Study on the pelletizing process of medium- and low-grade phosphate rock powders

Abstract

Abstract: In this paper, the impact of several pelleting process parameters on the quality of the resultant pellets was investigated by using a disk pelletizer with low- and medium-grade phosphate rock powders as the raw material. The results show that the optimized compressive strengths of raw and dried pellets were 12.84 N and 54.58 N, respectively, when the material fineness was -0.074 mm with an 86.60% content, the amount of added bentonite was 2.5%, the wetting moisture was 8% and the raw pellet moisture content was 10%. The compressive strength of the finished product reached 930 N using a preheating temperature of 600 °C for 10 min, and calcination temperature of 1200 °C for 10 min. A study on the mineral phase of the finished balls showed that the increased pellet strength after calcination was caused by a solid-state reaction within the pellets during the high-temperature calcination process. This process caused volume shrinking and a compacted structure of the pellets, and the pellet particles were sintered into a plate.