Addition of Carbonaceous Materials in Pellet Induration Process

Induration test of pellet with addition of carbonaceous material was carried out by using an experimental pot grate furnace. A simulation model for analyzing induration phenomena of the pellet was also developed, in which consideration was given to the combustion of carbon, the decomposition of limestone, the oxidation of magnetite and the heat transfer between gas and solid. (1) Simulation analysis results agreed comparatively well with experimental ones. Therefore this model was considered to be applied to determine the operation conditions of the pot grate furnace and estimate the heat pattern in the pellet layers for commercial pellet plant. (2) As the carbonaceous material content in pellet increased, the pellet temperature of bottom zone became higher than that of upper zone due to the transference of combustion heat of carbon from upper to bottom layer. This resulted in difference in pellet properties between upper and bottom layer. (3) From this result, it was concluded that the limit of the content of carbonaceous material was about 1.0%. (4) It was estimated that the reduction of heat consumption was about 80000 kcal/t for the addition of 1.0% carbonaceous material. (5) The separate addition of carbonaceous material to the pellet bed and the granulation of double layers as to the content of carbonaceous material were found very effective to improve pellet properties.