JPH075939B2 - Method of charging raw material into blast furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a blast furnace that succeeds in increasing the stability of blast furnace operation by appropriately charging the specified raw material into the blast furnace shaft center portion. The present invention relates to a raw material charging method.

[Prior Art] In the blast furnace operation, since the production scale is large, the production amount fluctuates depending on the quality of the furnace, and the influence on the planned operation of the next process is significant. Therefore, it is particularly important to stably maintain a good operating condition in order to stabilize the production amount at a high level, and in that sense, it is required to appropriately control the distribution of the raw material fed into the furnace. That is, the ore charged in the furnace is reduced while being heated by the high-temperature reducing gas rising in the furnace. In order to efficiently perform this heating and reduction, the distribution of the charged raw material is kept uniform, It is necessary to supply reducing gas evenly to all ore layers. However, in actual operation, it is difficult to maintain a uniform distribution state due to various factors such as the characteristics of the raw material charging device, the flow characteristics and the deposition characteristics of the charging material, and the raw material distribution state is disturbed. Eventually, the deterioration of the furnace condition is unavoidable. That is, a localized drift of the reducing gas occurs, causing frequent hanging, slipping, flooding, and the like. Therefore, in order to maintain stable operation even if there is such a change in the furnace conditions, the gas flow in the furnace is not simply evenly distributed, but a part of the gas flow is maintained in a certain area, especially the blast furnace core. The idea that it is better to concentrate on the central part (hereinafter referred to as the central flow) to fulfill the safety valve function of the gas pressure in the furnace is becoming the general view, but the technology for maintaining the stable central flow is still complete. There was nothing that was done.

For example, if the ordinary raw material charging method such as the bell method is used, the ore and coke will drop into the furnace wall and then flow into the blast furnace axis, but generally the repose angle of ore is smaller than the repose angle of coke. The ore easily flows toward the axial center, and the thickness ratio of the ore layer and the coke layer (Ore / Coke, hereinafter simply referred to as O / C) becomes high in the core. In particular, in a blast furnace using pelletized ore, the repose angle of the pelletized ore is smaller, so that the inflow of the ore to the axial center side is more remarkable, and the O / C in the axial center part of the blast furnace is further increased. However, since the air permeability in the blast furnace tends to decrease in the area where most of the molten ore is present, the air permeability deteriorates in the blast furnace shaft center where the O / C is high, and most of the reducing gas flow rises on the furnace wall side. A surrounding gas flow operating condition is created. Therefore, in order to improve the air permeability of the blast furnace shaft side for central flow operation, a movable armor is attached to the bell-type raw material charging device to drop a large amount of coke with good air permeability into the blast furnace shaft side. The method has been adopted. That is, a movable armor consisting of a collision plate that can move forward and backward or rotate is provided on the trajectory of the raw material falling from the lower bell, and the falling raw material is bounced early and dropped to the blast furnace shaft side. If coke is selectively charged and deposited on the shaft center side of the raw materials,
Since the O / C decreases, the coke ratio on the axial center side increases and the tendency of forming the central flow becomes stronger.

However, according to the applicant's examination of the results, the O / C change mode obtained by the above method is such that the O / C gradually decreases from the furnace wall side toward the shaft center side. It was found that the internal gas flow velocity gradually increased from the furnace wall side to the shaft center side in an increasing pattern, and the gas utilization rate and thermal efficiency could not be sufficiently increased.

In this situation, the applicant has further researched on the shape of the softening cohesive zone and the correlation with the central flow in the furnace, which are known to have a significant effect on the quality of the operating state, as a result,
It was found that the characteristics of the core solid reducing agent layer spreading below the softening cohesive zone in the blast furnace (permeability, etc.) have an important role in maintaining the shape of the softening cohesive zone and hence the stable operation of the central flow. Then, a method for stabilizing the blast furnace operation at a high level was completed by controlling the characteristics of the solid core reducing agent layer, and a patent application was previously filed (Japanese Patent Application No. 62-220981 etc.).

That is, in the above-mentioned prior application method, a smooth flow of reducing gas and droplets through the core solid reducing agent layer is ensured by maintaining good air permeability and liquid permeability of the core solid reducing agent layer. It is possible to stably maintain the central flow operation.

In the above-mentioned prior application method, as a means for maintaining the characteristics of the solid core reducing agent layer in good condition, a high-grade coke having a large grain size or particularly high strength is charged in a certain region of the blast furnace core in the coke layer. Or, it was found that a high-grade or ordinary coke (hereinafter, the raw material charged aiming at this fixed region is referred to as a specific raw material) is charged into the fixed region of the ore layer, and by this means, It was confirmed that the specific raw material descends with the descent of other raw materials while maintaining the shape at the time of charging as much as possible, and that these form a solid core reducing agent layer with good characteristics, and a control method for it is also established. did.

[Problems to be Solved by the Invention] In carrying out the above-mentioned prior application method, it is necessary to intensively charge a specific raw material into a predetermined region of the blast furnace shaft center portion.
A bell-type charging device equipped with a movable armor as described above cannot handle this. Therefore, as an alternative device, it was considered to arrange a raw material charging chute from the upper side of the blast furnace to the vicinity of the blast furnace shaft core below the bell, and use this chute as a blast furnace shaft core charging special chute. It was

However, according to the charging of the specific raw material into the blast furnace shaft center by the raw material charging chute, the specific raw material charging position is not correct depending on the in-reactor situation, and the core solid reducing agent layer is controlled. There was the inconvenience that the accuracy deteriorated. That is, the tip of the charging chute is stopped at a position slightly before the axial position of the blast furnace in view of the fact that the raw material discharged from the tip of the chute also draws a parabola and flies in the horizontal axis (X axis) direction. It is designed so that the specific raw material discharged from the tip of the charging chute flies in the inner space of the furnace for a certain distance and is deposited on the in-core material deposit layer at the blast furnace axial center position. Therefore, when the above-mentioned charging chute is used, the drop height (in the Y-axis direction) of the specific raw material changes depending on the height of the raw material deposition layer in the furnace, and therefore the flight distance of the X-axis, which is a function of the Y-axis, also changes. As a result, the specific raw material will be implanted at a position far away from the blast furnace axis. As a result, the characteristic control accuracy of the core solid reducing agent layer deteriorates, the central gas flow cannot be maintained in a good state, and the gas flow distribution in the furnace is disturbed.

The present invention has been made in view of such circumstances, and by accurately charging a specific raw material into the blast furnace shaft core portion, the properties of the core solid reducing agent are controlled, and eventually the central flow operation is stabilized. To maintain it in a positive manner.

[Means for Solving the Problems] However, the method of the present invention which has achieved the above-mentioned object, is to deposit the specific raw material into the blast furnace shaft central portion through the shaft central portion charging chute in a concentrated manner. The gist is that the specific raw material discharge pressure from the shaft portion charging chute is controlled according to the level to adjust the specific raw material reaching position.

[Operation and Examples] The present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional explanatory view showing a specific raw material charging apparatus for carrying out the method of the present invention. 1 is a blast furnace, 2 is large, 3 is a small bell, 8 is a movable armor, 9 is a charging chute. Each one is shown. In FIG. 1, the raw material introduced from the raw material charging conveyor 6 to the swirling chute 5 via the switching chute 7 enters the furnace from the swirling chute 5 and drops while being sequentially diffused by the small bell 3 and the large bell 2, and the blast furnace Deposited inside. The raw material falling from the large bell 2 collides with the movable armor 8 whose degree of advancement is adjusted as necessary, and the position where it falls onto the deposits in the blast furnace is adjusted. When charging the specific raw material at the blast furnace axial center position of the coke-ore alternately deposited layer thus charged and deposited, the specific raw material dispensed from the charging conveyor 6 to the chute 10 (in this case, normal coke is usually used as the core of the ore layer). A charging method of charging the core is used) is stored in a storage tank 11 and then charged into a hopper 14 via a slide gate 12 and a cutting feeder 13. The specific raw material thus charged into the hopper 14 temporarily stays in the pressurizing chamber 19 and then is charged from the charging chute 9 into the blast furnace shaft center portion. A N ₂ supply line _{11 and a} N ₂ discharge line ₁₂ are connected to the pressurizing chamber 19, and a pressurization valve 17 and a discharge valve 18 are provided in each line. Seal valves 15 and 16 are provided between the pressurizing chamber 19 and the hopper 14, and between the pressurizing chamber 19 and the charging chute 9, respectively. In the above-mentioned specific raw material charging process, in the present invention, the coke-ore alternating deposition state (deposition height and deposition inclination angle α) in the furnace is measured by a scale gauge 23 and a profile meter (not shown), and the measurement is performed. Pressurized chamber based on the result
Control the N ₂ gas pressure in 19. That is, when the pressure in the pressurizing chamber 19 is increased or decreased by opening or closing the pressurizing valve 17 or the exhaust valve 18 of the N ₂ supply line l ₁ or the N ₂ exhausting line l ₂ , the seal valve 16 is released to release the pressurizing chamber 19. The discharge pressure when the specific raw material therein is discharged to the charging chute 9 is increased or decreased, and accordingly, the discharge speed of the specific raw material discharged from the charging chute 9 can be adjusted.

That is, as illustrated in FIG. 2, when the raw material deposition state in the furnace is in the state A, the specific raw material from the charging chute 9 can be dropped as shown by the broken line in the figure, so the charging chute The pressure in the pressurizing chamber 19 located on the upstream side of 9 is maintained at a pressure equalizing state, that is, at a steady, relatively low pressure to suppress the charging rate of the specific raw material. As a result, the specific raw material drops and deposits on the blast furnace shaft center on the deposited raw material at the level A. On the other hand, when it is found that the raw material deposition state in the furnace is at the B level by the detection with the scale meter 23 and the profile meter, N ₂ in the pressurizing chamber 19 is
The pressure, that is, the material discharge pressure is increased. As a result, the specific raw material drops vigorously from the charging chute 9 along the locus shown by the solid line in FIG. 2, and can be accurately charged into the blast furnace shaft center position of the deposited raw material at the B level. By the way, if the N ₂ gas pressure in the pressurizing chamber 19 is kept at the pressure equalizing state at the deposition level B, the charged specific raw material falls along the trajectory of the broken line and is deposited at the position of b ′. The deposition position is eccentric from the blast furnace axis.

FIG. 3 shows the eccentricity of the deposition level (represented by V in FIG. 2) and the maximum temperature of the throat gas with respect to the reference level in the blast furnace schematically shown in FIG. It is an experimental graph which calculated | required the relationship of quantity. According to this, V
At 2.5 m, the eccentricity was almost 0 mm both when the specific material discharge pressure was changed (the present invention) and when it was not changed (conventional example), and no eccentricity at the furnace gas maximum temperature point was observed. , V changes to 1.5 m or 3.5 m, the maximum temperature of the furnace mouth gas is largely eccentric in the conventional example, whereas in the present invention, the material discharge pressure is controlled according to the fluctuation of V, so Almost no eccentricity of the temperature point is observed.

[Advantages of the Invention] The present invention is configured as described above, and it is possible to correct the specific raw material dropping position in accordance with the raw material deposition level in the furnace.

Thus, the specific raw material can be accurately deposited on the blast furnace core, and the core solid reducing agent layer can be maintained in a preferable state to stably form the central gas flow. As a result, the blast furnace operation can be stably performed with high productivity.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a blast furnace and a raw material charging apparatus for carrying out the present invention, FIG. 2 is an explanatory diagram showing a difference in raw material charging loci during pressure equalization and pressurization, and FIG. It is a graph which shows the relationship between the amount of eccentricity of the raw material deposition level in the furnace of the present invention and the conventional example, and the furnace mouth gas maximum temperature point. 1 ... Blast furnace, 2 ... Large bell 3 ... Small bell, 4 ... Seal valve 5 ... Swivel chute, 6 ... Charging conveyor 7 ... Switching chute, 8 ... Movable armor 9 ... Charging chute , 10 ...... Chute 11 ...... Coke tank, 12 ...... Slide gate 13 ...... Cut-out feeder 14 ...... Input hopper, 15, 16 …… Seal valve 17 …… Pressurization valve, 18 …… Exhaust pressure valve 19 …… Pressurization Chamber, 20 …… Pressure gauge 21 …… Coke layer, 22 …… Central coke 23 …… Scale gauge, 24 …… Deposit inclination angle

Claims (1)

[Claims] 1. When a specific raw material is intensively charged into the shaft core of a blast furnace through a shaft charging chute, the specific raw material is discharged from the shaft charging chute in accordance with the raw material deposition level in the furnace. A method for charging a raw material into a blast furnace, which comprises controlling a pressure to adjust a specific raw material reaching position.