EP0200996B1 - Method for controlling the charging installation of a shaft furnace and charging installation using this method - Google Patents

Description

The present invention relates to a method for controlling the operation of a loading installation of a shaft furnace comprising a rotary or oscillating distribution chute, a hopper with a central flow opening above the chute controlled by a metering member with symmetrical action around the central axis of the furnace and surmounted by at least one airlock provided with upper and lower sealing valves, as well as a metering valve for regulating the flow towards the hopper. The invention also relates to an installation for implementing this method.

Conventional loading installations with rotating or oscillating chute have two juxtaposed airlocks operating alternately. It is well known that these installations have the drawback of an asymmetrical fall on the chute, due to the eccentric position of the airlocks relative to the central axis. To remedy this, several systems for rectifying the fall trajectory have already been provided.

The object of the present invention is to provide a loading method and installation which allow a vertical and symmetrical fall of the loading material.

To achieve this objective, the method proposed by the invention is characterized in that the material being contained in the airlock and the metering valve of the hopper being closed, the metering valve of the airlock is first opened to cause the flow of a quantity of material sufficient for the formation of a barrage of material above the flow tubing of the hopper, in that the metering flap of the latter is only opened after the formation of this barrier, in that we weigh separately and throughout the loading time both the hopper and the airlock which is in communication with the hopper, in that we generate signals representing respectively the quantity of material contained in the hopper, the quantity of material contained in the airlock and the sum of the quantities of material contained in the hopper and the airlock and in that the position of the metering valve of the hopper is adjusted so that the hopper flow rate is not greater than the flow rate d e the flow from the airlock to the hopper.

The invention also provides an installation for loading a shaft furnace comprising a rotary or oscillating distribution chute, a hopper with a central flow opening above the chute controlled by a metering valve with symmetrical action around the central axis of the oven and surmounted by two storage airlocks juxtaposed on either side of the vertical axis of the oven and carried by means of load cells, these airlocks being each provided with flow pipes directed towards the hopper , a pair of sealing valves and a pair of metering valves respectively associated with the flow pipes for placing the airlocks alternately in communication with the interior of the oven, characterized in that said hopper is contained in a sealed carcass in which penetrate the flow pipes, in that said hopper is suspended from the carcass by means of load cells and in that means are provided outside the carcass for weak re turn the hopper around the axis of the oven and to activate its metering valve through the central suspension of the hopper.

The hopper metering valve is preferably constituted by an element movable vertically and defining with the wall of the hopper an annular flow opening whose section is variable by vertical displacement of said element.

The hopper suspension consists of a vertical cylinder axially crossing the upper part of the carcass at a sealing bellows and carried by the load cells resting on the carcass, a hollow rod arranged coaxially in said cylinder, the lower part of this rod being connected by means of one or more crosspieces to the hopper, while its upper part undergoes, outside the carcass, the action of a drive means for rotating it around of the vertical axis of the oven and by a rod coaxially passing through said hollow rod, the lower part of this rod being connected to the metering valve, while its upper part undergoes the action of a jack outside the carcass to cause the vertical displacement of the rod and the metering flap.

The outer cylinder of the hopper suspension is preferably connected to the carcass by flexible horizontal stabilization elements which do not impede the freedom of vertical movement of the hopper suspension.

• la figure 1 montre schématiquement une vue latérale d'une installation de chargement avec une trémie de formation d'un barrage de matières de chargement;
• la figure 2 représente un graphique qui montre l'évolution du poids d'un sas de la trémie lors du chargement et
• la figure 3 montre schématiquement une vue d'ensemble, partiellement en coupe verticale axiale d'une installation selon la présente invention.

Other particularities and characteristics will emerge from the detailed description of a preferred embodiment presented below, by way of illustration, with reference to the appended figures in which:

• Figure 1 schematically shows a side view of a loading installation with a hopper for forming a barrage of loading materials;
• FIG. 2 represents a graph which shows the evolution of the weight of an airlock of the hopper during loading and
• FIG. 3 schematically shows an overall view, partially in axial vertical section of an installation according to the present invention.

Figure 1 shows the upper part of a blast furnace 10 in the head of which is mounted a rotary distribution chute 12 with adjustable angle of discharge. Above the oven 10 is a frame 14 which supports the installation for feeding the material

loading. This installation includes, among other things, a hopper 16 whose flow opening is located above the chute 12 on the central axis O and which is controlled by a metering valve 18 composed of two registers with symmetrical action around of axis 0. The frame 14 also supports one or more airlocks, only one of which is represented by the reference 20. This airlock communicates with the hopper 16 through a valve cage 22 which includes a sealing valve not shown and a metering valve 24 controlling the flow of the airlock 20, similar to the valve 18.

In accordance with the present invention, the hopper 16 rests on a number of load cells 26 which make it possible to continuously supply signals representative of the weight of the hopper and of its content. In the same way, the airlock 20 rests on several load cells 28 making it possible to supply signals representative of the content of the airlock 20. To allow the hopper 16 and the airlock 20 to be weighed separately, compensators 30 and 32 have been provided for both 'other of the hopper 16 to separate it from the airlock and the oven.

We will now describe a loading phase with reference to FIGS. 1 and 2. By loading phase, we mean the deposition of a uniform layer of weight P _o on the loading surface in the oven 10. At the start of during the loading phase, all the quantity of loading material with weight P _o is in the airlock 20, the metering valve 24 of which is still closed. The hopper 16 which is empty is also closed by its metering valve 18.

The simplest and most advantageous method in the embodiment of Figure 1 is to use the valve 24 simply as a check valve and open it fully to allow the flow of material in the hopper up to when the flow stops naturally, which is shown in FIG. 1. The metering is then carried out by the valve 18 and the material descends, without falling, from the airlock through the cage 22 into the hopper 16 as and as it flows from it.

It is of course also possible to cause the formation of a barrier of reduced height, which does not extend into the airlock 20. In this case, the valve 24 must be used as a metering valve to regulate the flow of the airlock 20 so as to maintain the dam in the hopper 16.

In FIG. 2, the curves P _t and P respectively represent the weight of the content of the hopper and the weight of the content of the airlock. It shows the evolution of the weight of these contents as a function of time T.

At time T - 0, we therefore see that the weight P is equal to P _o , while the weight P _t is equal to 0. As soon as the metering valve 24 of the airlock is opened, the content of the airlock 20 decreases so linear, which is represented by the fall in the curve P _S. At the same time, the weight of the content of the hopper 16 increases (its valve 18 being always closed), which is represented by the rise of the curve Pt.

The flow of the airlock 20 stops automatically when the loading material accumulates at its angle of rest in the hopper 16 through the communication between the airlock and the hopper as shown in Figure 1. This situation is detected by the evolution of the weight of the hopper 16 and the airlock 20 which no longer changes as soon as the flow stops, which is illustrated in FIG. 2 from time t, where the curves P _t and P _s take directions horizontal.

Thanks to the separate measurement of the weights of the hopper 16 and the airlock 20, it is therefore possible to detect the moment t, when the desired barrier has been formed above the flow opening in the hopper 16. We can then open the valve 18 to start the real loading process. This opening is carried out at time t ₂ . It should be noted that until this moment t ₂ , the sum of the weights P _t and P _s is always equal to P _o , which is illustrated in FIG. 2 by the curve in broken lines.

As soon as the valve 18 is opened, the load flows from the hopper 16 towards the interior of the oven. The flow rate of the material flowing from the hopper 16 is adjusted by the valve 18 so that it is not greater than the flow rate of the flow from the airlock to the hopper 16, so that the weight of the contents of the hopper 16 remains constant as long as the loading material is still in the airlock 20. This is represented by the horizontal evolution of the curve P _t beyond the point t ₂ . On the other hand, the continuous descent of the curve P illustrates the progressive flow from the airlock 20 towards the hopper 16. The total weight P _s + P _t decreases, of course, also from the moment t ₂ , which is illustrated by the fact that the curve in broken lines descends parallel to the curve P _s .

When the airlock 20 is empty at time t ₃ , its lower sealing valve and its metering valve 24 are closed to allow refilling. During this time, the flow of the hopper 16 continues, which is represented by the regular descent of the curve P _t from the time t ₃ until the time t ₄ when it is empty, in turn.

For the loading to take place in optimal conditions, it is important that the material barrier above the flow pipe of the hopper 16 remains throughout the loading phase, that is to say that the valve metering 18 is adjusted so that the flow rate of the hopper 16 is not greater than that of the airlock 20. This control can be easily performed by observing the curve P _t . This must indeed remain horizontal between points t ₂ and t ₃ , that is to say that the material flowing from the hopper 16 must be replaced by the material flowing from the airlock to the hopper 16 Any correction of the position of the valves 18 must be carried out automatically from a signal representative of a deviation of the curve P _t from its horizontal evolution.

Instead of carrying out this control by measuring the weight of the hopper 16, it is also possible to provide level sensors in the wall of the hopper 16 which constantly check the level of the dam above the pipe. flow and provide a signal when the level falls too low, that is to say that the valve 18 is too open or that the valve 24 is not enough.

FIG. 3 shows an embodiment of an installation for implementing the method described above, and which is becoming more and more advantageous for large capacity ovens. In fact, a well-known problem in loading installations with a distribution chute is that of the segregation of the particles, that is to say their separation inside an enclosure according to their particle size. This phenomenon, discussed in more detail in patent LU-85,810 intensifies with the increase in the diameter of the enclosure. This problem is also likely to arise, more or less pronounced, in the hopper in which the dam is caused during the implementation of the method described above, in particular because of the fact that the dam is formed by growth the along the conical wall of the hopper into the upper tubing of one of the airlocks.

In this FIG. 3, we can see the upper part of a tank oven 40 in the head of which there is a distribution chute 42 actuated by a drive mechanism located in a housing 44 on the head of the oven 40. A carcass watertight 46 of substantially conical shape, carried by a frame 48 supported by the head of the oven 40 is connected by its lower part by means of a compensator 50 to the housing 44 and communicates through this compensator 50 with the interior of the oven 40.

The carcass 46 carries, by means of several load cells 52 two airlocks 54 and 56 whose oblique flow pipes 58 and 60 penetrate inside the carcass 46. The flow of these pipes 58 and 60 is controlled by metering members 62 and 64. The seal between each of the airlocks 54 and 56 and the interior of the carcass 46 and the oven 40 is produced by two sealing valves 66 and 68 cooperating with seats mounted in the carcass.

Whereas in conventional loading installations with a rotating chute, the loading material flows directly from the pipes 58 and 60 along the inclined wall of the carcass 46 onto the chute 42, provision has been made in the installation proposed by the present invention for the implementation of the method described above, a conical hopper 70 inside the carcass 46. The lower flow opening of this hopper 70 is controlled by a metering valve 72 whose the aim is to cause the formation of a dam of the material in the hopper 70 as described above with reference to FIG. 1.

To reduce the phenomenon of segregation in this hopper 70, the installation includes means for rotating this hopper 70 around the vertical axis 0 of the oven 40. This rotation in fact allows better filling of the hopper 70 and a filling which takes place over 360 ° rather than an embankment which climbs from the metering valve 72 to the airlocks of the airlocks 54 and 56 and which promotes the phenomenon of segregation. However, the problem caused by the rotation of the hopper 70 is the need to be able to control the flow of the material by weighing the hopper 70, weighing which with a stationary hopper presented no problem.

To be able to solve this problem, the hopper 70 is suspended by one or more cross members 74 from a hollow rod 76 disposed on the central axis 0 and held inside an external coaxial cylinder 78 which crosses, in a sealed manner, the upper part of the carcass 46 at the level of a bellows 80. This cylinder 78 rests on the outside on several load cells 82 which supply signals representing the weight of the hopper 70, of its content and of all its suspension and accessories 'training. The rod 76 is connected, outside the carcass 46, to means not shown to rotate it with the hopper 70 around the central axis 0 as symbolized by the arrows A and B. The metering valve 72 which regulates the flow out of the hopper 70 is designed in the form of a disc or bell which, by vertical displacement, defines an annular opening of variable section with the wall of the hopper 70. For this purpose, the metering valve 72 is carried by the end of a rod 84 passing coaxially through the rod 76 and undergoing outside the carcass 46 the action of a jack 86 to move the metering valve 72 between the closed position illustrated in solid lines and a position open illustrated in dotted lines.

To ensure a certain horizontal stability of the suspension of the hopper 70, the cylinder 78 is connected by blades 88 to the carcass 46, these blades being flexible enough not to hinder the freedom of vertical movement of the cylinder 78, that is to say that is, to exert a harmful influence on the results of the weighing.

It is therefore possible to weigh the content of the hopper 70 while the latter rotates around the vertical axis. The weighing of the hopper 70 and that of the airlock in the flow phase allow the control and command of the loading, in particular the operation of the metering valve 72 by providing signals representing the content of the hopper 70 and that of one of the airlocks 54 or 56, that is to say during the weighing, the airlock in the flow phase and the hopper are considered as a single container.

Of course, it is also possible to use the weighing of the hopper 70 for monitoring the level of its content. However, given that for equal weight, the volume and the level curve of the content of the hopper may vary, it is preferable to monitor the filling level of the hopper by level detectors such as for example ultrasonic, isotope, optical probes, etc.

The installation described above allows you to proceed in two different ways to empty the contents of an airlock in the oven. It is possible to proceed according to the diagram in FIG. 2, that is to say to open the metering valve 72 only after the flow has stopped through the pipe 60, that is to say say after the formation of a dam from the bottom of the hopper 70 to one of the airlocks 54 or 56.

It is however also possible and generally preferable because of the rotation of the hopper 70 in the embodiment of FIG. 3, to open the metering flap 72 before the flow through the tubing 60 stops and to adjust, by controlling the level of the content of the hopper 70, the metering valves 62 or 64 of the airlock in the flow phase, so as to maintain a constant loading level in the hopper 70.

Claims (9)

1. Process for charging a shaft furnace with a charging installation, comprising a rotary or oscillating spout, a hopper with a central discharge pipe above the spout, the discharge aperture of the said pipe being controlled by a dosing device operating symmetrically around the central axis, surmounted by at least one chamber provided with an upper and a lower sealing valve, and also a dosing valve serving to regulate the rate of discharge to the hopper, characterized by the fact that the material being contained in the chamber and the dosing valve of the hopper being closed, the dosing valve of the chamber is first of all opened in order to bring about the discharge of a sufficient quantity of material for the formation of barrage of material above the discharge pipe of the hopper, that the dosing valve is not opened until after the formation of the said barrage, that both the hopper and the chamber in communication with the hopper are weighed separately and throughout the duration of the charging, that signals are produced which represent, respectively the quantity of material contained in the hopper, the quantity of material contained in the chamber and the sum of the quantities of material contained in the hopper and in the chamber, and in that the position of the dosing valve of the hopper is adjusted to ensure that the rate of discharge from the hopper does not exceed the rate of flow of material from the chamber to the hopper.

2. Process in accordance with claim 1 characterized in that the rates of discharge of material are adjusted to ensure that the weight of the quantity of material in the hopper remains constant as long as material is in the chamber. 3. Process in accordance with anyone of claims 1 or 2, characterized by the fact that the dosing valve of the hopper is not opened until after the flow of material out of a chamber has ceased naturally as a result of the formation of a barrage ascending as far as the said chamber.

4. Process in accordance with anyone of claims 1 or 2, characterized by the fact that the dosing valve of the hopper is opened before the natural cessation of the flow of material out of a chamber and that the position of the dosing device of this latter is adjusted to ensure that the barrage in the hopper will be maintained.

5. Charging installation for a shaft furnace (40) comprising a rotary or oscillating distribution spout (42), a hopper (60) with a central discharge aperture situated above the spout (42), and controlled by a dosing valve (72) acting symmetrically about the central axis 0 of the furnace (40) and surmounted by two storage chambers (54, 56) juxtaposed on each side of the vertical axis 0 of the furnace (40) and supported via balances (52), the said chambers (54, 56) being provided with discharge pipes (58, 60) directed towards the hopper (70), a pair of sealing valves (66, 68) and a pair of dosing valves (62, 64) associated respectively with the discharge pipes (58, 60) and serving to enable the chamber (54, 56) to communicate in alternation with the interior of the furnace (40), characterized by the fact that the said hopper (70) is contained in a tight carcase (46) into which the discharge pipes (58) and (60) extend, that the said hopper (70) is suspended from the carcase (46) via pressure cells (82) and that means are provided outside the carcase (46) to cause the hopper (70) to rotate about the axis 0 of the furnace (40) and to actuate its dosing valve (72) via the central suspension system of the hopper (70).

6. Installation in accordance with claim 5, characterized by the fact that the dosing valve (72) of the hopper (70) consists of a vertically movable element which in conjunction with the wall of the hopper (70) defines an annular discharge aperture of which the cross section can be varied by moving the dosing valve (72) vertically.

7. Installation in accordance with anyone of claims 5 or 6, characterized by the fact that the suspension system of the hopper (70) consists of a vertical cylinder (78) passing axially through a bellows-type sealing device in the upper part of the carcase (46) and supported by pressure cells (82) resting on the carcase (46), a hollow bar (76) positioned coaxially in the said cylinder (78), the lower part of this bar being connected to the hopper (70) via one or more cross bars (74) while its upper part is subjected outside the carcase (46) to the action of a driving means to cause it to rotate about the vertical axis O of the furnace (40) and by a bar (84) passing axially through the said hollow bar (76), the lower part of this bar (84) being connected to the dosing valve (72) while its upper part is subjected outside the carcase (46) to the action of a jack (86) in order to move the bar (84) and the dosing valve (72) in the vertical direction.

8. Installation in accordance with claim 7, characterized by the fact that the cylinder (78) of the suspension system of the hopper (70) is connected to the carcase (16) via flexible elements (88) for horizontal stabilization.

9. Installation in accordance with any one of claims 5 to 8, characterized by the fact that level- detectors are associated with the hopper (70).

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