US3547418A

US3547418A - Rotary kilns with cooler tubes

Info

Publication number: US3547418A
Application number: US757925A
Authority: US
Inventors: Flemming Edwin Jensen
Original assignee: FLSmidth and Co AS
Current assignee: FLSmidth and Co AS
Priority date: 1967-09-22
Filing date: 1968-09-06
Publication date: 1970-12-15
Anticipated expiration: 1987-12-15
Also published as: NL156235B; SE332687B; ES358189A1; GB1137246A; FR1585698A; NL6812949A; BE721083A; DE1758967A1; DE1758967B2

Description

United States Patent Great Britain No. 43,332/67 ROTARY KILNS WITH COOLER TUBES 5 Claims, 7 Drawing Figs.

Int. Cl F27!) 7/00 Field of Search 263/32, 3 2C, 52

Primary Examiner-John J. Camby Attorney-Pennie, Edmonds, Morton, Taylor and Adams ABSTRACT: A rotary kiln having a number of cylindrical cooler tubes mounted in planetary fashion around the outlet end of their kiln with their axes parallel or substantially parallel to the axis of the kiln, with the inlet end of each cooler tube being connected to an outlet end of the rotary kiln by a supply chute. Helical conveyor flights are provided in the tubes to lift the material in each cooler tube and discharge it in the form of falling curtains of material inclined to the axis of the tube so that cooling air must pass through curtains before entering the kiln. The improvement is in a ring of scoops provided at the air inlet end of each tube to produce a transverse curtain of material over that side of the tube in which the conveyor flights are moving upwards to impede the entry of incoming air into channels formed between adjacent inclined curtains PATENI'ED nan 5197s saw 1 BF 2 INVENTOR FLEMMING EDWIN JENSEN I ATTORNEYS PATENTED 0521 51916 35472418 sum 2 a? 2 FIG. 3

FIG.6 $56.5 FIG.4

INVENTOR FLEMMING EDWIN JENSEN R, ww MAT ATTORNEYS ROTARY KILNS WITH COOLER TUBES BACKGROUND OF THE INVENTION 1 Field of the Invention This invention relates to that kind of rotary kiln which has a number of cylindrical cooler tubes mounted in planetary fashion around the outlet end of the kiln with their axes parallel or substantially parallel to the axis of the kiln, the inlet end of each cooler tube being connected to an outlet of the rotary kiln by a supply chute. The tubes may extend away from the kiln, but more usually they extend from the outlet end of the kiln in the direction towards the inlet end of it.

2. Description of the Prior Art The assembly of these tubes is commonly called a planetary cooler and is a well-known construction widely used in the ceramic industry, particularly for cooling cement clinker formed by burning in the rotary kiln.

The hot material leaving the rotary kiln through the communicating chutes is cooled in the cooler tubes by air which passes through the tubes in countercurrent to the stream of hot material. The movement of the hot material is caused by the rotation of the kiln, with which the cooler tube is integral. In order to enable the material in the kilnto move easily along it, the kiln axis is normally slightly inclined to the horizontal. The tubes may be parallel to the axis and extend towards the inlet of the kiln, and then the material must move uphill through them, or they may be so arranged that the material moves downhill through them. In any case, the movement of the material is often furthered by means of built-in lifters or other conveying devices, and if the material moves uphill through the tubes, such devices must be provided for conveying the material through the tubes against the action of gravity.

Commonly the lifters or conveying devices are of such a design that the material is lifted up inside the cooler tube and discharged again into the stream of air flowing through the tube. If so, improved cooling of the material is obtained through the intimate contact achieved between the air and the material.

In the cooler the air takes up heat, which is subsequently utilized in the kiln as secondary combustion air. However, it is important that the amount of preheated air thus supplied to the kiln is correlated with the total amount of combustion air actually needed. The size of the cooler andthe amount of the cooling air required are therefore closely related to size of the kiln and the rate of production in it.

If large amounts of cooling air pass too quickly through the tubes, there will not be adequate contact between the air and the hot material, and accordingly the efficiency of the cooler will be low. To avoid this helical conveyor flights have been provided to lift the material in each cooler tube and discharge it in the form of falling curtains of material inclined to the axis of the tube, so that the cooling air must pass through curtains before entering the kiln. However, the air tends always to take the easiest path through the tube, and in consequence to flow through the channels formed between adjacent curtains, and only to pass through the curtains where these offer low resistance to it.

SUMMARY OF THE INVENTION tube to produce a transverse curtain of material over that side of the tube in which the conveyor flights are moving upwards and thus to impede the entry of the incoming air into some of the channels formed between adjacent inclined curtains.

The scoops may be separate from the conveyor flights or formed in the ends of those flights. Advantageously they are equal in number, but angularly staggered in relation, to the flights.

Preferably a ring of scoops is provided at the air-outlet end of each tube to produce a transverse curtain of material over that side of the tube in which the conveyor flights are moving downwards.

It is important that the conveyor flights should act efficiently in both conveying the material through the tube and providing an adequate number of curtains, and it is found that this is best done when the pitch of the helix of each of the flights is such that theitrace of the flight on the wall of the tube forms an angle of between 15 and 25 with the generatrix of the tube. 6 I

One construction according to the invention will now be described by way of example with reference to the accompanying diagrammatic drawings, in which:

DESCRIPTION OF DRAWINGS FIG. 1 is a longitudinal section through the outlet end of a rotary kiln equipped with cooler tubes according to the invention;

FIG. 2 is a section on the line 2-2 of FIG. 1;

FIG. 3 is an enlargement of part of FIG. 1 showing in detail a longitudinal section through a cooler tube;

FIG. 4, 5 and 6 are sections through the cooler tube taken on the lines 4-4, 5-5, and 6-6 in FIG. 3, respectively; and

FIG. 7 is a diagrammatic view of a cooler tube from above, showing the distribution of material inside the tube.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the lower end of a rotary kiln 1 having a refractory lining 2 and outlet openings 3 communicating through chutes 4 with twelve cooler tubes 5 arranged in plane tary fashion around the end of the rotary kiln with their axes parallel to the axis of the kiln.

The cooled material leaves each cooler tube through outlet opening 6 in the air-inlet end of the tube, and all the openings 6 are surrounded by a stationary housing 7, the bottom of which is formed as a hopper 8 for collecting the material. The cooled material is discharged through a bottom opening 9 in the hopper 8.

The parts described so far and shown in FIGS. 1 and 2 are of the conventional construction. In the invention, each cooler tube has trough-shaped conveyor flights 11 running helically from one end of the tube to the other as shown in FIG. 3, and at the air-inlet end a ring 12 of scoops 13 is provided. These scoops have sidewalls, not shown, and constitute a series of buckets, which pick up material from the bottom of the tube and carry it upwards as shown in FIG. 6 until the kiln, and therefore the tube, reaches such an angular position in the course of rotation that the material begins to fall out of the scoops 13 to form a curtain 14 extending over approximately half the cross-sectional area of the tube.

At the air-outlet end of the tube there is a ring 15 of scoops 16 constructed likewise to engage and carry material upwards, but to hold the material until the kiln has passed through a much greater angle of rotation and thus to discharge it as a curtain 17 over approximately the other half of the cross sec- 1 tion of the tube from that occupied by the curtain 14.

The conveyor flights 11 have the trough shape shown in FIG. 5, and lift the material and in the course of rotation discharge it again in the form of curtains 18, which are inclined to the axis of the kiln. At any given instant these curtains 18 may be regarded as occupying the position shown by dotted lines in FIG. 7, and channels 19 are formed between adjacent curtains 18. It will be seen that the curtain 14 extends across the inlet ends of two comparatively long channels, leaving only a comparatively short channel for the unimpeded entry of air. The arrows in FIG. 7 show approximately the paths taken by the air and the FIG. shows how the air is forced to pass through a number of inclined transverse curtains. At the airnoutlet end, the presence of the curtain l7 prevents the air from passing uninterruptedly into the kiln along two comparatively long channels 19, the mouth of only a comparatively short channel being open to allow the unimpeded passage of air.

The conveyor flights shown serve not merely to produce the curtains, but also to convey the material towards the air-inlet end of the tube.

By means of the invention the heat exchange in the tube is improved, and in consequence the diameter of each tube and also the length of the tube may be reduced in comparison with conventional planetary coolers. This in turn makes it possible to increase the number of cooler tubes, and accordingly to allow a greater quantity of material to be cooled in the planetary cooler, so that the invention is of particular value in kilns of high output.

lclaim:

1. In a rotary kiln having cylindrical cooler tubes mounted in planetary fashion around the outlet end of the kiln with their axes parallel or substantially parallel to the axis of the kiln, the inlet end of each cooler tube being connected to an outlet of the rotary kiln by a supply chute, in which troughshaped conveyor flights run helically along the inner wall of each cooler tube to lift the material above the horizontal plane through the axis of the tube and discharge it as curtains extending over substantially the whole width of the tube and inclined to the axis of the tube, the improvement in combination therewith comprising a ring of scoops provided at the air inlet end of each tube configured to lift scoopfuls of material and later cause it to fall out-therefrom to produce a transverse curtain of material over that side of the tube in which the conveyor flights are moving upwards and impede the entry of the incoming air into some of the channels formed between adjacent inclined curtains.

.2. A kiln according to claim 1 in which a ring of scoops is provided at the air-outlet end of each tube to produce a transverse curtain of material over that side of the tube in which the conveyor flights are moving downwards.

3. A kiln according to claim 1 in which the scoops at the airoutlet end are formed in the ends of the conveyor flights.

4. A kiln according to claim 1 in which the scoops at the airinlet end are equal in number, but angularly staggered in relation, to the flights.

5. A kiln according to claim 1 in which the pitch of the helix of each of the flights is such that the trace of the flight on the wall of the tube forms an angle of between 15 and 25 with the generatrix of the tube.