Method for determining the optimal throat and waist diameter ratio of blast furnace based on CFD process simulation

Abstract

The present invention relates to a method for determining the optimal throat-waist diameter ratio of a blast furnace based on CFD process simulation. A CFD blast furnace process model is constructed to simulate the comprehensive performance indicators and internal states of blast furnaces with different throat-waist diameter ratios. The distribution of fluid velocity, pressure, temperature, etc. in the furnace can be obtained, and the conclusions are quantified. The coke ratio, yield, tuyere pressure, and internal state of the blast furnace are comprehensively considered to determine the optimal throat-waist diameter ratio of an industrial blast furnace based on the principle of minimum total energy consumption. At the same time, the method of the present invention is efficient, convenient, and low-cost. The blast furnace type optimized and designed using the method of the present invention has low blast furnace production cost, good thermal energy utilization, and high safety. This method makes up for the shortcomings of the current research on the throat-waist diameter ratio of blast furnaces, which is mostly based on engineering experience, with vague conclusions and the inability to clearly define the specific impact of changes in the throat-waist diameter ratio on the smelting performance of the blast furnace.

Description

Technical Field

[0001] The present invention relates to the technical field of CFD simulation of blast furnace production process, in particular to a method for determining an optimal throat and waist diameter ratio of a blast furnace based on CFD process simulation. Background Art

[0002] Blast furnace smelting is a continuous production process that reduces iron ore into pig iron. Blast furnace energy consumption accounts for 70% of the energy consumption of the entire steel production process, and its CO2 emissions (including coking, sintering, and pelletizing processes) account for 70-90% of the total emissions of the entire steel production process. A blast furnace is a blast furnace that produces liquid pig iron. Its working space is built with refractory materials, and the shape of the internal working space cross-section is called the blast furnace type. According to current practice, blast furnace types are generally divided into four levels according to the size of the furnace: small blast furnaces (≤1000m 3 ), medium-sized blast furnace (1000-2500m 3 ), large blast furnace (>2500m 3 ), giant blast furnace (>5000m 3 The essence of blast furnace smelting is the heat and mass transfer between the rising coal gas flow and the descending charge. Therefore, appropriate space must be provided, and the blast furnace configuration must adapt to the requirements of the raw material and fuel conditions to ensure smooth smelting. A reasonable blast furnace configuration is one that achieves good yield, fuel ratio, and low energy consumption. It is a key factor in achieving high production, high quality, low consumption, and longevity.

[0003] After a long period of development, the blast furnace has gradually evolved into a system consisting of five parts, from top to bottom: throat, body, waist, bosh and hearth. Figure 1 Among them, the throat-waist diameter ratio (R D=d1 / D) is the primary parameter characterizing the shape of the upper portion of a blast furnace. It is directly related to the size of the furnace shaft angle and significantly influences the distribution of charge descent and gas flow as it rises. During furnace design, the throat-waist diameter ratio is often set empirically, typically between 0.6 and 0.75. Numerical research on the throat-waist diameter ratio currently focuses on two main approaches: analysis of existing engineering blast furnaces and CFD (Computational Fluid Dynamics) simulation. The former collects, studies, and organizes the internal profiles of existing engineering blast furnaces, analyzing the evolution of these profiles and the impact of differences in furnace shaft structure on gas flow distribution within the blast furnace, thereby exploring appropriate operational furnace structure and design. This type of research, based on engineering practice, is highly reliable and yields conclusions with strong applicability. However, its scope is narrow and limited, making it impossible to clearly define the specific impact of different throat-waist diameter ratios on blast furnace performance and quantitatively determine the optimal value. The latter numerically solves the governing equations for fluid flow, enabling simulation of related physical phenomena such as fluid flow, heat transfer, and mass transfer. CFD simulation can simulate complex operating conditions and simultaneously determine the distribution of fluid velocity, pressure, temperature, and other characteristics. This is particularly true for the high-temperature, high-pressure, and complex multiphase heat and mass transfer and chemical reaction environments of blast furnaces. CFD simulation can capture this distribution information within the furnace and quantitatively investigate the impact of the throat-to-waist diameter ratio on blast furnace smelting performance.

[0004] So far, due to the complex internal process mechanism of the blast furnace, the harsh environment, and the difficulty in detecting key parameters, the research on the blast furnace throat-waist diameter ratio has not been quantified. It is impossible to clarify the influence of the throat-waist diameter ratio on the comprehensive performance of the blast furnace, and thus it is impossible to propose the optimal throat-waist diameter ratio. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention provides a method for determining the optimal throat and waist diameter ratio of a blast furnace based on CFD process simulation, thereby obtaining a design scheme that minimizes the total energy consumption of the blast furnace.

[0006] The technical solution adopted in the present invention is as follows:

[0007] The present invention provides a method for determining an optimal throat and waist diameter ratio of a blast furnace based on CFD process simulation, comprising the following steps:

[0008] S1. Establish corresponding blast furnace geometric models for different throat-to-waist diameter ratios and perform meshing on the blast furnace geometric models;

[0009] S2. Determine input parameters, which include blast furnace geometry, upper adjustment parameters, and lower adjustment parameters;

[0010] The geometric dimensions of the blast furnace include the effective volume of the blast furnace, the diameter of each section, and the height of each section;

[0011] The upper adjustment parameters include ore parameters, coke parameters, and distribution system;

[0012] The lower adjustment parameters include tuyere related parameters, air supply system, and injection system;

[0013] S3. Determine the temperature and composition of the gas generated after the combustion reaction, and the size and shape of the tuyere raceway according to the input parameters;

[0014] S4. Preliminary calculation of the solid flow field and iterative calculation to determine the three-dimensional dead material column contour;

[0015] S5. Determine solid flow time contours based on the solid velocity field, mark positions based on the solid flow time contours, and track the layered positions of coke and iron ore in the blast furnace after each loading of materials, thereby determining a three-dimensional layered charge structure in the blast furnace;

[0016] S6. Without considering chemical reactions, the gas flow field, temperature field, and concentration field are initially solved iteratively through the discretized mass conservation, momentum conservation, and energy conservation differential equations until the iteration converges;

[0017] S7. Based on the temperature field obtained after iterative convergence, the soft melting zone area is determined using the heterogeneous layered processing method;

[0018] S8. Taking chemical reactions into account, recalculate the gas flow field, solid flow field, temperature field, and concentration field to obtain the pressure, temperature, and heat consumption in the blast furnace;

[0019] S9. Treat the molten iron and slag in the blast furnace as liquid phases, consider the combined effects of gas, solid, and gravity on the liquid, calculate the blast furnace liquid phase flow, and obtain the tuyere pressure and heat input;

[0020] S10, judging whether the soft melting zone area has converged, if not, repeating S8 to S9 until it converges, and then proceeding to S11;

[0021] S11, determine whether the coke consumption is balanced. If not, repeat S3 to S10 until it is balanced. Predict the yield based on the calculation result and proceed to S12;

[0022] S12, judging whether the liquid temperature in the blast furnace is equal to a preset value according to the energy conservation differential equation; if not, repeating S3 to S11; if equal, proceeding to S13;

[0023] S13. Based on the calculation results, various comprehensive performance indicators and total energy consumption are counted to obtain the throat-waist diameter ratio with the lowest total energy consumption.

[0024] Further technical solutions are:

[0025] In step S4, the solid flow field is preliminarily calculated and the three-dimensional dead material column profile is determined by iterative calculation, including:

[0026] Firstly, without considering the three-dimensional dead material column, the initial solid flow field is solved according to the boundary conditions of the blast furnace solid phase inlet, outlet and wall.

[0027] Secondly, the region in the initial solid flow field where the velocity is less than the critical velocity is determined as a three-dimensional dead material column, and its volume V is determined. d1 ;

[0028] Third, the velocity field of the three-dimensional dead material column is set to zero, and the boundary of the three-dimensional dead material column is set as the new boundary of the solid flow field, and the solid flow field is re-solved;

[0029] Fourth, obtain the new three-dimensional dead material column wheel volume V d2 , V d2 With V d1 Make comparisons;

[0030] Repeat the third and fourth steps until the difference between the three-dimensional dead material column volumes in the two previous calculations is less than the preset value.

[0031] In step S5, position marking is performed according to the solid flow time contour line, including:

[0032] Initialize the timeline at the top of the blast furnace to 0, and calculate the time t required to load each layer of ore and coke using the following formula batch :

[0033] t batch =m batch / ρ bulk u feed A throat ;

[0034] Where m batch represents the total mass of a layer of ore and a layer of coke, ρ bulk represents the average density of a layer of ore and a layer of coke, u feed Represents the charge filling rate, A throat represents the cross-sectional area of ​​the furnace throat;

[0035] Obtain the volume fraction of ore in each loading material;

[0036] t batch Multiply by the corresponding ore volume fraction to obtain a series of moments, and convert t batchAnd a series of moments obtained by calculation, starting from the time line at the top, are marked at corresponding heights along the height direction, so as to obtain the dividing lines between each layer of ore and coke, and obtain a three-dimensional layered charge structure.

[0037] In step S7, the method of determining the soft melting zone region by adopting the heterogeneous layered processing method includes:

[0038] The area with solid temperature between 1473K and 1673K in the three-dimensional layered charge structure in the blast furnace is defined as the soft melting zone;

[0039] Define the normalized shrinkage ratio Shr * In order to divide the indicators, the soft melting zone area is subdivided into areas with different states according to the preset rules;

[0040] Shr * =Shr / Sh r,max , Shr is the shrinkage rate of iron ore in the soft melting zone, Sh r,max is the maximum shrinkage rate.

[0041] The preset rules include:

[0042] 0.7 <Shr * ≤1.0, indicating that the ore is melted and in liquid state, and the corresponding area is completely occupied by the liquid phase;

[0043] 0.5 <Shr * ≤0.7, representing the softening and melting state of the ore;

[0044] 0.0 <Shr * ≤0.5, representing the ore softening stage;

[0045] Among them Sh r,max =0.7.

[0046] In step S9, the calculation of the blast furnace liquid phase flow includes:

[0047] According to the force balance model of three-dimensional liquid dripping flow, the three forces acting on the liquid, namely gas, solid, and gravity, are calculated. The governing equation of the force balance model is as follows:

[0048]

[0049] Where F is the force on the liquid, the superscripts g and s indicate the source of F, representing gas and solid respectively, and the subscript l represents the liquid; ε l is the liquid volume fraction, g is the acceleration due to gravity, C DG and C DS are the resistance coefficients of gas and solid respectively; A g-l and A s-lare the effective contact areas with gas and solid respectively; ρ g and ρ l are the gas and liquid densities, U g and U l are the gas and liquid velocities, respectively.

[0050] In step S13, the statistics of various comprehensive performance indicators and total energy consumption are collected to obtain the throat-waist diameter ratio with the lowest total energy consumption, including:

[0051] S131. Based on various comprehensive performance indicators and total energy consumption, preliminarily obtain the throat-waist diameter ratio and corresponding operating conditions with the lowest total energy consumption;

[0052] S132. Post-process the internal state of the blast furnace under this operating condition to determine whether the internal state of the furnace, including the distribution of the soft melting zone, the gas pressure field, the gas velocity field, the solid temperature field, and the indirect reduction rate distribution, is reasonable. If so, obtain the optimal throat-waist diameter ratio; otherwise, proceed to S133.

[0053] S133. Reselect the furnace throat-furnace waist diameter ratio when the total energy consumption is the lowest, or the furnace throat-furnace waist diameter ratio when the total energy consumption is the second lowest, and the corresponding operating conditions, and repeat S132 until the furnace state is reasonable.

[0054] In step S13, the various comprehensive performance indicators include the ore-to-coke ratio, the yield, the tuyere pressure and the heat input; the total energy consumption includes the physical energy consumption Wm=Q·Pη·p·V, and the chemical energy consumption; wherein Q is the blower exhaust volume, P is the blast pressure, η is the blower motor efficiency, p is the yield, and V is the effective volume of the blast furnace; the chemical energy consumption, i.e., the heat input, is the sum of the blast heat and the combustion heat.

[0055] In step S6, without considering the chemical reaction, the chemical reaction rate term in the mass conservation and energy conservation differential equations is assigned a value of 0, and then iterative calculation is performed;

[0056] In step S8, the chemical reaction rate term in the mass conservation and energy conservation differential equations is calculated and assigned a value using the chemical reaction rate formula, and then iterative calculation is performed, taking the chemical reaction into consideration.

[0057] The ore parameters include ore type, batch weight, ore composition, ore particle size distribution, reducibility, ore thermal conductivity, softening and melting characteristics, low-temperature reduction pulverization, and thermal cracking properties;

[0058] The coke parameters include coke composition, coke particle size distribution, coke reactivity, and coke thermal conductivity;

[0059] The distribution system includes the particle size distribution of ore and coke, and the ore-coke ratio distribution;

[0060] The tuyere-related parameters include tuyere position, number and size;

[0061] The air supply system includes hot air temperature, oxygen enrichment rate, blast volume and blast humidity;

[0062] The injection system includes the type of injection fuel, the composition of the injection fuel, the injection amount and the position of the injection gun.

[0063] The beneficial effects of the present invention are as follows:

[0064] The present invention uses CFD to establish a blast furnace ironmaking process model, describing the complex coupled gas / solid / liquid flow, heat transfer, mass transfer and chemical reaction between the furnace top charge surface and the furnace hearth slag surface, and realizing the visualization and digitization of the multiphase flow and thermochemical behavior inside the blast furnace.

[0065] The present invention constructs a CFD blast furnace process model, simulates the comprehensive performance indicators and internal states of blast furnaces with different throat-waist diameter ratios, comprehensively considers coke ratio, yield, tuyere pressure and the internal state of the blast furnace, and determines the optimal throat-waist diameter ratio of the industrial blast furnace by the principle of minimum total energy consumption (the sum of physical energy consumption and chemical energy consumption). Under the blast furnace type optimized by this method, the blast furnace production cost is low, the thermal energy utilization is good, and the safety is high. At the same time, the distribution of fluid velocity, pressure, temperature, etc. in the furnace can be obtained, the conclusion is quantitative, and it is efficient, convenient, and low in cost. It makes up for the current research on the blast furnace throat-waist diameter ratio, which is mostly based on engineering experience, the conclusion is vague, and it is impossible to clearly define the deficiency of the specific impact of the change of the throat-waist diameter ratio on the blast furnace smelting performance.

[0066] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a schematic diagram of a blast furnace in the prior art.

[0068] Figure 2 This is a schematic diagram of the furnace status during the blast furnace ironmaking process in the prior art.

[0069] Figure 3 Schematic diagram of a method flow in an embodiment of the present invention.

[0070] Figure 4 The different throat-waist diameter ratios (R D ) Schematic diagram of the blast furnace geometric model.

[0071] Figure 5 Schematic diagram of the iterative calculation process of the three-dimensional dead material column in an embodiment of the present invention.

[0072] Figure 6 A schematic diagram of the structure of a layered soft melting zone is determined for an embodiment of the present invention.

[0073] Figure 7 Schematic diagram of carbon balance according to an embodiment of the present invention.

[0074] Figure 8 These are the calculation results of various comprehensive performance indicators of the embodiments of the present invention.

[0075] Figure 9 The physical energy consumption and chemical energy consumption of blast furnaces with different throat-waist diameter ratios calculated in accordance with the present invention are shown.

[0076] Figure 10 The total energy consumption of blast furnaces with different throat-waist diameter ratios calculated in accordance with the present invention.

[0077] Figure 11 The best throat-waist diameter ratio of the blast furnace (R D =0.6) of the internal state.

[0078] Figure 12 This is a geometric diagram of a blast furnace with an optimal throat-waist diameter ratio obtained by simulation calculation according to an embodiment of the present invention. DETAILED DESCRIPTION

[0079] The specific embodiments of the present invention are described below with reference to the accompanying drawings.

[0080] This embodiment provides a method for determining the optimal throat-waist diameter ratio of a blast furnace based on CFD process simulation. The method constructs a CFD blast furnace process model, simulates the comprehensive performance indicators and internal states of blast furnaces with different throat-waist diameter ratios, and obtains a complete technical solution for determining the optimal throat-waist diameter ratio.

[0081] See also Figure 2The blast furnace ironmaking process targeted by this embodiment is as follows: Solid raw materials such as iron ore, coke, and flux are fed into the blast furnace in batches via the top charging device according to specified proportions, with the charge level at the furnace throat maintained at a certain height. The coke and ore form an alternating layered structure within the furnace. At the bottom of the blast furnace, air is heated by a hot blast stove and enters through the tuyere. This hot air is pumped through the tuyere at a high gas velocity, forming a vortex zone where it combusts with the surrounding coke to produce high-temperature coal gas. This high-temperature coal gas flows upward, heating the solid charge and reducing the iron ore as it rises. The coal gas temperature and composition continuously change before ultimately leaving the blast furnace through the top. During this period, the consumption of coke near the tuyere's whirlpool zone frees up space for the ore and coke particles above it, allowing the solid charge to move downward. During its descent, the reducing gases and ore particles come into contact, undergoing a reduction reaction. Vigorous heat, mass, and momentum transfer occurs between the ore and the rising gas stream, gradually reducing, softening, and melting the iron-containing charge. Ultimately, molten iron and slag drip into the furnace hearth. The accumulated molten iron and slag are regularly discharged from the taphole and slag outlet, completing the blast furnace ironmaking process. The internal structure of a blast furnace can be divided from top to bottom into the massive zone, the soft melting zone, the dripping zone, and the dead column, each with its own unique characteristics. This makes it an extremely complex, high-temperature, high-pressure reactor. In the massive zone, indirect reduction primarily occurs, with water in the charge evaporating and decomposing due to heat. A small amount of direct reduction occurs, with heat exchange between the charge and the gas. Within the blast furnace, there is a region where the ore gradually transitions from solid to liquid, known as the soft melting zone. The charge begins to soften at the upper boundary of the melting zone and melts and drips at the lower boundary, primarily undergoing direct reduction reactions and slag formation. Molten iron is produced in the melting zone, flows downward through the dripping zone, and is deposited around the dead material zone at the bottom of the blast furnace (this layer is relatively stagnant, hence the name dead material zone).

[0082] For the above ironmaking process, see Figure 3 The method for determining the optimal throat and waist diameter ratio of a blast furnace based on CFD process simulation in this embodiment specifically includes the following steps:

[0083] S1. For multiple different throat-to-waist diameter ratios, corresponding blast furnace geometric models are established and meshed.

[0084] In this embodiment, 5000m 3 Taking the blast furnace as an example, except for the throat-waist diameter ratio, other geometric parameters are kept constant. When meshing different types of blast furnaces, the number of grids should be consistent. The specific geometric dimensions are as follows: Figure 4 shown.

[0085] Figure 4 The CPC gives six different throat-waist diameter ratios R D Schematic diagram of the blast furnace geometric model, R D They are 0.4, 0.5, 0.6, 0.7 and 0.8 respectively.

[0086] S2. Determine input parameters, which include blast furnace geometry, upper adjustment parameters, and lower adjustment parameters;

[0087] The geometric dimensions of the blast furnace include the effective volume of the blast furnace, the diameter of the furnace throat, the diameter of the furnace waist, the diameter of the hearth, and the heights of the hearth, the furnace belly, the furnace waist, the furnace body, and the furnace throat;

[0088] The upper adjustment parameters include:

[0089] Ore parameters, including ore type, batch weight (the weight of the charge loaded into the blast furnace from the top each time, which mainly includes iron ore, coke, flux, etc.), ore composition, ore particle size distribution, reducibility, ore thermal conductivity, softening and melting characteristics, low-temperature reduction pulverization, and thermal cracking resistance;

[0090] Coke parameters, including coke composition, coke particle size distribution, coke reactivity, and coke thermal conductivity;

[0091] The distribution system includes the particle size distribution of ore and coke, as well as the ore-coke ratio. The ore-coke ratio is defined as the amount of coke consumed per ton of qualified pig iron, and its consumption is directly related to the level of production costs.

[0092] The lower adjustment parameters include:

[0093] Tuyere-related parameters, including tuyere location, number and size;

[0094] Air supply system, including hot air temperature, oxygen enrichment rate, blast volume and blast humidity;

[0095] The injection system includes the type of injected fuel, the composition of injected fuel, the injection amount and the position of the injection gun.

[0096] As a specific implementation, the input parameter values ​​of this embodiment are shown in Table 1.

[0097] Table 1 Input parameter values ​​of blast furnace simulation

[0098]

[0099]

[0100] The RDI value of iron ore refers to the pulverization rate during low-temperature reduction at 500°C. This value is an important indicator for measuring the degree of pulverization of iron ore during the reduction process in the upper part of the blast furnace. The higher the RDI value, the more likely the iron ore is to pulverize during the reduction process in the upper part of the blast furnace. This affects the blast furnace's air permeability and the rate of charge descent, which in turn affects the blast furnace's operation and output.

[0101] S3. Determine the temperature and composition of the gas generated after the combustion reaction, and the size and shape of the tuyere swirl zone based on the input parameters.

[0102] The tuyere raceway, also known as the coke circulation zone, is the area in front of the tuyere in the blast furnace where the coke burns while rotating under the influence of high-speed hot air during ironmaking. It serves as one of the calculation boundaries. The size of the tuyere raceway includes height, depth, and width.

[0103] It can be understood that the remaining calculation boundaries are the geometric boundaries of the blast furnace, including the shape and size of the blast furnace. For example, the size and shape of the throat, shaft, waist, bosh, hearth and other areas have been determined in step S1.

[0104] S4. Preliminary calculation of the solid flow field and iterative calculation to determine the three-dimensional dead material column contour.

[0105] See also Figure 5 The calculation process of the three-dimensional dead material column profile specifically includes the following steps:

[0106] Firstly, without considering the three-dimensional dead material column, the initial solid flow field and initial velocity field are solved according to the boundary conditions of the solid phase inlet, outlet and wall of the blast furnace;

[0107] Secondly, the region in the initial solid flow field where the velocity is less than the critical velocity is determined as a three-dimensional dead material column, and its volume V is determined. d1 ;

[0108] Third, the velocity field of the three-dimensional dead material column is set to zero, and the boundary of the three-dimensional dead material column is set as the new boundary of the solid flow field, and the solid flow field is re-solved;

[0109] Fourth, obtain the new three-dimensional dead material column wheel volume V d2 , V d2 With V d1 Make comparisons;

[0110] Repeat the third and fourth steps until the difference between the three-dimensional dead material column volumes in the two previous calculations is less than the preset value.

[0111] The solid phase consists of coke, iron-containing furnace charge (sintered and / or pelletized), and flux. In this embodiment, regions within the solid flow field with velocities below the critical velocity are treated as dead columns. The critical velocity is defined as the velocity per minute equal to one-ninth the particle diameter.

[0112] S5. Determine the solid flow time contour line based on the solid velocity field, mark the position based on the solid flow time contour line, track the layered position of coke and iron ore in the top charge batch weight loaded from the top of the blast furnace each time, and thus determine the three-dimensional layered charge structure in the blast furnace.

[0113] The step of marking a position according to the solid flow time contour line includes:

[0114] Initialize the timeline at the top of the blast furnace to 0, and calculate the time t required to load each layer of ore and coke using the following formula batch :

[0115] t batch =m batch / ρ bulk u feed A throat ;

[0116] Where m batch represents the total mass of a layer of ore and a layer of coke, ρ bulk represents the average density of a layer of ore and a layer of coke, u feed Represents the charge filling rate, A throat represents the cross-sectional area of ​​the furnace throat;

[0117] Obtain the volume fraction of ore in each loading material;

[0118] t batch Multiply by the corresponding ore volume fraction to obtain a series of moments, and convert t batch And a series of moments obtained by calculation, starting from the time line at the top, are marked at corresponding heights along the height direction, so as to obtain the dividing lines between each layer of ore and coke, and obtain a three-dimensional layered charge structure.

[0119] Specifically, the volume fraction of ore in each charging material can be obtained based on the batch weight of the furnace top material.

[0120] Specifically, t batch The calculated series of moments are marked on the CFD grid.

[0121] Therefore, this step essentially uses the "timeline tracking" method to clarify the boundary between each layer of ore and coke, thereby determining the three-dimensional layered charge structure.

[0122] S6. Without considering chemical reactions, the gas flow field, temperature field and concentration field are initially solved iteratively through the discretized differential equations of mass conservation, momentum conservation (Navier-Stokes equations) and energy conservation until the iteration converges.

[0123] The mass conservation equation is:

[0124]

[0125] In the formula, ε represents the volume fraction, ρ represents the density, u represents the velocity, S is the source term, which represents the mass change due to chemical reaction or interphase mass transfer; β represents the stoichiometric coefficient, is the chemical reaction rate; the subscripts i and k represent different phases and different chemical reactions, respectively.

[0126] The momentum conservation equation is:

[0127] Gas phase:

[0128] Solid phase:

[0129] Liquid phase:

[0130] In the formula, the subscripts g and s represent gas and solid respectively; ε is the gas porosity, ρ is the gas density, u is the gas velocity, τ represents the gas stress tensor, p is the pressure, and g is the gravitational acceleration. Indicates the force exerted by the solid on the gas, μ is the dynamic viscosity of the gas, and I is the unit tensor; l and d in the following table represent the flowing liquid, represents the force exerted by the gas on the flowing liquid, represents the force exerted by the solid on the flowing liquid, Represents the force of gravity on the flowing liquid.

[0131] Among them, the differential equation for conservation of energy (i.e., conservation of heat and components) is:

[0132]

[0133] In the formula, refers to a universal variable (enthalpy or mass fraction), Г represents the integrated diffusion coefficient, and the subscripts i and m represent different phases and different material components in a phase, respectively.

[0134] like H i,m (enthalpy), then:

[0135] Γ i =k i / c p，i

[0136]

[0137] Where k represents thermal conductivity, c represents constant pressure specific heat capacity; δ is the heat exchange intensity coefficient, h is the interphase heat transfer coefficient, α is the heat exchange area, T represents temperature, η represents the proportionality coefficient, and ΔH represents the enthalpy change; subscript i represents a different phase, subscript j represents the other phase corresponding to phase i, and is used to describe the interaction between phases; subscript k represents different chemical reactions;

[0138] like ω i,m (mass fraction), then:

[0139]

[0140] where D represents the basic diffusion coefficient, It can refer to the mass fractions of different components in the gas phase (CO, CO2, H2, H2O, N2) and the mass fractions of iron oxides (Fe2O3, Fe3O4, FeO) and flux in the solid phase.

[0141] In this step, the chemical reaction rate The value is set to 0, thus achieving the iterative calculation without considering the chemical reaction. Because the convergence criterion of the solution in this step does not need to be strict, the residual can be relatively high.

[0142] S7. According to the temperature field obtained after iterative convergence in step S6, the soft melting zone area is determined by adopting a heterogeneous layered processing method (ie, considering the ore layer and the coke layer in the soft melting zone separately).

[0143] The soft melting zone refers to the area inside the blast furnace where the charge starts to soften and then drips. In this embodiment, it refers to the area where the solid temperature is between 1473K and 1673K. Figure 6 Since the softening and melting state depends on the high temperature characteristics of the ore and specific operating conditions, the soft melting zone iron ore is distinguished according to the shrinkage rate Shr, which is defined as the ratio of the volume reduced due to softening and melting to the original volume of the iron-containing material.

[0144] In this embodiment, determining the soft melting zone area specifically includes the following steps:

[0145] The area with solid temperature between 1473K and 1673K in the three-dimensional layered charge structure in the blast furnace is defined as the soft melting zone;

[0146] Define the normalized shrinkage Shr * In order to divide the indicators, the soft melting zone area is subdivided into areas with different states according to the preset rules;

[0147] Shr * =Shr / Sh r,max , Shr is the shrinkage rate of iron ore in the soft melting zone, Sh r,max is the maximum shrinkage rate.

[0148] The preset rules include:

[0149] 0.7 <Shr * ≤1.0, indicating that the ore is melted and in liquid state, and the corresponding area is completely occupied by the liquid phase;

[0150] 0.5 <Shr * ≤0.7, representing the softening and melting state of the ore;

[0151] 0.0 <Shr * ≤0.5, representing the ore softening stage;

[0152] Among them, Sh r,max =0.7.

[0153] S8. Taking chemical reactions into consideration, recalculate the gas flow field, solid flow field, temperature field, and concentration field to obtain the pressure, temperature, and heat consumption in the blast furnace.

[0154] Compared with the case where the chemical reaction is not considered in step S6, this step takes the chemical reaction into consideration, that is, the corresponding chemical reaction rate is calculated using the general chemical reaction rate formula. And bring it into the mass conservation and energy conservation equations for iterative calculation.

[0155] S9. Treat the molten iron and slag in the blast furnace as liquid phases. Consider the combined effects of gas, solid, and gravity on the liquid. Calculate the liquid phase flow in the blast furnace to obtain the tuyere pressure and heat input.

[0156] Among them, the heat input is the sum of blast heat and combustion heat.

[0157] There are two main liquid components in the blast furnace, namely molten iron (liquid iron) and slag. Although the physical properties of molten iron and slag are completely different, since the two liquids follow similar flow mechanisms, this embodiment treats them as a liquid phase.

[0158] The calculation of blast furnace liquid phase flow includes:

[0159] Based on the force balance model of three-dimensional liquid dripping flow, the three forces acting on the liquid, namely gas, solid, and gravity, are calculated. The governing equations of the force balance model are formulas (a) to (c):

[0160]

[0161] Where F is the force on the liquid, the superscripts g and s indicate the source of F, representing gas and solid respectively, and the subscript l represents the liquid; ε l is the liquid volume fraction, g is the acceleration due to gravity, C DG and C DS are the resistance coefficients of gas and solid respectively; A g-l and A s-l are the effective contact areas with gas and solid respectively; ρ g and ρ l are the gas and liquid densities, U g and U l are the gas and liquid velocities, respectively.

[0162] S10, judging whether the soft melting zone area has converged, if not, repeating S8 to S9 until convergence, and then proceeding to S11.

[0163] Specifically, considering the complexity of the blast furnace process, the convergence criterion of the soft melting zone in this embodiment is that the relative position change between two iterations is less than 10%.

[0164] S11. Determine whether the coke consumption is balanced. If not, repeat S3 to S10 until it is balanced. Predict the yield based on the calculation result and proceed to S12.

[0165] The carbon in the blast furnace is consumed mainly through the following ways: direct reduction, melt loss reaction (the carbon in the blast furnace reacts with carbon dioxide to produce carbon monoxide), combustion in the vortex zone before the tuyere, carburization and other chemical reactions. Figure 7 As shown, the coke (A) loaded into the furnace = carbon consumption by melting loss reaction (B) + carbon consumption by direct reduction (C) + carbon consumption by water gas reaction (D) + carbon consumption by silica reduction (E) + carbon consumption by combustion (F) + carburizing (G).

[0166] In each iteration, the total coke consumption is calculated as B + C + D + E + F + G, based on the reaction rate across the entire computational domain. This total coke consumption is used to determine the total amount of coke (A) and ore added in the next iteration. This process is repeated until A = B + C + D + E + F + G meets the specified tolerance. The coke consumption caused by carburization is considered constant. If the specified tolerance is not met, that is, if the coke consumption balance is not reached, S3 to S10 are repeated. If equilibrium is achieved, the yield is calculated based on the calculated results.

[0167] Preferably, the specified error is 0.1 kg / tHM.

[0168] Among them, the yield is the ratio of the amount of molten iron produced by the blast furnace per unit time to the effective volume of the blast furnace. It is used to measure the intensity of ironmaking production. The higher the value, the stronger the ability to produce molten iron.

[0169] S12. Determine whether the liquid temperature in the blast furnace is equal to a preset value based on the heat and component conservation in S6. If not, repeat S3 to S11. If equal, proceed to S13.

[0170] The liquid in a blast furnace is primarily liquid iron (molten iron), with a temperature generally ranging from 1723.15K to 1823.15K. Under the same set-up conditions, a higher fuel ratio results in a higher molten iron temperature. Preferably, the preset value in this step is 1813K. By fixing the molten iron temperature, the effects of varying throat-to-waist diameter ratios can be compared and analyzed.

[0171] S13. Based on the calculation results, various comprehensive performance indicators and total energy consumption are counted to obtain the throat-waist diameter ratio with the lowest total energy consumption.

[0172] In this step, the CFD blast furnace process model quantitatively evaluates the differences in comprehensive performance indicators of the blast furnace under different throat-waist diameter ratios, and determines the optimal throat-waist diameter ratio by comparing the total energy consumption of the blast furnace.

[0173] The comprehensive performance indicators include the ore-coke ratio (i.e., the input parameter in step S2), the yield (which can be obtained from step S11), the tuyere pressure (which can be obtained from step S9), and the heat input (which can be obtained from step S9). The specific calculation results are as follows: Figure 8 As shown in (a), (b), (c) and (d).

[0174] The total energy consumption includes physical energy consumption Wm=Q·Pη·p·V and chemical energy consumption.

[0175] The physical energy consumption, Wm, refers to the energy consumed to pressurize the gas. High-speed airflow entering through the tuyere creates a high pressure near the tuyere. Therefore, the blower must pressurize the gas to this pressure before it can blow air. The higher the pressure, the greater the pressurization energy consumption. Here, Q is the blower exhaust volume, P is the blast pressure, η is the blower motor efficiency, p is the yield, and V is the effective volume of the blast furnace.

[0176] The chemical energy consumption, i.e., the heat input, is the sum of the blast heat and the combustion heat.

[0177] In addition to the above, the comprehensive performance indicators also include: effective utilization coefficient, fuel ratio (including coal ratio in addition to coke ratio), bed pressure drop, furnace top gas temperature, furnace top gas utilization rate, iron tapping temperature, and furnace wall heat loss.

[0178] The statistical analysis of various comprehensive performance indicators and total energy consumption to obtain the throat-waist diameter ratio with the lowest total energy consumption specifically includes the following steps:

[0179] S131. Based on various comprehensive performance indicators and total energy consumption, the throat-waist diameter ratio with the lowest total energy consumption and the corresponding operating conditions are preliminarily obtained.

[0180] The calculation results of physical energy consumption, chemical energy consumption and total energy consumption of blast furnaces with different throat-throat diameter ratios in this embodiment are as follows: Figure 9 、 Figure 10 As shown. It can be seen that the throat-throat diameter ratio R D When it is 0.6, the total energy consumption is the lowest.

[0181] S132. Post-process the internal state of the blast furnace under this working condition to determine the internal state of the furnace. If it is reasonable, obtain the optimal throat-waist diameter ratio; otherwise, proceed to S133.

[0182] The furnace conditions include the multiphase flow field (velocity distribution), bed permeability index distribution, gas pressure field, multiphase temperature field, gas composition field, iron ore reduction degree distribution, ore coke particle size distribution, soft melting zone shape and position, and chemical reaction rate distribution. This example focuses on whether the furnace conditions, including the soft melting zone distribution, gas pressure field, gas velocity field, solid temperature field, and indirect reduction rate distribution, are reasonable.

[0183] Specifically, the internal state of the blast furnace under this working condition is post-processed using Tecplot software. D The specific furnace status information when it is 0.6 is as follows Figure 11 As shown, Figure 11 (a), (b), (c), and (d) show the distribution of the soft melting zone and the gas pressure field, solid temperature field, gas velocity field, and indirect reduction rate, respectively. This indicates that the internal permeability, thermal state, and reaction state of the blast furnace are good.

[0184] S133. Reselect the furnace throat-furnace waist diameter ratio when the total energy consumption is the lowest, or the furnace throat-furnace waist diameter ratio when the total energy consumption is the second lowest, and the corresponding operating conditions, and repeat S132 until the furnace state is reasonable.

[0185] The CFD simulation of this embodiment uses the blast furnace geometry, upper adjustment parameters and lower adjustment parameters as input parameters, and the output results that can be obtained include comprehensive performance indicators and various internal states. Based on the comprehensive performance results of the blast furnace, this embodiment comprehensively determines the optimal throat-waist diameter ratio of the industrial blast furnace. For actual production, the operation of the blast furnace should try to meet the requirements of low coke ratio, high yield and low energy consumption. Taking all factors into consideration, 5000m 3 Blast furnace throat-waist diameter ratio R D When the coke ratio is 0.6, it is low (361kg / tHM) and the yield is high (2.33tHM / m 3 / day), the lowest total energy consumption (3.955GJ / tHM), and the furnace is in good condition, the blast furnace operation efficiency is high and the cost is low, so it is the final determined 5000m 3 The best throat-waist diameter ratio of blast furnace, the specific dimensions of the furnace are as follows Figure 12 shown.

[0186] Those skilled in the art will understand that the foregoing descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will be able to modify the technical solutions described in the foregoing embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for determining the optimal throat and waist diameter ratio of a blast furnace based on CFD process simulation, characterized in that: The following steps are involved: S1. Establish corresponding blast furnace geometric models for different throat-to-waist diameter ratios and perform meshing on the blast furnace geometric models; S2. Determine input parameters, which include blast furnace geometry, upper adjustment parameters, and lower adjustment parameters; The geometric dimensions of the blast furnace include the effective volume of the blast furnace, the diameter of each section, and the height of each section; The upper adjustment parameters include ore parameters, coke parameters, and distribution system; The lower adjustment parameters include tuyere related parameters, air supply system, and injection system; S3. Determine the temperature and composition of the gas generated after the combustion reaction, and the size and shape of the tuyere raceway according to the input parameters; S4. Preliminary calculation of the solid flow field and iterative calculation to determine the three-dimensional dead material column contour; S5. Determine solid flow time contours based on the solid velocity field, mark positions based on the solid flow time contours, and track the layered positions of coke and iron ore in the blast furnace after each loading of materials, thereby determining a three-dimensional layered charge structure in the blast furnace; S6. Without considering chemical reactions, the gas flow field, temperature field, and concentration field are initially solved iteratively through the discretized mass conservation, momentum conservation, and energy conservation differential equations until the iteration converges; S7. Based on the temperature field obtained after iterative convergence, the soft melting zone area is determined using the heterogeneous layered processing method; S8. Taking chemical reactions into account, recalculate the gas flow field, solid flow field, temperature field, and concentration field to obtain the pressure, temperature, and heat consumption in the blast furnace; S9. Treat the molten iron and slag in the blast furnace as liquid phases, consider the combined effects of gas, solid, and gravity on the liquid, calculate the blast furnace liquid phase flow, and obtain the tuyere pressure and heat input; S10, judging whether the soft melting zone area has converged, if not, repeating S8 to S9 until it converges, and then proceeding to S11; S11, determine whether the coke consumption is balanced. If not, repeat S3 to S10 until it is balanced. Predict the yield based on the calculation result and proceed to S12; S12, judging whether the liquid temperature in the blast furnace is equal to a preset value according to the energy conservation differential equation; if not, repeating S3 to S11; if equal, proceeding to S13; S13. Based on the calculation results, various comprehensive performance indicators and total energy consumption are counted to obtain the throat-waist diameter ratio with the lowest total energy consumption.

2. The method according to claim 1, characterized in that In step S4, the solid flow field is preliminarily calculated and the three-dimensional dead material column profile is determined by iterative calculation, including: Firstly, without considering the three-dimensional dead material column, the initial solid flow field is solved according to the boundary conditions of the blast furnace solid phase inlet, outlet and wall. Secondly, the region in the initial solid flow field where the velocity is less than the critical velocity is determined as a three-dimensional dead material column, and its volume V is determined. d1 ; Third, the velocity field of the three-dimensional dead material column is set to zero, and the boundary of the three-dimensional dead material column is set as the new boundary of the solid flow field, and the solid flow field is re-solved; Fourth, obtain the new three-dimensional dead material column wheel volume V d2 , V d2 With V d1 Make comparisons; Repeat the third and fourth steps until the difference between the three-dimensional dead material column volumes in the two previous calculations is less than the preset value.

3. The method according to claim 1, characterized in that In step S5, position marking is performed according to the solid flow time contour line, including: Initialize the timeline at the top of the blast furnace to 0, and calculate the time t required to load each layer of ore and coke using the following formula batch : t batch =m batch / ρ bulk u feed A throat ; Where m batch represents the total mass of a layer of ore and a layer of coke, ρ bulk represents the average density of a layer of ore and a layer of coke, u feed Represents the charge filling rate, A throat represents the cross-sectional area of ​​the furnace throat; Obtain the volume fraction of ore in each loading material; t batch Multiply by the corresponding ore volume fraction to obtain a series of moments, and convert t batch And a series of moments obtained by calculation, starting from the time line at the top, are marked at corresponding heights along the height direction, so as to obtain the dividing lines between each layer of ore and coke, and obtain a three-dimensional layered charge structure.

4. The method according to claim 1, wherein In step S7, the method of determining the soft melting zone region by adopting the heterogeneous layered processing method includes: The area with solid temperature between 1473K and 1673K in the three-dimensional layered charge structure in the blast furnace is defined as the soft melting zone; Define the normalized shrinkage ratio Shr * In order to divide the indicators, the soft melting zone area is subdivided into areas with different states according to the preset rules; Shr * =Shr / Sh r,max , Shr is the shrinkage rate of iron ore in the soft melting zone, Sh r,max is the maximum shrinkage rate.

5. The method according to claim 4, characterized in that The preset rules include: 0.7 <Shr * ≤1.0, indicating that the ore is melted and in liquid state, and the corresponding area is completely occupied by the liquid phase; 0.5 <Shr * ≤0.7, representing the softening and melting state of the ore; 0.0 <Shr * ≤0.5, representing the ore softening stage; Among them Sh r,max =0.

7.

6. The method according to claim 1, characterized in that In step S9, the calculation of the blast furnace liquid phase flow includes: According to the force balance model of three-dimensional liquid dripping flow, the three forces acting on the liquid, namely gas, solid, and gravity, are calculated. The governing equation of the force balance model is as follows: Where F is the force on the liquid, the superscripts g and s indicate the source of F, representing gas and solid respectively, and the subscript l represents the liquid; ε l is the liquid volume fraction, g is the acceleration due to gravity, C DG and C DS are the resistance coefficients of gas and solid respectively; A g-l and A s-l are the effective contact areas with gas and solid respectively; ρ g and ρ l are the gas and liquid densities, U g and U l are the gas and liquid velocities, respectively.

7. The method according to claim 1, characterized in that In step S13, the statistics of various comprehensive performance indicators and total energy consumption are collected to obtain the throat-waist diameter ratio with the lowest total energy consumption, including: S131. Based on various comprehensive performance indicators and total energy consumption, preliminarily obtain the throat-waist diameter ratio and corresponding operating conditions with the lowest total energy consumption; S132. Post-process the internal state of the blast furnace under this operating condition to determine whether the internal state of the furnace, including the distribution of the soft melting zone, the gas pressure field, the gas velocity field, the solid temperature field, and the indirect reduction rate distribution, is reasonable. If so, obtain the optimal throat-waist diameter ratio; otherwise, proceed to S133. S133. Reselect the furnace throat-furnace waist diameter ratio when the total energy consumption is the lowest, or the furnace throat-furnace waist diameter ratio when the total energy consumption is the second lowest, and the corresponding operating conditions, and repeat S132 until the furnace state is reasonable.

8. The method according to claim 1, characterized in that In step S13, the various comprehensive performance indicators include the ore-to-coke ratio, the yield, the tuyere pressure and the heat input; the total energy consumption includes the physical energy consumption Wm=Q·Pη·p·V, and the chemical energy consumption; wherein Q is the blower exhaust volume, P is the blast pressure, η is the blower motor efficiency, p is the yield, and V is the effective volume of the blast furnace; the chemical energy consumption, i.e., the heat input, is the sum of the blast heat and the combustion heat.

9. The method according to claim 1, characterized in that In step S6, without considering the chemical reaction, the chemical reaction rate term in the mass conservation and energy conservation differential equations is assigned a value of 0, and then iterative calculation is performed; In step S8, the chemical reaction rate term in the mass conservation and energy conservation differential equations is calculated and assigned a value using the chemical reaction rate formula, and then iterative calculation is performed, taking the chemical reaction into consideration.

10. The method according to claim 1, characterized in that The ore parameters include ore type, batch weight, ore composition, ore particle size distribution, reducibility, ore thermal conductivity, softening and melting characteristics, low-temperature reduction pulverization, and thermal cracking properties; The coke parameters include coke composition, coke particle size distribution, coke reactivity, and coke thermal conductivity; The distribution system includes the particle size distribution of ore and coke, and the ore-coke ratio distribution; The tuyere-related parameters include tuyere position, number and size; The air supply system includes hot air temperature, oxygen enrichment rate, blast volume and blast humidity; The injection system includes the type of injection fuel, the composition of the injection fuel, the injection amount and the position of the injection gun.

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