Rotary kilns regulation

Because acrylonitrile is listed as a hazardous substance, disposal of waste acrylonitrile is controlled by number of federal regulations (see Chapter 7). Rotary kiln, fluidized bed and liquid injection incineration are acceptable methods of acrylonitrile disposal (HSDB 1988). Underground injection is another disposal method. The most recent quantitative information on amount of acrylonitrile disposed in waste sites is for 1987. Emissions were 0.9 metric tons in surface water, 152 metric tons disposed through Publicly Owned Treatment Works (POTW), 92 metric tons disposed of on land 1,912 metric tons by underground injection (TR11988). Because acrylonitrile is relatively volatile and is also readily soluble in water, release to the environment from waste sites is of concern. 

Hexachloroethane and waste containing hexachloroethane are classified as hazardous wastes by EPA. Generators of waste containing this contaminant must conform to EPA regulations for treatment, storage, and disposal (see Chapter 7). Rotary kiln or fluidized bed incineration methods are acceptable disposal methods for these wastes. Underground injection may also be used (HSDB 1995). 

Controlled-air incinerators have a lower capital cost since they do not normally require air pollution control equipment (unless acid gas emissions are excessive). But since this facility must comply with new stringent regulations and acid gas emissions may be excessive, a rotary kiln system may be more advantageous. 

There are over 280 million scrap tires produced annually in the United States. Of these over 100 million are used as fuel and most of these are burnt to supplement fuel use in cement and other rotary kiln operations. The cement process is particularly convenient for tire combustion because the reinforced steel wire in the tire tread can be a source of iron for the cement chemistry. Kilns burning tires must comply with the EPA s boiler and industrial furnace act and hence are heavily regulated as a pollution source. Table 6.3 gives a typical average composition of tires supplied by the Rubber Manufacturers Association of America. 

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