US2859955A - Cooling apparatus for use with rotary kilns - Google Patents

Description

L. PETERSEN COOLING APPARATUS FOR USE WITH ROTARY KILNS Nov. 11, 1958 2 Sheets-Sheet 1 Filed Aug. '7, 1955 FIG. 2

ATTORNEY Nov. 11, 1958 L. PETERSEN COOLING APPARATUS FOR USE WITH ROTARY KILNS Filed Aug. v, 195e 2 Sheets-Sheet 2` Els. 5

FIG. 4

, @y mi United States Patent cooLING APPARATUS FoR UsE wrrn ROTARY KILNs Louis Petersen, Rye, N. Y., assignor to F. L. Smidth & Co., New York, N. Y., a corporation of New Jersey Application August 7, 1956, Serial No. 602,552

Claims. (Cl. 263-32) This invention relates to the cooling of cement clinker, lime, nodulized ores, and like products, which have been burned in rotary kilns and must be cooled before they are subjected to further treatments. More particularly, the invention is concerned with a novel method for cooling such hot burned products and with apparatus, by means of which the method may be advantageously practiced.

Rotary kilns have been constructed heretofore with a cooler disposed at the discharge end of the kiln in position to receive the material issuing from the kiln, and one such kiln and cooler combination is illustrated and described in the Fasting Patent 2,019,179, issued October 29, 1935. In the kiln installation of the patent, the lower end section of the kiln is enclosed within a hood and a grate is mounted within the hood beneath the kiln in position to receive hot material from the kiln. The material is advanced along the grate by ights attached to the kiln and air is passed through the grate and the material thereon to cool the material, after which the heated air enters the kiln and serves as secondary air of combustion. While the cooler of the Fasting patent has been successfully used, it is subject to the limitation that the cooling air used must be restricted to that required for combustion purposes, sovthat, when the kiln is being operated with a low output, the amount of air, which may be used for cooling, may be insuflicient to cool the material to the temperature desired.

The present invention is directed to the provision of a novel method of cooling hot burned material discharged from a rotary kiln, which provides more eiectivecooling of the material than can be achieved in the prior apparatus and supplies heated air to the kiln for use in combustion therein without being restricted bythe requirements of the kiln for varying amounts of combustion air under varying loads. In the practice of the new method, the burned material from the kiln is preliminarily cooled on a grate by air passed through the grate and material and into the kiln, after which the partially cooled material is separated into tine and coarse fractions and the coarse fraction is crushed. The crushed product and the line fraction are'then combined and entrained in an air stream and carried to a separator, and, in its movement with the air stream, the material gives up heat to Ficc For a better understanding of the invention, reference' may be made to the accompanying drawings, in which Fig. 1 is an elevational view of a rotary kiln installation, which includes apparatus for the practice of the new method; s

Fig. 2 is a sectional view on the line 2-2 of Fig. 1; an'd Figs. 3 and 4 are sectionalviews on the lines 3-3 andv 4-4, respectively, of Fig. 2.

The kiln installation illustrated in the drawings includes a rotary kiln 10 mounted for rotation with its axis at a low angle to the horizontal and having its lower end lying within a hood 11. A burner tube 12 extends through an opening in the hood wall into the end Vof the kiln and is supplied with air by a blower 13 having its outlet connected to the tube.v Fuel is supplied to the tube through pipe 14 to form a fuel-primary air mixture,

- which issues from the tube and is burned within the kiln.V

the air and its cooling to the desired temperature is completed. In the separator, the material is removed from the stream of heated air, and a controlled amount ofthe heated air from the separator is supplied to the kiln burner for use as primary air in the fuel-air mixture, while another part of the heated air is delivered beneath the grate and used in the iirst stage of the cooling. Any residual heated air is conducted to the intake of the fan producing the air stream and, if necessary, atmospheric air may be admitted at the fan intake. In carrying out the method, the material is cooled in two stages and all the heated air may be utilized. However, the cooling effect is independent of the requirements of the kiln for air for combustion under varying conditions of operation.

Ypipe 41, respectively, may be controlled.

out door 17 in the end wall of the hood. The pieces of material escaping through the openings in the screening ring fall upon the curved bottom wall of the hood 11. This wall is formed partly by an imperforate arcuate section 18 having a refractory lining 18a and partly by a curved grate 19, which extends from the vertical plane through the axis of the kiln along the side of the kiln moving upwardly. The space beneath the grate serves as an air chamber 20, which is defined at its ends by imperforate walls 21, 22 and, at its sides, by a vertical lined partition 23 and the lined side wall 24 of the housing.

The end section of the kiln upward from the screening ring is enclosed within a cylindrical sleeve 25, which is of larger diameter than the kiln shell, so that cooling air maybe introduced by one or more nozzles 26 into the space between the sleeve and the shell. A plurality of conveyor flights 27 and Vskimmer flights Z8 are mounted on the outer surface of the sleeve and the conveyor ights advance the material along the grate in the form of a bed, while the skimmer flights agitate the bed, as the sleeve is rotated with the kiln.

The upper end of housing 11 is provided'with an eX- tension 29, which encloses a cylindrical screen 30 mounted on a radial ilange 31 attached to the sleeve 25. A plurality of balls 32 roll on screen 30 and are held in place by a lip 30a on the screen and a flange 19a on the grate. The extension 29 has a hopper bottom 33 having its outlet connected to the casing 34 of a screw conveyor. The conveyor has a shaft 35 with ights disposed within casing 34 and driven by a motor 36 and the shaft ter@v minates short of the end of the casing, so that material being conveyed forms a plug'P within the casing serving as an airllock.

' The casing 34 is connected to a riser pipe 37 leading from the outlet ofra fan 38 to the inlet of a cyclone sep arator 39 having the usual bottom outlet for separated; solids and an outlet for gas at its top. A pipe 40 leads from the gas outlet of the separator tothe intakefof fan 38 and abranch pipe 41 leads from pipe 40to the air chamber y20 beneath Vthe grate 19. Flowfrom pipe 40. into the branch pipe 41 is controlled by a ap valve 42, so that the relative amounts of air from the separator, which go to the intake of fan 38 and enter the branch A second branch pipe 43 containing a damper 44 leads from pipe 41 to the intake of fan 13 supplying primary combustion air to the burner tube 12. The pipe 40 has an intake 45 Y for atmospheric air between the junction of pipes 40 and 41 and the intake of fan 38 and intake 45 contains a damper 46 for controlling the ow of air therethrough.

. The Y.limiting .11 is provided with a vent stack. 47 extending through an opening in the top of the housing and the stack contains a controllable damper 48. The stack is used to discharge excess cooling -air not `needed for combustionin the kiln and also for `emergency purposes. -i In the Practice of the method of the invention inthe installation described, the hot burned material traveling downward through the kiln is separated into large and small pieces by the screening yring and the small pieces passing through'the'holes 16 in the ring f allupon the lower wall of housing 11 andare advanced lengthwise of the grate 19 by llights 27 in the form o f a bed, which is continually agitated by flightsrZS. Heated air from the separator 39 and supplied to the air chamber 20 below the grateA passes throughthe bed of material on the grate to provide the preliminary cooling thereof and the air, which has been further heated by its contact with the material, enters the lower end of the kiln and serves as secondary air of combustion. The partially cooled material discharged at the upper end of the grate falls upon screen and a fine fraction of the material falls through the screen, while the coarse fraction remaining on the screen is crushed by the balls 32 to the desired size. The ne fraction and the crushed product passing the screen enter the casing of the screw conveyor and are advanced toward the riser pipe 37. The material continually maintains the plug P as material is discharged from one end of the plug into the air stream in the riser pipe and additional material is added at the other end Vof the plug. The material entering the air stream in the riser pipe 37 is carried upwardly through the pipe and is cooled by giving up its heat to the air. In the separator, the solids are separated from the heated air and the air is drawn through the separator gas outlet through pipe 40 by fan 38. Part of the air is supplied to the chamber 20 beneath the grate through pipe 41, while another part of the air is conducted to fan 13 and enters the burner pipe 12 to form part of the fuel-primary air mixture.

` The velocity of the air stream traveling through riser pipe 37 should be substantially constant in order that the material entrained in the stream may be properly cooled in its travel to the separator. The amount of air, which can be utilized in the kiln for combustion purposes, depends upon the conditions of operation and, if a large amount of fuel is being consumed, it may be necessary to deliver all the heated air to the chamber beneath the grate and. to the burner tube and to admit atmospheric air continually through Vintake leading to blower 3S to provide the desired air stream within the riser pipe. However, if the kiln .is Ynot being operated at maximum capacity, the Vvolume Vof air traveling through the riser pipe maybe more than is required for combustion in the kiln and, in that event, a part of the air may be delivered to the intake; of fan 38 for recirculation, while the atmospheric intake 45 is closed. Accordingly, in the practice ofthe method by the yapparatus described, the hot material issuing from the kiln is cooled in two stages to the desired temperature and the cooling operation is not restricted because vof a limitation on the amount of air, Which'may be supplied to the kiln for combustion purposes.

I claim: l 1. A method of producing a linely divided cooled product burned in a rotary kiln, which comprises burning a raw material in the kiln by passing the material down- 4 ward through the kiln countercurreut to gases Produced by combustion of a fuel-primary air mixture in the kiln in the presence of secondary air, initially coolingthe burned material issuing from the kiln by advancing the material in the form of a traveling bed, while passing air through the bed, separating the initially cooled material into line and coarse fractions, crushing the coarse fraction, combining the line fraction with the crushed product, introducing the combined material into a stream of air to be carriedalong therein and to give up heat thereto, separating the material from the heated air, conducting at least part of the heated air into the lower end of the kiln for use in combustion of the fuel, and adding any residual heated air to the air stream.

2. The method of claim l, in which part of the heated air separated from the material is passed through the bed of material and enters the kiln for use as secondary air. l

3. The Vmethod of laim l, in which part of the heated air separated from the material is used to form the fuelprimary air mixture.

4. T he method of claim 1, in which the velocity of the air stream is maintained substantially constant by addition of atmospheric air thereto.

5. The method of claim 4, in which atmospheric air is added to the airV stream in an amount equal to the amount of the heated air separated from the material, which is used as primary air and secondary air.

V6. A'rotary kiln installation, which comprises a rotary kiln, a burner for delivering a fuel-primary air mixture into the lower end of the kiln for combustion therein, a grate receiving the hot burned material issuing from the kiln, means for advancing the material along the grate, means for crushing the material discharged from the grate, a fan producing a stream of air, means for deliver' ing the crushed product into the stream of air to be carried' along therein and to give up heat thereto, a separator receiving the material-laden air stream and acting to separate the material from the heated air, vthe 'separator having separate outlets for solids and gases, connections for conducting heated air from the separator gas outlet to the burner and to the grate to pass through the material thereon, and a connection between the separator gas outlet and the fan intake.

7. The rotary kiln installation of claim'6, in which the grate is disposed beneath the lower end section of the kiln, and the means for advancing the material Valong the grate are flights attached to the outer surface.

8. The rotary kiln installation of claim 6, in which the crushing means include a screen encircling the kiln and balls rolling on the inner surface of the screen.

9. The rotary kiln installation of claim 6, in which the connections between the separator gas outlet and the burner, the grate, and the fan intake contain control means -for determining the relative amounts of heated air passing therethrough.

l0. -The rotary kiln installation of claim 9, in which the connection between the separator gas outlet and the fan intake has a controllable inlet for atmospheric air.

References Cited in the tile of this patent UNITED STATES PATENTS Newhouse -..,l- May 8, 19745

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