Numerical simulation method of blast furnace lump ore behavior characteristics based on CFD-DEM

Abstract

The invention discloses a CFD-DEM-based blast furnace lump ore behavior characteristic numerical simulation method, which comprises the following steps: establishing a blast furnace multiphase flow system geometric model according to an LKAB test blast furnace, and carrying out grid division on a fluid calculation region in the blast furnace multiphase flow system geometric model; setting basic simulation parameters and boundary conditions of the blast furnace multiphase flow system; establishing a fluid phase control equation set and a solid phase control equation set in the blast furnace multiphase flow system; carrying out numerical calculation on the multiphase flow phenomenon of the blast furnace containing the lump ore based on a CFD-DEM coupling method to obtain a velocity field, a temperature field and reduction degree distribution of the lump ore in the furnace and a velocity cloud picture, a pressure cloud picture, a temperature cloud picture, a cloud picture of each component and the like of a gas phase; the influence of the lump ore proportion, the lump ore size and the radial position distribution of the lump ore in the furnace on the state in the furnace and the comprehensive performance index of the blast furnace is obtained through simulation and result analysis, and a lump ore charging operation optimization strategy is formulated according to the influence.

Description

Technical Field

[0001] The invention belongs to the technical field of blast furnace metallurgy numerical simulation, and in particular relates to a numerical simulation method for blast furnace lump ore behavior characteristics based on CFD-DEM. Background Art

[0002] At present, 70-80% of blast furnace charges are sintered ore, pellets account for about 15%, and lump ore accounts for 5%-10%, with the lowest proportion of lump ore. Lump ore belongs to raw materials with the lowest comprehensive cost, and lump ore does not need high-temperature roasting before entering the furnace, which has a significant effect on reducing carbon emissions. Therefore, it is of great significance to reduce the cost of the steel industry and achieve energy conservation and emission reduction by scientifically and rationally increasing the proportion of lump ore entering the furnace and optimizing the charge structure. However, since lump ore has poorer metallurgical properties than sintered ore and pellets, it will have an adverse effect on blast furnace performance, resulting in a low proportion of its use in blast furnaces. Therefore, the study of the behavior of lump ore in blast furnaces is still in the exploratory stage, and the use of lump ore in blast furnaces is mostly based on experience. Therefore, in order to increase the proportion of lump ore entering the furnace and optimize the charge structure, it is urgent to solve the problem that there is no complete and reliable theoretical model support for the current application of lump ore in blast furnaces. Summary of the invention

[0003] Purpose of the invention: In order to increase the proportion of lump ore entering the furnace, optimize the charge structure, and solve the problem that there is no complete and reliable theoretical model support for the current application of lump ore in blast furnaces, the present invention proposes a numerical simulation method for the behavior characteristics of blast furnace lump ore based on CFD-DEM, which provides theoretical guidance for the application of lump ore in blast furnaces and realizes the optimization of charge structure.

[0004] Technical solution: A numerical simulation method for the behavior characteristics of blast furnace lump ore based on CFD-DEM, comprising the following steps:

[0005] According to the LKAB test blast furnace, a blast furnace multiphase flow system geometric model is established, and a fluid calculation area in the blast furnace multiphase flow system geometric model is meshed;

[0006] Set the basic simulation parameters and boundary conditions of the blast furnace multiphase flow system;

[0007] Establishing a fluid phase control equation group in a blast furnace multiphase flow system, wherein the fluid phase control equation group includes a continuity equation, a momentum equation, an energy equation and a component equation;

[0008] Establishing a solid phase control equation group in a blast furnace multiphase flow system, wherein the solid phase control equation group includes a particle motion equation, an energy equation, and a component equation;

[0009] Based on the CFD-DEM coupling method, the multiphase flow phenomenon of the blast furnace containing lump ore is numerically calculated to obtain the velocity field, temperature field and reduction degree distribution of the lump ore in the furnace, as well as the velocity cloud map, pressure cloud map, temperature cloud map and each component cloud map of the gas phase;

[0010] By analyzing the velocity field, temperature field and reduction degree distribution of lump ore in the furnace, as well as the velocity cloud map, pressure cloud map, temperature cloud map and component cloud map of the gas phase, the influence of lump ore on the furnace state and comprehensive performance indicators under different lump ore ratios, lump ore sizes and different radial position distributions of lump ore in the furnace is obtained, and the optimization strategy for lump ore feeding operation is formulated based on this.

[0011] Furthermore, according to the LKAB test blast furnace, a blast furnace multiphase flow system geometric model is established, and the fluid calculation area in the blast furnace multiphase flow system geometric model is meshed, and the specific operations include:

[0012] According to the LKAB test blast furnace, a blast furnace geometric model was established. Its specific size parameters are: the radius of the furnace is 0.6m, the radius of the furnace waist is 0.8m, the radius of the furnace throat is 0.5m, the height is 7.52m, and the thickness direction is 4 times the particle diameter; the structured method is used to mesh the fluid calculation area;

[0013] Furthermore, the basic simulation parameters and boundary conditions of the blast furnace multiphase flow system are set, including:

[0014] Set the inlet gas velocity to 70m / s, gas density to 1.2kg / m3, ore density to 3500kg / m3, coke density to 1081kg / m3, particle sizes of pellets, sintered ore and lump ore to 10mm, 15mm and 20mm respectively, coke particle size to 40mm, and simulation time step to 0.001s; the inlet adopts velocity inlet boundary condition, the outlet adopts pressure outlet boundary condition, and the wall adopts periodic boundary condition.

[0015] Furthermore, in the fluid phase control equations, the continuity equation is expressed as:

[0016]

[0017] In the formula, ρ f is the gas density, ε f is the local void fraction of the gas, and u is the superficial velocity of the gas.

[0018] Furthermore, in the fluid phase control equations, the momentum equation is expressed as:

[0019]

[0020] Where p is the gas pressure, F fpis the interaction force between gas particles per unit volume; g is the gravitational acceleration, represents the gradient operation, represents the divergence operation, and τ is the gas phase stress tensor.

[0021] Furthermore, in the fluid phase control equations, the energy equation is expressed as:

[0022]

[0023] Where, T f is the gas temperature; c pf is the specific heat of gas; k e is the thermal conductivity of gas; Q f,i is the heat convection between gas and particles; Q f,wall is the heat convection between gas and wall; Q f,rad is the radiation heat flux of the gas and the surrounding environment; Q reaction is the gas reaction volume heat flux.

[0024] Furthermore, in the fluid phase control equations, the component equations are expressed as:

[0025]

[0026] In the formula, C m is the concentration of gas component m; Γ m is the diffusion coefficient of component m; S m is the production or consumption rate of gas component m.

[0027] Furthermore, in the solid phase control equations, the particle momentum equation is expressed as:

[0028]

[0029]

[0030] In the formula, m i is the mass of the ith particle; v i is the horizontal velocity of the ith particle; f e,ij is the elastic force between the i-th particle and the j-th particle; f d,ij is the viscous damping force between the i-th particle and the j-th particle; f pf,i is the force between the ith particle and the fluid; m i g is the gravity of the ith particle; I i is the moment of inertia of the ith particle; ω i is the rotation speed of the ith particle; T t,ij is the tangential moment between the i-th particle and the j-th particle; T r,ijis the rolling friction torque between the i-th particle and the j-th particle.

[0031] Furthermore, in the solid phase control equations, the energy equation is expressed as:

[0032]

[0033] Where, T i is the particle temperature; c p,i is the particle specific heat; Q i,j Q is the heat flow between gas particles; i,f is the convective heat flow between particles and gas; Q i,rad is the radiation heat flux of the particle to the surrounding environment; Q i,wall is the heat flow between the particle and the wall; Q i,reaction is the heat flow of the chemical reaction.

[0034] Furthermore, in the solid phase control equation group, the component equation is expressed as:

[0035] m i dc i,m / dt=s i,m

[0036] In the formula, c i,m is the concentration of component m in the particle; s i,m is the consumption rate of component m in the particle.

[0037] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0038] (1) The method of the present invention establishes a blast furnace multiphase flow numerical model based on the LKAB test blast furnace geometric model. The blast furnace multiphase flow numerical model simulates the movement, heat transfer and chemical behavior of lump ore in the entire blast furnace system, and can obtain detailed lump ore behavior characteristic information;

[0039] (2) The present invention has the advantages of high computational efficiency, high precision, strong reliability, and intuitive results after comparison and evaluation with experimental results, and can be used to simulate the application of lump ores of different types and particle sizes in blast furnaces;

[0040] (3) The present invention can perform parameter optimization simulation, and simulate the behavior of the lump ore in the furnace and its influence on the furnace state and comprehensive performance indicators of the blast furnace by changing the lump ore ratio, lump ore size, radial position distribution of the lump ore in the furnace, and blast conditions, so as to further provide a theoretical reference for optimizing the operation of lump ore feeding into the furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A flow chart of a numerical simulation method for blast furnace lump ore behavior characteristics based on CFD-DEM proposed by the present invention;

[0042] Figure 2 The blast furnace geometric model size and grid structure division diagram proposed by the present invention;

[0043] Figure 3 This is the initial charge layer structure and temperature distribution diagram of the blast furnace proposed by the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the present invention clearer, the numerical simulation method of the behavior characteristics of blast furnace lump ore based on CFD-DEM proposed by the present invention will be further explained in conjunction with the accompanying drawings in the present invention.

[0045] like Figure 1 As shown, the numerical simulation method of the behavior characteristics of blast furnace lump ore based on CFD-DEM proposed in this embodiment mainly includes the following steps:

[0046] (I) According to the LKAB test blast furnace, a geometric model of the blast furnace multiphase flow system is established, and the fluid calculation area in the geometric model of the blast furnace multiphase flow system is meshed. The specific operations include:

[0047] The geometric model of the blast furnace multiphase flow system is established based on the LKAB test blast furnace, such as Figure 2 As shown in (a), the specific size parameters are: the radius of the furnace is 0.6m, the radius of the furnace waist is 0.8m, the radius of the furnace throat is 0.5m, the height is 7.52m, and the thickness direction is 4 times the particle diameter; the structured method is used to divide the fluid calculation area into grids. Figure 2 As shown in (b) in .

[0048] (II) Set the basic simulation parameters and boundary conditions of the blast furnace multiphase flow system; specifically, set the inlet gas velocity to 70 m / s and the gas density to 1.2 kg / m 3 , ore density 3500kg / m 3 , coke density 1081kg / m 3 The particle sizes of pellet ore, sintered ore and lump ore are 10mm, 15mm and 20mm respectively, the particle size of coke is 40mm, and the simulation time step is 0.001s. The velocity inlet boundary condition is used at the inlet, the pressure outlet boundary condition is used at the outlet, and the periodic boundary condition is used on the wall.

[0049] (3) establishing a group of fluid phase control equations in a blast furnace multiphase flow system, the group of fluid phase control equations comprising a continuity equation, a momentum equation, an energy equation and a component equation;

[0050] The continuity equation is expressed as:

[0051]

[0052] In the formula, ρ f is the gas density, kg / m 3 , ε f is the local void fraction of the gas, and u is the superficial velocity of the gas, m / s.

[0053] The momentum equation is expressed as:

[0054]

[0055] Where p is the gas pressure, Pa, F fp is the interaction force between gas particles per unit volume, N; g is the acceleration due to gravity, m / s 2 , represents the gradient operation, represents the divergence operation, τ is the gas phase stress tensor, Pa.

[0056] The energy equation is expressed as:

[0057]

[0058] Where, T f is the gas temperature, K; c pf is the specific heat of gas, J / (kg·K); k e is the thermal conductivity of gas, W / (m·K); Q f,i is the heat convection between gas and particles, W; Q f,wall is the heat convection between gas and wall, W; Q f,rad is the radiation heat flux of the gas and the surrounding environment, W; Q reaction is the gas reaction volume heat flux, W.

[0059] The component equation is expressed as:

[0060]

[0061] In the formula, C m is the concentration of gas component m; Γ m is the diffusion coefficient of component m, m 2 / s;S m is the production or consumption rate of gas component m, kg / (m 3 ·s).

[0062] (iv) establishing a solid phase control equation in a blast furnace multiphase flow system, the solid phase control equation including a particle momentum equation, an energy equation and a component equation;

[0063] The particle momentum equation is expressed as:

[0064]

[0065] In the formula, m i is the mass of the ith particle, kg; v i is the horizontal velocity of the ith particle, m / s; f e,ij is the elastic force between the i-th particle and the j-th particle, N; f d,ij is the viscous damping force between the i-th particle and the j-th particle, N; f pf,i is the force between the ith particle and the fluid, N; m i g is the gravity of the ith particle, N; I i is the moment of inertia of the ith particle, kg·m 2 ;ω i is the rotation speed of the ith particle, rad / s; T t,ij is the tangential moment between the i-th particle and the j-th particle, N·m; T r,ij is the rolling friction torque between the ith particle and the jth particle, N·m.

[0066] The energy equation is expressed as:

[0067]

[0068] Where, T i is the particle temperature, K; c p,i is the particle specific heat, J / (kg·K); Q i,j is the heat flow between gas particles, W; Q i,f is the convective heat flow between particles and gas, W; Q i,rad is the radiation heat flux of the particle to the surrounding environment, W; Q i,wall is the heat flow between the particle and the wall, W; Q i,reaction is the chemical reaction heat flow, W.

[0069] The component equation is expressed as:

[0070] m i dc i,m / dt=s i,m

[0071] In the formula, c i,m is the concentration of component m in the particle, kg / m 3 ;s i,m is the consumption rate of component m in the particles, kg / s.

[0072] (V) Numerical calculation of multiphase flow phenomena in blast furnaces containing lump ore particles based on the CFD-DEM coupling method is performed to obtain the velocity field, temperature field and reduction degree distribution of the lump ore particles in the furnace, as well as the velocity cloud map, pressure cloud map, temperature cloud map and cloud maps of each component of the gas phase; the specific operations include:

[0073] like Figure 3 As shown in (a) in the figure, firstly, pelletized ore particles ( Figure 3 Red particles in the sintered ore particles ( Figure 3 Blue particles in the middle), lump ore particles ( Figure 3 The initial blast furnace charge structure layer consists of the yellow particles in the figure) and coke; then the particle temperature field is initialized, such as Figure 3 As shown in (b) in the figure; then the gas flow field and gas input components are initialized; finally, the gas-solid flow, heat transfer and mass transfer of the coupled process are calculated, and the flow field, temperature field and component field of the gas and particles are continuously updated; when the state in the furnace reaches stability and reaches the preset simulation time, the calculation ends.

[0074] (VI) Analyze the velocity field, temperature field and reduction degree distribution of the lump ore particles in the furnace calculated in (V), as well as the velocity cloud map, pressure cloud map, temperature cloud map and cloud map of each component of the gas phase, to obtain the movement and thermochemical behavior characteristics of the lump ore in the blast furnace and the law of its influence on the state in the furnace.

[0075] (VII) Optimization strategy for lump ore particle feeding operation: Based on the results analysis in (VI), the influence of lump ore on the furnace state and comprehensive performance indicators of blast furnace under different lump ore ratios, lump ore sizes and different radial position distributions of lump ore in the furnace was obtained. For example, under other conditions unchanged, appropriately increasing the lump ore ratio can increase the yield. If the lump ore ratio exceeds 25%, the blast furnace condition will gradually deteriorate, affecting the stable operation of the blast furnace; when the lump ore size is less than 20mm, the permeability in the furnace decreases and the pressure drop increases; when the lump ore is evenly distributed along the radial direction, the reducibility in the furnace is better. Therefore, under the premise of ensuring good operating conditions of the blast furnace, if the lump ore size and lump ore ratio are not changed, the radial distribution of the lump ore in the furnace can be adjusted to maintain stable and good blast furnace performance indicators, thereby improving the yield; if the distribution method and lump ore ratio are not changed, lump ore with a certain particle size range is selected to ensure good permeability in the furnace. These influence rules can provide a reference for the actual operation optimization of lump ore feeding into the furnace.

[0076] The method of this embodiment can reveal the behavior characteristics and influencing rules of blast furnace lump ore, and provide a theoretical basis for increasing the proportion of lump ore used and optimizing the blast furnace.

Claims

1. A numerical simulation method for the behavior characteristics of blast furnace lump ore based on CFD-DEM, characterized by: The following steps are involved: According to the LKAB test blast furnace, a blast furnace multiphase flow system geometric model is established, and a fluid calculation area in the blast furnace multiphase flow system geometric model is meshed; Set the basic simulation parameters and boundary conditions of the blast furnace multiphase flow system; Establishing a fluid phase control equation group in a blast furnace multiphase flow system, wherein the fluid phase control equation group includes a continuity equation, a momentum equation, an energy equation and a component equation; Establishing a solid phase control equation group in a blast furnace multiphase flow system, wherein the solid phase control equation group includes a particle motion equation, an energy equation, and a component equation; Based on the CFD-DEM coupling method, the multiphase flow phenomenon of the blast furnace containing lump ore is numerically calculated to obtain the velocity field, temperature field and reduction degree distribution of the lump ore in the furnace, as well as the velocity cloud map, pressure cloud map, temperature cloud map and each component cloud map of the gas phase; By analyzing the velocity field, temperature field and reduction degree distribution of lump ore in the furnace, as well as the velocity cloud map, pressure cloud map, temperature cloud map and component cloud map of the gas phase, the influence of lump ore on the furnace state and comprehensive performance indicators under different lump ore ratios, lump ore sizes and different radial position distributions of lump ore in the furnace is obtained, and the optimization strategy for lump ore feeding operation is formulated based on this.

2. The numerical simulation method of blast furnace lump ore behavior characteristics based on CFD-DEM according to claim 1, characterized in that: In the fluid phase governing equations, the continuity equation is expressed as: In the formula, ρ f is the gas density, ε f is the local void fraction of the gas, and u is the superficial velocity of the gas.

3. The numerical simulation method of the behavior characteristics of blast furnace lump ore based on CFD-DEM according to claim 1, characterized in that: In the fluid phase governing equations, the momentum equation is expressed as: Where p is the gas pressure, F fp is the interaction force between gas particles per unit volume; g is the gravitational acceleration, represents the gradient operation, represents the divergence operation, and τ is the gas phase stress tensor.

4. The numerical simulation method of the behavior characteristics of blast furnace lump ore based on CFD-DEM according to claim 1, characterized in that: In the fluid phase governing equations, the energy equation is expressed as: Where, T f is the gas temperature; c pf is the specific heat of gas; k e is the thermal conductivity of gas; Q f,i is the heat convection between gas and particles; Q f,wall is the heat convection between gas and wall; Q f,rad is the radiation heat flux of the gas and the surrounding environment; Q reaction is the gas reaction volume heat flux.

5. The numerical simulation method of blast furnace lump ore behavior characteristics based on CFD-DEM according to claim 1, characterized in that: In the fluid phase governing equations, the component equations are expressed as: In the formula, C m is the concentration of gas component m; Γ m is the diffusion coefficient of component m; S m is the production or consumption rate of gas component m.

6. The numerical simulation method of the behavior characteristics of blast furnace lump ore based on CFD-DEM according to claim 1, characterized in that: In the solid phase governing equations, the particle momentum equation is expressed as: In the formula, m i is the mass of the ith particle; v i is the horizontal velocity of the ith particle; f e,ij is the elastic force between the i-th particle and the j-th particle; f d,ij is the viscous damping force between the i-th particle and the j-th particle; f pf,i is the force between the ith particle and the fluid; m i g is the gravity of the ith particle; I i is the moment of inertia of the ith particle; ω i is the rotation speed of the ith particle; T t,ij is the tangential moment between the i-th particle and the j-th particle; T r,ij is the rolling friction torque between the i-th particle and the j-th particle.

7. The numerical simulation method of blast furnace lump ore behavior characteristics based on CFD-DEM according to claim 1, characterized in that: In the solid phase governing equations, the energy equation is expressed as: Where, T i is the particle temperature; c p,i is the particle specific heat; Q i,j Q is the heat flow between gas particles; i,f is the convective heat flow between particles and gas; Q i,rad is the radiation heat flux of the particle to the surrounding environment; Q i,wall is the heat flow between the particle and the wall; Q i,reaction is the heat flow of the chemical reaction.

8. The numerical simulation method of blast furnace lump ore behavior characteristics based on CFD-DEM according to claim 1, characterized in that: In the solid phase governing equations, the component equations are expressed as: m i dc i,m / dt=s i,m In the formula, c i,m is the concentration of component m in the particle; s i,m is the consumption rate of component m in the particle.

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