An efficient numerical simulation method for hot blast stove process optimization

Abstract

The present invention belongs to the field of parameter control of hot blast furnaces in metallurgical engineering, and in particular, relates to an efficient numerical simulation method for hot blast furnace process optimization. By using the average temperature and mass flow rate of high-temperature flue gas flowing from the top into the heat storage chamber during the combustion period calculated by the three-dimensional model as the inlet boundary conditions of the two-dimensional model, a high-efficiency cycle simulation of the operation of the hot blast furnace in continuous multiple cycles is achieved. Compared with the prior art, the beneficial effects of the present invention are: the present invention not only provides an accurate and reasonable visual reference for the combustion, mixing and flow state of the gas in the hot blast furnace in a specific operation cycle and the thermal saturation state of the checker bricks, but also provides accurate guidance for the operation control and optimization of each operation cycle of the hot blast furnace in a short time. The present invention systematically simulates the operation process of each cycle of the hot blast furnace, which can provide a guiding basis for improving the combustion efficiency and the heat storage capacity of the checker bricks, reducing the outlet flue gas temperature, increasing the hot blast temperature and saving gas consumption.

Description

Technical Field

[0001] The invention belongs to the field of parameter control of hot blast furnaces in metallurgical engineering, and in particular relates to a high-efficiency numerical simulation method for hot blast furnace process optimization. Background Art

[0002] At present, China's steel industry has entered a deep adjustment stage. With the increasingly stringent environmental protection requirements and the severe situation of sustainable development faced by steel enterprises, energy conservation and emission reduction have become one of the primary goals pursued by enterprises. As a device for heating and blasting blast furnaces, hot blast furnaces are an indispensable and important part of modern blast furnaces. In order to achieve the goal of energy conservation and emission reduction, iron and steel plants urgently need to reduce gas consumption while ensuring the required wind temperature level for production. The numerical simulation (simulation) technology based on computational fluid dynamics (CFD) can provide the above basis and provide theoretical guidance for optimizing the operation of hot blast furnaces, reducing gas consumption, and achieving the goal of energy conservation and emission reduction.

[0003] According to the literature reports so far, the current numerical simulation calculations for hot blast stoves are limited to the study of combustion, gas flow and heat transfer phenomena within a specific operation cycle (combustion period or air supply period), and the operation of the hot blast stove is not tracked to simulate its continuous multi-cycle operation. The main reason is that the hot blast stove body is very large, and the combustion, flow and heat transfer inside it are generally in an unstable state. The amount of calculation for the three-dimensional unstable numerical simulation of the hot blast stove as a whole is too large. Under the existing computing resources, the required computing time will be greatly extended, and it is difficult to obtain the calculation results in a short period of time. Therefore, it is impossible to track the operation of the hot blast stove and provide timely guidance for operation and regulation.

[0004] The Chinese patent application with publication number CN102221820B discloses "a model for optimizing and controlling the combustion reversing cycle of a blast furnace top-fired hot blast stove". The patent introduces a heat balance calculation module, a heat transfer simulation calculation module and a hot blast stove combustion reversing cycle optimization module in the modeling method. The optimal combustion and air supply time of the hot blast stove can be obtained through the combined calculation of these three modules. This can not only ensure that the hot blast temperature meets the high wind temperature requirements, but also avoid the problem of gas waste caused by too long combustion time and the reduction of the service life of the refractory materials in the hot blast stove. However, the model does not consider the influence of the type of checkered brick material in the heat storage chamber on heat transfer, so the optimal combustion and air supply time obtained is an idealized result, and the model still has room for optimization.

[0005] The Chinese patent application with publication number CN102819643B discloses "the establishment method and application of the heat transfer and heat storage simulation model of the hot blast furnace". The method provides a heat transfer and heat storage simulation model of the hot blast furnace that can understand the flow and heat transfer characteristics in the heat storage chamber, simulate the temperature change characteristics of the heat storage body with space and time during the heat storage process, and calculate the increase of the heat storage of the checker brick during the furnace burning. Through this model, the increase value and consumption time of the heat storage when reaching the end of the combustion under different combustion strategies can be calculated under the same initial conditions. The best and most efficient combustion strategy can be obtained by comparison, so as to maximize the energy accumulated during the heat storage period and achieve the purpose of increasing the wind temperature. However, this method does not consider the mixing and combustion of fuel and air after entering the hot blast furnace and the influence of the airflow distribution before entering the heat storage chamber on the subsequent heat transfer of the heat storage chamber. Therefore, the heat storage obtained by this method is under an ideal state, and the guiding value for the actual operation of the hot blast furnace is not high. There is still room for optimization of this method.

[0006] The Chinese patent application with publication number CN105907906A discloses "Modeling and Energy Consumption Optimization Method and System for Spherical Hot Blast Furnace Burning Process". This patent uses the established transient heat transfer model of the regenerator and the corresponding boundary conditions to calculate the temperature distribution of the regenerator and the flue gas or blast, and finally optimizes the gas consumption to minimize the total gas consumption of the hot blast furnace under production constraints. This method does not consider the impact of the combustion and airflow distribution of the gas before entering the regenerator on the subsequent heat transfer of the regenerator. In the absence of an overall analysis of the combustion, flow and heat transfer of the gas in the hot blast furnace, the results obtained by this method will deviate from the actual results obtained under the same operation, and this method still has room for improvement.

[0007] The Chinese patent application with publication number CN103293955B discloses a method for modeling and coordinated optimization control of a hybrid system of a blast furnace hot blast stove. The patent collects and preprocesses the hot blast stove data by designing experiments, and obtains the state space model of the blast furnace hot blast stove by applying the subspace identification method. The obtained space model is synthesized, and a hybrid logic dynamic modeling method is applied to establish a hybrid system model and design a controller based on a predictive control method to achieve coordinated optimization control of the combustion period and the air supply period of the hot blast stove. It has the function of reflecting the working cycle of the hot blast stove and reasonably controlling the air supply quality of the hot blast stove. However, the spatial identification in this optimization method is relatively general in its response to the hot blast stove process, and the combustion period model and the air supply period model obtained may deviate from reality, resulting in the final coordinated optimization control failing to achieve the desired effect. Therefore, there is still room for improvement in this method. Summary of the invention

[0008] The technical problem to be solved by the present invention is to propose an efficient numerical simulation method for hot blast stove process optimization, which provides a fast and sufficiently accurate reference basis for tracking the continuous multi-cycle operation control and optimization of the actual hot blast stove.

[0009] In order to solve the above problems, the present invention adopts the following technical solutions: First, the inventor believes that the flow and heat transfer in other fluid areas (such as the combustion chamber, the vault and the furnace column area) in the hot blast furnace except the heat storage chamber are close to a stable state, so a three-dimensional steady-state CFD model of the hot blast furnace as a whole can be established to perform steady-state numerical simulation analysis on these areas; for the heat storage chamber lattice brick area where non-steady-state heat transfer is dominant, the inventor assumes that the gas flow in all the pores of the lattice bricks and the heat exchange conditions between the lattice bricks and the solid lattice bricks are the same, and thus a two-dimensional non-steady-state CFD model of a single pore of the heat storage chamber lattice bricks is established to perform numerical simulation analysis on this area. The outstanding advantages of the two models constructed are their fast calculation speed and high operating efficiency. By using the average temperature and mass flow rate of the high-temperature flue gas flowing into the heat storage chamber from the top during the combustion period calculated by the three-dimensional model as the inlet boundary conditions of the two-dimensional model, the two models are organically combined to operate, thereby realizing the "combustion period" operation of the hot blast furnace for continuous multi-cycle operation. The numerical simulation strategy of the present invention has the potential to track the actual hot blast stove operation and provide guidance for operation control and optimization in a timely manner.

[0010] The specific simulation process of the present invention is as follows:

[0011] (1) First, a three-dimensional model is used to perform a steady-state numerical simulation of the Kalujin hot blast stove and the internal combustion hot blast stove in the combustion period, and the average temperature and mass flow rate of the high-temperature flue gas flowing into the top surface of the regenerator of the Kalujin hot blast stove and the top surface of the regenerator of the internal combustion hot blast stove are calculated;

[0012] (2) Then, the average temperature and mass flow rate of the high-temperature flue gas flowing into the top surface of the regenerator calculated by the three-dimensional model were used as the inlet boundary conditions of the checker brick channel, and the checker brick single-channel two-dimensional model was run to simulate the start-up stage of the hot blast stove (i.e., the initial temperature of the checker brick and the gas in the brick hole were set to room temperature 27°C); this stage is called the first cycle combustion period;

[0013] (3) The checker brick temperature at the end of the first combustion cycle calculated by the checker brick single-channel two-dimensional model is used as the initial condition, and the model is run to simulate the operation of the first air supply period of the hot blast furnace;

[0014] (4) The checker brick temperature at the end of the first air supply period calculated by the checker brick single-channel two-dimensional model is used as the initial condition, and the model is run to simulate the operation of the hot blast furnace in the second combustion period;

[0015] (5) The checker brick temperature at the end of the second combustion cycle calculated by the checker brick single-channel two-dimensional model is used as the initial condition, and the model is run to simulate the operation of the second air supply period of the hot blast furnace;

[0016] (6) Repeat the calculation steps (4) and (5) repeatedly to simulate the "combustion period" of the third, fourth, fifth and subsequent cycles of the hot blast furnace. The heating and cooling operations during the "air supply period" are tracked to realize the numerical simulation of the hot blast stove operation for multiple consecutive cycles.

[0017] Compared with the prior art, the beneficial effects of the present invention are: the present invention not only provides accurate and reasonable visual reference for the combustion, mixing and flow state of the gas in the hot blast furnace in a specific operation cycle and the heat saturation state of the checker brick, but also provides accurate guidance for the operation control and optimization of each operation cycle of the hot blast furnace in a short time. The present invention systematically simulates the operation process of each cycle of the hot blast furnace, which can provide guidance for improving the combustion efficiency and the heat storage capacity of the checker brick, reducing the outlet flue gas temperature, increasing the hot blast temperature and saving gas consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 , Figure 2 and Figure 5 They are respectively the computational domain geometry and mesh division diagram of the overall three-dimensional steady-state CFD model of the Kalujinding combustion hot blast furnace and the computational domain geometry and mesh division diagram of the two-dimensional unsteady-state CFD model of the checker brick single channel of the regenerator in the embodiment of the present invention;

[0019] Figure 3 The geometric model of the internal combustion hot blast stove according to the embodiment of the present invention;

[0020] Figure 4 Grid division for CFD calculation of internal combustion hot blast stove according to an embodiment of the present invention;

[0021] Figure 6 The calculation domain geometry and mesh division diagram of the two-dimensional non-steady-state CFD model of the single-channel checker brick in the regenerator according to the embodiment of the present invention;

[0022] Figure 7 This is a simulation flow chart of an embodiment of the present invention;

[0023] Figure 8 The flow field and temperature field in the hot blast furnace during the combustion period simulated by the overall three-dimensional steady-state CFD model of the Kalujin top-fired hot blast furnace in the embodiment of the present invention;

[0024] Fig. 9 The temperature distribution along the height direction of the regenerator changes with time as simulated by the two-dimensional non-steady-state CFD model of the single-channel checker brick of the Kalujin top-fired hot blast furnace in the embodiment of the present invention;

[0025] Fig.10 The flow field, temperature field and CO concentration field in the hot blast stove during the combustion period simulated by the overall three-dimensional steady-state CFD model of the internal combustion hot blast stove in the embodiment of the present invention;

[0026] Fig.11 The temperature distribution of the checker bricks during the combustion period and the temperature distribution of the hot air during the air supply period along the height direction of the regenerator simulated by the two-dimensional non-steady-state CFD model of the checker bricks of the internal combustion hot blast furnace in the embodiment of the present invention are as follows: (a) the temperature of the checker bricks during the combustion period, (b) the temperature of the hot air during the air supply period;

[0027] Fig.12 The relationship between the dome temperature and the air consumption coefficient during the combustion period simulated by the three-dimensional steady-state CFD model before and after the optimization of the operation of the Kalujinding combustion hot blast furnace in the embodiment of the present invention and the comparison with the field measurement results;

[0028] Fig.13 The relationship between the outlet hot air temperature and the air consumption coefficient during the air supply period simulated by the two-dimensional non-steady-state CFD model before and after the optimization of the operation of the Kalujin top-fired hot blast furnace in the embodiment of the present invention and the comparison with the field measurement results;

[0029] Fig.14 The average outlet hot air temperature during the air supply period calculated by the two-dimensional non-steady-state CFD model of the single-channel checker brick in the regenerator of the internal combustion hot blast furnace in the embodiment of the present invention is compared with the field measured results (average value of 44 months).

[0030] In the figure: 1-Kalujin top-burning hot blast furnace body; 2-precombustion chamber; 3-combustion chamber; 4-regenerator top surface; 5-regenerator upper section (silicon brick area); 6-regenerator middle section (silicon brick + clay brick mixed area); 7-regenerator lower section (clay brick area); 8-regenerator bottom surface; 9-furnace pillar area; 10-combustion air inlet; 11-gas inlet; 12-hot air (air) outlet; 13-smoke outlet; 14-cold air (air) inlet; 16-internal combustion hot blast furnace body; 17-regenerator upper section (silicon brick area); 18-regenerator lower section (clay brick area); 19-regenerator top surface; 20-regenerator bottom surface; 21-furnace pillar area; 22-gas inlet; 23-combustion air inlet; 24-smoke outlet; 25-hot air (air) outlet; 26-cold air Wind (air) inlet; 27-combustion chamber; 28-vault area; 30-checker brick single-hole flow channel area; 31-checker brick solid area; 32-smoke inlet during combustion period or hot air outlet during air supply period; 33-smoke outlet during combustion period or cold air inlet during air supply period; 34-heat storage chamber top surface height position; 35-heat storage chamber bottom surface height position; 36-silica brick checker brick area; 37-silica brick and clay brick checker brick mixed masonry area; 38-clay brick checker brick area; 39-checker brick single-hole flow channel area; 40-checker brick solid area; 41-smoke inlet during combustion period or hot air outlet during air supply period; 42-smoke outlet during combustion period or cold air inlet during air supply period; 43-heat storage chamber top surface height position; 44-heat storage chamber bottom surface height position; 45-high alumina brick checker brick area; 46-clay brick checker brick area. DETAILED DESCRIPTION

[0031] The following is an example to illustrate the contents and results of the hot blast stove operation simulation of the present invention.

[0032] 1. Establishment of the overall three-dimensional steady-state CFD model of the hot blast stove

[0033] 1. Assumptions

[0034] (1) The hot blast furnace is assumed to be a three-dimensional steady-state flow and heat transfer process; (2) The checker brick area is assumed to be a porous medium area; (3) The refractory material of the furnace lining is ignored, and only the fluid flow area is considered; (4) The gas is assumed to be an ideal gas.

[0035] 2. Three-dimensional physical model of hot blast furnace and computational grid division

[0036] The three-dimensional physical model and computational domain mesh division of the Kalujinding combustion hot blast stove and the internal combustion hot blast stove are as follows: Figures 1 to 4 shown.

[0037] 3. Control equations

[0038] The basic control equations are the theoretical basis and starting point for numerical simulation of the mixing and turbulent combustion process of the hot blast stove burner. The partial differential equations to be solved include the continuity equation, momentum equation, Realizable k-ε turbulence equation, energy equation and component equation.

[0039] (1) Control equation of the fluid space outside the regenerator in the hot blast furnace:

[0040] Continuity equation:

[0041]

[0042] Momentum equation:

[0043]

[0044] Realizable k-ε turbulence equation:

[0045]

[0046]

[0047]

[0048] In the formula,

[0049] The energy equation for the coupled radiation heat transfer model:

[0050]

[0051] Mixture fraction transport equation:

[0052]

[0053] Mixture fraction variance transport equation:

[0054]

[0055] The symbols in equations (1) to (8) have the following meanings: ρ: density, kg / m 3 ; Velocity vector, m / s; p: pressure, Pa; μ: dynamic viscosity, Pa·s; μ t : turbulent viscosity, Pa·s; k: turbulent kinetic energy, m 2 / s 2 ; ε: turbulent kinetic energy dissipation rate, m 2 / s 3 ; σ k : Prandtl number of turbulent kinetic energy; σ ε : Prandtl number of turbulent kinetic energy dissipation rate; P k: Turbulence kinetic energy generation rate, W / m 3 ; h: enthalpy, J / kg; T: temperature, K; λ eff : Effective thermal conductivity, W / (m·K); Q r :Heat source, W / m 3 ; f: mixture fraction; σ t : diffusion Prandtl constant; f ′2 : Mixture fraction mean square value; C 1 : Model coefficient; C 2 , σ k and σ ε : Model constant.

[0056] (2) Control equation inside the hot air furnace regenerator (porous medium area):

[0057] Continuity equation:

[0058]

[0059] Momentum equation:

[0060]

[0061]

[0062] Δp=S i Δn (12)

[0063] Energy equation:

[0064]

[0065] The symbols in equations (9) to (13) have the following meanings. i : Momentum equation source term, N / m 3 ; C 2 : Inertial resistance coefficient, 1 / m; α: Permeability, m 2 ; E f : total energy of fluid, J / kg; ρ f : Fluid density, kg / m 3 ρ s : Solid medium density, kg / m 3 ;γ: porosity; k eff : effective thermal conductivity of medium, W / (m·K); Energy equation source term, W / m 3 .

[0066] 4. Boundary conditions

[0067] The gas inlet is set as a constant mass flow inlet and is preheated to 180°C; the combustion air inlet is set as a constant mass flow inlet and the combustion air is preheated to 180°C; the flue gas outlet is set as a constant pressure outlet: the value is 0Pa; all walls are set as non-slip walls; the heat loss of the dome area is set to 2021W / m 2 The heat dissipation loss in the silicon brick area is 761W / m 2 The heat loss of the checkered brick masonry area is 584W / m 2 , the heat loss in the clay brick area is 385W / m 2 .

[0068] 5. Calculation method

[0069] The CFD numerical simulation software ANSYS Fluent is used to solve equations (1) to (13). The control equations (1) to (13) are discretized using the control volume method and solved using the SIMPLEC algorithm.

[0070] 2. Establishment of two-dimensional non-steady-state CFD model of single channel of checker brick in heat storage chamber

[0071] 1. Assumptions

[0072] (1) Two-dimensional non-steady-state flow and heat transfer; (2) The flow and heat transfer of each grid hole of the checker brick on the same height horizontal plane are the same, so the heat flux at the interface between each adjacent hole is zero; (3) The residual combustion phenomenon in the checker brick holes during the combustion period is ignored; (4) The short-term (about 10-15 minutes) "furnace change" operation between the combustion period operation and the air supply period operation is ignored.

[0073] 2. Computational meshing of the two-dimensional model of a single-channel checkerboard brick

[0074] According to the structural characteristics of 19-hole lattice bricks (hole diameter is 30 mm) in the heat storage chamber of the Kalujin top combustion hot blast stove and 7-hole lattice bricks (hole diameter is 40 mm) in the heat storage chamber of the internal combustion hot blast stove, the calculation grid division of the lattice brick single-channel 2D CFD model is as follows: Figure 5 and Figure 6 shown.

[0075] 3. Control equations

[0076] According to the flow and heat transfer characteristics of high-temperature flue gas in the hot blast stove combustion period and normal-temperature air in the air supply period in the heat storage chamber, a mathematical model is established. The unsteady partial differential equations to be solved include the continuity equation, momentum equation, standard k-ε turbulence equation and energy equation of the coupled radiation heat transfer model as follows.

[0077] Continuity equation:

[0078]

[0079] Momentum equation:

[0080]

[0081] Standard k-ε turbulence equation:

[0082]

[0083]

[0084]

[0085] The energy equation for the coupled radiation heat transfer model:

[0086]

[0087] The symbols in equations (14) to (19) have the following meanings: ρ: density, kg / m 3 ; Velocity vector, m / s; p: pressure, Pa; μ: dynamic viscosity, Pa·s; μ t : turbulent viscosity, Pa·s; k: turbulent kinetic energy, m 2 / s 2 ; ε: turbulent kinetic energy dissipation rate, m 2 / s 3 ; σ k : Prandtl number of turbulent kinetic energy; σ ε : Prandtl number of turbulent kinetic energy dissipation rate; P k : Turbulence kinetic energy generation rate, W / m 3 ; h: enthalpy, J / kg; T: temperature, K; λ eff : Effective thermal conductivity, W / (m·K); Q r :Heat source, W / m 3 , calculated by the aforementioned DO radiation heat transfer model.

[0088] 4. Boundary conditions

[0089] like Figure 7As shown, as the initial condition for the combustion period simulation, the gas velocity in the grid hole is set to 0m / s, and the initial temperature of the gas and the grid bricks are both set to room temperature 27°C (i.e. 300K). This initial condition means that the calculation starts from simulating the start-up stage of a hot blast furnace. That is, the grid bricks are gradually heated and heated by the high-temperature flue gas from a cold state until the temperature of the flue gas outlet section (BD) of the grid brick hole (i.e. the temperature of the regenerator grate) is close to 390°C. The present invention refers to this grid brick heating stage as the "first cycle combustion period". Then, the grid brick temperature at the end of the "first cycle combustion period" is used as the initial condition, the BC boundary is used as the inlet of cold air (temperature is room temperature 27°C), and the AF boundary is used as the outlet, and the air supply simulation calculation is performed. This paper refers to this grid brick cooling stage as the "first cycle air supply period". Then, the grid brick temperature at the end of the "first cycle air supply period" is used as the initial condition, the AF boundary is used as the inlet of high-temperature flue gas, and the BC boundary is used as the outlet, and the "second cycle combustion period" simulation calculation is performed. On this basis, the BC boundary is used as the cold air inlet and the AF boundary is used as the outlet to simulate the "second cycle air supply period". This cycle is repeated for the "third cycle", "fourth cycle" and "fifth cycle" and the "combustion period" of each subsequent operation cycle. "Air supply period" cycle simulation calculation.

[0090] 5. Calculation method

[0091] The CFD numerical simulation software ANSYS Fluent is used to solve equations (14) to (19). The control equations (14) to (19) are discretized using the control volume method and solved using the SIMPLE algorithm.

[0092] 3. Simulation Results

[0093] The inventors have carried out CFD numerical simulation calculations for two consecutive operation cycles (i.e., the first cycle of furnace opening and the subsequent second cycle) for the Kalujin top-fired hot blast furnace and the internal combustion hot blast furnace. As an example, the simulation calculation results for the combustion period and the air supply period of the second cycle are introduced as follows.

[0094] 1. Numerical simulation results of Kalujinding combustion hot blast stove

[0095] Figure 8 The flow field and temperature field in the hot blast stove during the combustion period simulated by the overall three-dimensional steady-state CFD model of the Kalujin top-fired hot blast stove are shown. Fig. 9 The temperature distribution along the height direction of the regenerator simulated by the two-dimensional non-steady-state CFD model of the 19-hole checker brick single-channel of the Kalujin top-fired hot blast furnace is shown as a function of time. This includes the temperature distribution of the checker bricks and flue gas during the combustion period and the temperature distribution of the checker bricks and hot air during the air supply period.

[0096] 2. Numerical simulation results of internal combustion hot blast stove

[0097] Fig.10 The flow field, temperature field and CO concentration field in the hot blast stove during the combustion period simulated by the overall three-dimensional steady-state CFD model of the internal combustion hot blast stove are shown. Fig.11 The temperature distribution of checker bricks during combustion period and the temperature distribution of hot air during air supply period simulated by the two-dimensional non-steady-state CFD model of a single-channel checker brick with 7 holes in an internal combustion hot blast stove along the height direction of the regenerator are shown.

[0098] IV. Model Verification and Implementation Benefits

[0099] 1. Results of the numerical model test of the Kalujinding combustion hot blast stove

[0100] The numerical simulation method disclosed in this patent is first applied to optimize the operation of the Kalujin top-fired hot blast furnace during the combustion period of a steel plant. The air consumption coefficient before the optimization of the operation of the hot blast furnace during the combustion period is controlled at 0.75-1.0, resulting in a higher gas consumption than the average level of similar hot blast furnaces at home and abroad under the condition of achieving the same dome temperature and hot blast temperature levels. The numerical simulation results of the present invention for optimizing the operation of the hot blast furnace during the combustion period show that the gas flow rate can be appropriately reduced while keeping the combustion air flow rate unchanged, that is, the air consumption coefficient can be increased to the range of 1.0-1.3, and the required dome temperature and hot blast temperature levels can also be achieved, thereby achieving the purpose of saving gas.

[0101] Fig.12 and Fig.13 The following are the relationship diagrams between the second cycle combustion period and air supply period simulated by the CFD model before and after the optimization of the hot blast furnace operation, and the air consumption coefficient of the on-site hot blast furnace test, the dome temperature, and the hot blast temperature. First, it can be seen from the figure that the results of the CFD simulation are basically consistent with the measured results, indicating the reliability of the constructed CFD model. In addition, the CFD simulation results also indicate that higher dome temperatures and hot blast temperatures can be achieved within the range of 1.0-1.1 for the air consumption coefficient, so there is still room for further optimization.

[0102] 2. Results of the numerical model test of the internal combustion hot blast stove

[0103] Fig.14 The figure shows the comparison between the average outlet hot air temperature of the second air supply period calculated by the two-dimensional non-steady-state CFD model of the checker brick single-channel of the internal combustion hot blast furnace regenerator and the field measured results. Due to the lack of field internal combustion hot blast furnace hot air temperature in a supply cycle in the measured data of the time change. Fig.14The field measurement results shown are the average values ​​of the hot air temperature historical data of the hot air stove for 44 consecutive months. As can be seen from the figure, the hot air temperature calculated by the CFD model gradually decreases with the extension of the air supply time, and this change trend is in line with the actual situation on site; moreover, the hot air temperature calculated by the CFD model varies within a certain range around the measured average hot air temperature. This shows that the numerical simulation method of the present invention also has a certain reliability in predicting the hot air temperature of the internal combustion hot air stove. Therefore, like the aforementioned simulation calculation for the optimization of the operation of the Kalujin top-fired hot air stove, the numerical simulation method of the present invention can also be used to optimize the simulation calculation for the operation of the internal combustion hot air stove to achieve the purpose of reducing gas consumption and achieving energy conservation and emission reduction.

[0104] 3. Effect of CFD model application

[0105] See Tables 1 and 2 below, which respectively list the statistical data of the measured results before and after the optimization of the operation of the on-site Kalujin top-fired hot blast furnace according to the optimal operating conditions obtained by the numerical simulation method of the present invention. Table 1 gives the measured results of 10 combustion cycles before the operation optimization; Table 2 gives the measured results of 10 combustion cycles after the operation optimization. From the comparison of the data in the two tables, it can be seen that by appropriately reducing the gas flow rate to increase the air consumption coefficient between 1.0 and 1.3, the average gas flow rate of 10 combustion cycles increased from 106488Nm before optimization to 106488Nm 3 / h is reduced to the optimized 97310Nm 3 / h(reduction is 9178Nm 3 / h or 8.6%); the average air flow rate is 53472Nm before optimization 3 / h increased to 78981Nm after optimization 3 / h; the corresponding average air consumption coefficient increased from 0.788 before optimization to 1.274 after optimization; the average dome temperature increased from 1231℃ before optimization to 1238℃ after optimization (an increase of 7℃ or 0.56%); the hot air temperature increased from 1146℃ before optimization to 1178℃ after optimization (an increase of 32℃ or 2.8%). Finally, the cumulative gas consumption in 10 combustion cycles increased from 2018960Nm before optimization to 1178℃ after optimization. 3 Reduced to 1736110Nm after optimization 3 (Reduction is 282850Nm 3 or 14%). It can be seen that the gas consumption saving effect achieved by adopting the optimization measures obtained by the present invention is extremely significant. This is mainly due to the improvement of the air consumption coefficient, which improves the combustion of gas in the hot blast stove (reaching complete combustion).

[0106] Table 1 Actual test results before optimization of Kalu Jinding combustion hot blast furnace operation

[0107]

[0108] Table 2 Actual test results after optimization of Kalujinding combustion hot blast furnace operation

[0109]

[0110] Estimation of the time consumption of CFD numerical simulation calculation of Kalujin top-fired hot blast furnace operation in the embodiment of the present invention. In order to compare the time consumed by the calculation method combining the three-dimensional stable state model and the two-dimensional unsteady state model of the present invention with the traditional three-dimensional whole furnace unsteady state model calculation method, the inventors estimated the time consumption of CFD numerical simulation calculation of Kalujin top-fired hot blast furnace operation by applying these two methods. The basic conditions for the estimation are as follows:

[0111] (1) The personal computer hardware configuration used for simulation calculation is Intel Core i7 8-core CPU with a main frequency of 2.3 GHz.

[0112] (2) The operation time of the combustion period of the first cycle of the hot blast furnace (i.e., starting a new furnace: the initial temperature of all areas in the furnace is set to room temperature 27°C) is set to the heating time required for the average grate temperature to reach 390°C; the operation time of the combustion period thereafter (i.e., the second, third, fourth... cycles) is set to 80 minutes; the operation time of the air supply period is set to 60 minutes.

[0113] The results of the comparison of the unit time consumption of the non-steady-state three-dimensional full furnace model and the two-dimensional checker brick single channel model using the above hardware configuration are shown in Table 3. As can be seen from the table, the unit time consumption of the non-steady-state three-dimensional full furnace model is 18h / min, that is, it takes 18 hours of calculation time to simulate the actual operation per minute; while the unit time consumption of the non-steady-state two-dimensional checker brick single channel model is only 0.0667h / min. In other words, the unit time consumption of the former is about 270 times that of the latter!

[0114] The time consumption for calculating the steady-state three-dimensional full-furnace overall model using the computer with the above hardware configuration is shown in Table 4. The table shows that the calculation time consumed for the steady-state three-dimensional full-furnace overall model calculation to reach the convergence requirement based on the estimated initial conditions is 24 hours; if the steady-state three-dimensional full-furnace overall model calculation is performed using the converged calculation results as the initial conditions, the calculation time used to reach the convergence requirement is shortened to 8 hours.

[0115] According to the data given in Table 3 and Table 4, Table 5 compares the calculation time used by the calculation method combining the steady-state three-dimensional model and the unsteady-state two-dimensional model of the present invention with the traditional unsteady-state three-dimensional full-furnace overall model calculation method. The time used for the calculation of the first cycle combustion period using the unsteady-state two-dimensional checker brick single-channel model shows that when the temperature at the bottom grate of the hot blast furnace regenerator is heated from the normal temperature of 27°C to 390°C, the required heating time is about 250 minutes. If the air supply time is set to 60 minutes, the operation time of the first cycle is:

[0116] Combustion period 250min + air supply period 60min = 310min.

[0117] Therefore, the CFD numerical simulation calculation time results are as follows:

[0118] (1) The calculation time required for the first cycle of the non-steady-state three-dimensional full-furnace overall model simulation is:

[0119] 18h / min*310min=5580h=232.5 days.

[0120] (2) The calculation time required for simulating the first cycle by combining the estimated initial value of the steady-state three-dimensional model with the unstable two-dimensional model is:

[0121] 24h+0.0667h / min*310min=44.667h=1.86 days.

[0122] (3) The calculation time required for simulating the first cycle of the steady-state three-dimensional model based on the convergence result initial value variable working condition calculation combined with the unsteady-state two-dimensional model is:

[0123] 8h+0.0667h / min*(80min combustion period+60min ventilation period)=17.333h=0.72 days.

[0124] (4) The calculation time required to simulate the second, third, fourth, and so on cycles by combining the steady-state three-dimensional model with the unstable two-dimensional model is:

[0125] 0.0667h / min*(80min combustion period+60min air supply period)=9.333h=0.39 days.

[0126] The above calculation time comparison results show that the calculation method proposed by the present invention can shorten the calculation time from 232.5 days required by the traditional non-steady-state three-dimensional full furnace overall model to 2 days or even half a day (1.86 days to 0.39 days). Therefore, the calculation method of the present invention has extremely high calculation efficiency. If supported by more powerful computer hardware, it is possible to achieve real-time tracking and simulation of the operation process of the hot blast stove and provide timely guidance for the operation of the hot blast stove.

[0127] Table 3 Unit time consumption of non-steady-state CFD numerical simulation calculation of Kalujin top-fired hot blast furnace operation

[0128]

[0129] *Calculation time (h) / actual operation time of hot air furnace (min)

[0130] Table 4 Calculation time of CFD numerical simulation of steady-state operation of Kalujin top-fired hot blast furnace

[0131] serial number Calculation Project Time consumed (h) 3 The steady-state three-dimensional full furnace model is calculated based on the estimated initial value 24 4 Steady-state three-dimensional full furnace overall model based on convergence results and variable operating condition calculation of initial values 8

[0132] Table 5 Comparison of CFD numerical simulation time for Kalujin top-fired hot blast furnace operation

[0133]

Claims

1. An efficient numerical simulation method for hot blast stove process optimization, It is characterized in that Using the CFD numerical simulation method, the overall three-dimensional steady-state model of the Kalujin top-fired hot blast stove and the internal-fired hot blast stove and the two-dimensional unsteady-state model of the single-channel checker brick of the regenerator are established respectively, and the two models are combined to simulate the operation of the hot blast stove; the former is used to calculate the combustion, flow and heat transfer in the hot blast stove and focuses on predicting the average temperature and mass flow rate of the high-temperature flue gas flowing from the top into the checker brick holes of the regenerator during the combustion period as the inlet boundary conditions of the latter; the latter performs unsteady-state calculations on the flow and heat exchange process of the flue gas during the combustion period and the cold air during the air supply period in the checker brick holes, so as to predict the time evolution of the flue gas temperature and checker brick temperature during the combustion period and the hot air temperature and checker brick temperature during the air supply period along the height direction of the regenerator under different operating parameters; the numerical simulation step The steps are as follows: (1) The flue gas temperature and mass flow rate at the inlet of the checker brick hole in the two-dimensional model are set to the values ​​calculated by the three-dimensional model; the gas flow rate in the grid hole is initially set to 0 m / s, and the initial temperatures of the gas and the checker brick are set to room temperature 27°C. The two-dimensional model is run to simulate the start-up stage of the hot blast furnace, which is called the first cycle combustion period. (2) The calculated checker brick temperature at the end of the first cycle combustion period is used as the initial condition, and the two-dimensional model is run to simulate the first cycle air supply period. (3) The calculated checker brick temperature at the end of the first cycle air supply period is used as the initial condition, and the two-dimensional model is run to simulate the second cycle combustion period. (4) The calculated checker brick temperature at the end of the second cycle combustion period is used as the initial condition, and the two-dimensional model is run to simulate the second cycle air supply period. (5) This cycle of calculation is repeated to simulate the hot blast furnace. The heating and cooling operations of each cycle can realize the tracking simulation of the continuous multi-cycle operation of the hot blast stove, and provide real-time prediction and guidance for the on-site hot blast stove operation control results.

2. According to claim 1, an efficient numerical simulation method for hot blast stove process optimization, Features: The calculation method for the first cycle combustion period is to use the flue gas temperature and mass flow calculated by the three-dimensional model as the boundary conditions of the inlet of the checker brick hole of the two-dimensional model. The two-dimensional model calculates that the checker brick is gradually heated by the high-temperature flue gas from a cold state until the temperature of the flue gas outlet end face of the checker brick hole reaches 390°C.

3. According to claim 2, an efficient numerical simulation method for hot blast stove process optimization, Features: The calculation method for the first cycle of air supply period is to use the checker brick holes on the top surface of the heat storage chamber of the two-dimensional model as the outlet, the checker brick holes on the bottom surface of the heat storage chamber as the inlet and let in cold air at a normal temperature of 27°C, and use the temperature of the checker bricks that have been heated at the end of the first cycle of combustion as the initial condition. The two-dimensional model calculates that the cold air at a normal temperature of 27°C is gradually heated by the high-temperature checker bricks to become hot air, and the air supply time is 60 minutes.

4. According to claim 1, an efficient numerical simulation method for hot blast stove process optimization, Features: The calculation method for the second cycle combustion period is to use the temperature of the checker bricks cooled by cold air at room temperature of 27°C at the end of the first cycle air supply period calculated by the two-dimensional model as the initial condition, and the flue gas temperature and mass flow rate calculated by the three-dimensional model as the boundary conditions of the inlet of the checker brick holes of the two-dimensional model. The two-dimensional model calculates that the checker bricks are gradually heated by the high-temperature flue gas, and the heating time is 80 minutes.

5. According to claim 4, an efficient numerical simulation method for hot blast furnace process optimization, Features: The calculation method for the second cycle air supply period is to use the flue gas temperature and mass flow calculated by the three-dimensional model as the boundary conditions of the inlet of the two-dimensional model checkerboard brick holes, and use the checkerboard bricks that have been heated at the end of the second cycle combustion period as the initial conditions. The two-dimensional model calculates that the cold air at room temperature of 27°C is gradually heated by the high-temperature checkerboard bricks to become hot air, and the air supply time is 60 minutes.

6. The efficient numerical simulation method for hot blast stove process optimization according to claim 1, Features: It also includes the third, fourth, fifth and subsequent operation cycles The checker bricks are alternately heated and cooled repeatedly by high-temperature flue gas and cold air at a normal temperature of 27°C; the heating and cooling times are 80 minutes and 60 minutes respectively; the cold air at a normal temperature of 27°C is intermittently heated by the high-temperature checker bricks to become hot air and supplied to the iron-making blast furnace.

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