LU86459A1 - PROCESS FOR SEALING A CASTING HOLE - Google Patents

Description

- 1 -

Method for plugging a tap hole ’The invention relates to a method for plugging a tap hole from a shaft furnace, in particular from a 5 blast furnace.

It is known that the tap holes of a shaft furnace, in particular of a blast furnace, are plugged with a sealing mass which is generally a clay-based refractory mass and which is injected into the casting at high pressure using a clay cannon. These guns have a clay chamber in which slides an ejector piston to release the clay through the nose of the barrel. The high back pressures of modern blast furnaces and the properties of the plug masses generally used require very high pressures for filling the tap holes. This is one of the reasons why the ejector piston of modern clay cannons is generally actuated by means of a hydraulic cylinder.

According to the capping methods currently used at present, the capper is brought at the end of the casting operation to the tap hole, its barrel being filled with sealing mass; and once the nose of the barrel is in contact with the outside orifice of the taphole, the sealing mass is injected at a constant speed into the taphole to push back the pig iron and the slag and plug the channel of the taphole casting.

The increase in backpressure in the blast furnace of modern blast furnaces, as well as the general tendency to increase the production of blast furnaces and therefore the number of ladles in a day, and thereby the flow of Large amounts of pig iron through the tap hole necessarily lead to a further degradation of the tap hole channel. Slag exerts a particularly strong influence on this destruction. Until the appearance of the slag, ladle pouring normally evolves without - 2 - f strong pressure, but as soon as the slag appears, the speed of flow of the melt begins to increase, often accompanied by turbulent formation gas, and there are signs of weathering the hole while much of it! pig iron and slag are still in the blast furnace.

The destruction of the tap hole results in the need to introduce larger quantities of refractory mass therein. After this operation, the tap holes are wet and it is necessary to devote a considerable time to their preparation. There have been known cases of ejection of the refractory mass from the tap hole after the withdrawal of the barrel from the capping machine.

15 In order to reduce the risk of blast furnace shutdowns due to a poorly closed tap hole, systematic research has been carried out in the past to improve the stability and the holding of tap holes by using different refractory masses 20 whose components vary from one blast furnace to another and sometimes from one tap hole to another. The composition of the plugging masses currently used is based on refractory clay (sometimes a mixture of different clays), chamotte, possibly a coke or carbon dust and a binder such as pitch. coal tar or natural or synthetic resin. Each producer of plugging masses has its own formulas which it claims to have to adapt to each installation and whose composition varies according to the type of blast furnace, according to the characteristics of the channel of the tap hole and according to the model of the tap hole filling machine.

If some progress has been noted by 35 new mixtures of capping masses, the general characteristics of which must meet the following criteria: - A degree of plasticity (if possible not very variable - 3 - over time) allowing regular capping with the machine used, - rapid hardening at the end of the capping operation, 5 - high resistance to abrasion and erosion by pig iron and slag, - no formation of smoke and harmful gases, all the problems of degradation of the tap hole could not be solved and it still too often happens that blockages are poorly made. Indeed, apart from the somewhat empirical choice of plugging masses, the plugging operation depends to a large extent on the user and / or the operator of the tap hole plugging machine.

Often a plugging carried out at too fast a speed does not allow time for the plugging mass to become encrusted in the channel of the tap hole; hence varying lengths of plugs or plugs (from one plugging operation to another) and a mushroom of fragile mass inside the blast furnace.

On the other hand, a too slow corking causes a shortening of the corking plug and a "rotten" mushroom by a mixture of overcooked mass, of cast iron and slag which either will disappear in the blast furnace or will be a source of problems during uncorking.

In summary, although some improvement in the capping operation could have been achieved by the use of better mixtures of corking masses, the capping method has remained substantially unchanged and is subject to talent or skill operator of the capper. It is the operator who, after choosing the closure mass, proceeds, based on his experience and appreciation, to the closure operation by injecting large quantities at a uniform speed (chosen according to his appreciation) of masses in the taphole channel (usually a large - 4 - multiple of the mass actually needed). For example, a tap hole with a diameter of sixty millimeters and a length of two meters is plugged with some twenty kilos of mass, while according to * 5 the generally applied method, one injects between 150 and . 250 kilos to clean the tap hole channel, redo the fungus, fill the cracks and finally plug the tap hole.

So not only do the conventional methods have the disadvantage of still too often leading to a refusal of corking or to a problematic capping, that is to say poorly done, but the operation can only be carried out with a significant waste of the corking product.

The invention proposes to avoid the disadvantages of the methods of plugging the tap hole of a blast furnace currently used.

In order to achieve the objective which it has set for itself, the present invention provides a method of plugging a tap hole of a shaft furnace, in particular of a blast furnace, using a clay gun capper comprising a clay chamber in which slides an ejector piston to release the plugging mass through the barrel nose, characterized in that during the plugging operation, the speed of the plugging mass is reduced during operation.

The features and advantages provided by the present invention will emerge more clearly from the detailed description of an embodiment given by way of example with reference to the appended drawings, in which:

Figure 1 shows a view of a capper with clay cannon in position in front of the taphole of a blast furnace;

Figure 2 shows the stapler of Figure 1 during the initial phase of the capping operation;

Figure 3 shows the capper of Figure 1 - 5 - during the final phase of the capping operation;

The same elements appearing in the different figures bear the same reference numbers.

Figure 1 shows in section the wall 1 of a blast furnace with its shield 2 and its refractory lining 3 in the vicinity of a tap hole with its channel 4 in the refractory lining 3 of the furnace, as well as the remains 13 of the mushroom from previous corking.

A capper 5 is in the operative position with its clay barrel 10 in front of the taphole and in alignment with the channel 4 of the taphole. The clay cannon 6 filled with plugging mass 7 comprises a piston 8 which is actuated by a hydraulic cylinder 9. The control of the hydraulic cylinder 9 is carried out so that the speed of movement of the piston 8 can be varied as desired either manually either automatically, during the capping operation.

According to a preferred embodiment of the closure method of the invention, the closure operation is carried out in two stages. At first tl, during the initial phase of the capping operation as shown in Figure 2, the piston 8 of the clay gun 6 is actuated with a rapid speed, so as to inject a relatively large amount of mass to plug 7 at high speed in channel 4 of the tap hole. This procedure allows cleaning of the channel 4 of the tap hole and pushing the residues 10 (cast iron-slag mixture) inside the oven, and also makes it possible to reconstitute the length of the plugging plug.

30 In a second step t2 of the plugging operation, the piston 8 of the clay cannon 6 is actuated with a substantially lower speed in order to allow the packing of the mass to be plugged which gradually forms a sort of mushroom 11 compact on the interior of the oven (Figure 3) which hardens as the sealing operation progresses. During this phase of the plugging, the mass is compressed, the —--- PsimwpHiiPisi ;, - 6 - cracks in the pouring channel 4 are plugged and the channel 4 is gradually closed, as shown diagrammatically by the reference 12 in FIG. 3 until 'at the moment when the operator notices a blockage refusal 5 at the end of injection when all the power of the corker is required.

Tests on different blast furnace installations working with different parameters and using different types of cappers have demonstrated that the capping method according to the preferred mode of the invention has given excellent results.

As in the past, the capping mass, in particular its degree of plasticity, must be adapted in each particular case to the particular characteristics of the capper.

By way of example, it has been observed that with the closure process described above, blast furnaces of different sizes having productions of pig iron, from 2,000 to 6,000 tonnes per day with different yields and working with hot wind pressures of 2 to 3.5 bars could be successfully plugged by injecting only 50 to 60 liters of plugging masses into the tap hole channel. Initially two thirds of the quantity of the mass to be capped (approximately 40 liters) are injected at a rapid rate of approximately 8 liters per second and secondly the third third of the quantity of the mass to be capped ( approximately 20 liters) is injected at a slow speed of approximately 1 liter per second.

30 Depending on the characteristics of the blast furnace, those of the capper and the mass of butcher used, it may prove to be advantageous either to progressively lower the capping speed from a rapid start speed to a slow speed. at the end of the injection, either to vary this speed in several stages (instead of the two described in the preferred example above), and this in spurts.

The main advantages of the capping process according to the invention lie in particular in the fact of a significant reduction in corking refusals. Similarly, the number of problematic closings is greatly reduced. In fact, the closure method according to the invention allows a safer and faster take-up of the closure mass while increasing the active (or effective) length of the closure stopper. The quality of the stopper pad being more homogeneous, it follows that the pouring takes place with better regularity and therefore a reduction in the risk of casting incidents which results in increased safety for the personnel. Since the amount of plugging mass required by applying the new method according to the invention is greatly reduced compared to the known plugging methods, this results in an appreciable saving in plugging for the users.

A particular merit of the invention resides in the fact that its implementation requires only a slight modification in the control system (hydraulic or electric) of the machine for plugging the taphole, modification being left in most cases easily done by a person skilled in the art.

Claims (2)

1. Method for plugging a tap hole of a shaft furnace, in particular a blast furnace, 5. using a clay cannon capper comprising a clay chamber in which a piston slides ^ ejector for releasing the plugging mass through the barrel nose, characterized in that during the plugging operation the speed of injection of the plugging mass is reduced. 2. The capping method according to claim 1, characterized in that the reduction in the capping speed during the capping operation is done gradually. 3. The closure method according to claim 1, characterized in that the closure speed is lowered from a rapid start speed to a relatively slow speed at the end of injection in several stages. 4. A capping method according to claim 3, characterized in that the capping operation comprises two stages, a first during which a substantial quantity of the mass to be capped is injected at a relatively high speed into the 25 plugging hole channel for a relatively short period of time and a second during which a smaller amount of plug mass is injected at a relatively low speed for a greater period of time compared to the first. 5. A method of capping according to claim 4, characterized in that two thirds of the quantity of capping mass necessary for a capping operation are injected at the rate of approximately eight liters per second and that the third third of the amount of the plugging mass is injected at a rate of about one liter per second.