Background of the Invention
(1) Field of the Invention
[0001] The present invention relates to a method and apparatus for directly observing slag-forming
conditions within a converter used for steel refining.
(2) Description of the Prior Art
[0002] In refining molten pig iron and steel in a converter, pure oxygen is ejected from
a lance inserted through the mouth of the converter into the converter body (below
"vessel"). The oxygen is blown onto the molten steel to both effect decarburization
and stir the molten steel. In addition, flux is charged into the converter to form
molten slag, thereby effecting dephosphorization, desulfurization, or the like due
to the reactions between the molten slag and steel.
[0003] Slag foaming occurs due to several slag conditions, such as the slag composition,
viscosity, the total amount of oxygen in the slag, etc. Too extensive slag foaming
causes the slag and even molten steel to overflow the converter mouth, which overflow
is referred to as "slopping". Of course, the composition of the molten steel and the
steel yield are greatly influenced by slopping. Also, various problems are caused,
such as reduction in the operational efficiency and in the calorific content of the
recovered gases, impairment of the operational environment, e.g., generation of brown
smoke, and damage to the steelmaking devices. Slopping therefore must be suppressed
as much as possible.
[0004] Various proposals have been made on how to enable prompt prediction of the slag conditions
within a converter and hence realize optional converter operation without slopping.
[0005] Japanese Unexamined Patent Publication (Kokai) No. 52-101618 discloses a method for
estimating the amount of slag by calculating the oxygen balance based on information
on the waste gases during blowing and then estimating the amount of oxides formed
in the converter, i.e., the molten slag. In this method, however, there is an unavoidable
time delay due to the gas analysis and mathematical analysis. In addition, since slopping
is not dependent upon just the amount of molten slag alone, the accuracy of prediction
of slopping is not very high.
[0006] Various attempts have also been made on detecting the slag level by physical means.
These include an acoustic measuring method (Japanese Unexamined Patent Publication
No. 54-33790), a vibration measuring method (Japanese Unexamined Patent Publication
No. 54-114,414), a method for measuring the inner pressure of a converter (Japanese
Unexamined Patent Publication No. 55-104,417), a method using a microwave gauge (Japanese
Unexamined Patent Publication No. 57-140812), and a method for measuring the surface
temperature of the converter body (Japanese Unexamined Patent Publication No. 58-48615).
[0007] In the acoustic measuring method, changes in the frequency and magnitude of the acoustics
generated in the converter are monitored to estimate the slag level and to predict
slopping.
[0008] In the vibration measuring method, changes in the magnitude of lance vibration and
the wave transition of the lance vibration are monitored during blowing to estimate
the slag level or conditions and then to predict slopping.
[0009] In the method for measuring the inner pressure of a converter, variations in the
ejecting pressure of the waste gases through the converter mouth are monitored to
predict slopping.
[0010] In the method using a microwave gauge, a microwave is directly projected into the
converter interior to directly measure the slag level based on the FM radar technique
and to predict slopping.
[0011] In the method for measuring the surface temperature of a converter body, the energy
emission from the upper and lower parts of the converter body is detected as temperature,
and the occurrence and magnitude of slopping are predicted based on the temperature
magnitude and peak values.
[0012] The acoustic measuring method, vibration measuring method, method for measuring the
inner pressure of a converter, and method for measuring the surface temperature of
the converter body are all indirect measuring methods and suffer from low accuracies
of prediction of slopping due to the inability to quantitatively measure the slag
level or conditions. The method using a microwave gauge enables direct measurement
of the slag level, but suffer from the fact that it is not easy to detect or estimate
abnormalities by microwave measurement, since the melt, slag, gases, and the like
effect considerably complicated movement in the converter during blowing. In addition,
this method requires sophisticated signal processing, which increases the cost of
the measuring device.
Summary of the Invention
[0013] The present inventors recognized, as a result of various studies concerning abnormal
reactions in a converter, that the occurrence of such abnormal reactions is closely
related to the slag-forming conditions, i.e., the foaming behavior of slag. The present
inventors studied the foaming behavior of slag and discovered that the light intensity
of the gaseous atmosphere and the wavelength characteristics of light emitted from
the gaseous atmosphere considerably differ from those of the slag. The present inventors
discovered that they could positively utilize such differences to detect the foaming
behavior.
[0014] The present invention provides a method and apparatus for directly observing slag-forming
conditions, i.e., the slag-foaming conditions, in a converter during blowing, thereby
allowing more precise and speedy observation than in the prior art and contributing
to a highly accurate converter operation.
[0015] The method according to the present invention is characterized in that at least one
light-detecting device observing the vessel-interior light is disposed in at least
one throughhole of the side wall of a converter so as to face the vessel interior
and observe the slag-forming conditions.
[0016] The apparatus according to the present invention comprises a light-detecting device
including a receptor, which receptor is disposed in a throughhole of the side wall
of a converter so as to face the vessel interior, and a device for detecting the intensity
and/or wavelength of a light signal input from the light-detecting device.
[0017] Dependent claims comprise additional features of the invention.
Brief Description of Drawings
[0018] In the drawings, Fig. 1 is a cross-sectional view of a top-blowing converter, schematically
showing an embodiment of mounting a light-detecting device observing the vessel-interior
light in the converter;
Figs. 2A through 2C are cross-sectional views of a converter, showing non-immersion
portions of the converter side wall;
Figs. 3A through 3C, Fig. 4, and Fig. 5 illustrate the principle of the present invention,
Figs. 3A through 3C showing the position of mounting the devices for observing vessel-interior
light and Figs. 4 and 5 showing time charts on the level of detected light signals;
Figs. 6 and 7 are partial cross-sectional views of a converter, showing different
mounting structures of a device for observing the vessel-interior light;
Fig. 8 is a schematic drawing of the arrangement of the device for observing the vessel-interior
light, relative to the converter;
Fig. 9 is a partial cross-sectional view of a converter and a cross-sectional view
of the device for observing the vessel-interior light, which device is gas-tightly
inserted into a throughhole of the converter;
Fig. 10A is an overall view of a supporting platform with a displacement mechanism;
Figs. 10B through 10E are partial views of the supporting platform shown in Fig. 10A;
Figs. 11 (I), (I'), (II), (11'), (III), and (III') illustrate the blowing conditions
of a converter and the operation of the device for observing vessel-interior light
according to the present invention;
Fig. 12 graphically illustrates the relationship between the wavelength and intensity
of light emitted from the slag and gaseous atmosphere above the slag;
Fig. 13 illustrates an example of a vessel-interior display, showing the variation
in the surface-area proportion with the lapse of blowing time;
Fig. 14 illustrates an example of the piping of purge gas;
Fig. 15 is a partial cross-sectional view of an example of a probe according to the
present invention;
Fig. 16 illustrates the relationship between the slag level and blowing time;
Fig. 17 is a block diagram of another example of the device for observing the vessel-interior
light;
Fig. 18 shows the mounting position of devices for observing the vessel-interior light
mounted on a top- and bottom-blowing converter;
Fig. 19 is a time chart of light signals detected by the devices shown in Fig. 18
and of the slag level detected by using a sublance;
Fig. 20 is a block diagram of method of detecting the slag-forming conditions according
to the present invention; and
Figs. 21 through 23 illustrate the slag level during blowing and a method for controlling
it.
Description of the Preferred Embodiments
[0019] Figure 1 is a cross-sectional view of a top-blowing converter, schematically showing
an embodiment of mounting a device for observing the vessel-interior light. Referring
to Fig. 1, a converter 1 is provided, on its side wall 2, with at least one throughhole
4 opening into the vessel interior 3. At least one light-detecting device 5 observing
the vessel-interior light is disposed in the throughhole 4 to face the vessel interior
3 and observes the intensity or the wavelength of the light emitted from the slag
and gaseous atmosphere within the converter 1. This light-detecting device 5 may be
a photometer and is hereinafter referred to as the photometer 5. In Fig. 1, only one
throughhole and observation device are shown.
[0020] It is possible, based on the measurement of intensity and or wavelength of the light,
to monitor whether slag-foaming occurs above or beneath a processing level X of the
photometer 5.
[0021] Figures 2A to 2C show non-immersion portions 8 of the converter side wall 2, i.e.,
in the converter upright position, tilting position for tapping, and tilting position
for charging the pig iron from the ladle, respectively. In each of the positions shown
in Figs. 2A, 2B, and 2C, the portion of the converter wall 2 where a trunnion shaft
6 is rigidly secured and the region around that portion are not immersed within a
melt 7. This portion and region, shown by the hatching are the non-immersion portion
8. The throughholes 4 can be formed through the non-immersion portion 8 to prevent
the melt 7 from entering the throughholes 4.
[0022] As is described below, the photometers 5 can also be removably inserted into the
tapping hole. When the molten steel is tapped through the tapping holes, the photometers
5 are removed therefrom.
[0023] Figures 3A through 3C, Fig. 4, and Fig. 5 illustrate the principle of the present
invention, Figs. 3A through 3C showing the portions of mounting the devices for observing
vessel-interior light and Figs. 4 and 5 showing time charts on the level of detected
light signals. Referring to Figs. 3A through 3C, three photometers 5a, 5b, and 5c
are arranged as seen in the vertical direction of the converter, so as to measure
the vessel-interior light at the levels Xa, Xb, and Xc, respectively. The position
of the throughholes 4, i.e., their distance from the bottom or mouth of the converter
1, must be empirically determined by the size and capacity of the converter 1. In
the case of a single throughhole 4, the throughhole 4 must be located at the highest
target slag level. In the case of plurality of throughholes 4, the highest and lowest
throughholes 4 must be located straddling the highest target slag level.
[0024] Figure 4 shows the light signal (ordinate) detected by any one of the photometers
5a, 5b, and 5c and then subjected to signal processing with the aid of an appropriate
filter. The abscissa of Fig. 4 indicates the blowing time periods, the former period
when the gaseous atmosphere is present beneath the level Xa, Xb, or Xc and the latter
being when foaming slag is present beneath the levels Xa, Xb, or Xc.
[0025] Figure 5 illustrates the results of continuous measurement of the vessel-interior
light by the photometers 5a through 5c. Under the slag-foaming conditions shown in
Fig. 3A, all of the photometers 5a through 5c face or are exposed to the gaseous atmosphere,
which indicates that the slag-foaming level y is located beneath the level Xc.
[0026] Under the slag-foaming conditions shown in Fig. 3B, the photometers 5a and 5b face
or are exposed to the gaseous atmosphere and the photometer 5c faces or is exposed
to the foaming slag. The slag-foaming level y is therefore located beneath the level
of the converter mouth 9 and between the levels Xb and Xc.
[0027] Under the slag-foaming conditions shown in Fig. 3C, all of the photometers 5a through
5c face or are exposed to the slag. The slag-foaming level y is therefore located
between the level of the converter mouth 9 and the level Xa of the photometer 5a.
[0028] The complicated foaming behavior of slag can therefore be accurately monitored by
means of mounting a plurality of the photometers in the vertical direction and continuously
measuring the vessel-interior light during the operation of the converter 1. If necessary,
photometers may also be mounted along the width of the converter 1.
[0029] As described above, the intensity of light of the gaseous atmosphere and the wavelength
characteristics of light emitted from the gaseous atmosphere considerably differ from
those of the slag. Therefore, by direct observation of the vessel-interior light,
it is possible to distinguish, without signal processing of the light, the light upon
facing or exposure to the slag from the light upon facing or exposure to the gaseous
atmosphere. However, if the vessel-interior light is subjected to signal processing
with regard to the intensity or wavelength of the light, a clearer image of the slag-forming
conditions can be obtained. Also as is described in detail hereinbelow, the obtained
signals can be advantageously utilized for controlling various blowing operations.
[0030] Using the slag-foaming behavior, one can preliminarily determine slag-forming criteria
specifying the relationship between such behavior and slag-forming conditions. Therefore,
according to an embodiment of the present invention, it is possible to compare the
detected intensity and/or wavelength of the vessel-interior light with the slag-forming
criteria determined for specific slag-forming conditions, such as formation of dephosphorizing
and/or non-slopping slag. The slag-forming criteria are determined for each converter
having a specified structure and vessel volume and for each blowing condition. the
value detected by the photometers 5a through 5c (Figs. 3A through 3C) is compared
with the slag-forming criteria, thereby achieving detection of slag-forming conditions.
[0031] An example of the slag-forming criteria is as follows. When the slag-forming level
y arrives at the level Xa of the higest photmeter 5a, this means there is excessive
slag formation and a high possibility of slopping. The level Xa can therefore be established
as the slag-forming criterion indicating excessive formation of slag.
[0032] The slag-forming criteria are determined for each type of slag formation. That is,
dephosphorization requires formation of a dephosphorizing slag having an appropriate
total amount of iron-oxide for a normal dephosphorization reaction and also having
a sufficient volume. The formation of the dephosphorizing slag can be verified by
monitoring the slag-forming level y, e.g., at the lowest level Xc of the photometer
5c. If the level of slag is beneath the lowest level Xc during the dephosphorizing
period, abnormality in slag formation occurs.
[0033] Although the above explanation was made with reference to a plurality of photometers
5a through 5c arranged in the converter 1, it is possible to satisfactorily observe
the slag-forming conditions even by a single photometer, as shown in Fig. 1 and as
described hereinbelow.
[0034] Figures 6 and 7 are partial cross-sectional views of a converter, showing different
mounting structures of a photometer. Referring to Fig. 6, a photometer 5 is mounted
in the throughhole 4 via a protective tube 11 having an inner cylinder 110. A cooling-water
circulating channel 111 is formed in the protective tube 11. Cooling water w is supplied
into the cooling-water circulating channel 111 via one of conduits 112. The water
w is withdrawn via the other conduit 112. The photometer 5 is installed within the
inner cylinder 110 in such a manner that its active side faces the vessel interior.
Purge gas, such as N
2, Ar, C0
2, or another inert gas g, is supplied to and passed through the inner cylinder 110
and then ejected through the aperture 113 into the vessel. During its passage and
ejection, the purge gas cools the photometer 5 and prevents gases including dust,
slag, or the like from entering the inner cylinder 110.
[0035] The signal detected by the photometer 5 is input via a cable 12 into a signal processing
device 13, such as a transmission filter, a computing device 14, and a display device
15.
[0036] The converter operation may be controlled either automatically or by a human operator.
In automatic control, the signal detected by the photometer 5 is compared with the
slag-forming criteria preliminarily input into the computing device 14 so as to automatically
detect the slag-forming conditions. A warning signal or operating command is thereupon
generated from the computing device 14 to various controlling devices (not shown).
In control by a human operator, the operator watches detected values indicated on
the display device 15 and compares them with predetermined slag-forming criteria,
to control the converter operation.
[0037] Figure 7 shows another examples of the photometer in Fig. 7, the same reference numerals
and symbols as those of Fig. 6 indicate identical members. An optical conductor 51,
i.e., a body capable of transmitting at a low loss the light emitted from a high temperature
body, e.g., a quartz-based optical fiber, is located in the inner cylinder 110 of
the protective tube 11. The optical conductor 51 is connected to the body 52 of the
photometer 5, which is disposed at an appropriate position outside the converter.
The structure shown in Fig. 7 is particularly advantageous, since the body 52 of photometer
5, which is expensive, can be located a safe distance from the high-temperature wall
2.
[0038] The photometer 5 is not limited to any particular form provided that it can measure
the intensity and/or wavelength of the vessel-interior light. The photometer 5 includes
various assemblies a MOS or CCD device assembled with an optical filter, and a lens;
a spectrometer and a photomultiplier; and an optical thermometer and a detector of
the temperature profile.
[0039] Figures 8, 9, and 10 show still another structure for mounting a photometer on a
displacement mechanism disposed in the neighborhood of the converter and provided
with means for retractably inserting the photometer into the throughhole.
[0040] Referring to Fig. 8, a support stand 21 located at the neighborhood of the converter
1 is equipped with a photometer 22. The photometer 22 includes an optical conductor
and a receptor 23 at the front end thereof. The receptor 23 can be retractably advanced
into the throughhole 4 by means of the displacement mechanism 24 which is secured
to the supporting stand 21. The receptor 23 can therefore be timely inserted into
the throughhole 4 when the vessel interior is to be observed and can be kept protected
from such detrimental environments as thermal load and dusts during the operation
period, e.g., the tapping period, in which the vessel interior is not to be observed.
The tapping hole can therefore be utilized as the throughhole 4. The vessel-interior
light received by the receptor 23 is transmitted via connector 25 into a photoelectric
converter 26 for generating an electrical signal. The electric signal is input into
an image processor 27 for detecting the intensity and/or wavelength of the vessel-interior
light. The detected signal is shown on a display 28 of the vessel-interior conditions
or a display 29 of the slag level.
[0041] Referring to Fig. 9, showing a detailed structure of the photometer as well as an
example of the seal mechanism of the throughhole 4, an inner brickwork lining 2a and
steel mantle 2b have an aperture of, e.g., 500 mm diameter. A cylindrical body 4a
has an inner refractory lining for defining the throughhole 4 and is welded to the
steel mantle 2b. A flange 4c having an aperture is secured to the cylindrical body
4a. A seal cap 4d is attached to the flange 4c by bolts and has a conical-shaped seal
surface spread toward the vessel exterior. A probe 22a provided with a photoconductor
therein (not shown) is equipped with a conical seal body 22b, the conical shape of
which body allowing gas-tight contact with the seal cap 4d. The position of the receptor
23 being provided at the probe tip end is adjustable by an adjusting bar 22c and adjusting
nut 22d, so that the probe tip end 23 can be positioned at an appropriate position
to receive the vessel-interior light. Th
'e probe 22a is displaced toward and locked to the seal cap 4d by displacement mechanism
24 (Fig. 8). The spring 22e, which is guided along the spring guide 22f, is not indispensable
but is preferable to further displace or and thus compress the probe 22a against the
seal cap 4d.
[0042] Refering to Figs. 10A, 10B, and 10C, showing an example of the displacement mechanism
24, a supporting platform 30 having wheels 30a and 30b is displaced along a pair of
rails 21 a. The wheels 30a are attached to the supporting platform 30 so that they
are engaged to the upper and lower surfaces of the rails 21 a, while the wheels 30b
are attached to the supporting platform 30 so that they are engaged to the inner surfaces
of the rails 21a. The probe 22a is provided, at its rear end as seen from the throughhole
(not shown), metallic fittings 22g and is loosely connected to the displacing platform
30c via the metallic fittings 22g and a bolt 30e. The displacing platform 30c is provided
with a probe-supporting base 30d on which the probe 22a is freely placed.
[0043] The displacement mechanism 24 described above with reference to Figs. 10A, 10B, and
10C, retractably displaces the receptor included in the probe tip end 23 into the
throughhole 4 by means of carrying the displacing platform 30 along the rails 21a.
The displacing platform 30 can be an automotive one directly equipped with a driving
mechanism or one which is driven via a rod, gear, wire, or the like by means of an
electric motor, pneumatic means, or hydraulic means installed separate from the displacing
platform 30.
[0044] The driven mechanism shown in Figs. 10A through 10C are hydraulic. The hydraulic
cylinder 24a is connected via the rod 24b to the metallic fittings 22h, thereby transmitting
the force of the hydraulic cylinder 24a to the probe 22a. As shown in Figs. 10D and
10E, the metallic fitting 22h the rod 24b are loosely connected with one another.
Since the probe 22a is loosely connected to both the displacing platform 30 and the
rod 24b as is described above and, further, since a clearance can be formed between
the wheels 30b and one of the rails 21 a, the probe 22a is somewhat displaceable in
any direction, thereby making it possible to realize a further highly gas-tight contact
between the conical seal body 22b and the conical seal surface of the seal cap 4d.
[0045] The probe 22a, including the photo-conductor therein, is generally a dual tube. Therefore,
the annular space between the inner and outer tubes can be used as the passage for
an inert gas blown toward the end of the probe so as to cool it or clean the receptor
located at its end.
[0046] In an embodiment of the method according to the present invention, described with
reference to Figs. 11,12, and 13, the photoelectrically conducted signal of the vessel-interior
light is divided into a plurality of ranges of wavelength. The proportion of area
of the light to the total image area of the receptor is computed with regard to each
wavelength range, and the computed area proportion compared with predetermined slag-forming
criteria.
[0047] Referring to Figs. 11 (I, I') through (III, III') the melt 7 is charged in the converter
1. A photometer 22 is displaced until it is inserted into the through-hole. Oxygen
begins to be blown through a lance 16, and then refining is initiated. The flux materials
are charged into the converter 1 and form molten slag.
[0048] The amount of slag 31 is still relatively small in Fig. 1 (I), and the circular field
of the receptor 23 gives a white image of the high-temperature gaseous atmosphere
32 of converter, as shown in Fig. 11 (I'). When the slag formation further advances,
the surface of the slag 31 (Fig. 11 (11)) is vigorously stirred by the oxygen blown
through the lance 16 and by the CO gas or the like formed due to the blowing reactions.
The slag 31, which is in an emulsion state and which has a lower temperature than
the high-temperature gaseous atmosphere 32, is detected by the circular field of the
receptor 22 as yellow waves. When the slag 31 (Fig. 11 (111)) overflows the convertor
mouth and slopping occurs, the circular field of the receptor 23 is entirely yellow.
The above changes in the conditions of slag formation can be continuously observed
by television with the naked eye or can be recorded as is explained with reference
to Figs. 12 and 13.
[0049] The intensity-wavelenth relationship of slag becomes clearly different from that
of the gaseous atmosphere above the slag, as shown in Fig. 12, when the slap forming
proceeds to an appreciable extent and the temperature of the gaseous atmosphere is
higher than that of the slag. Therefore, the vessel-interior light can be subjected
to wavelength separation by means of, for example, a blue-transmitting filter, so
as to pass through the filter light having the wavelength range where the intensity
of light emitted from the slag is dominant. The filtered light is subjected to a computing
process so as to obtain the proportion of the filtered light to the entire area of
the circular field of the receptor. The obtained surface-area proportion is plotted,
as shown in Fig. 13, with time.
[0050] Referring to Fig. 13, A indicates the pseudo slag signal generated during the blowing
start period, in which the temperature of the gaseous atmosphere is low, and B indicates
an abrupt increase of the surface-area ratio and thus occurrence of slopping. Prior
to the occurrence of slopping, the surface-area ratio intensely varies. The slopping
can therefore be predicted on the basis of such intense change.
[0051] When a throughhole is exposed to the gaseous atmosphere, the vessel's contents progressively
deposit on the throughhole, resulting in clogging. In an embodiment of the method
of the present invention, described in with reference to Figs. 14 and 15, observation
of the vessel interior is carried out while blowing through the probe an oxygen-containing
purge gas to prevent clogging of the throughhole. Clogging of throughhole is one of
the most serious problems impeding the observation of the vessel interior. The situation
is not so serious when using the tapping hole as the throughhole for observation.
Since the tapping hole is brought into contact with molten steel at each tapping,
the tapping hole can be maintained at an extremely high temperature even during the
blowing period. The deposits on the tapping hole, composed of contents of the vessel,
therefore cannot solidify that much and can be blown out even by inert purge gas blown
through the probe tip end. Contrary to this, a throughhole formed at the nonimmersing
portion 8 (Figs. 2A, 2B, and 2C) cools due to non-contact with the molten steel and
further cools if the inert purge gas is blown to it through the probe tip end. Still,
deposits on the throughhole can be melted due to the latent heat of the slag when
the end of the throughhole is exposed to the foaming slag. In this case, the deposits
can be blown out by inert purge gas, thus preventing accumulation of deposits.
[0052] Oxygen-containing purge gas is preferred purge gas discovered after various investigations
of the assignee of the present application. In this regard, while the coolant gas
of the probe can be blown at an almost constant rate to attain the intended cooling,
the flow rate of the oxygen-containing purge gas for attaining the intended purge
greatly varies depending upon the position of the throughhole, quality and quantity
of the vessel's content, temperature, and vessel interior conditions. Control of the
flow-rate for the purge is therefore difficult. It is more desirable and convenient
to control and to vary the oxygen content of the purge gas.
[0053] Referring to Fig. 14, inert gas is fed from a source A and is separately blown into
conduit systems 34 and 40. The conduit system 34 includes a stop valve 35 and a reducing
valve 36, a flow-rate adjusting device 37 with an orifice and flow-control valve,
and a stop valve 38 successively arranged in the flow direction. The inert gas blown
through the conduit system 34 flows via a flexible hose 39 into an inner cylinder
62 (Fig. 15) which is connected via an inlet port 63 (Fig. 15) to the flexible hose
39. The inert gas is further blown through a small aperture 42 of a front tip 41 screwed
into a probe 61. The inner gas is then released from a tip aperture 43 into the vessel
interior while preventing fogging or contamination of a front glass 67 of the probe
61.
[0054] The inert gas flowing through the conduit system 40 is mixed with oxygen fed from
a source B into the conduit system 44. The mixture gas flows via a flexible hose 45
and inlet port 65 into an outer cylinder 64 to cool the outer surface of the inner
cylinder 62 and the front tip 41. The mixture gas is released into the vessel interior
from the outer cylinder 64 through an opening 66. The flow rate ratio of oxygen to
inert gas is adjusted by a flow-rate controller 33 connected to the conduit systems
40 and 44. The reverse Z 0 symbol indicates the check valves located upstream of the
joining point of the conduit systems 40 and 44. The probe 61 includes a photo conductor
therein. The symbol 26, 27, 28, and 29 indicate a photoelectric converter, image processor,
display device of the vessel-interior condition, and slap level-display device, respectively.
[0055] In an embodiment of the method according to the present invention, the amount of
slag is controlled on the basis of the detected slag-forming conditions so as to maintain
the amount of slag within an appropriate range at a high accuracy. This embodiment
aims not only to predict the occurrence of slopping but also to enhance operational
efficiency and improve the steel quality by means of observing the slag level at a
high accuracy, monitoring the variation tendencies in the slag level, and suppressing
detrimental tendencies. A typical example of this embodiment is described with reference
to Fig. 16.
[0056] Referring to Fig. 16, the level of slag at which slopping is likely to occur is denoted
by 72. Reference numeral 74 indicates the change of the slag level with time, allowing
one to maintain the level of slag lower than the level 72 over the entire blowing
period. The level of slag at with the slag formation is poor is denoted by 73. Reference
numeral 75 indicates the change of the slag level with time, allowing one to ensure,
at a certain initial preparatory blowing period, a slag level higher than 75. In this
example, target slag-level control is effected to control the level of slag between
the levels 74 and 75 during the entire blowing period. The symbols I, II, and III
indicate the slag-level control actions.
[0057] In an embodiment of the present invention, information is extracted from the signal
obtained by the photometer so as to monitor the surface-area proportion of yellow
base color to the entire color signal and variation in that proportion. The proportion
and variation are compared with predetermined color criteria. This embodiment enables
very accurate detection of the slag-forming conditions, as described with reference
to Fig. 17.
[0058] Figure 17 is a block diagram for computing and outputting the proportion described
above. The probe 61, more specifically the photo-conductor, is provided with a connector
25 and photoelectric converter 26. The light detected by the probe 61 is electrically
converted to an image signal 77 which is transmitted to the wavelength-range divider
78. Analog signals 79, i.e., one (B-blue) having a wavelength range of from approximately
0.3 to 0.4 µm, another (G-green) having a wavelength range of from approximately 0.4
to 0.6 pm, and the other (R-red) havingh a wavelength range of from approximately
0.6 to 0.8 pm, are generated by the wavelength range-divider 78. The analog signals
are converted at an appropriate threshold level to binary signals 80 which are input
into an area-computing device 81. In the area-computing device 81, the binary R signal,
the binary G signal, and the bindary B signal are multiplied by a count pulse of,
for example, 0.134 useç (7 MHz) in a reset cycle of 16.7 msec, and the number of pulses
of R-G on and B off is counted. Thus, the area proportion of yellow base color is
counted for each 16.7 msec cycle and is generated as the output signal of yellow 82,
which is observed with a area-proportion display device 91.
[0059] In an embodiment of the method according to the present invention, in accordance
with the observed slag-forming conditions, at least one of the following control operations:
controlling the oxygen-blowing rate; controlling the lance height; charging the auxiliary
raw materials, such as lime or iron ore; and controlling the bottom-flowing gas rate
are carried out. This allows stabilization of the slag composition to drastically
reduce the occurrence of slopping and to improve the slag quality.
[0060] In another embodiment of the method of the present invention, one or more of dolomite
powder, quick lime powder, coal powder, and cokes powder is blown, into the vessel
preferably through an additional throughhole of the side wall, upon the prediction
of occurrence of slopping so as to stabilize the blowing. The present invention will
be further clarified by the ensuing examples, which, however, by no means limit the
invention.
Example 1
[0061] Figure 18 shows a 170 ton top- and bottom-blowing converter which has a top lance
16 for blowing 0
2 and a bottom nozzle 17 for blowing C0
2.
[0062] Throughholes 4 were formed at levels 1.5 m, 2.5 m, and 3.5 m beneath the converter
mouth 9. Protective tubes 11 having an inner cylinder 110 (Fig 7) were inserted into
the throughholes 4. An optical conductor 51, having a diameter of 12 mm, was stationarily
located in each cylinder 110 and was connected to each body of photometers 52. The
photometers 52 were ITV cameras equipped with short wavelength- transmitting filters.
Signals from the ITV cameras were transmitted into signal processing units 13 including
digital memories to store the signals in the digital memories. The digital information
was subjected to signal processing for generating an image. The difference in the
intensity of light between the gaseous atmosphere and the foaming slag was more distinct
than by conventional photometers.
[0063] In addition to the observation of the slag-forming conditions as described above,
observation using a sublance, hithertofor believed to be the most reliable, was carried
out. The temperature of the foaming level of slag was intermittently measured by lowering
the sublance equipped with a consumable thermometer at the tip end thereof.
[0064] The results are shown in Fig. 19. As is apparent from Fig. 19, there is no appreciable
difference between the value measured by the sublance method and the value detected
by the method according to the present invention. Thus, the present invention attains
measurement of the slag level y at a high accuracy. The present invention attains,
furthermore, continuous measurement, which makes it possible to successfully detect
or predict the dynamic slag-forming behavior within the convertor.
[0065] Table 1 shows the relationship between the total number of heats in which the foaming
level of slag y arrived at the respective levels of the photometers and the occurrence
of slopping, the relationship being determined by investigations of the assignee.
[0066] In the present example, the slag-forming criterion was defined as the time when the
photometer 5a detected the foaming slag, i.e., the slag-forming criterion indicated
abnormal or excessive formation of slag. The intensity of vessel-interior light was
continuously measured during blowing by the photometers 5a, 5b, and 5c. When the photometers
5a, 5b, and 5c detected the above-mentioned slag-forming criterion, the warning signal
shown by Z in Fig. 19 was generated to warn of abnormal or excessive formation of
slag. On the basis of the warning signal, control actions, such as reduction in the
0
2-flow rate, through the top-blowing lance 16, and charging of unburnt dolomite into
the converter 1, were carried out. Due to such control actions, the occurrence of
slopping could be reduced to as low as 0.5% or less.
Example 2
[0067] A converter having an outer diameter of approximately 7 m and a height from the bottom
to mouth of 8 m was pierced by a throughhole 150 mm in diameter through the side wall.
A probe having an outer diameter of 80 mm and a photoconductor having an outer diameter
of 40 mm were used.
[0068] The type of probe and also the type of purge-gas blowing conduit systems were as
described with reference to Figs. 14 and 15. As the inert gas, C0
2 was used.
[0069] By means of varying the flow rate ratio of the oxygen to inert gas, the influence
of oxygen upon the burning out of deposits was investigated. The results are shown
in Table 2.
[0070] As understood from Table 2, when the purge gas is free of oxygen, clogging of the
throughhole cannot be sometimes prevented even by blowing a large amount of inert
gas. In addition, when the purge gas contains too high a concentration of oxygen,
the bricks around the throughhole greatly erode due to oxidizing. An appropriate oxygen
concentration is from 30 to 45% by volume. In this case, repeated observtion of the
vessel interior is possible without trouble such as clogging of the throughhole and
erosion of the bricks.
[0071] The purge gas blowing exerted no detrimental influence upon the blowing operation
and quality of tapped steels.
Example 3
[0072] A 170 ton top- and bottom-blowing converter 8 m in height was charged with melt 1.5
m in depth. A throughhole was formed at the converter wall 2.5 m perpendicularly under
the mouth. An optical fiber 12 mm in diameter was used as as photoconductor and inserted
into a cooling protective tube. A CCD color-camera was used as a photoelectric converter.
The slag level was detected by method as described with reference to Fig. 17 of computing
the area ratio of yellow base color. The relationship between the area ratio of yellow
base color and the position of the optical fiber was so established that the area
ratio was 50% when the slag level coincided at the center of field of the optical
fiber. The area ratio 100% and 0% corresponded to the slag levels above and below
the throughhole, respectively. The threshold levels in the binary circuit were K 35%,
G 35%, and B 25%.
[0073] Slopping was detected by the following method, described in reference to Fig. 20.
The area ratio signal of yellow base color 82 from a circuit 81 was divided and transmitted
into two circuits. In one of the circuits, the area ratio signal was converted in
the binary circuit 83 having appropriate threshold level (10%), into a binary signal
84. In the other circuit, the area-ratio signal of yellow base color 82 was passed
through a high-pass filter 85 (cut frequency of 5Hz) and then converted to a positive
value at a circuit 86. The positive signal was converted to a binary signal 88 in
the binary circuit 87 having an appropriate threshold level (50%), which binary signal
88 indicated the changes in the area ratio. The two binary signals 84 and 88 were
input into a decision circuit 89 which produces a final control signal 90. The possibility
of occurrence of slopping was decided as shown in Table 3.
[0074] The control actions to attain the target slag level were as shown in Table 4.
[0075] One or more of the operating objects were manipulated as described with reference
to Figs. 21 through 23. Referring to Fig. 21, when the slag level varies during operation
as shown by a curve 71 and exceeds the target slag level 76 at the points 92 and 93
and when there is no possibility of occurrence of slopping, an increase in the bottom-blowing
flow rate (No. 1) is effective to atain the target slag level 76.
[0076] Referring to Fig. 22, when the slag level varies during operation as shown by the
curve 71 and falls under the target slag level 76 at the points 94 and 95, a decrease
in the bottom-blowing flow rate (No. 1) is first employed. If the slag level seemingly
will not reach the target level 76 approximately 2 minutes after the decrease in bottom-blowing
flow rate, the lance is lifted (No. 2) or the oxygen-flow rate is decreased (No. 3)
to promote the foaming of slag.
[0077] Referring to Fig. 23, when the slag level varies during operation as shown by the
curve 71 and exceeds the target slag level 76 at the point 97 and when there is a
possibility of occurrence of slopping, continuous addition of ore and dolomite is
effective to attain the target slag level 76 and to prevent slopping.
[0078] It was found that the operations are preferably carried out in the order of Nos.
1, 2, 3 and 4. It was also found that, for action I in Fig. 16, increasing the bottom
blowing rate was effective and, for action II, either decreasing the bottom blowing
rate or lifting the lance (increasing the lance height) was effective.
[0079] The operations as described above were carried out for 50 heats. The results are
shown in Table 5.
Example 4
[0080] Blowing was carried out as in Example 3 except for the following: In addition to
the throughhole (for observing the vessel interior), another throughhole was formed
in a non-immersing portion of the side wall of the converter to charge the auxiliary
raw materials therethrough. The additional throughhole was equipped with a nozzle
for blowing auxiliary raw materials, purge gas and carrier gas. Purge gas consisting
of 75% CO
2 and 25% 0
2 was blown without interruption at a rate of 120 Nm
3/hr to prevent clogging of the additional aperture. When the occurrence of slopping
was predicted, the CO
2 gas was blown with flow rate by 500 Nm
3/hr as carrier gas, and coke powder (5 mm or less) ws blown into the vessel interior.
Alternatively, instead of the coke-powder injection, lump dolomite was charged.
[0081] The results of blowing were as shown in Table 6.
[0082] When the prediction signal of slopping disappeared 1 minute or less after the blowing
of the auxiliary materials to suppress the slopping, the heats were deemed to be successfully
blown. This was used as the criterion for effective suppression of slopping.
[0083] As is understood from Table 6, the coke-powder injection is more effective than the
lump dolomite charging.
[0084] Since the auxiliary material was directly injected through the additional throughhole
into the foaming slag, blowing could be initiated immediately after the prediction
of occurrence of slopping.
Example 5
[0085] Blowing was carried out as in Example 4 except for the following: Instead of addition
of another throughhole for injection of pulverized auxiliary raw materials using purge
gas to the throughhole for observation of the vessel interior, and assembled probe
was equipped, which had an observation device and injection mechanism. This kind of
probe is a modified one shown in Fig. 15 in the following points. Inlet port 65 into
an outer cylinder 64 is connected to the powder injection unit. The injected powder
in carrier gas is released into the vessel interior from the outer cylinder 64. The
probe 61 includes a photoconductor therein. The purge gas is released from an inlet
port 63 and blown through a small aperture 42 of a front tip 41 screwed into a probe
61. The purge gas is mixed with oxygen concentration with 30 to 40% by volume.
1. Verfahren zur Beobachtung der Bedingungen für die Schlackenbildung in einem Gefäß
eines Konverters, worin zumindest eine Licht anzeigende Vorrichtung (5), die das Licht
im Gefäßinneren beobachtet, in zumindest einem Durchgangsloch (4) der Seitenwand (20)
des Konverters (1) angeordnet ist, die dem Gefäßinneren gegenübersteht, und daß die
Bedingungen für die Schlackenbildung durch diese zumindest eine Beobachtungsvorrichtung
(5) beobachtet werden.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Intensität und/oder
Wellenlänge des Lichtes des Gefäßinneren durch diese zumindest eine Licht anzeigende
Vorrichtung (5) angezeigt wird.
3. Verfahren nach Anspruch 2, dadurch gekennzeichnet, daß die angezeigte Intensität
und/oder Wellenlänge des Lichtes des Gefäßinneren mit dem Kriterium der Schlackenbildung
verglichen wird, das für eine spezifische Bedingung der Schlackenbildung bestimmt
wurde, wie für die Bildung von Entphosphorisierungs- und/oder Nicht-Auswurf-Schlacke.
4. Verfahren nach Anspruch 2, dadurch gekennzeichnet, daß das Licht des Gefäßinneren
photoelektrisch in ein Signal umgewandelt wird, das Signal in eine Vielzahl von Wellenlängenbereichen
geteilt wird, das Verhältnis des Lichtbereiches zum gesamten Bildbereich der Beobachtungsvorrichtung,
bezogen auf jeden Wellenlängenbereich, berechnet wird, und das berechnete Flächenverhältnis
mit einem bestimmten Kriterium der Schlackenbildung verglichen wird.
5. Verfahren nach Anspruch 2, bei dem die Information aus dem Signal gewonnen wird,
das durch die Licht anzeigende Vorrichtung (5) erhalten wird, um das Verhältnis der
gelben Grundfarbe zu allen Farbsignalen und die Veränderung in diesem Verhältnis zu
beobachten und dieses Verhältnis und die Veränderung mit einem bestimmten Farbkriterium
verglichen werden.
6. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Beobachtung durchgeführt
wird, während durch eine Meßfühler ein sauerstoffhaltiges Spülgas geblasen wird, um
das Verstopfen des zumindest einen Durchgangsloches (4) zu verhindern.
7. Verfahren zur Durchführung des Blasens in einem von oben und unten eingeblasenen
Konverter unter Verwendung eines der Verfahren nach den Ansprüchen 1 bis 6, dadurch
gekennzeichnet, daß entsprechend der beobachteten Bedingungen für die Schlackenbildung
zumindest eines der folgenden Regelverfahren durchgeführt wird: Regelung der Sauerstoffbiasmenge,
Regelung der Lanzenhöhe, Beschickung von Hilfsrohmaterialien wie Kalk oder Eisenerz
und Regelung der Blasmenge des Bodengases.
8. Verfahren zur Durchführung des Blasens in einem Konverter unter Verwendung eines
der Verfahren nach den Ansprüchen 1 bis 6, dadurch gekennzeichnet, daß zumindest eines
von Dolomitpulver, Ätzkalkpulver, Kohlepulver und Kokspulver bei der Voraussage des
Auftretens des Auswurfs, vorzugsweise durch ein Durchgangsloch der Seitenwand, in
das Gefäß eingeblasen wird, um das Blasen zu stabilisieren.
9. Vorrichtung zur Beobachtung der Bedingungen der Schlackenbildung in einem Gefäß
eines Konverters, die eine Licht anzeigende Vorrichtung, die einen Rezeptor umfaßt,
wobei der Rezeptor in einem Durchgangsloch der Seitenwand des Konverters angeordnet
ist und dem Gefäßinneren gegenübersteht, und eine Anzeigevorrichtung der Intensität
und/oder Wellenlänge eines Lichtsignal-Eingangswertes aus der Licht anzeigenden Vorrichtung
umfaßt.
10. Vorrichtung nach Anspruch 9, dadurch gekennzeichnet, daß die Licht anzeigende
Vorrichtung auf einem Verschiebungsmechanismus befestigt ist, der in der Umgebung
des Konverters angeordnet ist und mit einer Einrichtung zum zurückziehbaren Einsetzen
des Rezeptors in das Durchgangsloch ausgestattet ist.