US1916863A - Method and apparatus for agglomerating metalliferous masses - Google Patents

Description

July 4, 1933. 1,916,863

METHOD AND APPARATUS FOR AGGLOMERATING METALLIFEROUS MASSES A. v. KROLL Filed Jan. 30, 1930 Patented July 4, 1933 UNITED STATES PATENT OFFICE ADOLPHE VICTOR KROLL, OF LUXEMBURG, LUXEMBURG Applicationfiled January 30, 1930, Serial No. 424,699, and in Germany February 9, 1929.

This invention relates to the agglomeration by treatment with a gaseous medium and heat, of fine ores and other metalliferous masses in general, not to omit concentrates .5 or residues and the most finely divided fluedusts which are causing great difficulties, if treated in layers of some extent by flowing gas, owing to their resistance to the passage of gases, together with the great mobility of their particles.

It has already been the purpose of numerous improvements in fine ore treating processes to eliminate these difficulties by causing the fine particles to be freely suspended in the gaseous medium during the treatment.

Such means have been tried more especially in the case of agglomerating fine-dust, but always the process has been abandoned, as the apparatus become of enormous dimensions. Furnaces of this kind have even been proposed in the shape of chimneys, wherein the dust freely showered to the bottom.

My invention is based on the same means of suspending the particles of mass in the hot gaseous medium and heating them, so as to undergo agglomeration, but it has the pecularity of impeding or preventing the fine particles'frorn being carried away by the gas over and beyond a limited space. That is namely obtained by retaining the heavier mass with the aid of centrifugal forces. Indeed, by the production of whirls within the gaseous medium, or of real dust-tornadoes, there are easily created sufficient centrifugal forces, to retain in a satisfactory manner fine particles of metalliferous masses, even in a most restricted room, whereas the already consumed or somewhat down-cooled gases are free toescape and may be replaced 40 by fresh ones.

The tendency of the particles of agglomerating together, ordinarily originating with the attainment of their softening point, may be considerably supported during the new process, by the violent and often repeated concussions of the said particles between themselves and with the walls.

The agglomerates generated. in this manner are withdrawing themselves by free fall or by being swung out from the gas-whirls,

not more capable of supporting the same, and leave the furnace automatically if the sole is provided inclined, but they may also remain deposited therein and even occur fixed or pasted to the Walls (the bottom ineluded), apt of being removed therefrom by mechanical means, or simply by an in creased heating effect. In this latter case they will completely melt down, drop or fiow out and leave the furnace as a liquid mass, no matter if melting is continuously prosecuted or only as a momentary proceeding or expedient.

The new process concerns with agglomerating fine ores without separating the same into metal and slag. The latter is a complete metallurgical treatment, also designed by the term reduction of the ore. The ideal purpose of the new process is the obtainment of a physical coherence between the particles m of the fine mass, partially composed of oxyds of heavy metals, and the formation of larger pieces of mass, by agglomeration. Chemical changes may accompany or even produce this physical event, but not be performed to such ?5 extent, as by the metallurgical reduction of the ore, featured by smelting out of metal and slag most completely if possible, under separation of one from the other.

In the art of agglomerating fine masses, so this new process is the more eificacious, the more rapid be the flowing and whirling of gases, as the centrifugal forces are increased in proportion to the square of the rapidity of movement and together with the inverse proportion of the diameter of the whirling circle, so that the efliciency grows, as the diameter of the furnace is diminished. That is, extreme efliciency with the smallest space appears to be what was mostly needed in the processes of agglomerating finely divided ores.

In order to clearly explain the means of working of the new process, I have adj oined a drawing, by which only a single example of practical execution of the process is given, without restricting it to the special features of this furnace or to the more schematic details and their disposition, as many changes may be made therein, or other forms of apparatuses or furnaces be employed for carrying out my invention.

Figure 1 is a longitudinal section through a lower round and flat 'furnace-room,-of which Figure 2 is the cross-section,and of an upper airand dust-preheater of the simplest form. Said furnace-room is surrounded by fire resisting lining and by an exterior water-mantle and is provided with an automatic scraper to remove the agglomerates from the inner furnace-walls and cause the products to fall through a lower aperture out of the furnace. The dust and the air are introduced by tangential pipes 10 or 19 in the circular furnace-room; combustible gases or other combustible matters may be entered through tangential pipes 8 or 9, with or without the hot or cold air of combustion. The waste gases escape through an upper aperture 3 into a preheater, heating the walls of it by their lost heat, and escaping in the highest part by a central flue-pipe. The

heated walls are hollow and divided in spirally winded channels through which the stream of air and dust to be preheated, is blown and moved inversely to the direction of the wastegas stream in the shaft. The dust of ore is contained in two silos 12 and distributed by helicoidal conveyors 14 to a system of pipes and nozzles, in which also compressed air is blown through a connected pipe 11, to suspend the dust and move it through pipe 16 to the preheater, and from it through pipe 19, or directly without preheating, through pipe 10 forming a tangential nozzle, into the furnace-room.

Now I will give a detailed description of the figures:

In the drawing, 1 represents an annular furnace-room, being enlarged towards the interior to a conical' room 2, which may be connected, for instance in its upper part, through an aperture 3 with a simple heatexchanger 4, preheating the air of combustion with the escaping gases, and may present in its interior part, through an aperture 5, an exit for the treated masses.

This whole room is rovided with a refractory lining 6, preferably cooled with water, over the exterior metal-mantle; or, there may be a real water-jacket 7, surrounding the furnace-room, or the wall of refractory lining of the furnace, provided then with a double protection.

If the inner lining is built up out of highly refractory and chemically neutral masses, such as are today available, as for instance: carbide of silicium, chromium-iron-ore, oxids and nitrids of aluminium; zirconic masses or the like, the outer water-mantle may be supzrfluous, or better utilized as an air-chamr, permitting some recuperation of calories for the process, by partly preheating the gaseous medium for it.

But the inner refractory lining may also be abolished, or be of small thickness, or formed out of refractory masses of less value, if the outer cooling is vigorously accomplished. Moreover it entirely depends upon the manner of operating the furnace, if the walls are diminished by erosion, or onthe contrary growing by formation of deposits or crusts, so that the question of the outer cooling, as much as that of the inner lining, have-to be decided in any case so as to correspond with the nature of the process and the behaviour of the furnace.

In the drawing are provided two burners 8, the number of which is of no significance, although it may be more recommendable to make use of a great number, than of one. Through these burners there is tangentially introduced into the furnace-room, for instance: preheated air for combustion together with combustible gas. As a guaranty for a prompt ignition, it may be advisable to provide a short pre-ignition-room 9, with a refractory lining, within the burner itself.

According to the manner of working preferred for any special case, the burner will be of a very difi'erent kind. It may even be successful to use the burner exclusively as an igniting-device, and to introduce, from another, separated aperture, the combustible matter in any form, preferably together with the finely divided mass to be treated. Certainly it is even possible, to introduce through the burner 8, the said mass. But more advisable is the use of separate nozzles and devices for that purpose, as such are illustrated, two in number, 10, in the drawmg.

Here also, the admission is preferably tangentially performed, so that compressed air is admitted through pipe 11 and charged with the finely divided mass, stored in the bunker 12, and automatically delivered by any device,for instance of the kind of that designated by 13 in the drawing, and formed by a controllable, rotating spiral-conveyor l4,the fine mass falling into the air-stream and being suspended within it and carried-by it, with great velocity, through the tangential nozzle 10, into the furnace-room.

In this manner, a whirl of gases and dust circulates around the total annular room, beginning from the part of the walls limiting the greatest diameter, and advancing to the centre in numerous spiral-windings, gaining the exit in the middle-part, where the gases slowly escape, having previously abandoned a great part of the heavy dust, retained by centrifugal forces, and more concentrated along the greatest circumference of the space.

For the rest, the part of the dust, which is carried away by the escaping gases, may be, if desired, recuperated without difiiculty, by the well-known, simple devices, in accordance with the value of the mass, as by zig-zagpipes, centrifugal cleaners, sack-filters or electro-filters, and the like.

It is not an absolute necessity, that the finely divided mass be blown, by a stream of alr or gas, into the furnace-room, as the mass may also be caused to slowly drop, by its own weight, into the furnace, where it may then be grasped by the whirl of gases, and be accelerated. This method of introducing the mass is principally applicable, Where ores of a coarser grain, are to be treated.

As to the nature of the combustible-needed by the new process, all possible fuel may be used, to begin with. the combustible gases, and not less the liquid combustible matters, which are rapidly gasified in the furnaceroom, or are introduced in finely dispersedstate, and permit of obtention of very high temperatures. tent of sulphur, and therefore of less value. are here of good use. Nearly of the same efliciency, is the use of pulverized coal, blown in by special burners, in the well-known manner. Even finely powdered coke is fit for use, preferably if the furnace has a special chamber provided for ignition, or by employing hot air for the dispersion. But easier is, mixing with the coke some amount of finely pulverized, bituminous, or somewhat gas-rich charcoal, or even, introducing with the fine coke, some combustible gas.

Also a coarse grain of the combustible matter is compatible with the process, the unburnt parts of the fuel being retained by centrifugal forces in the reaction-room.-

Mention may also be made to the particularity, that, while using any of the combustible matters, combustion may already be partially, or even completely performed, before the entrance to the furnace-room, the hot gases carrying the heat into it.

Instead of introducing the combustible matter through special nozzles, separately from the fine ore, it may also enter together with the same. So, for instance, the fine mass to be treated, may be blown in by a combustible gas, or also a mixture of the fine mass and of pulverized, solid fuel, may previously be formed, and be blown into the furnace-room, by an air-stream; or such a mixture may only be created within the injection-device, or within the furnace-room itself. I

Often, the mixture with combustible mat.- ter, is already preexisting, so, for instance, in numerous kinds of flue-dusts, which commonly carry very considerable quantities of coke-dust. There, it may be suflicien't, to artificially preheat the furnace and to induce the process, then cutting off the burner and only blowing in air and flue-dust, the latter containing the combustible matters. But it is better to operate continuously small ignit mg-burners, these being at the same time of through which Oils, with a considerable cona certain aid for the heat-generation, and

for augmenting the whirling-effect of the.

ply caloric ones. Also an excess of air or of combustible gas, in the gaseous medium of the process, may be of good use. 0

Inthe drawing are illustrated two lateral apertures 15,

p the interior of the furnace may be observed, and also deposits and crusts or the like, adherent on the inner walls, may be removed. That may be done manually or automatically.

. Forthe purpose of strippingoif the agglomerates from the walls, there is further represented a mechanical device 18 being rotated by a motor, from the centre and the bottom (or from the top) of the furnace. To avoid a rapid wearing away of this device, the stirrer is best madeout of chromiumnickel-steel and provided with an inner water-cooling, by which latter, cleaving on of the products is evitated.

The simplest means for removing the deposits of agglomerates from the walls, is in many cases their. melting off. That is readily obtained, by increasing the heat in the furnace, or by diminishing or momentarily cutting off theentry of fine ore-mass.

The angle of inclination of the furnacebottom, is naturally of considerable importance for removing the agglomerated masses, whether solid or liquid, and that more, if working is done without use of any stirring device, of which the presence is sometimes dispensable, but generally useful and in numerous cases most necessary.

It is for the new process of greatest utility, to regain by recuperation or regeneration, as much as possible of the lost heat, carried away by the escapinggases orby the agglomerated mass, and that may be done by preheating therewith the gaseous medium for theprocess, or the finely divided mass to be treated, or. both ingredients. I

Devices giving that result, have already been sufliciently described in conjunction with various metallurgical processes, and in my drawing, I have given some scheme of a simple preheater for the air, built up by refractory matter and heat-resisting steel, 4.

Preheating the fine mass, may be done in a most simple way,where a specially designed furnace with a cylindrical or conical shaft of some height is to be avoided,by introducing the dust together with the cold airin the upper part of the preheater l. In that case the feedingdevice 13 with the bunker 12' is placed on a higher level (over the summit of the preheater 4), or,as shown in the drawing, asimple branch 17, is provided on the pipe 11 and connected with it through in. a tangential direction,

llt

Before beginning the operation, the furnace-room 1 is brought nearly to a white-heat,

for instance by blowing combustible gas and air through the nozzles 8. As a finely divided mass to be ag lomerated, we may choose for instance flueust from blast-furnaces of the iron-metallurgy, and suppose that it already contains a suificient amount of combustible matter for the process. Said dust is stored in the bunker 12. Now, opening thecompressed-air-admission 11, and causing the spiral conveyor 13 to rotate with a certain, well defined rapidity, the dust is slowly and continuously admitted into the hot furnaceroom, by the nozzles 10. At the same time, hot air is introduced through the nozzles 8 or 19,-the combustible gas being shut off;- and the stirrer 18 is caused to rotate, not too rapidly and preferably in a continuous manner, thus expelling the agglomerates in form of lumps,-as the dust is brought by the combustion-heat of its combustible matters to the softening point, while the centrifugal forces of the whirl, created by the tangential introduction of the air into the annular room,

retain the dust within the narrow limits of the same, or aid the phenomenon of agglutination of the fine mass to be accomplished, especially when the. latter is vehemently thrown against the walls to paste thereon.

In the same example, instead of a slow and continued admittance of the flue-dust, there also may be a rapid charging of the furnace, by suddenly blowing in a considerable amount of dust, and then completely interrupting its introduction for a time. But the air through the nozzles 19, is admitted during all the time, producing a whirl with the dust-charge along the extreme walls of the furnace room,--and gradually burning out the combustible matters of the dust, agglomeration is performed by their heat, while the stirrer 18 is working continuously, or intermittently. During the charging period, the main air-draft may also be shut off.

If the mass to be treated, has no suflicient or not any content of combustible elements, the process may be properly performed in a very similar manner, except that, for. instance, combustible gas in convenient proportion is introduced, together with the main air-current; through the nozzles 8, for the heatin and agglomerating operation.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The process of agglomerating metalliferous masses, divided to parts of a small size, consisting in exposing the divided, solid mass, to the influence of a gaseous medium and simultaneously to centrifugal forces, by creating whirls with said mass and gases, in a suitable furnace-room, heating the whirling mass, by burning combustible matters, so as to agglomerate at least a part of it by sintering, separating the waste gases from a great part of the dust and of the agglomerated product by centrifugal action, and removing the said product out of the furnace, substantially as described.

2. The process of agglomerating metalliferous masses, divided to parts of a small size, consisting in exposing the divided, solid mass,- to the influence of a gaseous medium and simultaneously to centrifugal forces, by

creating whirls with said mass and gases,

in a suitable furnace-room, heating the whirling mass,vby burning combustible matters, so as to agglomerate at least a part of .it by sintering, thereby depositing or fixing at least a part of the mass onto the inner surface of the furnace-walls, and removing it by mechanical means out of the furnace, substantially as described.

3. The process of agglomerating metalliferous masses, divided to parts of a small size, consisting in exposing the divided solid mass,

to the influence of a gaseous medium and simultaneously to centrifugal forces, by creating whirls with said mass and gases, in a suitable furnace-room, heating the whirling mass, by burning combustible matters, so as to agglomerate at least a part of it, separating the Waste gases from a great part of the dust and of the agglomerated product by centrifugal action, and removln the said product, by completly fusing it down, so as to drop or flow out of the furnace, without a predominant separation to metal and slag, substantially asdescribed.

4. The process of agglomerating metalliferous masses, divided to parts of a small size, consisting in exposing the divided, solid mass, to the influence of a gaseous medium and simultaneously to centrifugal forces, by creating whirls with said mass and gases, in a suitable furnace-room, forcing the main part of the divided mass, to remain near and circulate along the inner surface of the furnace-walls, by giving a suflicient violence to the whirls, heating the whirling mass, by burning combustible matters or gases, so as to agglomerate at least a art of it, and removing the product out o the furnace substantially as described.

5. The process of agglomerating metalliferous masses, divided to parts of a small size, consisting in exposing the divided solid mass, to the influence ofa gaseous medium and simultaneously to centrifugal forces, by creating whirls with said mass and gases, in a suitable fu1'nace-room,-heating the whirling mass, by burning combustible matters or gases, using also heat regained from the process, by preheating its material ingredients or part of them, so as to agglomerate at least a part of the mass by sintering, separating the waste gases from a great part of the dust and of the agglomerated product by centrifugal action, and removing the said product out of the furnace, substantially as described. I

6. The process of agglomerating metalliferous masses, divided to parts of a small size,

. consisting in exposing the divided, solid mass,

to the influence of a gaseous medium and simultaneously to centrifugal forces, by creating whirls with said mass and gases, in a suitable furnace-room, heating the whirling mass, by burning combustible matters, using also heat regained from the process, by preheating its material ingredientsor partof them, so as to agglomerate at least a part of the mass, separating the waste gases from a great part-0f the dust-and of the agglomerated product by centrifugal action, and removing the said product, by completely fusing it down, so as to drop or flow out of the furnace, Without a predominant separation to metal and slag, substantially as described.

7. The process of agglomerating metallif erous masses, dividedto parts of a small size, consisting in exposing the divided, solid mass, to the influence of a gaseous medium and simultaneously to centrifugal forces, by creating whirls with said mass and gases, in

a suitable furnace-room, heating the whirling mass, by burning combustible matters, using also heat regained from the process, by preheating its material ingredients or part 'of them, so as to agglomerate at least a part of the mass by sintering, thereby depositing or fixing at least a part of the mass onto the inner surface of the furnace-walls, and removing it bymechanical means out of the furnace, substantially as described.

8. The process of agglomerating metalliferous masses, divided to parts of a small size, consisting in exposing the divided, solid mass, to the influence of a gaseous medium and simultaneously to centrifugal forces, by creating whirls with said mass and gases, in a suitable furnace-room, heating the whirling mass, by burning combustible matters, so as to agglomerate at least a part of it by sintering, thereby depositing or fixing at least a part of the mass onto the inner surface of the furnace-walls, and removing it by producing a shaving or shoveling action ADOLPHE VICTOR KROLL.

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