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By Philip D. Pearson

Competition is the problem and modernization is the solution in today's underground iron operations on the Lake Superior Range. Profound changes in the iron ore picture during recent years have prompted correspondingly great changes in the economic position of the Lake Superior underground mines. To meet the ever growing competition from other lower cost iron sources, underground operators are becoming increasingly aware that the newest advancements in mining technology must be incorporated in their operations. UNDERGROUND POSITION TODAY The extraction of iron ore by underground methods has been going on for many decades in the Lake Superior region, starting in 1872 on the Menominee Range. The number of mines has changed gradually over the years as new ones were opened and old ones were exhausted, but in recent years, the most drastic change occurred from 1960 to 1961. In 1960, there were 31 underground mines operating in Michigan, Minnesota and Wisconsin, but at one period in 1961 only 20 were operating (Table I). In western Ontario so far there has been only some temporary curtailment of operations. Of the 11 U.S. mines which ceased operations in 1961, some may he closed only temporarily, but some will remain closed for our lifetime, at 'east, unless there is a tremendous reversal of the present trend in the iron ore market

Jan 3, 1962

By T. H. Alden, H. W. Schadler

The strain rate dependence of the flow stress of the eutectoid Zn-Al alloy has been determined as a function of mechanical processing, microstructure, and temperature. The best superplastic properties result from the ultrafine, equiaxed structure produced by solution treatment and isothermal transformation at 0°C. Lamellar structures produced by isothermal transformation and coarse equiaxed structures produced by annealing also exhibit strain rate sensitivity in excess of 0.5, but at higher stresses and lower strain rates than the finest structure. Solution treatment and isothermal transformation eliminate the effect of prior processing history. Small composition variations in the binary alloy do not influence the mechanical properties. Below the eutectoid transformation temperature (.275C) increasing temperature lowers the flow stress at all strain rates. The data do not favor any of the present proposals for the mechanism of superplastic flow. ALLOYS of zinc and aluminum, near the eutectoid composition, have been investigated for: 1) the flow stress-strain rate and elongation behavior,1, 2) the transformation kinetics,3 and 3) structure,3"5 but the structure sensitivity of the mechanical properties is poorly understood. Using a near eutectoid alloy water-quenched from 380°C, Backofen et aL2 estab- high and increases with increasing strain rate. They found a correlation between strain rate sensitivity and tensile elongation as expected from the increased resistance to necking that a high strain rate sensitivity provides.296 The large elongation at high strain rates is attractive for metal forming. Since most other superplastic alloys7-l3 do not show high strain rate sensitivity at such a high strain rate (for the exception see Ref. 12) there is the possibility of a unique deformation mechanism for this alloy. The sensitivity of the mechanical properties of the eutectoid alloy to thermal history1 suggests a structure sensitivity that has not been demonstrated. Gar-wood and Hopkins3 identified a lamellar product for material transformed between 200" and 260°C. The size of the lamellae decreased with decreasing temperature. They also demonstrated that an unresolved transformation product formed below 200°C. A granular two-phase material was resolved for specimens quenched to below 150°C by Mitbauer and sauerwald4 who observed coarsening of the structure after annealing. The role of grain boundaries in superplastic deformation is suggested by the strong effect of grain refinement in encouraging this phenomenon at high strain rateS7-11, 13 and is emphasized in several proposals about rnechanism7, 8, 12 and in a theory14 of high-temperature deformation. Alden8 showed metallographic evidence that grain boundary sliding is occurring extensively at strain rates where m is large but less at high strain rates where normal plasticity is observed. Holt and Backofen10 have shown that sliding also oc-

Jan 1, 1969

By H. H. Pentz

This paper gives the derivation of a practical formula for the calculation of slopes in seismic reflection prospecting. The derived formula is an approximation and can be used where the slope of the reflecting horizon is less than 250 ft. per 1000 and the depth to the reflecting horizon is greater than 2500 ft. The slope of sediments in oil regions is generally considerably less than 250 ft. per 1000. This is particularly true of the Gulf Coast, with the exception of the salt domes, which usually have the sediments at a greater slope than 260 ft. per 1000. Derivation In Fig. 1, o represents the image of the shot point a. Then the length of the path acb is equal to ob and ae'd is equal to od. In the triangle aob, p is equal to ob, x is equal to , and c is equal to ao. The angle u is the apparent dip of the reflecting horizon. Angle oab is equal to (90" - u). The quantity m is the slope of a line tangent to the curve, defined by equation 1, at the point (p, x). The quantity m' is the slope of the line tangent to the curve at the point (p', 2').

Jan 1, 1940

By H. H. Pentz

This paper gives the derivation of a practical formula for the calculation of slopes in seismic reflection prospecting. The derived formula is an approximation and can be used where the slope of the reflecting horizon is less than 250 ft. per 1000 and the depth to the reflecting horizon is greater than 2500 ft. The slope of sediments in oil regions is generally considerably less than 250 ft. per 1000. This is particularly true of the Gulf Coast, with the exception of the salt domes, which usually have the sediments at a greater slope than 260 ft. per 1000. Derivation In Fig. 1, o represents the image of the shot point a. Then the length of the path acb is equal to ob and ae'd is equal to od. In the triangle aob, p is equal to ob, x is equal to , and c is equal to ao. The angle u is the apparent dip of the reflecting horizon. Angle oab is equal to (90" - u). The quantity m is the slope of a line tangent to the curve, defined by equation 1, at the point (p, x). The quantity m' is the slope of the line tangent to the curve at the point (p', 2').

Jan 1, 1940

(Members are urged to send in for this column any notes of interest concerning themselves or their fellow-members.) Members who registered at Institute headquarters during September: William B. Phillips, Austin, Texas. Will L. Clark, Jerome, Ariz. Olof Wenstrom, Boston, Mass. Robert H. Richards, Boston, Mass. Anthony F. Lucas, Washington, D. C. Hennen Jennings, Washington, D. C. P. H. Griffin, New York, N. Y. Waldemar Lindgren, Boston, Mass. H. N. Lawrie, Portland, Ore. C. Snelling Robinson, Youngstown, 0. Clarence P. Linville, Everett, Pa. E. P. Ross, Johnson, Tenn. Members of the XII International Geological Congress who made the Institute Office their headquarters while in New York A. Bigot, Caen, France. E. Gentil, Paris, France. J. Caillebotte, Paris, France. H. Saint-Clivier, Paris, France. John Ashworth, Manchester, England. Tadasu Hiki, Kioto, Japan. T. Dahlblom, Falun, Sweden. L. Milch, Greifswald, Germany.

Jan 10, 1913

By E. E. Malouf

Rapid depletion of the world's mineral deposits combined with the expanding demand for metals places great pressure on our ability to provide technologically and economically feasible processes to recover greater amounts of metals from progressively lower grade sources. Chemical mining is one area in which expanding research and development can provide new processes or refinements to existing ones. These new techniques could result in increased production of metals from materials now considered uneconomic to process by current technology. To mine by chemicals requires the interaction of such disciplines as hydrometallurgy, microbiology, chemistry (both organic and inorganic), fluid flow, mineralogy, geology, and of course, economics. One of the least understood areas but one which may end up being an essential part of any chemical mining process is microbiology, i.e., the role of microorganisms in altering minerals and metals in solution.

Jan 1, 1971

By C. D. Rugen

GROUND raw material as fed to the cement kiln generally is a mixture of two to four components, each of which may have widely varying physical and grindability characteristics. Chemically similar materials found in the same or different deposits may also differ appreciably in physical properties, depending on their crystalline structure. The calcareous or principal cement raw material may vary from a soft chalky limestone or friable cement rock at one plant to a hard limestone or oyster shell at another plant. Argillaceous materials include clays, shales and granulated slag. Siliceous and/or iron-bearing material, including sand, iron ore and cinders, may also be required in addition for certain types of mixes. Frequently differences in grindability characteristics are not given the attention they deserve in comparing grinding results at one plant with those at another or in selecting suitable circuits or equipment. Many types of crushing and grinding units are used, with numerous open and closed circuit arrangements. Both wet and dry processes are used successfully. When rebuilding or installing a new grinding department, the choice of process or circuit in some cases may be dictated by the nature of the materials being ground but in other cases it may be the result of good salesmanship or a compromise. An over-all evaluation of wet process vs. dry process grinding should not be made without considering the effects on all other producing departments in the plant. In general, the more recent grinding installations, both wet and dry, have employed closed circuits, but many older open circuits are still in successful operation. In our experience, closed-circuit raw grinding pays, because of lower power consumption and less operating labor per ton of product. However, some dry open-circuit mills with improved equipment and operating methods compare favorably in performance with dry closed-circuit units. CHARACTER OF GROUND RAW MIX (KILN FEED) Grinding in the cement plant in general requires a considerably finer product than in most ore-grinding operations. A distinction between fineness of kiln feed and of cement may be made in that kiln feed preferably should be ground to a limiting size, whereas finished cement should include a range of size fractions including sufficient fine flours to give a product with satisfactory physical qualities. Grinding raw mix for kiln feed therefore is more comparable to ore grinding, although the limiting size is smaller. Most kiln feeds are ground from 85 to 95 per cent passing 200-mesh, depending on mix composition. Some cement chemists believe that raw materials cannot be too fine, since finer particles theoretically combine more readily and intimately in the kiln. However, there are certain definite practical objections to extremely fine kiln feed, such as loss of kiln dust, unstable material flow through the kiln and greater difficulty in control of chemical composition due to dust loss, and the disproportion of fines from the more easily ground component. Our

Jan 1, 1945

By Arnt Solbu, Jomar Thonstad

The reaction between CO, and aluminum in cryolite-alumina melts in contact with aluminum has been studied by passing CO2 over the melt. In unstirred melts a homogeneous reaction between dissolved metal and dissolved CO2 was observed. In stirred melts in which convection was induced by bubbling argon through the melt, the dissolved metal apparently reacted mainly with gaseous CO2. The rate of formation of CO increased slightly with increasing depth of the melt, and it did not depend on whether CO2 was passed over or bubbled through the melt. The rate of formation of CO increased with increasing area of the metal/melt interface and with the application of anodic current to the metal. It is concluded that the dissolution of metal into the melt is the rate-determining reaction. THE current efficiency in aluminum electrolysis is determined by the rate of the recombination reaction between the anode gas and the metal: 2A1 + 3CO2—A12O3 + 3CO [1] as originally stated by Pearson and waddington.1 The occurrence of this reaction in cryolite-alumina melts in contact with aluminum was first verified experimentally by Schadinger.2 Thonstad3 has shown that the reaction may proceed further to give free carbon: 2A1 + 3CO— A12O3 + 3C [2] Normally only a few percent of the CO formed undergoes such reduction. The mechanism of these reactions has not yet been clarified. Aluminum, as well as CO,, is soluble in the melt. The solubility of aluminum in cryolite-alumina melts at around 1000°C corresponds to 75 x 10- 6 mole A1 per cu cm,4 while that of CO2 is only 3 x 10-6 mole CO, per cu cm.5 Taking into account the stoichiometry of Reaction [I], the ratio between dissolved aluminum and dissolved CO2 available for the reaction in a saturated melt is about 40. Therefore, as will be shown in the following, the reaction probably mainly occurs between gaseous COa and dissolved aluminum. The dissolved aluminum presumably consists of subvalent ions of aluminum and sodium.4'6 Since the interpretation of the present results is not dependent upon the nature of this solution, the dissolved metal will be designated solely as Al+ in the following. The reaction can then be divided into four steps: A) dissolution of metal, e.g., 2A1 + Al3 — 3A1+ [3] B) diffusion of dissolved metal through a boundary layer; C) transport of dissolved metal through the bulk of the melt; D) Reaction [1]. If dissolved CO, takes part in the reaction, three additional steps embodying the dissolution and transport of CO2 must be added. schadinger2 observed, when bubbling CO2 through the melt, that the rate of formation of CO (in the following designated rfco) did not depend on the distance from the metal surface. The results also indicate that the rate of bubbling did not affect the rfco. When passing CO, over the melt, Revazyan7 found that the loss of metal did not depend on the depth of the melt above the metal or on the flow rate of CO2, and concluded that Step A is rate-determining. In an unstirred melt, however, Gjerstad and welch8 found that the rfCo decreased with increasing depth of the melt, indicating that step C was rate-determining. It thus appears that the rate control of the process depends on the experimental conditions, particularly on the convection. In the present measurements the reaction has been studied in unstirred as well as in stirred melts. EXPERIMENTAL AND RESULTS The experiments were carried out at 1000°C in a Kanthal furnace with a 10-cm uniform temperature zone (±0.l°C). The melts were made up of "super purity" aluminum (99.998 pct), hand-picked natural cryolite, and reagent-grade alumina. In experiments where alumina crucibles were used, the alumina content in the melt was close to saturation (13.5 wt pct9); otherwise it was 4 wt pct. Pure Co2 (99.85 pct) was passed over the melt, and the exit gas was analyzed for CO2 and CO by the conventional absorption method.3 From the weighed amount of CO (as CO2) the rfco was calculated as the number of moles of CO formed per min per sq cm of the surface area of the melt. The amount of carbon formed by Reaction [2] was not determined. As already indicated the rfco is much higher than the rfC, by Reaction [2]. Since the rfC probably is proportional to the rfco, the measured rfco should then the proportional to, but slightly lower than, the total rate of Reactions [I] and 121. In general the scatter of results obtained in duplicate measurements was ±5 to 10 pct, while within a given run a precision of ±3 to 5 pct was obtained. The various crucible assemblies that were used will be described below. Measurements in Unstirred Melts. When carrying out aluminum electrolysis in small alumina crucibles. Tuset10 observed that after solidification the lower part of the electrolyte was gray and contained free metal, while the upper part near the anode was white and contained no metal. One may test for the presence of free metal by treating with dilute hydrochlorid acid.

Jan 1, 1969

By H. Scott

IN a paper read before the Institute of Metals, Rosenhain 1 described a new type of furnace designed primarily for the thermal analysis of metals by the inverse-rate method and used by him in the metallurgical department of the National Physical Laboratory with considerable success. In his discussion of this furnace, Rosenhain pointed out some difficulties met with in its operation, such as uniformity of rate of heating or cooling being inadequate for the degree of accuracy aimed at. To overcome this difficulty, he suggested, in place of motor propulsion, a gravity drive controlled by a"hydraulic cylinder with a relief valve whose width of opening can he regulated to allow of any desired rate of motion." The authors, in constructing a thermal-analysis furnace of Rosenhain's type, have therefore followed this suggestion and also added certain features that increase somewhat the convenience and simplicity of its operation. Requests for information regarding this furnace and the highly satisfactory results obtained from its use, it is believed, justify describing its construction and operation in sufficient detail to make possible its duplication or improvement. Description of Furnace.-The details of the furnace construction are shown in Fig. 1, which is drawn to scale. The heating tube is of /4 in. (6.35 mm.) wall "alundum" heated at the upper end by seventeen turns of 0.52 mm. platinum wire, which is coated with "alundum" cement supplied for this purpose. The cement coating is essential when a high temperature (over 1000° C.) is required, as it prevents hot spots with the resulting burning out of the heater. This platinum-wire winding, unlike "nichrome," is entirely satisfactory for temperatures of at least 1000° C. It has been maintained at that temperature continuously for 2 months and shows no signs of deterioration. This temperature is maintained by a current of 5 amp. drawn from 30 volts potential, so its necessarily continuous operation is quite economical.

Jan 8, 1919

By T. E. Watkins, M. D. Nelson

INTRODUCTION Deeper drilling for oil is becoming more and more the rule rather than the exception. With deeper drilling come additional problems, perhaps the greatest being those brought on by the higher temperatures encountered down the hole. particularly in the Gulf Coast region of Texas and Louisiana. Temperature gradients of the order of 1.8° to 2.0°F/100 ft are not unusual, and a gradient of 2.3"F.'100 ft is found in some areas of Texas. With a mean surface temperature of 74oF, the following temperatures could be expected for a geothermal gradient of 2.0°F; 100 ft: at 10,000 it. 271°F. 12,000 ft, 314°F: 14,000 ft, 354,oF; and 16.000 ft. 394°F. Severe gelation of lime-base drilling fluid in wells that have high bottom hole temperatures has become perhaps the most serious difficulty enconntered in drilling under such conditions. Lime-base drilling fluids have been very succesefully and widely used in the drilling of wells in the Gulf Coast region because of their inherent stability toward contaminants. their ability to suppress the swelling dispersion of bentonitic shales, and their ease of maintainance. The gradual recognition: during the past few years, that these muds were. in themselve. the cause of many difficulties experienced in drilling has led to wide-pread efforts by the drilling industry. to determine the reasons for the failure of these mud systems and to develop mud systems capable of performing satisfactorily under high-temperature conditios. MANIFESTATIONS OF HIGH-TEMPERATURE GELATION it is generally possible to recognize the symptons of high-temperature gelation early enough that advance predictions can be made of serious difficulties. in mud control, and the useful life of the drilling fluids can be extended by proper treatment. Following i.; a list of the manifestations of high-temperature gelation: (1) The drill string 'takes weight' while going in the hole after a trip. In early stages of high-temperature gelation it is possible to notice a slight reduction in drill string weight as the drill pipe is lowred near the bottom of the hole. (2) Excessive pump pressure is required to .tart the circulation of drilling fluid at or near the bottom of the hole when going hack to bottom after a trip. As the severity of the gelation increases it may be necessary to break circulation a number of times when going in the hole. (3) The drilling fluid from the bottom of the hole is thick and often granular or lumpy when pumped up after making a round trip. In a severely gelled drilling fluid system such a condition may be irreversible; that is, it cannot be stirred or chemically treated to produce a satisfactory drilling fluid. (4) Completion tool.. such as logging tools or perforating guns will not sink to the bottom of the hole. On some occasions completion tools will become stuck and require a fishing job to retrieve them if the wire line attached to them is broken. It is often difficult to determine whether the condition of the drilling fluid is responsible for sticking the tool or whether the wire line becomes key seated in a crooked hole and causes the allow difficulty. When there are 110 other symptoms of high-temperature gelation. then the difficulty may usually be attributed to the latter cause. (5) In extreme cases of high-temperature gelation it is necessary to "wash" and "ream" when going back to bottom after coming out of the hole. (6) In many -instance. it has been found to be extremely difficult and expensive to 1111 production packers 2nd tubing in moderately deep oil wells which had been drilled with a lime-base drilling fluid. In such instances-the original mud had apparently "set" to a consistency approaching that of a weak cement. CAUSES OF HIGH-TEMPERATURE GELATION Extensive test; have indicated that a lime-base mud does not develop a highly gelled condition at temperatures below 250°F. whereas above that temperature such condition often develops rapidly. (Fig. 1) concurrently. the following changes are evident ill the mud: (1) The alkalinity of the mud decreases to a very low value. with both caustic soda and lime being consumed. (2) The quartz content of the mud decreases sharply. (3) The bentonitic content of the mud decreases or di-appears, with concurrent decrease or loss of base exchange capacity of mud solids. (4) New compounds formed in the mud have been found to be cal-cium silicate, calcium aluminum silicate, and calcium sodium aluminum silicate. (5) The mud loses the ability to form a filter cake of low permeability. The above characteristics have been discussed, in part. by other authors

Jan 1, 1953

By T. S. Lundy, F. R. Winslow

DIFFUSION coefficients of Hf181 in the high-tem-perature bcc phase of reactor-grade hafnium were determined at temperatures of 1795° to 1995°C by standard lathe-sectioning techniques. The temperature dependence of the data may be described by an Arrhenius-type expression for this limited temperature interval. However, hafnium is classed with the "anomalous" bcc metals zirconium, titanium, and y uranium by the low values of Do and Q observed in this study. The hafnium metal was received as 1/2-in.-diameter crystal bar. Analyses by the Analytical Chemistry Division of Oak Ridge National Laboratory showed the major impurity to be zirconium— about 2.1 pct. The total interstitial content was about 225 ppm with 190 ppm of this oxygen. The Hf"' was supplied as HfC12 in HC1 solution by the Isotopes Division of Oak Ridge National Laboratory. The hafnium bar was cut into disk-shaped specimens 3/8 in. long. One of the flat faces of each specimen was metallographically treated and then the isotope was deposited by vacuum evaporation from a tungsten filament. A 3 by 3 in. NaI (Tl) crystal with a single-channel analyzer was used for counting y rays with energies of 0.3 to 0.7 Mev. The as-deposited layers of isotope had counting rates of about 200 counts per sec. Specimens were annealed in argon in a tantalum resistance furnace. Temperatures were measured with a microoptical pyrometer calibrated for the particular furnace sighting conditions. All sectioning was done by standard lathe techniques. Section weights were determined on a semimicrobalance. A density of 12.5 g per cu cm was used in determinations of section thicknesses. Activities associated with the various sections were measured and the penetration data were treated using the computer code by winslow.' In all cases, except for specimens annealed at temperatures below 1795°C, normal Gaussian penetration behavior resulted. At lower temperatures, plots of In A(x) vs x2 were nonlinear [~(x) = relative activity at a distance x from the

Jan 1, 1965

By P. Martinez, A. F. Hoyte, F. E. Senftle

The possibility of applying a neutron activation technique for silver exploration is considered. A mobile positive-ion accelerator type neutron source is used to irradiate a small area of rock or soil in situ. By using a short period of irradiation and gamma ray spectral analysis, a technique is shown for silver exploration. Two different mobile units are described. Laboratory and preliminary field tests both indicate that a sensitivity of less than 1 oz of silver per ton of ore can be achieved. The increasing consumption of silver for industrial uses and also for coinage has caused a serious shortage of silver in this country. The silver shortage has been reviewed and analyzed by kiilsgaard1 who concludes that, "The best hope for meeting future demands for silver is through accelerated exploration for precious ores." As almost all the exposed "bonanza" type silver deposits evidently have been found, it is urgent that some sensitive geophysical technique be found to detect large, extended, but generally low-grade, secondary ores, as well as hidden vein deposits. Silver is easily made radioactive by exposure to slow neutrons; hence a neutron activation method appears promising for locating silver deposits. The principles of mineral beneficiation using neutron activation techniques were discussed some years ago.2-4 Using the same approach, a preliminary description5 has been published of neutron activation as a mineral exploration tool. An exploration technique is described in which silver is made radioactive in situ and detected with a gamma radiation counter. The technique is similar to the well-known method used for uranium exploration. THEORETICAL CONSIDERATIONS Elemental silver consists of two isotopes, Ag107 and Ag109, having naturally occurring isotopic abundances of 51.4% and 48.6%, respectively. For short periods of irradiation of silver by thermal neutrons, the long-lived 250 day, half-life isotope, Ag110m, is not produced in significant quantities. However, significant quantities of 2.3 min half-life Ag108 and 24.5 sec half-life Agl10 are formed by the following reactions. Ag108 and Agl10 emit a 0.44 Mev (million electron volts) and a 0.66 Mev gamma ray, respectively. Ag107 + n + Ag108 (2.3 min) Ag109 + n + Ag110 (24.5 sec). Because of the large capture cross section (110 barns) of Ag109, and short half-life of Ag110 (24.5 sec), the 0.66-Mev gamma ray is the most prominent emission from silver for neutron activation periods of about a minute's duration.* The 0.44-Mev gamma ray from Ag108 will also be present, but will be one or two orders of magnitude lower in intensity. The decay scheme of Ag110 is shown in Fig. 1. If the neutron irradiation time is limited to about 100 sec, the Ag110 activity will essentially reach saturation and can be used to detect the presence of silver. In a neutron flux of 10 8 neutrons/cm2/set, the induced 0.66-Mev activity in 1 g of silver will be about 2 x 107 disintegrations per sec. This is about 1000 times the measurable gamma activity of 1 g of uranium in equilibrium with all its decay products; hence there is ample activity for detection. Under the same conditions of activation, most of the other elements do not reach this relatively high disintegration rate. Although this is in favor of the proposed technique, other problems must be considered. For mobile operation, it is desirable to obtain the largest neutron flux to weight ratio. Hence we have used a small 150-kev accelerator-type neutron source rather than an isotopic source such as an americium-beryllium neutron source. By use of remote control system, an accelerator-type neutron source can be safely used without the massive shield required for an isotopic source. Moreover, an accelerator-type source is more versatile in that it allows one to use a flux of either 14-Mev or 3-Mev neutrons, depending on whether a tritium or a deuterium target is used. With a 14-Mev generator, one can obtain a flux of 10 9 neutrons/cm 2/sec, and with a 3-Mev generator, the flux is generally two orders of magnitude less. Although silver will become activated with either generator using proper moderation, detection may be

Jan 1, 1968

By H. M. Zoerb

Based on the belief that operating details are a definite contributing factor to major economies, this paper traces the development of crushing cavity design in Symons cone crushers to attain maximum liner utilization. Wear rates are analyzed and compared in this presentation and drawings illustrate succeeding design changes. IN these times of rising labor and material costs, it has become more and more necessary that attention be paid to some operating details which, in their obscurity, may he the key to major economies. Liner wear in crushing cavities of secondary and tertiary crushers can become an appreciable cost item when the material to be crushed is hard and abrasive. This item of cost not only includes the value of the crushing members, but also more intangible costs such as labor and lost production due to more frequent replacement. The variables which are encountered in ores and minerals to be reduced; the design of plant and machine application; the sizes, shape, and fineness, characteristics of the crushed product; the moisture; hardness; friability; and abrasiveness of the material to be crushed are all influencing factors which must be taken into consideration in the selection of a crusher, and particularly in the design of crushing cavity and liners to be used in a crusher. Through a research program undertaken in cooperation with many operators of Symons cone crushers a new approach to crusher cavity design was made, resulting in the development of liners for specific operations which showed: 1—maximum utilization, as high as 70 to 80 pct of original weight of metal, and 2— maximum capacity of unit during the greater portion of its life. It has been found that liners so designed for a given operation will show added economies in power consumption, maintenance, and general wear and tear on the crushing unit. Initial work in the so-called tailoring of crushing cavitles was begun on the tertiary or fine crushing units where as a rule reduction ratios were low, varying from 3 to 6. Parallel or sizing zones in the lower portion of the crushing cavity were too long, resulting in a tendency to pack. It was found that very little additional crushing was done in the parallel zone after the initial impact in that zone and that a relatively small amount of' additional crushing was done by attrition, which required very careful feed control. A small amount of over-feeding would result in packing which not only consumed power but caused unnecessary liner wear as well. The illustrations which follow in this discussion will show only contours of crushing cavities, and for purposes of simplification the cavities will be considered only in their closed position. The first step, therefore. was to reduce the sizing zone to a minimum. This was done by removing the lower portion of the liner as shown in Fig. 1. The result of the change was a saving of 15 to 20 pct in liner cost, less power consumption, with no change in capacity. This change in design, while an improvement, did not go far enough. As wear took place, the change in the liner was not uniform throughout its entire length, resulting in a restriction of the feed opening and thereby loss of capacity. Furthermore, progressive wear of the liner had the effect of lengthening the parallel zone until finally the entire crushing cavity was all parallel zone, see Fig. 2. It is obvious from the reduced feed opening of the worn liner that the ability of the machine to receive material is lessened considerably. Furthermore, the long parallel zone with its worn, irregular profile did not operate at its highest efficiency. The first attempt to overcome this difficulty was carried out on a 5 1/2-ft crusher installed in a plant producing roofing granules. The material being crushed was a very hard graywacke and the crusher was closed-circuited with a screen having .232-in. slotted openings. A radical change in contour was developed, as illustrated in Fig. 3. Equal wear lines on both concave and mantle are designated 1, 2, 3, etc. The method of development of this contour is as follows: Since adjustment for wear is vertical, corresponding intersections of wear lines and vertical lines developed concave and mantle contours which maintained equal but lengthening wear surfaces in the parallel zone. The ideal contour, of course, is one in which the length of the parallel zone remains constant, but because of present foundry practice and heat treating characteristics this is impossible.

Jan 1, 1954

By W. C. Schroeder

During the post-war period, and particularly during the past few years, coal production has been maintained at a reasonably constant level. This is in contrast to the greatly expanded demand for oil and natural gas. Certain markets for coal, such as the railroad and for home heating, have tended to decrease, but this decline has been offset by an increase in demand for other uses, particularly for electric power. Since the United States has very large reserves of coal and relatively limited reserves of natural gas and oil, from the conservation viewpoint, it would be better if the increased demand were to fall more heavily on coal. Where coal has lost certain markets, the decision has not always been made on the basis of price, and, in fact, in many instances, the markets have been lost where coal could show a price advantage. There are various reasons for this situation but it can be attributed in the main to the preference of certain consumers for the convenience offered by liquid and gaseous fuels. In the production of chemicals such as benzene, phenol, or ammonia, coal still plays an important role. As co-products from coke-oven operations, a wide variety of aromatic chemicals are available. In recent years, however, the production has not been sufficient to supply the demand, and it is not profitable to build coke ovens to make chemicals unless there is a market for the coke as well. As a result, the petroleum industry is beginning to take a stronger part in the production of aromatic chemicals. Natural gas has almost displaced the coke-oven water-gas machine for the production of hydrogen for the synthesis of ammonia, as well as for the synthesis of methyl alcohol and other oxygenated compounds. This information is not new and is given here only as a basis for the discussion of the broad significance of the development of the gasification process. It is clear that if coal is to regain some of its old fuel markets, as well as to maintain a position in the field of chemical synthesis, processes must be available for converting coal to the type of fuel the customer wants, and for a cheap method of furnishing gaseous raw material to the chemical industry. The operation of coke ovens and water-gas machines is not the answer to this problem for at least two important reasons: (1) the limited supply and relatively high price of good coking coals, and (2) the relatively high costs of the combined operations of coking and manufacture of water gas.

Jan 1, 1953

By W. A. LaVenue, W. M. Houston

Pebble phosphate mines of Florida have been established from south of Hardee County to north of the Georgia state line, a distance of over 200 miles. Mining has been carried out on an ever-increasing scale since 1885, but phosphate deposits that can be mined on the economical standards of today, are confined in a roughly circular area about 30 miles in diameter, generally within Polk and Hillsborough Counties, in the central part of the State. The phosphate deposit, which is in the Bone Valley formation of Pliocene age, is covered by Pleistocene terrace deposits of unconsolidated quartz sand. The matrix is composed of approximately 1/3 clay slimes, 1/3 silica sand and 1/3 phosphate pebbles. The phosphate usually occurs as rounded pebbles, ranging in size from about 1 in. down to approximately 400 mesh. The phosphate may vary from well-defined hard pebbles to soft weathered rock. The color and character of the phosphate will range from smooth buff pebbles to black and white "salt-and- pepper rock." The screen size distribution varies considerably between locations; the recoverable phosphate may extend down to the 400-mesh size in some areas, while in others the phosphate may cut off sharply at about 35 mesh.

Jan 11, 1962

By F. C. Sturges

FOR some time mining engineers have been interested in the possibility of using small diameter shafts, sunk by core drilling, as aids to ventilation and as emergency escapeways. The possibilities are interesting to contemplate, but new methods involve unknowns, and interest tends to remain passive until these unknowns are solved. Recently we have completed two 36-in. diam. core drilled shafts, and wish to make the data on these available to the industry. Both shafts were drilled for the McLain Fire Brick Co., one at its Buckeye mine and the other at its Colonial mine. Both mines are in the fireclay underlying the Lower Kittanning coal. Both mines have been in operation for a number of years [ ] and have required expensive maintenance work on return airways. It was decided that considerable savings could be effected by short-circuiting the air to the surface through small shafts. It was also realized that these holes, located near the present workings, would be of added value as emergency escapeways. Originally, 48-in. diam. shafts were considered, but actual computations showed 36-in. diam. shafts were more than ample at both mines. The shaft at the Buckeye mine is 240 ft deep, and that at the Colonial mine 258 ft deep. Both holes were started in the lower part of the Conemaugh formation and penetrated Conemaugh and Allegheny strata. The holes were started through the unconsolidated materials overlying bedrock by constructing a concrete collar with a wall thickness of 8 in. Then the shafts were drilled by the shot-core drill method. An annular groove was cut in the rock by the abrading action of chilled steel shot run under the shoe of the core barrel. The drilling was done in stages, the core barrel drilling the groove for a certain distance depending on conditions encountered, and then the cores broken off and taken out in sections. The core barrel had a 36-in. o.d. and the finished diameter of the shaft measured almost 37 in. The major questions that could not be answered until the completion of the first shaft were, (I) how much ground water would be encountered, how would it hinder the drilling, and how difficult would it be to seal off, and, (2) how would the walls of the hole stand up. The holes of course could be cased or lined, but that is considerable added expense in any shaft.

Jan 1, 1947

By Jay A. Carpenter

IN six years the construction of Hoover Dam and the power plants probably will have reached the operating stage and this vast new source of power will then be continuously available for industry. The height of the darn will be 580 ft. and the average annual flow of the Colorado River is calculated at approximately 24,000 cu.ft. per sec. If this full head and average flow can be maintained the year round, about one million horsepower will be generated. The U. S. Reclamation engineers, taking into consideration the probable range in flow and head, have set the figure for power contracts at 660,000 firm horsepower, which can be assured at all times of the year. During the months of heavy run-off of water from the Colorado River Basin the power plants should be able to generate the full 1,000,000 hp. capacity of the power plants, so there will be 340,000 excess or secondary horsepower. The cost of firm power at the switchboard will be close to 2.15 mills per kw.-hr., equal to $14.05 per hp.-yr., and the cost of the secondary or off-peak power will be close to 0.8 mills per kw.-hr., or $5.22 per hp.-yr. In no place in the country can such cheap power be obtained today. The electrochemical industry is in a state of flux because the power costs from its old sources have increased so much (to $30 per hp.-yr. at Niagara) that the industries have had to seek new sources, so they have gone to Canada and Norway and built new plants.

Jan 1, 1932

By F. L. Grammer

In these day, when anthracite is less extensively used as a blastifurnace fuel than it was a generation ago, and managers endeavor to maintain regular and known ore-mixtures, the " freezing " of tuyeres, cinder-notch or iron-notch is infrequeut; and, consequently, the oil-burner or " kerosene blowpipe "* is seldom employed; and furnace-foremen have, to a considerable degree, forgotten their former cunning and persistency in the use of the drill and sledge. Still, in starting new or abandoned plants with untrained labor, and in running some of our large 100-ft. furnaces, slips, resulting in very cold furnaces, may occur, even under experienced managers. During my superintendence of the Cleveland, O., blast-furnaces, such a misfortune, owing to a dearth of trustworthy foremen, was experienced; and our electrician, Mr. Thomas Martin, proposed to open the tuyeres and cinder-notch by means of the heat of the electric arc. We have heard that the surface-cracks or marks developed in rolling heavy plates have been closed by electric welding, as by a soldering-iron, and also that an electric burner has been employed at some German blast-furnaces; but the experiment was quite novel to us; and I think it constituted one of the first, if not the very first, successful application of this device, for the purpose named, in the United States. †

Jan 1, 1902

By L. D. Wooddy, Robert Moscrip

The simultaneous solution of the volumerric balance and the unsteady-state equation has been used for several years to make performance calculations for combination drive reservoirs. This method makes possible the calculation of volumetric changes of fluids in the gas cap, oil zone, and aquifer which occur as a result of withdrawals and reservoir pressure changes. It does not provide a means for the determination of reservoir fluid distribution changes corresponding to these vollrmetric changes. A knowledge of the fluid saturation distribution in the reservoir at various stages of depletion is important for the determination of the efficiency of gas and water as oil-displacement media and, therefore, for the reliable predicrion of ultimate oil recovery. To provide this knowledge, the displacement equations are solved simultaneously with the volumetric balance and unsteady-state equations. The described calculation procedure has been used satisfactorily to analyze the past performance and to predict the future behavior of combination drive reservoirs under both primary and pressure-maintenance operations. INTRODUCTION The three basic mechanisms by which oil is displaced from a reservoir are: (1) dissolved gas drive—the displacement of oil by the expansion of liberated solution gas, (2) water drive—the displacement of oil by water which enters the oil zone from the aquifer, and (3) gas cap drive—the displacement of oil by gas which ex- pands into the oil zone from the gas cap. The action of gravitational forces may be effective in increasing the efficiency of the basic drive mechanisms. Gravitational forces favor the segregation both of gas and oil and of oil and water, thus tending to shorten the transition zone between oil and displacing fluids. Most reservoirs produce under the influence of a combination of these drives and are designated "combination drive reservoirs". Fig. 1 is a cross section of a typical combination drive reservoir. A calculation procedure for analyzing the performance of combination drive reservoirs has been developed by combining the displacement equations' with the volumetric balance equation' and the unsteady-state equations. The pressure-production performance and the positions of the gas-oil and oil-water contacts are calculated for several stages of reservoir depletion by solving these equations simultaneously, thus affording a basis for: 1. Determining instantaneous and ultimate oil, gas, and water production under various operating conditions. 2. 'Establishing a maximum efficient rate of production, 3. Determining the advantages of pressure maintenance and unitization, and 4. Designing surface installations necessary for primarv and pressure-maintenance operations. DEFINITIONS The calculation procedure for combination drive res-

Jan 1, 1957

By Walter Miller

Construction of new large refineries was small in 1937, but extensive modernization and expansion of existing plants were made, bearing out the observation of the Bureau of Mines that the trend is strongly toward fewer and larger refineries. Building the first large combination skimming and cracking unit of 20,000-bbl. capacity was a startling achievement four or five years ago, but it has been exceeded many times since, and at least four units with a capacity of 30,000 bbl. or more were contracted for during 1937, as well as many other units of smaller but still substantial capacity. Installation of polymerization plants for producing high-antiknock blending naphthas from refinery gases progressed at an accelerated rate in refineries affording sufficient raw gas to make the use of the process profitable. The total productive capacity of polymerization units built and contracted for in the United States is now about 25,000 bbl., equivalent to the gasoline production from approximately 55,000 bbl. of crude oil a day. Octane Fuels Also utilizing refinery gases—the butylene fractions in particular—the plants for manufacture of iso-octane increased in number to such an extent that the combined capacities will enable the air forces of the United States shortly to go entirely to the use of 100-octane fuel, indications being that the Army will reach that position in 1938, with the Navy not far behind. Commercial air-lines are expected to take advantage of the greater power of high-antiknock fuels to gain the increased power and increased pay loads possible with their use. Work done on producing fuels with octanes beyond the 100 point has recently been reported, and their production can be expected, although at high cost, when the economics of the situation justifies and engines capable of utilizing them efficiently are available. In the field of motor fuels, important work was reported to the A.P.I. at its annual meeting, on the effect of altitude on antiknock requirements

Jan 1, 1938