US2230141A - Rotary kiln lining - Google Patents

Description

Jan. 28, 1941. R. P. HEUER 2,230,141

ROTARY KILN LINING Filed Oct. 24, 1939 IIIIIII/I/III/I/ Patented Jan. 28, 1941 UNITED STATES PATENT OFFICE General Refractories of Pennsylvania Compa LV, a corporation Application October 24, 1939, Serial No. 300,999

I 7 Claims.

The present invention relates to refractory linings for rotary kilns.

A purpose of the invention is to restrict heat losses from a rotary kiln without shortening the 6 life of the refractory lining or rendering the lining more susceptible to failure through crushing.

A further purpose is to provide insulating means for a refractory lining while providing a unitary column support for he individual bricks of the lining directly on the metallic shell of the kiln.

A further purpose is to prevent the possibility of lateral change of relation between refractory lining elements and insulating elements of ro- 16 tary kilns.

A further purpose is to employ nonacid refractory lining bricks, preferably unburned, in a rotary kiln, to integrate-the bricks to one another by oxidizable metallic spacer plates and to prevent destruction of the integrated joint by providing unitary column support of each brick on the metallic shell of the kiln.

A further purpose is to provide magnesite or other nonacid refractory bricks in a rotary kiln with an adequate base and 'a base which is unshiftable as far back as the metallic shell of the kiln.

Further purposes appear in the specification and in the claims.

80 In the drawing no attempt has been made to illustrate all of the possible forms in which the invention may be embodied. The forms shown in the drawing have been chosen from the standpoint of satisfactory operation and convenient 36 illustration of the principles involved.

Figure 1 is a transverse section through a rotary kiln, the section not being quite vertical because the kiln is sloping with respect to the horizontal. Figure 1 is diagrammatic as to de- 40 tails not important to the invention.

Figure 2 is an enlarged fragment of Figure 1.

Figure 3 is a perspective view of. one of the bricks of Figures 1 and 2.

Figure 4 is a section of Figure 3 on the line Figures 5, 6, '7 and 8 are perspective views of variations in the character of the bricks, Figur 7 being to reduced scale. 4

Figure 9 is an end elevation of a variant form 60 of brick.

In the drawing like numerals refer to like parts.

The following description is by way of illus- (crass-a2) rotary cement kiln, but also to include the rotary calcining kiln used in the preparation of ores, building materials, refractory materials and the like.

In the comparatively recent past, rotarykilns 5 were provided with a refractory lining of fire, clay or high alumina brick which was not insulated in the burning zone. The problem of insulation in the burning zone, using brick of the character mentioned, was not solved because [0 the insulation increased the temperature of the working face of such brick beyond the point which the brick could stand when in contact with lime and other fluxes present in the charge. In the zone of intermediate temperature, between 15 the burning zone and the preheating zone, the refractory brick were frequently surrounded by a separate annular layer of insulating brick which rested against the outershell or supporting structure of the kiln.

More recently success was had in employing nonacid refractory brick, particularly magnesite (magnesia) brick, in the burning zone. This zone was then insulated by inserting between the nona'cid refractory brick lining and the kiln shell, a 25 separate course of insulating bricks of perhaps 1 inch to 2% inches in thickness.

This arrangement of an inner refractory lining and a separate heat insulating brick layer has caused difliculty through short life of the lining. Study of the problem by the present inventor indicates that a major factor in such reduced lining life is slight lateral shift between the inner annulus or layer of refractory brick and the outwardly adjoining annulus or layer of heat insulating brick. In many cases the heat insulating brick do not conform exactly to the dimensions of the outer surfaces of the refractory brick, even when the lining is originally installed, so that an individual refractory brick may be backed up in part by one insulating brick and in part by another, or even conceivably in part by four different insulating bricks. Even if this condition does not occur when the lining is installed, shifting of the inner annulus or layer of refractorybricks with 48' insulating material.

preciated when we remember'that, during each rotation of the kiln, each refractory brick shifts from a condition of no load (topmost position), to a condition of maximum load when it is under maximum compression from the weight of the charge and the weight of the linin (lowermost position). When the inner layer or refractory bricks shifts with respect to the outer layer of heat insulating bricks; the chance that an individual refractory brick will be unevenly based on parts of several insulating bricks, or will shift its base from one heat insulating brick to another with consequent change in its loading, is relatively great. Under these conditions the possibility of localized uneven loading of the heat insulating bricks is considerable and heat insulating bricks undergo crushing. Once a heat insulating brick begins to give way, localized loading on adjoining bricks is increased and progressive failure of the base of the refractory bricks occurs with development of concentrated stress in the refractory bricks, and failure of the refractory bricks themselves.

The present inventor has discovered that, without loss of the advantage of a heat insulated lining, an individual column support, firm and unshiftable, may be carried back to themetallic shell for each individual refractory brick. Thus each individual refractory brick retains the same basethroughout the life of the lining, and the possibility of shifting its base or being based partly on one heat insulating brick and partly on another is entirely prevented.

This result is preferably accomplished by using a unitary brick whose working face is of nonacid refractory material and whose cold face is of heat Under this arrangement, no matter how much the brick as a whole may change its position, it is always assured of an integrally united even insulating base.

The principles of the present invention are particularly desirable in a lining whose bricks are integrated together by oxidizable metallic" spacer plates. The integrally united insulating base of the present invention prevents uneven stressing of the refractory bricks and thus pref vents breaking of the joint between bricks p r duced by the oxidizable metallic spacer plate. Thus in rotary kilns the integration of bricks'by means of oxidizable metallic spacer plates is very much more permanent where the refractory bricks are integrally based on the metallic shell, than where a separate insulating layer is employed. Oxidizable metallic spacer plates are' particularly desirable where unburned nonacid brick .are being used, since'unburned nonacid brick,

particularly magnesite brick, shrink to a considerable extent during use, and growth of the spacer plates with oxidation, due to the fact that the oxide occupies a larger space than the original metal, compensates for the shrinkage of the refractory bricks and prevents looseness of the joints due to shrinkage.

Figure 1 illustrates a typical rotary kiln such as a cement kiln or calcining kiln for ores, building materials, refractories or the like. The outer supporting structure of the kiln consists of a metallic shell 29 having at intervals metallic bands 2! which turn on rollers 22 rotatably supported on permanent structure, not shown. The mechanism for rotating the kiln is not important to the present invention and is not illustrated. Within the metallic shell 29 is a refractory lining 23 consisting of refractory bricks 24, as

shown more in detail in Figures 2, 3 and 4. Each of the briks 24 has a hot face 25 and a cold face 26, wh ch is usually referred to herein as the base. It is important to note that the cold face 26 rests directly upon the metallic shell 20, so that there is direct and nonshiftable column support by an integral brick extending clear through from the hot face 25 to the cold face or base 26.

The brick 24 consists of two portions, 9. refractory portion 21 and a heat insulating portion 28 united at 29 preferably by refractory cement. A suitable refractory. cement is a clay base cement containing sodium silicate. Or the cement of Heuer U. S. Patent No. 1,714,506, granted May 28, 1929, for Brick and cement for furnace use may be employed if desired.

The refractory portion 21 of the brick will preferably be nonacid refractory such as magnesite (magnesia), chrome (chrome-iron ore), chrome-magnesite or magnesite-chrom'e. Most desirably the refractory will be unfired, that is,

facture; No. 1,851,181, granted March 29, 1932,

for Dense mix for refractories and process of preparing the same} No. 1,859,512, granted May 24, 1932,'for Refractory and method of making it; No, 1;992,482, g'rantedFeb. 26, 1935, for Highpressure brick containing magnesia, and procvess of making thasame; No. 1,992,483, grant Feb. 26, 1935, for High pressure chrome refractory; No. 2,068,411, granted Jan. 19, 1937, for Highpres'sure -non'plastic refractory and method of making the same; No. 2,087,107, granted July 13, 1937,-for Chrome-magnesia refractory and method; No. 2,154,813, granted April 18, 1939, .for Suspended furnace roof; and No. 2,155,165, granted April 18, 1939, for Furnace roof. These patents are incorporated herewith by reference and made a part hereof.

The heat insulating portion 28 of. the brick may desirably be made of asbestos, diatomaceous earth, or more refractory materials such as kaolin or fire clay provided with high pore space, as due to burning out of organic matter or evolution of gas, as well known in the art of preparing heat insulating materials. The insulating material will preferably have a cold crushing strength greater than 250 pounds per square inch.

Ordinarily it will be preferable to mold the portions 21 and 28 separately and to secure them together with suitable furnace cement as Just described. It will however be permissible to mold one or the other portion first, and then unite the other portion to it by placing the portion first? molded in a mold and molding the later-formed portion in contact with the portion thus uniting the two together.

It is very desirable in many installations to integrate the refractory together by the integrating action of oxidizable metallic spacer plates,.

suitably plates of sheet iron or steel of suitable thickness, such as A 34 or inch in thickness. Spacer plates are shown at 30 covering one of the longitudinal faces 3| of each brick. The spacer plates will ordinarily be applied in their first formed,

unoxidized or as rolled condition, and as the kiln is heated they will become oxidized and will unite to the nonacid refractory material on each side as explained in Heuer Uf. S. Patents Nos. 2,154,813 and 2,155,165, above referred to. I

The plates may be loose or fastened to the bricks prior to installation, and any suitable means of fastening of the plates to the bricks may be employed. Figures 1 to 5 illustrate plates fastened to the bricks by co-moldlng, that is, placing the formed plate in the mold at the time the brick is molded. During the molding, projectingfingers 32 from side arms 33 of the plates are suitably embedded in the bricks to interlock the plates with the bricks. Co-molding of spacer plates and bricks is shown in Heuer U. S. patent application Serial No. 198,426, filed March 28, 1938, for Refractory brick process, machine and structure; and in Serial No. 238,505, filed November 3, 1938, for Refractory brick structure.

Metallic spacer plates may be affixed to the brick in any'other suitable manner, as by cementing to the faces of the brick, shown at 34 in Figure 6, or resiliently gripping the brick by the spacer plate as shown in Figure 7, where the side arms 33' of the spacer plate resiliently grip the brick, preferably fitting into a slight recess 35 molded onthe face of the brick. In the form of Figure 7 the spacer plate may conveniently be aflixed at or immediately before the time of installation of the brick.

It ordinarily is not economical to extend the spacer plate to cover the insulating portion 28 of the brick, as the chemical reaction with the spacer plate which integrates the bricks does not take place with the insulating material ordinarily used. Therefore in Figures 1 to 5, the spacer plate 30 extends only over the longitudinal face of the nonacid refractory.

Where very high temperatures are used, it may be necessary to keep the rear end of the spacer plate in contact with the metallic shell to sufficiently cool the spacer plate by conduction of heat and prevent the unoxidized rear portion from melting out. For this purpose the spacer plate may extend over the entire side of the brick as shown at 30' in Figure 6.

In some instances it is desirable to extend the spacer plate over the refractory and the heat insulation on one of the side faces of the brick, and also over the cold face. In this case the plate assists in maintaining the bond at 29 between the refractory and the heat insulation, armors the corners of the relatively weak heat insulation at the cold face, and insures good heat transfer contact between the spacer plate and the metallic shell. Figure 9 illustrates a brick having an integral oxidizable metallic spacer plate 30 of L form covering the longitudinal face 3| of the brick and the cold face 26. The spacer plate 30 is desirably cemented to the brick.

It is usually desirable to employ the spacer plate only on the longitudinal faces of the bricks, but if preferred, the spacer plate may extend over a longitudinal and an end face also as shown at 36 in Figure 6. In order that the spacer plates may contact refractory on both faces, avoiding as much as possible contacting of a spacer plate on one brick with a spacer plate on an adjoining brick (except at the small arm portions 33), it is preferable to place the spacer plate only on one longitudinal face, and if desired, also on one lateral face of the brick.

While spacer plates are desirable, the invention may be applied without using spacer plates. Figure 8 illustrates a brick 24' which is like the bricks of Figures 1 to 5 except that it has no spacer plate attached to it. This brick can be laid with mortar or with a loose spacer plate as desired.

The thickness of the refractory lining and'the relative proportion of the lining which consists of the refractory material 21 and the insulating material 28 will of course depend upon the design of the furnace and particularly the working temperature. In order to illustrate that the insulating material may in an individual case be a smaller -or larger proportion of the total thickness of the lining, Figure 5 illustrates a brick in which the insulating material 28 is relatively thinner than that in Figure 3.

The relative dimensions of the brick are of course not critical in the present invention. Whereas Figures 1 to 6 illustrate brick of wedge shape, with the longer cross-sectional dimension lengthwise of the furnace, key brick may be employed, with the longer cross-sectional dimension extending annularly and the spacer plate on one of the tapered faces, as shown at 24' in Figure '7.

It will be evident that in each of the forms of the invention, the means for insulating at the cold face and the refractory at the hot face are integrally united and function as a single unitary column, providing an adequate base and an unshiftable base for the refractory, and carrying back the load clear through to the cold face of the insulating means, at which point it is applied to the outside metallic shell of the rotary kiln.

In view of my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the structure shown, and I, therefore, claim all such in so far as they fallwithin the reasonable spirit and scope of my invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A rotary kiln having a metallic shell, in combination with a kiln lining consisting of unitary bricks extending clear through from the interior of the lining to the metallic shell and providing direct and unshiftable column support for the hot face from the shell, the interior of each individual brick consisting of nonacid refractory in unfired condition, and the exterior consisting of heat insulating material and the exterior and interior portions being integrally and unshiftably united.

2. A rotary kiln having a. metallic shell, in combination with a refractory lining consisting of unitary bricks extending from the shell to the hot face, there being unfired nonacid refractory material at the portions of the bricks toward the interior of the kiln and heat insulating material extending over the entire face of the brick adjoining the metallic shell, the refractory and heat insulating material being integrally and unshiftably united, and oxidiza'ble metallic spacer plates interposed between unfired nonacid refractory material of adjoining bricks.

3. A rotary kiln lining consisting of unitary bricks extending from the hot face to the metallic structural support of the lining, said bricks consisting of nonacid refractory material at the hot face and heat insulating material extending over the entire cold face,-the refractory and heat insulating materials being integrally and unshiftably united and the heat insulating material providing an individual base for the refractory material of each brick, unshlftable with respect to the refractory material of that brick, and oxidizable metallic spacer plates between nonacid refractory material of adjoining bricks.

4. A rotary kiln brick having a hot face and a cold face, the portion of the brick adjoining the hot face consisting of nonacid refractory mate rial, the portion of the brick adjoining the cold face consisting of heat insulation and the two being integrally and unshiftably united together.

5. A rotary kiln brick having a hot face and a a cold face, the portion of the brick adjoining the hot face consisting of nonacid refractory material, the portion of the brick adjoining the cold face consisting of heat insulating material,

, and the two being integrally united together and an oxidizable metallic spacer plate secured to one of the faces of the brick covering the nonacid refractory material at that point.

6. A rotary kiln brick having a hot face and diza'ble-metallic spacer plate secured to one of the faces of the brick covering the nonacid refractory material and the heat insulating material of that face, whereby the unoxidized portion of the spacer plate may be cooled during use by contact with external metallic structure.

7. The rotary kiln 'brick having a hot face, a cold face and. a side face, the material of the brick adjacent the hot face consisting of refractory and the material adjacent the cold face consisting of heat insulation, the refractory and the heat insulation being integrally and unshiftably united, and an oxidizable metallic spacer plate extending over the side face and the cold face.

RUSSELL P. HEUER.

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