<Original Papers>Study on the Pelletizing of Iron Ores.(II) : Fundamental Study on the Pelletizing Characteristics of Magnetite Ore

In order to establish the pelletizing characteristics of different types of fine raw materials represented by magnetite, hematite and limonite and the general rule for using these raw mixes, the authors studied following the previous report, the relation between the size of finely divided magnetite ore, balling conditions, properties of green pellets and amounts of water as binding medium, etc. Especially more attention was paid to the study on the strength of pellets as affected by the magnetic property and the mixing of very fines on balling, and investigated the microstructure of the thin sections of dry and burnt pellets by means of thin section. Results obtained are summarized as follows : (1) Optimum moisture content necessary to balling decreased with the lowering of feeding speed and with the decrease in the size of fines.(2) The maximum of the compressive strength of green pellets was nearly in agreement with the maximum of apparent de nsity, corresponding to about 70% of the saturation of the void space between the particles with water.(3) It was recognized that the relation between the compressive strength of green pellets and the specific surface of fines measured by the permeability method was expressed by a straight line, and that the green pellets from magnetite fines and oxidized magnetite fines located on the same line except those from the mixture of very fines.(4) It was recognized from the microstructure of the thin sections of pellets that the compressive strength of dry pellets was dependent on the packing behaviour of fine particles