Metallurgical apparatus – Means for treating ores or for extracting metals – By means applying heat to work – e.g. – furnace
Reexamination Certificate
1999-09-23
2001-04-24
Kastler, Scott (Department: 1742)
Metallurgical apparatus
Means for treating ores or for extracting metals
By means applying heat to work, e.g., furnace
C266S241000, C266S286000
Reexamination Certificate
active
06221312
ABSTRACT:
The invention relates to a refractory wall structure, suitable in particular for use in a metallurgical vessel for a continuous production of crude iron in a smelting reduction process under conditions of an extremely high thermal load in a highly abrasive environment of molten slag with a high FeO content. The invention also relates to a metallurgical vessel and to a method for a continuous production of crude iron, in particular for the final reduction of the Cyclone Converter Furnace (CCF) smelting reduction process.
According to the state of the art crude iron is produced in a blast furnace. In this process iron ore is reduced with the aid of coke. There are different processes being developed for the direct reduction of iron ore which however not yet have been applied industrially. The most promising are the so-called in-bath smelting reduction processes. A bottleneck with these processes is the service life of the refractory wall structure of the metallurgical vessel in which the reduction into crude iron takes place. This is determined by a particularly high thermal load and a highly abrasive environment due to the presence of FeO at a temperature level of approximately 1,700° C. In the case of a blast furnace whereby the same conditions occur in a somewhat less aggressive form and whereby a thermal load of 300,000 W/m
2
can occur, the refractory wall structure consists, at its most threatened place, going from the outside to the inside, of an armour-plating and a lining of refractory bricks, for example bricks containing SiC which is cooled by cooling elements. Cooling elements according to the state of the art are either so-called cooling plates, reaching removably into the lining, as described in Dutch patent application NL 7312549 A, or so-called staves which form a water-cooled wall between the armour-plating and the lining. At present with this structure it is possible to reach a service life in the order of 10 years. European patent application EP 0 690 136 A1 describes an apparatus in which iron compounds in particle form are melted in a gas atmosphere. The shell or armour construction of this apparatus is water-cooled. With smelting reduction processes the thermal load is much higher and can even reach 2,000,000 W/m
2
locally. Therefore no acceptable service life can be achieved with a known wall structure for a blast furnace.
The object of the invention is to provide a wall structure for a process of direct reduction which has an acceptable service life.
This is achieved in accordance with the invention with a wall structure comprising, going from the outside to the inside,
(1) a steel jacket;
(2) a water-cooled copper wall;
(3) water-cooled copper ledges extending towards the inside;
(4) a lining of refractory material resting on the ledges.
With this basic structure it is possible, due to a maximal thermal contact between the lining and the water-cooled copper wall -and ledges, to realise a refractory wall structure with which a low thermal resistance is attained. As a result of this even under a high thermal load a good stable residual thickness of the lining is achieved resulting in a long service life. The most threatened area in the metallurgical vessel in which the reduction into iron ore takes place is where the molten slag layer containing a high amount of FeO floats on the crude iron bath. There the lining wears away to a balanced residual thickness onto which a layer of slag solidifies which layer functions as a wearing and insulation layer. The solidified layer stops the lining being attacked and the structure is capable to resist further attack. The cooling by the ledges improves the service life of the refractory structure.
Preferably the ledges are preferably movable vertically. The advantage of this is that, when being assembled cold, the refractory wall structure can settle in the vertical direction under the effect of its own weight so that the horizontal joints are closed as much as possible.
Preferably the ledges at the top extend upwards towards the inside obliquely, the ledges at the bottom extend downwards towards the inside obliquely, and the ledges are distributed up the height of the wall. The advantage of this is that the lining is secured relative to the water-cooled copper wall.
Preferably the water-cooled copper wall is composed of panels. This facilitates fabrication and assembly of the water-cooled copper wall.
Preferably the ledges are installed staggered in height up the width and/or the circumference. This achieves the effect that the passages of the cooling water feed and discharge pipes are distributed uniformly throughout the steel jacket and clusters of them are avoided.
Preferably the lining rests without mortar on the ledges and the lining bears against the water-cooled wall without mortar. This avoids high thermal resistances as a consequence of mortar-filled joints, and is it possible to allow a high thermal load.
Preferably the lining is composed of blocks of graphite with a coefficient of thermal conductivity in the range 60-150 W/m° K and/or of blocks of semi-graphite with a coefficient of thermal conductivity in the range 30-60 W/m° K. As a result of the high coefficient of thermal conductivity a low thermal resistance is achieved as a cause of which it is possible to allow a high thermal load.
In an alternative embodiment the lining preferably consists of refractory bricks, more preferably of bricks of a type that is used in converters for steel production or in electric furnaces for steel production and most preferably the bricks are magnesite-carbon bricks. Bricks of this type known for steel production have a high resistance to abrasion.
Preferably, going from the outside to the inside, the lining consists of a layer of graphite which bears against the copper wall and a layer of refractory bricks. With this embodiment, once the balanced thickness has established itself, the lining consists of a layer of wear resistant refractory bricks and a layer of graphite with a low thermal resistance.
Preferably the wall inclines backwards from bottom to top. This improves the stability of the lining. In addition this widening shape achieves the effect that the level of the slag layer in the metallurgical vessel varies less.
Preferably the copper wall and/or the copper ledges consists of red copper with a content of ≧99% Cu and a coefficient of thermal conductivity in the range 250-300 W/m° K. This achieves an acceptably low thermal resistance of these elements.
Preferably the steel jacket forms part of a pressure vessel and the passages through the steel jacket of cooling water feed and discharge pipes of the water-cooled copper wall and the water-cooled copper ledges are sealed following assembly of the wall. This achieves the effect that the process may be run under overpressure.
Preferably the wall is resistant against a thermal load of over 300,000 W/m
2
and against slag with approximately 10% wt. FeO at a temperature level of approximately 1,700° C., and the wall has a service life of at least 6 months continuous use. This allows the wall to be operated under conditions of a high thermal load in a highly abrasive environment with an acceptable service life.
In another aspect the invention is embodied in a metallurgical vessel, in particular for the final reduction of the Cyclone Converter Furnace (CCF) smelting reduction process that comprises a refractory wall structure in accordance with the invention.
In yet another aspect the invention is embodied in a method for a continuous production of crude iron, in particular for the final reduction of the Cyclone Converter Furnace (CCF) smelting reduction process in a metallurgical vessel in which a refractory wall structure in accordance with the invention is applied.
REFERENCES:
patent: 4849015 (1989-07-01), Fassbinder
patent: 5662860 (1997-09-01), Kiaassen et al.
patent: 5676908 (1997-10-01), Kubbutat et al.
patent: 3607774 (1986-03-01), None
Tijhuis Gerardus Jozef
van Laar Jacobus
Hoogovens Staal B.V.
Kastler Scott
Stevens Davis Miller & Mosher LLP
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