Optimization of feed blends to enhance the roasting performance of pellets made from Western Australian ultrafine magnetite concentrate

The conducted roasting tests were studied which pellets were made from blends of Western Australia ultrafine (WAU) magnetite concentrate and domestic magnetite concentrate or Brazilian hematite concentrate. The results show that the pellets made from 100% WAU magnetite concentrate exhibit inferior preheating and roasting performance under the following conditions:preheating at 1050℃ for 20 min and roasting at 1300℃ for 40 min, with compressive strengths of the preheated and fired pellets of each pellet 502 N and 2313 N, respectively. When blended 40% domestic magnetite concentrate or 20% Brazilian hematite concentrate with 60% or 80% WAU magnetite concentrate, the appropriate preheating and firing temperatures of the pellets are reduced from 1050℃ to 950℃ and 975℃, and from 1300℃ to 1250℃ and 1280℃, respectively. Moreover, the compressive strength of the fired pellets obviously improves to more than each pellet 2500 N. The microstructure of fired pellets made from WAU and domestic magnetite concentrate is characterized by fully grown Fe₂O₃ grains and close interlinkages among the hematite grains, which leads to low porosity and strong consolidation. In contrast, 20% Brazilian hematite concentrate blended with WAU magnetite concentrate yields nearly grown Fe₂O₃ grains in the fired pellets and only relatively close interlinkages between the hematite grains. The preheating and roasting performance of WAU magnetite concentrate pellets can be improved by optimizing the ore matching.