Search Documents

By Andrew A. Blair

The increased importance and value of chemical analysis in connection with metallurgical operations is largely, if not entirely, due to the increased accuracy of the analytical methods used for the quantitative determination of the foreign elements always associated with the metal operated upon. This applies especially in the working of iron and steel, and to the determination of the amounts of such elements as phosphorus, carbon, and silicon. The influence of greater or smaller amounts of these elements upon the physical properties of iron and steel will be better understood when the proper experiments shall have been made upon samples whose chemical composition is known with almost absolute certainty. From the present standpoint of analytical chemistry, it is easy to see that at least one reason for the failure of many attempts to solve this problem, is the inaccuracy of the analytical methods used. Even at the present time the frequent want of agreement (over and above the unavoidable error due to manipulation) between chemists working on the same sample, leads one to think that there is still at least a choice in the methods used. It is true that very frequently a faulty method in the hands of a skilful analyst may be made to give corroborative results

By H. M. Strong, R. A. Oriani

THE technological interest attaching to light, age-hardening alloys for structural uses has been pointed out to one of us.1 A potentially interesting alloy would be titanium-rich Ti-Mg alloy, provided that sufficient solid solubility exists. or could be induced at high pressure. and provided also that age hardening can be induced by proper temperature and/or pressure annealing. It was decided therefore to explore the feasibility of producing a Ti-Mg alloy in the high-pressure apparatus. Experimental. Three high-pressure runs have been carried out. In each case the geometry of the sample was that of a cylinder of titanium of commercial purity, into which a narrow hole had been drilled along the axis; this hole was filled with magnesium wire,

Jan 1, 1967

By Fred J. Hurst

In 1934, Irvin Lavine (A), University of North Dakota, stated that the low-rank coals (lignite and subbituminous) of this country represent a vast tonnage of fuel of commercial value and predicted that some day they will play an important role in our economic welfare. Lavine also pointed out that one of the major problems with efficient utilization of the low-rank coals is their high moisture content. Following the discovery of uranium-bearing lignite in the Williston basin of North and South Dakota in 1948 by D. G. Wyant and E. P. Beroni, detailed investigations were conducted (primarily during 1950 to 1954) by members of the U. S. Geological Survey to evaluate the geologic factors and economic possibilities of the radioactive lignites as a source of uranium. The information gained in these studies and summarized in several papers indicated that a large potential reserve of uranium is contained in the subbituminous coal and lignite deposits of the Dakotas and Wyoming (2,3,4). Most investigators concluded that an epigenetic emplacement of uranium in the coal by means of circulating groundwater and the more extensive concentrations of uranium in coal are apparently related to the permeability of the rocks enclosing the coal beds. Breger (5) and others have shown that uranium is readily adsorbed by coal and is held irreversibly as a disseminated adsorbed constituent. Briefly, lignite beds containing 0.1 to 10% uranium have been discovered in the Dakotas and Wyoming. The distribution of uranium was found to be erratic and was usually concentrated in thin layers, which were characteristically 10 to 14 in. thick and occasionally 30 to 36 in. thick. Lignite beds more than 3 ft. thick generally contain more uranium at the top of the bed than at the bottom. Special strip mining techniques are required to mine these thin

Jan 1, 1983

By Oliver Bowles

WHILE vast quantities of limestone and dolomite. are used in metallurgy, the estimated production in 1926 being 23,860,000 tons, there are many problems connected with their use which have not received adequate study. The literature of metallurgy is notably lacking in comprehensive discussions of fluxing or furnace stone. Approximately 900 lb. of limestone is used for every long ton of pig iron produced in the blast furnace, but this important constituent of the charge receives little attention compared with the intensive study that has been applied to ores and fuels, the other important constituents of the charge. In an effort to elucidate some of the doubtful points, the writer has made a wide review of metallurgical literature, and has had the disappointing experience of finding not more than a paragraph or two on metallurgical stone' for each two or three thousand pages of literature reviewed. Furthermore, the limited information supplied is in some instances contradictory and even absurd. For example, a correspondent in a reputable metallurgical magazine classifies magnesia and silica together as impurities in flux "that must be melted and run off as slag." From the furnace operator's viewpoint it is desirable that as complete knowledge as possible be obtained concerning the effects of chemical composition and physical character of the stone on its action in the furnace and on the quality of the metal produced. A better knowledge of these features is advantageous also to the quarry operator in that it enables him to work more intelligently in producing stone that will best satisfy the metallurgists' requirements. The following pages comprise a brief compilation of data now available. Much of the information is well established and probably acceptable to most metallurgists. On some points there is room for debate, and the chief purpose in presenting a paper at this time is to arouse discussion which will throw more light on controversial points and thus assist the author in preparing a more comprehensive and accurate discussion of metallurgical limestone problems.

Jan 1, 1928

By J. T. Jones, H. V. Winchell

In the history of mining in this country there has been nothing exactly similar to the Mesabi iron-range in Minnesota, and the conditions there prevalent. Soft-ore mines are found in many parts of the country. In some the deposits are vertical, and are worked in open pits, or have been so worked, until it was found cheaper to go under ground. In other localities, the ore is scattered through clay beds in the form of hard lumps. These clay beds are sometimes excavated in open pits, and the ore separated by washing. On the Mesabi, the ore itself occurs in strata, and these strata appear quite flat to one standing upon the ground. The ore is soft in the main, and does not require much sorting to free it from foreign or deleterious substances. It is usually covered by the glacial drift-mantle, but occasionally passes beneath a capping of jasperoid rock called " taconite." The ore is twice or three times the thickness of the layer of drift lying upon it. This drift consists of clay, sand, and gravel, with occasional beds of large boulders. There is great difference of opinion among competent miners as to the cheapest methods of mining this ore. It is admitted that local conditions will govern largely ; but there is such a similarity among many of the mines that it seems possible to arrive at some general conclusions on the subject. A typical example of a Mesabi mine is found in the Biwabik. It is one of the largest, and is the most advanced in development. Not a single ton of ore has yet been shipped from this mine, but the expense of the explorations upon which the following description is based has exceeded $60,000. It is seldom that such accurate and complete exploration of a deposit of this magnitude has been possible in the space of time which has elapsed since the discovery of this ore-body. It lies in a new. region, and was remote from railroads until last August, yet, not only the width and length but the depth and quality of the ore-deposit have been learned, and the probable expense of' mining its 20,000,000 tons of ore has been closely figured. After careful consideration, the method of stripping and

Jan 1, 1893

By F. Lynwood Garrison

The future of the Witwatersrand depends upon the possibility of mining and milling profitably the large tonnage of relatively low-grade gold ores known to exist in that area. The problem must be solved if the existence of the gold-mining industry in South Africa is to be saved and continue. To show that this disaster may be avoided, or at least postponed for another decade or longer, the following official statement is of interest: "There is a fairly large area of possible orebody on the East Rand of whose value and depth from the surface we have some though not very accurate knowledge. There is a far larger area south of the Central Rand which probably carries much payable ore, but at depths that at present appear too great to mine. Finally, there is a narrow strip of country over 100 miles in length stretching south from the Rand to Klerksdorp and beyond, which may contain large ore-bodies. The Witwatersrand rocks outcrop over portions of this ground and in places conglomerates occur in it that carry small bodies of payable ore. There is reason to believe that conglomerates of the Witwatersrand system exist over all this strip, though they are for the most part covered by later sediments. It seems probable also that there are large blocks of payable reef in this belt, at any rate in the area that lies close to the present western limit of the developed mines. The structure in this neighborhood is however very complicated and to prove the orebodies will be both difficult and costly." Ores in the Witwatersrand It should be explained in this connection that the conglomerates mentioned here were originally old gravel beds now consolidated into bedded sedimentary rocks, very hard because strongly cemented with secondary silica. The gold exists in this cement and is rarely found in the pebbles composing the rock or bed called locally reef. It is important to realize that these gold deposits are beds; not veins as generally understood by mining engineers and geologists. In addition to these low-grade ore reserves we have also to consider the ore left behind in the old stopes of the upper levels near the surface,

Jan 1, 1931

By Jei Y. Choi, P. G. Shewmon

Using a scratch smoothing technique, the magnitude and the ratio of the surface diffusion coefficients (D,) in two orthogonal directions have been measured on copper for over 100 different surface orientations. Anisotropy was found for all surface orientations except those lying near the (100) and (111); however, these anisotropies were rarely greater than 2.0. The direction of maximum D, appears to coincide with the direction of step edges on any given surface, and if no such steps exist, no anisotropy is found. Thus the jump frequency along a step edge is shown to be faster than the frequency of a jump over the step. The values of Ds and AH for the (100) and the (111) orientations agree quite well with those obtained earlier by the grain boundary grooving technique. It is proven that the directions of maximum and minimum D, (the principal axes) for any surface orientation are known if the perfectly ordered plane corresponding to the given surface orientation possesses a plane of mirror symmetry. Thus the principal axes of D, for orientations lying along the sides of the unit stereo-graphic triangle are always known independent of the extent of thermal disorder or impurity adsorption. The merits and shortcomings of King and Mullins' recently published equations relating Ds to the rate of scratch smoothing are discussed. 1N an earlier paper the authors have reported the variation of the surface diffusion coefficient (Ds) with surface orientation on copper.' In that study Ds was determined from the rate of growth of grain boundary grooves on symmetric bicrystals. This gave values of Ds from 850° to 1070°C in a given direction on each of the six surfaces. It was found that the activation energy for surface diffusion was essentially the same for all six surfaces. The theory developed to explain these data assumed that the free energy of any given type of surface site depends only on the number of nearest neighbors the atom has. This same theory predicted that on any given surface Ds should be independent of direction. The primary aim of this study was to check the validity of this prediction for a wide range of surface orientations on copper. The growth of grain boundary grooves is ideal for studying Ds in a given direction on a given surface over a range of temperatures, because the same specimen can be repolished and used again. However, there is considerable work involved in growing a symmetric bicrystal, and for a survey of Ds in two or more directions on many surface orientations, the technique would be arduous. A better technique appeared to be the scratch method used primarily by Mykura. 2 If a scratch is placed in a surface whose surface tension is independent of orientation, the surface will smooth out in time under the influence of surface tension. To determine D, from this flattening, Blakely and Mykura2 used an approximate solution which was assumed to describe the rate of flattening. Recently King and Mullins3 (hereinafter K and M) have given a more exact analysis of the flattening of an isolated scratch. A second aim of this paper was to check the validity of this newer analysis and compare the values of Ds determined thereby with the values obtained from grain boundary grooving techniques. EXPERIMENTAL PROCEDURE In an effort to work with a particular predetermined surface orientation, light orthogonal scratches

Jan 1, 1963

By Cyril Stanley Smith, Earl W. Palmer

STRIP of any of the metals used for deep drawing operations occasionally yields cups that are defective because of a rim that varies in height around the cup in a wave-like manner. Some such defects are traceable to tools or other press factors, but when the protuberances formed (usually four in number on brass and other copper alloys) are symmetrically disposed with respect to the rolling direction of the strip, they are invariably attributable to the metal. The effect is known as "earing" and the protuberances are called "ears." Other terms frequently heard are "tips," "scallops," and "corners." It is recognized that the effect is most commonly a result of a directional crystal structure produced by rolling and annealing operations in the manufacture of the metal strip. 'Numerous papers dealing with various aspects of the earing effect have appeared in the literature, those listed in the references1 being especially interesting and valuable. An investigation of the factors influencing earing of brass cups has been in progress in the laboratories of the American Brass Co. for several years, and it was thought desirable to make some of the results generally available in summarized form. The present paper discusses many factors that do and do not contribute to ear formation. In addition, a section is devoted to methods of minimizing the earing tendency of brass sheet by proper selection of the cold-rolling and annealing schedule by which it is produced. In the space available, it is impossible to quote detailed experimental procedures and numerical results. However, the authors make no statement that they do not believe to be properly substantiated, either by experimental evidence obtained under laboratory conditions or by experience in the actual production of deep-drawing brass in the brass mill. MECHANISM OF EAR FORMATION It must be clearly understood that the formation on cups of symmetrical ears, four or more in number, is attributable solely to the strip metal, and results from the strip having different deformation characteristics in different directions. The tools used in the drawing process, or the type and completeness of lubrication of the strip, have nothing to do with the problem of ears, although they do, of course, greatly affect the "drawing quality" of the strip and the general appearance of the cup. A single tip may be drawn up on the rim of a cup because of misalignment of the tools, or because the gauge of metal varies from side to side of the strip. The two-ear form that sometimes appears is also traceable to gauge variations. However, the four-ear and six-ear symmetrical forms that we are concerned with here are caused by factors inherent in the structure of the metal itself.

Jan 1, 1942

By L. E. Shiffman

W. J. Parton—Those operators faced with the problem of treating fine coal whether in bituminous or anthracite will find this paper most timely. I would like to take this opportunity of discussing Mr. Schiffman's paper and at the same time express certain views relating to our Tamaqua plant. I would like to ask the author what type of impeller and diffuser is used in the Denver cells? Screen analysis of products from individual cells indicate that coarser material resists flotation and only floats after greater retention time in the last few cells. Also, the need for a scavenger screen to reclaim non-floated coal particles further stresses this point. I have always felt that more efficient means of cleaning coal between 10-mesh and 28-mesh existed than flotation. Reagent and power costs are high for the flotation process. When floating +28-mesh particles, cell capacity is lowered and some of the particles are lost with the refuse. The Tamaqua plant of the Lehigh Navigation Coal Co. floats —28-mesh coal and capacity of recoverable coal is 40 tph for 1800 cu ft of Denver cells; or 0.05 tons per cu ft of cell. At Kimberly 7.75 tph for 600 cu ft of cell gives 0.013 ton per cu ft of cell. At Bessie 14 tph for 800 cu ft of cell gives 0.017 tons per cu ft of cell. It would be appreciated if the author would comment on what he feels is the upper size limit of particle to attain most efficient utilization of the flotation process. The dewatering screw is a very interesting development since it offers a simple way to prepare coal sludge for more complete clewatering by drainage or mechanical dewatering on screen or filters. In other words it could be used to accomplish the same thing as a thickener tank. I would appreciate having the author's comment on how he thinks such a screw dewaterer would work on a froth.* The process as used in floating coal at the Bessie and Kimberly plants may be referred to as more of a bulk oil float in contrast to a froth flotation process. Experiments on increasing capacity of cells is most interesting since we are going through such an experi- mental period at the present time. Recently a double overflow was installed on our No. 30 Denver cells. So far results are not conclusive. In reviewing this paper the following comments are made pertaining to investigation of methods for increasing capacity: Supercharging: Supercharged air in matte flotation or for that matter the use of the normal amount of air drawn in by the impeller would in all probability cause such an aeration in the cell as to destroy the buoyant effect given to the coal particles by the excessive amount of kerosine used. In other words, air creates an agitation zone throughout the cell, creating a boiling and thereby giving a lower recovery in the cell. It would be interesting to know whether the 7 pct increase in recovery was with no air being admitted to the stand pipe. Changing Impeller Speed: The speed of a receded disc impeller for a No. 30 cell as recommended by the Denver Equipment Co. is, I believe, approximately 250 rpm. At this speed and using supercharged air in excess of 8-oz pressure, we have observed a boiling action in the cells. In our flotation we endeavor to obtain some degree of froth flotation using pine oil as a frother. The boiling action as caused by increasing the amount of air added to the cells is detrimental to recovery in froth flotation. It is our belief that to obtain increased recovery from a cell in froth flotation, additional air must be introduced but at the same time this air must be dispersed throughout the pulp in the form of small bubbles and this can only be done by increasing the speed of the impeller. Therefore, if Mr. Schiffman decreased the speed of the No. 30 impellers and at the same time continued to use supercharged air, the boiling action may have been increased because larger bubbles developed. The lower recovery as reported could be due to this factor. Decreasing the impeller speed will definitely decrease the power consumed but may have other disadvantages. First, we believe it will permit "sanding" in the cell and this in our opinion will increase the wear on the impeller and diffuser, especially so, if there is pyrite and/or sand present in the feed. "Sanding" in the cell when air is used, as in froth flotation, will effect the dispersion of this air and cause boiling.

Jan 1, 1951

By L. E. Shiffman

W. J. Parton—Those operators faced with the problem of treating fine coal whether in bituminous or anthracite will find this paper most timely. I would like to take this opportunity of discussing Mr. Schiffman's paper and at the same time express certain views relating to our Tamaqua plant. I would like to ask the author what type of impeller and diffuser is used in the Denver cells? Screen analysis of products from individual cells indicate that coarser material resists flotation and only floats after greater retention time in the last few cells. Also, the need for a scavenger screen to reclaim non-floated coal particles further stresses this point. I have always felt that more efficient means of cleaning coal between 10-mesh and 28-mesh existed than flotation. Reagent and power costs are high for the flotation process. When floating +28-mesh particles, cell capacity is lowered and some of the particles are lost with the refuse. The Tamaqua plant of the Lehigh Navigation Coal Co. floats —28-mesh coal and capacity of recoverable coal is 40 tph for 1800 cu ft of Denver cells; or 0.05 tons per cu ft of cell. At Kimberly 7.75 tph for 600 cu ft of cell gives 0.013 ton per cu ft of cell. At Bessie 14 tph for 800 cu ft of cell gives 0.017 tons per cu ft of cell. It would be appreciated if the author would comment on what he feels is the upper size limit of particle to attain most efficient utilization of the flotation process. The dewatering screw is a very interesting development since it offers a simple way to prepare coal sludge for more complete clewatering by drainage or mechanical dewatering on screen or filters. In other words it could be used to accomplish the same thing as a thickener tank. I would appreciate having the author's comment on how he thinks such a screw dewaterer would work on a froth.* The process as used in floating coal at the Bessie and Kimberly plants may be referred to as more of a bulk oil float in contrast to a froth flotation process. Experiments on increasing capacity of cells is most interesting since we are going through such an experi- mental period at the present time. Recently a double overflow was installed on our No. 30 Denver cells. So far results are not conclusive. In reviewing this paper the following comments are made pertaining to investigation of methods for increasing capacity: Supercharging: Supercharged air in matte flotation or for that matter the use of the normal amount of air drawn in by the impeller would in all probability cause such an aeration in the cell as to destroy the buoyant effect given to the coal particles by the excessive amount of kerosine used. In other words, air creates an agitation zone throughout the cell, creating a boiling and thereby giving a lower recovery in the cell. It would be interesting to know whether the 7 pct increase in recovery was with no air being admitted to the stand pipe. Changing Impeller Speed: The speed of a receded disc impeller for a No. 30 cell as recommended by the Denver Equipment Co. is, I believe, approximately 250 rpm. At this speed and using supercharged air in excess of 8-oz pressure, we have observed a boiling action in the cells. In our flotation we endeavor to obtain some degree of froth flotation using pine oil as a frother. The boiling action as caused by increasing the amount of air added to the cells is detrimental to recovery in froth flotation. It is our belief that to obtain increased recovery from a cell in froth flotation, additional air must be introduced but at the same time this air must be dispersed throughout the pulp in the form of small bubbles and this can only be done by increasing the speed of the impeller. Therefore, if Mr. Schiffman decreased the speed of the No. 30 impellers and at the same time continued to use supercharged air, the boiling action may have been increased because larger bubbles developed. The lower recovery as reported could be due to this factor. Decreasing the impeller speed will definitely decrease the power consumed but may have other disadvantages. First, we believe it will permit "sanding" in the cell and this in our opinion will increase the wear on the impeller and diffuser, especially so, if there is pyrite and/or sand present in the feed. "Sanding" in the cell when air is used, as in froth flotation, will effect the dispersion of this air and cause boiling.

Jan 1, 1951

By Kenneth B. Ray, George R. Gardner

The application of wet cleaning processes for the beneficiation of bituminous coal has created in some localities a problem in the recovery and disposal of fine solids in the washery water. The maximum allowable concentration of these solids in the washery circuit that is consistent with satisfactory operation of the cleaning units remains a controversial point. It has, however, been generally recognized for a number of years that some degree of control should be exerted over the concentration of such material. Early methods of control involved intermittent or continuous discharge of a portion of the plant slurry into near-by streams or settling ponds, and this persisted even after the adoption of settling tanks or cones. The practice is not always economical, for two reasons: first, because of the waste of coal, and, second, because it is sometimes difficult and expensive to obtain an adequate supply of water. The latter condition often is aggravated by chemical treatment of the make-up water that is necessary to prevent excessive corrosion of plant equipment. The modern approach to this problem has been the adoption of continuous thickening devices. However, because such equipment occupies considerable plant space and is somewhat expensive to construct, the practice of loading these thickeners beyond their rated capacity is widespread, therefore often the performance of such units is not altogether satisfactory. In recent years, European washeries have increased the rate of settling of the fine coal from the slurry by the addition of specially prepared starch solutions. These reagents cause flocculation of the solid particles and thereby increase the rate of sedimentation. The first important work on the flocculation and clarification of coal slurry was done by Henry, who developed the Henry process and used it successfully in Belgian preparation plants. Soon after the initiation in Belgium, the process was introduced into England, where subsequent, investigation developed similar processes, which were successfully used in

Jan 1, 1939

By George R. Gardner, Kenneth B. Ray

The application of wet cleaning processes for the beneficiation of bituminous coal has created in some localities a problem in the recovery and disposal of fine solids in the washery water. The maximum allowable concentration of these solids in the washery circuit that is consistent with satisfactory operation of the cleaning units remains a controversial point. It has, however, been generally recognized for a number of years that some degree of control should be exerted over the concentration of such material. Early methods of control involved intermittent or continuous discharge of a portion of the plant slurry into near-by streams or settling ponds, and this persisted even after the adoption of settling tanks or cones. The practice is not always economical, for two reasons: first, because of the waste of coal, and, second, because it is sometimes difficult and expensive to obtain an adequate supply of water. The latter condition often is aggravated by chemical treatment of the make-up water that is necessary to prevent excessive corrosion of plant equipment. The modern approach to this problem has been the adoption of continuous thickening devices. However, because such equipment occupies considerable plant space and is somewhat expensive to construct, the practice of loading these thickeners beyond their rated capacity is widespread, therefore often the performance of such units is not altogether satisfactory. In recent years, European washeries have increased the rate of settling of the fine coal from the slurry by the addition of specially prepared starch solutions. These reagents cause flocculation of the solid particles and thereby increase the rate of sedimentation. The first important work on the flocculation and clarification of coal slurry was done by Henry, who developed the Henry process and used it successfully in Belgian preparation plants. Soon after the initiation in Belgium, the process was introduced into England, where subsequent, investigation developed similar processes, which were successfully used in

Jan 1, 1939

By J. A. Jr. Church

I. EARLY FURNACES. COPPER blast-furnace construction in America has long recognized a general standard in the rectangular mater jacketed shaft with separate forehearth. The details, however, and especially those relating to shaft dimensions, have had to meet a great variety of conditions, and show no uniformity whatever. Selecting a few of the present day Western plants, we find furnace lengths varying from 12.5 to 87 ft., widths at tuyere level from 42 to 84 in., and heights above tuyeres from 5 ft. 4 in. to 22 ft. 4 in. ; and comparing present designs with those of the past, we meet contrasts no less striking. Unlike its transverse section, the length of a furnace has come to depend rather on the size of unit desired than on the requirements of smelting ; and if the question of length be ignored, several of the various existing designs can be grouped together on the basis of a common transverse section. This section, having a width at tuyere level of 56 in. and a height above tuyeres of 18 ft., was developed at Great Falls, and the story of its development contains some interesting features. Ground was broken for the Great Falls works in the spring of 1891. About a year later, the concentrator was able to begin operation, followed within the next few mouths by the Brueckner, reverberatory, and converter departments, and in April, 1893, by the first blast fur-

Jan 7, 1913

By Michael A. Farrugia, Marcel Michaud

Remoteness of western Canadian coals has always been a barrier to the use of Canadian coals domestically. However, the world energy crunch, increased mining costs, stricter environmental controls, labor shortages, etc., are such that by 1980 a shortfall from traditional U.S. sources will prevail. Of necessity, Canada must then bring western coals east, requiring major new transportation initiatives. CN, CP Rail and Neptune Terminals are proceeding jointly with the design of a $30 million, fully automated, coal terminal at Thunder Bay. This element forms part of a $400 million integral transportation system to open new lines, improve trackage, acquire rolling stock and ships, for an initial capacity of 3 million tpy.

Jan 1, 1977

By F. D. Delve

RECENT studies by the author on the reduction of titanium from TiO2-bearing slags have been accompanied by difficulties that are attributed to

Jan 1, 1959

By Alan R. Grant

The Cascade Range of Washington can be considered metallogenetically to be primarily a copper province. Structural and chemical data compiled from examination of numerous copper occurrences in the Cascades indicate a marked parallel of physical conditions for sulfide deposition. In probable order of significance, the environmental criteria are as follows: 1) adjacent or subjacent, postregional metamorphism high-level intrusive activity, most commonly in the time range from 15 million years to 30 million years; 2) transverse northeast trending structural belts which obliquely cut the northwest regional trend of the range; 3) potassium-silica wall rock alteration; most important of the alteration suite of silicates are orthoclase secondary biotite and quartz; 4) the intersection of northwest trending and northeast trending structures. The varying geologic environments in the Washington Cascades present a complex setting for the sulfide deposits. The North Cascades are comprised of predominantly pre-Tertiary metamorphic rocks invaded by Tertiary calcalkaline intrustive rocks. The Central Cascades, lying south of the North Cascades, exhibit a younger, higher level geologic environment comprised of predominantly early to middle Tertiary volcanic rocks and subordinate sedimentary rocks which are intruded by Tertiary calc-alkaline igneous rocks. Although the Tertiary Cascade intrusions are dominantly quartz dioritic, copper mineralization is commonly found in rocks of quartz monzonite to granite composition. These acid rocks appear to be the product of late stage magmatic K alteration of the original quartz diorites. Sulfide concentrations are considered to be in part dependent on the degree of K-silicate activity and the intensity of transverse structural deformation.

Jan 1, 1973

By Joseph Kuti

Longwall mining is the term used for the underground extraction of a wide and deep panel of coal. Such a panel may be blocked out by one or more entries on either side ("head" and "tail") of a longwall face. If all the entries are pre-driven, the panel extraction is termed longwall retreat mining. With one exception, all the longwall faces in the United States are of this type3 Prior to the general decline in the rates of production with Continuous Miners, the development of the multiple entries generally kept ahead of the longwall extraction rate. This is no longer the case: longwall extraction rates far exceed the rate of development. In addition to this problem, in newly established mines, the development of a haulage and bleeder system based on multiple entries results in a lead-time of three years or more before longwall mining can be applied. This is one reason why earlier projections and much of the optimism attached to longwall mining as a principal "savior" in the energy crisis should be viewed with some caution. The alternatives to retreat mining with multiple entries are: Modified retreat mining- where the tail-entry is being formed during the mining of-the panel ("2"-system). Some form of advance mining-where the head-entry or both head and tail entries are being formed as part of the longwall extraction process. These methods are well-known and well-established. Variants of them are being practiced in Canada, Central and South America, but not in the US. It is primarily the laws governing ventilation-conceived for room and pillar mining which prevent the rapid development of these techniques. Another aspect of longwall mining is that it requires a systematic and consistent approach in organization, roof control, ventilation and transport. It is for this reason that compliance with health and safety regulation is fairly well ensured if the longwall system has been well laid out and is subsequently well-run. Nevertheless, a management mentality raised in the great flexibility of the room and pillar system cannot always come to terms with the degree of forward planning and rigid discipline required to successful longwall mining. Research, development and other investments in the partial aspects of longwall mining are always of interest, but no massive trend to longwall can be expected realistically unless these major stumbling blocks in the basic law and basic approach are effectively removed.

Jan 1, 1980

By S. A. Hovanessian

Analytical solutions are obtained for calculating the pressure distribution in rectangular fields due to injection and/or producing wells located anywhere within the field. The field is assumed to be homogeneous with either constant pressure or no-flow boundaries. These solutions are extended to include the calculation of average reservoir pressure and permeability from pressure build-up curves. Numerical examples are given to illustrate the application of equations to practical problems. INTRODUCTION Pressure distribution analyses are of considerable importance in the field of reservoir mechanics. A number of papers dealing with this subject have appeared in the petroleum literature. perrinel in 1956 presented a summary of the methods available for pressure build-up calculations and discussed the applicability of each in some detail. More recently (1958), Hazebroek, et a1,2 discussed a theoretical method for obtaining pressure distribution in a radial field. Also in 1958, Nisle3 gave a theoretical solution of the pressure distribution in a field extending to infinity with a partially penetrating line source at the origin. Mathews, et a1,4 applied the method of images to existing solutions for pressure distribution in radial fields and obtained expressions for calculating pressures in bounded reservoirs. However, a literature survey revealed that a general analytical solution for the pressure distribution in a rectangular field, with injection and/or production wells located anywhere within the field, was not available. Such a solution could be used to approximate the pressure distribution in a field the shape of which is nearly rectangular. Furthermore, it could be applied to pressure calculations pertaining to a single well taken from a system of wells which were drilled in a rectangular pattern. In this case the boundaries of the well drainage area are considered to be the perpendicular bisectors of the lines joining the well and its nearest neighbors. The basic problem considered in this paper consists of a rectangular field with either constant-pressure 01 no-flow boundaries and with either an injection or production well located anywhere within the field. The physical properties of the rock and fluids present are considered to be constant. Analytical expressions are obtained for the pressure distribution within the field during the production or injection periods. These expressions, which are infinite series, can be used to evaluate pressure at any point within the field as a function of time and position. For fields containing more than one well (production and/or injection), the solutions for each well acting independently are superposed. That is, at any point in the field, the pressures due to each injection 01. production well acting alone can be algebraically added to give the pressure resulting from all wells acting simultaneously. Evaluation of the series solutions given in this paper is readily accomplished by means of an electronic digital computer; and, in most cases, sufficient accuracy is obtained by setting the upper limits of summation at 20. These solutions are extended to include the calculation of average reservoir pressure and permeability from build-up data. A number of numerical examples are given to illustrate application of the solutions to actual field problems. ANALYTICAL SOLUTIONS The partial differential equation representing the pressure distribution in a homogeneous rectangular field (see Fig. I.), having a single source or sink of strength (2, can be written*

By C. B. Scotty, E. F. Egan

INTRODUCTION The neutron-garnma log has been used for stratigraphic correlation by the oil industry for a number of years. In the past few years, the quantitative application of the log to provide information with respect to porosity has received considerable attention. The basic concept of quantitative interpretation has been pointed out in the literature.1 It shall be the purpose of this paper to develop by empirical means a method whereby the relationship of porosity to neu. tron-gamma deflection may be predicted for various bore hole diameters. This relationship is applicable to the present commercially available neutron-gamma log run in open hole. Data available at present are insufficient to establish similar correlations for cased holes. Through the development of such a correlation, the importance of the various factors which influence the log become evident. NEUTRON-GAMMA CURVE The logging tool conisists of a source of neutrons and a means of detecting and measuring gamma rays, the detector being shielded from the direct emission from the source. The gamma rays reaching the detector have three sources of origin: (1) the natural gamma radiation emitted by the formations, (211 induced gamma radiation resulting from neutron bombardment. (3) gamma rays emitted by the source and scattered by the formation. It has been found that a neutron derived porosity correlation is best for shale-free formations. Under this condition the natural gamma ray radiation is quite low, and therefore, will be neglected in this work. The induced gamma ray radiation resulting from neutron bombardment is predominantly a function of the hydrogen atom concentration of the substance penetrated. Due to the geometry of the presently used system, the neutron-gamma curve indicates low radioactivity opposite high hydrogen concentration and high radioactivity opposite low hydrogen concentration (Figs. 1 and 2). Having a curve which measures hydrogen atom concentration, it follows that if the matrix of the formation penetrated consists only of atoms other than hydrogen, and if the fluid filling the pores is either oil or water, the curve should be an indication of porosity (both oil and water have practically the same number of hydrogen atoms per unit volume'). The above criteria for a porosity (Correlation are fulfilled in clean sandztones and limestones in which the pore volume is completely filled with liquids (oil or water), but not in formations containing either free gas or shale or both. Free gas. even under pressure, contains considerably less hydrogen per unit volume than oil and water; therefore, a variation in response on the curve would be expected. Camp- bell and Winter,' indicate that this difference in hydrogen concentration is sufficient to distinguish between sands containing water or oil and those containing dry gas. Shale is a mineral that contains hydrogen in its molecular structure in addition to the hydrogen which is present in the water of hydration. Thus, in formations containing variable amounts of shale, the hydrogen concentration indicated by the curve is not a direct indication of porosity. Bush and Mardock' have indicated that a correction may be made by use of the gamma ray curve to provide a porosity correlation. Since the induced gamma rays are predominaiitly a function of hydrogen concentration, it would be anticipated that the fluid filled bore hole would materially influence the logs. It has been pointed out that the neutron-gamma curve response decreases with increase in hydrogen concentration, therefore, the response due to the induced gamma ray component decreases with increase in fluid filled hore hole diameter. The scattered gamma ray component of the log increases with increase in bore hole diameter. Although there is an

Jan 1, 1952

By Norman Weiss, H. W. Kaanta

CUSTOM ores reach across the New Mexican mesa to American Smelting & Refining Co.'s new lead-zinc mill at Deming. The influx of ores justified increasing mill capacity from 12,000 tons per month to 20,000 tons per month with the installation of a second milling section. Deming mill has met a complex material handling problem with the successful instrumentation of modern machinery and knowledge. A tight, compact plant does a big job with the aid of the latest ore moving equipment. Location and Layout The mill is located three miles northwest of Deming in the tumbleweed covered valley of the Mimbres River, 30 miles north of the Mexican border. Deming has a population of 4000 and is about halfway between Lordsburg and Las Cruces and 54 miles southeast of Silver City. The AT&SF and the SP railroads and U.S. Highways 70, 80, and 260, cut across the mesa to the town. Asarco mill station is east of the AT&SF single track, and north of Deming. The nearly level terrain is covered with fine sand supporting only yucca and tumbleweed. Compacted gravel at depth affords excellent foundation bearing. The climate is semi-arid, but the district is underlain by water-bearing strata. Tailing disposal space is plentiful. The Deming site appeared favorable because of easy rail and highway access, central location in a mining district, excellent climate, plentiful water supply, space for all present and future requirements, and proximity to a town. The milling plant is a 250-ft square. The rail spur forms the west side; sampling plant, fine-ore conveyor and bins are on the east; track hopper, primary conveyor, and crushing plant lie on the south; and the mill building completes the north side of the square. Construction The mill site was chosen and the land purchased in 1,946 and 1947. Design began in 1948, and Stearns-Roger Mfg. Co. of Denver started construction in June 1949 completing work in April 1950. Construction is steel and concrete throughout, with main concrete floors supported on cellular steel beams. The building is covered by galvanized corrugated iron, attached to the frame by welded Nelson studs, and made dust tight at the joints with roofing paper and asphalt sealing compound. Crushing and Sampling Custom ores, delivered to the mill by railroad cars or trucks, are weighed on arrival. A Robbins car shaker dumps the ore into a 100-ton capacity steel hopper. Adjacent is a 40-ton truck hopper. Three 36-in. Pioneer apron feeders supply ore from the receiving hoppers to a 36-in. conveyor which runs to the crushing plant. A tramp-iron detector protects the primary crusher except when handling magnetite containing ores. A 2 ½ -in. spaced grizzly precedes the primary Traylor 24x36 in. jaw crusher set at 4 in. A Symons 4-ft cone crusher in closed circuit with 48x78 in. Robbins Gyrex screen completes crushing to 5/8 in. The discharges of both crushers drop upon a common conveyor, which, after gaining sufficient elevation, transfers ore to a return conveyor. This return conveyor passes under a suspended magnet and over a magnetic head pulley to the Gyrex screen. Screen undersize is conveyed by a 20-in. belt to the sampling plant. Crushing rate varies from 60 to 90 tons per hour. Ores containing magnetite and pyrrhotite nullify the magnetic detector and overload the magnets

Jan 1, 1952