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By R. N. Woody, S. J. Work

Crushing development at Duval Corp.'s Sierrita concentrator in Sahuarita, Ariz., has been a continuing effort since plant startup in January 1970. The original crushing system was designed to produce 65 000 t/d (72,000 stpd) of ore. However, in the summer of 1970 the Sierrita plant was averaging only 43 000 t/d (47,000 stpd) due to coarser than expected secondary crushing plant feed, lower than design crusher operating availability, and inability to achieve design tertiary crusher power draught at an acceptable hydraulic support pressure.

Jan 4, 1979

By Earl H. Miller, Henry H. Bruhn

COMMERCIAL beds of sylvite ore were discovered by the Snowden & McSweeney Co. while drilling a wildcat oil well some 25 miles northeast of Carlsbad, N. NI., in 1925. After a preliminary core drilling program the U. S. Potash Co. sank a 1060-ft shaft within 4 miles of the original discovery. This shaft was in an isolated location in a sand desert area with only the roughest of dirt roads connecting it with the neigh- boring town of Carlsbad some 21 ½ miles west.

Jan 6, 1954

By Wasyl Kunda

High grade jig and low grade flotation concentrates used in the following experiments, are produced from silver ore at the mine. The study was carried out to recover the silver and other metals from these concentrates by hydrometallurgical methods. The concentrates were subjected to two stage oxida¬tion leaches in a HNO3-H2SO4 medium. The dissolved metals were recovered by selective precipitation of: (a) silver chloride, (b) iron-arsenic-bismuth residue, (c) copper sulphide, (d) cobalt-nickel sulphide. The effluent solution contained only ammonium sulphate and ammonium nitrate. The silver chloride was further processed to the high purity silver powder by the AgCl ? Ag2S ? Ag2SO4 ? Ag° route. The recovery of silver from the concentrates was over 98% and other metals from 95 to 99%.

Jan 1, 1984

By S. Korman, S. B. Tuwiner

Chalcocite flotation is affected by agitation intensity during conditioning. Sodium sulphide in minute quantity may activate or depress, depending on conditions. Oxygen is a depressant while oxygen and sulphide neutralize each other by re-action at the mineral surface. Diffusion across a stagnant film at the surface governs reaction rates, while film thickness is reduced upon increase of agitation intensity.

Jan 2, 1950

By G. J. Roe

Drawing largely on desulfurizing practices which have been developing abroad in the last several years, this paper will cover the main ways in which producing steels with low sulfur provides appreciable benefits -- beginning with improvements in ingot processing and carrying over into improved product properties, in particular cleanliness, formability, notch toughness and weldahility. Because the raw materials and fuels used in steelmaking are sources of sulfur and the removal of this element is difficult, sulfur has tended to be accepted as an unavoidable incidental contaminant of steel. Although it was early recognized that sulfur significantly affects several mechanical properties, the main concern was with its effect on hot shortness. Concentrating on countering this effect, operators have traditionally added manganese in sufficient multiples of the sulfur content to form manganese sulfide and thus avoid iron sulfide formation, the assumption being that the steel would then be acceptable in terms of both processing and mechanical properties.

Jan 1, 1972

By N. P. Peterson

THE Castle Dome copper deposit is of the porphyry type and occurs in a body of quartz monzonite intruded into the pre-Cambrian formations and possibly into the lower part of Paleozoic limestones. The hypogene sulphide minerals include pyrite, chalcopyrite, and a little molybdenite, sphalerite, and galena. Pyrite and chalcopyrite are disseminated or occur in small closely spaced veins. The hypogene mineralization shows distinct zoning in the distribution of pyrite and chalcopyrite, so that the mineralized area can be subdivided into pyrite and chalcopyrite zones. Supergene enrichment, though not extensive, played an important part in the formation of the ore body, the chalcopyrite zone being the protore. Several thin, gently dipping, diabase sills occur in the mineralized area, and the copper content of the rock in and near these sills is substantially higher than average. The formation of the ore body was caused by the combined effects of three forces: I. Zoning of the hypogene mineralization, 2. Richer copper metallization associated with the diabase sills, and 3. Supergene enrichment.

Jan 1, 1947

Jan 1, 1947

Jan 1, 1955

By O. Lietard, J. Yvon, R. Mercier, J. F. Delon, J. M. Cases

INTRODUCTION Fineness is one of the main characteristics of powders and this parameter is the object of several definitions based on criteria connected with their uses as well as their determination methods. In trying to obtain the best reaction surface, fineness is characterized by the determination of the specific surface, but in other cases, particle size analysis is used. These two main methods are not, in fact, entirely independent and their complementary nature provides information concerning the morphology of the particles. In the case of a product formed by isodimensional spheres, the relationship between the specific surface and the diameter is well known: [S = 6 spd] where p is the specific weight of the material and d the diameter of the spheres. With no monodimensional spheres, but rather a granulometric distribution whose occurrences follow a mathematical law (1), the relationship is more complicated. The relationship between the specific surface measured by gas adsorption and the data of the particle size analysis is much more difficult to predict in the case of asymmetric porous particles, whose particle size distribution curves do not correspond to a known statistical law.

Jan 1, 1980

By R. B. Sosman, J. C. Hostetter

We have shown in the preceding paper that practically all natural oxides of iron contain a determinable percentage of ferrous iron, and in many cases the percentage approaches that in magnetite itself. Some of these oxides are true homogeneous solid solutions. Others are not homogeneous, and can be separated magnetically into fractions. The nature and cause of this inhomogeneity in certain special cases form the subject of the present paper. Magnetic FRactionation of Oxides of Iron The magnetic fractionation of a sample of oxide can be conveniently carried out by powdering the material very fine, and exposing it at various distances from the poles of an electromagnet. The magnet that we used was specially designed1 to give a strong field together with a steep gradient outside of the poles. It is set in a frame, with the pole pieces directed downward. A glass plate can bc adjusted at various distances beneath the poles. If the fine iron oxide powder is placed just beneath the glass plate, successive portions of the powder are picked up by the magnetic attraction and are caught against the glass plate, the most magnetic portions being taken up at the greatest distance from the poles. Some natural oxides can thus be separated into several fractions of different magnetic susceptibilities. Among other natural iron oxides, we examined the powder obtained by crushing some crystals of hematite from Elba.2 We found that

Jan 1, 1918

Prof. Mathesius analyzes the running of Howland's furnace No. 19, according to the method described by him in Stahl and Eisen, 1916, Nos. 30 and, 31, and in his work "Die physikalischen und chemischen Grundlagen den Eisenhüttenwesens" (Spamer, Leipzig). By assuming 500 Cal. lost from the hearth by radiation and cooling water per kilogram of pig iron made, a throat-gas temperature of 600° C., and taking the ratio of C02/CO as 0.64, he finds that his diagram would show 0.68 kg. of carbon oxidized per kilogram of pig iron, while Howland gives 0.66 kg. He expresses himself as well satisfied with this test of the accuracy of his theory. Making the further assumption that the heat losses from the shaft are 1,000 Cal. per kilogram of pig iron (twice as

Jan 5, 1917

By Albert Roberts

Summary In response to a growing intolerance towards ground vibrations and noise as environmental pollutants the engineer must consider the effects of his operations as they are likely to be judged subjectively by the public at large. Much work has been done on the study of vibration damage to structures, but the damage criteria normally applied do not take into account any resonance effects, nor do they embody any subjective criterion. Mu1tiple criterion techniques of subjective appraisal have proven to be of value .in the assessment of environmental comfort in relation to ventilation, air conditioning, and lighting. One such scale, the Reiher-Meister Scale, has also been applied to ground vibrations and noise, and an attempt has been made to correlate this scale with objective criteria, using the parameters of frequency and displacement. This paper quotes examples and compares ground vibrations resulting from blasting, the operation of, vibrating and impact-hamner pi1e drivers, forge hammers, and railway and road traffic. The Reiher- Meister Scale was applied to a subjective-objective correlation in relation to vibrations from railway traffic and gave results which did not conflict with experience.

Jan 1, 1971

By J. E. Spurr

CONTENTS. [ ] I. INTRODUCTION. The region here discussed is that part of western Nevada in which, during the last few years, discoveries of rich gold- and

Jan 1, 1913

By James P. Kimball

BY the term weathering of coal is meant the process of deterioration to which under various circumstances it may be exposed at ordinary temperatures, both from outward agencies on the one hand, and on the other hand from its own constitutional qualities. This process involves along with some minor qualitative changes certain quantitative changes resulting in a gradual and limited reduction in the quantity of the organic elements, and relatively a corresponding increase of its inorganic or mineral constituents as represented by its ashes, and often in an increase of the absolute weight of the coal. In common with many mineral substances, coal absorbs oxygen

Jan 1, 1880

By William G. Schultz

Sylvite’s potash mine probably ranks as one of the most highly mechanized and automated mining operations in the world. Employing, on a normal 10-hr production shift, one supervisor and a crew of seven operators, Sylvite is able to mine at an average rate in excess of 600 tph. The ore is produced by two Marietta miners weighing 258 tons, making them the largest and heaviest piece of equipment ever taken underground. The ore produced by these two Marietta miners is conveyed to the shaft area, cycled through a 15,000 ton storage system and hoisted to surface completely automatically. The operation of all equipment in the mine can be monitored and controlled from a central control panel located underground.

Jan 7, 1972

By James E. York

The honor so fairly earned and so incompletely and tardily paid to Henry Cort, the inventor of the puddling-furnace and the rolling-mill, has been fully set forth by Mr. Charles H. Morgan,' and needs no further emphasis here. In view of the importance of the rolling-mill in the treat ment of iron and steel, the paucity of information concerning it is surprising. With the exception of a book, written about 35 years ago, by Peter Ritter von Tunner, an Honorary Member of this Institute, and of desultory articles on simple sections, which have appeared in technical journals, I know of no publication attempting to treat this subject, although volumes have been written on the scientific theory and technical manipulations involved in other branches of the iron- and steel-industry. This strange anomaly may be due to the fact that roll-turning cannot be called a scientific business. It does not ordinarily come within the range of an educated engineer; yet it cannot be performed by an ordinary mechanic. It demands some of the qualifications of an engineer, in designing, and those of a mechanic, in execution. The men who have followeci this trade have controlled the training of their successors. In many cases the technical knowledge required has

Jan 1, 1907

By Richard Miller

The investigations of large-grained specimens carried out by Polanyi and Schmid,1 Sykes,2 Goucher,3 Yamaguchi,4 Gough, Cox, and Sopwith,5 Carpenter and Elam,6 Aston,7 and others have shown qualitatively that grain boundaries restrain the deformation of adjacent crystals. But whether or not the influence of the grain boundary is confined to the glide planes intersected by the boundary has not been demonstrated in any of these investigations, nor has there been carried out any quanti-tative analysis, of the influence of a boundary on the deformation of a crystal. Indeed, the specimens employed in the previous work con-

Jan 1, 1934

By James P. Kimball

By the term weathering of coal is meant the process of deterioration to which under various circi~mstances it may be exposed at ordinary temperatures, both from outward agencies on the one hand, and on the other hand from its own constitutional qualities. This process involves along with some minor qualitative changes certain quantitative changes resulting in a gradual and limited reduction in the quantity of the organic elements, and relatively a corresponding increase of its inorganic or mineral constituents as represented by its ashes, and often in an increase of the absolute weight of the coal. In common with many mineral substances, coal absorbs oxygen

Jan 1, 1880

By T. N. Andersen, K. J. Richards, C. N. Wright

The kinetics of the important reactions occurring in an electrowinning cell have been determined. This information has been used to quantify relationships between the operating variables of current density, solution composition, agitation, and temperature and the resulting current efficiency and deposit quality. Analysis of these results has shown (1) the importance of dissolved iron in determining maximum possible current efficiency and corrosion rate at the cathode suspension loop, (2) the role of agitation, current density, inert salts and temperature in*determining deposit quality and (3) the effects of non-uniformity in the hydrodynamic conditions from the bottom to top of the cell. The significance of the results of this study to the operation of a commercial plant directly treating acid leach solutions is discussed.

Jan 1, 1973

Jan 1, 1910