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By Stephen R. La Brooy, Tong Deng, Pritam Singh, David M. Muir, A. J. Monhemius, G. W. Warren, E. Peters

The controlled addition of ammonia to cyanide solutions inhibits the leaching of copper minerals but extracts up to 80% Au using as little as 10% of the cyanide compared with conventional cyanidation of copper-gold ores. The solubility of copper minerals and copper speciation in solution is dependent on NH3, CN-, pH and Eh. Rotating disc and electrochemical studies show that gold is leached by a mixed Cu-CN--NH3 complex with either Cu(II) or O2 as oxidant. This complex is slowly oxidised to CuCN and Cu(OH)2 by air.

Jan 1, 1993

By Terry Ritzel

Predictive maintenance technologies include vibration analysis, tribology, infrared thermography, ultrasonic detection and electrical measurements. These technologies have been applied to large electric mining shovels at the Cyprus Sierrita Mine outside of Tucson, AZ. The predictive maintenance program was initiated on the P&H models 2300 and 4100 electric shovels during August 1996. Results of these technologies have shown the potential for improving electric min- ing shovel availability and minimizing maintenance costs. Predictive technologies provide the tools to assess machinery condition. Availability is enhanced by the condition-based planning of component replacement. Maintenance costs are minimized by focusing resources through condition-based prioritization.

Jan 1, 1997

By Guerry H. McCullen, Bruno Despujol

Quartz and phosphate grains from concentrates and ores from Atlantic Coastal Plain sediments often are wholly or partially coated by humates. Coatings were studied in situ using infrared microscopy, by transmission Fourier transform infrared of extracts, and scanning electron microscopy. The 14C age of the coatings is about 20,000 years, much younger than the mineral substrates. Coatings on double flotation concentrates indicate that the conditioning pH may be too low, allowing coated quartz grains to follow phosphate grains through beneficiation. Organic matter from coatings may contribute to processing problems as well as affect final product quality.

Jan 1, 1999

By F. F. Aplan, D. D. Xu

A novel system for the depression of pyrite and the ash-forming minerals has been developed. A metal ion, including but not restricted to Fe+2, is added to form a hydroxide coating on the pyrite or ash-forming minerals. A polymeric depressant is then added to attach to these re- surfaced minerals. Nearly 200flotation tests with I1 different coals indicate the effectiveness of this system. Many of the important process variables such as the coal source, frother- collector system. grind size and procedure, pH, metal ion, and depressant type and concentration have been studied.

Jan 1, 1995

By L. Xiao, P. Somasundaran

Using potassium oleate as a collector and alizarin red S as a modifying agent, selective depression of dolomite from francolite was achieved in an alkaline medium (pH > 9.0). Adsorption of alizarin reds alone on dolomite was found to be higher than that on francolite. Complimentary adsorption experiments of alizarin red S and oleate showed that oleate adsorprion was increased in the presence of alizaring red S. The results are explained in terms of comparative adsorption for the active sites on francolite and dolomite by oleate and alizarin red S and their interactions with dissolved mineral species in solution.

Jan 1, 1990

By A. J. Monhemius, R. G. Reddy, G. W. Warren, E. Peters

Thermodynamic solubility of chromium in pickling solutions (i.e., HF- HN03-H2O solutions) was determined as a function of HF and HNO3 acid concentrations at 298K. Pure Cr, AISI type 316 and 416 stainless steel were used in this study. The results showed that the solubility of Cr increased with increase in the concentrations of HF and HNO3 acids in solutions. The solubility of Cr increased in the order of pure Cr > 416 SS > 316 SS. The theoretically calculated Cr solubility data were in reasonable agreement with the experimental data.

Jan 1, 1993

By P. Somasundaran

The use of chemical additives in ultrafine grinding will be reviewed in this paper for the case of grinding of quartz in solutions of surfactants and inorganic electrolytes including some dispersants under different conditions of pH and ionic strength Mechanisms are examined by correlating the grinding effects with those obtained for the influence of these chemicals on zeta potential, pulp fluidity and flocculation/dispersion characteristics The analysis suggests grinding depends mainly on the state of aggregation of the ground products inside the mill and pulp fluidity Implications of the observed effects on ultrafine grinding in general are discussed

Jan 1, 1983

By D. M. Muir

Thiosulfate offers a nontoxic alternative to cyanide for processing gold ores. The mechanism of leaching gold using ammoniacal thiosulfate solution is driven by the Cu(II)-Cu(I) redox couple and is complicated by competing ligands such as NH3 and S2O32; It is shown that an understanding of the copper speciation and sulfur speciation is required to optimize this system. This paper presents Eh-pH and speciation diagrams for varying concentrations of Cu(II), S2O32- and NH3 and discusses the conditions under which various copper and sulfur species are stable.

Jan 1, 2002

By K. Hanumantha Rao, K. S. E. Forssberg, H. R. Manouchehri

The responses of calcite, feldspar and quartz minerals in a laboratory free-fall electrostatic separator after tribocharging with stainless steel, PVC and copper plates were investigated. The effects of H3BO3 and BaC12 chemical pretreatment on the electrical properties of the above minerals were examined. The changes in the electrical properties are discussed along with the determined charge, dielectric constant and electrical conductivity of the mineral samples. The electrical properties of the minerals and their responses to the electrical field during separation after tribocharging and chemical pretreatment are explored relative to the electrical behavior of the minerals.

Jan 1, 2000

By Carl D. Wood

Traditionally, when one considers the optimization of a flotation circuit, the scope of work focuses on a review of unit process equipment. This usually includes topics such as grinding ball typed, grind size, classifier efficiency, mill liner design, chemical reagent addition rates, alternative chemical reagents, on-line process analysis, and automated control strategy. However, since very few companies can afford the capital expenditure needed to completely automate the processes, the flotation operator remains as a critical link in optimization of the circuit. Therefore, upgrading of operator skills and knowledge through training must be considered as equally as important as unit process review. This paper will review some concepts and approaches to innovative operator training. INTRODUCTION Consider for a moment the fantastic changes that have occurred in process automation at many flotation plants during the last several years. Flowmeters, density gages, and on-stream analyzers now routinely measure process conditions and effect control strategy. These functions had until recently been entrusted to human flotation operators. Now with a little stretching of the imagination it is possible to envision a plant where very little human intervention would be required. However, when one begins to calculate the capital cost required to fully install automatic equipment, it quickly becomes apparent that many parts of flotation plants will continue to require skilled, knowledgeable operators to ensure successful operation. Additionally as these automatic systems are put into place, the operator's duties become increasingly complex. Therefore no flotation plant can be considered optimized without upgrading each operator's skill and knowledge to match the technology utilized. BACKGROUND At Henderson, one of the hardest steps towards the optimization of operators was to realize that present level of operator skill and knowledge was not sufficient. Since Henderson had a track record of producing the highest quality molybdenum concentrate in the world, it was difficult to accept the idea that change was needed, or even possible. This realization came about as Henderson began a program to modernize the cleaner plant circuit. Henderson utilizes a complex cleaner flotation circuit involving multiple stages of flotation, with a counter- current routing of flotation tailings. Since start-up in 1976 Henderson had relied upon next-day laboratory analysis techniques, that provided an after the fact measurement of process. Hour to hour process control was implemented by the operator, the basis for the operators' control decisions was primarily the individual operator's experience and "feel'. Bench marking of current flotation technology indicated that on-stream analysis was a proven state-of-the-art method for improving process control. An Outokumpu Courier 30 analyzer was purchased and installed to provide real-time analysis of critical cleaner plant flows. The analyzer quickly began to provide valuable assay information, allowing the metallurgists to develop specific target values for important flotation variables. However due to the complexity of the circuit, the analyzer information showed that a problem was usually caused when several targeted parameters went out of range simultaneously. This made it difficult for the operator to determine just where to implement the proper corrective action. It became apparent that to take full advantage of the new analyzer information each operator would have to become proficient at understanding the material balance of the entire circuit. TRAINING PLAN CONCEPTS With the goal of giving each operator a working knowledge of a circuit material balance the following concepts were applied to develop a training plan: - Most operators were high school graduates, but had fairly weak mathematical skills, and had very little experience at metallurgical calculations. - The training would have to address a wide range of topics from basic fundamentals to complex material balance. The basic sequence decided upon, was to present a fundamental topic to the entire group, break into small groups to work a “hands on'”case study example of that topic, and design the case study results so that they could be combined to highlight a major portion of the material balance concept.

Jan 1, 1993

By Laurindo De Salles Leal Filho

Microflotation tests with sodium oleate, in alkaline pH, were performed with apatite and some silicates (phlogopite, quartz, and chlorite) that commonly occur in Brazilian phosphate ores. Further flotation tests were carried out with selected ores containing the same silicates as important gangue minerals. The results showed that apatite recovery is highly affected by competition with silicate minerals, probably activated by calcium ions dissolved in flotation pulp. Inorganic chemical species (sodium tripolyphosphate, sodium carbonate/ bicarbonate, and carbon dioxide) that could act as water softeners were used as modifier agents. They proved to be capable of improving flotation recovery and selectivity.

Jan 1, 1999

By Regina N. Tempel, Timothy E. Eastep, R. Craig Ford, Bryce R. Roming, Geoff Clothier, Maggy F. Lengke

The Climax Mine, near Leadville, Colorado treats acid drainage in a lime neutralization chemical treatment system. Chemical treatment has been successful in reducing the concentration of metals to below surface water discharge effluent limits, but lime usage has not been optimized. A geochemical modeling approach has been developed to increase the efficiency of lime neutralization. The modeling approach incorporates two steps: (1) calibration, and (2) calculation of amount of lime needed to increase pH and remove metals. Results of our work quantify the lime treatment process and improve our ability to predict overall water quality.

Jan 1, 2000

By John W. Rushton

THE PLANNED MAINTENANCE PROGRAM All concentrators should start with a planned maintenance program from day one. Every- body thinks they have a program in place before start-up, but in reality, most have only a fraction of what is needed to avoid the "Post Start-up Disaster" (PSD) - two years for start-up is not that uncommon. An effective program has all of the following: (1) Good people. (2) Area Maintenance. (3) Good PM Checklists. (4) Daily Work Schedules. (5) Written Work Orders. (6) Equipment Histories. (7) Backlog Control. The installation of a workable program takes hard work, talent, and commitment. You have to know what you are doing (hard work will not replace talent). Good People Good people are available in any location if you make the effort. Always check references carefully (both superiors, peers and subordinates). Was the last concentrator they worked at successful? Was it clean? Find out! Success or failure follows people around. I know people who are experts on PSD because they have lived through it three or four times. You need some college trained people with hands-on experience. There are no secrets, you have to make the effort. If you make a mistake in hiring (and you probably will), make the tough decision necessary to rectify it quickly. Area Maintenance Area maintenance refers to organization of supervision such that one person is uniquely accountable for every inch of ground and piece of equipment. Avoid overlapping authority if at all possible. You must have a planner as a staff position. A foreman cannot effectively plan and

Jan 1, 1986

By Takashi Sakaguchi, Takehiko Tsuruta, Akira Nakajima

Some attempts were made to recover gold from aqueous systems using immobilized persimmon tannin. This adsorbent adsorbed gold from solutions containing hydrogen tetrachloroaurate (III) with high efficiency, whereas there was minimal adsorption from solutions containing gold (I) sodium thiomalate and sodium dicyanoaurate (I). The adsorption of gold was rapid, and was affected by the pH of the solution, temperature, external gold concentration and amount of adsorbent. Adsorbed gold was easily desorbed with 1 M thiourea solution, indicating that immobilized persimmon tannin can be repeatedly re-used for the recovery of gold using adsorption-desorption cycles.

Jan 1, 1995

By Mary Ann Harrington Baker, John Trudnowski, Marietta Canty, Marek Zaluski

Three Sulfate-Reducing Bacteria (SRB) passive field-bioreactors were constructed at an abandoned mine site near Butte, Montana, to mitigate AMD emanating from a waste rock pile. Each SRB field-bioreactor contains chambers of an organic source, limestone, and cobbles. The field-bioreactors are configured differently to test the effect of different environmental conditions on the SRB. Preliminary observations indicate that, during start up and the first eight months of operation, the quantity of organic carbon supply significantly impacts the SRB activity. To date, the dissolved metals have been reduced significantly and the pH has increased.

Jan 1, 2000

By L. Mao, R. Yoon

The thin film balance (TFB) technique was used to measure the equilibrium thicknesses of the water films formed between two oil phases. The measurements were conducted with dodecane at varying concentrations of dodecylammonium chloride, pH, and electrolyte concentration. The data obtained in the present work were used to calculate the surface forces acting between the two oil phases. The calculation was carried using the Extended-DLVO theory with the surface potentials calculated from the Gibbs adsorption isotherm. The results show that oil droplets suspended in water are hydrophobic and the hydrophobicity changes with surfactant and electrolyte concentrations.

Jan 1, 2004

By J. Grubb

"The undertakings described in the paper titled “Study on correlation of quantified coal rank with self-heating temperature” by Wang and Luo in the November 2015 issue of Mining Engineering (Wang and Luo, 2015) are mathematically sustainable and an acceptable extension of work performed by Smith and Lazzara (1987) for the U.S. Bureau of Mines. The paper is not an accurate explanation of the currently accepted leading practice for determining the propensity of a coal seam for spontaneous combustion. The paper could lead a practitioner to an oversimplified conclusion on how to determine the propensity of a coal seam to spontaneously combust.The spontaneous combustion of coal is a complex and not fully understood reaction. What is understood is that many more factors other than selfheating temperature (SHT) and coal rank are required to sufficiently evaluate the risk of spontaneous combustion in a particular coal seam. A superficial assessment can lead to an improper response to the risk. Some statements on the next steps through an appropriate literature search would have made the authors’ conclusions more credible.The SponCom 2.0 software, updated by the National Institute for Occupational Health and Safety (NIOSH) in 2011, provides a path for evaluating the susceptibility of a coal seam to spontaneous combustion. In addition to proximate and ultimate analyses to establish coal rank, and therefore an estimate of SHT, the program includes the history of heatings, friability, seam thickness, overburden thickness, rider seam presence, pyrite presence, face and butt cleat densities, geothermal source presence and other geological features in the assessment. Mining conditions including floor heave, rib sloughage and rate of advance are also assessed to conclude a propensity for spontaneous combustion."

Jun 1, 2016

By K. P. Madhusudhanan, R. K. Bhatia, K. S. Narasimhan, R. N. Singh

A typical case study of a coal washery of capacity 500 t/h raw coal input has been presented and discussed with particular reference to the techno-economics for flotation column vis-a-vis the conventional flotation cells, keeping parameters like input capacity and product ash same. The results presented indicate that substitution of flotation cells by columns in a coal washery results in advantages of increased fine coal recovery, better quality of concentrates, lower capital and production costs etc.,. The effect of increasing the specific capacity of the column by design modifications on the cost benefit is also analysed.

Jan 1, 1988

By Ian Larkins

The Ruby Hill Mine agglomerates crushed low-grade ore (nominally -1 .5'') with high-grade filtered tailings (filter cake, nominally 80% -65#). Cement is added as a binding agent. The agglomerated ore is then conveyed and stacked on the heap. In 1998 approximately $480 000 was spent on cement for agglomeration. Cement for mill pH control and agglomeration was the largest single reagent cost at Ruby Hill. In an effort to reduce agglomeration costs a test-work program was initiated to investigate alternative binders and optimum binder additions. This paper summarizes the test­work results to-date.

Jan 1, 1999

By R. Hiebert, M. Foote, S. Nordwick, M. Canty

An innovative biological treatment system designed to detoxify cyanide and nitrate and immobilize metals from cyanide leach operations is described. A pilot-plant demonstration was conducted to detoxify cyanide and immobilize several metals from a process stream at the McCoy/Cove Mine. Testing was performed under the EPA’s Mine Waste Technology and Superfund Innovative Technology Evaluation Demonstration Programs. This technology was successful in detoxifying cyanide and effective in removing metals. The pH was consistently neutralized and nitrates were successfully removed. Results show that biological treatment can offer an innovative, cost-effective alternative for the treatment of mining wastewaters.

Jan 1, 1999