US3458134A - Lance structure for refining metals by oxygen blast - Google Patents

Description

July 29, 1969 TERUO SHIMOTSUMA ET AL 3,458,134

LANCE STRUCTURE FOR REVINING METALS BY OXYGEN BLAST 2 Sheets-Sheet 1 Filed Feb. 23, 1966 FIEL4 r//////////// Al.. M

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LANCE STRUCTURE FOR REFINING METALS BY OXYGEN BLAST Filed Feb. 23, 1966 2 Shets-Sheet z F1515 FILER 6 Angle of Haring 01 Nozzle Opening (degrees) INVENTOR 754200 Sly 4407:0404 KHZHO smw M4 AM/m1 m/vwm BY United States Patent Office 3,458,134 Patented July 29, 1969 3,458,134 LANCE STRUCTURE FOR REFINING METALS BY OXYGEN BLAST Teruo Shimotsuma, Kazuo Sano, and Takaaki Kimura,

Kawasakishi, Japan, assignors to Nippon Kokan Kabushiki Kaisha, Tokyo, Japan Filed Feb. 23, 1966, Ser. No. 529,479 Claims priority, application Japan, Feb. 24, 1965, 40/ 10,161 Int. Cl. B05b 1/14, 3/02 U.S. Cl. 239--132.3 8 Claims ABSTRACT OF THE DISCLOSURE A lance structure for refining metals by oxygen blast. The lance structure includes an elongated lance having a longitudinal axis along which the lance is formed with an interior bore through which oxygen is supplied. The lance terminates at its bottom end in a tip formed with only two openings which are respectively situated symmetrically with respect to and on opposite sides of the longitudinal axis of the lance, these openings communicating with the axial bore of the lance, so that the oxygen is supplied through the single pair of openings situated at the tip of the lance.

This invention relates to a lance structure for refining metals by oxygen blast, more particularly to an improvement of a lance structure used in refining metals wherein metals are refined at high efficiency by utilizing two opening type nozzles instead of oxygen nozzles of the single or multiple opening type which have been used in the blast refining of metals and has its principal object to increase the efiiciency of metal refining and to decrease the quantity of molten metal splashed from furnaces.

Heretofore, single opening type nozzles have been used in most of blast refining processes carried out in the LD converter and the like. Recently, however, for the purpose of decreasing the time for blast refining and for decreasing splash as well as flooding of the furnaces content, or according to the tendency of using blast refining furnaces of increasing large capacity, use of multiple opening type nozzles has become common. Good results were generally obtained in the early stage of utilizing these multiple opening type nozzles, especially of three opening type, for blast refining of metals. However, notwithstanding the utilization of such multiple opening nozzles variation in the condition of blast refining caused by the increasing requirement for further increasing the eificiency of refining, and by the variation in the ratio of mixing molten cast iron in steel manufacturing process have resulted in various problems such as increase in the iron content in slag, inequality of the results of blast refining, decrease in the yield of high quality products and the like in addition to the problems of splashing and flooding of the furnace content during the process of blast refining.

Prior multiple opening type nozzles are provided with at least three openings and so far as the applicant is aware, nozzles having two openings have not yet been utilized. This is because with nozzles having two openings the merit of blast refining is greatly decreased owing to the fact that the area of the surface of molten metal to which oxygen is effectively blasted is limited to a particular diametrical portion and in the substantial area in the direction perpendicular to said diameter, the blast of oxygen is not effective. Whereas, with a nozzle having three or more nozzles the area of dead surface is advantageously decreased. However, even with nozzles having three or more openings it is not always possible to entirely eliminate such dead surface so that it is necessary to effectively use such dead surface in order to further increase the efiiciency of refining.

We have succeeded to perfectly eliminate the dead surface over the entire surface area of the molten metal whereby to provide uniform blast of oxygen throughout the surface of the molten metal to increase the efiiciency of the blast refining and to decrease splashing and flooding of the molten metal out of the furnace. According to the novel method nozzles of two opening types which have not yet been used in the past are used and blast refining is accomplished while the nozzles are rotated about their longitudinal axis.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which we regard as our invention, it is believed that th invention will be better understood from the following description taken in connection with the accompanying drawings in which:

FIG. 1 shows a longitudinal cross section of a portion of an oxygen nozzle for refining metals utilized in carrying out the method of this invention;

FIG. 2 shows a cross sectional view taken along the line II--H in FIG. 1;

FIG. 3 is cross sectional view, similar to FIG. 2, of a modified nozzle;

FIG. 4 is a diagrammatic side view of a lance rotating device associated with the nozzle;

FIG. 5 shows a longitudinal section of the lance rotating device shown in FIG. 4;

FIG. 6 is a graph to explain the relation between the rotation speed of the nozzle and the loss of metal by splash and FIG. 7 shows curves to explain the relation between the angle of flare of the opening of various nozzles and the loss of metal by splash.

The process of this invention will be described in detail together with some experiments made by us. In addition to nozzles having one opening, three openings and four openings respectively, nozzles provided with two openings as shown in FIGS. 1 and 2 were prepared for experimental use in a tons converter for manufacturing steel. The lance 3 shown in FIGS. 1 and 2 comprises an inner water packet 1, an outer water jacket 2 concentric therewith and two substantially longitudinal nozzle openings 4 at the tip of the nozzle adapted to eject oxygen which is supplied through the lance 3 to the blast refining furnace, not shown. The total area of the throats 5 of the nozzle openings was designed to be the sam as that of conventional nozzles provided with one, three or four openings, and the difierence in the pressure losses of respective nozzle openings was compensated by the dynamic pressure distribution due to the height of the lanc thus equalizing the energy on the surface of the molten steel. These nozzles were used independently for the blast refining of steel without rotation as has been the prior practice and the time of blast refining required for preparing steels of substantially the same component, and the loss of molten steel by splash (weight percent based on the weight of molten steel) were measured and the results are shown in th Table 1 below.

TABLE 1.-COMPARISON OF RESULTS OF PRIOR ART METHODS As can be clearly noted from Table 1, with two opening nozzle the splash loss is far smaller than any other of the same quality were measured in each case and the results are shown in Table 2 below.

TABLE 2.-COUPARTSON OF THE RESULTS OBTAINED BY THE METHODS OF THIS INVENTION AND OF THE PRIOR ART nozzles. Thus the splash loss when using two opening type nozzle is less than /3 of that of single opening type nozzle, less than /2 of that of three opening type nozzle and less than of that of four opening type nozzle. However, since the contact area between the surface of the molten metal and ejected oxygen is small, the required time of blast refining is the maximum.

Accordingly, we have made experiments for eliminating or minimizing the dead contact area between the bath surface and oxygen by carrying out the blast refining process with nozzles having two openings and rotated about their longitudinal axis in order to decreas the time required for blast refining while preserving their advantage of low splash loss.

An example of design of the roating device for the lance nozzle utilized in these experiments is schematically shown in FIGS. 4 and 5. As shown by these figures, an oxygen supply pipe 12 is inserted from upper side into a cylindrical casing 11 of the roating device and is suitably connected thereto. The enlarged upper end of a lance pipe 15 provided with an inner jacket 13 and an outer jacket 14 for circulating cooling water is hermetically connected to the inner end of the fixed oxygen supply pipe 12 through a suitable heremetic packing ring 16a to be rotatable about its axis. Beneath the joint between the lance pipe 15 and the fixed oxygen supply pipe 12, there are interposed vertically spaced packing rings 16b and 160 between the upper portion of the water cooled inner jacket 13 and a stationary inner cylindrical member 1711 within the casing 11. A cooling water inlet pipe 18 is connected to th cylindrical member 17a between the upper and lower packing rings 16b and 16c to introduce the cooling water in the rotary inner water jacket 13 through a number of perforations 19 (only one of them is shown in the drawing) near the upper end of the inner jacket 13. Similarly, a pair of vertically spaced packing rings 16d and 16:; are interposed between the upper portion of the outer water jacket 14 which may be integral with the lance pipe 15 and the inner water jacket 13 and a second cylindrical member 17b located within the easing 11, and a cooling water outlet pipe 20 is connected to the cylindrical member 17b between these packing rings 16d and 16a to discharge the cooling water which has circulated through and cooled the inner and outer jackets 13 and 14 through perforations 21 provided near the upper end of the latter. Beneath the botton of the casing there is fixed a disc 22 on the outer wall of the outer water jacket 14, which is provided with a gear 23 on the lower surface thereof which is arranged to be driven by an electric motor 25 through a suitable reduction gear 24. Thus, while the nozzle is rotated about its longitudinal axis by the motor and cooled by the circulating cooling water, oxygen is ejected from the tip of the nozzle.

A number of tests for preparing low carbon rimmed steel were made by using nozzles respectively provided with one opening, two openings and three openings and under the same conditions as mentioned above. In one run the nozzles are held fixed While in the other run nozzles were rotated (at a speed of 4 r.p.1n.) and the blast refining time and splash loss required to obtain steels From this table it can be readily noted that, with nozzle having two openings, rotation thereof does not result in any increase in the splash loss and the percent splash is almost negligibly small when compared with thos of nozzles provided with a single opening or three openings. Yet the time required for effecting blast refining was reduced by 2.5 minutes when compared with the case wherein a fixed nozzl having two nozzles was used and showed the minimum value. As shown in Table 2 a rotary nozzle with three openings was also tested without remarkable improvement.

The cross-sectional configuration of openings of the two opening type nozzle is generally circular as shown in FIG. 2, but a nozzle having two semicircular Openings 4, as shown in FIG. 3 showed a slightly better whirling action than the nozzle shown in FIG. 2.

In the above described experiments it was found that the percent splash loss varied dependent upon the number of revolutions of the two opening type nozzle. The curve of FIG. 6 illustrates the relation between the number of revolutions of the nozzle and the amount of splash loss in percent, which shows that the minimum splash loss appears at a speed of 14 rpm.

Further the amount of splash loss varies dependent upon the angle of fiaring of the openings of multiple opening type nozzle. FIG. 7 shows a set of curves illustrating the relation between splash loss in percent and the angle of flaring of the nozzle opening for various nozzles provided with one, two, three and four openings, respectively. These curves show that in each nozzle the splash loss is reduced at angles from 3 to 6 degrees and above 10 degrees. It is to be understood that these angles are the angles between the vertical axis normal to the surface of molten steel and the inclined side surfaces of the conical exits at the discharge ends of the openings.

As has been fully described, according to this invention wherein a nozzle provided with two openings for passing oxygen are rotated the splash loss of molten metal to be blast refined and the time required for blast refining are substantially reduced. Thus the reduction in the time required for blast refining not only results in the improvement of the operating efliciency but also in the saving of oxygen consumption (in fact, the oxygen efiiciency was improved by 2 to 3% over prior methods). Moreover, it was found that iron content in slag at the end of the refining operation was reduced by more than two percent than prior methods thus resulting in the corresponding increase in the yield of the product.

The novel method can be applied for converters for manufacturing steel wherein pure oxygen is blasted upwardly as well as for refining similar metals by oxygen blast.

What is claimed is:

1. A lance assembly for refining metal by oxygen blast, comprising an elongated lance body having a longitudinal axis and formed with an interior oxygen-supply bore extending along said longitudinal axis and terminating short of a bottom nozzle tip of said lance body, said body being formed at said nozzle tip thereof with only two nozzle openings passing through said nozzle tip of said body and communicating with said bore so that oxygen will flow through said nozzle openings from said bore out of said lance body, said nozzle openings respectively terminating in outer ends respectively spaced from said axis, and rotating means operatively connected to said lance body for rotating the latter about its longitudinal axis.

2. The combination of claim 1 and wherein said nozzle openings are symmetrically situated with respect to said longitudinal axis at diametrically opposed sides thereof, respectively.

3. The combination of claim 2 and wherein said openings are of circular cross section.

4. The combination of claim 2 and wherein said openings are of semi-circular cross section.

5. The combination of claim 4 and wherein said openings of semi-circular cross section respectively have flat surfaces at those parts of said openings which are closest to said longitudinal axis.

6. The combination of claim 2 and wherein said openings respectively extend along axes which diverge from said longitudinal axis so that said openings flare outwardly.

7. The combination of claim 6 and wherein the angle 8. The combination of claim 6 and wherein the angle formed by the axis of each opening with said longitudinal axis is greater than 10".

References Cited UNITED STATES PATENTS 3,043,577 7/1962 Berry 26634 3,065,916 11/1962 Kurzinski 239l32.3 3,170,016 2/ 1965 Grace 26634 2,807,506 9/ 1957 Gehring -60 3,212,882 10/1965 Garfinkle 75-60 3,323,906 6/1967 Miltenberger et a1. 75--60 X FOREIGN PATENTS 872,368 7/ 1961 Great Britain. 700,224 11/ 1953 Great Britain.

EVERETT W. KIRBY, Primary Examiner US. Cl. X.R. 239-246, 601

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