JP3305404B2 - Granulation method of raw materials for sintering - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for granulating raw materials for sintering, and more particularly to a method for improving the granulation properties of raw materials for sintering using a sintering drum mixer.

[0002]

2. Description of the Related Art In a conventional sintering process in the iron and steel industry, air is sucked from the upper portion to the lower portion of a raw material layer in which fine coke is mixed with fine ore, so that the mixed fine coke is sequentially burned, and The sintering reaction and the melting reaction between particles are promoted, and a massive sinter having high porosity is obtained.
At that time, in order to efficiently burn coke breeze as a heat source, to ensure sufficient permeability of the raw material layer,
In order to obtain a strong bond between the product sinters, two conditions that are incompatible with the close contact between the ores are required. It is difficult to find a particle size range of the raw material that satisfies such conditions. Therefore, in the sintering process, prior to the sintering step,
Pre-processing of mixing, humidity control, and granulation is performed by a rotary drum type sintering drum mixer (hereinafter simply referred to as a mixer).

FIG. 2 shows a sintering process flow. In this figure, a plurality of raw materials cut out from a plurality of compounding tanks 1 are mixed and granulated in a mixer 2, guided to a feed hopper 3, and passed onto a sintering machine 6 via a drum feeder 4 and a belt feeder 5. A fixed amount is cut out, the coke in the raw material is ignited by the ignition furnace 7, and the pallet 6 is moved through the heat preservation furnace 8 and fired by downward suction ventilation.

[0004] As a raw material, for example,
Eight tanks from No. 101 to No. 108 have ore and plain ore 9
However, Limestone 10 was stored in No. 109 and 110 tanks, while No. 111 and 112
Coke 11 was charged in each of the two tanks.
The return ore 12 from the sintering machine 6 is charged into the two tanks 3 and 114 via the pan conveyor 13. Further, bedding ore 14 is supplied from a bedding hopper 15 provided on the sintering machine 6.

[0005] In the mixer 2, the raw material containing the fine powder is converted into pseudo-particles, so that the space-retaining force of the packed bed is used on the ventilation surface and the reactivity of the fine powder portion in the pseudo-particles is used on the reaction side. I have. In this way, the mixer 2 plays an important role of mixing the raw materials and forming pseudo particles.
FIGS. 3 (a) and 3 (b) show the overall outer shape of the mixer 2 and its drive system. The drum body 16 is made of a steel plate and has a feed port 16a at one end. Mineral port 16 on the other side
b and a sprinkling pipe 17 are provided. A tire 18 attached to the drum circumference is rotatably supported by a support roller 19, and a girth gear 20 is driven by a drive source 23 such as a high-voltage squirrel-cage induction motor via a pinion gear 21 and a speed reducer 22.
Is driven to rotate. The drum body 16 is provided with, for example, an inclination of about 3/100 in order to improve the flow of the raw material.

FIG. 4 shows the behavior of the raw material inside the mixer 2. The raw material 24 supplied from the ore supply port 16a is repeatedly scraped (transported) and rolled down (rolled) and discharged from the ore discharge port 16b. , And is discharged as the ore 25 from the ore discharge port 16b. In this process, the mixing of the raw material 24 and the formation of pseudo particles are promoted. By the way, as the drive source 23 of the mixer 2, a high-speed squirrel-cage induction motor or a constant-speed rotation of a water-resistance starting high-voltage winding-type induction motor has been applied as described above. In order to express the motion state of the raw material in the mixer 2, that is, the evaluation of the process of generating the pseudo particles, the number of fruds Fr and the space factor Φ (%, the ratio of the raw material volume to the volume in the mixer) shown in FIG.
It has been reported that the mixing of raw materials and the formation of pseudo particles progress in the normal rolling region in the figure.

Fr = D · N ² / (g × 3600) (1) Φ = 4Q · T / (D ² · π · L · ρ) ······· (2) D: Mixer diameter (m), N: Mixer rotation speed (rp
m), g: gravity acceleration, Q: raw material supply (t / min), T: raw material residence time in the mixer (min), L: mixer body length (m),
ρ: Raw material bulk density (t / m ³ ).

On the other hand, FIG. 6 shows an appropriate range of the rotation speed and the space factor obtained by the experiment of the model mixer. Here, the critical rotation speed Nc is a value at which the raw material moves integrally with the inner periphery of the mixer by a high-speed centrifugal force, and is expressed by Nc = 42.3 / √D.
These equations do not include the element of the raw material moisture content, but this is based on the assumption that the optimal moisture content constant control is always performed.

[0009] The promotion of proper pseudo-particle formation in the mixer 2 in this way greatly contributes to the improvement of the operation of the sintering machine in a chain, as shown in the flow chart of FIG. That is, when the granulation property is improved, the ventilation of the sintering bed is improved first, whereby the amount of quicklime used is reduced and the usage ratio of the fine ore can be increased.
In addition, since it is possible to increase the thickness of the sintering bed, it is possible to improve the yield and productivity of sinter products, and since the thermal efficiency of the sintering bed is improved, it is possible to improve the basic unit of coke. It becomes possible.

[0010]

However, as is apparent from the above-mentioned FIGS. 5 and 6 and the equations (1) and (2), an operation for performing proper pseudo-particle formation requires an esoteric operation. You. In other words, when rearranging again, (a) As seen from equations (1) and (2), it is made up of many different factors, and it is not actually possible to set the operating state of the appropriate granulation area. Above, very esoteric.

(B) Operationally stable in the long term due to changes in the production volume, and in the short term due to fluctuations in the feedstock quantity Q to the mixer due to changes in the pallet speed due to the control of the sintering point of the sintering machine. Operational disturbances occur. Above all, short-term fluctuations due to pallet speed changes are caused by changes in the raw material cut-out amount in the upstream mixing tank due to changes in the level of the feed hopper 3 shown in the sintering process flow in FIG. Since the change in the raw material supply amount Q to No. 2 occurs almost constantly and the raw material supply amount Q changes in FIGS. 5 and 6, the space factor changes and the granulation state changes greatly. Become. Note that the same situation occurs when a change in production volume occurs.

(C) There is no suitable means or method for sensing, for example, the space factor indicating the operation state, and therefore, realizing closed loop control based on sensing information is an unknown field. Therefore, it is considered impossible to obtain constant and appropriate granulation properties by the conventional operation method.

By the way, as a method of controlling the mixer 2 as described above, for example, Japanese Patent Publication No. 58-44136 discloses a method of disposing an adjusting plate on the outlet side of the mixer so as to obstruct the discharge, and setting the position of the adjusting plate. Technology to control the space factor to be constant by adjusting the
Japanese Patent Publication No. JP-A-63-24408 and JP-A-59-213432 disclose a technology for specifying the space factor and the number of fluids. Techniques have been proposed to achieve sintering granulation control with a constant quality by controlling the rate at a constant level.

However, in the control of Japanese Patent Publication No. 58-44136 described above, even if an attempt is made to adjust the position of the adjusting plate in the event of a change due to the adhesion of the raw material to the adjusting plate and a change in the amount of the supplied raw material, the space factor of the occupying ratio is reduced. There is a problem that control cannot be performed freely because there is no appropriate sensing means. In addition, Japanese Patent Publication No. Sho 60-28888, Japanese Patent Publication No. Sho 63-24408,
The technique of 213432 has a disadvantage that the control becomes unstable when the raw material supply changes.

The present invention has been made in order to solve the problems of the prior art as described above.
The raw materials which are also variable values with respect to the mixer diameter (D), the rotation speed (N), the gravitational acceleration (g), and the mixer body length (L) which are bound by the fixed values in the equations (1) and (2). Regarding changes in the supply amount (Q) and the raw material residence time (T) in the mixer, the operation state is not dependent on the means and method for sensing the space factor, for example, but on the basis of the sensing information. Without using the closed loop control means of
It is an object of the present invention to provide an operation method capable of always obtaining an optimum and constant granulation property.

[0016]

SUMMARY OF THE INVENTION According to the present invention, when mixing and granulating raw materials for sintering using a sintering mixer, the mixer is provided with a rotational speed control means to control the rotational speed, and Based on the signal of the amount of raw material cut out from the upstream blending tank with respect to the change in the space factor due to the amount of ore supply, based on the signal of the amount of raw material cut out from the upstream mixing tank, the fluctuation of the amount of raw material supply and the arrival timing of the fluctuation of the raw material supply amount to the mixer are detected, In response to changes in space factor due to fluctuations in raw material supply,
Calculate the rotation speed based on the following formula and the space factor will be constant
And controlling the rotational speed of the sea urchin sintering mixer, where, the detection
A method for granulating a raw material for sintering, characterized in that control start is delayed by a time corresponding to the arrival timing . Φ = 4 × Q / (π ² · D ³ · tan ν · N · ρ) where Φ: space factor (%) Q: raw material supply (t / min) D: mixer diameter (m) tan ν : Sinus angle of the mixer as S (°) and angle of repose of the raw material as θ (°) sin S / sin θ N: Mixer rotation speed (rpm) ρ: Bulk density of raw material (t / m ³ )

[0017]

The present inventor has sought to solve the above problems.
As one of the measures, the characteristics of various mixers were experimentally investigated. According to the analysis result of those data, the torque Tq (kg · m) for operating the mixer is changed to the raw material supply amount Q (t /
min), the number of rotations N (rpm) of the mixer, etc., it was demonstrated that the determination can be made only by the space factor Φ (%). This can be expressed as a mathematical expression as shown in the following expression (3).

Tq = a · Φ + b (3) Incidentally, in the case of the mixer to which the present invention is applied, a = 29.
2, b = 94.5. The result is shown in FIG. Therefore, in order to maintain the operation at the optimum space factor Φ even with the change in the raw material supply amount Q, it is understood that the torque Tq should be controlled to be constant by operating the rotation speed N.

On the other hand, the space factor Φ on the horizontal axis of FIG.
Equation (2) is another relational expression representing the raw material residence time T in the mixer. Equation (4): T = L / (π · D · tan ν · N) (4) where tan ν is tan ν = sin S / sin θ, where S (°) is the inclination angle of the mixer and θ (°) is the angle of repose of the raw material.
It is. By substituting, Φ = 4 × Q / (π ² · D ³ · tan ν · N · ρ)... (5) is obtained. Further, when this equation (5) is expressed with the eigenvalues when the present invention is applied, Φ = 0.07871 × Q / N (6) The fact that the above equation (3) holds regardless of changes in the raw material supply amount Q and the rotation speed N of the mixer also holds true for the expression (6) over all the raw material supply amount Q and the rotation speed N. This is the event that occurred.

Therefore, the present invention is intended to directly control the rotational speed N by the following equation (7) which is a modification of the above equation (6), and consequently to control the torque Tq or the space factor Φ constant. It is an idea to do. N = 0.07871 × Q / Φ (7) Here, Φ in the equation (7) is an optimal space factor setting value for always maintaining a constant operation, and Q is as described above. It is the total actual value of the amount cut out from the plurality of compounding tanks 1 in FIG. 2, that is, the raw material supply amount.

In this way, if the control is performed based on the equation (7), the target torque Tq and the space factor Φ can be obtained as is clear from FIG. However, since there is no time factor in equation (7), the result of this equation cannot be directly incorporated into the control of the number of revolutions of the mixer. That is, the present invention is characterized in that two preliminary processes of dead time and time constant are performed on the raw material supply amount Q.

[0022] The dead time here, adding material conveyance time from a plurality of blending tanks 1 of the above-mentioned FIG. 2 to the mixer 2 as T _L. The dead time T _L may be a fixed value.
The time constant means the raw material residence time T in the mixer. This is shown in FIG. That is, the vertical axis is the raw material supply amount Q, and the horizontal axis is the time axis. The solid line indicates the change in the total actual value of the cut-out amount from the plurality of compounding tanks 1, and the dotted line indicates the change in the raw material supply amount Q, which affects the space factor of the mixer. Here, t ₁ indicates the timing when the cutout amount total actual value changes, t ₂ indicates the timing when the change amount reaches the mixer inlet, and t ₃ indicates the timing when it reaches the mixer outlet. is there. Therefore, the time of the difference between t ₂ and t ₁ corresponds to the dead time T _L.

As the pre-processing of the dead time, it is sufficient to simply shift the signal by the dead time T _L , and the time constant T
As the processing, the moving average processing method which can be approximated as a model of the raw material residence time in the mixer is used, but the processing may be performed by a first-order lag filter (exponential smoothing method). Here, the raw material residence time in the mixer, which is the time constant, is equal to the rotational speed N, as already shown in the above equation (4).
However, when this is expressed by the characteristics of the mixer applied to the present invention, it is as shown in FIG. That is, it is understood that the time constant T needs to be changed according to the rotation speed N. Therefore, in the present invention, the following
The time constant T is varied using the function of the equation (8). The time constant T is the same as the raw material residence time T.

T = C / N (8) Here, C is a constant, and the time constant, that is, the residence time is determined by the rotation speed N.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A control method according to the present invention will be described below in accordance with a control sequence based on a control system diagram of FIG. 1 showing an embodiment of the present invention. First, at the time of starting, a relatively high speed set value is given in advance by the speed setting device 31, and the SW1 and the limiter 32 are set.
The mixer 2 is forcibly rotated at a high speed by a variable voltage variable frequency controller (VVVF) 33 and a high-voltage squirrel-cage induction motor 23. This is to prevent the raw material from being abnormally retained in the mixer 2 by being started at a high rotation speed.

After a certain time at which the raw materials in the mixer 2 are stably conveyed at this high speed, SW1 is opened and S
When W2 is closed, the rotational speed is switched to the rotational speed N set by the rotational speed setter 35 and specified by the target rotational speed calculator 36.
Thereafter, as described above, the mixer 2 rotates at this rotation speed N. The above is the description of the method of controlling the number of revolutions of the mixer 2, whereby the constant number of revolutions control is executed.

On the other hand, while the above-described constant rotation speed control is being executed, the rotation speed conversion calculator 38 executes the calculation of the above equation (7). That is, the appropriate space factor setting value Φ is input from the space factor setting device 37, and the raw material supply amount Q is the total amount of the mixing tank cutout extracted from the mixing tank cutout control device 39. After being removed, the delay time processing device 41 performs a process of delaying by a dead time T _L , and then the time constant processing device 42 suppresses the change to a gradual change according to the time constant T. Entered in 38.
The time constant T is calculated by the time constant calculator 43 based on the rotation speed N output from the rotation speed conversion calculator 38, and the time constant processing device 42 will be given.

The mixer 2 performs control in the space factor mode by opening the switch SW2 and closing the switch SW3 after a predetermined time from the execution of the rotation speed constant control. This makes it possible to perform a constant control of the space factor by the change in the number of rotations in a flexible manner with respect to the space factor Φ set by the space factor setting device 37, following the change in the raw material supply amount Q. .

[0029]

As described above, according to the present invention,
Since the mixer is provided with a rotation speed control means with a constant space factor, the feedstock amount, which is a variable value, also varies with respect to the mixer diameter and mixer body length, which are constrained by fixed values in the mechanical specifications of the mixer. In addition, it is possible to always obtain an optimum and constant granulation sintering material even with the fluctuation of the material residence time in the mixer.

[Brief description of the drawings]

FIG. 1 is a control system diagram showing an embodiment of the present invention.

FIG. 2 is a system diagram showing a sintering process flow.

FIG. 3 is (a) a side view of the entire outer shape of the mixer, and (b) a plan view showing a drive unit.

FIG. 4 is a (a) perspective view and (b) a cross-sectional view taken along the line XX for explaining a raw material movement state in the mixer.

FIG. 5 is a characteristic diagram showing the relationship between the number of fluids Fr and the space factor.

FIG. 6 is a characteristic diagram showing a relationship between a mixer rotation speed and an appropriate granulation range.

FIG. 7 is a characteristic diagram showing the spread of the improvement in granulation properties.

FIG. 8 is a characteristic diagram showing a relationship between a mixer rotation speed, an output, and a torque.

FIG. 9 is a characteristic diagram showing a relationship between a mixer rotation speed and a raw material residence time.

FIG. 10 is a diagram illustrating processing of a time constant.

[Explanation of symbols]

 2 Mixer (Drum mixer for sintering) 16 Drum body 16a Feed port 16b Drain port 17 Sprinkler tube 18 Tire 19 Support roller 20 Girth gear 21 Pinion gear 22 Reduction gear 23 Drive source (high pressure cage type induction motor) 24 Raw material 25 Drain Ore 31 Speed setting device 32 Limiter 33 Variable voltage variable frequency control device (VVVF) 35 Revolution speed setting device 36 Revolution speed target value calculation device 37 Occupancy ratio setting device 38 Revolution speed conversion calculation device 39 Mixing tank cutout control device 40 Filter 41 Dead time processor 42 Time constant processor 43 Time constant calculator

Claims (1)

(57) [Claims] When mixing and granulating raw materials for sintering using a sintering mixer, the mixer is provided with a rotation speed control means to control the rotation speed, and the space factor fluctuation due to the amount of raw material supplied. On the other hand, based on the signal of the raw material cut-out amount from the upstream mixing tank, the fluctuation of the raw material supply amount and the arrival timing of the fluctuation of the raw material supply amount to the mixer are detected, and the space occupied by the fluctuation of the raw material supply amount is detected. With respect to the rate variation, the number of rotations is calculated based on the following equation to control the number of rotations of the sintering mixer so that the space factor is constant, and in accordance with the detected arrival timing,
A method for granulating a raw material for sintering, characterized in that the start of control is delayed by the time . Φ = 4 × Q / (π ² · D ³ · tan ν · N · ρ) where Φ: space factor (%) Q: raw material supply (t / min) D: mixer diameter (m) tan ν : Sinus angle of the mixer as S (°) and angle of repose of the raw material as θ (°) sin S / sin θ N: Mixer rotation speed (rpm) ρ: Bulk density of raw material (t / m ³ )