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By Nathaniel Arbiter

In contrast to pyrometallurgy's 6000year history in metals production, hydrometallurgy is of relatively recent origin. The earliest reference to it was in the 16th century, with the first applications to copper in the 17th and 18th centuries. In the 19th century, increased demands for pure metal resulted in the development of electrolytic refining, and early in this century electrowinning. The rapid growth in copper production in the 20th century, particularly in the United States and Chile, stimulated the development of new technology for leaching and for the recovery of copper from leach solutions. In the past 25 years, solvent extraction has become a major factor by permitting novel leaching technology that produces dilute or complex solutions. In addition, solvents other than sulfuric acid, and chemical methods for precipitating copper metal are now of increasing interest. These are trends that should grow in importance with the need to process lower grade and more complex materials. The evolution of copper hydrometallurgy is reviewed. Key factors in recent major developments are presented with details of specific operations and with trends for the future indicated. The relative importance of copper hydrometallurgy is compared with that of pyrometallurgy in the light of probable changes in ore supplies and character.

Jan 1, 1994

By Takeshi Tanaka, Yasuhiro Komamura, Yuusaku Tominaga, Takayoshi Iwamoto

In order to assist better countermeasures for ventilation control in normal/abnormal condition of mine ventilation network in real time, branch relation table derived from a macroscopic characteristic of ventilation network is introduced in this study. The main results in this study are as follows; 1) One of macro characteristics of a ventilation network, as a relation between airflow rates in two branches chosen arbitrarily, is specified under the change of aerodynamic resistances in a branch. Airflow rate in a branch can be estimated by airflow rate in other branch changing aerodynamic resistance by using empirical formula. The empirical formula by computer simulation of the Horonai coal mine, Japan is considered to be a one-valued function with monotone or extremums. 2) A branch relation table shows the macro characteristics, mentioned above, of all the set of two-branch combinations in a network. Elements in the table give both information of control possibility range of airflow rate and total number of extremums in an empirical formula. 3) It is important that when aerodynamic resistance change in a branch is estimated by measuring airflow rates in two typical branches, the two branches should be chosen from branch combinations with monotonous relation in the branch relation table. 4) A flexible expert system to assist ventilation control in the specified branch in real time has been developed by using a branch relation table for a ventilation transfer diagram of the specified branch, such a coal face and an advancing face. A fuzzy reasoning is utilized in the recognition of the safety factor, methane concentration, in the system. And when conviction degree in recognition for methane concentration at the specified branch is too low, the system searches for other branch combinations in the branch relation table stored in the system, to use other ventilation transfer diagram of the specified branch. When a needed ventilation transfer diagram is not stored in the system, the expert system asks automatically the ventilation simulation from other computers linked to the main computer automatically. The system repeats consultation until conviction value of safety in the specified branch approached

Jan 1, 1993

By H. H. Murray

Significant changes in ownership and production of industrial clays have occurred since 2000. Clays covered in this presentation are kaolins, ball clays, smectites, (bentonite), and palygorskite (attapulgite)-sepiolite. IMERYS discontinued production of paper coating kaolins at their Cornwall operations and have expanded their kaolin production in Brazil. J. M. Huber sold their kaolin operation in Georgia to KaMin whose headquarters are in Ft. Worth, Texas. BASF purchased Engelhard?s kaolin and attapulgite operations in Georgia. ActiveMinerals purchased Southeastern Kaolin in South Carolina, Wilkinson County Kaolin in Gordon, Georgia, and Zemex Attapulgite in Quincy, Florida. Chemical Lime purchased Spinks Ball Clay Company in Paris, Tennessee. Most of the ball clays used in Italy and Eastern Europe comes from expanded operations in the Ukraine. Bentonite operations have expanded production in Wyoming and Montana because of strong demand for drilling mud, foundries, cat litter, and iron ore pelletizing. The production and exports of palygorskite in China continues to increase. Nanoclays utilizing sodium montmorillonite, palygorskite, and halloysite are actively being developed.

Jan 1, 2009

By Archie W. Fletcher, R. J. Wesely, Nathaniel Arbiter, A. D. Zunkel

In contrast to pyrometallurgy's six thousand year history in the production of metals, that of hydrometallurgy is of relatively recent origin. The earliest reference to it at all was in the 16th century, with the first applications to copper in the 17th and 18th. In the 19th century, increased demands for pure metal resulted in development of electrolytic refining, and early in this century electrowinning. The rapid growth in wpper production in the present century, paricularly in the United States and Chile, stimulated the development of new technology for leaching, and for the recovery of copper from leach solutions. Solvent extraction has become a major factor during the past quarter century by permitting novel leaching technology which produces dilute or complex solutions. In addition, solvents other than sulphuric acid, and chemical methods for precipitating copper metal are now of increasing interest. These are trends which should grow in importance in the future with the need to process lower grade and more complex materials. The evolution of copper hydrometallurgy is reviewed briefly and key factors in recent major developments are presented with details of specific operations and with trends for the future indicated. The relative importance of copper hydrometallurgy is compared to that of pyrometallurgy in the light of probable changes in ore supplies and character.

Jan 1, 1993

By Esko O. Nermes

Outokumpu flash smelting of copper concentrates was introduced in 1949 and flash smelting of nickel concentrates in 1959, both at Harjavalta in southwest Finland. The first flash smelter outside Finland was started up in 1956 in Ashio, Japan. Between 1956 and the present about 25 flash smelters for copper, and nickel concentrates have been put into operation in different parts of the world. Outokumpu"s research organization has been highly involved in the development of flash smelting. For example, a direct blister flash smelting process was developed in 1975 and introduced in Glogów, Poland, in 1978, and another has been designed for Zaire. This straight metal process is based on low iron content of the concentrate, which reduces the amount of recycling slag copper. Additionally, the concentrates are rather low in impurities.

Jan 1, 1982

By D. C. Shumway

Mining in Cushenbury Canyon began in 1860 when John Cushenbury left his Holcomb Valley gold prospect and discovered a silver vein in the limestones of the present day Cushenbury Mine. Cushenbury Canyon is located along the western boundary of the Mojave Desert in Southern California and on the north slope of the San Bernardino Mountains. The Holcomb Valley, immediately southeast of Cushenbury Canyon was the most prolific gold producer in Southern California. Gold mining dominated the area until World War II when interest in the Lucerne Valley Limestone deposits was peaked by the construction of the Kaiser Steel Plant in Fontana, California. The steel making process required large amounts of metallurgical grade limestone and Kaiser geologists located claims in most of the limestone deposits. Kaiser Cement constructed a cement plant and limestone mine in Cushenbury Canyon in 1956. Kaiser Cement modernized the facility in 1982 to a four stage preheater-precalciner system. Mitsubishi Cement Corp. purchased the property in April, 1988, and through further system modifications have created the most efficient and modern cement plant in the United States.

Jan 1, 1992

By B. Moudgil, Hassen El-Shall

Particle shape and size distributions are among the most important parameters that affect the filtration efficiency of phosphogypsum in wet- process phosphoric acid production. Cost-effective enhancement in filtration rate is desired by phosphoric acid producers for higher plant capacity and lower operating costs. In this regard, numerous research efforts have been carried out in different laboratories as well as in pilot and plant testing. Nevertheless, changes in phosphogypsum crystal shape and size distribution deserve special attention. In this study, the results obtained in the presence of Crysmod and Hiflo-S5 surfactants are discussed. The influence of such additives on crystal morphology and size distribution are studied under different sulfate contents (supersaturation). The obtained data are correlated with process efficiency parameters such as filtration rate, digestion of rock, and recovery of phosphate values. Up to 60% increase in filtration rate is obtained. In addition, an increase in digestion efficiency and P205 recovery is achieved due to addition of surface active agents. The observed beneficial effects are explained in the light of the changes induced in crystal habit, size, and size distribution.

Jan 1, 1999

By Fredrick J. McGarry, Fred Moavenzadeh

In order to reduce the resistance of hard rocks to excavation by the available cutters, and in order to reduce the wear of the cutters and thus to increase the efficiency of the conventional tunneling machines and to improve their rate of advance in hard rocks, surface active agents have been studied in the controlled laboratory environments and have been experimented with in the field of actual tunneling operations. The laboratory study utilized a notched beam test to measure the effectiveness of 30 different surface active agents on the amount of surface energy required to cause stable fracture in the rock specimens. In addition to the type of rocks, geometry of the specimens, type of surface active agents, the effects of environmental factors such as temperature and degree of saturations were studied. The principle mechanism responsible for weakening of rocks in the presence of surface active agents was believed to be that of stress activated corrosion. The application of surfactants in the laboratory resulted in a reduction of up to 50% in rock strength, while limited experiments in the field have shown a 10 to 20% increase in the rate of advance. Substantial efforts both in the laboratory and in the field are needed to fully understand the mechanism involved and to utilize the effectiveness of surfactants as weakening agents for hard rocks.

Jan 1, 1997

By Harry R. Price, Jerome C. Neyer

INTRODUCTION Safety must be a primary consideration in the design and construction of tunnels. Tunnel construction has historically been considered a high-risk business. During the construction of the 14.8 kilometer (9.25) mile St. Gotthard Tunnel in the Swiss Alps in the 1870s, 310 lives were lost and another 877 workers permanently disabled. In more recent days, two tunnel construction accidents in 1971, one in Michigan and one in California, claimed the lives of 38 workers. Prior to 1971, most regulations governing safety in tunnel construction were developed by the U.S. Bureau of Mines. These included a 1941 Bulletin 439, "Some Essential Safety Factors for Tunneling" and a 1968 Bulletin 644 which updated Bulletin 439. In 1970, the United States passed the Occupational Health and Safety Act (OSHA) which became effective in early 1971. That act covered all sorts of workplace activities including Tunnels and Shafts in 29 CFR 1926.800. In 1989, a revised and renamed 29 CFR 1926.800 was issued for Underground Construction. Some of the changes introduced in this rule were the outgrowth of improvements made in the California and Michigan codes after the 1971 accidents. These new regulations are the "Rules to Live By" for tunnel construction in the United States and are generally accepted as appropriate for tunnel construction throughout the world.

Jan 1, 1995

By Magnus Ericsson

The unexpectedly quick recovery in world crude steel production in the second half of 2009 was due almost entirely to increased production in China that began in late 2008. Previous peaks in monthly production in China were matched by April 2009. The rest of the world had still not reached pre-crisis production rates by May 2010. Chinese production drives growth, but there has been some growth in most other larger crude steel producing countries as well, compared to production in 2009. If the production rate of the first four months of 2010 continues, the total output of crude steel in 2010 will be somewhere around 1,410 Mt (1.5 billion st), the same as in the record year of 2007.

Jan 1, 2010

By P. Raffinot, C. H. G. Bushell, S. Hodgson, E. F. Milner, H. J. Bosshardt, N. Draper, D. E. Pickett, Edwin T. McKnight, J. Prieto

Zinc ranks third and lead fourth in world nonferrous metal conumption. In 1972 the free world consumed 3,333,000 mt of refined lead and 4,422,000 mt of refined zinc. The lead tonnage was divided into the following end uses: storage batteries (42%), lead allows (7%), pigments and chemicals (11%), cable sheathing (9%), gasoline additives (13%), pipes and sheets (8%), and miscellaneous uses (10%). The corresponding distribution of zinc uses in 1972 was galvanizing (39%), die casting (26%), brass (15%), rolled zinc (8%), oxide excluding American Process zinc made directly from concentrate (6%), and other uses (6%). The pattern of usage of lead and zinc varies considerably from country to country. During 1972 in the USA 49% of refined lead was consumed in storage batteries, 19% in gasoline additives, and only 3% in cable sheathing, whereas in the United Kingdom 28% of the lead was consumed in batteries, 14% in cable sheathing, and 14% in gasoline additives. For zinc the major US uses were die casting (41%) and galvanizing (37%), with about 3% consumed as rolled zinc; corresponding usages in the same applications in France were 12, 28 and 28% and in Australia 12, 67, and 3%, respectively. The outstanding resistance of lead to corrosion, its density, and

Jan 1, 1985

By J. Hoover

Real growth in the economy, increasing demand for electricity, and consumer stockpiling for a possible United Mineworkers of America (UMW) strike in October made 1984 a banner year for coal. Production and consumption climbed to record heights. Precautionary purchases brought inventories close to the peak levels of early 1981 when coal miners walked out for 72 days. Production slowed in the fourth quarter after labor and management concluded negotiations without a walkout. But output in every major coal producing state showed significant gains during the year US coal production totaled 807 Mt (890 million st) in 1984. This is a 13.8% increase over 1983 output. Lower production rates, principally in Appalachia, and sustained demand in the final quarter put downward pressure on coal stocks by the end of the year. Demand All market sectors experienced greater requirements for coal in 1984. Electric utility coal consumption increased 6.3%; exports climbed 4.8%; coke plants consumed 18.9% more coal; coal requirements in the other industrial sector expanded by 11.8%; and consumption in the residential/commercial sector rose 8.1%. Domestic consumption of coal reached a record 718 Mt (791 million st) in 1984. This is a 7.4% gain over the previous consumption high of 668 Mt (737 million st) in 1983. Electric Utilities The 4.6% increase in electric power generation in 1984 was coupled with expanding coal use relative to other energy sources. This resulted in a 6.3% rise in coal consumption, totaling 603 Mt (664 million st) for the year. Thirty-eight of 45 states where coal-fired electric power plants were operating shared in the 36-Mt (39 million-st) increase in electric utility coal consumption

Jan 5, 1985

By Joseph R. Wojcik

Introduction Placer deposits account for one-half to two-thirds of the total gold produced worldwide. As many as 311 t (10 million oz) have been produced from some major districts. Several others are credited with 155 t (5 million oz). All the major districts and many lesser ones have similar characteristics. Consideration of these characteristics offers insight into the origin of gold in the deposit. Knowing the gold deposit's geologic history leads to useful conclusions in exploring for placer deposits and for deposits in consolidated areas. Placer Deposit Characteristics Table 1 lists 17 placer gold districts around the world and their characteristics. These include type and age of, mineralized source rocks, associated intrusive rocks, and age of intermediate sedimentary cycles. Although quartzite or sandstone occurs in the bedrock sequence in four of the 17 districts, slates, phyllites, or schists are present in all of the districts. Additionally, in all but three, the slates are pre-Mesozoic. And, in six of the remaining 14, the slates are Precambrian. Rocks intrusive into the slates are all of intermediate to acidic composition and are emplaced as stocks, dikes, or sills, rather than being batholithic in proportions. Intermediate interceptors have not been recognized in only three of the 17 districts. Data from China and Mongolia are inconclusive as to this characteristic. Black Shale Gold Higher than average gold values are found in modern sedimentary rocks in coarse granulites, conglomerates, sandstones, and gray-wackes. Not so predictably, higher than average gold values also occur in black shales and carbonaceous argillities. Li and Shokena (1974) found that, in the Proterozoic sedimentary and equivalent metamorphic rocks of the Enisei Ridge, carbonaceous and graphitic phyllites and schists were particularly enriched in gold. Korotayeva and Polikarpochkin (1969) reported gold content in organic rocks to be enriched up to 15 times more than the organic free shales and siltstones of the Nerchinsk Zavod region of eastern Transbaikal. Black shales can be gold interceptors as are rocks of the granulite facies. Gold occurs in shales in particulate, free form, in pyrite, adsorbed on clays, and precipitated on carbon. In copper-bearing shales of Poland's Fore-Sudetic monocline, Kucha (1973) reported gold present in organic compounds as well as in silver bearing minerals. Anoshin (1969) found a strong correlation between gold and the pelitic fraction of sediments in certain rocks of the Atlantic Ocean basin. Heavy metal absorption on clays results in agglomeration to the extent that the particles settle with the heavy mineral fraction in enriched strata. Piper and Graef (1974) think that gold in sediments on the flank of the East Pacific rise is of lithogenic origin. Crockett (1973), however, proposed a volcanogenic exhalative origin. A strong correlation between gold and volcanic activity exists in rocks of the Canadian Shield where tuffaceous sediments and porphyries are more frequently enriched in gold than rocks with no volcanic components. Volcanic rocks of intermediate to acidic composition are considered here to be the primary source of gold in black shales. Gold is concentrated in shales as detrital free grains with diameters less than 50 µm (270 mesh), as precipitates, and in pyrite or other sulfide minerals. This is the first step in the history of gold placer deposits. Grain Size Modification Gold, as free grains with diameters less than 50 µm (270 mesh), is too light to be concentrated hydraulically into placer deposits. Some process has increased the average size of the gold grains. Mobilization during regional metamorphism converts most of the gold into particulate grains or entrains it in microfractures in the sulfide minerals. With moderate folding, small, white, vitreous quartz veins develop. As deformation continues, larger, more conspicuous quartz veins are formed. The larger veins are folded and faulted and contain native gold as minute specks and flakes not visi-

Jan 11, 1984

By James R. Craig

The Central and Southern Appalachians were the major sources of gold in the United States throughout the first half of the 19th century and have continued to yield gold to the present day. Small amounts of gold were probably extracted by the Indians and the Spaniards but the first documented report of gold in the region was made by Thomas Jefferson who found a four pound lump of gold ore, which yielded 0.85 troy oz., in the Rappahannock River of Virginia in 1782. Gold was subsequently discovered in North Carolina between 1793 and 1799, in Virginia in 1806, in South Carolina in 1827, in Georgia in 1829 and in Alabama about 1830 (Becker, 1894-5; Pardee and Park, 1948). The gold belts of the Central and Southern Appalachian Piedmont and Blue Ridge Provinces are shown in Figure 1. The superimposed circles indicate the mount of production from some of the more productive and well known areas. Although North Carolina produced far more gold than the other states, the most significant concentrated area of production is the Dahlonega District in Georgia which yielded more than 500,000 troy ounces. After discovery, gold production increased rapidly as shown in Figure 2. Production was at its maximum between 1830 and 1852 with combined totals generally exceeding 30,000 troy ounces per year. Production dropped sharply after the California gold rush in 1849 as experienced miners moved westward in search of bigger and easier stakes. After the Civil War briefly halted gold mining in the Appalachians, production rose to an average of about 8,000 ounces per year from 1865 until 1878 and to an average of about 13,000 ounces per year from 1881 until 1915 when it again fell to near nil (Pardee and Park, 1948). Minor resurgences occurred in the 1930's and 1940's. Although there has been no reported production in recent years, it is likely that "weekend panners" still remove hundreds of ounces from streams annually. The total reported production for the area through 1959 is in excess of 2.5 million troy ounces.

Jan 1, 1981

By Edward Skolnik

The concept of using fluid dense media to separate heavy ore constituents from the lighter gangue dates back to 1858, when it was patented by Sir Henry Bessemer. Its use in coal did not begin until after 1917, however, when Chance invented a process (which bears his name) in which lighter coal floats in a suspension of fine sand in water while heavier refuse sinks. Conklin used fine magnetite in suspension as a medium for floating anthracite in 1922, DuPont designed a plant employing organic liquids in 1936, and Belknap used a solution of calcium chloride (which Bessemer had suggested, among other media) in 1937. Separation of magnetic media by magnetic separators from the suspensions in which they were carried was introduced in a Butler Brothers ore concentrator pilot plant in 1937. The media first used were crushed steel and various grades of ferrosilicon. Since 1940, when American Cyanamid used magnetic separators to recover and clean magnetite in a coal washing circuit, virtually all heavy medium circuits have been of that type. As long as static baths are employed, as they are in the processes above, coal smaller than 9.5 mm or 6.4 mm cannot be cleaned economically in heavy medium. The settling velocities of the fine material are very low, and consequently the time required to separate the lighter coal from the heavier refuse becomes excessive. In addition, stray currents in the vessel and the upward velocities induced to keep media solids in suspension affect the finer solids to the degree that physical size becomes a more important factor than specific gravity.

Jan 8, 1980

By Lars Söderberg, Eric Sandström, Per G. Broman

INTRODUCTION Boliden Mineral AB currently mines sulfide ores in 18 mines and processes them in eight concentrators. Most ores are typically complex. Gold consti¬tutes a considerable part of the value of the ore reserves. The value of total production in 1984, distributed by different metals is shown in the pie chart below. Traditionally, gold has been recovered as a byproduct, or coproduct, along with silver in floated copper and lead concen¬trates. Gold-price trends over the past decade have prompted comprehensive efforts by Boliden to increase the recovery of gold in concentration processes. Gravimetric recovery of gold in the grinding circuit is one method that has led to quick results. This method supplements tradi¬tional recovery processes based on flotation. The development of a feasible circuit, and the results obtained by its application in the central concentrator at Boliden, in the northern Swedish province of Västerbotten, are reported below. GOLD MINERALOGY IN BOLIDEN ORES The gold content in Boliden Mineral's ores is primarily in the form of alloys with the elements silver and mercury. A minor quantity appears in an unalloyed form.

Jan 1, 1986

By M. A. Trevits

The explosion hazard presented by methane gas in coal is confronted daily in the mining industry. Research has developed several viable methods for gas control in addition to conventional dilution by ventilation. Such methods include the drilling of horizontal or cross-measure boreholes from a mine opening and vertical boreholes hydraulically stimulated in advance of mining or for gob gas drainage. The long-term production history of five gas drainage installations was studied. Three installations were completed in the Pittsburgh Coalbed: two in West Virginia and one in Pennsylvania. The remaining installations were completed in the Mary Lee Coalbed in Alabama and the Sunnyside Coalbed in Utah. The types of drainage methods utilized included horizontal and vertical boreholes. The length of production studied ranged from 860 days to 36 years. The cumulative production from the five sites was in excess of 155 Mm3, representing a significant volume of gas.

Jan 1, 1985

By Ralf Winterberg, Axel G. Nitschke

"Macro synthetic fiber reinforced concrete or shotcrete is seen by many design engineers as offering a viable alternative to steel reinforcement in tunnel linings. The technology is now commonplace for primary and permanent ground support in both mining and civil tunnel applications. It has for instance become the standard form of reinforcement in the Australian mining industry, and has been used for a majority of permanent tunnel linings in recent tunnel construction in Norway. Similarly, macro synthetic fibers are becoming a standard solution for the initial lining in the USA.The use of macro synthetic fiber offers innovative solutions, yielding robust and sustainable tunnel lining designs. Citing recent research and actual projects, this paper presents state-of-the-art design considerations for fiber reinforced tunnel linings relating to structural and long-term performance. Topics include seismic resistance, crack width control, corrosion and durability, as well as sustainment of performance with age.INTRODUCTIONMacro synthetic fiber reinforced concrete (MSFRC) and shotcrete (MSFRS) has reached maturity as an engineered material and is widely used in all forms of tunnel linings, for temporary as well as permanent ground support in both, mining and civil tunnel applications. In the Australian underground mining industry, it became the standard form of reinforcement, where 2014 literally marked the end of steel fiber use in shotcrete [1], and has been used for over 80 percent of permanent tunnel linings in recent tunnel construction in Norway. Similarly, macro synthetic fibers are becoming a standard solution for tunnel initial linings in the USA. Recent examples in civil tunneling are the Devil’s Slide Tunnel and Caldecott Fourth Bore Tunnel in California or the Anacostia River Tunnel Intershaft Connector Tunnel in Washington D.C. In addition, an increasing number of tunnels are adopting shotcrete permanent linings using macro synthetic fibers. Examples include the A3 Hindhead tunnel near Guildford in the UK and the North Strathfield Rail Underpass in Sydney, Australia [2, 3]."

Jan 1, 2016

By Christopher J. Bise

During the past two decades, the emphasis on technological advances in US underground coal mining has focused on longwall mining. But there also has been a steady, although less spectacular, advance in the state-of-the-art in room-and-pillar mining. This has been stimulated by the successes of longwall mining in mine cost reduction, increased availability and improvements in haulage infrastructure, such as conveyor belt haulage. In addition, changes in management practices, such as nine- or 10-hour shifts, and marketing pressures have resulted in changes in the use of equipment. The net result of these changes has been the creation of modern room-and-pillar operations where average production levels currently exceed those considered very good 20 years ago. In fact, current production levels considered outstanding were considered unattainable two decades ago.

Jan 1, 1995

By T. Brasier, K. Oakes, S. Crabtree, B. Lusk

Destructive wave interference has been studied in theory for many years. In application however, limited information can be found. Recently, circumstances have enabled a multidisciplinary team to utilize electronic detonators and seismograph analysis to create destructive wave interference in an underground production blasting application. Springfield Underground, located in Springfield, MO, in conjunction with Orica, ETI, White Industrial Seismology, and the University of Missouri – Rolla has shown the ability to use destructive wave interference in underground blasting to reduce ground vibrations directly above. In order to develop additional reserves a reduction in vibration levels was necessary for tunneling under the Springfield Municipal Water Supply. The paper discusses the process by which the reduction in vibration was achieved in practice, as well as a technical explanation of the effects of destructive wave interference and sacrificial holes.

Jan 1, 2006