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By Adam Zanker

Smooth roll crushers are widely used as secondary crushers, operating most effectively when set for size reductions in a ratio between 3 or 4 to I. The feed supplied to these units varies from 13 to 102 mm in size and the product obtained ranges from 13 mm to about 20 mesh. Smooth roll crushers produce very few fines and absolutely no oversize. The diameter otfhe rolls varies with the clearance between them, feed size, and the coefficient of internal friction ofmaterial to be crushed, Detailed calculations of this relationship may be found in Unit operations of Chemical Engineering, (McCabe, W. L., and Smith, J. C., 1967, McGraw Hill, NY, Chapter 26, pg. 825). The geometrical arrangement of the roll crusher is shown on the accompanying sketch. A relatively simple relationship between the diameter of feed, the roll, and the gap between them is as follows:

Jan 6, 1980

By J. B. Hiskey

Of the halogens, the gold iodide complexes are the most stable in aqueous solutions. A series of experiments were performed to investigate the kinetics and mechanism of the leaching reaction between gold and iodide. Using a rotation disk technique, the effects of rotation speed, iodide and iodine concentration, temperature, pH and in the presence of different electrolytes were measured. Oxygen and hydrogen peroxide were also examined as oxidants in the iodide system. The first order reaction rate was found with respect to 13 and half order reaction rate with respect to 1-. The comparison of gold leaching between iodide and cyanide is also presented, in which a rate constant of about 2.6x10-9 mol/cm2? sec for 10-2 M I- and 5x10-3 M I2 was obtained. This value is close to that -for typical cyanidation. Cyclic voltammetry experiments were also performed to examine the electrochemical nature of the reaction which will be presented in part II of this study.

Jan 1, 1990

The administration came on as a strong supporter of the mining industry in April of 1982 when President Reagan delivered his long-awaited minerals policy statement. He promised to reduce America's minerals vulnerability, and called for spending billions on meeting stockpile goals for strategic minerals, opening up federal lands for mineral exploration, elimination of barriers to deep sea mining, and regulatory relief. He defended the favorable tax incentives in the Economic Recovery Act as a stimulus to private research and development that would ensure the availability of materials essential to the nation's economy and national defense. But the administration just didn't seem to get anywhere. Congress, environmentalists, and even foreign governments fought White House-proposed legislation on all fronts, delivering the ultimate coup in forcing Environmental Protection Agency Administrator Anne Burford's resignation and the subsequent EPA staff house cleaning in early 1983. Anti-Reaganites scored victory after victory against Reagan's efforts to stimulate the minerals industry. Congress was stalemated on so many mining-related issues that not much was done either for or against the industry. And the US was not to get its way on the issue of sea mining either. Most of Reagan's mineral policy objectives failed to be met. Three months after the National Materials and Minerals Program Plan was presented and the Cabinet Council on Natural Resources and the Environment was made its coordinator, the head of the Cabinet Council James Watt blamed lack of progress in reviving the mining industry and creating a better strategic stockpile on the weak economy and the House of Representatives, which repeatedly thwarted efforts to open wilderness lands to mining. Congress The 97th Congress spent much of its time saying no in 1982-to the Reagan administration's deep cuts in energy and environment programs, to major changes in clean air and water laws, to oil and gas leasing in wilderness, and to killing the Department of Energy. Most of 1982 (and 1981) was spent in heated budget disputes. Some things that did not happen: • The administration and industry failed to get changes in controls of hazardous air pollutants and sulfur dioxide emissions that are implicated in the phenomenon known as acid rain. Industry had wanted to relax requirements for new industries building in clean air regions where the air act demands prevention of significant deterioration (PSD) of air quality, and to relax requirements tightening up the regulation of emissions of hazardous air pollutants. The air battle is expected to continue on five major fronts-acid rain, hazardous air pollutants, PSD, automobile pollution, and nonattainment. • Regulatory reform legislation to overhaul the way government carries out the law died a slow death last year. Business groups and the administration said federal agencies should be required to consider cost-effective measures of reaching regulatory objectives of protecting public health, safety, and the environment. Opponents, including environmentalists, feared such action would delay, weaken, or scuttle important regulations. • Congress turned thumbs down several times on proposals for oil and gas leasing in wilderness but could not agree on any new wilderness recommendations (see The Wilderness Battle). • Congress refused to open the door to the Reagan administration's plan to raise up to $4 billion a year from sales of federal lands. The administration identified surplus and excess federal lands, mostly obsolete buildings or isolated tracts of land, that could be sold by the General Services Administration (GSA) to help out the federal budget deficit. Congress took no action. Some things that did happen: • Congress extended the Defense Production Act (DPA) for six months through March 1983 without changing the 32-year-old law. That came after it failed to resolve sharp differences over proposals for critical minerals programs. Differences concerned both the amount of funds and the scope of programs that would be authorized under the DPA's Title III. Some proponents pressed for $5 billion in funding for loan guarantees or purchase commitments to spur domestic production of minerals such as cobalt. Other members of Congress wanted smaller amounts of funding, and the Reagan administration, until about November, had opposed any use of federal funds for strategic mineral programs. These measures were certain to come up again before the DPA extension expired in March. • House supporters of the Critical Materials Act of 1982 were unable to come up with the twothirds majority needed to pass the bill, so it died on the House floor in December. The bill proposed that a council be established with responsibility for coordinating federal materials research and development. The administration opposed the council creation contending that the Cabinet Council

Jan 5, 1983

By Georgene Renner

With more than 800 booth spaces sold and 540 exhibiting companies displaying their wares, there was something for everyone on the exhibit floor of the 2014 SME Annual Meeting in Salt Lake City, UT Feb. 23-26. The following is a sample of what was offered at the 2014 meeting.

By R. Sellaro

It has long been understood that extended occupational exposures to respirable mine dusts can lead to chronic lung disease. In underground coal mines, coal workers pneumoconiosis (CWP) and silicosis are major concerns. While there have been many studies aimed at understanding total dust concentrations and silica content associated with different mining conditions (e.g., locations/occupations within a mine, cutting methods, geologic strata), little research has been completed to more comprehensively characterize respirable dust (i.e., by distributions of particle composition, size or shape). For such analysis, scanning electron microscopy with energy dispersive X-ray (SEM-EDX) may represent a powerful tool. This article is a preliminary investigation of SEM-EDX to characterize respirable dust from an underground coal mine in Central Appalachia. Samples were collected from various locations in the study mine, and individual dust particles were identified and classified by mineral type. A continuous personal dust monitor was also used to estimate respirable dust concentrations during sampling. This data was compared to particle densities observed under the SEM. Dust is generally defined as small, solid particles with an effective diameter between 1 and 100 µm. In underground coal mines, dust is produced by a variety of activities such as coal and rock cutting, materials handling, haulage and from a variety of materials. While the coal itself is primarily made up of organic carbon, it is estimated that as much as 60 percent of coal mine dust consists of mineral matter, including clays, metal oxides and sulfides, carbonates, quartz, phosphates and heavy minerals (WHO, 1997). Mineral matter may be ingrained in the coal seam or associated with adjacent or interlying strata, and may also be contributed by specific activities such as rock dusting. When dust is generated or made airborne, suspended particles tend to settle slowly with gravitational forces, but can remain airborne for extended periods of time depending on environmental conditions such as air velocity (Courtney et al., 1986) and particle properties such as size (ISO, 1995; WHO, 1999). Thus, miners working underground are routinely subject to occupational dust exposures ? with highly variable characteristics between and even within mines.

The Anshan Iron and Steel Co. (AISC) broke its steelmaking design capacity in 1978, bringing its total production of steel products to 6.86 Mt. Located south of the industrial city of Shenyang, Liaoning Province, in northeastern China, it is by far China’s most important iron and steel complex, ranking twentieth among world centers. The complex represents a unique blend of old ecluipment and new ideas for increased production and improved products. Under a state plan, the Chinese hope to raise capacity to almost 15 Mt/a in the future. Originally started by the Japanese in the early 1920s, Anshan has had a rather turbulent 60-year history. It was disassembled by the Soviets after World War II, only to be reassembled by them in the 1950s. Production was also suppressed during the Cultural Revolution. Since the present-day organization, AISC, emerged, the center has experienced progressively improving conditions as well as increased production. Today, the center includes 10 blast furnaces, 24 open hearths, and two basic oxygen units, designed for 7 Mt/a ironmaking and 6.5 Mt/a steelmaking. In addition, it has six batteries of cokemaking facilities with combined 4.4-Mt/a capacity. Solid Iron Resources Anshan’s iron resources consist of a proven reserve base of over 7 Gt of 30~0 Fe, according to Kao Yang, president of the Anshan Iron Mining Co., a subsidiary of AI SC, Most of that, he continued, is amenable to surface mining. Five major mines located to the north and northeast of the city of Anshan are the principal iron ore producers. These mines trend in a somewhat circular manner and combined, represent an estimated 28.6 Ylt/a of ore capacity. In addition, some 2.2 Gt of magnesite, a necessary ingredient in steelmaking, are also part of the reserve base, according to Kao. Annual production is around .2 Mt/a of 47% magnesite, well over the steelmaking center’s annual requirements, Excess production is shipped to other steel-making centers. The largest of Anshau’s open-pit mines is the Chitashan operation with a design capacity of 8 Mt/a. Ore reserves here are well over a billion tons of 30% Fe. Earlier plans to expand production at this mine to 15 Mt/a, with the help of US Steel, have been temporarily shelved. The other mines in the district and their rated design capacity are: Kungchangling, 7 Mt/a; Donganshan, 6.4 Mt/a; Dakushan, 4.2 Mt/ti; and Yenchienshan, 3.0 Mt/a. The Kungchangling mine is the richest in terms of ore grade at 6076 Fe. Reserves are somewhat smaller at 100 Mt. The unit also operates a small shrinkage stoping operation. Ore grade at the other mines is usually 30-327. Fe. Llost mines operated at reduced capacity during 1979 owing to a natural gas shortage at the mills. The general

Jan 3, 1980

By Serdar Aktaş, Burcu Nilgün Çetiner

According to critical statistical studies, antimony is one of the rarest elements in the world, and global resources could be exhausted by 2050. In light of these observations, its extraction will be costly due to poor-quality ore, deep mining, remote locations, and high energy consumption. In the present study, an alkaline leaching process was carried out on stibnite concentrate to evaluate the effect of reaction parameters on the percentage of antimony extraction. The leaching efficiencies of different sulfur and hydroxide sources were studied and compared to one another to create a better understanding of the reaction process. Kinetic models were investigated to identify the reaction pathway and calculate the activation energy. The activation energy of the stibnite dissolution was assessed as 19.13 kJ/mol using a two-dimensional diffusion-reaction model. The value of activation energy indicates the quantity of energy necessary for a reaction to proceed. As expected, potassium hydroxide leaching was significantly more successful than was sodium hydroxide; however, in terms of economics, the use of sodium hydroxide was found to be more cost-efficient. Interestingly, this finding indicated that caustic leaching is still the most effective method for stibnite extraction.

Jul 23, 2020

By C. V. Baltzer, E. L. J. Bingham

Compliance with the EPA's emerging Clean Water Act regulations can be challenging. Open pit copper mines in Arizona have found themselves in a tangled web of changing rules, regulations, and guidance documents regarding storm water and process water discharges. Large mining properties must come up to speed on a myriad of issues including the definition of zero discharge, what constitutes a process related spring or seep, and tailings and waste rock Best Management Practices. The example of the Pinto Valley Mine in Arizona is used to illustrate National Pollution Discharge Elimination System regulatory issues.

Jan 1, 2001

By Ralph M. Foecking

The disposal of the phosphate slimes produced by Florida beneficiation operations is perhaps the biggest single problem of the phosphate mining industry. This is an old problem which has not been solved and which is becoming increasingly severe. In a typical phosphate mining operation, the phosphate rock mined is initmately mixed with sand and clay, constituting what is known as matrix. During the beneficiation, the clay and other fine materials are separated usually at -150 mesh, and washed from the phosphate rock in a form of diluted slurry known as phosphate slimes. The quantity of slimes solids and their composition vary considerably with the location but usually represent from 25 to 35% of the ore mined. Because of the affinity that clays have for water, large volumes of water are required to separate the granular material in the matrix forming a dilute slime suspension (1.5 to 3% solids) of colloidal material, which settles very slowly, and thus requires immense impounding areas, which never becomes totally usable land. These ponds also contain about 25 to 35% of the total P205 values mined. The magnitude of the problem represented by the slimes can be appreciated better if we realize that there are around

Jan 1, 1971

By John W. Shield

Oxide gold reserves are being rapidly depleted, especially in regions with long histories of gold mining, such as the Black Hills of South Dakota. However, these districts often have substantial additional deposits, where gold is refractory. It is not amenable to traditional cyanide extraction due to the presence of sulfide minerals that encapsulate or otherwise preclude the economic extraction of the gold. Several technologies have been developed to render refractory sulfide deposits amenable to traditional cyanide processing. These include roasting and pressure autoclaving. Unfortunately, these oxidation processes require substantial capital investment and incur significant operating costs. Microorganisms that obtain energy for their life processes by the oxidation of iron sulfides can be used to treat gold-bearing refractory sulfide minerals. As the bacteria convert the sulfide to sulfate, they expose any gold associated with the sulfide matrix. This makes the gold amenable to cyanide extraction.

Jan 1, 1996

By Paul Richardson

This paper will review several projects completed during the period from 1976 through 1984 which have been carried out utilizing big hole drilling concepts. The projects discussed will be from various industries to demonstrate the extent that big hole drilling methods are being used along with the current state of development. There will be a discussion of projects planned for the future where big hole drilling methods are the only technology being considered. Also included in the discussions will be an overview of the most recently completed heavy oil recovery project. During the next decade, big hole drilling methods will be used more and more in all industries where underground access is required. The safety, speed and economics associated with shaft sinking using drilling methods are becoming more and more recognized and the technology is rapidly becoming an accepted shaft sinking method.

Jan 1, 1985

By O. M. Arafat, J. A. Finch

Since its development, the functional performance equation for ball milling (McIvor, 1988) has facilitated a new understanding of industrial circuit cause and effect relationships, leading to significant strides in operational performance. Success stories of this approach to plant circuit performance improvement are now too numerous to list. Finch and McIvor (circa 1986) also discovered that the functional performance mill grinding rate at the size of interest was the same cumulative grinding rate that is calculated from mill feed and discharge size distributions using a first-order rate equation. By calculating these cumulative grinding rates for all screen sizes, a complete ball mill model is generated (as used by Finch and Ramirez, 1981). Others in industry, Hinde and Kalala (2009), for example, have noted the same. Lacking the complexity needed to maintain their interest, most researchers have ignored this model, broadly opting instead for Epstein’s (1948) characterization of grinding as a chemical reaction, combining selection rate and breakage size distribution functions. The much simpler ball mill model has previously been incorporated into a proprietary circuit modeling program (McIvor, 2005) and used for plant improvement work (for example, see McIvor and Finch, 2007, and McIvor, 2014). Now, by combining this business-friendly ball mill model with optimization criteria from functional performance analysis, a circuit modeling system (including the needed supplementary steps to assure successful plant implementation of circuit design changes) is at the disposal of every plant metallurgist, grinding equipment/ material provider and circuit designer.

Jan 11, 2017

By Priscilla P. Nelson

Many concepts concerning equipment selection, performance prediction, and evaluation of support requirements for tunnel construction in soil or hard rock tunnels cannot be extrapolated directly for application in soft rock (compressive strength between 1.0 and 35.0 MPa). Case histories for small diameter (less than 3.5 m) tunnels in Austin, Texas, are analyzed to gain insight into particular problems encountered during tunnel excavation in weak sedimentary rock, and the performance of different excavation systems are compared.

Jan 1, 1987

By Isabel F. Barton, MarkD. Barton, Christian A. Rathkopf

Molybdenite is the world’s principal source of rhenium (Re), a critical element in multiple high-tech applications. However, the Re contents in molybdenite vary by orders of magnitude on scales ranging from single grains to whole deposits. In order to better understand the systematics of this variation and what geochemical factors control molybdenite Re concentration, and hence overall Re resources, we examine global patterns in molybdenite Re contents through a compilation of > 3000 measurements of Re in molybdenite from > 700 mainly ore-bearing moderate- to high-temperature hydrothermal systems of different types. Our results are similar to but expand on those of earlier studies. Rhenium concentration in molybdenite has a lognormal distribution and varies systematically with type of geologic system, intrusive lithology, and Mo grade. The lowest-Re molybdenite occurs in greisens (geometric mean 1 ppm ± a multiplicative standard deviation of 9), quartz vein-hosted W-Sn deposits (2 ± 5 ppm), unmineralized granites and granodiorites (12 ± 8 ppm), intrusion-related deposits (24 ± 8 ppm), and porphyry W-Sn deposits (16 ± 11 ppm). Rhenium is most enriched in molybdenites from volcanic sublimates (23,800 ± 5 ppm), with skarn Fe and Au (560 ± 5 ppm and 540 ± 3 ppm respectively) and porphyry Cu and Cu-Au deposits next (470 ± 4 and 430 ± 7 ppm respectively). Among porphyries, skarns, and quartz vein-hosted deposits, Re is most highly concentrated in molybdenites from Cu and Au systems and its concentration decreases systematically through Cu-Mo, Mo, Sn, and W deposits. In nearly all cases, molybdenites from systems associated with intermediate igneous rocks contain more Re than molybdenites from systems of the same type with more felsic rock associations. The disparity between Re contents of molybdenite in felsic and intermediate systems is largest for porphyries, quartz vein-hosted, and skarn deposits and is near zero for subeconomic or barren granite and granodiorite Mo systems; felsic intrusion-related deposits have slightly higher molybdenite Re than their equivalents associated with intermediate intrusions. In most systems, molybdenite Re content does not correlate with metal grade, but may have an inverse correlation with Au grade in intrusion-related deposits (based on a small number of data points) and does exhibit a strong inverse correlation with deposit Mo grade. Dilution of Re through larger amounts (higher deposit grades) of molybdenite explains about 40% of this correlation, but the relative enrichment of Re in molybdenite from low-Mo deposits must also reflect some selective enrichment of Re/Mo in porphyry Cu systems compared to porphyry Mo systems. We found no evidence for secular increase or other systematic temporal variation in molybdenite Re content. The data regarding the use of molybdenite Re content as a proxy for mantle influence are ambiguous. Nearly all observed empirical correlations can be traced back to differences in redox state and sulfide concentration, the two geochemical factors identified here and by previous experimental work as the controlling influences on Re mobility under hydrothermal conditions. Hydrothermal systems with reducing conditions (W- and Sn-rich) tend to have low molybdenite Re even though compiled whole-rock data indicate that their source rocks have as much or more Re as those of more oxidized systems (e.g., Cu-rich). Vapor-phase exsolution, crustal assimilation, and mixing with external fluids may all enrich molybdenite Re concentrations in individual deposits and deposit types, but their extent and importance in overall hydrothermal concentration of Re is uncertain. Thus, it appears that the available molybdenite Re resource in an ore deposit largely depends on how the deposit’s redox and sulfidation conditions have varied over time and space during the timespan of hydrothermal activity. Oxidized, high-sulfide conditions tend to concentrate Re in molybdenite, whereas reducing conditions tend to leave Re dispersed at low concentrations in the bulk rock.

By İsmail İnce

The purpose of this study is to investigate the index-mechanical properties of igneous rocks by using the electrical resistivity method. Electrical resistivity, index (P-wave velocity, dry density, and porosity), and uniaxial compressive strength values of 48 different igneous rock samples were measured in the laboratory. Simple regression analysis was performed between index-mechanical properties and electrical resistivity values. Strong exponential and logarithmic correlations were found between electrical resistivity and the index-mechanical properties of the igneous rock samples.

Jan 21, 2022

By C. L. Jiang, B. K. Parekh, X. Shao

Among the impurities present in phosphate ore, dolomite is the most difficult to remove. This is because dolomite and phosphate have similar chemical compositions and because the dissolved species of dolomite is adsorbed on the surface of the phosphate mineral. A new amphoteric surfactant was found to be a suitable collector for the separation of dolomite and phosphate. Flotation results showed that the new amphoteric collector had a high flotation selectivity for dolomite over a wide pH range. studies on the flotation of francolite and dolomite in each other's supernatant demonstrated that the dissolved ions had little effect on the selectivity of the new collector. It was found, however, that the dissolved ions were detrimental to the flotation separation using sodium oleate as collector. From a mixture offrancolite and dolomite containing 26.2% P2O5, a phosphate concentrate containing 35.2% P205 with a 90% recovery was obtained using 290 g/t of the amphoteric collector. The rejection of MgO was 81.41 %.

Jan 1, 1999

By Lynn B. Hales

Unfortunately, the term "control" has a negative connotation in the minds of many of our operating plant personnel. Whereas the opposite is true of those associated with research and technical centers in our industry. The magnitude of this difference in opinion and actual experience has often proved to be a major factor influencing the success or failure of process control applications. Through the years, many plant people have endured a number of unsuccessful attempts by "outside" people to "optimize" their plants; and these experiences have proved to have had quite a callousing effect on them. On the other hand, in many plants, successful process control efforts have made firm allies of the operating personnel, and have increased the number of metallurgical people who are well qualified and experienced in process control. The instrumentation industry, computer industry, and the mining industry's ability to quantify what is really happening in our processes have grown and developed rapidly since the first control efforts were made in the 1930's (1). Because of this-,: new control opportunities are becoming increasingly more feasible and older well established ones are becoming even more practical and necessary with regard to the economic s of our industry.

Jan 1, 1979

By Carl Rampacek

Laboratory and small-scale continuous pilot-plant investigations made at the Tucson Metallurgy Research Laboratory of the Bureau of Mines have demonstrated that the copper segregation process is applicable to the treatment of oxidized and mixed oxide-sulfide copper ores regardless of the gangue constituents. The process comprises heating the ore to a temperature of 750° C. with small quantities- of sodim chloride and coke to produce metallic copper, which then is recovered by flotation. Tests were made on' 23 copper ores of different types containing 0.8 to 5 percent Cu, .The copper recoveries ranged from 73 to 96 percent in concentrates assaying 10 to 62 percent Cu, depending on the grade and type of ore, The direct operating cost for a 1,000-ton-per-day furnace and flotation plant is estimated at about- $3 per ton of ore.

Jan 1, 1960

By Kurt M. Larson

Future haulage cost projections led Foster Yeoman Limited into developing a fully mobile crushing and conveying system at its Torr Works quarry in Somerset, England. The purpose-built system has an effective throughput of 2,500 tonnes/hour and features an Orenstein and Koppel (O & K) manufactured walking frame, a Fuller-Traylor type 54 X 74 TC gyratory crusher, and unique mobile conveyor modules designed and manufactured by Foster Yeoman. Used in a single-bench operation in this 6 million-tonne per annum limestone aggregate quarry, the system is fed at the production face by 2 Caterpillar 992C loading shovels. The entire system is moved on a daily basis following production face locations.

Jan 1, 1986

By Terrence R. Lejcher

Strip mining has played a key role in the production of coal used to produce energy in this country. About 56 percent of the 1.3 x 106 hectares (3.2 x 106 acres) that had been disturbed by surface mining as of 1965 can be attributed to stripping (Udall, 1967). The runoff from these stripped areas is usually heavily polluted with high concentrations of total dissolved solids, iron, aluminum, manganese, sulfates, and has low pH values with high acidity. Another problem of a most serious nature in our large cities is the volume of treated solids to be disposed of after sewage treatment. Chicago is presently producing about 664 metric tons/day of dry weight solids (Horn and Earles, 1968). Disposal methods most commonly used include lagooning, incineration, and landfilling. The high cost of land in an urban community is prohibitive of lagoon storage. Incineration and landfill disposal create air and water pollution problems. Many countries including Australia, England and Israel have long realized the value of sewage solids if they are recycled back to the land. In the United States, the value of such solids in reclaiming strip mined land has been recognized by relatively few people. This paper is concerned with the use of anaerobically digested sludge to reclaim strip mined land.

Jan 1, 1972