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By Jian Liu

The dissolubility of a natural sphalerite (ZnS) in the entire pH range was theoretically calculated, and its practical dissolution in an aqueous solution at different pH values in an inert environment, together with its surface properties after dissolution, was fully investigated. The results of the investigation indicate that the total concentration of Zn (CZnT) decreases significantly with the increase of pH value, while the pH value is set below 8; however, it reverses when the pH value reaches 8. Such a tendency is similar to that of the theoretical calculations, although the experimental CZnT were much higher than those of the theoretical calculations. The X-ray photoelectron spectroscopy (XPS) of the sphalerite surface after its dissolution under alkaline solution shows that a polysulfide (Sn 2-) surface layer with a binding energy (BE) value of 162.96-163.25 eV is present on the surface, and the percentage of Sn 2- increases significantly with an increase in pH value; the undissolved and dissolved sphalerites under the acidic solution have a negligible difference in S2p peaks. The surface S/Zn ratio of all dissolved sphalerites shows a marked Zn enrichment and S deficiency. An atomic force microscope (AFM) view of the sphalerite surface, after its dissolution under the alkaline solution at a pH of 12, shows that the surface is significantly different in morphology from that of the undissolved one.

May 1, 2012

Continued market pressure on the US coal industry was the overriding factor affecting developments in underground mining in 1986. An oversupply of coal in the spot market kept prices low throughout the year and caused a number of operations to close their doors. Operators stepped up their efforts to improve productivity at existing operations. They made technology advances and improved their relations with employees. A continuing market-related development during 1986 was the divesting of coal properties and operations by major oil companies, which were faced with economic pressures in both the oil and coal industries. Further increases in contract mining production resulted as some larger operators were unable to compete in a tough economic environment. Longwall mining is still seen by many as the technology that will provide the necessary productivity to remain cost-effective. But the number of active faces in the US declined in 1986, as reserves were depleted and economics forced some closures. At the first Longwall USA meeting in June, much attention was placed on improved technology, as electro-hydraulic controls for roof supports gained acceptance. Other recent developments include shearer initiation of roof supports, automatic horizon control for shearer drums, and collection and storage of machine data for predicting maintenance requirements. The government and academic communities continued their research on dust control at longwall faces. Jankowski, Kissel, and Daniel, (October 1986, Mining Engineering), gave an overview of progress in longwall dust control. And Mukherjee, Singh and Jayarman (November 1986, Mining Engineering), recommended design guidelines for improving water spray systems for dust control. Surface subsidence Increasing attention is being given to surface subsidence. This is primarily because of longwall mining and the Surface Mining Control and Reclamation Act. Improved methods of prediction of surface subsidence, especially computerized methods, are being continually developed. Mining engineering faculty at major universities such as Virginia are helping develop public policy and regulations concerning subsidence. As part of this effort, Unrug and Johnson identified major subsidence areas of Western Kentucky. Peng and Chen (February 1986, Mining Engineering), gave an overview of history and research of surface subsidence. And Elifrits and Aughenbaugh, (February 1986, Mining Engineering), discussed effects of moisture variations and overburden on subsidence. This research culminated in a Symposium on Surface Subsi¬dence at the SME 1986 Fall Meeting in St. Louis and the 2nd Workshop on Surface Subsidence at West Virginia University. Ground control in coal mining continued to be an item of major research interest. Some 30 papers were presented at the 5th International Conference on Ground Control in Mining at West Virginia University. And six sessions were related to coal mining at the 27th US Symposium on Rock Mechanics at the University of Alabama. At the 4th Annual Workshop, Generic Mineral Technology Center, Mine Systems Design and Ground Control emphasized efforts of the participating universities to improve ground control. Peng and Chiang summarized results of studying support capacity and roof behavior with longwall shield supports. And Unrug, Johnson, and Nandy analyzed the process of deterioration of shale roof in a case study of a room-and-pillar coal mine. The importance of geologic conditions in determining mining productivity is receiving increased attention in coal mine design in the US. Mullenex related, through case studies, the benefits to be derived through analyzing the depositional system of coalbeds as an integral part of mine design. Improved technology in this area was related by Lloyd, Semborski, and Stolarczyk. They discussed a case study of using radio imaging to indicate coal-seam discontinuities in advance of mining. Improved coal mining technology in general is being researched more heavily, to help improve US coal competitiveness. However, much of this research and development process has yet to be widely implemented. Equipment manufacturers are devoting more resources to development of continuous-haulage systems, mobile roof-supports, mine-monitoring systems, and predictive-maintenance systems using computers to extract machine data.

Jan 5, 1987

By K. Heasley, A. Yassien, A. Khair, S. Peng

There are three major components of a fully grouted roof bolt which primarily determine its ability to develop and sustain load: the steel rebar, the resin annulus, and the rock/grout interface. The untensioned, fully grouted roof bolt is subjected to loading only when the surrounding rock deforms. Vertical rock deformation is generally a result of strata sagging and bedding plane separation, whereas horizontal deformation is typically a result of bedding plane sliding. These two types of deformation create different types of internal loads with-in the roof bolt, tensile stress for vertical rock deformations and shear stress for horizontal rock deformations. Also, as a result of the mutual load transfer between the rock and bolt, shear stress will be developed along the grout/rock interface. According to the exact bolt loading conditions, different failure modes may occur: bolt axial failure, bolt shear failure, and shear failure along the grout/rock interface. Understanding these possible failure modes and their root causes is the key to eliminating roof failures in underground mines employing fully grouted resin bolts. Using ABAQUS 5.8, a finite element model was developed to simulate the components of the fully grouted bolt and its interaction with the surrounding roof strata. Several models were conducted to investigate how load transfer occurs between the rock and the bolt under different geological and mining conditions. The effects of bed-ding plane location and properties, and strata sequence on bolt stability were studied. Also, the effects of hole roughness on bolt stability were discussed. Bolt axial failure was not observed within the range of the studied parameters; however, a combination of high overburden depth, a bedding plane located at 2 to 3 ft from the roofline or a low coefficient of friction along the bedding plane caused strata sliding and shears failure in the bolt. Also, in the case of a weak immediate roof, the shear stress at the grout/rock interface could exceed its ultimate capacity lead to slippage.

Jan 1, 2004

By G. E. S. Valadao, J. D. Miller, C. L. Lin

Filtration is an important solid liquid separation technology employed widely in the mineral processing industries. The effectiveness of the filtration operation can be influenced by numerous variables, related to the particulate phase, the slurry rheology and the equipment. The classical approach for analysis is based on Darcy's law. Knowledge of the cake poremicro structure and its correlation to macroscopic cake properties is required to model the filtration operation from a fundamental point of view. Since cake formation seems to occur randomly, a 3D Monte Carlo method was used to simulate cake formation. The configuration for simulation was a space with width of 500 m, length of 500 m and height of 4000 m. Size distributions of five different industrial products whose particle size distributions follow the Rosin Rammler distribution function were used. The particle shape was assumed to be spherical. The simulated cake structures were described in terms of volume porosity (volume of pore space per unit volume of cake) and surface porosity (area of pore space per unit area of a cross section). The results indicate: 1) it is possible to simulate 3D packing, which mimics cake structure, using the Monte Carlo method,2) segregation phenomena occurs during simulated cake formation, 3) the values of calculated porosity for simulated samples B, C, D, and E were lower than those determined for corresponding industrial products Br, Cr, Dr, and Er, and 4)some structures of simulated samples seem to correlate with laboratory leaf test data obtained for different products from plant operations.

Jan 1, 1999

By A. Adu-Acheampong

Stope instability at Ashanti Goldfields Company Ltd. (AGC) is a major concern. Using information from field mapping, major discontinuity sets were defined, Rock Quality Designation (RQD) was determined. The stability of wedges in the stope walls was assessed using the commercially available computer program UNWEDGE(Rock Science, 1992). Analytical results indicate that the presence of graphite infilling in joints contributes to instability, while steeply dipping joints control wedge slabbing and wedge toppling in the hanging wall. Stable stope widths and dimensions were determined to range from8.1 to 30 meters (m).

Jan 1, 2003

By T. McKeon, G. Luttrell

Spiral separators are commonly used to upgrade sand-sized particles in both the coal and mineral processing industries. Many plants utilize multiple stages of cleaning and/or scavenging spirals to improve recovery and/or final product grade. Field studies suggest, however, that the layout of industrial spiral circuits is often less than optimal. This oversight can usually be attributed to a failure by plant designers to consider fundamental process engineering rules that govern the layout of complex separation circuits. This article reviews some of these important rules as specifically applied to multistage spiral circuit design. Two industrial case studies, one involving the upgrading of heavy mineral sands and a second involving the cleaning of fine coal, are presented to illustrate the impact of good design protocols on spiral circuit performance.

Jan 1, 2007

By I. Gombköto, J. Bohm

"In Europe, and therefore in Hungary opening a new mine is harder and harder. Depletion of mines, unfavourable legal and economic changes, and growing public concerns are the main reasons. Social and economic interests require total utilization of mineral raw materials of the operating mines, and furthermore utilization of waste heaps of the former mines. There are 5-6000 waste heaps of the operating and the closed mines in Hungary. 2000 of these waste heaps have already been estimated, and researches show that total amount of waste heaps can be calculated to 1 billion tones. These researches left out of consideration waste heaps exploited and placed in deep lignite mining. In several projects and researches we analysed processing of waste heap and possibilities to use its components. A processing technology for utilizing waste heaps has been developed based on laboratory and pilot plant tests. Great amount of useful materials of quarrying waste heaps can be utilized with this technology. Tests were also done for processing waste heap of a former ferrous metals mining. The developed processing technology contributes to use these waste heaps as aggregate for cement industry, as dielectric and aggregate for construction. The essay presents in details main characteristics of waste heaps, technologies already used for processing waste heaps of quarrying and ferrous metals mining, mass balances and qualitative parameters of the end products."

Jan 1, 2011

By J. D. Potts

Installation of a horizontal air blocking shelf around the inside perimeter of the surface mining drill deck shroud is proposed to improve dust capture. Without the use of this shelf, a strong coanda effect airflow pattern results in dust leakage to the environment, especially at the shroud-to-ground interface. Bailing air exits the drill hole and travels along the drill steel to the underside of the table, where it fans out across the bottom of the drill table and continues down the sides of the shroud. This dust-laden bailing air then strikes the ground and fans out under gaps between the shroud and the ground. The proposed shelf prevents dust-laden air from striking the ground by redirecting it toward the center of the enclosure, where it can be captured. Laboratory tests demonstrated that the shelf reduced dust levels outside of the shroud by 81% under operating conditions consisting of a 1.9:1 collector to bailing airflow ratio, and a 5.1-cm (2-in) gap between the shroud and ground. The shelf was 15.2-cm (6-in) wide and located at a height equal to 2/3 the distance measured from the bottom of the shroud to the bottom of the drill table. The air blocking shelf was also capable of overcoming the adverse impact of vertical leakage along the shroud seams as long as this leakage was confined to an area below the horizontal plane defined by the shelf location.

Jan 1, 2009

By G. Biles, K. Loughran, R. Anand

The Eskay Creek Mine, a high-grade gold and silver underground mine in northwestern British Columbia started operations in late 1994. For the first three years of operation, ore was crushed to minus 2 inch; blended to satisfy smelter terms and direct shipped to smelters in Japan and Canada. Before commencing the above operations, preliminary evaluations had indicated that an extremely complex metallurgical facility, requiring a large capital investment, would be required to recover the precious and other economic metals. Subsequently markets for raw ore were identified and underground mining and ore transportation operations, at a nominal production rate of 300 tonnes per day, were commenced. Exploration diamond drilling in 1995 and 1996 discovered additional lower grade mineralised zones, which are less economic or uneconomic as direct shipping ore. Test work demonstrated that these lower grade zones could be upgraded to marketable concentrates in a simple flotation mill. The mill was built in 1997 and has been in operation since late 1997. The mining rate now has increased to 400 tonnes per day including 250 tonnes per day of the direct shipping ore and 150tonnes per day of the mill ore. Prime Resources Group Inc. wholly owns the Eskay Creek Mine. Homestake Canada Inc. owns 50.6% of Prime’s shares and manages and operates the mine on Prime’s behalf. This paper discusses the mining and milling operations as well as ore shipment and smelter contracts' administration.

Jan 1, 1999

By A. Martikainen

Field tests concerning a fog mesh method for fog removal are discussed. The first tests were performed at the Pyhäsalmi Mine, Finland. As this study gave promising results, further studies were completed at the Orivesi Mine. The results of these most recent field tests are presented and the two studies are compared. The Orivesi test set consisted of four materials. These included air filter fabric, fibrous filter fabric, a plastic greenhouse mesh, and an aluminium mosquito net. The variation of the Orivesi results was more noticeable than what was found previously. The best fog removal effect of all tests was achieved with the aluminium mosquito net, while the plastic green-house mesh performed worst. The humidity reduction by aluminium net was more profound than any of its precedents. More mesh materials will be tested in the near future.

Jan 1, 2007

By S. M. Carpenter

In response to the FY2008 Consolidated Appropriations Act (H.R. 2764; Public Law 110?161), the United States Environmental Protection Agency (USEPA) issued the final Mandatory Reporting of Greenhouse Gases Rule (MRR). The rule, signed by the USEPA Administrator, Lisa Jackson, on September 22, 2009, requires reporting of greenhouse gas (GHG) emissions from large sources and suppliers in the United States, and is intended to collect accurate and timely emissions data to inform future policy decisions. The MRR will go into effect on January 1, 2010, and a report of the total emissions for calendar year 2010 will be due to the USEPA by March 31, 2011. Under the final MRR, suppliers of fossil fuels or industrial greenhouse gases, manufacturers of vehicles and engines, and certain facilities that emit 25,000 metric tons or more per year of GHG emissions are required to submit annual reports to the USEPA. The gases covered by the rule are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFC), perfluorocarbons (PFC), sulfur hexafluoride (SF6), and other fluorinated gases as outlined in Table A-1 of Subpart A of the MRR, which is also provided in Appendix A of this report.

Jan 1, 2011

By Steve Kral

In 2002, many in the mining industry — companies, academia and government — realized that the industry would soon be facing a serious shortfall in salaried and hourly employees. Depending on whose numbers are to be believed, 20 percent to 50 percent of current mining professionals are expected to retire within five to 10 years. And there are not enough students currently enrolled in mineral-related programs to the fill the need. Part of the impending shortage in professionals was brought on by the industry’s negative image, which discouraged students from enrolling in mining engineering programs. Another part was that the industry was in the doldrums and was seen by the public as a dying industry.

Jan 1, 2006

By J. Hollow, D. Walsh

The Fort Knox Mine is located in Alaska’s interior, where the average ambient air temperatures range from -24oC in January to 16oC in July. The mill processes a free milling gold ore utilizing both a gravity recovery circuit and a conventional cyanide leach/carbon-in-pulp circuits. Mathematical models have been developed to accurately predict the impact of leach circuit slurry temperature on gold leach, carbon adsorption and cyanide destruction kinetics. Additionally, an energy balance approach has been used to model the seasonal variations in slurry temperatures throughout the Fort Knox mill. The energy balance model, combined with the kinetics models previously developed to predict plant performance, was used to justify a tailing thickener installation at the Fort Knox Mine. This paper describes the development of the energy balance model and its prediction of plant performance assuming a tailings wash thickener to reduce heat loss from the mill. Also presented is an analysis of the post project plant performance that validates the model and shows the mine produced an additional 596 kg (19,155 ounces) of gold, while reducing mill reagent costs by $6,302,000 during the first 38 months of operation.

Jan 1, 2007

By D. Lawrence, H. Lawrence, G. Saevil

Plant operators in the mineral processing industry have been implementing expert systems for several years now, with the intent to increase production and reduce costs. Most systems have been installed on grinding circuits of some type and have proven that the technology is viable in that application. However, few applications on other processes have been attempted for various reasons, such as lack of reference sites, complexity of the process, lack of suitable measurements and lack of confidence in the technology. The successful application of an expert system on an Alumina Calcining kiln is the first such application in the West Indies Alumina Company (Windalco), and demonstrates how this technology can be successfully applied to other processes. The key objective of an expert system is to optimize the process. To achieve this the process must first be stabilized, followed by optimization of the operating parameters. The steps taken by this expert system to optimize the process are: • Check for abnormal conditions and deal with them using a prioritized set of special actions. • Use a selection of rule blocks to stabilize the process. • Once the process is stable, achieve additional benefits through further optimization of the process. The potential benefits that a user can expect to achieve through installing an expert system can be assessed on the basis that performance will improve from that of an "average operator" to that of the "best operator" performing at his optimum for 24 hours a day, every day. The quantifiable process benefits include: • Increased production • More consistent product quality • Reduced operating costs • Reduced standard deviation of key variables • Consistent plant operation The success of this project was measured in several ways: project implementation, realised economic benefits, and realised non-economic benefits. With a commitment to maintain the system over the long term, the longevity of the system is assured and will become an important part of the Alumina Calcining control strategy at Windalco. This paper discusses the various phases of implementing the ABB Expert Optimizer expert system, what the benefits were and the procedure that is in place to maintain the system to ensure continued long term success.

Jan 1, 2002

By Lawrence H. Roth

Past failures of coal refuse embankments have resulted in intensified efforts in inspections of coal refuse sites by the Mining. Enforcement, and Safety Administration (MESA). MESA inspections however, are mainly qualitative and are often time consuming, Therefore, in August 1975 CH2M HILL was awarded a contract to identify, develop, and test a rapid system for monitoring coal refuse embankments to aid in MESA inspections. The rapid monitoring system developed uses convergent and vertical photography from conventional fixed-wing aircraft. The system was tested on an active landslide and on two coal refuse facilities using both black and white and color infrared film. Field tests showed the system was capable of accurate measurement while providing qualitative data through photo interpretation. The accuracy of the system allows it to be used to monitor coal refuse embankments, tailings dams, major earth dams, and natural slopes. Based on CH2M HILL results cost for monitoring by rapid system was approximately 25 percent of cost by conventional ground survey.

Jan 1, 1980

By K. Oraee

Mining Ventures are considered as high risk projects and therefore managing the risks is inevitable. Risk assessment is an important part of the complex process of risk management, hence applying appropriated and practical methods for ranking the risks associated with projects, can help to perform a better risk management. In this research the applicability of using Techniques for Order Preference by Similarity to Ideal Solution (TOPSIS) method for risk ranking in an underground mine, extracting by block caving method, was studied. Via this method, the risk associated with reserve estimation ranked as the first while in conventional method (P-I Matrix method) located in the sixteenth. Also there were significant differences in ranks of the other risks. Considering the more criteria, with different weights, in comparison with conventional methods, the results comprised from TOPSIS method are more reliable. By implementing this method risks are ranked better and more realistic and consequently then will be managed more efficient.

Jan 1, 2011

By F. Calizaya

The PT Freeport Indonesia‘s Deep Ore Zone(DOZ) copper deposit is located in the province of Irian-Jaya, Indonesia. Currently, a block cave mine is being developed around this deposit. Production is scheduled to start in year 2000 and to ramp up to25,000 tpd by year 2003. The air quantity requirement for this mine is equal to 780 m3/s. To supply this quantity, the mine will require five centrifugal fans (one 450 and four 750 kW fans). This study summarizes the technical aspects related to the installation and commissioning of one of these fans. The fan was installed on the surface in a parallel arrangement with two others. It has a design capacity of 240 m3/s of air at 2.2 kPa of static pressure. The study presents the installation details from the underground shaft excavation and portal development through fan testing and commissioning. It also presents the results of a monitoring system that was installed to determine the fan duties.

Jan 1, 2000

Many states rely upon the Pennsylvania 1957 “Gas Well Pillar Study” to evaluate the coal barrier surrounding gas wells (Commonwealth of Pennsylvania, 1957). The study included 77 gas well failure cases that occurred in the Pittsburgh and Freeport coal seams over a 25-year span. At the time, coal was mined using the room-and-pillar mining method with full or partial pillar recovery, and square or rectangle pillars surrounding the gas wells were left to protect the wells. The study provided guidelines for pillar sizes under different overburden depths up to 700 ft. The 1957 study has also been used to determine gas well pillar sizes in longwall mines since longwall mining began in the 1970s. The original study was developed for room-and-pillar mining and could be applied to gas wells in longwall chain pillars under shallow cover. However, under deep cover, severe deformations in gas wells have occurred in longwall chain pillars. Presently, with a better understanding of coal pillar mechanics, new insight into subsidence movements induced by retreat mining, and advances in numerical modeling, it has become both critically important and feasible to evaluate the adequacy of the 1957 study for longwall gas well pillars. In this paper, the data from the 1957 study is analyzed from a new perspective by considering various factors, including overburden depth, failure location, failure time, pillar safety factor (SF), and floor pressure. The pillar SF and floor pressure are calculated by considering abutment pressure induced by full pillar recovery. A statistical analysis is performed to find correlations between various factors and helps identify the most significant factors for the stability of gas wells influenced by retreat mining. Through analyzing the data from the 1957 study, the guidelines for gas well pillars in the 1957 study are evaluated for their adequacy for room-and-pillar mining and their applicability to longwall mining. Numerical modeling is used to model the stability of gas wells by quantifying the mining-induced stresses in gas well casings. Results of this study indicate that the guidelines in the 1957 study may be appropriate for pillars protecting conventional gas wells in both room-and-pillar mining and longwall mining under overburden depths up to 700 ft but may not be sufficient for protective pillars under deep cover. The current evaluation of the 1957 study provides not only insights about potential gas well failures caused by retreat mining but also implications for what critical considerations should be considered to protect gas wells in longwall mining.

Jul 28, 2020

By R. J. R. Cornelissen

The elimination of the incidence of silicosis in employees in industries such as mining and pottery is an ongoing international initiative. After many decades of industrial activity in these industries and many dollars spent on preventative measures, silicosis is still occurring. The exposure-prevention measures taken so far have certainly improved the working environment dust concentrations; however, the illness is still regularly diagnosed in workers. More funding is needed for interventions to improve working conditions. Many aspects of dust prevention and suppression will be researched and exposure assessment methodologies and equipment will need to be reviewed for the purposes of improvements in effectiveness. This paper presents results from laboratory tests carried out on gravimetric sampling pumps and cyclones. It highlights the erratic flow produced by gravimetric pumps of three different manufacturers who claim their respective pumps are equipped with flow stabilisers. The standard BS EN 1232:1997 is used as a basis for the tests. A method, albeit impractical for fieldwork, is shown for the elimination of the pulsation in the flow. This method serves to prove the method and protocol used in this study. The pressure loss caused air-flow resistance of cyclones is measured. The air inlet aperture size of cyclones is measured. The large discrepancy in the two criteria between individual cyclones is shown. The paper concludes that all the pumps tested failed the prescribed limits of BS EN 1232:1997 regarding the pulsation of the gravimetric sampling flow. The difference in flow characteristics of the cyclones, together with the erratic flow produced by the pumps, throws into question the accuracy of the exposure assessments. It is suggested that substantial resources be channelled towards solving these flow problems in parallel with measures taken to reduce exposure. In principle, the accurate assessment of exposure and dust concentration levels is a prerequisite for effective management of the problem of silicosis.

Jan 1, 2009

By II Browne

After a decade of high copper prices, major mining companies are renewing their interest in purchasing operating properties and/or development of ore bodies. An existing operation carries with it a history that can present unique opportunities, while a greenfield operation allows for the establishment of a defined culture. Capital investments are distinctly different. A comparison of BHP Copper Robinson Operation, a greenfield property, and BHP Copper Tintaya Operation, a government owned Peruvian property, will provide insights into mining, concentrating and cultural differences between North and South American Operations.

Jan 1, 1997