US1573543A - Tunnel kiln - Google Patents

Description

Feb. 16,1926. 1,573,543

F. A. J. FITZ GERALD TUNNEL KILN I Filed June 1, 1925 avweuto'c Patented Feb; 16, 1926.

UNITED STATES PATENT OFFICE.

FRANCIS A. J. GERALD, Oi NIAGARA FALLS, NEW YORK, ASSIGNOR TO HARPER ELECTRIC FURNACE CORPORATION, A CORPORATION OF NEW YORK.

TUNNEL KILNZ- Application filed 'June 1, 1925. Serial Molasses.

To all whom, it may concern:

Be it known that I, FRANCIS GERALD, a citizen of the United States, resid ing at- Niagara Falls, in the county of Niagara andState of New York, have invented certainnew and useful Improvements in Tunnel Kilns, of which the following is a specification.

p This invention relatesv to tunnel kilns and particularly to an improved kiln wherein the heat wasted is reduced to a minimum.

In the Operation of tunnel kilns it is the practice to convey the material or articles to be heattreated through the kiln on trucks or-other carriers, the articles, in general, be ing supported in saggers mounted on refractory supports carried-by trucks. Any heat conveyed to the refractories supporting the saggers or to the body of the truck'diminishes the thermal efficiency of the heattreating process, as'this heat serves no useful purpose and is ultimately lost. The higher the temperature required for the heat-treatment,the greater is the loss, for where this temperature is very" high a considerable thickness of refractories must be interposed between the bottom of the lowest sag er and the top of thetruck, and these reti' actories absorb a large quantity of heat .which is wasted. The principal object of the present invention is to provide an improved means for supporting the material to be heat-treated, or the saggers containing such material, from the truck, which means has high heat-insulating properties and is sufiiciently refractory to be unaffected by the highest temperature to which it is sub- 'jected.

Other objects of my invention will appear vfrom the following, description, taken in connection with the accompanying drawing, wherein Fig. 1 shows diagrammatically in transverse section a tunnel kiln, and shows in elevation, partly broken away, a truck and sagger support embodyingone form of my invention. a

Fig. 2 is a detail view similar to Fig. 1

l ig. 3 is a top plan view of the sagger supporting tray shown in Fig. 2.

Fig. 4 is a section taken onthe line a -a I of Fig. 3.-

lteferring to Fig; 1 of the drawing,

A. J. Frrz represents a kiln of heat-insulating material which forms a heating chamber 2, through which tracks 3 carrying the saggers 4 are adapted to be moved. Means, not shown, is

provided for supplying heat to the upper portion of the chamber 2 to heat the articles contained in the saggers'. To reduce the heating of the lower portion of the chamber 1 2 and the lower portion of the trucks 3, the

walls of the kiln' are thickened at their lower portion, thereby forming shoulders 10, and the upper portions of the trucks are formed wider than the lower portions so that the narrow clearance spaces 11 between the trucks and the walls of the kiln are angular in vertical section and prevent any direct radiation of heat from the upper to the.

the knobs 5 and forms in effect a tray which is filled with refractory material 6 of high heat-insulating properties. The material 6 may consist of any suitable refractory of sufficiently high heat-insulating properties and will vary with the workingtempera-' ture of the kiln and other special conditions. Thus, if the maximum temperature of the bottonrsagger in the kiln were not more than 900 C. infusorial earth may be employed. At very high temperatures, where the atmosphere of the kiln is strictly reducing, powdered charcoal may be employed.

If, however, at this high temperature an OXlClIZIIIg' atmosphere exists, some such material as silico-carbide may be used. When silico-carbide is employed, known as fibrox (descrlbed in Transactions A, E, S, Vol. 27, 1915, pp. 267 et seq.) may be employed to advantage. In certain cases the receptacle at the top of the truck may be filled with a mixture of highly refractory material and sawdust or the likc,-and the mixture then burned at a temperature where the refractory material is sintered so as to that varietyform a porous, highly refractory material which on account of its porosity will have very low hcat-comluctivity.

The material 6 being of low .hcat-conductivity, forms a heat-insulating medium between the ggers and the body of the truck. T he suppoi tray may be formed as a separate receptacle placed on or suitably secured to the top of the truck body. In Fig. 2 I have shown a modification of my invention in which the saggcrs 16 are supported on a tray 15 which, in turn, is supported and spaced from the top of the truck by uprigl'its 14-. The tray 15 may be formed of any suitable retractory material and comprises thin and rather deep side walls 17 and upwardly extending thin ribs 18 and 19. V

I claim:

1. A sagger carrier for use in tunnnel kilns consisting of a metal body the top of which is formed as a receptacle, divided refractory heat-insulating material contained in said receptacle, and sagger-supporting members in said material.

2. A sagger carrier :tor use in tunnel kilns having a receptacle at its top, charcoal in said receptacle, and thin sagger-sup-- porting members in said charcoal.

A sagger carrier for use in tunnel kilns having a receptacle at its top, silicocarbide in said receptacle, and thin saggersaid means and so arranged as to form a heat-insulating medium between the saggers on said carrier and the body of said carrier.

6.1K tunnel kiln having a chamber, a series of abutting carriers in said chamber, said carricrshaving body portions whose sides lie closely adjacent to the sidewalls of said chamber, whereby said chamber is divided into an upper and lower portion, the tops of said carriers being formed to hold divided material and being formed with thin upwardly-extending sagger-holding projections, divided refractory heat-insulating materlal surrounding said pro ect1ons, and

means for heating the upper portion of said chamber.

7. A sagger carrier for use 1n tunnnel kilns, a tray mounted on said carrier in spaced relation thereto, said tray being formed with thin interior sagger-supporting ribs, and divided refractory heat-insulating material contained in said tray.

8. A carrier having at its top a saggersupporting member and means carried by said member for forming a heat-insulating medium between the carrler and the saggers supported thereby, said means consisting of a material formed by heating a mixture of sawdust and refractory material until the refractory material is sintered.

FRANCIS A. J. FITZ GERALD.

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