TATION Fred D. DeVaney, PICKANDS MATHER a co.,HIBBING,
H E first full year of peace has changed, to a considerable degree, developments in the field of flotation. The feverish activity of the war years to increase production of old plants and to develop new processes for the recovery of scarce minerals is now over. In its place has come a somewhat quieter phase, that of finding cheaper and more efficient means of separation to meet increased competition. The tendency of companies, which expanded considerably during the war, to go into new fields has been noted in the increased number of those investigating the production of reagents for the flotation industry. A number of excellent papers on flotation theory were published during the year. These include a study made by Gaudin and Preller (15) on the surface areas of flotation concentrates and the thickness of collector coatings. They found that, the usual collector coating is an incomplete mono-ionic layer and also that the denser the packing in the mono-layer, the higher the recovery. Taggart and Hassialis (86) studied solubility product and bubble attachment in flotation, and postulate that all conditioning and collecting reactions involving ions are predictable on the basis of the solubility product of the least soluble compound involved in the reaction. Undissolved frother was shown to accolerate bubble attachment greatly, and the lower reagent consumption found in mill work was attributed partly to the presence in the ore of small amounts of lubricants. Rogers and associates ($4) in Australia investigated the use of long-chain paraffin salts a3 collectors by the use of contact bubble tests, cylinder tests, and flotation cell tests; they found that substituted amines are of most value in floating acidic minerals, and the anionic agents-for example, soaps-are of greatest value for basic minerals. Gaudin and Sun (17) correlated behavior in cataphoresis or electrophoresis and in 5otation through the use of a new criterion called the ‘(zeta” coefficient. Zeta potential represents difference in potentia1 between immovable and movable liquid layers. Two papers dealing with the composition of flotation frothers were published in 1946. Bishop (5) described the properties of the various components of pine oil and discussed their relation to flotation. The technical application of cresylic acids to flotation was described by Bates and Miller (4). Since cresylic acid is now being produced from petroleum as well as from coal tar, some differences in the properties of the acids exist, and the properties of these complex materials must be known in order to alIow selection of the material best suited for a particular separation. Although the newer and rapidly developing field of nonmetallic flotation has attracted most of the spotlight in the last few years, developments have not been neglected in the oId established field of sulfide flotation. The big producers of nonferrous metals are constantly improving flotation practices. Many of these developments are not spectacular because the industry has already arrived a t a high stage of efficiency; they are, nevertheless, important. Molybdenite is one of the most floatable of minerals; to secure the optimum recovery and grade with a minimum amount of grinding, a rather complex flowsheet has been developed at Climax Molybdenum Company (10). Flotation reagents used in the primary circuit consist of pine oil, a saturated petroleum fraction, and a sulfated monoglyceride. The flotation feed in the roughing circuits is rather coarse, approximately -35 mesh. Climax-Weineg subaeration machines of the hog trough type are used. The value of flotation research at this plant is shown by a steady increase in the recovery of molybdenite from approximately 80% in 1936 to 93% in 1945.
MI”,
The separation of chalcopyrite concentrate is being accomplished by a novel method at the San Francisco Mines of Mexico, Ltd. (8). Here the bulk lead concentrate is treated by sulfur dioxide and zinc hydrosulfite, which tend to clean the chalcopyrite surfaces. The pulp is dispersed with common cornstarch, aiid amyl alcohol is used as a frother. Copper carbonate minerals are being recovered from 2% ore by flotation at Ohio Coppers Company’s Big Indian Mine, Utah ( 2 ) . Flotation concentration of lead-zinc ore from the Grandview Mine, Wash., was described ( I ) , and treatment of lead-zinc-iron sulfide ore at a custom mill in the Platteville district of Wisconsin was discussed by Pett ($2). Graphite is one of the most floatable of minerals, but frequently particular conditions make special treatment necessary. I n the So0 Fidelis district mine in Brazil it was necessary to dry, grind, and classify the ore before flotation to prevent an undue amount of fines (27). The procedure used in floating graphite ore from the rather large deposit in Burnet County, Texas, was described by Needham (222). The large scale flotation separations of copper nickel ore at the Sudhury, Ont., plant of the International Xickel Company wa9 also reported (6). In the field of nonmetallics there have been many new developments. Probably the most authoritative series of articles on tbe practical treatment of the nonmetallic or industrial minerals by flotation are those by Barr (3). He described in Considerable detail the minerals which may be separated, the machines used, flow sheets employed, and type of reagents used. Articles by Gisler and Wright (19) give an excellent survey of separations in both the metallic and nonmetallic field. Gaudin (14) presented a thought-provoking paper on how to improve flotation of nonsulfide minerals; he discussed the relation of crystal structure to flotation and the effects of mineral lattice structure and particle size, and suggested avenues of research. In the nonmetallic field the phosphate district of Florida is relying more and more on this method to recover mineral that would be unrecoverable by older methods. Several large plants are under construction in Florida. One being built by International Minerals and Chemical Corporation at Noralyn Mine will have an annual capacity of 1,OOO,OOO tons. The trend in phosphate flotation is toward production of higher grade concentrate, by floating silica with amines from the rougher concentrates floated with fatty acids. Recently Le Baron (80) described the effect of various flowsheets on efficiency of phosphate recovery a t the Peace Valley plant. He found that stage addition of reagents w m definitely beneficial and that, by the use of scavenger cells, the plant was able to recover 90% of the phosphate when the feed was 32% B.P.L. (bone phosphate of lime). Practice at the Coronet Phosphate Company was reported by Gisler (18). A novel form of agglomerate tabling is carried out on the coarser portion of the feed on continuously moving belts. This plant is being expanded, and cationic flotation by amines of silica from the fatty acid circuit will be utilized. Gisler also described the wet storage tanks used to store the deslimed mill feed. There has been little decrease in the demand for high grade fluorspar as a result of the cessation of war, since the use of fluorine chemicals seems to be definitely on the increase. The greatly increased demand for acid-grade fluorspar during the war years was supplied almost entirely by production from flotation plants. The largest domestic producer was the Mahoning Mining Company of Rosiclaire, Ill., and the operation at this plant waa recently the subject of a detailed paper by Duncan (If). At this
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January 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY
plant four separate flotation concentrates are made: lead concentrates, zinc concentrates, acid-grade fluorspar concentrates, and metallurgical-grade fluorspar concentrates. I n making these separations, precise control is necessary, and continuous pH indicating and recording equipment has been installed. All of the water used in the flotation circuit is softened by the zeolite process. In the fluorspar flotation section the pulp is thickened t o 38% solids and heated in steam-jacketed conditioners to 8090 O F. The reagents usually employed are soda ash, quebracho extract, and oleic acid. The quebracho serves EIS a depressant for calcite and the small amounts of remaining sulfides. Since fatty acid flotation concentrates tend to clog duck filter cloths rapidly, this plant filters its acid-grade fluorspar concentrates on a Swenson drum filter covered by 60 X 60 mesh, twill-weave, stainlesssteel screen, which is backed by a 4-mesh, stainless-steel screen. The filtrate is returned to the original thickener to recover the solids in the filtrate. The use of stainless-steel screens for filtering flotation concent,rates was also described by Reck (IS). Such filters operate in much the same manner a3. precoat filters and, in addition to high capacity, have a long life. As a war measure Fine and O’Meara ( l a ) investigated the possibility of treating metallurgical-grade fluorspar by flotation and converting a portion into acid-grade fluorspar. Their tests indicated that, a certain recovery of such a product could be made by several methods. In the cement i n c h t r y the use of froth flotation is coming into increased use in adjusting the Si02-Ca0-A1208-Fn08 ratio. In discussing the use of cationic flotat,ion in the treatment of cement rock by the Valley Forge Cement Company at Conshohocken, Pa., Williams described the operation in detail (88). At this plaut the main objective of the concentrating process is to produce a kiln feed lower in mica than the average rock. When this is done, the result is to give a product lower in alumina, alkalies, and magnesia and higher in lime. A two-stage process is used in which the high lime fraction is floated with anionic reagents. A deslimed portion of the tailing €rom this first treatment is then treated with a cationic collector, DP-243 (the hydrochloride of technical laurylamine), which floats the mica. This mica is marketed after drying, grinding, and air classification. Reagent consumption in the cationic circuit is about 0.243 pound of DP243 and 0.05 pound of B-23 frother per ton of cell feed. It was found true at this plant as in many other plants using cationic reagents that a well deslimed feed is essential for a fast-float lowreagent consumption and a good-quality froth. Much of the potash now obtained in this country is from the flotation of sylvite-halite ores in saturated brines. Either mineral may be floated away from the other by suitable reagents. The practices a t the Booneville, Utah, deposit were recently described (7) and are of peculiar interest because the deposit occurs as a dried lake bed. The brines from the salt bed are evaporated by solar heat in a series of nine evaporating ponds. The crystallized Palt mixture containing about 67% sodium chloride and 33% potassium chloride is harvested by scrapers. The mineral sylvite is collected in a froth by the use of an Armour aliphatic amine (Arnieen T.D.). These concentrates contain from 85 to 90% potassium chloride and are further improved by a short freshwater wash which brings the grade up to 95%. Use of flotation for recovering fine coal from coal washery sludge product is attracting interest. At one plant 60 to 90 tons per hour of - 28 mesh coal sludge are treated in two four-cell banks of No. 30 flotation cells, which reduce ash content from 30 to 13%. Flotation of iron ores has not yet progressed beyond the pilot plant stage. Extensive test work was carried out on washing plant tailings from mills on the Mesabi Eange of Minnesota. The Mineral Separation Company did test work at the Canisteo mill. Pilot plant tests were also being made at Pickands Mather’s Danube mill. Some of the details of American Cyanamid’s process for floating iron ores were described by Falconer (12). Thoroughly deslimed ore is conditioned with an anionic reagent at high solids content. All reagents are added in the conditioner.
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The flotation operation described by Falconer was tried in a 10ton-per-hour plant at Butler Brothers Patrick mill during 1945. The actual flotation operation was carried on in four No. 20 Steffensen air flotation machines. The results of these and later tests indicate that excellent separations can be made on well deslimed ores. If the ore is inadequately deslimed, or if it contains soft iron minerals that break down to form slimes during the conditioning or flotation treatment, the separation suffers. The results of a laboratory investigation on the flotation of finely disseminated tin ore high in iron oxides were described by Gaudin and associates (16). In their suggested process the ore is given an acid leach followed by flotation of the cassiterite, using oleic acid as a collector and sodium silicate and tartaric acids as conditioning agents. American Cyanamid Company has introduced two series of flotation reagents that are being rather widely tested. Series 600 are gangue depressants and are being tried, among other places, on southwestern copper ores for increasing the grade of concentrates and for cleaning sphalerite concentrates in the Rosiclaire district. Reagent series 800 are of the anionic type and are being tried as promoters for iron oxides and for the flotation of such nonmetallic minerals as fluorspar, barite, garnet, feldspar, scheelite, and wolframite (12). Oronite Chemical Company is marketing chemicals derived from petroleum for the flotation industry. These include cresylic, naphthenic, and aliphatic acids. The latter are used chiefly as collectors for nonmetallic minerals. Rose of International Nickel stirred up controversy in his discussion (16)of how big flotation machines can be built for efficient operation. He concludes that there is an optimum size beyond which the efficiency of the cell decreases; by inference one concludes that cells much larger than 100 cubic feet are not practical. The Dow Chemical Company published its annual “Flotation Index” which contains a bibliography of articles written on flotation as well as a list of patents granted (9) LITERATURE CITED
(1) Anonymous, Mining Congr. J.,Jan., 1946, 26-31. (2) Anonymous, Mining Vorld, Jan., 1946, 11-14. (3) Barr, J. A., Jr., Rock Products, 1946, July, 65-7, Aug., 128-32; Sept., 71-5. (4) Bates, W. A., and Miller, R. J., Am. Inst. Mining Met. Engrs., Tech. Pub. 2015 (July 1946). (5) Bishop, W. T., Ibid., 2011 (March 1946). (6) Can. Mining J., May, 1946,423-30. (7) Denver Equipment Co., Deco Trefoil Bull. M4-B39 (1946). (8) Deshler, G. O., and Herndon, T. R., Eng. Mining J., May, 1946,67-9. (9) Dow Chemical Co., “Flotation Index”, June 15, 1946. (10) Duggan, E. J., Mining and Met., June, 1946,322-7. (11) Duncan W. E., Am. Inst. Mining Met. Engrs., Tech. Pub. 2040 (Sept. 1946). (12) Falconer, 5. A., Eng. Mining J., Feb., 1946, 104-7. (13) Fine M. M , and O’Meara, R. G., Am. lnut. Mining Met. Engrs., Tech Pub. 2055 (Sept. 1946). (14) Gaudin, A. M., Eng. Mining J., Dec., 1945, 91-5. (15) Gaudin, A. M., and Preller, G. 9., Am. Inst. Mining Met. Eners.. Tech. Pub. 2002 M a v 1946). (16) Gaudin, A. M., Schuhmakn, R., Jr:, and Brown, E. G., Eng. Mining J . , Oct., 1946,54-9. (17) Gaudin, A. M., and Sun, S. C., Ibid., 2005 (May 1946). (18) Gisler, H. J., Denver Equipment Co., Deco Trefoil Bull. M4-B40 (1946). (19) Gisler, H. J., and Wright, H. M., Ibid., B10-B2Z (1946). (20) Le Baron, I. M., Am. Inst. Mining Met. Engrs., Tech. Pub. 2079 (Sept., 1946). (21) Needham, A. B., U. S. Bur. Mines, I n f . Circ. 7339 (Jan., 1946). (22) Pett, G. H., Mining Congr. J., Nov., 1945, 22-7. (23) Reck, W. H., Deco Trefoil, Nov.-Dec., 1945,4. (24) Rogers, J., Jr., Sutherland, I(. L., Wark, E. E., and Wark, I. W., Am. Inst. Mining Met. Engrs., Tech. Pub. 2022 (July 1946). (25) Rose, E. H., Eng. Mining J . , June, 1946,82-3. (26) Taggart, A. F., and Hassialis, M. D., Am. Inst. Mining Met. Engrs., Tech. Pub. 2078 (Sept. 1946). (27) Von der Weid, F. C., Ibid.. 2012 (Sept. 1946). (28) Williams, J. C., Ibid., 1901 (Jan. 1946).
