EP0101846B1 - Process and device for monitoring a tiltable shute and its use in charging a shaft furnace - Google Patents

Abstract

A method and apparatus for controlling the movement of an oscillating spout is presented wherein uneven distribution of spout discharge material is eliminated or at least substantially reduced by a compensating action of varying the angular speed of rotation of the spout in accordance with the angular position of the spout. The present invention is particularly suited for use in conjunction with a charging installation of a shaft furnace, particularly those charging devices having a spout with a cardan suspension system.

Description

The present invention relates to a method of controlling the movement of an oscillating chute which can pivot around two orthogonal axes and actuated, for this purpose, by two drive means independent of each other to move the end of the chute following concentric circles or a spiral around a vertical axis.

The invention also relates to a device for implementing this method as well as an installation for loading a shaft furnace equipped with such a device and implementing this method.

Luxembourg patent application no. 83,280 proposes a device for loading a shaft furnace by means of an oscillating distribution chute, generally designated in the field in question as a suspension gimbal of the "gimbal" type.

The Applicant has noted, during recent tests and experiments on a prototype of this kind that the layers of material deposited by means of an oscillating chute have irregularities in the thickness of the deposit. If we consider only one layer, these irregularities would not have a harmful effect on the loading of a shaft furnace. Unfortunately, these irregularities occur, for each layer deposited, in the same places corresponding to precise angular positions of the chute, so that there is an effect of accumulation of layer in layer which ultimately results in a level of loading in saddle shape. It has also been observed that this defect is not specific to the device as proposed in the aforementioned patent application, but that it occurs in a more or less pronounced manner for all loading devices with suspension of the chute of the type "Gimbal", whatever the drive and control means.

The reason is that these types of distribution chute undergo twice during each revolution, this in diametrically opposite and well determined locations, pivotings, although weak, but nevertheless perceptible, around their longitudinal axis. During such a pivoting, the friction when the load passes through the chute decreases, that is to say that the falling speed increases. In other words, during such a pivoting, the loading material reaches its drop point more quickly, and the thickness of the deposited layer increases at the places where the drop point occurs corresponding to the angular position of the chute in which this pivoting occurs. Of course, the opposite effect occurs at the end of this pivoting of the chute when the friction inside the chute increases again, which produces a decrease in the thickness of the deposit.

The object of the present invention is to provide a new method for controlling the movement of an oscillating chute making it possible to eliminate, if not to attenuate, this irregularity by compensation. An auxiliary object of the invention is to provide a device for the implementation, as well as its application to a loading installation of a shaft furnace.

To achieve this objective, the invention provides a method of controlling the movement of the chute, which is characterized in that the angular speed of rotation of the chute is modified around the vertical axis at the angular positions of the chute defined. in the horizontal plane in which the thickness of the deposited layer risks being irregular.

The angular positions of the chute in which the pivots which cause the deposit irregularities occur can be determined experimentally or by calculation. Knowing these angular positions, the invention therefore proposes to increase the angular speed of rotation of the chute at the places where the thickness of the deposited layer tends to increase, and to reduce the angular speed where the thickness has tendency to decrease.

The angular speed of the chute movement is regulated according to a preferred embodiment, according to the formula

Advantageously, to increase the uniformity of the deposit, the procedure is as follows by iteration:

• ω₁, ₀)₂ représentent les vitesses angulaires corrigées,
• ωα représente la vitesse angulaire non corrigée,
• e_m représente une fonction de la position angulaire.

In these formulas:

• ω ₁ , ₀ ) ₂ represent the corrected angular velocities,
• ωα represents the uncorrected angular velocity,
• e _m represents a function of the angular position.

• La figure 1 montre schématiquement une goulotte de distribution lors du déversement d'une couche annulaire.
• La figure 2 montre l'inclinaison de la goulotte par rapport à l'axe central.
• La figure 3 montre un diagramme polaire illustrant l'épaisseur d'une couche de matière déversée au moyen d'une goulotte oscillante.
• La figure 4 montre un diagramme polaire de la vitesse angulaire.
• La figure 5 montre un schéma synoptique d'un circuit de commande.

Other features and characteristics of the invention will emerge from the detailed description below, with reference to the appended figures, in which:

• Figure 1 schematically shows a distribution chute during the pouring of an annular layer.
• Figure 2 shows the inclination of the chute with respect to the central axis.
• FIG. 3 shows a polar diagram illustrating the thickness of a layer of material discharged by means of an oscillating chute.
• Figure 4 shows a polar diagram of the angular velocity.
• Figure 5 shows a block diagram of a control circuit.

FIGS. 1 and 2 show an oscillating distribution chute 10 in a well-defined angular position, in which it occupies an inclination β (see FIG. 2) relative to a vertical axis 0 and an angular position y (FIG. 1) a horizontal reference axis, for example, the X axis. We will assume that the chute, in this inclination is animated by a gyratory movement, clockwise shows, around the axis 0 with an angular speed ω to effect an annular deposition of the loading material on the melting bed, the relation therefore being

The reference 12 designates an annular deposit of material when the chute 10 rotates around the axis 0 with an inclination β. The reference 14 designates the horizontal projection of the circular path of the lower end of the chute 10.

This loading material discharged from the chute therefore has a fall path 16 with a vertical component and an angular component due to ω. In other words, the loading material does not fall to the point targeted by the chute at the precise moment when the material leaves this chute. This is illustrated in Figure 1.

Assuming that a particle leaves the chute when it is in the angular position a and that the chute continues its gyratory movement at speed ω clockwise, the impact of this particle occurs when the chute occupies, for example, an angular position y, while the point of impact 18 of this same particle is located somewhere between the two positions a and y, for example, in the position a + Aa. In other words, there is an angular offset Aa between the moment of exit of a particle from the chute and the moment of its impact on the fusion bed. The amplitude of this angular offset Aa is not only a function of the particle size of the material, but also of its falling speed, that is to say that depending on its falling speed, the particle reaches faster or slower the fusion bed and its drop point will be before or beyond the position Aa.

This is the phenomenon which occurs for all oscillating distribution chutes with cardan suspension which, as already mentioned above, undergo during each revolution, two pivotings around their longitudinal axis and thereby modifying the friction between the material and the wall of the chute. This change in friction accelerates or slows down the fall of particles.

When there is acceleration, the offset Aa decreases up to, for example Aa-s, which tends to cause an increase in the thickness of the deposit at a location being offset by an angle Aa-s from the position angular of the chute where this pivoting occurred. Similarly, when there is a slowdown, the offset Aa becomes Aa + ε, which causes a decrease in the thickness of the deposit of the material. This slowdown occurs at the end of the pivoting phase and the reduction in thickness is therefore offset by an angle Aa + s from the angular position in which the pivoting of the chute ends.

FIG. 3 shows, in polar coordinates, the thickness of an annular layer of material poured onto the fusion bed, this thickness being proportional to their distance to the origin.

The curve e _m represents the optimum average thickness that can be calculated for example from the content of a storage tank and the surface area of the melting bed. This thickness being uniform, the curve representing e _m is necessarily a circle.

The curve represented by e _r is the actual thickness of a layer deposited by an oscillating chute animated by a gyratory movement at constant angular speed ω ₀ and affected by the irregularities described above. The thickness for each angular position a is represented by the length of the vector e. The curve e ,, whose outline has been deliberately exaggerated, allows two positions of maximum thickness to be recognized at the points E _r-max located at the angular positions of 0 ° and 180 °, as well as two positions with minimum thickness at the points E _{r- min} located respectively at the angular positions of 90 ° and 270 °.

Figure 4 is a polar diagram similar to that of Figure 3, but for the representation of the angular velocities ω. Thus ω _o is the constant angular velocity for the deposition of the real irregular layer e _r of FIG. 3.

The curve ω _c is a curve of compensated speeds obtained by the modification of the curve ω _o according to the formula

The angular velocity for each angular position is represented by the length

• ω₁ =ω_c =vitesse angulaire modifiée
• ω_o =vitesse angulaire non modifiée qui engendre e_r
• f = est une fonction de a et de Aa, c'est-à-dire des paramètres déterminants de la modification de la vitesse angulaire.

In this formula:

• ω ₁ = ω _c = modified angular speed
• ω _o = unmodified angular speed which generates e _r
• f = is a function of a and Aa, that is to say of the parameters determining the modification of the angular speed.

The function f is defined by f (a) = e, (α) = thickness measured before compensation.

The purpose of the angular speed compensation is that the phenomena due to the pivoting of the chute and those due to the variation of the angular speed compensate each other to obtain a uniform deposited layer.

The curve e _c in FIG. 3 corresponds to the curve ω _c in FIG. 4, that is to say the thickness of the layer deposited by modifying the angular speed according to the above formula. The curve e _c is of course offset by an angle Aa relative to the curve ω _c to take account of the fall time.

The effect of this compensation for the angular velocity according to FIG. 4 is that the layer e _r is modified so as to produce a curve e approaching the ideal circular curve e _m , that is to say by changing the chute faster at the angular positions corresponding to increases in the thickness of the deposit along curve e, and more slowly at the angular positions corresponding to smaller thicknesses of deposit in curve e ,, there is a tendency to reduce thickness irregularities of the deposited layer.

• Soit e, (a) l'épaisseur de la couche pour ω_o = constant et présentant les irrégularités dues au pivotement;
• Soit e_v (a) l'épaisseur de la couche pour ω_c = variable sans considération des irrégularités dues au pivotement.
  

The mathematical explanation of the compensation formula is as follows:

• Let e, (a) the thickness of the layer for ω _o = constant and presenting the irregularities due to the pivoting;
• Let e _v (a) be the thickness of the layer for ω _c = variable without considering the irregularities due to the pivoting.
  

The average theoretical thickness resulting from the superposition of the two phenomena is

In other words, the compensated thickness approaches the ideal uniform thickness e _m .

et éventuellement ainsi de suite.If a first compensation by means of the angular speed adjustment does not yet allow the desired result to be obtained, it is possible to proceed by iteration and perform a finer compensation according to the formula:

and possibly so on.

The determination of ₀ ) ₁ , 02, ... is carried out either by tests or by calculation, since the parameters involved in this determination can be measured or calculated.

Given that a is a function of β and of the grain size of the loading material, the compensated angular velocities ω ₁ , 0) 2, ... can be determined for different inclinations β and for different grain sizes.

These different values of the compensated angular speed can be stored in a microcomputer which can calculate, at any time, by linear interpolations the exact value of the compensated angular speed of the chute.

FIG. 5 represents a block diagram of an embodiment of a control circuit for the compensation of the angular speed of the chute.

The microcomputer of which question above, is represented by the reference 10. This microcomputer receives information concerning the inclination β and the nature of the loading material for the calculation of the compensated angular velocities.

A motor 12 for driving the chute is subject to the control signals of an angular speed variator 14 comprising, inter alia, an integrated comparator.

Reference 16 designates the mechanical part of a pulse transmitter, while references 18 and 20 respectively designate an angular speed detector and a position detector, these two detectors can however be combined, since

The angular speed detector 18 generates at each instant signals corresponding to the real speed instant _r and sends these signals to the variable speed drive 14. Likewise, the position detector generates, at every instant, signals corresponding to the angular position a of the distribution chute and sends these signals to the microcomputer 10. This microcomputer 10 calculates, at each instant, on the basis of the information received, that is to say a, β and the parameters corresponding to the nature of the loading material, the compensated angular speed ω _c , thanks to the above formulas. Signals corresponding to the angular speed Oc calculated by the microcomputer 10 are sent to the angular speed variator 14. The integrated comparator thereof compares at all times the compensated angular speed ω _c with the actual angular speed Or of which it receives the information from the detector 18 and, depending on the result of this comparison, the drive motor 12 will be accelerated or slowed down.

The method for correcting the angular speed of the chute, proposed above, is particularly suitable for a drive device of the type proposed in the aforementioned Luxembourg patent application No. 83,280 because of the fact that the gyratory movement of this oscillating chute is caused by a circular movement drive device. It should however be noted that the correction device proposed is also suitable for other devices for driving an oscillating chute with cardan suspension, for example that driven by a pair of hydraulic cylinders.

Claims (6)

1. A process for controlling the movement of a tiltable spout capable of pivoting about two orthogonal axes which for this purpose are actuated by two driving means independent of each other, in order to move the end of the spout over concentric circles or over a spiral course around a vertical axis, characterized by the fact that the angular rotation speed of the spout around the vertical axis is modified at the angular position occupied by the spout, and defined in the horizontal plane, where the thickness of the layer deposited tends to become irregular.

2. Process in accordance with Claim 1, characterized by the fact that the operation of regulating the angular speed of the movement of the spout is performed on the basis of the formula

wherein:

ω₁ is the modified angular speed,

ω_o is the non-modified angular speed of the curve e,,

e_m is the optimum average thickness of a layer deposited;

e, is the real thickness of a layer deposited by a spout performing a giratory movement at a constant angular speed ₀)₀

a is the angular position of the spout considered in the horizontal plane with regard to a reference axis.

Aa is the change of the angular position a of the spout during the falling time of the material between the end of the spout and the charging surface;

f is a function of a and of Aa, i.e. of the angular positions and of the angular differences caused by the duration of the fall of the material respectively.

3. Process in accordance with Claim 2, characterized by the fact that the values of the angular speed are determined by progressive iterations based on the formula

4. Process in accordance with anyone of Claims 2 and 3, characterized by the fact that the compensated values ω₁, ω₂, ... of the angular speeds are stored in a micro-computer and that the exact values of the annular speeds are determined at each moment by linear extrapolation between the values stored.

5. Device for the performance of the process covered by any one of Claims 1-4, characterized by an angular position detector (207) real angular speed detector (18) connected to a micro-computer (10) and a variator (14) for the angular speed, respectively, and comprising a comparator serving to compare the real angular speed (ω) with the compensated speed (ωo) determined by the micro-computer (10) and, as a function of this comparison, to generate signals serving to regulate the angular speed of the movement of the spout.

6. Application of the device according to Claim 5 and of the process according to Claims 1-4 to a shaft furnace charging installation.

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