US3413852A

US3413852A - Radiometer and oxygen lance combination

Info

Publication number: US3413852A
Application number: US432095A
Authority: US
Inventors: Engel Frederik; Alwyn F Wiebe
Original assignee: Barnes Engineering Co
Current assignee: Barnes Engineering Co
Priority date: 1965-02-12
Filing date: 1965-02-12
Publication date: 1968-12-03
Anticipated expiration: 1985-12-03

Description

Dec. 3, 1968 F. ENGEL ET AL RADIOMETER AND OXYGEN LANCE COMBINATION Filed Feb. 12, 1965 2 Sheets-Sheet 2 I N VEN TORS. FEEDER/K E/VGEL ALWY/V F W/EB BY Mfi ATTORNEY United States Patent 3,413,852 RADIOMETER AND OXYGEN LANCE COMBINATION Frederik Engel, Greenwich, and Alwyn F. Wiehe, Ridgefield, Conn., assignors to Barnes Engineering Company, Stamford, Conn., a corporation of Delaware Filed Feb. 12, 1965, Ser. No. 432,095 4 Claims. (Cl. 73355) This invention relates to an oxygen lance and radiometer combination for measuring temperatures in steel furnaces and other apparatus where a cooled lance is used for introducing gases.

The problem of measurement of the temperature of molten steel in furnaces such as open hearth converters and the like has long been a serious one. In the older Bessemer converters temperature was frequently determined by the appearance of the flame from the converter. This was not very accurate and resulted in a considerable variation in quality of the steel produced. The problem became much more acute with the modern oxygen process in which oxygen is introduced from above the melt through a 50 feet long water cooled lance. This process has constituted so great an improvement that steel furnaces are rapidly being converted to use the prOcess. However, for best operation an accurate knowledge of the temperature is necessary and this has created a serious problem because, of course, if the temperature is not maintained right and a steel melt is spoiled the costs of such an occurrence can be very high. Also, though perhaps less spectacularly serious, if the temperature is not maintained accurately the quality of the steel produced may not be an optimum.

Various proposals have been made to measure the temperature of the steel, for example, expendable thermocouple probes have been used but this has not proven to be entirely satisfactory as the probe has to be actually lowered or dropped into the melt.

At first glance it would seem that the problem might be solved by radiometry using a radiation pyrometer looking down on the surface of the steel melt. This, however, is not very practical because the surface may become covered with a thin layer of slag or other impurities and so wrong temperature readings or at least inaccurate temperature readings result.

The first oxygen lances used were open at the bottom, the wall of the lance being water cooled and it might appear practical to place a radiometer at the top of the lance. However, this early form of lance is no longer preferred and modern lances have their bottoms closed except for a number of holes, the longitudinal axis of which is on a slant with respect to the lance body proper. Typically there may be three holes pointing out at an angle that may be of the order of Such a lance cannot be used with a radiometer because the radiometer would see the bottom wall, the temperature of which bears but little relation to the actual temperature of the steel.

The present invention solves the problem of radiometric measurement in a modern oxygen lance and is free from the disadvantages of other temperature measurements which have been proposed. Essentially in the present invention one or more, usually three, radiometers are located in the water chamber nearest the inner wall of the lance. The structure of the lance is altered by providing side tubes extending through the inner wall into the water space and having the radiometers mounted at their upper end. The directions of the tubes are such that they are substantially aligned with the slanted tubes at the bottom of the lance. Radiation from the surface of the steel or, as will be pointed out in more detail below, other materials located near the surface such as hot gases,

ice

pass up the inclined side tubes in the inner wall of the lance and strike the entrance pupils of the radiometers. Normally a protective window is provided and one or more bandpass filters. It is also possible to utilize beam directing means such as a prism in the entrance pupil of the radiometer but for practical purposes this is ordinarily not necessary as the amount of radiation available is high and the inclination of the tubes in the bottom of the lance is small. Therefore, in preferred practical instruments a beam directing means is eliminated because the energy loss is small and the remaining energy is still more than sufficient for good radiometer response. However, the present invention does not exclude a more sophisticated structure with beam directing means.

The location of the radiometers in the coolant passage of the lance brings them fairly close to the angled tubes at the end of the lance, for example, about three feet. This permits viewing of a larger area of the surface of the steel and so avoids possible spurious results if there are small areas, the temperature of which differs markedly from that of the melt as a whole. When a radiometer was used at the top of an old style lance the path to the steel was so long, up to nearly 50 feet, that collecting optics were needed and only a relatively small surface of steel could be viewed. This introduced a further disadvantage in that local hot spots might give an incorrect reading. The location of the radiometer, preferably in the inner coolant passage of the lance, permits a normally quite stable environment at relatively moderate temperature far below the boiling point of water. This minimizes any effects of instrument temperature on readings. However, if desired the radiometer may be provided with a temperature sensing element such as a thermocouple or thermistor so that excessive temperatures can be avoided when the lance is being built and the outer wall welded The radiometers are provided with electronics which produce an output signal that can be used for temperature readout, preferably at a location removed from the actual furnace. The present invention is not concerned with any new form of electronics or any new type of readout instruments. The exact design of these elements, therefore, does not form any part of the present invention and so will not be shown in detail. Although they are not new in the present invention suitable electronics and readout elements are necessary to utilize the invention practically.

The radiometers present no very serious problem. The dimensions of the water channel, however, dictate a long and narrow radiometer with its associated electronics and in this shape of radiometer it is normally not necessary to use collecting optics. However, as pointed out above, the present invention is not broadly limited to any particular radiometer for, of course, the exact shape and dimensions of the radiometers are a mere matter of proper engineering design.

Although any suitable radiometer can be used, there i an important advantage in utilizing radiometers as described in the Weiss Patent 3,161,775, Dec. 15, 1964 and such radiometers are preferred and in a more specific aspect of the invention constitute part of the combination claimed. The Weiss radiometers use photomultiplier tubes for detection and utilize wavelengths of radiations which are much shorter, for example, from /2 to /6 the wavelength of that for maximum radiation. This permits an important additional advantage. When operating a considerable distance from the wavelength for maximum radiation the changes in radiation with temperature follow a much higher power of absolute temperature, than is the case at the wavelength for maximum radiation. For example, at maximum radiation wavelength the response is in proportion to the fifth power of the absolute temperature but at one-half the wavelength the response is in accordance with a much higher power of the absolute temperature. Since the emissivity of the body, the temperature of which is to be measured, is a linear function it becomes so small in comparison to the effect of a change in temperature that it can be practically neglected. Even with an enormous emissivity variation of 2 to l the accuracy is better than percent and so the temperature measurements may be considered practically independent of emissivity of the surface of the steel. This is a very great practical advantage because surface scum can change the emissivity quite markedly even though it is, to considerable extent, blown away by the oxygen blast. Therefore, in a preferred aspect of the present invention for the most perfect practical instruments, the greater precision of the Weiss radiometers is of real importance and so this type of radiometer is preferred and constitutes a part of the combination of the preferred specific embodiment of the present invention.

Apart from the desirability of using a Weiss radiometer with its narrow bandpass filter the present invention is not particularly concerned with the elements which are used in the radiometer and its electronics, except for the practical requirements of operating at an elevated temperature which may reach 100 C. in the case of a defective circulation of water in the lance. The radiometer must also have a high degree of shock resistance bebecause when not in use lances are subject to fairly rough treatment in a steel mill.

In the case of electronic elements temperature is practically the only problem except for the detector. Photomultiplier tubes, as described in the Weiss patent, are preferred and when this type of radiometer is used photomultiplier tubes must be chosen which operate reliably even under conditions of severe shock, vibration and fairly elevated temperature. There are available today commercially photomultiplier tubes which are completely incapsulated except for a small radiation window and which have self-contained voltage divider resistors for the various dynodes so that only three wires are needed for ground, high voltage and signal output. This type of photomultiplier tube is preferred. It is, however, an advantage of the present invention that a common commercially available photomultiplier tube can be used and specially fabricated detectors are, therefore, not necessary.

The Weiss radiometers utilize wavelengths from onehalf to one-sixth that for maximum black body radiation. In the case of the steel furnace the temperatures may vary from 1200 to about 1800 C. This corresponds to A of from about 1.95 1. to 1.45 For maximum precision one would ordinarily utilize wavelengths in the near ultraviolet. In fact the Weiss radiometers are often loosely referred to as ultraviolet radiometers. In the case of the present invention, however, another result can be obtained under special circumstances by departing somewhat from the theoretical maximum precision as set out in the Weiss patent though still well within its operating range. Thus it has been found that for the radiometer or radiometers which are receiving radiation from the surface of the molten steel, a narrow band of radiation in the yellow green at about 560 me, can be used to give good precision even with quite large variations in emissivity and it performs the additional function of being blind to strong emission lines of carbon monoxide and carbon dioxide which are the most common gases which might be encountered having strong emission lines.

The present invention has a further advantage when more than one radiometer is used, for example, when three are used, in the case of the most usual configuration of modern oxygen lances. The use of multiple radiometers permits an added protection against radiometer failure and a check of one radiometer reading against another. Radiometers are quite rugged instruments and have long useful lives but no instrument is free from the possibility of breakage or malfunction and so if more than one radiometer is present the added redundancy enormously decreases the possibility of complete failure with the large losses which can result from a spoiled steel melt. The additional cost of more than one radiometer is quite small when amortized over their long lives. Therefore. there is a real practical advantage in using more than one radiometer per lance even though it is not desired to measure radiation from gaseous emission bands.

The Weiss radiometer in its preferred form presents an important additional advantage. When photomultiplier tubes are used it is possible to make measurements at .1 fixed current, for example, 10 ,ua., by varying the high voltage on the anode of the photomultiplier tube. This effects a logarithmic compression which is extremely valuable as the temperature range in a particular steel melt may run over several hundreds of degrees from start to finish and this can result in a radiation variation of as much as 400:1. The invention is not, of course, limited to the use of a photomultiplier tubes as a radiation detector and the compression feature described above. If a different type of detector is used the electronics are preferably of logarithmic or semilogarithmic type to effect the necessary compression. When the preferred form of Weiss radiometer is used the compression is effected by the operation of the photomultiplier tube itself at constant current and this is the preferred modification.

The smaller angled tubes at the bottom of the lance in conjunction with the short path radiometers also permit an additional advantage, namely that it is easier to calibrate the instrument when the lance is out of the steel melt because the area of such a calibrating source of known temperature is considerably smaller and so makes calibration easier. It is an advantage of the present invention that the important improved results are obtained without any compromise and even with additional advantages.

The operation of a Weiss radiometer in order to increase precision by measuring at a much shorter wavelength than that corresponding to maximum radiation requires only that the wavelength band be at least sufiiciently short. In other words, a long wave cutoff filter is essential. If it is desired to avoid interference from emission bands of gases, of course, the range of radiation must be much narrower and so that filters used have to have a short wave cutoff as well as a long wave cutoff. In many cases the gas emission interference is not serious and then the filters can be simpler and cheaper providing only for a long wave cutoff.

The invention will be described in greater detail in conjunction with a typical oxygen lance, only one radiometer. however, being shown. The invention will also be described in conjunction with the drawings in which:

FIG. 1 is a vertical section through one side of an oxygen lance, and

FIG. 2 is a horizontal section above the radiometer looking down at the end of the lance.

The lance itself is made up with an outer wall 1, a middle Wall 2 and an inner wall 4. This forms two

channels

3 and 5 through which water circulates, down in the inner channel and up in the outer channel. An inclined tube 6 is mounted in the inner wall 4 having an inclination corresponding to that of a tube 18 which is shown in FIG. 2. At the top of the tube there is a mounting flange 7 on which is mounted a window 8, a sharp cutting filter 9 and the radiometer with a photomultiplier tube 10 forming its entrance pupil and incapsulated as shown at 11 and its electronics at 12. Since the design of the radiometer is not ditferent from that described in the Weiss patent except for its elongated shape, it is not shown in detail but only diagrammatically. From the electronics three wires 15 emerge passing through a connector 14 mounted on an upper flange 16. Suitable water tight seals are shown, for example, at 19 to prevent any possibility of water getting into the radiometer and to provide a suitable firm seating therefor.

If more than one radiometer is used, for example three, there will be three side tubes through the inner wall of the lance each one registering down a particular tube 18. It should be noted that the openings in the bottom wall 20 of the lance are circular but the view through the inclined tube is more or less lenticular as shown at 18.

The invention has been described in conjunction with structure in Which the inclined tubes extend only into the inner coolant passageway and the radiometers are located therein. It is, of course, possible for the inclined tubes to extend further either into the outer coolant passageway to mount the radiometers in the outer coolant passageway. While such modifications are operative and are not excluded from the board aspects of the present invention the preferred modification illustrated in the drawings has marked advantages. It is cheaper, and the temperature environment in the inner coolant passage is better for radiometer operation. Therefore, this modification is preierred.

I claim:

ll. An oxygen lance and radiometer structure comprising:

(a) a lance with cylindrical walls forming two coolant passages,

(b) a bottom wall with at least one opening angled out at a small angle,

(c) at least one inclined tube in the inner wall of the lance extending upwardly at least onto the inner coolant passage and having its axis aligned with the axis of one of the openings in the bottom of the lance,

(d) a radiometer mounted on the upper end of said inclined tube having means for selecting a predetermined wavelcngth band of radiation and being 10- cated so that the entrance pupil of the radiometer receives radiation through the inclined tube, and (e) the radiometer being provided with a radiation detector responsive to the predetermined radiation range and electronics receiving signal from said detector and producing an output which is a function of temperature of the materials whose radiations are received by the radiometer. 2. A lance and radiometer structure according to claim 1 in which the inclined tube extends only into the inner coolant passage and the radiometer body is located in said passage.

3. A lance and radiometer structure according to claim 1 in which the radiometers are provided with filtering means including at least a long wave cutotf to restrict the radiation to a wavelength not longer than one-half the wavelength of maximum radiation of the steel for the range of temperatures being measured, whereby emissivity changes in the surface do not significantly interfere with accuracy of reading.

4. A lance and radiometer structure according to claim 3 in which a plurality of radiometers are used each one aligned to receive radiation from a different inclined tube.

References Cited UNITED STATES PATENTS 1/1950 Mead 73-355 XR 12/1964 Weiss 73-355 XR

Claims

1. AN OXYGEN LANCE AND RADIOMETER STRUCTURE COMPRISING: (A) A LANCE WITH CYLINDRICAL WALLS FORMING TWO COOLANT PASSAGES, (B) A BOTTOM WALL WITH AT LEAST ONE OPENING ANGLED OUT AT A SMALL ANGLE, (C) AT LEAST ONE INCLINED TUBE IN THE INNER WALL OF THE LANCE EXTENDING UPWARDLY AT LEAST ONTO THE INNER COOLANT PASSAGE AND HAVING ITS AXIS ALIGNED WITH THE AXIS OF ONE OF THE OPENINGS IN THE BOTTOM OF THE LANCE, (D) A RADIOMETER MOUNTED ON THE UPPER END OF SAID INCLINED TUBE HAVING MEANS FOR SELECTING A PREDETERMINED WAVELENGTH BAND OF RADIATION AND BEING LOCATED SO THAT THE ENTRANCE PUPIL OF THE RADIOMETER RECEIVES RADIATION THROUGH THE INCLINED TUBE, AND (E) THE RADIOMETER BEING PROVIDED WITH A RADIATION DETECTOR RESPONSIVE TO THE PREDETERMINED RADIATION RANGE AND ELECTRONICS RECEIVING SIGNAL FROM SAID DETECTOR AND PRODUCING AN OUTPUT WHICH IS A FUNCTION OF TEMPERATURE OF THE MATERIALS WHOSE RADIATIONS ARE RECEIVED BY THE RADIOMETER.