Method for determining optimal furnace throat and furnace bosh diameter ratio of blast furnace based on CFD (computational fluid dynamics) process simulation

Abstract

The invention relates to a method for determining the optimal furnace throat-furnace bosh diameter ratio of a blast furnace based on CFD process simulation, which constructs a CFD blast furnace process model, simulates the comprehensive performance indexes and internal states of the blast furnace with different furnace throat-furnace bosh diameter ratios, can obtain the distribution conditions of fluid velocity, pressure, temperature and the like in the furnace, quantifies the conclusion, and provides a method for determining the optimal furnace throat-furnace bosh diameter ratio of the blast furnace. And comprehensively considering the coke ratio, the yield, the tuyere pressure and the internal state of the blast furnace, and determining the optimal furnace throat-furnace bosh diameter ratio of the industrial blast furnace according to the principle of lowest total energy consumption. Meanwhile, the method is efficient, convenient and low in cost. According to the blast furnace profile optimally designed through the method, the production cost of the blast furnace is low, heat energy utilization is good, and safety is high. The method overcomes the defects that most research on the throat-bosh diameter ratio of the blast furnace at present is based on engineering experience, the conclusion is relatively fuzzy, and the specific influence of the change of the throat-bosh diameter ratio on the smelting performance of the blast furnace cannot be determined.

Description

Technical Field

[0001] The 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 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 process of heat and mass transfer between the rising coal gas flow and the descending charge. Therefore, the corresponding space must be provided, and the blast furnace type must adapt to the requirements of the raw fuel conditions to ensure the smooth progress of the smelting process. The reasonable blast furnace type refers to the blast furnace type that can achieve good yield, fuel ratio and low energy consumption. It is an important condition for the blast furnace to achieve high yield, high quality, low consumption and long life.

[0003] After a long period of development, the blast furnace has gradually evolved into five parts, from top to bottom: throat, body, waist, belly and hearth. The specific distribution is as follows: Figure 1 Among them, the throat-waist diameter ratio (R D=d1 / D) is the main parameter characterizing the shape of the upper part of the blast furnace, which is directly related to the size of the furnace body angle and has a significant impact on the distribution state of the process of charge descent and gas flow ascent. In the design of the furnace type, the throat-furnace waist diameter ratio is mostly based on experience, generally 0.6-0.75. For the numerical study of the throat-furnace waist diameter ratio, there are currently two main methods: analyzing and studying the existing engineering blast furnace and CFD simulation (Computational Fluid Dynamics). The former collects, studies and organizes the internal type of the existing engineering blast furnace, analyzes the evolution of the furnace type and the influence of the differences in the furnace body structure on the gas flow distribution in the blast furnace, and discusses the reasonable operation furnace type structure and design. This kind of research based on engineering practice has high reliability and the conclusions obtained are more applicable, but its research scope is narrow and limited, and it is impossible to clarify the specific impact of different throat-furnace waist diameter ratios on the performance of the blast furnace, and it is impossible to quantitatively determine the optimal value. The latter solves the fluid flow control equation by numerical methods, and can simulate and simulate related physical phenomena such as fluid flow, heat transfer, and mass transfer. CFD simulation can simulate complex working conditions and obtain the distribution of fluid velocity, pressure, temperature, etc. Especially for the internal environment of blast furnace, which is high temperature, high pressure, accompanied by complex multiphase heat transfer, mass transfer and chemical reaction, CFD simulation method can obtain the distribution information in the furnace and quantitatively study the specific influence of throat-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 deficiencies of the prior art, 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 by 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. For a plurality of different throat-waist diameter ratios, corresponding blast furnace geometric models are established respectively, and meshing is performed 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 material 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, preliminarily calculate the solid flow field, and iteratively calculate and determine the three-dimensional dead material column contour;

[0015] S5. Determine the solid flow time contour according to the solid velocity field, mark the position according to the solid flow time contour, track the layered position of coke and iron ore in the blast furnace after each loading of materials, and thus determine the 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 discretized mass conservation, momentum conservation and energy conservation differential equations until the iteration converges;

[0017] S7, according to the temperature field obtained after iterative convergence, the soft melting zone area is determined by using anisotropic layer processing method;

[0018] S8. Under the consideration of chemical reactions, the gas flow field, solid flow field, temperature field and concentration field are recalculated to obtain the pressure, temperature and heat consumption in the blast furnace;

[0019] S9. Consider the molten iron and slag in the blast furnace as liquid phase, consider the combined effects of gas, solid and gravity on the liquid, calculate the liquid phase flow in the blast furnace, 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, judging whether the coke consumption is balanced, if not balanced, repeating S3 to S10 until balanced, predicting the yield based on the calculation results, and proceeding 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 furnace throat-furnace 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 volumes of the three-dimensional dead material column in the two 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 a layer of ore and a layer of coke each time by the following formula batch :

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

[0034] In the formula, 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 boundary 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 a 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 * To divide the index, the soft melting zone area is subdivided into areas of different states according to the preset rules;

[0040] Shr * =Shr / Sh r,max , Shr is the shrinkage rate of soft melting zone iron ore, 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 of gas, solid and gravity acting on the liquid are calculated. The control 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 gravitational acceleration, 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, the throat-waist diameter ratio with the lowest total energy consumption and the corresponding operating conditions are preliminarily obtained;

[0052] S132, post-processing the internal state of the blast furnace under the working 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 reasonable, the optimal throat-waist diameter ratio is obtained, otherwise, S133 is performed;

[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 state inside the furnace 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 by 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 explosion properties;

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

[0059] The material 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 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 establishes a blast furnace ironmaking process model through CFD, describes the complex coupled flow, heat transfer, mass transfer and chemical reaction of gas / solid / liquid between the furnace top material surface and the furnace cylinder slag surface, and realizes 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 index and internal state of blast furnaces with different throat-waist diameter ratios, comprehensively considers coke ratio, yield, tuyere pressure and 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 the method, the blast furnace has low production cost, good thermal energy utilization and high safety. At the same time, the distribution of fluid velocity, pressure, temperature, etc. in the furnace can be obtained, and the conclusion is quantitative, and it is efficient, convenient and low in cost. It makes up for the current research on the throat-waist diameter ratio of the blast furnace, which is mostly based on engineering experience, and the conclusion is vague, and it is impossible to clarify the deficiency of the specific influence of the change of the throat-waist diameter ratio on the smelting performance of the blast furnace.

[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 type in the prior art.

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

[0069] Figure 3 The figure is a schematic diagram of a method flow of 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 It is the calculation result of various comprehensive performance indicators of the embodiment of the present invention.

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

[0076] Fig.10 The total energy consumption of a blast furnace with different throat-waist diameter ratios calculated in the embodiment of the present invention.

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

[0078] Fig.12 This is a schematic diagram of the blast furnace geometry with the best throat-waist diameter ratio obtained by simulation calculation in an embodiment of the present invention. DETAILED DESCRIPTION

[0079] The specific implementation of the present invention is 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 by the furnace top charging device according to the specified proportion, and the throat charge surface is kept at a certain height. Coke and ore form an alternating layered structure in the furnace. At the bottom of the blast furnace, air is heated by the hot blast stove and enters the blast furnace from the tuyere. The hot air is blown in through the tuyere at the bottom of the blast furnace at a high gas flow rate to form a vortex zone and burn with the surrounding coke to produce high-temperature coal gas. The high-temperature coal gas flows from bottom to top, heats the solid charge and reduces the iron ore during the rising process, and the coal gas temperature and composition change continuously, and finally leaves the blast furnace from the top of the furnace. During this period, the consumption of coke near the tuyere whirlpool zone makes room for the ore and coke particles above it, and the solid charge moves from top to bottom. During the descent, the reducing gas and ore particles contact each other and undergo a reduction reaction. There is intense heat transfer, mass transfer and momentum transfer between the rising coal gas flow, and the iron-containing charge is gradually reduced, softened and melted, and finally forms molten iron and slag that drip into the furnace. The molten iron and slag accumulated in the furnace are regularly discharged from the iron outlet and slag outlet to complete the blast furnace ironmaking process. The internal structure of the blast furnace can be divided into a block zone, a soft melting zone, a dripping zone and a dead material column from top to bottom. Different areas have their own characteristics. It is an extremely complex high-temperature and high-pressure reactor. In the block zone, indirect reduction reactions mainly occur, the water in the charge evaporates and decomposes due to heat, a small amount of direct reduction, and heat exchange occurs between the charge and the coal gas. Inside the blast furnace, there is an area where the ore gradually changes from solid to liquid, which is called the soft melting zone. The charge begins to soften at the upper boundary of the soft melting zone, and melts and drips at the lower boundary, mainly undergoing direct reduction reaction and slag formation. Molten iron is produced in the soft 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, so it is called the 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 a plurality of different throat-waist diameter ratios, corresponding blast furnace geometric models are established respectively, and the blast furnace geometric models are meshed.

[0084] In this embodiment, 5000m 3 Take 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 is kept consistent. The specific geometric dimensions are as follows: Figure 4 shown.

[0085] Figure 4 Six different throat-waist diameter ratios R are given. 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 furnace hearth, and the heights of the furnace hearth, furnace belly, furnace waist, furnace body, and 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 of the blast furnace each time, the charge 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 explosion;

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

[0091] The material distribution system includes the particle size distribution of ore and coke, and the ore-coke ratio distribution. The ore-coke ratio is defined as the amount of coke consumed for smelting one ton of qualified pig iron, and the amount of coke consumed is directly related to the production cost.

[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 Blast furnace simulation input parameter values

[0098]

[0099]

[0100] Among them, the RDI value of iron ore refers to the pulverization rate of low-temperature reduction at 500℃, which is an important indicator to measure 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 easier it is for the iron ore to pulverize during the reduction in the upper part of the blast furnace, which will affect the permeability of the blast furnace and the descending speed of the charge, and further affect the operation and output of the blast furnace.

[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 according to the input parameters.

[0102] Among them, the tuyere whirlpool area refers to the area in front of the tuyere in the blast furnace where the coke in front of the tuyere in the furnace whirls and burns under the action of high-speed hot air during the ironmaking process. It is also called the coke circulation area and is used as one of the calculation boundaries. The size of the tuyere whirlpool area 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, such as the size and shape of the throat, body, waist, belly, 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 blast furnace solid phase inlet, outlet and wall.

[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 volumes of the three-dimensional dead material column in the two calculations is less than the preset value.

[0111] The solid phase is composed of coke, iron-containing furnace charge (sintered and / or pelletized) and flux. In this embodiment, the area in the solid flow field where the velocity is less than the critical velocity is treated as a dead column. The critical velocity is defined as the velocity per minute equal to one ninth of the particle diameter.

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

[0113] Wherein, position marking is performed according to the solid flow time contour line, including:

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

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

[0116] In the formula, 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 boundary 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 according to 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 utilizes the “timeline tracking” method to identify 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 mass conservation, momentum conservation (Navier-Stokes equations) and energy conservation differential equations 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 caused by 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. represents 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 gas on flowing liquid, represents the force exerted by the solid on the flowing liquid, Represents the force of gravity on a 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 common 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 heat exchange intensity coefficient, h is interphase heat transfer coefficient, α is heat exchange area, T represents temperature, η represents proportionality coefficient, ΔH represents enthalpy change; subscript i represents different phases, subscript j represents another phase corresponding to phase i, which 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 is 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] This step will be the chemical reaction rate The value is 0, which realizes the iterative calculation without considering the chemical reaction. Because the convergence standard 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 differentiated 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 ratio Shr * To divide the index, the soft melting zone area is subdivided into areas of different states according to the preset rules;

[0147] Shr * =Shr / Sh r,max , Shr is the shrinkage rate of soft melting zone iron ore, 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 the chemical reaction 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 And bring it into the mass conservation and energy conservation equations for iterative calculations.

[0155] S9. Treat the molten iron and slag in the blast furnace as liquid phase, consider the combined effects of gas, solid and gravity on the liquid, calculate the liquid phase flow in the blast furnace, and 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 uniformly as liquid phases.

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

[0159] According to the force balance model of three-dimensional liquid dripping flow, the three forces of gas, solid and gravity acting on the liquid are calculated. The control 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 gravitational acceleration, 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 it has converged, and then proceeding to S11.

[0163] Specifically, considering the complexity of the blast furnace process, the convergence standard 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 results and proceed to S12.

[0165] The carbon in the blast furnace is consumed mainly through the following ways: direct reduction, melting reaction (the carbon in the blast furnace reacts with carbon dioxide to generate carbon monoxide), combustion in the cyclone zone before the tuyere, carburization and other chemical reactions. Figure 7 As shown, the coke loaded into the furnace (A) = 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 B+C+D+E+F+G, which is calculated based on the reaction rate over the entire computational domain according to the convergence results. This total coke consumption is used to determine the total amount of coke (A) and ore added in the next iteration, and the process is repeated until A=B+C+D+E+F+G satisfies the specified error, and the coke consumption caused by carburization is considered a constant. If the specified error is not met, that is, the coke consumption balance is not reached, S3 to S10 are repeated, and if the balance is reached, the yield is obtained based on the calculation 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 according to the conservation of heat and components in S6. If not, repeat S3 to S11. If equal, proceed to S13.

[0170] The liquid in the blast furnace is mainly liquid iron (molten iron), and its temperature is generally between 1723.15K and 1823.15K. Under the same setting conditions, the higher the fuel ratio, the higher the molten iron temperature. Preferably, the preset value in this step is 1813K. By fixing the molten iron temperature, the influence of different throat-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 furnace throat-furnace waist diameter ratio with the lowest total energy consumption.

[0172] In this step, the CFD blast furnace process model quantitatively evaluates the differences in the 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] Among them, the physical energy consumption Wm refers to the energy consumption of gas pressurization. The high-speed airflow blown in through the tuyere will cause a large pressure near the tuyere. Therefore, the blower needs to pressurize the gas to this pressure before blowing. The higher the pressure, the greater the pressurization energy consumption. In the formula, 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 specifically 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 the physical energy consumption, chemical energy consumption and total energy consumption of the blast furnace with different throat-throat diameter ratios in this embodiment are as follows: Fig. 9 , Fig.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 judge the internal state of the furnace. If it is reasonable, obtain the optimal throat-waist diameter ratio, otherwise proceed to S133.

[0182] Among them, the furnace state includes multiphase flow field (velocity distribution), bed permeability index distribution, gas pressure field, multiphase temperature field, gas component field, iron ore reduction degree distribution, ore coke particle size distribution, soft melting zone shape and position, chemical reaction rate distribution. The furnace state that this embodiment focuses on includes whether the soft melting zone distribution, gas pressure field, gas velocity field, solid temperature field, indirect reduction rate distribution, etc. are reasonable.

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

[0185] The CFD simulation of this embodiment uses the geometric dimensions of the blast furnace, the upper adjustment parameters and the 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. Comprehensive consideration, 5000m 3 Blast furnace throat-waist diameter ratio R D When the coke ratio is 0.6, the coke ratio 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 5000m 3 The best ratio of throat to waist diameter of blast furnace, the specific dimensions of the furnace are as follows Fig.12 shown.

[0186] Those skilled in the art can understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope 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. For a plurality of different throat-waist diameter ratios, corresponding blast furnace geometric models are established respectively, and meshing is performed 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 material 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, preliminarily calculate the solid flow field, and iteratively calculate and determine the three-dimensional dead material column contour; S5. Determine the solid flow time contour according to the solid velocity field, mark the position according to the solid flow time contour, track the layered position of coke and iron ore in the blast furnace after each loading of materials, and thus determine the 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 discretized mass conservation, momentum conservation and energy conservation differential equations until the iteration converges; S7, according to the temperature field obtained after iterative convergence, the soft melting zone area is determined by using anisotropic layer processing method; S8. Under the consideration of chemical reactions, the gas flow field, solid flow field, temperature field and concentration field are recalculated to obtain the pressure, temperature and heat consumption in the blast furnace; S9. Consider the molten iron and slag in the blast furnace as liquid phase, consider the combined effects of gas, solid and gravity on the liquid, calculate the liquid phase flow in the blast furnace, 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, judging whether the coke consumption is balanced, if not balanced, repeating S3 to S10 until balanced, predicting the yield based on the calculation results, and proceeding 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 furnace throat-furnace 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 volumes of the three-dimensional dead material column in the two 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 a layer of ore and a layer of coke each time by the following formula batch : t batch =m batch / ρ bulk u feed A throat ; In the formula, 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 boundary lines between each layer of ore and coke, and obtain a three-dimensional layered charge structure.

4. The method according to claim 1, characterized in that: In step S7, the method of determining the soft melting zone region by adopting a 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 * To divide the index, the soft melting zone area is subdivided into areas of different states according to the preset rules; Shr * =Shr / Sh r,max , Shr is the shrinkage rate of soft melting zone iron ore, 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 of gas, solid and gravity acting on the liquid are calculated. The control 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 gravitational acceleration, 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, the throat-waist diameter ratio with the lowest total energy consumption and the corresponding operating conditions are preliminarily obtained; S132, post-processing the internal state of the blast furnace under the working 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 reasonable, the optimal throat-waist diameter ratio is obtained, otherwise, S133 is performed; 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 state inside the furnace 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 by 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 explosion properties; The coke parameters include coke composition, coke particle size distribution, coke reactivity, and coke thermal conductivity; The material 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 injection fuel, the injection amount and the position of the injection gun.

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