The flotation process . to preventthe blanketing of the porous medium by coarse sand collecting onthe bottom. The air from the separatory cells has so far been furnished frompositive blowers, but turbine-blowers would be preferable wherethe size of the installation justifies their adoption. An air-pressureof 15 lb. is ample for the Pachuca mixer and 25 cu. ft. of freeair per minute is sufficient volume for mixing 250 tons of minus48-mesh pulp, and of course should be furnished from a low-pressurecompressor. The density of the pulp may vary from 2^ : 1 on a sandy feedup to 7 : 1 on a strictly s
The flotation process . to preventthe blanketing of the porous medium by coarse sand collecting onthe bottom. The air from the separatory cells has so far been furnished frompositive blowers, but turbine-blowers would be preferable wherethe size of the installation justifies their adoption. An air-pressureof 15 lb. is ample for the Pachuca mixer and 25 cu. ft. of freeair per minute is sufficient volume for mixing 250 tons of minus48-mesh pulp, and of course should be furnished from a low-pressurecompressor. The density of the pulp may vary from 2^ : 1 on a sandy feedup to 7 : 1 on a strictly slime-feed. The particular density is nota matter of so much importance as that the supply of pulp shallbe uniform as to its density, since each variation in the densityrequires a readjustment of the oil-supply, the quantity of oil requiredincreasing in proportion to the increased volume of the pulpindependent of its solid content. The advantages of the pneumatic scheme are greater recoveries, FLOTATION OF COPPER ORES 67. JOJDJlS^ V3nt/0VJ , 68 THE FLOTATION PROCESS less oil, greater simplicity, and less skill required to operate. Thedifference in wear and tear is obvious. Proof of the increased recoveries is shown in Table I, whichrepresents a 30-day competition. It is noticeable that this increasein recovery lies principally in the finer and slime portions of thefeed. Table I ANALYSIS OF TAILING THIBTY-DAY PERIOD Total copper. Copper oxide Flotation tailing. Table tailing, in combined Mesh. Weight. tailings. :c % % % % % + 65 + 100 + 150 + 200 — 200 Average, all sizes. ... ... Table II ANALYSIS OF CONCENTRATES For the same period Cu, Insol., % % Agitating process Pneumatic process The resulting concentrates from the same competition are shownin Table
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