US3708159A

US3708159A - Method and apparatus for locating the surface of a liquid metal bath

Info

Publication number: US3708159A
Application number: US00110496A
Authority: US
Inventors: Bray H De
Original assignee: Steel Corp
Current assignee: United States Steel Corp
Priority date: 1971-01-28
Filing date: 1971-01-28
Publication date: 1973-01-02
Anticipated expiration: 1990-01-02

Abstract

A method and apparatus for locating the surface of a liquid metal bath, particularly intended for use with a basic oxygen steelmaking furnace or an open hearth in which oxygen is used. Oxygen is introduced to such furnaces with a lance which is lowered by a cable and drum to start a blowing operation. The invention measures the apparent weight of the lance as it is lowered. When the lance first contacts the bath, the bath exerts a momentary buoyant effect thereon. The resulting change in the apparent weight of the lance is detected. A memory device remembers the position of the lance when it makes contact, and this position is displayed on a recorder.

Description

United States Patent 1 De Bray I. I

[ 51 Jan. 2, 1973 541 METHOD AND APPARATUS FOR LOCATING THE SURFACE OF A v LIQUID METAL BATH A [75] Inventor: Harold W. De Bray, Monroeville Borough, Pa.

[73] Assignee: United States Steel Corporation,

Pittsburgh, Pa.

22 Filed: Jan. 28, 1971 [21] Appl. N0.: 110,496

[52} U.S.Clt ..2 66/34LM, 75/60 [51] Int. Cl ..C2lc 7/00 [58] Field of Search ..75/59, 60; 266/34 L, 34 LM, 266/35; 33/1266, 126.7 A

[56] References Cited UNITED STATES PATENTS 3,540,879 11/1970 Carlson ....75/60 3,140,609

7/1964 Mayes ..33/l26.6

3,128,557 4/1964 Childs 33/1266 3,372,023 3/1968 Kraineretal ..75/60 Primary Examiner-Gerald A. Dost Attorney-Walter P. Wood ABSTRACT A method and apparatus for locating the surface of a liquid metal bath, particularly intended for use with a basic oxygen steelmaking furnace or an open hearth in which oxygen is used. Oxygen is introduced to such furnaces with a lance which is lowered by a cable and drum to start a blowing operation. The invention measures the apparent weight of the lance as it is lowered. When the lance first contacts the bath, the bath exerts a momentary buoyant effect thereon. The resulting change in the apparent weight of the lance is detected. A memory device remembers the position of the lance when it makes contact, and this position is displayed on a recorder.

10 Claims, 4 Drawing Figures POSITION TRANSMITTER COMPUTER ZPEN RECORDER ,PATENTEDJAK 2197s SHEET 1 UF 2 POSITION TRANSMITTER RECORDER LOGIC COMPUTER Z PEN RECORDER 'nwewran 0 H. DE BRA) a/HJZ his Alforna'y I'M R0 AIENTEDM 191's 3.708.159 A SHEET 2 OF 2 22 F T r hrs-L 3 RED LINE EEW L/IVE INVENTOR HAROLD m 05 any [MM Z v his Alla/00y METHOD AND APPARATUS FGR LOCATING TI-IE water-cooled lances which extend into the furnace from above. Conventionally the lance is suspended from a hoist, which at the start of a blowing operation lowers the lance into the furnace. It is important that the operator position the lance tip in proper relation to the bath surface. In an oxygen furnace the lance tip commonly is positioned several inches above the bath surface, while in an open hearth it is usually positioned at the surface or a little below. An improperly positioned lance not only leads to waste of oxygen and a less efficient steelmaking process, but may contribute to atmospheric pollution. The operator has difficulty in determining the exact location of the bath surface, which is wholly obscured in an oxygen furnace and extremely hard to observe in an open hearth.

An object of my invention is to provide an improved method and apparatus for locating the surface of a bath, to which gas is introduced through a lance, wherein the criterion for locating the surface is the momentary loss of weight in the lance as the lance contacts the bath.

A further object is to provide a method and apparatus for locating the bath surface in which I continuously measure the distance the lance travels as it is introduced to a vessel and transfer this measurement of position to memory at the exact time that a momentary V The lance is alsoequipped with a safety chain 19 which I supports it with the tip out of contact with the furnace and the pen of which continuously traces a line 22' representative of the weight on a chart 23. In actual practice I may dispense with this recorder, but I have shown it to facilitate the explanation of my invention.

FIG. 2 illustrates a typical chart 23. obtained with recorder21. The chart travels downwardly in the recorder; hence the lower end of line 22 represents the weight when the operator begins to lower the lance. Whenever the weight drops or increases, the line moves to the left or right respectively. The first segment 22a of the line is vertical except for minor disturbances. When the lance tip first contacts the metal M,the metal exerts a buoyant effect on the lance and there is a sudden drop in its apparent weight. This weight is only momenweight lossis detected. The output of the memory is FIG. I is adiagrammatic view of a basic oxygen steelmaking furnace and lance equipped with my apparatus for locating the bath surface in the furnace;

FIG. 2 is a recorder plot of the lance weight as the lance is lowered into a furnace as shown in FIG. 1;

FIG. 3 is a recorder plot obtained with my preferred apparatus embodying a computer or special purpose logic system for detecting momentary weight loss in the lance; and I FIG. 4 is a block diagram illustrating my preferred arrangement of modules in the computer or logic system.

FIG. 1 shows diagrammatically a conventional basic oxygen furnace 10, which contains a bath of liquid ferrous metal M and an overlying slag layer 8. The furnace is equipped with the usual water-cooled lance 12 for introducing oxygento the metal, and hood 13 for collecting off-gases. The lance is suspended from a cable 14, which runs over a sheave l5 and winds on a drum 16. A reversible electric motor 17 drivesthe drum in either. direction for lowering or raising the lance, An operator controls the motor through a push-button switch 18.

tary, as oxygen discharging from the lance blows the metal aside, as indicated at 24 in FIG. I. This momen-- tary drop shows up as a spike 22b in line 22. If the operator continues to lower the lance until the cable 14 is fully unwound from drum 16, the safety chain 19 supports the lance. This shows up as a straight vertical segment 220 near the left edge of the chart, indicative. of a negligible voltage signal from the load cell 20. When the operator raises the lance to its proper position for blowing, the line again becomes essentially vertical, as indicated at 22d.

the operator observes how much cable 14 has been unwound from drum 16 when the recorder pen traces the spike 22b, he knows the exact location of the bath surface. He can then position the lance 12 any desired distance above or below this surface. However, it would be extremely difficult for an operator to make an accurate observation directly, and my apparatus preferably includes a logic computer 28 to facilitate making this observation.-

I mechanically connect a position-transmitter 29 to the cable drum 16. The transmitter developes a voltage signal of a magnitude proportional to the position of rotation of thedrum and-hence of the lance position. In the illustrated circuit, this signal is'at its maximum value (e .g. 10 volts) when cable 14 is fully. wound on the drum and zero when lance 12 is at its extreme limit of travel in furnace 10, although I could reverse this relation. Voltage signals from both the load cell 20 and the position-transmitter 29 go to the computer 28. The voltage signal from the position-transmitter also goes to a two-pen recorder 30, one pen of which traces a line 31 (green line") representative of the lance position on a chart 32. As the lance 12 is lowered into the furnace 10, the computer 28detect's the weight drop when the tip contacts the metal and remembers this position. The otherv pen of recorder 30 traces a line 33(red line) which jogs when the computer transmits a signal I v to the recorder that the lance tip has madecontact.

two-pen downwardly in therecor'der, and the lower ends of both

lines

31 and 33 represent conditions before the operator begins to lower the lance l2. Whenever the lance moves downwardly or upwardly, the green line moves .to the left or right respectively. The first segment 31a of the green line is vertical and near the right edge of the chart. The green pen traces this segment while the lance is stationary before the cable starts to unwind. The next segment 31b slopes upwardly toward the left and is traced as the lance moves downwardly. The first segment 33a of the red line 33 is vertical and near the left edge of the chart. The red pen traces this segment before the computer signals that the lance tip has made contact. The contact signal shows up as a jog 33b toward the right in the red line. Thereafter the red line continues vertically upward, as indicated at 33c. The position of the green line when the jog 33b occurs locates the bath surface. Normally the operator discontinues lowering the lance once he observes the jog and raises it away from the bath surface, as indicated by segment 31c of the green line. When the lance is positioned' properly for blowing, the operator stops the lance as indicated by segment 31d.

FIG. 4 shows in block diagram the preferred arrangement of my electric circuit, including the essential modules of my computer 28. The voltage signal from the load cell goes through anamplifier 36 and thence to relays 37 and 38, and to a differentiating module 39 of the computer. I connect the output side of module 39 to another relay 40. The voltage signal from the position-transmitter 29 goes through an amplifier 43 and thence to a relay 44, to a track-andhold" module 45 of the computer, and to the two-pen recorder 30. l connectthe track-and-hold" module to a voltage source through normally closed contacts 370 and 38a and normally open contacts 40a and 44a of .the respective relays, and through a one-shot" 46. l connect the output side of module 45 to the two-pen recorder 30.

I set relay 37 so that it is energized whenever the signal from the load cell 20 indicates a weight below a predetermined maximum, and relay 38 sothat it is energized whenever the signal from the load cell in-' dicates a weight above a predetermined minimum. For

' example, if the lance weighs 600 pounds, I may set the level of course is known. Thus the weight must be within a predetermined range to maintain contacts 37a and 380 closed and the lance must reach a predetermined position to close contact 440. Unless these contacts are all closed, the computer 28 does not transmit a signal to the two-pen recorder 30. ln this manner I prevent false observations from appearing as a signal that the lance tip has contacted the bath.

The differentiating module 39 continuously determines AW/Ar (weight with respect to time), but ignores the minor disturbances such as take place in segment 220 on chart 23 (FIG. 2). As long as the weight is essentially constant, this module produces no signal. When the weight drops sharply as the lance tip reaches the bath surface, the sudden change induces the module to transmit a measurable signal which corresponds with spike 2212. This signal energizes relay 40 whereupon contact 400 closes. The one-shot" 46 transmits a standardized pulse to the "track-an'd-hold" memory module 45, provided contacts 37a, 38a and 44a are closed. Module 45 now stores in memory and transmits to the two-pen recorder 30 the signal which.

produces the jog 33b in the red line 33.

l have not describedin detail the various components I use in my apparatus, since per se they are known commercially available items. One example of a suitable load cell 20 is available from Revere Corporation of America, a subsidiary of Neptune Meter Company, Wallingford, Connecticut, under the designation "USPl-S-A. One example of a suitable recorder 21 (if included) is available from Esterline Corporation, lndianapolis, Indiana, under the designation Esterline Angus. One example of a suitable position-transmitter 29 is available from Helipot Division of Beckman lnstru- 'ments, Fullerton, California, under the designation Helipot, Model A RSK 1.25. One example of a suitable two-pen recorder 30 is available from Consolidated Electrodynamics, a subsidiary of Bell and Howell, Bridgeport, Connecticut, under the designation l 8- 300 Series Recorder. One Example of a module suitable for use both as a differentiating module 39 and asa track-and-hoid" module 45 is available from Control; Products Division, Bell and Howell, under the designation 19-407 Dynamic Response Module". One example of a suitable one-shot" is available from the lastname source under the designation 19-507".

From the foregoing description it is seen that my invention'affords a simple method and readily constructed apparatus for positively locating the surface of a liquid metal bath in a vessel where visibility is wholly or partially obscured. As applied to steelmaking furnaces, the invention enables as oxygen lance to be positionedat a precise distance with respect to a bath surface. Thusthe invention not only promotes efficiency, but assists in overcoming atmospheric pollution.

v lclairn:

1. In the operation of a process wherein a gas is introduced through a lance to a liquid bath, the lance is lowered from above into the vessel which contains said bath, and when the lance initially contacts the bath, the buoyant effect of the bath produces a drop in the ap parent weight of the lance, which drop is only momentary as gas from the lance blows the liquid of the bath 1 aside, an improved method of locating the bath surface comprising continuously measuring the distance through which the lance is lowered, continuously measuring the apparent weightof the lance as it is lowered,

2. An operation as defined in claim 1 in which said bath is ferrous metal and the gas is oxygen.

3. An'operation as defined in claim 1 in which the lance position is continuously recorded and the ap parent weight drop of the lance is recorded on the recording of the lance position.

I 4. A method as defined in claim 3 in which the weight drop is measured through a computer;

5. The combination, with a vessel for containing a liquid bath, a lance for introducing gas to said bath,- and means for suspending said lance and lowering it into said vessel or raising it therefrom, whereby the buoyant effect of said bath produces a drop in the apparent weight of said lance when the lance initially contacts the bath, which drop is only momentary as gas from the lance blows the liquid of the bath aside, of an apparatus for locating the bath surface, said apparatus comprising means connected with said lance-suspending means for measuring the apparent weight of said lance as it is lowered into said vessel, means connected with said lance-suspended means for measuring the distance said lance, and said firstmamed measuring means includes a 1 load cell connected with said cable.

7. A combination as defined in claim 5 in which said suspending means includes a motor-driven drum and a cable winding on said drum and connected to said lance, and said second-named measuring means includes a position-transmitter connected with said drum.

8. A combination as defined in claim 5 in which the means for determining the distance the lance has traveled when its weight drops includes a computer connected with said first-named measuring means for transmitting a signal that a'drop in weight has occurred,

and a recorder connected to said second-named mea-' suring means and to said computer.

9. A combination as defined in claim 8 in which said computer includes means for preventing transmissionof signals unless the lance weight is within a predetermined range and the lance position is within a predetermined distance of the bath surface.

10. A combination as defined in claim 5 in whichsaid suspending means includes a motor-driven drum and a cable winding on said drum and connected with said lance, said first-named measuring means includes a load cell connected with said cable, said second-named measuring means includes a position-transmitter connected with said drum, and means for determining the distance the lance has traveled when its weight drops includes a computer connected with said load cell and Ya recorder connected with said position-transmitter and with said computer.

Claims

1. In the operation of a process wherein a gas is introduced through a lance to a liquid bath, the lance is lowered from above into the vessel which contains said bath, and when the lance initially contacts the bath, the buoyant effect of the bath produces a drop in the apparent weight of the lance, which drop is only momentary as gas from the lance blows the liquid of the bath aside, an improved method of locating the bath surface comprising continuously measuring the distance through which the lance is lowered, continuously measuring the apparent weight of the lance as it is lowered, detecting the momentary drop in the apparent weight, and recording the lance position at the point at which said drop occurs.

3. An operation as defined in claim 1 in which the lance position is continuously recorded and the apparent weight drop of the lance is recorded on the recording of the lance position.

4. A method as defined in claim 3 in which the weight drop is measured through a computer.

5. The combination, with a vessel for containing a liquid bath, a lance for introducing gas to said bath, and means for suspending said lance and lowering it into said vessel or raising it therefrom, whereby the buoyant effect of said bath produces a drop in the apparent weight of said lance when the lance initially contacts the bath, which drop is only momentary as gas from the lance blows the liquid of the bath aside, of an apparatus for locating the bath surface, said apparatus comprising means connected with said lance-suspending means for measuring the apparent weight of said lance as it is lowered into said vessel, means connected with said lance-suspended means for measuring the distance said lance travels as it is lowered into said vessel, and means connected with tHe two measuring means for detecting the momentary drop in apparent weight and determining the distance said lance has traveled when said drop occurs.

6. A combination as defined in claim 5 in which said suspending means includes a motor-driven drum and a cable winding on said drum and connected to said lance, and said first-named measuring means includes a load cell connected with said cable.

8. A combination as defined in claim 5 in which the means for determining the distance the lance has traveled when its weight drops includes a computer connected with said first-named measuring means for transmitting a signal that a drop in weight has occurred, and a recorder connected to said second-named measuring means and to said computer.

9. A combination as defined in claim 8 in which said computer includes means for preventing transmission of signals unless the lance weight is within a predetermined range and the lance position is within a predetermined distance of the bath surface.

10. A combination as defined in claim 5 in which said suspending means includes a motor-driven drum and a cable winding on said drum and connected with said lance, said first-named measuring means includes a load cell connected with said cable, said second-named measuring means includes a position-transmitter connected with said drum, and means for determining the distance the lance has traveled when its weight drops includes a computer connected with said load cell and a recorder connected with said position-transmitter and with said computer.