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By Victor deWolfe

INTRODUCTION The Henderson Mine, located near Empire, Colorado, utilizes a continuous panel caving system to extract ore as one of the world's major producers of molybdenum. Any mine using a caving-by-gravity technique of mining must rely on closely controlled draw of the caved ore. This control is essential to insure proper caving action, to avoid damaging load concentrations of weight and to minimize the dilution of ore with waste material. Henderson is no exception. Draw control is a major factor in all production planning, from long- range plans to short-range and day-to-day ore scheduling. Draw control is reviewed constantly and administered daily in an effort to optimize production efficiency, ore recovery, and cave management. MINING METHOD The cave at Henderson is massive, moving slowly through large panels that are 244 m (800 ft.) wide by 610 m (2,000 ft.) long. Generally two cave areas are drawn at one time. The areas under active draw vary in size but can be as large as 244 m (800 ft.) by 244 m (800 ft. ) containing 400 draw points. Each draw point contains 45,360 mt (50,000 st) on the average and takes about two and one half years to exhaust. A complete panel is worked for seven to ten years. No pillar exists between panels, but rather a buffer zone of broken ore, or "static face," is left in each panel to be drawn with the adjacent, yet-to-be-caved panel in efforts of minimizing dilution of a working area from an exhausted one. (Figure 1) Production drifts are driven on 24.4 m (80 ft.) centers through the ore body. Between the production drifts are funnel-shaped draw bells on 12.2 m (40 ft.) x 24.4 m (80 ft.) centers to receive ore from the cave. Each bell is accessed by two draw points, one from the production drift on either side, thus forming a 12.2 m (40 ft.) x 12.2 m (40 ft.) draw pattern. Extraction of the ore is by rubber-tired, 3.8 m3 (5 yd3) load-haul-dump equipment. The LHDs then tram the ore a maximum of 49 m (160 ft.) to ore passes. Cave initiation and bell development are done from the undercut drifts which are parallel to and 17 m (55 ft.) directly above the production drifts. Longhole rings are drilled and blasted from the undercut drifts to define the bells and establish the undercut for caving. (Figure 2) DRAW CONTROL Since the cave line at Henderson is constantly advancing, it is necessary to be continually initiating new cave at one end while exhausting it at the opposite end. There must exist, therefore, an angle on the ore-waste contact in the broken rock from initiation to exhaustion. The basic concept of draw control is to keep this angle as smooth and even as possible, particularly at the time of exhaustion. If this is achieved, draw points are exhausted more or less in a line, avoiding pockets of remaining ore surrounded by exhausted areas. These pockets would cause spotty ore extraction at the time of exhaustion, increasing the amount of dilution occurring while introducing the potential for significant weight problems in the production area. To arrive at the desired angle on the ore- waste contact, maximum tonnage percentages are assigned to each row of draw points increasing at 10% or 15% increments (depending on cave size and velocity of draw) working away from the cave line. The available tonnage indicated by these percentages is the maximum allowable tonnage to be extracted from each draw point until the available tonnage percent- age is increased. As the cave moves, these percentages increase for each draw point regularly. However, in general the tonnage drawn from each draw point is kept at about 50% of this allowable maximum in order to maintain adequate available tonnage in the cave to sustain production for seven months if cave initiation were to cease. This available tonnage cushion is a safeguard built into the draw control program at Henderson to accommodate fluctuations in the rate of cave advance. When draw points move past the row of 100% tonnage availability, they are drawn past the desired 50% at the same increments per row until exhausted. (Figure 3) To achieve proper draw control, the number of LHD buckets to be taken from each draw point is assigned daily. The actual buckets taken, which may at times deviate from the

Jan 1, 1981

By J. B. Morrow, D. H. Davis

THERE are two general approaches to the problem of increasing profits from an operation. One is to lower expense; the other is to raise income. Mechanical preparation of coal may be used for either purpose but a prudent consideration of many details must precede any decision lest the results be negative instead of positive. It is quite possible that any net gain will result from a combination of the two. Since mechanically prepared coal invariably is a better product qualitatively than a hand-picked coal from the same mine, it is a reason¬able expectation that the customer will be willing to increase the pro¬ducer's income by paying a higher price. Or there may be the possibility that a combination of mechanical mining plus mechanical cleaning will give a lower over-all production cost for the coal in the railroad car. More likely, there will be found a combination of these two factors. From the customer's point of view, the competitive delivered cost per B.t.u. considered in relation to such incidental factors as dust nuisance, handling properties, ash disposal, and ash fusibility determines what he will pay. In a bulk tonnage product such as coal, freight is a very considerable part of the delivered fuel cost, and obviously freight paid on incombustible ash has no economic attractions.

Jan 1, 1943

By P. K. Chatterjee

The overall success of many strip coal mining operations depends primarily upon the efficient use of draglines to remove overburden. These machines require enormous capital investment and unless used efficiently the profitability of a venture is adversely affected. It is important that the dragline works continuously and it is imperative that the walking path and other facets of its operation be predetermined exactly so that the desired production rate is achieved with a minimum of non-productive time. Details of dragline operations which are of particular interest are walking path, prediction of best cut and positioning to maximize production, the angle of swing which produces the swiftest operation, optimum fill factor allowable for the type of material and conditions of ground, the maximum depth from which it can excavate and operating level with respect to the elevation of the high wall. The aims of the present paper are: 1. To establish a cut-off point in the cost-depth ratio. 2. Predict the most economic method of stripping in a given area using graphical plots of walking path implemented with information necessary to ensure optimum production. The optimum operating efficiency of the dragline in relation to the terrain and other conditions imposed on its operation will be evaluated. The model is based upon operating data which has been collected from site observations of a large strip coal mining operation in Central Queensland, Australia.

Jan 1, 1977

By Stanley Gill

The apparatus is composed of sections of small diameter, seamless steel tubing welded into a continuous flexible tube. At the bottom end a 1/4-in. pipe nipple with a 10 to 15-lb. weight is attached, together with a registering thermometer and a pair of ball check valves. The entire length of tubing is coiled in a single layer upon a drum 4 ft. in diameter which can be attached to the platform of a truck and provided with devices for winding and unwinding the tubing. Connections are made with the upper end of the tubing through a stuffing box, thence to a gas manifold to which a pressure gage is connected. Hydrogen gas is carried in standard 2-ft. cylinders and readings are taken by admitting gas into the tubing from one (or both) of the hydrogen cylinders until the pressure has been built up above that to be measured. At this time the gas supply is cut off. Excess gas escapes through the open end of the tubing and when equilibrium is reached, the pressure is read at the surface gage. Corrections are made for the weight of the column of gas. The advantages claimed for the apparatus include accuracy and the ability to measure the pressures at any number of points without removing the gage. Among the disadvantages of the apparatus are the somewhat bulky size of the equipment and its relatively high initial cost.

Jan 1, 1933

By Nathaniel Herz

IN the operation of any ore processing plant, no matter what beneficiation process or combination of processes may be used, certain fundamental figures are regularly needed for essential records and accounting. These include amounts of ore treated and products made, with their assays, as well as quantities of labor and supplies used, with their cost. Usually labor and supplies are broken down and allocated to certain operations by the accounting department, and resulting tabulations are available for study by the milling plant management. However, to avoid too many minor details that would make these reports cumbersome and involved, much information that could be useful to the plant operator is often consolidated in such a manner as to have lost a considerable part of its value. To clarify this point, it may be stated that top management is most concerned with production figures and cost of production, while the plant operator is also interested in quantities of labor in man- hours and amounts of supplies used. Due to varying unit prices of labor and supplies, comparisons on a dollar basis alone are often misleading. With rising unit costs of the past few years now about twice as high as they were a few years ago, constant study of quantities involved is required to improve efficiency and productivity.

Jan 6, 1957

By John Hays Hammond

This is an era of " expansion; and, conformably with the change in commercial conditions, the function of the mining engineer, as well as that of his confreres in many other professions, has also expanded. From the position of an engineer, limited to the determination of technical questions, the engineer of to-day has come to assume an economic importance in those branches of industry dependent upon engineering skill for their development. He is indeed an engineer of limited usefulness who does not go further professionally than to submit a purely technical report on subjects presented for his consideration. While he has the same responsibility as formerly in the solution of the technical problems involved, he is further expected to supplement his report with advice on the financial and commercial aspects of these problems. For the great majority of problems presented to the engineer ultimately involve the determination of the pecuniary, relations of the propositions under consideration. The great corporation lawyer no longer earns his fee by merely submitting his opinion as to the legal issues involved in law-suits affecting the corporation; he now assumes charge of the entire legal work, including both the organization of the corporation and the maintenance of its legal status thereafter. In like manner, the engineer, whose report was, as I have said, formerly confined to the determination of the geological and other cognate features of a mining enterprise, is now expected, not. only to embody information on these subjects in his report, but also to give his opinion whether the property offered for sale in pursuance of such an enterprise is worth the price asked for it. Moreover, if he recommends the purchase of a property, he incurs a certain moral responsibility for its efficient manage-

Nov 1, 1908

By C. E. Lesher

THIS paper reports a study of the reactivity of 950°F and 1650°F cokes as measured by relative rates of reduction of iron oxides at temperatures up to 2200°F. Previous work cited shows general acceptance of the theory that reduction by carbon is a gaseous reaction, and that kind and character of carbon as well as particle size have measurable effect on the velocity of reaction. As will be shown, the data obtained in this study confirm those conclusions. The work was not designed to examine iron oxide reduction equilibrium, but if reaction velocity be defined as the speed with which "a reaction tends to approach conditions of equilibrium," the data here presented may be considered as a study of reaction rates, and the relative degree of reduction to metallic iron as the measure of reactivity. Three standardized combinations of Lake Superior brown iron ore with carbon were tested by similar procedures. One combination was a mechanical mixture of carefully sized high-temperature coke (1650°F) with the ore. The second was a mechanical mixture of the ore with Disco* obtained by carbonizing the identical coal at 950 °F. The third was an agglomerate prepared by carbonizing the coal and ore at 950°F, premixed in proportions to give as nearly as possible the same relative amounts of carbon and ore as the mechanical mixtures. This agglomerate, obtained by heating the finely divided ore (through 30 mesh) with coking coal through the plastic temperature range so as to form solid aggregates, gives a product in which the oxide particles are impregnated with, and intimately bound together with low-temperature coke. The agglomerate-—ore-Disco—was most active in oxide reduction; the mechanical mixtures of Disco and ore next in order, with coke the least reactive. General Discussion: Carbon exists in many forms and it is well known that the form or nature of the carbon used in reduction of oxides is related to the critical temperature of reduction. Sugar carbon, charcoal, and lampblack are forms of carbon that will reduce oxides at lower temperatures than high-temperature coke, and coke will, in turn, give a lower critical reduction temperature than graphite. There have been many investigations of this characteristic of carbons. Johnson' reported a difference of 130°F (70°C) in the critical reduction temperature of zinc oxide as between charcoal 1891 °F (1033°C) and Acheson graphite turnings 2021°F (1105°C) with zinc oxide. Bodenstein2 using charcoal and coke, found a difference of 138°F (77°C) comparing an experimental figure of 2066°F (1130°C) for coke and 1928°F (1053°C) for charcoal, in the reduction of zinc oxide. He concluded that this is very marked and observed that the "type of carbon merely raises or lowers the temperature at which rapid reaction takes place." Comparing the effectiveness of types of carbon in reduction of zinc oxide, it was found that a "brown coal coke" gave 97 pct zinc elimination at 1832°F (1000°C), as compared with 48 pct with "hard coal coke."' A wide range of metallic oxides was studied by Tammann and Sworykin,4 who found that the temperature at which decomposition of oxides begins depends on the nature of the carbon used. Carbon in the form of graphite, lampblack, and sugar carbon was investigated. Sugar charcoal will reduce Fe2O3 to Fe3O4 at 842°F (450°C) as compared with 1112°F (600°C) for coke, according to Meyer." Direct reduction of iron oxides by charcoal begins at 1382°F (750°C), but "first becomes intense" at 1652°F (900°C), whereas with coke, direct reduction begins at 1742°F (950°C), and "first becomes appreciable" at 2012°F (1100°C).6 he total reduction of the sample under certain conditions when heated in a current of CO with charcoal was about 100 pct for limonite and about 77 pct for magnetite. Using coke under the same conditions, the respective percentages were 75 and 47. In a study of processes for sponge iron7 by the Bureau of Mines, the conclusion was reached that a low-temperature char from noncoking subbituminous coal is the most satisfactory solid reducing agent. In a critical study of zinc smelting from a theoretical viewpoint Maier8 concluded that the reduction is by CO, that the reaction between ZnO and CO is intrinsically more rapid than the subsequent reduction of CO2 by C, which is limited by diffusion rates, which in part effectively limits the smelting process. Maier said that the operation is improved with the activity of the reducing carbon. An active carbon, he said, is one maintaining a low CO, content in the retort. Reactivity of Carbon: One form of carbon is more potent in reducing oxides than another. A carbon that reacts faster than another at a given temperature is said to be more reactive. Reactivity is measured by several methods, using carbon dioxide, air, or steam as reactants.9 ebastian and Mayers" have developed a method for the determination of absolute reaction rates between coke and oxygen by a study of ignition points under certain conditions. These and other investigators have established the relative reactivity of types of carbon. Lignite, charcoal, bituminous coal, cokes in the ascending order

Jan 1, 1951

By C. E. Lesher

THIS paper reports a study of the reactivity of 950°F and 1650°F cokes as measured by relative rates of reduction of iron oxides at temperatures up to 2200°F. Previous work cited shows general acceptance of the theory that reduction by carbon is a gaseous reaction, and that kind and character of carbon as well as particle size have measurable effect on the velocity of reaction. As will be shown, the data obtained in this study confirm those conclusions. The work was not designed to examine iron oxide reduction equilibrium, but if reaction velocity be defined as the speed with which "a reaction tends to approach conditions of equilibrium," the data here presented may be considered as a study of reaction rates, and the relative degree of reduction to metallic iron as the measure of reactivity. Three standardized combinations of Lake Superior brown iron ore with carbon were tested by similar procedures. One combination was a mechanical mixture of carefully sized high-temperature coke (1650°F) with the ore. The second was a mechanical mixture of the ore with Disco* obtained by carbonizing the identical coal at 950 °F. The third was an agglomerate prepared by carbonizing the coal and ore at 950°F, premixed in proportions to give as nearly as possible the same relative amounts of carbon and ore as the mechanical mixtures. This agglomerate, obtained by heating the finely divided ore (through 30 mesh) with coking coal through the plastic temperature range so as to form solid aggregates, gives a product in which the oxide particles are impregnated with, and intimately bound together with low-temperature coke. The agglomerate-—ore-Disco—was most active in oxide reduction; the mechanical mixtures of Disco and ore next in order, with coke the least reactive. General Discussion: Carbon exists in many forms and it is well known that the form or nature of the carbon used in reduction of oxides is related to the critical temperature of reduction. Sugar carbon, charcoal, and lampblack are forms of carbon that will reduce oxides at lower temperatures than high-temperature coke, and coke will, in turn, give a lower critical reduction temperature than graphite. There have been many investigations of this characteristic of carbons. Johnson' reported a difference of 130°F (70°C) in the critical reduction temperature of zinc oxide as between charcoal 1891 °F (1033°C) and Acheson graphite turnings 2021°F (1105°C) with zinc oxide. Bodenstein2 using charcoal and coke, found a difference of 138°F (77°C) comparing an experimental figure of 2066°F (1130°C) for coke and 1928°F (1053°C) for charcoal, in the reduction of zinc oxide. He concluded that this is very marked and observed that the "type of carbon merely raises or lowers the temperature at which rapid reaction takes place." Comparing the effectiveness of types of carbon in reduction of zinc oxide, it was found that a "brown coal coke" gave 97 pct zinc elimination at 1832°F (1000°C), as compared with 48 pct with "hard coal coke."' A wide range of metallic oxides was studied by Tammann and Sworykin,4 who found that the temperature at which decomposition of oxides begins depends on the nature of the carbon used. Carbon in the form of graphite, lampblack, and sugar carbon was investigated. Sugar charcoal will reduce Fe2O3 to Fe3O4 at 842°F (450°C) as compared with 1112°F (600°C) for coke, according to Meyer." Direct reduction of iron oxides by charcoal begins at 1382°F (750°C), but "first becomes intense" at 1652°F (900°C), whereas with coke, direct reduction begins at 1742°F (950°C), and "first becomes appreciable" at 2012°F (1100°C).6 he total reduction of the sample under certain conditions when heated in a current of CO with charcoal was about 100 pct for limonite and about 77 pct for magnetite. Using coke under the same conditions, the respective percentages were 75 and 47. In a study of processes for sponge iron7 by the Bureau of Mines, the conclusion was reached that a low-temperature char from noncoking subbituminous coal is the most satisfactory solid reducing agent. In a critical study of zinc smelting from a theoretical viewpoint Maier8 concluded that the reduction is by CO, that the reaction between ZnO and CO is intrinsically more rapid than the subsequent reduction of CO2 by C, which is limited by diffusion rates, which in part effectively limits the smelting process. Maier said that the operation is improved with the activity of the reducing carbon. An active carbon, he said, is one maintaining a low CO, content in the retort. Reactivity of Carbon: One form of carbon is more potent in reducing oxides than another. A carbon that reacts faster than another at a given temperature is said to be more reactive. Reactivity is measured by several methods, using carbon dioxide, air, or steam as reactants.9 ebastian and Mayers" have developed a method for the determination of absolute reaction rates between coke and oxygen by a study of ignition points under certain conditions. These and other investigators have established the relative reactivity of types of carbon. Lignite, charcoal, bituminous coal, cokes in the ascending order

Jan 1, 1951

By E. H. Erwin Gartner

The Rhenish lignite deposit in the Nordrhein-Westphalia province of the German Federal Republic covers an area on the left bank of the Rhine River of about 970 sq miles (Fig. 1). Here, in the Miocene era, some 20 million years ago a lignite seam was formed and later broken, through tectonic movements into several blocks, some thrown down into depths of over 1,500 ft. This deposit consists of a single seam, in places up to 300 ft thick, but averaging about 150 ft. In a few areas, it is split into as many as five seams, separated by barren strata. It contains about 60 billion tons (2000 lb/short ton) of lignite which, however, being relatively young geologically, has, because of approximately 60% moisture, 2 to 8% ash, and low sulfur, a net calorific value of 3,340 Btu. That calorific value increases, however, with rising thickness of the cap rock. About one-third of the yearly production of 90 to 100 million tons of raw lignites is converted into briquets. Raw lignite is pulverized and dried to about 18% water content and then pressed without binder into briquets under a pressure of about 14,000 psi. The briquets are being used primarily for residential heating; their sales, however, have been declining sharply since 1963. On the other hand, the volume of raw lignite used in steam power plants has been rising steadily and amounts at present (1968) to about two-thirds of the total production. Huge steam power plants, such as Frimmersdorf, shown in Fig. 2 (which, with an installed capacity of 2,600 MW [megawatt], represents the world's largest steam power plant) with a generating capacity of up to 300 MW per unit and a total installed capacity of over 6,000 MW, contribute about 26% of the total electric power production of the German Federal Republic.

Jan 1, 1969

By Stanly A. Easton

SEVEN years ago there was installed in the hospital of the Bunker Hill & Sullivan Mining & Concentrating Co. at Kellogg, Idaho, an ultra-violet ray quartz lamp, the standard equipment which is found everywhere in the offices of physicians and among usual hospital equipment. The use of this lamp was con- fined largely to treatment of pathological cases, still treatment of under-nourished children, run-down anemic people, both men and women, and, as a general tonic, was part of the routine hospital procedure. At the latitude of the Ceur d'Alene district and especially because of the position of the towns in deep canyons, with much overcast and cloudy weather, sunshine is not plentiful at any time of the year; for many of the winter months there is scarcely any. Underground workers, particularly during the winter, have little sun- shine; it is not unusual to have none at all for weeks at a time. Treatment by the ultra-violet ray lamp in the hospital has resulted in many extraordinary benefits but the use of the lamp is expensive and limited. Some weeks ago attention was directed to the automatic solarium equipment of the Burdick Corporation. The doctors strongly recommended the increased use of the ultra-violet lamp for its curative powers and tonic effects, urging that it be made accessible to all employees. Real interest was . . also displayed by employees with the possibility of securing ultra-violet ray treatment for themselves and families under better conditions than it was possible to have by the limited use of the lamp at the hospital. This resulted in the installation of the so-called sun room or automatic solarium as an adjunct to the mine change-house. An annex was built to the change-house, with dressing rooms for women, children and men from other departments, and the outfit put into use on Sept. 5, 1929. The installation consists of an escalator, or

Jan 1, 1929

By O. Skiredj, J. F. Elliott

It has been necessary to collate the available data on the solubility of graphite in Fe-Si-Mn alloys for a study of slag-metal equilibria in ferromanganese production. That study will be reported later; the collation is reported here. The carbon content of graphite-saturated liquid iron above 1153ºC by Chipman and co-workers1 is: %C= 1.34 + 2.54 x 10~3t(°C) [l] For graphite-saturated manganese above 1322ºC it is: %C = 2.68 + 3.52 x 1CT3 t(°C) [2]

Jan 1, 1963

By Worthen Bradley

A BETTER understanding of what is happening in the domestic quicksilver industry, and what is likely to happen, can be had after reviewing some of the highlights of the past four years. Hitting the high spots in chronological order, they are: February 1939-Army and Navy Munitions Board starts investigation on civilian and war needs of certain "strategic materials," including quicksilver, with a view to recommending stock piles. Every known producer is canvassed by the end of the year.

Jan 1, 1942

By Rossiter W. Raymond

(Chattanooga Meeting, October, INS.) THE formal outline of Mr. Hague's life and work is embraced in the following statement, chiefly based upon data furnished by him, at my request, shortly before his death. At that time the probability that I would survive to record his death was apparently small; but I urged upon him the duty of providing, whether for me or for my successor as Secretary of the Institute, trustworthy material for the notice which somebody would some day have to write-and which might otherwise be incomplete or incorrect. Mr. Hague, with characteristic promptness and freedom from affectation, did what I asked of him; and I am therefore . able to present an authoritative sketch-concerning the details of which I shall add my own comments, and some particulars obtained from others of his personal friends. James Duncan Hague was born Feb..24, 1836, at Boston, Mass., where his father, Rev. William Hague, D.D., an eminent clergyman, then resided. After a preliminary, education in private. schools, be studied in 1854 at the, Lawrence Scientific School of Harvard University; in 1855 and 1856 at the University of Göttingen, Hanover; and from 1856 to 1858 at the Royal Mining Academy of Freiberg, Saxony. In 1859-1861 he was attached as chemist to a South Sea exploring expedition, sent by W. H. Webb, of New York, to examine Jarvis, Baker, and other islands for phosphate-deposits. After the outbreak of the Civil War, he entered the U. S. Navy, serving for a year as Judge Advocate to the fleet stationed at Port Royal, S. C. In 1863 he became Superintendent of the Albany and Boston copper-mine, in the Lake Superior region, where he was also connected with the earliest development of the Calumet and Hecla property. In 1867 he became the First Assistant Geologist in Clarence King's famous Exploration of

Feb 1, 1909

By AIME AIME

ON March 14, the University of Tulsa was accepted as a member of the North Central Association of Colleges, which ranks Tulsa among the leading universities of the country. A. G. OIiphant recently donated to the new school of petroleum engineering a splendid collection of books on geology, valued at $25,000. Waite Phillips, an oil producer and chairman of directors of The Independent Oil & Gas Co., donated $150,000 for a petroleum engineering building

Jan 1, 1929

By K. D. Jacob

ALL types of commercial phosphate rock produced throughout the world contain fluorine in quantities ranging from approximately 0.4 to 1.3 per cent in the Curacao and Christmas Island phosphates to 3.1 to 4.2 per cent in the phosphates of the United States and North Africa1. For a given type of rock, the fluorine content is usually roughly propor-tional to the phosphorus content. SIGNIFICANCE OF FLUORINE IN PHOSPHATE ROCK On the basis of chemical and X-ray diffraction studies, Hendricks and co-workers2 concluded that fluorapatite, Ca10F2(P04)6, is the essential phosphatic constituent of the commercial types of domestic phosphate rock. On the other hand, Bredig and co-workers3 have recently advanced the opinion, also based on X-ray diffraction studies, that the mineral phosphates usually contain carbon dioxide in the apatite lattice, and that the phosphate rocks of. the United States are really fluorcarbonate apatites. However, the domestic types of phosphate rock do not seem to differ greatly from coarsely crystalline fluorapatite in their behavior toward chemical reagents in general, and for the purpose of this paper it will suffice to consider fluorapatite as being the essential phosphatic constituent of these types of rock.

Jan 1, 1936

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

(Under this heading will be published notes sent to the Secretary of the Institute by members or other persons introduced by members.) Mining Engineer. Graduate of Colorado School of Mines, 1912, experienced in coal, lead manganese and limestone mining, wishes execu¬tive position. A-2146. Graduate Mining Engineer.-Discharged, reserve officer, age 32, single, 7 years' experience holding responsible executive positions, in iron, copper, and talc mining. Well recommended. A-4913. Mine Manager, Superintendent or Engineer. Age 41, graduate of Michigan College of Mines; 20 years' experience in responsible positions in connection with large operations; in iron, copper, pyrites, lead and zinc mines; successful in finding and developing orebodies, increasing production, and reducing costs. Desires a position with a future. A-4081. Mining Engineer.-Graduate from Polytechnicum, Stockholm; 14 years' practical experience in Sweden, United States, Belgium, and Spain, in iron-ore development, mining, and milling; thorough knowledge of English, French and Spanish; desires position as superintendent or assistant manager. Good references; member; now in Sweden. A-4914. Research Engineer. Now in Chile on the erection of a 50-ton mill with modern machinery for the treatment of Chilean nitrate. Desires connection from the first of next year; with firm operating in South or Central America. A-4915. Metallurgical Engineer. Junior member, age 26, single, graduate Columbia School of Mines; recently discharged as lieutenant in the heavy artillery. A-4916. General Superintendent. Technical graduate, age 35, desires position over a group of four or five mines or as assistant general superintendent for a large. company. Has had experience in superintending mines, construction work, opening new and abandoned mines, safety and effi-ciency engineering and handling organized labor. At present employed by a coal company in the middle West. A-4917.

Jan 11, 1919

By W. H. Bassett

W H. BASSETT was elected first vice-president at . the executive session of the new Board on Tues- day afternoon. Karl Eilers, H. Foster Bain, Thomas T. Read, and H. A. Maloney were respectively re-elected as treasurer, secretary, assistant secretary and assistant treasurer. The new Executive Committee will consist of W. H. Bassett, Chairman, and Richard Peters, Jr., H. C. Bellinger, E. De Golyer, Edgar Rickard. The Finance Committee will be J. V. W. Reynders, Chair- man, Henry Krumb and H. G. Moulton. George D. Barron was reappointed Chairman of the Admissions Committee, and F. Julius Fohs put in charge of the Papers and Publications Committee.

Jan 1, 1929

By Edwin Hopkins

THE year 1923 started a few days after the Venezuelan Oil Concessions, Ltd., discovered a 140,000-bbl. well at. La Rosa and a well of between 2500 and 5000 bbl. at La Paz, on the opposite side of Lake Maracaibo. These nearly simultaneous events changed, overnight, the general aspect of oil affairs in Venezuela. Up to that time, big things had been expected by the companies then in the district, but many major companies had shown little interest in the country. Within a few weeks the Pure Oil. Co. and the Gulf Oil Corpn. entered the field and acquired large properties. The Texas Co. purchased several concessions and the Standard of California, Atlantic Refining Co., and Mexican Petroleum Co. established offices. Representatives of many other companies visited the district during the first few months of the year. The sudden influx of buyers naturally caused a great rise in prices and this, together with overproduction in the United States, doubtless caused the slowing up of concession transfers in the latter part of the year. The following property transfers occurred: (1) The Gulf Oil Corpn. contract with the Maracaibo Oil Exploration Corpn., whereby the Gulf acquired the right to select 100,000 acres from the Maracaibo's zones. (2) The Gulf Co. purchase of one-quarter interest in seven concessions of the New England Oil Corpn., Ltd. (3) The Gulf Oil Corpn. purchase of several concessions of Kunhardt and others in the Perija district. (4) The Gulf Oil Corpn. purchase of certain portions of the one-kilometer Lake zone that were not covered by parcels or Government reserves (namely the "sobrantes"). (5) Pure Oil Co. purchase of all Government reserves turned back by Maracaibo Oil Exploration Corpn. in the districts of Mara and Miranda. (6) Standard Oil Co.: of New Jersey deal with the British Controlled Oilfields, Ltd., for control of approxi-mately the eastern third of the .district of Buchivacoa, state of Falcon. (7) Royal Dutch deal with the British Controlled Oilfields, Ltd., for the control of the central third of the district of Buchivacoa, Falcon. (8) The Texas Co. purchase of several concessions in Perija and one west of Mene Grande on the east side of Lake Maracaibo. (9) Purchase by the British Equatorial Oil Co., Ltd., of Goverment reserves corresponding to certain Creole Syndicate parcels under the margin of Lake Maracaibo near La Paz. (10) The Lago Petroleum Co. acquired a concession on all of Lake Maracaibo except a 1-Km. strip along the shore.

Jan 3, 1924

By Enrique Hauser

FIRE-DAMP is a mixture of methane with other inert gases or combustible gases. The inert gases in question are carbonic acid, water vapor, nitrogen, etc. The combustible gases are hydrogen, ethane, etc. The study of the properties of fire-damp, therefore, becomes a study of the properties of methane and the influence on its properties of the different gases we have mentioned. Characteristic Properties of Methane 1. Respirability.-Methane being a paraffin is characterized by its weak chemical affinities. From the physiological, point of view one could substitute it for nitrogen of the air at least momentarily, without experiencing any difficulty in breathing the mixture consisting of 21 per cent. 02 + 79 per cent. CH4. I .have tried this on myself, making the gas exhaled -from the lungs burn subsequently in a Bunsen burner.1 From the chemical point of view, this weak affinity permits the gas to be burned in certain circumstances with hydrogen and oxide of carbon in an oxygenated mixture, with the result that the last two gases achieve only a fractional combustion. This practice has been utilized with success in the methods of analysis which I have perfected and which I describe later in this paper. 2. Retardation of Flashing Point.-A characteristic property of methane is its retardation of flashing point, noted by Davy in 1816 and studied by Mallard and Le Chatelier in 1883.2 Taffanel and Le Floch have recently confirmed these results.3 Let us recall the nature of this retardation:

Jan 2, 1916