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By J. D. Rice, H. H. Rachford, G. H. Bruce, D. W. Peaceman

The problem of unsteady-state gas flow through porous media leads to a second-order non-linear partial differential equation for which no analytical solution has been found. In this paper a stable numerical procedure is developed for solving the equation for production of gas at constant rate from linear and radial systems. An electronic digital computer is used to perform the numerical integration using an implicit form of an approximating difference equation. Solutions are presented in graphical form for various values of dimension-less parameters. The solutions are compared with the laboratory study of gas depletion in a linear system. INTRODUCTION Production of fluids from porous rock reservoirs is essentially a transient process. Transient gradients develop as soon as production begins, and further withdrawals continue to cause disturbances which propagate throughout the reservoir, each adding in some way to the prior ones. A correct mathematical analysis of this behavior is complicated by the fact that the transient or unsteady-state flow of compressible fluids must be described by difficult second-order partial differential equations. As a practical matter, three distinctly different cases arise: 1. Flow of single-phase liquid 2. Flow of gases 3. Multiphase flow The first of these has been found to give a linear second-order equation similar to the well-known heat flow equation. where 7 is fluid density, 8 is time, and a a constant for the system, provided d 7 = r cdp, where the compressibility, c, is constant over the range of pressure, p, considered. Solutions of Equation (1) for both linear and radial flow are available in several forms.2'3' On the other hand. the second case, which is the flow of gas, gives a non-linear second-order equation, the solution of which is not known. Although a number of approximate solutions have been proposed, each is limited in value by the associated simplifying assumptions. Inasmuch as the analysis of transient flow is limited to liquid systems, a solution of the second case is necessary if further progress is to be made in studying underground fluid movement. For this reason a solution of Equation (2) was undertaken by means of numerical integration of approximating difference equations. BASIC DIFFERENTIAL EQUATION Equation (2; is derived by combining the equation of continuity, the perfect gas law, and Darcy's law to give the basic differential equation Strictly speaking, the fluids present in a gas reservoir are not perfect gases. Furthermore, there are indications that over certain velocity ranges, Darcy's law is not applicable. It would not be practicable. however, to attempt to obtain numerical solutions which would take into account all the possible variations from these laws which could occur in actual systems. The

Jan 1, 1953

By Lawrence A. Garfield

From the bottom of a shallow fissure the near-naked man-animal hacked out a hand-sized chunk of the red rock-like material which, when beaten between other rocks, could be drawn out to the thinness of a flint edge. Unlike flint, however, it did not shatter when, as the point for a spear or arrow, it went wide of its mark and fell amongst the rocks or tree branches. For this reason and others, the red rock- like material was specially sought and much time was spent in trying to break it from the real-rock in which it grew. Only infrequently was a chunk broken free and in this area many hours had been spent to win but a few fragments. What luck then, to remove so large a piece where before nothing but real-rock dust formed whenever the stone hammer hit. Why did this happen? Did yesterday's food-fire, burning on top the red rock, loosen its hold on the real-rock and cause it to break free when struck with the stone hammer? It is not a matter of recorded history that the first heat assisted extraction of native copper from country rock occurred under the circumstances or in the manner related but it is known that crude mining operations using these techniques were conducted by primitive man. In this way the first mineral production may have been achieved and the original example of rapid excavation unknowingly given to the world. Rapid excavation is not a method of removing rock or ore from an insitu condition nor does the term refer to a type of equipment which is specifically employed in mining and underground construction. It is, rather, the nomenclature currently popular in industry-primarily in underground construction- relating to a comparative rate of performance.

Jan 1, 1971

UNITED ENGINEERING TRUSTEES, INC James L Head, '51 E C Meagher, '52 Gail F Moulton, '53 ADVISORY COMMITTEE TO REAL ESTATE COMMITTEE Cleveland Dodge Herbert Hoover Paul D Merica HOOVER MEDAL BOARD OF AWARD Scott Turner, '56, Chairman Cadwallader Evans, Jr , '52 Paul D Merica, '54

Jan 1, 1951

Copper ores from small mines in the area south of Tucson, where the Twin Buttes mine is located, were first operated in the 1880's. Today this area is one of the great copper mining centers of the world. In 1963, Anaconda Company acquired the property from Banner Mining Company and in recent years joined with AMAX in a 50/50 partnership to work the Twin Buttes property. From the beginning, Anaconda had relied on conveyors to remove overburden, oxide material for eventual leaching, and ore from the open pit. In the large st preproduction stripping program in mining history, Anaconda in a four-year period (1965 to 1969) removed 266 million tons of overburden of an average depth of 500 ft (152 m) lying over the ore body. The alluvium overburden was stripped by scrapers carrying 70 to 80 tons and push-loaded by two D9 tractors operating in tandem. The scrapers delivered their loads to bins which fed a 60 in. (1.52 m) conveyor having a capacity of 8500 tph. The 25% slope belt conveyor, which was 2100 ft (640 m) long, transported the material to the brow of the pit, where it was transferred to an 8300 ft (2530 m) surface belt to a 1000 ton loadout bin. At this point, the overburden was trucked to the sites of the tailings ponds, where it was used for dam construction. During 1976, the one billionth ton of overburden was removed from the Twin Buttes mine. The Twin Buttes quartz monzonite porphyry contains only scattered mineralization of which chalcopyrite is the most abundant mineral, associated with chalcocite, covellite, minor bornite, and several oxide minerals. Oxidation has progressed to variable depths of up to several hundred feet below the base of the alluvium. Because of the depth of the sulfide and oxide ores and hard rock waste, two in-pit crushers and conveyor systems were also installed for their transport out of the pit; and in 1976 a third crusher and conveyor system was installed lower in the pit for waste rock only. The two initial crushing and conveying systems were designed to handle any of three functions: crushing waste to be disposed of by a rail-mounted stacker -conveyor, crushing oxide ore for conveyor and then truck transport to stockpiles for future leaching, and primary crushing of sulfide ore for conveyor transport to the two 30 in. by 70 in. (0.76 by 1.78 m) secondary crushers and the two 7 ft (2. 13 m) standards and four 7 ft shortheads in the third and fourth stage crushing plant. A third standard crusher has been in- stalled recently. Mining is done by 15 yd (11.5 cum) shovels which load 100- and 150-ton

Jan 1, 1978

By AIME AIME

THE coal classification session* on Monday morning, Feb. 17, was opened by a paper by M. R. Campbell, entitled "Natural Groups of Coal and Allied Fuels," in which he pointed out, by means of graphical presentation of selected proximate analyses of coal, that coals can be classified on the basis of their moisture content. He proposes four groups of coal, brown coal, hydrobituminous, bituminous, and anthracite, each subdivided into two or three sub-groups. In a written discussion of this G. H. Cady, of the Illinois Geological Survey, showed that there is, in general, a progressive decrease in the moisture of Illinois coals from north to south, and that it would be very difficult to draw any arbitrary line dividing the coals of the State into two groups on the basis of moisture content.

Jan 1, 1930

By T. H. Weldon, L. V. Whiton, R. R. McNaughton, J. H. Hargrave

Oxygen enriched air is being used quite extensively in the metallurgical plants of The Consolidated Mining and Smelting Co. of Canada, Limited, at Trail, B.C. The oxygen used for this purpose is a by-product from the Company's chemical plants located in the area. Most of the ore treated in the Trail metallurgical plants comes from Com-inco's Sullivan Mine at Kimberley, B.C. At Kimberley the ore is milled to produce lead and zinc concentrates which are shipped to Trail for further treatment to metal. One section of this paper deals with the use of oxygen enriched air in the suspension roasting of the zinc concentrates. In this process the concentrate is calcined for leaching preparatory to electrolytic recovery of the zinc. A second section of the paper describes the use of oxygen enriched air in operations at the lead smelter. There oxygen enriched air is used in the blast to the lead blast furnaces and in the slag fuming furnace which recovers the lead and zinc contained in lead blast furnace slag. The final section of the paper outlines the precautions necessary for the safe use of oxygen enriched air in any plant operation. The Use of Oxygen Enriched Air in the Suspension Zinc Roasters The suspension roasting of zinc concentrate developed at Trail, B.C., has been described in AIME Vol. 121, "The Electrolytic Zinc Plant of The Consolidated Mining and Smelting Company of Canada, Limited" by B. A. Stimmel, W. 11. Hannay and K. D. McBean. Since the publication of that paper, the use of oxygen enriched air in suspension roasting has been introduced as regular practice with marked advantage. The relative importance of a specific advantage may vary with changing conditions, but, in general, it may be stated that improved operation has been achieved at increased capacities. Suspension roasting is carried out at Trail in converted standard 25 ft diam Wedge roasters. The 2nd, 3rd, 4th and 5th roasting hearths have been removed and the drying hearth covered over. Drying of the concentrate is done on the drying hearth and the 1st roasting hearth. The dried concentrate, after any lump's have been broken up in a ball mill, is fed to a single burner located in the upper part of the combustion chamber. Oxygen is introduced at the burner fan along with the gases from drying, returned combustion gases from the waste heat boiler outlet and the required amount of new air. Up to 60 pct of the concentrate settles out on the 6th roasting hearth, the rest passilig out of the roaster. The product collected in the waste heat boiler is finished calcine, but the dust collected in the cyclones after the boilers is returned to the base of the combustion chamber where the sulphate is decomposed. Gases from the c'yclones go to a Cottrell precipitator. The discharges from the 7th roasting hearth and the waste heat boiler are combined with the Cottrell dust to give the finished calcine. Following small scale tests started in 1933, oxygen enriched air has been used continuously in the suspension roasting of zinc concentrate in Trail, beginning in 1937. A significant factor in promoting its use in this operation was the availability of by-product oxygen from the Company's near-by Chemical and Fertilizer Division. To-day it is standard practice at Trail to use oxygen enriched air for zinc concentrate roasting. The most important requirement in roasting a zinc concentrate for an electrolytic plant is that the zinc in the calcine should have maximum solubility. It is also desirable at Trail that the gas produced for the manufacture of suhhuric acid should have a ~naximum concentration of SO2 and that a substantial recovery of waste heat from the gas be achieved. High solubility of zinc requires that the sulphide sulphur and zinc ferrite in the calcine be kept low. These are both functions of temperature and time, with formation of zinc ferrite also dependent on contact between the iron and zinc particles. One of the inherent advantages of suspension roasting is that minimum time and contact are achieved. The limit on temperature is imposed by the fusion point of the concentrate and not by the need to control zinc ferrite formation. Operating temperatures are normally maintained within the limits of 1725" and 1850°F. A relatively low zinc sulphate in the calcine is required at Trail, and this results from discharging the calcine from the high sulphur dioxide atmosphere at a temperature above 1600°F.

Jan 1, 1950

Executive A R LEDUC, Chairman ARTHUR S DWIGHT R V NORRIS EDWIN LUDLOW E L DEGOLYER Membership J V W REYNDERS, Chairman E L DEGOLYER R M RAYMOND EDGAR RICKARD W Y WESTERVELT Finance WALTER H ALDRIDGE, Chairman GALEN H CLEVENGER J V W REYNDERS Library Chairman JOHN H JANEWAY GEORGE C STONES ROBERT LINTON ALEXANDER C HUMPHRLYS, - BRADLEY STOUGHTON

Jan 1, 1923

By Will H. Coghill

WITH gold at $35 for the last four years, almost double the old figure, and 'an unlimited market, there is perhaps more activity in the mining and milling of that metal than in that of any other of the widely distributed ores. Despite threats from Russia, the Rand district is still dominant. In South Africa in 1936, 48,200,000 tons of gold ore was crushed after sorting out about 10 per cent of that mined. The pounding of 5914 trusty stamps on the 60 mi. of Rand reefs is noteworthy. At the end of 1935, 466 tube mills were operating on the Rand, the popular size being 6 1/2 by 20 ft. The grinding medium normally consists of ore pebbles picked from the ore but recently a composite load of 3-in. steel balls and pebbles has found favor for added capacity, a ratio of 2.5 tons of pebbles to one ton of halls being maintained. The total ore fed to the mills is only about 0.14 ton per hp.-hr. Such a slow rate 'of feed cannot help but result in overgrinding. Ball mills, 9 by 8 ft., some of which have come from Canada, are now being tried. Stamps have been ousted from all new flow sheets, but the old stamp mills are continually renovated and kept on duty as they are at the Homestake in the United States. Half of the world's gold and silver ores is still crushed by stamps, a few of which are single, dropping in individual mortars.'

Jan 1, 1938

By Walter J. Johnson

The coals in northern Wyoming and Montana are free-burning and non-caking and range from lignite to bituminous C in rank. Strip and underground mining are employed to supply railroad, utility, industrial, and domestic fuel. The market area includes Iowa, Nebraska, Minnesota, North and South Dakotas, Wyoming, Montana, the Pacific Northwest, and western Canada.

Jan 12, 1953

By P. D. Southgate

VIBRATION, both ultrasonic and sonic, can affect the course of a variety of metallurgical processes. Reports of work on this subject have appeared at intervals over the last twenty years and a thorough review has been made by Hiedemann,' who gives a full list of references. It has been established that both refinement of structure and outgassing of the melt can be produced in most metals with sufficiently intense vibration. Many of the experiments in this field have been carried out using alloys of direct commercial interest in production- type casting equipment. Here a different approach is adopted, and simple binary alloys which exhibit different types of structure are used to facilitate examination of the effects produced under well-controlled conditions. Results from this kind of experiment should enable the basis of larger scale experiments with similar types of materials to be better substantiated. The alloys selected for this work are: 1) aluminum of 99.2 pct purity, the principal impurity being iron, near 0.4 pct; 2) A1-1.8 pct Fe, which is near eutectic composition; 3) A1-4 pct Fe—the second phase, of composition FeAl3, forms distinct acicular crystals; and 4) A1-12 pct Si—although this is of eutectic composition, the silicon normally appears in the form of large plates. Experimental Method There are three practicable methods by which acoustic vibration can be transferred to liquid metals: a) vibration of the whole of the container; b) electromagnetic induction; and c) insertion of a vibrating probe into the liquid. Method c is chosen here, and a frequency of 8 kc per sec is used. The end of the probe is electrically heated so that the metal near it will be the last to solidify. This ensures that vibration is transmitted directly to the liquid metal without passing through any solidifying and pasty intermediate region, which would attenuate acoustic waves severely. In addition, the heating prevents solid metal adhering to the probe, with consequent detuning. The transducer assembly is shown in Fig. 1. A stack of Permendur laminations 30 cm long acts as a half-wave vibrator and a winding along its length carries polarizing and energizing currents. It is joined by a half-wave coupling bar to a mild steel exponential horn, which tapers from 3.8 to 1.1 cm diam. A stainless steel stub 3 cm in length is welded on the free end. The assembly is supported by a plate located at the node of the coupling bar. Acoustic radiation losses are minimized by allowing the free end of the transducer to protrude above the surface of the cooling water. The exponential horn serves the function of matching the acoustic output impedance of the transducer to the radiation resistance of the probe into the melt. Electrical drive is provided by a 1 kw generator. Measurements of probe vibration amplitude during melt treatment are obtained from a gramophone pick-up with the needle attached to the wide end of the horn. This device is calibrated with a microscope before use. Liquid aluminum is very actively erosive and solution of materials with which the molten metal comes into contactcauses difficulties. Erosion of the probes in particular can be severe since it is greatly accelerated by the vibration. Tests of various acous-

Jan 1, 1958

ST. LOUIS LOCAL SECTION Executive Committee ARTHUR THACHER, Chairman R. A. BULL, Vice-Chairman WALTER E. MCCOURT, Secretary-Treasurer, Washington University, St. Louis, Mo. H. A. BUEHLER R. R.-S. PARSONS HERBERT A. WHEELER On the afternoon of May 1, 1915, 42 members of the St. Louis Section, as the guests of E. S. Catch, President, and his associates in the Granby Mining & Smelting Co., visited the new zinc smelter of that company at Roselake, Ill. The annual meeting, which was preceded by a dinner at the St. Louis Club, was attended by 54 members and guests. The Chairman, H. A. Wheeler, presided. The Chairman rendered a report on the activities of the Section during the past year and the Treasurer presented a financial report. The following Executive Committee was elected: Arthur Thacher, Chairman; R. A. Bull, Vice-Chairman; W. E. McCourt, Secre-tary-Treasurer; H. A. Buehler, R. R.. S.. Parsons. H. A. Wheeler, as retiring Chairman, retains membership in the committee. W. L. Saunders, President of the Institute, made an address. H. W. Gepp, of Australia, described the lead and zinc deposits of Broken Hill, Australia, and V. H. Hughes, of Tulsa, spoke on the geology of the Cushing oil pool, Oklahoma. WALTER E. MCCOURT, Secretary.

Jan 6, 1915

By R. Simon, D. J. Graue

This paper presents correlations for predicting the solu-lility, swelling and viscosity behavior of CO2-crude oil sys8i.m~. The correlations were developed from experimental data obtained by the authors. These data are also presented. The data were determined by measuring the properties of mixtures of CO, and nine different oils. Experiinental conditions covered a range of 100 to 250°F and pressures up to 2,300 psia. Properties predicted by the correlations have average deviations, expressed as per cent of experimental value, of 2 per cent for solubility, 0.5 per cent for swelling and 12 per cent for viscosity. INTRODUCTION Interest in CO2 injection as an oil recovery process has led to the development of performance prediction methods which can be applied to specific reservoirs.1 iS To use these performance prediction methods, it is necessary to know the solubility, swelling and viscosity properties of CO2-crude oil mixtures at reservoir conditions. Some information on these properties has appeared in the literature; however, this information did not cover the range of different oils and conditions needed to prepare generalized correlations for reservoir engineering purposes. Consequently, an experimental program was undertaken to collect the data needed. The data obtained and the correlations developed from the data are described in the following sections of this paper. SOLUBILITY OF CO2 IN CRUDE OILS CO2 solubility data in the literature come from six principal sources. The solubility prediction method of Welker and Dunlop3 is limited to 80F. The information in Ref. 4 is of two types: the first includes binary and ternary mixtures of CO, and light hydrocarbons (C1 to C6), and the second gives data for CO1 and heavy hydrocarbons for a temperature range of 40 to 90F. Ref. 5 contains a KCO2 chart for systems whose convergence pressure is 4,000 psia. The KCO2's are based mainly on CO2-natural gas mixtures. Poettmann's work covered CO2 solubility in one condensate and one crude oil6,7 Ja-coby and Rzasa measured CO? solubilities as a function of pressure and temperature for two natural gas-absorber oil mixtures and two natural gas-crude oil mixtures.'8 CO, concentration in these four systems was fixed at 5 mol per cent. The work reported in this paper extends CO, solubility data to a variety of different crude oil types in a temperature range from 110 to 250F and pressures up to 2,300 psia. The experimental procedure used by the authors to obtain the solubility data consisted of combining known amounts of pure CO, and crude oil in a visual cell at a fixed temperature and measuring the bubble point of the mixture. Measurements were made for a total of 40 different CO2-oil mixtures and the results are shown in Table 2. The mixtures included nine different oils (seven crude oils and two refined oils) whose properties are listed in Table 1. All nine oils had vapor pressures less than 1 atm at the experimental temperatures. Consequently, analysis of the bubble-point vapor showed a CO, concentration over 99 mol per cent. At no time during these experiments was a second, more dense, liquid phase observed. The solubility correlation which was developed from the data in Table 2 is presented in Figs. 1, 2 and 3. In these figures, solubility is expressed as xco2 the mol fraction of CO, in the CO2-oil mixture. Fig. 1 shows solubility as a function of CO2 fugacity6 and temperature. Fig. 2 shows the same solubility data expressed as a function of saturation pressure and temperature. The solubility shown in Figs. 1 and 2 is for an oil whose UOP characterization factor is 11.7. UOP characterization factors of crude oils can be determined from Ref. 10 if the viscosity and APT gravity of the oil are known. Fig. 3 gives the solubility correction factor for oils whose UOP characterization factors differ from 11.7. The solubility correlation in Figs. 1, 2 and 3 predicted

Jan 1, 1966

By D. C. Seidel, M. C. Fuerstenau, R. J. Roman

The role of surface charge in soluble salt flotation, which was developed in Part I, is extended to relate the theory to the specific phenomena of KCI-NaC1 separations. Temperature-collector solubility relationships, metal ion activation, and particle size effects are discussed. The initial paper in this series developed and presented the hypothesis that one of the mechanisms of soluble salt flotation may involve electrical attraction between the collector and mineral surface. This hypothesis was developed from a combination of experimental data and free energy calculations, and details of the logic are presented in this first paper.* The studies have indicated that KC1 has a positive surface charge and NaCl a negative charge. KC1 can therefore be floated with sulfonate ion (RSO;) or with an aqueous polar species such as the aqueous amine chloride, RNH3C1(,,). The chloride end of the RNH3C1(,,) molecular dipole is probably negative and will be attracted to the positive surface of the KC1 particles and absorb (actually probably fit into a vacant chloride site) on the mineral surface. The amine end of the collector molecule would extend into the solution phase and provide the air avid surface required for flotation. NaCl particles are floated by such collectors as aqueous molecules of fatty acid salt, RCOONa(,,), in which the positive inorganic end of the dipole is attracted to the negatively charged surface of the NaCl and, in this case, adsorb and probably fit into a vacant sodium site on the surface. The aminium cation, RNH~, should also be a collector for NaC1. For certain collectors, actual precipitates of the collector must be formed before a sufficient amount of the polar aqueous molecule is present to effect flotation. In a system of this type there is a three-way equilibrium between: Aqeous Molecular Solid Precipitate - A of the Collector (Not Dissociated) . Ionic Species (Dissociated). The controlling equilibrium is probably between the precipitated form of the reagent and the aqueous

Jan 1, 1969

By N. A. Zeigler

The present publication is a continuation of the work on gas analysis described in a paper presented before the Institute of Metals Division year ago.' While that paper was largely descriptive in character dealing with the various parts of the apparatus and method of operations the present one gives numerical data obtained as a result of a series c experiments with iron-carbon alloys. The apparatus and the method applied are essentially the same as previously described, changes bein only in minor details. Attention should be called to the fact that in the present work we ar dealing with the gaseous mixtures obtained as a result of vacuum meltin of various ferrous alloys. It should be understood that when the term "degasified sample" and "products of degasification" are used, the refer to the sample remaining after the vacuum fusion of the alloy an the gaseous products removed therefrom, respectively. The write does not wish to create the impression that the metallic products of thj process are absolutely free from any gaseous elements, nor that the gase obtained are present as such in the original sample. These two point are not yet definitely known and are subjects for future investigatior The point, however, which has been established beyond doubt, i that all the gases dealt with come from the metallic charge and ar present either in the charge as such, or are produced as a result of chemic: reactions going on within the charge. The suggestion that the gases an due to the reactions between the metallic charge and the refractor materials has no valid basis. General Procedure A series of iron-carbon alloys was prepared in a magnesia-line graphite crucible placed in a high frequency laboratory furnace open t the atmosphere. The materials used were Westinghouse electrolyti iron and Acheson graphite. Each alloy, after it was completely molter was kept in the liquid state for 10 min., cast into a small iron mold, an

Jan 1, 1929

By C. A. Heiland

A. INTRODUCTION (C. A. HEILAND) I. PRINCIPLES OF TEMPERATURE COMPENSATION IN MAGNETIC INSTRUMENTS The principle underlying the majority of magnetic intensity variom-eters is a comparison of the force to be measured with another force of known magnitude. The known force may be (a) of a magnetic nature, such as magnetic fields produced by magnets or coils, or (b) of a mechan-ical nature, such as (1) the elastic forces of wires, or (2) the force of gravity, such as employed in bifilar magnetometers and magnetic balances. In instruments of such type, usually a magnetic system is employed, free to move about either a horizontal or vertical axis, on some sort of a suspension. If the earth's magnetic field alone were present, such a system would adjust itself into the direction of the field or that of its components. Owing to the simultaneous action of the comparison force, however, the magnetic needle assumes a position that differs from the direction of the magnetic force; for all such instruments, the angle of deflection a is given by tan a = F/X, where F is the known and X the unknown earth magnetic force component. In other words, the magnetic system merely serves as an "indicator" for the position of balance of the two forces. Considering the matter from this point of view, it is not immediately obvious why the temperature of such a magnetic system should modify the results. In magnetic instruments, we may distinguish two different effects of temperature: (1) a magnetic effect and (2) a mechanical effect. The first is due to the fact that the magnetic moment of a magnet drops with an increase in temperature. This drop is characterized by the temperature coefficient of the magnetic moment µ (see equation 1). The second effect is due to the change in the .torsion of suspension wires with temperature or to the expansion of lever arms of masses acting on magnetic balances.

Jan 1, 1932

By J. J. Carrigan

IN all mining operations a considerable portion of the work performed, especially underground; is accomplished under artificial light, yeti this subject is often not given proper attention. Poor illumination decreases mining efficiency, impairs the sorting or grading of ores, and increases the risk of accidents. In the beginning, and for several years afterward in the metal-mining industry of Butte, Montana, candles placed in candlesticks were carried by the men. Sconces or holders for candles were also provided at stations and curves in drifts to furnish better light for men engaged in. hand tramming. It was also common practice to place clusters of candles on the ground, with no provision for guarding against an underground fire other than the exercise of sufficient care by the men themselves. An accumulation of candle grease from this source was the direct result of the first serious fire in the Anaconda mine, in 1889.

Jan 1, 1936

By Francis L. Bosqui

The following paper embodies a report which I made on the filter-press treatment of slimes at the Liberty Bell mine, Telluride, Colo. At the time this report was submitted, the management deemed it wiser to defer the installation of so costly a plant as the one required, in the hope that some of the many investigators in the field might soon evolve a cheaper and more perfect method of slimes-treatment, and one better suited to the conditions at Telluride. The Liberty Bell ore consists essentially of quartz and clay, with iron pyrites disseminated through the quartz in very fine particles. There is considerable iron and manganese stain in some of the ore, the latter especially in the clays, which are sometimes quite black. Occasionally particles of galena, zincblende, gray copper and a few other minerals are seen, but they are comparatively rare, and not in sufficient quantity to affect considerations of treatment. Free gold is occasionally seen in the quartz, and one or two instances of mire silver have been observed. The milling-plant consists of an 80-stamp amalgamating mill which crushes through 20-mesh screens; 20 Wilfley concentrating tables, taking out, in iron sulphides, about 2 per cent. of the total ore crushed; and a cyanide plant consisting of two tiers of 33 ft. vats, five in each tier, fed by revolving pipe-die tributers. The slimes overflow from the upper settling tanks through gates with adjustable outlets, and thence to a large canvas-plant, which efects only a small saving. This slimes product, of which about 100 tons escape per day (or 38 per cent. of the total ore crushed), contains about 3 per cent. of dry solids. Of this approximately 93 per cent. will pass a 200-mesh screen. The slimes range in value between $3.90 and $4.87 per ton, the values being about equally distributed between gold and silver. The actual averages for ore and slimes during the years 1900-

Jan 1, 1904

By Sixten Wollmar

A RESUME. of some important points regarding the life of drill steel, which have so far been learned from investigations carried out in the SKF Hofors' mines, Sweden, by L. Nordenfelt, is given below. By examining all fatigue breakages which occurred in the test it has bees conclusively proved that when a rock drill of the self-rotating type is used all break-ages of this kind start from the surface of the hole in the steel. It has further been proved that the rough hole surfaces (i.e., the marks left by the indentations of the sand core), are the starting points for the fatigue cracks and that the corrosive action of the water has .a very detrimental influence on the life of the steel. It is now a well known fact that this corrosive action concentrates at the bottom of the indentations left by the sand. The corrosive action of water has been well described by U. R. Evans in his paper, "Some Recent Work on the Corrosion of Metals," delivered on March 31, 1926, before the Liverpool Engineering Society, which is quoted in part below: "It is well known that, under ordinary conditions, most metals do not corrode in water unless dissolved oxygen is present. The strange feature of corrosion in submerged metals, however, is that the attack does not proceed mainly over those portions of the surface which could be reached readily by oxygen; deterioration takes place at certain points which are relatively, inaccessible to oxygen. When. a metal becomes pitted by corrosion, further attack usually deepens the pits, and in many cases it could be proved that there was no free oxygen at the bottom of the pits. None of the older theories of corrosion explain the fact that, although oxygen is necessary for rapid corrosion to take place, the attack actually occurs at the very points which could not be reached directly by oxygen.

Jan 6, 1928

By Frederick Laist

THE past year has witnessed no radical changes in methods for the reduction and refining of copper. The Carson litigation was finally brought to a close ant1 the copper smelter is again free to introduce charge into his reverberatory furnaces in whatever manner suits him best. This litigation naturally led to much experimentation with various methods of charging and with various types of bath. In some cases the charge was introduced more or less centrally on a relatively dry hearth and in other cases into a bath of greater or less depth. The results of these furnaces were meticulously compared with the results obtained in side-charger furnaces, and it was apparent that it made little, if any difference how a given furnace \\.as charged so long as care was taken that there was always something in the furnace for the flames to work on. So long as this requirement was complied with, consumption of fuel per ton of charge smelted and tonnage smelted per furnace day remained substantially the same regardless of the method of charging or the depth of bath employed. In some instances the center-charged deep-bath furnaces gave slightly better results than the side-charged particularly with respect to copper losses. The slags of the deep-bath furnaces are generally a little cleaner

Jan 1, 1930

By G. S. Brooks

DURING the past few years, the Mineral Point Zinc Co. has had under consideration the improvement of various types of gas-filtering apparatus used in the removal of dust from crushing and milling plants, in the manufacture of oxide, and on blast-furnace fume and sintering furnaces. The original equipment of the various plants of the company was, of course, along lines of the standard stationary bag house. These houses required large surfaces, hand shaking, and varied only in the manner of the collection of solids and in the distribution of the gas. Early in 1908, the first trial of a mechanical bag house was made at Nassau Plant at Depue, Ill. The duty of this installation was on dust-laden gas from a fine-crushing mill. The Printz and Rau bag machine was finally adopted and put into operation. This ingenious machine embodied what were then to us two novel features in bag-house practice: 1. An intermittent crinkling and snapping of the filtering fabric to free the meshes of solids. i 2. A reversal of gas flow for a short period by a temporary connection w th the suction trunk. This equipment worked fairly well except in cold weather, when we ran into condensation troubles. Had we at that time understood more fully some of the limitations of fabric filtering work, these might well have been remedied. We were impressed by this experience, however, with the efficiency of sudden tension on the fabric under suction. After a study had been made of some of the Western blast-furnace houses using the reversal-of-flow feature, experiments were started early in 1914 with a view to developing an automatic equipment along the best lines of our past experience. The objects sought were: 1. Keeping labor out of the houses for hygienic reasons. 2. Reduction of labor costs. 3. Reduction in -size of hag houses. 4. Accessibility. 5. Ability to handle relatively hot gases where required.

Jan 11, 1917