"TROLLEY WITH TILTED TABLE AND ROLLS FOR CHANGING TUYERE COOLING BOXES"

Field of this patent:

• Productivity and Work Security in blast furnace maintenance.

State of the Art.

Blast furnaces constitute the core of the steel industry. It is in them that the iron oxid ores, granulated or pre-processed to make "sinter", are subjected to the hot chemical reduction process, having the carbon as reagent, and they are turned into a metallic alloy composed of more than 97% of the iron element, called "pig iron".

The metallic iron in liquid state, with a temperature of about 1 ,500 Centigrade degrees and that flows from the blast furnaces in the runs, is taken to the other pieces of equipment of the steel plant, which will process it to turn it into steel, that is, a complex alloy of iron and other elements with the fewest contents of sulfur, phosphorus and other contaminants as possible.

We say that the blast furnaces are the core of the steel industry because they provide raw material to all the subsequent processes.

The modern blast furnaces are located in the center of a complex of peripheral pieces of equipment that are responsible for their high productions and quality; the regenerators increase their thermal economies allowing the air injection through their tuyeres to be done at about 1 ,200 Centigrade degrees, special lances make the coke or charcoal fines (breeze) be injected through their tuyeres in order to rise their thermal performances, they receive sinter rather than the granulated ore, besides a stoichiometric amount of water steam in such a way, due to their geometry, that they use the hydrogen formed as a reducing element.

Nowadays, supported by the technological advances in the last 50 years and by the recent automation support, the blast furnaces are considered to be near their maximum evolution limit, that is, obtaining improvements in the industrial

reduction process for oxidated iron ores is only possible with radical changes of paradigm.

Due to economical matters related to the productivity and to the cost reduction, the blast furnaces must have bigger and bigger production capacities, of about millions of tons/year.

The current operational indices are around 99% of the time and the high productivities reached are also due to the millions of dollars invested in the automation and computerization of the blast furnaces.

However, when the costs of each stopped hour are observed, a huge need of innovating the processes and maintenance equipment of the pieces and of the most wear-to-be equipment is noticed so that the stopped hours can be reduced.

A blast furnace with a production of 2,800,000 tons per year produces 7,670 tons a day or 320 tons an hour. For the current prices of US$250.00 per ton of pig iron, there is a theorical production loss of US$80,000 per stopped hour.

Taking the finished products of about US$500.00 per ton into consideration, the production loss per stopped hour is that of US$160,000.00.

One should also take into account that when a blast furnace process is interrupted, it is rather slowly than abruptly, previously decreasing the production for several hours and similar timings are necessary for returning to the status of maximum production process.

This means a loss of basic production - despite other systemic losses - of about US$200,000.00 per stopped hour. However, despite the great technological advances of the blast furnaces and of the peripheral pieces of equipment that support them, those simplest pieces of equipment, such as the equipment and tooling for changing tuyeres and many others, have been the same for decades.

Analyses reveal that the maintenance halts, whether programmed or not, of the simplest pieces of equipment which are auxiliaries for the blast furnace work, such as the sealing refractories of the iron notches, are responsible for great losses of their productivities. Thus, the equipment productivity and the operational processes improvements, known as "supportive services and equipment to the blast furnace", have been the target of great managing efforts, once their importance is clear in order to reduce the number of stopped hours.

It must be stated that the maintenance services performed in the blast furnaces are carried out in extremely hard conditions, due to the high temperatures near such equipment, due to the restricted conditions of space for movement and correctly anatomic positioning, besides always demanding great physical efforts, as they deal with heavy pieces and tools that are hard to handle; in other words, such tasks take long to be carried out due to the local conditions and to comply with the work security.

According to the current State of the Art, the two most difficult and that take the longest time to be removed and replaced are the tuyeres and their cooling boxes, for the following reasons:

1 ^st - They are pieces that respectively weigh an average of 150 and 750 kilos;

2 ^nd - They are very difficult pieces to be handled and they cannot get scratched or suffer any other kind of damage;

3 ^rd - The places where the tasks are carried out are restricted and extremely hot; 4 ^th - The cooling boxes are connected with the tuyeres by pressure in order to generate sealing, by a perfect overlapping; the tuyeres have a straight contact with the hottest area of the blast furnace, that through which the heated air enters at around 1.200 degrees Centigrade, enriched by five percent more of oxygen; it is through them . that the coal fines dragged by the nitrogen are injected. As both the tuyeres and part of their

cooling boxes operate under extremely complex and aggressive chemical conditions, both accumulate fused metal and a number of other compounds on their surfaces that come to weld among themselves and with the places where they are fit in the blast furnaces and, therefore they are extremely hard to be removed.

5 ^th - The average time for replacing these two pieces is around 17 hours and the operation must be performed when the blast furnace is stopped; taking the aforesaid values into account, one can see the value of the losses due to the current State of the Art for these two pieces replacement.

The object of this patent " "TROLLEY WITH TILTED TABLE AND ROLLS FOR CHANGING TUYERE COOLING BOXES" constitutes the result of investments and systematic efforts in researches and experiments in the sense of reducing the number of stopped hours for removing and replacing the tuyeres and their cooling boxes.

Advances in the State of the Art of the object of this patent.

The use of the "TROLLEY WITH TILTED TABLE AND ROLLS FOR CHANGING TUYERE COOLING BOXES", object of this patent, comes as a substitute for the tooling and the tuyere cooling boxes replacement process, which consists of removing them from the places where they are installed and take new tuyere cooling boxes to these places, which by the present state of the art is done by using pulleys, metallic ramps, winches and it requires a great human effort, besides being a source of risks to the work security.

By using the ""TROLLEY WITH TILTED TABLE AND ROLLS FOR CHANGING TUYERE COOLING BOXES"", the State of the Art advances as it gets to:

A - reduce the average time of the tuyere and cooling boxes replacement operation, decreasing the losses due to production interruption as cited above;

B - minimize the workers' physical efforts and allow them to be made under better postural conditions, complying with the norms of Work Hygiene;

C - increase the operation security; D - minimize the equipment damage risk.

Illustrations, description and the work of the "TROLLEY WITH TILTED TABLE AND ROLLS FOR CHANGING TUYERE COOLING BOXES", object of this patent, which consists of a trolley with wheels that has a tilted table on its upper part which contains cylindrical rolls and makes up an angle determined with the horizontal and it is of such dimensions that it can be placed inside the holder both to take the tuyere cooling box to the place it will be installed and to remove it from there, when replacing it, thus, preventing human efforts under bad postural conditions when dealing with pieces of about 750 kilos, in a restricted height setting and under high temperatures, as it is done by the State of the Art these advances come to replace.

The "TROLLEY WITH TILTED TABLE AND ROLLS FOR CHANGING TUYERE COOLING BOXES" is operable by two workers only under high security conditions and with the least human effort and it speeds up the process it is purposed to, bringing a great economy of time for its operation. For perfectly understanding the advances of the State of the Art acquired by the object of this patent, Figure 1 illustrates the relation between the "tuyere cooling box" set with the other pieces of the blast furnace when it is ready for being operated ; Figure 2 shows the details of the working area, where the "TROLLEY WITH TILTED TABLE AND ROLLS FOR CHANGING TUYERE COOLING BOXES" will be operated after the blast furnace stall and the disassembling of the pieces which are necessary for the tuyere cooling box removal operation, and, inversely, its replacement.

Figure 1 is a schematic frontal cut that, for simplicity matters, omits the representation of pieces which are unnecessary for understanding the issue, such as the refractories, displays, refrigeration water fast coupling hoses, etc.; in it, we can see the ring-shaped tube, which is the heated air distributor (1), the

straight tube (2), the dilatation joint (3), the various flanges (4) that put these pieces together, the pipe bend (11), the conic tube (5), the conic tube (5) nozzle (6), the cooling box (7), the tuyere (8), the tuyere (8) seat (9) and the cooling box (7) seat (10), such piece conformations that, respectively, allow the perfect adaptation and seal between the conic tube (5) nozzle (6) and the tuyere (8) and between this and the cooling box (7).

Figure 1 also shows the blast furnace carcass (13) onto which the holder (12) is fixed, which is seen in a frontal cut in this figure and must be understood as a welded ring or hooked by any other means to the blast furnace carcass (13) and where the pipe bend (11) and, therefore, the conic tube (5) are firmly fixed by tie rods, thus keeping the cooling box (7) and the tuyere (8) contained in it put in their operational places.

Figure 2 is the same as Figure 1 , illustrating the working area ready for removing and placing the cooling box (7), that is, in it, the conic tube (5), the tuyere (8) and the pipe bend (11) indicated in Figure 1 are removed and, therefore, are not represented; the cooling box (7), the blast furnace carcass (13) and the holder (12), besides the lines A-B and C-D that indicate, respectively, the ground level and the maximum height of the working area, limited by the straight tube (2) flange (4), can also be seen. The height is of such a degree that it makes the workers work inclined.

By using the "TROLLEY WITH TILTED TABLE AND ROLLS FOR CHANGING TUYERE COOLING BOXES" (14), it is unnecessary to remove the straight tube (2), which is a big and heavy piece and whose removal takes very long; the trolley table tilt, as it will be seen ahead, allows the cooling box removal operation without removing the straight tube (2) because its tilt creates a larger space for performing such job.

Figure 3 is a schematic side view of the "TROLLEY WITH TILTED TABLE AND ROLLS FOR CHANGING TUYERE COOLING BOXES" (14) where the structure (17), the tilted table (16) with its positioning support (15), the rolls (18) and the wheels (19) can be seen.

Figure 4 is a schematic frontal view of the "TROLLEY WITH TILTED TABLE AND ROLLS FOR CHANGING TUYERE COOLING BOXES" (14) where the structure (17), the tilted table (16) with the rolls (18), the wheels (19) and the positioning support (15) can be seen. Figure 5 illustrates the "TROLLEY WITH TILTED TABLE AND ROLLS FOR CHANGING TUYERE COOLING BOXES" (14) positioned in its working area, that is, introduced inside the holder (12) for the cooling box (7) removal operation, where the structure (17), the tilted table (16) with the rolls (18), the wheels (19) and the positioning support (15) can be seen; for understanding the spacial difficulties of the working area and the bad postural conditions the situation makes the workers take in order to perform such tasks, we can see the heated air distributor (1), the straight tube (2), the dilatation joints (3) and the flange (4).

Figure 6 is a view of the "TROLLEY WITH TILTED TABLE AND ROLLS FOR CHANGING TUYERE COOLING BOXES" (14) positioned in its working area for the cooling box (7) removal operation with it having already been removed from its operational place and it is found on the rolls (18); the structure (17), the tilted table (16), the wheels (19) and the positioning support (15), the blast furnace carcass (13) and the holder (12) can also be seen. Although the work of the "TROLLEY WITH TILTED TABLE AND ROLLS FOR CHANGING TUYERE COOLING BOXES" is simple and blatant, as described above and illustrated by the shown Figures, it takes to the aimed time savings, operational comfort, work security and hygiene.