US783044A - Process of smelting ores in blast-furnaces. - Google Patents

Description

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PROCESS OF SMELTING ORE S IN BLAST FURNACES.

APPLIOATION FILED APR.9, 1903.

2 SHEETS-SHEET 1.

No. 783,044. PATENTED FEB. 21, 1905.

J. E. JOHNSON, JR- I PROCESS OF SMELTING ORES IN BLAST FURNACES.

APPLICATION FILED APR. 9, 1903.

2 SEEETSSHEBT 2.

UNITED STATES Patented February 21, 1905.

PATENT OFFICE.

PROCESS OF SMELTING ORES -lN BLAST-FURNACES.

SPECIFICATION forming part of Letters Patent No. 783,044, dated February 21, 1905.

Application filed April 9. 1903. Serial No. 151,763.

To 1!, whom, it nutg concern:

Be it known that I, J osnrn E. JOHNSON, Jr. a citizen of the United States, and a resident of Longdale,in the county of Alleghany and State of Virginia, have invented certain new and useful Improvements in Processes of Smelting Ores in Blast-Furnaces, of which the following is a specification.

My invention relates to a process of treating ore in a blast-furnace; and its novelty consists in the several successive steps of the process.

In a blast-furnace of common form the fuel, ore. and flux are so charged as to form successive approximately horizontal layers extending substantially across the entire area of the furnace. The stock descends through the furnace in approximately horizontal alternating layers extending from wall to wall of the furnace; but after it has passed into the zone of fusion the fuel is the only one of the materials charged which remains solid, the others in the form of iron or slag melting and running down through the mass of incandescent fuel into the well or crucible at the bottom of the furnace. The blast enters just above this and unites with the fuel to form carbon monoxid, which passes up through the materials as they descend and is there oxidized to a greater degree, forming mixtures of carbon monoxid and dioxid of proportions difiering with the circumstances.

It is a fact that a mixture of carbon dioxid and carbon monoxid behaves during a considerable range of temperatures in a precisely opposite manner in the presence of free carbon and in the presence of oxygen-bearing ores and within a certain wide range of temperatures. In the first place, in the presence of free carbon-for instance, in the form of fuel-the carbon dioxid absorbs an amount of carbon equal to that which it already contains and becomes carbon monoxid. In the second place, in the presence of oxygenbearing ores for instance. hematitea' portion of the carbon monoxid absorbs oxygen therefrom and becomes carbon dioxid. It follows from these reactions that as the gases resulting from the combustion of the fuel consisting almost wholly as to combustible elements of carbon monoxid initially pass upward through the furnace they are subjected to rapidly-alternating conditions having precisely opposite tendencies, and any oxidation of the fuel which goes beyond the monoxid stage is effected under difficulties. The result of this condition of things is that in ordinary good practice about one-third of the carbon entering the furnace as fuel is oxidized to the dioxid stage. Another result is that the carbon derived from the flux (carbonate of lime) is liberated therefrom in the form of carbon dioxid, and consequently after undergoing the reactions referred to passes out of the furnace as two-thirds monoxid and onethird dioxid. These reactions mean a loss of heat and of carbon from the fuel. It is obvious that if some of these disadvantageous reactions could be prevented a great economy in 'fuel could be secured, and it is furthermore obvious that they can be prevented if the gases resulting from the combustion of the fuel after the desirable reactions necessitating contact of the fuel and ore have taken place are prevented from coming subsequently into contact with the incoming fuel and confined to contact with the incoming ore or ore and flux. The first step of my process therefore consists in making the gases resulting from the combustion of the fuel pass through the incoming ore and flux alone and out of contact with the incoming fuel immediately before being discharged from the furnace. In ordinary blast-furnaces also it is evident that it is necessary to secure a certain temperature, which for the sake of convenience I will call the critical temperature, below which it is impossible to accomplish the desired reactions between the fuel, the gases'derived therefrom. the ore, and the flux. The energy expended in bringing the products of combustion up to this critical temperature is therefore unavailable for these reactions which can only take place at or above that temperature, though it is useful in the preparatory or preliminary reactions of the process which occur at lower temperatures. The

efficiency of the furnace depends much upon the amount of heat available above this critical temperature. hthout going into any detailed discussion of the matter or presenting in detail facts which are well known to blastfurnace engineers I may state that it is a fact that much of the heat which would otherwise be available for use in this connection is carried off by the nitrogen derived from the air of the blast and that a smaller though important quantity of the heat is used in decomposing the moisture accompanying the aircurrent. It is obvious, therefore, that if the amount of nitrogen and moisture commonly present in the blast could be reduced the amount of heat available for the efficient working of the furnace would be increased. This leads me to another step of my invention, which consists in supplying the blast with a current of, air rich in oxygen and substantially free from moisture, and thus obtaining the advantages referred to.

I carry out the process referred to in the form of apparatus illustrated in the accompanying drawings; but it will be understood that I do not limit myself to the mechanical devices here illustrated, because when the principles underlying my invention are once understood the skilled blast-furnace engineer can probably devise a number of forms of apparatus for use in carrying out the process founded thereon.

In the drawings, Figure 1 is a central vertical section of a blast-furnace embodying my improved apparatus; Fig. 2 is a section and partial perspective of the ore-hopper, and Fig. 8 is a bottom plan view of the mantle.

In the drawings, 1 is the stack, of usual construction, provided with a hearth 2, crucible 3, twyers 4 4, blast-pipes 5, and boshes 6 6. 7 is the throat of the stack. All of these parts are constructed in the usual manner common to the art and need no detailed or other description.

Suitably supported at the mouth of the stack is a platform 20, to. which the ore is con veyed and from which it is dumped into a conical hopper 200, and from this hopper it is fed into the stack as required. At one or more points in the stack there are flues 22 for the removal of the gases, which normally occurs through the down-comer 32 of the customary type; but one of the fines is carried up and ends in a bleeder or explosion-door 30, 01' both combined, which differ but slightly from those of the ordinary type.

At the center of the hopper 200 is a vertically-placed mantle 40, composed in its upper portion41 of a cylindrical body and in its lower portion 42 of a fluted conical body. It

is preferably made of metal with hollow walls,

having between them an annular space 42, adapted for the circulation of a cooling medium such as water, air, steam, or the likesupplied from a suitable source and coming in and going out through proper valve-controlled pipes 42".

At the top of the mantle 40 is mounted the conical fuel-hopper 43, secured firmly to a framework 44, supported from the stack.

A pusher 45, of hemispherical form and having its plane surface undermost and resting upon the upper surface of the fuel, is 'provided for charging the fuel. Secured to the pusher 45 by a ball-joint 45, with its center approximately in the plane surface of the pusher, is a rod 46, extending vertically upward through a bell 47 and itself terminating in a piston 48, fitting snugly within the cylinder 49, mounted upon the upper frame of the stack. The pusher 45 has an opening in its top to admit of a movement relative to the rod, the opening being covered by a fixed collar 45", of corresponding shape, fast on the rod 46. This construction enables the pusher to accommodate itself to the surface of the fuel I within the hopper 43 without danger of leaving a gap at the side past which the fuel can be crowded. The pusher 45 is operated by the piston 48 in the cylinder 49, a pressure being maintained of such an amount upon the upper side of the piston as will cause the quantity of fuel to be discharged from the mantle which will be properly proportioned to the quantity of ore passing the lower end thereof at the same time. Thecylinder 49 is provided with suitable valve-controlled inletpipes 49, 49 and 49 In order to charge the fuel, it is put into the hopper 43 above the bell 47. The bell 47 is then raised by admitting steam through the pipe 49 to raise the piston 47 allowing the fuel to come in on top of the pusher 45, the latter being in the position shown at the bottom of the fuel-hopper. The bell is then closed and the pusher 45 raised to its highest position by admitting the steam through the pipe 49, allowing the fuel to enter the mantle 40 below it. It is 'then' sent down until it reaches the fuel and establishes the desired pressure upon it, following it down with the fuel until the bottom of its stroke is reached, when the operation is repeated.- It will of course be understood that the pressure in the cylinder 49 is variable at will.

The bell 47 is provided with an annular rod 47, extending upward and surrounding the rod 46 and terminating in a piston 47", fitting snugly within the cylinder 49 and below the piston 48. I have not shown any means for operating the bell 47 because this is a common form and involves nothing new. It will be observed that this construction provides substantially a means for feeding the fuel which constitutes a lock or gas seal intermediate between the mantle and the source of fuel-supply.

The mantle 40 is fluted at its lower portion, the change being gradual and the outer extremities of the flutes being divergent rather than the inner ones being convergent from the line of the initial cylinder. This might be otherwise expressed by saying that the inner lobes of the flutes do not fall much, if any, within the initial cylinder, while the outer lobes are tangent to a divergent cone outside of it. The result of this form of mantle is that the fuel is discharged therefrom in a fluted or star-shaped column surrounded on all sides by the descending ore, which comes down between the external surface of the mantle and the inner wall of the stack. An intimate contact between the ore and fuel is thus effected.

The ore-charger consists of the conical hopper 200, secured to the stack, and the bell 21, terminating in the sleeve 51, which fits snugly around the cylindrical portion 41 of the mantle 40. Brackets 52 are secured to the bell at suitable points and in turn are secured to the forks 53 of a lever 54, fulcrumed in suitable bearings at the side of the stack and which lever is actuated bya piston-rod 55, terminating in a piston 56, which moves in a cylinder 57 and is controlled by fluids, such as steam, which may be admitted and discharged through the valve-controlled pipes 57 and 57 The movement of the bell 21 with relation to the conical hopper 200 provides an opening the control of which by means of the lever 54 is simple and enables the operator to gage the amount of ore fed with accuracy. The upper edge of the sleeve 51 abuts against an annular shoulder on the mantle and makes a tight fit.

In the improved form of furnace if the mantle and the furnace outside of it were both kept full to an approximately constant height the proportion between the fuel and the ore charged would be determined by the areas inside and outside of the mantle at its lower end and the weights of the respective columns of materials above these areas and would be approximately constant,whether right or wrong, if no provision were made to vary this ratio. The ore being heavier than the fuel will tend to cut off the descent of the fuel, and the column of the fuel is therefore made higher to compensate for this. The purpose of the piston 48 and pusher 45, which works with a free fit within the cylindrical portion of the mantle 40 and presses upon the fuel, is introduced as an adjustable factor to enable the ratio of. the amount of ore and fuel charged into the furnace to be controlled.

I have invented a form of apparatus and sundry processes carried out therein whereby there can be economically and readily extracted from the atmosphere a large proportion of its oxygen. This invention forms no part of the present invention and forms the subject-matter of another application for Letters Patent of the United States, Serial No. 154,945, filed April 30, 1903. The supply of oxygen which I thus secure is introduced into the twyers and blast-pipes of the furnace illustrated and is forced into the bottom of the furnace by means of a blowingengine of any suitable type and which needs no specific description. The quantity of oxygen giving the most successful results in practice varies greatly with different conditions even with the same furnace and in comparatively brief intervals and the purity of the oxygen obtainable being regulable by the adjustment of my apparatus for producing it such regulation takes the place of the regulation of the temperature of the blast now commonly practiced. Under all normal conditions, however, the oxygen in the blast will be associated with much less nitrogen than occurs with atmospheric air. By using this oxygen-laden gas as the material forthe blast I can do away with the heating-stoves now required for the blast and with many of the accessories thereto, with a resulting economy.

In the present form of furnace using the existing methods of filling as the fuel forms continuous layers across the furnace it is necessary that the blast be able to traverse these. In fact, the openness of the fuel is the principal factor in case of driving the blast and the gases resulting therefrom up through the furnace, which is a very important point in the practical operation of furnaces. For this reason coke has come to be the principal blastfurnace fuel and few kinds of coal can be used. On account of their bituminous nature it is impossible to use most soft coals, because when they become hot they stick together and practically seal the furnace up, making the passage of the gases impossible. By my method of filling, however, the fuel is charged in a continuous column of fiuted cylindrical section through which there is no necessity that the gases should pass, it being, in fact, undesirable that they should do so to any great extent, and accordingly bituminous fuels are workable and even desirable, the fact that they cohere into one solid mass when hot protecting them largely from the dissolving action of carbon dioxid. The fuel column being in the center of the furnace is also out of contact with the walls of the same, and therefore any possibility of hanging by the adherence of the fuel to the wall is thereby prevented. The gaseous products resulting from the distillation of the coal as it is heated, which are very combustible and have a powerful deoxidizing effect, pass up through the column of ore and assist in the mode of deoxidation.

It is to be noted that I do not employ a blast containing an excess of oxygen to raise the temperature in the furnace, but to increase the amount of heat which is at the critical high temperature requisite for performing that part of the smelting operation which can only take place at the highest temperature produced in blast-furnaces employing an airblast. NVhile the necessary temperature can be kept up in the ordinary blast-furnace in which the charge contains fuel throughout, the complete oxidation of the escaping gases by finally passing them through an incoming body of ore containing no fuel requires an additional supply of high-temperature heat to prevent the temperature of the escaping gases from being; reduced to a point where they will no longer react on the ore. There is thus a true combination between the step of supplying a blast containing an excess of oxygen and that of passing the escaping gases through a body of ore containing no fuel. The gases escaping from my furnace are high in carbon dioxid and low in carbon monoxid and nitrogen, the fuel being fully oxidized and the heat evolved by the reaction being utilized for reduction rather than in heating such large amounts of nitrogen as are present in the ordinary air-blast. The use of a blast which is substantially free from water also decreases the heat losses and adds to the effectiveness of the other steps of the process.

The use of a mantle or fuel-chute which is provided with cooling means makes it possible to use bituminous coal, which would otherwise adhere to thechute as soon as it began to distil and impede or prevent the fuel from being fed into the furnace.

hat 1 claim as new isl. The process of smelting ores in a blastfurnace, which consists in feeding separate bodies of ore and fuel into the furnace, smelting the charge and increasing the amount of heat available for smelting, and especially for these reactions which require a high temperature, by supplying a blast containing an excess of oxygen, and utilizing the heat in the fuel by passing the gases escaping from the furnace through the incoming body of ore and maintaining them out of contact with the incoming fuel, the waste gases thus being high in carbon dioxid and low in carbon lnonoxid and nitrogen, as set forth.

2. The process of smelting ores in a blastfurnace, which consists in feeding separate bodies of ore and fuel into the furnace, smelting the charge and increasing the amount of heat available for smelting, and especially for those reactions which require a high temperature, by supplying a blast containing an excess of oxygen and substantially free from water, and fully utilizing the heat in the fuel by passing the gases escaping from the furnace through the incoming body of ore and maintaining them out of contact with the incoming fuel, the waste gases thus being high in carbon dioxid and low in carbon monoxid and nitrogen, as set forth.

3. The process of smelting ores in a blastfurnace, which consists in supplying to the charge a blast containing an excess of oxygen, and varying the proportion of oxygen in the blast in accordance with the varying conditions in the furnace, as set forth.

4:. The process of smelting ores in a blastfurnace, which consists in supplying to the charge a blast containing an excess of oxygen and substantially free from water, and varying the proportion of oxygen in the blast in accordance with the varying conditions in the furnace, as set forth.

5. The process of smelting ores in a blastfurnace, which consists in introducing separate bodies of ore and fuel by gravity into the top of the furnace, and controlling the ratio of the amounts of ore and fuel supplied by increasing the pressure on the body of fuel to compensate for the difference in the specific gravity of the fuel and ore. as set forth.

6. The process of smelting ores in a blastfurnace, which consists in feeding separate bodies of ore and fuel into the furnace, the fuel being supplied in the form of a column having laterally-projecting portions which extend into the surrounding body of ore, whereby an intimate contact between the ore and fuel is effected, as set forth.

7. The process of smelting ores in a blastfurnace, which consists in feeding separate bodies of ore and bituminous or coking fuel into the furnace, the fuel being supplied in the form of a solid column having fluted portions which extend into the surrounding body of ore, whereby an intimate contact between the ore and fuel is effected and the gases distilled from the fuel are compelled by the relative imymnetrability of the column of fuel to pass through the ore and are thereby effectively utilized for reduction, as set forth.

8. The process of smelting ores-in a blastfurnace, which consists in feeding a column of fuel into the furnace through a conduit, feeding the ore into the furnace around the column of fuel, and cooling the surface of the column of fuel to prevent its adhesion to the walls of said conduit, as set forth.

\Vitness my hand, this 19th day of March, 1903, at Longdale, in the county of Alleghany and State of Virginia.

JOSEPH E. JOHNSON, J11.

\Nitnesses:

S. R. ROBINSON, XV. Al (J. JONES.

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