US2886306A - Method of and apparatus for distributing the charge in blast furnaces - Google Patents

Description

y 1959 H. H. MEYNADIEYR 2,886,306

METHOD OF AND APPARATUS FOR DISTRIBUTING 4 Sheets-Sheet 1 v THE CHARGE IN BLAST FURNACES Filed Sept. 15. 1954 ay 2, 959 H. H; M EYNAl Dl ER 2,886,306

METHOD OF AND APPARATUS FOR DISTRIBUTING THE- CHARGE IN BLAST FURNACES Filed Sept. 13. 1954 I 4 Sheets-Sheet 2 ew; 4 W.

May 12, 1959 H. H.MEYNADIER 2,386,306

METHQD OF AND APPARATUS'FOR DISTRIBUTING THE CHARGE IN BLAST FURNACES Filed'sepjz. 15. 1954 4 Sheets-Sheet s H. MEYNADIER METHOD OF AND APPARATUS FOR DISTRIBUTING May 12, 1959 THE CHARGE IN BLAST FURNACES 4 Sheets-Sheet 4 Filed. Sept. 13, 1954 f United States Patent METHOD OF AND APPARATUS FOR DISTRIBUT- ING THE CHARGE IN BLAST FURNACES Henri H. Meynadier, Homecourt, France Application September 13, 1954, Serial No. 455,733 Claims priority, application France September 16, 1953 2 Claims. (Cl. 26627) It has been found that in a blast furnace having a charging bell, a grading action of the ore and coke takes place, the finer materials falling almost vertically from the edge of the bell, while the coarse materials are distributed in variable proportions between thecentral zone and the peripheral zone, depending on the method of charging and the ratio between the diameters of the throat and of the bell.

The blast furnace thus normally contains a cylindrical annular zone of fine materials, which is less permeable than the other zones in the furnace and is located immediately beneath the lower edge of the bell, between a central zone and a peripheral zone which are more permeable. Depending on the ratio between the diameters of the throat and of the bell and the speed of the air at its exit from the tuyeres, the blast furnace has a tendency to work either more towards the axis or towards the walls.

In blast furnaces having large hearths, this low penneable annular cylindrical zone impedes a good distribution of the gases in the furnace and may, in certain cases, give rise to the formation of an inactive zone along the axis of the hearth (dead man) which has been observed in some steel works.

In order to enable the gases produced in front of the tuyeres to be satisfactorily distributed as between the central zone and the peripheral zone of the blast furnace, the bell must be given a fairly large diameter in order that the ring formed by the fine materials be located, in horizontal projection, at such a distance from the extremities of the tuyeres that, with a given speed of the air at the exit of said tuyeres, a portion of the flow of gas is forced into the central zone of the blast furnace, whilst the other portion remains in the peripheral zone outside I the ring of fine materials and works against the walls.

By reason of the relative impermeability of the ring of fine materials, the two rising currents of gas follow more or less separate'paths.

For the distribution of gases, everything goes on as if two concentric blast furnaces were actually being used, between which exchanges are relatively diflicult.

This will explain why graphs of the results of chemical analysis of gas samples taken from the shaft at various levels and depths, plotted in a diametral direction, exhibit very irregular curves for those corresponding to equal contents of CO and CO as also do the isotherms plotted in the same manner.

In practice, the diameter of the charging bell being fixed once and for all in accordance with experience already acquired from previous blast furnaces, the only way of modifying the relative magnitudes of the two currents of gas is to control the blower, that is, the working speed of the blast furnace.

Another phenomenon which has been met with very many times is that, at the moment when the charge is introduced into theblast furnace, a drop in the pressure of the gas in the ofitakes is observed; this pressure drop due to the fact that the ore, as it falls, constitutes an impervious annulus or screen which momentarily throttles the passage of the gas from the centre of the blast furnace towards the offtakes. Since the cross-section available for its passage is very considerably reduced, the speed of the gas increases and the latter carries away not only all the powdery particles from the ore but'also less fine elements which would have remained in the blast furnace if they had been able to reach the top of the charges by escaping from the effects of this forced draught.

It is to recover a part of these elements that, in many blast furnaces, large intake gas conduits are provided.

The object of the present invention is to provide a method of and an apparatus for the distribution of the charge, more particularly useful when the latter is composed of crushed or unciushed ore comprising a fairly high proportion of fine materials, method and apparatus overcoming the disadvantages referred to above.

The great majority of equipments for distributing the charges which have been previously described or used in shaft furnaces, were designed for distributing the fine elements over the whole section of the shaft or for collecting them in the form of a cylinder more or less remote from the walls. These fine elementstend to fill up the spaces left free between the largest pieces and in- Y crease the average resistance ofiered by the charge to the passage of the gases. In addition, the charge forms around the bell and beneath the bell, during its delivery into the furnace, a flared screen through which the gasm must pass.-

The method of my invention for improving the permeability of the charge in a blast furnace and facilitating its blowing, consists in dividing, during the charging operation, the annulus or screen of materials flowing around the lower periphery of the charging bell into peripheral portions by means of radial arms of inverted trough-like or dihedral cross-section and located in a spider formation below said charging bell, sothat at least a part of the materials of each portion are deflected into two opposite peripheral directions; causing'the materials of each portion to fall into the furnace when leaving said radial arms; adjusting the upper level of the charge in the furnace at a level well below the level of said arms for obtaining a segregation between the small pieces and the big pieces of said charge during the fall of said materals, said level being such that the small pieces fall and collect in radial areas substantially vertically disposed between the successive radial arms, and the big pieces, which are more'peripherally deflected than the small pieces, fall and collect below said arms, whereby more permeable sectors, (hereinafter referred to as breaches") are provided vertically in the charge through almost the full height of the shaft; providing at the bottom of the furnace a number of tuyeres twice the number of said arms; and setting the direction of said arms with respect to the direction of the tuyere axis, so that the breaches formed of the big pieces of the charge are radially disposed vertically above alternate tuyeres.

The arms having an inverted trough-like section may be either immediately located below the charging bell of the furnace or arranged aroundthe lower portion thereof, and in this last case the said arms may be either rigidly fixed to the said bell or hingedly attached thereto.

The arms or gutters having an inverted trough-like section are surmounted by dihedron members forming a roof above, and are arranged in such a way that vertical breaches should be made in the charge of the shaft below, facing some of the tuyeres; in these conditions, the blast from these tuyeres is forced right through to the central 'zone of the blast furnace, whilst the blast from the other tuyeres provides a peripheral air blast.

In order to-avoid errors of interpretation, it should be observed that in the mind of the inventor, it is clearly not a matter of considering that in the standard method of distribution, the ring of fine ore descends vertically to the bottom of the blast furnace, and that the forced draft from thetuyeres themselves strikes against it (various researches having shown that is front of the tuyeres, there is located a zone of combustion which is more or less empty of solid material, and that the ore itself does not fall'below a determined zone in the bushes, the temperature of-which corresponds to the point of fusion of its constituent parts). The object of the spider distribution of the fine elements of the ore and of the coke, is to create in the charge breaches which are more permeable and enable the gases injected in the zone of combustion to bejudiciously distributed at the level of the melting zone and to-make it possible for them, during their upward course in the shaft, to produce a better balance of pressures and speeds between the central zone and the peripheral zone, and thus'to make their composition and temperature more uniform and improving their action on the ore.

In accordance with the invention, it is quite easy to regulate the value of the central forced draft and the peripheral draft by modifying the section of the corresponding'tuyeres or'by fitting them with control bushes.

Another object of my invention is to provide devices for carrying out the method mentioned above into practice.

These and other objects will become apparent from the following detailed description of some embodiments of my invention with reference to the appended drawings in which:

Fig. l is a diagramamtic vertical cross-section of part of the upper portion of a blast furnace provided with a charge distributor in accordance with the invention, the cross-section being taken along the line II of Fig. 2.

Fig. 2 is a horizontal cross-section along the line 11-11 of Fig.. 1 in respect of the left-hand part of the figure, and along theline IIa of Fig. 1 in respect of the righthand part of the figure.

Fig. 3 is a vertical cross-section through the plane IIIIH of Fig. 1.

Fig. 4 is a diagrammatic view showing in partial development, the arrangement of the tuyeres and the members of the distributor with respect to the charge.

Fig. 5 is an alternative form of Fig. 1 showing the case of a bell with deflecting arms.

Fig. 6 is a detail plan view of the bell shown in Fig. 5.

Fig. 7 is a cross-section through the plane VII-VII of Fig. 6.

Fig. 8 is a horizontal half cross-section in diagrammatic form of the shaft, on which the position of the tuyeres is indicated, showing, with respect to the latter, the position of the columns of fine material and of the breaches constituted by the coarse ore.

Fig. 9- is a view of an alternative form of the bell shown in Fig. 5 with pivoted deflecting arms.

Fig. 10 is a view of a detail of Fig. 9.

Fig. 11 is a cross-section. through the plane XIXI of'Fig. 10.

In the embodiment shown in Figs. 1 to 3, which corresponds to a blast furnace having twelve tuyeres, the

distribution device, located between the charging cone or bell a and the upper level of the charges b (Fig. 4), is constituted by a central cylindrical member 0 (known as the cigar), retained in position and fixed to the metal I wall of the throat by the sheet steel construction or The arms d are preferably surmounted by roofs g having the shape of dihedrons, in the portion Where the ore falls during charging. This is in the free spaces or sectors g (Figs. 2 and 4) existing between the arms, by which the ore passes as it falls when it is discharged into the furnace by lowering the bell a. The annulus or screen formed by the ore as it falls only shuts off the sectors situated between the arms. The section of these latter is calculated so as to ensure a sufficient evacuation of gastowards the peripheral part of the throat, from which it is directed to the gas offtakes without having to pass through the ore during its fall, and thus without carrying with it a proportion of dust.

As shown in the drawing, the roofs. g are given the shape of dihedrons which may be symmetrical, but it will be quite clear that these roofs could be replaced by inclined planes.

The number of arms of the spider member which constitute the distributor is equal to half the normal number of tuyeres of the blast furnace, the axis of each of the arms being located exactly vertically above the tuyeres as is shown on Fig. 4, in which the arrangement of the charge b and the roofs g of the arms 0! of the distributor c have been shown diagrammatically with respect to the tuyeres Nos. 1 to 6.

The finer elements of the charge which fall on the roofs slide approximately vertically off each of the arms and are thus distributed radially; the angle ofthe upper face of the roofs and the vertical distance between said roofs and the materials of the charge in the furnace being such that the coarser elements of the charge falling on to one of said roofs are thrown peripherally under the neighboring arms of the distributor on top of the charge in th furnace.

In Fig. 4, the path followed by the fine material as it falls has been shown in dotted lines, the path of the medium material in chain-dotted lines, while the path of the coarse material has been shown by the heavy chain-lines with two dots.

The tuyeres of the row of odd numbers (for example) which are located immediately below the arms of the dis-' tributor, thus blow in a sector wherein the charge above said tuyeres contains a small proportion only of fineel'ements and is therefore relatively permeable, the blast issuing from said tuyeres having thus a tendency to reach the central zone of the blast furnace (see Fig. 8).

The intermediate tuyeres (of the row of evennumbers) on the other hand, are in a sector wherein the charge above is less permeable because the proportion of fine elements in it is relatively large, and these tuyeres work closer to the walls.

In the standard method of charging, there is a uniform blowing circle which gives rise to a forced draught at the centre or at the periphery over which it is not possible to exercise any substantial degree of control.

With the radial method of loading, which results in th formation of breaches, there is obtained at the same time a forced draught at the centre and at the periphery, which it has" previously been attempted to obtain by means of a double system of tuyeres operating at different pressures.

In accordance with the invention, it is thus possible to control the relative values of the blowing at the centre and at the periphery of the furnace, and this by modifying, for example, the cross-section of the corresponding tuyeres, or by providing them with control bushes.

It has been-indicated above that the upper part of the arms or the roofs g could be replaced by inclined surfaces; it is even possible to envisage a certain inclination of such surfaces either towards the right or to the .left, so as to vary the distribution of the charge if the working of the blast furnace should so require. It is even pos sible to arrange for the angle of these deflectors to be variable at will. However, in order to adhere to principles of simple and robust construction, it is in general prefer.- able not to make use of such modifications, except very occasionally and during the period when the blast furnace 1s not in use.

Many modern blast furnaces are not provided with fabricated members known as cigars'under the large cone. The installation of a cylindrical member of this kind, provided with hollow arms for evacuation of the gases, may lead to difliculties in construction.

In this case, it is still possible to produce, within a certain measure, a circuit for the gases which will answer a the same purpose, without it being necessary to proceed to the installation of the distributor described above.

It will then be suflicient, in accordance with the invention, to arrange radial deflectors or arms at the base of the bell, of which they may form an integral part, as shown at d in Figs. 5 to 8.

These arms d1 are much shorter than in the previous case, since it will sufiice for them to deflect peripherally the annulus or screen of fine ore sliding along the surfaces of the bell at the beginning of the opening period of this latter. 1

In the case of a blast furnace using coarser ore, or scrap-iron, if it is feared that the pieces will remain caught on the upper portion of the arms of the bell, the latter may be mounted separately so as to constitute independent arms d (see Figs. 9 to 11) suspended from the base of the bell a, each of the arms being movable vertically about a horizontal axis h which is itself fixed to the bell, as shown at 11 a counterweight i, adjustably mounted on the rod h integral with the pivotal axis h, retaining the arm d in its normal horizontal position.

An abnormally large lump of ore or a piece of scrapiron arriving on one of the arms would cause the latter to pivot and would then continue its course without danger of becoming wedged between the arms and the seating of the bell, which would prevent the latter from closing.

The bell, provided with fixed or pivoted arms, should be guided in such a way that each of the arms always remains in the same meridian plane immediately above a tuyere. Finally, the arms d (Figs. 1 to 4) or d (Figs. 9 to 11) may be mounted in such a manner as to provide for the possibility of giving them an angular displacement in the horizontal plane, the amplitude of which will be (where n is the number of tuyeres that is to say twice the number of the arms on the bell); in this way, it will be possible, if need be, to alter the peripheral position of each of the columns made in the charge by the fine elements of ore from a radial plane containing a tuyerea strong tendency to accompany the coarser elements of the ore.

It will, of course, be understood that modifications may be made to the embodiments of my invention which have just been described, in particular by substitution of equivalent technical means, without thereby departing from the scope of the present invention as defined in the fol- What I claim is:

1. In a shaft furnace having a moving bell and a fixed hopper charging system at its top and an even number of blast tuyeres at the lower part of the shaft; a charging apparatus for distributing the materials of the charge in a manner segregating the, big pieces of said materials from the small particles and forming in the furnace vertical radiating columns having a high permeability mainly made of big pieces of said materials separated by vertical columns of lower permeability mainly composed of small particles of said materials, each of said columns vertically facing one of said tuyeres; said apparatus comprising radial arms equal in number to the half number of the blast tuyeres, said arms being made of small beams having an I section vertically disposed and secured by their inner extremities to a hollow member centrally disposed in the top portion of the furnace, with their vertical median plane containing the axis of alternate blast tuyeres and being secured horizontally in the top portion of the furnace at a level lower than the lower edge of the charging hopper; spacing means located on the top portion of said shaft for vertically spacing said radial beams from the upper portion of the shaft of the furnace; brackets secured to the inner surface of said spacing means and adapted to loosely support the outer ends of said beams and permit an angular displacement of said outer ends about the axis of said shaft; said hollow member having a lower cylindrical portion, an open end at its lower extremity and a closed end at its upper extremity and being connected along said cylindrical portion with inverted trough like structures opening therein secured to the webs of said beams and straddling the lower flanges thereof; dihedron sections secured to the upper flanges of said beams and overlying said inverted trough-like structures, with the apices of their cross sections turned up, said dihedron sections having plane faces slanting laterally with approximately the same slope on either side of the median vertical planes of said beams, said dihedron sections radially extending from a position located adjacent the periphery of said bell to a position above and at a short distance of the inner peripheral surface of the shaft; said beams being supported by said spacing means at a distance allowing a complete segregation of the big pieces from the fine pieces of a fresh charge during the'fall of same from the lower edges of said dihedron sections on top of the charge in said shaft. 1

2. A shaft furnace having a charging apparatus as claimed in claim 1, wherein said brackets permit a total angular displacement of said outer ends of said beams having a value equal to

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