Dry separation of particulate iron ore using density-segregation in a gas–solid fluidized bed

A gas–solid fluidized bed has been used to separate particulate iron ore (+250–500 μm in size) by segregating the particles by density. The ore particles were put into a cylindrical column of inner diameter of 100 mm and bed height of 50 mm, and were fluidized at a given air velocity u0/umf = 1.2–3.2 for 10 min. u0 and umf are the superficial air velocity and the minimum fluidization air velocity, respectively. The bulk density of the ore particles after fluidization was measured as a function of height through the bed in 5 mm increments (the 50 mm height was divided into 10 layers) to investigate the density-segregation. The size of the particles in each of the 10 layers was also measured to investigate size-segregation. It was found that both density-segregation and size-segregation occurred as a function of height through the bed after fluidization at u0/umf = 2.0. However, the segregation did not occur near the bottom of the bed for lower u0/umf and did not occur near the top of the bed for larger u0/umf. The origin of the segregation-dependence on the air velocity was discussed considering the air bubbles size and the fluidizing intensity at upper and lower sections of the bed. The Fe content of the 10 layers at u0/umf = 2.0 was measured to calculate the Fe-grade and Fe-recovery. The ore-recovery was also calculated using the weight of ore particles as a function of height through the bed. The feed Fe-grade (before separation) was 52.1 wt%. If the ore particles in the bottom half of the bed were regarded as the product, the Fe-grade was 59.0 wt%, and the Fe-recovery and the ore-recovery were 68.5 wt% and 60.5 wt%, respectively.