Improvement in pelletization of Brazilian specularite by high-pressure roller grinding

The processing and mechanism of the improvement in pelletization of Brazilian specularite by high-pressure roller grinding (HPRG) were investigated. SEM observations show that after being pretreated by HPRG in a closed flow path at an optimized cyclic loading, the specific surface area of Brazilian specularite increases greatly and its ballability is dramatically improved. The pellet feed composed of 70% specularite and 30% magnetite was pretreated by HPRG at 71%-product cyclic loading in a closed flow path, mixed with 2.4% bentonite and balled for 15 min under the 8% moisture. Experimental results show that all indexes of green pellets are much higher than those of the pellets made of the same feed without the pretreating. The drop number is up to 4.5 times from the 0.5m height, the compression strength is 10.25 N per pellet, and the thermal shock temperature is 455℃. The compression strength of fired pellets was tested up to 2690.88 N per pellet by preheating at 1050℃ for 10 min and by roasting at 1280℃ for 12 min, which meets the demand of strength for commercial pellets.