What is claimed is
1. A basic oxygen converter comprising
2. The converter set forth in claim 1 wherein the half tubes have a semicircular cross section.
3. The converter set forth in claim 1, wherein the half tubes, over the major part of the circumference of the converter shell, are bent in a single plane which is perpendicular to the converter axis.
4. The converter set forth in claim 1, wherein several tube coil groups are arranged one above the other and the half tubes of one group are connected with the half tubes of the next group by slanting connecting tubes.
5. The converter set forth in claim 1, wherein several tube coil groups are arranged one above the other, the half tubes of each group being joined to a common coolant distributor and to a common coolant collector.
6. The converter set forth in claim 1, wherein several tube coil groups are arranged one above the other, the half tubes of each group being joined to an appurtenant coolant distributor and collector.
The invention relates to a basic oxygen converter having a metal shell comprising at thermally highly stressed areas, in particular in the area between the carrying ring and the converter mouth, at least one pipe coil group through which a coolant is flowing and which includes several half tubes of preferably semicircular cross section welded to the converter shell and joined at one end to a coolant distributor and at the other end to a coolant collector.
It is necessary to protect thermally highly stressed parts of industrial furnaces by specific cooling devices from damaging heat influence. For this purpose these furnace parts are either designed to be hollow or they are provided with a jacket so that by passing through a cold fluid coolant excess heat damaging these furnace parts may be guided off. Also cooling coils or cooling canals are known which are formed by half tubes or similar sections welded onto the furnace parts as this has e.g. been proposed in the German printed application No. 1,103,952.
In basic oxygen converters it is necessary to cool the so-called converter head, i.e. the converter part above the carrying ring up to the converter mouth. From the German registered design No. 6,605,707 such a converter head cooling is known which comprises individual tubes which are split up in the longitudinal extension of the tubes and welded to the converter shell, several tube coils being individually joined with their respective delivery parts and discharge parts to a common coolant distributor and a common coolant collector. Each individual coolant coil is laid in one or more windings, spaced from the other windings, around the converter shell to form a so-called multiple helix. The cooling agent is supplied through a bore in the converter carrying trunnion or through the hollow converter carrying ring in the surroundings of which the mentioned coolant distributors and coolant collectors are arranged. This system of cooling in which individual cooling coils are employed and each coil is separately joined to a coolant collector and distributor, respectively, has been taken over from the boiler construction and is described e.g. in the book by Ledinegg, M.: "Dampferzeugung," Springer-Verlag, Vienna, 1952, pages 16, 17, 38, 39, 45, 46, 47 and 49.
This known cooling system for a converter has several disadvantages. In cooling coils arranged separately by themselves, already when they are taken into operation, there is the danger that, owing to mounting inaccuracies at the welded junctures of the tubes and faulty welding seams, cross section constrictions occur within such a cooling coil, so that a pressure loss occurs in the coolant, the current becomes uneven and as a further result the cooling effect is marred. Irregularities in the supply of the individual cooling coils have to be expected also because the cooling coils have varying curvatures and deflections, which also cause changes in the current resistance for the coolant. As a result of a non-uniform cooling of the converter shell, in particular at the converter head in the area of the converter mouth, zones of different temperatures may occur so that in the metal shell different thermal expansion stresses arise, which is of disadvantage both for the metal shell itself and also for the refractory lining of the converter. After a prolonged operation period there is also the danger that the cooling system is constricted by mechanical impurities and/or by the deposition of lime; they may be both local deposits or also occlusions. This may result in the fact that in tube coils arranged separately only a part thereof is completely flown through by the cooling agent, while an other part with reduced through flow is overheated so that the cooling agent evaporizes. These drawbacks can lead to serious catastrophes in the steel work plant.
A further disadvantage of the known cooling system resides in that the make and mounting of tubes which are split in their longitudinal extension and may e.g. have a semicircular cross section present great difficulties, because these half tubes have to be bent in two planes, so that they may be adapted to the conical, spherical and cylindrical wall of a converter. The main work has to be performed during mounting because the laying of the tubes in a helical line necessitates appropriate adaptation and changing operations which cannot completely be carried out earlier in the workshop; mounting thus is rather expensive.
The invention is aimed at avoiding these disadvantages and difficulties by creating a converter shell cooling system which is improved in current technological and operating safety respects, which, moreover, may easily be produced and whose mounting is inexpensive.
In a basic oxygen converter of the kind defined in the introduction the invention resides in that for the purpose of obtaining a pressure equalization and a uniform flow of the cooling agent, the half tubes of each group are interconnected by means of cross canals on at least one site.
A further important feature of the invention resides in that the half tubes, over a major part of the circumference of the converter shell are bent in a single plane which is perpendicular to the converter axis.
According to an embodiment of the invention several tube coil groups may be arranged one above the other and their half tubes may be connected with each other by slanting connecting tubes.
A second embodiment is characterized in that several tube coil groups are arranged one above the other, the half tubes of each group being joined to a common coolant distributor and to a common coolant collector.
Finally, in a third embodiment also several tube coil groups may be arranged one above the other, the half tubes of each group being joined to a coolant distributor and collector each.
In order that the invention may be more fully understood three embodiments thereof shall now be explained with reference to the accompanying drawings.
FIG. 1 is a lateral view of an upper part (head) of a basic oxygen converter, partly in section; three tube coil groups are provided one above the other and current technologically they are arranged one after the other. FIG. 2 is a similar representation as FIG. 1, but in this embodiment the three tube coil groups are current technologically arranged in parallel, these groups being joined to a common, vertically arranged coolant distributor and collector, respectively. FIG. 3 is a similar represenation as that of FIG. 2, the three tube coil groups are current technologically in parallel but each of the groups is separately joined to a coolant distributor or collector, respectively.
In FIG. 1 numeral 1 denotes the metal shell of the converter, which is provided with a refractory lining 2 and a mouth ring 3. In the area of the converter carrying ring (which is not shown) a coolant distributor 4 is provided for supplying coolant water via the connecting tubes 5 to 8 to a tube coil group which comprises half tubes 9 to 12 which are welded to the converter shell. These tubes preferably have a semicircular cross section; it is, however, possible to use also other commercial, open sections, such as channel sections, trough sections, semi-elliptical sections and the like. The half tubes 9 to 12 are laid in parallel in horizontal planes, i.e. in planes which are perpendicular to the longitudinal axis of the converter, and they surround the major part of the circumference of the metal shell 1. In order to provide a transition to the next higher tube coil group 9' to 12' slanting half tube pieces 13 to 16 are provided. The tube coil group 9' to 12' is connected with the next higher tube coil group 9" to 12" again by slanting half tube pieces 13' to 16'. The collecting part of the cooling system comprises tubes 17 to 20 which connect the half tubes 9" to 12" of the uppermost tube coil group with the cooling agent collector 21. The current direction of the coolant is indicated by arrows. As may be derived from FIG. 1, the tubes 9 to 12, 9' to 12' and so on, for their adaptation to the contour of the metal shell 1, need be bent only in a single plane which is perpendicular to the converter axis 23. According to the invention, at several places between the individual half tubes of each tube coil group, cross canals 22 are provided which likewise may be formed by half tubes welded to the converter shell 1, so that within one tube coil group the pressure is equalized and the flow of the cooling medium is rendered uniform. It is possible that in the individual tube coil groups different numbers of cross canals 22 are provided which also may be arranged differently around the circumference of the converter shell. For instance, it is suitable to provide more cross canals at the thermally higher stressed places, such as at the discharge side of the converter shell, in order to guarantee the desired equalization of pressure and flow.
According to FIG. 2 three horizontal tube coil groups with half tubes 24 to 27, 24' to 27' and 24" to 27" are provided which surround the total circumference of the metal shell 1 and which are joined to a common, vertically arranged cooling agent distributor 28 and a common cooling agent collector 29. Coolant distributor 28 and coolant collector 29 are formed of differently dimensioned tube parts 30 to 32 which are connected with the individual half tubes of the tube coil groups by connecting tubes 33. The individual half tubes of the tube coil groups are closed at their ends; these ends are denoted with 34. The cross canals between the half tubes of each tube coil group are again denoted with 22.
According to FIG. 3, a tube coil group formed of the half tubes 35 to 38 is connected by tube pieces 39 to 42 with an individual cooling agent distributor 43 and by tube pieces 44 to 47 with a cooling agent collector 48 of its own. The cross canals connecting the half tubes of each tube coil group are again denoted with 22. The tube coil group lying below is formed by the half tubes 49 to 52, which likewise are connected by tube pieces 54 to 57 with a cooling agent distributor 53 and by the tube pieces 58 to 61 with a coolant collector 62 of its own. The coolant distributors 43, 53 and the coolant collectors 48, 62 are spaced around the converter shell by 120°. A third coolant collector and coolant distributor (not shown) are arranged at the back side of the converter and they are connected in the described manner with a third tube coil group, comprising the half tubes 63 to 66.