JPS60135507A - Method for charging raw material to blast furnace - Google Patents

Abstract

PURPOSE:To charge uniformly a raw material in the circumferential direction of a bell-less blast furnace using a swiveling chute with a titled method for said furnace by changing specifically the swiveling speed of the swiveling shute. CONSTITUTION:Falling flow 5 drifts along the right wall of a vertical chute 3 and the point 7a at which the flow 5 rides on a swiveling chute 4 deviates from the swiveling shaft 6 of the chute 4 when a raw material is discharged from, for example, a furnace top hopper 1a. The time when the chute 4 is in the position L is designated as 0 deg. and the distance (d) from the point 7a to the outlet of the chute with respect to the clockwise rotating angle xsi thereof is a cosine curve. The dimensionless distribution of the charging quantity when the chute 4 swivels at an invariable speed can be approximated at the sine curve around 1 with respect to the central angle zeta. The charging quantity is max. at xsi=90 deg. and zeta=180 deg. according to the example shown in the figure and therefore the periodic function to maximize the swiveling speed at the point of the time when the raw material arrives at the outlet of the chute and to minimize the swiveling speed at the point of the time corresponding to xsi=270 deg. and zeta=360 deg. is determined as the swiveling speed. The distribution of the charging quantity in the circumferential direction is thus made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for charging raw materials into a blast furnace, and more specifically, in a blast furnace having a bellless charging device consisting of two furnace top hoppers, a vertical chute, a rotating chute, and a rotating chute drive device, The present invention relates to a raw material charging method for uniformizing the charge distribution in the circumferential direction of the furnace.

Recent advances in blast furnace operating technology are largely due to improvements in the control technology for charge distribution in the radial direction within the furnace.

In order to further stabilize operations and save energy, it is necessary to establish a method for controlling charge distribution not only in the radial direction but also in the circumferential direction, for which no suitable method has been established at present, and to improve the heat flow ratio in the circumferential direction. We need to be able to control the distribution.

Whether the heat flow ratio distribution in the circumferential direction of the furnace is appropriate is determined by: (1) Indication of multiple sensors of the same type installed in the circumferential direction at the same level in the height direction of the blast furnace, such as sauging devices and stave thermometers. (2) Deviations in the composition and temperature of hot metal and slag between multiple tap holes arranged in the circumferential direction of the furnace.

If these deviations in the circumferential direction of the hearth exceed the allowable range, the operation becomes unstable, and in more extreme conditions, it may cause the hearth to cool down. Therefore, when there is a deviation in the heat flow ratio in the circumferential direction of the furnace, the coke ratio of the blast furnace as a whole is increased extra in order to maintain the hot metal temperature and (Si) always above the specified value even in the circumferential direction on the side where the furnace heat level is low. It is common to do so, which impairs energy conservation.

An increase in the deviation in the circumferential direction of the furnace leads to an increase in the compositional variation and temperature variation of the hot metal from tap to tap, which becomes a cost factor in the subsequent hot metal pretreatment and steelmaking process.

In addition, it also has a negative impact on blast furnace equipment. for example,
This can cause damage to bricks on the furnace wall in a specific direction around the furnace, damage to the staves and siding, and the formation and falling off of materials attached to the furnace wall. Therefore, deviation in the circumferential direction must be avoided in order to extend the life of the blast furnace.

In a blast furnace, heat transfer and chemical reactions occur as the solid phase of ore and coke and the gaseous phase of reducing gas come into countercurrent contact, and a temperature distribution is formed depending on the progress of the reaction. Preferably, this three-dimensional furnace temperature distribution is axially symmetrical. However, in reality, the axial symmetry breaks down due to various reasons. Among the causes, the following two are important.

(a) Non-uniformity in the charge distribution in the circumferential direction during raw material charging (b) Non-uniformity in the rate of descent of the charge in the furnace circumferential direction These two factors combine to increase the heat flow ratio This results in deviation in the circumferential direction, resulting in asymmetry in temperature distribution. The result is detected as the deviation in the circumferential direction as described above.

The present invention is intended to prevent the above cause (a), and to have a favorable effect on the above cause (b), and is aimed at a blast furnace having a bellless charging device.

In a blast furnace having a bellless charging device shown in Fig. 1,
When the raw #1 type charged into each of the two furnace top hoppers is changed to ore and coke, the layer thickness of ore and coke is calculated from 2°, Qc, which is the difference in the charging surface level before and after charging. As shown in FIG. 4, the layer thickness ratio 2°/flC is reversed as the top hopper charge is changed. In other words, a fairly large deviation in layer thickness distribution occurred in the circumferential direction of the furnace, and it can be inferred that the raw material charging rate was non-uniform in the circumferential direction of the furnace.

First, I will explain the cause.

As shown in FIG. 1, the raw material is transferred to the furnace top hopper la.

The raw material is discharged from lb with the discharge speed controlled to be almost constant by the flow control valves 2a and 2b, and charged into the furnace via the rotating chute 4 via the vertical shoes 1 and 3. In this case, it is desirable that the center of the falling flow 5 of the charge coincides with the intersection 7 of the pivot axis 6 of the pivot chute and the inner surface of the pivot chute. However, in actual equipment, the diameter cross-sectional dimensions of the vertical chute 3 are such that even when the raw material discharge amount corresponds to the maximum expected pig iron production in the blast furnace, the raw material does not become clogged in the flow control valve or within the vertical chute and smoothly. Since the material is designed with a margin in mind so that it can flow, the raw material does not fill the entire diameter cross section of the vertical chute 3, and as shown in Fig. 1, when the raw material is discharged from the left furnace top hopper la. ,
The falling flow 5 is deflected along the right side walls of the vertical shoes 1 and 3, and the point 7a where the falling flow 5 rides on the rotating chute 4 is offset from the pivot axis 6 of the rotating chute 4.

Raw material charging is performed by alternately discharging raw materials one by one from the two top hoppers according to the charging schedule.

During the raw material discharge of 1 batch, the rotating shoes 1 and 4 rotate several times or more to distribute the raw material in the circumferential direction of the furnace, but when looking at any one of the rotations, point 7a is fixed to the rotating shoes 1 and 4. When viewed from the coordinate axes, as the rotating chute 4 rotates,
The position of point 7a changes around point 7, and returns to the original position with one rotation of the rotating chute. In Fig. 1, when the swing chute 4 is centered in the direction of the furnace top hopper la, that is, at the position L shown in Fig. 1, the distance #d1 from the point 7a to the swing chute exit is during the swing When the rotating chute is in the opposite direction, that is, at the H position shown in Figure 1, this distance d2 becomes the shortest value.When the rotating chute is in the L position, the distance d2 is 00. If the rotation angle ξ is taken as the position of the rotating chute 4 in the clockwise direction, that is, the normal rotating direction of the rotating chute 4, then the distance d from the point 7a to the exit of the rotating chute is
becomes a cosine curve shown in FIG. 2 with respect to the rotation angle ξ. 1st
In Fig. 2, when the distance d decreases from dl to d2, the falling flow 5 seems to be chasing the raw material flowing down the rotating chute 4, and in that time period, the point 7
While the raw material volume of the rotating shoe 1-4-1- at point a becomes larger than the average value and the apparent charging speed increases, in the time period when the distance d increases from d2 to dl,
The falling bed flow will retreat toward one end of the rotating chute, and the apparent charging speed will be less than the average charging speed. The position in the furnace circumferential direction when the raw material falls onto the charging surface is expressed as the central angle ζ of the blast furnace. However, the central angle ζ in the circumferential direction of the furnace is set to be exactly the same as the rotation angle ξ of the rotating shoe 1.

For example, when ξ = 90°, the raw material volume reaches its maximum at point 7a, and the raw material reaches the charging surface at ζ = 180'.
At this time, the layer thickness becomes maximum. On the other hand, in this case ξ=270°
, the layer thickness is minimum at ζ-360°. Such a phenomenon occurs when raw material is discharged from the furnace top hopper la. now,
If ore is charged into the furnace top hopper 1a, the next batch of coke will be discharged from the furnace top hopper lb, and the relationship between the direction of drift and the layer thickness will be approximately 1800 deviated from the case of ore in the central angle. It will appear.

Figure 3 illustrates this situation, with the horizontal axis representing the blast furnace center angle ζ, and the vertical axis representing the ore amount assuming that one batch of ore and coke is uniformly charged in the circumferential direction of the furnace. The local layer thicknesses QQ and QC are made dimensionless using the respective average layer thicknesses of coke and coke. Below, Qo/'fo/' or Qc/
Wc will be referred to as the dimensionless charging amount V. From FIG. 3, conversely, there is less coke in the furnace circumferential direction where there is more ore, while there is more coke in the furnace circumferential direction where there is less ore. In the example shown in Figure 3, (no/Qc)/(mu/Σ.) is the average value,
It varies within a range of 113%.

Converting this to a coke ratio, the average coke ratio is 460
In a full coke operation of kg/THM, the fluctuation is equivalent to ±60 kg/THM, which is a serious problem.

CQO/Qc) / (fo
/ΣC), by changing the top hopper of ore and coke every 2n patches (where n is an integer), and by averaging the 2n charges, the overall charge can be made uniform. This method is often used. In this case, to reduce the effect, it is necessary to reduce n. However, increasing the number of bunker transfer opportunities requires waiting time for charging, which causes other problems such as instability of radial charge distribution due to stock line changes, which is not a good idea.

Based on the above facts, the present inventor investigated a raw material charging method for uniformly controlling the layer thickness distribution of the charge layer in the circumferential direction of a blast furnace having a bellless charging device, and developed the present invention. It was completed.

The present invention provides a raw material charging method for avoiding the above-mentioned drawbacks of the conventional method and uniformizing the charging amount and layer thickness distribution in the circumferential direction. In the method, when controlling the charge distribution in the circumferential direction of the blast furnace, the rotating speed Nω of the rotating shoe 1 is centered around the reference average rotating speed of 80, and the - A method of charging raw materials to a blast furnace characterized by charging raw materials evenly in the circumferential direction of the furnace by charging the raw materials while changing the speed of rotation of the rotating shoe 1 so as to form a periodic function that repeats every rotation. This is how to enter. That is, the gist of the present invention is to provide a material charging method for a bellless blast furnace using a rotating chute, in which the rotating chute is operated at a speed that is a superposition of a reference average rotating speed and a rate of change that forms a periodic function with a constant phase difference and a constant amplitude. This is a method of charging raw materials into a blast furnace, which is characterized in that the material is rotated while continuously and repeatedly changing between a maximum value and a minimum value for each rotation.

As described above, the dimensionless charge distribution when the rotating chute 4 rotates at a constant speed can be approximated by a sine curve centered at 1 with respect to the central angle ζ. Strictly speaking, this requires that the raw material discharge rate from the furnace top hopper be constant from the beginning to the end of the discharge, but according to the inventor's research, if the opening of the flow control valve is kept constant, Although the discharge rate is smaller than the average value at the beginning and end of discharge from the furnace top hopper, this period is less than 10% of the total discharge time, and the above-mentioned condition of constant raw material discharge rate is almost satisfied. In principle, therefore, a sinusoidally varying charge distribution can be compensated for by a sinusoidally varying shift swing.

According to the example of FIGS. 2 and 3, ξ-90°.

Since the charging amount is maximum at ζ = 180°, the turning speed is maximized when this raw material reaches the exit of the turning chute 4, and at the opposite times corresponding to ξ = 270° and ζ = 360°,
By realizing a periodic function that minimizes the rotation speed as the rotation speed, it is possible to make the charging amount distribution in the circumferential direction of the furnace uniform.

Expressing this in the formula, Nω=A s i n ((πNω pieces/30)×(τ−
Δτ)) 10 Nω books...(1) Here, Nω: Turning speed of the turning chute (instantaneous value) (rpm) at arbitrary time τ (seconds) Nω*: Average turning speed of the turning chute (rpm) A: Amplitude (rpm) of (Nω-80 pieces) Δτ biphasic Discrepancy (seconds) τ: Time (seconds).

τ=0 means that the turning chute 4 is facing in the direction of ξ-0, and if Δτ-0, (Nω-N0 pieces) becomes a sine curve that changes periodically every l turning, and Δτ Hong 0 and Then, it becomes a sine curve whose phase is advanced in the normal turning direction of the turning shoe j. Normally, in a blast furnace equipped with a bellless charging device, a value of around 8 rpm is adopted as the rotation speed, and the above 80 rods can be set to the rotation speed of such constant speed rotation, but if the 80 rods are set to 8' rpm. It is not limited and may be any desired value.

1. When the rotating speed of the rotating chute is very small, and the discharge rate of raw material from the top hopper is constant, even if there is a drift in the vertical chute, the charging amount distribution in the circumferential direction is theoretically maintained. No deviation occurs. However, as shown in Figure 5, when the rotating chute rotates at a constant speed, the deviation in the charging amount distribution becomes more severe as the rotating speed increases. value must be selected. FIG. 5 depicts the change in dimensionless charging amount when the constant rotation speed is set to 4.8, 8, 10, and 12 rpm.

First, in FIG. 3, it is assumed that the dimensionless charge distribution is a perfect sine curve.

Maximum value Vyaax and minimum value vIIli of dimensionless charging amount V
From n, A = (Vmax - Vmin) /2XN (11 pieces = ASt... (2) By determining 2Δτ in equation (1) so that Δτ is the maximum or minimum, it is possible to achieve uniformity of the charging amount distribution in the circumferential direction.

In reality, the dimensionless charge distribution is not exactly sinusoidal but distorted. This is because the above-mentioned increase or decrease in the distance d from the point 7a to the outlet of the rotating chute changes the degree of acceleration that the material receives on the rotating chute 4, and the speed at the outlet of the rotating chute 4 changes. In the case of rotation, a new force is added due to the angular acceleration of the rotation chute in the rotation direction, and especially when A in equation (2) above becomes large, the mechanical relationship regarding the raw material becomes complicated, and it is necessary to strictly control the charging amount distribution. Although more complicated speed change control is required to achieve complete uniformity, in reality, a sufficiently satisfactory uniformity effect can be obtained by the above-mentioned speed change rotation. The driving device of the swinging chute consists of many gears and shafts, so if A in equation (2) above becomes large, extra force will be applied to them compared to when swinging at a constant speed, which will reduce the life of the equipment. Since this is not desirable, it is preferable to select an appropriate value.

Next, as an example, we will take the case of ore shown in Fig. 3 as an example.
An example of canceling out will be explained with reference to FIGS. 6 and 7.

Average turning speed N0 = 8 rpm Dimensionless maximum charging 1Vmax = 1.07 Dimensionless minimum charging amount Vmin = 0.93 Ast = O, 07Nω
It becomes a book.

Assuming that A=Ast, when increasing (πNω pieces/30) It becomes uniform, and Vmax - Vmin = 0.05, which is reduced to about 1/3 of the case of constant speed turning.

Roughly setting Δτ = 25/Nω and changing A within the range Ast±O, 4A, st, the change in the dimensionless charging amount V becomes as shown in Fig. 7, where A = O, 8 Ast, and Vmax - Vmi
The most uniform charge distribution in the circumferential direction of n = 0.02 could be obtained.

[Brief explanation of drawings]

Figure 1 is a partial cross-sectional view of the blast furnace showing the flow of the bellless charging device and raw materials, Figure 2 is a graph showing changes in the distance from the point where the raw material rides on the rotating chute 4 to the chute outlet, and Figure 3 is a dimensionless diagram. A graph showing the distribution of charging amount in the circumferential direction of the furnace. Figure 4 is a graph showing the situation where the layer thickness ratio in the blast furnace is reversed due to bunker transfer. Figure 5 is the rotation speed and dimensionless charging amount when rotating at a constant speed. Graph showing the relationship between the distribution of
The figure is a graph showing the relationship between the phase shift of the rotation speed during variable speed rotation and the distribution of non-dimensional charging amount in the circumferential direction of the furnace. It is a graph showing the relationship with distribution. la, lb...Furnace top hopper 2a, 2b...Meteor control valve 3...Vertical chute 4...Swivel shoe I/5 5...Falling flow of raw material 6...Rotation axis of the swing chute 7... Intersection point 7a between the rotating axis of the rotating chute and the bottom surface of the rotating chute... Intersection points 8a and 8b between the center line of the falling material flow and the bottom surface of the rotating chute... Sounding device applicant Kawasaki Steel Corporation representative Patent attorney Yoshi Kosugi Male patent attorney Kazunori Saito 6 Fig. 2 0 90 180 270 360 5 6 7 8 9 10 1
1 120-Arcstone C: Coke

Claims (1)

[Claims] ■ In a material charging method for a bell-less blast furnace using a rotating chute, the rotating chute is rotated at a maximum speed for each rotation at a speed that is the superposition of the standard average rotating speed and the rate of change that forms a periodic function with a constant phase difference and constant amplitude. A method for charging raw materials into a blast furnace, characterized by rotating the material while continuously changing the value between the value and the minimum value.