CN112446134B - A method for calculating heat loss in different regions of furnace body during electric arc furnace steelmaking - Google Patents

Abstract

The invention discloses a method for calculating the heat loss of a furnace body zone in an electric arc furnace steelmaking process. The heat loss Q ₁ of the upper furnace shell part, the heat loss Q ₂ of the lower furnace shell part, the heat loss Q ₃ of the furnace bottom part, the heat loss Q ₄ of the furnace cover part and the radiation heat transfer heat loss Q ₅ of the furnace body area, and then calculate the total heat loss loss Q. The invention is based on the division of the electric arc furnace body, and simultaneously calculates the heat loss of each region according to the temperature characteristics, geometric parameters and relative positions of different parts of the electric arc furnace body region, which can ensure the reliability and universality of the results. And the parameters in the final calculation formula can be directly measured and obtained, which reduces the tedious measurement steps.

Description

A method for calculating heat loss in different areas of furnace body during electric arc furnace steelmaking

technical field

The invention belongs to the technical field of steelmaking, and in particular relates to a method for calculating heat loss in different regions of a furnace body in an electric arc furnace steelmaking process.

Background technique

The energy composition of electric arc furnace steelmaking is diverse and complex. The oxygen supply, power supply and other operations in the smelting process cause energy changes in the molten pool at various stages and fluctuations in the heat dissipation of the furnace body; the temperature rise of the molten steel pool is caused by the heat of chemical reaction. It is produced by the synergy of multiple energy methods such as electricity, heat dissipation and so on. Heat loss during electric arc furnace steelmaking is an important factor affecting energy efficiency.

Researchers at home and abroad mainly focus on the heat and mass exchange methods, characteristics and influencing factors of materials such as scrap steel, molten steel and slag in the molten pool area, focusing on the flow and heat transfer mechanism inside the molten steel. A large part of the heat loss and material output in the steel process is carried out outside the electric arc furnace. The radiation heat transfer caused by the high temperature difference and the convective heat transfer caused by the fluid flow between the electric arc furnace body and the external environment are There are very few studies on this part of the heat loss. At present, this part of the heat loss cannot be quantified by specific measuring instruments and calculation methods, and lacks sufficient attention. The reliability and universality of the calculation results are not ideal, which brings great influence to the optimization of the energy structure of electric arc furnace steelmaking. Great influence.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology, and provide a method for calculating heat loss in different regions of the furnace body in the process of electric arc furnace steelmaking, so as to improve the reliability and universality of the calculation results. .

In order to solve the above-mentioned technical problems, the technical scheme proposed by the present invention is:

A method for calculating heat loss in different areas of a furnace body in an electric arc furnace steelmaking process. The furnace body area of an electric arc furnace is divided into an upper furnace shell part, a lower furnace shell part, a furnace bottom part and a furnace cover part, and the upper furnace shell part is calculated separately. Heat loss Q ₁ , lower shell part heat loss Q ₂ , furnace bottom part heat loss Q ₃ , furnace cover part heat loss Q ₄ and furnace body area radiative heat transfer heat loss Q ₅ , and then calculate the total heat loss Q.

Among them, Q ₁ includes the heat taken away by the cooling water in the upper furnace shell and the heat taken away by the air convection in the upper furnace shell; Q ₂ includes the heat taken away by the cooling water in the lower furnace shell and the air convection in the lower furnace shell. , Q _C2 includes the air convection heat loss Q _C2.1 per unit time of the vertical wall surface of the lower furnace shell part and the air convection heat loss Q _C2.2 per unit time of the horizontal heat exchange area of the lower furnace shell part; Q ₃ includes the furnace bottom The heat taken away by part of the cooling water and the heat Q _C3 taken away by the air convection in the furnace bottom part, Q _C3 includes the heat taken away by the air convection in the horizontal projection area of the furnace bottom part and the air convection in the vertical projection area of the furnace bottom part; Q ₄ includes the heat taken away by the cooling water of the furnace cover part and the heat taken away by the air convection of the furnace cover part Q _C4 , Q _C4 includes the heat taken away by the air convection in the horizontal projection area of the furnace cover part and the air convection in the vertical projection area of the furnace cover part The heat taken away; _Q5 includes the net radiative heat exchange per unit time between the surface of the electric arc furnace body and the surrounding walls and the radiative heat transfer heat loss G at the door of the electric arc furnace.

Compared with the prior art, the beneficial effects of the present invention are:

(1) A calculation method for determining the heat loss in the different regions of the electric arc furnace body is proposed. Based on the division of the electric arc furnace body, and according to the temperature characteristics, geometric parameters and relative positions of different parts of the electric arc furnace body area, the electric arc furnace is divided. The furnace body is divided into the upper furnace shell part, the lower furnace shell part, the furnace bottom part and the furnace cover part, and the heat loss of each area is calculated separately, which can ensure the reliability and universality of the results. And the parameters in the final calculation formula can be directly measured and obtained, which reduces the tedious measurement steps.

(2) The convective heat transfer coefficient h value between the furnace body area and the surrounding air during the EAF steelmaking process was determined by calculation formula, rather than selected by empirical parameters. And the measurement method of temperature parameters is defined to make it more in line with the actual calculation needs.

(3) The order of magnitude of heat loss in the furnace body area during the EAF steelmaking process can be understood and quantified from an intuitive perspective, laying a theoretical foundation for the green smelting and energy saving and consumption reduction of EAF steelmaking.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are For some embodiments of the present invention, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without any creative effort.

Fig. 1 is the division of the whole area of the electric arc furnace and the geometric composition of the furnace body area;

Figure 2 is the detailed division of each component in the furnace body area of the electric arc furnace;

Figure 3 is a perspective view of the furnace body area of the electric arc furnace;

4 is a perspective view of the upper furnace shell part of the furnace body area of the electric arc furnace;

Figure 5 is a perspective view of the lower furnace shell part of the furnace body area of the electric arc furnace;

Fig. 6 is the horizontal heat exchange surface at the connection of the lower furnace shell part and the upper furnace shell part in the furnace body region of the electric arc furnace;

Fig. 7 is the top view of the horizontal projection area of the lower furnace shell part of the furnace body area of the electric arc furnace and its related parameters;

8 is a perspective view of the furnace bottom part of the furnace body area of the electric arc furnace;

FIG. 9 is a perspective view of the furnace cover part of the furnace body area of the electric arc furnace;

Figure 10 is a schematic diagram of the radiation heat exchange between molten steel and the furnace door in the electric arc furnace.

Among them: 1. furnace body area; 2. molten pool area; 11. furnace cover part; 12. upper furnace shell part; 13. lower furnace shell part; 14. furnace bottom part; 3. furnace door; 4. molten steel.

Detailed ways

In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and in detail below with reference to the accompanying drawings and preferred embodiments of the specification, but the protection scope of the present invention is not limited to the following specific embodiments.

Unless otherwise defined, all technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention.

Based on the basic theory of heat transfer, the invention proposes a calculation method for determining the heat loss of the different regions of the furnace body in the electric arc furnace steelmaking process, so as to determine the difference between the electric arc furnace body and the temperature of the electric arc furnace body due to higher temperature during the electric arc furnace steelmaking process. The magnitude of the radiative heat transfer and convective heat transfer heat loss caused by the low surrounding building envelope, the large temperature difference between air and cooling water, and the magnitude of this part of the heat loss can be understood from an intuitive point of view. The mathematical modeling and theoretical derivation process of the present invention is as follows:

1 Electric arc furnace partition and heat transfer behavior

1.1 Electric arc furnace partition

The characteristics and paths of heat transfer in the process of EAF steelmaking are analyzed, and the EAF is divided into "melting pool area" and "furnace body area", as shown in Figure 1. The molten pool area 2 in the figure is the part surrounded by the black dotted line, which mainly refers to the molten pool area in the electric arc furnace. There are mainly molten steel and slag inside, as well as supplementary materials such as injected oxygen and carbon powder, which are used for chemical reaction. And the main area of heat and mass transfer inside the electric arc furnace, the furnace body area 1 refers to the area outside the molten pool area of the electric arc furnace, that is, the part outside the black dotted line, mainly refers to the physical components of the electric arc furnace body, such as the upper furnace shell , lower furnace shell and other geometric elements.

Through this step, the main body of the electric arc furnace is divided, and the calculation area of the present invention, namely "furnace body area" is indicated.

1.2 Heat transfer behavior in furnace area

The heat loss in the furnace body area of the electric arc furnace is analyzed, and it is concluded that the heat dissipation methods of the furnace body area of the electric arc furnace mainly include:

(1) Objects emit radiant energy for various reasons, among which the phenomenon of radiating energy due to heat is called thermal radiation. Various chemical reactions take place in the electric arc furnace, and there is external input energy. The furnace body area has a high temperature during the smelting process, which will radiate a lot of heat to external objects. Radiation heat transfer heat loss caused by temperature difference between the furnace body area of the electric arc furnace with a higher temperature and the building envelope with a lower temperature. The heat transfer type is the radiation heat transfer between the cavity and the inner envelope. The radiant heat loss of the EAF furnace body mainly includes the radiant heat loss of the EAF furnace body and the radiant heat loss of the EAF furnace door.

(2) During the smelting process of the electric arc furnace, the temperature of the furnace body is high, the air in the surrounding environment is heated and rises, and convection heat exchange is carried out with the furnace body. The convection heat exchange method belongs to the natural convection heat exchange in large space.

(3) In order to prevent overheating damage caused by overheating in the furnace shell and furnace cover of the electric arc furnace, it is often necessary to provide cooling water for cooling by means of cooling water pipes coiled in the relevant areas, and convection between the cooling water and the furnace body of the electric arc furnace The heat exchange method is the partition wall convection heat exchange.

The main purpose of this step is to partition the electric arc furnace, and at the same time determine the type and method of heat loss in the furnace body area during the steelmaking process of the electric arc furnace, so as to facilitate subsequent calculations.

2. Geometric composition and heat transfer characteristics of the furnace body area of the electric arc furnace

Based on the division of the electric arc furnace body, and according to the temperature characteristics, geometric parameters and relative positions of different parts of the electric arc furnace body area, the electric arc furnace body is divided into an upper furnace shell part 12, a lower furnace shell part 13, and a furnace bottom part 14. And the furnace cover part 11, these four parts constitute the geometrical elements of the furnace body area of the electric arc furnace.

As shown in FIG. 1 , the furnace bottom part 14 refers to the area of the furnace bottom of the electric arc furnace, and more specifically, as shown in FIG. 2 , refers to the inclined curved surface part and a part of the vertical surface of the furnace bottom of the furnace body area of the electric arc furnace. The heat transfer characteristic is that when the convective heat transfer is performed with the air in the surrounding environment, the convective heat transfer for heating the air on the vertical wall surface and the convective heat transfer for heating the air with the hot surface facing down.

The lower furnace shell part 13 is the lower furnace shell in the geometric structure of the electric arc furnace, and mainly refers to the vertical cylindrical region and a part of the horizontal region coupled with the furnace bottom part of the furnace body region of the electric arc furnace. When the convective heat transfer is performed between the air in the vertical wall, the convective heat transfer of the heating air on the vertical wall and the convective heat transfer of the heated air with the hot surface facing upward.

The upper furnace shell part 12 is the upper furnace shell in the geometric composition of the electric arc furnace, mainly refers to the area coupled with the lower furnace shell and the furnace cover part of the electric arc furnace, and its heat transfer characteristic is to conduct convection exchange with the air in the surrounding environment. When hot, convective heat transfer of heated air for vertical walls.

The furnace cover part 11 includes the electric arc furnace cover and its surrounding annular area, and its heat transfer characteristic is that when convective heat exchange is performed with the air in the surrounding environment, the convective heat exchange for heating the air for the vertical wall surface and the hot surface facing upward Convective heat transfer of heated air.

The purpose of this step is to further divide the furnace body area of the electric arc furnace. According to the heat transfer characteristics of different components, different heat transfer calculation methods are subsequently used to obtain the heat transfer loss of the relevant components.

3 Heat loss in the furnace body area of the electric arc furnace

Based on the above analysis, the heat loss in the furnace body area of the EAF steelmaking process includes the heat loss of the upper furnace shell part of the EAF furnace body area, the heat loss of the lower furnace shell part of the EAF furnace body area, the heat loss of the furnace bottom part of the EAF furnace body area and The heat loss of the furnace cover part of the furnace body area of the electric arc furnace. By determining the relative size of these four parts of heat loss, the summation of energy can be used to obtain the final total heat loss, that is, the heat loss in the furnace body area of the electric arc furnace steelmaking process.

Based on the previous analysis, the heat loss path of the electric arc furnace body area mainly includes the following three parts:

(1) The heat lost between each component of the electric arc furnace body area and the cooling water flowing through it in the form of heat exchange between the partitions.

(2) The heat lost by natural convection heat transfer in large space between each component of the furnace body area of the electric arc furnace and the air in the surrounding environment.

(3) The heat lost in the form of radiative heat transfer in the form of cavity and inner envelope between each component of the electric arc furnace body area and the surrounding building envelope.

Among them, the calculation process of convective heat transfer heat loss between the furnace body area of the electric arc furnace and the air in the surrounding environment is relatively complex, involving a variety of situations and judgments, the selection of calculation formulas, and the determination of criterion numbers and characteristic numbers. There is no effective calculation method in the field of steel and can only be selected from empirical data.

The next content is to focus on the analysis of the calculation process of the heat loss of air convection heat transfer between the components of the electric arc furnace body area and the surrounding environment.

The fourth edition of "Heat Transfer" provides experimental correlations for natural convection in large spaces on pages P269 to PP271:

in:

其中T是定性温度，K；l为流体(空气)所流经的电弧炉炉体区换热壁面的特征长度，m；ν为由定性温度T所确定的流体(空气)运动粘性系数，m²/s；α为流体(空气)的热扩散系数，m²/s；λ为流体(空气)的导热系数，W/(m·K)；c为由定性温度T确定的流体(空气)比热容，J/(kg·K)；ρ为由定性温度T确定的流体(空气)密度，kg/m³。In the formula: Nu _m is the Nusselt number, which represents the relative size of the dimensionless temperature gradient on the wall of the electric arc furnace; Gr is the Grashof number, which represents the natural convection flow state, the relative size of the buoyancy force and the viscous force; Pr is the general Ronte number, which represents the relative magnitude of momentum diffusivity and thermal diffusivity; g is the acceleration of gravity, m/s ² , the recommended value is 9.81m/s ² ; α _V is the fluid (air) around the furnace body area of the electric arc furnace. The bulk expansion coefficient, for gases that conform to the ideal gas properties, in the Gr number

Where T is the qualitative temperature, K; l is the characteristic length of the heat exchange wall in the furnace body area of the electric arc furnace through which the fluid (air) flows, m; ν is the fluid (air) kinematic viscosity coefficient determined by the qualitative temperature T, m ² /s; α is the thermal diffusivity of the fluid (air), m ² /s; λ is the thermal conductivity of the fluid (air), W/(m·K); c is the fluid (air) determined by the qualitative temperature T Specific heat capacity, J/(kg·K); ρ is the fluid (air) density determined by the qualitative temperature T, kg/m ³ .

Therefore, the Prandtl number can be further expressed as:

For the coefficient C and the index n in the formula (3-1), the values can be taken according to Table 3-1 according to the actual fluid (air) flow state around the furnace body area of the electric arc furnace.

Table 3-1 Values of coefficient C and exponent n in formula (3-1)

At the same time, for the natural convection heat transfer process, Nu _m can also be calculated by the following formula:

Where: h is the average surface convection heat transfer coefficient of the heat exchange wall in the furnace body area of the electric arc furnace, W/(m ² ·K);

Therefore, from formulas (3-1) and (3-5), the calculation formula of the average surface convection heat transfer coefficient of the heat exchange wall surface in the furnace body area of the electric arc furnace can be obtained:

Then it can be concluded that the heat taken away by the convection heat transfer between the heat exchange wall surface of the furnace body area of the electric arc furnace and the surrounding air is:

For the vertical wall surface of the furnace body area of the electric arc furnace, the characteristic length l is the height of the heat exchange wall surface; for the horizontal heat exchange wall surface of the furnace body area of the electric arc furnace, it is determined by the following formula:

In the formula: _AP is the heat exchange area of the horizontal heat exchange surface in the furnace body area of the electric arc furnace, m ² ; P is the perimeter length of the horizontal heat exchange surface in the furnace body area of the electric arc furnace, m.

The convective heat transfer coefficient of the heat exchange wall in the furnace body area of the electric arc furnace can be determined by the formula (3-6), and the convection heat transfer coefficient of the heat exchange wall surface in the furnace body area of the electric arc furnace can be determined by the formula (3-7). .

Therefore, next, calculate the heat loss of the components of the furnace body area of the electric arc furnace, that is, the upper furnace shell part, the lower furnace shell part, the furnace bottom part and the furnace cover part, and obtain the heat loss of each component, which is used for the follow-up. The basis for calculating the total heat transfer heat loss in the electric arc furnace steelmaking process.

3.1 Heat loss of the upper furnace shell in the furnace body area of the electric arc furnace

The upper furnace shell part of the furnace body area of the electric arc furnace, and its related view is shown in Figure 4. There is a cooling water pipe on the outside of the upper furnace shell part of the furnace body area of the electric arc furnace, which is used to cool the upper furnace shell part of the furnace body area of the electric arc furnace. -9) Do the calculation:

Q _W1 =c ₁ ρ ₁ V ₁ (T _out1 -T _in1 ) (3-9)

为由冷却水进、出口温度平均值确定的定性温度，由式(3-10)确定，K；c₁为由定性温度

确定的冷却水比热容，J/(kg·K)；ρ₁为由定性温度

确定的冷却水密度，kg/m³；V₁为电弧炉炉体区上炉壳部分冷却水单位时间内的体积流量，m³。In the formula: Q _W1 is the heat taken away by the cooling water of the upper furnace shell part of the furnace body area of the electric arc furnace, J; T _in1 and T _out1 are the inlet and outlet temperatures of the cooling water part of the upper furnace shell part of the furnace body area of the electric arc furnace respectively; K;

is the qualitative temperature determined by the average value of the cooling water inlet and outlet temperatures, determined by the formula (3-10), K; c ₁ is the qualitative temperature

Determined specific heat capacity of cooling water, J/(kg·K); ρ ₁ is the qualitative temperature

Determined cooling water density, kg/m ³ ; V ₁ is the volume flow of cooling water per unit time in the upper furnace shell part of the furnace body area of the electric arc furnace, m ³ .

The temperature of the upper furnace shell part in the furnace body area of the electric arc furnace is relatively high. After the surrounding air flows through the upper furnace shell part, a part of the heat will be removed due to the convective heat transfer. The calculation of this part of the heat (convective heat transfer) can be carried out by the following calculation methods:

The outer circumference of the upper furnace shell part of the furnace body area of the electric arc furnace:

P ₁ =πd ₁ (3-11)

Therefore, convection heat exchange is carried out between the upper furnace shell part and the surrounding air in the furnace body area of the electric arc furnace, and the heat exchange area is:

A ₁ =P ₁ H ₁ =πd ₁ H ₁ (3-12)

Sum formulas (3-2), (3-4), (3-6), (3-7) selected according to the numerical ranges of laminar flow, transitional flow and turbulent flow in Table 3-1, and take the furnace body area of the electric arc furnace The characteristic dimension l=H ₁ of the upper furnace shell part can be combined with the geometric characteristics of the upper furnace shell part of the furnace body region of the electric arc furnace to obtain the average surface convection heat transfer coefficient calculation formula of the upper furnace shell part of the furnace body region of the electric arc furnace and the electric arc furnace. The calculation formulas for the heat loss of air convection heat transfer per unit time in the upper furnace shell part of the furnace body area are formulas (3-13), (3-14), (3-15) and formulas (3-16), (3) -17), (3-18).

为由电弧炉炉体区上炉壳部分平均温度和周围主流空气温度确定的空气定性温度，由式(3-19)确定，K；ρ_A1为由定性温度

确定的空气密度，kg/m³；c_A1为由定性温度

确定的空气比热容，J/(kg·K)；ν_A1为由定性温度

确定的空气运动粘性系数，m²/s；λ_A1为由定性温度

确定的空气导热系数，W/(m·K)；In the formula: Q _C1 is the heat taken by the air convection heat transfer zone of the upper furnace shell part of the furnace body area of the electric arc furnace, J; h ₁ is the average surface convective heat transfer coefficient of the upper furnace shell part of the furnace body area of the electric arc furnace, W/(m ² K); d ₁ is the outer diameter of the cylinder of the upper furnace shell part in the furnace body area of the electric arc furnace, m; H ₁ is the height of the cylinder part of the upper furnace shell part of the furnace body area of the electric arc furnace, m; T ₁ and T _A1 are respectively Indicates the average temperature of the upper furnace shell part and the surrounding mainstream air temperature in the furnace body area of the electric arc furnace, K; g is the acceleration of gravity, m/s ² , the recommended value is 9.8m/s ² ;

is the air qualitative temperature determined by the average temperature of the upper furnace shell part of the furnace body area of the electric arc furnace and the surrounding mainstream air temperature, determined by formula (3-19), K; ρ _A1 is the qualitative temperature

Determined air density, kg/m ³ ; c _A1 is the qualitative temperature

Determined specific heat capacity of air, J/(kg·K); ν _A1 is the qualitative temperature

Determined air kinematic viscosity coefficient, m ² /s; λ _A1 is the qualitative temperature

Determined air thermal conductivity, W/(m K);

The specific applications of formulas (3-13), (3-14), (3-15) and formulas (3-16), (3-17), (3-18) need to be based on the upper furnace shell in the furnace body area of the electric arc furnace The flow state of the surrounding air during heat exchange with the surrounding air is determined, and its specific application is determined by formulas (3-20), (3-21), (3-22), as follows:

Therefore, the calculation formula of the heat loss of the upper furnace shell part of the electric arc furnace body area due to air convection and cooling water heat transfer is:

Q ₁ =Q _W1 +Q _C1 (3-23)

Among them, the calculation formula of Q _C1 needs to be judged and selected according to the actual measured parameters.

3.2 Heat loss of the lower furnace shell in the furnace body area of the electric arc furnace

There is a cooling water pipe on the outside of the lower furnace shell part of the furnace body area of the electric arc furnace, which is used to cool the lower furnace shell part of the electric arc furnace. Calculation:

Q _W2 =c ₂ ρ ₂ V ₂ (T _out2 -T _in2 ) (3-24)

为由冷却水进、出口温度平均值确定的定性温度，由式(3-25)确定，K；c₂为由定性温度

确定的冷却水比热容，J/(kg·K)；ρ₂为由定性温度

确定的冷却水密度，kg/m³；V₂为电弧炉炉体区下炉壳部分冷却水单位时间内的体积流量，m³。In the formula: Q _W2 is the heat taken away by the cooling water of the lower furnace shell part of the furnace body area of the electric arc furnace, J; T _in2 and T _out2 are the inlet and outlet temperatures of the cooling water part of the lower furnace shell part of the furnace body area of the electric arc furnace respectively; K;

is the qualitative temperature determined by the average value of the cooling water inlet and outlet temperatures, determined by formula (3-25), K; c ₂ is the qualitative temperature

Determined specific heat capacity of cooling water, J/(kg·K); ρ ₂ is the qualitative temperature

Determined cooling water density, kg/m ³ ; V ₂ is the volume flow of cooling water per unit time in the lower furnace shell part of the furnace body area of the electric arc furnace, m ³ .

The lower furnace shell part of the furnace body area of the electric arc furnace, and its related view is shown in Figure 5. At the same time, it should be noted that when the lower furnace shell part and the upper furnace shell part of the furnace body area of the electric arc furnace are connected, there will be a horizontal area, as shown in Figures 3 and 6. There is high temperature molten steel inside the lower furnace shell part of the furnace body area of the electric arc furnace, and its surface temperature is high, and the surrounding air will take away part of the heat after passing through the lower furnace shell part, so the lower furnace shell part of the furnace body area of the electric arc furnace When conducting convective heat transfer, the heat exchange surface has a vertical wall surface and a horizontal wall surface with the heat surface facing upward. It is necessary to calculate the average surface convective heat transfer coefficient and heat dissipation of these two heat dissipation surfaces respectively.

(1) Calculation of convection heat transfer heat of vertical wall of the lower furnace shell part of the furnace body area of the electric arc furnace

Figure 7 shows the relevant parameters in the top view of the lower furnace shell part of the furnace body area of the electric arc furnace. At the same time, it should be noted that the horizontal projection of the bottom part of the furnace body area of the electric arc furnace and the horizontal projection area of the lower furnace shell part of the furnace body area of the electric arc furnace should be coincident.

The perimeter and area of the irregular region in the horizontal projection of the lower furnace shell in the furnace body area of the electric arc furnace can be calculated by the following formula:

Therefore, convective heat exchange is carried out between the lower furnace shell part of the electric arc furnace body area and the surrounding air, and the heat exchange area in the vertical direction is:

In the formula: Angles A and B are respectively the actual sector angle of the top of the furnace bottom part of the furnace geometry model of the electric arc furnace, °; r is the reference circle radius of the top surface of the eccentric area of the furnace bottom part of the furnace body area of the EAF, m; R is the electric arc furnace The reference circle radius of the top surface of the furnace bottom part of the furnace body area, m; L is the furnace length of the furnace bottom part of the furnace body area of the electric arc furnace; D is the length of the hypotenuse of the reference circle connecting the top surface of the furnace bottom part of the furnace body area of the electric arc furnace, m;

Sum formulas (3-2), (3-4), (3-6), (3-7) selected according to the numerical ranges of laminar flow, transitional flow and turbulent flow in Table 3-1, and take the furnace body area of the electric arc furnace The characteristic dimension of the lower furnace shell part l=H ₂ , the calculation formula of the average surface convection heat transfer coefficient of the vertical wall surface of the lower furnace shell part in the furnace body region of the electric arc furnace can be obtained by combining the geometric characteristics of the lower furnace shell part of the furnace body region of the electric arc furnace and the calculation formulas of air convection heat transfer heat loss per unit time on the vertical wall of the lower furnace shell part of the furnace body area of the electric arc furnace, which are formulas (3-29), (3-30), (3-31) and (3) -32), (3-33), (3-34).

为由电弧炉炉体区下炉壳部分平均温度和周围主流空气温度确定的空气定性温度，由式(3-35)确定，K；ρ_A2为由定性温度

确定的空气密度，kg/m³；c_A2为由定性温度

确定的空气比热容，J/(kg·K)；ν_A2为由定性温度

确定的空气运动粘性系数，m²/s；λ_A2为由定性温度

确定的空气导热系数，W/(m·K)；In the formula: Q _C2 is the heat taken away by air convection in the lower furnace shell of the furnace body of the electric arc furnace, J; h ₂ is the average surface convection heat transfer coefficient of the lower furnace shell of the furnace body of the electric arc furnace, W/(m ² · K); H ₂ is the height of the cylinder of the lower furnace shell in the furnace body area of the electric arc furnace, m; T ₂ and T _A2 respectively represent the average temperature of the lower furnace shell part and the surrounding mainstream air temperature in the furnace body region of the electric arc furnace, K; g is Gravitational acceleration, m/s ² , the recommended value is 9.8m/s ² ;

is the air qualitative temperature determined by the average temperature of the lower furnace shell part of the furnace body area of the electric arc furnace and the surrounding mainstream air temperature, determined by the formula (3-35), K; ρ _A2 is the qualitative temperature

Determined air density, kg/m ³ ; c _A2 is the qualitative temperature

Determined specific heat capacity of air, J/(kg·K); ν _A2 is determined by the qualitative temperature

Determined air kinematic viscosity coefficient, m ² /s; λ _A2 is the qualitative temperature

Determined air thermal conductivity, W/(m K);

The specific applications of formulas (3-29), (3-30), (3-31) and formulas (3-32), (3-33) and (3-34) need to be based on the lower furnace shell of the electric arc furnace body area. The flow state of the surrounding air during heat exchange with the surrounding air is determined, and its specific application is determined by formulas (3-36), (3-37), (3-38), as follows:

(2) Calculation of the horizontal heat exchange at the connection between the lower furnace shell part and the upper furnace shell part of the electric arc furnace body area

The horizontal heat exchange surface area of the lower furnace shell part in the furnace body area of the EAF = the horizontal projected area of the lower furnace shell part in the furnace body area of the EAF - the horizontal projected area of the upper furnace shell part in the furnace body area of the EAF, that is, there is the following formula:

The perimeter of the horizontal heat exchange area of the lower furnace shell part of the electric arc furnace body area is calculated by the following formula:

Therefore, the characteristic length of the horizontal heat exchange area of the lower furnace shell part of the electric arc furnace body area can be determined according to the formula (3-8), that is, the characteristic length is:

Because the calculation formula of the two parts constituting the characteristic length is too long, it is not written out here, but can be searched in the above formula.

According to the calculated values, calculation ranges and equations (3-2), (3-4), (3-6), (3-7) and (3-41) of the horizontal thermal surface facing up in Table 3-1, it is Combined with the geometric characteristics of the horizontal heat exchange area of the lower furnace shell part of the EAF furnace body area, the calculation formula of the average surface convection heat transfer coefficient of the horizontal heat exchange area of the lower furnace shell part of the EAF furnace body area and the calculation formula of the lower furnace shell part of the EAF furnace body area can be obtained. The calculation formulas of air convection heat transfer heat loss per unit time in the horizontal heat exchange area of the furnace shell part are formulas (3-42), (3-43) and formulas (3-44), (3-45).

The specific applications of formulas (3-42), (3-43) and formulas (3-44) and (3-45) are determined by formulas (3-46) and (3-47), respectively, as follows:

Therefore, the calculation formula of heat loss due to air convection and cooling water heat transfer in the lower furnace shell part of the furnace body area of the electric arc furnace is:

Q ₂ =Q _W2 +Q _C2 =Q _W2 +Q _C2.1 +Q _C2.2 (3-48)

Among them, the calculation formula of Q _C2 needs to be judged and selected according to the actual measured parameters.

3.3 Heat loss in the furnace bottom part of the furnace body area of the electric arc furnace

There is a cooling water pipe on the outside of the furnace bottom part of the furnace body area of the electric arc furnace, which is used to provide cooling protection for the furnace bottom of the electric arc furnace. calculate:

Q _W3 =c ₃ ρ ₃ V ₃ (T _out3 -T _in3 ) (3-49)

为由冷却水进、出口温度平均值确定的定性温度，由式(3-50)确定，K；c₃为由定性温度

确定的冷却水比热容，J/(kg·K)；ρ₃为由定性温度

确定的冷却水密度，kg/m³；V₃为电弧炉炉体区炉底部分冷却水单位时间内的体积流量，m³。In the formula: Q _W3 is the heat taken away by the cooling water in the furnace bottom part of the electric arc furnace body area, J; T _{in3 and T out3 are} the inlet and outlet temperatures of the cooling water in the furnace bottom part of the electric arc furnace body; K;

is the qualitative temperature determined by the average temperature of the cooling water inlet and outlet, determined by the formula (3-50), K; c ₃ is the qualitative temperature

Determined specific heat capacity of cooling water, J/(kg·K); ρ ₃ is the qualitative temperature

Determined cooling water density, kg/m ³ ; V ₃ is the volume flow rate per unit time of cooling water in the furnace bottom part of the furnace body area of the electric arc furnace, m ³ .

The bottom part of the furnace body area of the electric arc furnace, and its related view is shown in Figure 8. The furnace bottom part of the furnace body area of the electric arc furnace has an inclined surface due to the existence of the eccentric area. When the surrounding air flows through the furnace bottom part, the heat taken away will be calculated by using the furnace bottom part projection. Therefore, when the convective heat exchange between the bottom part of the furnace body area of the electric arc furnace and the surrounding air is carried out, the heat exchange surface has a vertical wall surface and a horizontal wall surface with the hot surface facing down. Now calculate the average surface convection heat transfer coefficient of these two heat dissipation surfaces and Heat output.

(1) Calculation of convective heat transfer heat in the horizontal projection area of the furnace bottom part of the furnace body area of the electric arc furnace

The horizontal projection area of the furnace bottom part coincides with the horizontal projection of the lower furnace shell part of the furnace body area of the electric arc furnace, which is an area with the hot surface facing downward, as shown in FIG. 7 . The perimeter and area of its horizontal projection area are shown in equations (3-26) and (3-27).

The characteristic length of the horizontal projection area of the furnace bottom part of the furnace body area of the electric arc furnace can be determined according to the formula (3-8), that is, the characteristic length is:

Because the calculation formula of the two parts constituting the characteristic length is too long, it is not written out here, but can be searched in the above formula.

Calculated values, calculation ranges and equations (3-2), (3-4), (3-6), (3-7), (3-51) of heating fluid with the horizontal hot surface facing down in Table 3-1 , the average surface convective heat transfer coefficient calculation formula of the horizontal heat exchange area of the furnace bottom part of the furnace body area of the EAF can be obtained by combining the geometric characteristics of the horizontal heat exchange area of the furnace bottom part of the EAF furnace body area and the The calculation formulas for the heat loss of air convection heat transfer per unit time in the horizontal heat exchange area of the bottom part are formula (3-52) and formula (3-53).

The use of the above formula still needs to be judged

Of course, for the electric arc furnace, it satisfies the formula (3-55), but for the sake of rigor, it needs to be checked.

为由电弧炉炉体区炉底部分平均温度和周围主流空气温度确定的空气定性温度，由式(3-54)确定，K；ρ_A3为由定性温度

确定的空气密度，kg/m³；c_A3为由定性温度

确定的空气比热容，J/(kg·K)；ν_A3为由定性温度

确定的空气运动粘性系数，m²/s；λ_A3为由定性温度

确定的空气导热系数，W/(m·K)；In the above formula: Q _C3.1 is the heat taken away by air convection in the horizontal projection area of the furnace bottom part of the furnace body area of the electric arc furnace, J; h _3.1 is the air convection average surface convective conversion of the horizontal projection area of the furnace bottom part of the furnace body area of the electric arc furnace Thermal coefficient, W/(m ² ·K); A _d3.1 is the area of the horizontal projection area of the furnace bottom part of the furnace body area of the electric arc furnace, m ² ; P _d3 is the circumference of the horizontal projection area of the furnace bottom part of the furnace body area of the electric arc furnace Length, m; T ₃ and T _A3 respectively represent the average temperature of the bottom part of the furnace body area of the electric arc furnace and the surrounding mainstream air temperature, K; g is the acceleration of gravity, m/s ² , the recommended value is 9.81m/s ² ;

is the air qualitative temperature determined by the average temperature of the furnace bottom part of the furnace body area of the electric arc furnace and the surrounding mainstream air temperature, determined by formula (3-54), K; ρ _A3 is the qualitative temperature

Determined air density, kg/m ³ ; c _A3 is the qualitative temperature

Determined specific heat capacity of air, J/(kg·K); ν _A3 is determined by the qualitative temperature

Determined air kinematic viscosity coefficient, m ² /s; λ _A3 is the qualitative temperature

Determined air thermal conductivity, W/(m K);

(2) Calculation of convective heat transfer heat in the vertical projection area of the furnace bottom part of the furnace body area of the electric arc furnace

The area of vertical projection should be a cylinder, and its vertical area is:

Sum formulas (3-2), (3-4), (3-6), (3-7) selected according to the numerical ranges of laminar flow, transitional flow and turbulent flow in Table 3-1, and take the furnace body area of the electric arc furnace The characteristic dimension l=H ₃ of the vertical projection area of the furnace bottom part can be combined with the geometric characteristics of the vertical projection area of the furnace bottom part of the furnace body area of the electric arc furnace to obtain the vertical projection area of the furnace bottom part of the furnace body area of the electric arc furnace The calculation formula of the average surface convective heat transfer coefficient and the calculation formula of the air convective heat transfer heat loss per unit time in the vertical projection area of the furnace bottom part of the furnace body area of the electric arc furnace, respectively, are formulas (3-57), (3-58) , (3-59) and formulas (3-60), (3-61), (3-62).

The calculation of the heat carried away in this vertical direction can be done by the following formula:

In the formula: Q _C3.2 is the heat taken away by air convection in the vertical projection area of the furnace bottom part of the furnace body area of the electric arc furnace, J; h _3.2 is the air convection average surface convection in the vertical projection area of the furnace bottom part of the furnace body area of the electric arc furnace Heat transfer coefficient, W/(m ² ·K); A _d3.2 is the area of the vertical projection area of the furnace bottom part in the furnace body area of the EAF, m ² ; H ₃ is the vertical projection area of the furnace bottom part in the furnace body area of the EAF Height of the area, m.

The specific application of formula (3-57), (3-58), (3-59) and formula (3-60), (3-61), (3-62) needs to be based on the bottom part of the furnace body area of the electric arc furnace The flow state of the surrounding air when the vertical projection area exchanges heat with the surrounding air is determined, and the conditions for its application are determined by equations (3-63), (3-64) and (3-65), as follows:

The heat loss from the bottom part of the furnace body area of the electric arc furnace due to air convection is as follows:

Q _C3 = Q _C3.1 + Q _C3.2 (3-66)

Therefore, the calculation formula for the heat loss of the furnace bottom part of the furnace body area of the electric arc furnace due to air convection and cooling water exchange heat transfer is:

Q ₃ =Q _W3 +Q _C3 (3-67)

3.4 Heat loss of the furnace cover part of the furnace body area of the electric arc furnace

There is a cooling water pipe on the outside of the furnace cover part of the furnace body area of the electric arc furnace, which is used to provide cooling protection for the furnace cover part of the electric arc furnace. calculate:

Q _W4 =c ₄ ρ ₄ V ₄ (T _out4 -T _in4 ) (3-68)

为由冷却水进、出口温度平均值确定的定性温度，由式(3-69)确定，K；c₄为由定性温度

确定的冷却水比热容，J/(kg·K)；ρ₄为由定性温度

确定的冷却水密度，kg/m³；V₄为电弧炉炉体区炉盖部分冷却水单位时间内的体积流量，m³。In the formula: Q _W4 is the heat taken away by the cooling water of the furnace cover part of the electric arc furnace body area, J; T _in4 and T _out4 are the inlet and outlet temperatures of the cooling water of the furnace cover part of the electric arc furnace body; K;

is the qualitative temperature determined by the average value of the cooling water inlet and outlet temperatures, determined by formula (3-69), K; c ₄ is the qualitative temperature

Determined specific heat capacity of cooling water, J/(kg K); ρ ₄ is the qualitative temperature

Determined cooling water density, kg/m ³ ; V ₄ is the volume flow of cooling water per unit time in the furnace cover part of the furnace body area of the electric arc furnace, m ³ .

Figure 9 shows the relevant view of the furnace cover part of the furnace body area of the electric arc furnace. The furnace cover part of the furnace body area of the electric arc furnace is connected with the upper furnace shell part of the furnace body area of the electric arc furnace. The furnace cover part of the furnace body area of the electric arc furnace has an inclined curved surface. The cover part projection is calculated. Therefore, when the convective heat exchange between the furnace cover and the surrounding air in the furnace body area of the electric arc furnace, the heat exchange surface has a vertical wall surface and a horizontal wall surface with the hot surface facing upward. Now calculate the average surface convective heat transfer coefficient of the two heat dissipation surfaces and Heat dissipation, its calculation process and formula are as follows.

(1) Calculation of convective heat transfer heat in the horizontal projection area of the furnace cover part of the furnace body area of the electric arc furnace

The horizontal projection area of the furnace cover part coincides with the horizontal projection of the upper furnace shell part of the furnace body area of the electric arc furnace, which is an area with the hot surface facing upward. The perimeter of the horizontal projection area is shown in formula (3-11), and the area is shown in formula (3-70).

The characteristic length of the horizontal projection area of the furnace bottom part of the furnace body area of the electric arc furnace can be determined according to the formula (3-8), that is, the characteristic length is:

Calculated values, calculation ranges and equations (3-2), (3-4), (3-6), (3-7), (3-71) for heating fluid with the horizontal hot surface facing up in Table 3-1 , the calculation formula of the average surface convection heat transfer coefficient of the horizontal heat exchange area of the furnace cover part of the furnace body area of the EAF and the calculation formula of the average surface convection heat transfer coefficient of the furnace cover part of the furnace body area of the EAF can be obtained by combining the geometric characteristics of the horizontal heat exchange area of the furnace cover part The calculation formulas for the heat loss of air convection heat transfer per unit time in the horizontal heat exchange area of the cover part are formulas (3-72), (3-73) and formulas (3-74), (3-75).

The specific applications of formulas (3-72), (3-73) and (3-74) and (3-75) need to be based on the flow state of the surrounding air when the lower furnace shell part of the electric arc furnace body area exchanges heat with the surrounding air. The specific application is determined by formulas (3-77) and (3-38) respectively, as follows:

为由电弧炉炉体区炉盖部分平均温度和周围主流空气温度确定的空气定性温度，由式(3-76)确定，K；ρ_A4为由定性温度

确定的空气密度，kg/m³；c_A4为由定性温度

确定的空气比热容，J/(kg·K)；ν_A4为由定性温度

确定的空气运动粘性系数，m²/s；λ_A4为由定性温度

确定的空气导热系数，W/(m·K)；In the formula: Q _C4.1 is the heat taken away by air convection in the horizontal projection area of the furnace cover part of the furnace body area of the electric arc furnace, J; h _4.1 is the average surface convection heat transfer of air convection in the horizontal projection area of the furnace cover part of the furnace body area of the electric arc furnace Coefficient, W/(m ² ·K); A _d4.1 is the area of the horizontal projection area of the furnace cover part in the furnace body area of the electric arc furnace, m ² ; P _d4 is the perimeter of the horizontal projection area of the furnace cover part in the furnace body area of the electric arc furnace , m; T ₄ and T _A4 represent the average temperature of the furnace cover part of the electric arc furnace body area and the surrounding mainstream air temperature, K; g is the acceleration of gravity, m/s ² , the recommended value is 9.8m/s ² ;

is the air qualitative temperature determined by the average temperature of the furnace cover part of the furnace body area of the electric arc furnace and the surrounding mainstream air temperature, determined by the formula (3-76), K; ρ _A4 is the qualitative temperature

Determined air density, kg/m ³ ; c _A4 is the qualitative temperature

Determined specific heat capacity of air, J/(kg·K); ν _A4 is the qualitative temperature

Determined air kinematic viscosity coefficient, m ² /s; λ _A4 is the qualitative temperature

Determined air thermal conductivity, W/(m K);

(2) Calculation of convective heat transfer heat in the vertical projection area of the furnace cover part of the furnace body area of the electric arc furnace

For the vertical projection area of the furnace cover, it is a vertical cylinder wall, so the calculation formula of the heat exchange surface area in the vertical direction is:

A _d4.2 =πd ₁ H ₄ (3-79)

Sum formulas (3-2), (3-4), (3-6), (3-7) selected according to the numerical ranges of laminar flow, transitional flow and turbulent flow in Table 3-1, and take the furnace body area of the electric arc furnace The characteristic dimension l=H ₄ of the vertical projection area of the furnace cover part can be combined with the geometric characteristics of the vertical projection area of the furnace cover part of the furnace body area of the electric arc furnace to obtain the vertical projection area of the furnace cover part of the furnace body area of the electric arc furnace The calculation formula of the average surface convective heat transfer coefficient and the calculation formula of the air convective heat transfer heat loss per unit time in the vertical projection area of the furnace cover part of the furnace body area of the electric arc furnace are respectively formulas (3-80) and (3-81) , (3-82) and formulas (3-83), (3-84), (3-85).

In the formula: Q _C4.2 is the heat taken away by air convection in the vertical projection area of the furnace cover part of the furnace body area of the electric arc furnace, J; h _4.2 is the air convection average surface convection in the vertical projection area of the furnace cover part of the furnace body area of the electric arc furnace Heat transfer coefficient, W/(m ² ·K); A _d4.2 is the area of the vertical projection area of the furnace cover in the furnace body area of the electric arc furnace, m ² ; H ₄ is the vertical projection of the furnace cover part in the furnace body area of the electric arc furnace Height of the area, m.

The specific application of formula (3-80), (3-81), (3-82) and formula (3-83), (3-84), (3-85) needs to be based on the bottom part of the furnace body area of the electric arc furnace The flow state of the surrounding air when the vertical projection area exchanges heat with the surrounding air is determined, and the conditions for its application are determined by equations (3-86), (3-87) and (3-88), as follows:

Finally, the heat loss of the furnace cover part of the furnace body area of the electric arc furnace due to air convection is:

Q _C4 = Q _C4.1 + Q _C4.2 (3-89)

Therefore, the calculation formula of the heat loss of the furnace cover part of the furnace body area of the electric arc furnace due to air convection and cooling water exchange heat transfer is:

Q ₄ =Q _W4 +Q _C4 (3-90)

3.5 Radiation heat transfer heat loss in the furnace body area of the electric arc furnace

The furnace body has a high temperature during the smelting process, which will radiate a lot of heat to external objects. The radiant heat loss of the EAF furnace body mainly includes the radiative heat transfer heat loss of the EAF furnace body and the radiative heat transfer heat loss of the EAF furnace door.

3.5.1 Radiation heat transfer heat loss of electric arc furnace body

The electric arc furnace is located in a closed workshop, and it performs radiative heat exchange with the walls of the workshop, which belongs to the radiative heat transfer between the cavity and the inner wall between the actual objects. The main purpose of the calculation is to determine the net radiative heat transfer between the electric arc furnace body and the surrounding walls. .

The net radiative heat transfer per unit time between the surface of the electric arc furnace body and the inner wall of the factory is calculated by formula (3-91):

In the formula: Q _5.1 is the net radiation heat exchange per unit time between the surface of the electric arc furnace body and the surrounding walls, W; ε _R is the emissivity of the electric arc furnace body, also known as blackness, and its value is always less than 1, It is related to the type and surface state of the object, but has nothing to do with the surrounding environment; _AR is the surface area of the electric arc furnace body area, m ² ; σ is the Stephen-Boltzmann constant, which is 5.67×10 ^-8 W/(m ² · K ⁴ ); _TW and _TA are the average temperature of the surface of the furnace body area of the electric arc furnace and the surface of the surrounding wall, K.

This formula is the formula for calculating the radiative heat transfer between the furnace body and the surrounding walls of the electric arc furnace, and it is also the recommended formula. This method requires less physical quantities to be measured, and the calculated order of magnitude will not be much different. .

It should be pointed out that since the electric arc furnace body is not located in the geometric center area of the steelmaking plant, the radiation energy received by the surrounding walls is not uniform, resulting in different temperatures on the surrounding wall surfaces. Therefore, it is recommended that the value of T _A should be The average temperature of each wall surface in the electric arc furnace steelmaking workshop; at the same time, because the electric arc furnace body is divided into the upper furnace shell part, the lower furnace shell part, the furnace bottom part and the furnace cover part, different parts because the heat transfer from the furnace to the outside of the furnace is not the same. Therefore, it is suggested that the value of _TW should be the average temperature of the upper shell part, the lower furnace shell part, the furnace bottom part and the furnace cover part of the furnace body area of the electric arc furnace.

3.5.2 Radiation heat transfer heat loss at the door of the electric arc furnace

The inside of the gate 3 of the electric arc furnace is high temperature molten steel 4, and the outside is air with a lower temperature, and the radiant heat is also large. The molten steel in the electric arc furnace can be regarded as a black body, and the calculation method of black body radiation in hemispheric space is used. Calculation, the calculation diagram is shown in Figure 10:

Radiation force of molten steel inside the electric arc furnace:

E _b =σT ⁴ (3-92)

In the formula: E _b is the radiant energy of the molten steel per unit time and unit radiation area, W/m ² ; T is the surface temperature of the molten steel, K;

The total energy radiated by the molten steel facing the upper hemispherical space:

F _A = AE _b (3-93)

In the formula: A is the molten steel surface area, m ² . When the molten steel depth is relatively large, the molten steel surface can be regarded as a circle, and it can be calculated by formula (3-94). It is recommended to directly obtain the area A from the CAD drawing of the electric arc furnace molten pool without intervening d, but d can also be introduced.

Where: d is the diameter of the molten steel surface, m. Equations (3-93) and (3-94) can be determined according to the parameters obtained by specific measurement, and their essence is the same.

The directional radiation intensity of molten steel inside the electric arc furnace is:

The furnace door should be located directly above the molten steel surface and offset by a certain distance. Therefore, from Figure 10, the input radiation energy of the internal molten steel obtained from the furnace door of the electric arc furnace is:

Where: H _d is the height from the center of the furnace door to the center of the molten steel surface, m; _ri is the radius of the molten steel surface, m; L _d is the distance from the center of the furnace door to the center of the molten steel surface, m; θ is the angle between the height from the furnace door to the molten steel level and the line connecting the center of the furnace door and the center of the molten steel surface; _Ad is the area of the furnace door, m ² . Putting equations (3-92) and (3-95) into equation (3-97), the final calculation formula of radiation heat transfer heat loss at the gate of the electric arc furnace is obtained:

Based on the above theoretical calculation and analysis, the calculation formula of radiation heat transfer heat loss in the furnace body area of the electric arc furnace is:

To sum up, the calculation formula of the total heat loss in the furnace body area due to cooling water, air convection heat exchange and radiation heat exchange between the furnace body and the wall surface of the surrounding building envelope during the EAF steelmaking process is:

Q=Q ₁ +Q ₂ +Q ₃ +Q ₄ +Q ₅ (3-99)

The above calculations need to pay attention to the following points:

(1) Air is regarded as an ideal gas in the calculation process. The temperature of the mainstream air side of the upper shell part, lower furnace shell part, furnace bottom part and furnace cover part of the furnace body area of the electric arc furnace is uniform and consistent, but there may be temperature differences in different parts of the region. The difference depends on the air temperature measurement value of the specific occasion.

(2) All the parameters mentioned in the text determined by the qualitative temperature can be obtained by checking the "Table of Physical Properties of Dry Air" or "Table of Thermophysical Properties of Saturated Water".

(3) For the calculation of the upper furnace shell part and the lower furnace shell part, it is simplified as a cylinder; for the irregular area of the furnace bottom part and the furnace cover part, it is simplified as a horizontal projection and a vertical projection. Calculation is performed, in which the calculation of vertical projection is simplified as a cylinder for calculation.

(4) Only the final result is given in this paper, and the derivation process is not given, and the characteristic parameters are also expressed as parameters that are easy to measure.

(5) The acquisition of temperature parameters should be based on the parameters measured in the actual steel mill environment. The mainstream air temperature refers to the temperature of the air stream that is at a certain distance from the surface of the furnace body and is not affected by the surface temperature of the furnace body and the temperature remains unchanged. Among them, for the measurement of air temperature in different parts of the region, it is recommended to arrange measuring points at intervals of 1.5m in the vertical direction along the circumferential direction, every 60°, and measure the mainstream air temperature. For the acquisition of temperature parameters in different parts of the furnace body area of the electric arc furnace, thermocouple measuring points or infrared measuring points should be arranged on the surface of the relevant parts. It is recommended to arrange a measuring point every 60° in the circumferential direction and every 80cm in the vertical direction in the corresponding part. point to obtain the temperature parameters of each component.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any form. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solutions of the present invention should fall within the protection scope of the technical solutions of the present invention.

Claims (5)

1. the heat loss calculation method of furnace body distinguishing area in a kind of electric arc furnace steelmaking process, it is characterized in that, electric arc furnace furnace body area is divided into upper furnace shell part, lower furnace shell part, furnace bottom part and furnace cover part, Calculate the heat loss Q ₁ of the upper furnace shell part, the heat loss Q ₂ of the lower furnace shell part, the heat loss Q ₃ of the furnace bottom part, the heat loss Q ₄ of the furnace cover part and the radiation heat transfer heat loss Q ₅ of the furnace body area, and then according to the following The total heat loss Q is calculated as: Q=Q ₁ +Q ₂ +Q ₃ +Q ₄ +Q ₅ Among them, Q ₁ includes the heat Q _W1 carried away by the cooling water in the upper furnace shell and the heat Q _C1 carried away by the air convection in the upper furnace shell; Q ₂ includes the heat Q _W2 taken away by the cooling water in the lower furnace shell and the lower furnace shell. The heat Q _C2 carried away by air convection, Q _C2 includes the air convection heat loss Q _C2.1 per unit time in the vertical wall of the lower furnace shell and the air convection heat loss Q _C2 per unit time in the horizontal heat exchange area of the lower furnace shell _.2 ; _Q3 includes the heat Q _W3 carried away by the cooling water in the furnace bottom part and the heat Q _C3 taken away by the air convection in the furnace bottom part, and Q _C3 includes the heat taken away by the air convection in the horizontal projection area of the furnace bottom part Q _C3.1 and The heat Q _C3.2 carried away by the air convection in the vertical projection area of the furnace bottom part; Q ₄ includes the heat Q _W4 carried away by the cooling water in the furnace cover part and the heat Q _C4 taken away by the air convection in the furnace cover part, and Q _C4 includes the furnace cover The heat Q _C4.1 carried away by air convection in part of the horizontal projection area and the heat Q _C4.2 carried away by air convection in the vertical projection area of the furnace cover; Q ₅ includes the unit time net between the surface of the electric arc furnace body and the surrounding walls Radiant heat transfer heat Q _5.1 and radiant heat transfer heat loss G at the door of the electric arc furnace; Q _W1 is calculated by: Q _W1 =c ₁ ρ ₁ V ₁ (T _out1 -T _in1 )

In the formula: T _in1 and T _out1 are the inlet and outlet temperatures of the cooling water in the upper furnace shell part of the furnace body area of the electric arc furnace respectively;

is the qualitative temperature determined by the average temperature of the cooling water inlet and outlet; c ₁ is the qualitative temperature

Determined specific heat capacity of cooling water; ρ ₁ is determined by the qualitative temperature

Determined cooling water density; V ₁ is the volume flow rate of cooling water in the upper furnace shell part of the electric arc furnace body area per unit time; Q _C1 is calculated by:

In the formula: d ₁ is the outer diameter of the cylinder of the upper furnace shell part of the furnace body area of the electric arc furnace; H ₁ is the height of the cylinder part of the upper furnace shell part of the furnace body area of the electric arc furnace; T ₁ and T _A1 respectively represent the furnace body area of the electric arc furnace The average temperature of the upper furnace shell and the surrounding mainstream air temperature; g is the acceleration of gravity;

is the qualitative air temperature determined by the average temperature of the upper furnace shell in the furnace body area of the electric arc furnace and the ambient mainstream air temperature; ρ _A1 is the qualitative temperature determined by

Determined air density; c _A1 is determined by the qualitative temperature

Determined air specific heat capacity; v _A1 is the qualitative temperature

Determined air kinematic viscosity coefficient; λ _A1 is determined by the qualitative temperature

Determined air thermal conductivity; The conditions corresponding to the first three equations above are:

The calculation of Q _W2 is the same as that of Q _W1 , and Q _C2.1 is calculated by the following formula:

The conditions corresponding to the first three equations above are:

In the formula: H ₂ is the height of the cylinder of the lower furnace shell in the furnace body area of the electric arc furnace; T ₂ and T _A2 represent the average temperature of the lower furnace shell part and the surrounding mainstream air temperature in the furnace body region of the electric arc furnace respectively; g is the acceleration of gravity;

is the air qualitative temperature determined by the average temperature of the lower furnace shell in the furnace body area of the electric arc furnace and the ambient mainstream air temperature; ρ _A2 is the qualitative temperature determined by

Determined air density; c _A2 is determined by the qualitative temperature

Determined air specific heat capacity; v _A2 is determined by the qualitative temperature

Determined air kinematic viscosity coefficient; λ _A2 is determined by the qualitative temperature

Determined air thermal conductivity; Angles A and B are the actual fan-shaped angles of the top of the furnace bottom part of the furnace geometry model of the electric arc furnace; R is the reference circle radius of the top surface of the furnace bottom part of the furnace body area of the electric arc furnace; D is the connection to the furnace body of the electric arc furnace The length of the hypotenuse of the reference circle on the top surface of the furnace bottom part of the zone; Q _C2.2 is calculated by the following formula:

The corresponding conditions for the above two equations are:

The calculation of Q _W3 is the same as that of Q _W1 , and Q _C3.1 is calculated by the following formula:

In the formula: A _d3.1 is the area of the horizontal projection area of the furnace bottom part of the furnace body area of the electric arc furnace; A _2.2 is the horizontal heat exchange surface area of the lower furnace shell part of the furnace body area of the electric arc furnace; l _2.1 is the lower part of the furnace body area of the electric arc furnace. The characteristic length of the horizontal heat exchange area of the furnace shell part; P _d3 is the perimeter of the horizontal projection area of the furnace bottom part of the furnace body area _of the EAF; T3 and T _A3 respectively represent the average temperature of the furnace bottom part of the furnace body area of the EAF and the surrounding mainstream air temperature; g is the acceleration of gravity;

is the air qualitative temperature determined by the average temperature of the furnace bottom part of the furnace body area of the electric arc furnace and the surrounding mainstream air temperature; ρ _A3 is the qualitative temperature determined by

Determined air density; c _A3 is the qualitative temperature

Determined air specific heat capacity; ν _A3 is determined by the qualitative temperature

Determined air kinematic viscosity coefficient; λ _A3 is determined by the qualitative temperature

Determined air thermal conductivity; The calculation of Q _W4 is the same as that of Q _W1 , and the calculation of Q _C4.1 is as follows:

The application conditions of the above two formulas are:

In the _formula : T4 and T _A4 represent the average temperature of the furnace cover part and the surrounding mainstream air temperature in the furnace body area of the electric arc furnace respectively; g is the acceleration of gravity;

is the air qualitative temperature determined by the average temperature of the furnace cover part of the furnace body area of the electric arc furnace and the surrounding mainstream air temperature; ρ _A4 is the qualitative temperature determined by

Determined air density; c _A4 is the qualitative temperature

Determined specific heat capacity of air; ν _A4 is determined by the qualitative temperature

Determined air kinematic viscosity coefficient; λ _A4 is determined by the qualitative temperature

Determined thermal conductivity of air. 2. in the electric arc furnace steelmaking process according to claim 1, the heat loss calculation method of furnace body distinguishing area is characterized in that, Q _C3.2 adopts following formula to calculate:

In the formula: H ₃ is the height of the vertical projection area of the furnace bottom part of the furnace body area of the electric arc furnace; The corresponding conditions for the above three equations are:

3. in the electric arc furnace steelmaking process according to claim 1, the heat loss calculation method of the furnace body division area is characterized in that, the calculation of Q _C4.2 is as follows:

In the _formula : H4 is the height of the vertical projection area of the furnace cover part of the furnace body area of the electric arc furnace; The application conditions of the above three formulas are:

4. The method for calculating heat loss in different regions of the furnace body in the electric arc furnace steelmaking process according to any one of claims 1 to 3, wherein the calculation of Q _5.1 is as follows:

Among them: ε _R is the emissivity of the electric arc furnace body; _AR is the surface area of the electric arc furnace body area; σ is the Stephen-Boltzmann constant; _TW and T _A are the surface of the electric arc furnace body area and the surrounding wall surface, respectively average temperature. 5. the heat loss calculation method of furnace body division area in electric arc furnace steelmaking process according to claim 4, is characterized in that, the calculation of G is as follows:

Among them: T is the surface temperature of the molten steel; A is the liquid steel surface area; L _d is the distance from the center of the furnace door to the center of the molten steel surface; θ is the height from the furnace door to the molten steel surface and the center of the furnace door and the center of the molten steel The included angle of the line connecting the center of the liquid level; A _d is the area of the furnace door.

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