. Transactions. he ore has to be ground to 60-mesh before a separationof the magnetite grains from the gangue can be successfully at-tempted. Crushing and grinding the ore to such a degree offineness produces a large amount of absolute fines. To separatethese dry is out of the question. To crush dry is possible, butnot advisable, as only with great difficulty can the fine dustproduced in the operation be kept reasonably well inclosed. Itwill pass through the finest cracks. Even with strong exhaust-fans connected to casings around the various machines, the dustescapes, fills the atmosphere in t
. Transactions. he ore has to be ground to 60-mesh before a separationof the magnetite grains from the gangue can be successfully at-tempted. Crushing and grinding the ore to such a degree offineness produces a large amount of absolute fines. To separatethese dry is out of the question. To crush dry is possible, butnot advisable, as only with great difficulty can the fine dustproduced in the operation be kept reasonably well inclosed. Itwill pass through the finest cracks. Even with strong exhaust-fans connected to casings around the various machines, the dustescapes, fills the atmosphere in the mill and makes the work in ^ Engineering Magazine, vol. xxxviii., No. 4, p. 533 (Jan., 1910). THE CONCENTRATION OF IRON-ORES. 53 the plant disagreeable and unliealthful, besides causing difficul-ties in the up-keep of the bearings, etc. Grinding in wet ball-mills can be done cheaply, and at thesame time permits a very simple layout of the plant. Afterthe preliminary crushing to size the ore is fed di-. Phos-phorus One Scale for Iron, Silica, Alumina, Lime and Percentaa:esAnother Scale for Soda and PotashA Third for Phosphorus Fig. 4.—Screen-Test of Iron-Ore Concentrates at Lyon Mountain, N. Y. rectly to the ball-mill and in one operation ground to 20- or30-mesh size in water. Driers, rolls, screens, and elevatorsare unnecessary. The ore, discharged from the ball-mill, is car-ried by a current of water directly to the separators. Withsome ores high-grade concentrates are here directly other ores a finer grinding is necessary if high-grade 54 THE CONCENTRATION OF IRON-ORES. concentrates are desired. The proper method, then, is touse after the ball-mills magnetic separators of such intensitythat they will pick up the greater part of the iron mineral, leav-ins: a tailino-s-product that can be wasted. The concentrate iscrushed finer in pebble-mills and re-separated, yielding a pro-duct of any desired quality. Among wet concentrating-plants for iron-ores in
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
