US3640119A

US3640119A - Carbon content measurement in a basic oxygen furnace

Info

Publication number: US3640119A
Application number: US34936A
Authority: US
Inventors: Bernard Blum; John W Schwartzenberg
Original assignee: Leeds and Northrup Co
Current assignee: Leeds and Northrup Co
Priority date: 1966-02-14
Filing date: 1970-05-06
Publication date: 1972-02-08
Anticipated expiration: 1989-02-08

Abstract

A system for controlling the operation of a basic oxygen furnace in response to measurements of the carbon loss through the exhaust gases and the oxygen flow rate to the lance. The carbon content of the bath as determined from the carbon loss rate and the measured oxygen flow rate as well as the calculated bath temperature provide a basis for controlling the furnace. Oxygen flow is maintained constant until silicon is removed and is then increased at a steady maximum rate. Simultaneously, the lance is brought down as slag buildup occurs. Oxygen flow is modified by a positive feedback signal responsive to carbon loss rate and is limited when carbon loss rate changes rapidly. Also, lance height is modified in response to rate of change of oxygen flow. The oxygen is then shut off and the lance raised when the carbon content of the bath, as determined from carbon loss rate divided by oxygen flow, is at a desired value and the temperature of the bath is also at a desired value.

Description

United States Patent [151 3,640,119

Blnm et al. 5] Feb. 8, 1972 [54] CARBON CONTENT MEASUREMENT 3,463,631 8/1969 Vagssiere et al ..75/60 IN A BASIC OXYGEN FURNACE Bernard Blum, Buffalo, N.Y.; John W. Schwartzenberg, Maple Glen, Pa.

Leeds & Northrup Company, Philadelphia, Pa.

Filed: May 6, 1970 Appl. No.: 34,936

Inventors:

Assignee:

Related US. Application Data Division of Ser. No. 534,617, Feb. 14, 1966, Pat. No. 3,528,800, which is a continuation-in-part of Ser. No. 479,867, Aug. 16, 1965, abandoned.

US. Cl ..73/23, 23/255 E, 75/60,

References Cited UNITED STATES PATENTS 7/1967 Onta et al. ..73/23 X Primary Examiner-Richard C. Queisser Assistant Examiner-C. E. Snee,1ll Attamey william G. Miller, Jr. and Raymond F. MacKay 1 1 ABSTRACT A system for controlling the operation of a basic oxygen furnace in response to measurements of the carbon loss through the exhaust gases and the oxygen flow rate to the lance. The carbon content of the bath as determined from the carbon loss rate and the measured oxygen flow rate as well as the calculated bath temperature provide a basis for controlling the furnace. Oxygen flow is maintained constant until silicon is removed and is then increased at a steady maximum rate. Simultaneously, the lance is brought down as slag buildup occurs. Oxygen flow is modified by a positive feedback signal responsive to carbon loss rate and is limited when carbon loss rate changes rapidlyv Also, lance height is modified in response to rate of change of oxygen flow. The oxygen is then shut off and the lance raised when the carbon content of the bath, as detennined from carbon loss rate divided by oxygen flow, is at a desired value and the temperature of the bath is also at a desired value.

5 Claims, 4 Drawing Figures mzman mi 81912 3.640.119

SHEET 1 OF 3 FIG. 1

FIG. 1A FIG. 1B

1s sea e00 804 l MEASUR'NG AND 22 M -RETRANSMITTER FIG. 2

mvmrores BERNARD BLUM JOHN W. SCHWARTZENBERG BY l m )7 M AGENT CARBON CONTENT MEASUREMENT IN A BASIC OXYGEN FURNACE CROSS-REFERENCE TO RELATED APPLICATION This application is a division of application Ser. No. 534,617 filed Feb. 14, 1966, now US. Pat. No. 3,528,800, which was filed as a continuation-in-part of application Ser. No. 479,867, Aug. 16, 1965, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to apparatus for providing a measuring system for determining the carbon content of the bath of an oxygen-blown, steel-refining vessel, particularly in the low carbon region toward the end of a heat.

In the process of refining pig iron to produce steel in a basic oxygen furnace, high-purity oxygen is introduced at a high velocity through a lance positioned above the bath in the furnace so that the oxygen impinges upon the surface of the bath. The high-purity oxygen combines with the impurity elements in the bath including the carbon, manganese, phosphorus and silicon as well as iron itself. By this process of combination the oxides of the impurity elements are formed. The oxides of carbon are evolved as gases while the other oxides are retained in a slag cover over the molten metal bath.

It is usually desired that the refining process be carried out until a particular percentage of carbon remains in the molten metal and the temperature of the molten metal is at a predetermined point. When the carbon content and the temperature are at the desired values, the process can be terminated. Thus, in using this process it is important to have an accurate measure of the carbon content of the bath during the final portion of the refining process when the carbon content is at a low value.

In carrying out this invention there is provided means for measuring the rate at which the carbon is removed from the bath by the generation of a signal whose magnitude is representative of the concentration of carbon containing gases in the exhaust gas recovery system of the refining vessel and means are provided which are responsive to that signal for indicating carbon content in the bath. When the oxygen supplied to the vessel is variable, the last-named means may include means for measuring the rate of flow of oxygen into the vessel and means for establishing the ratio between the rate of carbon removal and the rate of oxygen flow. That ratio is representative of the efficiency of carbon removal from the bath and that ratio has been found to be indicative of the carbon content of the bath at low carbon values.

It is an object of this invention to provide an improved means for measuring the carbon content in the bath of a basic oxygen furnace.

It is a further object of this invention to provide a means for determining the carbon content of the bath of a basic oxygen furnace during the final portion of the heat in order to determine the time at which the heat has been completed.

For a complete description of this invention, reference should be made to US. Pat. No. 3,528,800 and more specifically to that portion of the specification starting at column 4, line 36 continuing to column 20, line 65. Particular reference with regard to the invention should be made to that portion of the specification found at column 18, line 67 continuing to column 19, line 57.

What is claimed is:

l. A measuring system for establishing a signal indicative of the carbon content of the bath in an oxygen-blown furnace comprising means for establishing from analysis of the exhaust gases of said furnace a signal indicative of the carbon loss rate of the furnace bath,

means for establishing a signal indicative of the flow of oxygen to the lance of said furnace, and

means for dividingsaid carbon loss signal by said oxygen flow signal. 2. A measuring system for determining the carbon content remaining in the bath of a basic oxygen furnace toward the 5 end of a low carbon heat comprising means for producing a first signal indicative of the rate of loss of carbon from the furnace,

means for producing a second signal indicative of the oxygen flow rate into said furnace,

means responsive to the ratio of said first to said second signal to produce a third signal indicative of the existing carbon removal efficiency of the heat, and

indicator means including a substantially logarithmic scale for measuring and indicating the carbon content of said bath.

3. A measuring system for measuring the carbon content of the bath in a basic oxygen furnace comprising means for producing a first signal representative of the concentration of carbon containing gases in the exhaust system of said furnace,

means for producing a second signal representative of the rate of flow of the gases in the exhaust system,

means for multiplying said first and said second signal to produce a third signal indicative of the carbon loss rate from said furnace,

means for producing a fourth signal representative of the rate of oxygen flow to the lance of said furnace,

means for introducing said fourth signal into a lagging network to obtain a lagged fourth signal, means for producing from said lagged fourth signal a signal indicative of the carbon equivalent of said oxygen flow,

means for dividing said carbon equivalent signal into said third signal to produce a signal indicative of the existing carbon removal efficiency, said carbon removal efficiency being related to the carbon content of said bath when said carbon content is low, and

indicating means having a substantially logarithmic scale in terms of carbon content connected to respond to said carbon removal efficiency signals to provide an indication of the carbon content of said bath.

4. A system for determining the efficiency of carbon removal from the bath of an oxygen-blown, steel-refining vessel comprising means for measuring the rate at which carbon is removed from the bath,

means for measuring the rate of flow of oxygen blown into said vessel, and

means for establishing the ratio between the rate of carbon removal and the rate of oxygen flow, said ratio being representative of the efficiency of carbon removal from said bath.

5. A system for determining the efficiency of carbon removal from the bath of an oxygen-blown, steel-refining vessel comprising means for measuring the rate at which carbon is removed from the bath including;

means for measuring the concentration of carbon-containing gases in the exhaust gas recovery system into which the gas leaving said refining vessel are drawn,

means for measuring the rate of flow of gases in said exhaust gas recovery system, and

means for multiplying said concentration of carbon-containing gases by said rate of flow of gases in said exhaust gas recovery system to produce a measure of the rate at which carbon is being removed from said bath;

means for measuring the rate of flow of oxygen blown into said vessel; and

means for establishing the ratio between the rate of carbon removal and the rate of oxygen flow, said ratio being representative of the efiiciency of carbon removal from said bath.

Claims

2. A measuring system for determining the carbon content remaining in the bath of a basic oxygen furnace toward the end of a low carbon heat comprising means for producing a first signal indicative of the rate of loss of carbon from the furnace, means for producing a second signal indicative of the oxygen flow rate into said furnace, means responsive to the ratio of said first to said second signal to produce a third signal indicative of the existing carbon removal efficiency of the heat, and indicator means including a substantially logarithmic scale for measuring and indicating the carbon content of said bath.
3. A measuring system for measuring the carbon content of the bath in a basic oxygen furnace comprising means for producing a first signal representative of the concentration of carbon containing gases in the exhaust system of said furnace, means for producing a second signal representative of the rate of flow of the gases in the exhaust system, means for multiplying said first and said second signal to produce a third signal indicative of the carbon loss rate from said furnace, means for producing a fourth signal representative of the rate of oxygen flow to the lance of said furnace, means for introducing said fourth signal into a lagging network to obtain a lagged fourth signal, means for producing from said lagged fourth signal a signal indicative of the carbon equivalent of said oxygen flow, means for dividing said carbon equivalent signal into said third signal to produce a signal indicative of the existing carbon removal efficiency, said carbon removal efficiency being related to the carbon content of said bath when said carbon content is low, and indicating means having a substantially logarithmic scale in terms of carbon content connected to respond to said carbon removal efficiency signals to provide an indication of the carbon content of said bath.
4. A system for determining the efficiency of carbon removal from the bath of an oxygen-blown, steel-refining vessel comprising means for measuring the rate at which carbon is removed from the bath, means for measuring the rate of flow of oxygen blown into said vessel, and means for establishing the ratio between the rate of carbon removal and the rate of oxygen flow, said ratio being representative of the efficiency of carbon removal from said bath.
5. A system for determining the efficiency of carbon removal from the bath of an oxygen-blown, steel-refining vessel comprising means for measuring the rate at which carbon is removed from the bath including; means for measuring the concentration of carbon-containing gases in the exhaust gas recovery system into which the gas leaving said refining vessel are drawn, means for measuring the rate of flow of gases in said exhaust gas recovery system, and means for multiplying said concentration of carbon-containing gases by said rate of flow of gases in said exhaust gas recovery system to produce a measure of the rate at which carbon is being removed from said bath; means for measuring the rate of flow of oxygen blown into said vessel; and means for establishing the ratio between the rate of carbon removal and the rate of oxygen flow, said ratio being representative of the efficiency of carbon removal from said bath.