US1898042A - Sand seal for tunnel kilns - Google Patents

Description

Patented Feb. 21, 1933 more!) STATES PATENT orrice EDWIN B. FORSE AND CHARLES F. GEIGER,

OF METUCHEN, NEW JERSEY, ASSTGNORS TO THE CARBOEUNDUM COMPANY, OF NIAGARA FALLS, NEV] YORK, A CORPORA- TION OF PENNSYLVANIA SAND SEAL FOR. TUNNEL KILNS Application filed October 24, 1930, Serial No.

This invention relates to a method of sealing in tunnel kilns and other continuous or periodic car type furnaces. This application is a continuation in part of our prior application U. S. Serial No. 276,222, filed May 8,

In the ordinary use of sand seals in tunnel kilns a number of difiiculties have developed principally from the overheating of the platform of the car truck and the consequent overheating of the gear beneath the car platform. The ordinary sand seal includes metal plates or aprons which depend from the car platform into sand troughs which extend along each side of the tunnel wall, the sand troughs being located a little above the car axle. The sand trough is considerably below the top of the car platform. In this type of seal it is found that for any extended run of a continuous tunnel kiln such great clearances must be provided between the car platform and the kiln wall that combustion gases have ready access to the sides of the platform and to the aprons which depend therefrom into the sand. Under these conditions the platform of the car and the running gear underneath the platform become unduly heated, causing rapid corrosion and resulting high maintenance costs for sand seal plates, wheels, bearings, etc. High leakage through the overheated sand seal or through corroded metal parts tends to cause poor atmospheric control in the kiln chamber.

Attempts have been made to overcome these diniculties by giving the passage between the car platform and the tunnel wall a Zigzag form (in a vertical plane) to increase the resistance to the movement of highly heated gases from the region above the platform toward the sand trough. It is found necessary, however, to employ large clearances between the cars and the wall because in operation the expansion tendencies which are cumulative cause the cars to be- 490,939, and in Great Britain July 3, 1928.

come wider and the kiln structure to be come narrower internally for the reason that the kllIl walls are prevented from moving outwardly by the bracing required to im- To overcome the difficulties referred to above the applicants have taken advantage of the fact that in kilns and furnaces of the type under consideration the vertical expansion is much less than the transverse expansion. The applicants have also made provision for additional sealing means at the top of the car platform.

The improved sealing arrangements are illustrated by the accompanying drawing in which:

Figure 1 is a vertical section of the lower portion of a tunnel kiln taken in a plane at right angles to its length; and

Figure 2 shows a modification of the form shown in Figure 1, and shows details of its particular sealing means on an enlarged scale.

Referring to the drawing in more detail, a car is mounted to run on rails 3- and is provided with an apron 4 extending into a sand trough 5. From the sides of the kiln wall extend ledges 6 of refractory material. The ledges 6 present rectangular edges 7 which are so situated with respect to corresponding recesses 8 of rectangular section in the blocks 9 carried by the cars that sand may be retained in considerable quantities between the ledges 6 and the corners 8 of the blocks 9. The sand so retained forms seals adjacent to the upper surface of the block 9 which are useful in greatly reducing the penetration of furnace gases into the region between the platform and the'tunnel wall and extending from the sand seal 5 to the ledge 6. In order to obtaln the manmum benefit from this type of seal it is desirable that the construction be such that as each car passes further and further into the furnace the clearance between the ledge 6 adjacent to the edge 7 and the block 9 becomes decreasingly less. As long as there is sufficient sand in this upper seal continuous contact is maintained between the ledge block 6 and the sand in the complementary recess to prevent the passage of gases through the intervening sand. Sand which is scraped from the shelf 11 falls down to lower sand seals. Instead of ordinary sand (SiO finely crushed material such as silicon carbide grain or powdered material composed of fused alumina, periclase, etc. may be employed as the sealing medium.

In the modification shown in Figure 2 two sand seals are shown adjacent the upper surface of the car platform. One of these seals is formed in the space between a rectangular recess in the refractory block 15 (mounted on the car) and the stationary ledge 16 which projects from the furnace wall. Below the sand seal just described is a recess 17 in the furnace wall. Sand which is scraped from the uppermost sand seal falls on a stationary ledge 18 and a seal is thus built up between the corner 19 of the a block 15 and the rectangular recess bounded by the ledge 18 and the vertical portion of the furnace wall denoted 20. The projection of the block 15 into the recess 17 affords a radiation shield from the hotter regions above the block 15 even when the amount of sand in the uppermost seal is small.

We claim:

1. In a tunnel kiln a car track, a refractory platform mounted to run on said track between the side walls of the tunnel, and means for reducing the transfer of heat from the chamber above the platform to the running gear underneath, said means comprising a projection from a side wall of the tunnel into a sand pocket included between the top of the platform and a projection extending laterally from the platform at a short distance below the top and into a recess below said wall projection to form an overflow sand seal fed from said firstmentioned seal, the projection from the side wall being sloped downward toward the track to provide a gradually diminishing clearance in the first-mentioned sand seal,

and a third seal formed by a thin plate extending down from the platform into a sand trough arranged to catch sand from said second sand seal.

2. In a tunnel kiln, a car having a refractory platform for carrying ware, side walls of said kiln adjacent said platform and interfitting therewith to form an overlapping ledge, a seal of loose granular refractory material on said ledge in contact with the tures.

EDWIN B. FOR-SE. CHARLES F. GEIGER.

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