US2553464A - Heat recovery device - Google Patents

Description

May l5, 1951 J. I-I. MGNEILI.

HEAT RECOVERY nEvIcI:

Filed July l5' 1948 I l I I I I I I I I I I I l I I I I I I I I I I I I I I I I I Fiel n .I LI uuuuuuuuu 1.1.

Inventor Gttomegs Patented May 15, 1951 2,553,464 HEAT RECOVERY DEVICE John H. McNeill, Millville, W. Va., assignor to The Standard Lime and Stone Company, Baltimore, Md., a corporation of Maryland Application July 15, 1948, Serial No. 38,922

3 Claims.

This invention relates to heat recovery devices for inclusion in tube kilns and the like.

In the manufacture of cements, metallurgical fluxes and other products extensive use is made of long inclined tubular kilns.

In one type of kiln crushed rock is fed to the .upper end of the inclined rotating tube and moves slowly in a rather shallow stream to the lower end of the kiln into which flames from burners are projected. The hot products of combustion discharge from the upper or feed end of the kiln, and for economy of operation it is desirable to transfer their heat as completely as possible to the feed.

In another type of operation it is desired to cool clinkers as they move through an inclined rotary tube.

The invention is applicable for these and similar purposes, one of which involves a heat ex change between gases and solids at the entrance end of the inclined tube, and the other involves a similar exchange at the exit end. S0 far as the inventivevidea is concerned it can be applied at any point in the length of a tubular device such as a kiln.

Attempts have been made to use pockets or lifters attached to the interior of the kiln tube at the appropriate point. These lift the granular material flowing through the kiln as they rotate with the kiln and cause it to shower through the gas stream flowing longitudinally through the tube. In the forms heretofore used these pockets completely discharge themselves in the rst 100 to 160 of rotation after they become loaded, so that the falling material does not cover the entire transverse area of the tube. As a consequence only a third to a half of the gases flow in contact with showered material and the heat transfer is inefficient.

The present invention provides a novel type of lifter which does not completely discharge until rotated approximately 270 after they have become filled, With the result that material is showered across the entire cross-section of the tube. The distribution is remarkably even and a greatly enhanced heat exchange is afforded.

The pockets can be constructed as simple castings of heat-resisting-iron alloy, or steel, and have no moving parts. Thus they are inexpensive to install and are characterized by long life.

A preferred embodiment of the invention which has already demonstrated utility in full scale test operations will noW be described by reference to the accompanying drawings, in Which:

Fig. 1 is a side elevation of the feed end of a cement kiln, showing in dotted line possible 1ocation of rings of lifters. y

Fig. 2, drawn on a larger scale than Fig. 1, is a cross-section through the kiln of Fig. 1 on the line 2 2. In this view only the ring of lifters adjacent the plane of section is shown, the purpose being to show how the lifters discharge through about 270 of kiln rotation.

Fig. 3 is a perspective View of a lifter discharging at the top of its path.

Fig. 4 is a similar view of a lifter at the lowest point in its path.

Fig. 5 is a section through a lifter on the median plane,

In Fig. 1 the tube of the kiln appears at II and the track on Which the kiln turns at I2. The rollers which support track I2 are conventionaland are not illustrated. As better shown in Fig. 2, the kiln has a refractory lining I3 of ordinary form.

According to the invention the kiln may have one or more circular rows of lifters, and for each such row there is an internal band or ring I4 attached to the tube II by bolts I0 which pass through the lining I3.

Attached to each ring I4 by any suitable means is a circular series of similarly mounted lifter pockets. Each lifter comprises a box-like rear portion I5, which geometrically defined is a rectangular parallelopiped, open at its front or leading face and closed on all other faces. The front face and rear face are very nearly radial. They lie in parallel planes between which the axis of the kiln lies and with which this axis is parallel. The front face is not entirely open for that side of the parallelopiped which is toward the axis of the kiln has an arcuate extension with a curved marginal flange I6 of a width less than the radial depth of the lifter so that it overhangs a minor portion of the open front face.

Fig. 2 shows a typical spacing of one circular series but the spacing could be closer or wider depending on the designers preference and on flow characteristics of the material being handled.

In all figures the arrows R indicate the direction of motion. In Fig. 2 different ranges of travel are designated by letters.

The feed reaches the pockets near the lowest point in the rotary path, say at A and is caught ahead of the pockets and carried up. Between B and C a small amount of the material showers over the ends of the box-like portion. From D to E it showers over the curved lip afforded by ular material.

the flange i6. Somewhere in the neighborhood of E the curvature of iiange I6 causes the remaining charge to crowd toward the middle and slows up discharge so that it continues to about F. The curved flange 6 causes the veil of showered material to assume the curved characteristic of this ange vthus `causing a more complete coverage of theecross-sectional area of theffkiln. .Th-is curvature of the veil of material is at a maximum when the lifter is at its uppermost position. Thus the point where the material falls the greatest distance is also the point where the fallingImaterial is dispersed over the greatest latitudinalrexpanse of the area. This increased'dispersionresults in improved heat transfer, asiureducesthe I horizontal spacing between veils at the very point where it tends to become greatest.

The above description perhaps overfsingplies what takes place, but in any event a substantial amount of material isshowered from the lifter throughout its travel in an arc'longer thanth-e top 180 of thelifter path. As a consequence, gases flowing longitudinally through the kiln tube do not escape` contact with showeredgran- Several rings of lifters may be used as suggested inlig.` l'to intensify the heat exchange to any practicable extent. AIn some cases it is' preferred to stagger the lifters inadjacent-rings .as shown for the rst and second rings inFig. l. v

The form of lifter illustrated inthe drawings was evolved by a series of tests in which form and vproportions were closelystudied. A lifter similar to the illustratedA embodiment Without therearward box-like portion was tested, but itY was found that too muchmaterial was discharged over the ends and that not enough Was carried tothe region`E to Fof vthe kiln. The addition of the VNbox-like portion Venabledthe `lifter to carry a 'greater load` and resulted in less material `being discharged over the ends from B to'C.

'The proportions."illustrated .in the drawing are l Theycan be modified to suit particular cases without departing from the general ingiin'combination with the kiln tube, ra plurality of box-like lifters arranged in series around .the internal surface of the kiln tube, each lifter projecting radially inward from said surface of -the kiln :tube and being spaced from al1 adjacentlifters the leading face of each lifter being V openexceptforfa' minor portion thereof at the rend toward thelgiln axis, the -end wall of the lifter toward the kiln axis having an extension which `projectsbeyondthe side walls in the direction of motion of the lifter and is bounded by a iiange which overhangs said minor portion and is connected at its ends with said side Walls.

l12."Ihe combination defined inclaimll iii-which the margin of the end wall extension ontheilifter `is curved andthe related'ange arches over' the minor portion of the filter'from side wall to side wall.

3. "The combination defined in claim 1 in which the margin :of the.. end wall extension on thej lifter is curved, the end wall at the crest of the curved margin'has a height approximately double'that of A'the sidewalls of the lifter, and the related 'angearohes over the minor portion of'thelifter from side wall to side wall.

'JOI-IN I-IfMcNEILL.

REFERENCES CITED The following references are of recordin :the iile Aof,this.,patent:

,UNITED STATES PATENTS Number Name Date 139845315 Morris Dec. 11,1934 '250841,'113 HThayer June'2/2,j 1937 FOREIGN PATENTS Number Country :Date

1071,249 vSwitzerland i Nov.' 28,1922

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