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By J. W. Leonard

Gravity based coal/mineral preparation plants must be operated to yield products of a quality satisfactory to existing markets; but, because of historic control problems, recovery is frequently sacrificed to achieve quality resulting in losses of valuable product. Plant control has ranged from intuitive in-plant spot quality judgments made by various operators to gross methods involving such devices as density gauges, floats, grab-sample on-the-spot sink-float tests, etc. Millions of tons of quality coal/minerals are lost to refuse each year, because of the historic lack of a continuous and dependable control system. The result is both serious economic as well as environmental losses. While the economic losses are obvious, less obvious environmental losses, in the case of coal, result from the misplacement of more ignitable quality fuel to refuse banks. A control system capable of supplying a market-grade coal/mineral product, while continuously minimizing product losses to refuse, has until recently escaped technology.

Jan 1, 1991

By J. Hunter, E. Jackson

This paper describes work done by Placer Dome Technical Services Limited, a subsidiary of Barrick Gold, and Nautilus Minerals Inc. in support of the conceptual design of a subsea mining system. It describes an overall concept design plus specific studies into mechanical excavation at depth. The concept design includes one or more subsea excavators connected to a suction riser, which transports the cut material to a shipboard dewatering and offloading system. A multi-phase investigation was performed into the mechanical excavation of seafloor massive sulphides at depths of around 1600m. Rock samples were recovered and tested for rock properties and cutting behaviour. A small pick drum cutter was procured and tested on a representative concrete slab in a lab and tested again while submerged in a test tank. Finally the cutter was tested on a massive sulphide ore body at 1600m depth. The cutting performance results, e.g. pick forces and specific energies, should provide valuable input to the design of future full scale subsea mining systems.

Jan 1, 2007

By K. L. Gabby

Selective removal of mercury from cyanide leaching solutions while retaining silver has been a long-standing problem, due to the chemical similarity of mercury and silver. In order to be practical, a mercury removal process needs to be both highly selective and use inexpensive materials. This paper reports the use of zinc sulfide (ZnS) as a precipitant for mercury. The mercury cyanide complex (Hg(CN)4 2-) undergoes a replacement reaction with the zinc sulfide, forming insoluble HgS, while the silver cyanide complex (Ag(CN)2 -) remains in solution. Under appropriate conditions, the separation of mercury from silver is nearly quantitative, with close to 100% removal of mercury, while nearly none of the silver is precipitated.

By Sidney A. Suhler

The persistent requirement for methods and equipment capable of detecting hazardous anomalies in advance of underground mining has led to the development by the U.S. Bureau of Mines of a directional radar probe. The probe operates from boreholes drilled from the surface into the underground region to be mined. The engineering model radar was completed in early 1982 and field demonstration tests were performed in May of that year at a selected coal mine. Preliminary in-situ electromagnetic tests were performed at several candidate coal mines to evaluate the radio-frequency characteristics of the coal. A coal mine in New Mexico was selected on the basis of low EM propagation losses in the coal and the presence of an extensive coal seam displacing fault as a radar target. The borehole radar was operated in two vertical boreholes which intersected the coal seam at approximately 25 and 40 feet from the fault interface. Radar reflections from the coal/ rock interface were detected in both tests. Underground tests in a horizontal borehole in the coal were less successful because of interfering reflections. Additional borehole-to-borehole tests were performed with a separate ground penetrating electromagnetic system to obtain radar range calibration data. The coal was found to be bounded by very lossy roof and floor sandstone and shale while propagation through the coal seam was obtained at distances up to 175 feet between test boreholes. Coal seam continuity was indicated by the hole-to-hole experiments through a section of the seam previously thought to be completely cut off by the fault.

Jan 1, 1983

By Larry R. Powell

The Bureau of Mines, in cooperation with the Illinois Mine Subsidence Insurance Fund, is monitoring the response of two foundations to ground movements induced by subsidence from high extraction mining in southern Illinois. The objectives of the monitoring program are to study the inter- action between the ground surface and a foundation during a subsidence event and to determine the capability of the tiltmeter to detect and monitor subsidence movements. Tiltmeter data were obtained on two foundations constructed near Sesser, IL. One of the 30-by 40- ft foundations was constructed with a typical poured concrete footing, the other with a rein- forced-concrete footing poured on top of pol yethylene sheeting placed over a compacted layer of sand. Soil-filled bins were placed on the perimeters of both foundations to simulate superstructure loads. Monitoring pins and tiltplates were installed on the corners and midpoints of the footing. Additional survey points were established on the five-acre site to track the mining advance. This paper describes the monitoring instrumentation and techniques as they relate to the mining and site conditions. The capability of a tilt- meter to detect and follow the tilt of the foundations is demonstrated.

Jan 1, 1986

To maintain its brand position in the competitive market of mining equipment, the Volvo Construction Equipment (Volvo CE) engineers were challenged to develop top-performing wheel loaders and articulated haulers even faster than before. To start, this meant reducing prototype test cycles by two-thirds. The final goal? Chopping in half the virtual prototyping time in early design phases. Creating a unified co-simulation solution In this ground-breaking project, the Volvo Construction Equipment design team in Eskilstuna, Sweden, replaced its piecemeal department-by-department process with a single solution based on LMS Imagine.Lab AMESim. With one unified model, they could simulate the behavior of four major vehicle subsystems in wheel loaders and articulated haulers: hydraulics, powertrain, thermal management and the actual driver. Subsystem models exchanged data seamlessly.

Jan 1, 2011

By Samer Sadek, Phoebe Cheng, Changmo Kwon, Myat Ohn

BART Facilities Standards (BFS) Structural Criteria is a living document that governs planning, design, and construction of all BART projects. Since its development, the document undergoes incremental changes and updates to reflect policy changes, changes in local, State, or national design codes and guidelines, advancements in engineering and technology, or based on the performance of past built infrastructure. In 2020, the BFS-Structural Criteria underwent a comprehensive update and was released with BFS version 3.2. This paper summarizes the updates to the Tunnels and Underground Structures Section of the Structural Criteria, and provides insights to the basis and logic of the requirements.

Dec 1, 2022

By John E. Tilton

The ability of companies and countries to mine copper and other mineral commodities competitively and in the process to generate new wealth depends on their mineral endowment. Chile, for example, produces and exports copper because it is well endowed with high-quality, low-cost deposits. This production creates wealth that benefits mining companies and their stockholders, the government, local communities, as well as copper consumers around the world. The widespread perception that mineral endowment must largely determine competitiveness, or what economists call comparative advantage, must be true at any particularly moment. Countries with abundant reserves must be competitive. This follows from the definition of reserves — the quantity of a mineral commodity found in discovered deposits that are profitable to exploit under current conditions. As a result, it is a tautology and not particularly interesting. The important question is what causes reserves to change over time, producing in the process new wealth and shifts in competitiveness?

Jan 1, 2003

By R. DasGupta

The dissolution behavior of gold in ammoniacal solutions at 75°C has been investigated. The variables investigated include concentration of lixiviants, pH of the solution and various oxidants. The anodic dissolution of gold was studied in the absence of oxidants using the potentiodynamic polarization technique. The cathodic reaction of oxidants was studied on a platinum electrode. Tafel polarization tests were also performed to determine the dissolution rate. The overall dissolution of gold in ammoniacal solutions was examined using a mixed potential theory. A comparative study on the role of cupric am mine, oxygen, hydrogen peroxide, sodium hypochlorite as oxidants for the dissolution of gold in ammoniacal solutions has been carried out.

Jan 1, 1996

By Rosa Malena Fernandes Lima, Kerollan da Silva Ramos, Joyce de Assis Silva, Geriane Macedo Rocha

This study evaluated the effects of collector type amide-amine compared with those of conventional etheramine acetate (both cationic collectors) on the surface properties of quartz and hematite. An examination of certain properties of the reagents indicated that the new collector amide-amine has CMC (critical micelle concentration) and pKa values (100 mg/L and 8.2, respectively) significantly lower than those of etheramine (800 mg/L and 9.4, respectively). Microflotation tests showed that the recoveries of quartz with amide-amine in all the concentrations tested were higher than those with etheramine. This is attributed to its lower CMC and pKa values. The selectivity window between quartz and hematite flotation using amideamine was higher at pH 10.5 (approximately 80% for 5 mg/L). Therefore, the use of starch is not necessary in siliceous itabirite flotation by amide–amine collector. Zeta potential measurements and infrared spectra reveal that the adsorption of amide-amine collector on quartz surface occurs mainly by electrostatic attraction. Considering the better collectability of amide-amine for quartz flotation and lower adsorption affinity for hematite surface than etheramine, the amide-amine is a promising collector to be used in reversal iron ore flotation.

Jul 30, 2021

By Zibo An, Yong Hu, Hao Zhang, Hong Cao, Jun Xue, Zhen Luo

Phosphogypsum (PG) is a by-product of solid waste produced by the phosphate chemical industry. Owing to large emissions and massive storage issues, it causes a potential threat to our environment. Hereby, a method based on the precipitation and crystallization properties of calcium phosphate-magnesium ammonium phosphate (CP-MAP) followed by its adsorption on active solid waste powder is used as the main principle to treat PG harmlessly. The treatment process and its influencing factors for orthogonal experiments along with the associated environmental safety have been studied in detail. The results showed that this method could simultaneously remove soluble phosphorus and soluble fluorine from PG. When ACP, FA, HBM, and Ur were added to PG at a dosage of 3%, 13.5%, 0.04%, and 0.04%, respectively, the residual phosphate and fluoride contents was 0.061 mg/L and 0.856 mg/L respectively in the PG leaching solution. Compared to state-of-the-art approaches, this method exhibited higher efficiency in removing phosphate and fluoride. Most importantly, this method does not cause any secondary pollution in the process, thereby showing a novel application in large-scale industrial treatment.

Aug 29, 2022

By G. P. Hand

The graphite industry as a whole has gone through many changes over the years. Most of the graphite used in major applications since the turn of the century were basic natural or electrode by-product synthetic materials, processed using simple crushing, screening, or grinding techniques. In the mid 1970's new thermal technology was developed which changed the face of the .graphite industry, and opened up a panacea of new products and capabilities. Materials produced through this new technology have helped revolutionize new products and processes in industries including automotive, batteries, fuel cells, electronics, iron, lubricants and steel. This paper outlines the continued improvements in those industries as well as the as well as the outlook for new technology in this rapidly changing area.

Jan 1, 1997

By ?. ?ivkovic

The silicate slag and copper matte that are the byproducts of smelting copper in a reverberatory furnace contain SiO2, FeO, Fe3O4, CaO and Al2O3, and Cu, Fe and S, respectively. These components influence the oxide (Cuox), sulfide (Cusul) and total (Cutotal) copper content lost in the waste slag. This paper uses multiple linear regression analysis (MLRA) to determine the degree of influence. The results of calculations obtained using MLRA were compared to actual measured results and found to have a large degree of correspondence, with the coefficient of determination R2 = 0.975. These results indicate that slag composition and copper content in the matte influence the copper losses in the waste slag with a probability of above 97%. It was determined that, of the total copper content of the slag, 74% is in sulfide and 26% in oxide form, and that this ratio is not dependent on the slag or matte composition.

Jan 1, 2010

By Katarína Gáborová, Marcela Achimovičová, María Florencia Márquez‑Zavalía, Jaroslav Briančin, Oľga Šestinová, Pavel Škácha

In this paper, the structure, morphology, chemical composition and leaching of naumannite ( Ag2Se) were studied. Mechanical activation of Ag2Se in a planetary ball mill resulted in increasing its specific surface area. The influence of milling time on the particle size was studied by particle size distribution analysis and scanning electron microscopy. The leaching kinetics of non-activated and mechanically activated samples in 3.5–7.9 mol/L HNO3 solutions were examined. Subsequently, the effect of leaching temperature in the range of 25–50°C on the recovery of silver from mechanically activated naumannite was documented. The maximum yield of silver 94% was achieved after 120 min of leaching in 7.9 mol/L HNO3 at 50°C for the sample mechanically activated for 30 min. Based on calculated activation energy values from the Arrhenius equation, a mixed leaching mechanism consisting of diffusion and surface chemical reaction as the rate-controlling steps of the solidliquid reaction was assessed.

Mar 4, 2023

By C. L. Karr

Establishing suitable control of pH, a requirement in a number of mineral and chemical industries, poses a difficult problem because of inherent nonlinearities and frequently changing process dynamics. Researchers at the U.S. Bureau of Mines have developed a technique for effectively controlling such systems. This technique successfully combines the process control capabilities of fuzzy logic and the search capabilities of genetic algorithms. Fuzzy logic offers an effective mechanism for handling nonlinearities, while genetic algorithms can provide fuzzy logic controllers with real-time adaptive capabilities. This Bureau-developed technique is applied to a laboratory acid-base neutralization experiment. Nonlinearities in the laboratory system are associated with the logarithmic pH scale and the changing process dynamics are due to alterations in pH and buffering capacity input solutions. Results indicate fuzzy logic controllers augmented with genetic algorithms offer a powerful alternative to conventional process control techniques in such nonlinear, rapidly changing systems.

Jan 1, 1992

By J. R. Piper

“Old Borate,” located in the Calico Mountains east of Barstow, California, lead domestic colemanite production from 1884 through 1907. Mineral exploration at “Old Borate” in the early 1980's, examined borate mineralization in Tertiary lacustrine strata. Surface sample and drill hole locations, geology and structure, were hand-drafted on paper maps. To re-evaluate this data, the information was digitized using Geographic Information Systems software. Digital Elevation Model based terrain modeling integrated surficial samples with drill hole data to locate favorable drilling targets. Structural relationships were used to identify hypothetical resources formed by the leaching of boron from surface exposures, redeposited at depth.

Jan 1, 2001

By S. Rukhaiyar, M. Ramulu, G. Pradeep, P. K. Singh, P. B. Choudhury

The drill and blast method is the most prominent rock excavation method used in mining and civil engineering projects. The ground vibration is the most undesirable effect of the blasting and needs to be controlled. The blasts are designed so that ground vibration at nearby structures must remain under the prescribed limit. Various empirical blast vibration attenuation models have been presented to estimate the ground vibration for designing purposes. These models assume ground vibration as a function of distance and maximum charge per delay. United States Bureau of Mines (USBM) model is most commonly used for the blast design. However, the uncertainty associated with these models is seldom characterized, thus diminishing its reliability. The probabilistic Bayesian approach associated with the Monte Carlo method can easily quantify uncertainties associated with the model and its parameters. Thirty-three blast vibration observation data from a granite quarry in Kerala, India, is used to estimate the probability distribution of model parameters. Markov Chain Monte Carlo (MCMC) approach is used for sampling 12,000 samples for obtaining the posterior distribution of parameters. The uncertainty associated with model parameters is quantified from the posterior distribution, and this is further used to estimate the credible and prediction limits of the model. The point estimate of the most optimum value of the parameter is estimated using maximum-aposteriori or MAP estimate. The model parameters are also obtained using the commonly used least-square error method, which is a maximum likelihood estimation or MLE approach. It has been observed that the accuracy of the model obtained using both MAP and MLE approach is almost equal. However, the MAP estimate as per Bayesian probabilistic analysis has the added advantage that it can estimate the uncertainty of parameters as well as the model, which is not possible using the MLE approach.

Sep 27, 2021

By T. W. Camm, J. C. Johnson, S. D. Rosenthal

"Most engineers are bright, hard-working, reliable and prefer to avoid conflict. An engineering curriculum tends to self-select these characteristics. By most standards, you would expect workers exhibiting these traits to require minimal supervision. But, is this true? Is this how most current engineering managers lead? Looking at some current theories on leadership combined with personal anecdotes, this article will look at some common misconceptions about leading engineers.Engineers are different. There, it has been said. From cartoons to movies to television shows and more, there is a reason stereotypes of engineers resonate. Yes, you can find a lot of individual variation among specific engineers that you may know, but they do not detract from some of the overarching commonalities that engineers are known for.Clash of culturesWhat distinguishes a professional? Raelin (1985), in his book Clash of Cultures, describes professionals as having superior intellectual training, maintaining their own standards of excellence and being supported by associations that maintain the quality of the profession. Engineers obviously fit all three of these ideas: an engineering degree is still regarded as one of the most difficult to attain. Standards are maintained both through peer review and in academia, through ABET accreditation and through professional associations like SME to promote the discipline and foster technical growth.Six characteristics representing professional status are described by Raelin (1985, p. 9):• Expertise — prolonged specialized training in a body of abstract knowledge.• Autonomy — the freedom to choose the means to solve a problem.• Commitment — primary interest is in pursuing the practice of one’s own chosen specialty.• Identification — identifying with the profession and with fellow professionals, both through formal associations and through peers external to the organization.• Ethics — providing service without concern for oneself or without becoming emotionally involved with the client.• Standards — committed to help in policing the conduct of fellow professionals."

Jan 1, 2018

By Inoka E. Perera, Michael J. Sapko, Marcia L. Harris

Experiments conducted with limestone dusts and dolomitic marble dusts have indicated that when rock dust is wetted and subsequently dried, it becomes a solid, non-dispersible cake. However, in order to be effectively inert a coal dust explosion, rock dust must be able to disperse as individual particles to air. To counteract this, rock dust manufacturers created treated rock dusts that will resist caking after moisture exposure. National Institute for Occupational Safety and Health (NIOSH) researchers conducted a series of laboratory-scale experiments on four base rock dusts and their treated counterparts to assess the effectiveness of various anticaking additives after being exposed tomoisture and then dried. The dusts were exposed tomoisture using humidity cabinets having a high relative humidity (99% RH) and by also exposing the rock dust bed to water through bottom wicking. The dusts were then evaluated for dispersibility after drying using the NIOSH-designed dust dispersion chamber. The anti-caking additives were different concentrations of stearic acid, oleic acid, and xylene-based surfactants. All results were compared to a reference rock dust used to conduct large-scale experiments in the Lake Lynn Experimental Mine (LLEM), Fairchance, PA. When the untreated dusts were dried after exposure to moisture for 1 day, no dispersion was measured. However, rock dusts treated with anti-caking agents were readily dispersible even after exposure to moisture for 6 months. This report details the analysis and characterization of anticaking additives using the NIOSH-designed dispersion chamber and the 20-L explosion test chamber.

Apr 12, 2021

By Wen Tao Liu, Tong Tian, Fu Sheng Niu, Xiu Man Liang

The level of automation employed in flotation production is relatively low. In an actual concentrator, operators use their judgment to adjust the production state based on the visual characteristics of the flotation froth surface. There are shortcomings, such as strong subjectivity and lagging process operation, that easily cause the waste of manpower and material resources. Machine vision technology is introduced to replace human visualization, achieving a quantitative description of the visual characteristics of the froth surface. The state variable parameters are provided for the identification of the flotation conditions.