US2719034A

US2719034A - Apparatus for flash preheating of pulverulent material

Info

Publication number: US2719034A
Application number: US435722A
Authority: US
Inventors: Petersen Louis
Original assignee: FLSmidth and Co AS
Current assignee: FLSmidth and Co AS
Priority date: 1954-06-10
Filing date: 1954-06-10
Publication date: 1955-09-27
Anticipated expiration: 1972-09-27

Description

Sept. 27, 1955 L. PETERSEN 2,719,034

APPARATUS FOR FLASH PREHEATING OF PULVERULENT MATERIAL Filed June 10, 1954 i 3o k 7 Tfl 26 FIG. I p 27 28 50 g; NVENTOR. BY @SQ VI ATTORNEYS United States Patent APPARATUS FOR FLASH PREHEATING OF PULVERULENT MATERIAL Louis Petersen, Rye, N. Y., assignor to F. L. Smidth & Co., New York, N. Y., a corporation of New Jersey Application June 10, 1954, Serial No. 435,722

2 Claims. 01. 263-33) This invention relates to the thermal treatment of granular and pulverulent material and is concerned particularly with a novel installation for such treatment, which includes a rotary kiln and means for carrying out heat exchange between the exhaust gases from the kiln and the material to be supplied to the kiln for burning therein. In the installation of the invention, the heat exchange is carried out by causing the materials to be entrained and carried along in suspension in the exhaust gas stream, after which the materials thus preheated are separated from the gases and introduced into the kiln.

In plants of the type described, and especially those employed in the burning of cement raw materials according to the dry process, the use of preheaters makes it possible to carry on so large a part of the heat exchange between the kiln gases and the materials to be burnt, that the kiln itself, may be of substantially shorter length than would otherwise be the case. The reduction in kiln length has resulted in the kiln gases leaving the kiln at a higher temperature and, in the usual installation, in which the upper end of the kiln extends into a smoke chamber connected to the preheater system, the higher temperature of the exhaust gases has subjected the smoke chamber and the sealing means between the kiln and the chamber to severer thermal stresses. Also, leakage of outside air into the gas stream at the seal between the kiln and the smoke chamber in such installation results in greater heat loss, because the drop in the temperature of gases occurs before they have given up any heat to the raw material.

The present invention is directed to the provision of a plant for thermal treatment of granular and pulverulent materials, which includes a preheating system but avoids the difficulties encountered in prior installations, in which short kilns and preheaters are employed. The new plant includes no smoke chamber and it is provided, instead,

with a connecting section, by which hot gases from the kiln may be led directly into a riser pipe forming part of the preheating means. In the new installation, the connection between the kiln and the riser pipe isof substantially less diameter than the kiln and sealing means are provided to prevent atmospheric air from traveling along the connecting section and entering the gas stream issuing from the kiln. Since the annular leakage path in the new plant is of substantially less diameter than the outer diameter of the kiln, the sealing of the path is easier than in prior installations including a smoke chamber and there is less heat loss as a result of leakage.

For a better understanding of the invention, reference may be made to the accompanying drawings, in which Fig. l is a diagrammatic view, partly in elevation and partly in vertical section, of one form of apparatus embodying the invention;

Fig. 2 is a fragmentary vertical sectional view on an enlarged scale of part of the apparatus shown in Fig. 1;

Fig. 3 is a view similar to Fig. 2, of a modified construction; and

Fig. 4 is a fragmentary vertical sectional view on an enlarged scale of the sealing means employed in the installation shown in Fig. 3.

The installation illustrated in Fig. 1, includes a rotary kiln 10, which is of conventional construction except vfor being provided at its upper end with a flange 11 extending radially inward. The cylindrical shell of the kiln and the flange are provided with the usual lining 12 and the flange has a central opening 13 for introduction of the material to be burned and the escape of exhaust gases. Theburned gases leaving the kiln enter a preheating system, which includes a generally vertical riser pipe 14 having an elbow 14a at its lower end, the elbow and pipe having a lining 15. A connecting section 16 of heat resistant metal and of generally conical form is mounted by means of its small end on the open end i of elbow 14a and the connecting section extends into the kiln through the opening 13 in flange 11, so that the large end of the section is wholly within the kiln. The leakage of gases along the connecting section through opening 13 into the kiln is prevented by sealing I 18 are bolted together and ring 17, which projects outwardly beyond ring 18, carries a cylindrical sleeve 19. A cylindrical section 20 is secured, as by welding, to the outer face of flange 11 on the kiln to encircle the sleeve 19 and section 20 has a circumferential flange 200, against which a sealing ring 21 is resiliently held by bolts 22 encircled by springs 23. The openings in ring 21, through which the bolts pass, are somewhat enlarged, so that ring 21 can adjust itself on flange 20a, as may be required. Ring 21 extends inwardly from section 20 and is provided at its inner end with a flange 21a, which bears against or is slightly separated from the outer surfaceof sleeve 19. With the construction described, the leakage of air along the connecting section 16 into the kiln through opening 13 is largely prevented and the sealing ring 21 may adjust itself, as the kiln expands and contracts, so that it will be eflective as a seal in cooperation with sleeve 19. j

The raw material to be burned is contained in a bin 24 having a hopper bottom, from which a duct 25 leads into the riser pipe 14 through an opening in the wall thereof. The lower end of duct 25 may be closed by a valve member 26 mounted on one end of a lever 27 pivotally mounted on the outside of pipe 14 and urged by a weight 28 to hold the valve member normally against the lower end of duct 25. The riser pipe 14 continues upwardly beyond the lower end of duct 25 to enter a cyclone separator 29 having an outlet for gases, which is connected by a pipe 30 to the intake of a fan 31. The discharge of the fan is connected by a pipe 32 to a dust collector 33 having a gas outlet connected by a duct 34 to a stack 35. The dust collector has a hopper bottom with an outlet for solids, from which a pipe 36 leads. The separator 29 has a hopper bottom with an outlet for separated solids, which is connected by a pipe 37 to an inlet 14b extending through the wall of elbow 14a of the riser pipe 14. A sealing device 38 of conventional construction is mounted in pipe 37 to permit the passage of material while preventing the passage of gases. The pipe 37 may be provided, if desired, with a fitting 39, to which pipe 36 from the solids outlet of the dust collector may be connected, so that the recovered dust may be mixed with the separated solids and introduced into the elbow 14a. The material thus entering the elbow flows along the inner surface thereof into the Patented Sept. 27, 1955,

connecting section 16, from which it is discharged into the upper end of the kiln.

With the construction described, it will be apparent that, since the connecting section 16 decreases in diameter in the direction of gas flow, the 'hot gases leaving the kiln will not'be subject to turbulence. As the gases travel through elbow 14a and enter the riser pipe, raw material is introduced into the gas stream through pipe and some of the material is entrained and carried along in suspension in the stream, while the remainder falls into the elbow 14a. In the travel with the gases, the material takes up heat from the gases and the entrained material is separated from the gases in separator 29 and fed intothelkiln. By feeding the preheated materials so that they flow along the inner wall of the elbow 14ainto the kiln, the materials can enter the kiln without'b'eing picked up thereby to an undesirable extent.

In the modified construction shown in Figs. 3 and 4, the connecting section between the kiln and the riser pipe is mounted on the kiln rather than on the pipe and appropriate changes in the sealing device are made. The kiln 10 is thus formed at its upper end with an integral extension '16 of generally conical form and serving as the connecting section. The riser pipe 14 has the form of a vertical stack with a lateral opening 40 at its lower end and the pipe is provided with a lining 41 and is cut away beneath and along the sides of opening 40, so that a part of the lining 41 defining the bottom and sides of the opening is unsupported. The opening at the end of the conical section 16 on the kiln is aligned with the opening '40 and, in order to prevent leakage into the stack through opening 40, a sleeve 42 is mounted on the riser pipe around opening 40 and spaced from the end of section 16'. An angle iron 43 is mounted within the sleeve with one flange extending inwardly and a fiat ring 44 is mounted within sleeve 42 in spaced relation to the inward flange of angle iron 43. A flat ring 45 loosely encircling the end of the conical extension 16' enters the space between the flange on angle iron 43 and the ring 44, and a pair of wear rings 46 engage opposite faces of ring 45 between the flange and ring 44. With the construction described, the leakage of air through opening 40 into the stack ispreve'nted.

In the installation shown 'in Figs. 3 and 4, the top of stack 14' is connected by a pipe 47 to a dust collector 48 .having a gas outlet connected by a pipe 49 to a stack (not shown). The raw material is fed by a conventional feeder 50 into the stack through a plurality of openings through the top of the stack. The material falling through the gas stream traveling upwardly through the stack is heated by the gases and collects in a pile 51 at the bottom of the stack. The material entrained by the gases is separated from the gas stream in the dust collector 48, which has a hopper bottom. The stack 14 has an inlet 52, to which a pipe 53 containing a conventional seal leads from the bottom of the dust collector 48. The solids from the dust collector are thus deposited on'the pile 51 and, when the pile has reached the proper height and slope, additional material landing upon the pile after traveling down through the stack 14 or through the pipe 53, slides down the surface of the pile and enters the kiln through the conical connectingsection16.

In both forms of the installation illustrated, the use of the connecting section mounted either on the riser pipe or on the kiln makes it unnecesary to employ the usual smoke chamber, into which the upper end of the kiln projects. As a result, the sealbetween the stationary and moving parts at the upper end of the kiln is of substantially less diameter than informer installations including a smoke chamber and the heat losses from air leakage are substantially reduced.

I claim:

1. An installation for thermal treatment of granular or pulverulent material, which comprises a rotary kiln having an opening at its upper end for introduction of said material to be burned and escape of exhaust gases of combustion, a riser pipe for conducting away the gases from the kiln and havingan open lower end opening for intake of the gases, a connecting section of generally conical form having its small e'nd secured to the pipe in alignment with the opening thereof, the section extending directly into the upper end of the kiln through the opening thereof, sealing means adjacent the small end of the connecting section mounted partly on thepipe and partly on the kiln and preventing passage of air along the outside of'the section into the kiln through the opening thereof, means for introducing material .into the pipe to be heated'by the gases, 'means for separating entrained material from the gases, and means for introducing the separated material through the connecting section into the upper end of the kiln.

2. An installation for thermal treatment of granular or pulverulent material, which comprises a rotary 'kiln having an opening at its upper end for introduction of said material to be burned and escape of exhaust gases of combustion, a riser pipe for conducting away the gases from th'e'kiln and having an open lower end opening for intake of the gases, a connecting section of generally conical form having its small end secured to the pipe in alignment with the opening thereof, the section extending directly into the upper end of the kiln through the opening thereof, sealing means adjacent the small end of the connecting section mounted partly on the pipe and partly on the kiln and preventing passage of air along the outside of the section into the kiln through the opening thereof, means for introducing material into the pipe to beheated by the gases, means for separating entrained material from the gases, and means for introducing the separated material into the riser pipe on an inclined inner surface adjacent the lower end opening, the material traveling along said surface and through the connecting section into the kiln.

References Cited in the file of this patent UNITED STATES PATENTS 1,319,700 Guild Oct. 28, 1919 1,679,337 Moulden et al July 31, 1928 2,332,724 Johnson Oct. 26,1943 2,590,090 De Vaney Mar. 25, 1952 2,648,532 Muller et al Aug. 11, 1953 2,663,560 Mulleret a1 'Dec. 22, 1-953