JPH037722B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for charging raw materials into a blast furnace, and particularly proposes a charging method suitable for obtaining an optimum particle size distribution in the radial direction of the furnace depending on the conditions inside the furnace.

In the operation of a blast furnace, the radial distribution of the charges (ores, coke) at the top of the furnace is one of the main factors that directly controls the operating conditions such as furnace conditions and firing ratio. Conventionally known adjustments to the charge distribution have been carried out primarily by adjusting the relationship between the coke layer thickness and the ore layer thickness in the radial direction.

An example is the control of charge distribution in a blast furnace using a bellless charging device that has a tank for temporary storage of raw materials (top bunker) at the top of the furnace and distributes the charge from the bunker into the furnace through a rotating chute. If you take it into account,
By changing the inclination of the rotating chute based on the amount of raw material discharged through the chute, the time since the start of discharge, or the number of turns, the material falling from the rotating chute into the furnace can be applied to the surface of the accumulated charge layer. The method was to adjust the thickness of the iron ore and coke layer by changing the landing position.

It is generally believed that the radial charge distribution at the top of a blast furnace governs the radial flow rate distribution of the gas flow that ascends approximately vertically within the furnace. Therefore, in order to obtain an appropriate gas flow distribution in the radial direction of the furnace, it is necessary to take into account the operating conditions of the blast furnace, such as the gas utilization rate, blowing pressure, and fuel ratio, the radial gas composition measured at the top of the furnace or the shaft, etc. Based on various information such as gas temperature, the charge distribution was adjusted by changing the layer thickness ratio using the method described above.

By the way, in a normally operated blast furnace, the raw material that falls onto the surface of the charge layer inside the furnace top slides toward the center because the shape of the surface of the charge layer is an inverted conical surface. or have a tendency to roll and move. In particular, in the case of coke and sintered ore, the particle size range is large, so the finer particles accumulate near the falling point, and the coarser particles roll and accumulate towards the central valley. ) grain size segregation occurs.

Of course, this phenomenon is already known, but since the permeability of a raw material is determined by the average particle size and particle size distribution of the raw material, it is necessary to adjust the charge distribution by taking into account the above particle size segregation as well as the layer thickness distribution. is essential.

However, although it has been conventionally recognized that grain size segregation in the radial direction is one of the important factors in adjusting the burden distribution, it is assumed that such grain size segregation is a given, and only the layer thickness distribution can be changed. The charge distribution was mainly controlled, and particle size segregation was not actively controlled.

Conventionally, the particle size of the raw material discharged from the raw material storage tank is
It is customary for workers to take samples from the outlet at the bottom of the raw material storage tank once or several times a day and perform particle size analysis. Moreover, in a blast furnace where the charge is charged 120 to 170 times/day, there are 4 to 10 raw material storage tanks, and there are large variations in particle size between tanks, and there is also a large variation in particle size within the same tank. Therefore, the above sampling was of little use for blast furnace operation.
In addition, there was a lack of recognition that radial grain size segregation at the top of the furnace is as important as the conventionally known adjustment of radial layer thickness distribution.

The present invention was developed based on the results of operational tests and various investigations in actual blast furnaces, and based on the knowledge that it is not necessarily possible to obtain the best operational results only by adjusting the radial layer thickness distribution of conventional ores and coke. , by adjusting the particle size change over time (in the order of discharge) of charges such as sintered ore discharged from the furnace top bunker,
This technology was developed based on good operational results.

In other words, in addition to the conventionally established layer thickness distribution control in the radial direction of the furnace, the material accumulation state or discharge state in the relay storage tank or the top bunker can be adjusted to achieve the desired particle size distribution in the radial direction within the furnace according to the furnace conditions. By maintaining conditions convenient for charging,
This technology is intended to meet the demand for optimal particle size segregation control as described above.

The configuration of the present invention that can meet the above-mentioned demands is such that charging raw materials discharged from a plurality of raw material storage tanks and relay storage tanks are stored in a furnace top bunker via a charging conveyor and then loaded into a furnace. The charging material is stored at least in the form necessary to achieve the optimum flow rate distribution in the radial direction of the furnace, which is selected according to the furnace conditions, at least in the top bunker. There is a method for charging raw materials into a blast furnace.

FIG. 1 is a diagram showing a raw material charging system of a blast furnace equipped with a bellless charging device. A fixed amount of ores such as sinter or coke is cut out from a plurality of raw material storage tanks 1 onto a collecting belt conveyor 2, and temporarily stored in a relay storage tank 3 during conveyance. At this time, the relay storage tank 3
The phenomenon of particle size segregation, which is often seen when feeding and discharging granular raw materials, usually occurs within the reactor. Second
The figure shows an example of sampling measurement results regarding particle size fluctuations of sintered ore discharged from the raw material storage tank 1.

In normal blast furnace operation, the charged raw material discharged from the 3 to 10 raw material storage tanks 1... group is supplied into the relay storage tank 3, but in each raw material storage tank 1... group, the remaining amount level in the tank Usually 5 to 50, taking into account the deposition condition.
Although it is controlled within the particle size range of mm,
Due to changes over time during discharge (differences depending on the order of discharge), the particle size of the raw material supplied to the relay storage tank 3 changes as shown by A and B in FIG. 3. As a result, the particle size of the raw materials discharged from the relay storage tank 3 also varies in the order of discharge. Therefore, when the charging material that has been conveyed by the charging conveyor 4 toward the blast furnace and supplied to the furnace top bunker 6 is charged into the furnace, the above-mentioned particle size fluctuation that has occurred up to that point is directly affected. This makes it difficult to maintain stable blast furnace operation.

In order to avoid such phenomena, the present inventors encountered an interesting and significant blast furnace operation phenomenon. As shown in Figure 4, A and B, there are cases where the collision plate 7 installed in the top bunker 6 is directly below the falling position shown in B, and cases where it is out of the position shown in A. We experienced a phenomenon in which the deposition and discharge conditions of raw materials changed, resulting in clear differences in operational performance.

When the collision plate 7 is in the positions shown in A and B in Fig. 4, A and B are the periods, respectively.
Figure 5 shows the top gas component distribution as the result of blast furnace operation at each period. The gas utilization rate (CO ₂ /
(CO + CO ₂ ) x 100 (%)) was good, and as a result, low fuel ratio operation was possible. In order to investigate the change in particle size of the charging material discharged from the top bunker 6 at this time, a model experiment was conducted, and the results showed that the change in particle size changes depending on the order of discharge, as shown in Figure 6. I found it.

From the above results, the particle size of the charging material charged from the top bunker 6 to the top of the furnace constantly changes over time, and the particle size distribution formed during deposition in the top bunker 6 and the time of discharge It was found that the flow rate changes in a certain pattern determined by the movement state of the raw materials in the storage tank.

Therefore, the present inventors proposed a method of adjusting the accumulation state and discharge state in the bunker, which was disclosed in Japanese Patent Application Laid-Open No. 56-108808. We conducted an experiment and were able to establish a means of adjustment here.

Next, we will specifically explain this through an experiment using a 1/10 scale model. The results of the experiment are shown in Sections 8 and 9.
As shown in the figure. FIG. 7 shows the presence or absence of a gutter-like inverted V-shaped chute 8 in the relay storage tank 3 and the top bunker 6 at the stage of conveying from the relay storage tank 3 to the top bunker 6.
This shows the difference in the state of accumulation depending on the presence or absence of a rectifying plate inside, and the size. Incidentally, the chute 8 is formed so that the charged raw material passes through the chute 8 (in the direction of the arrow), falls from both ends thereof, and is deposited in the tank. When this chute 8 is used, the sediment profile in the tank is deposited in the shape of an inverted cone with a concave center. The rectifying plates 7 installed above the discharge port in the furnace top bunker 6 are a set of two plates, which can be stacked one on top of the other so that the area can be changed.

Now, when the particle size change at the time of discharge of the raw material discharged from the relay storage tank 3 is shown in correspondence with A and E corresponding to A and B in Figure 7, it is as shown in Figure 8. There is a noticeable difference in overall fluctuations between the middle and final stages. This is due to the fact that the raw material loading conditions in the relay storage tank 6 are different between A and E.

For example, in case A, the transported raw materials are piled up in a mountain shape with a high center at the time of charging. At this time, grains of average size are located at the bottom of the tank, while fine grains are deposited in the center, and coarse grains are deposited on the wall side of the tank.

To explain this in more detail, if the particles in the above-mentioned piled state are discharged to the bottom of the relay storage tank 3, the change in particle size over time during discharge on the charging conveyor 4 is shown in Figure 8. As shown in Figure A, at the beginning of discharge, particles of average size are cut out, then in the middle, fine particles in the center are discharged, and at the end, coarse particles on the side of the tank wall are cut out. It will be discharged.

On the other hand, if it is E in the case shown in Fig. 7B where the center is concave, and if this is discharged onto the charging conveyor 4, the coarse grains in the center will be preferentially cut out at the beginning of discharge, and eventually the middle part will be cut out. The fine grains on the tank wall side continue, then the grains of average size are gradually discharged, and finally the coarse grains thinly deposited on the top layer are discharged. By changing the deposition state in the tank in this way, it is possible to automatically adjust the change in particle size in the order of discharge, and the present invention focuses on this point.

In addition, when adjusting the deposition state, it is also possible to use an inverted V-shaped chute 9 as shown in FIG. 10, for example.
Using a droplet 9a provided in the center of the
A rotatable collision plate 10 is provided above the collision plate 10, and the raw material is applied to the collision plate 10 and then supplied onto the chute 9, or the collision plate 10 is retracted as shown in FIG. It is also possible to drop it from the drop opening 9a to achieve the same deposition condition as in the past. Further, as shown in FIGS. 12 and 13, the collision plate 11 forming a stone box that is slidably suspended horizontally above the furnace top bunker 6 may be used instead of the above-mentioned rotation.

The present invention focuses on the fact that the particle size distribution of the next deposited layer after discharge can be controlled by adjusting the deposition state in the tank as described above, and applies this to the furnace top bunker 6. This method is designed to control particle size distribution.

B to H in FIG. 9 change the stacking state of the raw material in the relay storage tank 3, cut it normally, charge it to the furnace top bunker 6 and deposit it, and change its area so that it can be used for discharging and charging. I made some adjustments. However, in Experimental Examples D and H, the deposition state was again changed as shown in FIG. 7E, and the current plates 7 were changed to those shown in C and G.

As can be seen from these results, due to the difference in the shape of the current plate 7 and the difference in the deposition state inside the bunker,
It can be seen that the discharge status of fine particles and coarse particles changes. For example, taking condition B, the deposits in the bunker are accumulated in the order in which the relay storage tank 3 is discharged as described above. The fine particles in the vicinity are gradually discharged, and then the coarse particles above the tank are gradually discharged. In this way, it is easy to adjust the particle size distribution of the contents in the blast furnace by adjusting at least the accumulation state in the storage tank or by installing a current plate alone or in an appropriate combination.

In addition, during actual blast furnace work, if the pattern of discharge particle size fluctuation is to be changed in order to obtain stable operation using the means shown in FIG. Alternatively, it is necessary to know in advance the particle size change based on the order in which the charged raw materials are charged into the bunker 6 on the entry side of the furnace top bunker 6. Therefore, the particle size of the raw material discharged from the relay storage tank 3 is measured using a non-contact type raw material particle size measuring device. This measurement method involves directly photographing the surface of the raw material layer using a TV camera, etc., and processing the captured image using an image processing device, or at the point where the raw material is supplied to the charging belt conveyor or at the point where it is discharged. A portion of the raw material is sampled, transferred using another conveyor or other transport means, an appropriate location is set for the raw material to fall, the raw material particles are photographed with a TV camera, etc. in an independent state without overlapping, and an image processing device is used to capture the raw material. A method of measuring the particle size by image processing, and a method of providing a laser transmitter/receiver on the charging conveyor 4 and measuring the distance between the laser transmitter and the receiver are used.

As described above, the particle size change of the charged material discharged from the relay storage tank 3 is measured by a non-contact method, and based on the value, the current plate 7 installed in the relay storage tank 3 or the furnace top bunker 6 Alternatively, it is possible to use the inverted V shoots 8 and 9 to prepare the charging material in the top bunker 6 so that it exhibits a desired grain size in the radial direction when it is charged into the furnace. It can be done.

In addition, as an extension of this invention, the above-mentioned change in particle size can be measured on the collection conveyor 2 after the raw material storage tank.
Although it is possible to adjust the particle size distribution in the final furnace by adjusting the deposition state of the raw material in the relay storage tank 3, this method does not allow for adjustment of the deposition state in the furnace top bunker 6. The effect is noticeable when used together.

Example Blast furnace volume: approx. 4500 cm ³ , capacity of relay storage tank and top bunker 6: approx. 100 cm ³ (ore charge amount: approx. 140 t)
An example is shown below in which a bell-less blast furnace was operated by charging ore with a particle size of 5 to 50 mm.

When the particle size change on the charging conveyor was measured when the relay storage tank was in a state of accumulation as shown in Figure 11A and discharged, using a non-contact particle size measuring device using a laser, the results were as shown in Figure 14. B It was in _{a 1} line condition. Then, the raw material was discharged inside the furnace top bunker by using a rectifier plate with a small area as shown in FIG. 7C.
The particle size change at that time was as shown by line _B1 in Fig. 15, with fine particles distributed toward the furnace wall and coarse particles distributed toward the furnace center. At that time, the gas distribution was as shown in line _B1 in Figure 16, and the operating conditions of the blast furnace were such that the central flow was too strong and unstable.

Therefore, the material was discharged by moving the collision plate 10 to change the deposition state in the relay storage tank as shown in FIG. At this time, the particle diameter of the discharged raw material changed as shown by line _B2 in FIG. 14, and the material was deposited as shown in FIG. 7G. The change in particle size discharged from the furnace top bunker was as shown by line _B2 in Figure 15. As a result, the particle size on the furnace wall side becomes slightly larger than the former, and the particle size on the furnace center side becomes slightly smaller than the former, and the gas distribution in this state is
The operating conditions of the blast furnace have become stable, with the distribution shown in line _B2 in the figure.

However, after that, the particle size of the raw material on the discharge side of the relay storage tank became smaller. At this time, the furnace top gas distribution became as shown in the B ₂ line in Figure 16, and the change in exhaust particle size was as shown in the 14th line B ₃ '. It was discharged as a large area as shown in F. The particle size change at this time is shown in Figure 15.
The gas distribution becomes as shown in line B ₃ in Figure ₁₆ , with slightly coarser particles distributed toward the furnace wall and toward the center of the furnace compared to the previous state. This enabled the operating conditions of the blast furnace to be stabilized over the long term.

In this way, the present invention adjusts the deposition state of the charging material in the relay storage tank, and subsequently measures the particle size on the conveyor after discharge using a non-contact measuring means, and the deposition state of the charging material in the furnace top bunker is determined by the particle size measurement. A rectifier in the bunker adjusts the deposition and/or discharge order to obtain the required morphology for the optimum particle size distribution in the furnace radial direction, which is selected based on the results and the behavior of the gas distribution in the furnace. Charging is carried out while adjusting the change in particle size over time.

In the above example, the method of measuring the particle size on the outlet side of the relay storage tank to adjust the deposition condition and the order of discharge from the furnace top bunker was mainly described. Needless to say, even more fine-grained raw material charging and operation can be achieved by arbitrarily combining various storage tank accumulation conditions, adjustment of discharge order, particle size measurement, etc.

As explained above, according to the present invention, the particle size distribution of the raw material supplied into the furnace can be adjusted to the operating state by adjusting the accumulation state of the raw material in the relay storage tank or the furnace top bunker and the discharge order. It can be adjusted to any desired value, and is effective in stabilizing blast furnace operation over a long period of time. Moreover, it is possible to change the charging method to immediately respond to changes in various operational orientations, such as low fuel ratio operation and high iron output ratio operation, which are adopted depending on the socio-economic situation at the time. It is possible to perform stable blast furnace operation even when

Furthermore, since the present invention measures the particle size in advance on the conveyor, the measurement results can be fed back to the raw material rectification process to arbitrarily adjust the particle size of the raw material supplied to the raw material storage tank 1 to a range suitable for the operation. Can be done. Therefore, it becomes easy to maintain stable blast furnace operation for a long period of time.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of raw material charging equipment with a bellless charging device, Figure 2 is a graph showing the particle size distribution at the time of raw material discharge, and Figure 3 A and B are particle size distributions of raw materials supplied to the relay storage tank. and a graph showing the change in particle size in the order of discharge, Figure 4 A and B are schematic diagrams showing the pattern of material falling depending on the collision plate position, Figure 5 is a graph of the furnace top gas component distribution, and Figure 6 is the furnace top. Graph showing the pattern of particle size change during bunker discharge, Figure 7 A and B are schematic diagrams showing examples of various raw material accumulation states in the relay storage tank and the furnace top bunker, and Figure 8 A and B are the particles discharged from the relay storage tank. Figure 9 (a) and (b) are graphs of particle size changes in the particles discharged from the top bunker, and Figures (a) and (b) in Figures 10 and 11 are the relationship between the chute in the storage tank, the raw material flow, and the deposition state, respectively. Schematic diagram showing 12th
A and B in the figure and FIG.
Fig. 14 is a graph of particle size change of the raw material discharged from the relay storage tank in the example of the present invention, Fig. 15 is a graph of particle size change of the raw material discharged from the furnace top bunker in the example, and Fig. 16 is a graph of the particle size change of the raw material discharged from the furnace top bunker in the example. It is a graph showing the distribution of gas components.

Claims (1)

[Scope of Claims] 1. When charging materials discharged from a plurality of raw material storage tanks and relay storage tanks are stored in a furnace top bunker via a charging conveyor and then charged into a furnace, at least A method for charging raw materials for a blast furnace, characterized in that the loaded raw materials are stored in a bunker in a form necessary to achieve an optimal particle size distribution in the radial direction of the furnace selected according to furnace conditions. 2. In a method in which charging raw materials discharged from multiple raw material storage tanks and relay storage tanks are once stored in a furnace top bunker via a charging conveyor and then charged into the furnace,
First, the deposition state of the charged raw material in the relay storage tank is adjusted, and then the deposition state of the charged raw material in the furnace top bunker is adjusted to achieve the optimum particle size distribution in the furnace radial direction selected according to the furnace conditions. A method for charging raw materials into a blast furnace, characterized in that the order of deposition and/or discharge is adjusted by a rectifying means in a bunker so that the grain size is adjusted so that the grain size changes over time at the time of discharge.