Roller hearth kiln

Special types of kilns are required in firing in a controlled atmosphere, such as in the manufacture of ferrites. The kilns are relatively small and at the entry and exit are provided with devices preventing air from penetrating into the firing space. The ware is shifted over a smooth surface or conveyed on revolving rollers of suitable refractory materials (roller-hearth kiln). 

Gas or electrical]y fired roller hearth kilns are also used for whiteware and electronics. Conveyer-type kilns with moving belt are used for decorating operations. 

Use High-temperature insulation of kilns and furnaces, packing expansion joints, heating elements, burner blocks rolls for roller hearth furnaces and piping fine filtration insulating electrical wire and motors insulating jet motors sound deadening. 

Other forms of straight-line continuous furnaces are woven alloy wire belt conveyor furnaces used for heat treating metals or glass lehrs (fig. 1.5), plus alloy or ceramic roller hearth furnaces (fig. 1.6) and tunnel furnace s/tunnel kilns (fig. 1.7). 

Deko-Press. A process intended to reduce the production costs of tableware by combining the dry-pressing of spray-dried powder with decoration and singlefiring in a roller-hearth kiln. Developed by Hutschenreuther AG. (Keram Z 36 (1984) 551.)... 

Roller-hearth Kiln. A tunnel kiln through which the ware, placed on bats, is carried on rollers. Tiles may be carried directly, without bats. 

Rollrod Kiln. A roller-hearth kiln for the rapid firing of tiles. The tiles rest on supporting rods which themselves glide on the kiln rollers at right angles to them. (Agrob Ab). 

Slit Kiln. A fast-fire kiln, usually a roller-hearth kiln, whose width is much greater than its height. The ware, usually tiles, is fired one-high. 

About 2000 new terms have been added. Though some existing terms have been modified to take account of changed emphases (roller hearth kilns are not the rarities of 30 years ago), very few have been removed. This is a twofold tribute to Dodd s original work. His definitions, concentrating on the essence of the meaning, have stood the test of time, even when the words now have much broader application in details. Where words have become obsolete, it has been thought worthwhile to preserve his accurate and authoritative definitions for historical record. 

Figure 4. Typical Fast Fire Curves For Roller Hearth Kiln...

Figure 4 illustrates a typical tile fast firing curve for a roller hearth kiln. Two basic types of kilns remain in service today with the older tunnel kilns being gradually replaced or outnumbered by roller hearth rapid fire kilns, illustrated in Figure 5. Firing in tunnel kilns is done on refractory setters, either manually or automatically loaded. Tunnel kilns remain in wide use today for smaller tile sizes such as 41/4 x 41/4 inch. Roller hearth kilns fire the tile on ceramic rollers, almost always automatically loaded.

The Calcimatic is a patented kiln of Canadian origin that is radically different from other kiln types. It consists of a circular traveling hearth of variable speed, supported on two concentric tiers of rollers. Kiln feed of 12.7 mm is fed onto the hearth in a 2.5—10 cm bed from a preheater chamber. The kiln is usually fired with natural gas or fuel oil, although the option of using pulverized coal has also been developed. After great interest, resulting in sales of many units throughout the world, the popularity of the Calcimatic has ebbed because of disappointment in the unit s mediocre thermal efficiency. 

---