Search Documents

By S. A. Beeson, C. Poole

This paper describes the development of a novel selective flocculation technique for recovering phosphate values from ores containing silicate or carbonate gangue minerals. Data from initial flocculation response and reagent adsorption studies on component mineral suspensions and synthetic mixtures were used to assess the influence of various process parameters (e.g., reagent dosages, particle size, solids concentration, and conditioning regimes) on single-stage selective flocculation tests involving natural silicate and carbonate ores. In these tests a high degree of selectivity was achieved using low dosages of a low-molecular-weight cationic dispersant and a mid-range molecular weight cationic flocculant. Testwork was then extended to the evaluation of several floc recovery systems (sedimentation, hydrocyclones, and floc flotation) in a multi-stage process involving redispersion and reflocculation. Results from these tests clearly demonstrated the feasibility of producing marketable phosphate concentrates from both ore types.

Jan 1, 1999

By Dennis A. Beiter, Kenneth G. Fields, Richard T. Stoltz

Section 56.5001 Title 30, [Code of Federal Regulations1], establishes requirements for respirable dust exposure in Metal and Nonmetal Mines based on the Threshold Limit Values (TLV's) adopted by the American Conference of Governmental Industrial Hygienists. Respirable dust samples collected by Mine Safety and Health Administration (MSHA) inspectors at a sandstone quarry showed certain workers were exposed to excessive concentrations during development of a "coyote tunnel" that was ventilated with a blowing system. Because exhausting face ventilation systems are known to control dust more effectively than blowing face systems, a change was proposed to improve worker respirable dust exposures. This paper describes the evaluation of the proposed exhausting ventilation system in the quarry's "coyote tunnel" and compares the respirable dust exposures with those measured by the MSHA inspectors with the blowing system. Results showed the proposed exhausting ventilation system reduced respirable dust exposures to less than 20 percent of those measured by MSHA inspectors when the blowing system was used.

Jan 1, 1993

By R. Hogg, T. F. Dumm

Procedures for particle size analysis on respirable dust from coal mines have been evaluated. Using respirable dusts dispersed in a laboratory dust chamber, size distributions measured using cascade impactors have been com- pared with the results of a variety of laboratory sizing methods performed on samples collected on filters placed side-by-side with the impactors. The laboratory techniques included centrifugal sedimentation, laser diffraction/scattering and automatic particle counting. The general agreement among the various methods was very good, with systematic differences which can be attributed to the different definitions of size used. Simple conversion factors have been obtained which can be used to transform the laboratory data to equivalent aerodynamic sizes. Similar comparisons have been made on samples collected in underground coal mines. Again, the results are in quite good agreement although small discrepancies were observed in some cases. These have been attributed to some degree of agglomeration in the airborne dust, leading to slightly coarser apparent distributions in the impactor samples.

Jan 1, 1987

By Owen Kreilis

By the time coal was discovered in Newcastle, Australia in 1791, it was already a most important industrial commodity in European countries. Coal was the first mineral to be discovered in Australia and the first to be mined. Today, coal remains Australia's most important mineral in terms of local use and international trade. The first mechanized longwall in Australia began operation in 1963. It contained self-advancing hydraulic supports and was installed at Coalcliff Colliery, located in the Southern Coalfields of New South Wales. After nine months and production of 53 kt (58,000 st), the unit was withdrawn, largely because of uncontrollable roof weight and with the problems of airborne dust and large coal still unsolved. Basically, roof support was insufficient. The European design of the Coalcliff longwall was inadequate for Australian conditions. Another type of support with modifications was installed and began operation at Kemira Colliery at Wollongong, New South Wales, in 1964.

Jan 1, 1995

By Mark E. Smith

Large scale copper heap leaching in Chile began in November 1980 when the Lo Aguirre heap leach project was put into operation. At almost the same time, El Indio gold mine began production. While El Indio was not a heap leach project, it was Chile's first major bulk tonnage, open-pit gold deposit. This paved the way for the introduction of North American gold heap leach technology in the early 1980s. Heap leaching has become more popular in Chile during the past five years because it allows the exploitation of large but relatively low grade ore bodies at a reasonable cost. Pioneering research in hydrometallurgy carried out at some Chilean universities and at the Centro de Investigaciones Minero Metalurgicas (CIMM) played an important role. There are more than 10 large copper heap leach and solvent extraction/ electrowinning (SX/EW) process plants in different stages of development in Chile. Total production from these facilities will eventually increase Chile's present copper exports about 50%.

Jan 1, 1995

By J. Hanna, R. Kalathur

Over the years, Alabama's coal industry has generated, during mining and cleaning operations, about 150 million st of fine waste coal, with this total increasing at a rate of 2 million stpy. Reclamation of the fine-size wastes (containing 20% - 60% clean coal by weight) provides, free of charge, mined and crushed feed stocks for coal recovery. Also, the removal or recovery of pyrite from the tailings should eliminate a major source of acid-water pollution. Tests were made on the impounded wastes and current plant discharges to recover the coal fraction by sizing, gravity and flotation techniques. Gravity separation of the +100-mesh material produced commercial-grade coal averaging 7.6% ash, 0.8% sulfur and 13,471 Btu/lb. However, the coal yield, at about 31 % - 56%, was relatively low. Froth flotation, using mechanical and froth column methods, gave similar coal products at much higher coal recovery rates of 87% - 93%. This coal analyzed 10% ash and 1.1% sulfur.

Jan 1, 1993

By Vas Choudhry, Randhir Sehgal

Conventional clean coal technologies which consist of coarse coal cleaning by gravity methods and treatment of natural fines by flotation can only remove a portion of the pyritic sulfur and ash in the coal. Higher (+90%) pyritic sulfur rejection is attainable when coals are ground to ultrafine sizes to enhance liberation of the mineral matter and then cleaned. However, cleaning of coal at very fine sizes poses a number of unsolved problems, the chief one being the loss of cleaning efficiency. This, of course, means that liberation of pyrites does not always equal its rejection. In addition, the dewatering of fine- cleaned coal, and its handling, transportation, and acceptability to the utility industry a1 so pose considerable technical and economic problems, especially when compared to the FGD alternative. This paper addresses some of the critical issues involved in the cleaning of ultrafine coal s.

Jan 1, 1989

By J. F. Abel, R. J. Spengler

Convergence measurement across the 17.4-m (57-ft) high shaft station/loading pocket at Mt. Taylor provided continuing verification of stability and safety. Three levels of instrumentation, consisting of three lines each, were installed and monitored. The instrumentation showed that the flexible lining restrained the adjacent rock. The flexible lining consisted of pea gravel with neat cement between rock and liner plate, wooden crush blocks between liner plate and steel ring beams. The loading pocket is elliptical, 11.6 x 9.6 m (38 x 31.5 ft) inside diameter. The crush blocks were designed to allow 15 cm (6 in.) of convergence. Maximum predicted convergence was 7.0 cm (2.75 in.), and 5.7 cm (2.25 in.) was measured. Convergence measurements also demonstrated decreasing deformation with respect to elapsed time and distance from the measurement station to the temporary bottom of the shaft excavation.

Jan 1, 1987

By Ron L. Schmiermund

The Ferris-Haggarty underground mine was abandoned circa 1910, and portal discharge has since resulted in degradation of a trout fishery in the receiving waters of Haggarty Creek. Although tunnel discharge varies dramatically in volume throughout the year due to infiltration of snowmelt, compositionally it is a nearly constant low-TDS, pH-neutral, low-sulfate, copper-silicate dominated water. Between infiltration events, components of ARD accumulate in unsaturated, oxygenated environments within upper workings and are delivered to the main haulage level by the subsequent annual snowmelt flush. Mixing with non-ARD mine waters results in neutralization, dilution, and precipitation of amorphous copper carbonate and silicate phases. These mechanisms, combined with variations in the water balance, control the composition of the portal discharge. Understanding the chemical and hydrologic control mechanisms was critical to the design of a passive treatment system to decrease effluent copper concentrations.

Jan 1, 2000

By Regina N. Tempel, Mae S. Gustin, Mark A. Engle

This study characterizes the hydrogeochemistry of groundwaters near opalite-hosted epithermal hot-spring type mercury deposits in the Ivanhoe mining district, Elko County, Nevada. Local groundwaters generally range from Ca-HCO3 to Ca-Mg-Na-SO4 type waters with background mercury concentrations ranging from 0.014 to 0.32 ug/l. Leaching experiments conducted on mineralized rocks, using typical water chemistries to represent local groundwaters, yield total mercury concentrations ranging from 6.3 ug/l to 27.4 ug/l after one year of reaction. Geochemical modeling indicates dissolved mercury is dominated by HgO(,) and that precipitation of quicksilver controls mercury concentrations to an upper limit of 63 ug/l.

Jan 1, 2000

By J. F. Stenebråten, W. P. Johnson

Carbonaceous material (CM) from the Barrick Goldstrike Mines, NV, was characterized with respect to its gold sorption (preg-robbing) and gold recovery behavior. The breadth of graphite peaks measured by X-ray diffraction were used to calculate crystallite dimensions (002) of the CM. The (002) dimension was found to vary inversely with preg-robbing activity and directly with gold-recovery behavior, indicating that the degree of graphitization (maturation) experienced by the carbonaceous material is correlated with gold-loss during ore processing. The inverse correlation of preg-robbing activity was improved when percent preg-robbing was regressed against (002) crystallite size and carbon content. The (101) crystallite dimensions of all samples were calculated from laser Raman analysis, and were not found to correlate with preg-robbing behavior of the CM. BET surface area and micropore size distribution results were affected by grinding history, negating comparison of these characteristics between samples.

Jan 1, 2000

Surface characterization techniques, i.e. contact angle measurement, atomic force microscopy (AFM) surface force and surface imaging measurement, were applied to investigate the molybdenite surface in aqueous solution. It was shown that the cleaved basal surface of molybdenite was very hydrophobic with a 92 degree water contact angle. The non-polar component of the solid surface free energy is 50.52 mJ/m2 while the polar components are almost zero. The solid surface was not reactive and was only weakly charged at the pH 6. When the aqueous media changes from water to 1×10-4 M KEX solution, the measured contact angle, adhesion force and surface roughness all increase slightly. However, ethanol rinsing made the surface change back to the bare substrate. It was suggested that the hydrophobic chemical, i.e. dixanthogen, which was shown in the morphology of patches by the AFM image, physically adsorbed on the hydrophobic molybdenite surface through the hydrophobic interaction.

Jan 1, 2009

By Meliton M. Garcia, Satya Harpalani

This paper discusses the results of an investigation carried out in an underground mine to characterize the volatile by-products adsorbed on airborne particulates following the detonation of four common explosives including ANFO. The primary objective of this study was to determine if any organic amine compounds, particularly nitrosamines, and any polycyclic aromatic hydrocarbons were produced and trapped in the dust that a miner might inhale during the workday. The production of these substances is of great concern because of their suspected carcinogenic nature. The results of the study indicated that a large variety of the by-products are adsorbed on the particulates generated, and thus remain airborne following the detonation of explosives. The major by-products retained by the dust were bis(2-ethylhexyl) phthalate, and aliphatic hydrocarbons with carbon chains ranging from C12 to C28. One explosive, a water gel, produced the polycyclic aromatic compound, trimethylnaphthalene. No nitrosamine compounds were detected.

Jan 1, 1989

By J. L. Huiatt, D. G. Foot, J. D. McKay

The US Bureau of Mines compared column flotation using either fine or coarse bubbles with conventional flotation on a Montana chromite ore. On deslimed ore, fine-bubble column flotation produced a &.7% Cr2O3-grade rougher concentrate with 87% recovery, compared with 43.8% and 43.5% Cr2O3-grade rougher concentrates with 85% and 77% recovery for coarse-bubble column flotation and conventional flotation, respectively. On undeslimed ore, coarse- and fine-bubble column flotation produced rougher concentrates containing approximately 41.5% Cr2O3 with 95% recovery, exceeding conventional flotation, which produced 35.6% Cr2O3 -grade concentrates with 87% recovery.

Jan 1, 1987

By Fred V. Carrillo

California was the leading state in industrial mineral production value with an estimated value of nearly $2 billion. In total value of U.S. non-fuel mineral production estimated for 1992 by the U.S; Bureau of Mines, California ranked second; 81 % of California's total production value was derived from industrial minerals. California led all other states in the production of boron minerals, portland cement, diatomite, calcined gypsum and construction sand and gravel, and ranked second in potash and soda ash production. California's five leading industrial minerals in terms of value were portland cement, construction sand and gravel, boron, crushed stone, and soda ash. California had 13 additional industrial minerals production with reported sales of over $1 million including; industrial sand and gravel, magnesium compounds, lime, salt, potash, natural sodium sulfate, clay, feldspar, crude gypsum, pumice, dimension stone, calcium chloride and perlite.

Jan 1, 1995

By J. Maiti, A. Bhattacherjee

A literature review on quantitative analysis of mine safely studies revealed that numerous investigators explored a wide- range of techniques, including the investigation of bivariate and multivariate statistical models. Although these researchers addressed various issues of accident causation and prevention, they, in general, did not investigate through the use of quantitative models the multivariate relationships of several factors affecting mine safety in a causal framework. In this paper, systems dynamics and structural equation modeling are presented to simultaneously represent and study the effect of policy variables related to accident prevention along with the factors causing accidents and injuries. The application of these models to a group of mines revealed that current training practices at these mines do not appear to alleviate accident occurrences. It is inferred that the use of these quantitative techniques can provide a new direction of research in mine-safety studies.

Jan 1, 2000

By J. R. Weber, R. D. Haddenham, J. H. Bailey

Introduction The Vernal Phosphate Operation is located in northeastern Utah, about 18 km (11 miles) north of Vernal, about 280 km (175 miles) east of Salt Lake City, UT. The plant began initial operations in 1961 under the name of the San Francisco Chemical Co. In 1981, Chevron purchased the operation from Stauffer Chemical Co. In 1982, plant capacity was doubled to about 72.6 kt/a (800,000 stpy) of phosphate concentrate. From 1984 to May 1986, another expansion increased the capacity to 1.2 Mt/a (1.3 million stpy) of concentrate. It also incorporated a number of equipment and process changes designed to increase the overall plant phosphate recovery. A 150-km (94-mile) slurry pipeline, the world's longest phosphate pipeline, was also constructed from the Vernal plant to a new Chevron Chemical and Fertilizer plant near Rock Springs, WY. Over the past five years, plant expansions and the pipeline construction have been accomplished without missing a single concentrate shipment.

Jan 1, 1987

By Noris Del Be1 Belluz

Drilling underground in the Grasberg dewatering drifts has routinely hit water aquifers with high flow rates and pressures. Two types of holes are used. Pilot holes probe ahead of the tunnel development to intersect aquifers ahead of the face. And dewatering holes dewater rock formations that will drain water from the Grasberg pit and allow tunnel development to proceed safely. Recently, static pressures of >8.3 MPa (> 1,200 psi) have been recorded with flows from a 100 mm (4 in.) HQ core hole measured at 5,700 L/min (1,500 gpm). The waterflows can be slightly acidic, necessitating the use of stainless-steel collar gear to resist corrosion. These rates were anticipated and contingencies were planned early on to deal with these conditions. PT Freeport Indonesia (PTFI) established procedures to maintain the safety of the drill crews, to enable coring of the rock, and to maintain the safety of the miners driving the drifts. The collar gear controls the waterflows because these drill holes are a vital source of water for the concentrator.

Jan 1, 1998

By J. Alvarez, S. H. Castro

The feasibility of chalcopyrite-pyrite separation in the flotation of a chalcopyritic copper ore, at reduced surface tensions regulated by methanol, was investigated. It was found that with methanol dosages from 0.5% to 1.5% v/ v, the chalcopyrite might be effectively separated from the pyrite, without use of other flotation reagents and pH regulators. However, under this simple condition, the chalcopyrite recovery was only around 50%, recommending the use of other reagents to reinforce the collector action. Low dosages of different collectors were tested, including SF-323 (Shell Float), S-6588 and S-7251 (Cytec), and S-701 (Molycop). Very promising results were obtained with low dosages of the collector S-701 and 1% v/v of methanol in the pulp, which evaluated against a reference test, gave similar copper recovery, higher Mo recovery and higher depression of pyrite. Consequently, this is an alternative process which does not require the use of lime to depress pyrite.

Jan 1, 1995

By Adolf J. Jonaitis

Outokumpu developed TankCell flotation cell technology beginning in 1990, following 35 years of successful flotation cell experience and application. In 1994, Outokumpu proved favorable operating success of 100-m3 (3,500-ft3) TankCells for porphyry copper and zinc flotation. In 1995, evaluation of a 150-m3 TankCell led to the successful application of these large cells in several operations. More than 350 TankCells of 100 m3 and larger in volume have been installed and are in operation. Key features of the Outokumpu TankCell design will be described. In addition, discussion of operating data from various metallic mineral flotation operations worldwide will be presented. Large flotation cell development continues today, with operating cell volumes of up to 160 m3 (5,500 ft3) in operation.

Jan 1, 1999