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By John H. Perry

Strata III is a full-spectrum roof control system which provides the mine operator the ability to upgrade his roof control in place. The procedure is easily adaptable with current roof bolting techniques. To use the system, the operator starts by installing a special hollow core mechanically anchored roof belt during the roof bolting cycle. This bolt can be upgraded to a fully grouted tensioned rebar bolt by injecting StrataGee G-300, a special polyurethane grout, around the bolt through an injection port in the roof plate. This same bolt can then be used to inject RokLok binders for roof consolidation by pumping the binders through the core of the bolt. This concept in roof control was developed to provide the mine operator a flexible way to maintain roof control in areas which deteriorate over time, or must be kept open for long periods of time. Possible locations of use would be: longwall set-up rooms, recovery rooms, headgates, intersections, and belt entries.

Jan 1, 1987

By George W. Sheary

Situated 45 miles west of Philadelphia and 50 miles southwest of Bethlehem Steel Company's Bethlehem plant, the integrated Grace mine facilities produce 4000 tpd of high-quality iron ore pellets. Startup of the Grace mill was in November 1958, and iron concentrates were shipped until March 1960, when the pellet plant went into operation. The underground mine, when fully developed, will hoist about 9000 tpd, including development rock. The crude ore, which has an iron content of approximately 42%, is magnetically cobbed and crushed in closed circuit with 3/4-in. slotted vibrating screens. The ore is washed and screened in the mill and the plus 1/4 in. screen product is again cobbed prior to feeding to the rod mills. Grinding is done in rod mills, and in ball mills that are in closed circuit with 30 in, cyclones, to 1% on 100 mesh and 65% minus 325 mesh. The ground ore is magnetically concentrated by three-drum permanent type finisher magnets to 67% Fe. The magnetite concentrate is pumped from the mill to a 50 ft thickener in the pellet plant. The thickened magnetite concentrate is relayed to the filters through a two-stage pump arrangement. The filter cake is fed by belt from filter concentrate bins to mixer-muller belts where it is intimately mixed with bentonite and a slight amount of water for moisture control. The fluffed concentrate then drops into balling cones. The green pellets from the balling cones are fed in a prescribed feed pattern to shaft furnaces through the use of shuttle car mechanisms. The green pellets are dried, heated to 2500°F and cooled to 1200°F as they descend through the furnace and into pellet coolers where the pellets are further reduced in temperature to 250°F. Heat is recovered in the cooling process through the use of air-to-air heat exchangers. The cooled pellets discharge on a rubber conveyor belt and are transferred to 6000-ton pellet railroad loading bin. The final pellet product consists of 90% plus 1/4 in. material (after tumble testing1) and contains 66% Fe plus 3% silica.

Jan 5, 1962

By Neil A. Brown

The trona deposits near Green River, in southwestern Wyoming are world class in size and quality. They contain more than 25 times the reserves of the next largest trona deposit at Lake Magadi in Kenya. Based on present rates of production, the Green River reserve should last for more than 500 years. Since their discovery in 1938, the Union Pacific Corp. has been instrumental in the promotion, development and production of soda ash in Wyoming. Union Pacific spent several years drilling the deposits and trying to promote them to chemical companies. In 1947, Westvaco and Union Pacific entered into what became the first trona lease agreement. Today, the Green River Basin leads the world in soda ash production, accounting for about 25% of the world's supply. Green River producers process more than 14.5 Mt/a (16 million stpy) of trona to produce more than 8 Mt/a (9 million stpy) of soda ash. The future for Green River soda ash looks good, with more of the world looking towards the cheaper and higher quality source of soda ash coming from the natural deposits. Production from the Green River deposits should continue to grow as trade barriers and tariffs begin to fall in Europe and energy and environmental costs force the synthetic producers to exit the market.

Jan 1, 1995

By Richard Elliott

Current methods for producing low-carbon manganese alloying materials for the steel industry are energy intensive and costly. To enable wider implementation of high Mn steel alloys, a novel solid-state Mn ore reduction strategy is therefore being investigated. This solid-state process, modelled on existing Direct Reduced Iron technology, employs a methane-containing atmosphere to reduce Mn ore pellets to a metal carbide. These pellets may then be smelted, yielding a Mn-rich master alloy. It is well established that CH4 is a suitable reductant for Mn ore powders; however, the reduction behaviour of industrially relevant Mn ore pellets by CH4 is poorly understood. The present work reports the results of an investigation undertaken to address this knowledge gap. The results of this study highlight the significantly different reduction behaviour exhibited by the Mn ore pellets relative to the ore powder under similar conditions and suggest that the diffusion of CH4 into the pellet interior is the limiting factor in achieving complete reduction.

By V. F. Parry, J. B. Goodman, W. S. Landers

"This investigation was conducted: under the direction of A.C. Fieldner, chief, Fuel and Explosives Branch, Bureau of Mines, Washington, D. C. The following members of a Technical .advisory Committee were helpful in advancing the investigation: L. C. Harrington, dean, College of Engineering, University of North Dakota; D. F. Pane, president, Sheridan-Wyoming Coal Co.; Carson W. Smith, president, Consolidated goal & Coke Co.; Durbin van Law, consulting, engineer, Denver & Rio Grande Western Railroad; and C. B. Carpenter, professor of metallurgy, Colorado School of Mines. Coal samples from the Northern Colorado field used in the stoker during 3 years of service were supplied through the cooperation of N. C. Brooks, secretary, Northern Colorado Coals, Inc.This report describes the development and practical tests made on a small stoker-fired system for heating service water automatically. The system was designed to take advantage of the favorable reactivity of low-rank fuels, and the objective was to devise a combination of stoker, heat-receiving, and hot-water storage system Which would be automatic for at least 30 days without attention, while heating service water at minimum cost. The system was developed to a point where coal consumption was less than 10 pounds (or less than 100,000 B.t.u.) per day. The total operating cost of hot water for an average-family-was about $1.00 per month, with coal retailing at $6.00 per ton and electric power at 4 cents a kilowatt-hour. The heating system was designed for the utilization of low-rank fuels, but the general features of the double-tank system can be 'employed fuels, either gas or liquid fuels.The Subbituminous Coal and Lignite Section of the Bureau of Mines began investigations on the utilization of low-rank fuels in domestic appliances during 1939. Tests were made on various devices to find out if they were suitable for the low-rank fuels. Most of the available appliances for burning coal have been designed for the higher-rank fuels, and they are not well-suited for burning the lower-rank coals at maximum efficiency, because subbituminous coals and lignite have high bed moisture ranging between 20 and 40 percent by weight, which lowers heating value to the range of 10,000 to 6,500 B.t.u. per pound. They are noncoking, and the ash content ranges between 4 and 6 percent, with a fusion temperature of about 2,0000 F."

Jun 1, 1946

By L. Chunpongtong

ABSTRACT The mining limit in oil sands is regulated by the ratio of total mining volume (ore, interburden, and overburden) one has to mine per volume of bitumen in place (TV/BIP). This paper presents a mathematical solution for creating the most economical pit outline where the TV/BIP ratio upper limit is 12, by combining mining economic theory and the Lerchs-Grossmann (LG) algorithm.

Jan 1, 2014

THE award from the fund established by Mrs. John-son, in memory of her husband, J. E. Johnson, Jr., to be given to some promising engineer, not over 40 years of age, because of meritorious research, inven-tion or contribution to the professional literature of iron and steel along the lines of blast-furnace process, has been given, for, 1928, to P. H: Royster. Mr. Royster was born at Raleigh, N. C., in 1888. and graduated from the University of North Carolina, in 1907, taking his A.M. degree at, the same school in 1908. He then went to Harvard where he continued research work in physics. After engaging for a while in commercial research in the turbine department of the General Elec-tric Co. and with Cutting and Washington he joined the staff of the Bureau of. Mines in 1916 and was assigned to work on the physical chemistry of the blast-furnace process. He worked with A. L. Feild on slag viscosity and they jointly presented-to the Institute the. papers on "Temperature and Viscosity Relations in the Ter-nary System CaO-A12O3-SiO2" (TRANS. LVIII, 658) and "Slag Viscosity Tables for Blast-furnace Work" (TRANS. LVIII, 650). He also presented a paper on "Production of Ferromanganese in the Blast 'Furnace" .(TRANS. LXII, 18), and jointly with T. L. Joseph contributed a paper on "Effect of Coke Combustibility on Stock Descent in Blast Furnaces" (TRANS. LXX, 236), and another on "Pyrometry in Blast-furnace Work" which was included in the special pyrometry volume published in 1920. The titles of these works perhaps sufficiently indicate the part Mr. Royster has played in the notable research work on the blast-furnace process carried on by the Bureau of Mines, and for which the committee recommended him to the Board of Directors to receive the Johnson award.

Jan 2, 1928

By Alan Jessop

A small group has been set up at the Dominion Observatory, Ottawa, to make a survey of terrestrial heat flow throughout Canada. Terrestrial heat flow is the heat rising from the interior of the earth and escaping at the surface, and is calculated from a knowledge of under-ground temperature distribution and the thermal conductivity of rocks. A small number of diamond drill holes are being sunk for the purpose of measuring temperatures below the surface, but the program is inadequate for a thorough survey. Mines and holes drilled for other purposes are being sought by the Dominion Observatory group to supplement their own drilling program. F ROM January, 1.962, to December, 1964, geo-physicists of many nations will be cooperating in the "International Upper Mantle Project." Unlike tl1e International Geophysical Year, which was mainly concerned with the fluid layers surrounding the earth, the Upper Mantle Project is an intensive study of the solid earth. Canada, with its large land area and extensive Precambrian Shield, is an active participant in the project.

Jan 1, 1964

By A. K. Basu

Rapid industrial growth in India has caused the country to realize the strategic importance of its zinc and lead deposits. Private companies, nationalized in 1965, are now a corporate public sector organization that is making great strides in developing the nation's lead-zinc mining capability. The main mining area is centered around Zawar at Rajasthan. It consists a group of mines - Mochia, Balaria, Zawarmala and Baroi. Mining activities have also been extended by opening the mines at Rajpura-Dariba at Rajasthan, Sargipallie at Orissa and Agnigundala at Andhra Pradesh. A huge deposit has been explored at Agucha in the Bhilwara district but full-scale production has not yet begun. Annual consumption of zinc and lead in India has risen steadily from 25 and 7.9 kt (27,500 and 8700 st), respectively, in 1973-1974 to 162.8 and 80 kt (179,450 and 88,000 st), respectively, in 1989-1990. Mine production has also risen consistently to cope with the increased metal demand. The mining company hopes to increase production at existing mines and upgrade the beneficiation and smelting facilities. Moreover, mining operations may be expanded by opening up new units that are now awaiting governmental clearances. Technology status Mining technology has undergone a rapid, large-scale transformation, with an accelerated pace of new, larger capacity mine development. Notable advances include the introduction of mechanized ore extraction methods and

Jan 1, 1991

By C. E. Jordan

Direct digestion of phosphate ores by the acid-alcohol method offers improved leaching selectivity for the exclusion of iron and aluminum in the product acid. The leaching kinetics of this process will have a major role in the eventual application of this technology. The Bureau of Mines investigated apatite dissolution to determine the reaction rate and mechanisms of the leaching kinetics. The dissolution kinetics were monitored on various sized fractions of pure apatite. The "shrinking-core" kinetics model was applied to the data to determine the rate controlling mechanisms. For each size fraction, the initial reaction rate was controlled by the dissolution reaction. After an hour the dissolution rate slowed indicating a diffusion controlled reaction caused by the formation of calcium sulfate hemi-hydrate coating on each particle. For complete dissolution of the apatite, the phosphate rock should be ground to near 10 µ m size.

Jan 1, 1993

By Henry S. Drinker

THE Butler Mine property is situated in the vicinity of Pittston, in the Wyoming coal-field of Pennsylvania. The coal has been worked out from the fourteen-foot or Baltimore vein for a number of years on part of the tract, the old chambers remaining open as when originally abandoned. This vein outcrops on the Butler property, and is nowhere more than sixty feet below the surface of the ground on the line of the cut-off to be described. Above the fourteen-foot vein and about, say midway, between it and the surface of the ground, there is another small vein or rider of coal, about twelve inches in thickness. The rock between the two veins is a carbonaceous slate, about twenty-five feet in thickness. Above the smaller vein is a bed of sandstone, varying in thickness, but generally not less than from eight to ten feet. This sandstone is also carbonaceous, but the proportion of carbon is much less than in the slate below. Both rocks have been analyzed, and before the next Institute meeting, the writer hopes to be able to furnish the exact proportions. The sandstone is overlaid with debris up to the surface of the ground. Some time during the spring of 1876, it was found that the coal left in the worked-out mine had been set on fire, and that the fire was gradually spreading. Inquiry developed the fact that the fire had originally been started by a woman, who had taken up her abode in an old tunnel leading into the workings. Owing to some delay in the early attempts made to extinguish the fire, it finally gained such headway that no ordinary means were found to be effectual. Finally, Mr. C. F. Conrad, civil and mining engineer, of Pittston, Penna., was called in as consulting engineer. He advised the making of a thorough cut through such portion of the old workings as had not been reached by the fire. It was found by survey that this cut could be limited to a length of about one thousand two hundred feet, as the vein faulted on both sides, and that the greatest depth of the cut would be about sixty feet. Subsequently it was decided to tunnel part of the way, thus saving the deepest portion of the cut. In 1856-7, there occurred a fire in the same mine. Two stone-walls in V-shape running from the apex of the V towards the outcrop, were built to cut the fire off, and these walls were carried as far as the vein had at that time been worked. After the walls were finished

Jan 1, 1879

By T. Xu

"The CTL-500 centrifugal extraction machine, which was independently developed by Baotou Shibo Rare Earth Extraction & Equipment Co., Ltd., is presented in this article. The machine is based on centrifugal extraction principle and has been used in P507-HCl-RECl3 extraction system. Automatic control has been utilized in the system. In this paper, a comparison is made between centrifugal extraction and conventional mixer-settler extraction and satisfactory results are shown. INTRODUCTIONCentrifugal extraction is a fast and efficient liquid-liquid extraction method. The process includes solute transfer and separation of the two liquid phases. In the CTL-500 machine, the organic and aqueous phases individually enter a lower mixing chamber in certain proportions and are mixed and dispersed and solute thereby transferred from one phase to the other. The mixed phases pass into a rotating drum and the two liquid phases are separated under centrifugal force. As it flows upward, the aqueous phase, which has a higher specific gravity, flows away from the rotating drum centre towards the drum wall and the organic phase flows towards the drum center. The two liquid phases enter into collection chambers through independent weir plates and are discharged from the machine.The centrifugal extraction machine has been widely used in liquid-liquid separation, either without solid or with small quantities of solids (Chen, Zhang, Zhuo, Chen & Li, 2008; Duan, Jing, Zhu & Chen, 2007; Duan, Zhou & Zhou, 2006). Examples of the use of the centrifugal contactor include the separation of water from crude oil, treatment of heavy oil and diesel to eliminate water and salt; the extraction of penicillin, garlic oil, malathion, and interferon; the hydrometallurgy recovery of nickel, copper and uranium; extraction of edible oil, spice, refined oil and food color; treatment and recycle of print and dyeing wastes; treatment of hydroxybenzene-contaminated sewage by multistage extraction and separation of water from oil in ship sewage."

Jan 1, 2012

By H. H. Schrenk

[A colorimetric method5/ for the determination of benzene in amounts as low as 0.001 mg has been developed recently at the U.S. Bureau of Mines Pittsburgh Experiment Station by the authors, with the assistance of chemical personnel fro a the Allegheny County (Pa.) Relief Works Division. The method is based on the direct nitration of either liquid - or gas - phase benzene, followed by neutralization, extraction with butanone, and final treatment with sodium hydroxide which produces a violet color. The color is matched with color standards of known values. Although the method is adaptable to many conditions the primary objective was a procedure that would be suitable for hygienic investigations. The development worth included a study of possible interference by chemicals that be present in those situations in which the method. would be employed. In this study it was found that a specimen of hexane prepared by the Gulf Research Laboratory, Pittsburgh, by fractionation of West Virginia natural gas gave positive result for benzene, whereas a specimen of pentane prepared in the same manner showed only a trace, and specimens of n -heptane and octane (2,2,4 trimethylpentane) supplied by Eastman Kodak Co. save a negative result. According to information obtained from the Eastman Kodak Co. the latter two compounds were highly purified, the n-heptene being prepared from line and the octane synthesized in the laboratory. On nitration of a larger amount of tae natural hexane a visible quantity, of needlelike crystals which resembled those of m-dinitrobenzene was obtained. The hexane from this nitration was recovered by distillation and again nitrated, but no crystals or colorimetric indication of benzene was obtained. This imitated that the specimen of natural hexane contained a substance which at least had the chemical behavior of benzene.]

Jan 1, 1935

By George A. Lawrence

A new super-large 100 m3 (3500 A3) pneumatic mechanical flotation cell is now available to meet future mineral processing challenges. Several innovative design concepts represent a marked departure from conventional flotation cell designs. The radial discharge from the pump action rotor and the overhung vane type stator is contained in a conical bottom cylindrical tank with no dead comers. Peripheral launders collect froth overflowing the entire circumference of the tank and these launders are of a hexagonal design permitting cells to be nested together in a honeycomb fashion. This new flotation cell is powered by a custom designed hydraulic motor package that provides infinite speed control in individual cells and a soft start under load

Jan 1, 1993

America.-Foreman, J. T. Ashland.-Sturdevant, J. C. AItalIa. Henderson, R. M. Bessemer.-Ball, E. M. Maschmeyer, W. L. McKenzie, W. C., Jr. Birmingham.-Abbott, C. E. Aldrich, T. H. Aldrich, T. H., Jr Aufderhaar, H. C. Berg, H. A. Blair, C. S. Bush, M. W. Clark, G. H.

Jan 1, 1923

By D. G. Westlake

Resistance was measured as a function of temperature, 77° to 350°K,for niobium with hydrogen concentrations up to 3.76 at. pct. Cooling curves exhibited a discontinuity in slope that was attributed to the initiation of hydride formation. A thermal hysteresis was explained in terms of diffusion and the effects of mechanical constraint on nucleation and growth. The heat of solution of hydrogen in saturated Nb-H solid solution was 2. 737 * 0.045 kcal per g-atom, including an unknown stress contribution. The critical ternperatures for hydride formation during cooling and for embrittlement are correlated but not coincident. This, too, has been explained in terms of mechanical constraint and stress-itlduced tratzsfomtation. Nb-H alloys undergo a ductile-brittle transition with decreasing temperature.'-3 Similar behavior has been noted for v-H.1,5 For the latter system, there is evi-dence6 suggesting coincidence of the temperature of minimum ductility and the critical temperature T, for initiation of metal hydride precipitation during cooling. A decrease in ductility due to the presence of brittle hydride particles is readily explainable. The fact that ductility begins to decrease at some temperature higher than T,4,5 has led us6 to suggest that precipitation may be strain-induced locally during tensile testing. Wood and Daniels' have reported that a plot of temperatures for 10 pct reduction in ductility vs hydrogen concentration in niobium is not coincident with, but parallels, the solvus.7,8 They believe this indicates a correlation of precipitation and embrittlement. Unfortunately, the two reported solvuses 7,8 to which Wood and Daniels refer are not in agreement with each other. Furthermore, neither solvus was determined experimentally: each was a plot of calculated solubilities. Thus. neither is highly dependable for determining whether embrittlement coincides with initiation of hydride precipitation. Longson 9 studied phase relations in the Nb-H system between 77° and 473°K by dilatometry. Comparison with metallographic observations convinced him that discontinuities in the slopes of his dilatometric plots were coincident with the initiation of hydride precipitation. Plotting the logarithm of the hydrogen concentration vs the reciprocal of the temperature at which precipitation was initiated during cooling, he obtained a straight line shown in Fig. 1. Walter and chandler,'' using X-ray techniques to detect the for mation of a second phase? have obtained three experimental points in the temperature range 295° to 338°K which fall within Longson's experimental error for this plot. A similar plotg of temperatures at which dissolution was completed during heating was a parallel line shifted toward higher temperatures. A straight-line plot was obtained, also, for the temperatures of the ductile-brittle transitions,9 but it was shifted toward still higher temperatures. Longson calculated an activation energy of 2.980 * 0.300 kcal per mole for the hydrogen embrittlement mechanism, compared with 3.180 * 0.400 kcal per mole for hydride formation. Despite this agreement, he concluded, "It seems unlikely that embrittlement results from hydride formation..." because hydrogen embrittlement was observed at temperatures above the solvus. It is our contention that embrittlement is correlated with precipitation of the hydride.6 Because only Longson has investigated Nb-H phase relations at sub-ambient temperatures, we deemed it advisable to re-determine the temperature dependence of the solubility using the resistometric technique already proven successful for the V-H system.6 Coincidence of our solvus with temperatures for embrittlement would

Jan 1, 1970

By V. G. Leak, R. A. Swalin

The dilhsion of silver and trace concentrations of tin in liquid silver has been rrzeasured in the temperature range from about 975° to 1350°C. The difBsion dala. fil lhe following equations: fov self-diffusion of silver The ratio of DSn to DAg is found to be about 1.34. The higher diffusivity of tin is interpreted in terms of the coullombic repulsion which results from the fact that tin dissolved in silver has a valence of +3 relative to silver. THE phenomenon of diffusion has been well-described theoretically for hard-sphere gases and solids and found to be in good agreement with experimental data for certain gases and solids. Liquid-diffusion phenomena have not been well described theoretically and there is generally a lack of good experimental data. In this investigation self-diffusion and solute diffusion in liquid silver were studied. Silver was chosen as a solvent for two main reasons. First, silver is a noble metal and the atoms are considered to have a spherically symmetric charge field; hence the liquid may be considered to be a random array of approximate hard spheres. Mercury, gallium, and other lower-melting metals were eliminated from consideration since it appears possible that in their liquid states there is some residual long-range order and directional bonding. Second, silver behaves as a monovalent solvent and, while cadmium, indium, tin, and antimony all have nearly the same atomic size, they have chemical valences relative to that of silver of +1, +2, + 3, and +4, respectively. Slifkin, Lazarus, and coworkers1-5 investigated the diffusion of these solutes in solid silver and found that their diffusion rates increased with an increase of the excess valence of the solute. In the solid state the diffusion-rate increase was calculated to be due to a change in local modulus of the solvent caused by the excess valence of the solute.1"3 For the present investigation it was planned to determine the effect of valence upon solute diffusion in liquid silver. It was deduced that a coulombic repulsion between solute and solvent might be responsible for larger volume fluctuations in the vicinity of the solute thereby enhancing the diffusion of the solute atoms. Tin was the first solute investigated and was chosen for experimental convenience. If an excess-valence diffusion effect exists in the liquid state, the solute tin with its excess valence of + 3 might show a large enough effect to distinguish it from the self-diffusion of silver in silver. The silver self-diffusion data were obviously required as a base line for comparison. In addition silver self-diffusion was investigated with a view toward examining the data in connection with the Sutherland- Einstein: Coheen-Turnbull,7 and swalin8 theories of diffusion in liquids. I) EXPERIMENTAL TECHNIQUES The diffusion coefficients for tin and silver in liquid silver were determined in separate experiments using the capillary-reservoir method of Anderson and saddingtono but following closely the experimental techniques outlined by Ma and Swa1in. The radioactive alloy bath was prepared by plating either tin-113 or silver-110 m isotope* onto 99.999 *Isotopes obtained from Oak Ridge National Laboratory. pct Ag rods.* The silver and isotope were melted *Silver obtained from Cominco Co. and mixed in a graphite crucible under a purified argon atmosphere, then outgassed for capillary filling. Some of the fused-silica capillaries were filled individually as reported by Ma and Swalin, but most were filled in a different manner. A long piece of capillary tubing was sealed off on one end and held in the system so that the open end was just above the surface of the molten alloy. The system was evacuated, the open end submerged into the alloy, and argon was admitted into the system up to atmospheric pressure. The molten alloy was forced up the capillary several inches where it solidified and was subsequently cut into segments of the proper length for diffusion annealing. The apparatus for diffusion annealing was the same as that used for capillary filling except that a Pt—Pt, 10 pct Rh therinocouple was placed in the solvent bath in order to accurately measure the temperature during the run. A diagram of the dif-

Jan 1, 1964

Assuming that a gold ore has been effectively ground to ensure maximum economic liberation of gold, the circuits that will have the most effect on the successful operation of a gold plant will be that of the leaching and carbon-in-pulp circuit (CIP). The reagent and utilities operating costs associated with leaching, adsorption, elution and regeneration would typically make up some 15% of total operating cost, whilst the capital costs associated with these areas is about 16% of the total. Although not largest (capital and operating costs associated with comminution are generally dominant) these items represent a significant proportion of capital and operating cost. Much more importantly, these plant areas represent the primary gold recovery process and their technical and operational efficiencies will have a significant impact on overall plant efficiency. The objective during process design of these sections is thus to develop a design which provides maximum technical and economic efficiency and which is robust to potential changes in ore throughput, mineralogical characteristics and head-grade. Experience has shown that, particularly for longer life and higher-grade projects typical of the South African underground gold mining industry, small changes in recovery and efficiency have a significant value over the life of the project.

Jan 1, 1999

By Pedro Lobarinhas

In the present work a two dimensional computational model is derived for the description of the time dependent heap leaching process. The flow inside the heap is calculated using the diffusion equations for the flow in porous media. The soil conductivity is also estimated assuming a close packed structure for the grain packing inside the heap. These equations, with appropriate boundary conditions, are solved using a time step splitting scheme. From this calculation the amount of leaching reagent in contact with the ore at any position inside the heap can be calculated and, once coupled with appropriate reaction equations, the amount of metals extracted can be computed and leaching agent concentration updated. The model is tested with available experimental data and the results have shown to be in a very good agreement. The model predicts all the transient features of the data.

Jan 1, 1999