CN112446134B - Method for calculating heat loss of furnace body region in electric arc furnace steelmaking process - Google Patents
Method for calculating heat loss of furnace body region in electric arc furnace steelmaking process Download PDFInfo
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Abstract
The invention discloses a method for calculating heat loss of furnace body regions in the steelmaking process of an electric arc furnace 1 Lower furnace shell part heat loss Q 2 Heat loss Q of furnace bottom 3 Heat loss Q of furnace cover part 4 And furnace body area radiation heat transfer heat loss Q 5 And then calculates the total heat loss Q. The method is based on the division of the electric arc furnace body, and simultaneously calculates the heat loss of each area according to the temperature characteristics, the geometric parameters and the relative positions of different partial areas of the furnace body area of the electric arc furnace, so that the reliability and the universality of the result can be ensured. And the parameters in the final calculation formula can be directly measured and obtained, so that the complicated measurement steps are reduced.
Description
Technical Field
The invention belongs to the technical field of steelmaking, and particularly relates to a method for calculating heat loss of furnace regions in an electric arc furnace steelmaking process.
Background
The steel-making energy composition of the electric arc furnace is diversified and complex, and the energy change and the furnace body heat dissipation fluctuation of a molten pool at each stage are caused by the operations of oxygen supply, power supply and the like in the smelting process; the temperature rise of the molten steel pool is generated under the synergistic action of multiple energy modes such as chemical reaction heat, electric energy, heat dissipation and the like. Heat loss during the steelmaking process in an electric arc furnace is an important factor affecting energy efficiency.
Researchers at home and abroad mainly develop heat and mass exchange modes, characteristics and influence factors of materials such as scrap steel, molten steel, slag and the like around a molten pool area, and focus on the flow and heat transfer mechanism inside the molten steel, but most of heat loss and material output in the steelmaking process of an electric arc furnace are carried out outside the electric arc furnace, the research on radiation heat transfer caused by high temperature difference between the furnace body of the electric arc furnace and the external environment and convection heat transfer caused by fluid flow is very little, the heat loss cannot be quantified through a specific measuring instrument and a calculation means at present, enough attention is not paid, the reliability and universality of a calculation result are not ideal, and the optimization of the steelmaking energy structure of the electric arc furnace is greatly influenced.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects and shortcomings in the background art, and provide a method for calculating the heat loss of the furnace body regional area in the steelmaking process of the electric arc furnace, so as to improve the reliability and universality of the calculation result.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
a method for calculating the heat loss of furnace body in different regions during smelting steel in electric arc furnace features that the furnace body is divided into upper and lower portions, bottom and cover, and the heat loss Q of upper portion is calculated 1 Lower furnace shell part heat loss Q 2 Heat loss Q of furnace bottom 3 Heat loss Q of furnace cover part 4 And the radiant heat transfer loss Q of the furnace body area 5 The total heat loss Q is then calculated.
Wherein Q 1 IncludedThe heat taken away by the cooling water of the upper furnace shell part and the heat taken away by the air convection of the upper furnace shell part; q 2 Including the heat taken away by the cooling water of the lower furnace shell part and the heat taken away by the air convection of the lower furnace shell part, Q C2 Air convection heat loss Q in unit time of vertical wall surface of lower furnace shell part C2.1 Air convection heat loss Q in unit time of horizontal heat exchange area of lower furnace shell part C2.2 ；Q 3 Comprises heat quantity taken away by cooling water at the bottom of the furnace and heat quantity Q taken away by air convection at the bottom of the furnace C3 ，Q C3 The heat convection of the air in the horizontal projection area at the bottom of the furnace and the heat convection of the air in the vertical projection area at the bottom of the furnace are carried out; q 4 Comprises heat quantity Q brought away by cooling water in the furnace cover part and air convection in the furnace cover part C4 ，Q C4 The furnace cover comprises heat carried away by air convection in a horizontal projection area of the furnace cover part and heat carried away by air convection in a vertical projection area of the furnace cover part; q 5 The method comprises the net radiation heat exchange quantity per unit time between the surface of the electric arc furnace body and the surrounding wall and the radiation heat transfer and loss G at the furnace door of the electric arc furnace.
Compared with the prior art, the invention has the beneficial effects that:
(1) The method is based on the division of an electric arc furnace body, meanwhile, the electric arc furnace body is divided into an upper furnace shell part, a lower furnace shell part, a furnace bottom part and a furnace cover part according to the temperature characteristics, the geometric parameters and the relative positions of different part regions of the electric arc furnace body area, the heat loss of each region is calculated respectively, and the reliability and universality of results can be guaranteed. And the parameters in the final calculation formula can be directly measured and obtained, so that the complicated measurement steps are reduced.
(2) The convective heat transfer coefficient h value between the furnace body area and the ambient air in the electric arc furnace steelmaking process is determined in a calculation mode, and is not selected by means of empirical parameters. And the measuring mode of the temperature parameter is defined, so that the method is more suitable for the requirement of actual calculation.
(3) The magnitude of heat loss of the furnace body area in the process of electric arc furnace steelmaking can be visually known and quantified, and the theoretical basis for green smelting, energy conservation and consumption reduction of electric arc furnace steelmaking is laid.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a division of the overall zone and the geometric construction of the body zone of an electric arc furnace;
FIG. 2 is a detailed division of the furnace zone components of the electric arc furnace;
FIG. 3 is a perspective view of an electric arc furnace body section;
FIG. 4 is a perspective view of a shell section on a body section of an electric arc furnace;
FIG. 5 is a perspective view of a lower shell section of the electric arc furnace body zone;
FIG. 6 is a horizontal heat exchange surface at the junction of the lower shell portion and the upper shell portion of the electric arc furnace body section;
FIG. 7 is a top plan view of a horizontal projection of a lower shell portion of the furnace body of the electric arc furnace and its associated parameters;
FIG. 8 is a bottom perspective view of the electric arc furnace body section;
FIG. 9 is a perspective view of a lid portion of the body section of the electric arc furnace;
FIG. 10 is a schematic view of the radiant heat exchange between molten steel in the electric arc furnace and the furnace door opening.
Wherein: 1. a furnace body area; 2. a molten pool zone; 11. a furnace lid portion; 12. an upper shell portion; 13. a lower furnace shell portion; 14. the furnace bottom part; 3. a furnace door opening; 4. and (3) molten steel.
Detailed Description
In order to facilitate understanding of the invention, the invention will be described more fully and in detail with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.
Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.
The invention provides a method for calculating heat loss of furnace body regions in the process of electric arc furnace steelmaking based on the basic theory of heat transfer science, which is used for determining the magnitude order of radiation heat transfer and convection heat transfer heat loss caused by large temperature difference between an electric arc furnace body with higher temperature and a surrounding building envelope structure with lower temperature, air and cooling water in the process of electric arc furnace steelmaking, and the magnitude of the heat loss is known from the visual angle. The mathematical modeling and theoretical derivation process of the invention is as follows:
electric arc furnace zoning and heat transfer behavior
1.1 electric arc furnace zoning
The characteristics and the way of heat transfer in the process of electric arc furnace steelmaking were analyzed, and the electric arc furnace was divided into a "molten pool zone" and a "furnace zone", as shown in fig. 1. In the figure, a molten pool area 2 is a part surrounded by a black dotted line, mainly refers to a molten pool area in an electric arc furnace, the inside of the molten pool area mainly contains molten steel and slag, and injected supplementary materials such as oxygen, carbon powder and the like, and is a main area for carrying out chemical reaction and heat and mass transfer in the electric arc furnace, and a furnace body area 1 refers to an area outside the molten pool area of the electric arc furnace, namely the part outside the black dotted line, and mainly refers to physical construction factors of an electric arc furnace body, such as geometric elements of an upper furnace shell, a lower furnace shell and the like.
Through the step, the electric arc furnace body is partitioned, and meanwhile, a calculation area, namely a furnace body area, of the method is shown, and the method mainly calculates the heat loss between the furnace body area and the surrounding environment in the electric arc furnace steelmaking process.
1.2 Heat transfer behavior of furnace zone
Analyzing the heat loss of the electric arc furnace body area to obtain the heat dissipation mode of the electric arc furnace body area, wherein the heat dissipation mode mainly comprises the following steps:
(1) An object emits radiant energy due to various causes, and a phenomenon in which radiant energy is emitted due to heat is called thermal radiation. Various chemical reactions occur in the electric arc furnace, external input energy exists, the temperature of the furnace body area is high in the smelting process, and a large amount of heat can be radiated to an external object. The radiation heat transfer heat loss generated by the temperature difference between the furnace body area of the electric arc furnace with higher temperature and the building envelope with lower ambient temperature is the radiation heat transfer between the cavity and the inner packing wall. The radiation heat loss of the electric arc furnace body mainly comprises the radiation heat loss of the electric arc furnace body and the radiation heat loss of the electric arc furnace door.
(2) In the smelting process of the electric arc furnace, the temperature of the furnace body is high, air in the surrounding environment is heated and rises, and convective heat exchange is carried out between the air and the furnace body, and the convective heat exchange mode belongs to large-space natural convective heat exchange.
(3) The regions such as electric arc furnace shell, bell cause overheated damage in order to prevent that the temperature is too high, often need provide the cooling water with the help of coiling at the regional cooling water piping of relevance and cool down, carries out heat convection between cooling water and the electric arc furnace body, and the heat transfer mode is dividing wall type heat convection.
The main purpose of the step is to divide the electric arc furnace into zones, and simultaneously judge the type and the mode of the heat loss of the furnace body area in the steel-making process of the electric arc furnace, so that the subsequent calculation is convenient.
2 electric arc furnace body area geometric constitution and heat transfer characteristics
Based on the division of the electric arc furnace body, the electric arc furnace body is divided into an upper furnace shell part 12, a lower furnace shell part 13, a furnace bottom part 14 and a furnace cover part 11 according to the temperature characteristics, the geometric parameters and the relative positions of different partial areas of the electric arc furnace body area, and the four parts form the geometric elements of the electric arc furnace body area.
As shown in fig. 1, the hearth portion 14 refers to a region of the hearth of the electric arc furnace, and more particularly, to an inclined curved portion and a part of the vertical plane of the hearth of the body region of the electric arc furnace, as shown in fig. 2. The heat transfer characteristic is that when the heat transfer is carried out with the air in the surrounding environment, the heat transfer is carried out by the convection of the air heated by the vertical wall surface and the heat transfer by the convection of the air heated by the downward hot surface.
The lower furnace shell part 13 is a lower furnace shell in the geometrical structure of the electric arc furnace, mainly refers to a vertical column body region coupled with the furnace bottom part of the furnace body region of the electric arc furnace and a part of horizontal region, and has the heat transfer characteristic that when the convection heat transfer is carried out between the lower furnace shell part and the air in the surrounding environment, the convection heat transfer is carried out for heating the air on the vertical wall surface and the convection heat transfer is carried out for heating the air with the hot surface facing upwards.
The upper shell portion 12 is the upper shell of the arc furnace geometry, and is primarily the area coupled to the lower shell and lid portions of the arc furnace, and is characterized by heat transfer by convection with the air in the surrounding environment, which heats the air to the vertical wall.
The lid portion 11 comprises an electric arc furnace lid and an annular region around the electric arc furnace lid, and is characterized by heat transfer by convection heat transfer between air in the surrounding environment, for heating air with a vertical wall surface, and for heating air with a hot surface facing upward.
The step is carried out for further dividing the furnace body area of the electric arc furnace, and different heat transfer calculation modes are subsequently adopted according to the heat transfer characteristics of different components to obtain the heat transfer loss of the relevant components.
3 furnace zone heat loss of electric arc furnace
Based on the above analysis, the heat loss of the furnace body area in the steelmaking process of the electric arc furnace comprises the heat loss of the furnace shell part on the furnace body area of the electric arc furnace, the heat loss of the furnace shell part under the furnace body area of the electric arc furnace, the heat loss of the furnace bottom part of the furnace body area of the electric arc furnace and the heat loss of the furnace cover part of the furnace body area of the electric arc furnace. The relative size of the four heat losses is determined, so that the final total heat loss, namely the heat loss of the furnace body area in the steelmaking process of the electric arc furnace, can be obtained by utilizing the energy additivity.
Based on the previous analysis, the heat loss path in the furnace zone of the electric arc furnace mainly comprises the following three parts:
(1) The heat lost between the components of the furnace area of the electric arc furnace and the cooling water flowing through the furnace area is in the way of partition wall heat exchange.
(2) The heat lost between each component of the furnace body area of the electric arc furnace and the air in the surrounding environment in a large-space natural convection heat exchange mode.
(3) The heat lost between the components of the furnace zone of the electric arc furnace and the surrounding building envelope is conducted in a radiant heat transfer manner in the form of a cavity and an inner cladding.
The calculation process of the heat loss caused by convective heat transfer of air in the furnace body area of the electric arc furnace and the surrounding environment is complex, the selection of various situations, judgment and calculation formulas and the determination of criterion numbers and characteristic numbers are involved, and an effective calculation method is not available in the field of electric arc furnace steelmaking at the present stage, and only can be selected from empirical data.
The following is a calculation process focusing on analyzing the heat loss of the components in the furnace area of the electric arc furnace and the heat loss of the convection heat exchange of the air in the surrounding environment.
The fourth edition of "heat transfer science", pages P269 to PP271, provides experimental correlations for natural convection in large spaces:
wherein:
in the formula: nu (Nu) m The Nusselt number represents the relative size of a dimensionless temperature gradient on the wall surface of the electric arc furnace; gr is the Gravadaff number, which represents the natural convection flow state, the relative size of the buoyancy lift force and the viscous force; pr is a Plantt number and represents the relative magnitude of momentum diffusion capacity and thermal diffusion capacity; g is the acceleration of gravity, m/s 2 The suggested value is 9.81m/s 2 ；α V The coefficient of bulk expansion of the fluid (air) surrounding the furnace zone of the electric arc furnace, within the Gr number for a gas corresponding to the desired gas properties
Wherein T is qualitative temperature, K; l is the characteristic length m of the heat exchange wall surface of the electric arc furnace body area through which the fluid (air) flows; v being a fluid determined by a qualitative temperature TCoefficient of viscosity in (air) movement, m 2 S; α is the thermal diffusion coefficient of the fluid (air), m 2 S; λ is the thermal conductivity of the fluid (air), W/(m · K); c is the specific heat capacity of the fluid (air) determined by the qualitative temperature T, J/(kg.K); ρ is the fluid (air) density, kg/m, determined by the qualitative temperature T 3 。
The prandtl number can therefore be further expressed as:
for the coefficient C and the index n in the formula (3-1), values can be taken according to the table 3-1 according to the actual fluid (air) flow state around the electric arc furnace body region.
TABLE 3-1 values of coefficient C and index n in equation (3-1)
Meanwhile, for the natural convection heat exchange process, nu m It can also be calculated from:
in the formula: h is the average surface convection heat transfer coefficient of the heat transfer wall surface of the electric arc furnace body area, W/(m) 2 ·K)；
Therefore, the calculation formula of the average surface convection heat transfer coefficient of the heat transfer wall surface of the furnace body area of the electric arc furnace can be obtained by the formulas (3-1) and (3-5):
and then can obtain the heat that is taken away because of convection heat transfer between electric arc furnace body district heat transfer wall and the surrounding air:
for the vertical wall surface of the furnace body area of the electric arc furnace, the height of the heat exchange wall surface is taken as the characteristic length l; for the horizontal heat exchange wall surface of the furnace body area of the electric arc furnace, the method is determined by the following formula:
in the formula: a. The P Is the heat exchange area of the horizontal heat exchange surface of the furnace body area of the electric arc furnace, m 2 (ii) a P is the perimeter length m of the horizontal heat exchange surface of the furnace body area of the electric arc furnace.
The size of the convection heat transfer coefficient of the heat transfer wall surface of the electric arc furnace body area can be determined by the formula (3-6), and the convection heat transfer quantity of the heat transfer wall surface of the electric arc furnace body area can be determined by the formula (3-7).
Therefore, heat loss calculation is carried out on the components of the furnace body area of the electric arc furnace, namely the upper furnace shell part, the lower furnace shell part, the furnace bottom part and the furnace cover part, so that the heat loss of each component is obtained, and a foundation is laid for the subsequent calculation of the total heat exchange heat loss in the steelmaking process of the electric arc furnace.
3.1 Heat loss from the furnace shell in the furnace zone of an electric arc furnace
The furnace shell part on the furnace zone of the electric arc furnace is shown in a relevant view in fig. 4. The outer side of the upper furnace shell part of the electric arc furnace body area is provided with a cooling water pipeline for cooling the upper furnace shell part of the electric arc furnace body area, and the quantity of heat taken away by cooling water of the upper furnace shell part of the electric arc furnace body area in unit time can be calculated by a formula (3-9):
Q W1 ＝c 1 ρ 1 V 1 (T out1 -T in1 ) (3-9)
in the formula: q W1 The heat taken away by the cooling water of the furnace shell part on the furnace body area of the electric arc furnace J; t is in1 And T out1 The temperatures of a cooling water inlet and a cooling water outlet of the furnace shell part on the furnace body area of the electric arc furnace are respectively measured; k;
is a qualitative temperature determined by the average value of the inlet temperature and the outlet temperature of the cooling water and is determined by the formula (3-10), K; c. C 1 Is determined by the qualitative temperature
The specific heat capacity of the cooling water is determined, and J/(kg.K); ρ is a unit of a gradient 1 Is determined by the qualitative temperature
Determined density of cooling water, kg/m 3 ；V 1 The volume flow m of cooling water per unit time for the furnace shell part on the furnace body area of the electric arc furnace 3 。
The temperature of the upper furnace shell part of the furnace body area of the electric arc furnace is high, and after the ambient air flows through the upper furnace shell part, a part of heat can be taken away due to convective heat transfer, and the calculation of the part of heat (convective heat transfer) can be carried out by the following calculation method:
outer circumference of the shell part on the electric arc furnace body zone:
P 1 ＝πd 1 (3-11)
therefore carry out heat convection between furnace shell portion and the air around in electric arc furnace body district, its heat transfer area is:
A 1 ＝P 1 H 1 ＝πd 1 H 1 (3-12)
the sum formula (3-2), (3-4), (3-6), (3-7) is selected according to the numerical ranges of laminar flow, transitional flow, turbulent flow in table 3-1, and the characteristic dimension l = H of the furnace shell part on the furnace body area of the electric arc furnace 1 So that the average surface pairs of the upper furnace shell parts of the furnace body area of the electric arc furnace can be obtained by combining the geometrical characteristics of the upper furnace shell parts of the furnace body area of the electric arc furnaceThe calculation formula of the heat transfer coefficient and the calculation formula of the heat loss of the air heat transfer convection in unit time of the furnace shell part on the furnace body area of the electric arc furnace are respectively the formulas (3-13), (3-14), (3-15) and the formulas (3-16), (3-17) and (3-18).
In the formula: q C1 Heat brought away by convection heat exchange of air of a furnace shell part on a furnace body area of the electric arc furnace J; h is 1 Is the average surface convection heat transfer coefficient of the furnace shell part on the furnace body area of the electric arc furnace, W/(m) 2 ·K)；d 1 The outer diameter m of the cylinder of the furnace shell part on the furnace body area of the electric arc furnace; h 1 M is the height of the shell cylinder on the furnace body area of the electric arc furnace; t is a unit of 1 And T A1 Respectively representing the average temperature of a furnace shell part on a furnace body area of the electric arc furnace and the temperature of surrounding main stream air, K; g is gravity accelerationDegree, m/s 2 The suggested value is 9.8m/s 2 ；
Is a qualitative temperature of air determined by the average temperature of the furnace shell part on the furnace body area of the electric arc furnace and the temperature of the ambient main stream air, determined by the formula (3-19), K; rho A1 Is determined by the qualitative temperature
Determined air density, kg/m 3 ；c A1 Is determined by the qualitative temperature
The determined air specific heat capacity, J/(kg. K); v is A1 Is determined by the qualitative temperature
Determined air movement viscosity coefficient, m 2 /s；λ A1 Is determined by the qualitative temperature
A determined air thermal conductivity, W/(m.K);
the specific application of the equations (3-13), (3-14), (3-15) and (3-16), (3-17) and (3-18) is determined according to the flowing state of the ambient air when the furnace shell part on the furnace body area of the electric arc furnace exchanges heat with the ambient air, and the specific application is determined by the equations (3-20), (3-21) and (3-22) respectively as follows:
therefore, the calculation formula of the heat loss of the furnace shell part on the furnace body area of the electric arc furnace brought away by air convection and cooling water heat exchange is as follows:
Q 1 ＝Q W1 +Q C1 (3-23)
wherein Q C1 The calculation formula (2) needs to be judged and selected according to the actual measured parameters.
3.2 Heat loss of lower furnace shell portion of furnace body area of electric arc furnace
There is cooling water pipeline outside the furnace shell portion under the electric arc furnace body district for the cooling of furnace shell portion under the electric arc furnace, the heat can be calculated by formula (3-24) in electric arc furnace body district lower furnace shell portion cooling water takes away the heat in unit time:
Q W2 ＝c 2 ρ 2 V 2 (T out2 -T in2 ) (3-24)
in the formula: q W2 The heat taken away by cooling water of the furnace shell part below the furnace body area of the electric arc furnace J; t is in2 And T out2 The temperatures of a cooling water inlet and a cooling water outlet of the lower furnace shell part of the furnace body area of the electric arc furnace are respectively set; k;
is a qualitative temperature determined by the average value of the inlet temperature and the outlet temperature of the cooling water and is determined by the formula (3-25), K; c. C 2 Is determined by the qualitative temperature
The specific heat capacity of the cooling water is determined, and J/(kg.K); ρ is a unit of a gradient 2 Is determined by the qualitative temperature
Determined density of cooling water, kg/m 3 ；V 2 The volume flow m of cooling water of the furnace shell part under the furnace body area of the electric arc furnace in unit time 3 。
The lower shell part of the furnace zone of the electric arc furnace is shown in a relative view in fig. 5. It should also be noted that when the lower shell part and the upper shell part of the furnace zone of the electric arc furnace are connected, there is a horizontal area, as shown in fig. 3 and 6. The furnace shell part under the electric arc furnace body area is internally provided with high-temperature molten steel, the surface temperature of the high-temperature molten steel is higher, and the surrounding air can take away a part of heat after flowing through the furnace shell part, so that when the furnace shell part under the electric arc furnace body area and the surrounding air carry out heat convection, the heat exchange surface is provided with a vertical wall surface and a horizontal wall surface with the hot surface facing upwards, and the average surface heat convection coefficient and the heat dissipation capacity of the two heat dissipation surfaces are required to be calculated respectively.
(1) Calculation of heat of convection heat transfer of vertical wall surface of lower shell part of electric arc furnace body zone
The relevant parameters in a plan view of the lower shell part of the furnace zone of the electric arc furnace are shown in fig. 7. At the same time, it should be noted that the horizontal projection of the furnace bottom part of the furnace body zone of the electric arc furnace and the horizontal projection of the furnace shell part of the furnace body zone of the electric arc furnace should coincide.
The perimeter and area of the horizontally projected irregular area of the shell portion below the furnace body section of the electric arc furnace can be calculated by the following formula:
so carry out the convective heat transfer between furnace shell portion and the surrounding air under the electric arc furnace body district, its heat transfer area is in vertical direction:
in the formula: the angles A and B are respectively the actual fan-shaped angles at the top of the bottom of the electric arc furnace; r is the reference circle radius of the top surface of the eccentric area at the bottom of the furnace body area of the electric arc furnace, m; r is the reference circle radius of the top surface of the bottom of the furnace body area of the electric arc furnace, m; l is the furnace length of the furnace bottom of the furnace body area of the electric arc furnace; d is the length of the bevel edge of a reference circle connected with the top surface of the furnace bottom of the furnace body area of the electric arc furnace, m;
the sum formula (3-2), (3-4), (3-6), (3-7) is selected according to the numerical ranges of laminar flow, transitional flow and turbulent flow in table 3-1, and the characteristic dimension l = H of the furnace shell part under the furnace body area of the electric arc furnace 2 The calculation formula of the average surface convection heat transfer coefficient of the vertical wall surface of the lower shell part of the electric arc furnace body area and the calculation formula of the air convection heat transfer heat loss of the vertical wall surface of the lower shell part of the electric arc furnace body area in unit time can be obtained by combining the geometrical characteristics of the lower shell part of the electric arc furnace body area, and the calculation formulas are respectively the formulas (3-29), (3-30), (3-31) and (3-32), (3-33) and (3-34).
In the formula: q C2 For electric arc furnacesHeat carried away by air convection of the lower furnace shell part of the furnace body area is J; h is a total of 2 Is the average surface convection heat transfer coefficient W/(m) of the furnace shell part under the furnace body area of the electric arc furnace 2 ·K)；H 2 M is the height of the cylinder of the shell part below the furnace body area of the electric arc furnace; t is 2 And T A2 Respectively representing the average temperature of the furnace shell part below the furnace area of the electric arc furnace and the ambient main stream air temperature, K; g is the acceleration of gravity, m/s 2 The suggested value is 9.8m/s 2 ；
The qualitative temperature of the air is determined by the average temperature of the furnace shell part under the furnace body area of the electric arc furnace and the temperature of the ambient main stream air, and is determined by the formula (3-35), K; ρ is a unit of a gradient A2 Is determined by the qualitative temperature
Determined air density, kg/m 3 ；c A2 Is determined by the qualitative temperature
A determined air specific heat capacity, J/(kg. K); v is A2 Is determined by the qualitative temperature
Determined air movement viscosity coefficient, m 2 /s；λ A2 Is determined by the qualitative temperature
A determined air thermal conductivity, W/(m.K);
the specific application of the equations (3-29), (3-30), (3-31) and (3-32), (3-33) and (3-34) is determined according to the flowing state of the ambient air when the furnace shell part at the lower furnace body area of the electric arc furnace exchanges heat with the ambient air, and the specific application is determined by the equations (3-36), (3-37) and (3-38) as follows:
(2) Calculation of convection heat exchange quantity of horizontal heat exchange surface at joint of lower furnace shell part and upper furnace shell part of electric arc furnace body area
The horizontal heat transfer surface area of the lower furnace shell part of the electric arc furnace body region = the horizontal projection area of the lower furnace shell part of the electric arc furnace body region-the horizontal projection area of the upper furnace shell part of the electric arc furnace body region, namely, there is the following formula:
the perimeter of the horizontal heat transfer zone of the shell section below the furnace body section of the electric arc furnace is calculated using the following formula:
the characteristic length of the horizontal heat exchange zone of the shell part below the furnace zone of the electric arc furnace can be determined according to the formula (3-8), namely the characteristic length is as follows:
because the two part calculation formulas for the characteristic length are too long, they are not written out at this point, and they can be searched in the above formula.
According to the calculation numerical values, calculation ranges and expressions (3-2), (3-4), (3-6), (3-7) and (3-41) of the table 3-1, the calculation expression of the average surface convection heat transfer coefficient of the horizontal heat transfer area of the lower shell part of the furnace body area of the electric arc furnace and the calculation expression of the heat loss by air convection heat transfer in unit time of the horizontal heat transfer area of the lower shell part of the furnace body area of the electric arc furnace can be obtained by combining the geometrical characteristics of the horizontal heat transfer area of the lower shell part of the furnace body area of the electric arc furnace, and the calculation expressions are respectively expressions (3-42), (3-43) and (3-44) and (3-45).
The specific applications of formulae (3-42), (3-43), and formulae (3-44), (3-45) are determined by formulae (3-46) and (3-47), respectively, as follows:
therefore, the calculation formula of the heat loss brought away by the furnace shell part under the furnace area of the electric arc furnace due to air convection and cooling water heat exchange is as follows:
Q 2 ＝Q W2 +Q C2 ＝Q W2 +Q C2.1 +Q C2.2 (3-48)
wherein Q C2 The calculation formula (2) needs to be judged and selected according to the actual measured parameters.
3.3 furnace bottom heat loss of electric arc furnace body zone
The outer side of the furnace bottom part of the electric arc furnace body area is provided with a cooling water pipeline for providing cooling protection for the furnace bottom of the electric arc furnace, and the cooling water of the furnace shell part under the electric arc furnace body area in unit time can take away heat and can be calculated by the formula (3-49):
Q W3 ＝c 3 ρ 3 V 3 (T out3 -T in3 ) (3-49)
in the formula: q W3 J, heat taken away by cooling water at the bottom of the furnace body of the electric arc furnace; t is in3 And T out3 The temperatures of a cooling water inlet and a cooling water outlet at the bottom of the electric arc furnace body are respectively set; k;
is a qualitative temperature determined by the average value of the inlet temperature and the outlet temperature of the cooling water and is determined by the formula (3-50), K; c. C 3 Is determined by the qualitative temperature
The specific heat capacity of the cooling water is determined, and J/(kg.K); rho 3 Is determined by the qualitative temperature
Determined density of cooling water, kg/m 3 ；V 3 Volume flow m of cooling water per unit time at the bottom of the furnace body of the electric arc furnace 3 。
The furnace bottom part of the electric arc furnace body zone is shown in a relevant view in fig. 8. The furnace bottom part of the furnace body area of the electric arc furnace has an inclined curved surface due to the existence of the eccentric area, and when ambient air flows through the furnace bottom part, the taken heat is calculated by adopting the projection of the furnace bottom part. Therefore, when the furnace bottom of the electric arc furnace body area carries out convective heat transfer with ambient air, the heat transfer surfaces comprise vertical wall surfaces and horizontal wall surfaces with downward hot surfaces, and the average surface convective heat transfer coefficient and the heat dissipation capacity of the two heat dissipation surfaces are calculated respectively.
(1) Calculation of convection heat transfer heat quantity of horizontal projection area at furnace bottom part of electric arc furnace body area
The horizontal projection of the furnace bottom section, which coincides with the horizontal projection of the lower furnace shell section of the furnace body section of the electric arc furnace, is a region with the hot side facing downward, as shown in fig. 7. The perimeter and the area of the horizontal projection area are shown in the formulas (3-26) and (3-27).
The characteristic length of the horizontal projection area of the furnace bottom of the furnace body area of the electric arc furnace can be determined according to the formula (3-8), namely the characteristic length is as follows:
because the two part calculation formula for the characteristic length is too long, it is not written out at this point, and the search can be performed in the above formula.
According to the calculated values and the calculated ranges of the horizontal heat-surface-downward heating fluid in the table 3-1, and the formulas (3-2), (3-4), (3-6), (3-7) and (3-51), the calculation formula of the average surface convection heat transfer coefficient of the horizontal heat transfer area at the furnace bottom part of the furnace body area of the electric arc furnace and the calculation formula of the heat loss by air convection heat transfer in unit time of the horizontal heat transfer area at the furnace bottom part of the furnace body area of the electric arc furnace can be obtained by combining the geometrical characteristics of the horizontal heat transfer area at the furnace bottom part of the furnace body area of the electric arc furnace, and the calculation formulas are respectively the formula (3-52) and the formula (3-53).
The use of the above equation still requires a judgment
Of course, for electric arc furnaces, this is satisfied by the formula (3-55), but for the sake of stringency, the test is required.
In the above formula: q C3.1 Heat brought away by air convection in a horizontal projection area at the bottom of a furnace body of an electric arc furnace body area is J; h is a total of 3.1 The average surface convection heat transfer coefficient of air convection in the horizontal projection area of the furnace bottom of the furnace body area of the electric arc furnace is W/(m) 2 ·K)；A d3.1 Is the area of the horizontal projection area of the furnace bottom of the furnace body area of the electric arc furnace, m 2 ；P d3 The circumference m of a furnace bottom horizontal projection area of a furnace body area of the electric arc furnace; t is 3 And T A3 Respectively representing the average temperature of the furnace bottom of the furnace body area of the electric arc furnace and the ambient main stream air temperature, K; g is the acceleration of gravity, m/s 2 The suggested value is 9.81m/s 2 ；
The qualitative temperature of the air determined by the average temperature of the furnace bottom part of the furnace body area of the electric arc furnace and the temperature of the ambient main stream air is determined by the formula (3-54), K; rho A3 Is determined by the qualitative temperature
Determined air density, kg/m 3 ；c A3 Is determined by the qualitative temperature
The determined air specific heat capacity, J/(kg. K); v is A3 Is determined by the qualitative temperature
Determined air movement viscosity coefficient, m 2 /s；λ A3 Is determined by the qualitative temperature
A determined air thermal conductivity, W/(m.K);
(2) Calculation of convective heat transfer heat of vertical projection area at furnace bottom part of electric arc furnace body area
The area of the vertical projection is a cylinder, and the area in the vertical direction is as follows:
the sum formulas (3-2), (3-4), (3-6) and (3-7) are selected according to numerical ranges of laminar flow, transitional flow and turbulent flow in the table 3-1, and the characteristic dimension l = H of a vertical projection area of a furnace bottom part of a furnace body area of the electric arc furnace 3 The calculation formula of the average surface convection heat exchange coefficient of the vertical projection area of the furnace bottom part of the furnace body zone of the electric arc furnace and the calculation formula of the air convection heat exchange heat loss in unit time of the vertical projection area of the furnace bottom part of the furnace body zone of the electric arc furnace can be obtained by combining the geometrical characteristics of the vertical projection area of the furnace bottom part of the furnace body zone of the electric arc furnace, and are respectively the formulas (3-57), (3-58), (3-59) and (3-60), (3-61) and (3-62).
The calculation of the amount of heat removed in this vertical direction can be performed by the following calculation:
in the formula: q C3.2 The heat which is taken away by air convection in a vertical projection area at the bottom of the furnace body of the electric arc furnace is J; h is 3.2 The average surface convection heat transfer coefficient of air convection in the vertical projection area at the bottom of the furnace body of the electric arc furnace is W/(m) 2 ·K)；A d3.2 Is the area of the vertical projection area of the furnace bottom of the furnace body area of the electric arc furnace, m 2 ；H 3 Is the height m of the vertical projection area of the furnace bottom of the furnace body area of the electric arc furnace.
The specific application of the formulas (3-57), (3-58), (3-59) and (3-60), (3-61) and (3-62) needs to be determined according to the flowing state of the ambient air when the vertical projection area of the furnace bottom part of the furnace body area of the electric arc furnace exchanges heat with the ambient air, and the applied conditions are respectively determined by the formulas (3-63), (3-64) and (3-65) as follows:
finally, the heat loss brought away by air convection at the bottom of the furnace body area of the electric arc furnace is as follows:
Q C3 ＝Q C3.1 +Q C3.2 (3-66)
therefore, the calculation formula of the heat loss brought away by air convection and cooling water heat exchange at the furnace bottom of the furnace body area of the electric arc furnace is as follows:
Q 3 ＝Q W3 +Q C3 (3-67)
3.4 furnace body zone furnace cover part heat loss of electric arc furnace
The outer side of the furnace cover part of the furnace body area of the electric arc furnace is provided with a cooling water pipeline for providing cooling protection for the furnace cover part of the electric arc furnace, and the quantity of heat taken away by cooling water of the furnace cover part of the furnace body area of the electric arc furnace in unit time can be calculated by the formula (3-68):
Q W4 ＝c 4 ρ 4 V 4 (T out4 -T in4 ) (3-68)
in the formula: q W4 Heat taken away by cooling water for a furnace cover part of a furnace body area of the electric arc furnace J; t is in4 And T out4 The temperatures of a cooling water inlet and a cooling water outlet of the furnace cover part of the electric arc furnace body are respectively measured; k;
is a qualitative temperature determined by the average value of the inlet temperature and the outlet temperature of the cooling water and is determined by the formula (3-69), K; c. C 4 Is determined by the qualitative temperature
The specific heat capacity of the cooling water is determined, and J/(kg.K); rho 4 Is determined by the qualitative temperature
Determined density of cooling water, kg/m 3 ；V 4 Volume flow rate m of cooling water per unit time for furnace cover part of furnace body area of electric arc furnace 3 。
The furnace body section of the electric arc furnace is shown in a relative view in fig. 9. The furnace cover part of the electric arc furnace body area is connected with the furnace cover part on the electric arc furnace body area, an inclined curved surface exists on the furnace cover part of the electric arc furnace body area, and when surrounding air flows through the furnace cover part, the taken heat is calculated by adopting the projection of the furnace cover part. Therefore, when the furnace cover part of the furnace body area of the electric arc furnace carries out convective heat transfer with ambient air, the heat transfer surfaces are provided with vertical wall surfaces and horizontal wall surfaces with upward hot surfaces, the average surface convective heat transfer coefficient and the heat dissipation capacity of the two heat dissipation surfaces are calculated respectively, and the calculation process and the calculation formula are as follows.
(1) Calculation of convection heat transfer heat quantity of horizontal projection area of furnace cover part of electric arc furnace body area
The horizontal projection area of the furnace cover part is coincident with the horizontal projection of the furnace shell part on the furnace body area of the electric arc furnace, and is an area with an upward hot surface. The circumference and the area of the horizontal projection area are shown in the formula (3-11) and (3-70).
The characteristic length of the horizontal projection area of the furnace bottom of the furnace body area of the electric arc furnace can be determined according to the formula (3-8), namely the characteristic length is as follows:
according to the calculated numerical values and the calculated ranges of the heating fluids with the horizontal heat surfaces facing upwards in the table 3-1, and the formulas (3-2), (3-4), (3-6), (3-7) and (3-71), the calculation formula of the average surface convection heat transfer coefficient of the horizontal heat transfer area of the furnace body cover part of the furnace body area of the electric arc furnace and the calculation formula of the heat loss of the air convection heat transfer in the horizontal heat transfer area of the furnace body cover part of the electric arc furnace in unit time can be obtained by combining the geometrical characteristics of the horizontal heat transfer area of the furnace body area of the electric arc furnace, and the calculation formulas are respectively the formulas (3-72), (3-73) and (3-74) and (3-75).
The specific application of the equations (3-72), (3-73) and (3-74), (3-75) is determined according to the flow state of the ambient air when the furnace shell part under the furnace zone of the electric arc furnace exchanges heat with the ambient air, and the specific application is determined by the equations (3-77) and (3-38), respectively, as follows:
in the formula: q C4.1 The heat which is 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 is J; h is 4.1 The average surface convection heat transfer coefficient of air convection in the horizontal projection area of the furnace cover part of the furnace body area of the electric arc furnace, W/(m) 2 ·K)；A d4.1 Is the area of the horizontal projection area of the furnace cover part of the furnace body area of the electric arc furnace, m 2 ；P d4 The circumference m of a horizontal projection area of a furnace cover part of a furnace body area of the electric arc furnace; t is 4 And T A4 Respectively representing the average temperature of the furnace cover part of the furnace body area of the electric arc furnace and the ambient main stream air temperature, K; g is the acceleration of gravity, m/s 2 The suggested value is 9.8m/s 2 ；
Is a qualitative temperature of air determined by the average temperature of the furnace cover part of the furnace body area of the electric arc furnace and the temperature of the ambient main stream air, determined by the formula (3-76), K; ρ is a unit of a gradient A4 Is determined by the qualitative temperature
Determined air density, kg/m 3 ；c A4 Is determined by the qualitative temperature
The determined air specific heat capacity, J/(kg. K); v is A4 Is determined by the qualitative temperature
Determined air movement viscosity coefficient, m 2 /s；λ A4 Is determined by the qualitative temperature
A determined air thermal conductivity, W/(m.K);
(2) Calculation of convection heat transfer heat quantity of vertical projection area of furnace cover part of electric arc furnace body area
For the vertical projection area of the furnace cover part, the vertical projection area is a vertical cylinder wall surface, so the calculation formula of the area of the heat exchange surface in the vertical direction is as follows:
A d4.2 ＝πd 1 H 4 (3-79)
the sum formula (3-2), (3-4), (3-6) and (3-7) are selected according to numerical ranges of laminar flow, transitional flow and turbulent flow in the table 3-1, and the characteristic dimension l = H of the vertical projection area of the furnace cover part of the furnace body area of the electric arc furnace 4 The calculation formula of the average surface convection heat transfer coefficient of the vertical projection area of the furnace body section furnace cover part of the electric arc furnace and the calculation formula of the air convection heat transfer heat loss of the vertical projection area of the furnace body section furnace cover part of the electric arc furnace in unit time can be obtained by combining the geometrical characteristics of the vertical projection area of the furnace body section furnace cover part of the electric arc furnace, and the calculation formulas are respectively the formulas (3-80), (3-81), (3-82) and (3-83), (3-84) and (3-85).
In the formula: q C4.2 The heat which is 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 is J; h is a total of 4.2 The average surface convection heat transfer coefficient of air convection in the vertical projection area of the furnace cover part of the furnace body area of the electric arc furnace is W/(m) 2 ·K)；A d4.2 Is the area of the vertical projection area of the furnace cover part of the furnace body area of the electric arc furnace, m 2 ；H 4 Is the height m of the vertical projection area of the furnace cover part of the furnace body area of the electric arc furnace.
The specific application of the equations (3-80), (3-81), (3-82) and (3-83), (3-84) and (3-85) is determined according to the flowing state of the ambient air when the vertical projection area of the furnace bottom part of the electric arc furnace zone exchanges heat with the ambient air, and the application conditions are respectively determined by the 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, which is taken away by air convection, is as follows:
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 brought away by air convection and cooling water heat exchange is as follows:
Q 4 ＝Q W4 +Q C4 (3-90)
3.5 radiant heat transfer loss in furnace body of electric arc furnace
The furnace body has higher temperature in the smelting process and can radiate a large amount of heat to external objects. The radiation heat loss of the electric arc furnace body mainly comprises radiation heat transfer loss of the electric arc furnace body and radiation heat transfer heat loss of the electric arc furnace door.
3.5.1 electric arc furnace body radiation heat transfer heat loss
The electric arc furnace is positioned in a closed plant and carries out radiation heat exchange with the wall of the plant, belongs to radiation heat transfer between a cavity between actual objects and the inner wall, and mainly aims to determine the net radiation heat transfer quantity between the furnace body of the electric arc furnace and the surrounding wall.
The net radiant heat exchange per unit time between the surface of the electric arc furnace body and the wall in the factory is calculated by the formula (3-91):
in the formula: q 5.1 The net radiant heat exchange quantity per unit time between the surface of the electric arc furnace body and the surrounding wall, W; epsilon R The emissivity of the body of the electric arc furnace, also called blackness, is always less than 1, and is related to the type and surface condition of the object and not to the surrounding environment; a. The R M is the surface area of the furnace body of the electric arc furnace 2 (ii) a σ is Stefan-Boltzmann constant, and has a value of 5.67 × 10 -8 W/(m 2 ·K 4 )；T W And T A The average temperature, K, of the surface of the furnace zone of the electric arc furnace and the surface of the surrounding wall, respectively.
The formula is a calculation formula for calculating the radiation heat exchange quantity between the furnace body of the electric arc furnace and the surrounding walls, and is also a recommended formula, the method needs less physical quantity to be measured, and the calculated order of magnitude is not greatly different.
It should be noted that since the electric arc furnace body is not located in the geometrically central area of the steel plant, the surrounding walls receive a non-uniform amount of radiant energy, resulting in a non-uniform temperature of the surrounding wall surfaces, and therefore T is recommended A The value is the average temperature of the surfaces of all walls in the electric arc furnace steel-making plant; meanwhile, because the furnace body of the 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 temperatures of the four parts are not consistent because the heat transmitted from the inside of the furnace to the outside of the furnace is different in different parts, T is suggested W The value is the average temperature of the upper furnace shell part, the lower furnace shell part, the furnace bottom part and the furnace cover part of the furnace area of the electric arc furnace.
3.5.2 heat transfer by radiation at the furnace door of electric arc furnace
The inside of the electric arc furnace door 3 is high-temperature molten steel 4, the outside is air with lower temperature, the radiation heat is also very large, the molten steel in the electric arc furnace can be regarded as a blackbody, a hemispherical space blackbody radiation calculation mode is adopted, calculation is carried out according to the following method, and a calculation chart is shown in fig. 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 molten steel in unit time and unit radiant area, W/m 2 (ii) a T is the surface temperature of the molten steel, K;
total energy radiated from the liquid surface of the molten steel to the hemispherical space at the upper part of the liquid steel is as follows:
F A ＝AE b (3-93)
in the formula: a is the area of the liquid surface of the molten steel, m 2 . When the depth of the molten steel is large, the liquid level of the molten steel can be regarded as a circle, and calculation is carried out by the formula (3-94). It is proposed to derive the area A directly from the electric arc furnace bath CAD drawing without intervention d, but d may also be introduced.
In the formula: d is the diameter of the liquid level of the molten steel, m. The equations (3-93) and (3-94) may depend on the parameters obtained by the specific measurement, and are identical in nature.
The directional radiation intensity of the molten steel in the electric arc furnace is as follows:
the furnace door should be offset a distance directly above the molten steel level, so the internal molten steel input radiant energy obtained from fig. 10, i.e. with the electric arc furnace door, is:
in the formula: h d M is the height from the center of a furnace door opening to the center of the liquid level of the molten steel; r is a radical of hydrogen i Is the radius of the liquid level of the molten steel, m; l is a radical of an alcohol d The distance m from the center of the furnace door to the center of the liquid level of the molten steel; theta is an included angle between the height from the furnace door to the liquid level of the molten steel and a connecting line between the center of the furnace door and the center of the liquid level of the molten steel; a. The d Is the area of the furnace door opening, m 2 . Substituting the formulas (3-92) and (3-95) into the formula (3-97) to obtain the final calculation formula of the radiant heat transfer and heat loss at the furnace door of the electric arc furnace:
based on the theoretical calculation and analysis, the calculation formula of the radiant heat transfer and heat loss of the furnace body area of the electric arc furnace is as follows:
in conclusion, the calculation formula of the total heat loss caused by convection heat exchange of cooling water and air and radiation heat exchange of the furnace body and the wall surface of the surrounding building envelope in the steelmaking process of the electric arc furnace is as follows:
Q＝Q 1 +Q 2 +Q 3 +Q 4 +Q 5 (3-99)
the above calculation requires attention to the following points:
(1) The air is regarded as ideal gas in the calculation process, the temperatures of the main flow air sides of the upper furnace 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 are uniform and consistent, but the difference of the temperatures of different part areas can exist, and the difference depends on the measured value of the air temperature of a specific occasion.
(2) All qualitative temperature-dependent parameters mentioned herein can be obtained by looking at the "Dry air Property parameters Table" or the "saturated Water thermophysical Property Table".
(3) For the upper furnace shell part and the lower furnace shell part, the calculation is carried out by simplifying the upper furnace shell part and the lower furnace shell part into cylinders; and the irregular areas of the furnace bottom part and the furnace cover part are simplified into horizontal projection and vertical projection for calculation, wherein the vertical projection is simplified into a cylinder for calculation.
(4) Only the final results are given, wherein the derivation is not given, and the characteristic parameters are also expressed in terms of easily measurable parameters.
(5) The temperature parameters should be obtained based on the parameters measured in the actual steel mill environment. The temperature of the main air refers to the temperature of the air flow beams which are away from the surface of the furnace body by a certain distance and are not influenced by the temperature of the surface of the furnace body, and the temperature of the air flow beams is kept unchanged. For measuring the air temperature of different partial areas, measuring points are suggested to be arranged at intervals of 1.5m in the vertical direction along the circumferential direction at intervals of 60 degrees to measure the temperature of main flow air. For acquiring temperature parameters of different parts of the furnace body area of the electric arc furnace, thermocouple measuring points or infrared measuring points are arranged on the surfaces of the relevant parts, and measuring points are suggested to be arranged on the corresponding parts at intervals of 60 degrees in the circumferential direction and at intervals of 80cm in the vertical direction to acquire the temperature parameters of all the components.
The foregoing is considered as illustrative of the preferred embodiments of the invention and is not to be construed as limiting the invention in any way. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention should fall within the protection scope of the technical scheme of the present invention, unless the technical spirit of the present invention departs from the content of the technical scheme of the present invention.
Claims (5)
1. A method for calculating heat loss of a furnace body region in an electric arc furnace steelmaking process is characterized in that the furnace body region of the electric arc furnace is divided into an upper furnace shell portion, a lower furnace shell portion, a furnace bottom portion and a furnace cover portion, and heat loss Q of the upper furnace shell portion is calculated respectively 1 Lower furnace shell part heat loss Q 2 Heat loss Q of furnace bottom 3 Heat loss Q of furnace cover part 4 And furnace body area radiation heat transfer heat loss Q 5 The total heat loss Q is then calculated according to the following equation:
Q＝Q 1 +Q 2 +Q 3 +Q 4 +Q 5
wherein Q 1 Comprising heat Q taken away by cooling water of the upper furnace shell part W1 Heat Q convectively taken away from the air of the upper furnace shell part C1 ；Q 2 Including heat Q taken away by cooling water of lower furnace shell part W2 Heat Q convectively taken away from the air of the lower furnace shell part C2 ，Q C2 Air convection heat loss Q in unit time including vertical wall surface of lower furnace shell part C2.1 And the air convection heat loss Q in unit time of the horizontal heat exchange area of the lower furnace shell part C2.2 ；Q 3 Comprising the heat Q taken away by the cooling water in the bottom part of the furnace W3 Heat Q convected away from air in the bottom part of the furnace C3 ，Q C3 Comprising heat Q convectively taken away by air in the horizontal projection area of the furnace bottom C3.1 Heat Q convected away from air in vertical projection area of furnace bottom part C3.2 ；Q 4 Including heat Q taken away by cooling water in the furnace cover part W4 Heat Q convected away from the air in the furnace cover C4 ，Q C4 Heat Q taken away by air convection in horizontal projection area of furnace cover part C4.1 Heat Q convected away from air in vertical projection area of furnace cover part C4.2 ；Q 5 Comprises the net radiant heat exchange quantity Q per unit time between the surface of the furnace body of the electric arc furnace and the surrounding wall 5.1 And an electric arcThe radiant heat transfer and loss G at the furnace door;
Q W1 calculated from the following formula:
Q W1 ＝c 1 ρ 1 V 1 (T out1 -T in1 )
in the formula: t is in1 And T out1 The temperatures of a cooling water inlet and a cooling water outlet of the furnace shell part on the furnace body area of the electric arc furnace are respectively set;
is a qualitative temperature determined by the average value of the inlet temperature and the outlet temperature of the cooling water; c. C 1 Is determined by the qualitative temperature
The specific heat capacity of the cooling water is determined; rho 1 Is determined by the qualitative temperature
The determined density of the cooling water; v 1 The volume flow of cooling water of the furnace shell part on the furnace body area of the electric arc furnace in unit time;
Q C1 calculated from the following formula:
in the formula: d 1 The outer diameter of the cylinder of the furnace shell part on the furnace body area of the electric arc furnace; h 1 The height of the cylinder of the furnace shell part on the furnace body area of the electric arc furnace; t is 1 And T A1 Respectively representing the average temperature of the furnace shell part on the furnace area of the electric arc furnace and the ambient main stream air temperature; g is gravity acceleration;
the qualitative temperature of the air is determined by the average temperature of the furnace shell part on the furnace body area of the electric arc furnace and the temperature of the ambient main stream air; rho A1 Is determined by the qualitative temperature
A determined air density; c. C A1 Is determined by the qualitative temperature
A determined specific heat capacity of air; v. of A1 Is determined by the qualitative temperature
A determined air movement viscosity coefficient; lambda [ alpha ] A1 Is determined by the qualitative temperature
A determined air thermal conductivity;
the first three formulas respectively correspond to the following conditions:
Q W2 is calculated and Q W1 Same principle, Q C2.1 Calculated using the formula:
the first three formulas respectively correspond to the following conditions:
in the formula: h 2 The height of a cylinder of a furnace shell part below a furnace body area of the electric arc furnace; t is a unit of 2 And T A2 Respectively indicating the average temperature of the lower furnace shell part of the electric arc furnace body areaTemperature and ambient mainstream air temperature; g is the acceleration of gravity;
the qualitative temperature of the air is determined by the average temperature of the furnace shell part under the furnace area of the electric arc furnace and the ambient main stream air temperature; rho A2 Is determined by the qualitative temperature
A determined air density; c. C A2 Is determined by the qualitative temperature
A determined specific heat capacity of air; v. of A2 Is determined by the qualitative temperature
A determined air movement viscosity coefficient; lambda A2 Is determined by the qualitative temperature
A determined air thermal conductivity; the angles A and B are respectively the actual fan-shaped angles of the top of the bottom part of the electric arc furnace; r is the reference circle radius of the top surface of the bottom of the furnace body area of the electric arc furnace; d is the length of the bevel edge of the reference circle of the top surface of the furnace bottom of the furnace body area of the electric arc furnace;
Q C2.2 calculated using the formula:
the two formulas respectively correspond to the following conditions:
Q W3 is calculated and Q W1 Principle same, Q C3.1 Calculated using the formula:
in the formula: a. The d3.1 The area of the furnace bottom horizontal projection area of the furnace body area of the electric arc furnace; a. The 2.2 The area of the horizontal heat exchange surface of the lower furnace shell part of the furnace body area of the electric arc furnace; l 2.1 The characteristic length of a horizontal heat exchange area of a furnace shell part below a furnace body area of the electric arc furnace; p d3 The circumference of a furnace bottom horizontal projection area of a furnace body area of the electric arc furnace; t is 3 And T A3 Respectively representing the average temperature of the furnace bottom part of the furnace body area of the electric arc furnace and the ambient main stream air temperature; g is the acceleration of gravity;
the air qualitative temperature is determined by the average temperature of the furnace bottom of the furnace body area of the electric arc furnace and the ambient main stream air temperature; rho A3 Is determined by the qualitative temperature
A determined air density; c. C A3 Is determined by the qualitative temperature
A determined specific heat capacity of air; v is A3 Is determined by the qualitative temperature
A determined air movement viscosity coefficient; lambda [ alpha ] A3 Is determined by the qualitative temperature
A determined air thermal conductivity;
Q W4 is calculated and Q W1 Same principle, Q C4.1 Is calculated as follows:
the application conditions of the first two formulas are respectively as follows:
in the formula: t is 4 And T A4 Respectively representing the average temperature of the furnace cover part of the furnace body area of the electric arc furnace and the ambient main stream air temperature; g is the acceleration of gravity;
the qualitative temperature of the air is determined by the average temperature of the furnace cover part of the furnace body area of the electric arc furnace and the temperature of the ambient main stream air; rho A4 Is determined by nature of temperatureDegree of rotation
A determined air density; c. C A4 Is determined by the qualitative temperature
A determined specific heat capacity of air; v is A4 Is determined by the qualitative temperature
A determined air movement viscosity coefficient; lambda [ alpha ] A4 Is determined by the qualitative temperature
A determined air thermal conductivity.
2. The method of claim 1, wherein Q is Q C3.2 Calculated using the formula:
in the formula: h 3 The height of a vertical projection area at the bottom of a furnace body area of the electric arc furnace;
the three formulas respectively correspond to the following conditions:
3. the method of claim 1, wherein Q is Q C4.2 Is calculated as follows:
in the formula: h 4 The height of a vertical projection area of a furnace cover part of a furnace body area of the electric arc furnace;
the application conditions of the three formulas are respectively as follows:
4. the method as claimed in any one of claims 1 to 3, wherein Q is a measure of the heat loss in the furnace zone during steelmaking in the electric arc furnace 5.1 Is calculated as follows:
wherein: epsilon R Is the emissivity of the body of the electric arc furnace; a. The R Is the surface area of the furnace body area of the electric arc furnace; sigma is Stefan-Boltzmann constant; t is W And T A The average temperature of the surface of the furnace zone of the electric arc furnace and the surface of the surrounding wall are respectively.
5. The method of claim 4, wherein G is calculated as follows:
wherein: t is the surface temperature of the molten steel; a is the liquid level area of the molten steel; l is d The distance from the center of the furnace door to the center of the liquid level of the molten steel; theta is an included angle between the height from the furnace door to the liquid level of the molten steel and a connecting line between the center of the furnace door and the center of the liquid level of the molten steel; a. The d Is the area of the furnace door opening.
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