US2306811A - Method of charging blast furnaces - Google Patents

Description

Dec. 29, 1942. T. H. K ENNEDY METHOD OF CHARGING BLAST FURNACES Filed Aug. 4, 1941 liweizfaiw 7l/MZ4/V A K /y; K .@i 5- large fiues.

Patented Dec. 29, 1942' METHOD OF CHARGING BLAST FURNACES S Truman Kennedy, McKeesport, Pa., assignor to National Tube New Jersey Company, a corporation of Application August 4, 1941, Serial No. 405,398

1 Claim. (cram-152) This invention relates to blast furnaces, and more particularly to the method of admitting and distributing the charge to the furnace.

Most commercial blast furnaces comprise a hopper, from wh ch they are admitted to the.

furnace in a regulated or controlled manner.

Usually the hopper comprises a unitary structure of an upper truncated cone from which there depends a lower inverted truncated cone. top of the upper truncated cone has a central opening with wh ch there commun cates a feeding 'cylinder. there extends a shaft carrying on its lower end a large bell valve which closes a central opening in the lower inverted truncated cone, together with a smaller bell valve which closes the lower end ofthe feeding cylinder. The upper small bell valve opens a number of times while the large bell is closed, to admit each skip load of material. After the hopper has been filled with the desired charge, the small bell valve is maintained in such position as to close the lower end of the feeding cylinder, and the large bell valve is opened to permit the received charge to flow through the central opening in the lower inverted truncated cone. Frequently the'small bell valve is rotated to provide better distribution.

In the operation of the furnace, hot air under pressure is forced into the lower part of the furn-ace from a large supply line through a series of tuyeres. ,This hot air rises through the massof ore, coke, and limestone, to the top of the furnace, and in its ascent the chemical constituents of the air combine with those of the ore, coke and limestone and the'products of combustion (exhaust gases) areconducted away by means of Due to the combustion of the coke, and the various reactions occurring in the body of the ore mass and the-periodic tapping of the molteniron, the whole body of material gradually sinks .and there is a constant downward movement of the entire contents of .the furnace. Subsequently new material is admitted to the stock line of the formation by the action of the bell and hopper described hereinbefore, and the cycle of"'operatfi n goes on continuously. As the furnace gases rise through the furnace charge, they The" pass more readily than other regions wherein they are retarded. The vertical center of the charge permits the gases to pass more readily than does the zone between the vertical center and the outer periphery. This last-namedzone (i. e.,between the vertical center of the charge and the periphery) which is more or less impervious to the flow of the gases, may fail to provide its. share of the flow passage, with the result that there is formed a verticalannular ring or column of material upon which there has been little gas action until approaching close to the bosh portion of the furnace which, as aforesaid, is adjacent the crucible at the bottom thereof.

Ordinarily, blast furnaces are constructed in the form of an elongated hollow truncated cone,

Through this feeding cylinder to permit the mass to spread out as it descends, whereby the rising gases flow more freely than i would otherwise be thecase. However, this con- .struction is not sufficient to eliminate the difficulties described hereinbefore.

Among blast furnace operators, it is commonly considered good practice to avoid the formation at any point-in the ore-fuel mass from the vertical center line-to the inner walls of the furnace,. any region so dense, as to be impervious to, or

block the flow of, the upwardly moving gases. That is to say, the materials should be deposited inthe furnace in such manner, sequence, and quantity that the result is a more even distribution of materials over the entire area of the stockline; fine materials should not be accumulated apart from the coarse materials, and the coarse materials should not be segregated apart from the-fine materials.

It is, of course, true that there are numerous variables in the quality and composition of ores, fu ls and limestone; but the relative diameters of hopper. bell and furnace wall, the slope of the bell surface, and the extension of the edge of the bell beyond the hopper and depth of the stock encounter zones or channels through which they line, are substantially constant.

As the large bell valve is lowered, the material falls to the sto ck line, and builds up an" annular ring of material, forming a peak which is sometimes at a distance from the wall of thefurnace.

This annular peaked ring is therefore a circular ridge running around the stock line of the furnace. On the inner slope (i. e., that which is toward the center of the furnace) the gradient of theridge is uniform, and conforms to the angle of repose of the material, while on the outer slope there may be a shallow pocket formed at the top which ray or may not entirely fill up with m s- 2 cellaneous materials. This shallow pocket is the result of prevention of the orderly formation of a slope due to the adjacency of the annular wall of the furnace.

It is among the objects of the present invention to provide va method of operating a blast furnace bell valve which will collectively result in the very even distribution of the charg within the blast furnace. More specifically, the invention seeks to so control the tendency of the fallingj material to form a peak that the ordinary circular ridge condition will be broken up, and in lieu thereof the pattern of material will have a sinuous or serpentine path or direction. This sinuous or serpentine path of direction is in contact with, or tangent with,the walls of the furnace at one point, and immediately leaves the wall region to traverse a region at any fixed and suitable distance away from the wall, returning again to the wall at regular intervals of space until the entire periphery of the outer rim of the stock bed has been zigzagged over and over. By the same device, two sinuous curves of ridge formation are established, one curve overlapping the other to the extent that the crests of one curve cover the troughs of the second, and the troughs of the first overlap the crests of the second.

To the accomplishment of this and other desirable objects and purposes, I have designed the present, preferred embodiments of the invention presented in the accompanying drawing forming a part of this specification and to which refer ence should be had in connection with the following detailed description, and in this drawing, for simplicity, like reference numerals have been employed to designate the same parts throughout the several views.

In said drawing, Figure 1- is a fragmentary cross-sectional elevation of the upper end of a blast furnacewith its feeding cylinder, hopper, small bell valve, etc., all of which are of conventional design; and illustrating in connection therewith the large bell valve of the present invention, which is shown in elevation.

Figure 2 is a horizontal sectional view of the stack of the blast furnace, with the large bell valve of Figure 1 shown in plan, together with a diagrammatic illustration of the manner in which the large bell valve is operated in accordance which the principles of the present invention are employed.

Referring more particularly to the drawing, the numeral I designates the top of the stack of a blast furnace of conventional design,'the said stack being cylindrical in shape and composed of refractory brickwork.

Superposed on the stack I is a frusto-conicaltop 2 which supports the hopper of the blast furnace. This hopper comprises an upper frusto-conical portion 3 and a lower inverted -fru'sto-conical portion 4. The upper portion 3 of the hopper-is provided with a central aperture through which there extends a feeding cylinder 6. Through the feeding cylinder 6 and into the hopper composed of the upper and lower portions 3 and krespectively, there extends a shaft I carrying at its lower end the large "bell valve 9 of the present invention. Within the feeding cylinder 6 the shaft I carries a slidable sleeve I9, between the lower end of which and the large bellvalve 9 is a small bell valve II which is adapted to seat against, and close, the lower end of the feeding cylinder 6.

In practice, the small bell valve I I on the lower end of the slidable sleeve I0 is opened a number of .times, while the large bell valve 9 on the lower end of the shaft 1 is maintained in closed position. After the hopper composed of the upper and lower portions 3 and A respectively, has been filled with the desired charge, the small bell valve-I I is maintained in closed position in order to close the lower end of the feeding cylinder 8, and the large bell .valve 9is opened to permit the received charge to flow through the central aperture in the lower portion of the hopper. In addition, rotation is imparted to the shaft I when in its lowered position, in order to more evenly distribute the materials to be charged to the blast furnace. The foregoing operation and the mechanism for accomplishing the same are believed to be so well known to those skilled in the art as not to require illustration herein.

The major portion of the large bell valve 9 has the conventional smooth conical surface, but, according to the teachings of the present invention, it carries an extended skirt portion I2 the edge or margin of which is provided with skill?" ous or serpentine serrations, the inwardly bellied portions of which are designated at I3 and the outwardly bellied portions at I4. As a specific embodiment, the extended skirt portion I2 of the large bell valve 9 may have six inwardly bellied portions I3 and. six intermediate outwardly bellied portions I4. Such an arrangement will space the inwardly bellied portions I3 and outwardly bellied portions ll at SO-degree intervals. The extended length of the skirt portionl2 of the large bell 9 may be varied to give the desired spread of peak ridges of fine material.

As the large bell 9 is lowered to the dotted line position, the material escapes from the hopper composed of upper and lower portions 3 and 4 respectively, and the extended skirt I2 on the margin of the large bell valve 9 determines the posi-- tion on the stock line on which the material will fall. Two factors determine the location of this position, one being the depth of the inwardly bellied portions I3 and outwardly bellied portions I4, and the other being the length of the extended skirt I2. The serpentine path of the peak ridge on the stock line makes a curve with deeper serrations than the corresponding ones on the margin of the large bell valve 9. This is due to the fact that the particles of material released from the hopper gain a certain momentum as they roll down this extension.

. The longer the extended skirt I2 extends beyond the hopper at the outwardly bellied portions M, the greater distance the particles will travel from the large bell valve 9 toward the walls of the furnace, and the shorter the extended skirt I! at the inwardly bellied portions I3, the less the momentum of the particles and the shorter distance they will travel from the bell valve, or the farther they will be from the vertical walls of the furnace. Therefore two factors enter into the location of pattern of peak ridge: first, the distance of the points [3 and I4 from the wall I and stock line of the furnace; and the distance on the extended skirt l2 from the inwardly bellied portions l3 and outwardly bellied portions M to the discharge aperture of the hopper.

Referring to Figure 2, the concavo-convex line 23-24 illustrates the path of the peak ridge of fine material upon the stock line when the large bell valve 9 is lowered vertically from the closed position. The crest or convex portions 24 of the concavo-convex line 23-44 are in direct contact with the circular interior wall of the blast furnace, as represented by the numeral l and the concave portions 23 of the concavo-convex line 23-24 are located at any desired distance therefrom. The extreme positions of the con cavo-convex line '23i-24 are connected by a smooth sinuous curve.

In the event that the large bell valve 9 embodies six inwardly bellied portions l3 and six intermediate outwardly bellied portions M, as in the embodiment described hereinbefore, as the said large bell valve 9 is raised it is rotated approximately 30 degrees, or about one-half of a serration. The raising and lowering of the large bell valve 9 and the manner of its rotation is,

as before stated, accomplished in a manner which is believed so well known to those skilled in the art as not to require illustration herein.

lifter the large bell valve 9 has been raised and rotated approximately 30 degrees, the hopper comprising the upper and lower portions 3 and 4 respectively, filled, and the large bell valve 9 again lowered to the position designated in Fig- 1 ure 1, the material will be discharged from the stock line in the same manner as that described hereinbefore, except that due to the 30-degree rotation the pattern of the peak ridge will take the form illustrated in dottedlines in Figure 2. This results in the supplanting of what was formerly a dense annular zone or pipe of fine materials, with a much broader zone, wherein the fine materials are well distributed throughout the coarse materials. Similarly, every zone from the outer rim to the vertical center is affected by this method of distribution and improved by a more eve distribution of materials and sizes over the entre area of the stock line.

With the approximately 30-degree 'rotation' described hereinbefore, the concavo-convex curves 23- 24 cross each other at nodal points designated at X. Constant repetition of these deposits may cause dense masses to accumulate at these nodal points X. However, a breakingportions 34 on the interior of the lower inverted frusto-ccnical portion 4 of the hopper. These inwardly bellied portions 33 and-outwardly bellied portions 34 may be formed as a component part of the hopper structure, as shown, or may take the form of a detachable insert. When using this modification, the large bell valve 39 takes an entirely smooth conical form in a manner well known to the prior art.

. When using the modification of Figures 3 and 4, as the conventionally formed large bell valve 39 is lowered and material allowed to escape out over the margin thereof, the particles composing the material imprisoned within the hopper will attain varying momentum as they roll down the oblique surface of the bell overhang. The momentum of the particles will vary from point-to point around the margin of the bell valve. Material released at point 40 will have less momentum than that released at point 4|. Material will, therefore, leave the conventional large bell valve with varying velocities and will land at unequal distances from its margin upon the stock line. Therefore there will have been formed, as in the embodiment first described,a deposit of material upon the stock line having a sinuous or serpentine direction reproducing in enlarged form the pattern of the serrated inner conformation of the hopper. the large bell valve need not be rotated. -Instead there may be employed means for rotating that portion of the hopper which has the sinuous curved inner surface, moving it an angular distance of one-half of one serration, or one-half of one serration plus or minus a given amount, in the manner of the preferred embodiment.

It is to be noted that in the device'of the preferred embodiment the entire margin of the large bell valve 39, or the points at which the rolling or sliding material leaves the same, are at fixed and equal distances from the furnace wall I and, therefore, the advantages of this form of the invention rest solely upon the conception of a variable overhang as measured from any point on the serrations in the hopper to the margin of the largebell valve.

While we have shown and described several specific embodiments of the invention, it will be understood that we do not wish to be limited exactly thereto, since variousfurth'er modifications may be made without departing from the scope of the invention as defined by the following claim.

I claim:

The method of charging material in a metalfore but with the sinuous ridge formed thereby intersecting at spaced points the sinuous ridge of the material previously charged.

TRUMAN H. KENNEDY.

In this proposal,

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