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By W. T. Turrall, D. Porter

The paper describes a machine developed for the purpose of concentrating clear optical grade fluorspar crystal from a feed material containing less than 1 pct impurities. The principle of concentration is based on the fact that in a liquid having an index of refraction equal to that of fluorite (n — 1.434) clear crystals are invisible, whereas crystals containing occluded impurities absorb a part of the light. As the crystals pass through a light beam, undesired crystals give themselves away by creating a shadow on a photoelectric receiver. .The shadow is converted by the photoelectric cell into an electric pulse. An electronic circuit amplifies this pulse and commands the operation of a mechanical concentrator. Hp HE crystal laboratory, Dept. of Physics, Massa--*- chusetts lnstitute of Technology, was confronted with the problem of obtaining a supply of optical grade calcium fluoride (CaF,) for use in growing synthetic CaF, crystals. A search of the known fluorspar deposits did not indicate that any quantity of optical spar could be obtained. Even the best material had to be sorted by hand to remove impurities. The process for growing CaF, crystals developed by Professor D. C. Stockbarger of the Dept. of Physics, M.I.T., necessitates very pure feed materials. Exclusion of impurities is required, even in amounts detectable only spectrographically. The impurities occurred as minute inclusions of SiO,, BaSO,, CaCO,, FeS2, water or air. Crystals up to 4 in. in diam and weighing several pounds are made by the Harshaw Chemical Co. in Cleveland. Since the time required to grow a 4-in. crystal is about one week, and since the cost of manufacture is high, removal of impurities by any concentration method appeared practical. The mineral engineering section of the Dept. of Metallurgy undertook to investigate the possibility of concentrating clear optical fluorspar, —4 mesh + 10 mesh, from a feed containing over 99 pct CaF,. Various innovations of the known methods of concentration were considered, but in each case the minute amount of impurities associated with the crystal produced such extremely small differences

Jan 1, 1953

By Yongxiang Yang, Yanping Xiao, Robert G. Harskamp

"Stricter environmental regulations demand for safer treatment and disposal of incineratior fly ashes. So far no sound technology and processes are available for a sustainable and ecological treatment of the waste incineration ashes, and only partial treatment is practised for temporary and short-term solutions. New processes and technology need to be developed for comprehensive utilization and detoxification of the MSW (Municipal Solid Waste) incinerator residues. The objective of the current research is to better understand the behaviour of the environmental harmful elements during low or high temperature treatment, and to find an optimum route for an efficient processing of the incineration fly ash. In the present study, the fly ashes including boiler ash and ESP (Electrostatic Precipitator) ash sampled from a MSW incinerator were washed with warm water, and the residues were dried and sintered or vitrified at high temperatures. The solutions from ash washing were analysed, and will be treated for salt extraction and purification. The ash residues before and after thermal treatment were also analysed. The results of vitrification and thermal behaviour were compared with those from the ashes without pre-washing. It was found that water pre-washing is an efficient way to remove certain water-dissolvable volatile salts such as chlorides, and thus the secondary emissions during vitrification could be reduced. INTRODUCTION The air pollution control residues from MSW incineration are classified as harzardous waste, including boiler ash, ESP ash and filter cake. The boiler ash is the firstly settled flue dust in the dust-collecting equipment under the boiler, the ESP ash is collected by an electrostatic precipitator in the second step, finally the flue-gas is further cleaned by the wet-scrubbers and residues are accumulated in the filter cake. Both the boiler ash and ESP ash are classified as hazardous materials, harmful to the environment due to the high concentrations of environmental hazardous elements. However, due to the different locations of the ash collection, the boiler ash has different compositions compared to the ESP ash, and is considered less toxic. Fly ash is generally toxic and with low bulk density, and has to be treated before final disposal. The current industrial practice is normally the landfilling after partial detoxification such as cement solidification."

Jan 1, 2008

S. F. EMMONS, Washington, D. C.: Papers of Collins, Vogt, DeLaunay, etc.-Mr. Collins tells us about facts in the veins of Cornwall that suggest secondary sulphide-enrichment is highly interesting; and I am free to confess that I have not studied the literature of that region as fully as I should have done. Nevertheless, even if it had been as familiar to me as it is to Mr. Collins, I should probably have hesitated to draw theoretical conclusions without having seen the mines myself; for the personal equation and the point of view of the observer play, perhaps, a larger part in the study of ore-deposits than in that of any other natural phenomena. One important purpose of my paper, and its publication at the time of the Washington meeting, was to call forth remarks from other geologists upon deposits with which they were personally familiar, or to lead them to re-examine such deposits with the idea of secondary enrichment in mind. Mr. Collins's remarks on Rio Tinto, which he has the advantage of personally knowing, are also interesting. With regard, however, to his suggestion-advanced as an apparent argument against our theory-that the re-precipitation of copper from cupric sulphate solution by pyrite can hardly take place there, since it would upset the commercial process, I would remark that, while he is undoubtedly right as to the fact, it does not militate against the reduction and re-precipitation of cupric sulphate in veins; since on the surface, as at Rio Tinto, there is free access of air, and consequently an excess of ferric sulphate, whereas in depth the ferric sulphate would have been mostly reduced to ferrous sulphate, and (there being no excess of acid to hold it in solution) the small amount of copper in the presence of an excess of iron sulphide would be precipitated either as sulphide or as native copper. To Professor Vogt's analogous remarks, that in his experience sulphuric acid is formed only in subordinate amount in the attack of sulphides by ferric sulphate, I would say that Dr.

Jan 1, 1902

By C. Baldwin Sawyer

J. S. Vanick,* Washington, D. C. (written discussion).—To those who have been confronted with the study of the gas-metal reactions, this paper is a most welcome contribution. My personal interest in work bearing upon this general problem, stimulated by an appreciation of the difficulties inherent to problems of this type, prompts a few words of discussion. Table 2 of the paper shows a gradual increase in the nitrogen content with an increase in pressure, and an interpretation follows in which nitrogcn is used as the compressed medium when the conditions admit that cyanogen gas could be active as a contaminating ingredient. Fusions of electrolytic iron made in the induction furnace in an atmosphere of deoxidized nitrogen and out of contact with contaminating materials have shown no microscopic evidence of -a nitrogen increase; using a refractory-lined graphite crucible in the furnace under the same conditions or admitting air often resulted in the occurrence of nitride needles in the solidified melt. These results suggested that a nitrogenous compound served as a vehicle for the introduction of nitrogen and that such compound was not available when the pure gas and carbon-free refractory were used. The fusion of pure iron in pure nitrogen is perhaps a matter of theoretical interest. The author's work serves a more practical purpose when applied to steels rather than iron. Table 2 reports the absence of nitride needles in melts made under pressure of one atmosphere, although the quantity of nitrogen present would seem to exceed microscopically detectable percentages. In some recent work29 on carburized iron, nitride needles have been observed in areas analyzing as low as 0.015 per cent. nitrogen. This low percentage of nitrogen would indicate that the solubility limit is less than 0.030 per cent. for hypoeutectoid steels. There is the possibility that the areas of pearlite which exist in a hypoeutectoid steel restrict the distribution of nitrogen and limit its presence to the ferritie fields. In view of this work and the references quoted by the author, I am led to expect that the value for the solubility of nitrogen in solidified iron may approach

Jan 1, 1924

By H. E. Lee, A. W. Edelen

The Teziutlan copper-zinc deposit is supposed to be of late Cambrian or early Paleozoic age. The country rocks are a series of schists or phyllites, flat lying and in the form of a plunging anticline. The ore deposit occupies a single horizon in the schist for a known horizontal extent of 1200 meters. Along its strike occur four large lenses or ore bodies. These ore bodies occupy positions along the flank and extend to the crest of the anticline. The primary mineralization is in the form of quartz, pyrite, sphalerite, chalcopyrite and galena, with a few scattered silver anti-monides. Quartz and pyrite form the mineralization between the ore lenses. Ill the ore lenses the sulphides appear as a massive, very fine-grained intergrowth of minerals. The intergrowth suggests a contemporaneous deposition of the heavy sulphides. The grain size, usually under 0.09 mm., makes the separation difficult and fine grinding important. The ore bodies were formed at great depth by solutions probably originating in the same basic magma that gave rise to the dolerite sills that are so common in their vicinity. Introduction The Teziutlan copper-zinc deposit is distinctly different from other ore deposits of Mexico in age and type. Previously stated to be pre-Cambrian in age, it is now quite generally supposed to belong to the late Cambrian or to the early Paleozoic period. Also, in contrast to the usual shallow-vein zone type of mineralization in Mexico, there is here exemplified an intermediate vein zone deposit of copper and zinc. So far as is known, the Tezintlan vein is unique in the history of Mexican geology and in a class by itself, its closest counterpart probably being the copper veins of the pre-Cambrian of Canada. The Teziutlan district is in the extreme northwestern corner of the State of Puebla, Mexico. Teziutlan, the terminus of a branch line of the National Railways from Mexico City, is connected to the mine at Aire Libre by a 17-km. narrow-gauge railroad owned and operated by the Teziutlan Copper Co. Owing to excessive grades on this short linc, Shay-geared locomotives arc used for the transportation of concentrates and supplies.

Jan 1, 1941

By I. Paredes, R. Díaz, H. Henao

Smelting of copper concentrate generates a significant amount of dusts which are collected in electrostatic precipitators. This material, which is a complex oxide of Cu, Fe, S, As, Sb, Bi and others, is difficult to recirculate into the smelting process due to the reported high concentration of arsenic. However, the dust also has concentration of copper above 10wt %, aside from reported contents of silver corresponding as much as 25wt% of the total inventories of this element in the smelters. Thus, it is of economic and environmental interest the development of a process able to reduce the concentration of arsenic in the dust and produce a material suitable to be recirculated into the smelting process. The present experimental work shows the results of a process of dust sulfidization-oxidition able to remove more than 65wt% of the arsenic present. INTRODUCTION Copper sulfide deposits worldwide exhibit increasing concentrations of arsenic. One case of interest would be the copper ores from the northern zone of Chile, which report high concentrations of enargite (Cu3AsS4) (Revista química, 2015) (Latinominería, 2014). The obtained concentrate from this ore is treated in a Fluidized Bed Roaster, producing calcines with low concentration of arsenic (<0.5 wt% As). This material is suitable to be treated in a Flash Furnace. At the roasting process, the arsenic is volatilized and then precipitated as fine particles of complex oxides. Most of this particulate material is removed from the gas stream through a device called Electrostatic Precipitator (Minería chilena, 2014). The experimental results reported in the literature indicate that arsenic present in these particulate materials (or dusts) cannot be eliminated in oxidizing atmospheres (air) or with inert gases (N2) in a Fluidized Bed Roaster even at temperatures as high as 700°C. There is also information that even the recovery of valuable metals from the dust is difficult through hydrometallurgical processes (private communication). This is how in some foundries these dusts are considered environmental liabilities. Regarding the decomposition of enargite (Cu3AsS4) in neutral atmosphere, it is reported in the literature (Padilla, 2001) that the main chemical reactions are:

Jan 1, 2019

By Y. C. Kim, S. L. Barua

Underground coal mine planning has traditionally focused on the mine design aspects concerning safety and efficiency in the quest to produce low cost coal. Very little attention has been given to coal quality control aspects of mine planning at most US underground coal mines. With the enactment of the Clean Air Act of 1970, the generally high sulfur content of coal has become a major concern for the coal-fired power plants in the east. Similarly, the ash and the Btu content of coal are equally important for boiler efficiency. Coal mine planning must incorporate coal quality control aspects as well as traditional safety and efficiency aspects. According to an article in Coal Age (March, 1982), nearly one-half of the US coal exported to Europe does not meet the contract specifications regarding ash, sulfur and Btu contents. Although one of the reasons cited for this problem was "inadequate sampling at the US ports," the more fundamental cause probably lies in the inadequate quality control of run-of-mine (ROM) coal at the source. To perform adequate quality control of ROM coal, mines need predicted short-term in-situ coal quality information. Such predictions are generally based on whatever available sampling information is around the mine workings. Unfortunately, the closest sampling information, in the form of diamond drill hole assays, is often several thousand feet away in most underground coal mines and is inadequate for short-term coal quality prediction purposes. This is because the diamond drill holes (DDH) were traditionally placed in the coal deposit during the mine development phase to determine coal seam continuity and overlying roof conditions. They were not placed for short- term mine planning. A study was undertaken by the University of Arizona for the Homer City Owners in Pennsylvania to show that there is a need for more closely spaced samples, if the short-term coal qualities are to be predicted with any "reasonable" degree of accuracy. Prior to this study, a short-term quality prediction model, STPM, had to be developed. This model uses not only DDH, but also other sample information obtainable during face development work to predict the qualities of in-situ coal that are available in the immediate future.

Jan 1, 1985

By Thomas Chance

ALL gravity methods for the separation of ore from gangue, or of slate and other refuse from coal, are based upon differences in the falling velocities, in some fluid medium such as air or water, of the materials to be separated. As all materials falling in a vacuum have the same velocity, independent of the size, shape, weight or specific gravity of their individual particles, it would be more accurate to describe the operation of these methods as depending upon the. retardation of falling velocities effected by the resistance of a fluid medium, this retardation being greater for small or light particles than for large or heavy particles. This generalization is true also of those appliances utilizing centrifugal force to replace or to supplement the action of gravity. The separation of materials of different specific gravities by means of a fluid having a specific gravity greater than that of the lighter particles and less than that of the heavier particles has not been applied commercially, or on a large scale, to the separation of ores or to the washing of coal, the method being limited to laboratory experimental work or to laboratory determinations for the purpose of checking up the work of jigs, classifiers, and other types of concentrating appliances. A solution of zinc chloride has thus come into general use inn the laboratory to separate coal, bony coal and slate, both to check up the work of coal-washing plants and for the purpose of making tests preliminary to the designing of coal-washing plants. The use of a heavy solution of some chemical in water has often been proposed for making such separations, especially in connection with the washing or preparation of coal. Practically insuperable difficulties, however, have prevented the commercial development of any such process, the difficulties being both physical and financial. The cost of the chemical used to make high-gravity solutions is usually prohibitive, and the freeing of the coal from all traces of the chemical is found to be practically impossible. Such solutions inevitably penetrate the individual lumps and particles of coal, transfusing into the pores and saturating the joint-planes, and very large quantities of wash water

Jan 2, 1918

By J. W. Richards

There are two essentially different &apos;types of case-hardening processes; that using a dry mixture in which the object to be case-hardened is packed and kept for the necessary time at the necessary temperature, and the "liquid" proccss, employing a bath of fused salts into which the object is immersed and which by immediate contact case-hardens the surface of the article. The Shimer process belongs to the second class, and was a war emergency invention. Of the liquid melts used as baths, the most effective and most frequently used are melted potassium cyanide and melted sodium cyanide. These may be used either pure or mixed with salts that reduce the melting point and the percentage of .cyanide present. The use of these baths since 1914 has met many commercial difficulties because of the high price and frequent commercial scarcity of the cyanide salts; at present sodium cyanide has practically entirely displaced potassium cyanide. Another trouble is the danger to the workmen handling the cyanide salts, which are extremely poisonous, and the annoying and poisonous vapors or gases given off in the workshop, unless an effective system of hoods and ventilation is provided, so as to prevent the gases from the baths mixing with the air of the room. Porter W. Shimer, of Easton, Pa., has invented a substitute1 for the bath of melted cyanides which case-hardens with equal or greater facility and effectiveness, gives off no poisonous vapors, and costs for chemicals materially less than the cyanide costs in the previously used baths. The process has been in use over a year in a large American works and the following statement embodies the results of practical experience in the use and operation of the process. The Shimer liquid or melted bath consists of a mixture of easily fusible salts that do not possess case-hardening properties, into which is immersed fresh calcium eyanamid, which imparts to the bath case-hardening properties. The composition of the non-case-hardening salts appears rather immaterial. Good results have been obtained by using a mixture of sodium chloride, calcium chloride, and barium chloride in equal proportions by weight; also a mixture of one part sodium chloride

Jan 1, 1920

By A. W. Gauger

Fox perhaps one hundred years scientists have been engaged in attempts at devising a satisfactory method of classification of coal. During this time many charts, tables and graphs have been proposed, some of which have had considerable merit, but no one system has been found to be applicable to all ranks of coal, nor has any one system received general acceptance. In many of the proposals, water eliminated between room temperature and 105° C. has been regarded as extraneous matter and calculations have been made to the air-dry or water-free basis. Such methods of. calculation do not lend themselves to satisfactory grouping of the high-moisture coals.1,2 A consideration not only of the properties of the high-moisture coals and their behavior on drying but of the generally accepted ideas of the coalification process and the role of water in this process indicates that water is an essential constituent of all coals and therefore should not be neglected. For example, in such low-rank coals as the lignites of the Northern Great Plains&apos; deposits the inherent moisture of the lignite as mined plays a very important part in the physical properties thereof. Freshly mined lignite contains upwards of 30 per cent water and is extremely tough and resistant to shock. Upon exposure to the atmosphere, the lump loses part of its moisture and checks and splits, leaving a friable and broken up residue. So far as we have been able to determine, water is the only thing lost in this process and we are forced to the conclusion that moisture plays an extremely important part in the structural properties of the original lignite. With reference to the coalification process, Mack and Hulett3 pointed out in 1917 the important part that water played therein. They observed that water cannot be removed from peat or coal by pressure alone, but only as the result of chemical reaction, and suggested that peat in its early stages may be largely a hydrosol. Slow chemical changes occur over a long period of time until finally the mass becomes more largely a hydrogel. These views are substantiated to some extent by the experi-

Jan 1, 1932

By Greg Hodges

Sand-and-gravel aggregates have become the number-one, nonmetallic-mineral resource in the world. Surficial aggregate deposits of economic size are becoming increasingly rare in most parts of Canada. In southern Saskatchewan, this is especially true, and detection and delineation of intertill sand-and-gravel deposits with airborne electromagnetic (EM) surveys have proven very successful. Airborne and ground geophysical surveys detect such deposits by their resistivity contrast relative to the surrounding clay-rich soils. Dighem helicopter-borne electromagnetic surveys map soil variations over a large area quickly and cost effectively, greatly reducing the cost of detecting and mapping deposits compared with traditional methods (air-photo interpretation, ground EM, and drilling.). The multiple-frequency EM system used by Dighem can map variations both horizontally and vertically. Magnetic data collected simultaneously are useful in mapping bedrock geology. Both resistivity and bedrock maps aid in the important task of reducing drilling costs and person-hours in the field. The results of the survey are presented as maps of ground resistivity, which are relatively easy to interpret. These maps are produced in the field at the time of the survey, making quick follow-up of the survey possible. Airborne EM surveys can map the extent and depth of aggregate deposits more effectively than is practical from the ground. Since aggregate deposits can vary tremendously in a very short distance (<300 m) large-area EM maps can show both local area variability and also help develop intertill trends. A test survey for the Saskatchewan Highways and Transportation Department over a 3-km by 5-km area mapped all the known deposits as well as some unknown deposits, subsequently proven by drilling. The test-survey data show that the method not only detected the deposits, but also gave an estimate of the shape (volume) of each of the deposits. Comparison of the data to drill sections shows excellent correlation. Theoretical modelling demonstrates that the multifrequency system can discriminate sand and gravel from bedrock ridges. Since the successful test work, about 725 km2 of ground have been surveyed, resulting in the discovery of four new deposits, which can be used immediately, resulting in significant savings for the Saskatchewan government and taxpayer.

Jan 1, 1999

By Eugene A. Stephenson

In most instances the fluids produced from underground reservoirs have been described as they appear at the surface, and usually it has not been necessary to distinguish between surface and reservoir phases. More recently it has become imperative to recognize the fact that changes in phase may occur between the reservoir and the receiving unit. The simple terminology of "wet" and "dry" gases and "crude petroleum oil" served our needs fairly well in the shallow, low-temperature and low-pressure fields. It has been left to the legislatures, regulatory commissions, and courts to decide whether a field is or was a gas field, an oil field, or both. This they have done by direct definition and also by implication. For example, in Texas:&apos; (d) The term "gas well" is any well (a) which produces natural gas not associated or blended with crude petroleum oil at the time of production, or (b) which produces more than one hundred thousand (100,000) cubic feet of natural gas to each barrel of crude petroleum oil from the same producing horizon, or (c) which produces natural gas from a formation or producing horizon productive of gas only encountered in a well bore through which crude petroleum oil is also produced through the inside of another string of casing. (e) The term "oil well" is any well which produces one (1) barrel or more of crude petroleum oil to each one hundred thousand (100,000) cubic feet of natural gas. In the state of Louisiana, the same general result is achieved largely by the following paragraph :* Wells producing both oil and gas shall not waste or blow into the air an amount of gas of more value at three cents per thousand cubic feet, than the market value of the oil recovered. The Commissioner of Conservation shall allow a reasonable time to determine the status of any well. This means that for wells making both oil and gas, if n represents the price of oil in dollars, and x the allowable gas waste expressed in M cu. ft. Per day,

Jan 1, 1938

By Leonard Larson

BEFORE direct or wet smelting of copper concentrate was adopted at the McGill smelter, in November 1932, actual furnace smelting tests had indicated the possibility of smelting between 400 and 500 dry tons of wet concentrate per furnace day. Under calcine smelting practice, solid charge up to 1165 tons per furnace day had been smelted. It was realized that in order to smelt wet tonnage in equivalent amount per furnace day, a higher combustion rate and higher temperatures would be neces-sary within the furnace. The reverberatory furnace considered in the following history of wet-smelting de-velopments is a unit 127 ft. long and 28 ft. 8 in. wide, inside dimensions (Fig. r). This furnace was in operation through all the years from 1934 to date. During 1933, the first complete year of direct or wet smelting, the plant was on a curtailed copper-production basis and the available concentrate tonnage to be smelted was limited. The average coal-firing rate in the reverberatory for that year was 124 tons per furnace day. This rate was lower than the average for years immediately preced-ing under calcine smelting practice. With this coal-firing rate, an average of 391 tons of new metal-bearing material (N.M.B.M.) was smelted per furnace day. The following year, 1934, the coal-firing rate was in-creased to 139 tons and the smelting rate increased to 448 tons N.M.B.M. per fur-nace day. In succeeding years production required that either more tonnage be smelted in the one furnace or an additional furnace be placed in operation. With this situation confronting the smelting depart-ment, it was determined to continue the program of increasing the coal-firing rate and also to intensify the temperature in the smelting zone of the furnace. In order to accomplish this, various improvements were made to aid combustion within the furnace. The burners were enlarged, in-creased primary air was supplied to the burners, and changes were made in the furnace to enlarge and streamline the out-let, thus increasing the furnace draft.

Jan 1, 1940

By John W. Langley

The papers of Mr. W. J. Keep, read before this Institute, have called attention to the influence of aluminum in cast-iron and on iron and steel castings. The information in these papers is interesting and valuable, as showing the modifications which iron undergoes when dosed with sufficient aluminum to form a distinct alloy, the quantity of the alloying metal used being such that the amount remaining in the casting is sufficient to be readily discovered by analysis. The same is also true of the so-called aluminum-steel patented by R. A. Hadfield, where the proportions specified are such as to leave in the finished steel from one-twentieth to one-tenth of one per cent. of aluminum. Whether these alloys are of practical utility or not has thus far . not been proved by any extended tests on a large scale, and until such evidence is forthcoming it may be safely held, provisionally, that such a use of aluminum is of doubtful utility. But there is another function which this metal can perform that has been known for some time, and which has passed beyond the experimental stage, viz.: its beneficial effect in securing sound ingots. It appears to be a general property of all metals when in the fluid state and at a temperature considerably above their points of fusion, to contain gas, either dissolved from the air or frorn the furnace, or else self-evolved by internal reactions. Silver, perhaps, shows this power in the highest degree, and mercury and lead in the least; midway stands steel—the quantity of gas which it can hold in solution, or " occlusion " as it has been called, varies with its temperature, its composition, and its mode of manufacture. When the steel sets in the mould, a portion of this gas escapes, causing blow-holes, surface defects, boiling-over, wildness, and quite a long train of troubles, familiar to all practical steel-makers. Ferro-silicon has long been used as a quieting agent. The first extended use of it for this purpose was made at Terre-Noire, in

Jan 1, 1892

By H. E. Lee, A. W. Edelen

The Teziutlan copper-zinc deposit is supposed to be of late Cambrian or early Paleozoic age. The country rocks are a series of schists or phyllites, flat lying and in the form of a plunging anticline. The ore deposit occupies a single horizon in the schist for a known horizontal extent of 1200 meters. Along its strike occur four large lenses or ore bodies. These ore bodies occupy positions along the flank and extend to the crest of the anticline. The primary mineralization is in the form of quartz, pyrite, sphalerite, chalcopyrite and galena, with a few scattered silver anti-monides. Quartz and pyrite form the mineralization between the ore lenses. Ill the ore lenses the sulphides appear as a massive, very fine-grained intergrowth of minerals. The intergrowth suggests a contemporaneous deposition of the heavy sulphides. The grain size, usually under 0.09 mm., makes the separation difficult and fine grinding important. The ore bodies were formed at great depth by solutions probably originating in the same basic magma that gave rise to the dolerite sills that are so common in their vicinity. Introduction The Teziutlan copper-zinc deposit is distinctly different from other ore deposits of Mexico in age and type. Previously stated to be pre-Cambrian in age, it is now quite generally supposed to belong to the late Cambrian or to the early Paleozoic period. Also, in contrast to the usual shallow-vein zone type of mineralization in Mexico, there is here exemplified an intermediate vein zone deposit of copper and zinc. So far as is known, the Tezintlan vein is unique in the history of Mexican geology and in a class by itself, its closest counterpart probably being the copper veins of the pre-Cambrian of Canada. The Teziutlan district is in the extreme northwestern corner of the State of Puebla, Mexico. Teziutlan, the terminus of a branch line of the National Railways from Mexico City, is connected to the mine at Aire Libre by a 17-km. narrow-gauge railroad owned and operated by the Teziutlan Copper Co. Owing to excessive grades on this short linc, Shay-geared locomotives arc used for the transportation of concentrates and supplies.

Jan 1, 1941

By Stanly A. Easton, H. M. Childs

Methods evolved at Kellogg have had primarily in view the safety of workmen and complete recovery of the ore; it is believed that these results have been secured at a minimum cost. The ore in the Bunker Hill mine is of good grade, relatively speaking; much of it is quite rich and no mining method would be successful which did not recover all of the ore. It would be possible to work certain of the orebodies by shrinkage methods, or some form of top-slicing, at probably lower costs than by the methods now applied, but the shapes of the orebodies are so irregular that satisfactory extraction of the ore in all its ramifications would be extremely difficult. In past years, much high-grade ore has been lost in blasting, due to the unskilful use of powder in a galena ore, which, by reason of its brittle-ness and great weight, tends to scatter widely. Any method by which large masses of ore and waste are broken together will result in an imperfect recovery of the ore, and whenever large masses are broken, ore and waste will unavoidably fall down together; ore and waste thus become entangled and, although a pile of broken material may seem to have been well picked over, quantities of ore will inevitably be lost. This fact has been shown by persons reworking the filling in stopes that were mined by methods defective in the foregoing particulars. Safety of the men is secured by avoiding large openings, and by working mainly under timber, and at small faces at close range and easily inspected. In former years the principal source of serious accidents was "falls of ground;" it is now over seven years since a serious accident has occurred from this cause. The most prolific source of accidents during recent years has been "timber and tools," workmen being struck by timbers passed into the stope from the level above; this danger has been greatly reduced by compressed-air warning whistles and the fencing in of dangerous areas. The lead-silver ore of the Bunker Hill and Sullivan and affiliated mines is found in bodies of almost every shape, although vertical or nearly

Jan 1, 1925

By C. R. Sandberg, N. Stein, L. D. Wiener, E. B. Elfrink

this paper presents the results of a study of the slip velocity of gases rising through liquids in vertical tubes, inclined tubes, and vertical annuli. The data were obtained in gas-liquid systems which included combinations of air, propane and natural gas (over 97 per cent methane) with water, lubricating oils, and crude oils. The 214 data points obtained in this study along with 11 data points reported in the literature are incorporated in an empirical correlation which relates the mean slip velocity of gases flowing through liquids with the parameters gas rate, tube size, ratio of liquid viscosity to liquid density, gas density, liquid density, and the angle of the tube from the vertical. The average numerical deviation of the measured slip velocity data from values obtained from the correlation is 9.2 per cent. The average algebraic deviation between measured and Predicted data is 0.31 per cent, an indication that the correlation is a satisfactory representation of the data. The correlation presented in this paper will be useful primarily in the design of subsurface gas-oil separation equipment for increasing the efficiency of oil-well pumping installations. but may perhaps be extended to other situations of gases rising through liquid columns. INTRODUCTION The production of oil by pumping is often complicated by the presence of free and dissolved gas in the oil at bottom-hole conditions. This gas can be drawn into the pump barrel and result in "vapor locking" the pump, thus reducing the efficiency of the pumping operation. Large amounts of free gas may be excluded from the pump by the use of a gas-anchor, which is designed to allow the separation of free gas from the oil before it is drawn into the pump. The design of a suitable gas-anchor depends on a knowledge of the difference between the velocity of the free gas and that of the oil as the oil travels down toward the pump intake. This rate of gas rise through the oil is termed "slip velocity." AS a first step toward the full understanding of this roblem, the mean slip velocities of gases flowing through static

Jan 1, 1952

By A. W. Edelen, H. V. Lee

THE Teziutlan copper-zinc deposit is supposed to be of late Cambrian or early Paleozoic age. The country rocks are a series of schists or phyllites, flat lying and in the form of a plunging anticline. The ore deposit occupies a single horizon in the schist for a known horizontal extent of 1200 meters. Along its strike occur four large lenses or ore bodies. These ore bodies occupy positions along the flank and extend to the crest of the anticline. The primary mineralization is in the form of quartz, pyrite, sphalerite, chalcopyrite and galena, with a few scattered silver anti-monides. Quartz and pyrite form the mineralization between the ore lenses. In the ore lenses the sulphides appear as a massive, very he-grained intergrowth of minerals. The intergrowth suggests a contemporaneous deposition of the heavy sulphides. The grain size, usually under 0.09 mm., makes the separation difficult and fine grinding important. The ore bodies were formed at great depth by solutions probably originating in the same basic magma that gave rise to the dolerite sills that are so common in their vicinity. INTRODUCTION The Teziutlan copper-zinc deposit is distinctly different from other ore deposits of Mexico in age and type. Previously stated to be pre- Cambrian in age, it is now quite generally supposed to belong to the late Cambrian or to the early Paleozoic period. Also, in contrast to the usual shallow-vein zone type of mineralization in Mexico, there is here exemplified an intermediate vein zone deposit of copper and zinc. So far as is known, the Teziutlan vein is unique in the history of Mexican geology and in a class by itself, its closest counterpart probably being the copper veins of the pre-Cambrian of Canada. The Teziutlan district is in the extreme northwestern corner of the State of Puebla, Mexico. Teziutlan, the terminus of a branch line of the National Railways from Mexico City, is connected to the mine at Aire Libre by a 17-km. narrow-gauge railroad owned and operated by the Teziutlan Copper Co. Owing to excessive grades on this short line, Shay-geared locomotives are used for the transportation of concentrates and supplies.

Jan 1, 1937

By L. J. Surges, C. Bazin, D. Hodouin

"A kinetic model was developed for the conditioning and flotation processes of an industrial lead concentrate dezincing circuit. The models were incorporated into a flowsheet simulator. Simulation results demonstrate the advantages of split conditioning of coarse and fine particles and the potential of this approach for the production of the heuristics required for the development of intelligent control strategies.The conditioning model relates the proportions of activated and hydrophobic surfaces and residual reagent concentrations to activator and collector reagent flowrates. The model accounts for the solids and water flowrates, and for the solids grade and size distribution. The flotation model uses the predicted proportion of hydrophobic mineral surface, the aeration rate and the froth depth to estimate cell, bank and circuit performances. IntroductionFlotation has been the object of modelling and simulation studies for more than two decades. The process is usually modelled as a kinetic one in which the particle flotation rate constants are key parameters. Rate constants are related to the operating variables (pH, reagent flowrates, aeration rate, etc), however these relationships are seldom established in the literature.In spite of the large amount of literature on flotation modelling and simulation, few papers deal with the interaction between flotation rate constants and operating variables. This important gap, which was identified in the early seventies by Woodburn (l970), still exists. One of the first attempts to include operating conditions in a flotation simulator was made by King (l973), who explicitly introduced the aeration rate into an air bubble loading model. Lynch et al. (1981) used an empirical model to relate the proportion of slow floating particles to the ratio of collector per ton of ore. Such empirical relationships are difficult to calibrate and cumbersome to use when an activator and a collector are added to slurries in which particle size distribution and surface characteristics are changing. Eascur and Herbst (l982) relate in a fundamental way the mineral flotation rate constants to the aeration rate, froth depth, agitation and frother concentration, however the model does not account for reagent flowrates. Niemi et al. (1982) have proposed a model for the conditioning of minerals and included it into a conventional flotation simulator."

Jan 1, 1988

By James Howard

ON Aug. 25, 1911, a rail failed on the Lehigh Valley Railroad, causing a disastrous wreck. The surface of the fracture was in a plane at right angles to the length of the rail. There was a dark-colored, oval spot on this surface, located on the gage side of the head, representing the part of the rail which was the first to fracture. The nucleus of this spot showed that the fracture had an interior origin. Other fractures of this kind, the peripheries of which had not reached the surface of-the rail, presented surfaces having a silvery luster. The darkened surface of the present fracture was caused, doubtless, by the air having had access to it. This fracture was recognized as a fatigue fracture, of a modified type, its interior origin having been due to a component in the rail which is not usually present in cases of fatigue fractures. The metal next the running surface of the head of the rail was in a state of internal compression, this being the component not commonly met with in other cases, and which caused the fracture to have its interior origin. For the purpose of giving this modified type of fatigue fracture a specific name, for identification, the term "transverse fissure" was applied. No mystery was thought to attach to its formation, or to its development. The explanation of its occurrence was obvious in the light of common knowledge upon the behavior of steel under repeated alternate stresses. By reason of the state of internal compression at the running surface, the maximum tensile stresses in the head, under bending loads, were along an interior element. Here the tensile strains were higher than in the fibers more remote from .the neutral axis. Under such conditions the fracture of the rail would be expected to have an&apos; interior origin. A discussion of the subject of transverse fissures essentially becomes a discussion of fatigue fractures, since they are identical. The descriptive term employed, merely for the identification of this type of fatigue fracture, had the appearance of creating alarm. Apprehensions arose that a new phenomenon in the physical properties of steel had presented itself, the explanation of which was sought in every

Jan 11, 1917