KR100332909B1 - Method for calculating radiation heat from staves of furnace body in corex melting furnace - Google Patents

Abstract

PURPOSE: A method which is capable of calculating radiation heat having credibility even when supply of cooling water is stopped at one or more staves of the furnace body by analyzing thermal conduction for staves of the furnace body using finite element method and calculating thus applying radiation heat. CONSTITUTION: The method for calculating radiation heat from staves of the furnace body in COREX melting furnace comprises first step of determining the range in which temperature of thermocouples is capable of being changed, and setting the minimum of the range as the lowest temperature and the maximum of the range as the highest temperature; second step of obtaining temperature distribution by using the lowest temperature as temperature of the boundary surface at position of the thermocouples, applying convection current boundary condition in case that cooling water is steadily flown on the boundary surface of the inner surface of cooling pipes, applying adiabatic condition in case that supply of cooling water is stopped, applying convection current condition to the boundary surface of the outer surface of metal case and applying adiabatic conditions to the rest of boundary surfaces, thereby solving a thermal conduction equation using finite element method; third step of obtaining radiation heat of the furnace body using the temperature distribution using the following equation I: Qr=Q1+Q2=hAs(Ts-Ta)+QHAt(Tt-Tw) where Qr is radiation heat emitted from stave , Q1 is radiation heat emitted from iron shell, Q2 is radiation heat emitted from cooling pipe, h is thermal conductivity coefficient on outer surface of iron shell, As is area of stave, Ts is mean temperature on outer surface of iron shell, Ta is atmosphere temperature, H is thermal conductivity coefficient in cooling pipe, At is sectional area of cooling pipe, Tt is mean temperature on outer surface of cooling pipe, and Tw is temperature of cooling water; fourth step of repeating the above steps from the second step by increasing temperature of the thermocouples of the second step as much as a certain amount of temperature if the temperature of the boundary surface is lower than the highest temperature and proceeding the following fifth step if the temperature of the boundary surface is higher than the highest temperature after determining whether temperature of the boundary surface at the position of thermocouples is higher or lower than the highest temperature; fifth step of deriving relation of the set thermocouple temperature (T) and obtained radiation heat (Qr) into a linear expression; and sixth step of obtaining radiation heat by substituting the actually measured temperatures of the thermocouples for the obtained linear expression.

Description

Calculation method of heat dissipation of corex melting furnace furnace stave

The present invention relates to a method for calculating the heat dissipation of a furnace stave of a corex furnace, and more particularly, the heat dissipation heat can be calculated even when one of the cooling water is stopped in the cooling pipe in the furnace stave or there are several cooling water inlet stops. It is about how it can be.

Correx melting furnace is shown in Figure 1, is a facility for producing pig iron by melting the heat of reaction generated by the combustion reaction of oxygen and coal blown through the ore reduced ore charged from the top of the furnace as a heat source. Since a high temperature (1000-1200 degreeC) is maintained inside such a melting furnace, the stave is employ | adopted as a cooling apparatus in order to protect a furnace shell. However, the problem that often occurs during operation is the case in which the shell is subjected to excessive heat load due to the furnace conditions or cooling conditions. Therefore, operators quantitatively calculate the heat dissipated by the stave and always monitor and manage the heat load of the shells.

Conventionally, there is a method of using the temperature of the input and output of the cooling water as a method of calculating the heat of dissipation. In this method, in order to calculate the heat of dissipation, the heat dissipation was calculated by the following equation 1 by measuring the inlet temperature and the outlet temperature of the cooling water.

Q _r = m Cp (T _out -T _in )

In Equation 1, m represents the flow rate of the cooling water, Cp represents the specific heat of the cooling water, and T _our , T _in represents the outlet temperature and the inlet temperature of the cooling water. That is, the heat of dissipation is represented by the change of sensible heat by the temperature increase of cooling water. However, this method has a problem that can not be applied if the supply of cooling water is interrupted because the stave is damaged. In addition, there are usually 4-5 cooling tubes in the stave, there is a problem that a large error occurs in the heat of dissipation by this method when the number of cooling tubes in which double cooling water supply is stopped.

In order to solve the above problems, the present inventors have repeatedly conducted research and experiments and propose the present invention based on the results. The present invention calculates heat dissipation by performing heat conduction analysis by finite element method on a furnace stave. By applying this, it is an object of the present invention to provide a method for calculating reliable heat dissipation even when one or more cooling water supply to the furnace stave is stopped.

1 is a schematic diagram of a corex melting furnace

2 is a flow chart related to a method for calculating heat dissipation heat according to the present invention.

3 is a cross-sectional view of the furnace stave

4 is a schematic diagram of a furnace stave divided into analysis regions;

5 is a schematic diagram of a furnace stave applied to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

1 ,,,, sill 2 .... stamp

3 .... stave 4 .... cooling line

5 .... lead and 7 .... thermocouple

In the present invention for achieving the above object is a method for calculating the heat dissipation heat of the core stave of the Korex melting furnace consisting of a lead, having a shell, a stamp, a stave, and a thermocouple, comprising a certain number of cooling tubes therein,

In the method for calculating the heat dissipation heat of the furnace stave of the Korex fusion furnace consisting of a shell, a stamp, a stave, and a lead having a thermocouple, and including a certain number of cooling tubes therein,

Determining a range in which the temperature of the thermocouple can change, setting a minimum of the range as a minimum temperature, and setting a maximum to a maximum temperature;

The minimum temperature of the interface at the thermocouple location is given to the minimum temperature, convection boundary condition is given when the coolant flows normally at the interface of the inner surface of the cooling tube, and adiabatic condition is provided when the supply of cooling water is stopped. 2 steps of obtaining a temperature distribution by solving the heat conduction equation by the finite element method by giving a thermal insulation condition to all other interfaces;

Applying the temperature distribution to Equation 2 below to obtain dissipation heat of the furnace body;

Q _r = Q ₁ + Q ₂

Where Q _r is the heat of dissipation of the stave, Q ₁ is the heat of dissipation to the shell, Q ₂ is the heat of dissipation to the cooling tube, h is the heat transfer coefficient at the outer surface of the shell, A _S is the area of the stave, and T _S Is the average temperature of the outer surface of the shell, T _a is the external air temperature, H is the heat transfer coefficient in the cooling tube, A _t is the cross-sectional area of the cooling tube, T _t is the average temperature on the outer surface of the cooling tube, and T _w is the temperature of the cooling water. Is displayed.)

It is determined whether the temperature of the interface at the thermocouple position is higher or lower than the maximum temperature. If the temperature is low, the thermocouple temperature of step 2 is increased by a certain amount of temperature and repeated from step 2, and if it is high, the next step 5 is determined. 4 steps;

A fifth step of deriving the relationship between the set thermocouple temperature (T) and the obtained heat of dissipation (Q _r ) by a first equation such as the following Equation 3;

Q _r = aT + b, where a and b are constants

It relates to a method for calculating the heat dissipation heat of the furnace stave of the Korex smelting furnace comprising six steps of obtaining the dissipation heat by substituting the measured temperature of the thermocouple into the primary equation obtained above.

Hereinafter, the present invention will be described in detail.

2 is a flowchart illustrating a method for calculating dissipation heat in a furnace stave according to the present invention. The present invention will be described in detail with reference to this flowchart.

First, in the present invention, the temperature range of the thermocouple can be determined, the minimum of the range is set to the minimum temperature, and the maximum is set to the maximum temperature.

Further, in the present invention, thermal conduction analysis is performed on the furnace stave by the finite element method.

In this step, in order to analyze the heat conduction of the furnace body stave, as shown in FIG. However, the furnace temperature is not known because it is not specially measured during operation. Therefore, in the present invention, the analysis region is connected to the position where the thermocouple is inserted. 4 shows this analysis region. This makes it possible to analyze the thermal conductivity of the furnace stave irrespective of the furnace temperature or the remaining thickness of the smoke. The boundary conditions are as follows.

That is, the interface at the thermocouple position gives the minimum temperature and is given by increasing the temperature by a certain amount as the thermal conductivity analysis is repeated. At the interface of the cooling tube, the convection warning condition is given when the coolant flows normally, and the insulation condition is given when the supply of coolant is stopped. Cooling by air cooling takes place in the boundary surface of the outer shell, so it is convective. All other interfaces give insulation. The thermal conductivity equation is solved by finite element method under the selected analysis range and boundary conditions to find the temperature in the analysis range.

In the present invention, the heat dissipation of the furnace body is obtained by the following formula.

Q _r = Q ₁ + Q ₂

Where Q _r is the heat of dissipation of the stave, Q ₁ is the heat of dissipation to the shell, and Q ₂ is the heat of dissipation to the cooling tube. In the above formula, h is the heat transfer coefficient at the outer shell surface, A _s is the area of the stave, T _s is the average temperature of the outer shell surface, and T _A is the outside air temperature. H denotes the heat transfer coefficient in the cooling tube, A _t denotes the cross-sectional area of the cooling tube, T _t denotes the average temperature on the outer surface of the cooling tube, and T _W denotes the temperature of the cooling water.

On the other hand, the average temperature on the outer surface of the steel shell and the average temperature on the outer surface of the cooling tube are as follows. First, the average temperature of the outer shell surface is the average value of the temperatures of the nodes belonging to the outer shell surface in the thermal conductivity analysis. That is, the average temperature T _S can be expressed as in the following equation.

Here, Tsi is the temperature at the node belonging to the outer shell surface, Ns is the number of nodes belonging to the outer shell surface. The average temperature at the outer surface of the cooling tube is also obtained by the following equation (3).

Here, Tti represents the temperature at the node belonging to the outer surface of the cooling tube, and Nt represents the number of nodes belonging to the outer surface of the cooling tube.

In addition, in the present invention, it is determined whether the temperature of the interface at the thermocouple position is higher or lower than the maximum temperature, and if it is low, the thermocouple temperature of step 2 is increased by a predetermined amount of temperature and repeated from step 2, and if higher, the next 5 steps Go through the process of judging the progress.

While repeating, the interface temperature at the thermocouple position is initially increased by a predetermined amount from the minimum temperature, and when the temperature becomes larger than the maximum temperature, the following process is performed.

In addition, in the present invention, the dissipation heat for each thermocouple temperature obtained during the repetitive process is arranged to derive a correlation equation as shown in the following equation.

Q _r = aT + b

The correlation is a linear equation that can be derived by obtaining the coefficients a and b.

In the present invention, the current temperature (actual temperature) of the thermocouple is substituted into Equation 4 to obtain the current dissipation heat.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example

The heat load according to the present invention was calculated in a Korex smelter with a daily yield of 2000 tons.

In the present embodiment, there are five cooling tubes as shown in Fig. 5 as staves at the seventh stage of the Korex melting furnace, and one cooling tube in which the supply of double cooling water is stopped. As shown in FIG. 5, the cooling tube in which the supply of cooling water is stopped is a cooling tube of a.

First, the changeable range of the thermocouple was set to 300-500 ° C.

In addition, thermal conductivity analysis was performed on the furnace stave under the conditions given above. In order to apply the finite element method, element division and boundary conditions are given as follows. The element division in the area was set to 10 elements in the bark, 20 elements in the stave, and 20 elements in the furnace wall edge. The boundary condition is air-cooled at the outer surface of the shell, which gives convective boundary conditions. The atmospheric temperature is 20 ℃ and the heat transfer coefficient is 20㎉ / ㎡ hr ℃. In the cooling tube, adiabatic conditions are given at the interface of cooling tube a, which stops the supply of cooling water. In other cooling tubes, convection is caused by the cooling water, which gives convection conditions. The cooling water temperature is 35 ℃ and the heat transfer coefficient is 2100㎉ / ㎡ hr ℃. Gave as. The temperature was given at the boundary of the thermocouple position with the furnace wall edge, and the temperature was 300 ° C as set above. Under the above finite element partition and boundary conditions, the thermal conductivity equation is solved by the finite element method to find the temperature in the analysis domain.

In addition, the temperature at each node belonging to the outer surface of the iron shell from the temperature results obtained above was summarized in Table 1 below.

Node number Exterior skin temperature One 88 ℃ 2 88 ℃ 3 95 ℃ 4 112 ℃ 5 151 ℃ 6 206 ℃

In the above, the average temperature at the outer surface of the steel bar is obtained by Equation (2), which is 123 ° C. By arranging the temperature at the inner surface of the cooling tube in the same manner, the average temperature at the outer surface of each cooling tube was calculated by Equation (3) and summarized as in Table 2 below.

Cooling pipe number Average temperature outside cooling tube a 251 ℃ b 235 ℃ c 224 ℃ d 210 ℃ e 205 ℃

On the other hand, the heat of dissipation is calculated as follows by the above formula (1). At this time, the outer surface of the iron shell of the corex melting furnace is given an area of 1.2 m 2 and the cooling tube outer surface of 0.10 m 2.

Q _r = 20 * 1.2 * (123-20) + 2100 * 0.01 * (251-35) + 2100 * 0.01 * (235-35) + 2100 * 0.01 * (224-35) + 2100 * 0.01 (210-35 ) + 2100 * 0.01 * (205-35) = 22Mcal / hr

In addition, it is determined whether or not the temperature (100 ° C) of the thermocouple set above is smaller than the maximum temperature (500 ° C), or the temperature of the thermocouple is increased to 100 ° C and started again at 400 ° C to dissipate heat with respect to the thermocouple temperature at that time. The process of obtaining was repeated, and the process which was performed at 500 degreeC again was repeated. At 500 ° C or higher, the loop was exited and the next step started.

Moreover, when the thermocouple temperature and the heat of dissipation calculated | required above are put together, it is obtained as following Formula 3.

Thermocouple temperature Room acid heat 300 ℃ 22 Mcal / hr 400 ℃ 31 Mcal / hr 500 ℃ 40 Mcal / hr

From this, the correlation between the thermocouple temperature and the heat of dissipation is obtained as follows.

Q _r = 0.0913 T-3.72

Q _r is the heat of dissipation, and T is the thermocouple temperature.

In addition, since the current temperature of the thermocouple of the Corex melting furnace in operation is shown to be 370 ° C, the heat of dissipation is obtained at 30 kW / hr by substituting the above formula.

Through the above examples, the method for calculating the heat of dissipation of the Corex melting furnace has been described.

As described above, when the dissipation heat calculation method in the furnace stave of the present invention is used, there is an effect that the heat dissipation can be accurately calculated even when the supply of cooling water is stopped or the number of such cooling tubes is several.

Claims (1)

In the method for calculating the heat dissipation heat of the furnace stave of the Korex fusion furnace consisting of a shell, a stamp, a stave, and a lead having a thermocouple, and including a certain number of cooling tubes therein, Determining a range in which the temperature of the thermocouple can change, setting a minimum of the range as a minimum temperature, and setting a maximum to a maximum temperature; The minimum temperature of the interface at the thermocouple location is given to the minimum temperature, convection boundary condition is given when the coolant flows normally at the interface of the inner surface of the cooling tube, and adiabatic condition is provided when the supply of cooling water is stopped. 2 steps of obtaining a temperature distribution by solving the heat conduction equation by the finite element method by giving a thermal insulation condition to all other interfaces; Applying the temperature distribution to the following equation to obtain dissipation heat of the furnace body; Q _r = Q ₁ + Q ₂

Where Q _r is the heat of dissipation of the stave, Q ₁ is the heat of dissipation to the shell, Q ₂ is the heat of dissipation to the cooling tube, h is the heat transfer coefficient at the outer surface of the shell, A _S is the area of the stave, and T _S Is the average temperature of the outer surface of the shell, T _a is the external air temperature, H is the heat transfer coefficient in the cooling tube, A _t is the cross-sectional area of the cooling tube, T _t is the average temperature on the outer surface of the cooling tube, and T _w is the temperature of the cooling water. Is displayed.) It is determined whether the temperature of the interface at the thermocouple position is higher or lower than the maximum temperature. If the temperature is low, the thermocouple temperature of step 2 is increased by a certain amount of temperature and repeated from step 2, and if it is high, the next step 5 is determined. 4 steps; A fifth step of deriving the relationship between the set thermocouple temperature (T) and the obtained heat of dissipation (Q _r ) by the following equation; Q _r = aT + b, where a and b are constants A method for calculating the heat dissipation heat of a furnace body of a Korex smelting furnace comprising six steps of obtaining dissipation heat by substituting the measured temperature of a thermocouple into the first equation obtained above.

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