Excessive amounts of alkalies can have deleterious effects upon the process of cement manufacture and the product. Normally much of the alkali present in cement raw materials is volatilized in the cement kiln and condenses on the particles of kiln dust which are carried out of the kiln by the combustion gases. Air pollution control devices, such as electrostatic precipitators and fabric filters, collect this dust. If it is subsequently returned to the kiln, an equilibrium circulating load of alkali is established. When this load is too high, serious kiln 'ring' formation can occur, which often leads to problems with operational continuity, as the alkalies alternately vaporize and condense. It is often necessary to discard at least a portion of the kiln dust. This disposal also represents poor land use, and can create a water pollution problem because of leachable alkali salts. This study reports on the determination of the feasibility of separation of cement plant kiln dust, into fractions which are alkali-rich and alkali-poor, by fluidized bed and flame-spray methods. The parameters varied were: The feeding system and fluidizing arrangement, the portion of the system designed for alkali entrapment, the dust collection mechanism, the temperature of the flame and collection system, and the collecting medium itself.

Grant no. 802196. Includes bibliographical references (page 60).