JPS6116405B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for estimating the layer thickness distribution of a charge charged in a blast furnace in the radial direction within the furnace. Specifically, the present invention relates to a method for determining changes in the coke layer thickness distribution caused by the collapse of a portion of the coke layer deposited in the upper layer of the furnace during ore charging.

(Prior Art) In blast furnace operation, efforts are being made to always adjust the gas flow distribution within the furnace to a desired pattern from the viewpoint of improving charge reduction efficiency and improving air permeability. Although the gas flow distribution varies depending on the powdering and melting conditions of the charge in the furnace, it is mainly controlled by the shape of the charge distribution at the top of the furnace.

For this reason, various measures have heretofore been taken to adjust the shape of the charge distribution at the top of the furnace to a desired shape. Broadly speaking, the measures can be divided into two: one is the introduction of means to artificially change the shape of the charge distribution, and the other is the introduction of measuring equipment that accurately detects the charge distribution.

The former measure includes the introduction of a movable repulsion plate called movable armor and a rotating chute charging device represented by a bellless charging device, while the latter measure includes the introduction of a rotary chute charging device such as a movable repulsion plate called a movable armor and a bellless charging device. One example is the introduction of a non-contact profile meter that uses laser light.

Movable armor and bellless charging devices are currently used in many blast furnaces, and are effective in adjusting the shape of charge distribution. However, since these devices are only means for changing the distribution shape, a desired distribution shape cannot be obtained unless changes in the distribution shape occurring within the furnace are accurately detected.

On the other hand, sounding meters and profile meters are devices that only detect the surface shape of the charge formed in the furnace, so measurements using these devices do not detect any changes in the shape that occur within the charge layer. It cannot be detected.

For this reason, even if the distribution adjusting means and surface shape detecting means are introduced, it is impossible to obtain a desired distribution shape for blast furnace operation unless the shape change occurring within the layer of the furnace contents is grasped. This also means that a gas flow distribution suitable for operation cannot be obtained.

Inside the blast furnace, ore and coke are charged alternately in fixed amounts intermittently, and ore is used as an iron source with a thickness of 5 to 50 mm
Coke with a particle size of 30 to 75 mm is charged in an amount of 10 to 20 tons at a time as a reducing gas source and heat source.

In this way, when ore or coke is charged into the blast furnace because the weight charged at one time is large, the coke or ore in the upper layer of the furnace collapses, but this collapse causes the material charged in the furnace to collapse. It cannot be grasped by detecting the surface shape of the surface.
Therefore, when collapse occurs, the layer thickness distribution of ore and coke in the radial direction of the furnace becomes completely different from the layer thickness distribution calculated by detecting the surface shape.

The gas flow distribution in the furnace radial direction in the blast furnace is
Because it is controlled by the layer thickness distribution of ore and coke after collapse occurs, it is not possible to determine an accurate gas flow distribution from the apparent layer thickness distribution determined by detecting the surface shape. .

Regarding the phenomenon of material collapse, attempts have been made to develop methods for detecting the phenomenon, but these methods have not yet been put to practical use. This is because it is extremely difficult to accurately measure the degree of collapse in a high temperature and dusty environment without causing disturbance to the charge layer in the furnace.

(Problems to be Solved by the Invention) The present invention has been made in view of the above situation, and it is an object of the present invention to understand the collapse phenomenon of the charge in the blast furnace, and to determine the true value in the radial direction of the blast furnace. The aim is to further improve the control of the gas flow distribution in the furnace by calculating the layer thickness distribution and feeding back to the charge charging method so that the ore/coke ratio in the radial direction of the furnace approaches the ideal distribution. This is the purpose.

(Means for Solving the Problems) The present invention prevents the charge charged from the top of the blast furnace and deposited in the furnace from collapsing due to the concentrated load of the charges subsequently charged thereon. In the situation that occurs,
In addition to finding the arc-shaped slip line that indicates the depth of the collapse, the slip line is moved toward the furnace center with an inclination corresponding to the internal friction angle of the charge to determine the extent of the collapse of the charge in the radial direction of the furnace. Determining the change in the shape of the deposited layer, and estimating the layer thickness distribution of the charge in the radial direction of the furnace from this result and the measurement results of the profile of the charge and the subsequently charged charges in the furnace. A method for estimating charge layer thickness distribution in a blast furnace is provided.

The present invention will be explained in detail below based on the drawings.

Regarding the collapse phenomenon of the charge, a schematic diagram is shown in FIG. 1, assuming that the top layer of the charge in the blast furnace is coke and ore is charged on top of it.

That is, the coke 2 that has already been charged through the bell 1 falls onto the furnace wall and then flows toward the center of the furnace, forming a V-shaped profile.

When ore 3 is similarly charged on top of this, a part 4 of coke near the furnace wall is shaved off by the falling load of the ore, and moves along with the ore along the slip line 5 generated within the coke layer. . Since this slip line 5 moves in contact with a line 6 defined by the internal friction angle of the coke, a part of the coke 4 is pushed out to the center of the furnace, and therefore the coke in the layer above the slip line 5 in the radial direction of the furnace The layer will collapse and flow into the center of the furnace.

Figure 2 shows an example of the results of measuring the collapse of the charge at the top of the blast furnace in a model experiment on the same scale as an actual blast furnace.

This figure shows the ore layer thickness/coke layer thickness distribution in the radial direction of the furnace calculated by measuring the surface shapes after charging coke and ore, and the coke layer thickness distribution calculated by measuring the surface shape after charging coke and ore, and the coke layer thickness distribution calculated by measuring the surface shape after charging coke and ore. This is a diagram showing a comparison of the ore layer thickness/coke layer thickness distribution determined by observing the cross section, and it can be seen that there is a large difference between the two. Therefore, it is clear that the gas flow distribution in the furnace cannot be controlled unless the collapse phenomenon caused by the charging of the charge is accurately grasped.

The present invention, etc. conducted a large-scale model experiment at the top of the blast furnace, as well as conducted numerous surveys of the distribution inside the blast furnace when charging the burden before firing, and found that the ease with which the burden collapses can be expressed by the following equation: I found out what I can do.

Collapse rate = resistance moment / sliding moment...
...(1) Here, Sliding moment: ΣRWi・sinα _i Resistance moment: Σ(Wi・cos〓i−ΔPi) tanφ Here, R is the distance (m) from the center of the circle formed by the slip line Wi is the unit amount of the moving charge on the slip line (Kg/m ² ) α _i is the angle between the perpendicular from the center of the circle and the moving charge on the slip line (°C) φ is the internal friction of the charge Angle (°) ΔPi is the drag force of the gas flowing in the moving charge layer (Kg/m ² ) i is the drag force of the gas flowing in the moving charge layer (Kg/m 2 ); Figure 3 shows an explanation of the coordinates related to numbering formula (1).

Considering the case where a virtual single position obtained by dividing the charging force into small parts is sequentially charged onto the surface of a piled layer where collapse occurs, a slip line passing through the center of gravity of the unit quantity or the position of the falling point is assumed. Then, as shown in FIG. 3, several arcs of the slip line 5 can be drawn, and the collapse rate for each arc can be calculated. 7 is the loading charge, 7'
represents the i-th strip portion, and 8 represents a matrix-like graph.

Since the collapse of the charge will occur along the arc (i.e., the slip line) where the collapse rate shows the smallest value, the arc (slip line) that shows the minimum value among the calculated collapse rates. All you have to do is find out. In order to find the collapse rate corresponding to a large number of circular arcs, it is practical to create a matrix-like graph as shown in Figure 3 and calculate the collapse rate of the circular arcs centered at each intersection position. In this way, the arc exhibiting the minimum collapse rate can be easily found.

FIG. 4 shows an example in which a line of equal collapse rate is determined from the calculated value of the collapse rate of the arc obtained for each intersection position. It can be seen that there is an origin position of the arc that exhibits the minimum collapse rate.

In the figure, 9 is the constant collapse rate line, 10 is the furnace wall,
Reference numeral 11 represents the charge layer that causes collapse, and 12 represents the origin of the arc showing the minimum collapse rate.

Here, if the calculated minimum collapse rate exceeds the critical collapse rate (the collapse rate when collapse is actually observed), if the next unit charge is further charged at this stage, , perform similar calculations.

If the minimum collapse rate falls below the critical collapse rate, at that point collapse will occur due to a single position of the charge that has been piled up to that point.

Note that the internal friction angle and critical collapse rate of the charge necessary for calculation are given by measuring each charge in advance.

In this way, if the unit charge amount of the charge is given, the slip line at the point at which collapse starts can be uniquely determined. Figure 5 shows an example of the calculation. Once the slip line at the point of starting collapse is determined, the slip line moves toward the center of the furnace in a cycloidal manner along a line determined by the internal friction angle of the charge layer that causes collapse. A conceptual diagram is shown in FIG. Cycloidal slip line 5
The relationship between line 6 and line 6 determined by the internal friction angle has already been clarified in soil mechanics.

As the slip line moves, the charge above the line determined by the internal friction angle collapses and flows into the center of the furnace. 14 represents the moving direction of the circular arc.

The critical collapse rate is based on the results of measurements using full-scale model experimental equipment that have been carried out many times, and the unit charge amount is 0.01~
Regarding 0.2 (Kg/cm ² ), it has been confirmed that it is approximately in the range of 0.6 to 0.9.

The critical collapse rate shows a different value when the charging speed and charging height of the charge to be charged later changes, but this means that it is necessary to select the critical collapse rate depending on the charging conditions of the blast furnace. Show that something is true.

The amount of collapse of the charge and the shape of the surface of the collapsed charge are determined by the cycloidal movement of the slip line toward the center of the furnace along a line determined by the internal friction angle.

In this case, the area where the charge layer collapses is the area separated by the surface scraped by the sliding surface moving toward the furnace center and the surface of the charge layer shown before the collapse on that surface. . On the other hand, the region into which the collapsed charge flows is defined as the region partitioned by the sliding surface at the final position that has moved toward the furnace center and the surface of the charge layer before it collapses. The final position of the sliding surface is determined by satisfying the condition that the amount of collapse is equal to the amount of inflow.

In addition, when the line 6 determined by the internal friction angle crosses the surface of the charge layer at a certain position in the radial direction of the furnace, a circle is formed along the surface of the charge layer near the furnace core before collapsing. Move the arc-shaped slip line. In this case as well, the slip line position is determined so that the amount of collapse is equal to the amount of accumulation in the area partitioned by the arcuate slip line from the surface of the charge layer before collapse. Figure 7 shows the changes in the shape of the sediment layer due to collapse. 15 is the profile before collapse, and 16 is the profile after collapse.
If there is a large amount of charge that has collapsed and flowed into the center of the furnace, the charge that was charged later will not reach the center of the furnace and the charge in the center of the furnace will be destroyed by the collapsed charge. A surface is formed, and in some cases, later charges are deposited on top of the collapsed charge, forming a charge surface. In either case, the shape of the broken charge in the radial direction of the furnace is defined by the surface determined by the slip line and the surface shape of the subsequently charged charge, and the surface determined by the slip line is determined by calculation. The surface shape of the charged material can be determined by actually measuring it using a laser beam profilometer, for example.

Therefore, the layer thickness of the ore layer and coke layer in the radial direction of the furnace is determined by taking into consideration the layer thickness change of the collapsed charge in the radial direction of the furnace and the profile of the later charged charge in the radial direction of the furnace. You can know the thickness distribution.

The thickness distribution of the ore layer and coke layer in the radial direction inside the furnace, determined by the above method, is compared with the results measured using the paraffin solidification method when filling the charge before firing in an actual blast furnace, as shown in Figure 8. Shown in and B. These examples show the case where ore is charged onto the coke layer, and it can be seen that a part of the coke layer 2 is broken down by the ore and flows into the center of the furnace. If the layer thickness distribution of ore and coke is known, the layer thickness ratio distribution of ore and coke in the radial direction within the furnace can be determined. It can be seen that the layer thickness ratio distributions of ore and coke in Figure 8 A and B are in good agreement.

In this way, by introducing the concept of collapse rate, the collapse state of the charge can be accurately calculated as the layer thickness distribution of ore and coke in the blast furnace in the radial direction of the furnace. Further, the collapse of the charge is noticeable when ore is charged onto a coke layer, but is extremely rare when coke is charged onto an ore layer. Therefore, when calculating the collapse of the charge in the blast furnace, it is sufficient for practical accuracy to consider the former case.

The degree of coke collapse varies depending on the amount of deposited ore, the charging position, the surface shape of the lower coke, etc.
In addition, the surface shape of the ore and coke after collapse is affected by the gas flow rate. Therefore, the final layer thickness distribution in the radial direction of the furnace must be calculated taking into account the above conditions or using the measurement results of a profile meter, but the layer thickness ratio ( Since the (ore/coke) and the charging method are in a well-corresponding relationship as shown in FIG. 9A, it is possible to adjust the coke crumbling amount distribution by selecting the charging method.

The radial gas flow distribution in the furnace is strongly controlled by the radial ore-to-coke layer thickness ratio distribution formed at the top of the furnace. Generally, a pattern as shown in FIG. 10 is desirable for the gas flow distribution, being small near the furnace wall and large at the center of the furnace.
The reason for reducing the gas flow velocity near the furnace wall is to prevent heat loss from the furnace wall and damage to the wall surface. This is to create a situation where water can flow easily to the center. In order to increase gas reduction efficiency in the middle part of the furnace, it is necessary to have a uniform gas flow rate.

To obtain such a gas flow distribution, generally the first
The thickness distribution of ore and coke as shown in Figure 1 is desirable.

In other words, the layer thickness ratio (ore/coke) decreases toward the furnace center in order to develop gas flow, and the furnace wall has a large amount of fine particles deposited with high gas flow resistance. It is necessary to adopt a distribution that lowers the layer thickness ratio so that the gas flow is not significantly suppressed toward the furnace wall surface.

Figure 12 shows the results of blast furnace operation using the method of the present invention to measure the layer thickness of the contents in the furnace, determine the ore/coke ratio in the radial direction of the furnace, and control the distribution to an ideal shape. This is shown in comparison with the conventional method.

In addition, when using the method of the present invention, the operation is carried out by feeding back the layer thickness measurement results of the contents in the furnace by selecting the furnace top charging method (for example, the combination method of the movable armor setting position as shown in Figure 9A). In the case of the conventional method, the operation was carried out without considering the collapse of the contents in the furnace.

(Effects of the invention) As shown in Figure 12, by applying the method of the present invention to blast furnace operation, [Si] in hot metal stabilizes at a low value, the number of slips decreases, and the top gas utilization rate improves. did. Furthermore, the coke ratio is 495Kg/t in the conventional method.
-P was reduced to 480Kg/tp, and a remarkable effect on blast furnace operation was obtained.

Note that the present invention is applicable not only to blast furnace operation but also to the measurement of the shape of piled materials in powder hoppers, silos, or reaction towers into which different types of powder and granules are alternately charged.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram illustrating the situation in which the charge accumulated at the top of the blast furnace is broken down by the charge charged later, and Figure 2 is a diagram showing the ore in the radial direction at the top of the furnace. A diagram showing the layer thickness ratio distribution of coke, Figure 3 is a schematic diagram explaining the variables necessary to determine the collapse rate, and Figure 4 shows the distribution of the equal collapse rate line and the existence of the position showing the minimum collapse rate. Figure 5 is a diagram showing the relationship between the load per unit amount of charge and the minimum collapse rate, and Figure 6 is a diagram showing the relationship between the line determined by the internal friction angle and the arc-shaped slip line moving along that line. Diagrams showing the relationship; Figure 7 A, B and C are diagrams showing changes in the shape of the deposited layer caused by collapse; Figure 8 A and B are diagrams showing the shape of the deposited layer of coke and ore at the top of the furnace. A shows the results of the investigation in the blast furnace, and B shows the estimated results according to the present invention. Figure 9 A shows the movable armor position (charging sequence C↓C↓O↓O↓, ↓ indicates charging into the furnace.The set position of the armor at each charging time is indicated by numbers, The smaller the number on the axis, the closer the charging is to the furnace wall)) and the layer thickness ratio. Fig. 11 is a diagram illustrating the layer thickness ratio in the radial direction of the furnace, and Fig. 12 is a diagram illustrating the transition of the operating status of a blast furnace in which the method of the present invention was applied to the blast furnace. It is a diagram. 1...Bell, 2...Coke, 3...Ore, 4
... Part of coke, 5 ... Slip line, 6 ... Line defined by internal friction angle, 7 ... Loading charge,
7'...i-th strip part, 8...matrix graph, 9...equal collapse rate line, 10...furnace wall,
DESCRIPTION OF SYMBOLS 11...Charge layer that causes collapse, 12...Origin of the arc showing the minimum collapse rate, 14...Movement direction of the arc, 15...Profile before collapse, 16...Profile after collapse.

Claims (1)

[Claims] 1 In a state where the charge charged from the top of the blast furnace and deposited in the furnace collapses due to the loading load of the charge subsequently charged on top of it, an arc-shaped curve indicating the depth of the collapse occurs. While finding the slip line,
The slip line is moved toward the center of the furnace at an inclination corresponding to the internal friction angle of the charge, and the change in the shape of the deposited layer of the charge in the radial direction of the furnace due to collapse is determined, and this result and the charge and Estimation of charge layer thickness distribution in a blast furnace characterized by estimating the layer thickness distribution of the charge in the radial direction of the furnace from the measurement results of the profile of the charge subsequently charged in the furnace Method.