KR100332908B1 - Method for repairing stave of furnace body of corex melting furnace - Google Patents

Abstract

PURPOSE: A method for repairing stave of the furnace body of COREX melting furnace is provided to repair the stave of the furnace body with thermal shock in the vicinity of cooling pipe being minimized by obtaining allowable temperature of thermocouple, thereby determining appropriate repairing time of the stave of the furnace body. CONSTITUTION: The method for repairing stave of the furnace body of COREX melting furnace comprises the steps of obtaining temperature distribution and thermal stress distribution corresponding to the thermocouple temperatures using finite element method by maintaining the concerned cooling pipe under the adiabatic condition after selecting any one cooling pipe in the stave of the furnace body, maintaining the boundary condition at position of the thermocouple at respective temperatures obtained as varying temperature of the thermocouple, maintaining boundary condition at the outer surface of metal case under the cooling condition by air cooling, and maintaining the other boundary conditions under the adiabatic condition; deriving a correlation of thermocouple temperature (T) and the maximum thermal stress (σ) in a shape as represented in the following expression by taking the maximum thermal stress in the thermal stress distribution corresponding to the respective thermocouple temperatures: T=a+σb (where a and b is constant, respectively); measuring the maximum allowable stress of the stave material of the furnace body, and obtaining the maximum allowable thermocouple temperature by substituting the measured values for the above expression; and performing repairing operation by stopping supply of cooling water in the state that operation is being operated in case that the actually measured temperatures are less than the maximum allowable thermocouple temperature by comparing actually measured temperatures with the maximum allowable thermocouple temperature when repairing of the selected cooling pipe is required, and performing repairing operation after the actually measured temperatures reach the maximum allowable thermocouple temperature by stopping operation in case that the actually measured temperatures are greater than the maximum allowable thermocouple temperature.

Description

How to repair the furnace stave of Korex melting furnace

The present invention relates to a method for repairing a furnace stave of a COREX melting furnace, and more particularly, to a method for repairing a furnace stave by finding an appropriate closing time of a cooling tube installed inside a furnace stave. .

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. The stave creates a cooling tube in the iron plate that allows the cooling water to penetrate the cooling water, thereby recovering the heat it will receive to keep the shell healthy.

Repair work is carried out when the furnace stave is broken or foreign matter has accumulated in the cooling tube. The maintenance work usually stops operation and after sufficient time has elapsed, the water supply to the cooling tube coolant starts after stopping. The longer the downtime is, the greater the economic loss due to reduced production, so it is important to decide when to pay for the repair. However, in the prior art, repairs started immediately after the end of the operation without a certain criterion for the repair time, or waited indefinitely for a predetermined time before repairing. However, if the water supply of the cooling tube cooling water of the furnace stave is stopped for repairing immediately after the end of the operation, the stave may be excessively heated and the stave may be damaged. In addition, if you wait for an indefinite period of time and stop the supply of cooling tube cooling water, there is no fear of breaking the stave, but the operation must be stopped for a long time, resulting in economic loss due to reduced production.

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 obtains a temperature distribution and a thermal stress distribution for a furnace body stave by a finite element method. Using this, to find out the allowable temperature of the thermocouple which is the standard for determining the maintenance time of the furnace stave, to determine the appropriate maintenance time of the furnace stave to provide a method of repairing to minimize the thermal shock near the cooling tube, The purpose is.

1 is a schematic diagram of a Korex melting furnace

Figure 2 is a cross-sectional view of the furnace body of the corex melting furnace

3 is a flowchart of a method for repairing a furnace according to the present invention;

4 is a schematic diagram dividing an analysis region for thermal conductivity and thermal stress analysis

Figure 5 is a graph showing the thermocouple temperature according to the elapsed time of operation for determining the maintenance time according to the present invention

* Description of the symbols for the main parts of the drawings *

1 ... Stamp 2 ... Stamp

3 ... stave 4 ... cooling tube

5 ... lead and 6 ... thermocouple

The present invention for achieving the above object is a method for repairing the furnace stave of the Korex smelting furnace composed of a lead having a shell, a stamp, a stave and a thermocouple, and including a certain number of cooling tubes therein, Select one of the cooling tubes in the eve and give the corresponding cooling tube as the insulation condition, give the boundary condition at the thermocouple position to each temperature while changing the thermocouple temperature, and the boundary condition at the outer surface of the shell by air cooling Giving a boundary condition other than that as a thermal insulation condition, and obtaining a temperature distribution and a thermal stress distribution corresponding to the thermocouple temperature by a finite element method;

Deriving the correlation between the thermocouple temperature (T) and the maximum thermal stress (σ) in the form of the following equation 1 by taking the maximum thermal stress in the thermal stress distribution corresponding to each thermocouple temperature;

T = a + σb, where a and b are constants

Measuring a maximum allowable stress of the furnace stave material and substituting the measured value into the equation to obtain a maximum allowable thermocouple temperature; And

If it is judged that repair is required due to a problem in the selected cooling pipe during actual operation, compare the measured temperature of the thermocouple with the maximum allowable thermocouple temperature, and if the measured temperature is lower than the maximum allowable thermocouple temperature, the operation is in operation. Performing maintenance work by stopping the supply of cooling water, and if the measured temperature is greater than the maximum allowable thermocouple temperature, stopping the operation to perform the repair work after the measured temperature reaches the maximum allowable thermocouple temperature; It relates to a method for repairing the furnace stave of the Korex smelting furnace comprising a.

Hereinafter, the present invention will be described in detail.

In the present invention, the heat conduction analysis and the thermal stress analysis for the furnace stave are performed assuming that the cooling water is stopped. 2 shows a Korex noce stave. The furnace stave is composed of barbed steel, stamp, stave and lead, and the thermocouple is inserted into the lead. In the present invention, the analysis area was taken as the bark, stave, stamp and lead, and in particular, the lead portion was taken only to the position of the thermocouple installed in the lead. The boundary condition at the thermocouple location gives the temperature as the thermocouple temperature. The boundary condition at the inner surface of the cooling tube is a case of adiabatic condition because the supply of cooling water is stopped. On the outer surface of the shell, boundary conditions give cooling conditions by air cooling. Other boundary conditions give adiabatic conditions.

In order to solve the thermal conductivity and thermal stress analysis equations in the case of the boundary and boundary condition, the temperature distribution and thermal stress distribution are obtained by the calculation by the finite element method. In general, a plurality of cooling tubes are installed in the furnace stave, and the temperature distribution and the thermal stress distribution are obtained for each cooling tube.

In the present invention, the correlation between the thermocouple temperature and the maximum stress inserted in the furnace stave is obtained. This correlation calculates the maximum thermal stress in the stave while varying the temperature of the boundary condition at the thermocouple location. Thus, a correlation between the thermocouple temperature (T) and the maximum thermal stress (σ) is derived.

In this case, the correlation is expressed as a first-order equation as in the following equation, and coefficients a and b are obtained.

T = aσ + b

In the present invention, if the maximum stress is substituted into the allowable stress of the stave according to the correlation obtained above, the allowable temperature of the thermocouple is obtained by defining the thermocouple temperature at that time as the allowable temperature of the thermocouple. The allowable stress of the stave is a value obtained by measuring the maximum allowable stress of the stave material.

In addition, in the present invention, when the current temperature of the thermocouple is compared with the allowable temperature of the thermocouple, when the current temperature of the thermocouple is smaller than the allowable temperature of the thermocouple, the supply of the cooling water is immediately stopped in operation and the repair is immediately performed. In this case, the operation will be stopped and the timing of repair should be determined. At this time, the remuneration date is determined as follows. That is, the thermocouple temperature drops after the operation stops, and after the time when the thermocouple temperature reaches the allowable temperature of the thermocouple, the maintenance time is determined. After this repair time, the supply of coolant coolant in the furnace stave is stopped and the repair is started. The repair can be carried out by conventional methods such as filling of the refractory.

Figure 3 is a flow chart showing the flow of the present invention as described above, showing the maintenance time determination method of the furnace stave according to the present invention in sequence.

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

Example

The method for determining the maintenance time of the furnace stave according to the present invention was carried out in a furnace of Korex having a daily output of 2000 tons.

This embodiment will be described by proceeding with each step as mentioned in the configuration of the invention.

First, thermal conduction analysis and thermal stress analysis of the furnace stave are performed. An analysis area for thermal conductivity and thermal stress analysis of a furnace body including a stave of a Korex melting furnace is shown in FIG. 4. In FIG. 4, the analysis region is divided into bar, stave, stamp and lead. The thermal conductivity of each region was 50 kcal / mhr ° C., stab 29kcal / mhr ° C., 0.8 / mhr ° C. stamp, 10 kcal / mhr ° C., and boundary conditions were as follows. The boundary condition inside the cooling tube is given as convection condition in the normal water supply, the heat transfer coefficient is 2900kcal / m ² hr ℃, and the coolant temperature is 35 ° C. . The boundary condition at the outer surface of the shell is convection by air cooling. The heat transfer coefficient is 20kcal / m ² hr ℃ and the ambient temperature is 20 ℃. The boundary condition at the thermocouple position is given by the temperature boundary, and the temperature is given in the range of 100-500 ° C. Other boundary conditions give adiabatic conditions. In order to solve the thermal conductivity equation and the thermal stress equation in the case of the boundary and the boundary condition, the temperature distribution and the thermal stress distribution were calculated by the finite element method.

Next, the correlation between the thermocouple temperature inserted in the furnace stave and the maximum stress was obtained. This correlation calculates the temperature of the boundary condition at the above-mentioned thermocouple position in the range of 100 to 500 ° C. In this embodiment, the temperature of 100 ° C, 200 ° C, 300 ° C, 400 ° C, and 500 ° C The maximum stress was calculated. The results were as shown in Table 1 below.

Thermocouple temperature Thermal stress 100 ℃ 141 MPa 200 ℃ 256 MPa 300 ℃ 372 MPa 400 ℃ 487 MPa 500 ℃ 603 MPa

When formulated using the values in Table 1, it is shown in Equation 2.

T = 1.155 σ + 25.333

Where T is the allowable temperature of the thermocouple and σ is the maximum thermal stress.

Next, the allowable thermocouple temperature corresponding to the allowable stress of the stave was obtained from the correlation between the thermocouple temperature and the thermal stress. The allowable stress of the stave installed in the Korex smelting furnace is 435 MPa, wherein the allowable thermocouple temperature was 355 ° C. obtained from Equation 2.

Next, since the current temperature of the thermocouple inserted into the furnace body of the Korex smelting furnace is 450 ° C, and this temperature is larger than the allowable thermocouple temperature of 355 ° C, the operation was stopped and the maintenance time of the furnace body stave was determined. Figure 5 shows the change over time of the thermocouple temperature from after the shutdown. This figure shows that the temperature of the thermocouple drops after the end of the operation, and the time to reach the allowable temperature of the thermocouple is obtained by 10 hours. After 10 hours the cooling water supply is turned off and the furnace stave is repaired.

As described above, using the furnace stave repair method of the present invention, there is an effect that the stave can be economically and safely repaired by stopping the supply of cooling water without giving the risk of excessive heat load to the furnace stave. .

Claims (1)

In the method for repairing the furnace stave of the Corex smelting furnace consisting of a lead, which has a shell, a stamp, a stave and a thermocouple, and includes a certain number of cooling tubes therein, Select any one of the cooling tubes in the furnace stave to give the cooling tube as an insulation condition, give the boundary condition at the thermocouple position to each temperature while changing the thermocouple temperature, and the boundary condition at the outer surface of the steel shell to air cooling. Giving a cooling condition by means of a cooling condition, giving a boundary condition other than that as a heat insulating condition, and obtaining a temperature distribution and a thermal stress distribution corresponding to the thermocouple temperature by a finite element method; Deriving a correlation between a thermocouple temperature (T) and a maximum thermal stress (σ) by taking a maximum thermal stress in the thermal stress distribution corresponding to each thermocouple temperature in the form of the following equation; T = a + σb, where a and b are constants Measuring a maximum allowable stress of the furnace stave material and substituting the measured value into the equation to obtain a maximum allowable thermocouple temperature; And If it is judged that repair is required due to a problem in the selected cooling pipe during actual operation, compare the measured temperature of the thermocouple with the maximum allowable thermocouple temperature, and if the measured temperature is lower than the maximum allowable thermocouple temperature, the operation is in operation. Performing maintenance work by stopping the supply of cooling water, and if the measured temperature is greater than the maximum allowable thermocouple temperature, stopping the operation to perform the repair work after the measured temperature reaches the maximum allowable thermocouple temperature; Core stave repair method of the Korex smelting furnace comprising a

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