Rotary kilns fuel types used

Two major types of lime caleiners are die rotary (Fig. I) and (he vertical kiln, In North America, rotary kilns are widely used for lime cnlcinuiion. whereas in Europe vertical kilns are most popular. Rotary kilns typically have higher output [up to 6 tons (545 metric tons)/da> and lower labor cost. Vertical kilns can be designed for higher fuel efficiency and lower capital investment. They handle down to about -in. (19-cnt) stone, hut... 

In addition to the different shaft kiln types, rotary kilns are often used for lime burning. This enables good quality quicklime to be obtained with cheap fuels. Smaller limestone particles (10 to 60 mm) are utilized. 

Figure 14 Incineration system flow diagram. Waste is incinerated in the presence of air and supplemental fuel the incinerator can be multiple hearth, fluidized bed, liquid injection, rotary kiln, or other types caustic or lime scrubbers are used to remove gaseous pollutants from exhaust gases (from Ref. 11).

The traditional/long rotary kiln (type J in Table 16.1 and Fig. 16.15) consists of a rotating cylinder (110 to 140 m long) inclined at an angle of 3 to 4° to the horizontal. Limestone is fed into the upper back-end and fuel plus combustion air is fired into the lower front-end . Quicklime is discharged from the kiln into a lime cooler, where it is used to pre-heat the combustion air. 

There are two types of incinerators used predominantly for incineration of hazardous waste. The first type is the rotary kiln, which operates at temperatures of approximately 2300 "F. More hazardous wastes are burned in this type of kiln than any other and it is the one for which most tests on destruction efficiencies have been done. A second type is the cement kiln, which is now being used more often. The temperature of the cement kiln reaches 3000 "F. The hazardous waste is blended with the fuel and used in the making of cement. By modifying the fuel blend, it is possible to obtain efficient destruction, even for chlorinated solvents. 

Late in the nineteenth century the rotary kiln was developed in Britain, introduced into the United States and, from that country, adopted in Continental Europe. With this kiln it had become possible to use any type of fuel solid, liquid or gaseous (coal, oil, gas). The raw materials were introduced into the rotating tube in the form of "slurry" (wet process) or "raw meal" (dry process). In comparison with the shaft kiln, the capacity of the rotary kiln was soon greatly increased, especially after very effective homogenization methods, preheating and precalcining systems had been developed, and efficient measuring and control instrumentation had been introduced. 

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