US1734417A - Rotary kiln - Google Patents

Description

Nov. 5, 1929. A. J. BRIGGS 1,734,417

ROTARY KILN Filed-Jan. 27, 1927 2 Sheets-Shee l INVENTOR 7112%M J,B1iggs K m, ATTORNEY Nov. 5, 1929. A. .1. BRIGGS ROTARY KILN Filed Jan. 27, 1927 2 Sheets-Sheet 2 Patented Nov. 5, 1929 UNITED STATES PATENT OFFICE ARTHUR J". BRIGGS, OF SYRACUSE, NEW YORK, ASSIGNOR TO INDUSTRIES OF AMERICA,

INC., A. CORPORATION OF DELAWARE ROTARY KIL'N Application filed January 27, 1927. Serial No. 163,899.

This invention relates to the treatment of ores and more particularly to the reduction of iron ores to produce therefrom metallic iron, although the invention may be utilized in any field for which it is adapted by the nature of the improvements.

An object of the invention is to provide an improved rotary kiln for carrying into eflect a process for production of sponge iron of the characterset forth in a report of the Bureau of Mines, Department of the Interior, U. S.

A., published in February, 1924, Serial No..

2,578. This process, briefly stated-consists in passing a mixture of iron .ore and coal through a rotary furnace heated at one end to a temperature sufficient to convert iron oxide to metallic iron, discharging, and. cooling the product, and separating the sponge iron from the residual coke and silic'ious material on a magneticseparator.

The furnace disclosed in the aforesaid publication comprises a cylindrical rotary kiln inclined slightly from the horizontal and made up of two sections of different diameters, the lower section being about one fourth as long and twice as wide as the up per one. Oil or other fuel is burned at the lower end, the products of combustion passing directly into the kiln. The charge of ore and coal is introduced at the upper and smaller end of the kiln and passes continually through the furnace, remaining in the small diameter section only long enough to drive out part of the volatile matter of the coal and to bring the temperature of the charge to about 900 degrees C.- The mixture then passes into the large diameter section, where it is heated uniformly and held at a tempera ture of 900 to 975 degrees C. for about one hour, after which it is discharged out of contact with oxidizing gases and cooled. the cooled product is treated on a magnetic separator. The concentrate produced is largely metallic iron but contains whatever gangue was present in the original ore particles. Some of this gangue material may he eliminated if fine crushing precedes magnetic concentration. llhe tailing consists of the unburned carbon, the coal ash and the gangue that was not attached to the ore particles. The carbon contained in the tailing is recovered by table concentration and may be used to replace an equivalent weight of coal in the charge.

A particularobject of the present invention is to provide a rotary kiln of relatively great total length, comprising separately formed reduction andpreheating cylindrical sections arranged in axial alignment and having their adjacent ends connected by a flexible joint,

-preferablyby arranging the ends in telescopic relatiomand preferably supported at their outerends respectively against axial movement at the said outer ends so that the relative axial movements of the kiln sections due to expansion when the kiln is heated, and when it is shut down and cools, are localized at the middle telescopic joint of the kiln and are compensated by the relative slippage of the telescoping cylinder ends.

Another object of the invention is to provlde an effective seal at the lower or discharge end of the reduction cylinder to prevent exposure of the sponge iron to oxidizing gases as the product passes to the cooling chamber, and the improved general structure of the present kiln contributes to the accomplishment of this object in a simple and effective manner, for the reason that as the lower end of the kiln is held against axial movement, 1t is only necessary to provide relatively simple sealing means to compensate for the wabbllng action of the lower end of the kiln due to the extent to which it may be bent by the weight of its charge and the effects of the heat to which it is subject.

Another object of the present invention is to provide for economy of fuel in preheating the charge in the up or section of'the kiln, by the introduction of air to the kiln at an intermediate region, in. order to provide for further combustion of the combustibe gases passing from the reduction section to the preheating section of the kiln. This may be accomplished very eflectively by introducing such air at the region of the telescoping joint, where a; certain amount of air would naturally enter unless special sealing means were provided to exclude such entry, and accordingly it follows that the novel telescopic ar- I nvaaeir rangement of the present invention furthers the provision for fuel economy while the provision for utilizing air at this region obviates the need for complicated sealingarrangements at the telescopic joint. Air introduced at this region mingles with the cornbustible gases from the reduction section at the region where it is desirable to stitect their further combustion and secure the proper temperature in the preheating section.

The invention has the further object of providing means to regulate the quantity of air thus introduced.

The above objects and other objects of the invention are-illustrated and described fully in the accompanying drawings and specification, and are pointed out in the claims:

in the drawings, I

Fig. 1 is view in longitudinal section of a rotary kiln in the construction of which the improvements have been embodied.

Fig. 2 is a view in end elevation of the lower or discharge end or the kiln, showing the sealing arrangements.

Fig. 3 is a vertical transverse section on the line 3-3 of Fig. 1.

, Fig. 4 is an enlarged sectional detail of a portion of the telescoping joint shown in Figs. 1 and 8, being taken on the line l-l of Fig. 3.

Fig. 5 is an enlarged detail view in'longitudinal vertical section of the delivery end oi the kiln, taken on the line VV of Fig. 2,

In the now-preferred embodiment of the inventionselectedforillustration and description, the parts designated by the reference numerals l and 2 respectively are cylindrical kiln members, arranged in axial alignment, and preferably disposed. so that a cylindrical member of smaller diameter 1 is at a higher elevation while a cylindrical member 2 of larger diameter is at a lower elevation; the cylinders thus disposed constituting a continuous working chamber, preferably inclined slightly as illustrated.

The cylindrical members 1 and 2 may be of any suitable material and general construction, being shown as constituted by iron cylinders having brick linings 3.

In pursuance of the invention, provision is made to support the cylinders in such a manner that relative axial play therebetween is localized at the region of the joint, which is preferably formed as a telescopic joint, for that purpose, while the other end of each cylinder is preferably supported against axial play, while permitting rotation of the cylinders freely.

As a suitable form of means to carry out this object of the invention, the lower cylinder 2 is shown as provided with a collar or ring 4 secured to the periphery of the cylinder and constituting the lower end thereof, having a flange 5 which serves as a circular track, adapted to run upon supporting rolls 6 journalled at 7 in bearings carried 1 y standards 8 mounted upon a suitable foundation 9.

Similarly the cylindrical member 1 is provided with a flange 10 secured upon the periphery or" the member 1 near the upper end thereof and constituting a circular track adapted to run upon supporting rolls 11 carried by standards 12 upon the portion 13 of the base.

The tracks 5 and 10 rotate freely upon the supporting rolls, but prevent axial play of the outer ends of members 2 and Jres'c-ectively. l

the region or the telescoping joint, ro v sion is preferably made for supporting telescoping ends rotatably, and such mean may take desirably the form of a ring ll constituting the upper end of cylinder 2 and provided with a flange l5 siniilar to those already described, constituting a circular track adapted to run upon supporting roll ers l6 journalled at l? in standards 18 mounted upon the portion 19 of the foundation or base.

As a convenient means for kiln structure as a whole, l have shown shaft 20 extendin from one of tee rollers 16 and provided wit a gear 21 whic by a reduction gear 22 upon a she electric motor 24. By this arrangement v :2 larger cylindrical member 2 is driven directly, and the cylindrical member 1 is rotated by frictional engagement the telescoping region.

in pursuance or? another object of the in vention, provision is preferably made tor the introduction of air at an intermediate portion of the furnace, preferably at the region o r the telescopic joint, and this may be provided for by suitable construction of joint to permit access oil the desired amount of air.

Any suitable structure may be adopted for this purpose, and as one convenient form or joint to serve the above purpose, 1 illus trates in detail, upon an enlarged scale, portion of such a joint.

In Fig. l the ring M is shown as provided with apertures 25 disposed in annular a rangement around the ring, and the adjacenc lining bricks 3 are provided with suitable channels to permit access of the air to the interior of cylinder 2 near the upper end thereof. The cylinder 1 is shown as provid= ed with a ring 26 constituting its lower end, and adapted to co-operate with the adjacent portion 27 or the ring 14, their surfaces being of such contour as to permit sliding relative movements of the contacting surfaces, and certain amount of wabbling action of these ends of the cylinders relatively to each other,

the inner surface 27 being shown as slightly convex for the above purpose.

At 28 l have shown a ring provided with apertures 29 which may be brought into "lull n. ow

llii

i 1. and swinging Irons intro ry with the apertures 25 of the flange M, or, by rotative movement of the ring 28, the apertures 29 may be turned out of complete registry so as to regulate the quantity of air admitted at this region, provision being thus made for controlling the quantity of air very readily and accurately.

In pursuance of another object of the invention, provision is made of suitable means to permit discharge of the product at the lower end of cylinder 2 without exposing the same to oxidizing gases.

Any suitable structure may be adopted for this purpose, and as an improved form of seal to accomplish the purpose illustration has been made in the drawings of a closure comprising a swinging ve v 2i, cupshaped metal apron 40 provided with a briclr lining ll, and embodying a ring 6h? preferably of suitably structure to permit circuiation of cooling water, the contour of this i j being suitable "to bear against the adjacent surface 50 of flange 5 on ring at all times, thus acting as a simple and effective seal to prevent access of air between the closure and the cyiinder member 2.

In order to provide for constant between the member 42 and the su;

s distortion under the cha "a e or by actic c l e 'erably susp 'votally at 4% to th L on mounted in suitable su shown.

The ciosure' is thus biased bv flange 5 and at the same time be withdrawn readily to give terior oi'cylindrical member 2 by swinging arms 43 around the supporting axis 45. A man-hole may be provided as shown at 46 to give access to the cylinder 2 without swinging the member 40 away from its upright position. I

At 47 a burner is shown adapted to introduce fuel to the lower end ofthe cylinder 2, the particular construction of this burner being varied according to the nature of the operation to be performed, such burners for firing rotary furnaces with powdered coal, oil or other suitable fuel, being well-known in the art.

At 48 is shown a chamber to receive the product from cylinder 2 and a discharge pipe is also shown at 49, which may lead to a suitable cooler for the product, it being apparent that the product may thus be discharged without being exposed to the oxidizing action of the atmosphere.

At the upper end of cylinder 1 is shown a hop er 51 through which the charge may be d uced to cylindrical member 1, and the upper end of cylinder 1 enters a suitable stack 52 through an opening 53, the products of combustion being carried off through the stack 52 for final disposition in any desired manner, as for example for utilization in drying the ore.

When the above described apparatus is used in the reduction of iron ore to produce sponge iron therefrom, the cylindrical member 2 serves as the reduction chamber or section of the apparatus and cylindrical member 1 serves as the preheating chamber for the charge of iron ore and coal, and the cylindrical members will be so designated herein.

In carrying the process into effect, the charge of ore and coal is introduced through the hopper 51 into the upperend of the preheating chamber 1 and passes continuously through the furnace, remaining in the preheating section long enough to drive out oi the volatile matter of the coal and to bring the temperature of the charge to about 900 C. The mixture then passes by gravity into the cylindrical member 2 constituting the reduction section, where it is heated uniformly and held at atemperature of about 900 to 9-50 degrees G. for a sumcient time to complete the reduction, being discharged radually into the reception l thence passing through the 49 to a suitable cooling cham- 16h the cooled product may be a i'nagnetic separator for removal is sponge iron particles, which are then utilization for any desired purpose. ..c reduction chamber or section 2 is dischar.

as for example by powdered coal with the roper amount of air to insure partial or complete combustion thereof to the extent appropriate for producing reducing conditions in the reduction chamber, from which atmospheric air is entirely excluded by the closure 40 and by the excess of internal ressure over atmospheric produced by the last through the burner 47.

The carbon monoxide and other combustible gases resulting from the reduction reaction in cylinder '2 tend to. pass upward through the cylinder 2 and thence into the preheating section 1. When they reach the region of the telescopic joint at the upper 'end of the reduction section, air admltted through the joint, as for example throughthe apertures 29 and 25 (see Fig. 4), is mingled with the combustible gases, so that further combustion of the mixture of gases is secured, and the desired heating temperature necessary for properly pre eating the mixture of iron ore and coal in the preheating section 1 is realized.

Furthermore, owing to the fact that the kiln comprises two cylinders in axial align- Ihent, the total length of the kiln may be relatively great without undesirably increased by tuelintroduced through the burner ing the unit length of cylinder, inasmuch as the cylinder 1 and the cylinder 2 can each be made longer than if the cylinder structure were integral. They can also be of more rigid structure without unduly increasing their weight than can a single cylinder, proportionately, and so they may accommodate a greater weight of charge without increasing too much the tendency to sag with the weight of charge. Accordingly there will be less distortion of the individual cylinders, less relative tendency to bind and less friction at the contacting parts, and less resultant Wabbling movement at the ends of the cylinders, so that the means for sealing the lower or discharge end of the kiln is relatively simple in structure and operation, acting very e'liiciently and without need for attention and repair.

By providing for driving the system of cylinders with gearing at the central region, the number of gears is diminished and less power is required in proportion to the charge treated.

The apparatus as a whole does not require highly skilled attendants, is compact, readily accessible in all its parts, and notably suitable for operation in multiple units with a single supervisor and tew assistants.

1 claim: s 1. A rotary kiln comprising a plurality of cylindrical sections joined in axial alignment and having their adjacent ends movable axial-V ly relatively to each other one of said members being supported against axial play at its other end, whereby relative axial movements of said sections are localized at the rigion of the joint therebetween.

2. A rotary kiln comprising a plurality of cylindrical sectionshaving their adjacent ends joined in axial alignment and supported for relative axial movement, and means to support said sections respectively against axial play at their other ends, whereby relative axial movements of said sections are localized at the region of said joint.

3. A rotary kiln comprising a plurality of cylindrical sections having their adjacent ends arranged in telescopic relation and supported against axial play at their other ends, whereby relative axial movements of said sections are localized at the region of the telescopic joint therebetween;

4. A rotary kiln comprising a pluralit of cylindrical sections arranged in axial alignment with their adjacent ends joined in axially movable relation, one of said sections being adapted to serve as a reduction chamber and the other section being adapted to serve as a preheating chamber for the charge and to deliver said charge to the reduction chamber, said kiln being inclined and supported against axial play at its discharge end, whereby said charge is fed by gravity through said section and relative axial movements of said wager? sections are localized at the region of the joint therebetween.

5. A rotary kiln adapted for use in the lowtemperature reduction of ores, said kiln comprising a cylindrical reduction section and a cylindrical preheating section having their adjacent ends joined co-axially, means to support said kiln in an inclined position, and means, acting upon said inclined structure at said joint, to rotate said kiln.

6. A rotary kiln comprising a rotatable cylindrical member, means to support said member against axial play at its discharge end, means to support the other end of said member, permitting axial play thereof, and an apron having means to receive the product from said discharge end; and means to sup port saidapron swingingly in position to be biased by gravity into contact with said discharge end.

7. A rotary kiln comprising a rotatable cylindrical member, means to support said member against axial play at its discharge end, means to support the other end of said member, permitting axial play thereof, and means to receive the product from said discharge end without exposure of said product to oxidizing gases, said means including a suspended swinging apron adapted to seal said discharge end and means to introduce fuel to said kiln through said apron, said apron having also a vent for said product.

8. A. rotary kiln comprising a continuous working chamber constituted by separately formed reduction and preheating cylinders joined in axial alignment, and means to introduce air to said chamber at the region of said joint, said means including an adjustable shutter forming part oi said join and serving to permit regulation of the supply of air.

9. A rotary kiln comprising a continuous working chamber constituted by separately formed reduction and preheating cylinders joined in axial alignment, and means to introduce air to said chamber at the region of said joint, said means including a flange forming part ot-said joint and provided with apertures communicating with said working chamber.

10. A rotary kiln comprising a continuous working chamber constituted by separately formed reductionand preheating cylinders joined in axial alignment, and means to introduce air to said chamber at the region oi said joint, said means including a flange forming part of said joint and provided with apertures communicating with said working chamber and an apertured ring co-operating rotatably with said apertured flange to regulate said air supply. j

In testimony whereof, I have signed this specification. I

' ARTHUR J. BREGGS.

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