Studies on the physical properties and reduction-swelling behavior of fired hematite iron ore pellets

Abstract

In view of generation of huge amount of iron ore and coal fines there is a need to develop a technique to utilize these fines. The present project work has been undertaken to study reduction and swelling characteristics of hematite iron ore pellets made from iron ore fines under different conditions. The physical properties of fired iron ore pellets were studied. The compressive strength and drop number of fired pellets increased with the increase of firing temperature due to the enhancement in the extent of sintering and consolidation of iron ore fines. The main objectives of the present work have been to study the effects of (i) Firing temperature (ii) Reduction temperature and time (iii) Addition of concentrated sugarcane juice on the reduction and swelling behaviours of fired iron ore pellets. The results indicated a decrease in the extent of reduction with increase of firing temperature. The reduction rate of fired iron pellets were found to increase with rise of reduction temperature from (850°C-1000°C). The degree of reduction of fired pellet increased with increase of reduction time, the rate being faster in the initial 20-30 minutes followed by a decrease thereafter. Extent of swelling in fired sakaruddin hematite iron ore pellets, in general, was found to be highest in the pellets reduced at 900°C followed by 950-1000°C. Reduction at a temperature of 850°C, in general, gave lowest degree of swelling in the reduced pellets. The highest degree of swelling at a reduction temperature of 900°C appears to be due to fibrous growth of iron in the reduced pellets. Slightly lower values swelling in the fired iron ore pellets reduced at 950°C and 1000°C appear to be due to sintering of iron particles in the pellets, as indicated by their SEM micrographs. Effect of reduction time in the range studied on the extent of swelling was not found to be distinguishable. The Indian coal gave higher rate of reduction than Australian, Indonesian and South African coals because of highest CO2 reactivity of Indian coal.