US2169512A - Rotary kiln - Google Patents

Description

Aug. 15, 1939. N s BQRCH 2,169,512

ROTARY KILN Filed Sept. 23, 19158 ATTORNEY Patented Aug. 15, 1939 .UNITED STATES PArErVr oFFIeE ROTARY KILN Application September 23, 1938, Serial No. 231,337

6 Claims.

This invention has to do with rotary kilns, and is concerned more particularly with a novel end section for use at the outlet end of such a kiln, the section of the invention having a longer life 5 and being less costly to maintain in proper condition than similar sections as heretofore constructed. The new end section may be used in rotary kilns for various purposes, but since it affords special advantages when used on a kiln lo employed for sintering or agglomerating materials, an embodiment of the invention for that use will be illustrated and described for purposes of explanation.

In kilns used for sintering or agglomerating 15 finely divided materials, such as pulve-rulent iron ore, blast furnace dust, and the like, the materials are heated to a temperature at which they become somewhat tacky so that the particles cohere and crusts are likely to be built up on the Z kiln lining. These crusts must be removed from time to time, and in order that this may be done from outside the kiln and without shutting down the latter, the kiln is operated under such conditions that the sintering Zone is short and as near the outlet end of the kiln as possible. The entire lining within the zone can then be Vreached by a suitable tool inserted through the kiln outlet and operated to break the crusts loose.

Since the sintering zone in such a kiln extends 30 to the outlet end an-d the material undergoing treatment reaches its highest temperature in this zone, all parts of the kiln at the outlet end are exposed to a high temperature, especially those with which the highly heated sintered material T15 comes in Contact. At the outlet end of such a kiln, it is common to provide an end section formed of a steel casting of channel shape, the outer surface of the casting being engaged by a part of the device forming a seal between the il) kiln and the hood into which the end of the kiln projects. The inner surface of the end section is then protected by a lining of refractory material, part of which lies in the channel, but the outer end flange of the ring is not protected by 45 the lining and is exposed dir-ectly to the sintered material leaving the kiln at a high temperature. 'Ihis flange of the end section lies within an oxidizing atmosphere and is exposed to a temperature of about 1000 C. As a result of these 50 conditions, the flange of the case steel and section heretofore employed has become rapidly burned away with the result that the entire end section requires replacement in a short time.

The present invention is, accordingly, directed 55 to the provision of a novel end section for use with rotary kilns, particularly those for sintering purposes, which overcomes the disadvantages of the prior end sections in that it has a much longer life and can be maintained in proper working condition at little expense. The end 5 section of the invention is made of two rings of channel shape secured to the kiln shell in alignment and concentrically therewith, and the inner ring, which is wholly protected from contact with the material by a refractory lining, is a single casting which may be made of any suitable material. The outer ring, which has an end flange beyond the lining and therefore exposed to the hot discharging material, is made of a heat-resistant alloy and consists of arcuate sections individually attached to the inner ring. With this arrangement, that portion of the end section which is directly exposed to the hot material is made of a metal selected for its ability to withstand the high temperatures, and since 9o this outer ring is made of arcuate sections',`no difficulties arise from the different rates of expansion of the two rings and individual arcuate sections can be replaced as required.

For a better understanding of the invention, reference may be made to the accompanying drawing, in which- Figure 1 is a longitudinal sectional view through the outlet end of a rotary kiln with the new end section in place;

Figure 2 is a fragmentary view similar to Figure 1 but on an enlarge-d scale; and

Figure 3 is an end view of the kiln illustrated in Figure 1.

Referring to the drawing, the kiln, as shown, comprises the usual shell It) with its refractory lining Il, and a ring I2 is mounted to encircle the shell near the kiln outlet, the ring having a radial flange I3. Beyond the ring I 2 is the end section, which includes an inner ring lli of channel section, held in place by having its flange I5 secured to the flange I3 of ring I2 by bolts I6. Extending between the flanges I2 and I? of the ring at intervals are strengthening webs I8.

Beyond the ring I4 and in alignment therewith 45 is an outer ring I9 which is made up of a plurality of arcuate sections 20 of channel form. In the construction shown, there are eight such sections and each section is connected individually to the ring I4 by bolts 2l passing through the 50 inner flange 22 of the section and the flange Il of the ring. Each section is provided with an outer flange 23 which extends inwardly a considerable distance beyond the end of flange 22, and the flanges are connected together at intervals by strengthening webs 24. The rings I4 and i9 are protected by a lining 25 of refractory material, portions of which lie within the channels, and the flange 23 of the outer ring, which lies beyond the lining, assists in hol-ding the latter in place. This flange is, therefore, exposed tothe hot materialY discharging from the kiln and the flange is thickened Vat itsedge, as at 2S, and is strengthened by ribs 21.

In the new end section constructed as described, it is possible to make those parts with which the hot sintered material directly contacts of a material which is heat-resistant and of great durability under the conditions of operation. Various materials may be used for the purpose, as, for example, cast steel and cast iron containing chromium and nickel, and since the outer ring is inV arcuate sections, the use of such materials for the sections in conjunction with other materialsforrthe inner ring causes no expansion difficulties. Heat-resistant materials of the type referred to are relatively expensive andthe cost of using them for making prior end sections in single castings has been prohibitive. With the new end section, the expensive materials are confined to the parts where their use is important, and forming the outer ring in sections which can be individually replacedl further reduces the cost of maintenance.

I claim: j

l.' Ina kiln, anV outlet end section comprising a pair of rings connected together in alignment, the outer ring being made up of arcuate sections, and a lining within the rings.

2. In a kiln having a shell, an outlet end section comprising a ring secured to the shell concentrically therewith, a second ring secured remade of heat-resistant material, both rings be ing inwardly channeled, and a lining within the channels. n

3. In a kiln, an outlet end section comprising a pair of rings secured together in alignment and concentrically with the kiln, both rings being of channel section and the outer ring being of heatresistant material and'having an internal flange at its outer end, and a lining of refractory material within the channels and held in place in part by the ange.

4. In a kiln, an outlet end section comprising a pair of rings secured together in alignment and concentrically with the kiln, both rings being of channel section and the outer ring being made up of arcuate sections, each having an edge ange at its outer end, and a lining of refractory material in the channels and held in place in part by the section ilanges.

5. In a kiln, an outlet end section comprising a pair of rings connected together andto the kiln concentrically with the latter, both rings being of channel section with webs across the channels, the outer ring being of heat-resistant metal, and a lining of refractory material Within the channels. Y Y

6. In a kiln, an outlet end section comprisin a pair of rings lying in alignment and concentrically with the kiln, the inner ring being secured to the kiln shellV and the outer ring being made upof arcuate sections individually connected to the inner ring, the outer ring being made of heat-resistant metal and having an edge flange, and a refractory lining within the Vrings and held in place in part by the flange. NIELS SOFUS BORCH.

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