Roller kilns

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. 

Fig. 4.7. Roller kilns with top- and bottom-fired small, medium-velocity burners. Type E flat flames above the ware would permit a lower roof and assure more even sidewise heat spread. Upflred burners from below are not wise for fear of crumbs falling into the burners. Radiant tubes can be used above and below the rollers and ware to protect the loads from contact with poc. Courtesy of North American Mfg. Co.

Minimizing heat storage in, and loss through, conveyors, trays, rollers, kiln furniture, piers, spacers, packing boxes, and protective atmospheres... 

Losses to Containers, Conveyors,Trays, Rollers, Kiln Furniture, Piers, Supports, Spacers, Boxes, Packing for Atmosphere Protection, and Charging Equipment, Including Hand Tongs and Charging Machine Tongs... 

Gypsum When gypsum is calcined in rotary kilns, it is first crushed and screened After calcining it is pulverized. Tube mills are usually used. These impart plasticity and workability. Occasionally such calcined gypsum is passed through ring-roller mills ahead of the tube mills. 

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). 

The continuous production with a daily output of 1500 of sheet slagsital was initiated in the USSR in 1966. A schematic diagram of the process is shown in Fig. 150. After melting in a tank furnace, a sheet is formed by pouring between rollers in a tunnel kiln crystallization is then performed in two stages. The sheet is 3 m in width and 5—25 mm in thickness. 

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. 

Preparation of Grist—The malt from the kiln is ground or, rather, crushed by passing between a pair of steel rollers... 

In roller presses, radial angle defining the line on the roller surface at which the speed of the particulate mass is identical with that of the roller in extruders, the angle between the extrusion surface (e.g. die plate) and the pressure generating device (e.g. extrusion blade, screw, roller). Formation of nearly spherical lumps (a lomerates) from a wet mixture of particulate solids by either drying or chemical reaction during tumbling typically accomplished in dryers or rotary kilns. 

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). 

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