Cement kiln plants

Abstract

A method is disclosed for operating a cement kiln plant in which impurities in the form of alkalis are present in vapor form in the hot dust laden gases generated in the kiln. According to the method, a portion of the hot dust laden kiln gases are directed upwardly through a first riser pipe which communicates with the kiln exit gas opening and thereafter the dust particles are separated from the gases and directed to the bottom portion of a second riser pipe having its lower end open to the atmosphere. Relatively cold atmospheric air is directed upwardly through the second riser pipe so as to contact the kiln dust particles separated from the by-passed kiln gases of the first riser pipe thus permitting the kiln dust particles to be cooled by the cold air while causing the air to be heated and providing its further use e.g. in a preheater. The velocity of the cold air directed through the second riser pipe is preferably controlled such that the heavier of the alkali kiln dust particles are permitted to fall downwardly through the second riser pipe countercurrent to the flow of air while the lighter of the kiln dust particles are entrained in the upwardly flowing air. Ultimately the kiln gases from the first riser pipe are combined with the preheated air from the second riser pipe and the combined gases may be directed to preheaters. Thus the method permits the removal of the heavier alkali laden particles from the cement kiln system by merely removing those particles from the second riser pipe. A cement kiln plant for practicing the inventive method is also disclosed.