US1898480A - Rotary kiln - Google Patents

Description

F; W. CORKILL Feb. 21, 1933.

ROTARY KILN Filed Aug. 12, 1929 f? TTOBA/EY Federated Feb. 21, I933 srA T FREDERICK W. GOBKILL, OF LOS ANGELES, CALIFORNIA, .A SSIGNOR TO PACIFIC COAST BORAX COMPANY, A. CORPORATION OF NEVADA ROTARY KILN' Application filed August 12, 1929. Serial No. 385,274.

This invention has to do with the art of calcination, and is directed to improvements in the construction of rotary kilns, whereby lit? the eficiency of such kilns and the uniformity and quality of the calcined product are greatly increased.

The usual construction of rotary kilns consistsof an elongated tubular shell, which is supported upon rollers and is provided with means for introducing material to be calcined at one end of the shell and with means for receiving the calcined material at the opposite end of the shell. Means are provided for rotating the shell at any desired speed,

and it is theusual practice to incline the shell slightly away from the end at whichthe material to be calcined is introduced.

The shell may be heated either externally or internally. It is the usual practice in the use of rotary kilns, however, to supply the heat by means of a burner placed atthe outlet end of the shell and adapted to direct a flame through the shell which is counter current to the direction of movement of the material therein.

In the use of kilns of this nature, the material to be calcined is first crushed to a size at which it may be conveniently handled, and the crushed material is introduced into the shell through suitable means, the inclination of the shell and the speed of rotation being such as to produce the desired extent of calcination of the particular material which is being used. 7

One 'ofthe most serious difiiculties which has been encountered in the useof kilns of this nature resides in the fact that it is economically impossible to produce a crushed ifthe kiln is operated so as to'properly calcine the fine material, the coarse material must be separated therefrom after the calcining step and must be subsequently subjectto either screen the crushed material before it is introduced into the kiln so that the material has a substantially uniform fineness, or toscreen the calcined material after it comes from the kiln and subject the coarse material t9 a second calcination step. Such an operation in connection with ores in which the calcination must be more or less accurately controlled to obtain the proper results, is obviously impracticable, and in any event is ineflicient and expensive.

It is a primary object of this invention to produce a rotary kiln in which the movement of the coarse material through the kiln is retarded, the retarding means being in the formof an obstruction or a plurality of ob structions, which are adapted to permit a substantially uninterrupted passage of fine material through the kiln, but which at the same time retard the movement of the coarse material so that both the fine and the coarse material receive the proper calcination.

It is also an object of this invention to produce a rotary kiln which is provided with baflies, associated with theobstructions mentioned above in a manner such that the flame passing through the'kiln is directed into engagement with the material passing over the obstruction, greatly increasing the thermal efliciency of the unit.

Details in the construction of my invention, together with other objects attending its productionfwill be better understood from the following description of the accompanying drawing, in which Fig. 1 is a sectional elevation, showing a preferred embodiment of my invention.

Fig. 2 is an end elevation, which may be considered as having been taken substantially in the direction of the arrow 2 in Fig. 1 v

Fig. 3' is a sectional elevation which may be considered as havingbeen taken in a plane represented by the line 33 in Fig. 1,

tially in a plane represented by the line -5 in Fig. 1, and illustrates the manner of 'ar- Q. ranging the-baflles in the shell.

More particularly describing the invention as herein illustrated, reference numeral 11 indicates an elongated shell, ,which is supported by means of rollers 12 and 12, enga 15 ing annular; channels 13 and 13, mounted upon the outer surface of the shell.

The shell 11 is adapted to receive rotation through the medium of a gear-14, mounted upon its outer surface and engaginga pinion 15, which-is adapted to be driven through the medium of 7 drive shaft 16 from any suit able sour of power (not shown).

It will be noted in Fig. 1, as was heretofore pointed out, that the shell 11 is set at a slight inclination, so thatthe material entering at the end 17 through the hopper 18'will pass downwardly through the shell during its ro-. tation, and will be delivered from the outlet 7 end 19 into a receiving hopper 20, from which it may be delivered onto a conveyor belt, such as is indicated byreference numeral 21.

Means for heating the material within the shell are illustrated as being in the formof a burner 22-, which is positioned at the outlet end of the shell, and may be supported in' any well knownmanner.

The inlet end of the shell is shown as being' surrounded by a draft chamber 23,'which is provided with-an outlet pipe 24, which, in 4 turn, may have a natural draft, or may be providedwith a fan 25 for providing a forced raft through the shell.

It will be understood by'those familiar with the art that the construction so far described is common to rotary kilns such as are now in use, and that the essence of my invention resides largely in means for governingthe passage of the material through the kiln. Such means, as has heretofore been. pointed out, comprises an obstruction or a lurality of obstructions so constructed an so positioned within the kiln as to permita substantially uninterrupted passage of the fine material through the shell, and at the same time to retard the passage of the coarse material therethrough. Such obstructions are,in the form illustrated, shown as comprising annular screen members 30, which are positioned in spaced relation with each other throughout the length of the. shell, and are retained withthe shell in any suitable manner, such as'by means of angular straps 31.

It was also mentionedas an object of this in vention to provide the shell with baflle means,

c3 whereby the bet gases passing through the shell would be directed into engagement with the material assing over the screens or obstructions. uch baflles are indicated in the drawing by reference numeral 32, and are shown as being in the form of circular plates, supported b angle straps 33, and positioned so that the ame passing through the shell is projected against the baflle and must pass over the material which is held back by the screens or obstructions 31.

In the use of my invention, it will be apparent that the material to be calcined, which -is introduced into the shell through the hopper 18 will, during the rotation of the shell, pass downwardly toward the outletend 19. a

The screens 31 permit the passage of the fine material, and it will be understood that the mesh of the screens and the number and arrangement thereof will be governed entirely by the quality and properties of the mate-, rial which is belng calcined in the kiln. The

' coarse material will, of course, build up be hind the screens and its passage through the shell will, accordingly, be retarded, so that it will be completely calcined before it is delivered from the outlet end 19.]

It is to be understood that, while I have herein described and illustrated one preferred embodiment of my invention, the same is-not limited to the precise construction set forth,

' but includes within its scope whatever changes fairly come within the spirit of the appended claims. v

I claim as m invention 2' 1. A'rota'ry comprising: anelongated tubular shell; mearis'for rotating said shell; means for injecting a flame into one of said shell; means. for introducing material to be calcined into theother end of said" shell a plurality of annular screens mounted insaid shell, adapted-to permit a substantially unin- V terrupted movement of fine material through said shell and at the same time retard the movement of the coarse material 'therethrough; and baflles mounted inthecenter of said shell adjacent said annular screens for directing the hot gases passing. through said" shell into contact with the material passing over said obstructions. r

2. Arotary kiln 'comprising:.an elongated tubular shell; means for rotating. said shell; means'for injecting a flame into one end of said shell; means for introduc' material to be calcined into the'other end of said shell; a

ioo

plurality of annular screens mounted in'said shell adapted to permit a passage of fine material therethrough and amovement of coarse material thereover; and a baflle associated w th said screens to deflect heat upon said coarse material. 1

In testimony whereof; I have hereunto set my hand at Los Angeles, California, this 30th day of'July, 1929.

FREDERICK w. poRKtLL. 1:0

Images