A method and system for simulating heat transfer processes of coke combustion in a sintering process

Abstract

The application provides a sintering process coke combustion heat transfer process simulation method and system, including the following steps: step one: establish a two-dimensional sintering cup geometric model in equal proportion for numerical simulation; step two: based on parameter analysis in the sintering experiment, simplify the numerical simulation calculation, and set the boundary and grid division of the sintering cup geometric model; step three: import the divided mass grid into the simulation system, and set the calculation model of the simulation system; step four: import the parameters corresponding to the simulation of coke combustion in the sintering process into the simulation system; step five: run the simulation system to obtain the temperature change data to be solved, and analyze the influence of gas-solid heat transfer temperature difference on the temperature of the material layer and the coke combustion rate. The application simulates the sintering process simulation system, simulates the heat transfer process of coke combustion, and has important significance for energy saving and carbon reduction of the steel production process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat transfer process simulation, in particular to a heat transfer process simulation method and system for coke combustion in a sintering process. BACKGROUND

[0002] The steel production process in China still mainly adopts the long process of blast furnace-converter. In the blast furnace charge, the proportion of sintered ore is close to 75%, and the sintering process is the second highest consumption in the entire steel production, only next to the blast furnace, and the solid fuel consumption accounts for about 70-80%. In addition, due to the large use of coke, the carbon emission of the sintering process accounts for 15% of the entire process. Under the trend of energy saving and environmental protection, it is imperative to save energy and reduce carbon in the sintering process. However, there are many influencing factors in the sintering process, involving a large number of physical changes and chemical reactions, including ignition of gaseous fuel, evaporation and condensation of water vapor, removal of crystal water, decomposition, oxidation and reduction of iron oxides, combustion of fuel, formation of liquid melt, solid phase reaction between minerals, decomposition of carbonates and sulfides, melt crystallization, cooling and re-oxidation of sintered ore, etc. Moreover, various factors are related to and influence each other. In order to achieve energy saving and carbon reduction of thick layer sintering, it is necessary to strengthen the research on the sintering mechanism of iron ore, clarify the change law of each phase in the ignition and sintering process, and seek the best sintering method for coke utilization.

[0003] At present, the research on the sintering mechanism of iron ore mainly includes semi-industrial experimental research, parameter optimization research and numerical simulation research. Semi-industrial experimental research, i.e. establishing a sintering cup experimental system, is a series of modeling devices smaller than the actual production established according to the similarity principle. The sintering cup is equal or similar to the actual production in terms of heat dissipation, heat storage and gas mechanics, as well as process conditions such as air volume, negative pressure and temperature. It can be understood as a unit body cut from the sintering machine, and then the various change laws in the sintering process are studied. However, it will consume a large amount of human and material resources, and the measurement can only know the local state information.

[0004] Parameter optimization research relies on artificial intelligence methods. The widely used artificial intelligence methods in the sintering field are expert systems, artificial neural networks and fuzzy control. Based on real data, the relationship between sintering process parameters and ore formation is obtained through training of a large number of data sets. However, it does not change the essence of the "black box" property of the sintering process, and cannot decompose the complex process of the sintering mechanism of iron ore. Therefore, it cannot obtain the change law of each phase in the ignition and sintering process.

[0005] Numerical simulation research is highly integrated with computer technology, which can efficiently reproduce the distribution of temperature, velocity, concentration and their evolution behavior in the sintering process, and provide more analysis perspectives and technical means for in-depth research of sintering process through the visualization of real-time state of the whole field of sintering process. Compared with traditional sintering experiments, due to high efficiency, the influence of process parameters on multi-physical field can be quickly analyzed through numerical simulation of sintering process under different ore and carbon conditions, thereby saving a lot of manpower and material costs in the experimental process. In the existing numerical simulation research, the influence of radiation heat transfer process is not considered in the numerical simulation research of coke combustion and similar processes, and the influence of the change of porosity caused by melt generation on convective heat transfer, and the research and analysis of heat transfer process of coke combustion are not comprehensive, which makes it difficult for the analysis conclusion to meet the needs of actual industrial production.

[0006] Application content

[0007] The present application is carried out in view of the above-mentioned problems, and the purpose is to provide a simulation method and system for heat transfer process of coke combustion in sintering process, which simulates the heat transfer process of coke combustion in ignition and sintering process by establishing a two-dimensional sintering cup geometric model and a simulation system, creatively considers the influence of radiation heat transfer process on heat transfer, introduces the influence of liquid melt fraction in the calculation of sintering process Nu number, enhances the credibility of the simulation process and the accuracy of the results, investigates the ignition depth and coke combustion rate, analyzes the gas-solid heat transfer characteristics of the material layer and the distribution of temperature field and concentration field, and has important significance for adjusting the steel production process and energy saving and carbon reduction.

[0008] Specifically, the first aspect of the present application provides a simulation method for heat transfer process of coke combustion in sintering process, comprising the following steps:

[0009] Step one: establish a two-dimensional sintering cup geometric model in proportion for numerical simulation;

[0010] The plane structure and specific size of the sintering cup is an inverted trapezoidal structure with an upper surface of 200 mm, a lower surface of 180 mm and a height of 800 mm, and a two-dimensional sintering cup geometric model is established in proportion.

[0011] Step two: based on the parameter analysis in sintering experiment, simplify the numerical simulation calculation, and set the boundary and divide the grid of the sintering cup geometric model;

[0012] The boundary of the two-dimensional sintering cup is set, the upper surface is the velocity inlet of air flow, the lower surface is the pressure outlet, and the side surface is the adiabatic wall; the two-dimensional sintering cup is divided into grid, and the number of structured grid obtained is 18760, the grid quality is greater than 0.99, which meets the calculation demand.

[0013] Step three: import the quality grid divided into the simulation system, set the simulation system calculation model, the calculation model includes gas-solid heat balance model, gas-solid non-thermal equilibrium model, porous medium model, radiation heat transfer model, equal particle size shrinkage core model, the formula is as follows:

[0014] Gas-solid heat balance model: based on the first law of thermodynamics. The first law of thermodynamics indicates that the energy of fluid is equal to the sum of the heat absorbed by the fluid and the work done by the fluid. Without considering the temperature difference between the gas phase and the solid phase in the sintering cup, the equation described by the local thermal equilibrium model of porous medium is:

[0015] Gas-solid heat balance energy conservation equation:

[0016] ;

[0017] Gas-solid non-thermal equilibrium model: for the case that the temperature of the gas phase and the solid phase in the sintering cup is not consistent, different energy equations are needed to describe the temperature change of the gas and the material layer, that is, the non-thermal equilibrium model of porous medium is introduced, and the gas-solid non-thermal equilibrium energy conservation equation is divided into gas non-thermal equilibrium energy conservation equation and solid non-thermal equilibrium energy conservation equation, the specific formula is as follows:

[0018] Gas non-thermal equilibrium energy conservation equation:

[0019] ;

[0020] Solid non-thermal equilibrium energy conservation equation:

[0021] ;

[0022] Among them: The solid phase temperature is K; : gas temperature, K;

[0023] : solid density, kg / m3; ; : gas density, kg / m3; ;

[0024] : solid specific heat capacity at constant pressure, J / (kg*K); : gas specific heat capacity at constant pressure, J / (kg*K);

[0025] : solid comprehensive thermal conductivity, W / (m*K); : gas effective thermal conductivity;

[0026] P : turbulent Prandtl number; 、 : source term of the chemical reaction heat, ;

[0027] : chemical reaction heat of reaction k, J / kg; : convective heat transfer specific surface area, ;

[0028] : gas-solid convective heat transfer coefficient, ;

[0029] ε: bed porosity; : gas phase flow velocity in j direction;

[0030] x j : displacement in cartesian coordinate system j direction, m;

[0031] μ g,t : turbulent viscosity, also known as apparent turbulent viscosity, Pa*s;

[0032] R k : chemical reaction rate of reaction k , mol / (m 3 *s);

[0033] q rad : radiative heat transfer quantity, ; t: reaction time, s;

[0034] Among the above parameters, the calculation formula of the source term of the chemical reaction heat is as follows:

[0035] ;

[0036] ;

[0037] Among them: : molar mass of the reactant corresponding to reaction k, kg / mol;

[0038] : reaction rate of the reactant corresponding to reaction k, mol / (m );

[0039] : chemical reaction heat of reaction k, J / kg; : distribution coefficient of the reaction heat between the gas and solid phases;

[0040] The calculation formula of the convective heat transfer specific surface area is as follows:

[0041] ;

[0042] wherein: : equivalent diameter of the mixture particles, m; ε: porosity of the bed;

[0043] Radiation heat transfer model: for the calculation of the radiation heat transfer of the natural gas burner and the high-temperature flame during the ignition process, the specific formula of the heat source generated by the bed is as follows:

[0044] Radiation heat exchange heat source q1 between the inner wall of the igniter and the surface of the bed:

[0045] ;

[0046] wherein: A B : inner wall area of the igniter, m 2 ; A L : surface area of the bed in the igniter, m 2 ;

[0047] X B,L : angle coefficient of the inner wall surface of the igniter facing the surface of the bed;

[0048] : emissivity of the surface of the bed, taken as 0.8; σ : Stefan-Bolzmann constant;

[0049] T B : temperature of the inner wall surface of the igniter, K; T L : temperature of the surface of the bed, K;

[0050] Radiation heat exchange q2 of the flame to the surface of the bed:

[0051] ;

[0052] wherein: ε g : blackness of the flame, taken as 0.149; α g : flue gas absorption ratio of the flame, taken as 0.219;

[0053] σ Stefan-Bolzmann constant; : temperature of the gas phase, K; T L : temperature of the surface of the bed, K;

[0054] The equal particle size shrinking core model: in this embodiment, it is considered that the coke combustion is controlled by diffusion-dynamics, the diffusion resistance includes material coating resistance and boundary layer resistance, and the calculation formula of the total reaction rate is as follows:

[0055] ;

[0056] Wherein: : reaction rate; : particle number density of coke powder in the iron ore sintering bed layer;

[0057] κ: incomplete combustion coefficient; π: circular constant; ζ: shape factor of coke particles, namely sphericity;

[0058] : equivalent particle size of coke particles in the reaction process; : comprehensive rate coefficient of coke combustion reaction;

[0059] : concentration of coke in the sintering bed layer ;

[0060] Step four: importing the parameters corresponding to the simulation of coke combustion in the sintering process into the simulation system;

[0061] Step five: running the simulation system to obtain the temperature change data to be solved, and analyzing the influence of the gas-solid heat transfer temperature difference on the bed temperature and the coke combustion rate.

[0062] Further, the numerical simulation calculation is simplified, specifically including: assuming that the gas and the bed are continuously distributed in the sintering cup, not considering the heat dissipation of the sintering cup wall surface, and assuming that the internal temperature gradient of the particles is zero.

[0063] Simplifying the numerical simulation calculation can simplify the complexity of the numerical simulation model and make the calculation process more efficient; assuming that the gas and the bed are continuously distributed in the sintering cup can help more accurately simulate the changes of the gas flow field and the gas-solid phase temperature field in the sintering process; not considering the heat dissipation of the sintering cup wall surface, the simulation focuses on the temperature distribution and temperature change of the coke combustion in the sintering process; assuming that the internal temperature gradient of the particles is zero can avoid errors caused by complex temperature distribution, so as to more accurately predict the change of the heat transfer process in the sintering process.

[0064] Further, the boundary setting specifically includes: setting the upper part of the geometric model as the velocity inlet of the gas flow, the lower part as the pressure outlet, and the others as the adiabatic wall surface.

[0065] Further, the grid division divides the number of structured grids to be 18700-18800, and the grid quality is greater than 0.99.

[0066] Meshing determines the degree of discretization and the scale of the model. By dividing the continuous object into discrete units, numerical calculation and analysis can be carried out, and the quality of meshing directly affects the accuracy of the subsequent numerical calculation and analysis results. Proper meshing can improve the calculation accuracy, reduce the degree of freedom of the model, and thus reduce the calculation time and resource consumption.

[0067] Further, the gas-solid thermal equilibrium model and the gas-solid non-thermal equilibrium model correspond to the case where the temperature difference between the gas phase and the solid phase inside the sintering cup is not considered and the case where the temperature difference between the gas phase and the solid phase inside the sintering cup is considered, respectively.

[0068] Further, the porous medium model functions to regard the sintering material layer as a porous medium and simulate the flow of gas through the sintering material layer by using the porous medium model.

[0069] The porous medium model simulates the flow of fluid in the porous medium by introducing a resistance coefficient, thereby simplifying the problem of geometric complexity and large scale span, reducing the amount of calculation, and accelerating the simulation process.

[0070] Further, the radiation heat transfer model functions to simulate the heat source generated by the radiation heat transfer of the natural gas burner and the high-temperature flame to the material layer during the ignition process.

[0071] Further, in the gas-solid non-thermal equilibrium model, a convective heat transfer model is used to simulate the heat transfer process in the coke combustion, and the formula is as follows:

[0072] ;

[0073] ;

[0074] Where: Nu is the convective heat transfer coefficient; ε is the porosity of the material layer; β is the liquid melt fraction;

[0075] η is the channel factor, and its initial value is 1; : the final value of the channel factor;

[0076] Re is the Reynolds number, which is the ratio of the inertial force to the viscous force of the fluid;

[0077] Pr is the Prandtl number, which is the ratio of the thermal diffusion ability of the fluid to its momentum diffusion ability.

[0078] Further, the equivalent particle size of the coke particles in the equal particle size shrinking core model is which needs to be calculated according to the unreacted shrinking core model, and the formula is as follows:

[0079] ;

[0080] Where: : mass fraction of ash in the coke particle; : mass fraction of ash in the coke particle;

[0081] : unreacted core particle size of the coke particle, m; : initial particle size of the coke particle, m.

[0082] The heat transfer process simulation system for coke combustion in a sintering process comprises a computer device, a flue gas analyzer and an infrared thermal imager.

[0083] The computer device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, and the processor implements the steps in the heat transfer process simulation method for coke combustion in a sintering process when executing the program.

[0084] The flue gas analyzer and the infrared thermal imager are respectively electrically connected to the computer device and are respectively used for detecting the composition of flue gas in the coke combustion process and part of the temperature data in the experimental process.

[0085] In a second aspect, the present application further provides a computing device having the function of implementing the method described in the first aspect, and the beneficial effects can be referred to the description of the first aspect, which will not be repeated here. The function can be realized by hardware or by hardware executing corresponding software. The hardware or software comprises one or more modules corresponding to the above functions. In one possible design, the structure of the device comprises an acquisition module and a training module, and optionally, a construction module. These modules can realize the functions of the training node in the method examples of the first aspect, and the specific description can be referred to the detailed description in the method examples, which will not be repeated here.

[0086] In a third aspect, the present application further provides a computing device for implementing the function of the method described in the first aspect, and the beneficial effects can be referred to the description of the first aspect, which will not be repeated here. The structure of the computing device comprises a processor and a memory, and the memory is used for storing instructions and / or data. The memory is coupled to the processor, and the processor can realize the functions of the training node in the first aspect examples when executing the program instructions stored in the memory. The structure of the computing device further comprises a communication interface for communicating with other devices.

[0087] In a fourth aspect, the present application further provides a computer readable storage medium, which stores instructions, and when the instructions are executed on a computer, the computer executes the method of the first aspect and each possible design of the first aspect.

[0088] In a fifth aspect, the present application provides a computer program product containing instructions which, when executed on a computer, cause the computer to perform the method of the first aspect and each possible design of the first aspect.

[0089] In a sixth aspect, the present application provides a computing chip connected with a memory, the chip being used to read and execute a software program stored in the memory, and execute the method of the first aspect and each possible implementation of the first aspect. BRIEF DESCRIPTION OF DRAWINGS

[0090] In order to more clearly illustrate the technical solutions in the embodiments or the prior art, the drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the drawings, and for those skilled in the art, other drawings can be obtained without creative labor based on the structures shown in the drawings.

[0091] Figure 1 Flow chart of a simulation method for heat transfer process of coke combustion in a sintering process;

[0092] Figure 2 Temperature and reaction rate distribution diagram at 120s after ignition under gas-solid heat balance condition;

[0093] Figure 3 Temperature and reaction rate distribution diagram at 350s after ignition under gas-solid heat balance condition;

[0094] Figure 4 Gas-solid temperature distribution diagram at 500s after ignition under gas-solid non-heat balance condition;

[0095] Figure 5 Gas-solid temperature distribution diagram at 1000s after ignition under gas-solid non-heat balance condition;

[0096] Figure 6 Gas-solid temperature distribution diagram at 1500s after ignition under gas-solid non-heat balance condition;

[0097] Figure 7 Comparison diagram of gas-solid temperature difference at different times under gas-solid non-heat balance condition;

[0098] Figure 8 Coke combustion rate distribution diagram at 1500s after ignition under gas-solid non-heat balance condition.

[0099] The implementation, functional features and advantages of the drawings will be further described with reference to the embodiments and the drawings. DETAILED DESCRIPTION

[0100] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be described and illustrated below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. Based on the embodiments provided herein, all other embodiments obtained by those of ordinary skill in the art without creative efforts should fall within the scope of the present application.

[0101] Obviously, the accompanying drawings in the following description are only some examples or embodiments of the present application, and for those of ordinary skill in the art, the present application can also be applied to other similar scenarios without creative efforts based on these drawings. In addition, it should also be understood that although the efforts made in this development process can be complex and lengthy, for those of ordinary skill in the art related to the content disclosed in the present application, some designs, manufacturing or production changes based on the technology disclosed in the present application are only routine technical means and should not be understood as insufficient disclosure of the present application.

[0102] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0103] If not specifically stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0104] If not specifically stated, all steps of the present application can be performed in sequence or randomly, and the preferred sequence is sequential. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method can also comprise step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0105] If not specifically stated, the "includes" and "contains" mentioned in the present application are open-ended and can also be closed. For example, the "includes" and "contains" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0106] If not specifically stated otherwise, the term "or" in this application is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": A is true (or present) and B is false (or not present); A is false (or not present) and B is true (or present); or both A and B are true (or present).

[0107] As shown in Figure 1 a simulation method of heat transfer process of coke combustion in sintering process, comprising the following steps:

[0108] Step one: establish a two-dimensional sintering cup geometry model in proportion for numerical simulation;

[0109] In this embodiment, the plane structure and specific size of the sintering cup is an inverted trapezoidal structure with an upper surface of 200 mm, a lower surface of 180 mm, and a height of 800 mm, and a two-dimensional sintering cup geometry model is established in proportion.

[0110] Step two: based on parameter analysis in sintering experiment, simplify numerical simulation calculation, and set boundary and grid division for sintering cup geometry model;

[0111] The boundary of the proportional two-dimensional structure sintering cup is set, the upper surface is the velocity inlet of air flow, the lower surface is the pressure outlet, and the side surface is the adiabatic wall surface; the two-dimensional sintering cup is divided into a structured grid, the number of which is 18760, and the grid quality is greater than 0.99, meeting the calculation requirements.

[0112] Step three: import the quality grid divided out into the simulation system, set the calculation model of the simulation system, and the calculation model includes the gas-solid heat balance model, the gas-solid non-heat balance model, the porous medium model, the radiation heat transfer model, and the equal particle size shrinkage core model, and the formula is as follows:

[0113] Gas-solid heat balance model: derived based on the first law of thermodynamics. The first law of thermodynamics indicates that the energy of a fluid is equal to the sum of the heat absorbed by the fluid and the work done by the fluid on the outside. Without considering the temperature difference between the gas phase and the solid phase in the sintering cup, the equation described by the local heat balance model of the porous medium is:

[0114] Gas-solid heat balance energy conservation equation:

[0115] ;

[0116] Gas-solid non-heat balance model: for the case that the temperature of the gas phase and the solid phase in the sintering cup is not consistent, different energy equations are needed to describe the temperature change of the gas and the material layer, i.e. the non-heat balance model of the porous medium is introduced, and the gas-solid non-heat balance energy conservation equation is divided into the gas non-heat balance energy conservation equation and the solid non-heat balance energy conservation equation, and the specific formula is as follows:

[0117] Gaseous non-thermal equilibrium energy conservation equation:

[0118]

[0119] Solid non-thermal equilibrium energy conservation equation:

[0120]

[0121] The calculation formula of the physical and chemical reaction heat source term is as follows:

[0122]

[0123]

[0124] The calculation formula of the convective heat transfer specific surface area is as follows:

[0125]

[0126] Wherein: : Equivalent diameter of mixture material particles, m; ε: Porosity of material layer;

[0127] Radiation heat transfer model: For the radiation heat transfer of natural gas burner and high temperature flame in the ignition process, the specific formula of the heat source generated by the material layer is as follows:

[0128] Radiation heat transfer heat source q1 between the inner wall of the igniter and the surface of the material layer:

[0129]

[0130] Radiation heat transfer q2 of the flame to the surface of the material layer:

[0131]

[0132] Equal particle size shrinkage core model: In the embodiment, it is considered that the coke combustion is controlled by diffusion-dynamics, and the diffusion resistance includes material coating resistance and boundary layer resistance. The calculation formula of the total reaction rate is as follows:

[0133]

[0134] Step four: import the parameters corresponding to the simulation of coke combustion in the sintering process into the simulation system;

[0135] Step five: run the simulation system to obtain the temperature change data to be solved, and analyze the influence of gas-solid heat transfer temperature difference on the temperature of the material layer and the coke combustion rate.

[0136] ​​​​​​​​​Further, the numerical simulation calculation is simplified, specifically including: assuming that the gas and the material layer are continuously distributed in the sintering cup, not considering the heat dissipation of the sintering cup wall surface, and assuming that the internal temperature gradient of the particle is zero.

[0137] Simplifying the numerical simulation calculation can simplify the complexity of the numerical simulation model, make the calculation process more efficient, assume that the gas and the material layer are continuously distributed in the sintering cup, which helps to more accurately simulate the changes of the gas flow field and the gas-solid phase temperature field in the sintering process, not consider the heat dissipation of the sintering cup wall surface, and focus on the temperature distribution and temperature change of the coke combustion in the sintering process, and assume that the internal temperature gradient of the particle is zero, which can avoid the error caused by the complex temperature distribution, so as to more accurately predict the change of the heat transfer process in the sintering process.

[0138] Further, the boundary is set, specifically including: setting the upper part of the geometric model as the velocity inlet of the gas flow, the lower part as the pressure outlet, and the other parts as the adiabatic wall surface.

[0139] Further, the grid is divided, and the number of the structured grid is 18700-18800, and the grid quality is greater than 0.99.

[0140] The grid division determines the degree of discretization and the calculation scale of the model. By dividing the continuous object into discrete units, numerical calculation and analysis can be carried out, and the quality of the grid division directly affects the accuracy of the subsequent numerical calculation and analysis results. Suitable grid division can improve the calculation precision, reduce the degree of freedom of the model, and thus reduce the calculation time and resource consumption.

[0141] Further, the gas-solid heat balance model and the gas-solid non-heat balance model correspond to the cases of not considering the temperature difference between the gas phase and the solid phase in the sintering cup and considering the temperature inconsistency between the gas phase and the solid phase in the sintering cup, respectively.

[0142] Further, the role of the porous medium model is to regard the sintering material layer as a porous medium, and simulate the flow of gas through the sintering material layer by using the porous medium model.

[0143] The porous medium model simulates the flow of fluid in the porous medium by introducing a resistance coefficient, thereby simplifying the geometric complexity and the problem of large scale span, reducing the calculation amount, and accelerating the simulation process.

[0144] Further, the role of the radiation heat transfer model is to simulate the heat source generated by the radiation heat transfer of the natural gas burner and the high-temperature flame to the material layer during the ignition process.

[0145] Further, in the gas-solid non-heat balance model, the heat transfer process in the coke combustion is simulated by using the convective heat transfer model, and the formula is as follows:

[0146] ;

[0147] ;

[0148] η is a channel factor, the initial value is 1, and linearly increases to the final value with the liquid phase melt fraction β, in this embodiment, the final value is 11. The calculation formula is that the liquid phase melt fraction is introduced into the existing calculation formula of Nu number to modify the calculation result.

[0149] The liquid phase melt fraction in the sintering process refers to the proportion of the liquid phase melt generated in the sintering process. This proportion reflects the melting degree of the material in the sintering process, and has an important influence on the density and performance of the final product. Liquid phase sintering refers to the coexistence of liquid phase and solid phase particles in the sintering process. In this case, the fluidity of the liquid can significantly improve the densification speed and final density of the sintered body.

[0150] The gas-solid heat exchange process in the sintering process is the core process affecting sintering. In addition to the heat absorption and release of chemical reactions, the convective heat transfer process between the gas flowing through the material layer and the material layer is also an important factor affecting the temperature of the material layer. The present application comprehensively uses the convective heat transfer models widely used in the literature to simulate the sintering process, and compares them with experimental data to determine the most suitable heat transfer model for this project.

[0151] Further, the equivalent particle diameter of the coke particle in the equal particle size shrinkage core model needs to be calculated according to the unreacted shrinkage core model, and the formula is as follows:

[0152] ;

[0153] A heat transfer process simulation system for coke combustion in a sintering process, comprising a computer device, a flue gas analyzer and an infrared thermal imager;

[0154] The computer device comprises a memory, a processor and a computer program stored on the memory and executable on the processor, and the processor implements the steps in the heat transfer process simulation method for coke combustion in a sintering process when executing the program;

[0155] The flue gas analyzer and the infrared thermal imager are respectively electrically connected with the computer device, and are respectively used for detecting the smoke composition in the coke combustion process and part of the temperature data in the experimental process.

[0156] The simulation analysis result of the heat transfer process of coke combustion is as shown in Figures 2-8 The simulation conclusion obtained is as follows:

[0157] As shown in Figures 2-3As shown, under gas-solid thermal equilibrium conditions, assuming that gas-solid heat exchange is completed instantaneously and there is no temperature difference between the feed layer and the gas, a single average temperature is used to describe the gas and solid phases. At 120 seconds after ignition, the high-temperature region is relatively small, with a maximum reaction rate of 30.30 mol / (m³∙s) and a maximum temperature of 1150℃. Because the gas-solid heat exchange is instantaneous, the heat storage effect is maximized, which greatly promotes coke combustion. Therefore, at 350 seconds, the maximum reaction rate in the combustion zone reaches 85.86 mol / (m³∙s), and the maximum temperature reaches 2327℃, which differs significantly from the actual values.

[0158] like Figures 4-6 As shown, under non-gas-solid thermal equilibrium conditions, considering only coke combustion, the gas-solid temperature difference is significant in the short period after ignition. As sintering progresses, the gas-solid temperature difference decreases, and when the entire sintering experiment in the sintering cup has been going on for 1500 seconds, the difference between the two is very slight.

[0159] Approximately 6 minutes after ignition, the gas temperature reached 1361℃, and the highest temperature of the material layer was 1269℃. At this point, the gas-solid temperature difference was mainly concentrated in the upper part of the sintering cup, and at the same location, the highest temperature difference reached 295℃. As sintering progressed, the gas temperature first decreased and then increased, while the material layer temperature continued to rise. The reason for the different trends in gas-solid temperature changes is that after the high-temperature flue gas from ignition heats the material layer, its temperature decreases, while the material layer temperature increases. Upon reaching the ignition point of the coke, the combustion reaction rate accelerates, releasing a large amount of heat, which in turn heats the gas, causing the flue gas temperature to rise. The reheated flue gas further promotes the expansion of the high-temperature zone in the material layer and the increase in its maximum temperature.

[0160] like Figure 7 As shown, the sintering process continued from 500s, with the gas-solid temperature difference gradually increasing from 295℃ to 345℃ at 1500s. In the later stages of sintering, although the gas-solid temperature difference increased further, the increase was significantly smaller than in the sintering stage after ignition. Furthermore, the gas-solid temperature difference distribution diagram also shows that in the initial stage of sintering, the gas temperature was significantly higher than the material layer temperature. As sintering progressed, the upper, already sintered area was gradually cooled by the drawn-in cold air, resulting in the material layer temperature in the upper region of the sintering cup being higher than the gas phase temperature, i.e., a negative gas-solid temperature difference.

[0161] like Figure 8 As shown, at 1500 s, the combustion zone had moved to the lower part of the sintering cup, at which point the maximum rate of coke combustion reaction was 38.37 mol / (m3∙s). (Comparison) Figure 7 It can be seen that the location with the largest gas-solid temperature difference coincides with the location of the coke combustion zone.

[0162] At the end of ignition, the ignition depth calculated by the gas-solid equilibrium heat transfer model is significantly smaller than that calculated by the gas-solid non-equilibrium heat transfer model, and there is a large difference from the actual situation, indicating that the gas-solid non-equilibrium heat transfer model is more in line with actual needs.

[0163] Based on the gas-solid non-equilibrium heat transfer model, the maximum temperature difference between gas and solid in the sintering process is about 345℃.

[0164] Based on the gas-solid non-equilibrium heat transfer model, the ignition depth is 23mm, and the combustion rate of coke in the sintering process is about 35mol / (m3·s).

[0165] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having substantially the same configuration and playing the same role and effect as the technical idea within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications that can be thought of by those skilled in the art are applied to the embodiments, and other ways constructed by combining part of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method of simulating heat transfer processes in coke combustion in a sintering process, characterized by, The method comprises the following steps: Step 1: proportionally establishing a two-dimensional sintering cup geometric model for numerical simulation; Step 2: based on parameter analysis in the sintering experiment, simplifying the numerical simulation calculation, and setting the boundary of the sintering cup geometric model and dividing the grid; Step 3: importing the divided mass grid into the simulation system, setting the calculation model of the simulation system, and the calculation model comprises a gas-solid heat balance model, a gas-solid non-thermal balance model, a porous medium model, a radiation heat transfer model, and an equal particle size shrinkage core model, and the formula is as follows: The gas-solid heat balance model: gas-solid heat balance energy conservation equation: ； The gas-solid non-thermal balance model: the gas-solid non-thermal balance energy conservation equation is divided into a gaseous non-thermal balance energy conservation equation and a solid non-thermal balance energy conservation equation, and the specific formula is as follows: The gaseous non-thermal balance energy conservation equation: ； The solid non-thermal balance energy conservation equation: ； wherein: Tsolidis the solid phase temperature, K; Tgasis the gas phase temperature, K; : solid phase density, kg / m3 ; : gas phase density, kg / m3 ; : Specific heat capacity at constant pressure in solid phase, J / (kg*K); : Specific heat capacity at constant pressure in gas phase, J / (kg*K); : solid phase overall thermal conductivity, W / (m*K); : gas phase effective thermal conductivity; P : turbulent Prandtl number; , : source term of the physico-chemical heat, ; : heat of chemical reaction for reaction k, J / kg; : convective heat transfer specific surface area, ; : gas-solid convective heat transfer coefficient, ; ε: layer porosity; : gas phase flow rate in j direction; x j : cartesian coordinate system j displacement in the direction, m; μ g,t : Viscosity of the vortex, also called apparent turbulent viscosity, Pa*s; R k : reaction k rate of the chemical reaction, mol / (m 3 *s); q rad : amount of heat transferred by radiation, t: reaction time, s; The radiation heat transfer model: The radiation heat transfer heat source q1 between the inner wall of the igniter and the surface of the material layer: ； wherein: A B : inner wall area of the igniter, m2 2 ; A L : surface area of the igniter charge, m2 2 ; X B,L : angle coefficient of inner wall surface of igniter to surface of material layer; : emissivity of the layer surface, taken as 0.8; σ : Stefan-Bolzmann constant; T B : Temperature of inner wall surface of igniter, K T L : Temperature of surface of material layer, K The radiation heat transfer q2 of the flame to the surface of the material layer: ； wherein: ε g : blackness of the flame, taken as 0.149; α g : soot uptake ratio of the flame, taken as 0.219; σ Stefan-Bolzmann constant; : gas phase temperature, K; T L : bed surface temperature, K; The equal particle size shrinkage core model: ； wherein: : reaction rate; : particle number density of coke breeze in the iron ore sinter bed layer; κ: incomplete combustion coefficient; π: circular constant; ζ: shape factor of the coke particle, namely sphericity; : equivalent particle diameter of coke particles during the reaction; : overall rate coefficient of the coke combustion reaction : concentration in the sinter bed : concentration Step 4: importing the parameters corresponding to the simulation of the coke combustion in the sintering process into the simulation system; Step 5: running the simulation system to obtain the temperature change data to be solved, and analyzing the influence of the gas-solid heat transfer temperature difference on the material layer temperature and the coke combustion rate.

2. The method and system for simulating heat transfer processes of coke combustion in a sintering process according to claim 1, characterized in that, The numerical simulation calculation is simplified, and specifically comprises the following steps: assuming that the gas and the material layer are continuously distributed in the sintering cup, not considering the heat dissipation of the sintering cup wall surface, and assuming that the internal temperature gradient of the particle is zero.

3. The method and system for simulating heat transfer processes of coke combustion in a sintering process according to claim 1, characterized in that, The boundary setting specifically comprises the following steps: setting the upper part of the geometric model as the velocity inlet of the gas flow, the lower part as the pressure outlet, and the other parts as the adiabatic wall surface.

4. The method and system for simulating heat transfer processes of coke combustion in a sintering process according to claim 1, characterized in that, The grid division comprises the following steps: the number of the divided structured grid is 18700-18800, and the grid quality is greater than 0.

99.

5. The method and system for simulating heat transfer processes of coke combustion in a sintering process according to claim 1, wherein, The gas-solid heat balance model and the gas-solid non-thermal balance model correspond to the cases that the temperature difference between the gas phase and the solid phase in the sintering cup is not considered and the temperature difference between the gas phase and the solid phase in the sintering cup is considered, respectively.

6. The method and system for simulating heat transfer processes of coke combustion in a sintering process according to claim 1, wherein, The porous medium model regards the sintering material layer as a porous medium, and uses the porous medium model to simulate the flow of the gas flowing through the sintering material layer.

7. The method and system for simulating heat transfer processes of coke combustion in a sintering process according to claim 1, wherein, The radiation heat transfer model simulates the heat source generated by the radiation heat transfer of the natural gas burner and the high-temperature flame to the material layer during the ignition process.

8. The method and system for simulating heat transfer processes of coke combustion in a sintering process according to claim 1, wherein, In the gas-solid non-thermal balance model, the convection heat transfer model is used to simulate the heat transfer process in the coke combustion, and the formula is as follows: ； ； Wherein: Nu: convection heat transfer coefficient; ε: material layer porosity; β: liquid phase melt share; η: channel factor, whose initial value is 1; : final value of the channel factor; Re: Reynolds number, the ratio of the inertial force to the viscous force of the fluid; Pr: Prandtl number, the ratio of the thermal diffusion capacity of the fluid to the momentum diffusion capacity thereof.

9. The method and system for simulating heat transfer processes of coke combustion in a sintering process according to claim 1, wherein, The coke particle equivalent diameter in the equal-particle-size shrinking core model This needs to be calculated according to the unreacted shrinking core model, and the formula is as follows: ； wherein: : equivalent particle diameter of coke particles, m; : mass fraction of ash in the coke particles; : unreacted coke particle core particle diameter, m : initial coke particle diameter, m 10. A system for simulating heat transfer processes in coke combustion in a sintering process, characterized by The computer device, the flue gas analyzer and the infrared thermal imager; The computer device comprises a memory, a processor and a computer program stored in the memory and capable of running on the processor, and the processor implements the steps in the heat transfer process simulation method for coke combustion in a sintering process according to any one of claims 1-7 when executing the program. The flue gas analyzer and the infrared thermal imager are respectively electrically connected with the computer device, and are respectively used for detecting smoke composition in the coke combustion process and part of temperature data in the experiment process.

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