JPS6040483B2 - How to operate a blast furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of operating a blast furnace, and more particularly, to a method of operating a blast furnace by controlling the distribution of gas flow in the furnace to an optimal state and stabilizing the furnace condition. .

In modern large-scale blast furnaces, it is essential to achieve stable furnace conditions by controlling the gas flow in the radial direction inside the furnace.

In other words, as one of the charging devices for blast furnaces, for example, movalve armor, bellless type, etc. are used, and in this method, charging is done through a rolling chute, etc., and the distribution of the charge at the top of the furnace is controlled. This controls the gas flow in the radial direction inside the furnace. The reason for this is as follows.

In recent years, blast furnaces have been dismantled one after another and investigations are being carried out.

Through these investigations, the existence of a cohesive zone in the furnace was confirmed, and the function of this cohesive zone was also elucidated.The shape of the cohesive zone is important for the stable operation of a blast furnace. It is believed that abnormalities in the fall of the charge, such as toffling and slip during operation, are deeply related to the shape of the cohesive zone. Furthermore, in recent blast furnace operations, emphasis has been placed on low fuel ratio operation.
In particular, it is required to reduce the fuel ratio to its limit, and the most important thing in maintaining its operation is to ensure the heat balance in the lower part of the furnace necessary for stable descent of the bags. In particular, if the balance of dissolving ability in the upper part of the blade is disrupted, stable operation cannot be maintained. Therefore, in order to ensure stable operation, it is necessary to distribute and supply the amount of gas in the furnace in an optimal state according to the amount of descent of the charge, but in the conventional example, the amount of gas in the furnace was is difficult to distribute. That is, FIG. 1a is an explanatory diagram of a detection mode of the radial in-furnace gas flow distribution in the upper stage of the blast furnace shaft according to the conventional example, and as shown in FIG. A fixed sonde or the like (not shown) is placed above the surface of the charge 3, and these sondes measure the temperature or composition of the gas in the furnace as shown in Figure 1 b and c. It is assumed that the gas flow rate itself in the furnace is large in areas where the gas temperature is high and the Co gas component is high, and based on this assumption, it is conventionally divided into a central flow and a peripheral flow, and further, the temperature of the furnace wall brick, The increase or decrease of the flow rate of gas in the furnace near the furnace wall is determined by considering the heat load on the furnace wall determined from the temperature of the stave cooling water, etc.

However, even if the judgment is made in this way, there are problems as follows. First, when the charge is lowered into chicks, the temperature of the charge at that level is determined by the rate of descent of the charge while it falls to that level, the temperature of the rising gas flow in the furnace, the amount of gas, etc. As in the conventional example, even if the judgment is based only on the change in the temperature of the furnace gas, it cannot be determined whether the necessary amount of furnace gas is actually flowing in that part. In addition, even if we focus on the composition of the gas in the furnace, it is difficult to determine whether the charging material at a given level has undergone the reduction process that should be carried out sufficiently at that level and whether the reduction has progressed to the desired level. It is difficult to make a sufficient judgment based on the composition of the gas. In other words, as in the conventional example, it cannot be determined from the temperature level, composition, etc. of the furnace gas whether or not the necessary amount of furnace gas is sufficiently secured in the portion of the furnace intended by the operator. The present invention aims to solve the above-mentioned drawbacks. Specifically, the operating conditions of a blast furnace are evaluated as the heat capacity flow rate of the charge descending in the furnace and the heat capacity flow rate of the rising gas in the furnace, that is, the heat flow ratio, We propose a method of operating a blast furnace that maintains this heat flow ratio constant to achieve stable operation.

That is, the method of the present invention provides two upper and lower parts above the heat storage zone of the blast furnace.
Temperature detection means arranged in stages and oriented in the radial direction of the blast furnace measure the temperature within 1/6 of the radius of the furnace from the blast furnace wall, and the difference between these two temperatures is calculated as the difference between the two temperatures. It is characterized by the fact that the fluctuation is 4.0 and the blast furnace is operated by storing it within a range.

The method of the present invention will be explained in detail below.

First, in a blast furnace, temperature detection means, such as sondes, are installed in two stages above and below the heat storage zone to measure the temperature inside the furnace, especially the rising temperature of the gas inside the furnace. In this case, each sonde is usually directed from the outside of the blast furnace in its radial direction, in particular from the blast furnace wall to about 1/6 of the inside diameter of the blast furnace.
The temperature of the gas in the furnace is detected in the range within the range, that is, around the walls of the blast furnace. Next, the temperature of the gas in the furnace is measured by each of the upper and lower sondes, and the temperature difference between these gas temperatures in the furnace is maintained so that the fluctuation of the components in the hot metal is small. , and operate by adjusting the air blowing conditions from the tuyeres.

When operated in this way, the heat flow ratio around the blast furnace walls can be easily controlled within a certain range in order to stabilize the operation. That is, for the stable operation of a blast furnace, it is necessary that the charging contents always have a constant reduction rate and constant temperature at a constant level in the height direction of the blast furnace. For this reason, the evaluation of blast furnace operation is not simply based on the gas temperature in the furnace as in conventional examples, but rather the ratio of the heat capacity flow rate of the bagged material that decreases per unit time to the heat capacity flow rate of the furnace gas that increases per unit time. The concept of ratio should be introduced and evaluated. The reason for this is that a constant heat flow ratio satisfies the above conditions for stable operation. Therefore, the essential factor to be controlled in blast furnace operation is the heat flow ratio, and operating to control the heat flow ratio within an appropriate range will ensure that the blast furnace maintains a stable furnace condition both thermally and reactively. is obtained. In this case, the heat flow ratio can be controlled by the temperature difference in the furnace temperature from the upper and lower sondes as described above, and stable operation can be maintained by controlling this temperature difference without directly controlling the heat flow ratio. To explain in more detail, when actually measuring the temperature inside the furnace with the upper and lower sondes, the stock line (SL) is
) is used as a reference, and from there, it is divided into two levels such as z, , z2, and sondes 4 and 5 are installed in the horizontal direction.

These sondes 4 and 5 detect the temperature of the furnace gas at each point on levels z and z2. These gas temperatures are above the heat storage zone and are an area with little heat loss and reaction heat, so the amount of heat exchanged between the furnace gas and the charge is equal, so the following [1 } formula, (2} formula holds true. w
g. Groove=HV-s(T-t) ・…-・'11wS. Groove = HV・s(T-t>... similar, but Ws:
The heat capacity flow rate of the charge falling per unit time (Kcal/h
r, °C) Wg: Heat capacity flow rate of gas in the furnace that increases per unit time (Kcal/hr, °C) t: Temperature of the charging material (°C) T: Temperature of the gas in the furnace (°C) Hv: Temperature of the gas in the furnace (°C) Heat transfer coefficient per unit volume between the furnace gas (Kcal/ hr, °C) S: Cross-sectional area (force) inside the blast furnace at an arbitrary level (z) However, in formula m and '2), On the other hand, stock line (SL
), z=○, T=To, and t=me, so if we solve by including this boundary condition, the following {Equations 3' and 41 are obtained for the furnace gas temperature T and the charge temperature t. It will be done.

Hv・S Ws T=；三三zue（W－・）Z+Wもト；と――8)H
v・SVmuras t=Tsai...30e(W-・)Z+W<=;T.

---E4) Sheep However, the heat flow ratio is expressed as W:Ws/Wg. Next, level z. Let the furnace gas temperature be T, level z
By substituting these values into the glue equation, the following equations '5} and [6} are obtained. Hv・SWS T,=Takutehata ye (w-・)Z, 10Wt Kenzo;.

-. ‐-t5) Hv・SWS To-to T2:7 Senkawave (W-1) Z20 Years Three'' Q--. [
6) If we delete Hv, S, and Ws from this '51 formula and the ■ formula and put it together, we get {n, 1 to) W-n, 1 to)} Z2 ni {(t-to) W-bi 2-1 )｝Z,
...'7, (To-)W
(To-to) W'7' formula is obtained, '7-formula mustard bell z. , z2, the heat flow ratio W can be easily determined. In particular, as in the method of the present invention, the temperature of the furnace gases at two levels, upper and lower, in the blast furnace shaft section is detected. However, it can be seen that when operating based on these temperatures, stable operation can be achieved by keeping the heat flow ratio W constant.

Next, while confirming that the heat flow ratio is related to the temperature of each furnace gas at the two levels Z and 'z2 as described above, we also researched the conditions for applying this relationship to actual blast furnace operation. The temperature difference between levels z, z2 is proportional to the heat flow ratio,
It was found that if this temperature difference was kept constant, the heat flow ratio could also be kept constant.

For example, Figure 3 shows various patterns of temperature distribution in the furnace in the height direction during actual operation of a blast furnace.
) is a reference temperature pattern, (D) is a temperature pattern during operation with a high heat flow ratio, (m) is a temperature pattern during operation with a low heat flow ratio, A is a heat reserve zone, and B is a temperature pattern during operation with a low heat flow ratio. indicates the tip of the wing. As is clear from Fig. 3, the temperature of the heat reserve zone does not change much during any operation, but the two sondes 4 and 5 are located in the upper part of the heat reserve zone A, and this temperature difference (△
T) is related to the heat flow ratio, and the temperature difference (ΔT) increases as the heat flow ratio increases. Therefore, when the relationship between the two was determined in actual blast furnace operation, the relationship shown in FIG. 4 was obtained.

That is, FIG. 4 is a graph showing the relationship between the temperature difference (ΔT) of the furnace gas at each level of the upper and lower two stages and the heat flow ratio (W) in actual blast furnace operation.

At this time, the temperature of the gas in the furnace is measured at multiple points within the range from the walls of the blast furnaces to within 1/6 of the radius of the blast furnace at that level in both the upper and lower stages, and the average value is used as the daily average. The average value is shown on the vertical axis in FIG. As is clear from Fig. 4, the daily average temperature difference (△T) of the furnace gas is proportional to the heat flow ratio (W),
To achieve safe operation, the heat flow ratio can be controlled reliably by measuring the temperature of the gas inside the furnace in two stages, the upper and lower stages, and evaluating it as the temperature difference (△T), without directly controlling the heat flow ratio. I found out that it can be done. Furthermore, the temperature of the furnace gas in the radial direction of each blast furnace was measured within 1/6 of the radius inside the blast furnace. In this case, the distribution of the charge is relatively flat, and the heat flow ratio at the furnace wall can be adjusted by adjusting the distribution of the charge in the radial direction by, for example, using a movalve armor or other charge distribution adjusting means as described above. This is because when controlling the temperature, it can be effectively controlled within 1'6 of the inner radius of the blast furnace from the furnace wall.

Note that the furnace gas temperature can be determined from within 1/6 of the furnace radius, that is, at the other 5/6, but the temperature difference and heat flow ratio in this case are as follows: The same relationship as above exists, but the sensitivity is a little low, so it is preferable to use it as an auxiliary for operational actions.

Furthermore, as mentioned above, it is preferable to evaluate the furnace gas temperature based on the daily average value, but the temperature of the furnace gas in the upper temperature detection means is about 400 to 60,000, whereas the temperature in the lower temperature detection means is about 400 to 60,000. The temperature of the gas in the furnace is 500-9
This is because it changes like 0000 and the change is large. In addition, the two measurement levels z, and z2 as described above need to be above the heat storage zone.
This is because the temperature change inside the furnace can be expressed by the equations {1} to {7-.

Therefore, since the starting position of the thermal storage zone exists approximately 10 to 15 meters below the charging surface of the charge such as ore, it is usually desirable to install the temperature detection means within this range. Furthermore, as described above, when the blast furnace is operated so as to maintain the temperature difference (ΔT), that is, the heat flow ratio (W) within an appropriate range, the operation can be maintained in a state where there is little variation in the components in the hot metal.

In other words, Fig. 5 is a graph showing the relationship between the heat flow ratio and the standard deviation (variation) of the Si content in hot metal. It can be seen that the Si content in the hot metal varies in accordance with the radial heat flow ratio up to 1'6, and in particular, there is an appropriate heat flow ratio at which the Si content in the hot metal varies minimally. Furthermore, when operating a blast furnace in order to maintain the heat flow ratio or temperature difference within an appropriate range, many factors can be manipulated to achieve this objective. It is preferable to change and adjust the conditions, air blowing conditions from the blade □, etc. To explain in more detail, for example, when changing the bagging conditions from the top of the furnace, for example, move valve
By driving the blast furnace and changing the stock level at the top of the furnace and changing the distribution of charges such as ore and coke in the radial direction of the blast furnace, the furnace heat can be easily maintained within the appropriate range.

In addition, when changing the air blowing conditions from the blade □, the amount of gas generated in the furnace must be changed by changing the amount of military oil injected, the amount of oxygen sucked, etc., and also changing the temperature conditions of the air blowing in front of the tuyere. '
That's enough. As explained in detail above, the method of the present invention detects the gas temperature in the furnace from the upper and lower temperature detection means at the upper part of the heat storage zone of the blast furnace, and detects the gas temperature in the blast furnace so that the temperature difference is within an appropriate range. It is something that operates. Therefore, when operating according to the method of the present invention, the heat flow ratio, which is said to have no effective evaluation method in blast furnaces, can be accurately evaluated and stable operation can be maintained. In addition, in order to maintain an appropriate temperature difference or heat flow ratio, it is usually sufficient to change the stock line etc. using movalve armor, etc., and change the distribution of gas in the blast furnace radial direction. In addition, in blast furnace operation, the standard is properly evaluated as the heat flow ratio, so the correspondence between the charging conditions at the top of the furnace and the blowing conditions at the blade section (for example, theoretical combustion temperature difference) becomes clear. The distribution of gas flow in the furnace can be controlled more precisely.

[Brief explanation of the drawing]

Figure 1a is an explanatory diagram of the detection mode of the radial in-furnace gas flow distribution in the upper part of the blast furnace shaft according to the conventional example, and Figures 1b and c are the in-furnace gas when measured as shown in Figure 1a. Fig. 2 is an explanatory diagram of the temperature distribution and the composition of the furnace gas, Fig. 2 is an explanatory diagram of the measurement position of the furnace gas in the blast furnace, and Fig. 3 is the relationship between the temperature difference and heat flow ratio between the upper and lower two stages. Figure 4 is a graph showing the relationship between the temperature difference (ΔT) between the upper and lower stages of the blast furnace and the heat flow ratio (W), and Figure 5 is a graph showing the relationship between the heat flow ratio (W) and the Si during welding.
It is a graph showing the relationship between the standard deviation (variance) of Code 1...Shaft, 2, 4, 5...Sonde, 3
...Charging material. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. Measure the temperature within 1/6 of the radius of the inside of the furnace from the walls of each blast furnace using temperature detection means arranged above the heat storage zone of the blast furnace in two stages, upper and lower, and oriented in the radial direction of the blast furnace.
A method of operating a blast furnace characterized by operating the blast furnace while maintaining the temperature difference between the two temperatures within a range in which fluctuations in components in the hot metal are small.