JPH07278627A - Cooling piping for bottom of blast furnace and method for cooling bottom of blast furnace - Google Patents

Abstract

PURPOSE:To effectively cool a furnace bottom refractory corresponding to the distribution of molten iron flow in the radial direction and restrain erosion of the furnace bottom refractory by arranging cooling pipes having individually inlets and outlets for cooling medium in concentric circle shape and separately controlling the temp. and/or the flow rate of the fed cooling medium. CONSTITUTION:The cooling pipings having 5-15 pieces are arranged so that the interval between each adjacent piping is equal or wider from the outer peripheral part of the furnace bottom toward the center part. Further, the inlet and the outlet are arranged in each cooling piping, respectively. At the time of cooling, the past and the present temps. of from the outer peripheral part of the furnace bottom to the center part are detected, and the remaining thickness of the refractory is calculated from the max. temp. heretofore in the furnace bottom refractory. Further, the thickness of solidified layer developed in the furnace bottom refractory is calculated based on the max. temp. at the past and the present temp., and the cooling medium temp. and/or flow rate for flowing into the cooling piping are controlled according to the refractory thickness and/or the solidified layer thickness developed on the refractory.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blast furnace bottom cooling pipe and a cooling method therefor.

[0002]

2. Description of the Related Art A coke filling area called a core exists in a hearth portion of a blast furnace, and hot metal and slag produced by reduction or melting of ore are accumulated in voids of the coke. Refractory containing carbon as the main component is usually used for the bottom brick, but in order to prevent erosion of the refractory due to the flow of hot metal and heat load, cooling can be done by installing a cooling pipe under the refractory. It is being appreciated. The flow of hot metal differs depending on the erosion profile of the furnace body, the shape of the lower end of the core, the liquid permeability in the core, etc., for example, the entire core floats higher than when it completely sinks to the bottom of the furnace. If there is a narrow gap between the furnace bottom and the furnace bottom, a large amount of hot metal flows in this space.If there is a gap around the center of the furnace core with the bottom of the furnace bottom, there is a gap. A circular flow is created toward the taphole. The furnace bottom refractory, which corresponds to a portion where a large amount of hot metal flows, has a high temperature and receives a large heat load. In a normal blast furnace operation, the thermometer embedded in the bottom refractory
Monitor the temperature change of refractory and take measures when the temperature rises.

The cooling pipes installed in the lower part of the furnace bottom generally have a method of flowing a cooling medium through the pipes arranged in parallel. In this method, when there is a heat load distribution in the bottom part of the furnace, The cooling capacity cannot be controlled according to the size.
In large-scale blast furnaces in recent years, an annular flow is often generated around the bottom of the furnace to increase the heat load.To prevent selective erosion of this part, the periphery of the bottom is cooled more strongly than the center of the bottom. It is often desirable to do so. In order to solve this problem, Japanese Patent Laid-Open No. 58-55509 and Japanese Patent Laid-Open No. 63-105913 disclose cooling control in which the central portion and the peripheral portion of the furnace bottom are separately cooled to change the cooling capacity. A piping method and a method of forming a region having different cooling ability by providing a heat transfer resistor in a part of the cooling pipe have been proposed. JP-A-5
No. 8-55509 discloses a method in which blast furnace bottom cooling ducts are provided in a plurality of stages, the lower duct is installed on the entire furnace bottom, and the upper duct is installed on the outer periphery of the furnace bottom to cool each independently.
Further, in Japanese Patent Laid-Open No. 63-105913, in a blast furnace in which cooling pipes at the bottom of the blast furnace are installed in straight parallel lines, a heat transfer resistor is attached to and detached from a part corresponding to the central part of the bottom of the blast furnace. A method for cooling the bottom of the furnace is described which can reduce the cooling capacity of the central part.

[0004]

However, the method disclosed in Japanese Patent Laid-Open No. 58-55509 has a complicated structure since a plurality of cooling ducts are provided in the peripheral portion of the furnace bottom, and the difficulty in facility construction increases. Also, JP-A-63-105913
The method disclosed in Japanese Patent Laid-Open Publication No. 2003-242242 has a drawback that it is difficult to provide a heat transfer resistor in the cooling pipe, resulting in high equipment cost and construction cost. The present invention provides a blast furnace bottom cooling pipe and a bottom cooling method capable of controlling the cooling capacity in the radial direction of the bottom according to the temperature distribution of the bottom without using special parts other than a complicated structure and piping. The purpose is to

[0005]

According to the present invention, the cooling pipes at the bottom of the blast furnace are formed concentrically, and the temperature or flow rate of the cooling medium is controlled according to the heat load at the bottom of the blast furnace. It is characterized in that it makes it possible to change the cooling capacity of the central part and the peripheral part of the furnace bottom without using a complicated structure. That is, the gist of the present invention is as follows: (1) In cooling pipes at the bottom of a blast furnace, cooling pipes having concentric circles of 5 or more and 15 or less arranged at equal intervals are provided. And a cooling medium inlet / outlet for each cooling pipe.

(2) In the cooling pipe at the bottom of the blast furnace, five or more and 15 or less concentric circles arranged so that the intervals between the adjacent cooling pipes are widened from the outer periphery of the furnace bottom toward the center of the furnace bottom. A cooling pipe for the bottom of a blast furnace, characterized in that each cooling pipe has a cooling medium inlet / outlet.

(3) In the blast furnace bottom cooling method using the blast furnace bottom cooling pipe according to (1) or (2), the past and present temperatures from the outer periphery of the furnace bottom to the center of the furnace bottom are detected, The refractory residual thickness is calculated from the highest temperature of the refractory internal temperature to the present, and the solidified layer thickness generated on the refractory is calculated based on the difference between the past maximum temperature and the present temperature of the refractory internal temperature. And controlling the temperature and / or the flow rate of the cooling medium flowing through the blast furnace bottom cooling pipe according to the residual thickness of the refractory and / or the thickness of the solidified layer formed on the refractory. It is in. The furnace bottom outer peripheral portion referred to herein means a furnace bottom refractory portion below the furnace inner peripheral portion, and the furnace bottom center portion refers to a furnace bottom refractory portion below the furnace central axis.

[0008]

When the cooling pipe of the present invention is used, the furnace bottom cooling capacity can be controlled as follows. A case where water is used as a cooling medium using an iron cooling pipe will be described as an example with reference to the drawings. That is, (1) When the cooling pipes 3 on the bottom surface of the blast furnace are formed into eight concentric circles at equal intervals as shown in FIG. 1, and each cooling pipe has a cooling medium inlet / outlet, respectively, In the concentric circles, the lower the cooling water temperature and the higher the cooling flow rate, the greater the cooling capacity can be obtained.

(2) As shown in FIG. 2, eight cooling pipes 3 on the bottom surface of the blast furnace are arranged so that the intervals between the adjacent cooling pipes 3 become wider from the outer peripheral portion of the furnace bottom toward the central portion of the furnace bottom. When the cooling pipes are formed in concentric circles and each has a cooling medium inlet / outlet, if the temperature and flow rate of the cooling water are constant, the cooling capacity from the outer periphery of the furnace bottom toward the center of the furnace bottom Becomes smaller, and a larger cooling capacity can be obtained as the temperature of the cooling water is made lower and the flow rate of the cooling water is made larger in each concentric circle portion based on this state.

In blast furnace operation, a thermometer is embedded in the bottom refractory to measure the temperature, and the erosion position of the refractory is determined by using the past maximum temperature and the difference between the past maximum temperature and the current temperature is used. The thickness of the solidified layer formed on the refractory is estimated. For example, the thermal conductivity of the furnace bottom brick and the solidified layer are λ, λ ^* (W /
m / ° C), the depth in the brick L ₁ , L ₂ (m)
The temperature measurement value of the thermocouple buried in the position of (L ₁ <L ₂ ) is T
_{If 1} , T ₂ (° C.), T, L, and l are estimated as the following relationships among these values, brick working surface temperature T, brick residual thickness L, and solidified layer thickness l.

[0011]

[Equation 1]

Reference numeral 1150 is the hot metal solidification temperature. That is, when T ₁ and T ₂ reach the maximum temperature, T = 1150,
Calculate L using the equation on the right, assuming l = 0, and calculate T and l using the current T ₁ and T ₂ and L. At a site where only one thermocouple (depth L ₂ ) is buried, the outside air temperature T ₀ and the convection heat transfer coefficient h between the brick and the outside air
Using (W / m ² / ° C.), the thermocouple position from equation (2)
Calculate the overall heat transfer coefficient H (W / m ² / ° C) between outside air,
Expression (3) is used instead of the right side of expression (1).

[0013]

[Equation 2]

The temperature and / or the flow rate of the cooling water are adjusted so that the remaining thickness of the refractory and the solidified layer formed on the refractory estimated by this method are thin, that is, the cooling capacity of the portion where the cooling is desired to be strong becomes large. If the control is performed, erosion of the bottom refractory can be effectively suppressed. The annular bottom flow and the temperature difference in the radial direction of the bottom of the furnace become a problem mainly in the case of a large blast furnace with an inner diameter of the hearth of 10 m or more. In the blast furnace of this scale, if there are less than 5 concentric circles, The intervals between the cooling pipes are too large to perform appropriate cooling control corresponding to the temperature distribution in the bottom of the furnace, and sufficient cooling capacity cannot be obtained. Also,
If the number of concentric circles is 5 or more, the controllability increases and the cooling capacity increases as the number increases, but on the other hand, the equipment becomes complicated and the equipment cost cools. If the number of concentric circles exceeds 15, the equipment becomes complicated and the equipment cost increases. Not just the effect.

[0015]

【Example】

(Example 1) As shown in FIGS. 1 (a) and 1 (b), eight iron cooling pipes 3 on the bottom surface of a blast furnace were arranged so that the intervals between adjacent pipes were uniformly 0.75 m. In a blast furnace with a hearth diameter of 12 m, which is formed in a concentric shape, and each cooling pipe has a cooling medium inlet / outlet, while checking the indicated value of the thermometer 4 embedded in the bottom refractory material, The operation was performed by changing the flow rate of cooling water. That is, the refractory remaining thickness and the solidified layer thickness are calculated from the past maximum temperature and the present temperature value by the method described in the section of action, and when the refractory remaining thickness is 1 m or more, the solidified layer thickness 1 m is used as a reference. The cooling water flow rate is reduced by
When the residual thickness of the refractory is less than 1 m, the standard cooling water flow rate was increased by a rate of less than 1 m.

FIG. 3 shows an example of the transition of the temperature inside the refractory at the upper part of the cooling pipe of the outermost concentric circle and the innermost concentric circle.
From the beginning, the outer concentric circles were operated with a larger flow rate so that the flow rate of the cooling water in the outermost part of the bottom of the furnace was 10% higher than in the central part, but the temperature of the outer periphery increased from the point in the figure Since the temperature of the central part tended to decrease, it was estimated that the solidified layer developed in the central part and the flow of hot metal decreased, and the annular flow tendency appeared in the outer peripheral part. Was increased by 20%, and the flow rate of the cooling water in the central portion was decreased by 20%. When this cooling state was continued for a while, the temperature increase in the outer peripheral portion and the temperature decrease in the central portion stopped after 3 days and gradually returned to the original temperature. At that time, the cooling water flow rate was returned to the original level.
By this action, it was possible to prevent the wear of the refractory material on the outer periphery of the furnace bottom without interrupting the smooth operation.

(Embodiment 2) As shown in FIGS. 2 (a) and 2 (b), the iron cooling pipe 3 at the bottom of the blast furnace has a radius of 0.75, 1.65, 2.5 from the center axis of the furnace bottom. 3.3, 4.0
In a blast furnace with a hearth diameter of 12 m, which has 8 concentric circles of 5, 4.75, 5.4, and 6.0 m, each cooling pipe has a cooling medium inlet / outlet, a bottom refractory material While observing the indicated value of the thermometer 4 embedded in the, the flow rate and the temperature of the cooling water flowing in each concentric circle were changed and the operation was performed. That is, the refractory residual thickness and the solidified layer thickness are calculated from the past maximum temperature and the present temperature value by the method described in the section of action, and when the refractory residual thickness is 1 m or more, the solidified layer thickness 1 m is used as a reference. The cooling water flow rate is decreased / increased only when the solidified layer thickness is increased / decreased, and when the refractory residual thickness is less than 1 m, 1
The standard cooling water flow rate was increased by the ratio reduced from m.

FIG. 4 shows an example of transition of the temperature inside the refractory at the upper part of the cooling pipes of the outermost concentric circle and the innermost concentric circle.
Initially, the flow rate and temperature of the cooling water flowing through the concentric circles were made uniform, but since the temperature at the outer periphery increased and the temperature at the center tended to decrease from the time in the figure, It is estimated that the solidified layer developed in the area and the flow of the hot metal decreased, and an annular flow tendency appeared in the outer periphery. For the four outer concentric circles, 20, 15, 10 and 5% cooling water flow rate from the outside For the two inner concentric circles from the outside,
Water heated to 10 ° C. was flowed, and the innermost two concentric circles were switched off by cutting the cooling water and flowing nitrogen at room temperature. When this cooling state was continued for a while, the temperature increase in the outer peripheral portion and the temperature decrease in the central portion stopped after 5 days and gradually returned to the original temperature. At that time, the cooling water flow rate was returned to the original level. By this action, it was possible to prevent the wear of the refractory material on the outer periphery of the furnace bottom without interrupting the smooth operation.

[0019]

The present invention has the following effects. (1) The erosion shape of the bottom of the blast furnace is controlled by controlling the temperature or flow rate of the cooling medium flowing in each concentric circle by using concentric cooling pipes without using complicated equipment at the bottom of the bottom. Corrosion of the furnace bottom refractory can be suppressed while effectively cooling in accordance with the radial distribution of the molten iron or the hot metal flow. (2) Cooling medium is formed at the same temperature and flow rate using concentric cooling pipes arranged so that the intervals between the adjacent cooling pipes are sequentially widened from the outer peripheral portion of the furnace bottom toward the central portion of the furnace bottom. Even when flowing, the cooling capacity of the outer periphery of the bottom of the furnace can be made larger than that of the center of the bottom to suppress the development of the solidified layer in the center of the bottom and the annular flow of the bottom of the furnace. In addition to controlling the temperature or flow rate of the cooling medium flowing through
Erosion of the bottom refractory can be suppressed more effectively.

[Brief description of drawings]

FIG. 1 is a furnace bottom cooling piping diagram of Example 1.

2 is a furnace bottom cooling piping diagram of Example 1. FIG.

[Fig. 3] Example of temperature change in refractory material at outer peripheral portion and central portion of furnace bottom (Example 1)

[Fig. 4] Example of temperature change in refractories at the outer peripheral portion and the central portion of the furnace bottom (Example 2)

[Explanation of symbols]

 1 Blast furnace furnace body 2 Furnace bottom refractory 3 Furnace bottom cooling pipe 4 Buried thermometer 5 Cooling water inlet / outlet

Claims (3)

[Claims] 1. The cooling pipes at the bottom of the blast furnace have at least five adjacent cooling pipes arranged at equal intervals.
A blast furnace bottom cooling pipe, which has 5 or less concentric cooling pipes, and each cooling pipe has a cooling medium inlet / outlet. 2. In the cooling pipe at the bottom of the blast furnace, 5 or more and 15 or less concentric circles are arranged such that the intervals between the adjacent cooling pipes are widened from the outer periphery of the furnace bottom toward the center of the furnace bottom. A blast furnace bottom cooling pipe characterized by having a cooling pipe, and each cooling pipe having a cooling medium inlet / outlet individually. 3. When cooling the blast furnace bottom using the blast furnace bottom cooling pipe according to claim 1 or 2, the past and present temperatures from the outer periphery of the furnace bottom to the center of the furnace bottom are detected, and The refractory remaining thickness is calculated from the maximum temperature of the refractory temperature to date, and the solidified layer thickness generated on the refractory is calculated based on the difference between the past maximum temperature and the present temperature of the refractory temperature. A method for cooling the bottom of a blast furnace, wherein the temperature and / or the flow rate of a cooling medium flowing through the cooling pipe for the bottom of the blast furnace are controlled according to the remaining thickness of the refractory and / or the thickness of the solidified layer formed on the refractory.