US3544710A - Method of controlling the operation of a shaft furnace - Google Patents

Description

United States Patent inventor Arthur Pool Embourg, Belgium Appl. No. 666,869 Filed Sept. 1 l, 1967 Patented l, 1970 Assignee Centre National De Recherches Metallurgiquea Brussels, Belgium a Belgian Body Corporate Priority Sept. 12, 1966 Belgium No. 51941 METHOD OF CONTROLLING THE OPERATION OF A SHAFT FURNACE 7 Claims, 4 Drawing Figs.

US. Cl. 178/6 Int. Cl...... *H04n7/02 Field of Search 178/61ND; 73/355, 351

[56] References Cited UNITED STATES PATENTS 3,021,385 2/1962 Sumerhayes 178/61ND 3,021,386 2/1962 Clark l 78/61ND 3,243,509 3/1966 Stut l78/6lND Primary Examiner-Robert L. Griffin Assistant Examiner-Barry Leibowitz Attorneyl-lolman, Glascock, Downing & Seebold ABSTRACT: A method of controlling the operation of a shaft furnace in which the upper surface of the charge is scanned by a a television camera sensitive to infrared radiation which transmits the signals and coordinates of the signals to a computer for measurement and display to show temperature distribution over the upper surface. A further feature provides measurement of the distance of each point relative to the camera, giving a three-dimensional picture of the charge and knowledge of the temperature at each point.

' PATENIEum mu SHEET 1 OF 2 'Ii mhv- R- vi s 1 I. METHOD OF CONTROLLING THE OPERATION OF A SHAFT FURNACE The invention relates to a method of controlling the operation of a shaft furnace.

Rational operation of a shaft furnace is, as is known, linked with knowledge of the course of the physical or'chemical reactions going on inside the furnace and of any measurable values connected with these reactions. In this connection, knowledge of the temperature distribution on the upper surface of the furnace charge greatly facilitates the operators task and enables him to have a better command of the working of the said furnace, its yield, safety and regularity of operation.

It should also be noted that the temperature prevailing at any given point of the charge and therefore of its surface is closely linked with the circulation of gases at that point. The temperature distribution on the surface therefore provides the user with information about the circulation ofgases and consequently about the reaction rate of the furnace at that point.

ln addition, it is well known that to obtain efficient use of the reducing power and sensible heat of the gases, leading to minimum fuel consumption, the gases should be distributed as uniformly as possible over the full cross section of the furnace.

It is also well known that with certain charges which have a tendency towards hanging i.e. clinging of the charge to the lining, the furnace must be given a faster rate of operation at the periphery of the surface (obviously a certain limited deterioration of furnace yields has to be accepted). This shows more clearly how important it is to know the temperature distribution on the surface of the furnace charge.

Various methods have already been established to measure these temperatures and determine their variations over the full surface of the charge.

To this end it has already been proposed to place thermocouples in the refractory lining of a shaft furnace in the vicinity of the upper surface of the charge.

This method has the disadvantage of being able to provide data only concerning the temperatures existing at a few points on the periphery of the furnace in the neighbourhood of the upper surface of the charge. Thus no indication can be obtained for the completeperipheral zone and still less for the central zone. I

Moreover, in case of accidental deterioration of a refractory block in which a thermocouple is fitted, the indications provided thereby can only lead to erroneous conclusions, for an increase of temperature indicated by this thermocouple comes not only from an increase of temperature of the gas, but also arises as a result of the deterioration of the refractory lining entailing an effective reduction of the thermal contact between the thermocouple and the atmosphere of which the temperature measurement is required.

According to another method already recommended, one introduces into the stack a probe intended to allow temperature measurement along a radius of a limited section of charge as well as the taking of a sample for the purpose of analysis of the gases circulating in the furnace at that place. That method has the disadvantage of being essentially discontinuous. Moreover, the data obtained by this method is incomplete, the probe is introduced only with difficulty into the furnace and is subject to bending and to breaking owing to the continuous descent of the charge through the furnace.

In order to mitigate these disadvantages, it was proposed to record all or part of the visible electromagnetic radiation emitted by the charge and as'soon as a lighter zone is observed on the charge, corresponding to a higher temperature, to take steps to counteract the presence of such a zone.

According to a development of this method, the surface of the charge is observed by means of a television camera, whose signals are displayed on a television screen thereby enabling the operator to follow the course of the charge temperatures with ease,

This process still has the disadvantage of relying on the necessarily subjective judgement of the observer. Indeed, although examination of the condition of the-charge by means 'of a television screen enables the observer to determine whether one point in the charge is hotter than another, it does wnot enable him to estimate the difference in temperature It is easy to understand that these disadvantages are at the root of the inadequacies of the measurements that the observer may have to make.

An object of this invention is a method enabling these disadvantages to be eliminated. v

The operation of a shaft furnace may be monitored by systematic scanning of the upper surface of the charge by means of a television camera sensitive to infrared radiation and to visible light.

By means of this scanning, an infrared or visible light signal emitted by any point on the surface of the charge in the solid angle of observation of the camera is recorded in direction and intensity by the camera.

The intensity of the infrared signal received is directly related to the temperature of the emission point and, other things being equal, it can be accepted that on the one hand two points emitting signals of the same intensity are of substantially the same temperature, and on the other hand two identical signals received for a single point at different times correspond to identical temperatures. It follows that if the infrared television camera is coupled to an electronic computer and if each signal received by the camera is transmitted to the computer for measurement, this signal is transformed into a numerical value representing the temperature of the point under consideration.

In order to obtain a distribution on a display screen of such numerical values the temperatures of the upper surface of the charge, the coordinates of each signal received by the television camera are recorded and transmitted to the, electronic received by the camera and the coordinates of the point emitting the signal; these coordinates corresponding in fact to the number of the sweep lines in which the signal is recorded and to the first sweep line (abscissa) at which the signal is recorded. .These three items easily allow the computer to frame the representative display screen with numerical values.

if, in addition to the intensity and the two coordinates of each signal, one transmits likewise to the computer the value of the distance of the point emitting the signal to a point fixed with respect to the camera, a numerical display can be obtained analogous'to that mentioned above, but the numerical indications will be corrected by the computer to allow-for the variation in intensity due to the greater or lesser distance of each point from the camera.

In the known way, the numerical display mentioned above allows of carrying out a continuous and complete controlling of the distribution of the charge with the passage of time. In practice, the average value of the numerical values displayed is determined, preferably continuously, which allows modification of the distribution of the different constituents of the charge to be deposited on the observed surface so as to reduce the difference between the average and the value observed on the numerical display.

A well-known way of modifying the distribution consists in feeding more coke onto the regions of lower temperature (that is to say, on those regions which the corresponding zones on the numerical display indicate the values are lower than the average) and more of the ore onto the regions of higher temperature.

The method of the present invention is based essentially upon the fact that the upper surface of the charge of a shaft furnace is subjected to the scanning of one or more television cameras, fixed or mobile, sensitive to infrared and visible radiation; that any infrared or visible light signal coming from tion desired. 1 v 7 These national subdivisions of the upper surface should not be confused with the zonal distribution of 'the numerical V the chargeand received by the camera is transmitted, there to I be measured, to an electronic computer; that the'indications of thecoordinates permitting the determination of the f 1 direction ofthe point of originofthe signal on the surface are likewiseztransmitted to the computer which allows the obtaining on a display screen a zonal distribution of numerical values i representing the distribution of temperatures on the surface of 1 the charge, each zone of the display screen corresponding to a region of the surface; thatth'e average valuelof this numerical distribution is calculated andthat the distribution of the com.- a 1 ponents of the charge. to v be. deposited. on .the surface is modified in such away asto reduce 'ornullify any difference 4 existing between the calculated average and .fany numerical value observed. According to requirements, morethanone camera maybe used, in which case each is judiciously trained on that portionof-the surface to be observed, and each of the cameras utilize the method described above., i

According toan advantageous variant of the invention,

there is likewise transmittedto the computer, atthe time as the coordinates determining the direction of the point of origin of a'definite signal," a'measur'ementofithe distance of the components of the charge'to be deposited.

. 1 According to another-variant, more advantageous still, the

observed surface of the charge is consideredas consisting of .two or more concentric-areas, each of these areas being in 'turn sub-divided into several sectorsor regions. The display screen, relating to the complete surface of the charge, shows the numerical valu'esinthe zones corresponding to each sec- Other methods of nationally sub-dividing adapted more orless specifically to the temperature distribuvalues on the display screen, although each zone of the display screen does correspond tof'a sector, or region, of theupper f surface.

The method of. the

ticular:

a. the measurements and calculations may be carried out continuously;

b. the measurements and calculations are objective;

. c. themethod may concern and a d, its precision does not vary with time;v

he invention will now be described with reference to the l accompanying diagrammatic drawings, which show an em I bodimentof the invention but in no restrictive sense. 'ln thedrawings; p v t t FlG. l shows in diagrammatic section, a part of a blast furna ce fwitha fixed television camera;

' FIG. 2 shows a screen of a television camera;

3 v f F163 is a block diagram of the circuit involved; and I $16. 1 is a diagramof scanning apparatusi'comprising a movabletelevisioneameras the uppersurface" t of the charge can obviously beenvisaged,each method being a V i present invention shows numerous ad-- I vantages with respect to the processesused heretofore, in parthe whole surface ofthe charge;

drawing; it is supposed thatthere is onlya single camera and a representation of the means forstopping and sealing the furnace,.with respect to the mouth and with respectto the camera, have been omitted. Naturally, more than .one'camera may be used if desired. j

FIG. 2 represents diagrammatically the receiving screen 5 of the television camera. Any point of the-observed surface i is, characterized bytheintensity I of the luminous spot which it causes to appear at 7 on the'screen and by the geometric coordinates Sand 9 of this spot. 7

The correspondingblock diagram (FIG, 3) thusincludes the television camera 3 and a connection 10 transmitting the signal I to an electronic computer 11; two-coordinate devices point 6 and likewise transmitting them to the computer 11 i this point from'a point of reference fixed with. respect tothe 1 camera, which allows the computer to automatically iny troducea. correction, depending on :this distance,of the numerical indications on the display screen and thereby localiz'-. 9

ing in an exact way every position on theupper surface of the I charge for which it is expedient to modify the distributionof 12 and 13 recording the values off8and 9 corresponding to which supplies the numerical display screen 14 by means of an appropriate digital converter 15. The screen 14 is divided up into distinct zones, each of whichdisplays atemperature corresponding-to a sector, or region, of the charge'surface. The determination of the distanceof the emitting point 6 to a line fixed with respect to the camera and passing, for example, through its optical center, can be done in the usual way by means of a conventional optical telemetric arrangement, which can be moved so as to observe-different points on the surface and thereby cover the entirety of the upper surface of the charge. The introduction into the electronic computer of the value of the distancefrom the pointconsidered to the optical center of the screen of the camera-will permit the correction due to the intensity I as a function of this distance.

ln the'event that it is intended to use the television camera itself to carryout the luminous measurement and the telemetric measurement, one may proceed as is shown in FIG. 4.

A telemetric device consists of a directional transmitter 21 and a receiver 22 (televisioncamera which also performs the luminous measurement), fixed with respect to one another.

" .teristics by which itcan be easil ydistinguished fromthe infrared or visible light signals emitted by any point whatever on the charge. This radiation beam 25, perpendicular to 23,

strikes the charge surface representedbythe solid line at a point 28.: Points 26 and 27 are other possible levels of the surface. The receiver 22 records in its image focal plane a trace 29 or 30 or 37, as the case may be, of the radiation reflected by one of thepoints 28, 27 or 26, respectively. The distance between the trace 29, 30 or 31and the trace of the optical center of the-camera in this same focalplane is in direct and i unambiguous relation with the angle formed by the'axis 23 and the line joining the optical center to the point 28, 27 or 26 respectively. A simple trigonometrical relationship allows of the determination of the desired distance, the value'of which is The actual signal emitted by the point observed can be recorded in the usual way by the camera and transmitted to the computer independently of any telemetric measurement, the two measurements, telemetric and luminous, being able,

q for example, to be carried out systematically one after the other for each point or each sector (region) of the surface V la the case where. the configuration of the space accessible to the solid angle of observation of a camera does not allow this toinclude the entire surface to be examined, other.

cameras are arranged in differentplaces, carefully chosen, so

, as to allow observation of the parts of the surface which are FIG. 1 shows the upper partlofablast furnace, the charge w and orientable and which can observe successively all or part not in the field of observation of th'efirst camera.

It can likewise be envisaged to include the entire surface of the charge by means of one or more cameras suitably arranged of the surface.

The use of an orientable camera, provided with an observation screen of relatively narrow angular aperture, allows of carrying out .of the observation of the entire surface of the charge by systematic scanning of .each of the national subdivisions above mentioned. There can thus be set up a numerical display representative of the thermal state of the upper surface of the charge by means of the numerical display screen having merical temperature values of all the points within that zone.

The general average may be calculated from all the point readings or by taking an average of the zone averages.

I claim:

1. A method of controlling shaft furnace operation comprising the steps of viewing the upper surface of the charge in the shaft furnace with at least one television camera which is sensitive to infrared and visible light radiation; transmitting the radiation intensity signals received by said camera to an'electronic computer for conversion into temperature representations; transmitting signals to said computer for determining the location on the charge surface of each intensity signal; creating a numerical display ona display screen divided into zones, which numerical display shows a zonal, distribution of numerical values representing the distribution of temperatures on the surface of the charge, each zone of the display screen corresponding to a particular region on said charge surface; calculating the average value of the numerical distribution; comparing the calculated average to the numerical values; and modifying the distribution of the shaft furnace charge material being placed in the furnace so as to reduce any difference between a given numerical value observed and the .calculated average.

2. A method as claimed in claim 1 comprising the further steps oftransmitting to said computer, simultaneously with the coordinate signals, further signals representing the distance between the point of origin of each intensity signal on the charge surface and a point of reference fixed with respect to the television camera; and correcting each numerical value displayed on the display screen as a function of viewing distance by said further signals.

3. A method as claimed in claim 1 wherein one camera scans the entire'upper surface of the charge. v

4. A method as claimed in claim 3 wherein the charge surface is dividedinto at least two areas, each area in turn is subdivided into several sectors, and the'scanning is carried out by successively scanning each of these sectors; said average value of the numerical distribution is ageneral average representing the average calculated value of the numerical values in each zone.

5. A method as claimed in 'claim 1 wherein the steps are carried out automatically and continuously during the operation of the shaft furnace.

6. A method as claimed in claim 1 wherein if a numerical value is greater than the calculated average, thereby indicating the particular location of the charg'esurface which that numerical value represents is too hot, more ore than coke is distributed on that location in the shaft furnace.

7. A method as claimed in claim 1 wherein if a numerical value is less than'the calculated average, thereby indicating the particular location of the charge surfacewhich that numerical value represents is too cold, more coke than ore is'distributed on that location in the shaft furnace.

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