US2404650A - Processing kiln - Google Patents

Description

July 23, 194-6;

D. L. NEWKIRK ET AL PROCESSING KILN Filed Aug. 11, 1943 D, L Newlrirlt E E Ensign IN VEN TOR afC/ffc BY Patented July 23, 1946 PROCESSING KILN Daniel L. Newkirk, Inkster, and Elbert E. Ensign, Ypsilanti, Mich., assignors to Ford Motor Company, Dearborn, Mich., a corporation of Delaware 1 ,APplic ation August 11, 1943, Serial No. 498,211

' 3 Claims. 1

This invention relates to a furnace structure and, more particularly, to a continuous kiln in which a charge is treated under controlled conditions.

Heretofore, continuous kiln structures have been of the rotary or fixed types, the operation of the former being dependent upon the rotary motion, while the latter utilizes a series of small cars or movable platforms to convey the charge through the kiln proper. These constructions made it necessary to subject the charge at all times to the conditions prevailing therein. Although in some constructions provisions are made for controlling temperatures at various zones, it is easily seen that the gaseous products of combustion would flow throughout the furnace interior. For example, in a fixed-type continuous kiln, heating gases may be directed only in certain portions of the kiln; nevertheless, the charge having been moved from theheatingstation is exposed to the action of the surrounding atmosphere.

Various attempts have been made at zone treatment in a rotary kiln of which the rotary kiln having telescopic sections is an example. In this type of construction the rotary kiln is composed of two or more telescoping parts wherein provisions are made, especially at the telescoping joints, to inject various gases or fuels, and thereby subject the charge to controlled conditions. However, due to the rapid diffusion rate of the gases it is extremely doubtful if this practice would be successful.

It is therefore an object of this invention to provide a furnace structure in which the charge may be continuously treated through various controlled zones. Another object of this invention is to provide a kiln in which the charge may be heated in one zone, chemically treated in another zone and either cooled or further treated in still another zone. Another object of this invention is to provide a continuous kiln which may be maintained under reduced pressure.

It is readily seen that the advantages ensuing from this invention are many, especially in processes requiring progressively controlled conditions. Within this category fall processes concerning roasting of ores, sintering of ore fines, calcining operations, processes requiring reduced pressures, processes requiring heating period followed by reducing atmospheres, preheating in controlled zones and many others.

With these advantages and other objects in view, our invention consists of the arrangement, construction and combination of the various parts i of our improved continuous kiln construction, as.

described in this specification, claimedin our claims and illustrated in the accompanying drawing, in which:

Fig. 1 is an elevation of the furnace structure in cross section.

Fig. 2 is a sectional View taken on line 2-2 of Fig. 1.

Fig. 3 is a sectional view of the kiln taken on I materials by means of small movable cars or by,

full rotational motion, we impart to the charge a forward motion by oscillating the kiln through an angle of less than 360, thereby obtaining many advantages which were lacking in the former practice.

Reference is made to Fig. 1, illustrating one of the many forms of construction by which cs cillatory motion is transmitted to the kiln. In Fig. 1, the kiln i0 is shown mounted in an inclined position, and is cradled by two circumferential rings ll securely fixed normal to the axis of the kiln. The peripheries of the circumferential rings travel on pivotally mounted rollers l2. In this instance the oscillatory motion is obtained by the mechanical means shown herein in which the arm [3 is pivotally attached to kiln Ill and is actuated by cam arm 14 by means of a speed reducer l5 and a motor [6.

Greater detail of the driving mechanism is shape and size of the opening 2| shown in Figs. 2

and 3. For most efficient service the baflle plates are designed so that the opening 2! conforms to the general cross section of charge as it is being propelled forwardly by oscillatory motion. Therefore, by increasing or decreasing the opening one may control the capacity of the kiln and yet maintain a reasonably efiicient bafile by which the various compartments are isolated from each ot er.

Baffle plates 20 divide the furnace into three compartments for carrying out a specific process. Compartment 22 is used for heating the charge, while compartment 23 provides a chemical treatment chamber and compartment 24, which is not lined with refractory material, becomes a cooling chamber.

In compartment 22, an opening 25 is shown in which suitable heating means 26 may be inserted.

A heating means, burning either solid, fluid or outlet '30 which couple the compartment to treating gas storage and gas exhausting units through the flexible conduits 3!. Compartment 24 may be used as a cooling chamber, as shown, or may be constructed similar to compartment 23 to thereby subject the charge to'further treatment. Also, this chamber may be converted to a quenching chamber by attaching either coils or a jacket chilled with brine.

'It is easily seen that in a furnace of this structure various combinations may be evolved whereby the charge is subjected to numerous combinations of treatments.

lhe oscillatory motionof this kiln makes it pssible to completely seal the treating chambers from atmospheric conditions. At the extremities ofthe kiln end plates and barrel valves 32 are attached so as to provide barometric seals. However, in order that the feed of incoming material maybe continuou and since the barrel valve pivots at the longitudinal axis of the kiln, the barrel valve 32 is-provided with a fan-shaped 4 positive pressure of hydrogen is maintained in compartment 23 and as the oxide powder is very porous, small quantities of hydrogen will permeate the adjacent chambers. The small quantity of hydrogen which escapes to the heating chamber will, of course, burn and is oflittleconsequence; likewisethat which escapes into a lower chamber provides a reducing atmosphere while the powdered iron is cooling to room temperature.

Through the use or a suitable barrel valve or barometric leg, low pressures are obtained within theoperating kiln so that low-pressure reduction of certain ores may be accomplished.

Processing of this-type would, however, eliminate the baiile plate ,and the use of flame-producing heating means, and resistant heaters are therefore substituted. The charges of raw materials and residues are conveyed through the sealing means described above, while the gaseous products are exhausted by one or more outlets to suitable condensing equipment or collectors.

It is therefore easily seen that the eflic'ie'ncy in recovery of gaseous by-produc'ts is extremely high, that the kiln is sealed at all times and that hopper 33 or a flexible connection between-the barrel va'lve hopper and the supply 'bin 34.

Another method of sealing the lower end of the furnace may be accomplished by replacing the barrel valve with abaronie'tric leg or a gooseneck, discharging spout which oscillates in a'fluid sealing means and thereby excludes atmosphere from the interior. subatmospheric condition, the gooseneck may be elongated to provide a suitable barometric leg. The fluid in which this gooseneck oscillates may be water, oil, molten metal or any ,fiuid suitable for the prevailing conditions.

The production of powdered iron by the reduction of iron oxide is readily carried out in a kiln of the present invention. The charge of iron oxide is fed into the furnace through the barrel valve 32and flows countercurrently to the heat produced by the burners. The powdered oxide is constantly agitated by the oscillating motion of the furnace and in this manner all particles are heated to temperatures that are dependent on the length of the heating chamber and'heatll'lg means. The heated oxide is then subjected to reducing atmosphere in the adjacent chamber. In chamber 23 the heated oxide is reduced by hydrogen, the hydrogen being kept at'a slightly positive pressure by means of the supply line 29. The reduced charge then enters compartment 24 and is cooled to atmospheric temperature under conditions preventing reoxidization. s

The level of the oxide and 'the design of the bafile are such that a relatively positive sealis maintained at the openings 2|. However, since If 'the'interior is to be kept under the gases may be withdrawn and recovered by conventional methods.

v A feature that may be incorporated in this invention is'an adaptation of the pendulum as shown in Figs. '1 and 4 in which the weight 35 is suspended from'the kiln at any convenient po"- sition by the rigid members '36. The use of a counterweight of this type in kilns is, of course, limited to a'kiln structure of thecharacter described.

It is apparent that substantial inertia must be overcome 'both at start and end'of each oscillation. This factor, therefore, requires power equipment of greater capacity than ordinarily necessary for plain rotary motion. The pendulum counterweightin conjunction with a variable speed motor more easily overcomes'the' inertia; and in fact, power savings are considerable since a pendulum, once having been started, re-

quires only a fraction of the energy to maintain a 7 T: 21r l g the period T is directlydependent 'on thelength (l) of the pendulum, at times extendingbelowthe floor level, is adjusted to the frequency-of oscillation of the kiln. In practice the power means does not bear directly the load of stopping and starting the kiln, but rather supplements the pendulum.

It has -been shown that this specialized continuous iurnac when operated through an angle of rotation of less'than 360, functions successfully and that many combinations and variations of processing various materials are easily efiected. By imparting oscillating motion'to a furnace, we have'been able to conduct these several processes continuously with many added advan-Q V placement of bu'rners at any point throughout the length of the furnace; The temperature-control and the differentials are successfully in-ain'- tained in the various'zones; a complete sealing of the furnace is effected; the ability *to'maintain controlled atmospheres in the various" zones possible the use of gases, fluids and collection of gases by-products have been obtained.

Some changes may be made in the arrangement, construction and combination of the various parts of our improved structure without departing from the spirit of the invention and it is our intention to cover by the claims such changes as may be reasonably included Within the scope thereof,

The invention claimed is:

1. In a continuous charging and discharging kiln structure, in combination, an elongated, cylindrical structure having an oblique axis of rotation, supporting abutments halving rollers mounted thereon on which the cylindrical structure rotates, power means attached to said structure providing rotation, a pendulum counterweight rigidly attached to said structure, length of said counterweight adjusted to give a period coinciding with the period of said kiln, heating means mounted within said structure, means sealing said kiln from the atmosphere during rotation, and said rotation being oscillatory motion.

2. In a continuous charging and discharging kiln, in combination, an elongated, cylindrical structure having an oblique axis of rotation, supporting abutments having rollers mounted thereon on which the kiln structure rotates, heating means mounted within said kiln structure, charging and discharging sealing means attached to the ends of said kiln, said kiln having an interior lined with refractory, baffles extending down-- wardly dividing the kiln into at least two compartments, said bafiles forming with a charge a seal permitting separate reactions in each com partment, one of said compartments comprising a heating chamber and at least one of the other compartments being a reacting chamber, said compartments having inlets and outlets through which fuels, treating atmospheres, and exhaust products are continuously passing to and from said kiln, said inlets and outlets connected to the kiln by flexible conduits, and means to rotate said kiln in an oscillatory cycle,

3. In a continuous charging and discharging kiln, in combination, an elongated, cylindrical structure having its axis oblique to the floor level, supporting abutments having rollers mounted thereon on which the kiln rotates, baffle plates dividing said kiln into compartments, said baffie,

plates forming with a continuously moving charge a seal permitting separate reactions in each of said compartments, a refractory lining in each of said compartments, heating means mounted in the uppermost and charge receiving compartment, other compartments comprising treating and cooling chambers, said chambers having inlets and outlets for introducing and exhausting gases through flexible conduits, means for sealing the ends of said kiln while providing a continuous flow of material, and means to rotate said kiln in an oscillatory cycle.

DAN L. NEWKlRK.

ELLBERT E. ENSIGN.

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