US3355158A

US3355158A - Shaft kiln

Info

Publication number: US3355158A
Application number: US545360A
Authority: US
Inventors: William W Campbell; Carl E Rossi; William R Good
Original assignee: Harbison Walker Refractories Co
Current assignee: Harbison Walker Refractories Co
Priority date: 1966-04-26
Filing date: 1966-04-26
Publication date: 1967-11-28
Anticipated expiration: 1984-11-28
Also published as: GB1110646A

Description

Nov. 28, 1967 w. w. CAMPBELL ET AL 3,355,158

SHAFT KILNv Filed April 2e, v196e Z ONE /A/l/EWT/PS. w/L 14M m @Af/P55, CARL E. R055/ d W WML/4M /e 6000 @SMMM United States Patent O 3,355,158 SHAFT KILN William W. Campbell, Carl E. Rossi, and William R. Good, Ludington, Mich., assignors to Harbison-Walker Refractories Company, Pittsburgh, Pa.

Filed Apr. 26, 1966, Ser. No. 545,360 4 Claims. (Cl. 263-29) ABSTRACT OF THE DISCLOSURE In a shaft kiln hot zone, short and elongate burners positioned throughout the zone, the elongate burners being water cooled and having spaced ports over the burners, the ports arranged to open on the exterior of the burner on substantially the lower 180 degrees thereof.

A shaft kiln is a refractory and metal structure which defines a long, narrow, hollow column or shaft through which raw materials may be passed to be burned. A raw material is charged at the top of the shaft kiln, and it passes progressively downward through preheating, calcining or sintering and cooling zones. Air for combustion and heat transfer is introduced =at the bottom of the kiln and passes, countercurrent to the raw material, upwardly through the kiln. Therefore, the cooling zone is located near thetop of the kiln, the burning Zone is located centrally, and the cooling zone is located near the bottom of the shaft. Fuel, generally gas, is introduced through various burners located in the calcining or sintering zone.

A primary desirable feature of a shaft kiln is its thermal efficiency. This thermal efficiency results because burned materials transfer most of their heat to incoming air before being discharged, and exhaust gases transfer most of their heat to incoming raw material before escaping from the shaft kiln. If a shaft kiln was long enough, the exhaust gases and discharge materials could leave -at the same temperature they entered. Then if there were no heat losses through the side of the shaft kiln, it would operate as a perpetual-motion machine. It is, of course, impossible to prevent heat losses through the sides of the shaft kiln, and it is impractical to make the shaft kiln long enough to completely cool the exhaust gases and discharge material. Nevertheless, it is still a primary object of shaft kiln operation to effect the most efficient heat transfer.

Channeling of air and gas, especially along the walls of the shaft kiln, results in very poor kiln efficiency. One method of improving the heat transfer in a shaft kiln is to move the combustion air and fuel uniformly throughout the charge material within the shaft kiln column so that heat created by the combustion of the fuel and air is transferred as much as possible t-o the charge and not to the shaft kiln walls. One technique for reducing channeling and promoting uniform treatment of the charge is to be found disclosed in United States Patent No. 3,165,- 304, assigned to the same assignee as the present case. That patent is concerned with the introduction of combustion air into the bottom of the shaft kiln.

It is an object of this invention to provide burners placed so that the fuel is more evenly distributed throughout the hot zone, thereby effecting more uniform heat transfer. It is another object of this invention to provide elongate, water-cooled burner construction for placing fuel uniformly within the sintering zone of a shaft kiln. Another object of the invention is to provide improved shaft kiln construction including a novel arrangement of burners.

Briefly, according to one aspect of this invention, a shaft kiln is provided having elongate, water-cooled burners extending into the sintering zone. These burners have spaced ports over the portion of the burner within the sintering zone arranged to open on the exterior of the burner so that they will not be plugged with falling dust. According to another aspect of this invention, an elongate burner is provided having a coupling end which positioned exterior a shaft kiln and a port end for positioning within the sintering zone of a shaft kiln. The burner is comprised of three elongate chambers, one being a fuel chamber and being substantially surrounded by two other chambers which are joined at the port end to constitute a water jacket. The fuel chamber has ports extending outward therefrom in communication with the exterior of the burner. The ports are spaced over the port end of the burner and arranged to open on the exterior of the burner so they will not be plugged by falling dust.

Other objects and further features and advantages of this invention will become readily apparent to those skilled in the art from a study of the following detailed description with reference to the appended drawings. In these drawings:

FIG. l is a schematic front elevation in section of a shaft kiln embodying the concepts of this invention;

FIG. 2 is a plan 'section taken along line A-A in FIG. 1;

FIG. 3 is a front elevation in section of an elongate burner according to the concepts of this invention;

FIG. 4 is -a sectioned end view of the burner taken along the line C C; and

FIG. 5 is a sectioned end view of the burner taken along line D-D.

FIG. 1 shows a front elevation in section of a shaft kiln embodying the concepts of this invention (the section is along the line B-B shown in FIG. 2). The shaft kiln has an inlet 10 and an outlet 11 which enable the passage of the charge through the shaft or column 12. The shaft is defined by a refractory lining or wall 14 held within an outer steel shell 15.

The shaft is preferably ovaloid in section, as shown in FIG. 2, to minimize the distance from the center of the charge and nearest Wall. To facilitate this detailed description, approximate dimensions for a particular shaft kiln are given as follows: The shaft is about 2.0 ft. tall, the short axis of the oval cross-section is about 2 ft., and the long axis about 8 ft. At the lower end of the shaft kiln is a plenum chamber 16 containing a combustion air inlet 18 and an air-tight valve 19 for removing the charge. The plenum chamber enables a positive pressure to be maintained at the discharge end 11 of the shaft kiln. The preheating, burning, and cooling zones are labeled on FIG. 1.

The burning zone contains a plurality of spaced rows of burners 20. The rows are spaced about 2 feet apart. Each row contains a plurality of burners spaced more or less uniformly about the circumference of the shaft kiln. An exemplary arrangement of burners within a row is shown in FIG. 2. According to this invention, -at least one elongate water-cooled burner extends into the hot zone. Preferably, a plurality of elongate, water-cooled burners are spaced substantially alternately with short burners about a row so that the passage of charge through the shaft kiln is not substantially interrupted. This arrangement is shown in FIG. 2, the elongate burners being labeled 20-L and the normal burners being labeled 2li-S. By short burners, we mean burners which do not extend into the shaft kiln, but deliver fuel to the edge of the charge. It is preferable if the elongate burners extend about one foot or about halfway into the shaft kiln.

An optimal arrangement of burners, which provides maximum fuel distribution with minimum obstruction to descending charge, has been found in pairs of elongate and short burners positioned within rows substantially opposite each other generally perpendicular to the long axis of the ovaloid cross-section. The elongate burners extend to about the long axis. The pairs are arranged so that moving around a row elongate land short burners substantially alternate. lf more than one row of burners is used, the pairs of burners should be arranged so that, moving vertically, substantially aligned elongate and short burners alternate.

FIG. 3 is a front section of a water-cooled elongate burner used in the practice of this invention. The burner has an outer shell or perimeter 21 and an inner shell 22 which, along with webs 23, dene three chambers. Two

chambers

24 and 25 substantially surround the third chamber 26. The surrounding chambers 24 and 2S constitute a water jacket for the inner chamber 26, which is the fuel chamber. The fuel chamber has ports 28 which pass through the webs and are in communication With the outside of the burner and spaced along the end of the burner to be positioned within the hot zone, hereafter referred to as the port end. The ports are arranged to open on the surface of the burner so that they will not be clogged with falling dust, that is, on substantially the lower 180 degrees of the burner. It is also preferable that the ports open to the sides of the burner so that combustion will not take place along the underside of the burner. The burner is provided with means 29 which enables it to be fastened to the shell 15 of the shaft kiln. This means may comprise a flange 30 welded to the burner containing an opening 31 whereby it can be bolted to a similar ange 32 which is threadably attached to la spacer 34, which spacer is threadably attached to the shell of the shaft kiln 15. The burner also comprises means for introducing and removing cooling

water

35 and 36. This means usually comprises threaded nipples for attaching a Water source. The burner further includes means 38 usually threaded for attaching the gas source.

According to this invention, g-as is introduced into the center of the burning zone by the elongate burners through the spaced ports. In this manner, combustion is substantially moved away from the walls of the shaft kiln. Better heat transfer is promoted and channeling is substantially prevented. Before the introduction of the elongate burners, we found that about 2 to 21/2 million B.t.u.s per ton of magnesite were required for dead burning. Furthermore, the refractory lining 14 had to be replaced on the average of about every three or four months. After the introduction of the elongate burners, it was found that only 1 to 11/2 million B.t.u.s per ton of charge was required, and the lining was in good repair longer than in previous experience. The fuel and refractory lining saved provides a much more economic operation.

We have found that the outer shell 21 may be suitably fabricated from a 11/2 diameter schedule 40 pipe. The inner shell may be fabricated from a 2%1" diameter schedule 40 pipe. One method of fabricating the burner is to divide the pipe used as the outer shell in two parts. The two halves are milled to accept the webs 23 which are welded to the inner shell 22. The two halves and the webs are then assembled and welded together. The parts extending outwardly from the inner shell 21 can be M3 holes drilled through the webs and the inner shell. Burners made accordingly can be extended at least one foot into the shaft kiln without being bent or distorted appreciably Iby the downward-moving charge.

Having thus described the invention in detail land with sucient particularity as to enable those skilled in the art to practice it, what is desired to have protected by Letters Patent is set forth in the .following claims:

We claim:

1. In a vertical shaft kiln including means defining preheating, deadV burning, and' cooling zones in which a raw/ material charge moves from top to the bottom, the im provement comprising short and elongate burners posi-- tioned in spaced rows throughout the dead burning zone: and extending into said dead burning'zone, the elongate: burners being water cooled and positioned alternately/ with short burners so that the downward ow of the: charge is not interrupted substantially, said elongate: burners having ports spaced over the portion of the burners within the dead burning zone, said ports arranged to open on the exterior of the burner on substantially the lower degrees thereof.

2. The vertical shaft kiln according to claim 1 having an ovaloid cross-section and pairs of elongate and short burners positioned within spaced rows, said pairs beingv substantially opposite each other and generally perpendicular to the long axis of the ovaloid cross-section, said elongate burners extending to about the long axis, said pairs being arranged so that moving horizontally around a row or vertically between rows substantially aligned elongate and short burners alternate.

3. An elongate burner for use in a shaft kiln having a coupling end and a port end comprising :means defining three elongate chambers, one being a fuel chamber substantially surrounded by the other two chambers, said surrounding chambers being in communication at the port end and constituting a water jacket, the means forming the water jacket including webs, said Webs extending between the means defining the fuel chamberl and the outer perimeter of the water jacket, and there being a plurality of ports extending from the fuel chamber through the webs and in communication with the exterior of the burner, said ports being spaced over the port end of the burner and on substantially the lower 180 degrees thereof, means on the burner for connecting the coupling end of the fuel chamber to a fuel source, means on the burner for connecting with water jacket to a water source, and means on the burner for lattaching it to the shaft kiln.

4. The burner according to claim 3 in which the ports open on the sides of the .burner such thatl combustion does not take place along the underside of the burner.

References Cited UNITED STATES PATENTS 1,185,205 5/1916 Kemp et al. 234-1323 1,660,866 2/1928 Dieu v 234-132 1,950,015 3/1934 Winder et al. 234-1323 X 2,108,118 2/ 1938 Greenawalt 263-30 X 2,408,282 9/ 1946 Wolf 157-73 X 2,491,705 12/1949 Bloom 158-73 2,933,297 4/ 1960 Erasmus et al. 263-30 3,260,514 7/1966 Asano .et a1. 263-30 JAMES W. WESTHAVER, Primary Examiner.

JOHN J. CAMBY, Examiner.

Claims

1. IN A VERTICAL SHAFT KILN INCLUDING MEANS DEFINING PREHEATING, DEAD BURNING, AND COOLING ZONES IN WHICH A RAW MATERIAL CHARGE MOVES FROM THE TOP TO THE BOTTOM, THE IMPROVEMENT COMPRISING SHORT AND ELONGATE BURNERS POSITIONED IN SPACED ROWS THROUGHOUT THE DEAD BURNING ZONE AND EXTENDING INTO SAID DEAD BURNING ZONE, THE ELONGATE BURNERS BEING WATER COOLED AND POSITIONED ALTERNATELY WITH SHORT BURNERS SO THAT THE DOWNWARDLY FLOW OF THE CHARGE IS NOT INTERRRUPTED SUBSTANTIALLY, SAID ELONGATE BURNERS HAVING PORTS SPACED OVER THE PORTION OF THE BURNERS WITHIN THE DEAD BURNING ZONE, SAID PORTS ARRANGED TO OEN ON THE INTERIOR OF THE BURNER ON SUBSTANTIALLY THE LOWER 180 DEGREES THEREOF.