JP4317504B2 - Blast furnace operation method - Google Patents

Description

  The present invention relates to a method for stabilizing a taphole depth in blast furnace operation.

  In a blast furnace, iron ore and coke are charged from the top of the furnace and accumulated in layers. On the other hand, high-temperature air (hot air) is blown from the tuyere at the bottom of the furnace, and the coke in the furnace burns. Hot reducing gas is generated, and the iron ore deposited in the furnace is reduced and melted while the hot reducing gas rises in the furnace, and the generated hot metal and hot metal flow down to the hearth. .

  In this way, iron ore is melted and disappears in the lower part of the furnace, and therefore, a coke packed layer called a core coke layer is formed in the lower part of the furnace.

  The hot metal and hot metal that have flowed down to the hearth are discharged out of the furnace by opening a spout provided in the hearth. In recent large-scale blast furnaces, there are a plurality of taps, and by alternately opening and closing these taps, the hot metal flowing down to the hearth, the operation of always discharging the hot metal outside the furnace, So-called continuous output is performed.

  The spout is opened with a tapping machine drill, and after finishing the spout, a filler called a mud is injected with a mud gun, and the mud is closed by heat solidifying. Part of this mud (referred to as the amount of mud pressing) is injected into the furnace from the inner tip of the tap outlet and solidifies to form a mud deposit layer that covers the side wall surface of the hearth and the bottom corner of the furnace. To do.

  This mud deposit has an important role in protecting the hearth refractory from erosion by the hot metal flow. Here, the penetration length of the drill (the length penetrating both the furnace wall refractory and the mud deposit layer) when the tap hole is opened by the tapping machine is called the tap hole depth.

  If this taphole depth becomes too shallow (that is, if the thickness of the mud deposit layer becomes thin), the bottom corner of the furnace cannot be covered with mud, and a space called free space is formed in this area, and the hearth The hot metal that has flowed down is discharged from the outlet through this free space, and a so-called hot metal annular flow is formed in the hearth. When such a hot metal annular flow is formed in the hearth part, the wear of the hearth refractory is accelerated and the life of the furnace is significantly shortened.

  On the other hand, if the depth of the outlet is made too deep in order to prevent the hot metal annular flow from being generated, the amount of mud used becomes excessive, and the operation cost increases remarkably.

  Therefore, in order to prevent the occurrence of hot metal annular flow and prolong the life of the blast furnace while suppressing mud usage and avoiding an excessive increase in operating costs, maintain the spout depth in an appropriate range. That is important (stabilization of the taphole depth). However, in the conventional blast furnace operation, the taphole depth is likely to fluctuate, and the fluctuation factor was not clear, so it was difficult to stabilize the taphole depth. Moreover, there are few prior arts regarding stabilization of the taphole depth, and only the following are found.

(Prior art 1)
A ventilation control valve is provided in the tuyere vent branch located above the tap outlet of the blast furnace to control the amount of hot air blown into the blast furnace through the tuyere, and the depth of the tap outlet The operation method of the blast furnace characterized by controlling the ventilation | air_flow volume of the said hot air from the said tuyere, and keeping the depth of the said tap hole in the appropriate value (refer patent document 1).

(Prior art 2)
When no increase in the amount of brewing is required or when it is not during brewing, the amount of air blown from the tuyere above the shed is equal to or relatively relative to the amount of air blown from the other tuyere. By reducing, the space between the coke filling layer (furnace core coke layer) and the mud deposition layer is reduced, or the coke filling layer (furnace core coke layer) covers the mud deposition layer, and the hot metal is heated. Blast furnace output that reduces the basic unit of mud by suppressing the wear of the mud layer exposed to the surface, and reducing the depth of the tap hole, that is, the amount of mud that compensates for the thickness of the mud layer. Control method (see Patent Document 2).
Japanese Examined Patent Publication No. 63-65730 JP 2000-256710 A

  The method of the above-mentioned prior art 1 makes it possible to stably serve and sag by controlling the amount of hot air blown from the tuyere according to the tapping depth and keeping the tapping depth at an appropriate value. It is. However, the quantitative relationship between the tap outlet depth and the amount of hot air blown from the tuyere is not disclosed at all, and how much the air blow amount should be changed in response to the change in tap outlet depth. It is unknown whether it is good. Therefore, in this method, every time the size of the blast furnace and the operating conditions are changed, the amount of blown air must be changed by trial and error, and there is room for improvement.

  Moreover, the method of the above prior art 2 aims at reducing the amount of mud used, and does not directly aim at maintaining the tap hole depth in an appropriate range. In addition, as in the case of the prior art 1, the quantitative relationship between the tap outlet depth and the air flow rate from the tuyere is not disclosed at all, and the air flow rate is changed by trial and error every time the blast furnace size and operating conditions change. There was room for improvement because it had to be changed.

  Therefore, the present invention can more reliably stabilize the tap outlet depth while suppressing the mud consumption and avoiding an excessive increase in operating cost without excessive trial and error, and can extend the furnace life. The purpose is to establish a blast furnace operating method.

  As described above, since the variation factor of the tap outlet depth was not clear in the conventional blast furnace operation, the present inventors first influenced the influence of various parameters that are assumed to affect the expansion and contraction of the tap outlet depth. In order to investigate, dimensional analysis was performed by the following formula (1) using the blast furnace operation data (see FIG. 1).

R _TH = C · R _RW α · MRβ · [% Si] γ · [% Ti] δ Formula (1)
Where R _{TH is} a dimensionless number (= r _TH / r _H ) in which the distance r _TH from the center axis of the blast furnace to the tip of the inside of the furnace port 1 is made dimensionless based on the hearth radius r _H , C: constant , R _RW : Dimensionless distance r _RW from the center axis of the blast furnace to the furnace inner tip of the raceway 3 formed inside the furnace at the tuyere 2 located above the tap 1 on the basis of the hearth radius r _H Dimensionless number (= r _RW / r _H ), MR: Mud basic unit (kg / thm), [% Si]: Si concentration in hot metal (% by mass), [% Ti]: Ti concentration in hot metal (% by mass) ), Α, β, γ, δ: exponents.

Here, in the above equation (1), as one of the parameters assumed to affect the expansion and contraction of the tap outlet depth L _TH (ie, R _TH ), the taps adopted by the conventional techniques 1 and 2 as the control factors. The reason why the depth L _RW (that is, R _RW ) of the raceway 3 formed inside the furnace of the tuyere 2 instead of the amount of air blown from the tuyere 2 located above the mouth 1 is as follows. .

That is, expansion and contraction of the taphole depth L _RW is a high temperature depending on the porosity of the furnace core coke layer 5 magnitude at the boundary portion between the furnace core coke layer 5 and the mud deposited layer 6 through the boundary molten iron It is assumed that the flow rate of the soot changes, and as a result, the amount of wear of the mud deposition layer 6 that is worn by being exposed to the molten iron changes. And it is thought that the porosity of the core coke layer 5 of the said boundary part changes with whether the core coke layer 5 settles on a furnace bottom, or leaves | separates from a furnace bottom. It is considered that the landing / floating of the core coke layer 5 is caused by a change in the balance between the load of the core coke layer 5 near the tap outlet 1 and the buoyancy due to the rising gas flow in the furnace. Therefore, the raceway depth L _RW (that is, R _RW ) that is directly related to the buoyancy due to the rising gas flow in the furnace was adopted as a parameter.

  Even if the blast volume is the same, the wind speed in front of the furnace tuyere varies depending on the tuyere diameter, the amount of auxiliary fuel blown from the tuyere, the blast temperature, etc., and the raceway depth varies. It is not appropriate to select the air volume.

Using the blast furnace operation data, dimensional analysis is performed according to the above equation (1). Based on the result, R _TH / R _RW (= r _TH / r _RW ) and raceway depth (ie, R _RW ) FIG. 2 shows the relationship with the index α representing the degree of influence on (that is, R _TH ). As shown in FIG. 2, when R _TH / R _RW (= r _TH / r _RW ) becomes 0.95 or more, α becomes substantially zero, so that even if the raceway depth (that is, R _RW ) is changed, it can be obtained. The mouth depth (ie, R _TH ) does not change. On the other hand, when R _TH / R _RW (= r _TH / r _RW ) is less than 0.95, α> 0 is always satisfied. Therefore, by changing the raceway depth (ie, R _RW ), R _TH ) can be changed.

  Based on the above findings, the inventors have completed the following invention.

The invention according to claim 1 adjusts the depth of the raceway (hereinafter referred to as “raceway depth”) formed inside the tuyere of the tuyere located above the taphole so as to satisfy the following formula. A method of operating a blast furnace that stabilizes the depth of the tap hole, the adjustment of the raceway depth, an operation action that increases or decreases the amount of fuel that is blown into the furnace from the tuyere, and the tuyere It is a blast furnace operating method characterized in that it is performed by one or both of the operation actions for increasing or decreasing the amount of air in the connected blower branch pipe .
Formula (2) r _TH / r _RW <0.95
Here, r _TH is the distance from the blast furnace central axis to the furnace inner tip of the tap outlet, and r _RW is the distance from the blast furnace central axis to the furnace inner tip of the raceway.

  Note that the value on the right side of the above formula (2) is more surely α> 0 as the value is smaller, and is preferably 0.94, and more preferably 0.93.

  According to the present invention, by maintaining the raceway depth within a predetermined range, the mud usage amount is suppressed without excessive trial and error, and an excessive increase in operating cost is avoided, and the taphole depth is reduced. It is possible to realize a blast furnace operation method that can stabilize more reliably and extend the life of the furnace.

  Hereinafter, the present invention will be described in more detail with reference to the drawings. In the following description, only one tap hole will be described, but in the case of a blast furnace having a plurality of tap holes, the same operation may be performed for each tap hole.

Embodiment
FIG. 1 is a partial longitudinal sectional view of the vicinity of a tuyere and a tap outlet of a blast furnace according to an embodiment of the present invention.

In FIG. 1, 1 is a spout, 2 is a tuyere located above the spout 1, 3 is a raceway formed inside the furnace of the tuyere 2, and 4 is a blow branch connected to the tuyere 3 5 is a furnace core coke layer, and 6 is a mud deposition layer. Further, L _TH is taphole 1 depth (taphole depth), L _RW represents the raceway 3 of the depth (Raceway depth), r _TH until the furnace inner end of the taphole 1 from blast furnace central axis , R _RW is the distance from the center axis of the blast furnace to the inner tip of the raceway 3, and r _H is the hearth radius.

The present invention, a raceway depth L _RW, and adjusted so as to satisfy the equation (2) that is reproduced in the following, is intended to stabilize the taphole depth L _TH.

Reprinting formula (2) r _TH / r _RW <0.95

Therefore, in order to achieve a stabilization of the taphole depth L _TH, it is necessary to determine the r _TH and r _RW, for the measures and taphole depth L _TH and raceway depth L _RW There is a need.

The tap hole depth L _TH can be obtained from the change in the drill driving torque or the like from the start of opening to the completion of opening when the tap hole 1 is opened with a tapping machine.

Further, the raceway depth L _RW irradiates toward the furnace from viewing window 8 provided a microwave from the waveguide 7 to the horizontal rear end of the blower branch pipe 4, be determined from the intensity of the reflected wave (See Matsui et al .: CAMP-ISIJ, vol. 16 (2003), p. 1036).

Then, r _TH and r _RW are calculated from the tap hole depth L _TH and raceway depth L _RW measured as described above and the known dimensions of each part of the blast furnace, and r _TH / r _RW is obtained.

Hereinafter, the case where r _TH / r _RW obtained as described above is 0.95 or more and the case where it is less than 0.95 will be described separately.

(A) When r _TH / r _RW is 0.95 or more When r _TH / r _RW obtained as described above is 0.95 or more (when r _TH is excessive, that is, output When the throat depth L _TH is excessively reduced), the degree of the influence of R _RW (ie, raceway depth L _RW ) in the formula (1) on R _TH (ie, the exit throat depth L _TH ) the exponent α that represents becomes substantially 0, you can not change the taphole depth L _TH If you change the raceway depth L _RW. Therefore, in order to increase r _RW so that r _TH / r _RW is less than 0.95, preferably less than 0.94, and more preferably less than 0.93 (ie, to reduce raceway depth L _RW ). Perform the operation action.

The following two operation actions are effective as the operation actions for reducing the raceway depth _LRW .

(A) Operation action to increase the amount of auxiliary fuel such as pulverized coal and waste plastic blown into the furnace from the tuyere 2 (b) Operation action to reduce the air volume in the blower branch 3 connected to the tuyere 2

When the operation action (a) is adopted, the combustion rate of high-temperature coke preheated in the furnace decreases and the combustion rate of auxiliary fuel at room temperature increases, so the flame temperature before the tuyere in the furnace decreases. As a result of the decrease of the gas flow velocity before the furnace tuyere, the raceway depth _LRW is decreased.

On the other hand, when the operation action (b) is employed, the amount of air passing through the tuyere 2 is reduced and the gas flow velocity in front of the furnace tuyere is lowered, so that the raceway depth _LRW is lowered.

As a specific means for reducing the air volume in the blower branch pipe 3, a method of replacing the tuyere 2 with one having a small inner diameter can be employed. If the inner diameter of the tuyere 2 is reduced, the gas flow velocity in front of the tuyere will increase, but the pressure loss in the tuyere 2 will increase and the air volume in the blow branch 3 will decrease, resulting in a decrease in the raceway depth L _TH (See FIG. 2 of “Matsui et al .: CAMP-ISIJ, vol. 16 (2003), p. 1036”).

Note that when lowering the taphole depth L _TH is significant, it is also possible to reduce the tuyere 2-0 completely raceway depth L _RW as blockage tuyeres.

  Only one of the operation actions (a) and (b) may be performed, or both may be performed simultaneously.

As a result of returning r _TH / r _RW to less than 0.95, preferably less than 0.94, more preferably less than 0.93 by the operation action, R _RW (that is, raceway depth L _RW ) in the above formula (1) is obtained. ) Is always positive, the index α representing the degree of influence of R) on R _TH (that is, the tap hole depth L _TH ). Therefore, by changing R _RW (that is, raceway depth L _RW ), R _TH (that is, tap hole depth L _TH ) can be changed.

For example, by reducing the raceway depth L _RW, in accordance with the mechanism described above, Chakuyukashi deadman coke layer 5 buoyancy by furnace ascending gas stream is reduced within the furnace bottom, the deadman coke layer 5 and the mud The porosity of the core coke layer 5 at the boundary portion with the deposition layer 6 decreases, the flow rate of the hot metal flowing through this boundary portion decreases, and the wear amount of the mud deposition layer 6 decreases, thereby reducing the tap depth. L _TH extends. Moreover, the molten iron annular flow is also suppressed by the landing of the furnace core coke layer 5 on the furnace bottom. As a result, wear of the hearth refractory is suppressed and the life of the furnace is extended.

The operation actions (a) and (b) above (increase in the amount of auxiliary fuel injection, decrease in the air flow rate of the blower branch) cause unevenness of unloading in the inner circumferential direction of the furnace and decrease in the hot metal production rate. Therefore, in the range where r _TH / r _R does not become 0.95 or more depending on the degree of extension (recovery) of the taphole depth L _TH , the operation opposite to the operation actions of (a) and (b) above is performed. It is preferable that the raceway depth _LRW is gradually increased to return to the original size by an action (reduction of the auxiliary fuel injection amount, increase of the blower branch airflow amount).

(B) if if r _TH / r _RW is r _TH / r _RW obtained as described above when becomes less than 0.95 was less than 0.95 (r _TH is in the proper range, i.e. out When the throat depth L _TH is in the appropriate range), α> 0 is always satisfied, and therefore, the exit throat depth L _TH can be changed by changing the raceway depth L _RW . Therefore, in this state, it is not necessary to perform the operation actions (a) and (b) above, and the mud push that only compensates for the wear of the thickness of the mud deposition layer 6 while keeping the raceway depth _LRW constant. It is only necessary to maintain the amount and keep the tap outlet depth L _TH constant. Thereby, while suppressing the amount of mud used and avoiding an excessive increase in operating cost, the taphole depth can be more reliably stabilized and the furnace life can be extended.

[Modification]
In the above embodiment, the means using the microwave is exemplified as the means for measuring the raceway depth r _RW , but means for inserting and measuring the probe from the tuyere 2 when the blast furnace is closed may be used. However, a means using a microwave is more preferable because it can be measured without affecting the inside of the furnace during operation.

  Moreover, although the example which reduces the internal diameter of the tuyere 2 was shown as a means to reduce the air volume in the ventilation branch pipe 3 in the said embodiment, you may make it insert a throttle part and an orifice in a ventilation branch pipe.

In order to confirm the effect of the present invention, a tuyere above one tap hole was experimentally tested in a blast furnace with an internal volume of 1845 m ³ , a tap hole: two, and a pulverized coal injection ratio: about 150 kg / thm. (1), the above-mentioned microwave outlet depth measuring device is installed, r _TH / r _RW = 0.91 (target value) as an invention example, and r _TH / r _RW = 0.98 as a comparative example. (Target value), each operation to maintain.

The test results in FIG. 3, shown in relation to the mud per unit MR and taphole depth L _TH. As can be seen from FIG. 3, even in the same range of the mud intensity unit MR, the invention example shows that the taphole depth _LTH is increased by about 12% as compared with the comparative example.

  Therefore, according to the present invention, compared with the prior art, without excessive trial and error, the mud consumption is suppressed and an excessive increase in operating cost is avoided, and the outlet depth is more reliably maintained within an appropriate range ( (Stabilization) was confirmed.

It is a fragmentary longitudinal cross-sectional view of the tuyere and the taphole vicinity of the blast furnace which concerns on one Embodiment of this invention. It is a graph which shows the relationship between _rTH / _rRW and the index _| exponent (alpha). Mud is a diagram showing the relationship between the intensity MR and taphole depth L _TH.

Explanation of symbols

1: taphole 2: tuyere 3: raceway 4: blast branch 5: core coke layer 6: mud deposition layer 7: waveguide 8: viewing window _LTH : taphole depth _LRW : raceway depth r _TH : distance from the blast furnace central axis to the furnace inner tip of the tap outlet 1 r _RW : distance from the blast furnace central axis to the furnace inner front end of the raceway 3 r _H : hearth radius

Claims (1)

The depth of the raceway formed inside the tuyere inside the tuyere above the taphole (hereinafter referred to as “raceway depth”) is adjusted so as to satisfy the following formula, and the depth of the taphole The blast furnace operating method is to stabilize the raceway depth by adjusting the raceway depth, the operation action to increase or decrease the amount of fuel blown into the furnace from the tuyere, and the air volume in the blower branch connected to the tuyere A method for operating a blast furnace, which is performed by one or both of the operation actions to be increased or decreased .
Formula r _TH / r _RW <0.95
Here, r _TH is the distance from the blast furnace central axis to the furnace inner tip of the tap outlet, and r _RW is the distance from the blast furnace central axis to the furnace inner tip of the raceway.

Images