Disintegration of dense hematite during the reduction at low temperatures

Disintegration of dense hematite accompanying the isothermal reduction has been studied at the temperature of 450°C. The crystalline grains of the dimensions of about 2-3 mm were selected. Reduction has been conducted in 3 vol.% CO and 97 vol.% CO 2 gas mixture. The texture and porosity of reduced grains of hematite were determined on the basis of microscopic analysis and mercury porosimetry. Cracking and disintegration of hematite appear simultaneously with reduction. During the reduction progress the gradation of subgrain magnitude occurs. It was found that the subgrains of dimensions of about 0.1 mm are the limit of disintegration. The creating of subgrains of smallest magnitude take place when the reduction degree reaches about 10-20%. The porosity of reduced sample indicates the presence of cracks between subgrains as well as of micropores in magnetite subgrains. The radius of micropores was estimated to range from 0.02 to 0.07 μm and the microporosity level of about 10% was found.