Method and system for matching KR mechanical stirring rotating speed with immersion depth

Abstract

The invention discloses a KR mechanical stirring rotating speed and immersion depth mutual matching method and system. The method comprises the steps that the geometric dimension of a ladle, the geometric dimension of a stirring paddle and the initial liquid level of molten iron in the current KR mechanical stirring process are obtained; predicting a molten iron multiphase flow field in the KR mechanical stirring process under different stirring paddle rotating speeds and immersion depths; obtaining a critical rotating speed influencing the immersion depth effect of the stirring paddle; obtaining a relational expression between the rotating speed and the immersion depth of the stirring paddle and molten iron multiphase flow field change; by outputting the shape and size of the KR mechanical stirring vortex, the relation between the shape and size of the KR mechanical stirring vortex and the molten iron multiphase flow field change is obtained; and calculating to obtain a rotating speed and an immersion depth critical value from the lowest point of the KR mechanical stirring vortex to the top of the stirring paddle. By adopting the technical scheme, the critical rotating speed and the immersion depth value for improving the stirring efficiency can be quantitatively obtained, scientific guidance can be provided for field production, the dispersing degree of a desulfurizing agent is improved, the desulfurization period is shortened, and the production practice is optimized.

Description

Technical Field

[0001] The present invention belongs to the technical field of steelmaking in the metallurgical industry, and particularly relates to a method and a system for matching the rotational speed and immersion depth of a KR mechanical stirrer. Background Art

[0002] The KR mechanical stirring method is widely used in the desulfurization process of hot metal pretreatment in the steelmaking process. Although the KR mechanical stirring desulfurization process has many advantages such as good desulfurization kinetics conditions and high desulfurization efficiency, there is still room for optimization. In particular, there is a relatively high proportion of dead zones in the flow field below the hot metal ladle and a low dispersion degree caused by the aggregation of desulfurizing agents at the bottom of the stirring vortex. The above phenomena will lead to a decrease in the desulfurization rate and the actual utilization rate of desulfurizing agents. At the same time, it will also have an adverse impact on iron loss and temperature drop during the treatment process. Research shows that the proportion of dead zones in the hot metal ladle and the aggregation degree of desulfurizing agents in the stirring vortex are directly related to the rotational speed and immersion depth of the stirring paddle. Unreasonable matching of the rotational speed and immersion depth of the stirring paddle will lead to a significant increase in the proportion of dead zones and the aggregation degree of desulfurizing agents. Obtaining the minimum critical rotational speed for reducing the proportion of dead zones and the aggregation degree of desulfurizing agents at different immersion depths, that is, achieving reasonable matching of the rotational speed and immersion depth of the stirring paddle, is crucial for further improving the desulfurization efficiency, reducing the consumption of desulfurizing agents, and shortening the desulfurization cycle. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method and a system for matching the rotational speed and immersion depth of a KR mechanical stirrer, which can quantitatively obtain the critical rotational speed and immersion depth value for improving the stirring efficiency, and realize the mutual matching of the rotational speed and immersion depth of the stirring paddle for the purpose of improving the dispersion degree of desulfurizing agents and reducing the desulfurization cycle.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for matching the rotational speed and immersion depth of a KR mechanical stirrer includes:

[0006] Step S1, obtaining the geometric dimensions of the hot metal ladle and the stirring paddle, as well as the initial hot metal liquid level, during the current KR mechanical stirring process;

[0007] Step S2, predicting the multiphase flow field of hot metal during the KR mechanical stirring process at different rotational speeds and immersion depths of the stirring paddle according to the geometric dimensions of the hot metal ladle and the stirring paddle, as well as the initial hot metal liquid level, during the current KR mechanical stirring process;

[0008] Step S3, obtaining the critical rotational speed affecting the action of the immersion depth of the stirring paddle based on the multiphase flow field of hot metal;

[0009] Step S4, determining the relational expression between the rotational speed and immersion depth of the stirring paddle and the change of the multiphase flow field of hot metal;

[0010] Step S5: Determine the relationship between the shape and size of the KR mechanical stirring vortex and the change of the molten iron multiphase flow field according to the shape and size of the KR mechanical stirring vortex.

[0011] Step S6: Obtain the critical values of the rotational speed and immersion depth when the lowest point of the KR mechanical stirring vortex reaches the top of the stirring paddle according to the relationship between the shape and size of the KR mechanical stirring vortex and the change of the molten iron multiphase flow field.

[0012] Preferably, the relationship between the rotational speed and immersion depth of the stirring paddle and the change of the molten iron multiphase flow field is:

[0013]

[0014] where C1 and C2 are constants; ε is the turbulent kinetic energy dissipation rate; h id is the immersion depth; n is the rotational speed; n id is the critical rotational speed that affects the effect of the immersion depth of the stirring paddle on the molten iron multiphase flow field.

[0015] Preferably, the relationship between the shape and size of the KR mechanical stirring vortex and the change of the molten iron multiphase flow field is:

[0016] ΔH d = C3·ε 0.67

[0017] where C3 is a constant; ΔH d is the vortex depth; ΔH h is the vortex height; ε is the turbulent kinetic energy dissipation rate.

[0018] Preferably, the relationship between the critical rotational speed and the critical immersion depth when the lowest point of the KR mechanical stirring vortex reaches the top of the stirring paddle is:

[0019]

[0020] where C4 is a constant; n cr is the critical rotational speed; h cr is the critical immersion depth.

[0021] The present invention also provides a system for matching the rotational speed and immersion depth of the KR mechanical stirring, including:

[0022] The first processing module is used to obtain the geometric dimensions of the ladle and the stirring paddle, as well as the initial liquid level of the molten iron during the current KR mechanical stirring process.

[0023] The second processing module is used to predict the molten iron multiphase flow field during the KR mechanical stirring process at different rotational speeds and immersion depths of the stirring paddle according to the geometric dimensions of the ladle and the stirring paddle, as well as the initial liquid level of the molten iron during the current KR mechanical stirring process.

[0024] The third processing module is used to obtain the critical rotational speed that affects the immersion depth of the stirring paddle based on the molten iron multiphase flow field;

[0025] The fourth processing module is used to determine the relationship between the rotational speed and immersion depth of the stirring paddle and the change of the molten iron multiphase flow field;

[0026] The fifth processing module is used to determine the relationship between the shape and size of the KR mechanical stirring vortex and the change of the molten iron multiphase flow field according to the shape and size of the KR mechanical stirring vortex;

[0027] The sixth processing module is used to obtain the critical values of the rotational speed and immersion depth when the lowest point of the KR mechanical stirring vortex reaches the top of the stirring paddle according to the relationship between the shape and size of the KR mechanical stirring vortex and the change of the molten iron multiphase flow field.

[0028] Preferably, the relationship between the rotational speed and immersion depth of the stirring paddle and the change of the molten iron multiphase flow field is:

[0029]

[0030] wherein, C1 and C2 are constants; ε is the turbulent kinetic energy dissipation rate; h id is the immersion depth; n is the rotational speed; n id is the critical rotational speed that affects the effect of the immersion depth of the stirring paddle on the molten iron multiphase flow field.

[0031] Preferably, the relationship between the shape and size of the KR mechanical stirring vortex and the change of the molten iron multiphase flow field is:

[0032] ΔH d = C3·ε 0.67

[0033] wherein, C3 is a constant; ΔH d is the vortex depth; ΔH h is the vortex height; ε is the turbulent kinetic energy dissipation rate.

[0034] Preferably, the relationship between the critical rotational speed and the critical immersion depth when the lowest point of the KR mechanical stirring vortex reaches the top of the stirring paddle is:

[0035]

[0036] wherein, C4 is a constant; n cr is the critical rotational speed; h cr is the critical immersion depth.

[0037] The present invention obtains the geometric dimensions of the ladle and the stirring paddle during the KR mechanical stirring process, as well as the initial liquid level of the molten iron; predicts the multiphase flow field of the molten iron during the KR mechanical stirring process at different stirring paddle rotation speeds and immersion depths based on the parameters obtained above; obtains the critical rotation speed affecting the action of the stirring paddle immersion depth by comparing the multiphase flow fields of the molten iron; obtains the relationship between the stirring paddle rotation speed and immersion depth and the change of the multiphase flow field of the molten iron based on the above parameters; obtains the relationship between the KR mechanical stirring vortex shape size and the change of the multiphase flow field of the molten iron by outputting the KR mechanical stirring vortex shape size; calculates the critical values of the rotation speed and immersion depth at which the lowest point of the KR mechanical stirring vortex reaches the top of the stirring paddle according to the relationships obtained above. The present invention can quantitatively obtain the critical rotation speed and immersion depth values for improving the stirring efficiency, provide scientific guidance for on-site production, improve the dispersion degree of the desulfurizer and reduce the desulfurization cycle, and optimize production practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0039] Figure 1 It is a flowchart of the method for matching the KR mechanical stirring rotation speed and immersion depth in the embodiment of the present invention;

[0040] Figure 2 It is a schematic diagram showing the change of the turbulent kinetic energy dissipation rate of the molten iron with the rotation speed and immersion depth in the embodiment of the present invention;

[0041] Figure 3 It is a schematic diagram showing the change of the vortex depth with the turbulent kinetic energy dissipation rate in the embodiment of the present invention;

[0042] Figure 4 It is a schematic diagram showing the change of the critical stirring speed and immersion depth in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0044] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0045] Example 1:

[0046] As Figure 1 shown, the embodiment of the present invention provides a method for matching the rotational speed and immersion depth of a KR mechanical stirrer, including:

[0047] Step S1: Obtain the geometric dimensions of the ladle and the stirrer paddle, as well as the initial liquid level of the molten iron, during the current KR mechanical stirring process;

[0048] Step S2: Based on the geometric dimensions of the ladle and the stirrer paddle, as well as the initial liquid level of the molten iron, during the current KR mechanical stirring process, establish a three-dimensional calculation domain for the KR mechanical stirring process. Further, use the VOF air-molten iron multiphase model and the k-ε flow model to numerically calculate the multiphase flow field distribution and vortex shape size of the molten iron during the KR mechanical stirring process at different stirrer paddle rotational speeds and immersion depths;

[0049] Step S3: Based on the multiphase flow field of the molten iron, obtain the critical rotational speed that affects the immersion depth of the stirrer paddle;

[0050] Step S4: Determine the relationship between the stirrer paddle rotational speed and immersion depth and the change in the multiphase flow field of the molten iron;

[0051] Step S5: List and compare the multiphase flow field distributions and vortex shape sizes at different stirrer paddles and immersion depths obtained by calculation, and fit to obtain the relationship between the vortex shape size of the KR mechanical stirrer and the change in the multiphase flow field of the molten iron;

[0052] Step S6: According to the relationship between the vortex shape size of the KR mechanical stirrer and the change in the multiphase flow field of the molten iron, obtain the critical values of the rotational speed and immersion depth when the lowest point of the KR mechanical stirrer vortex reaches the top of the stirrer paddle.

[0053] As an implementation manner of the embodiment of the present invention, step S3 specifically includes:

[0054] Set the immersion depth of the stirrer paddle to the minimum value, change the rotational speed of the stirrer paddle, and calculate the first multiphase flow field distribution of the molten iron;

[0055] Set the immersion depth of the stirrer paddle to the maximum value, change the rotational speed of the stirrer paddle, and calculate the second multiphase flow field distribution of the molten iron;

[0056] According to the first multiphase flow field distribution and the second multiphase flow field distribution of the molten iron, determine the critical rotational speed n id .

[0057] As an implementation manner of the embodiment of the present invention, in step S4, the relationship between the stirrer paddle rotational speed and immersion depth and the change in the multiphase flow field of the molten iron is:

[0058]

[0059] wherein, C1 and C2 are constants; ε is the turbulent kinetic energy dissipation rate; h id is the immersion depth; n is the rotational speed; n id is the critical rotational speed that affects the action of the immersion depth of the stirring paddle on the molten iron multiphase flow field.

[0060] As an implementation manner of an embodiment of the present invention, in step S5, the relationship between the KR mechanical stirring vortex shape size and the molten iron multiphase flow field change is obtained as:

[0061] ΔH d = C3·ε 0.67

[0062] wherein, C3 is a constant; ΔH d is the vortex depth; ε is the turbulent kinetic energy dissipation rate.

[0063] As an implementation manner of an embodiment of the present invention, in step S6, combining the relationship between the rotational speed and immersion depth of the stirring paddle and the molten iron multiphase flow field change ε = C2·n in step S4 3 and the relationship between the KR mechanical stirring vortex shape size and the molten iron multiphase flow field change ΔH d = C3·ε 0.67 , the relationship between the KR mechanical stirring vortex depth and the rotational speed is obtained as:

[0064] ΔH d = C4·n 2

[0065] When the lowest point of the KR mechanical stirring vortex reaches the top of the stirring paddle, the vortex depth is equal to the immersion depth minus the stirring paddle height 950, and further the relationship between the critical rotational speed and the critical immersion depth is obtained as:

[0066]

[0067] wherein, C4 is a constant; n cr is the critical rotational speed; h cr is the critical immersion depth.

[0068] In the embodiment of the present invention, the capacity of the hot metal ladle is 230 tons, and the initial height of the hot metal is 3601 mm. The top and bottom diameters of the hot metal ladle are 3869 mm and 3248 mm respectively. The rotation radius of the stirring paddle is 727 mm. The initial height of the hot metal is 3601 mm. The entire computational domain is divided into approximately 530,000 structured grid cells, and a fine gradient grid is adopted near the interface between the hot metal and the slag. Table 1 summarizes other detailed parameters used in the current study. The physical property parameters of the hot metal and air phases are as shown in Table 1. By obtaining the geometric dimensions of the hot metal ladle and the stirring paddle, as well as the initial liquid level of the hot metal during the current KR mechanical stirring process, the multiphase flow field of the hot metal during the KR mechanical stirring process at different stirring paddle speeds and immersion depths is predicted. As Figure 2 shown, based on the minimum immersion depth of the stirring paddle being 1400 mm and the maximum being 1800 mm, the critical speed n id affecting the effect of the immersion depth of the stirring paddle is determined to be 90 rpm. As Figure 3 shown, it is further determined that C1 and C2 in the relational expression between the stirring paddle speed and the immersion depth and the change of the multiphase flow field of the hot metal are 6.62×10 -10 and 7.36×10 --7 respectively. By outputting the shape and size of the KR mechanical stirring vortex, it is determined that C3 in the relational expression between the shape and size of the KR mechanical stirring vortex and the change of the multiphase flow field of the hot metal is 1.68. Further calculation shows that C4 in the relational expression between the critical speed and the critical immersion depth when the lowest point of the KR mechanical stirring vortex reaches the top of the stirring paddle is 0.130. As Figure 4 shown, it can be obtained that when the working immersion depths of the stirring paddle are 1400 mm, 1600 mm, and 1800 mm, the critical speeds are 58.8 rpm, 70.7 rpm, and 80.9 rpm respectively.

[0069] Table 1

[0070]

[0071] In the embodiment of the present invention, the comprehensive influence of parameters such as the stirring paddle speed and the immersion depth on the multiphase flow field distribution of the hot metal during the KR mechanical stirring process and the shape and size of the KR mechanical stirring vortex is calculated. Based on the determination conditions of the present invention, the stirring paddle speed and the immersion depth can be reasonably matched according to the actual production conditions, so as to provide scientific guidance for on-site production, improve the dispersion degree of the desulfurizer, reduce the desulfurization cycle, and optimize production practice.

[0072] Example 2:

[0073] The embodiment of the present invention also provides a system for matching the KR mechanical stirring speed and the immersion depth, including:

[0074] The first processing module is used to obtain the geometric dimensions of the ladle and the agitator paddle during the current KR mechanical stirring process, as well as the initial liquid level of the molten iron.

[0075] The second processing module is used to predict the multiphase flow field of the molten iron during the KR mechanical stirring process at different agitator paddle rotation speeds and immersion depths based on the geometric dimensions of the ladle and the agitator paddle during the current KR mechanical stirring process, as well as the initial liquid level of the molten iron.

[0076] The third processing module is used to obtain the critical rotation speed affecting the immersion depth of the agitator paddle based on the multiphase flow field of the molten iron.

[0077] The fourth processing module is used to determine the relationship formula between the agitator paddle rotation speed and immersion depth and the change of the multiphase flow field of the molten iron.

[0078] The fifth processing module is used to determine the relationship formula between the KR mechanical stirring vortex shape size and the change of the multiphase flow field of the molten iron according to the KR mechanical stirring vortex shape size.

[0079] The sixth processing module is used to obtain the critical values of the rotation speed and immersion depth when the lowest point of the KR mechanical stirring vortex reaches the top of the agitator paddle according to the relationship formula between the KR mechanical stirring vortex shape size and the change of the multiphase flow field of the molten iron.

[0080] As an implementation manner of the embodiment of the present invention, the relationship formula between the agitator paddle rotation speed and immersion depth and the change of the multiphase flow field of the molten iron is:

[0081]

[0082] wherein, C1 and C2 are constants; ε is the turbulent kinetic energy dissipation rate; h id is the immersion depth; n is the rotation speed; n id is the critical rotation speed affecting the action of the agitator paddle immersion depth on the multiphase flow field of the molten iron.

[0083] As an implementation manner of the embodiment of the present invention, the relationship formula between the KR mechanical stirring vortex shape size and the change of the multiphase flow field of the molten iron is:

[0084] ΔH d = C3·ε 0.67

[0085] wherein, C3 is a constant; ΔH d is the vortex depth; ΔH h is the vortex height; ε is the turbulent kinetic energy dissipation rate.

[0086] As an implementation manner of the embodiment of the present invention, the relationship formula between the critical rotation speed and the critical immersion depth when the lowest point of the KR mechanical stirring vortex reaches the top of the agitator paddle is:

[0087]

[0088] Among them, C4 is a constant; n cr is the critical speed; h cr is the critical immersion depth.

[0089] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for matching the rotational speed and immersion depth of a KR mechanical stirrer, characterized in that, Including: Step S1: Obtain the geometric dimensions of the ladle and the agitator paddle during the current KR mechanical stirring process, as well as the initial molten iron level; Step S2: Predict the multiphase flow field of the molten iron during the KR mechanical stirring process at different agitator paddle rotation speeds and immersion depths based on the geometric dimensions of the ladle and the agitator paddle during the current KR mechanical stirring process, as well as the initial molten iron level; Step S3: Based on the multiphase flow field of the molten iron, obtain the critical rotation speed affecting the action of the agitator paddle immersion depth; Step S4: Determine the relationship between the agitator paddle rotation speed and immersion depth and the change in the multiphase flow field of the molten iron; Step S5: According to the shape and size of the KR mechanical stirring vortex, determine the relationship between the shape and size of the KR mechanical stirring vortex and the change in the multiphase flow field of the molten iron; Step S6: According to the relationship between the shape and size of the KR mechanical stirring vortex and the change in the multiphase flow field of the molten iron, obtain the critical rotation speed and immersion depth values when the lowest point of the KR mechanical stirring vortex reaches the top of the agitator paddle.

2. The method according to claim 1, wherein the rotational speed and immersion depth of the KR mechanical stirring are matched with each other, characterized in that The relationship between the agitator paddle rotation speed and immersion depth and the change in the multiphase flow field of the molten iron is: where, C1 and C2 are constants; ε is the turbulent kinetic energy dissipation rate; h id is the immersion depth; n is the rotational speed; n id is the critical rotational speed that affects the action of the immersion depth of the stirring paddle on the molten iron multiphase flow field.

3. The method for matching the rotational speed and immersion depth of the KR mechanical stirring according to claim 2, wherein The relationship between the shape and size of the KR mechanical stirring vortex and the change in the multiphase flow field of the molten iron is: ΔH d = C3·ε 0.67 where C3 is a constant; ΔH d is the vortex depth; ΔH h is the vortex height; ε is the turbulent kinetic energy dissipation rate.

4. The method for matching the rotational speed and immersion depth of the KR mechanical stirring according to claim 3, characterized in that The relationship between the critical rotation speed and critical immersion depth when the lowest point of the KR mechanical stirring vortex reaches the top of the agitator paddle is: where C4 is a constant; n cr is the critical speed; h cr is the critical immersion depth.

5. A system in which the rotational speed and immersion depth of a KR mechanical stirrer are mutually matched, characterized in that, Including: The first processing module is used to obtain the geometric dimensions of the ladle and the agitator paddle during the current KR mechanical stirring process, as well as the initial molten iron level; The second processing module is used to predict the multiphase flow field of the molten iron during the KR mechanical stirring process at different agitator paddle rotation speeds and immersion depths based on the geometric dimensions of the ladle and the agitator paddle during the current KR mechanical stirring process, as well as the initial molten iron level; The third processing module is used to obtain the critical rotation speed affecting the action of the agitator paddle immersion depth based on the multiphase flow field of the molten iron; The fourth processing module is used to determine the relationship between the agitator paddle rotation speed and immersion depth and the change in the multiphase flow field of the molten iron; The fifth processing module is used to determine the relationship between the shape and size of the KR mechanical stirring vortex and the change in the multiphase flow field of the molten iron according to the shape and size of the KR mechanical stirring vortex; The sixth processing module is used to obtain the critical rotation speed and immersion depth values when the lowest point of the KR mechanical stirring vortex reaches the top of the agitator paddle according to the relationship between the shape and size of the KR mechanical stirring vortex and the change in the multiphase flow field of the molten iron.

6. The system according to claim 5, wherein the rotational speed and immersion depth of the KR mechanical stirring are matched with each other, characterized in that The relationship between the agitator paddle rotation speed and immersion depth and the change in the multiphase flow field of the molten iron is: wherein, C1 and C2 are constants; ε is the turbulent kinetic energy dissipation rate; h id is the immersion depth; n is the rotational speed; n id is the critical rotational speed that affects the action of the immersion depth of the stirring paddle on the molten iron multiphase flow field.

7. The system according to claim 6, wherein the rotational speed and immersion depth of the KR mechanical stirring are matched with each other, characterized in that The relationship between the shape and size of the KR mechanical stirring vortex and the change in the multiphase flow field of the molten iron is: ΔH d = C3·ε 0.67 where C3 is a constant; ΔH d is the vortex depth; ΔH h is the vortex height; ε is the turbulent kinetic energy dissipation rate.

8. The system according to claim 7, wherein the rotational speed and immersion depth of the KR mechanical stirring are matched with each other, characterized in that The relationship between the critical rotation speed and critical immersion depth when the lowest point of the KR mechanical stirring vortex reaches the top of the agitator paddle is: where C4 is a constant; n cr is the critical speed; h cr is the critical immersion depth.

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