JP2007284725A - Blast furnace operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stable blast furnace operation method by controlling a race way depth in the suitable range corresponding to the operational condition of the blast furnace. <P>SOLUTION: An inverted conical hopper 1 is supposed, in which the horizontal section of the race way 2 is an exhaust port of coke as powdery material and a high speed descending zone of the coke between a bosh part 3 and a suspected stagnation zone 5 formed on a furnace center coke 4 is a hopper part 6. A pulsating frequency f of the coke exhausting flowing rate from the hopper 1 by calculating the following formula 1, is controlled to ≤0.002 Hz. The formula 1 is f=πUγ<SB>d</SB>[(Z<SB>0</SB>-Z<SB>6</SB>)tanθ]<SP>2</SP>/[W(γ<SB>s</SB>-γ<SB>d</SB>)]. wherein, U is an average mass speed of the powdery material; Z<SB>0</SB>is a height of the hopper part; Z<SB>4</SB>is a distance from the upper end surface of the hopper part to the top point of a sliding line; θ is a half opening angle of the hopper part; W is a volume of a compacted powdery material layer determined by the filling-up height when the powdery material pressure is equaled to the ultimate pressure; γ<SB>s</SB>is a bulk density of the compacted powdery material layer; and γ<SB>d</SB>is a bulk density of the powdery material layer when the layer is in a fluidized state. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for controlling a raceway depth in blast furnace operation.

The blast furnace is charged with iron ore and a reducing material such as coke, and blown with hot air from the bottom to cause a series of reactions such as reduction and melting of the iron ore to produce pig iron. A series of reactions such as iron ore reduction and dissolution can be efficiently performed by adjusting the particle size of the furnace interior so that an appropriate gas flow velocity distribution in the radial direction can be obtained in the blast furnace and appropriately controlling the blowing conditions. It progresses and it becomes possible to operate efficiently with a low reducing material ratio.
A plurality of tuyere are formed on the side wall of the lower part of the blast furnace, and hot air that has passed through the hot stove, hot air pipe, hot air annular pipe, and hot air branch pipe is blown through the tuyere. ing. Further, an auxiliary reducing material such as pulverized coal is blown from the tuyere.

  In the blast furnace, in front of the tuyere, a hollow portion in which coke called a raceway exists in an extremely sparse state is formed by blowing air from the tuyere. In the raceway near the tuyere, most of the coke charged into the blast furnace and auxiliary reducing materials such as pulverized coal injected from the tuyere are combusted. The reducing gas required in the furnace, iron ore, etc. Most of the heat required for dissolution and reaction is supplied from this part.

  Here, since it is difficult to accurately grasp the size and shape of the raceway, the distance between the deepest part of the raceway and the tuyere is the raceway depth in the blast furnace radial direction. It has been treated as a representative value for size and shape.

  The size and shape of the raceway (raceway depth) has a strong influence on the state of charge drop in the blast furnace, which in turn has a very significant impact on the stability and productivity of the blast furnace. It is believed that.

  Therefore, the inventors have used a device for measuring the raceway depth online during operation using microwaves (see Patent Document 1), and the raceway depth measured based on the raceway depth actually measured by the measurement device or the like. A blast furnace operating method (see Patent Document 2) that adjusts the amount of fuel injected from the tuyere to prevent the way from collapsing was proposed.

  The raceway depth can be accurately measured during operation by the measuring device disclosed in Patent Document 1, and the fuel injection amount is adjusted based on the actually measured raceway depth by the method disclosed in Patent Document 2. As a result, it was possible to more reliably prevent the raceway from collapsing or shrinking, and eventually the tuyere breakage.

However, when the blast furnace operation conditions are changed, it is considered that the range of the appropriate raceway depth that does not adversely affect the charge descent situation, etc. will change, but the blast furnace operation only with the above measuring device and operation method. The range of the appropriate raceway depth corresponding to the conditions cannot be quantitatively grasped in advance, and a method for more quantitatively controlling the raceway depth has been demanded.
JP 2005-99006 A JP 2005-97733 A

  Accordingly, an object of the present invention is to provide a stable blast furnace operation method by controlling the raceway depth within an appropriate range corresponding to the blast furnace operation conditions without adversely affecting the descending state of the charge. To do.

  The invention according to claim 1 is a blast furnace operating method in which a plurality of tuyere are provided in the circumferential direction and a raceway is formed in the vicinity of the tuyere, and the pulsation frequency of the raceway is 0.002 Hz or less. The blast furnace operating method is characterized in that the raceway depth is controlled so that

The invention described in claim 2 is formed on the blast furnace morning glory and the core coke slope above the raceway, with the raceway horizontal section as the pulsation frequency of the raceway, with the coke discharge port as powder. Assuming an inverted conical hopper whose hopper portion is a high-speed descent region of coke between the quasi-stagnation area, the pulsation frequency f of the discharge flow rate of coke from the inverted conical hopper calculated by the following equation 1 is used. 1 is a method for operating a blast furnace according to 1.
Formula 1 f = πUγ _d [(Z ₀ −Z ₄ ) tan θ] ² / [W (γ _s −γ _d )]
Here, U: average mass velocity of powder, Z ₀ : hopper height, Z ₄ : distance from the top surface of the hopper to the top of the slip line, θ: half angle of opening of hopper, W: limit of powder pressure The volume of the compacted powder layer determined from the filling height when equal to the pressure, γ _s : the bulk density of the compacted powder layer, and γ _d : the bulk density of the powder layer when in a fluid state .

Invention of Claim 3 is performed by adjusting the wind pressure fluctuation | variation index PI based on the pressure fluctuation of the hot air in the hot air branch pipe connected to a tuyere defined by following formula 2 to below a predetermined value. The blast furnace operating method described in 1.
Formula 2 PI = (Σ _{i = 1, n} | P _Bi −P _Bi−1 |) / n
Here, P _Bi is the hot air pressure instantaneous value at i minutes.

  Invention of Claim 4 is a blast furnace operating method of any one of Claims 1-3 which controls raceway depth in the range of 1.15-2.5m.

  According to the present invention, since the raceway depth is controlled so that the pulsation frequency of the raceway is equal to or lower than a predetermined critical value (0.002 Hz), the charge descent condition is maintained well, so that While ensuring stable operation, blast furnace operation with a low reductant ratio and high productivity can be realized, and the wear of the furnace wall refractory due to the pulsation of the coke descending speed is suppressed, leading to an extension of the blast furnace life.

  Hereinafter, the present invention will be described in more detail.

Embodiment 1
The present invention provides a method for operating a blast furnace in which a plurality of tuyere are provided in the circumferential direction and a raceway is formed in the vicinity of the tuyere so that the pulsation frequency of the raceway is 0.002 Hz or less. It is characterized by controlling the way depth.

  Here, the reason why the pulsation frequency of the raceway is set to 0.002 Hz or less is as follows.

That is, in one tuyere of a blast furnace with an internal volume of 4550 m ^3, the raceway depth is intentionally changed by sequentially changing the tuyere diameter and changing the gas flow velocity before the tuyere, and the raceway at each raceway depth is changed. An experiment was conducted to measure the pulsation frequency. The raceway depth was measured by installing the raceway depth measurement device using the microwave disclosed in Patent Document 1 in the tuyere. Further, the pulsation frequency of the raceway was obtained by the reciprocal of the decay period of the raceway, and the decayway of the raceway was obtained from the change over time in the raceway depth. FIG. 1 shows the relationship between the raceway depth and the raceway pulsation frequency obtained from the above measurement results. As is clear from the figure, when the raceway depth is decreased from the deep side, the pulsation frequency of the raceway is a low value that is almost constant (0.002 Hz or less) up to a predetermined critical value (1.15 m). However, it was found that the pulsation frequency of the raceway suddenly increased when it was shallower than the critical value. Therefore, the pulsation frequency of the raceway is defined to be 0.002 Hz or less as a critical value that allows stable blast furnace operation for a long period of time without deteriorating the descending state of the charge.

  In order to apply the present invention to actual blast furnace operation, for example, the microwave disclosed in Patent Document 1 is applied to any one or a plurality of tuyere of the tuyere as described in the above experiment. Install the used raceway depth measurement device, calculate the raceway pulsation frequency from the change over time of the raceway depth measured by this measurement device, and so that the pulsation frequency is 0.002 Hz or less, the tuyere diameter, The raceway depth may be controlled by appropriately adjusting the air temperature, tuyere gas pressure, fuel injection amount, and the like.

[Embodiment 2]
In the first embodiment, as an example, the raceway pulsation frequency is measured using a raceway depth measurement device installed at the tuyere, but the raceway and the region above the raceway are regarded as a powder storage tank (hopper). Alternatively, the pulsation frequency of the powder discharge flow rate from the hopper calculated by an estimation formula based on theoretical analysis may be used. Hereinafter, this means will be described in detail.

  As shown in FIG. 2, the horizontal cross section of the raceway 2 is used as a coke discharge port as powder, and the morning glory 3 above the raceway 2 and the pseudo-stagnation zone 5 formed on the slope of the core coke 4 are formed. Assume an inverted conical hopper 1 in which the coke descending zone is the hopper portion 6.

Then, the coke discharge flow rate from the inverted cone hopper 1 according to the following formula 1 (Hidaka et al .: Chemical Engineering Papers, Vol. 20, No. 3 (1994), p. 397) which is an estimation formula based on theoretical analysis. The pulsation frequency f of is calculated.
Formula 1 f = πUγ _d [(Z ₀ −Z ₄ ) tan θ] ² / [W (γ _s −γ _d )]
Here, U: average mass velocity of powder, Z ₀ : hopper height, Z ₄ : distance from the top surface of the hopper to the top of the slip line, θ: half angle of opening of hopper, W: limit of powder pressure The volume of the compacted powder layer determined from the filling height when equal to the pressure, γ _s : the bulk density of the compacted powder layer, and γ _d : the bulk density of the powder layer when in a fluid state .

  The value of each variable in the above equation 1 can be obtained as follows.

  The average mass velocity U of the powder can be obtained from the mass of the coke burned by the hot air excluding the amount of the hot air blown from the tuyere for burning the blown fuel.

The hopper height Z ₀ is calculated from the height from the raceway 2 to the hopper top end surface 6a, the raceway depth _DRW, and the slope angle φ _V of the pseudo-stagnation zone 5 formed on the slope of the core coke 4 It can be obtained geometrically. Note that the slope angle φ _V of the pseudo-stagnation zone 5 corresponds to the velocity characteristic line derived from the plastic theory by the slope of the pseudo-stagnation zone 5 (Takahashi et al .: Chemical Engineering, No. 38 (1974), p. 746). It can be estimated that φ _V = 80.2 ° was obtained in this blast furnace.

Distance Z ₄ from hopper upper end surface 6a to the apex 7a of slip lines 7 can be obtained as follows. That is, the slip line vertex 7a is a point where the powder pressure distribution in the height direction of the hopper 6 shows a maximum value, but the method of Aoki et al. (Aoki et al .: “Powder storage and supply device” (1963), As a result of calculating the powder pressure distribution in the height direction of the hopper section 6 using Nikkan Kogyo Shimbun), when φ _V = 80.2 °, the powder was in (Z ₀ −Z ₄ ) / Z ₀ = 0.2 It was found that the pressure showed a maximum value. Thus, the _Z 4 = 0.8Z ₀ in this blast furnace.

Half angle theta opening of the hopper section 6 may be determined by the slope angle phi _V than θ = 90 ° -φ _V pseudo stagnant zones 5, in this blast furnace becomes θ = 9.8 °.

  The volume W of the compacted powder layer determined from the filling height when the powder pressure becomes equal to the ultimate pressure is the volume of the truncated cone between the horizontal plane including the slip line vertex 7a and the horizontal cross section of the raceway 2. Can be sought.

The bulk density γ _s of the compacted powder layer can be obtained by actually measuring the bulk density of the packed bed in which the coke is densely packed.

The bulk density γ _d of the powder layer when it is in a fluidized state approximates the shape of the raceway to a sphere, and is released from the raceway surface from the total amount of gas released from the raceway and the surface area of the raceway. The superficial velocity U _RW of the gas is calculated and can be obtained by the following formula 3.
Formula 3 γ _d = γ _s [1- (U _RW / U _umf ) ² ]
Here, U _umf : fluidization start speed of coke.

Here, the raceway depth D _RW is sequentially changed, and the raceway decay period which is the inverse 1 / f of the pulsation frequency f calculated as described above, and the race based on the actual measurement using the microwave described in the first embodiment. The relationship with the way collapse period is shown in FIG. As is clear from the figure, it was confirmed that the calculated value and the actually measured value almost coincided.

  Therefore, according to the present embodiment, it is possible to accurately predict the pulsation frequency of the raceway by calculation without actually measuring the raceway depth, and even when the blast furnace operating conditions are changed, an appropriate range of the raceway depth is set. Can be set with high accuracy in advance.

[Embodiment 3]
In the first embodiment, an example is shown in which the raceway pulsation frequency is measured using a raceway depth measurement device using microwaves near the tuyere, and the raceway depth is controlled based on the measured pulsation frequency. However, instead of this, the raceway depth may be controlled using the wind pressure fluctuation index PI based on the pressure fluctuation of the hot air in the hot air branch pipe connected to the tuyere. The wind pressure fluctuation index PI is defined by the following formula 2.

Formula 2 PI = (Σ _{i = 1, n} | P _Bi −P _Bi−1 |) / n
Here, P _{Bi is an} instantaneous value of hot air pressure (gf / cm ² [where 1 gf / cm ² = 98.0665 Pa]) in i minutes.

That is, as shown in FIG. 4, it was found that the raceway depth and the wind pressure fluctuation index PI showed a strong correlation. Therefore, the raceway depth is measured for a certain period for the blast furnace to which the present invention is applied, and a relational expression with the wind pressure fluctuation index PI is obtained. Thereafter, using the relational expression, the wind pressure fluctuation index PI ₀ (10 gf / cm ² or less in this blast furnace) corresponding to the raceway depth (1.15 m or more) at which the pulsation frequency of the raceway is 0.002 Hz or less is used. The raceway depth may be controlled so that Thus, if the raceway depth is measured only for a certain period when the present invention is applied, the raceway depth can be indirectly controlled via the wind pressure fluctuation index PI without actually measuring the raceway depth thereafter.

  In the first to third embodiments, the example in which the raceway pulsation frequency f or the wind pressure fluctuation index PI is used as an index for controlling the raceway depth has been described. It is desirable to control in the range of 1.15 to 2.5 m. That is, when the raceway depth becomes shallower than 1.15 m, as shown in FIG. 1 and FIG. 4, the pulsation and wind pressure fluctuation of the raceway become remarkable, and the operation trouble is likely to occur, while the raceway depth is 2 This is because, if the depth exceeds 0.5 m, the pulsation and wind pressure fluctuation of the raceway are sufficiently reduced, but the possibility that the unloading (the lowering of the load) becomes defective increases.

It is a graph which shows the relationship between a raceway depth and the pulsation frequency of a raceway. It is the conceptual diagram which considered the raceway and the upper direction as the reverse cone hopper. It is a graph which shows the relationship between the pulsation frequency based on the measurement by a microwave, and the pulsation frequency calculated with the estimation formula. It is a graph which shows the relationship between a raceway depth and the wind pressure fluctuation index PI.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reverse cone hopper 2 ... Raceway 3 ... Morning glory part 4 ... Core core coke 5 ... Pseudo-stagnation zone 6 ... Hopper part 6a ... Upper end surface 7 ... Slip line 7a ... Vertex

Claims (4)

  In a blast furnace operating method in which a plurality of tuyere are provided in the circumferential direction and a raceway is formed in the vicinity of the tuyere, the raceway depth is controlled so that the pulsation frequency of the raceway is 0.002 Hz or less. A method of operating a blast furnace, characterized by: As the pulsation frequency of the raceway, the horizontal cross section of the raceway is used as a coke discharge port as powder, and the coke between the blast furnace morning glory above the raceway and the pseudo stagnation zone formed on the core coke slope The blast furnace operating method according to claim 1, wherein a pulsation frequency f of the discharge flow rate of coke from the inverted conical hopper calculated by the following equation 1 is used assuming an inverted conical hopper having a high speed descending region as a hopper portion.
Formula 1 f = πUγ _d [(Z ₀ −Z ₄ ) tan θ] ² / [W (γ _s −γ _d )]
Here, U: average mass velocity of powder, Z ₀ : hopper height, Z ₄ : distance from the top surface of the hopper to the top of the slip line, θ: half angle of opening of hopper, W: limit of powder pressure The volume of the compacted powder layer determined from the filling height when equal to the pressure, γ _s : the bulk density of the compacted powder layer, and γ _d : the bulk density of the powder layer when in a fluid state . The blast furnace operating method according to claim 1, wherein the wind pressure fluctuation index PI defined by the following formula 2 is adjusted to a predetermined value or less based on the pressure fluctuation of the hot air in the hot air branch pipe connected to the tuyere.
Formula 2 PI = (Σ _{i = 1, n} | P _Bi −P _Bi−1 |) / n
Here, P _Bi is the hot air pressure instantaneous value at i minutes.   The blast furnace operating method according to any one of claims 1 to 3, wherein the raceway depth is controlled in a range of 1.15 to 2.5 m.

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