Pelletizing mechanism of pretreated limonite without bentonite
In order to broaden the range of raw materials in pellet and reduce production costs,a wet ball milling process was used to pretreat the relatively inexpensive limonite powder for pellet production.The result shows that the limonite powder cannot be directly used in pellet production after pretreatment because the burst temperature is lower than 300 ℃ and the strength of finished pellet is lower than 1 300 N/P.25％limonite ball milled for 15 min is mixed with 75％magnetite concentrate,in the case of zero bentonite,the dropping strength of green pellet reaches 4.1 times(0.5 m),the burst temperature is 420 ℃,and the strength of finished pellet is 2 445 N/P.The research on balling mechanism of pretreated limonite without bentonite shows that the static pelletizing index and specific sur-face area of limonite after pretreatment are the key parameters to realize pelletizing without bentonite.After wet ball milling for 15 min,the specific surface area of limonite reaches 1 591.10 cm2/g,and the static pelletizing index rea-ches 1.42.Due to the higher temperature required for bound water and the recrystallization of primary Fe2O3,the compressive strength of the pellet by limonite alone is generally lower.After mixing with magnetite concentrate,the oxidation heat of magnetite during roasting is conducive to the recrystallization of Fe2O3,forming a relatively com-plete hematite crystal,and a large amount of slag phase is formed and fills in the gap,then the compressive strength of the pellet increases.However,when the proportion of limonite is greater than 25％,the pores in the pellets grad-ually increase,the oxidation heat gradually decreases,and the amount of liquid phase generated in the pellets decrea-ses by 28％,then the compressive strength of the pellets decreases.In general,the optimal process parameters can be obtained when the limonite is wet ball milled for 15 min and its adding ratio is 25％.This study can provide im-portant reference for pellet production to reduce the amount of bentonite,improve pellet grade and reduce production costs.
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万方数据
维普
