JPS58153714A - Operation of blast furnace - Google Patents

Abstract

PURPOSE:To stabilize the condition of tapping slag by keeping the time between the iron tapping and the slag tapping short and to continuously keep the sulfur in iron at a low level, by controlling the brick temperature of furnace bottom and furnace wall in a region wherein viscous layer is at least formed on blast furnace hearth. CONSTITUTION:In the operation of blast furnace, the controlled value of the viscous layer thickness of furnace hearth wall and furnace bottom is determined for the purpose of protecting both the thickness of viscous layer and the workability of tapping slag in the past and furnace body. In that case, when the viscous layer is 0.3m in thickness, the controlled brick temperature of furnace hearth wall and furnace bottom become about 110 deg.C and 125 deg.C. This temperature control is carried out by controlling, for example, the cooling water flow of stave cooler and cooling tube, the cooling capacity of water cooler, etc. By this operational method, the extraction of tapping slag may be steadily continued, and the quality of hot metal may be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of operating a blast furnace, in particular, stabilizing the ventilation inside the furnace and the tapping slag condition (operation), and reducing the S (%) in the iron.
This provides a method for operating a blast furnace that lowers and stabilizes the

In the operation of a blast furnace, stable management of the tap iron slag operation is extremely important not only to stabilize the ventilation inside the furnace but also to stabilize and maintain the quality of hot metal at a high level.

Stability in the tap slag operation means being able to extract the slag at an appropriate speed when opening the blast furnace tap hole [1]. 1] It is believed that the trade of blast furnace mud material, which acts as a plugging material, the thermal condition of the hearth, and the stability of ventilation inside the blast furnace are important control items for blast furnace operation.

By the way, in the current blast furnace, hot metal and molten slag are extracted from the same tap 1. The difference is used to separate pig iron and slag71).

Usually, when the taphole is opened, hot metal flows first, continues for a certain period of time, and hot metal slag comes out at the same time. Generally, the time from the start of tapping to the start of slag (hereinafter abbreviated as the time from tapping to slag) is often used as an index to indicate the stability of the tapped slag condition. If the variation between pig irons is small and stable, the lapping ratio described below is small and the slag condition is good, and it is evaluated that hot metal slag is extracted at an appropriate speed. In the current blast furnace,
It is equipped with two or more tapholes, and taps are made by using two or more tapholes as appropriate to prevent the ventilation in the furnace from becoming unstable due to residual iron slag. In order to prevent
Lap tapping (tapping from two or more tap irons 1-1 at the same time) is performed in rows, b raps 1, for example 1. : The lap rate is defined as (total tapping time for Ili/total tapping time for one day)x+o+)). What is the above lug tapping time?2
Two (usually two) pig iron taps [from 1 to simultaneous tap γ
It's been 6 hours since then. Therefore, the stability of the slag condition can be evaluated by this ramp rate, that is, the tapping time.The smaller the rap rate, the more stable the slag condition is. It has been evaluated that there are no oily problems. - Conventionally, the method of keeping the tapped slag condition of the blast furnace completely stable was to change the tap depth, tap diameter, and mud material as described above. The time from tapping to slag is managed, but due to the mutual fixed relationship, there is a large variation in the time taken to tap iron, which is insufficient for operational management.

In addition, the blast furnace hearth is protected by a stave cooler placed around the outer periphery of the hearth wall bricks (rl-II).
Cooling fluid (cooling water) is constantly supplied at a constant flow rate to the bottom cooling pipe installed in the bottom foundation of the electric furnace or in the bottom wall/gauge to cool the hearth wall and bottom pipe Jj. Is going.

The furnace operation system of the present invention was developed in view of the following two facts, and it was focused on the fact that the tap slag condition is greatly related to the shape of the viscous layer formed in the hearth. The purpose is to quantitatively find out the relationship between the thickness of the viscous layer and the state of the tap slag, and manage the thickness of the viscous layer. This allows stable extraction of slag by shortening the time from tapping to slag, and at the same time extends the contact time of the slag, which is achieved by shortening the time from tapping to slag.
The purpose is to improve the quality of hot metal (lower S% in the pig iron) by activating the metal reaction.

The blast furnace operating method of the present invention will be explained below.

The viscous layer will be explained.

1 [A] and [B] show vertical cross-sectional schematic diagrams of the hearth part of a blast furnace. 4, and normally the hearth bricks 2 are eroded due to the long-term flow of hot water. As a result, erosion lines 5 are formed.

12 However, changes in the above-mentioned erosion factors and production volume adjustment (changes in operating conditions such as changes in air blowing, changes in brick cooling conditions from the outside, especially changes in water temperature depending on the season of cooling water in stave coolers and cooling pipes, etc.) In some cases, a very viscous layer ( ) of high viscosity is formed along the erosion line 5 of the hearth part 1 and is easily overlooked. This high viscosity viscous layer 6
is considered to be in a mixed solid-liquid state. This viscous layer 6,
For example, tap iron 1-1 (r shown in the figure) of [11dl2B]
The amount of viscous layer formed in front of the hearth wall brick 4 (j2-tm) at the lower F high level hVc>vf can be calculated using the temperature gradient and absolute temperature at level A.

ts[l:m, 11 of the hearth wall brick shown in Figures 1 and 2
and +9 [m] position (temperatures detected by hearth wall brick thermometers 8 and 9, 1T (ta) and rctq).

The heat transfer coefficient λC of the hearth wall brick at this time is λC=K] T
m 10 to 2---・(ljHowever'l"m -(T(7s
)+TC1cr) ]/2. Kt, K2:
Constant temperature T(ts) and T(+9) (D relationship is ΔT=T
(4s) T(19) --= (2)ΔT2 K3
T (+9) K4 --- (31 However, Ka
+K4: Becomes a constant. On the other hand, by substituting equations (1,) and +3) into equation (4), the flow-through heat amount Q (kcaA/m'hr) can be calculated as follows:
) However, 5, Ka, K7 are constants or by substituting equation (2) into equation (4).

Let the temperature at point Am be Tx, and the initial brick thickness fLc as shown in Figure 1 (A), t□1 (7c) holds.Now, for example, the 1150℃ line is the erosion line 5.
shall be. Lm can be found from equation (7).

The Am obtained by Doroki is called the thickest dipping line.

In this way, the maximum erosion at the present time is known with the 1 + 5 o-c line as the erosion line, and from then on, the temperature at point tm is calculated from equation (7) in H. The viscous layer thickness can be calculated as follows. That is, from equation (7), when (D above Tx is 'rx≧], at 150°C, L
/7 Judging that the erosion of Jj has progressed from the maximum erosion line above, the new erosion line tl in Figure 2 is found as t], and this t] is the new maximum erosion line 1m, that is, tm = t1. Keep it.

On the other hand, when the above Tx is 'f'x (] I 50°C, it is judged that a force of viscosity + m 1 m is generated.Then, the viscous hearth in Fig. 2 - I2, which is the outer surface fin of the hot metal slag, is removed. demand.

In addition, λS in the open equation is the heat transfer coefficient of the viscous layer, and 1 m is (9)
Formula V (according to 'l' x calculation time 1 m f is used.

Therefore, from equation (11), the thickness of the viscous layer at level A (12
-4m) becomes λS (I2-1m)=-(115O-Tx)-(12) (calculated by substituting (9) into equation I21).

In Equation (J3), λS; heat transfer coefficient λC of the viscous layer; heat growth coefficient tm of the brick; maximum erosion line (past R scale) Q; penetration heat amount −λCΔT/zs−m1.

ai”; depth lsc”? The viscous layer thickness can be calculated by detecting ΔT and T(I9) as shown in the difference between the temperature 'r(I8) of J and the temperature T(I9) of t9cm'J. Note that the above Δ′1゛ and r(z, +)
and have a mutual correlation as shown in FIG. 3, and the viscous layer thickness (I2-1m) can also be expressed as -C as a function of T(I9).

FIG. 4 shows the relationship between the temperature T (I9) and the calculation line t2 before the implementation of the present invention, that is, before the start of the viscous layer thickness control, and Lm in the figure shows the maximum erosion line.
It is clearly shown that as F(79) increases, the viscous layer thickness decreases.

It also shows that the viscous layer thickness can be controlled by actively manipulating the brick temperature. The temperature of the bricks can be controlled by controlling the cooling conditions of the bricks, that is, the cooling conditions of a brick cooling device such as a staple cooler or a furnace bottom cooling pipe.

Therefore, by manipulating the cooling conditions of the brick cooling device, the brick temperature can be controlled, and by manipulating the brick temperature, the viscous layer thickness can be controlled.

The above has explained how to determine the thickness of the viscous layer on the hearth wall, but the thickness of the viscous layer on the hearth bottom can also be determined by setting the thickness of the viscous layer at a fixed distance from the hearth as shown in Figure 1 [B]. Hearth bottom 1//ga temperature 1j
From the detected temperature of support i1 lo, ] l (12' tm
).

Figures 5 and 6 show the thickness of the viscous layer at the hearth wall and hearth bottom.
n) and the relationship between iron tapping and slag tapping time (minutes).
As shown in the figure, there is a strong correlation between the roughness, viscous layer, thickness, and tapping/slag tapping time.3 In other words, as the viscous layer becomes thinner (brick temperature), W becomes more cylindrical. )
Accordingly, the time from tapping to slag is shortened. Conversely, as the thickness of the viscous layer increases (brick temperature decreases), the tapping-to-slag time increases.

The data for finding the relationships shown in Figures 5 and 6 above and Figures 3 and 4 above was obtained over a period of 1 year and 6 months when brick cooling protection was carried out by supplying a constant flow of cooling water to the staple cooler and hearth cooling pipe, respectively. This sample was taken during blast furnace operation F during the period, and it is clear that the brick temperature naturally fluctuates and the viscous layer thickness also fluctuates.

Figure 7 shows the relationship between hearth wall brick temperature and hearth brick temperature during the period during which the data in Figures 5 and 6 were collected, and there was a positive correlation.

Therefore, the viscous layer thickness - tapping to slag tapping time characteristics shown in Figures 5 and 6 are considered to be such that the larger the hearth section volume, the shorter the tapping time to slag tapping, and furthermore, as shown in Figure 0. Characteristics [As the viscous layer becomes larger, the area near the tap 1 located on one side of the viscous layer measurement level becomes buried in the viscous layer, the degree of inhibition of pig iron slag extraction increases, and the tapping speed decreases. However, as a result, it is thought that the tapping time and slag tapping time will become longer.

By managing, operating, and controlling the viscous layer thickness as described above, the tapping-slag tapping time can be managed, operated, and controlled.

If the thickness of the viscous layer is controlled to be constant, the time from tapping to slag tapping can be made constant for each tapping. Furthermore, when the viscous layer thickness is zero, that is, when no viscous layer is formed, the time from tapping to slag can be minimized. However, if a viscous layer is not formed, the hearth bricks and hot metal slag will come into face-to-face contact, resulting in severe brick erosion, which poses a problem in terms of protecting the furnace body.

Therefore, in the present invention, by controlling the temperature of the furnace bottom and hearth wall bricks in the area where the erosion line, that is, the viscous layer, which is not a problem from the perspective of protecting the furnace body, is formed at a minimum, the iron tapping to slag tapping The time (lap rate) is kept short, the tap iron slag condition is stabilized, and the pig iron middle (S) is maintained at a low level. Specifically, we will determine the control value (target value) of past viscosity 4j speed, tapping N, dryness and furnace protection (viscous layer on hearth wall and hearth bottom). . In the results shown in Figures 3 and 6, it is preferable to control the valley viscous layer thickness at 0, 3 nl 4%' at a time. The brick control temperature is determined from this relationship shown in FIGS. 4 and 7. Viscous layer thickness o, 3 (nt
), the control temperature of the hearth wall and hearth bottom/moth is +10°
G and +25”.

Specifically, the method of controlling the temperature to the above-mentioned temperature is as follows: 1) For example, using a stave cooler or a cold chisel for cooling pipes 1) Using the water flow rate and the cooling capacity of the cooling water cooler, that is, the water flow direction of the cooler, the number of coolers in operation, etc. 1.Explain the Eiho Ordinance.

Figure 8 shows the actual results from January 1974 to June 1980 (from tapping iron to slag tapping time, light, viscous layer thickness, hearth wall brick temperature), and was published in January 1980. When the invention method was fully implemented, the brick cooling conditions, total cooling water flow rate and/or cooling water cooler cooling capacity were manipulated so that the viscous layer thickness was o, 3 m.

Specifically, the brick temperature and viscous layer thickness were detected every 51:1, and the above operating means was operated.

Note that before January 1972, the cooling water flow and cooling water cooler cooling capacity were not maintained constant and operated.

After the start of implementation of the present invention, where the brick varnish degree and viscous layer thickness are fluctuating, the viscous layer thickness is close to the target value of 0.3 m,
As a result, it is clear that the time from tapping to slag will converge to 20 minutes.The temperature of the furnace bottom and hearth wall bricks k! till l1 lil L.

By keeping the amount of viscous layer formed at the necessary minimum of 0.3 m to protect the brickwork at the hearth, the tapping time and slag tapping time are shortened and stabilized compared to before the implementation of the present invention. As a result, the number of taps decreased from 231Mj/day to 13 times/day, the total number of taps decreased from 15 times to 14 times/day from 7 days, and drilling costs were reduced by 100%.

In addition, the tapping work has stabilized, furnace conditions have stabilized, and the madder furnace fuel ratio has decreased. Furthermore, the pig iron S (%) is also 0. (128% to 11
．． F was lowered to 0.025%. In addition, in the above-mentioned specific operation example, the thickness of the viscous layer was determined on a regular basis and the cooling conditions were manipulated. It is also possible to detect the temperature of the viscous layer and to manipulate the cooling material so that this brick temperature corresponds to the target viscous layer thickness.

[Brief explanation of the drawing]

Figure 1 (A) [:BE is a schematic diagram of the perpendicular cross section of the hearth of the hearth, 1 comb, an explanatory diagram of the viscous layer, and Figure 2 is an explanation of calculation of the amount of viscous layer thickness formed. Figure 3 is an explanatory diagram of the relationship between the temperature of one of a pair of bricks H1 provided at a predetermined distance apart from the original brick, and the temperature difference. Figures 5 and 6 are diagrams to explain the relationship between the viscous layer thickness on the hearth wall and hearth bottom and the tapping to slag tapping time. Figure 7 is a diagram to explain the relationship between the hearth wall brick temperature and the hearth bottom. FIG. 8 is an explanatory diagram of a specific example of operation of the present invention. 1. Hearth part 2. Hearth part L/Ngai (hearthstone brick 4. Hearth wall brick 5 - erosion lie/ 6. Viscous layer (high viscosity If layer) 7 Viscous layer-molten metal slag interface line 8.9 Hearth wall brick thermometer 10, II Hearth brick thermometer Fig. 2-63- Fig. 4Z l″r2. ) @tSZC Shuno No. 6

Claims (1)

[Claims] A blast furnace characterized in that the cooling conditions of the bricks are controlled so that the thickness of the viscous layer of the blast furnace hearth becomes the minimum thickness necessary to protect the hearth wall bricks and the hearth bottom bricks. Operating method.