Iron Ore Processing for the Blast FurnaceEach primary mill contains several 4" steel balls that grind the ore as the mills turn. When the ore is reduced to 3/4" or less, it moves out of the mill in a slurry solution. The mill discharge is screened at 1/4" on trommel screens attached to the mill. Ore smaller than. 1/4" is pumped in slurry solution to the wet cobber magnetic.trammel screen iron ore grinding,Iron Ore Benefication Plants - Iron Ore Beatification Plants Exporter .Star Trace iron ore processing mainly includes crushing by crusher, separating by vibrating screen, grinding by ball mill and classifying by classifier; the separation of minerals consists of weight, flotation, and electric separation, etc. Dehydration of minerals includes enrichment, filtration, drying, and other procedures.