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By Pradeep K. Rohatgi, Clyde M. Adams

Dendritic aggregate of ice formed on freezing of aqueous soluitions has been studied. Chlorides of sodium, potassiutn, lithiunz , and hydroget1 were used as solutes. The spacing between ice platelets or den-drites was experimenlally found proportzonal to the square root of freezing time when the freezing rate was constant from beginrting to end of solidification; the constant freezing rates were obtained during freezing of small droplets of aqueous soliitions surrounded by relatively large heat sinks. The transverse growth velocity of the ice platelets is proportional to the square root of the freezing rate. During unidirectional freezing from a constant temperuture chill, the solution at each location is subjected to a spectrum of freezirtg rates. The freezing rate is ini- FREEZING of solutions has been a subject of investigation in many disciplines. Aqueous solutions offer the advantage of transparenty; their study is of special significance due to the increasing interest in freezing processes for desalination. In addition dendritic solidification of aqueous solutions is in many ways analogous to freezing of metallic solutions. Aqueous solutions of most ionic salts freeze with tially low, passes through a maximum, and then decreases until solidificatimz is complete. The den-drite spacing increases linearly with the distance from the chill surface; it is inversely profiortional to the square root of the maximum freezing rate. The dendrite spacings in the two systems (the constanl freezing rate and the varying freezing rate) are equal, when the maximum freezing rate of the varying freezing rate system equals the average freezing vale of the constant freezing rate system. Mass transport in interdendritic liquid duriug solidificatiotz is analyzed; the experimental observations indicate that maximum concentration difference (AC) and supercooling (AT) in the interdendritic liquid are indepexdent of freezing rate. the separation of practically pure ice crystals from the liquid phase; with very few exceptions there is no solid solubility of ionic salts in ice. As an ice crystal grows there is rejection of solute from the moving interface into the liquid. Since the rejected solute moves primarily by diffusion, concentration gradients are established in the liquid. The highest solute concentrations are found in liquid immediately adjacent to liquid-solid interfaces and lowest concentrations farthest from the interface. Two-phase equilibrium obtains only at the solid-liquid interface; at other locations the liquid becomes supercooled because temperature gradients are negligible compared to concentration gradients. This is an immediate consequence of the fact that thermal diffusivities are considerably higher than mass diffusivities.

Jan 1, 1968

By Waugh D. M

investigations have been undertaken into the flow characteristics of mineral slurries from a number of Australian metallurgical plants including Mount Isa Mines Ltd., North Broken Hill Ltd., and Broken Hill South Ltd. Experimental equipment installed for this work included facilities for continuous recording of flow rate and pressure drop and detection of sedimentation.Although the method has subsequently been described in published literature, it is believed that the investigations included the original application of a method for correlation of the flow rate and pressure drop data. This method depends on solving by graphical methods the values of the constants k, and c in the relationship EQUATION 1 where D is pipe diameter; ?P, pressure drop; L, length; and V, mean linear velocity. Discussion of this correlation also reveals why sedimentation velocity does not necessarily vary greatly with pipe diameter.INTRODUCTIONIn order to design pumps and pipeline installations for a Newtonian fluid, measurements of the fluid's density and viscosity in any of a number of instruments are sufficient. Substitution of these values in well known equations to calculate Reynolds numbers and subsequent correlation to determine friction factors are all that is required for engineering specification.As a result of work during the last decade, particularly that of Metzner and Reed (1955) and Dodge and Metzner (1959), it is now possible to design for homogeneous non-Newtonian fluids using relatively simple instrumental measurements.These methods can sometimes be applied to thick slurries which behave as if homogeneous. However, for the...

Jan 1, 1965

By P Lever, D Hainsworth, H Gurgenci

The ACARP Landmark initiative has created the opportunity to advance the level of automation in the coal industry by first focusing on the core production area of longwall mining. A Landmark Longwall Automation project was commenced in July 2001. The major outcome of automation using on-face observation has been divided into ten outcome areas that have been fully scoped for a three-year initial project life. A major facilitating technology has been the implementation inertial navigation system (INS) technology that can map the shearer position in 3D. A focus of the project is to deliver a system that is at least as productive as the current most productive manually controlled longwall face.

Jan 1, 2002

By Janusz S. Laskowski

Studies carried out over the last 10 years reveal that precipitating particles which may appear in alkaline solutions of long-chain amines and in acidic solutions of fatty acids exhibit clear isoelectric points around pH 10.6-1 1 for dodecylamine and around pH 2.5-3 for fatty acids. These colloidal species can accumulate at solid/liquid and liquid/gas interfaces and affect flotation. While the precipitate in solutions of fatty acids apparently can chemically interact with the mineral surfaces and is flotation-active if sufficiently long conditioning time is available, the cationic flotation of quartz in alkaline solutions is depressed by the colloidal precipitate. The experimental data available in literature on the adsorption, electrokinetic, contact angle and surface forces measurements in the solutions of the weak electrolyte collectors are analyzed and the role played by the precipitate is discussed. It is shown that these concepts allow for an explanation of the selective flotation of sylvite from halite with long-chain amines in potash ore flotation.

Jan 1, 1999

By Miguel A. Cuba

Trends in the mean and/or variance are a longstanding challenge in mineral resource modeling. Geologic modeling and/or grade domaining are often employed to account for heterogeneities in mineral grades; however, this is only practical up to a certain point since the number of data available for reliable model construction can be severely reduced. In such cases, trends remain present in certain geologic/grade domains and directly impact the modeling methodology; the trend must either be handled explicitly or a suitable approach is adopted to implicitly account for it. This is highly dependent on understanding the source of the trend. We propose an approach that detects the source of non-stationarity, which is based on quantifying the impact of non-stationarity in the mean and the variance via the semivariogram. By expanding the methodof- moments approximation of the semivariogram, we decompose the experimental semivariogram is into three terms: 1) trend in mean component, 2) trend in variance component and 3) stationary component. We can then assess the source of trend by calculating the contribution of each component at every lag. Two cases are presented to illustrate this tool. Firstly, a synthetic reference model is simulated and different trend patterns are added; the influence of these patterns in the experimental semivariogram calculation are analyzed and discussed. Secondly, a real dataset is considered where the impact due to the presence of trends in the mean and variance are assessed. The results of this paper reveal the semivariogram to be a tremendously powerful tool in determining the source of the trend. This insight may be useful in the selection of a suitable modeling approach for resource estimation.

Oct 1, 2009

By D. E. Traut

A fluidized, countercurrent ion-exchange system was developed, operated, and evaluated by the Bureau of Mines in support of its objective to help assure an adequate uranium supply for future national needs. The system consisted of integrated multiple-compartment absorption and elution columns in which the solution flows are continuous, except for short periods when resin increments are withdrawn. The exchange of uranyl sulfate between a simulated acid-leach-uranium solution and a strong-base, ion-exchange resin was studied, together with subsequent elution using an acidified sodium chloride solution. The effects of the number of compartments, compartment height, amount of resin withdrawal, solution flow rate, and column diameter were investigated. Also examined were the kinetic and equilibrium relationships for the absorption and elution steps. The experimental data indicate a strong interdependence between variables. Solution retention time appears to be a major limiting variable in the absorption process, while resin residence time is the determining factor in the elution process. The columns system was efficient over a range of conditions, but close control was needed for optimum operation.

Jan 1, 1978

By M. K. Mohan

During the processing of metals like Cu, Ni, Co, large quantities of solutions, which contain co- products such as Sb, Cd, Pb etc. are generated. These solutions if processed to recover the metals help in conservation of metals as well as environment preservation. The present study was taken up to recover antimony from process solutions using zeolites. The effect of pH of the solution, time and type of zeolite viz., chabazite, mordenite, erionite and clinoptilolite on the sorption of antimony was investigated. Rate of sorption increases with pH and about 77-pct. antimony sorption was observed with chabazite at a pH of 6. Optimal conditions were established for the maximum recovery of antimony fiom process solutions. The mechanism of sorption for Sb was proposed in terms of adsorption and intraparticle diffusion. The calculated adsorption constants from Langmuir and Freundlich equations indicated that the adsorption of antimony on chabazite was strong.

Jan 1, 1999

By David C. Grant

A laboratory technique for simulating in-situ uranium mining was developed and used to determine the effects of leaching variables on permeability, uranium recovery, leach solution interaction with the ore-aquifer environment, and post-leach chemical leakage. In particular, ammonium bicarbonate, the commonly-used leach solution, was examined in great detail. Agitation leach tests were conducted to examine the effect on ammonium sorption and desorption of clay content, solution and clay ammonium levels, pH, and the type and concentration of other anions and cations in solution. Initial column tests were performed to determine the degree of ore-aquifer interaction that could be expected for various leach solutions; sulfuric acid, and ammonium, sodium, and potassium bi-carbonates. Subsequent tests examined various methods to restore the ores by lowering the post-leach chemical leakage. The restoration tests examined the use of reducing agents (e.g., ammonium bisulfite, sodium bisulfite; and sodium sulfite), ore blocking and stabilizing agents (e.g., sodium silicate, aluminum chloride, and magnesium-calcium salt).and ammonium displacement agents (e.g., aluminum chloride and lanthanum chloride-sulfate)

Jan 1, 1980

By S. Acar, M. Botz

Introduction In 2007, Newmont Mining Corporation will begin construction of a milling and cyanidation leaching circuit for the Yanacocha site in Peru. Ore to be processed in the circuit contains a relatively high level of cyanide-soluble copper, and as a result, leach solutions are expected to contain elevated levels of copper and WAD cyanide. As the means of controlling copper levels in leach solution, a circuit will be installed to precipitate copper sulfide from barren solution using sodium hydrosulfide. In addition, a circuit will be installed to recover cyanide from barren solution, with recovered cyanide to be returned to the leaching circuit and treated solution to be utilized as make-up in existing heap leaching facilities. As needed to support design of the copper precipitation and cyanide recovery circuits, pilot testing was conducted in 2005 to determine preferred operating conditions and evaluate the performance of the processes. This paper presents results from the pilot testing where 99% copper reduction was achieved and 95% to 98% cyanide recovery was achieved.

Jan 1, 2007

By John Hoelle

Coal mines in southern West Virginia, south-western Virginia and eastern Kentucky have experienced coal bumps at least since 1933. Most of the bumps have occurred due to high cover, strong roof and floor strata and stress concentrations due to the mining sequence. A longwall mine in eastern Kentucky first experienced coal bumps on the tailgate side of the longwall face in 1989. The bumps continued until 1996. The bumps were the result of: Thick overburden up to 2200 feet Strong roof and floor (strata strengths up to 25,600 psi UCS and elasticity modulus up to 4,800,000 psi Previous over-mining in places Sandstone channels Not all characteristics occurred simultaneously. The bumps produced seismic events recorded up to 4.3 (Richter scale magnitude), and damaged pillars that were up to 147 by 152 feet in size.

Jan 1, 2008

By C. R. Van Hise

Introduction.............29 The Three Zones of the Lithosphere ..30 Zone of fracture............31 Zone of flowage............ 31 Factors influencing depth at which flowage occurs.. 32 Zone of combined fracture and flowage.. 33 The Water-Content and Openings in Rocks....36 Condition of rater in the zone of fracture.. 36 The openings in rocks...........38 Size and number of openings..... 40 Ore-deposits derived from zone of fracture..45 The source of underground water......... . 47 The cause of the flowage of underground water..47 Belts of underground circulation.. 51 Upper belt of underground circulation.. 51 Lower belt of underground circulation.. .... .52 Capacity of water for work in the lower belt of underground circulation........... 53 Movementsof water in the lower belt of underground circulation. 54 The preferential use by water of large channels.. 60 Physico-Chemical Principles Controlling the Work of Under ground Waters..........62 Chemical action............63 Underground aqueous solutions..64 The relations of solution and temperature..... 65 The relations of solution and pressure..66 Precipitation........... 67 Precipitation by change in temperature..68 Precipitation by change in pressure..69 Precipitation by reactions between aqueous solutions.. . 69 Precipitation by reactions between liquid solutions and solids. 70 Precipitation by reactions between gases and solutions. and solids............71 The General Geological work of Underground Waters.. . 71 Division of the zone of fracture into a belt of weathering and a belt of cementation............72

Jan 1, 1901

Ground falls (roof and rib) have historically been responsible for about 50% of all fatalities in bituminous underground coal mines. In some recent years, the number of ground fall fatalities has approached zero, indicating that significant progress has been made. On the other hand, last year?s Crandall Canyon twin mine disasters, in which 9 miners perished in violent coal bumps, provided a stark reminder that complacency is premature. One important success has been a great reduction in the number of miners killed inby roof supports. Throughout the 1990?s these accounted for nearly half of all roof fall fatalities, but there have just been two inby incidents in the past 5 years. Progress has also been made in pillar recovery. Safer mining technologies have reduced the number of fatal incidents, but some recent failures have underlined the need for careful management of the retreat mining process. On the other hand, more than 400 miners continue to be injured each year by rock falling from between supports, and 100 more are injured by rib falls. Together, these two categories also account for a large percentage of recent ground fall fatalities. Available technologies such as roof screen, rib bolting, and inside control roof bolters could dramatically reduce injury and fatality rates if they were used more widely. Further advances in these areas will likely be the next big advance in ground control safety. Disclaimer: The findings and conclusions in this report have not been formally disseminated by the National Institute for Occupational Safety and Health and should not be construed to represent any agency determination or policy.

Jan 1, 2009

Review of the mining legislation in New Zealand has coincided with a number of radical changes. These include a redirection of economic management towards a more open and competitive economy; major reform of the state sector aimed at greater efficiency, transparency and accountability; a new environmental administration; and a fundamental review of policy for management of natural and physical resources. These changes provide an opportunity to develop a consistent and coherent approach in the minerals and related statutes that will achieve objectives of economic efficiency, equity, practicability and good environmental management.

Jan 1, 1987

By K. L. Gabby

Since mercury is chemically similar to silver, it tends to dissolve along with the silver and gold during cyanide leaching. Ultimately mercury is recovered along with the silver as mercury/silver/gold amalgam which requires retorting to remove the mercury prior to refining the silver and gold. A possible approach to separating mercury from silver and gold in cyanide leach solutions is to take advantage of the replacement reaction between [Hg(CN)4]2- and Ag2S, which results in precipitation of mercury as HgS while dissolving silver as [Ag(CN)2]-. Results are presented demonstrating that mercury can be removed from cyanide solutions with high effectiveness, while, at the same time, recovering additional silver in solution. Initial experiments with static flasks in the laboratory showed a high degree of mercury removal could be achieved. Results using actual metallurgical plant products in bottle roll tests indicate the process works on a larger scale, but also results in significant gold losses if the solution being treated has high gold levels, such as carbon stripping pregnant eluent solution.

Feb 23, 2014

By AIME AIME

WILLIS McGERALD PEIRCE-"Jerry" to his host of friends, and on that account a hit of a puzzle to those who have known him only as "W. 14."-a native of Buffalo, educated at Penn State College, Illinois: and Yale universities, has bee11 associated throughout all of his professional career with the New Jersey Zinc Company. Jerry has served successively as investigator, section chief, and division chief in the research department of the company and has just been promoted to chief of research.

Jan 1, 1937

By William D. Riley

In order to evaluate the corrosion resistance of zirconium in mineral extraction processes, such as a clay-hydrochloric acid leaching process for extracting alumina, the Bureau of Mines conducted corrosion studies in HCl-AlC13-FeC13 environments. A series of weight loss and electrochemical tests were conducted at 25° and 65° C in aluminum chloride (AlC13) plus hydrochloric acid (HCl) solutions containing 0 to 1,000 ppm ferric ion. It was determined that zirconium, which normally exists in a passive state in chloride-containing solutions, undergoes pitting attack in solutions containing more than 100 ppm of ferric ion. It is also shown that an oxide film prepared in air at high temperature offers protection in acid solutions containing levels of ferric ion from 300 to 1,000 ppm.

Jan 1, 1981

By R. A. Anderson, O. D. Sherby, J. E. Dorn

Solid solution alloying increases the plastic properties of aluminum at elevated temperatures by solid solution strengthening, by restraining recovery and recrystallization, and by a Cottrell effect. When binary aluminum alloys are strained and aged at 1940° to 300°K they develop a yield point. This is attributed to a migration of dislocations to solute atoms during aging. IN view of the ever expanding interest in applications of metals and alloys to high temperature service conditions, it becomes increasingly important to be cognizant of the effect of various metallurgical factors on the strength of alloys at elevated temperatures. One problem of wide interest, not only because of its engineering significance but also due to its fundamental scientific importance, is the elucidation of the effect of alloying elements on the plastic properties of homogeneous a solid solutions at elevated temperatures. It is indeed astonishing to note that in spite of its importance, and in spite of extensive random testing of alloys at elevated temperatures, no systematic investigation has been reported yet on the effect of alloying additions on the plastic properties of a solid solutions at elevated temperatures. This deficiency in our knowledge prompted the investigation described in this report. Rather extensive data are currently available on the effect of alloying elements on the plastic properties of a solid solutions at atmospheric and sub-atmospheric temperatures. Such data might be ex- trapolated to higher temperatures and reasonable guesses might be made regarding the influence of such factors as recovery and recrystallization in order to hazard a qualitative estimate of the effect of alloying elements on the plastic properties of a solid solutions at elevated temperatures. Such

Jan 1, 1952

By Karl S. Hughes

ANY one of the mining engineers who spent three years under the benevolent and protective custody of the military forces of His Imperial Nipponese Majesty will admit that he has survived a most disagreeable experience, but our friends here in the States all demand that we tell them something about our thrilling adventure. Many of the younger men who were on Luzon in December 1941 joined up with the Army, either as civilian technical employees or through their reserve officer status. They served through the Bataan and Corregidor defense and had five months of thrills and hardship, if that is what constitutes adventure. Unfortunately, too many of them are not alive to tell their stories. But for most of us, our internment as alien civilians was just one long, drawn-out pain in the neck. Yes, we starved; yes, we contracted beriberi, dysentery, typhus, dengue, and for a while had no quinine to fight the ever-present malaria; but these things are not exciting, neither is the account of them interesting. Our contingent from Mindanao, 250 .in number including 25 mining men, went through one period of starvation at Davao. When the activity of the Allied fleet interfered with the importation of staple foodstuffs, and the natives stopped bringing fruit and vegetables into the market, the food situation became acute, and in December 1943, with stocks in sight and in prospect insufficient to provision their own soldiers, our custodians decided that we must be moved to Manila. The story of that ten-day voyage in an antiquated Jap freighter is too disgusting to tell, but hardly more adventurous than the account of a game of solitaire.

Jan 1, 1945

By S. W. Churchill

A digital computer was used to obtain an exact numerical solution for the transient behavior of the insulation and earth adjacent to an isothermal, submerged flat surface for a single set of parametric values. Comparison of the computed results with analytical solutions for limiting conditions revealed that a complete and general solution for all parametric values could be constructed from these limiting solutions. Complete and general solutions for insulated spheres and cylinders can also be constructed from limiting solutions. The procedure is illustrated in part for an insulated spherical tank. The heat flow was found to fall rapidly to a pseudo-steady state; after some time, it then decreased slowly to zero for a flat plate and cylinder, and to a low steady-state rate for a sphere. The accumulative heat flow during the initial falling-rate period may be a significant fraction of the heat flow during the entire first year. INTRODUCTION Underground storage of liquefied natural gas and liquefied petroleum gas has received considerable recent attention. The rate of heat flow from the earth to the storage cavity and the resulting temperature field in the earth are important factors in the technical and economic evaluation of such storage facilities. The objective of this paper is to indicate how complete solutions can be developed for the transient flux and temperature field for various geometrical configurations. The representative properties and dimensions, and the resulting parameters utilized in the illustrative results, are indicated in Table 1. The results presented herein are for dry earth. The effect of the latent heat of solidification of water in the soiI will be described in a subsequent paper. The temperature field in the insulation and earth is determined by energy balances, boundary conditions and initial conditions. The physical problem can be described mathematically with virtually no idealizations insofar as physical properties are known. It appears possible to solve the equations by numerical integration on a high-speed digital computer for any geometrical configuration and conditions. For complex situations, however, the computations are expensive and the results are highly specific. Analytical solutions have been developed for a few simple but important geometrical configurations and conditions, including one-dimensional heat transfer from (or to) earth at an initially uniform temperature to (or from) flat plates, spheres and circular cylinders. The solution for an insulated flat plate has also been derived but is in the form of a slowly converging series involving taklated functions. It was planned to use a computing machine to evaluate this series for a number of representative conditions. However, upon examination of the results of preliminary computations it was discovered that a complete, general and accurate solution could be developed by interpolation between several much simpler solutions for limiting conditions. This technique then was used to develop a a complete solution for an insulated sphere. The equations presented herein are derived in Carslaw and Jaegerl and other books on applied mathematics, or they are simple extensions of these previous results. Hence, all derivations are omitted. Emphasis is instead placed on the results and their

By k. Osei-Boakye

This paper presents the calibration of a real-time aerosol monitor, the TSI DustTrak?, to the NIOSH 5040 method being used by the Mine Safety and Health Administration (MSHA) for compliance enforcement evaluation. The standard NIOSH 5040 instrument for compliance evaluation of diesel particulate matter (DPM) has an inherent time lag of up to two weeks for laboratory processing of sample results. Therefore, providing the underground mines with a means of quantifying DPM conditions in real-time, will enable them to efficiently and effectively manage DPM levels to ensure compliance with the regulated limit.

Jan 1, 2009