under the designed conditions, because it is very difficult for the systems, equipment, loads and various parameters to be all in the designed states during operation. In this sense, off-design conditions are the main operating conditions. Therefore, it becomes a very necessary and important topic to study the states of the units and systems under off-design conditions, as well as their safety and economy under off-design conditions.

[0003] Performing off-design calculations on the thermal system is the basic method to understand off-design conditions and an important means to explore the safety and economy of the thermal system. It can be said without exaggeration that in-depth analysis and research on the economy of any unit thermal system cannot do without off-design calculations. The main steam pressure and temperature of the boiler are important technical parameters that are key monitored in coal-fired units. Usually, as the boiler combustion rate increases, the main steam pressure and temperature of the unit change, which simultaneously affect the boiler thermal efficiency and the turbine heat consumption rate, and further affect the power generation coal consumption rate and the power supply coal consumption rate of the unit.

[0004] The existing methods for analyzing the influence of the main steam pressure change on the boiler thermal efficiency mainly rely on the off-design thermal calculation method of the boiler unit. Usually, the off-design calculation of the boiler is carried out by detailed thermal calculations for each heating surface. However, the calculation often requires hundreds of complex formulas and numerous heating surface structure parameters. It can be seen that the calculation is very complicated and requires a large amount of original data. Although using computerized calculation will make this calculation more convenient, it is still heavy compared with the tasks of thermal system calculations. Sometimes, due to insufficient original data, the calculation cannot be carried out, resulting in the actual situation that the operating personnel often have to analyze the influence of the main steam pressure change of the unit on the boiler thermal efficiency without effectively obtaining the structure data of the boiler heating surface. Even if the calculation can be carried out, there are still large errors in the results. At this time, it is necessary to construct a more accurate quantitative calculation model for the influence of the boiler steam pressure change on the boiler thermal efficiency. Summary of the Invention

[0005] The object of the present invention is to provide a quantitative calculation method and related device for the influence of the steam pressure change of a once-through boiler on the boiler thermal efficiency, so as to overcome the problems existing in the prior art. The present invention can establish a quantitative calculation model for the influence of the steam pressure change of the boiler on the boiler thermal efficiency, which is convenient for accurately analyzing and calculating the quantitative influence of the steam pressure change on the boiler thermal efficiency only according to the parameters in the operation data of the reference working condition under the off-design conditions of the boiler unit, significantly improving the convenience and efficiency of the calculation, making up for the defect of the large amount of structural data required in the existing methods for calculation, and realizing a more efficient and practical calculation.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] In the first aspect, the present invention provides a quantitative calculation method for the influence of the steam pressure change of a once-through boiler on the boiler thermal efficiency, including the following steps:

[0008] According to the boiler heat balance equation and combining with the differential theory, a function expression between the enthalpy value of the main steam working medium, the boiler fuel quantity and the boiler thermal efficiency is obtained. Then, by differentiating the enthalpy value of the main steam working medium, a function expression between the temperature change amount of the main steam working medium and the enthalpy change amount is obtained;

[0009] According to the approximate calculation equation of the critical condition flow rate of the steam turbine and the empirical equation of the reduced temperature of the main steam working medium, a function expression between the main steam working medium pressure and the main steam working medium temperature is obtained. Combining the function expression between the main steam working medium pressure and the main steam working medium temperature with the function expression between the enthalpy value of the main steam working medium, the boiler fuel quantity and the boiler thermal efficiency obtained above, and the function expression between the temperature change amount of the main steam working medium and the enthalpy change amount, a function expression between the main steam working medium pressure, the boiler fuel quantity change and the boiler thermal efficiency change is obtained;

[0010] A relationship equation between the furnace outlet flue gas temperature and the boiler fuel quantity is established and differentiated. The differentiated relationship equation between the furnace outlet flue gas temperature and the boiler fuel quantity is obtained as the expression of the boiler flue gas temperature change amount through a correction method. Then, according to the change amount expression of the boiler thermal efficiency, the function expression between the main steam working medium pressure, the boiler fuel quantity change and the boiler thermal efficiency change obtained above, the differentiated relationship equation between the furnace outlet flue gas temperature and the boiler fuel quantity, and the expression of the boiler flue gas temperature change amount, a quantitative calculation model for the influence of the steam pressure change of the boiler on the boiler thermal efficiency is obtained, and the change amount Δη of the boiler thermal efficiency is obtained through the quantitative calculation model for the influence of the steam pressure change of the boiler on the boiler thermal efficiency;

[0011] Furthermore, the function expression between the enthalpy value of the main steam working medium, the boiler fuel quantity and the boiler thermal efficiency is specifically:

[0012]

[0013] where h′ T is the enthalpy value of the main steam working medium, with the unit of kJ / kg; δh Σ is the total enthalpy increase of the working medium after passing through the boiler, with the unit of kJ / kg; B is the fuel flow rate, including the air supply volume corresponding to the fuel flow rate, with the unit of kg / s; η is the boiler thermal efficiency, with the unit of %;

[0014] Further, the specific functional expression between the temperature change amount and the enthalpy change amount of the main steam working medium is:

[0015]

[0016] where h′ T is the enthalpy value of the main steam working medium, with the unit of kJ / kg; θ′ T is the temperature of the main steam working medium, with the unit of °C; c P is the isobaric specific heat of the working medium, with the unit of kJ / (kg·°C); k θ is a non-constant coefficient, p′ T is the pressure of the main steam working medium, with the unit of MPa;

[0017] Further, the approximate calculation equation for the critical condition flow rate of the steam turbine is specifically:

[0018]

[0019] The reduced temperature empirical equation for the temperature of the main steam working medium is specifically:

[0020]

[0021] The functional expression between the pressure of the main steam working medium and the temperature of the main steam working medium is specifically:

[0022]

[0023] where D is the steam flow rate, with the unit of kg / s; K is the flow coefficient; p′ T is the pressure of the main steam working medium, with the unit of MPa; is the reduced temperature of the main steam working medium, with the unit of °C; θ′ T is the temperature of the main steam working medium, with the unit of °C; Footnote 0 represents the parameters at the original steady state;

[0024] Further, the functional expression between the pressure of the main steam working medium and the changes in the boiler fuel quantity and the boiler thermal efficiency is specifically:

[0025]

[0026] wherein, p′ T is the main steam working medium pressure, with the unit of MPa; is the reduced temperature of the main steam working medium temperature, with the unit of °C; δh ∑ is the total enthalpy increase of the working medium after passing through the boiler, with the unit of kJ / kg; c P is the isobaric specific heat of the working medium, with the unit of kJ / (kg·°C); B is the fuel flow rate, including the air supply volume corresponding to the fuel flow rate, with the unit of kg / s; η is the boiler thermal efficiency, with the unit of %;

[0027] Further, the relationship equation between the differentiated furnace outlet flue gas temperature and the boiler fuel flow rate is specifically:

[0028]

[0029] wherein, T1′ t is the flue gas temperature at the furnace outlet, with the unit of K; T a is the theoretical combustion temperature, with the unit of K; the subscript 0 represents the reference condition or the condition before the fuel flow rate changes; B is the fuel flow rate, including the air supply volume corresponding to the fuel flow rate, with the unit of kg / s;

[0030] Further, the expression of the change in the boiler flue gas temperature is specifically:

[0031]

[0032] wherein, θ py is the boiler flue gas temperature, with the unit of °C; ζ is a correction coefficient less than 1; T1′ t is the flue gas temperature at the furnace outlet, with the unit of K;

[0033] Further, the quantitative calculation model of the influence of the boiler steam pressure change on the boiler thermal efficiency is specifically:

[0034]

[0035] wherein, η is the boiler thermal efficiency, with the unit of %; p′ T is the main steam working medium pressure, with the unit of MPa; is the reduced temperature of the main steam working medium temperature, with the unit of °C; δh ∑ is the total enthalpy increase of the working medium after passing through the boiler, with the unit of kJ / kg; c P is the isobaric specific heat of the working medium, with the unit of kJ / (kg·°C); T a is the theoretical combustion temperature, with the unit of K; θ pyis the flue gas temperature of the boiler, with the unit of °C; footnote 0 represents the parameters at the original steady state; t0 is the ambient temperature, with the unit of °C; ζ is a correction factor less than 1; T1′ t is the flue gas temperature at the furnace outlet, with the unit of K; q2 is the heat loss of the boiler flue gas, with the unit of %.

[0036] In a second aspect, the present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the above approximate calculation method for the quantitative influence of the fuel quantity disturbance of a once-through boiler on the steam temperature are implemented;

[0037] In a third aspect, the present invention also provides 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 above approximate calculation method for the quantitative influence of the fuel quantity disturbance of a once-through boiler on the steam temperature are implemented.

[0038] The above technical solutions have the following advantages or beneficial effects:

[0039] In a first aspect, the present invention provides a quantitative calculation method for the influence of the steam pressure change of a once-through boiler on the boiler thermal efficiency. By differentiating the heat balance equation, the influence of the fuel quantity change on the enthalpy value of the main steam working medium is deduced. Then, combined with the reduced temperature empirical equation of the main steam working medium temperature and the approximate calculation equation of the critical condition flow rate of the steam turbine, the specific influence of the boiler steam pressure change on the boiler thermal efficiency is calculated. Finally, by correcting the change amount of the boiler thermal efficiency, the calculation model is further obtained and optimized, overcoming the defect that the boiler steam pressure change cannot accurately calculate and quantitatively analyze the boiler thermal efficiency. Moreover, the calculation method is very simple, accurate, and scientific. Only based on the parameters in the reference condition operation data, the change amount Δη of the boiler thermal efficiency can be quickly, conveniently, and accurately calculated, greatly simplifying the calculation steps, optimizing the boiler operation efficiency, reducing the power generation coal consumption rate, and achieving the purpose of accurately calculating and analyzing the quantitative influence of the boiler steam pressure change on the boiler thermal efficiency. Secondly, the quantitative calculation model obtained by the present invention for the influence of the main steam pressure of the once-through boiler on the boiler thermal efficiency is applicable not only to the units without reheat but also to the units with reheat, providing theoretical guidance for boiler operators and having significant economic and social benefits.

[0040] In a second aspect, the present invention also provides a computer device. By executing a specific computer program by the processor, the steps of the quantitative calculation method for the influence of the steam pressure change of a once-through boiler on the boiler thermal efficiency of the present invention can be efficiently implemented. When the computer device executes data processing tasks, it can accurately perform numerical calculations and logical judgments, avoiding errors caused by human factors. At the same time, due to the high stability and reliability of the computer program, the accuracy and consistency of the data processing results can be ensured.

[0041] In a third aspect, the present invention also provides a computer-readable storage medium. By programming the steps of a quantitative calculation method for the influence of steam pressure change on boiler thermal efficiency in the present invention into a computer program and storing it on the computer-readable storage medium, users can easily load these programs onto any compatible computer device and execute them without having to rewrite or convert the code, greatly improving the convenience and flexibility of program execution. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic flow chart of the quantitative calculation method for the influence of steam pressure change on boiler thermal efficiency in the present invention;

[0043] Figure 2 It is a schematic diagram of the influence among fuel quantity change, main steam parameters and boiler thermal efficiency in the present invention;

[0044] Figure 3 It is a schematic structural diagram of the computer device in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The following further describes the present invention in detail with specific embodiments, which are explanations of the present invention rather than limitations.

[0046] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0047] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0048] Embodiment:

[0049] See Figure 1, the present invention provides a quantitative calculation method for the influence of the steam pressure change of a once-through boiler on the boiler thermal efficiency, including the following steps:

[0050] Step 1: According to the boiler heat balance equation and combining with differential theory, obtain the function expression between the enthalpy value of the main steam working medium, the boiler fuel quantity and the boiler thermal efficiency. Then, by differentiating the enthalpy value of the main steam working medium, obtain the function expression between the temperature change amount and the enthalpy change amount of the main steam working medium;

[0051] In the embodiment of the present invention, Step 1 is specifically as follows:

[0052] For a non-reheat unit, the heat absorption of the boiler at static state is equal to the heat carried away by the working medium, that is, the boiler heat balance equation is:

[0053] Q ∑ =D(h' T -h w )=Dδh ∑ =ηqB (1);

[0054] In the formula, Q ∑ is the total heat absorption of each heating surface of the boiler, with the unit of kJ / kg; D is the steam flow rate, with the unit of kg / s; h′ T is the enthalpy value of the main steam working medium, which can also be called the enthalpy value of the working medium in front of the steam turbine, approximately equal to the enthalpy value of the working medium at the boiler outlet, with the unit of kJ / kg; h w is the feed water enthalpy value, with the unit of kJ / kg; δh ∑ is the total enthalpy increase of the working medium after passing through the boiler, δh ∑ =h′ T -h w , with the unit of kJ / kg; η is the boiler thermal efficiency, with the unit of %; q is the calorific value of unit mass of fuel, with the unit of kJ / kg; B is the fuel flow rate, including the air supply volume corresponding to the fuel flow rate, with the unit of kg / s;

[0055] Taking the natural logarithm of Equation (1) gives:

[0056] lnD + ln(h' T -h w ) = lnη + lnq + lnB (2);

[0057] Taking the increment on both sides of Equation (2) and assuming that the calorific value q of the fuel remains unchanged, we get:

[0058]

[0059] When there is a heat disturbance, assuming that the feed water and spray water flow rates remain unchanged, so the steam flow rate finally remains unchanged, that is, △D = 0. Since the enthalpy value of the feed water remains unchanged, then h w= 0. Therefore, Equation (3) can be simplified to obtain the function expression between the enthalpy value of the main steam working medium, the boiler fuel quantity, and the boiler thermal efficiency as follows:

[0060]

[0061] Since the enthalpy value of the working medium is a function of temperature and pressure, i.e., h′ T = f(θ′ T , p′ T ), taking the differential increment of the main steam enthalpy value, the change amount Δh′ of the main steam working medium enthalpy value is obtained as follows: T Expression:

[0062]

[0063] In the formula: θ′ T is the temperature of the main steam working medium, which can also be called the steam temperature before the turbine governing valve, with the unit of °C; p′ T is the pressure of the main steam working medium, which can also be called the steam pressure before the turbine governing valve, with the unit of MPa; c P is the isobaric specific heat of the working medium, with the unit of kJ / (kg·°C); k θ is a non-constant coefficient,

[0064] Therefore, from Equation (5), the function expression between the change amount of the main steam working medium temperature and the change amount of the enthalpy value can be obtained, which can also be called the change amount expression of the steam working medium temperature at the boiler outlet:

[0065]

[0066] Step 2: According to the approximate calculation equation of the turbine critical condition flow rate and the empirical equation of the reduced temperature of the main steam working medium, which can also be called the empirical equation of the reduced temperature of the steam before the turbine governing valve, obtain the function expression between the main steam working medium pressure and the main steam working medium temperature. Combining the function expression between the main steam working medium pressure and the main steam working medium temperature with the function expressions obtained above between the main steam working medium enthalpy value, the boiler fuel quantity, and the boiler thermal efficiency, and between the change amount of the main steam working medium temperature and the change amount of the enthalpy value, obtain the function expression between the main steam working medium pressure and the changes in the boiler fuel quantity and the boiler thermal efficiency;

[0067] In the embodiment of the present invention, Step 2 is specifically as follows:

[0068] According to the approximate calculation equation of the turbine critical condition flow rate:

[0069]

[0070] In the formula, K is the flow coefficient; The reduced temperature of the main steam working medium temperature, also known as the reduced temperature of the steam before the turbine regulating valve, in °C;

[0071] The empirical equation for the reduced temperature of the main steam working medium temperature, which can also be called the empirical equation for the reduced temperature of the steam before the turbine regulating valve, can be expressed as:

[0072]

[0073] In the formula, Subscript 0 indicates the parameters in the original steady state;

[0074] Taking the natural logarithm of equation (7), combining it with (8), and then taking its increment, we get:

[0075]

[0076] When the unit is in steady state operation, the steam flow rate remains unchanged, △D=0, and the function expression between the main steam working medium pressure and the main steam working medium temperature is obtained by rearranging formula (9):

[0077]

[0078] Where:

[0079] By combining equations (4), (6) and (10), we can obtain the function expression of the main steam working medium pressure, the change of boiler fuel quantity and the change of boiler thermal efficiency, which can also be called the expression of the change of working medium pressure at the turbine inlet or approximately at the boiler outlet under fuel quantity disturbance:

[0080]

[0081] Generally speaking, can be ignored, so equation (11), that is, the function expression of the main steam working medium pressure and the change of boiler fuel quantity and boiler thermal efficiency, can be approximately expressed as:

[0082]

[0083] Step 3: Establish a relational equation between the flue gas temperature at the furnace outlet and the boiler fuel quantity and perform differentiation. Through a correction method, obtain an expression for the change in the boiler's exhaust gas temperature from the differentiated relational equation between the flue gas temperature at the furnace outlet and the boiler fuel quantity. Then, based on the expression for the change in the boiler thermal efficiency, the functional expressions for the main steam working medium pressure, the changes in the boiler fuel quantity and the boiler thermal efficiency, the differentiated relational equation between the flue gas temperature at the furnace outlet and the boiler fuel quantity, and the expression for the change in the boiler's exhaust gas temperature, obtain a quantitative calculation model for the influence of the boiler steam pressure change on the boiler thermal efficiency. Through this quantitative calculation model for the influence of the boiler steam pressure change on the boiler thermal efficiency, obtain the change Δη in the boiler thermal efficiency;

[0084] In the embodiment of the present invention, Step 3 is specifically as follows:

[0085] When the fuel quantity changes, the flue gas temperature at the furnace outlet changes, which further causes a change in the boiler's exhaust gas temperature. Perform differentiation on the calculation equation for the flue gas temperature at the furnace outlet to obtain the relational equation between the differentiated flue gas temperature at the furnace outlet and the boiler fuel quantity:

[0086]

[0087] In the formula, T′ 1t is the flue gas temperature at the furnace outlet, with the unit of K; T a is the theoretical combustion temperature, with the unit of K; the subscript 0 represents the reference condition or the condition before the fuel quantity change;

[0088] When the fuel quantity changes, the flue gas temperature at the furnace outlet changes, which in turn causes a change in the boiler's exhaust gas temperature. However, due to the "self - recovery characteristic" of convective heat transfer, the change in the exhaust gas temperature is less than the change in the flue gas temperature at the furnace outlet. Therefore, the influence of the fuel quantity change on the boiler's exhaust gas temperature can be calculated by multiplying the flue gas temperature at the furnace outlet by a correction factor. Thus, the expression for the change in the boiler's exhaust gas temperature can be represented as:

[0089]

[0090] In the formula: θ py is the boiler's exhaust gas temperature, with the unit of °C; ζ is a correction factor less than 1, which can be obtained through experiments;

[0091] When the fuel quantity changes, ignoring the change in unburned carbon, the change in the boiler thermal efficiency is mainly related to the boiler's exhaust gas temperature. Therefore, the expression for the change in the boiler thermal efficiency can be represented as:

[0092]

[0093] In the formula, q2 is the heat loss of the boiler exhaust, with the unit of %; t0 is the ambient temperature, with the unit of °C;

[0094] Combining equations (12)-(15) gives a quantitative calculation model for the impact of the steam pressure change of a once-through boiler on the boiler thermal efficiency, which can also be called a quantitative calculation model for the impact of the main steam pressure of a once-through boiler on the boiler thermal efficiency:

[0095]

[0096] Equation (16) is applicable to both reheating and non-reheating units.

[0097] In an embodiment of the present invention, taking the parameters of a 600MW power plant boiler at 100% BMCR operating conditions as an example, a quantitative calculation method for the impact of the steam pressure change of a once-through boiler on the boiler thermal efficiency is described. The collected data of the unit operating parameters are shown in Table 1.

[0098] Table 1 Operating data table of the reference condition

[0099]

[0100]

[0101] The total enthalpy increase δh of the working fluid after passing through the boiler ∑ is:

[0102] δh ∑ = h′ T - h w = 3400.5 - 1239.3 = 2161.2;

[0103] The reduced temperature of the main steam working fluid is:

[0104]

[0105] The change in boiler thermal efficiency Δη is:

[0106]

[0107] See Figure 3, in an embodiment of the present invention, a computer device is provided. The computer device includes a processor and a memory. The memory is used to store a computer program, and the computer program includes program instructions. The processor is used to execute the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, and is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function. The processor described in the embodiment of the present invention can be used for the operation of the quantitative calculation method of the influence of the steam pressure change of a once-through boiler on the boiler thermal efficiency.

[0108] In an embodiment of the present invention, a computer-readable storage medium is provided, specifically a computer-readable storage medium (Memory). The computer-readable storage medium is the memory device in the computer device and is used to store programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and, of course, the extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space, and the operating system of the terminal is stored in this storage space. Moreover, one or more instructions suitable for being loaded and executed by the processor are stored in this storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. One or more instructions stored in the computer-readable storage medium can be loaded and executed by the processor to implement the corresponding steps of the quantitative calculation method of the influence of the steam pressure change of a once-through boiler on the boiler thermal efficiency in the embodiment.

[0109] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method or a computer program product. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) containing computer-usable program code.

[0110] The present invention is described with reference to the flowcharts and / or block diagrams of methods and computer program products according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 block or multiple blocks.

[0111] These computer program instructions can also be stored in a computer-readable memory capable of guiding a computer or other programmable data processing devices to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including instruction means, and the instruction means implement the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 block or multiple blocks.

[0112] These computer program instructions can also be loaded onto a computer or other programmable data processing devices, so that a series of operation steps are executed on the computer or other programmable devices to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable devices provide steps for implementing the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 block or multiple blocks.

[0113] See Figure 2 , in an embodiment of the present invention, the concept and principle of a quantitative calculation method for the influence of the steam pressure change of a once-through boiler on the boiler thermal efficiency of the present invention are explained:

[0114] When the fuel quantity of the boiler changes, the enthalpy value of the main steam working medium of the boiler changes, which in turn affects the boiler thermal efficiency. Assuming that the feed water enthalpy value remains unchanged, the change in the enthalpy value of the main steam working medium can reflect the changes in the pressure and temperature of the main steam working medium;

[0115] The reduced temperature of the main steam working medium, which can also be called the reduced temperature of the steam before the turbine governing valve, is a function of the pressure and temperature of the main steam working medium of the boiler. With the help of the empirical equation of the reduced temperature of the main steam working medium, which can be called the reduced temperature of the steam before the turbine governing valve, and the turbine flow equation, the relationship expression between the pressure of the main steam working medium of the boiler, the change of the boiler fuel quantity, and the change of the boiler thermal efficiency can be obtained;

[0116] When the boiler fuel quantity changes, the flue gas temperature at the boiler furnace outlet changes, and then the boiler flue gas discharge temperature changes. The change amount of the boiler flue gas discharge temperature can be corrected through the change amount of the flue gas temperature at the furnace outlet. Assuming that the unburned carbon content in the boiler remains unchanged, the change amount of the boiler thermal efficiency can be obtained;

[0117] The boiler thermal efficiency can also usually be expressed as a functional relationship of the change of the fuel quantity. Therefore, through further calculation and arrangement, the functional expression between the main steam working medium pressure and the boiler thermal efficiency can be obtained, that is, the quantitative calculation model of the influence of the boiler steam pressure change on the boiler thermal efficiency.

[0118] Based on the above concept, according to the characteristics that the change of the boiler fuel quantity causes the simultaneous change of the boiler thermal efficiency and the main steam pressure, and based on the boiler unit heat balance theory, combined with the differential idea, etc., the principle followed to implement the technical solution of the present invention can be further proposed, that is:

[0119] Through the boiler heat balance equation, combined with the differential theory, the functional expression between the enthalpy value of the main steam working medium, the boiler fuel quantity, and the boiler thermal efficiency is obtained. Further, by differentiating the enthalpy value of the main steam working medium, the expression of the change amount of the main steam working medium temperature is obtained;

[0120] With the help of the empirical equation of the reduced temperature of the main steam working medium, the approximate calculation equation of the turbine critical condition flow rate, as well as the above functional expression between the enthalpy value of the main steam working medium, the boiler fuel quantity, and the boiler thermal efficiency, and the expression of the change amount of the main steam working medium temperature, the expression of the change amount of the main steam working medium pressure is obtained;

[0121] By establishing the relationship equation between the flue gas temperature at the furnace outlet and the boiler fuel quantity, the expression of the change amount of the boiler flue gas discharge temperature is obtained through the correction method. Combining the expression of the change amount of the boiler thermal efficiency and the expression of the change amount of the main steam working medium pressure, the relationship expression between the steam working medium pressure, the change of the boiler fuel quantity, and the change of the boiler thermal efficiency is obtained, that is, the quantitative calculation model of the influence of the boiler steam pressure change on the boiler thermal efficiency.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A quantitative calculation method for the effect of steam pressure change of a once-through boiler on boiler thermal efficiency, characterized in that: The following steps are involved: According to the boiler heat balance equation, combined with differential theory, the function expression between the main steam working medium enthalpy value and the boiler fuel amount and boiler thermal efficiency is obtained, and then the function expression between the main steam working medium temperature change and the enthalpy change is obtained by differentiating the main steam working medium enthalpy value; The function expression between the main steam working medium pressure and the main steam working medium temperature is obtained according to the approximate calculation equation of the critical condition flow of the steam turbine and the reduced temperature empirical equation of the main steam working medium temperature. The function expression between the main steam working medium pressure and the main steam working medium temperature and the function expression between the main steam working medium enthalpy value and the boiler fuel amount and the boiler thermal efficiency obtained above, and the function expression between the main steam working medium temperature change and the enthalpy change, are combined to obtain the function expression between the main steam working medium pressure and the boiler fuel amount change and the boiler thermal efficiency change. The relationship equation between the furnace outlet flue gas temperature and the boiler fuel amount is established and differentiated. The differentiated relationship equation between the furnace outlet flue gas temperature and the boiler fuel amount is modified to obtain the boiler exhaust gas temperature change expression. Then, based on the boiler thermal efficiency change expression and the above-obtained function expression of the main steam working fluid pressure and the boiler fuel amount change and the boiler thermal efficiency change, the differentiated relationship equation between the furnace outlet flue gas temperature and the boiler fuel amount and the boiler exhaust gas temperature change expression, a quantitative calculation model for the influence of boiler steam pressure change on boiler thermal efficiency is obtained. The change Δη of boiler thermal efficiency is obtained through the quantitative calculation model for the influence of boiler steam pressure change on boiler thermal efficiency.

2. The quantitative calculation method of the effect of steam pressure change of a once-through boiler on boiler thermal efficiency according to claim 1 is characterized in that: The functional expression between the main steam working medium enthalpy value, the boiler fuel amount and the boiler thermal efficiency is specifically: In the formula, h′ T δh is the enthalpy of the main steam working medium; ∑ is the total enthalpy increase of the working fluid after passing through the boiler; B is the fuel flow rate, including the air supply volume corresponding to the fuel flow rate; η is the thermal efficiency of the boiler.

3. The quantitative calculation method of the effect of steam pressure change of a once-through boiler on boiler thermal efficiency according to claim 1 is characterized in that: The functional expression between the temperature change of the main steam working medium and the enthalpy change is specifically: In the formula, h′ T is the enthalpy of the main steam working medium; θ′ T is the main steam working medium temperature; c P is the isobaric specific heat of the working fluid, k θ is the extraordinary coefficient, p′ T Main steam working pressure.

4. The quantitative calculation method of the effect of steam pressure change of a once-through boiler on boiler thermal efficiency according to claim 1 is characterized in that: The approximate calculation equation for the critical condition flow of the steam turbine is specifically: The reduced temperature empirical equation of the main steam working medium temperature is specifically: The functional expression between the main steam working medium pressure and the main steam working medium temperature is specifically: Where D is the steam flow rate; K is the flow coefficient; p' T is the main steam working medium pressure; The equivalent temperature of the main steam working medium temperature; θ′ T is the main steam working medium temperature; Subscript 0 indicates the parameters in the original steady state; 5. The quantitative calculation method of the effect of steam pressure change of a once-through boiler on boiler thermal efficiency according to claim 1 is characterized in that: The functional expression of the main steam working medium pressure, the change of boiler fuel quantity and the change of boiler thermal efficiency is specifically as follows: Where p′ T is the main steam working medium pressure; The reduced temperature of the main steam working medium temperature; δh ∑ is the total enthalpy increase of the working fluid after passing through the boiler; c P is the isobaric specific heat of the working fluid, B is the fuel flow rate, including the air supply volume corresponding to the fuel flow rate; η is the thermal efficiency of the boiler.

6. The quantitative calculation method of the effect of steam pressure change of a once-through boiler on boiler thermal efficiency according to claim 1 is characterized in that: The relationship equation between the furnace outlet flue gas temperature and boiler fuel quantity after differentiation is specifically: Where T1′ t is the flue gas temperature at the furnace outlet; T a is the theoretical combustion temperature; the subscript 0 represents the reference condition or the condition before the fuel amount changes; B is the fuel flow rate, including the air supply volume corresponding to the fuel flow rate.

7. The quantitative calculation method of the effect of steam pressure change of a once-through boiler on boiler thermal efficiency according to claim 1 is characterized in that: The expression of the variation of the exhaust gas temperature of the boiler is specifically: In the formula, θ py is the exhaust gas temperature of the boiler; ζ is a correction coefficient less than 1; T1′ t is the flue gas temperature at the furnace outlet.

8. The quantitative calculation method of the effect of steam pressure change of a once-through boiler on boiler thermal efficiency according to claim 1 is characterized in that: The quantitative calculation model of the effect of boiler steam pressure change on boiler thermal efficiency is specifically: Where η is the boiler thermal efficiency; p′ T is the main steam working medium pressure; The reduced temperature of the main steam working medium temperature; δh ∑ is the total enthalpy increase of the working fluid after passing through the boiler; c P is the isobaric specific heat of the working fluid, T a is the theoretical combustion temperature; θ py is the exhaust gas temperature of the boiler; footnote 0 indicates the parameters in the original steady state; t0 is the ambient temperature; ζ is a correction coefficient less than 1; T1′ t is the flue gas temperature at the furnace outlet; q2 is the heat loss of boiler flue gas.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

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