US3531097A - Oxygen lance - Google Patents

Description

M. PAULINA OXYGEN LANCE Sept. 29, 1970 2 Sheets-Sheet :3

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Filed March 24, 1967 A Tram/5V5 United States Patent 3,531,097 OXYGEN LANCE Michael Paulina, Perryopolis, Pa., assignor to Pittsburgh Steel Company, Pittsburgh, Pa., a corporation of Pittsburgh Filed Mar. 24, 1967, Ser. No. 625,740 Int. Cl. C21c 5/32, 5/46 US. Cl. 266-34 2 Claims ABSTRACT OF THE DISCLOSURE In producing steel by that method, scrap and molten iron and fluxes are charged into a tiltable furnace through an opening at its top. A long water-cooled upright lance then is lowered into the furnace until the lower end or nozzle of the lance is near the top of the charge. Substantially pure oxygen, supplied under high pressure to the upper end of the lance, issues from its nozzle and causes great turbulance as an exothermic reaction increases the temperature of the charge in the furnace until all of it is melted and converted into steel. The lance then is with drawn and the furnace is tilted to pour the molten metal from it.

While the lance is in use, molten metal and slag splatter around in the furnace and adhere to the lance. This builds up a coating on the lance that eventually makes it necessary to take the lance out of service and remove the deposit by burning and chipping, which is costly and timeconsuming.

It is among the objects of this invention to provide a vertical oxygen lance, in which the portion that is inserted in the furnace is formed in such a manner that no appreciable amount of metal and slag can build up on it while the lance is in use.

In accordance with this invention, a long vertical oxygen pipe is adapted to be connected at its upper end to a source of oxygen under pressure, and its lower end is connected to a nozzle. This pipe is encircled by a concentric tube, the lower end of which is joined with the nozzle. A long length of the lance is adapted to be inserted down into a steel-making vessel forming a basic oxygen furnace. The tube, adjacent the upper end of the portion in the furnace, is enlarged relative to the tube above and tapers gradually downwardly therefrom to a point adjacent the nozzle. The taper is at least inch per lineal foot. As a result, slag and metal that become deposited on the lance during the blow periodically fall away from it and into the furnace.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which FIG. 1 is a fragmentary side view, partly in section, of

ported at its upper end by a car 3 that runs on vertical tracks 4 and that can be moved up and down by a cable 5 from a hoist 6 operated in any suitable manner. The lance extends down through an exhaust hood 7 directly above the charging opening in the furnace. The furnace is supported in conventional manner so that it can be tilted for charging and discharging while the lance is raised.

As shown in FIG. 3, the outer wall of the lance is made from a tube 8 which, for the major portion of its length, is in the neigborhood of a foot in diameter. The one shown is actually 10% inches in diameter above the furnace. Joined to the lower end of this tube there is a nozzle 9 provided with one or more downwardly directed passages 10. The diameter of the nozzle is substantially the same as the tube above the furnace. Disposed inside the tube concentrically therewith is an oxygen pipe 12, the lower end of which is joined to the nozzle around the passages therein. The upper end of this pipe extends above the sealed end of tube 8 and is connected with a high pressure oxygen hose 13 (FIG. 1) that delivers oxygen to the pipe from a suitable source. The pipe is spaced from the inside of the tube so that a water jacket can be formed around the pipe in order to cool the tube. To provide a path for circulating the cooling water in the tube, another pipe 14 encircles the oxygen pipe and is spaced from it and the outer tube. The spaces at opposite sides of this second pipe are closed at its top but are connected down in the nozzle to form concentric vertical passages connected at their lower ends. At the upper end of the lance the passage between the two pipes is connected with a water supply hose 15, while the passage between the outer pipe and the tube is connected with a Water discharge hose 16. Consequently, water is circulated down inside pipe 14 and then up in contact with the inner surface of the tube.

The apparatus described thus far is conventional.

It is a feature of this invention that the lance will periodically shed any coating of molten metal that splatters onto it inside the furnace during the blow. To cause this shedding, the portion of the lance in the furnace is tapered downwardly. Thus, near the top of the furnace the diameter of the lance tube 8 is enlarged, such as by flaring the tube downwardly for a short distance, for example, about two feet. For a lance of the dimensions shown, the diameter of the lower end of the flare is about three inches greater than the straight tube above it. From this point down to the nozzle the tube is tapered. Due to the length of the portion of the lance inside the furnace, the taper is very gradual. It should be at least M inch per foot to obtain the desired result but, due to factors that limit the size of the lance at the upper end of the tapered portion, the taper is not likely to exceed 43 inch per foot.

The splattering slag and metal that build up a coating on the tapered portion of the lance will, because of the weight of the deposit, release from the lance periodically and slide down it into the furnace, thereby making it unnecessary to burn or chip away the deposit. Whereas, friction alone can prevent such a coating from sliding down a cylindrical lance, the slightest amount of downward movement of the deposited material on the tapered lance will eliminate friction and allow the deposit to fall away. If a coating is deposited on the lance while it is retracted, the deposit will cool and shrink. During the next blowing cycle, however, the heat will expand the coating, causing it to drop ofi. If too thick a deposit appears to be building up on the lance without releasing itself, removal can be accelerated by striking the lance a few heavy blows to cause it to vibrate and shed the deposit.

With a lance such as described herein, the expense heretofore resulting from having to periodically take a cylindrical lance out of service to chip or burn the accumulated deposits from it, no longer is incurred.

According to the provisions of the patent statutes, I

3 have explained the principle of my invention and have illustrated and described What I now consider to represent its best embodiment.

I claim:

1. An oxygen lance for a basic oxygen furnace, comprising a long rigid vertical tube having a lower portion of predetermined length adapted to be inserted down into such a furnace, a nozzle joined to the lower end of the tube and provided with a passage for oxygen, an oxygen pipe rigidly mounted inside the tube concentric therewith and spaced therefrom to form an annular cooling chamber which surrounds the pipe and extends substantially through the entire length of the nozzle, the lower end of the oxygen pipe being connected with the upper end of said nozzle passage and the upper end of the pipe being adapted to be connected to a source of oxygen under pressure, and a water pipe encircling the oxygen pipe and spaced therefrom and from said tube to divide said cooling chamber into concentric vertical water passages communicating within the nozzle, the tube adjacent the upper end of said lower portion being enlarged relative to the References Cited UNITED STATES PATENTS 3,239,205 3/1966 MetZ 266 4 X 3,338,570 8/1967 Zimmer 26634 X FOREIGN PATENTS 60,387 4/1912 Switzerland. 1,212,695 10/1959 France.

I. SPENC-ER OVERHOLSER, Primary Examiner R. S. ANNEAR, Assistant Examiner

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