JPH058249B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for controlling the filling state of the solid reducing agent layer in the blast furnace core by charging the solid reducing agent in the axial center. The present invention relates to a method for dealing with cases where there is circumferential deviation or local uneven distribution in the filling state of the layer. In addition to coke, various carbonaceous materials such as charcoal and lump charcoal are exemplified as the solid reducing agent, but in this specification, coke will be taken up as a representative example of the solid reducing agent.

[Prior art] Fig. 2 is a cross-sectional explanatory diagram showing the situation inside the blast furnace, in which ore O and coke C are charged alternately from the top of the blast furnace.
gradually descends through the massive zone K while exhibiting a layered structure, and is reduced by the action of reducing gas (CO) generated by the reaction between the hot air blown from the tuyere B and the coke C, forming a softened cohesive zone SM. After forming, the droplets pass through the gaps in the coke layer A of the furnace core and are stored as hot metal F at the bottom of the furnace. This hot metal F is periodically or continuously extracted from the tap E.

In order to operate such a blast furnace stably and efficiently, it is important to appropriately control the gas flow distribution rising inside the furnace. That is, FIGS. 3 and 4 are main part sectional views showing the flow of gas in the furnace near the raceway L in the furnace, and as shown in FIG. 4, the filling state (air permeability) of the furnace core coke layer A is If the situation worsens, the hot air blown from the tuyeres B will have difficulty entering the furnace core side and will flow toward the furnace wall side, forming a peripheral flow. The peripheral flow of gas causes blow-through and the formation of deposits, and the cohesive zone becomes W-shaped, making blast furnace operation unstable. On the other hand, as shown in Figure 3, when the permeability of the core coke layer A is good, the hot air easily penetrates to the center of the core coke layer A, and the gas flow forms a central flow to soften and melt. The shape of the belt is also inverted V-shape. As a result, the operating conditions of the blast furnace are stabilized.

On the other hand, the results of blast furnace dismantling investigations indicate that the biggest problem with damage to the bottom refractories is abnormal erosion at the joints (corners) between the bottom and the side walls of the furnace core. A new fact confirmed by these authors is that the filling state of the core coke layer A has a deep relationship with abnormal corner erosion. That is, FIGS. 5 and 6 are horizontal cross-sectional views showing the flow of hot metal in the hearth. As shown in FIG. The slag bypasses the core coke layer and flows along the side wall of the furnace core to form a peripheral flow, and this peripheral flow promotes abnormal erosion of the corner portion. On the other hand, as shown in Figure 5, when the filling state of the furnace core coke layer A is good, the hot metal and slag flow throughout the furnace body through the gaps in the furnace core coke layer A. Forms a central flow. As mentioned above, the filling state of the core coke layer (air permeability, liquid permeability) is a factor that has a significant impact on the operational status of the blast furnace and the life of the bottom refractory, and is one of the important monitoring items in the operation of the blast furnace. However,
At present, no effective means to control this has been found. Furthermore, Utility Model Publication No. 61-42896, which discloses a means for controlling the central gas flow, and Japanese Patent Application Laid-open No. 61-227109, which discloses a method for equalizing the charge distribution, have been filed, but both of these patent applications apply to furnaces. This paper does not attempt to control the filling state of the core coke layer, nor does it describe the influence of the core coke layer on blast furnace operation.

[Problems to be Solved by the Invention] Focusing on these circumstances, the present inventors have investigated a method for controlling the filling state of the core coke layer, which has a significant effect on the stabilization of blast furnace operation and the wear and tear of the bottom refractory. As a result, when charging coke and ore from the top of the blast furnace, it is necessary to appropriately charge coke into the core region of the ore layer or to improve air permeability and liquid permeability in the core region of the coke layer. Completed a method to properly control the filling state of the furnace core coke layer by appropriately charging appropriate coke, and filed a separate patent application [Patent application (1) filed on September 3, 1985]
did.

The above-mentioned application method has shown excellent effects in practical blast furnaces, but when the operating conditions are biased in the circumferential direction, the control method of the above-mentioned application (1) assumes that there is no variation in the circumferential direction. It was found that some modification of the method was necessary.

That is, the present invention aims to provide a method for accurately grasping the deviation in the circumferential direction of the operational state, which is a problem in actual operation, and furthermore, providing a method for dealing with the deviation. The purpose of this invention is to fully improve the effectiveness of the method for controlling the filling state of the coke layer in the furnace core.

[Means for Solving the Problems] According to the method of the present invention, when the solid reducing agent and ore are alternately charged from the top of the blast furnace and the solid reducing agent layer and ore layer are stacked, the ore layer is The blast furnace can be improved by appropriately charging a solid reducing agent into the axial center area or by appropriately charging a solid reducing agent suitable for improving air permeability and liquid permeability into the axial center area of the solid reducing agent layer. While the basic control is to adjust the air permeability distribution or liquid permeability distribution of the solid reducing agent layer in the core, the above-mentioned axis The gist of this method is to eccentrically change the renewal area of the furnace core by injected coke and adjust the filling structure of the solid reducing agent layer in the furnace core.

[Function] The process leading to its completion and an overview of the method of application (1), which occupies an important position in understanding the method of the present invention, will be explained.

The present inventors first investigated the streamlines of the charge as it descends inside the blast furnace using a 1/37 scaled model of the entire circumference of the blast furnace. Fig. 7 is a cross-sectional explanatory diagram schematically showing the flow lines of the contents in the blast furnace obtained from the model experiment, and from this figure, the coke supplied to the furnace core A is charged into the top axis of the furnace. It was found that it was dominated by coke. In the experiment, an extraction port Ex was provided at a position corresponding to the tuyere of the blast furnace model to extract coke at a predetermined speed, and the bottom of the furnace was formed with a circular table that could be raised and lowered, and the coke was extracted at a predetermined speed during the experiment. By lowering it, we reproduced the consumption of core coke (combustion and carburization/dissolution into hot metal) in an actual furnace. In other words, after the coke deposited at the axial center of the furnace top falls to the top of the furnace core coke layer, the rate of descent of the furnace core coke is slow (it is said that it takes 1 to 2 weeks for the furnace core coke to be replaced). The coke flows to the periphery along the slope of the core coke layer, and in the process, part of the coke deposited in the shaft core is taken into the core and forms the core coke layer. Therefore, we further investigated how the core-charged coke deposited at the core of the furnace top affects the formation of core coke.

In other words, the dimensionless radius of the furnace top axis shown in Figure 7
rt/Rt (rt: deposition radius of centrally deposited coke at the furnace top, Rt: furnace top radius) is 0.06, 0.08,
When tracer coke was fed into the 0.10 and 0.12 regions, the renewal status of the furnace core by tracer coke (changes in the concentration distribution of tracer coke in the furnace core) was investigated, and the results shown in Figure 8 were obtained. That is, as is clear from FIG. 8, the furnace core coke layer is renewed by the tracer coke descending down the shaft center of the blast furnace, and the renewal area is the tracer coke charging radius with respect to the furnace top shaft center, that is, rt/
It can be seen that it expands as Rt increases.
For example, when tracer coke is charged in the region of rt/Rt: 0.12, almost the entire area of the furnace core is renewed with tracer coke except for a part of the periphery, and the furnace core is ventilated in this region. It can be seen that by charging coke for the purpose of adjusting the air permeability and liquid permeability, it is possible to arbitrarily control the filling state of the coke layer in the furnace core, that is, the permeability and liquid permeability of the furnace core.

After accumulating these experimental results, we found that even if the core coke is renewed by the coke charged in the core, the shorter the renewal period of the core coke, which is influenced by the scale of the blast furnace and various operating conditions, the above. It is necessary to widen the charging area of core-charged coke, and it was found that for long renewal periods, the composition of core coke can be controlled even if the charging area is quite narrow (details will be discussed later). . As a result of comprehensively considering these, the dimensionless radius rt/Rt
(rt: deposition radius of centrally deposited coke at the top of the furnace, Rt: radius of the furnace top) is the lowest limit in the core region of the furnace shaft of 0.03, and is suitable for improving air permeability and liquid permeability in the coke layer forming area If coke is charged or coke is charged separately into the ore layer forming area in the area, the core coke layer will be occupied by the coke, and as explained in Figures 2 and 3, the blast furnace will rise. The gas forms a central flow, and the softened cohesive zone maintains a stable inverted V-shape, which not only guarantees high operational efficiency, but also ensures that the molten metal flows throughout the hearth area as explained in Figure 5. This allows the melt to flow in the direction of the tap outlet, minimizing melting damage to the walls around the bottom of the furnace. Note that the above limit value of rt/Rt≧0.03 was specified based on the time slightly longer than 14 days, which is the longest since the normal core coke renewal time in blast furnaces is 7 to 14 days. When it gets shorter
The allowable lower limit value of rt/Rt is greater than 0.03. By the way, Figure 9 shows that the period for renewing the total amount of core coke is 7.
rt/Rt and rh/Rh for days, 10th and 14th
(rh: radius of the core coke layer A updated by core charged coke at the hearth position, Rh: hearth half meridian);
(a), (b), and (c) show the results when the update time was 10 days, 7 days, and 14 days, respectively.

And (a), (b), and (c) can be respectively expressed by the following equations.

(a)…(rt/Rt)=0.164(rh/Rh)+0.082 (b)…(rt/Rt)=0.227(rh/Rh)+0.073 (c)…(rt/Rt)=0.114( rh/Rh)+0.036 The structure and effects of the method of application (1) are as outlined above, but this method is constructed on the premise that there is no variation in the operating conditions of the blast furnace in the circumferential direction. (see Figures 7 and 8), when the coke charged to the furnace top axis descends almost directly downwards, forming a downward charge flow line that reaches the top of the furnace core coke layer. The coke charged at the top of the furnace can be efficiently and uniformly deposited in the furnace core.

However, the filling state of the furnace core coke layer is not necessarily uniform in the circumferential direction, and if the permeability or liquid permeability of the furnace core is locally (or partially) deteriorated, the gas flow or hot metal This creates an imbalance in the flow, which causes a decrease in the reaction efficiency and thermal efficiency of the blast furnace, an increase in heat loss, and destabilization of unloading.

In the present invention, in order to deal with such local deterioration of the filling state of the core coke bed, a method of eccentricity of tuyere combustion is adopted as shown in the above configuration, and this makes the above-mentioned application (1) We succeeded in solving the problems in this method.

Figure 1 shows a case in which unloading in the X direction was stopped by blocking several of the tuyere-equivalent extraction ports Ex provided on the circumference of the blast furnace model near the X direction in a model experiment. This is a cross-sectional explanatory diagram showing the charge descending flow line (corresponding to tuyere combustion stoppage in an actual blast furnace), and the charge particles descending down the shaft center are directed in the opposite direction to the X direction at the surface layer of the core. It is descending with an incline. This means that if the combustion in the tuyeres around the entire circumference of the blast furnace is stopped or the output is reduced only in a specific direction, unloading in that direction will be stopped or delayed, and the core-charged coke will be moved in the opposite direction. This means that coke can be supplied in a concentrated manner, suggesting that only the coke in the furnace core that has been supplied in a concentrated manner can be replaced.

That is, while carrying out the control of the filling state of the furnace core coke layer by the shaft-centered coke according to the above-mentioned application (1),
If for some reason the filling condition of the furnace core coke layer deteriorates locally or on one side, resulting in an imbalance in air permeability or liquid permeability, in order to correct this imbalance,
While performing the above control, by stopping combustion or reducing the output at the tuyeres in the direction 180° opposite to the region where the filling condition has deteriorated, the combustion balance in the circumferential direction is eccentrically adjusted, and the furnace core is oriented in the desired direction. The core coke can be renewed by supplying core-charged coke to the side. As a result, the air permeability and liquid permeability in the desired direction can be arbitrarily brought close to the target values, and furthermore, it is possible to eliminate variations in furnace body temperature caused by unbalanced furnace conditions.

The basic configuration of the method of the present invention is as described above,
When charging coke to the core of the furnace top, the permeability and liquid permeability of the core coke layer can be adjusted as desired by adjusting the particle size distribution, cold strength, hot strength, etc. of the coke charged at the core. can be controlled. Further, if attention is focused solely on the air permeability or liquid permeability of the furnace core, the core charge need not necessarily be limited to coke, but lump charcoal, bricks, etc. can also be used.

Also, as a method of charging coke into the shaft center,
For example, as shown in Figures 10 and 11, in a bell-type or bell-less type charging device, a charging chute that reaches the center of the blast furnace is provided in an inclined manner from the side of the upper part of the blast furnace to the furnace axis. The axially charged coke may be charged from the tip of the charging chute. In addition, in the bellless type charging device, by directing the distribution chute near the axial center position of the furnace mouth, accurate axial center charging can be carried out.

[Effects of the Invention] The present invention is configured as described above, and while controlling the filling state using the axially charged coke according to the filling state of the furnace core coke layer, it is possible to control the filling state with respect to the filling state in the circumferential direction. In such cases, the bias can be corrected by eccentrically adjusting the circumferential balance of the blast furnace tuyere combustion so as to offset the bias, and the control effect of the method of application (1) can be fully exerted. As a result, the air permeability and liquid permeability of the furnace core can be improved.

In this way, the operating conditions of the blast furnace can be stabilized and damage to the bottom refractory can be prevented.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional explanatory diagram showing the internal state of the blast furnace model furnace, showing the load lowering situation when unloading in the X direction is stopped, Fig. 2 is a cross-sectional schematic diagram showing the internal state during blast furnace operation, and Fig. 3 Figure 4 is a schematic cross-sectional view of the main part showing the operating status under the central gas flow, Figure 4 is a schematic cross-sectional view of the main part showing the operating status under the peripheral gas flow, and Figures 5 and 6 are horizontal diagrams showing the flow of hot metal during tapping. 7 is a schematic diagram showing the falling situation of center-charged coke, and FIG. 8 is a graph showing the tracer coke concentration in the furnace core when the tracer coke charging area (rt/Rt) is changed. Figure 9 shows that the furnace core coke renewal time is 7 days.
Graphs showing the relationship between (rt/Rt) and (rh/Rh) in the case of 10th and 14th days, and FIGS. 10 to 12 are cross-sectional explanatory views showing an embodiment of the coke center charging method. O...Ore (layer), C...Coke (solid reducing agent)
layer, K...massive zone, SM...softened cohesive zone, B...tuyere,
L... Raceway, A... Furnace core coke (solid reducing agent), F... Hot metal, E... Tap, Ct... Tracer coke, 1... Bell, 2, 4... Raw material charging chute,
3...Distribution shot.

Claims (1)

[Claims] 1. When the solid reducing agent and ore are alternately charged from the top of the blast furnace and the solid reducing agent layer and ore layer are stacked, the solid reducing agent is appropriately charged into the core region of the furnace axis of the ore layer, or the solid reducing agent is By appropriately charging a solid reducing agent suitable for improving air permeability and liquid permeability into the axial region of the reducing agent layer, the air permeability distribution or liquid permeability distribution of the solid reducing agent layer in the blast furnace core can be improved. By making the circumferential balance of combustion in the blast furnace tuyere eccentric, the renewal area of the furnace core by the axially charged coke is eccentric, and the solid reducing agent layer in the furnace core is adjusted. A method for controlling a furnace core filling structure, the method comprising: adjusting the filling structure of a furnace core.