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THERE was presented for discussion at the February (1924) meeting of the American Institute of Mining and Metallurgical Engineers a report of a committee named by the United States Bureau of Mines on the Use of Oxygen or Oxygenated Air in Metallurgy and Allied Processes. An extensive discussion followed the presentation of the papers, which dealt with the matter entirely from a theoretical standpoint. The results of only a limited, amount of research work were presented and discussion centered around the question: "Is it worth while to carry on research and expend money in determining what can be done in metallurgical operations if cheap oxygen can be produced?" More experimental work on this subject has not been done because metallurgists have not thought that cheap oxygen could be produced, thinking "Why waste time experimenting. with a reagent that cannot be procurable in commercial quantities?" While the producers of oxygen have said " Why waste money on the development of a process to make cheap oxygen unless we know that there will be a market for it when produced?" The discussion brought out two facts: First, many metallurgists believe that their operations can be conducted more economically if they can add oxygen to the air used in various smelting operations; second, a number of chemists believe that relatively pure oxygen can be produced in metallurgical quantities at very small cost. Negative views were expressed to both propositions, but so overwhelming was the view that if cheap oxygen could be produced, many metallurgical operations would benefit that it was voted to recommend that the Bureau of Mines continue its research work, pending the production of the cheap oxygen hoped for. Few experimental data being available, and the attitude of disputants being based largely on theoretical considerations or on reactions and temperatures incapable of positive proof, it has been decided to publish only a summary of the papers and discussions arising from their presentations. It is believed, however, that this will be sufficient to show the lines of reasoning that have been adopted, and be a guide to others who are to make their own calculations or engage in experimental work.

Jan 11, 1924

By J. A. Musselman, J. B. Cheatham

In recent years considerable effort has been expended in the search for new ways of drilling into the earth's crust and for improvements of existing methods. A number of novel techniques have been explored such as explosive, flame, electric arc, abrasive jet, chemical, and various percussion-type dri1ls.l Some of the new methods are useful in isolated situations, but rotary drilling continues to be the most versatile and generally economical method for rock drilling. An understanding of rock failure during drilling can lead to improved rotary drilling techniques and to the development of new methods. Experiments 2-4 have shown that rock strength and ductility increase with increasing pressure; therefore, meaningful experimental investigations should be carried out under conditions similar to those encountered at the depths to which oil wells are drilled. The action of a roller-cone bit is not pure rolling in all cases but frequently involves gouging and scraping action. However, vertical penetration of a horizontal rock surface by a single punch has served as a first approximation of the rock/bit tooth interaction during drilling.5,6 In these experiments semi-infinite smooth rock surfaces are indented by steel tools with configurations having various degrees of dullness. Both static and dynamic tests have been investigated; however, static loading provides a good approximation of the loading rates occurring during rotary drilling. As a more realistic approximation to actual drilling conditions, chip generation must also be considered. Recently, studies have been made of indexing or chipping from a bit tooth to a previously formed crater.7-9 The purpose of the present investigation is to study indexed penetrations in greater detail. Fig. 1-A illustrates the general problem. Pittman and Cheatham 10,11 have used plastic limit analysis to study the idealized plane-strain indexing problem for a material having a linear Coulomb-

Jan 1, 1972

By Jan M. Mutmansky, Y. J. Wang

Mine ventilation analysis is an engineering discipline that can be considered a branch of the body of science known as network analysis. Likewise, the group of engineering procedures known as the critical- path method (CPM) is considered a branch of network analysis. It is therefore not surprising that mine ventilation network analysis and CPM have many similarities. These similarities are useful in analyzing several types of mine ventilation problems and will be utilized in this paper. The analogy between the free split in a ventilation circuit and the critical path in a scheduling network has been recognized by Owili-Eger (1973). While this was recognized as a property of a general ventilation network, many important applications to controlled- splitting problems also exist. The mathematical procedures necessary to apply CPM and network methods have previously been presented (Wang, 1981; Wang, 1982). This paper will illustrate the implementation of these methods by application to mine ventilation networks.

Jan 1, 1982

By Lewis Delano

IT HAS been generally recognized that, owing to the extreme friability of, galena, fine grinding has a tendency to cause excessive sliming of the mineral, so operators of lead mills have attempted to avoid this condition by commencing concentration at as coarse sizes as any mineral is freed. Jigging has been the basis of the milling process, making a clean coarse concentrate and a large amount of tailing, which was considered sufficiently low-grade to be rejected. However, developments and improvements in concentration processes are everywhere changing the low-grade tailing of yesterday into material worth retreating today. Investigations of the work of the Hancock jig on the Bonne Terre ore- have shown that the best results to be expected will give a tailing assaying 0.75 per cent. lead; the average over all conditions and grades of ore will be between .0.80 and 0.90 per cent. By crushing the jig tailings in ball-mills and retreating by tables and flotation, a tailing of considerably lower grade can be made; the problem then becomes an economic one of increased crushing costs versus higher recovery. In considering the entire elimination of jigging, the increased smelting charges; due to a greater amount of slime galena will be counterbalanced by the lower operating cost, in-creased recovery, and the many advantages of a simpler flow sheet. In developing these problems in the Bonne Terre mill of the' St. Joseph Lead Co., a long series of tests has been carried out covering every stage of crushing and concentration, and a large number of possible flow sheets were considered and tried. Only the final results and a few comparisons will be given here. At the same time, a careful and detailed cost-keeping system has enabled us to compare milling costs with the various flow sheets, and to calculate the economics of the problem' with great accuracy. .

Jan 8, 1920

Efficient energy utilization in the electrolytic zinc process, relative to other zinc processes, is one of the reasons for its wide adoption in recent years, says John D. Siddle, zinc plant superintendent at the Bunker Hill Co., Kellogg, Idaho. Designers and operators of electrolytic zinc plants have pioneered process improvements, new equipment, and operating techniques to conserve energy. As energy costs increase it the future and competitive pressure mounts against less-efficient producers, these energy-saving improvements will he regarded as necessary for economic survival. Plant designers and operators should not lose sight of the savings in operating costs possible through intelligent utilization of all available forms of energy.

Jan 11, 1977

By N. A. MacLeod

Ball wear in wet grinding mills has been the subject of considerable discussion in the last few years. Its importance to millmen is obvious in view of the fact that ball wear may cost from 2 to 4 per ton of ore for the more fortunate operators and many times this cost when a refractory ore must be reduced to a fine state of comminution. Consequently, any factual information that may be obtained on the nature of ball wear may be applied to introduce changes leading to lower ball consumption and therefore also to lower costs. In 1940, while employed with the Britannia Mining and Smelting Co., Britannia Beach, B.C., I had occasion to investigate factors that might affect ball consumption. We performed a number of tests, which will be briefly described. These tests originated as a result of changing from a 3½-in. ball to a 2-in. ball of different type of manufacture and were motivated by the desire to obtain the best possible type of 2-in. ball. Our testing was helped by the fact that the company operated a one-ton electric furnace, so that it was quite easy to make steel changes. It should be emphasized at the beginning that these tests produced results that in their general application to milling should be interpreted qualitatively rather than quantitatively. As will be evident in the description of the method used in testing, the balls were subjected to an intermittent batch grinding treatment, which may have produced results in rate of steel wear that may not have an accurate correlation with steel consumption in full scale mill operation. However, with this bed and rather arbitrary method of testing, results were obtained that may be of some interest and may stimulate further work on this subject. Unfortunately, owing to pressure of war work, our tests, which we had intended to repeat on a continuous grinding operation, had to be discontinued. Method of Testing Tests Were made in a Small cylindrical mill, rotating at 72 r.P.m. Internal dimensions of the mill were 10½-in. dia. by 9 in. The cylindrical inner surface was lined with rubber and the two ends were formed by steel plates. A charge of 2000 grams dry feed and 2000 C.C. of water was added evev 2 hr., the mill being drained of pulp before the addition of each charge, by tilting and sluicing with water. The mill was run On afternoon and night shift for daily periods of about 15 hr. total grinding time, and each test lasted from 60 to 150 hr. This batch method of testing involved a higher average pulp temperature in the mill, which undoubtedly affected comparative results in Some of the tests. Hardness oF Ball vs. Wear In these tests, special "eutectoid" steel balls were used, some of which were chill-Cut and quenched, some sand-cast and quenched, and some sand-cast and annealed to a dead soft condition. The results obtained, using as mill feed an ore containing considerable free quartz and

Jan 1, 1947

By N. A. MacLeod

Ball wear in wet grinding mills has been the subject of considerable discussion in the last few years. Its importance to millmen is obvious in view of the fact that ball wear may cost from 2 to 4 per ton of ore for the more fortunate operators and many times this cost when a refractory ore must be reduced to a fine state of comminution. Consequently, any factual information that may be obtained on the nature of ball wear may be applied to introduce changes leading to lower ball consumption and therefore also to lower costs. In 1940, while employed with the Britannia Mining and Smelting Co., Britannia Beach, B.C., I had occasion to investigate factors that might affect ball consumption. We performed a number of tests, which will be briefly described. These tests originated as a result of changing from a 3½-in. ball to a 2-in. ball of different type of manufacture and were motivated by the desire to obtain the best possible type of 2-in. ball. Our testing was helped by the fact that the company operated a one-ton electric furnace, so that it was quite easy to make steel changes. It should be emphasized at the beginning that these tests produced results that in their general application to milling should be interpreted qualitatively rather than quantitatively. As will be evident in the description of the method used in testing, the balls were subjected to an intermittent batch grinding treatment, which may have produced results in rate of steel wear that may not have an accurate correlation with steel consumption in full scale mill operation. However, with this bed and rather arbitrary method of testing, results were obtained that may be of some interest and may stimulate further work on this subject. Unfortunately, owing to pressure of war work, our tests, which we had intended to repeat on a continuous grinding operation, had to be discontinued. Method of Testing Tests Were made in a Small cylindrical mill, rotating at 72 r.P.m. Internal dimensions of the mill were 10½-in. dia. by 9 in. The cylindrical inner surface was lined with rubber and the two ends were formed by steel plates. A charge of 2000 grams dry feed and 2000 C.C. of water was added evev 2 hr., the mill being drained of pulp before the addition of each charge, by tilting and sluicing with water. The mill was run On afternoon and night shift for daily periods of about 15 hr. total grinding time, and each test lasted from 60 to 150 hr. This batch method of testing involved a higher average pulp temperature in the mill, which undoubtedly affected comparative results in Some of the tests. Hardness oF Ball vs. Wear In these tests, special "eutectoid" steel balls were used, some of which were chill-Cut and quenched, some sand-cast and quenched, and some sand-cast and annealed to a dead soft condition. The results obtained, using as mill feed an ore containing considerable free quartz and

Jan 1, 1947

By Clarence Wright

THE average lead and zinc content of the ores mined and milled in the Joplin district is low as compared with that of other lead and zinc deposits throughout the United States. Because of this fact and of the high grade of the concentrates, the ratio of concentration is unusually high. Most of the operating companies have aimed to produce as high a grade of concentrate as possible in order to obtain the highest price for their product. They have done this at the sacrifice of the percentage of zinc recovered. The average percentage of zinc recovery is from 60 to 70 per cent. For percentage of recoveries from actual mill tests, see tables. The concentration is commonly effected by crushing the ore to h-in. (12.7 mm.) size and subjecting it to a roughing and cleaning over two or more large Cooley jigs, of the Harz type, the finer sands being treated on the usual types of sand and slime tables. The treatment of slimes by flotation is being tested at several of the larger mills. COARSE CONCENTRATION When the ore. has been hoisted from the mine it is dumped onto a chute leading to a grizzly made of iron bars, usually heavy rails, spaced 4 to -5 in. (101 to 127 mm.) apart. The oversize is caught on the grizzly, the mineralized pieces are broken with sledge hammers so as to pass through, and the boulders that are practically barren are sorted out by hand and trammed to the waste-rock pile. The proportion of waste rock thus sorted out varies from a fraction of 1 per cent to 15 per cent., depending on the nature of the rock.

Jan 10, 1917

By Alan K. Burton

An industry-wide demand for bigger and more efficient trucks, with their supposed economies of scale, is well established. Some trucks have been, and often are brought "off the shelf," with the manufacturer offering only certain minor options, much as in the private automobile industry. The market is well established; there is keen competition; in recent years there have been few significant changes, and few are expected. With large trucks (100-ton-capacity and over), however, the situation is different. Here, with an individual truck costing several hundred thousand dollars, there is an ever in- creasing trend to engineer a truck for a specific application. The body will be designed and sized for the material that the truck will carry; the engine and transmission will be geared to the haul profile, and tires will be designed to suit road conditions and work requirements. Early Truck Development Haulage trucks designed expressly for open-pit mine service were introduced during the 1930's. The first models to arrive on the scene hauled about 15 tons, and easily outperformed the modified highway trucks that had been used for mine haulage up to that time.

Jan 8, 1975

By J. A. Fulton

GOLD was discovered in the Sierra Nevada by J. W. Marshall on Jan. 2, 1848. The town: of Grass Valley soon sprang up and contained several stores in 1849; but the population of the town has always reflected the fluctuations in quartz mining. Gold-bearing quartz was found on Gold Hill in September 1850, and in the next two years most of the quartz bearing veins in the vicinity were located. At first, the quartz was crushed in mortars with spring poles; the Huff Co. took out $20,000 in this manner during the winter and spring of 1851. The first mill was put up in January, 1851. In 1866, there .were in Grass Valley 248 stamps, crushing 71,420 tons of ore with an average yield of $30 to $35; in Nevada City, there were 142 stamps, crushing 14,200, tons, with an average value of $25. But in 1918, only two properties in. this region, the Empire and the North Star, were producing. Since then, there has. been a revival of mining in the district and the following properties are being opened up: The Golden Center, Grass Valley Gold. Mines CO , Idaho-Maryland Mines Co., while the Sultana is kept unwatered and work is going on in a half dozen small properties.

Jan 2, 1926

By Hans Neuberger

INTRODUCTION IN our everyday life, visual perception plays perhaps a more important role than any of the other senses with which we are equipped by nature. It is, therefore, quite understandable that the average person associates 'with the term "atmospheric pollution," clouds of dust, palls of smoke or deposits of soot, phenomena which are so familiar to the residents of industrial cities. On the other hand, "air" is usually considered the prototype of the invisible, of the intangible, and any suspensions in the air which do not conform to this concept, are regarded as foreign to the atmosphere and thus as "pollution." According to Webster, the term "pollution" implies uncleanness, impurity, in short, something undesirable. Although the scientist often accepts popular concepts, he is generally inclined to suspect that apparently "obvious" phenomena imply, literally, "more than meets the eye." To show that this suspicion is also justified with regard to atmospheric pollution, is the objective of this discussion. It will be shown that what seems foreign to the air at first sight, is by nature an integral part of it, and that the more important aspects of pollution generally escape attention. THE ATMOSPHERIC CONSTITUENTS We can distinguish two classes of atmospheric constituents: the permanent gases, chiefly nitrogen, oxygen, traces of argon, neon, and others, and the variable constituents which include water in its different states, carbon dioxide, ozone, and various suspensions, either in gaseous, liquid or solid form. These suspensions, known by the collective term "Aerosol,"20 will be considered in detail. DUST There are two general types of aerosols: the first type is represented by the socalled "neutral" particle 3, commonly known as dust and experienced by everyone, as it is the more conspicuous type of suspensions. . It often represents a special problem to the mining engineer, the mechanical engineer, the industrial engineer, and many other professional men. Dust consists of finely divided solids derived from weathering, drilling, handling and preparation of rocks and coal. Dust may also consist of organic or inorganic particles resulting from manufacture of a variety of products such as flour, rubber, lime and steel, from traffic on land be it on the highways, on rails or in city streets, from decomposed vegetation or from volcanic eruptions. Perhaps the most reviled member of this class of suspensions is the soot and fly ashes from coal fires and other combustion processes. The cosmic source of dust, namely the injection of meteoric matter into the atmosphere, is of minor significance because the concentration of particles is exceedingly small despite the relatively large mass of material invades the earth’s atmosphere from space

Jan 1, 1948

By N. B. Aughenbaugh, W. C. Patrick

The availability of a thorough, simple-to-use roof fall classification system is desirable for several reasons. First, such a system would expedite the reporting of falls for the purposes of estimating material removal costs, analyzing damage levels, and complying with federal regulations to report falls in certain areas of the mine. Second, the classification system would allow the mining engineer to record falls routinely with little time and effort expended. This would encourage him to make observations concerning what type of roof support would work best in a given situation. Third, and probably most important, an

Jan 3, 1979

By Gary Mack, Donald E. Scheck

To help management keep key machines or processes at peak efficiency, draglines, shovels and blast hole drills have been equipped with micro- processor based monitors. The dragline and shovel monitors log operating data such as energy consumption, bucket position, cab rotation and the clock time of key elements within each cycle as well as maintenance information. The output consists of maintenance and management data such as the number of cycles, average cycle times, swing angles, depths and downtimes. Extensive experimentation has shown that a blast hole monitor can provide a log of each blast hole in which the hard to fragment zones are indicated. The logs are printed on board the drill and serve as the design basis for decked loading of the holes. As a result, the fragmentation of the overburden has improved markedly with the same or less powder consumption. This material is based upon work supported in part by the Bureau of Mines, Department of the Interior under Grant Numbers G1115006, G1115391 and G5 105006. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the Bureau of Mines, Department of the Interior.

Jan 1, 1983

By William A. Berg

Vegetation on mine wastes was an important topic at the International Symposium on Ecology and Revegetation of Drastically Disturbed Areas held at Pennsylvania State University August 3-16, 1969. This article summarizes the Symposium papers that dealt with the nutritional and physical aspects of plant establishment on mine wastes. Surface Coal Mining Spoils Germany-In toxic spoil banks created by open-cast coal mining, the material was extremely acid and low in nutrients. It sometimes contained toxic quantities of minor elements and also had a water repellency that resulted in little leaching and high erosion. However, applications of calcareous and hygroscopic ash, fertilization and deep mixing (60 cm) have promoted growth on hundreds of acres. Knobe, N., Rhine Inst. Air Pol., Essen.

Jan 1, 1970

By W. F. McDermott

This is the dawning of the computer age in process control. As 1968 drew to a close, many plants had computer installations which were being used for logging, monitoring and reporting. Today, computer usage is given serious consideration before the construction of any major minerals processing plant. Unitized automatic control of individual processes is abundant. Many plants are considering closing these control loops, i.e., allowing the computer to direct the operation of the controllers (Digital Analog Control-DAC). The next step is to make the computer itself the controller (Direct Digital Control-DDC)1 Perhaps the most important future use of computers will be in controlling interrelated operations and control units. Progress along these lines depends on the steadily improving capabilities in the field of mathematical modeling.

Jan 1, 1970

By F. L. Holderreed

A choosy in what they would smelt. The furnace charge had to be coarse, and it had to be rich. They discarded fines in excess of about 1/10 the total weight. They wanted 10% copper content and fussed about anything with as low as 5%. They concentrated the copper content of the charge as much as they could by prior selection. They roasted off enough sulfur to further enrich the copper content of the succeeding fall of matte (a melt of cuprous and ferrous sulfides or Cu2S.FeS). Then they desulfurized the iron and fluxed it by carefully adding silica (quartz, not silicates) for a slag of lower density than the cuprous sulfide (Cu2S or white metal). After skimming off the slag, they further desulfurized the white metal by blowing the molten bath with compressed air. The result was blister copper. Yesterday Their techniques and furnaces? Some experimented with mechanically rabbled roasters, but their standard roasting practice was burning coarse sulfide ore in 250-ton heaps. These heaps, approximately 24 x 24 x 6 ft, were burned for about 75 days down to 6-10% sulfur. The turnaround time for a given roasting position was 100 days. Assuming the base was a hearth, the calculated rate of treatment was on the order of 0.004 tpd per sq ft.

Jan 1, 1971

By John V. Beall

Runding the bottom corner of the West Africa11 hump, one hovers off the coast of the tiny Republic of Liberia. But not for long-as Portuguese navigators, Blackbirders, and Farrell Line captains have learned. The ponderous swell of the Atlantic is driven by an on-shore wind that never dies. As remorseless as the Atlantic chewing away at the unbroken shoreline, is the country beyond-West Africa, where white meets black, where desert blends to bush to impenetrable jungle, where elephants chomp the foliage of young trees. This is a land from which the tsetse fly has driven the cattle, and the root crops grow big and voluptuous above the ground and are shrunken and barren of nutrient below. This is the environment of Liberia which is elbowing an iron ore market for itself on crowded shelves. Liberia is an anomaly in Africa. It was the first republic on the continent in modern times, having been established in 1848. While most of Africa was benefiting from the investment of foreign capital under colonial regimes, Liberia was going it alone. To be sure, Liberia was aware of foreign activity as hunks of territory were lopped off by neighboring French and English colonies. Today the country is about 43,000 sq miles, the size of Tennessee, which, in the language of exploration men, is a workable size unit.

Jan 12, 1962

By Jose M. Sobral

Approximate figures for petroleum production in Argentina for 1929 show an increase of only about 300,000 bbl. over production for 1928. This increase is due to greater yield in the Plaza Huincul and in the Salta regions. Table 1 shows the distribution of production in the various fields of the whole country, using estimates for the later months of the year. The outlook for production remains about the same as in 1928. It is believed that in northern Argentina there are regions that contain oil, but they are yet unexplored. Notable traces of oil at depths between 1280 and 1390 m. have appeared in a 1500-m. boring in Comodoro Rivadavia, but their importance is unknown.

Jan 1, 1930

WHEN one leaves the busy street and enters a library, the closing of the door behind him marks his passage into another world. Outside is the world of phenomena and appearances-of thronging pedestrians bustling about their business, of gregarious sights and sounds, of insistent auto-mobiles. Inside, on dusty shelves, is the stored learning of civilized man-the recorded ideas of countless generations. It is somewhat of a magic world. Here are the theories and secrets for which thousands of men toiled and gave their heart's blood. To produce one book on one phase of an ob-scure-subject may have required the best efforts of a group of men unique in their period. To prove one theory, or es-tablish a single application of a theory, may have taken the devotion of a genius who sacrificed his life to his work. This theory is perhaps stated in one paragraph of unassum-ing type, and the library contains millions of such para-

Jan 11, 1927

By Charles Brush

THE general subject of accurate pyrometry, its great development in recent years, and the importance of its application in arts and manufactures is so ably treated in other papers that this paper will bee confined to a resume of some research work on certain temperature effects in carbon and other steels, some of which appear to, be new. The results of these researches are embodied in several papers presented to' various scientific societies during the last few years, most of them under the general title of Spontaneous Generation of Heat in Recently Hardened Steel.1 Several years ago, when studying the behavior, tinder certain conditions, of specimens of hardened tool steel, I observed that they all spontaneously generated a small quantity of heat, the rate of generation diminishing from day to day for several weeks before generation became imperceptible in the sensitive calorimeter used. In each case the steel had been hardened only a few days prior to its use. It seemed highly probable that the generation of heat was associated with some sort of "seasoning" or incipient annealing process, perhaps accompanied by slight changes of volume, and that it would be most rapid immediately after hardening. I subsequently investigated this curious phenomenon more fully. Twelve ½ in. round bars of tool steel, 5 in. long and with machined surfaces, were hardened by heating to high cherry red in a reducing atmosphere of a gas furnace and quenched in cold water. The bars then had a thin strongly adhering coating of black oxide. They were next stirred in a large quantity of water at room temperature, to acquire that temperature, wiped dry, and oiled with heavy, neutral mineral oil to prevent generation of heat by further surface oxidation, wiped free of excess of oil and placed in the copper cylinder of a heat-insulated box.

Jan 9, 1919