CN115261551B - Converter bottom blowing process optimization method and optimization system - Google Patents
Converter bottom blowing process optimization method and optimization system Download PDFInfo
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- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
- C21C5/30—Regulating or controlling the blowing
- C21C5/34—Blowing through the bath
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Abstract
The invention provides a converter bottom blowing process optimization method, and belongs to the field of steelmaking process control. The method comprises the steps of drawing a converter geometric model, giving a nozzle position and angle arrangement mode, determining a bottom blowing process calculation area and carrying out grid division; constructing a bottom blowing process simulation model based on VOF, DPM, component transport models and coupling of the three models in the divided grids; and respectively giving different to-be-selected bottom blowing gas flows under the set positions and angle arrangement modes of each bottom blowing nozzle, determining bottom blowing parameters, solving a control equation in a bottom blowing process simulation model according to the bottom blowing parameters, and comparing all the nozzle positions, angle arrangement modes and steel and gas multiphase flow field parameters, molten pool dead zone distribution and mixing time obtained under the condition of bottom blowing gas flow velocity to obtain the optimized bottom blowing process parameters of the current converter. The invention optimizes the bottom blowing process under different experimental conditions or production conditions, and improves the production quality and efficiency of the converter.
Description
Technical Field
The invention belongs to the field of steelmaking process control, and particularly relates to a converter bottom blowing process optimization method and system.
Background
The top-bottom combined blown converter combines the advantages that the top-blown converter is easy to control slag formation and dephosphorization and the bottom-blown converter is beneficial to enhancing the stirring force of a molten pool, and is a main mode of converter smelting at present. In a top-bottom combined blown converter, top blowing is mainly used for slag making smelting, the stirring effect of a molten pool mainly comes from bottom blowing, the stirring effect of the bottom blowing determines the mixing characteristics of the whole molten pool, and a reasonable bottom blowing process is beneficial to stably controlling C, T, O of a converter end point and reducing the number of inclusions; promoting balance of slag steel, reducing the endpoint P content of a converter, and improving uniformity of molten pool components and temperature; meanwhile, with the enhancement of the stirring of a molten pool, the TFe content of the final slag of the converter is further reduced, and the consumption of steel materials can be reduced. The unreasonable increase of the bottom blowing strength can aggravate the scouring and erosion of the bottom blowing nozzle and peripheral refractory materials, and the service life of the converter bottom is reduced. Therefore, it is very important to determine the appropriate bottom blowing process parameters.
In the prior art, the bottom blowing process of the converter generally comprises parameters such as bottom blowing strength, bottom blowing nozzle arrangement mode, quantity and the like. For the bottom blowing strength, the stirring effect of molten steel increases with the increase of the bottom blowing flowThe mixing efficiency can be improved by improving the bottom blowing flow, and on the premise of reducing the total bottom blowing flow, the mixing efficiency can also be improved by adopting an effective bottom blowing flow distribution mode, but when the bottom blowing flow exceeds 0.15m 3 In the case of (min.t), the influence on the reduction of the mixing time is not great, and only the bottom blowing strength is regulated to have a certain limit; for bottom blowing nozzle arrangements, when the bottom blowing nozzles are supplied in a non-uniform arrangement, it is advantageous to improve mixing time and velocity profile characteristics; however, when the bottom blowing nozzles are asymmetrically arranged, stronger shearing stress is generated, so that more serious abrasion of the bottom blowing nozzles and surrounding refractory materials is caused; in addition, the number of bottom blowing nozzles has important influence on the mixing effect of a molten pool, and some scholars consider that the mixing effect of the molten pool is best when the number of bottom blowing elements is 3; some students consider that when the number of the bottom blowing nozzles of the converter is 6, the metallurgical effect is obvious; the 16 bottom blowing nozzles are also known to the learner as the most reasonable solution to arrange in concentric circles. Due to the differences of experimental conditions and the actual conditions of various steel plants, proper bottom blowing parameters cannot be determined.
Disclosure of Invention
In view of the above-mentioned defects or shortcomings in the prior art, the present invention aims to provide an optimization method and an optimization system for a bottom blowing process of a converter, which construct a simulation model based on a VOF, DPM and component transportation coupling model, and adjust parameters of the simulation model according to different experimental conditions or production conditions, so as to optimize the current bottom blowing process and improve the production quality and efficiency of the converter.
In order to achieve the above purpose, the embodiment of the present invention adopts the following technical scheme:
in a first aspect, an embodiment of the present invention provides a method for optimizing a bottom blowing process of a converter, including the following steps:
step S1, drawing a geometric model of a converter to be optimized, and giving a nozzle position and an angle arrangement mode under each position;
s2, determining a bottom blowing process calculation area, and dividing a converter geometric model into grids in the calculation area according to the position and angle arrangement mode of the nozzles;
s3, constructing a bottom blowing process simulation model based on the VOF model, the DPM model, the component transportation model and the coupling of the three models in the divided grids; the model comprises: a molten steel flow characteristic control equation and a momentum equation based on the VOF model; a control equation and a turbulence control equation based on interaction with molten steel in the rising process of bottom blowing bubbles of a DPM model; diffusion transport equations based on component transport models for convective transport by the circulating stream, turbulent diffusion transport, and concentration differential diffusion of the tracer;
step S4, respectively giving different bottom blowing gas flow rates to be selected for each set bottom blowing nozzle position and angle arrangement mode; for each gas flow, determining steel, gas physical parameters, outlet pressure, bottom blowing bubble diameter, speed and mass flow;
S5, solving a molten steel flow characteristic control equation and a momentum equation based on the VOF model according to the determined steel and gas physical parameters; solving a control equation and a turbulence control equation of interaction with molten steel in the process of rising the bubbles based on a DPM model according to the diameter, the speed and the mass flow of the bottom blowing bubbles; combining the two solving results, and analyzing the fluid flow characteristics to obtain steel and gas multiphase flow field parameters and molten pool dead zone distribution;
step S6, according to the outlet pressure and the two solving results, a diffusion transmission equation is solved, and the mixing time under the current condition is obtained;
and S7, comparing the steel and gas multiphase flow field parameters, the dead zone distribution of a molten pool and the mixing time which are obtained under the conditions of all nozzle positions, angle arrangement modes and bottom blowing gas flow velocity, and obtaining the optimized bottom blowing process parameters of the current converter.
As a preferred embodiment of the present invention, the nozzle positions and the angular arrangement of each position in step S1 include:
the inner diameter of a converter molten pool is D, and nozzles are respectively arranged at the positions of 0.35D, 0.42D, 0.45D and 0.55D; the nozzles at each position are respectively provided with two angle arrangement modes, namely a scheme A and a scheme B; in the scheme A, the nozzle forms an angle of 30 degrees with the trunnion and forms an angle of 30 degrees with a central line perpendicular to the trunnion, in the scheme B, the nozzle forms an angle of 80 degrees with the trunnion at the tapping side and the charging side and forms an angle of 25 degrees with the trunnion.
As a preferred embodiment of the present invention, in the step S2, a 1/4 converter body is taken as a calculation area.
As a preferred embodiment of the invention, when grid division is carried out, the grids at the bottom blowing gas inlet are encrypted, and the grids in other areas are uniformly distributed.
As a preferred embodiment of the invention, the construction of the bottom blowing process simulation model comprises the following steps:
step S31, determining a basic assumption, including:
first, steady state assumption: the physical parameters of the substances in the converter are not changed along with the temperature, and the flowing state is steady-state flow.
Secondly, neglecting all chemical reactions of molten steel in the steelmaking process;
thirdly, the converter steelmaking process is considered to be in a fully developed turbulent flow state;
fourth, neglecting the wall thickness of the converter body, the wall thickness has little influence on the simulation result. The converter lining is an insulator;
fifthly, the molten steel in the converter is regarded as incompressible fluid;
step S32, based on the basic assumption, selecting a control equation, including:
step S321, selecting a molten steel flow characteristic control equation and a momentum equation based on the VOF model;
step S322, selecting a control equation for interaction with molten steel in the rising process of bottom blowing bubbles based on the DPM model; further adopting a standard low-Reynolds number k-epsilon model to represent the turbulent flow behavior of the gas-liquid two-phase flow in a molten pool of the top-bottom combined blown converter, and selecting a corresponding turbulent flow control equation;
Step S323, selecting a diffusion transport equation for the convective transport, turbulent diffusion transport, and tracer concentration difference diffusion by the circulating stream based on the component transport model.
As a preferred embodiment of the present invention, the flow characteristic control equation is shown in formula (1):
in the formula (1), alpha q A value of the q-th phase volume fraction; ρ q Is the density of the q-th phase volume fraction,
is the flow speed of molten steel;
the momentum equation is shown in formula (2):
in the formula (2), p is the static pressure,
is gravity; />
The external force is the acting force of the DPM model on the continuous phase; ρ and μ are dependent on the volume fractions of Ar and the steel water phase in the grid where they are located, and represent the average density and average velocity of all term volume fractions, respectively, ρ and μ are represented by formulas (3) and (4):
ρ＝ρ g α g +ρ l α l (3)
μ＝μ g α g +μ l α l (4)
in formulas (3) and (4), α is the volume fraction of the phase in each unit, ρ is the density of the phase, and g and l subscripts represent the gas phase and the liquid phase, respectively.
As a preferred embodiment of the present invention, the control equation for the interaction with molten steel during the rising of the bottom blowing bubbles is expressed as:
in the formula (5), the amino acid sequence of the compound,
for the speed of molten steel, ">
At Ar speed ρ b For bubble density, F is an additional acceleration term,
the resistance per bubble mass, which can be expressed as F D ：
In the formula (6), mu is the viscosity of molten steel, C D The resistance coefficient of the bubble, re' is the motion Reynolds number of the bubble;
the turbulence control equation is as follows:
in the formulae (7) and (8), μ eff Is the turbulence effective viscosity coefficient, and:
mu in the formula (9) m Is the molecular viscosity of the fluid, wherein C 1ε ，C 2ε ，C μ ，σ k ，σ ε Is constant, preferably the values are C 1ε ＝1.44，C 2ε ＝1.92，C μ ＝0.09，σ k ＝1.3，σ ε ＝1.0。
As a preferred embodiment of the present invention, the diffusion transfer equation is as follows:
in the formula (10), c n To showConcentration of the tracer, sc t Is the turbulent schmitt number, S n For vortex motion viscosity, D n Is the turbulent diffusion coefficient.
As a preferred embodiment of the invention, the selected bottom blowing gas flow rates are 0.04, 0.06, 0.08, 0.10, 0.15Nm 3 And/t.min is a group.
In a second aspect, an embodiment of the present invention further provides a converter bottom blowing process optimization system, where the system includes: the system comprises a geometric model and initial parameter construction module, a grid division module, a coupling simulation model construction module, a bottom blowing parameter setting module and a result analysis and output module; wherein,
the geometric model and initial parameter construction module is used for drawing a geometric model of the converter to be optimized and giving the position of the nozzle and the angular arrangement mode of each position;
The grid division module is used for determining a bottom blowing process calculation area and carrying out grid division on the converter geometric model in the calculation area according to the position and angle arrangement mode of the nozzles;
the coupling type simulation model construction module is used for constructing a bottom blowing process simulation model based on the coupling of the VOF model, the DPM model, the component transportation model and the three models in the divided grids; the simulation model is also used for solving the simulation model according to the parameters given by the bottom blowing parameter giving module and sending the result to the result analysis and output module;
the bottom blowing parameter setting module is used for respectively setting different bottom blowing gas flows to be selected under the arrangement mode of the set positions and angles of each bottom blowing nozzle, and also is used for determining steel and gas physical parameters, outlet pressure, bottom blowing bubble diameter, speed and mass flow for each gas flow;
the result analysis and output module is used for analyzing the fluid flow characteristics to obtain steel and gas multiphase flow field parameters and molten pool dead zone distribution, and selecting and outputting the optimized bottom blowing process parameters of the current converter by combining the mixing time.
The technical scheme provided by the embodiment of the invention has the following beneficial effects:
According to the converter bottom blowing process optimization method and the converter bottom blowing process optimization system, through simulation of converter molten steel turbulence behavior, dead zone distribution and mixing time, model parameters are calculated, so that optimization of the converter bottom blowing process is achieved, the optimized bottom blowing process is low in speed interference among bottom blowing nozzles, uniform in speed distribution, relatively low in speed of boundary parts, and strong in stirring capability for molten steel; the fluidity of the molten steel is better, the analysis of the mixing time is integrated, and the reasonable bottom blowing nozzle radius and the mixing time are finally determined, so that the optimization of the bottom blowing process of the converter is completed.
Of course, it is not necessary for any one product or method of practicing the invention to achieve all of the advantages set forth above at the same time.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person of ordinary skill in the art.
FIG. 1 is a flow chart of a converter bottom blowing process optimization method provided by an embodiment of the invention;
FIG. 2 is a model solving flow chart in an embodiment of the invention;
FIG. 3 is a schematic plan view of a rotary kiln in accordance with an embodiment of the present invention;
FIG. 4 is a schematic view showing an arrangement of a bottom blowing nozzle of a transfer in accordance with an embodiment of the present invention;
FIG. 5 is a schematic view of another arrangement of a bottom blowing nozzle of a transfer in accordance with an embodiment of the present invention;
FIG. 6 is a schematic diagram of meshing of a transfer furnace in accordance with an embodiment of the present invention;
FIG. 7 is a schematic view of a bottom-blowing nozzle arrangement in an embodiment of the invention;
FIG. 8 is a schematic diagram of meshing of a transfer furnace in accordance with an embodiment of the present invention;
FIG. 9 shows a bottom blowing flow rate of an embodiment of the present invention1056Nm 3 A bar graph of the volume average flow rate of the bath at/h;
FIG. 10 shows a bottom blowing flow of 1056Nm in an embodiment of the invention 3 A speed distribution diagram of a converter molten pool at the time of/h;
FIG. 11 shows a bottom blowing nozzle position of 0.42D and a bottom blowing intensity of 0.15Nm in two nozzle arrangements according to an embodiment of the present invention 3 A velocity vector diagram of the steel water level/t.min;
FIG. 12 is a distribution of a dead zone of a ladle flow in a ZX30 section (800 mm below the level of molten steel) when the bottom blowing nozzle angle is arranged in the mode of scheme A in the embodiment of the present invention;
FIG. 13 is a distribution of a dead zone of a ladle flow in a Z800 section (800 mm below the level of molten steel) when the bottom blowing nozzle angle is arranged in the mode of scheme A in the embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention and the accompanying drawings. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. It should be noted that, in the case of no conflict, the embodiments of the present invention and features in the embodiments may also be combined with each other.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures. In the description of the present invention, the terms "first," "second," "third," "fourth," and the like are used merely to distinguish between descriptions and are not to be construed as merely or implying relative importance.
The invention provides an optimization method and an optimization system for a converter bottom blowing process, which simulate the flow of a bottom blowing nozzle and a layout mode to a converter dynamics strip by utilizing commercial software ANSYS FLUENT19.3 and coupling a two-phase flow fluid volume model (Volume of Fluid Model, VOF), a discrete particle model (Discrete Particle Models, DPM) and a component transportation model And the influence of the piece optimizes the bottom blowing process. When the top of the converter is blown back, bottom blowing gas is sprayed into a molten pool from a bottom blowing nozzle, and molten steel is driven to move in the upward movement process, so that inverted conical speed distribution is formed; with a bottom blowing strength of 0.04-0.15Nm 3 The mixing time and the dead zone proportion are reduced along with the increase of/t.min, the mixing time is at least 48.4s, and the dead zone area ratio is at least 24.43%; when the bottom blowing nozzles are arranged at 0.42D, the included angle of the bottom blowing nozzles is 30 degrees with the trunnion and the included angle of the bottom blowing nozzles is 30 degrees with the center line perpendicular to the trunnion, the converter has good fluidity. Experiments prove that the optimized bottom blowing process has strong stirring capability on molten steel, the molten steel state has strong uniformity, the flow characteristic of the molten steel is improved, and the mixing effect of a converter molten pool is good. According to the invention, the influence of the bottom blowing flow and the bottom blowing nozzle arrangement mode on the molten steel flow characteristics of the converter is analyzed by adopting a method combining numerical simulation and physical simulation, the result is more similar to the actual converting condition through a large number of simulation experiment schemes, the arrangement of a bottom blowing system is optimized, and a theoretical basis is provided for improving the dynamics condition of a molten pool of the converter.
Referring to fig. 1, the method for optimizing the bottom blowing process of the converter provided by the embodiment of the invention comprises the following steps:
Step S1, drawing a geometric model of a converter to be optimized, wherein the inner diameter of a converter molten pool is D, and nozzles are respectively arranged at the positions of 0.35D, 0.42D, 0.45D and 0.55D; the nozzles at each position are respectively provided with two angle arrangement modes, namely a scheme A and a scheme B; in the scheme A, the nozzle forms an angle of 30 degrees with the trunnion and forms an angle of 30 degrees with a central line perpendicular to the trunnion, in the scheme B, the nozzle forms an angle of 80 degrees with the trunnion at the tapping side and the charging side and forms an angle of 25 degrees with the trunnion.
And S2, determining a bottom blowing process calculation area, and dividing the geometric model of the converter into grids in the calculation area according to the position and the angle arrangement mode of the nozzles.
In this step, the converter is axisymmetric, and 1/4 of the converter is taken as a calculation region. When grid division is carried out, the method comprises the following steps: setting boundary conditions, cutting blocks based on the boundary conditions, establishing a mapping relation with the geometric model, generating grids according to the mapping relation, and finally optimizing the quality of the grids. In order to ensure the convergence of the calculation result and avoid the numerical value diffusion, the calculation area adopts an orthorhombic hexahedral structure grid, and meanwhile, the grid number is controlled within 500,000 in order to reduce the load of a computer. The grids at the argon inlet are encrypted, and the grids in other areas are uniformly distributed.
And S3, constructing a bottom blowing process simulation model based on the VOF model, the DPM model, the component transportation model and the coupling of the three models in the divided grids.
In the step, all control equations in the converter bottom blowing process simulation model are discretized and calculated by adopting commercial software ANSYS FLUENT 19.3. And carrying out three-dimensional modeling on a converter with preset tonnage, and constructing a converter bottom blowing process simulation model by coupling the VOF, the DPM and the component transport model to simulate the influence process of the position, the angle arrangement mode and the flow of a bottom blowing nozzle on the dynamic conditions of the converter.
The bottom blowing process simulation model construction process comprises the following steps:
step S31, determining a basic assumption, including:
first, steady state assumption: the physical parameters of the substances in the converter are not changed along with the temperature, and the flowing state is steady-state flow.
Secondly, neglecting all chemical reactions of molten steel in the steelmaking process;
thirdly, the converter steelmaking process is considered to be in a fully developed turbulent flow state;
fourth, neglecting the wall thickness of the converter body, the wall thickness has little influence on the simulation result. The converter lining is an insulator;
fifth, the molten steel in the converter is considered to be an incompressible fluid.
Step S32, based on the basic assumption, selecting a control equation, including:
Step S321, a molten steel flow characteristic control equation and a momentum equation based on the VOF model; wherein, the flow characteristic control equation is shown in formula (1):
in the formula (1), alpha q A value of the q-th phase volume fraction; ρ q Is the density of the q-th phase volume fraction,
is the flow speed of molten steel;
the momentum equation is shown in formula (2):
in the formula (2), p is the static pressure,
is gravity; />
The external force is the acting force of the DPM model on the continuous phase; ρ and μ are dependent on the volume fractions of Ar and the steel water phase in the grid where they are located, and represent the average density and average velocity of all term volume fractions, respectively, ρ and μ are represented by formulas (3) and (4): />
ρ＝ρ g α g +ρ l α l (3)
μ＝μ g α g +μ l α l (4)
In formulas (3) and (4), α is the volume fraction of the phase in each unit, ρ is the density of the phase, and g and l subscripts represent the gas phase and the liquid phase, respectively.
In the step, the flow characteristics of molten steel in a converter are simulated by adopting a VOF model, different fluid components share a set of momentum equations in the VOF model, and tracking of phase interfaces of each calculation unit is realized by introducing phase volume fractions; in each control volume, the sum of all phase volume values is 1, all variables and their attributes are shared in each phase in the control volume and represent the volume average; the variables and their properties within any given control volume represent a mixture of one or more phases and are determined by the phase volume fraction.
Step S322, selecting a control equation for interaction with molten steel in the rising process of bottom blowing bubbles based on the DPM model; and further adopting a standard low-Reynolds number k-epsilon model to represent the turbulent flow behavior of the gas-liquid two-phase flow in the molten pool of the top-bottom combined blown converter, and selecting a corresponding turbulent flow control equation.
In the step, the calculation method of the DPM discrete model is a Lagrangian method, in the Lagrangian method, FLUENT regards a main phase as a continuous phase, sparse phases as discrete particles, navier-Stockes equations are adopted to solve the continuous phase, bottom blowing bubbles are used as discrete phases, the bottom blowing bubbles are solved by tracking the motion of the bottom blowing bubbles in molten steel, and momentum exchange is carried out between the bottom blowing bubbles and the molten steel phases, so that interaction between the bottom blowing bubbles and the molten steel in the rising process is simulated by calculating interaction between the bubbles and the molten steel. The inertia of the bubble during its ascent due to the force balance is equal to the force acting on the bubble, expressed as:
in the formula (5), the amino acid sequence of the compound,
for the speed of molten steel, ">
At Ar speed ρ b For bubble density, F is an additional acceleration term,
the resistance per bubble mass, which can be expressed as F D ：
In the formula (6), mu is the viscosity of molten steel, C D For the bubble drag coefficient, re' is the bubble motion Reynolds number.
The turbulence control equation is as follows:
in the formulae (7) and (8), μ eff Is the turbulence effective viscosity coefficient, and:
mu in the formula (9) m Is the molecular viscosity of the fluid, wherein C 1ε ，C 2ε ，C μ ，σ k ，σ ε Is constant, preferably the values are C 1ε ＝1.44，C 2ε ＝1.92，C μ ＝0.09，σ k ＝1.3，σ ε ＝1.0。
Step S323, selecting a diffusion transport equation for the convective transport, turbulent diffusion transport, and tracer concentration difference diffusion by the circulating stream based on the component transport model.
In this step, in the simulation study of the mixing uniformity time, a certain amount of tracer is taken and added to the converter, and when the concentration Cn sampled and analyzed from any point in the converter is equal to the initial concentration Ci, that is, (Cn/ci=1), the mixing is theoretically considered to be completely uniform. For a specific mixing process, cn/ci=1±0.05 is currently generally chosen, so that after the tracer is added, the concentration sampled from a given point is in the range of 0.95 to 1.05, i.e. the mixing requirement is considered to be met, and the time taken is called the mixing time.
For a specific mixing process, the tracer is transported and uniformly mixed in the top-bottom combined blown converter mainly in three modes, namely, convective transportation by a circulating flow, turbulent diffusion transportation and concentration difference diffusion of the tracer, and the diffusion transportation equation is as follows:
In the formula (10), c n For the concentration of tracer, sc t Is the turbulent schmitt number，S n For vortex motion viscosity, D n Is the turbulent diffusion coefficient.
The converter bottom blowing process simulation model constructed by the embodiment of the invention is characterized in that corresponding parameters are input into the simulation model according to experimental conditions or production conditions, the bottom blowing flow, the bottom blowing nozzle arrangement mode and the number in the bottom blowing process simulate the stirring process of molten steel, and reasonable parameters are judged from the parameter changes in the simulation process to optimize the bottom blowing process.
Step S4, respectively giving different bottom blowing gas flow rates to be selected for each set bottom blowing nozzle position and angle arrangement mode; for each gas flow, the steel, gas physical parameters, outlet pressure, and bottom blowing bubble diameter, speed, mass flow were determined.
In this step, argon is generally used as the bottom blowing gas. Given different bottom-blowing gas flows to be selected, e.g. 0.04, 0.06, 0.08, 0.10, 0.15Nm 3 And/t.min is a group.
S5, solving a molten steel flow characteristic control equation and a momentum equation based on the VOF model according to the determined steel and gas physical parameters; solving a control equation and a turbulence control equation of interaction with molten steel in the process of rising the bubbles based on a DPM model according to the diameter, the speed and the mass flow of the bottom blowing bubbles; and combining the two solving results, and analyzing the fluid flow characteristics to obtain steel and gas multiphase flow field parameters and molten pool dead zone distribution.
As shown in fig. 2, in this step, when solving the molten steel flow characteristic control equation and the momentum equation, the volume force term is simultaneously considered according to the VOF model; when solving a control equation and a turbulence control equation which interact with molten steel in the rising process of bubbles, according to a DPM model, simultaneously considering an aspheric drag force term, a virtual mass force term, a pressure gradient force term and bidirectional turbulence coupling.
Meanwhile, when solving the turbulence control equation in the step, grids at different positions are respectively considered. The flow of the turbulence core area is solved by using k-epsilon, and the wall function is directly used in the wall area to link the physical quantity on the wall with the solving variable of the turbulence core area, so that the variable value of the node adjacent to the wall for controlling the volume can be directly obtained without solving the flow of the wall area. The flow field near the wall surface is calculated by adopting a standard wall surface function, the axisymmetric boundary is of an axisymmetric type, the normal direction speed on the symmetric boundary is zero, and the normal gradients of other physical quantities are zero.
On the solving algorithm, based on a pressure solver, the pressure and the speed are coupled by adopting a PISO algorithm, unsteady state calculation is carried out, and the dispersion of pressure, momentum, volume fraction and turbulent energy solute diffusion items all takes a first-order differential windward format. After the initialization is completed, the Patch command is used to define the volume area of the two phases at the beginning. Calculating the time step to obtain 1×10 -4 The convergence criterion of this study was less than 1.0X10 as a dimensionless residual curve of energy variable -6 Residual errors of other variables are less than the threshold value 1.0X10 -3 。
And S6, according to the outlet pressure and the two solving results, solving a diffusion transmission equation to obtain the mixing time under the current condition.
In this step, as shown in fig. 2, the diffuse energy term is considered at the same time in the solving process.
And S7, comparing the steel and gas multiphase flow field parameters, the dead zone distribution of a molten pool and the mixing time which are obtained under the conditions of all nozzle positions, angle arrangement modes and bottom blowing gas flow velocity, and obtaining the optimized bottom blowing process parameters of the current converter.
In the solving result, the steel and gas multiphase flow field parameters comprise the average flow speed of a molten pool body, the distribution of the molten pool speed, the stirring capability of molten steel and the speed interference between nozzles. When the average flow speed of the molten pool body is high, the speed distribution of the molten pool is uniform, the stirring capacity of molten steel is strong, and the speed interference between nozzles is small, the corresponding technological parameters are optimized parameters; and if the mixing time is short, the corresponding process parameters are optimized parameters.
By adopting the converter bottom blowing process optimization method provided by the embodiment of the invention, process optimization and technical transformation are carried out on a 200t top-bottom combined blown converter of a certain steel mill in China. The optimization procedure is as follows. The geometric parameters adopted by the 200t top-bottom combined blown converter are listed in table 1, the geometric model is determined by the selection of the parameters, and the geometric model is closely related to grid division, for example, converters with different capacities, the diameters of melting pools are different, and the number of grids is different; the number of nozzles is different, and the number of the grid divided areas is different. Meanwhile, a water model experiment is carried out on the converter under the parameters so as to verify the rationality of the model adopted by the process optimization of the embodiment.
TABLE 1
Fig. 3 is a schematic plan view of a converter, and fig. 4 and 5 are schematic views of two arrangements of bottom blowing nozzles of a converter. As shown in fig. 3 to 5, the nozzles are arranged in the angular manner of a scheme a (30 ° angle to the trunnion, 30 ° angle to the center line perpendicular to the trunnion) and a scheme B (80 ° angle to the tapping side and the charging side, 25 ° angle to the trunnion) in the present embodiment, and the diameters of the arrangements are 0.35D, 0.42D, 0.45D, 0.55D (D is the bath inner diameter).
The above preferences are listed in Table 2.
TABLE 2
As shown in table 2, the arrangement positions of the bottom blowing nozzles, the gas flow rates, and the number of nozzles were included. In the table positions 0.35D, 0.42D, 0.45D and 0.55D represent the distances between two bottom-blowing nozzles axially symmetric in the converter, which represent the bath diameter, of 35%, 42%, 45% and 55%, respectively. The gas flow rate represents the instantaneous total flow rate of bottom-blown Ar gas through all the bottom-blowing nozzles. The number of nozzles 8 indicates 8 bottom blowing nozzles in total at the bottom of the converter.
Step S2 is performed. Fig. 6-8 are schematic diagrams of meshing results. As shown in fig. 6, boundary conditions of a 1/4-body converter geometric model are set first; as shown in fig. 7, dicing is performed according to different positions and angular arrangements of the bottom blowing nozzles; as shown in fig. 8, after dicing within the boundaries and creating the mapping relationship, grids are generated, and in the subsequent model calculation, the grids meeting the quality requirement are imported into ANSYS flow 19.3 to calculate the distribution of the flow field.
Step S3-7 is performed. And optimizing the bottom blowing process of the converter. And drawing the analysis map of fig. 9-13 according to the model calculation result of the step S3-7.
FIG. 9 shows a bottom blowing flow of 1056Nm 3 It can be seen from fig. 9 that the volume average velocity of the bath at/h is greater when the bottom-blowing nozzle angle is arranged in the manner of variant a than when it is arranged in the manner of variant B. When the bottom blowing nozzle included angle is arranged in the mode of scheme A, when the bottom blowing nozzle is arranged at the position of 0.35D, the average speed of the molten pool is 0.0781m/s, when the bottom blowing nozzle is arranged at the position of 0.42D, the average speed of the molten pool is 0.0908m/s, the average speed of the molten pool is increased by 14%, when the bottom blowing nozzle is arranged at the position of 0.45D, the average speed of the molten pool is increased by only 3.9%, and compared with the position of 0.35D, the average speed of the molten pool at the position of 0.55D is reduced by 17.8%, which indicates that the stirring capability of the molten pool is strong when the bottom blowing nozzle is arranged at the position of 0.42D, and good fluidity is achieved. On the other hand, it has been shown that when the bottom-blowing nozzle transitions away from the hearth center and toward the furnace wall (0.55D), the average volume velocity of the bath is greatly reduced, and the dynamic conditions of the bath are easily deteriorated.
FIG. 10 shows a bottom blowing flow of 1056Nm 3 And/h, speed distribution of the converter molten pool. The bottom blowing gas is sprayed into the molten pool from the bottom blowing nozzle, and the bubbles exchange energy with molten steel under the combined action of impact force, buoyancy, gravity and the like, so that the molten steel is driven to move in the upward movement process, the reverse conical speed distribution is formed, and the full buoyancy model of the movement of the bottom blowing gas of the converter is met.
And taking a half model, and analyzing the disturbance conditions of stirring capacity of molten steel and speed between bottom blowing nozzles when the bottom blowing modes are arranged in different modes.
FIG. 11 shows the position of the bottom blowing nozzle at 0.42D and the bottom blowing strength at 0.15Nm in two arrangements 3 Velocity vector diagram of steel water level/t.min (z=1.75m).In the arrangement mode of the scheme A, the speed distribution is relatively uniform, and the speed interference between the bottom blowing nozzles is relatively small; under the scheme B arrangement mode, the part with larger speed is concentrated near the bottom blowing nozzles, the speed distribution at the position far away from the bottom blowing nozzles is sparse, the speed at the junction of the bottom blowing nozzles is larger, and the speed interference between the bottom blowing nozzles is more obvious, so when the bottom blowing nozzles are arranged in the scheme A mode, the stirring capability of molten steel is stronger, the molten steel state at the moment has stronger uniformity, and the result of the water model experiment is consistent.
In order to study the quantitative analysis of the flow characteristics of a converter molten pool by a bottom blowing process, statistics is carried out on the volume fraction of the liquid phase speed in the converter molten pool. The region of velocity <0.05m/s is generally considered to be a flow dead zone where fluid flow is almost stagnant, and the contribution to mass and heat transfer is negligible, thus minimizing the distribution of flow dead zones.
FIGS. 12 and 13 show the distribution of the flow dead zone of the ladle in ZX30 section and Z800 section (800 mm below the level of the molten steel) when the bottom-blowing nozzle angles are arranged in the mode of scheme A, respectively, the region of 0.05m/s or less being marked with light gray, i.e., the molten steel phase dead zone; areas of >0.05m/s are marked dark grey.
From fig. 12 and 13, it can be seen that the area of the molten steel phase dead zone decreases as the bottom blowing flow rate increases, indicating that increasing the bottom blowing flow rate can improve the flow characteristics of molten steel. The bottom blowing nozzle was arranged at 0.55D with the largest dead zone area of the molten steel phase and at 0.35D with the smallest dead zone area of the molten steel phase, indicating that the molten steel phase had good fluidity when the bottom blowing nozzle angle was set in the scheme a and at the 0.42D position.
The present application analyzes the percent change in dead zone area with bottom blowing flow and bottom blowing nozzle position change when bottom gun angles are arranged in schemes a and B, respectively. When the bottom blowing nozzle is arranged in the scheme A, the dead zone percentage of the molten steel phase with the ZX30 section is reduced along with the increase of the bottom blowing flow, which means that the energy exchange between the bottom blowing air flow and a molten pool drives molten steel to stir due to the rising of bottom blowing bubbles, and the bottom blowing air flow enters the molten steel along with the increase of the bottom blowing flow The energy of the pool is gradually increased, the stirring force of the bottom blowing air flow is increased, and the better the mixing effect of molten steel is, the smaller the dead area is. When the bottom blowing nozzle was disposed at the 0.42D position, the bottom blowing flow rate was 0.15Nm 3 At/t.min, the dead zone area percentage was minimum, the minimum was 24.43%, and the specific bottom blowing flow rates were 0.04Nm, respectively 3 /t.min、0.06Nm 3 /t.min、0.08Nm 3 /t.min、0.10Nm 3 The reduction of the ratio of the total amount of the components/t.min is 20.91%, 18.21%, 11.61% and 4.39%. In addition, from the arrangement position of the bottom blowing nozzles, when the bottom blowing nozzles are arranged at the 0.55D position, the dead zone area percentage is the largest, 0.35D times, and when the bottom blowing nozzles are arranged at the 0.42D position, the dead zone area percentage is the smallest, which means that when the bottom blowing nozzles are arranged near the center of the furnace bottom or the furnace wall, the stirring effect of the molten pool is poor, the dead zone ratio is increased, and the dynamics condition of the molten pool is deteriorated, so that both the bottom blowing nozzle arrangements should be avoided.
The law presented by the scheme a when the bottom blowing nozzles are arranged in the scheme B mode, but the percentage of the total dead area increases, and when the bottom blowing nozzles are arranged at the 0.42D position, the bottom blowing flows are respectively 0.04Nm 3 /t.min、0.06Nm 3 /t.min、0.08Nm 3 /t.min、0.10Nm 3 The increase in/t.min is 1.73%, 2.82%, 1.82% and 1.64%.
When the dead zone area percentage is analyzed, the cross section Z800 and the cross section ZX30 also have the same change rule. However, from the overall trend analysis of dead zone area, the Z800 section is larger than the ZX section by percentage of dead zone area because the longitudinal sections ZX30 and ZX25 include only the bottom-blowing direct influence region, while the cross section Z800 includes the entire flow field region, so the analysis of the dead zone area of the cross section Z800 is more representative. The same holds that the percentage of dead zone area is minimal when the bottom blowing nozzle is in the 0.42D position and the bottom blowing flow is inversely proportional to the percentage of dead zone area.
In addition, the change rule of the mixing time of the molten pool along with the bottom blowing flow and the arrangement angle and the arrangement position of the bottom blowing nozzle is analyzed. And analyzing the influence of the bottom blowing process on the dynamic conditions of the converter molten pool, and carrying out simulation experiments on the mixing time of the converter molten pool under different working conditions by using steel balls with the same components and introducing a component transmission model on the premise of stable flow field.
Analysis showed that the mixing time of the bath was inversely proportional to the bottom blowing flow and that when the bottom blowing flow was from 0.08Nm 3 Increase/t.min to 0.10Nm 3 At/t.min, the mixing time was reduced to a maximum, and when the bottom blowing nozzle angle was set in the scheme A and the position was set at 0.42D, the bottom blowing flows were respectively 0.04Nm 3 /t.min、0.06Nm 3 /t.min、0.08Nm 3 /t.min、0.10Nm 3 /t.min、0.15Nm 3 The mixing time per t.min is respectively 70.5s, 67.1s, 60.2s, 52.8s and 48.4s, and the mixing time is respectively reduced by 4.8 percent, 10.3 percent, 12.3 percent and 8.3 percent, which shows that the stirring uniformity of a molten pool can be improved by increasing the bottom blowing flow rate, but when the bottom blowing flow rate is increased to 0.10Nm 3 After/t.min, the mixing time is increased again, and the reduction degree of the mixing time is reduced, probably because the excessively large bottom blowing flow can increase the erosion degree of the ground blowing nozzle and surrounding refractory materials, and the dynamic conditions of a converter molten pool are adversely affected, and the method does not belong to the parameters selected by the optimization process.
The influence of the arrangement position of the bottom blowing nozzle on the mixing time is as follows: the mixing time at the 0.42D position is minimum, the mixing time at the 0.55D position is maximum, and similarly, when the bottom blowing nozzle angle is arranged in a scheme B mode, the total mixing time is larger than that of a scheme A mode, the total mixing time is consistent with the analysis result of the dead zone area percentage of the converter, and the mixing time is consistent with the result of a water model experiment, so that the accuracy of the numerical simulation result is demonstrated. Therefore, when the included angle of the bottom blowing nozzles is arranged in the scheme A, the mixing effect of the converter molten pool is best when the position of the bottom blowing nozzles is 0.42D, and the minimum mixing time is 48.4s.
According to the analysis result, the 200t top-bottom combined blown converter of the steel mill is subjected to process optimization and technical transformation, the flow, the arrangement position and the angle of the bottom blowing nozzle are optimized, the components are more homogenized after the converter transformation, the whole blowing process is more stable due to the improvement of the dynamic condition of a converter molten pool, the splashing is reduced, the dephosphorization and decarbonization rate is improved, the carbon-oxygen balance value of the converter end point is obviously reduced, and the average value is reduced from 0.0024 to 0.0022 and 8.3%.
According to the technical scheme, the optimization method of the converter bottom blowing process provided by the embodiment of the invention is characterized in that the model parameters are calculated through the simulation of the turbulent flow behavior, dead zone distribution and mixing time of the molten steel of the converter, so that the optimization of the converter bottom blowing process is realized, the optimized bottom blowing process has smaller speed interference among bottom blowing nozzles, more uniform speed distribution and relatively smaller speed of a junction part, and the stirring capability of the molten steel is stronger; the fluidity of the molten steel is better, the analysis of the mixing time is integrated, and the reasonable radius of the bottom blowing nozzle and the mixing time are determined.
Based on the same thought, the embodiment of the invention also provides a converter bottom blowing process optimization system, which comprises: the system comprises a geometric model and initial parameter construction module, a grid division module, a coupling simulation model construction module, a bottom blowing parameter setting module and a result analysis and output module;
the geometric model and initial parameter construction module is used for drawing a geometric model of the converter to be optimized, and giving the position of the nozzle and the angular arrangement mode of each position;
the grid division module is used for determining a bottom blowing process calculation area and carrying out grid division on the converter geometric model in the calculation area according to the position and angle arrangement mode of the nozzles;
the coupling type simulation model construction module is used for constructing a bottom blowing process simulation model based on the coupling of the VOF model, the DPM model, the component transportation model and the three models in the divided grids; the simulation model is also used for solving the simulation model according to the parameters given by the bottom blowing parameter giving module and sending the result to the result analysis and output module;
the bottom blowing parameter setting module is used for respectively setting different bottom blowing gas flows to be selected under the arrangement mode of the set positions and angles of each bottom blowing nozzle, and also is used for determining steel and gas physical parameters, outlet pressure, bottom blowing bubble diameter, speed and mass flow for each gas flow;
The result analysis and output module is used for analyzing the fluid flow characteristics to obtain steel and gas multiphase flow field parameters and molten pool dead zone distribution, and selecting and outputting the optimized bottom blowing process parameters of the current converter by combining the mixing time.
The modules in this embodiment are implemented by a processor, and the memory is appropriately increased when storage is required. The processor may be, but is not limited to, a microprocessor MPU, a central processing unit (Central Processing Unit, CPU), a network processor (Network Processor, NP), a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), other programmable logic devices, discrete gates, transistor logic devices, discrete hardware components, or the like. The Memory may include random access Memory (Random Access Memory, RAM) or may include Non-Volatile Memory (NVM), such as at least one disk Memory. Optionally, the memory may also be at least one memory device located remotely from the aforementioned processor.
In the above embodiments, it may be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, produces a flow or function in accordance with embodiments of the present invention, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a computer network, or other programmable apparatus. The computer instructions may be stored in or transmitted from one computer-readable storage medium to another, for example, by wired (e.g., coaxial cable, optical fiber, digital Subscriber Line (DSL)), or wireless (e.g., infrared, wireless, microwave, etc.).
In addition, it should be noted that the optimizing system of the converter bottom blowing process in this embodiment corresponds to the optimizing method of the converter bottom blowing process, and description and limitation of the method are also applicable to the system, and are not repeated here.
The above description is only of the preferred embodiments of the present invention and the description of the technical principles applied is not intended to limit the scope of the invention as claimed, but merely represents the preferred embodiments of the present invention. It will be appreciated by persons skilled in the art that the scope of the invention referred to in the present invention is not limited to the specific combinations of the technical features described above, but also covers other technical features formed by any combination of the technical features described above or their equivalents without departing from the inventive concept. All other embodiments, which can be made by a person skilled in the art without making any inventive effort, are intended to be within the scope of the present invention.
Claims (9)
1. The converter bottom blowing process optimizing method is characterized by comprising the following steps:
step S1, drawing a geometric model of a converter to be optimized, and giving a nozzle position and an angle arrangement mode under each position;
S2, determining a bottom blowing process calculation area, and dividing a converter geometric model into grids in the calculation area according to the position and angle arrangement mode of the nozzles;
s3, constructing a bottom blowing process simulation model based on the VOF model, the DPM model, the component transportation model and the coupling of the three models in the divided grids; the bottom blowing process simulation model comprises: a molten steel flow characteristic control equation and a momentum equation based on the VOF model; a control equation and a turbulence control equation based on interaction with molten steel in the rising process of bottom blowing bubbles of a DPM model; a diffusion transport equation based on a component transport model for convective transport by the circulating stream, turbulent diffusion transport and concentration difference diffusion of the tracer;
the construction of the bottom blowing process simulation model comprises the following steps:
step S31, determining a basic assumption, including:
first, steady state assumption: the physical parameters of substances in the converter are not changed along with the temperature, and the flowing state is steady-state flow;
secondly, neglecting all chemical reactions of molten steel in the steelmaking process;
thirdly, the converter steelmaking process is considered to be in a fully developed turbulent flow state;
fourthly, neglecting the wall thickness of the converter body, wherein the wall thickness has little influence on the simulation result, and the converter lining is an insulator;
Fifthly, the molten steel in the converter is regarded as incompressible fluid;
step S32, based on the basic assumption, selecting a control equation, including:
step S321, selecting a molten steel flow characteristic control equation and a momentum equation based on the VOF model;
step S322, selecting a control equation for interaction with molten steel in the rising process of bottom blowing bubbles based on the DPM model; further adopting a standard low-Reynolds number k-epsilon model to represent the turbulent flow behavior of the gas-liquid two-phase flow in a molten pool of the top-bottom combined blown converter, and selecting a corresponding turbulent flow control equation;
step S323, selecting a diffusion transmission equation of convective transportation, turbulent diffusion transmission and tracer concentration difference diffusion of the circulating flow stream based on the component transportation model;
step S4, respectively giving different bottom blowing gas flow rates to be selected for each set bottom blowing nozzle position and angle arrangement mode; for each gas flow, determining steel, gas physical parameters, outlet pressure, bottom blowing bubble diameter, speed and mass flow;
s5, solving a molten steel flow characteristic control equation and a momentum equation based on the VOF model according to the determined steel and gas physical parameters; solving a control equation and a turbulence control equation of interaction with molten steel in the process of rising the bubbles based on a DPM model according to the diameter, the speed and the mass flow of the bottom blowing bubbles; combining the two solving results, and analyzing the fluid flow characteristics to obtain steel and gas multiphase flow field parameters and molten pool dead zone distribution; when solving a control equation and a turbulence control equation which interact with molten steel in the rising process of bubbles, simultaneously considering an aspheric drag force term, a virtual mass force term, a pressure gradient force term and bidirectional turbulence coupling according to a DPM model;
Step S6, according to the outlet pressure and two solving results, a diffusion transmission equation is solved, and in the solving process, a diffusion energy item is considered at the same time, so that the mixing time under the current condition is obtained;
and S7, comparing the steel and gas multiphase flow field parameters, the dead zone distribution of a molten pool and the mixing time which are obtained under the conditions of all nozzle positions, angle arrangement modes and bottom blowing gas flow velocity, and obtaining the optimized bottom blowing process parameters of the current converter.
2. The method according to claim 1, wherein the nozzle position and the angular arrangement of each position in step S1 comprise:
the inner diameter of a converter molten pool is D, and nozzles are respectively arranged at the positions of 0.35D, 0.42D, 0.45D and 0.55D; the nozzles at each position are respectively provided with two angle arrangement modes, namely a scheme A and a scheme B; in the scheme A, the nozzle forms an angle of 30 degrees with the trunnion and forms an angle of 30 degrees with a central line perpendicular to the trunnion, in the scheme B, the nozzle forms an angle of 80 degrees with the trunnion at the tapping side and the charging side and forms an angle of 25 degrees with the trunnion.
3. The method according to claim 1, wherein 1/4 of the converter body is taken as the calculation region in the step S2.
4. The optimization method of converter bottom blowing process according to claim 3, wherein when grid division is performed, the grids at the bottom blowing gas inlet are encrypted, and the grids in other areas are uniformly distributed.
5. The converter bottom-blowing process optimization method according to claim 1, wherein the flow characteristic control equation is shown in formula (1):
in the formula (1), alpha q A value of the q-th phase volume fraction; ρ q Is the density of the q-th phase volume fraction,
is the flow speed of molten steel;
the momentum equation is shown in formula (2):
in the formula (2), p is the static pressure,
is gravity; />
The external force is the acting force of the DPM model on the continuous phase; ρ and μ are dependent on the volume fractions of Ar and the steel water phase in the network, ρ and μ represent the average density and average viscosity of the volume fractions of all phases, respectively, ρ and μ are represented by formulas (3) and (4):
ρ＝ρ g α g +ρ l α l (3)
μ＝μ g α g +μ l α l (4)
in formulas (3) and (4), α is the volume fraction of the phase in each unit, ρ is the density of the phase, and g and l subscripts represent the gas phase and the liquid phase, respectively.
6. The method for optimizing a bottom-blowing process of a converter according to claim 1, wherein the control equation of the interaction with molten steel during the rising of the bottom-blowing bubbles is expressed as:
in the formula (5), the amino acid sequence of the compound,
for the speed of molten steel, " >
At Ar speed ρ b For bubble density, F is an additional acceleration term,
the resistance per bubble mass, which can be expressed as F D ：
In the formula (6), mu is the viscosity of molten steel, C D Re is the bubble resistance coefficient ′ The Reynolds number for the movement of the bubbles;
the turbulence control equation is as follows:
in the formulae (7) and (8), μ eff Is the turbulence effective viscosity coefficient, and:
mu in the formula (9) m Is the molecular viscosity of the fluid, wherein C 1ε ，C 2ε ，C μ ，σ k ，σ ε Is constant and has the value C 1ε ＝1.44，C 2ε ＝1.92，C μ ＝0.09，σ k ＝1.3，σ ε ＝1.0。
7. The converter bottom-blowing process optimization method according to claim 1, wherein the diffusion transfer equation is as follows:
in the formula (10), c n For the concentration of tracer, sc t Is the turbulent schmitt number, S n For vortex motion viscosity, D n Is the turbulent diffusion coefficient.
8. The method for optimizing a bottom blowing process of a converter according to claim 1, wherein the given different bottom blowing gas flows to be selected are selected from 0.04, 0.06, 0.08, 0.10, 0.15Nm 3 And/t.min is a group.
9. A converter bottom blowing process optimization system, the system comprising: the system comprises a geometric model and initial parameter construction module, a grid division module, a coupling simulation model construction module, a bottom blowing parameter setting module and a result analysis and output module; wherein,
The geometric model and initial parameter construction module is used for drawing a geometric model of the converter to be optimized and giving the position of the nozzle and the angular arrangement mode of each position;
the grid division module is used for determining a bottom blowing process calculation area and carrying out grid division on the converter geometric model in the calculation area according to the position and angle arrangement mode of the nozzles;
the coupling type simulation model construction module is used for constructing a bottom blowing process simulation model based on the coupling of the VOF model, the DPM model, the component transportation model and the three models in the divided grids; the simulation model is also used for solving the simulation model according to the parameters given by the bottom blowing parameter giving module and sending the result to the result analysis and output module; when the bottom blowing process simulation model is constructed, the following steps are executed:
step S31, determining a basic assumption, including:
first, steady state assumption: the physical parameters of substances in the converter are not changed along with the temperature, and the flowing state is steady-state flow;
secondly, neglecting all chemical reactions of molten steel in the steelmaking process;
thirdly, the converter steelmaking process is considered to be in a fully developed turbulent flow state;
fourthly, neglecting the wall thickness of the converter body, wherein the wall thickness has little influence on the simulation result, and the converter lining is an insulator;
Fifthly, the molten steel in the converter is regarded as incompressible fluid;
step S32, based on the basic assumption, selecting a control equation, including:
step S321, selecting a molten steel flow characteristic control equation and a momentum equation based on the VOF model;
step S322, selecting a control equation for interaction with molten steel in the rising process of bottom blowing bubbles based on the DPM model; further adopting a standard low-Reynolds number k-epsilon model to represent the turbulent flow behavior of the gas-liquid two-phase flow in a molten pool of the top-bottom combined blown converter, and selecting a corresponding turbulent flow control equation;
step S323, selecting a diffusion transmission equation of convective transportation, turbulent diffusion transmission and tracer concentration difference diffusion of the circulating flow stream based on the component transportation model;
the bottom blowing parameter setting module is used for respectively setting different bottom blowing gas flows to be selected under the arrangement mode of the set positions and angles of each bottom blowing nozzle, and also is used for determining steel and gas physical parameters, outlet pressure, bottom blowing bubble diameter, speed and mass flow for each gas flow;
the result analysis and output module is used for analyzing the fluid flow characteristics and solving a molten steel flow characteristic control equation and a momentum equation based on the VOF model according to the determined steel and gas physical parameters; solving a control equation and a turbulence control equation of interaction with molten steel in the process of rising the bubbles based on a DPM model according to the diameter, the speed and the mass flow of the bottom blowing bubbles; combining the two solving results, and analyzing the fluid flow characteristics to obtain steel and gas multiphase flow field parameters and molten pool dead zone distribution; when solving a control equation and a turbulence control equation which interact with molten steel in the rising process of bubbles, simultaneously considering an aspheric drag force term, a virtual mass force term, a pressure gradient force term and bidirectional turbulence coupling according to a DPM model; according to the outlet pressure and the two solving results, a diffusion transmission equation is solved, and in the solving process, the diffusion energy item is considered simultaneously, so that the mixing time under the current condition is obtained, the steel and gas multiphase flow field parameters and the dead zone distribution of a molten pool are obtained, and the mixing time is combined, and the optimized bottom blowing process parameters of the current converter are selected and output.
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