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By D. A Dahlstrom

THE necessity for slime elimination from valuable mineral and coal products has become increasingly significant within the past 5 years.' , Most of the mechanized mining and present beneficiation methods have resulted in larger tonnages of extreme fines, silts, and clay, commonly called slimes, processed by the preparation plant. Economics in turn have forced the plant operator constantly to lower the bottom size of effective beneficiation, necessitating an almost complete recovery of valuable solids regardless of particle size. When these important factors are considered, the need for an efficient slime removal method for fine solids becomes self-evident. Ordinarily slimes have been classified as ranging from 75 microns, or 200 mesh, down to colloidal dimensions of less than one micron. At the same time there is general agreement that the most troublesome slimes are primarily clays, silts and extreme fines, so that the actual top size may be placed at approximately 30 to 40 microns. This immediately restricts any desliming operation to classification, as screening or other methods would be both uneconomical and grossly inefficient at such dimensions. The liquid-solid cyclone has been recognized as one of the most efficient fine size classifiers available to the mining industry. Applications of cyclones to thickening, high efficiency solid recovery, degritting,

Jan 1, 1953

By D. A. Dahlstrom

THE necessity for slime elimination from valuable mineral and coal products has become increasingly significant within the past 5 years.' , Most of the mechanized mining and present beneficiation methods have resulted in larger tonnages of extreme fines, silts, and clay, commonly called slimes, processed by the preparation plant. Economics in turn have forced the plant operator constantly to lower the bottom size of effective beneficiation, necessitating an almost complete recovery of valuable solids regardless of particle size. When these important factors are considered, the need for an efficient slime removal method for fine solids becomes self-evident. Ordinarily slimes have been classified as ranging from 75 microns, or 200 mesh, down to colloidal dimensions of less than one micron. At the same time there is general agreement that the most troublesome slimes are primarily clays, silts and extreme fines, so that the actual top size may be placed at approximately 30 to 40 microns. This immediately restricts any desliming operation to classification, as screening or other methods would be both uneconomical and grossly inefficient at such dimensions. The liquid-solid cyclone has been recognized as one of the most efficient fine size classifiers available to the mining industry. Applications of cyclones to thickening, high efficiency solid recovery, degritting,

Jan 1, 1953

Jan 1, 1947

Jan 1, 1927

Jan 1, 1946

Jan 1, 1941

PRESIDENT L. D. RICKETTS,1 NEW YORK, N. Y. PAST PRESIDENTS BENJAMIN B. THAYER,1 NEW YORK, N, Y. WILLIAM L. SAUNDERS,2 NEW YORK, N. Y. FIRST VICE-PRESIDENT SIDNEY J. JENNINGS,1 NEW YORK, N. Y. TREASURER GEORGE C. STONE,1 NEW YORK, N. Y. SECRETARY EMERITUS ROSSITER W.. RAYMOND NEW YORK, N. Y SECRETARY BRADLEY STOUGHTON NEW YORK, N. Y.

Jan 6, 1916

Jan 1, 1953

Jan 1, 1938

Jan 1, 1929

By Sherwin F. Kelly

Airborne techniques enter hard rock exploration field. . . the gap between pure geophysics and engineering seen as closing rapidly.

Jan 2, 1951

Jan 1, 1915

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Jan 1, 1938

(Under this heading will be published notes sent to the Secretary of the Institute by members or other persons.) Mine and mill accountant for Mexico. Knowledge of Spanish desirable. Salary $150 to $200 gold per month with living quarters. No. 60. Master mechanic familiar with mine and cyanide plant machinery for Mexico; $200 gold per month and living quarters. No. 61. Electro-metallurgist for production of ferro-alloys, salary $200 to $400 depending on experience. No. 62. Man familiar with ferro-tungsten products of electric furnaces to draw up specifications for machine tools, to watch these tools in service and revise specifications accordingly. Salary $150 to $200 per month. No. 63. Engineers under 35 years of age for placer mining work in Belgian Congo; $1,500 to $1,700 plus traveling and living expenses, two years' contract. No. 67.

Jan 2, 1916

By Frank Firmstone

(Ottawa Meeting, October, 1889. Substituted for the briefer note on the same subject. pre sented at the meeting and subsequently distributed in preliminary pamphlet edition.) Prof. H. Hoefer's theory of blasting was published in the Oesterr. Zeitschrift, xxviii., 1880, and xxix., 1881; and Part 111. in Nos. 15, 16 and 17, xxx., 1882, and subsequent numbers of that

Jan 1, 1890

By G. Almgren

Swedish cut-and-fill mines are described with regard to location, production volumes, and grades. Development goals (such as higher productivity and better working conditions) are presented, and different methods of development, such as mechanization, new layouts, etc., are discussed. Development methods are described with examples from drilling, loading, haulage, and rock mechanics. Special attention is paid to filling techniques. Figures are given for productivity and relative costs.

Jan 1, 1977

By Roshan B. Bhappu, George M. Potter

The chemistry involved in the recovery of gold and silver from natural resources through hydrometallurgical and pyrometallurgical processes is reviewed. Process metallurgy for the cyanidation, activated carbon adsorption, carbon stripping, and electrowinning of gold and silver is discussed. The application of zinc sodium sulfide use for silver recovery from cyanide solutions is covered. Electrooxidation, other oxidation methods and roasting processes for problem ores and concentrates containing organic carbon and impurities such as arsenic, antimony, and tellurides are summarized. The smelting of cathodes, precipitates, and other products, and the various wet and furnace steps in separating dore metal are also reviewed.

Jan 1, 1981

By N. Arbiter, C. C. Harris

Analysis of ball and pulp flow in ball mills indicates that three factors may become critical with increasing mill diameters: ball size, fraction critical speed, and average pulp flow velocities. Ball diameters may need to be decreased and fraction critical speeds increased with ores which show decreased breakage rate coefficients above 1.2 mm (14 mesh). With 5.5-m (18 ft) and larger mills at higher circulating loads, pulp flow velocities may become capacity limiting and also may limit increases in ball mill diameters.

Jan 1, 1985

By H. A. Kuhn

The Pittsburgh coal field in Western Pennsylvania is conceded to be the most important in the world.

Jan 1, 1915