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By V. L. Brant

The estimated total energy demand for the U. S. is 60 quadrillion BTU for 1970 and is expected to more than double by the year 2000. Today the energy crunch is here. It is evidenced by brownouts to conserve electrical energy, and the shortage of gas and oil. Many such headlines, including suggestions for energy rationing, are in the news today. Paradoxically we have an abun¬dant source of energy in the form of coal. Energy consumers, however, are geared to use fuel in other forms. It is the intent of this presentation to discuss processes under development for conversion of the energy contained in these vast coal reserves to more usable forms. Coal conversion to synthetic fuels should be of particular interest to those engaged in mining. Coal consumption in a single conversion plant is expected to range from 10,000 to 40,000 tons per day. Plants will be located at the mine mouth and will operate continuously 24 hours per day, seven days per week. Further, many such plants will be needed., For example, looking at natural gas only, the supply/demand gap is estimated to reach 13 trillion cubic feet per year by 1985. Assuming that gas from coal conversion were to fill only 101, of this gap, 15 plants producing 250 MMSCFD would be required. These plants would consume about 90 million T/Y of coal or 135 million T/Y of lignite. It will indeed be a challenge to mine, suitably prepare, and transport coal at these projected volumes without interruption. Many ideas have been conceived for better utilization of coal and these are in various stages of development. Those supported by public money are covered by the Annual Report of the Office of Coal Research (OCR), Department of Interior. The two processes to be discussed, the Consolidation Coal Company's (Consol) C02 Acceptor Process (1)(2)(3) and The Pittsburg and Midway Coal Mining Company's (PAMCO) Solvent Refined Coal Process (4)(5) are both sponsored by OCR.

Jan 1, 1970

By H. Huang, R. N. Gow

"Previously, Gibbs’ phase rule was applied to mass-balanced EH-pH diagrams for the Cu-As-S-H2O system. Diagrams were generated using the stoichiometry of enargite as a basis. In this study, the calculations were expanded to cover the stoichiometries of three other Cu-As-S minerals (tennantite, sinnerite, and lautite) and compared to enargite. Stability regions within the resulting EH-pH diagrams were found to change with stoichiometry such that a particular mineral would predominate if its stoichiometry was used in the calculation. Solution speciation was also found to vary, with thioarsenate being the best example. This stoichiometric effect helps to explain results reported in the literature and would be difficult to realize if it were not for mass-balanced calculations. INTRODUCTION A comprehensive thermodynamic review has recently been conducted on the aqueous copper-arsenic-sulfur system (Gow et al., 2014a-d). The free energies of over 100 species were collected from various authors and thermodynamic databases to produce mass-balanced EH-pH diagrams, using the thermodynamic equilibrium calculation software, STABCAL (Huang, 2014). The full database was listed and discussed by Gow et al. (2014A). Resulting diagrams were generated for enargite and confirmed with Raman spectroscopy using bulk mineral electrodes in order to identify reactions spectroelectrochemically. Theoretical calculations agreed well with the experimental results under alkaline conditions (Gow et al., 2014a), acid conditions (Gow et al., 2014b), and alkaline sulfide leaching conditions (Gow et al., 2014c). In this study, additional mass-balanced EH-pH diagrams are generated by changing the copper-arsenic-sulfur stoichiometry from enargite (Cu3AsS4) to tennantite (Cu12As4S13), sinnerite (Cu6As4S9) and lautite (CuAsS). Regions for the thermodynamically stable species are shown to change with the four different mineral compositions. Potential leach conditions, both for co-dissolution and selective dissolution techniques, were examined for differences in predominant species according to changing copper-to-arsenic ratios, sulfur compositions, and sulfur oxidation states."

Jan 1, 2015

By C. Y. Haas

Of all the industrial clay minerals, attapulgite probably enjoys the widest variety of applications. A review published over three years ago by Haden and Schwint (18) cited some 80 individual uses, a list which continues to grow. In its near half-century of commercial life, attapulgite has received a generous share of research study and patent development effort, both on the part of producers as well as consumers. This work has been divided between understanding the mineral's structure or properties and applying it to specific end-uses. Naturally, information gained from the former has pointed toward opportunities in the latter. References of particular significance are cited throughout the text. Attapulgite's variety of uses derives from the unique three-dimensional structure and needle-shaped particle form of this crystalline hydrated magnesium aluminum silicate. Its inherent colloidal and sorptive properties are well known, and distinguish it from its sister clay minerals. Attapulgite is characterized by its high surface area, porosity, sorptivity, and decolorizing power. Its slips or slurries are viscous and thixotropic, however, unlike bentonite are not flocculated by electrolytes. In Table I are compared the general properties of attapulgite, bentonite, and kaolin. The properties in Table I are documented in greater detail by the wealth of scientific literature which has been published on the composition (14)(15), structure (6)(16), surface (16)(4)(22)(24), adsorption (31)(4)(5)(25), rheology (10-11)(12)(13)(26)(27)(32), plasticity (30) (31), and chemistry (23)(3)(7) of attapulgite. Attapulgite is the principal mineral constituent (70 to 80%) of attapulgite clay as it is commercially produced in the Georgia-Florida area of the United States. As mined, this clay also contains 10 to 1S% montmorillonite, sepiolite, and other clays; 4 to 8% quartz, and 1 to 5% calcite or dolomite. (18) During processing, non-clay fractions are removed so that commercial products are enriched to 85 to 90% attapulgite. By wet processing (such as practiced in the

Jan 1, 1971

By Cory Dippold, Michael Mett, Jérôme Steinkühler, Kristi Latimer

For decades, tunnels of all types have been a significant part of our infrastructure. In particular, water tunnels carry millions of gallons of fresh water every day to major metropolitan areas and surrounding communities. As a critical piece of public health infrastructure, it is important to inspect the condition of these tunnels regularly to ensure reliable and continuous operation. A specific challenge with water infrastructure is that it’s often difficult or impossible to shut down the system for long periods of time to perform the needed inspections. The latest method of tunnel condition assessment is the use of hybrid reality 3-D scan data. Photogrammetric and LiDAR based 3-D data ensure a reliable and objective view of tunnel conditions. The data can be used to support a detailed digital inspection including the compilation of databases that consist of a wide variety of deficiencies such as cracks and spalls within the structure. Mott MacDonald, a design engineer company worked closely with Dibit, used a 360-degree scanning system to collect high-resolution photogrammetric and LiDAR data on a recent project involving a water tunnel. The allows for full 360-degree coverage of the tunnel surface including a water covered invert. It operates at walking speed and ensures a fast and reliable data acquisition which can reduce the time of tunnel shutdowns. Several allocated inspection weeks can reduce to few days, with the final work product being a higher quality and more complete deliverable than traditional inspection methods would have provided. The true-color 3D-model has a photo resolution of 1 × 1 mm (0.039 × 0.039 inches) which makes cracks visible with a width of down to 0.3 mm (0.011 inches). The assessment of water tunnels, its technical challenges and the results of the 3D-tunnel inspection case study are illustrated and described in this publication.

Dec 1, 2022

By A. W. Hamilton

If you don't know a gauss from a grasshopper, you may be better off than you, think, particularly if you're an ore dressing engineer charged with the responsibility of selecting magnetic equipment for minerals separation and beneficiation. Gauss is a unit of measure for a magnetic field. It indicates the number of imaginary lines of force per square centimeter or per square inch radiating from a magnet. In discussing the strength characteristics of a magnet, we have come to speak of a magnetic field of 800 gauss, for example, meaning 800 lines of force per square centimeter. Gauss became the standard for selecting drum type separators many years ago under an arbitrary set of circumstances. The standard has continued to this day even though magnetics applications engineers have long considered it inadequate. The configurations of the older gauss meter were such that the most accurate and convenient readings on a drum type separator could be made at distances greater than one inch. So, an arbitrary distance of two inches was established and that two inches became the standard. Since then, it has become commonplace to specify magnetic strengths for drum separators according to average gauss readings at two inches; for example 500 gauss average at two inches, 750 gauss average at two inches and so on, even though gauss readings at two inches have much less to do with the separating and beneficiating function of a given application than was formerly believed. The standard was adopted as a means of gauging the strengths of electromagnetic drum type separators, for they were the only ones around at the time. These machines were usually designed with no magnetic considerations other than that the material to be separated should be agitated vigorously and the magnetic fields should be deep and strong. Drums built this way performed well enough, so it seemed logical to measure their magnetic strengths. Hence, gauss at two inches. Now, new improvements in magnetic techniques have made average gauss measurements at 2 inches positively obsolete.

Jan 1, 1971

By Bruce Watzman

"Few issues are more important to the National Mining Association (NMA), the U.S. mining industry and NMA’s MINExpo International 2016 exhibitors than safety.Global mining safety and health is a journey necessitating continuous improvement, collaboration and innovation on the part of both mining operators and their suppliers.MINExpo 2016, which takes place Sept. 26- 28, 2016, in Las Vegas, provides attendees with the opportunity to view technologies to help refine management of mining safety and health, utilizing NMA’s CORESafety system. CORESafety ‘One of the best’Launched by NMA in 2011 and moving forward ever since, CORESafety is driving continuous improvement in safety and health performance among participating industry companies by shifting from a command-andcontrol regulatory approach to a risk-based systems approach built on the Plan-Do-Check-Act model (Fig. 1).Considered an exemplary safety and health management system, NMA’s CORESafety system helps mining operators change their approach to safety and health management by enhancing the safety and health culture throughout their organizations. Although it is challenging to consistently and completely control all the factors and variables occurring in daily mining operations, experience has shown that applying systematic controls to as many variables as possible is the most successful approach for improvement in mining safety and health.When embarking upon the development of the CORESafety framework, NMA’s leadership set an ambitious goal to eliminate fatalities and reduce the injury rate 50 percent in five years, or the “0-50-5” goal. While the goal has not been met yet, the steady progress has been extraordinary with fatalities among participating companies dropping 45 percent during the period 2011-2015 (Fig. 2). Data also demonstrate that, as participating companies increase their level of implementation, total injury rates have also declined (Fig. 3).In a September 2015 interview with NMA, Penn State University mining engineering Professor Jeffrey Kohler praised CORESafety as “an inspired and timely program that brings together key elements to achieve safety and health goals.”"

Sep 1, 2016

By James C. Bradbury

Tripoli is a naturally occurring, finely divided form of silica found chiefly in midwestern and southeastern states and used commercially in fillers and abrasives. The name comes from the location of a silica deposit in North Africa and was applied in the latter part of the 19th century to similar material near Seneca, Missouri. Subsequently, the North African material was found to be diatomite, composed of siliceous skeletons of microscopic marine plants called diatoms, and the material's name was changed to tripolite. The name, tripoli, remained with the Missouri silica, which is inorganic in origin, and tripoli is now used to designate all naturally occurring silica that is similar in characteristics and origin to the Missouri material. Just to confuse things further, in commercial trade tripoli usually designates silica from the Missouri-Oklahoma field, whereas silica from southern Illinois, the other major producing area, is called amorphous silica. Each term, however, may be used commercially for any material, regardless of place of origin that has the characteristics or uses ascribed to material from either major producing area. For example, Engineering and Mining Journal routinely lists under "tripoli," prices "f.o.b. Elco, I11." and "f.o.b. Seneca, Mo. and Rogers, Ark.", and under "silica, amorphous," prices "f.o.b. I11 and "f.o.b. Dierks, Ark." "Soft silica" is another term that has been applied to tripoli from Illinois, west central Arkansas, and Tennessee, presumably to distinguish it from the more compact Missouri material. It has also been used in the ceramic trade to distinguish tripoli from "hard" silica, or silica flour, which is produced by pulverizing silica sand. Tripoli is produced mainly in extreme southwestern Illinois, in the Missouri-Oklahoma district in Newton County, Missouri, and Ottawa County, Oklahoma; and in the novaculite belt of west central Arkansas. Some tripoli is produced for local and specialized uses near Austin, Texas.

Jan 1, 1980

By Chee Theng

"In 2013, Coeur Mining had more than $55 million in general and administrative (G&A) costs and less than $100 million in cash flow. This year, its G&A costs stand at $30 million, down by more than 40 percent, its all-in sustaining costs have shrunk by more than 30 percent, and its cash flow is above $200 million. To realize this, the company aggressively reduced both its corporate overhead cost and operating cost and repaid more than $300 million in debt.The more robust balance sheet meant the precious-metals producer was well positioned to reap the rewards of an upsurge in commodity prices in the early part of 2016. Its stock price soared from $1.75 in January to $15.98 in August. Although the stock price has since dropped to around $9 due to a stronger dollar and a more hawkish Federal Reserve that recently raised U.S. interest rates, shifting the opportunity-cost argument away from buying gold and silver, Coeur remains attractive to analysts in light of its prudent spending and improved fundamentals.Focus on balanced portfolioCoeur is the largest primary silver producer and one of the largest gold-producing companies in the United States and one of the largest silver companies in the world. Incorporated in 1928, the U.S.-listed company has a total of five operations: three in the United States, one in Mexico and one in Bolivia. About two-thirds of its revenue comes from the United States.The company is conscientious about having a balanced portfolio, so no single mine accounts for more than about 30 percent of its business. Being in three different jurisdictions provides further diversification, and its revenue split of about 60 percent from gold and 40 percent from silver gives it some metals mix. This year, it expects to produce about 466 t (15 million oz) of silver and 10.3 t (330,000 oz) of gold."

Feb 1, 2017

By J. P. Ramsey

This is a description of the efforts of a research project intended to demonstrate methods of alleviating pollution from coal mine refuse piles and slurry lagoons. These are mainly derelict barren sites. Some are burning and some are vulnerable to wind erosion which causes air pollution. Some occupy valuable land near metropolitan areas. They are an integral part of the landscape of the Appalachian and Midwestern Coal Fields. They are important in the light of growing civic awareness of the great general problem of waste disposal and environmental improvement. In the V-shaped valleys of the Pocahontas Region, they continue to be piled higher and higher. In flatter topography, they tend to form broad, flat ridges. Some contain more metal forms than others and some have a minimum of metal, but weather to a fine talc, which chokes streams with a fine particle suspension. Most are burning or have burned, but burning or weathering, most all are sources of pollution to the atmosphere and to adjacent waterways. This demonstration project is being carried out at an abandoned mine near the town of Du Quoin in southern Illinois. It is jointly sponsored by the Truax-Traer Division of Consolidation Coal Company and by the Federal Water Pollution Control Administration of the Department of the Interior. The site area is a refuse pile and slurry lagoon, each of fifty acres. It is hoped that basic data from this study will be generally applicable to other sites and will provide a basis for rational and efficient engineering design of future reclamation projects. Most refuse piles have extremely long term capabilities to produce highly potent acidogenic oxidation products typifying the more serious aspects of acid mine drainage contamination. Numerous sites remain where the abandoned mine no longer discharges acid waters, but its associated refuse pile continues to generate significant quantities of acid and other oxidation products even after many years.

Jan 1, 1969

By Vladimir G. Kochnev

Crushing and grinding account for the major portion (60 to 80 percent) of the overall expenses for ore processing. Autogenous (AG) and semiautogenous grinding (SAG) have been considered a step forward in comparison to conventional grinding circuits with several stages of crushing and using ball (and/or rod) grinding mills (Bassarear, 1982, MacPherson, 1989, Pithois, Casalis, 1983, Maripuu et al., 1983). However, there remains room for improvement to existing AG and SAG technologies and both technologies have immense economic benefit potential. Experience gained by the Technics & Technologies of Disintegration Ltd. (TTD) in the research of grinding processes shows that grinding in AG and SAG mills can be performed in a more effective way. The company's approach comprises the following elements: ? Novel mill design. ? New liners and lifters. ? Novel discharge grid design. ? Technique of treating material of critical particle size. Comparative tests that demonstrated the usefulness of these innovations are described in this article. Currently, there are hundreds of AG and SAG mills in operation throughout the world. Application of new internal elements of the mills and reconsideration of the circuit design of the existing grinding equipment using present technological solutions would significantly increase the throughput rate and diminish power requirement.

Jan 1, 2008

By B. Anameric, S. K. Kawatra, K. B. Rundman

The iron nugget process is an economical, environmentally friendly, cokeless, single-step pig iron making process. Residence time dependent process requirements for production of pig iron nuggets at a fixed furnace temperature (1425 C) were investigated. Three chemically and physically different products were produced after complete reduction to iron, depending on the residence time in the furnace. These products were direct reduced iron (DRI), transition direct reduced iron (TDRI), and pig iron nuggets (PIN). The increase in the carbon content of the system as a function of residence time was detected by optical microscopy and Microhardness measurements. Sufficient carbon dissolution for the production of pig iron nuggets was obtained after 40 minutes residence time. The pig iron nuggets produced had chemical and physical properties similar to blast furnace pig iron. They were liquid state products and slag was completely separated from the metal.

Jan 1, 2005

By Subhash Bhagwat

The definition of high sulfur coal varies from plant to plant and is subject to changes over time as the environmental regulations change. In plants constructed after September 1978 hardly any domestic coal can currently be burned without the use of Flue Gas Desulfurization (FGD) because a 70 percent reduction in potential S02 emission is mandatory even when the potential emission is less than 0.6 lbs. S02/106 Btu heat input. On the other hand older power plants may in many cases be legally emitting up to 6 lbs. S02/106 Btu or more under some State Implementation Plans (SIP). The Clean Air Act requires, however, that in the long run all stationary sources of S02 pollution must abide by the ceiling of 1.2 lbs S02/10 Btu heat input.. Coals with a potential to exceed this limit must, therefore, be considered as high sulfur coals. Such a definition would be unrealistic because many SIP's aim at an emission level of 1.8 to 2.0 lbs. SO2/106 Btu for existing plants and a stricter limit does not appear to be enforceable in the next 5 to 10 years. As a result, coals with an emission potential of greater than 2.0 lbs of S02 per 10 Btu heat input are considered high sulfur coals for the purpose of this investigation. Based on this definition and the 1984 actual consumption of coals by U.S. electric utilities (table 1) only 7 out of the 24 coal producing states could be categorized as low sulfur states. The actual S02 pollution, however, depends on total tonnage of a type of coal as well as the sulfur content of the coal. Table 1 also indicates that only 6 states--Kentucky, Illinois, West Virginia, Ohio, Pennsylvania and Indiana-account for nearly 77 percent of S02 pollution potential in the United States. These 6 states have therefore been chosen for this investigation.

Jan 1, 1986

By Richard M. Crowell, John W. Shield, Todd J. Harvey

Facing lower gold prices, gold mine operators throughout the world are seeking ways to reduce costs for treating refractory sulfide ores. Many gold mines, currently producing oxide ores, have underlying refractory sulfide deposits and the operators could extend the mine life by processing these sulfides. Fortunately, oxidation technologies for refractory ores need not be complex nor costly. GeoBiotics, Inc. has developed heap biooxidation technologies (GEOCOAT™) for treatment of refractory gold ores and concentrates. GEOCOATTM uses simple low cost unit operations common to heap leaching of gold and copper ores. The cost effectiveness and flexibility of GEOCOAT™ heap biooxidation allows mining companies to expand operations to include refract01y ore. In addition, GEOCOAT™ can be utilized to supplement or replace existing oxidation processes such as roasting, autoclaving, or agitated tank biooxidation, and to treat a lower resource grade than is currently economic. The GEOCOAT™ technology involves coating sulfide concentrates onto sized support rocks and biooxidizing the sulfides in a heap configuration. After biooxidation the concentrate is stripped from the support rock, neutralized and leached in conventional cyanidation facilities. Ashanti Goldfields Company Ltd. (AGC) produces over 885,000 ounces of gold per year from oxide and refractory ores at its Obuasi operations in Ghana. Refractory flotation concentrates are treated in roasters and in the world's largest stirred tank biooxidation facility. In August 1998, AGC and GeoBiotics jointly constructed and operated a field demonstration heap of the GEOCOATTM process at the Obuasi operations. The heap contained I 082 tonnes of support rock and 125 tonnes of concentrate. The heap was approximately 19 meters square at the base and 3.8 meters high, and ran for 88 days after which the concentrate was reclaimed. Average gold recovery after biooxidation was 91.5% with a NaCN consumption of 8.6 kg/t. Baseline gold recovery by direct cyanidation of the concentrate was 53.8%.

Jan 1, 1999

By Gary Jobson

The Mt Todd Gold mine is situated near Katherine in the Northern Territory of Australia. Commissioning of an 8 Mtpa processing facility incorporating a four stage crushing circuit, ball mills, flotation, concentrate regrinding, high rate thickening and CIL processing was commenced during late 1996. A 4.5 M tonne /annum crushing and heap leach facility was commissioned during late 1994, and was subsequently upgraded to a nominal 6 M tonne / annum circuit during 1995. Processing equipment used included primary gyratory, secondary cone and tertiary Barmac VSI crushers. Some of the features of that crushing circuit and heap leach facility were presented at the Randol Perth 95 conference by myself. The location is described as sub tropical with average climatic conditions including 1100 millimetres annual rainfall, predominantly during the December. to March wet season, and 3000 millimetres evaporation and maximum temperatures ranging from around 26 to 46 °C. The main gold occurrence at the Mt Todd site is the Batman deposit, with current published Reserves of some 60 Mt@ 1.20 g Au / tonne ( 0.0425 oz Au / ton ). The primary ore from the Batman deposit is an extremely competent greywacke and is very hard at an average Bond Ball Mill Work Index of26.5 kWhrs/ tonne. Other indicators include a Bond Impact Crush Work Index of 20 kWhrs I tonne, an Abrasion Index of 0.15 and Ultimate Compressive Strength values of 100 - 200 MPa. The main gold occurrence is very finely disseminated free gold (at an average grain size of around 5 micron) within a combination of quartz and mixed sulphide. This gold bearing component is confined to largely parallel veins ranging from 0.5 to 25mm wide within a greywacke matrix. Although the gold is essentially non­refractory, there is a strong recovery versus grindsize relationship due mainly to the liberation characteristics and the relatively low permeability of the host greywacke rock.

Jan 1, 1997

By Robert S. Mayo

My subject today is "Drilling-and-Blasting of Small Rock Tunnels". I am sure that there will be some people, primarily college students but perhaps Consulting Engineers, who will say: "Drilling-and-Blasting? I thought that went out with the invention of the Tunnel Boring Machine". A few years ago I talked to Dick Robbins and he told me that they did not try to sell a "Robbin's Mole" unless the tunnel was two miles long. For easy calculations I use 10,000-ft. (3km) A Mole today costs about $2 million which works out to $200 per lineal foot. This is "front money". You cannot place the order unless you are the uncontested low-bidder and then you must wait at least six months for delivery. Of course you can use that time to square up your portals, ready to turn-the-eye, or maybe you have shafts to sink to reach the tunnel grade. But this is "dead-time" and it is a heck of a feeling to have a job and cannot get started on it until you get the Mole. I do not have the American figures on lengths of tunnels but there was an article a few years ago in a British magazine: NEW CIVIL ENGINEER, on this subject. This stated that 75% of the jobs in Britain which were bid were for small tunnels, 10-ft x 10-ft (3m x 3m) or smaller, and that they were less than 5,000-ft (1.5km) in length. This does not mean that 75% of the footage in Britain was less than 10-ft in diameter. It means that 75% of the jobs being bid were less than a mile in length. From my experience in the U.S. I believe that we have substantially the same ratio: so many of the jobs with which I was associated were short, 1,000-ft, 2,000-ft and sometimes 3,000-ft and the bores

Jan 1, 1981

The mining industry has indeed gone global. International minerals producers are spending big money to move into countries that were off limits a few years ago. Due mostly to political reasons, these countries' huge mineral deposits - worth billions of dollars - were locked up and mining companies could only sit on the side and wonder "what if." Now much of the world is going the free market route. Once closed countries and developing nations are rewriting their mining and tax laws hoping to attract foreign investment to develop their natural resources. And big businesses - mining companies included - are lining up to get their share. But with new opportunities come new risks. While emerging nations are slowly accepting the free market concept and the privatization that goes along with it, many remain plagued with political instability and violence. Even developed nations carry their unique risks. Some of these include inadequate or contradictory legal and regulatory infrastructures, political patronage and outright corruption. So companies hoping to expand into new regions of the world must do more than examine the market. They must study the political stability and structure of a country, as well as its tax and environmental laws. And they must guarantee the safety of their employees. Control Risks Group is an international management consulting company that assists companies preparing to move into a new country. It employs about 225 people in 14 offices throughout the world. Control Risks personnel include lawyers, bankers and former law enforcement officers and intelligence people. The company held a one-day seminar in Washington, DC to update some of its clients on the state of affairs in various regions of the world. The seminar also covered extortion, corruption and product diversion. About 175 people attended the seminar. Speakers included Control Risks' operators, analysts and investigators. Here is a summary of what some of those people had to say.

Jan 1, 1998

By M. J. Wilhelm

Bromine is the intermediate member of the halogen family of elements between iodine, a solid, and chlorine, a gas. The name is derived from the Greek bromos, meaning stench. Bromine is the only nonmetallic element that is liquid at room temperatures, with a melting point of -7.2°C and a boiling point of 58.78°C. Reddish brown in color, it dissolves easily in water to yield a red solution. Bromine volatilizes at ordinary temperatures to a red vapor that is very irritating to the eyes, nose, and throat. Density of the liquid is 3.12, and gas weighs 7.59 gpl in standard conditions. Because the element is highly active, it exists in nature only as bromide compounds. Bromine was discovered by Antoine Jerome Balard in seawater bitterns in 1825 and began to find commercial applications shortly thereafter in photography, medicine, and dyes. The first commercial production of bromine was in 1846 in Freeport, PA, followed by production in Germany in 1865. OCCURRENCE Bromine is widely distributed in nature, and compounds occur in solution in natural brines, in seawater, saline lakes, oil and gas well brines, and in evaporite chloride minerals. The concentration of bromine salts ranges from 60 to 65 ppm in seawater to several thousand ppm in oil well brines and saline lakes. The distribution of bromine in marine evaporite minerals and in the solutions from which they crystallized was determined many years ago by H.E. Boeke (1908). Theoretical aspects regarding the geochemistry of bromine have been published in numerous papers (Raup and Mite, 1969). Bromine occurs in solid solution in carnallite and sylvite associated in potash deposits, in halite in salt beds, salt in oil shales, and in trona deposits. Its presence is useful as a guide in geochemical exploration. The analysis of small amounts of bromides in the presence of large amounts of chlorides is discussed by W. Schwerdtner (1963). Manganese, iron, and iodine may interfere with the determination. Other analytical methods are discussed at length in literature (Stenger and Atchison, 1964).

Jan 1, 1994

By Gene E. McClelland

4.1 INTRODUCTION Metallurgical testing is required on any ore, waste or tailing material before amenability to heap leaching treatment can be accurately determined. The amount of testing necessary to determine and optimize heap leach amenability and conditions for any feed material is determined by the ore type, grade, size of deposit, and the overall financial commitment a particular company is willing to make. It is very easy to either "under-test" or "over-test" a particular deposit or feed material. A good heap leach testing program will provide the necessary design information without "bogging" down in too much detail. The three basic stages of ore testing include: • Preliminary--bottle roll tests and small column percolation leach tests; • Detailed--larger column tests, different feed sizes, and feed size optimization; and • Pilot-Scale--Column or field heap. The following subchapters describe the stages of heap leach testing necessary to put a viable property into production. 4.2 PRELIMINARY METALLURGICAL TESTING The two types of preliminary tests that can be undertaken include bottle roll or cyanide agitation tests and small column leach tests. Each of these is described below, along with information about what the test results provide in terms of furthering knowledge of ore qualities. 4.2.1 Bottle Roll Tests The first step in a heap leach testing program is preliminary bottle roll tests at a relatively coarse feed size to determine the ore's leachability. Bottle roll tests are usually conducted on reverse circulation drill cuttings samples (= 1/4 inch (6 mm) in size). Bottle roll tests provide initial information about precious metal recovery, recovery rate, and reagent requirements. The recovery results are to be considered maximums because attrition grinding creates fines and liberates recoverable values that would not be liberated from the material during a static leach. Bottle roll tests can be conducted on up to 25 lb (11 kg) ore charges of up to two inches (50 mm) in size. However, the coarser the feed the more attrition grinding occurs during rolling.

Jan 1, 1988

By Vas Choudhry

INTRODUCTION Traditionally mineral processing equipment has been procured based on (equipment) specifications prepared by the engineers. As newer materials of construction are being used for equipment manufacture and plant control systems become more sophisticated, the need for thorough and detailed specifications is greater than ever. For example, it is not uncommon to find plants looking at grinding circuits consisting of semiautogenous mills with variable speed, gearless, drives of large horsepower. Technical specifications for the mill, wrap- around motor and control system must, therefore, be carefully prepared to ensure that the respective equipment supplied by vendors meets overall grinding needs. Various engineering and design companies have expended considerable time and effort in developing the specification format. Equipment manufacturers have also given significant effort to developing data sheets aimed at collecting information regarding not only the duty of the equipment, but also the conditions under which it will be operated. As engineers moved from one company to another, the specification format became cross-fertilized and further developed. As a result, specifications on file with various engineers have improved considerably over a period of time. Equipment specifications from earlier projects are commonly used as a basis for tailoring new ones. To keep equipment specifications short, general technical considerations are often compiled as separate specifications. For example, general considerations applicable to the design, manufacture and supply of the mechanical equipment are consolidated under "Standard Requirements for Mechanical Equipment” and included along with that specified for purchase. As the economic feasibility of the project has been established during earlier studies, purchase-related activities can be initiated following completion of the specifications. Procurement itself is a major activity, however, in this chapter only those activities directly related to the purchase of equipment will be discussed. PREPARING EQUIPMENT SPECIFICTION Specification for process equipment or machinery is written in such a way as to define exactly what is required of the equipment. Generally, mechanical

Jan 1, 1986

By Omar A. Muhtadi

6.1 INTRODUCTION The three most critical factors in successful heap leaching operations are: • The methods employed to pretreat ore (i.e, crushing and agglomeration); • Placement of ore on the leach pad (heap building techniques); and • Wetting of the ore with cyanide (solution application techniques). Improper execution of any of these initial steps may result in a substantial sacrifice of total metal extraction or, in the worst case, in project failure. Ore preparation in terms of crushing and agglomeration was discussed in Chapter 5; this chapter therefore focuses on commonly employed techniques for heap construction and solution application. The main objective of heap construction is to obtain the most homogeneous heap possible. "Channeling" of leachate in heaps with preferential seepage paths leads to preferential leachate distribution and uneven/incomplete extraction. The two main contributing causes of channeling are inadequate attention to heap construction and uneven solution application. These pitfall s can best be avoided through a knowledge of the various techniques available and the applicability and success of these techniques with various ore types and site conditions. The remainder of this chapter provides a discussion on these two subjects. 6.2 HEAP BUILDING TECHNIQUES Successful heap building techniques vary with the type of ore and, since no two orebodies are exactly alike, some slight modifications are usually necessary for each specific project. However, it is possible to generalize in terms of the appropriate techniques to be used with ores having similar characteristics. This section discusses the three most commonly used methods of heap construction and provides some guidelines with regard to ore types, construction constraints, and lift height parameters for each of the three. 6.2.1 Run-of-Mine Dumping and Dozing The run-of-mine method of heap building can only be used with ore of a highly silicious nature (i.e., ore which will not generate a large amount of

Jan 1, 1988