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By H. E. Johnston

There are currently a number of options in terms of plant feed comminution tests: Bond work index tests, JK drop weight and SMC tests, SPI, low impact crusher work index tests, to name a few. However, information regarding specific energy requirements for regrind mills is often requested, which can be difficult or very expensive when only a small mass of concentrate is produced from bench-scale flotation tests. This research was aimed at developing a test methodology that would produce a similar result as an IsaMill Signature Plot but require less sample mass allowing for preliminary estimates of regrinding power at a lower cost. Initially, the laboratory test methodology was completed on a single sample in comparison to the IsaMill Signature Plot for that sample. Results indicated a very good correlation between the laboratory tests and the IsaMill Signature Plot for this sample, though some parameters did impact laboratory regrind mill efficiency. The developed methodology is subsequently being applied to a range of concentrates, investigating a range of material particle sizes and material types, in comparison to a full IsaMill Signature Plot on the same sample. This new test procedure has been called ‘The Eliason Test’.

Jan 1, 2014

By R. P. O’Shea

AS part of a program to investigate phase relationships in ternary systems containing semiconducting elements and compounds, an X-ray survey of alloys in the system Pb-Te-Bi was carried out which revealed that the pair PbTe-Bi probably formed a quasibinary system. This portion of the ternary was examined fully by thermal analysis, X-ray, and microscopic procedures. More than twenty-five alloys were made by melting together the proper combinations of the elements in quartz tubes at a temperature of 1000o C. The compositions which were high in PbTe content were prepared in evacuated, sealed, quartz tubes, allowed to freeze in vacuum, and then transferred to Crucibles for thermal analysis. The bismuth-rich alloys were made directly in the crucibles under a protective gas cover. The starting elements were obtained from the American Smelting and Refining Co. and had a purity greater than 99.99 pct. Cooling curves were made with about 50 g of alloy in graphite crucibles which were placed in a covered quartz container in which a protective atmosphere of helium or nitrogen was maintained. The thermocouple protection tube was made of mul-lite and served as a stirring rod when connected to a reciprocating stirring motor. Temperatures were

Jan 1, 1962

By Lee W. Abramson

INTRODUCTION The design of rock support for underground nuclear waste repositories requires consideration of special construction and operation requirements, and of the adverse environmental conditions in which some of the support is placed. While repository layouts resemble mines, design, construction and operation are subject to quality assurance and public scrutiny similar to what is experienced for nuclear power plants. Exploration, design, construction and operation go through phases of review and licensing by government agencies as repositories evolve. This paper discusses (1) the various stages of repository development; (2) the environment that supports must be de signed for; (3) the environmental effects on support materials; and (4) alternative types of repository rock support. Much of the information presented in this paper was derived from work conducted for Basalt Waste Isolation Project. Most of the information, however, would apply to other hard rock repositories. REPOSITORY DEVELOPMENT AND THE NEED FOR ROCK SUPPORT Repository development can be characterized by five general stages: exploration and design, excavation, waste emplacement, re trievability period, and backfilling. It is helpful to understand these phases of development to see where and when rock supports are required and how the design is verified. The description that follows is simplified. Details have been omitted, and future plans may not conform to this scenario.

Jan 1, 1984

By M. E. Wadsworth, R. D. Groves, B. W. Madsen

Experimental results obtained from large-scale (7 ton), long-term (500 days) leaching of low-tenor copper sulfide ores were interpreted by a geometric model involving the movement of a reaction zone through the ore fragments. The postulated leaching mechanism involved mixed kinetics and included diffusion of the reacting species through the host rock and a chemical reaction at the surface of the mineral particles. Ore properties which were considered were Ore particle size and shape, grade of ore, and mineral content. Excellent agreement between the mixed kinetic model and the laboratory leaching results was obtained when -1/2-in. ore particles were not included in the leach. Also, a satisfactory prediction of copper recovery from +1/2-in. ore with a different particle size distribution was made; however, it was necessary to modify the shape factor in the model. Prediction of copper recovery from an ore sample which included the -1/2-in. fine fraction and leaching for 460 days was 56.5%, and the recovery from leaching was 47.0%. The presence of fines caused solution channeling and a deficiency of oxygen which inhibited the leaching rate. Also, compaction of fines around coarser particles interfered with circulation around the ore particles, and bulk solution transport probably was a rate controlling factor.

Jan 1, 1976

By Steven J. Page, Robert A. Jankowski, John A. Organiscak

Quartz dust is one of the most significant ongoing health concerns in coal mining today. Since initial verification of this health risk in coal mines by the Mine Safety and Health Administration (MSHA) during the early 1980’s, the Bureau of Mines has conducted numerous studies in underground mines to identify the sources of quartz dust and its fundamental characteristics. The most significant underground quartz dust source was found to be the continuous miner excavating rock. The percentage of quartz was also found to be higher in the smaller size fractions of the dust when significant amounts of rock was mined by the continuous miner. Furthermore, the quartz content in the continuous miner return remained fairly consistent at greater distances from the face. Another important factor speculated to affect quartz dust generation and its size characteristics is the morphology of the quartz bearing rock. The quartz content of dust between mines had notable differences with respect to the differences between kaolinite content in the dust. Low kaolinite content was associated with higher quartz content and increased size segregation of quartz into smaller dust particles, indicating that the free silica bonding matrix in the rock is most likely another factor responsible for quartz dust produced through mechanical comminution.

Jan 1, 1991

By Alden Greninger

ALTHOUGH the crystallography of lattice transformations has been studied extensively during the past few years, these studies have been limited, with few exceptions1,2, to specimens in which the transformed lattice appears as a, segregate phase. A realization of the technical importance of the segregation mechanism, especially in the formation of martensitic structures and in age-hardening phenomena, has undoubtedly stimulated research in this direction. In the crystallographic studies of segregation, the general problem has been to relate the orientation of the parent crystal to that of the segregate crystals. The technique has been complicated by the fact that it has been necessary to deal with the presence of as many as 24 ideal segregate orientations within one parent lattice; furthermore, the segregate lattices are invariably scattered (seldom less than ±2°, often as much as 15° or 20°) about these ideal positions. It is probable that a more complete picture of phase transformations may result from a study in which complete lattice relationships between individual grains are evaluated, thereby providing an additional param-eter which, when it is necessary to work with multiple segregate-orienta-tions, cannot be evaluated. The present paper presents the results of such a study, ? wherein a peritectic reaction is made use of to produce the transformed lattices.

Jan 1, 1937

By Randal J. Barnes

There are many methods available for the estimation of geologic parameters (Popoff, 1966; Barnes, 1980). In the last decade a new and relatively sophisticated technique using statistical theory has emerged: geostatistical kriging (David, 1977; Journal and Huijbregts, 1978; Rendu, 1978). An interesting property of geostatistical estimation is that when a geologic parameter is estimated for a given volume, not only is the estimate generated but an associated measure of certainty is produced as well. This statistical measure of estimation confidence is called the estimation variance. While the concept of an estimation variance is universally considered to be a good idea, mining engineers and geologists do not currently have the tools to incorporate it into their planning and quantitative analysis. This paper attempts to develop and present some of the necessary tools required to incorporate estimation uncertainty into mine planning. Geologic uncertainty is portrayed as an economic business risk. This risk is objectively characterized, and-the associated cost is quantified. Geologic delineation sampling is viewed in this light as an economic commodity with an associated cost and value. A coal mine planning example is used as a focus in this presentation. The data used is real, though it has been modified to maintain data security and project anonymity.

Jan 1, 1986

By Colin J. Douch

New Zealand has been a significant producer of gold for over a century. Total recorded production is over 850 tonnes. There were three major periods of production: the first and biggest was between 1860 and 1880, the second was between 1895 and 1920 and the third was between 1930 and 1945. After 1945 gold production fell continually until 1980 when the major upward adjustment in gold price led to renewed interest. There have been important new developments in each of the known gold-rich areas: Westland, Otago and Coromandel and exploration for gold in these areas and in previously unprospected regions has reached unprecedented levels. In Westland over 140 gold processing plants are each producing between two and six ounces a day from low-grade placers. A major gold dredging operation will soon be producing over a tonne of gold annually and other new dredges are proposed. There are still vast reserves of gold-bearing gravels in Westland and prospecting is continuing to reveal new resources. In the Reefton area there is renewed interest in gold-bearing quartz reefs which were the source of over a million ounces of gold between 1900 and 1951. New large opencast reserves are now defined.

Jan 1, 1988

By Vincent T. Ricca, Kurtis Chow

When dealing with acid mine drainage as to treatment levels, costs, and evaluation of abatement schemes, predictions of the quantity and quality of the discharges are needed. An acid mine-drainage model is presented in this paper. In essence, the model is a hybrid of computer programs for stream flow simulation and acid mine drainage. Two major aspects of the model are discussed: mine-water generation and acid-load production. The former is based on hydrologic concepts and the latter on pyrite oxidation kinetics and oxidation product removal. The total model is programmed for the high-speed digital computer. The major inputs are: climatological, basin characteristics, and mine characteristics data. By the use o f the hydrologic model the amount of water that flows through the pyritic system is determined. From this information, acid loads removed by leaching, inundation, and gravity diffusion are then predicted. The outputs from the total model are: average daily mine-water discharge, the associated acid concentration or load, plus the average daily flow in the receiving streams or at basin outlets. The capabilities of the separate models have been tested individually and the joint model has been applied to a small drift mine in southeastern Ohio.

Jan 1, 1975

By S. J. Ripke

To pelletize fine moist magnetite concentrate, a 40% water slurry must be dewatered to about 10% by filtration, before it can be agglomerated into pellets. Slurry pH, typically ranging from 8 to 11, gives the magnetite particle surface a strong negative charge and thus causes two adverse effects. First, this negative charge attracts calcium and magnesium cations, which strongly retard the effectiveness of the bentonite clay binder added during agglomeration. Second, a repulsive force created by the negative charge functions as a dispersant that reduces filtering production rates. Tests were conducted to remove these cations during filtration, by rinsing the moisture remaining in the filter cake with a small amount of water adjusted to pH 6 with HCl. Laboratory work was also conducted at Michigan Technological University (MTU) and at Cliff’s Mining Services Company (CMSC) to corroborate the plant tests. In some cases HCl caused filter bag blinding, therefore CO2was investigated to reduce pH. The CMSC lab tests showed that using carbon dioxide to reduce slurry pH from 7.6 to 7.0 improved filtering production rates by 11%. Plant-scale filtering rates were improved by 23.7% when carbon dioxide addition reduced the slurry pH from 8.6 to 6.7.

Jan 1, 2004

By John L. Reuss

A laboratory study was conducted by the Bureau of Mines to investigate the technical feasibility of decomposing hydrous magnesium chlorides by using a steam pyrohydrolysis technique. This procedure consisted of injecting steam into the atmosphere of a decomposition furnace containing samples of hydrous magnesium chloride and determining the rate of hydrolysis by measuring the rate of chloride evolution. The variables investigated were temperature, amount of water vapor in the decomposition atmosphere, and hydration stage of magnesium chloride. The application of steam was shown to accelerate both the rate and completeness of magnesium chloride decomposition reactions. For example, when magnesium chloride hexahydrate is exposed to a furnace temperature of 600' C in an air atmosphere for 20 minutes, the decomposition is 37 percent. Under identical conditions in a steam atmosphere, the decomposition is in excess of 70 percent. The magnesium oxide produced by the steam pyrohydrolysis of magnesium chloride dihydrate at 800° C contained 98 percent magnesium oxide. Based on magnesium oxide composition, this is equivalent to that of burned magnesite produced at temperatures in excess of 1,300° C. To demonstrate the quality of the product on a practical basis, metal reduction tests have shown it to be equivalent to reagent-grade magnesium oxide as a carbothermic reduction feed material.

Jan 1, 1974

Improve the field-of-view into the front-right blind spot for drivers of large haulage trucks, thereby reducing the growing collision hazard in surface mines. Approach Reduce the glare problem found in the first generation fresnel lens blind area viewer design by eliminating the upward-looking section of the fresnel lens and adding a rear hood to reduce backlighting. How It Works The first generation blind area viewer was developed and in-mine tested as an aid to improved visibility for large haulage trucks. Other aids were improved left-and right-hand mirrors. Evaluations showed that a blind area viewer mounted on the right-front of the radiator deck was effective and was readily accepted by drivers. Nevertheless, because glare was a problem under certain conditions, a low-profile viewer was developed. Glare control louvers from the earlier design were kept and a backlighting glare control hood was added. The height of the hardware was reduced by eliminating the top three inches of the fresnel lens. This portion of the lens contained an upward-looking segment which originally was thought to be needed so the driver could see the horizon when he looked through the viewer and be better

Jan 1, 1982

This paper presents the water management plan of the Mae Moh Project in the North of Thailand, which includes a large lignite opencast mine and thermal power plants. Lignite production will increase from the present 5.5 million tons per annum to approximately 20 million tons per annum by 1995 when the pit area will be about 20 sq.km. and the depth at over 300 meters. Seven power plants are proposed of which two are under construction. The total capacity to be installed is 2,925 MW. The principles considered for water management are firstly flood protection, including drainage of the mining pit and diversion of the Mae Moh stream away from proposed future mining areas; and secondly, a plan to meet the water requirement of the thermal power plants, while maintaining downstream supplies for irrigation and other purposes. The limited annual run-off of Mae Moh and Mae Chang watershed basins are inadequate for the proposed power plants. A study has been prepared to compare two approaches, namely conveying water from remote watersheds to meet the water requirement of the power plants up to total installed capacity; or by limiting future total generation, at the existing site, to only 2025 MV.

Jan 1, 1988

By Sh. Arshadnejad

Stress analysis in a rock medium is essential to determine the stress concentration between two consecutive circular holes and prediction of fracture behaviour. When two consecutive circular holes in a hard rock medium such as granite are loaded internally by the pressure of non-explosive expansion material (NEEM), stress concentration occurs between the holes which then causes the rock to fracture. In this work, finite element (FE) analysis using Phase2 code was employed to study the stress concentration between two consecutive circular holes under internal pressure induced by NEEM. Effects of different hole diameters and spacings, rock properties and NEEM pressures have been analysed. The data gained from the numerical analysis and analytical solutions were then used to develop two models. These models were then modified by using the FE data and polynomial regression analysis. The developed analytical models showed to be in a very good agreement with the FE analysis. Hence, the developed models can be used with confidence to determine stress distribution and concentration factors around two consecutive circular holes in a hard and brittle rock which are loaded internally by the pressure induced from the NEEM. Keywords Finite element method, non-explosive, quarry mining, stress concentration..

Jan 1, 2011

By O. G. Motlogelwa

Any company operating a fleet of trucks will be greatly advantaged if the associated fuel costs can be decreased. The optimal tonnage that trucks should be hauling to ensure minimum consumption of diesel fuel has been investigated. The fuel consumption in litres per ton for a fleet of trucks hauling different tonnages of iron ore was recorded in a time-motion study and the optimal tonnage was determined. The following points emerged as a result of the research: > The diesel fuel consumption in litres per ton decreased with increasing tonnage, which means that in order to improve fuel efficiency, the trucks should carry 21 t > As a result of queuing, Africa Truck Hire (one of the two equipment contractors) loses R282.57 per day to diesel that the trucks burn when they are left idling. It is thus advisable that the company adopt a policy of requiring the drivers to switch their engines off while queuing at the stockpile > Filling up the trucks during each shift or rationing the quantity of diesel to 200 litres each shift has a negligible impact on the trucks' fuel efficiency > For the company to spend 35% of their revenue on fuel, the diesel price would have to be between R8.14 and R8.78 per litre.

Jan 1, 2013

By John A. Meech, J. G. Paterson

Activated carbon is a strong adsorbent for amyl xanthate, capable of removing from solution up to a quarter of its own weight in xanthate. In selective flotation system where depression is unstable, separation efficiency increases with activated carbon additions. The improvements observed are brought about by two mechanisms. First, by removing stripped and residual collector ions from solution, competition between depressant and xanthate is reduced and depression is stabilized. In addition, the texture of the froth phase at high pine oil concentrations is modified by activated carbon such that better drainage between the air bubbles takes place, alleviating the mechanical entrapment of depressed mineral particles. In treating a bulk copper/lead concentrate produced from GECO ore, selectively between galena and chalcopyrite is increased when activated carbon is used. Although the rate of flotation of galena is marginally lowered by activated carbon, a small extension in the duration of flotation allows the lead recovery to increase by 19% at the same recovery of copper. An addition rate of 0.75 kg/ton (1.5 lb/st) of bulk concentrate is suggested as optimum from this testwork. However, the actual level used in the mill is dependent upon the residual concentrations of collector and frother in the bulk concentrate pulp.

Jan 1, 1979

By John Devine

DURING the past few years the Bureau of Mines has been studying hydrogen-sulfide corrosion in the petroleum and natural-gas industries. Early work was confined to investigating the various practical, or operat-ing, factors that control the corrosion reaction when ordinary mild steel is being attacked. In that work it was shown that, if the optimum operating conditions1 are obtainable, . gas containing hydrogen sulfide can be handled at ordinary temperatures without serious corrosion resulting. However, frequently "sour" gas must be handled under other than optimum operating conditions, and combating corrosion then becomes a problem to be considered more during the construction of a system than during its subsequent operation. That is, where economi-cally practicable in such cases the designer will seek to substitute for mild steel other steels or ferrous metals more resistant to corrosion by hydro-gen sulfide. The comparative resistance of various commercial steels and alloy steels to corrosion by hydrogen sulfide at elevated temperatures has been reported systematically by previous investigators,2 but similar information for corrosion at ordinary temperatures is available only from scattered sources, representing different methods of testing. As the value of comparative corrosion tests depends largely upon the use of a

Jan 1, 1934

By E. H. Bronson

PROPERTY of Malartic Gold Fields Ltd. is situaated in the great clay belt in the northern part of the Province of Quebec. This belt represents the floor of the glacial lake Barlow-Ojibway. The clay blanket has a gently rolling, almost flat surface, with here and there projecting knobs and ridges that outline the large irregularities of the surface on which the clay was deposited. At irregular intervals glacial eskers dominate the landscape. The ore-bearing country rock is covered by strata of clay, sand, and silt to a depth varying to 40 ft. There are serious structural problems when it is necessary to place loads of unequal intensities on this surface to support buildings and machinery for a modern mining plant. Earlier mining companies and their engineers paid little attention to the science of soil mechanics, partly because they believed it unnecessary and partly because they knew little of the subject. The results are evident in some of the tottering structures in older camps. Careful analysis of soil problems is well worth-while, since cost of foundations may vary from 20 to 50 pct of the final cost of a structure. Low operating and maintenance costs can be achieved only in this way.

Jan 11, 1957

Permit quicker, safer clearance of hang-ups in the ore passes and chutes of underground mines. Approach Develop a device that can be operated from a safe distance to explosively propel a projectile into the hang-up. How It Works The Hang-Up Clearance Module, consisting of a stand, steel disk, explosive charge, and aiming device, is placed at a location convenient for line of sight aiming at the hang-up. This placement can be more than 100 feet from the target. Once aimed, the charge is remotely detonated, and the disk is converted by explosive force into a slug and propelled to the hang-up, bringing it down. The steel disk and an explosive charge are contained by a plastic casing. A small booster which is placed at the rear center of the explosive makes up the last component of the charge. Initiation is accomplished by standard means such as detonating cord or a number 8 blasting cap. When Initiated, a detonation wave travels through the explosive, inverting and consolidating the steel disk into a large slug. This slug is propelled at high velocity to the hang-up, delivering more than 5 million foot-pounds of energy on impact.

Jan 1, 1981

By Sean Gallagher, Thomas G. Bobick, Diane M. Doyle-Coombs, Richard L. Unger

The U.S. Bureau of Mines has developed an in-house facility to evaluate selected effects of whole-body vibration (WBV) levels experienced by underground mobile equipment operators, Vertical vibration data were collected from a coal haulage vehicle via a uniaxial accelerometer attached to the machine frame under the operator&apos;s seat. Data were analyzed and processed so a computer-controlled platform could approximate the vibration signals. Eight men (35.5 yr 2 6.5 SD) participated in a pilot study to evaluate the effects of shock and kBV on heart rate (HR), blood pressure (BP), and subjective discomfort. Subjects were exposed to vibration for 30-min periods while seated in a typical seat (backrest angle at 90° or 130°) &apos;that was plain steel or modified with 2 in foam padding. Subjects repeated the same protocol on a separate day, without the vibration. Results indicated the vibration significantly increased the HR (Q< 0.01), systolic BP, mean BP, the number of times subjects reported discomfort, and overall subjective discomfort rating (pc 0.85). When seated in the steel seat, the overall discomfort rating (E< 0,081) ad the number of times discomfort was reported (p< 0.05) increased significantly. Seatback angle had no significant effect on any of the dependent measures.