1965 Volume 51 Issue 7 Pages 1227-1239
This is the fourth report in a series of studies which have been concerned with pre-reduction of iron sand with a rotary kiln. In this paper we deal with agglomeration of fine are and with re-oxidation of sponge in the rotary kiln which has influence on the adhesion'troubles.
By means of various measurements on the operating kiln, it has been shown that moderate re-oxidation near the discharge end of kiln may contribute to agglomeration of material, while excessive re-oxidation may cause a heavy adhesion of material called‘dam-ring’(coagulate in the shape of a narrow ring) on the brick wall of kiln. The heavy agglomeration of material growing into a big lump is a troublesome phenomenon for the operation of rotary Inn, and it has been regarded as an abnormal agglomeration such as a snowball, the nucleus of which is a spall of self-coating, and which stays long in the furnace because of the serious dam-ring. The longer the dam-ring and heavy agglomeration are kept in the furnace, the more steady they become, and consequently the more difficult to remove. In the rotary kiln, materials have tendency to segregate in such form as belt type or striped cycles because Gf different repose angles between iron sand and reducing agent, and the segregations disappear in the reduction zone under the normal condition of furnace. But the segregation will-hold on through the reduction zone in some occcasional accidents or especially at the starting time for operation, and may cause a serious coagulation of dam-ring.
When the rotary kiln is employed as a reducing device, the dam-ring trouble becomes a fatal obstruction. Therefore, we need some operational improvements to prevent an adhesion'trouble and keep the operation constant and secure.