GB510323A - Improvements in or relating to separation by froth flotation - Google Patents

Abstract

510,323. Froth-flotation processes. EARLE, T. Jan. 27, 1938, No. 2658. [Class 82 (ii)] Naturally occurring granular materials such as sands and sandstones to be purified by froth flotation concentration are first comminuted so as to liberate the constituent particles without rupturing the grains and the granular particles are separated from the slimes. The granular particles are then brought to the moist state, by which is meant a state in which the moisture content is in excess of that which the material will absorb from the air under normal atmospheric conditions but less than that necessary to produce water films of the maximum possible thickness on all the liberated particles ; no interstitial water must be present. The moist materials are then conditioned with flotation reagents, e.g., fatty acids or soaps, allowed to stand for a time if desired, and then transferred to the flotation cell, further reagents, e.g., frothers, being added if required. To bring the material to the moist state after desliming a dewatering treatment more drastic than draining, e.g., one involving evaporation, is necessary ; the dewatering may be controlled so that the desired water content is left in the material, or the material may be completely dried and the necessary water added. The process is particularly applicable to the purification of silica sands, sandstones &c. to be used in glassmaking. These sands may contain as impurities substances such as biotite mica, magnetite &c. which have a greater absorptive power for fatty acid reagents than pure silica and also discoloured particles and other substances having a less absorptive power than silica. In this case the moisture content of the sands after desliming may be so regulated, e.g., to 5 per cent., that only the silica and particles of lower absorptive power are filmed with water, the fatty acid is then absorbed to the mica &c. which is floated in the cell. The tailings are then dried and the water content adjusted to 0.1 per cent. which enables the pure silica to be recovered after a second conditioning. If the material contains readily floatable particles these may be floated directly after desliming, the tailings being then brought to the moist state, conditioned, and subject to flotation. Specification 510,322 is referred to.