Types of Incinerators
This chapter discusses four types which are currently the most common types used in incinerating biosolids: multiple-hearth furnace (MHF), fluid-bed furnace (FBF), cyclonic furnace (single rotary furnace), and the electric furnace (EF). The MHF is the most widely used biosolids incinerator in the United States. This is probably the case because the MHF has the advantage of being easy to operate and capable of handling wide fluctuations in feed loading rate and in quality of the biosolids cake. Unlike the MHF, where ash is carried out the bottom of the furnace, in the FBF ash is carried out the top of the furnace and removed by air pollution control devices such as wet venturi scrubbers. The cyclonic furnace is a vertically oriented, single-rotary hearth furnace that is cylindrically shaped, refractory-lined, with a domed steel shell. Like the multiple-hearth furnace, the electric furnace is usually divided into zones: feed, drying, combustion, and ash discharge zones.