EP0258929A1

EP0258929A1 - Oxygen steelmaking plant having a sublance installation

Info

Publication number: EP0258929A1
Application number: EP87201570A
Authority: EP
Inventors: Petrus Cornelis Hendrikus Zonneveld
Original assignee: Hoogovens Groep BV
Current assignee: Tata Steel Ijmuiden BV
Priority date: 1986-08-29
Filing date: 1987-08-19
Publication date: 1988-03-09
Also published as: NL8602195A; EP0258929B1; DE3760812D1

Abstract

An oxygen steelmaking plant has a steel converter (4), a hood (5) for the converter, two arms (l7,l8) for carrying oxygen lances (7) pivotable to bring an oxygen lance above the converter, and a sublance installation comprising a sublance (l0), a carriage (9) from which the sublance (l0) is suspended movable to transport the sublance along a path which intersects the pivoting arms (l7,l8) and a pickup station (l9) at which the sublance picks up a sensor to be transported inside the converter to perform a measurement. The hood has a lance entrance hole (6) and a sublance entrance hole (l3). To enable the sublance (10) to opeate fully when the oxygen (7) lance is in operation, the hood (5) has a second sublance entrance hole (l4) and the sublance installation has a second pickup station (20), the first said sublance entrance hole (l3) and the first said pickup station (l9) on the one hand and the second sublance entrance hole (l4) and the second pickup station (20) on the other hand being located on opposite sides of the lance entrance hole (6), and the carriage (9) being arranged to transport the sublance (10) to both said pickup stations (l9,20) and both said sublance entrance holes (l3,l4).

Description

The invention relates to an oxygen steelmaking plant having at least one steel converter, a hood for the converter, two pivoting arms for carrying oxygen lances and a sublance installation which comprises a carriage, a sublance suspended from the carriage and a pick up station for a sensor which is to be transported by the sublance into the converter, the hood having a lance entrance hole and a sublance entrance hole. The invention also relates to a method for operating a sublance installation in such an oxygen steelmaking plant.
Oxygen steelmaking plants of this type are in general use in the iron and steel industry. The molten pig iron is processed in the converter until the required composition of the liquid pig iron bath is achieved. Oxygen is blown into the liquid iron bath from above using an oxygen lance, to burn up certain impurities and raise the temperature of the liquid iron bath. During this blowing an inert gas may be injected through a few bottom bricks of the converter, in order to promote good mixing of the liquid iron bath.
In oxygen blowing there is the problem of monitoring the temperature of the liquid iron bath, together with the percentages of carbon, sulphur and phosphorus in the liquid iron bath. In some oxygen steelmaking plants this is done by interrupting oxygen blowing after a certain time, then tipping the converter, measuring the temperature with a measurement sensor inserted by hand and taking a bath sample which can be analysed. There are metallurgical problems involved in this procedure, while stopping blowing reduces capacity. In addition this measurement procedure reduces the service life of the converter.
In many oxgyen steelmaking plants a sublance installation as described above is used. See for example NL-A-780846l. This makes it possible to carry out the necessary measurements by inserting a sensor at the end of the sublance from above into the converter and into the liquid iron bath. It is then possible to carry out a measurement without interrupting oxygen blowing. A method of exchanging the sensor carried by the sublance at a pick-up station is described in EP-A-ll3653.
It is of very great importance that the measured values are accurately representative of the temperature and percentage of C, as the remaining oxygen blowing time is calculated from these values. An inaccurate measurement will result in the wrong quality of the liquid iron bath after the end of blowing and hence will give a bath composition which is unusable for the desired purpose.
The quality of the measurement is determined by inter alia the time of the measurement. An early measurement is unusable because not all the scrap put in the converter will be completely molten, where the temperature of the liquid iron bath is still below l536°C. In addition a correct prediction of the final composition and final temperature of the liquid iron bath where a long blowing time remains is much more difficult. A somewhat later measurement is the obvious answer, but here there is a limit in the reduction in the quantity of carbon as a result of blowing. As a result of this reduction, the stirring effect of combustion is reduced and as a result the homogeneity of the liquid iron bath falls. The measurement is therefore unreliable.
Not only the time of the measurement, but also the place where the sublance is inserted is very important for a representative measurement. Horizontally the distance between the measurement point and the "hot surface" where the oxygen from the oxygen lance hits the liquid iron bath, must be as great as possible. On the other hand the measurement point should not be too close to the wall of the converter. Vertically the measurement sensor must be placed just below the iron/slag interface in the liquid iron bath. The right immersion depth depends on the size of the converter used.
When constructing a sublance installation the requirements stated above must be taken into account so that unusable measurements are avoided. It is often possible to design a place in the hood of the converter for the insertion of the sublance, which meets the requirements specified. This is more successful where the sublance installation is incorporated in a new oxygen steelmaking plant under construction. In view of the advantages of the use of a sublance, it is desired also to equip existing oxygen steelmaking plants with a similar sublance installation.
During this modernisation of an oxygen steelmaking plant a number of limitations must be taken into account. It must be possible to remove the converter for renovation of its brickwork; and during operation it must be possible to change the oxygen lance. In view of the high costs, no far-reaching changes must be made to the oxygen steelmaking plant.
In particular the arrangement of the pivoting arms by which the oxygen lances are brought into their blowing position can form a problem, where they only leave a little space for the sublance installation. This applies with all the more force where the pivoting arms with the oxygen lances and the sublance installation all have to be housed in the converter bay which may have restricted installation height.
One problem arises where the pivoting arms for the oxygen lances, in the operating position of an oxygen lance, extend from a position near a first wall of the converter bay to a position near an opposite second wall of the converter bay. In this circumstance the sublance cannot be moved from the position of its entrance hole to the pick up station for the sensor and vice versa if the pivoting arm in operation is the one located at the same side of the converter as the pick up station. This can be remedied by designing the sublance installation such that the sublance can be lifted sufficiently, but this necessitates expensive structural provisions in and on the converter bay which must be avoided.
The object of the present invention is to provide a sublance installation which avoids the necessity for expensive additions or changes to an existing oxygen steelmaking plant and by which limitations in movement of the sublance described above are avoided. Thus the desired freedom of operation is made possible. The invention is also applicable to the construction of new oxygen steelmaking plants.
The invention is set out in claim l. By virtue of the invention, irrespective of which pivoting arm is in operation carrying an oxygen lance, the sublance can be moved between a pickup device for a sensor and a sublance entrance hole.
Preferably the first and second sublance entrance holes are located symmetrically with respect to the lance entrance hole. This improves the interchangeability of the sublance measurement via either of the sublance entrance holes, because there is no difference in the position of the two sublance entrance holes with respect to the lance entrance hole. It is also preferable for the pickup stations to be located symmetrically with respect to the converter, which has the advantage that the movement pattern of the sublance is independent of the choice of pickup station and entrance hole, and only the transport direction has to be adapted according to the chosen pickup station or entrance hole.
To facilitate assembly of the converter and dismantlement, it is preferable to locate the first pickup station on a hood carriage which carries the hood and is movable away from the converter.
Where the oxygen steelmaking plant has at least two steel converters, each equipped with hood, pivoting arms and sublance installation as described in claim l, it is preferable, at least from the point of view of cost, to locate a pickup station between each adjacent pair of the converters, this pickup station being used for both converters of the pair.
The invention also relates to a method for operating a sublance installation in an oxygen steelmaking plant in accordance with the invention, as set out in claim 6.
An embodiment of the invention will be described below by way of non-limitative example with reference to the accompanying drawings, in which:-

Fig. l is a partly sectioned side view of a converter bay of an oxygen steelmaking plant, this bay being located midway between the charging bay and the casting bay. The figure shows the converter, the hood, part of an oxygen lance and sublance installation.
Fig. 2 is a view of the converter hood and the entrance holes through the hood and the pickup stations, looking in the direction of arrow P in Fig. l.
Fig. 3 is a top view of the converter bay showing the pivoting arms for the oxygen lances and the carriage of the sublance installation, together with an adjacent converter bay.

Fig. l shows, midway between the casting bay l and the charging bay 2, the converter bay 3 of an oxygen steelmaking plant. The converter 4 is installed in the limited space of the bay 3 and has a hood 5 which is partly shown. The hood 5 is movable away from the converter on a carriage. Located on the line of the axis of the converter is a lance entrance hole 6 in the hood, see Fig. 2. An oxygen lance 7 is shown schematically in Fig. l. Fig. 3 shows that each converter has two pivoting arms l7,l8 pivotable around respective axes l7a,l8a, each of which can carry an oxygen lance at its end remote from the pivoting axis, so as to bring the lance into place above the lance entrance hole 6 of the hood, whereafter the lance is lowered through the hood into the converter. Two pivoting arms l7,l8 are provided so that the lance can be changed without halting production significantly.
The converter 4 also has associated with it a sublance installation, consisting of a carriage 9 which moves on a platform 8 above the converter. A sublance l0 is suspended from the carriage 9. The carriage 9 includes a device ll by which the height of the sublance l0 can be adjusted. The sublance is able to move, under control of the carriage 9, between two pickup stations l9,20 for measurement sensors or other probes which are located approximately symmetrically on each side of the converter beneath the path of movement of the carriage 9. The mechanism by which the sublance picks up a probe or sensor is known and does not need to be described. The hood 5 has two sublance entrance holes l3,l4 located symmetrically with respect to the lance entrance hole 6 in the upper surface of the hood and beneath the path of movement of the carriage 9. After picking up a probe or sensor from one of the pickup stations l9,20, the sublance carries it to above the closer of the two sublance entrance holes l3,l4 and then lowers it through the hole into the converter. After the desired measurement or other operation has been performed in the converter, the sublance then lifts the probe or sensor out of the converter and returns it to the pickup station.
It can be seen from Figs. l and 3 that, when one of these pivoting arms l7,l8 is in position swung across the converter with the sublance 7 operating in the converter, the sublance l0 cannot move freely across the whole width of the converter, since its path of movement intersects the arm l7 or l8. Because, according to the present invention two pickup stations l9,20 and two sublance entrance holes l3,l4 are provided, the sublance is still able to move to one of the pickup stations, being the one on the side of the converter opposite the side from which the operating one of the arms l7,l8 moves. The sublance can then carry a probe or sensor to or from the sublance entrance hole l3 or l4 on the same side as the chosen pickup station. The Fig. 3, righthand side, shows in full lines the arm l7 in the non-operating position swung away from the converter while the arm l8 is in the operating position above the converter. The reverse positions of the arms are shown by the broken lines in Fig. 3.
Fig. 3 also shows that the two adjacent converters 4,22 are associated with a total of three pickup stations l9,20 and 2l. The intermediate pickup station l9 is common to the two converters and is used by the sublances of both converters.

Claims

1. Oxygen steelmaking plant having a steel converter (4), a hood (5) for the converter positionable above the converter, two pivoting arms (l7,l8) for carrying oxygen lances (7) which arms are each pivotable to bring an oxygen lance into position above the converter, and a sublance installation comprising a sublance (l0), a carriage (9) from which the sublance (l0) is suspended and which is movable to transport the sublance along a path which intersects the path of at least one of the pivoting arms (l7,l8) and a pickup station (l9) at which the sublance picks up a sensor which is to be transported by the sublance inside the converter to perform a measurement, wherein the hood has a lance entrance hole (6) for insertion of the oxygen lances into the converter and a sublance entrance hole (l3) for insertion of the sublance into the converter, characterised in that the hood has a second sublance entrance hole (l4) also for insertion of the sublance into the converter and the sublance installation has a second pickup station (20) for pickup of a sensor by the sublance, the first said sublance entrance hole (l3) and the first said pickup station (l9) on the one hand and the second sublance entrance hole (l4) and the second pickup station (20) on the other hand being located on opposite sides of the lance entrance hole (6), and the carriage being arranged to transport the sublance to both said pickup stations (l9,20) and both said sublance entrance holes (l3,l4).

2. Oxygen steelmaking plant according to claim l, wherein the first and second sublance entrance holes (l3,l4) are located symmetrically with respect to the lance entrance hole (6).

3. Oxygen steelmaking plant according to claim l or claim 2, wherein the pickup stations are located symmetrically on opposite sides next to the converter.

4. Oxygen steelmaking plant according to any one of claims l-3, wherein the hood (5) is mounted on a hood carriage, and the first pickup station is located on the hood carriage.

5. Oxygen steelmaking plant according to any one of claims l-4 which comprises at least two steel converters each equipped with hood, pivoting arms and sublance installation as set out in claim l, and wherein between each adjacent pair of the converters a said pickup station is located, which is used for both converters of the pair.

6. Method of operating a sublance installation in an oxygen steelmaking plant in accordance with any one of the preceding claims, wherein (a) the movable carriage of the sublance is placed in a position on a first side selected from the right and left sides of the converter, (b) thereafter an oxygen lance is moved from a rest position on the other of the right and left sides of the converter into the operating position, (c) then the movable carriage is moved at least once between the pickup station located on the said first side of the converter and an operating position of the sublance, which operating position corresponds to the sublance entrance hole which is on the said first side of the converter with respect to the lance entrance hole.