JPS61238904A - Method for adjusting distribution of gaseous flow in blast furnace in stage of changing operation - Google Patents

Abstract

PURPOSE:To adjust the distribution of the gaseous flow in a blast furnace exactly and quickly and to stabilize the operation of the blast furnace by determining the layer thickness ratio of a furnace wall part after the change of an operation from the flow rate of the air passing in the furnace and a heat flow ratio in the stage of said changing and controlling a charge distribution so as to attain said ratio. CONSTITUTION:The layer thickness ratio of the furnace wall part after the change of the operation of the blast furnace is determined from the predetermined relation among the flow rate of the air passing in the furnace, the heat flow ratio and the layer thickness layer of the furnace wall part in the stage of changing said operation. The predicted value of the layer thickness ratio of the furnace wall part which is the index for the target gaseous distribution ratio is determined as the target and the distribution of the charge such as coke and ore is controlled in such a manner that the above-mentioned layer thickness ratio of the furnace wall part is obtd. The exact and quick adjustment of the distribution of the gaseous flow in the stage of changing the operation is thus made possible and the stable blast furnace operation is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention belongs to the field of so-called blast furnace operating methods, and includes gas flow distribution adjustment performed when changing the operation of a blast furnace.
This invention relates to a method of controlling the burden distribution, particularly by adjusting the layer thickness ratio of the furnace wall.

(Prior art) A common method for controlling charge distribution for the purpose of adjusting gas flow distribution when changing blast furnace operations is to adjust the layer thickness distribution of ore and coke in the radial direction of the furnace. This is done to normalize the unloading of raw materials and the furnace heat by optimizing the gas flow in the furnace.

Such control of the charge distribution is normally performed using a bell rest tube, a movable armor, etc., which are top charging devices.

Conventional methods for adjusting gas flow distribution or charge distribution have been disclosed in Japanese Patent Application Laid-Open No. 58-87209 and Japanese Patent Application Laid-open No. 56-163205. The most typical method is based on gas sampler analysis (
The method for adjusting the gas distribution in the furnace is described below.

Figure 4 shows the gas flow distribution in the furnace during a typical operational deterioration.

Line (a) shows the gas distribution of a hypercentral flow, and is a waiting period in which ore falls to the siding part due to frequent slips due to inactivity of the furnace wall and insufficient reduction, causing damage to the siding. On the other hand, vA(b) is
The gas flow distribution is excessively peripheral, and the heat load on the furnace wall is high.
This is the time when the stave is damaged or the siding is melted. In this way, if either the central flow or the peripheral flow is too strong, some type of furnace condition abnormality will occur. Therefore, as a gas flow distribution that does not cause these troubles, we aim for a gas distribution between the above (a) and (b), and in order to adjust the charge distribution to satisfy this goal, we use bellless patterns and movable armor. It is a way to move.

Next, other known methods for adjusting the gas flow distribution in the furnace will be described. That is, the second method is to measure the stave heat load (an index of furnace wall flow) from the temperature difference and flow rate of the stave water supply and drainage for cooling the furnace body, and adjust the charge distribution so that this is always constant. .

Figure 5 shows the progress of stave heat load and distribution adjustment when changing the operation to gradually increase the amount of iron tapped in the blast furnace. For example, in the figure, the coke charging condition is kept constant and the ore pattern is changed to This is an example of a system that was operated as expected, but the operation was unstable due to the time delay in feedback.

The above two examples are typical methods of conventional gas flow distribution adjustment, but even if carried out using a fixed sonde temperature distribution or a profile meter without using a gas sampler,
The same results can be obtained even if sensors such as the furnace body temperature level, skin flow thermometer, shaft pressure, etc. are used instead of the stave heat load.

(Problems to be Solved by the Invention) However, the above-mentioned conventional method still has the following serious problems.

■ Control based on gas flow distribution as shown in the first example requires that the target gas distribution changes depending on the operational level (for example, when decreasing or increasing the fuel ratio, or when increasing or decreasing production). Therefore, the target gas flow distribution is not always the same, and the process is always carried out by trial and error, so there is a problem that it is not possible to follow particularly sudden changes in operation, and it is difficult to respond to changes in operation.

■ The adjustment method using the stave heat load as an index as shown in the second example is a method of repeating trial and error, and is a follow-up adjustment method after the results are obtained. Therefore, there is a problem in that too much or not enough action is taken, and it takes time to obtain a stable gas flow distribution.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention predicts the target layer thickness ratio at the time of operational change in advance and controls the burden distribution accordingly. By a completely different method than before,
This is a method to derive a suitable gas flow distribution in the furnace. In other words, the gist is that in a method of guiding the target gas flow distribution in the blast furnace by controlling the charge distribution during operational changes, At the time of operational change, the furnace wall thickness ratio after the change is determined from the planned relationship of the ratio, and the burden distribution is controlled so that the target furnace wall thickness ratio is achieved. It is in the gas flow distribution adjustment method in a blast furnace.

(Function) Hereinafter, the background behind the idea of the present invention will be explained based on the knowledge of the present inventors. There are various ways to operate a blast furnace, such as increased or decreased production, different fuel ratios such as high coke ratio, low coke ratio, fuel injection, and oxygen enrichment. It was found that they can be classified based on two physical indices: ratio and air flow rate inside the furnace.

Here, the heat flow ratio is the ratio of the heat capacity of the Bosch gas to the heat capacity of the descending raw material, and the closer this is to 1.0, the better the heat exchange is. Further, the amount of air passing through the furnace is the amount of gas inside the furnace generated per unit time, and is defined as the amount of air passing per unit time per l m 2 so that blast furnaces with different furnace capacities can be evaluated uniformly.

Now, Figure 2 shows a conceptual diagram of the operation when the horizontal axis is the heat flow ratio and the vertical axis is the air flow rate through the furnace. The third quadrant shows a low pig iron production ratio with a low fuel ratio, and the fourth quadrant shows a low pig iron production ratio with a high fuel ratio. If blast furnace operation is evaluated using the heat flow ratio and the amount of air passing through the furnace as parameters in this way, it becomes possible to compare the operations of each furnace using the same criteria even when the operation of each furnace is changed.

Now, the operation mode can be expressed by the above two parameters, but in order to change the operation, it is necessary to adjust the gas flow distribution, and for this purpose, a method of controlling the charge distribution is usually adopted. However, this means of controlling the charge distribution also has errors due to differences in the furnace top charging equipment, such as a bellless chute or a movable armor, and errors also occur depending on the measurement point when measuring the layer thickness distribution. In one aspect, it is not possible to make a unified evaluation of gas flow distribution.

Therefore, the present inventors focused on the layer thickness ratio of the furnace wall. That is, the layer thickness of coke and ore charged for each charge is read by a computer, and the furnace wall layer thickness ratio (LO/L
We decided to evaluate the gas flow distribution in relation to C).

That is, it has been found that there is a strong correlation between the heat flow ratio and the amount of air passing through the furnace, and the furnace wall layer thickness ratio (LO/LC). FIG. 1 summarizes these relationships as a ternary phase diagram. As can be seen from this figure, the higher the heat flow ratio, the lower the furnace wall layer thickness ratio (LO/LC).
results in a high result. Therefore, if you want to operate with a high heat flow ratio such as a low fuel ratio, you should go for peripheral flow, which lowers (LO/l, c), and if you want to operate with a high pig iron production ratio, you should go for low A predetermined gas flow distribution can be obtained by operating in the direction of suppressing the peripheral flow by increasing /Lc. The so-called target gas flow distribution during operational changes can also be estimated quantitatively from this diagram.

For example, using Figure 1, when changing from operation at point A to operation at point B, from the theoretical calculation of the material heat balance of the blast furnace, the flow rate of air passing through the furnace is 0.1 Na+1/min, n+
' and the heat flow ratio will decrease by 0.1, so it can be predicted that the furnace wall 0/C should be raised to 0.65-0.80. In this way, the present invention utilizes the furnace wall layer thickness ratio (LO/L
C) can be predicted based on the air flow rate and heat flow ratio in the furnace, and if the burden distribution is adjusted according to this method, problems such as taking too much action or not taking enough action as in the past can be resolved. be able to.

(Example) Using the method of the present invention, a coke ratio of 470 kg/l-p and an air flow rate of 650 ONm were produced in a blast furnace with an internal volume of 4500 m'.
/lll1n, iron tap ratio 2. Ot/d, - from operation (a) with low fuel ratio and low output ratio, coke ratio 490 kg/l
-p, air flow rate 625ONm”/min, iron tap ratio 1.7
A method of controlling the charge distribution when changing to operation (b) with a high fuel ratio and low iron output ratio of t/d, m' will be shown.

Based on the material heat balance of the blast furnace (from theoretical calculations, the former (a) has a heat flow ratio of 0.85 and a flow rate of air passing through the furnace of 2.0 Nm37m1n
, m3, and the latter (b) is predicted to have a heat flow ratio of 0.83, an air flow rate of 1.90 Nm''/min, and m3.

Therefore, according to FIG. 1 above, the layer thickness ratio L O / L C
It can be seen that it is sufficient to change from point 0 (0,75) to point D (0,78). Therefore, as shown in Figure 3, we changed the operation and adopted bellless patterns (a) and (b).

Adjustment to change to (c) is carried out step by step, layer thickness ratio Lo/L
When we adopted a method of peripheral flow that increased c by 0.03, we were able to change to high fuel ratio and low iron production ratio operation as expected (although it was difficult to do so).

(Effects of the Invention) As explained above, according to the present invention, it is possible to directly measure the gas flow distribution and control the distribution through trial and error each time as in the past, or to control the distribution based on the measurement results such as the stave heat load. There is no need to adjust the distribution due to error and error, and since the appropriate layer thickness ratio on the furnace wall side can be predicted in advance due to changes in operation, the burden distribution control can be adjusted, allowing for appropriate and quick burden distribution when changing operations. This makes it possible to adjust the gas flow distribution, allowing for smooth and stable blast furnace operation.

[Brief explanation of drawings]

Figure 1 is a ternary state diagram of heat flow ratio, air flow rate through the furnace, and furnace wall layer thickness ratio. Figure 2 is an explanatory diagram of the operating state using the heat flow ratio and air flow rate through the furnace as parameters. Figure 3 4 is a graph showing the gas flow distribution in the radial direction of the furnace. FIG. 5 is a graph showing the stave heat load control by adjusting the charge distribution. It is a graph. Patent applicant: Kawasaki Steel Corporation Figure 1 Figure 2

Claims (1)

[Claims] 1. In a method of guiding the target gas flow distribution in the blast furnace by controlling the burden distribution at the time of operational changes, Gas flow distribution in a blast furnace during operational changes characterized by determining the furnace wall layer thickness ratio after the change from the relationship and controlling the charge distribution so as to achieve the target furnace wall layer thickness ratio. Adjustment method.