JPS61186411A - Method for discriminating period when protection of refractory brick of blast furnace is necessary - Google Patents

Abstract

PURPOSE:To predict and discriminate exactly the time when the protection of the refractory bricks of a blast furnace under operation is necessary by determining the tendency of the max. value of the measured temp. to an increase with time from the measured value of the change of said refractory bricks with time and predicting the future period when the refractory bricks are damaged. CONSTITUTION:The temp. is continuously measured at multiple points in the wall on the bottom side of the blast furnace under operation. The max. value 1 and min. value 2 are determined upon lapse of time and the tendency of the max. value to the increase with time is plotted on a logarithmic graph from the measurement data or is determined quantitatively by a method of least squares. The period when the max. value of the temp. of the refractory bricks attains the preset upper limit temp. of the refractory bricks corresponding to the required residual thickness of the refractory bricks is discriminated by using such graph for the tendency of the value 1 to the increase with time. Whether the refractory bricks are in the period requiring the protection or not is discriminated from period requiring the protection or not is discriminated from the period discriminated in the above-mentioned manner and the stable operation of the blast furnace is executed without the shutdown.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for determining when blast furnace refractory bricks require protection.

(Conventional technology) Generally, the degree of damage to blast furnace refractory bricks is determined by measuring the temperature of the refractory bricks on the shell side, calculating the remaining thickness of the bricks from the measured temperature value through heat transfer calculations, and determining the degree of damage. was. Conventionally, it has been determined whether or not the refractory bricks are in need of protection by comparing the calculated remaining thickness of the bricks with the set required remaining thickness of the refractory bricks.

(Problems to be Solved by the Invention) The conventional method described above for determining whether or not a refractory brick is in need of protection can only be determined at the time when the temperature of the refractory brick is measured; It was not possible to predict when protection would be needed. Therefore, in cases where the refractory bricks were rapidly eroded or peeled off, protective measures could not be taken in time and blast furnace operation had to be stopped.

In view of the above, the present invention relates to a method for determining when blast furnace refractory bricks need protection, which can be useful for taking prompt protective measures by predicting the timing of future damage to blast furnace refractory bricks.

(Means for Solving the Problems) The technical measures taken by the present invention to solve the problems of the prior art are characterized by measuring changes over time in the temperature of refractory bricks in an operating blast furnace. By quantitatively determining the increasing tendency of the maximum value of the measured temperature over time and using the quantitative increasing tendency, the maximum value of the refractory brick temperature can be determined as the upper limit of the refractory brick corresponding to the set required residual thickness of the refractory brick. The point is to determine the time when the temperature value is reached, and from that time to determine whether or not the refractory bricks are in the need of protection.

(Example) Embodiments of the present invention will be described below based on the drawings.

First, at many points on the bottom side wall of a blast furnace in operation,
The temperature near the iron skin of the refractory bricks was measured over time over a period of approximately four years after firing. FIG. 1 shows the measurement results at one of the measurement points, and shows the change in the temperature of the refractory brick over time. According to the measurement results, the temperature of the refractory brick changes in a pulsating manner over time, showing a maximum value of 1 and a minimum value of 2. Moreover, the maximum value 1... shows a gradual upward trend over time.

Next, in order to quantitatively determine the increasing trend over time of the maximum value 1 of the measured temperature of the refractory brick, the maximum value 1 was plotted on a logarithmic graph as shown in FIG. Then, the upward trend of the maximum value 1 over time could be approximated by a straight line as shown in the figure, and could be determined quantitatively.

In addition, in order to quantitatively determine the upward trend of the maximum value 1 over time, the temperature values of the refractory bricks measured over time may be directly plotted on a log-log graph as shown in Figure 3. If linear approximation is difficult on a double-logarithmic graph, the maximum value 1 may be expressed numerically as a function of time by the least squares method and then quantitatively determined.

Further, FIG. 4 shows three temperature measurement points r and n of the temperature measurement points on the bottom side wall of the blast furnace in operation in the same manner as above.

Maximum value 1 of refractory brick temperature measured over time in ■
... is plotted on a log-log graph. From this figure, each measurement point 1. It can be seen that the upward trend over time of the maximum value 1 in Il, III can be approximated by a straight line, and that the upward trend differs depending on the measurement point.

Next, in FIG. 4, each measurement point 1. Find the time when the maximum temperature 1 of the refractory bricks n and III reaches 260°C. At this time, the upward trend of the local maximum value 1 can be approximated by a straight line, so it can be determined by predictive reading from the scale on the graph.

Then, in terms of the period from burning, the temperature reached 260℃ at measurement point I within 5 years, and at measurement point ■ within 7 years.
At measurement point ■, it was after the 7th year. Here, the temperature of 260° C. is the upper limit temperature value of the refractory brick corresponding to the set required remaining thickness of the refractory brick. Note that the specific set value varies depending on the expected safety factor, and also varies depending on the temperature measurement position, the material of the refractory brick, etc.

Next, if we quantitatively determine the rising trend of the maximum value of the refractory brick temperature at all measurement points in the same manner as in Figure 4, we will find that the maximum value will reach 260℃ within 5 years after firing, similar to the measurement point. It was predicted that 25% of all measurement points would reach this point (this will be referred to as Group A).

Also, like measurement point ■, 23% of all measurement points (these are group B) were said to reach 260℃ within 7 years after burning; 260 after 7th year
℃ was reached at 52% of all measurement points (this is defined as group 0).

Therefore, at the time of measurement, four years had passed since the burning, so
It was determined that it was necessary to take protective measures for the refractory bricks in Group A, and protective measures were taken.

As a protective measure, the hot air blowing tuyeres above the refractory bricks in Group A should be closed for a certain period of time. T in molten iron
Add i to increase the viscosity of molten iron and make the vortex flow gentler. The use of specific iron exits may be suspended for a certain period of time.

Then, temperature measurements were continued as they were, and at the 6th year after the firing, the increasing trend of the maximum value of the refractory brick temperature at all measurement points was again quantitatively determined. As shown in Figure 5, only 3% of all measurement points in Group A actually reached 260°C in the 5th year after the fire started, and it is expected that the temperature will reach 260°C in 7 years. Deaf group B increased to 40%, and group 0, who would reach 260 degrees Celsius after the seventh year, increased to 57%.

This is due to the fact that the refractory bricks of group A, for which protective measures were taken four years after burning, fell into group B or group 0.
Those who were in Group B or Group 0 in 2008 were never in Group A.

This shows that it was appropriate to determine whether or not the refractory bricks were in need of protection four years after burning.

The reason why the above-mentioned method can appropriately determine when the protection of refractory bricks is required has not been completely elucidated theoretically, but the following is assumed.

In other words, the temperature of the refractory bricks in a blast furnace during operation becomes thinner due to erosion and peeling inside the furnace due to the stirrup pig iron, so the temperature at the temperature measurement point on the shell side will be the same as long as there is no change inside the furnace. It should rise gradually. However, in reality, as mentioned above, the temperature of refractory bricks changes in a pulsating manner over time.
The local maximum value and local minimum value are shown.

This is because the vortex flow state is not uniform in the furnace, and in areas where the flow is slow, the amount of heat transferred to the refractory bricks decreases due to external cooling, and an adhesion layer is formed on the moving surface of the refractory bricks, which gradually increases the temperature measured. decreases. Then, when the vortex flow state changes and the flow speeds up in that part, the adhesion layer of the refractory bricks is melted away, the refractory bricks are further eroded and peeled off, and the measured temperature is gradually increased, and this process is repeated.

Additionally, if a crack occurs inside the refractory brick, it expands and acts as a heat insulating layer, causing the measured temperature to gradually drop. Then, as the refractory bricks erode and peel, the measured temperature gradually increases, and this process is repeated.

On the other hand, since blast furnaces have large structures, the condition of the furnace construction using refractory bricks varies depending on the location, and the vortex flow condition is not uniform (
The progress of erosion and spalling of refractory bricks differs depending on the location due to the concentration of vortex flow, especially near the taphole.

Due to such changes in the conditions inside the furnace, the measured temperature value of the refractory bricks fluctuates over time, and the manner in which the temperature changes varies depending on the location. However, there is no difference in the fact that the remaining thickness of the refractory bricks gradually becomes thinner, so the maximum value of the measured temperature gradually increases over time, and the upward trend over time is consistent with the rate at which the remaining thickness of the refractory bricks becomes thinner. handle.

Based on the above, by using the increasing tendency of the maximum value of refractory brick temperature over time, we can determine when the maximum value of refractory brick temperature reaches the upper limit temperature value of the refractory brick corresponding to the set required residual thickness of refractory brick. By determining the period, it can be determined whether the refractory bricks are already in need of protection or not.

As a result, instead of knowing the degree of damage to bricks only at the time of measuring the temperature of the refractory bricks, as in the past, it is possible to determine whether or not the refractory bricks are in need of protection by predicting the degree of damage to the bricks in the future. This allows prompt protective measures to be taken. In particular, by measuring the temperature at multiple points as described above, it is possible to predict the damage tendency of the entire hearth bottom, and it is also possible to estimate the hearth bottom life.

(Effects of the Invention) According to the method of the present invention, by using the tendency of the maximum value of the refractory brick temperature to rise over time, the maximum value of the refractory brick temperature is determined to be the refractory that corresponds to the required residual thickness of the refractory brick. The time when the bricks reach the upper limit temperature value is determined, and from that time it is determined whether the refractory bricks are already at the point where protection is required. As a result, instead of knowing the degree of damage to bricks only at the time of measuring the temperature of the refractory bricks, as in the past, it is possible to determine whether or not the refractory bricks are in need of protection by predicting the degree of damage to the bricks in the future. This allows immediate protective measures to be taken against the refractory bricks.

[Brief explanation of the drawing]

The drawings relate to embodiments of the present invention, and FIG. 1 is a measurement diagram of changes in the temperature of refractory bricks over time, FIGS. 2 and 3 are diagrams showing the tendency of the maximum value to increase over time, and FIG. FIG. 5 is a diagram showing the tendency of the maximum value to increase over time at different fixed points on two sides, and FIG. 1.-Local maximum value.

Claims (1)

[Claims] 1. Measure the change in the temperature of the refractory bricks in the operating blast furnace over time, quantitatively determine the upward trend of the maximum value of the measured temperature over time, and use this quantitative upward trend to determine the temperature of the refractory bricks. The present invention is characterized in that the time when the maximum value reaches the upper limit temperature value of the refractory brick corresponding to the required residual thickness of the refractory brick is determined, and based on that time, it is determined whether or not the refractory brick is in a period where protection is required. Method for determining when blast furnace refractory bricks require protection.