U.S. patent application number 10/387544 was filed with the patent office on 2004-09-16 for system for optically analyzing a molten metal bath.
Invention is credited to Cates, Larry E..
Application Number | 20040178545 10/387544 |
Document ID | / |
Family ID | 32961908 |
Filed Date | 2004-09-16 |
United States Patent
Application |
20040178545 |
Kind Code |
A1 |
Cates, Larry E. |
September 16, 2004 |
System for optically analyzing a molten metal bath
Abstract
A system for optically analyzing a molten metal bath wherein a
high velocity gas stream is passed from a lance to the bath and is
maintained coherent by a flame envelope to provide a clear sight
pathway through the gas stream for sighting the molten metal bath
longitudinally through the gas stream from a remote or spaced
sighting point.
Inventors: |
Cates, Larry E.;
(Brownsburg, IN) |
Correspondence
Address: |
PRAXAIR, INC.
LAW DEPARTMENT - M1 557
39 OLD RIDGEBURY ROAD
DANBURY
CT
06810-5113
US
|
Family ID: |
32961908 |
Appl. No.: |
10/387544 |
Filed: |
March 14, 2003 |
Current U.S.
Class: |
266/100 |
Current CPC
Class: |
F27D 3/16 20130101; F27D
2019/0006 20130101; F27D 2003/164 20130101; F27D 19/00 20130101;
F27D 21/00 20130101; C21C 5/4606 20130101; C21C 5/4673 20130101;
F27D 2019/0003 20130101; F27D 2003/166 20130101; F27D 21/0014
20130101 |
Class at
Publication: |
266/100 |
International
Class: |
C21B 007/24 |
Claims
1. A method for optically analyzing a molten metal bath comprising:
(A) forming a coherent gas stream by passing a gas stream out from
a lance and surrounding the gas stream with a flame envelope; (B)
passing the coherent gas stream to a molten metal bath; (C)
sighting longitudinally through the coherent gas stream to view the
molten metal bath and obtain optical data therefrom; and (D)
passing the optical data to an analyzer.
2. The method of claim 1 wherein the sighting through the coherent
gas stream comprises using a light source transmitting light
through the coherent gas stream.
3. The method of claim 2 wherein the light source is a laser.
4. The method of claim 1 wherein the flame envelope extends from
the lance to the molten metal bath.
5. The method of claim 1 wherein the coherent gas stream has a
supersonic velocity when it contacts the molten metal bath.
6. The method of claim 1 wherein the coherent gas stream comprises
oxygen.
7. The method of claim 1 wherein the optical data enables the
determination of the composition of the molten metal of the molten
metal bath.
8. The method of claim 1 wherein the optical data enables the
determination of the temperature of the molten metal of the molten
metal bath.
9. The method of claim 1 wherein the molten metal bath comprises
unmelted scrap and the optical data enables the determination of
melted versus unmelted scrap in the molten metal bath.
10. The method of claim 1 wherein the molten metal bath comprises
molten metal and a slag layer above the molten metal, and wherein
the coherent gas stream passes through the slag layer to the molten
metal.
11. Apparatus for optically analyzing a molten metal bath
comprising: (A) a molten metal furnace containing a molten metal
bath; (B) a lance having an ejection end for passing a coherent gas
stream to the molten metal bath; (C) a sight glass mounted on the
lance aligned so as to view the molten metal bath longitudinally
though the coherent gas stream to obtain optical data; and (D) an
analyzer and means for passing the optical data to the
analyzer.
12. The apparatus of claim 11 further comprising a light source for
generating light for passage through the coherent gas stream.
13. The apparatus of claim 12 wherein the light source is a
laser.
14. The apparatus of claim 11 wherein the lance is positioned so as
to provide the coherent gas stream to the molten metal bath in a
direction perpendicular to the surface of the molten
metal-bath.
15. The apparatus of claim 11 wherein the sight glass is positioned
on the lance on the end opposite the ejection end of the lance.
16. The apparatus of claim 11 wherein the means for passing optical
data to the analyzer comprises a light guide assembly comprising
optical fiber passing from the sight glass to the analyzer.
17. The apparatus of claim 11 wherein the means for passing optical
data to the analyzer comprises a light guide assembly comprising a
system of lenses and mirrors.
18. The apparatus of claim 11 wherein the analyzer comprises an
optical spectrometer.
19. The apparatus of claim 11 wherein the analyzer comprises a
pyrometer.
Description
TECHNICAL FIELD
[0001] This invention relates generally to refining molten metal,
e.g. steel, and, more particularly, to analyzing the molten metal
bath during the refining.
BACKGROUND ART
[0002] Metals such as steel are typically produced and refined in a
refractory lined vessel by heating charge materials such as metal
bearing scrap, pig iron, ore, limestone, dolomite, etc. to a molten
state and blowing oxygen into the resulting molten metal bath in
order to oxidize impurities. It is not always possible to know the
precise chemical composition of the charge materials prior to the
start of processing. Therefore, the composition must be determined
after the charge materials have become molten and thoroughly mixed.
Moreover, the changing composition of the molten metal bath must be
at least periodically determined so as to know the timing and
quantity of additives made to the refining vessel contents. The
standard method for determining the composition of a molten metal
bath is to stop the production process, withdraw a small sample of
material, and analyze this sample using a mass spectrometer.
[0003] Continuous on-line measurement is more desirable but the
high temperature and the presence of dust, fume, and slag do not
permit locating measuring devices inside the molten metal bath.
Those skilled in the art have attempted to deal with these problems
by using optical fibers close to the surface of the molten metal
bath or using such aids as lenses, mirrors and prisms in order to
pass data from the molten metal bath to an analyzer. However such
arrangements are unsatisfactory because they are complicated to set
up and difficult to maintain during the refining process, thus
compromising the accuracy of the data gathered and compromising the
integrity of the analysis based on such data.
[0004] Accordingly it is an object of this invention to provide a
system for optically analyzing a molten metal bath which can be
used on a continuous basis during the refining period which
overcomes the problems inherent with presently available analysis
systems.
SUMMARY OF THE INVENTION
[0005] The above and other objects, which will become apparent to
those skilled in the art upon a reading of this disclosure, are
attained by the present invention, one aspect of which is;
[0006] A method for optically analyzing a molten metal bath
comprising:
[0007] (A) forming a coherent gas stream by passing a gas stream
out from a lance and surrounding the gas stream with a flame
envelope;
[0008] (B) passing the coherent gas stream to a molten metal
bath;
[0009] (C) sighting longitudinally through the coherent gas stream
to view the molten metal bath and obtain optical data therefrom;
and
[0010] (D) passing the optical data to an analyzer.
[0011] Another aspect of the invention is:
[0012] Apparatus for optically analyzing a molten metal bath
comprising:
[0013] (A) a molten metal furnace containing a molten metal
bath;
[0014] (B) a lance having an ejection end for passing a coherent
gas stream to the molten metal bath;
[0015] (C) a sight glass mounted on the lance aligned so as to view
the molten metal bath longitudinally through the coherent gas
stream to obtain optical data; and
[0016] (D) an analyzer and means for passing the optical data to
the analyzer.
[0017] As used herein, the term "flame envelope" means a combusting
stream around at least one other non-combusting gas stream.
[0018] As used herein, the term "coherent gas stream" means a gas
stream whose diameter remains substantially constant.
[0019] As used herein, the term "molten metal bath" means the
contents of a metal refining furnace comprising molten metal and
which also may comprise slag.
[0020] As used herein, the term "optical data" means a value
describing a characteristic of a molten metal bath which can be
sensed by a receiver spaced from the molten metal bath.
[0021] As used herein, the term "longitudinally" means in line with
the major axis.
[0022] As used herein, the term "sight glass" means an optically
transparent material, such as sapphire or quartz, capable of
providing a seal between a pressurized stream of gas in a lance and
the fiber optic cable or other optical components. A light source,
such as a laser, may be fitted to the sight glass to increase the
energy of the molten metal bath observed through the coherent jet
so as to improve the effectiveness of the analysis.
BRIEF DESCRIPTION OF THE DRAWING
[0023] The sole FIGURE is a simplified cross sectional
representation of one preferred arrangement which may be used in
the practice of the invention.
DETAILED DESCRIPTION
[0024] The invention will be described in detail with reference to
the Drawing. Referring now to the FIGURE, there is shown molten
metal furnace 10 which contains a molten metal bath comprising
molten metal 4 and a slag layer 5, which may be molten or solid,
above the pool of molten metal. Typically the molten metal will
comprise iron or steel. The slag layer generally comprises one or
more of calcium oxide, silicon dioxide, magnesium oxide, aluminum
oxide and iron oxide.
[0025] Lance 1 is positioned so as to provide gas to the molten
metal bath. The embodiment illustrated in the FIGURE is a preferred
embodiment wherein the lance is positioned so as to provide gas to
the molten metal bath in a direction perpendicular to the surface
of the molten metal bath. Alternatively, the lance could be
positioned through a sidewall of furnace 10 so as to provide gas
angularly to the surface of the bath.
[0026] While any useful gas may be used in the gas stream provided
to the bath from the lance, typically and preferably the gas is
oxygen, such as commercial oxygen, or a gas mixture comprising
oxygen. Other gases which may be used in the gas stream in the
practice of this invention include nitrogen, argon, carbon dioxide,
hydrogen, helium, steam, hydrocarbon gases, and gas mixtures
comprising one or more thereof. The gas is provided from the lance
at a high velocity, preferably at sonic or supersonic velocity.
Generally the velocity of the gas stream 3 provided from the lance
has a velocity of at least 1000 feet per second (fps) and
preferably at least 1500 fps. Most preferably the gas stream has a
supersonic velocity upon ejection from the lance and also has a
supersonic velocity when it contacts the bath surface.
[0027] Fuel and oxidant are provided out from the lance around the
gas stream and combust to form a flame envelope 2 around the gas
stream 3. Preferably, as shown in the FIGURE, the flame envelope
extends for the entire length of the gas stream within the furnace
from the lance ejection end to the bath. The fuel used to form
flame envelope 2 is preferably gaseous and may be any fuel such as
methane or natural gas. The oxidant used to form flame envelope 2
may be air, oxygen-enriched air having an oxygen concentration
exceeding that of air, or commercial oxygen having an oxygen
concentration of at least 90 mole percent.
[0028] Flame envelope 2 serves to keep ambient gas, e.g. furnace
gases, from being drawn into or entrained into gas stream 3,
thereby keeping the velocity of stream 3 from significantly
decreasing and keeping the diameter of gas stream 3 from
significantly increasing, generally for a distance of at least 20 d
where d is the diameter of the nozzle at the lance ejection end
from which gas stream 3 is ejected. That is, flame envelope 2
serves to establish and maintain gas stream 3 as a coherent gas
stream generally for a distance of at least 20 d. Preferably, as
shown in the FIGURE, gas stream 3 is a coherent gas stream from the
lance to the bath.
[0029] The gas or gas mixture passed to the bath in gas stream 3
serves to refine the molten metal by reacting with bath
constituents and/or mixing the bath. Preferably, as shown in the
FIGURE, the high velocity and coherent nature of gas stream 3
serves to drive gas stream 3 through slag layer 5 and deep into
molten metal 4 so as to enhance the refining and/or mixing action
of the gas delivered to the bath in gas stream 3. In the embodiment
of the invention illustrated in the FIGURE the gas in gas stream 3
comprises oxygen which reacts with carbon in the molten metal to
decarburize the molten metal, in the process forming gas bubbles 6
of carbon dioxide and/or carbon monoxide.
[0030] As has been discussed above, it is desirable at least
periodically, and preferably continuously, to monitor the condition
of the molten metal to determine, for example, its composition,
temperature and/or the proportion of scrap that has been melted. In
the practice of this invention these parameters are monitored by
sighting through sight glass 9. Preferably, as shown in the FIGURE,
sight glass 9 is mounted on lance 1 on the end opposite the
ejection end to provide a pressure seal to prevent leakage of
oxygen or other gases from the lance while providing an optically
transparent view port.
[0031] The coherent nature of gas stream 3, which keeps furnace
gases, fumes, particles, etc. from being entrained into gas stream
3, enables a clear line of sight to form from sight glass 9 to the
molten metal bath. This enables viewing the molten metal bath by
sighting longitudinally through the unobstructed pathway provided
by coherent gas stream 3. This viewing enables the gathering of
optical data from the bath. Data that can be gathered by viewing
the molten metal through the coherent jet include temperature by
way of optical pyrometry, measurement of the quantities of various
elements contained in the molten metal bath and slag by way of
spectroscopic analysis, and conditions of the process such as the
proportion of melted scrap by analysis of the temperature
trends.
[0032] The optical data is passed to an analyzer 7, such as by
light guide assembly 8 which may comprise fiber optic cable or a
system of lenses and mirrors. Analyzer 7 may be, for example, an
optical spectrometer optical pyrometer, or a combination of these
instruments. Analyzer 7 employs the data to provide measurements of
temperature and composition of the molten metal bath, thereby
enabling the operator to make adjustments to the amounts and timing
of additional charge materials, fluxing agents, alloys, electrical
energy, and reactive agents such as oxygen, to facilitate arriving
at the desired endpoint of the refining process.
[0033] By observing the current temperature of the molten bath and
the quantity of carbon, chromium, manganese or other elements
remaining in the molten metal bath, the operator can determine when
the processing of the metal has reached the conditions specified
for the type of metal being produced. Further, if the quantity of
certain trace elements such as copper are observed to be outside
the quality limitations for the metal being produced, the operator
will be able to make adjustments to bring the product into
specification before the completion of processing. By knowing the
proportion of scrap melted, the operator will know the appropriate
time to add additional scrap to the furnace.
[0034] By the use of the invention one can obtain continuous and
on-line measurement of molten metal bath properties without need
for using optical fibers close to the surface of the molten metal
bath or using such aids as lenses, mirrors and prisms. Although the
invention has been described in detail with reference to a
preferred embodiment, those skilled in the art will recognize that
there are other embodiments of the invention within the spirit and
the scope of the claims.
* * * * *