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By J. A. Cole

The mill project at Lone Tree was commissioned in October, 1993, followed by the commissioning of the autoclave pressure oxidation circuit in February, 1994. Discussion of the first year of milling operations at Lone Tree is presented. The mill is currently operating above the design rate of 2,267 mt/d (2,500 st/d). Both phases of the start-up were essentially trouble free. The few problems that were encountered and the respective solutions are addressed.

Jan 1, 1995

By M. N. Herrera

The bioleaching of mineral sulfide pulps in a bench-scale rotating drum reactor has been studied. The reactor includes horizontal paddles in the inner wall for lifting of the mineral pulp. The performance of the reactor was tested in the bioleaching of a refractory pyritic gold concentrate in the presence of pure Thiobacillus ferrooxidans strain (ATCC 19859). The concentrate was efficiently bioleached at 50% pulp density with the drum operating at 0.5 -1.0 rpm Attempts of bioleaching the concentrate at the same pulp density in conventional stirred reactor showed severe inhibition of bacterial activity. The results demonstrated that the drum reactor allows to operate at much higher pulp densities than the conventional stirred tank reactor. This behavior is explained in terms of an improvement of the bacterial activity due to a better control of the attrition of the mineral particles.

Jan 1, 1997

By Ronald D. Hill

The occurrence of acid mine Drainage (AMD) with coal mining has been well documented. (1) Less documentation is available of its association with other types of mining, e.g., copper, gold, zinc, and sulfur. Yet there are many locations in the western states where acid mine drainage is as great a pollution problem as in Appalachia and in some cases, because of the high copper, zinc, and arsenic concentrations, they present an even more difficult problem. Until a few years ago, it was generally believed that the neutralization of acid mine drainage was uneconomical thus, AMD was allowed to discharge freely into our streams. However, the demand for good water finally dictated that the mining industry be included under pollution laws. In 1964 the Commonwealth of Pennsylvania passed a law requiring that all active mine discharges meet a discharge standard of pH 6-9, iron less than 7 mg/1, and the water must have a net alkalinity. Several other states now require active mines to treat AMD. In all but a few cases, lime neutralization, often in conjunction with aeration, has been the treatment method used. The high cost of lime as compared to limestone and the poor quality sludge, (slow settling, large volumes, and low solids content) has stimulated work in the utilization of limestone. This paper reports on the current state-of-the-art of limestone treatment of AMD.

Jan 1, 1970

By K. Chandrasekaran

Carbon-in-Leach (CIL) is conventionally used in gold processing operations when preg robbing components are present in the ore. CIL process is becoming attractive even in other situations when preg robbing is not a factor. This paper discusses the situations in which the CIL circuit can be applied. The results of Leach/CIP and CIL circuits at Newmont's Mill No.2, 4 and 5 are presented for comparison. Newmont's Mill No. 4 was initially designed for a throughput of 4500 tons per day. The mill is presently operating at an average throughput of 7300 tons per day without significant changes to the original design. The design considerations of the Mill No.4 CIL circuit are discussed.

Jan 1, 1991

By T. Kontos

Rogers Group, Inc., is the nation's largest privately held aggregates producer (primarily producing crushed limestone and secondarily sand & gravel) and a major regional asphalt paving construction contractor. The company also has interests in building supplies and coal. Facilities are concentrated in five states in the central U.S. (Ohio, Indiana, Kentucky, Tennessee, and Alabama), with an additional location in Southwestern Virginia. At the request of its then CEO and with support from the company's ownership, Rogers embarked on a strategic planning program in late 1986 by retaining an outside management consulting firm. The ultimate goal of this program was to develop a self-sustaining strategic planning process to inject a strategic dimension into every manager's business thinking and to improve company performance. Since then, Rogers has internalized the outside consultants' strategic planning framework --initially, using it wholesale, and later, greatly streamlining and tailoring both the planning process and product to meet the specific needs of the company. Implementation of strategies developed from strategic planning has resulted in significant improvements throughout the organization. The latest product of the strategic planning effort is a company-wide (or, "corporate") strategic plan that carries the theme of "Market Leadership through Excellence". This paper provides a case study of successful corporate strategic planning by examining the evolution of strategic planning at Rogers and by summarizing the key elements of a sound planning process and product.

Jan 1, 1994

Power consumption of stirred media mills has been studied by an approach developed from work on stirred reactors. Relationships between torque required to rotate both disc and pin impellers immersed in dense particulate media as a function of speed, impeller and tank dimensions, and other relevant variables are evaluated. Data collected during numerous different experimental conditions are analyzed. The results can be summarized and presented in the form of characteristic plots, general equations and dimensionless group correlations involving power and modified Reynolds numbers. Special attention is directed towards the rheological properties of the media, which is considered as non-Newtonian liquids and hence, the equation of power law liquids is employed. Procedure for estimating parameters of effective viscosity and scale-up guidelines with respect to power consumption are put forward.

Jan 1, 1994

By S. K. Sharma

The Bureau of Mines has investigated the fundamentals of the flocculation process. The objective of this study was to determine the effects of various physico-chemical parameters such as shear rate, polymer dosage, and polymer concentration on floc growth and to determine the applicability of a model in predicting polymer flocculation behavior. A rapid in-line particle size analyzer was used to follow the progress of both the floc growth and the breakage as a function of time. A genetic algorithm (GA) was used to determine the unknown parameters in the model and to fit a curve to the experimental data. Results show that the model, using GA as a tool to determine the unknown parameters, reproduces the experimental data with only reasonable accuracy and was relatively insensitive to the parameters. Results of the flocculation study showed that increases in polymer dosage had greater effect on the time required to reach the maximum floc size than on the floc size itself. It was also determined that, given all the aforementioned parameters, the degree of slurry mixing during the flocculation process had the greatest bearing on the floc growth.

Jan 1, 1993

By R. J. Matetic

The Bureau of Mines, as part of a program to improve mine planning and development, is currently investigating the effects of pillar load transfer, which can impact mining operations within a multiple-seam configuration. A comparative study was performed at two separate mine sites to determine the effects of this load transfer mechanism. The Bureau installed and monitored instrumentation at both sites to gather pertinent data on rock mechanics. At mine site A overburden depth varied dramatically in the vicinity of the study area and reached a topographic high at the study site: inner burden thickness was less than a pillar width (40 to 45 ft) (12 to 14 m): floor heaving was experienced in both coalbeds where sandstone and/or shale floor units were observed: overlays of the mine layouts show pillars were not totally super-positioned: a maximum of 5 in (13 cm) of roof to floor convergence was measured and pressure readings indicated pillar core loading only and increased to a maximum of 7,000 psig (48,300 kPa) over instrument setting pressure.

Jan 1, 1989

By L. H. Pye

For large mining sites in the west, the traditional method for performing an ecological risk assessment (ERA) provides little useful information for risk managers faced with selecting and designing sound remedial options. Current U.S. Environmental Protection Agency (EPA) risk assessment guidance largely supports quantitative risk characterization of individual species as surrogates for population and ecosystem-level effects. Developing a work plan for investigating and remediating ecosystem-level changes potentially caused by large-scale historic mining/smelting contaminant release requires a decision process that incorporates a more holistic ecosystem management approach. Some of the most wasteful efforts associated with mine site ecological risk assessments arise when the risk analysis and data collection programs are not specifically linked up-front to the risk manager's decision needs. The following paper discusses the importance of employing a decision-based, ecosystem management framework when conducting ecological risk assessments at large mining sites. A case study of an ecological risk assessment currently being performed at a large New Mexico copper mine site is presented.

Jan 1, 1999

By D. R. Nagaraj

Editor&apos;s note: Minerals concentration is a disparate area, one involving many disciplines. Flotation, flocculation, reagents, microbial processes, gravity and magnetic separation, and the areas of coal and oil shale - concentration is relevant to all of these. In his article, Nagaraj reviews the latest developments and findings in concentration that have ocurred during the past year. Flotation The Monograph Series "Development in Mineral Processing," (Elsevier, 1985) was devoted to "Flotation of Sulfide Minerals." This volume has 26 articles covering the aspects of flotation chemistry, process development, plant design and equipment, and modeling and process control. The numerous articles on sulfide flotation had one recurring theme - the role of electrochemical processes and redox potentials in flotation and depression. Significant advances have been made in this area. A differential desorption-reflotation process was developed for the beneficiation of calcitic phosphate pebble (Hsieh and Lehr, Industrial Engineering and Chemistry, 1985). The carbonate and phosphate minerals were first separated from silica using fatty acid and the modifiers diphosphonic acid and HF. The collector on phosphate was then desorbed using sulfuric acid, and calcite was selectively floated without additional collector. A two-stage conditioning - initially at pH 10, followed by that at pH < 4.5 - with sodium oleate was developed to improve the separation between apatite and dolomite (Moudgil and Chanchani, Minerals and Metallurgical Processing, MMP, 1985). Separation of Mussorie rock phosphate in India from gangue calcite, dolomite, silicates, pyrite, and carbonaceous impurities was achieved with a three-stage flotation only on -75 µm (-200 mesh) fraction (Vaman Rao et al., International Journal of Mineral Processing, IJMP, 1985). The separation of fine SiC whiskers from other products of coked rice hulls by immiscible liquid and froth flotation was achieved using M1BC, pine oil, and mineral spirits (Parekh and Goldberger, MMP, 1985). Flotation was more economical. The carrier flotation separation of hematite fines from quartz fines was effected using coarse hematite as a carrier and oleic acid and ferric chloride (Cristoveanu and Meech, CIM Bulletin, 1985). Potash recovery from brines by laboratory-pan solar evaporation and amine flotation was discussed by Foot and Juiatt (Salts and Brines &apos;85, Proceedings, 1985). Flotation in a 45-kg/h (99-lb per hour) unit recovered more than 95% of the potash in schoenite and sylvite concentrates containing 28% and 62% K2O, respectively. The effects of fresh concrete into cement and aggregate by a single-step flotation process in aqueous suspension was described (Naegle, Chemical Engineering Science, 1985). The physico-chemical principles for the selective separation of proteins from mixtures using flotation were discussed by Ostermaier and Dobias (Colloids & Surfactants, 1985). Selective flocculation of hematite from silica was studied by Bagster and Mcllvenny (IJMP, 1985). Selective flocculation was more favorable with more highly charged anionic polyacrylamides and with high molecular weight. The cationic and non-ionic polymers flocculated both minerals. In minerals mixtures, there appeared to be very little selectivity unless a combination of dispersant and electrolyte was used. The effect of dissolved minerals species, such as Cu, Fe, and Ni on flocculation of chalcopyrite, pentlandite, millerite, pyrrhotite, and covellite was studied by Acar and Somasundaran (SME-AIME, 1985). Reagents There were some major advances made in reagent development for the minerals processing industry. Cyanamid introduced several classes of collectors, one of which - the diaryl monothiophosphates as acid circuit col¬lectors of sulfides and oxidesulfide ores - was commercialized in 1985. The monothiophosphates are more stable and powerful collectors than the xanthates and dithiophosphates. Hydrolyzed dithiophosphate containing 80% monothio and 20% dithiophosphate was found to give optimum recovery of copper from crude cementation precipitate and separation of Cu and Ni sulfides from matte (Akimova et al., Obogashch, Tonkov, Rud, OTR, 1985). A new class of O-alkyl-Nallyl

Jan 9, 1986

By A. Datta

An appropriate scale-up methodology is very useful for ball mill design and optimization of the grinding circuit. To date, the scale-up is based on the selection and breakage function model using lab mill data. However, a major drawback of that approach is that the charge motion in a lab mill is vastly different from that in a large industrial mill. Therefore, in the methodology proposed here, first the energy of individual collision in the mill is computed employing the discrete element method (DEM). Then the breakage of particles as a function of collision energy is studied in a separate experiment. Together, this information constitutes what is known as collision energy based population balance model. The appropriateness of this model is shown for different batch grinding mills.

Jan 1, 1999

By W. B. Hayes

The origin of the titanium pigment and metal? industries began with the discovery of the element titanium in 1791 by an Anglican clergyman named William Gregor. The titanium was discovered in magnetic black sands found in the beaches near Cornwall. England. The name titanium was established by the German chemist who discovered the mineral rutile in Hungary. Rutile is the oxide of the element titanium, which he called titan alluding to the mythological titans, giants of ancient Greece. The commercialization of titanium minerals began probably in 1916 with the production of titanium tetrachloride which was to be used in tracer bullets, flares and smoke screens during World War 1. In the 1920&apos;s composite pigments based on TiO2 barium sulfate and calcium sulfate were produced, followed by the introduction of the sulfate process anatase TiO2 crystal in the 1930s. The U.S. Bureau of Mines in 1938 began investigating titanium metal technology and promoted the development of the Kroll process. which is the magnesium metal reduction of titanium tetrachloride to produce titanium metal sponge.

Jan 1, 1989

By A. F. Edwards

The Main Pass sulphur and oil deposit is located at Main Pass Block 299 in the Gulf of Mexico, 30 miles east of Venice, Louisiana, in 210 feet of water. The deposit was discovered by Freeport-McMoRan and its joint venture partners, IMC Fertilizer and Homestake Mining, in late 1988-early 1989. The sulphur deposit contains 67 million long tons of recoverable sulphur. The sulphur occurs in bio-epigenetic limestone replacing anhydrite caprock on top of a salt diapir. Recoverable reserves of 39.4 million barrels of oil and 9.1 billion cubic feet of gas are also contained in the limestone caprock and in supracap sandstone stringers.

Jan 1, 1992

By M. D. Bath

Minproc Engineers Inc. (Minproc) recently completed the construction and start-up of a process facility to treat 14,000 t/d of gold-silver ore at Kori Kollo, Bolivia. The comminution circuit consists of crushing and SAG-ball mill grinding. Breakage characteristics of the ore were determined and a circuit model developed. This enabled variations of the circuit to be simulated, and evaluated in terms of predicted performance to provide the criteria for final engineering design. Subsequently, analysis of the operating circuit provided data for circuit model-fitting. The validity of the original model and circuit performance predictions are discussed.

Jan 1, 1994

By Mary Nelima Ondiaka, Oladunni Oyelola Alabi, Fatai Olufemi Aramide, Francis Gitau, Talabi Henry Kayode

Iron ore is essential in steelmaking but high-grade ores have diminished, making it necessary to turn to low-grade ores, which need further beneficiation to upgrade the iron content. Biobeneficiation techniques such as bioleaching, bioflotation and bioflocculation have proven successful in iron ore processing. Consequently, these methods have emerged as sustainable alternatives to conventional beneficiation. The biobeneficiation processes occur in mild conditions using bioreagents and biosurfactants derived from microbes, and offer a reduction of chemicals used in processing. This potentially offers methods that are relatively energy efficient, cost effective and environmentally friendly while tackling the constraints of dwindling high-grade iron ore resources.

Sep 1, 2024

By J. Reyher, R. Bratton, G. Luttrell, B. Li

"Flotation is regarded as the best available method of upgrading minerals and coal fines. However, its efficiency deteriorates rapidly with decreasing particle size. Further, ultrafine concentrates are difficult to be dewatered economically, forcing companies to discard part of the ultrafine materials to impoundments. To overcome these problems, a new method of separating and simultaneously dewatering ultrafine particles has been developed. Following extensive laboratory-scale test work, the process, known as hydrophobic-hydrophilic separation (HHS), has been tested successfully in continuous operations at proof-of-concept (POC)- and pilot-scale tests. The results show that the HHS process is capable of producing high quality clean coal with high recoveries and low moistures. INTRODUCTION Coal preparation plants are designed with up to four parallel processing circuits for treating coarse (> 12 mm), intermediate (12x1 mm) small (1x0.15 mm), and fine (<0.15 mm) particles. The plus 0.15 mm fractions can be effectively cleaned efficiently with gravity separation methods (Wills, 2006). At present, the only commercially viable option for cleaning the finest fraction is froth flotation (Yoon et al., 1999). In flotation, air is dispersed in the form of small air bubbles in a tank in which coal fines are suspended. The small air bubbles selectively collect the hydrophobic coal particles and float to the surface, forming a froth phase which overflows into a launder. As is well known, ultrafine coal particles of less than 30-50 µm are difficult to be collected by the air bubbles, resulting in low recoveries. Furthermore, fine particle flotation suffers from low carrying capacities and poor selectivity due to entrainment problems. (Bethell et al., 2005; Luttrell et al., 2014). In addition, the froth products containing ultrafine coal are difficult to dewater. Mechanical dewatering in general becomes inefficient with decreasing particle size due to small cake porosity and high surface area, resulting in high moistures (Hucko et al., 1988). The cost often becomes prohibitive with particles of smaller than ~45 µm (Bethell et al., 2005). Moreover, the high-moisture products are difficult to handle and incur high shipping costs and lower thermal efficiencies (Honaker et al., 2013)"

Jan 1, 2016

By G. J. Hartman

The Fort Cady in situ borate mining project involves recovery of boron from a mineral deposit located over 1400 feet below the surface. The resource recovery method is being developed using in situ mining technology employing weak acid solution injected directly into the ore body. As the acid contacts the calcium based ore (primarily natural colemanite), the contained borate values are digested as boric acid. This boric acid solution is then pumped to the surface by use of submersible pumps. At the surface the borate values are recovered as a finely divided solid white powder after a series of chemical reactions and precipitations resulting in the production of calcium borate. The refined product is then sold under the trade name CADYCAL 100.TM All environmental permits for up to a production rate of 90,000 tons per year have been obtained. These permits required an Environmental Impact study (EIS) for federal lands and an Environmental Impact Report (EIR) for the private portion of the property. Regulatory permitting required over 5 years to obtain all the various authorizations for this project. The ore body has an average thickness of 118 feet extending over 273 acres. At a production rate of 90,000 tons per year with only a 70 percent resource recovery allowance, in place reserves are sufficient to sustain production for over one hundred years.

Jan 1, 1997

By J. Wiebmer

The two most important influencers of cost-per-ton in an underground mining machine are its productivity (tons/hour) and its availability-utilization (hours/year). Operating cost and initial price have far less impact. This paper reviews a cost-per-ton sensitivity analysis for underground mining equipment and discusses benchmarks for measuring its performance. The conclusion is that miner-supplier partnerships and the Information Age are the two most significant trends in cost-per-ton reduction.

Jan 1, 1997

By K. N. Han, Q. Xu

The adsorption behavior of gold in ammoniacal solutions on activated carbon was studied. The gold adsorption capacity of the activated carbon and the recovery efficiency were examined. The parameters affecting the adsorption of gold on the activated carbon included temperature, agitation speed, the concentration of cation and anion and the concentration of ammonia. It was found that the maximum gold adsorption was about 10 kg/t of carbon. The recovery of gold by the adsorption, from ammoniacal solutions was found to be dependent upon the initial gold concentration. Under experimental conditions, a gold recovery of 98% was obtained after 120 hrs of adsorption. It was also found that the initial adsorption rate was relatively fast, when compared to the entire adsorption period. The apparent activation energy for the adsorption was determined to be 15.8 kJ/mol. It was believed that the kinetics of gold adsorption on the activated carbon was controlled by pore diffusion.

Jan 1, 1997

In the estimation of recoverable resources, geostatistical techniques such as Multiple Indicator Kriging require a change of support correction to derive theoretical recoveries based on an assumed level of mining selectivity. The change of support models most widely used in practice entail model based generalized corrections either on a global or local basis. Examples include the affine and indirect lognormal methods. Change of support corrections derived empirically through short-scale conditional simulation realizations often show notable differences compared with theoretical corrections determined using model variogram parameters. The existing changes of support models are reviewed and an alternative method is proposed.

Jan 1, 1999