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By F. E. Marcy

IT is not my purpose to write a lengthy article or to attempt the solotion of the problem I am presenting, but to call attention to what I believe an important issue, hoping that it may arouse in some one, or in some company, a sense of responsibility. I am referring particularly to modern up-to-date milling plants discharging tailings which under existing conditions cannot be further treated or from which a recovery cannot be made at a profit, but where a quantitative and qualitative analysis shows that a portion of these tailings might profitably bee treated, at some future time when our metallurgical knowledge has advanced, when we have cheaper power, chemicals, labor or other advantageous conditions. Early Methods In our early milling methods very little attention was given to the care of tailings. It was thought that if the mill could be located by a stream or a river where the final disposal of the tailings could be forever lost sight of, it was highly desirable. We can now see acid estimate what was lost in these rich tailings, not recoverable from the streams and the great rivers. Fortunately for many, the depositing of tailings in these streams and rivers was objected to by the farmers and finally prohibited by the State Legislatures. In looking back over our past milling methods, it seems that, the first endeavor was to make the maximum amount of money for a particular period, or year, regardless of the future, the depletion of the mine, or the conservation of the total mineral content. The dumping and sluicing of 3,000 tons per day, for a period of many years, of a copper tailing carrying

Jan 8, 1917

By S. C. Geol, C. H. Page

INTRODUCTION Mining at Mindola Mine, Rokana Division of Nchanga Consolidated Copper Mines Limited is the deepest on the Zambian Copperbelt. Mining extends to 1150 metre depth so far and the present plans extend to 1500 metres, although reserves exist below this level. Mindola Mine is the major producer of copper/cobalt ore at Rokana Division and produces approximately 200,000 tonnes of copper/cobalt ore per month. A standard open stoping method is the only method used for mining with minor variations in positioning drilling drives and other development, figure 1. The standard main haulage interval is 75m but in flat dipping areas the full stope height is split into two or three panels. In 1970 severe mining problems were experienced when mining deeper than 850111 below surface. The main problems included: - Heavy support requirements in drilling drives near stope face. - Premature closure of blast holes necessitating pre-charging of the holes with explosives immediately after drilling and well before the day of blasting. - Severe bumping and spitting due to rock movements on drive surfaces and remotely within the rock mass under high stress. - Low mining efficiency due to dilution from the waste hangingwall. - These stress related factors also caused some premature detonations of precharged but unprimed blast holes which became a serious safety hazard. A number of alternatives have been considered to overcome these problems. A search for leas sensitive explosives to avoid the premature detonation problem has been partially successful, however, the need for a method of reducing stress levels at the mining face is still considered essential as the mine goes deeper. This paper describes experiments with Regional Support Pillars as a method of reducing stresses at the mining face.

Jan 1, 1981

By Brian F. Osborne

A continuous on-line particle-size analysis system for solid/liquid suspensions is described. The basic sensor utilizes a centrifugal principle to separate particles according to size, the resultant separation being measured by means of beta-ray attenuation. Results obtained when analyzing a variety of materials at sizes from 65 mesh (210 µ) to 20 w are discussed in detail. Accuracies better than 2% are demonstrated. The effects of particle specific gravity, and mixtures of materials of diverse specific gravities, are discussed from both a practical and a theoretical viewpoint. It is demonstrated that particle specific gravity has a minimal effect on the size reading obtained. This renders the instrument suitable for handling materials where the ratio of light to heavy component may change. The design of the first commercial installation of this instrument is described in detail. This installation will be capable of analyzing three streams in sequence, measurement at three particle sizes being effected on each stream.

Jan 1, 1975

By Otto F. Pfordte

In my paper on " The Refilling of Sulphides Obtaihed in the Lixiviation-Process with Hyposulphite Solutions " (Trans., xx., 37), I gave the outlines of a process for refining sulphides. In a subse-

Jan 1, 1893

By John B. Gayle

PRESENT flotation processes depend almost entirely on the buoyant properties of air bubbles to effect separations of mineral and gangue, but there is no convenient method for measuring aeration in flotation cells. Consequently the relation between aeration and cell performance has not been definitely established. In connection with a comparative study of kerosene and froth flotation processes, a modification of the displacement method' was developed in which air escaping from the cell surface is measured with a wet-test meter. The arrangement shown in Fig. 1 is satisfactory for use with a number of cells and is not critical, except that care must be taken to use connections and tubing large enough to avoid excessive back pressures. Attempts to use smaller tubing resulted in back pressures that caused displacement of the liquid level in the receiver, so that some air was lost around the sides, an occurrence readily visible when measurements were taken with only water passing through the cell. With the arrangement shown, the manometer indicated an average reading of about ½ -in. water pressure. No loss of air was evident.

Jan 7, 1958

By P. R. Sperry

A METHOD was recently devised to indicate two or more successive stages of the migration of grain boundaries in aluminum, and to record the direction of the migration. This technique was used for the study of the various types of boundary migration occurring in high purity aluminum.' The method employs alternate annealing and electrolytic etching treatments, repeated as many times as desired. All successive sets of grain boun- dary positions revealed by the various etches appear superimposed on each other. The last etch is designed to leave an oxide film on the surface which is optically anisotropic. The orientation of the oxide film at each point is determined by the orientation of the underlying aluminum grain. When viewed with polarized light using crossed nicols and a Biot-Klein quartz plate, grains with differing orientations appear in different colors, as described by Hone and Pearson.' The last boundary positions are revealed by these color differences. The first step of the process is to obtain a desired starting grain size by annealing, for example, if high

Jan 1, 1951

By R. W. Kobler, D. A. Dahlstrom

Since the development of the pelletizing process in the fifties for relatively high purity pellets from low grade taconites, there have been several distinctive changes in filter construction for the dewatering step preceding balling. In the original large pilot plant run by Reserve Mining Co. in Babbitt, MN, the disk type filter employing agitation (Agidisc filter) was selected as the most economical. Size was limited to 2.1 m (6 ft, 9 in.) in diameter. The second generation occurred in the sixties with a jump to 2.70 m (8 ft, 10 in.) in diameter to reduce capital costs per annual ton of pellet. In the early seventies, the third generation was the steam drying disk filter which became necessary to achieve balling moistures with specific surface areas of 2200 cm2/g to as high as 3800 cm2/g caused by finer grinding to obtain higher purities. Finally, the fourth generation has recently been developed to reduce maintenance costs and further improve hydraulics to ensure minimum moisture contents.

Jan 1, 1980

By C. W. Bildt

During many years of service in the iron and steel industry I have frequently found, as have also many other engineers, that the common devices used for feeding coal into gas-producers are not what they ought to be in order to secure the best economy. The hopper-and-cone so generally used is familiar to all, and a brief study of its action will surely satisfy everybody that this device has several serious faults. In the first place, the charging is intermittent, and depends entirely upon an attendant. When the hopper is frequently emptied, it may work fairly well, but even then it suddeinly discharges into the hot producers a large body of coal, which is often violently converted into gas that rushes into the furnace, and, as the damper for the combustion-air cannot be regulated every time the producer is charged, there will be an excess of gas, which goes up the chimney unburned. Between the chargings the quantity of gas generated decreases, and there will often be an excess of air in the furnace,

Jan 1, 1899

TO THE BOARD OF DIRECTORS OF THE AMERICAN INSTITUTE OF MINING AND METALLURGICAL ENGINEERS Gentlemen: - I herewith present a report of some. of the more important activities of the Institute for the year of 1922. The outstanding feature of the year is the optimism felt by our members despite the continued depression in the mining industry. January 1, 1921, found many of our members out of employment or drifting into other industries to tide them over the depression, but almost universally the feeling has been that this was but a temporary condition and that sooner or later the necessary production of raw materials would enable these members to return to their former activities and renew their participation in Institute affairs. As the year passed conditions improved and, before it ended, many had found employment in their previous occupations. Bearing in mind that this depression has been very real, we have reason to be well satisfied with the work that the Institute has been able to do. The loss of members through inability to pay, dues has been large, and income has been correspondingly reduced, but it proved to be materially in excess of that anticipated early in the year, so that a substantial and unanticipated balance was carried forward toward the activities of 1923. PUBLICATIONS Following the example of other technical societies, and to conserve our resources, no Year Book was published in 1922. The lack of an up-to-date membership list for the use of our members was regrettable, but the saving of $5000 proved to be worth while. During the year, Volumes LXV, LXVI, and LXVII were printed and sent to members. These volumes were composed largely of the papers of 1920 and 1921, publication of which had been delayed partly through lack of funds and partly for the purpose of segregating into volumes those papers dealing with the same general subject. The segregation of papers had been suggested by a number of members who had advised that they were not primarily interested in all subjects

Jan 1, 1925

By C. A. Wright

Since the adoption by the U. S. Bureau of Standards several years ago of specifications for standard 100- and 200-mesh sieves, frequent requests have been received that this Bureau test and certify sieves of other sizes than these. With a view to the adoption of a series of standard testing sieves which might be of use to all industries making fineness tests, this Bureau for two years has been studying the question of such a standard screen scale. Various scales that have been proposed were considered, and information was sought of representative firms in the various industries interested as to their requirements. Manufacturers of sieves have also been consulted as to the desirability of different screen scales and the practicability of their manufacture. As a result of this study of the question, a conference was called at the Bureau of Standards, Apr. 20, 1916, of representatives of various committees of the American Society for Testing Materials, American Society of Civil Engineers, American Institute of Mining Engineers, American Foundrymen's Association, Mining and Metallurgical Society of America, American Water Works Association, American Institute of Metals and the American Spice Trade Association; also representatives of the Committee of Revision of the U. S. Pharmacopæia, the U. S. Geological Survey, the U. S. Bureau of Mines, the U. S. Office of Public Roads and Rural Engineering, the U. S. Office of Grain Standardization and the U. S. Bureau of Standards; also representatives of a number of private firms engaged in industries in which sieves are used, such as the glass, the drug milling, the abrasive, the asphalt, the mining, the spice, the chemical, and the graphite industries; also representatives of the firms in this country manufacturing wire cloth and sieves. This Conference, after considering the various screen scales either proposed or now in use, adopted as a Standard Screen Scale that given in Table 1, and recommends that it be adopted generally by scientific,

Jan 1, 1918

By A. B. Kinzel

THE demands of the petroleum and chemical industries for steels to be used in pressure vessels and similar structures at artificially low tempera-tures are continually increasing, and the writing of proper specifications with suitable tests becomes increasingly important. Likewise, the selec-tion of suitable steels for such applications is of increasing concern to the metallurgist. It is generally recognized that highly alloyed steels of the austenitic stainless type retain their properties even at very low tempera-tures and represent the best technological solution of the low-temperature steel problem. However, in many instances less expensive carbon or low-alloy steels suitable for service within limited temperature ranges are available. The problem thus becomes one of defining the various factors involved in the production and fabrication of these less expensive steels and determining the temperature ranges in which their properties justify engineering application. Most of the applications involve welded structures, and the heat effect of welding as well as the nature of the weld metal are matters of prime concern. The first problem that the metallurgist faces is the determination of the type of test to be used as a criterion of the performance of the steel in low-temperature service. It has been generally recognized that the static properties of steel as determined in the ordinary tensile test undergo a gradual and relatively slight change as the temperature of test is lowered in the range of current interest; i.e., from room temperature to minus 120° C. It is further generally recognized that the behavior of steel under impact involving notch sensitivity is definitely affected at the lower temperatures. While the major subject of this paper is the effect of grain-refining deoxidizers, of low-alloy additions and of welding on the low-temperature notched-bar impact properties, an inquiry into the general behavior of steel under low-temperature impact testing is included. This is a pertinent portion of the investigation and the results thereof are

Jan 1, 1937

By F. A. Emmerton

I have used for about two years, in the laboratory of the Joliet Steel Company, a rapid method for the determination of phosphorus in iron, steel, and ores, which possesses one or two features sufficiently novel to warrant description. In general, it is the method described by Mr. Benjamin B. Wright (Transactions, vol. x., p. 197), involving the precipitation of the phosphorus by means of molybdate solution, and its estimation in the yellow precipitate by reduction of the molybdic acid, and titration of the resulting oxide with a standardized permanganate solution, according to the principles laid down by Werncke (Fres, Zeit., vol. xiv., p. 1). In the use of this method, I had difficulty at first in obtaining a yellow precipitate of reasonably uniform composition. It is a well-known fact that, to secure this result, the conditions of precipitation must not vary. The principal condition is temperature; and acidity, concentration, proportion of nitrates and chlorides, and time, are important elements. I am aware that uniformity in these conditions has been obtained to a reasonable extent by many chemists,. so that they are enabled to use with success, methods based on the

Jan 1, 1887

By Carl A. Zapffee

FOR a number of years a puzzling phenomenon of brittleness in Class II ferritic stainless steels, developing in the temperature range near 475C, has received increasing attention, but its nature remains essentially unknown. During an investigation of the fractographic structures in stainless steels, conducted in the author's laboratory the past several years, principally under sponsorship of the Office of Naval Research, some observations of a new kind were found for "475 °C embrittlement." While the details of the study cannot be given here,' three fractographs will suffice to carry the

Jan 1, 1952

By J. E. Schaefer

A summary of oil and gas development in Ohio for 1936 is necessarily brief and, in some details incomplete, owing to the lack of a central state agency for the collection of data and statistics on well drilling and production. The information used in this report was compiled from the records of the several companies operating in the state. Drilling activity in Ohio increased during 1936 as compared to the two preceding years. During the year 1157 wells were completed, as compared to 1022 wells in 1935 and 1055 wells in 1934. However, in spite of this increase in drilling activity, both oil and gas production declined for the year. Activity by Fields Trenton Sand Field.—The Trenton sand field is located in 15 counties of northwestern Ohio, trending from Toledo on the north, south and west through Findlay into Indiana. About 40 years ago the Trenton field was one of the most important oil-producing fields in the United States, but it has declined to a position of minor importance. During the year 1936 there were 52 completions in this field—29 gas wells, 19 oil wells and 4 dry holes. Clinton Sand Field.—The Clinton sand is by far the most important gas-producing field in the state. Production is located in small pools separated by nonproducing areas, on a band of varying width reaching from Cleveland on the north to Lawrence County on the Ohio River on the south. During 1936 a small pool of patchy character was developed in Butler township, Knox County. Seventeen wells were completed in the Clinton sand, of which 13 were gas wells and 4 were dry holes. The average initial production secured per well drilled, including dry holes, was 1,288,000 cu. ft. The average depth of the Clinton sand was 3000 feet. A gas well was completed in lot 9 of Franklin township, Tuscarawas County. Production was found in the first Clinton sand at a depth of 4354 ft. The initial open flow after shot was 828,000 cu. ft. and the rock

Jan 1, 1937

By J. T. Richards

ELASTIC constants, including E-modulus, G-modulus, Poisson's ratio, and compressibility, are affected by temperature, but not necessarily to the same degree nor in the same direction. Theoretical expressions relating the temperature coefficients for the various elastic constants have been introduced by Gruneisen. In considering the thermoelastic characteristics

Jan 1, 1955

By Dietmar Espig

Very useful general relationships between operating parameters and the operating results for open- and closed-circuit grinding under steady- state conditions are described. The basic idea of the developed methods consists of the introduction of a known reference state. The relations derived from very simple approximations to individual processes allow one to evaluate fineness and mass flow of the desired state after changing the parameters (feed rate, fineness of the feed material, mill length, transport behavior through the mill, classifier characteristics). It was also possible to derive some general relationships, e.g., * an equation for the influence of the operating parameters of the mill on the fineness of the mill output * a criterion to establish if the desired state of a closed grinding circuit is steady state at all * a possibility to substitute the common influence of the transport behavior of the mill and of the classifier by-pass fraction with the coarse stream on the mill outlet product by means of a fictitious worse transport behavior. The applicability of the described methodology to many problems in grinding practice, including questions of controlling grinding circuits, is demonstrated by some examples. In particular, a working diagram of the standard closed grinding circuit has been established.

Jan 1, 1984

By Jan M. Mutmansky

The primary purpose of this presentation is to analyze the strategies available to an operator using either stripping or stripping and subsequent punch mining on a given coal property. The initial concern is the formulation of a mathematical model, which allows an operator to determine and utilize the particular highwall height, which will maximize : (1) Total profit or (2) Profit per unit of operating time. The analysis centers on the relative costs and recoveries involved in a typical coal seam amenable to stripping, augering, and punch mining. The model defines the point to which the high-recovery stripping operation with increasing overburden removal and reclamation costs should proceed before the low-recovery augering and punch mining methods are employed so that the desired objective is achieved. Examples are presented, which exhibit the use of the model on typical operations. Present mining methods as practiced in the Eastern United States are examined in the light of the results. Recommendations for improving present strategies are made and the resulting economic ramifications are analyzed. Particular attention is given to the stripping ratios presently used and recommendations for improving present mining practice are presented. Implications of these recommendations to the design of strip mining equipment are discussed.

Jan 1, 1977

By George A. Lamb

AMONG the main interesting developments in the coal market have been the changes that have taken place between the consumer groups. Important signs of these changes began to appear many years ago, but in a modest way, and were apparent only to the few fuel experts making broad statistical determinations. It is doubtful, however, that any of these experts appreciated the significance of their early findings, and perhaps none had the imagination to consider how extensive these changes might be eventually with respect to solid fuels sales and distribution. (Reference here will be principally to bituminous coal.) Railroad Fuel Major changes in coal use did become pronounced after World War II, and it did not take an expert to see what was taking place and how serious the impact was likely to be. First, was the case of the steam and diesel locomotives. The railroads had been considered the best coal customers; they were steady and large purchasers and usually paid a better price than most others. Railroad fuel provided the basic mine realization and it often was the source for operating cash during general market slumps. It was the outlet for 20 pct of the bituminous coal production, as much as 110 million tons in 1946.

Jan 2, 1957

By Victor Phillips

Cyclone thickeners have emerged from the development stage and now can be accepted as useful tools for the recovery of fine coal from a preparation plant circulating water. As primary thickeners in a closed water circuit operation, their advantages over conventional thickening methods are twofold-the lower initial investment and reduced area requirements.

Jan 8, 1951

By R. N. Orava

TO the author's knowledge, only one satisfactory high-resolution technique for etch-pitting dislocations in Cu-Zn alloys has been published.' In that account, pits in 70/30 brass single crystals were produced by etching electrolytic ally in a 30 pct orthophosphoric acid bath. Thereafter, observations were made from surface replicas by electron microscopy. The method of pitting and observation permitted the high resolution necessary for the distinction of individual dislocations in arrays of pile-ups. However, no comment was offered concerning the possibility of obtaining pits which are amenable to optical resolution. Moreover, for adequate results, the electrolytic pitting process is invariably preceded by a polishing stage which could obscure the surface features of interest. Consequently, it would be desirable to be able to delineate, by solely chemical means, dislocations which could be detected by both optical and electron metallo-graphic techniques. This was achieved by the simple expedient of modifying two etchants reported by young2 to reveal dislocations on the (100) planes of pure copper. Single crystals of 70/30 a brass, described previously,3 were sectioned to provide a surface parallel to a set of {100) planes, mechanically polished, and subsequently electropolished at 2.4 v in a solution comprised of 2 parts H3PO4, 4 parts ethanol, and 3 parts water. The inclusion of ethanol tended to inhibit nonuniform surface attack. Etch-pitting was effected by a 2 to 3 sec immersion in a 70 pct aqueous solution of HNO3. The samples were then washed in a fast-flowing stream of water, and rinsed further in distilled water, and ethanol, before drying. It is important to note that this reagent should be either used immediately after mixing, or, if allowed to cool, reheated to about 35°C prior to use. No pitting was obtained at room temperature. Typical results are shown in Fig. 1 where (a) is an optical view of the pitted surface and (b) is an electron micrograph of a silicon monoxide replica shadowed with tungsten oxide. The former is characteristic of a somewhat longer etching time (-6 to 8 sec) which varied with bath temperature. Similar pits accrued from a 1/10 aqueous dilution of another of Young's solutions2—2 M FeC1,6H20 and 7.8 M HBr.

Jan 1, 1968