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By Hussin A. M. Ahmed

Oxidized coals are difficult to float. Therefore, in this paper, a special flotation procedure was investigated for upgrading this type of coal. The procedure is called direct contact flotation. It relies on mixing dry coal either with pure (anhydrous) flotation reagent(s) or microemulsion. By applying the new direct contact flotation procedure, a coal yield reaching > 95% using anhydrous flotation reagents was achieved, but with relatively high consumption of reagents (up to 30 g/kg). This high reagent consumption may be attributed to the fines included in the flotation feed (100% less than 0.5 mm, with 40% less than 75 µm). On the other hand, the clean coal yield was found to be approximately 88% when mixing dry oxidized coal with microemulsion droplets from dodecane and dodecyl tetra (ethylene glycol) ether (C12E4) in water at a total reagent dosage of 10 g/kg. The direct contact of coal either with unhydrous reagents or microemulsion also provided a high flotation selectivity.

May 1, 2012

By B. Oraee

Accurate estimation of equipment costs is a key factor in feasibility study and evaluation of design alternatives of mining projects. In this paper, capital and operation costs of backhoe loaders are estimated using multiple linear regression (MLR), based on principle component analysis (PCA). These cost functions are consisted of five independent variables; bucket size, digging depth, dump height, weight and horse power. The MLR is conducted in two steps. At the first correlation between independent variables is omitted using PCA technique. Thereafter, MLR functions are established using selected significant PCs and total cost functions are constituted as functions of initial variables. At the end, accuracy of functions are evaluated using mean absolute error rate method.

Jan 1, 2011

By J. K. Hrica, T. J. Orr, J. Navoyski, B. Macdonald, C. L. Hoebbel, J. L. Bellanca, B. Demich

Haul truck fatal accidents and injuries continue to be a significant concern for the mining industry. However, the availability of high-quality training materials continues to be limited. Near-miss incident accounts, if packaged well, could help fill this gap, because for every fatality, there are hundreds of reportable accidents and thousands of undocumented near misses. Researchers from the National Institute for Occupational Safety and Health (NIOSH) collected detailed accounts of 21 near-miss incidents in virtual interviews with mineworkers at surface mining operations across the country. From these interviews, researchers created four simulation videos. The videos bring these events to life through first-person retelling and various visual perspectives of actual events. Each video exemplifies a critical safety message and a common haul truck hazard. This paper describes the process of taking narratives and turning them into impactful visual stories. NIOSH plans to co-release these simulation videos with the Mine Safety and Health Administration (MSHA) to the mining industry to raise awareness and ultimately help reduce haul truck-related accidents and fatalities in mining.

Feb 1, 2023

By C. E. Semler

A multiyear program involving online, in-vessel exposures at Barrick Goldstrike Mines Inc. (BGMI) has provided information and experience about the materials and designs for brickwork linings in pressure oxidation autoclaves. A variety of brick and mortar products was evaluated. Properties before and after exposure were used to document the performance. Some benefits include the development of a new silicate mortar, a better understanding of brick requirements and increased autoclave operating time between maintenance shutdowns. BGMI operates six pressure oxidation autoclaves at its Eureka County, NV gold operation. These autoclave process 15.8 k/ld (17,500 stpd) of gold ore. Figure 1 is a flowsheet of the six autoclave circuits. The gold ore is refractory, in which the gold particles are mineralogically encapsulated on a micro- and submicroscopic level. The autoclaves are 4.4- m- (14-ft-) diam and 26 m (85 ft) long (tip-to-tip). Inside of each is a full brickwork (brick plus mortar) lining that divides the vessel into five compartments. Each compartment has a motor-driven agitator that keeps the slurry suspended and disperses the oxygen to enhance reaction. During autoclave operation, the conditions are steady state at 210° to 232° C (410° to 450° F) and 61 to 62 kPa (420-430 psi). As shown in Fig. 1, there are other accessory vessels (splash and flash towers) in the autoclave circuits that are also brickwork-lined. The linings used to date, other than small test sections, have all been acid-resistant fireclay bricks, bonded with alkali silicate mortar, PbO- based mortar and/or vinyl ester mortar, but mainly alkali silicate mortar.

Jan 1, 1997

By J. S. Gardner, K. E. Houston, A. Campoli

INTRODUCTION Disposal of coal refuse is a costly and challenging problem facing the coal industry today. After the Martin County Coal Company slurry spill and the subsequent regulatory changes state and federal agencies are now beginning to require companies to justify new slurry impoundments. The authors have performed an analysis of different means of disposing of coal refuse for a major coal producing company located in the eastern Kentucky coalfields (the name of which will be withheld for the purpose of this paper). The company’s existing slurry impoundment is nearing its maximum permitted elevation and also an elevation where it may come in contact with abandoned underground workings. Due to the increased concern with underground mine works near slurry impoundments, additional consideration was given to raising the existing impoundment. Several other alternatives were evaluated, including but not limited to raising the existing impoundment, constructing a new slurry impoundment, constructing slurry cells, belt presses and others. This alternatives analysis was performed as part of a Section 404 permit for a valley fill and is currently being reviewed by the U. S. Army Corp of Engineers. All of the known possible alternatives were discussed in detail in the analysis. Due to the findings of the alternatives analysis, the company considers the engineered construction of the proposed impoundment to be the most favorable option of all the other alternatives evaluated, from both an economic and environmental standpoint. ALTERNATIVES EVALUATION FOR COALREFUSE/SLURRY DISPOSAL Background The company currently operates several deep mines and employ over 300 people and produces over 3.9 clean Mt/a (4 million stpy) of high quality, low sulfur coal. Currently, coarse refuse is belted to a valley fill, while, fine refuse is pumped to the existing impoundment. Coarse refuse is trucked to the existing impoundment as needed for construction purposes. The average recovery is approximately 50%; therefore, over 3.9 Mt/a (4 million stpy) of coal refuse must also be separated and placed.

Jan 1, 2003

By Jonathan M. Pachter

Introduction The Bailey mining complex is located in Greene County, PA, in the Talley Run valley. It includes two Pittsburgh No. 8 seam deep mines (Bailey and Bailey No. 2), a coal preparation plant, and two refuse areas. Clean coal is shipped from the complex by way of a 24-km (15-mile) rail spur. It con¬nects to the Monongahela Railroad in Waynesburg, PA. In early 1981, Consolidation Coal Co. (Consol) began a permitting effort aimed at building the mine. Construction began in Dec. 1981, less than six months after the first application submittal. Clean coal was produced by the Bailey preparation plant in Sept. 1984. Several factors allowed quick permitting at Bailey. Effective project planning, including early formulation of a project planning team, and identification of red flag issues helped. So did innovative responses to environmental questions, and development of environmentally sound project designs. Forming a project planning team Consol management decided that Bailey mine construction had to begin in late 1981. A project permitting team was immediately formed to see that this goal was achieved. Team members included a project manager and personnel from Consol's engineering, environmental, and operating departments. Communications among all team members was crucial in obtaining the various state and Federal environmental permits. All project permitting team members participated in weekly meetings during application preparation. Discussions at these meetings ranged from recent public contacts, to application content, to environmental design considerations. Establishing a project manager was critical to the team's success. The project manager was responsible for seeing that permit acquisition, facility construction, and operation of the mining complex proceeded on schedule. The project manager had the final word, mediated disagreements, and frequently served as project spokesman to the public. Identifying red flag issues Red flag issues are those environmental factors with the most potential for delaying the schedule or stopping the project. The first red flag issue identified was organized local opposition. This opposition had completely derailed a US Soil Conservation Service proposal to build a multipurpose dam on Enlow Fork, a short distance

Jan 9, 1985

By Nancy L. Jackson, Leslie C. Thompson

Acid rock drainage is one of the most complex issues facing regulators and mining companies for management and remediation of mining wastes. All mining waste units, including open pits, underground workings, tailings, waste rock and leached spent ore have the potential to generate acidic leachate based on the acid generation or neutralization potential of the material. This paper uses a case study of the Walker Mine in northern California to give an overview of the available control and mitigation methods. Wetland design is emphasized as a low-cost alternative treatment option for wastewater remediation. The Walker Mine is located on the eastern flank of the Sierra Nevada, 20 miles north of Portola in Plumas County, California. The Walker Mine was an active copper mine between 1915 and 1941. During active mining, tailings were discharged into an area 1 mile west of the site at the confluence of Dolly Creek and Grizzly Creek. In addition, there were two main sources of metal-rich, acid waters impacting Dolly Creek: discharge from the mine tunnel portal, and seepage and surface runoff from waters contacting mine waste downslope from the portal area. A mine portal seal was installed in 1987 which prevented the majority of mine water drainage from further contaminating the area. Minor drainage from the portal and seeps discharge into a holding pond which overflows into Dolly Creek when elevation exceeds 6,200 feet. A site characterization study was performed to evaluate the potential water quality threat to Dolly Creek from mine tunnel discharge and waste rock seeps. Based on the results of this study several remedial options were investigated, both on a design and cost basis, to determine which abatement alternatives could be realistically implemented. The remedial options considered include both in situ containment (landfill, waste pile) or removal (backfilling into underground workings and/or sinkholes) of solid wastes. Waste water remedial options include long-term, seasonal treatment of the portal mine water, or long-term, passive treatment of portal discharge and waste pile leachate.

Jan 1, 1993

By R. Dorey

The Kennecott Ridgeway Mine in South Carolina is scheduled to complete mining and ore processing in the last quarter of 1999. Tailings are disposed in a 300 acre, lined tailings impoundment. To facilitate closure and reclamation, modification of the tailings impoundment operation has been adopted. Mining involved the sequenced development of two open pits. In 1996 mining of the South Pit was completed and backfilling of the pit with waste rock from the North Pit was initiated and will continue until mining ceases. Both pits will be reclaimed as fresh water lakes. This paper presents the physical, geochemical and hydrogeochemical evaluation of the operational and post operational management of the project. Comparison of the operational monitoring data against predicted performance is reviewed.

Jan 1, 1999

By Kal V. S. Sastry

Conventional iron ore balling circuits exhibit undesirable surging behavior which is known to result from uncontrolled occurrence of the mechanisms of nucleation, coalescence and layering. This study was undertaken to investigate the mechanism of pellet growth by layering. Several laboratory experiments have been carried out to delineate the effect of feed moisture content and feed quantity. This paper presents an analysis of the experimental results and a simple model to describe the layering process.

Jan 1, 1993

By T. P. Meloy

Like our wives, the comminution of brittle solids is easy to recognize but difficult to describe. However, describing it we must. Describing the fracture mechanism of brittle solids permits the eventual mathematical quantification of the results, process optimization and control strategies. This paper presents a physical model of brittle solid comminution that explains why the slope of the log-log size distribution curves have a slope of one or less in the smaller particle sizes. To develop the hypothesis, modifications of the Gaudin Meloy physical model are made. In brittle solids, comminution takes place by cracks propagating through the material. These cracks may bifurcate as they move. Cracks may terminate either on the original surface of the material, or on a secondary crack within the material formed earlier in the comminution process.

Jan 1, 1994

By R. Bruce Thorndycraft

This paper will describe several modifications to design of con­ventional oxide gold heap leaching. They are targeted at reduc­ing costs and simplifying heap operations. These modifications were conceptualized during consulting work on over 90 differ­ent heap leaches. In 1995, a unique opportunity arose to imme­diately apply all of these design concepts to the permitting and construction of a new facility at the American Girl Mine in southeastern California. American Girl Mine has operated since 1987. In April 1995, the mine faced a situation with grave consequences for cash flow. Approval for mining of a new ore zone, Oro Cruz, had just been granted, after lengthy delays by California regula­tors. All existing pad space would be filled by October. Only 6 months were available, and new pad siting and design were still undecided. Permitting of a new pad had not begun. Options were quickly reviewed. A strong criteria for pad site selection and design was ease of permitting. There was also a strong desire to install a system that would achieve better met­allurgical recovery and reduced operating costs, compared to previous heaps at this mine. One site offered the best chance for rapid permitting. It was the site of the original 1987-90 heap leach. This already dis­turbed ground contained 1.6 million tons of heaped ore. The old heap had just completed detoxification and was about to be signed off as a Group C waste, ready for reclamation. Instead of recontouring and revegetating the old heap, which the reclamation plan anticipated, we offered BLM and the County something even better. We proposed to off-load much of the detoxed old heap, and reuse the space. The off-loaded material would be back-filled into the original open pit, imme­diately adjacent. While the footprint of the proposed new pad was much larger, the reuse of disturbed ground, and backfilling of the open pit, had very strong appeal to the regulators. Our permitting strategy included the technical design of the proposed new facility. Many of the new design details also appealed to the regulators, particularly the "zero active ponds" concept.

Jan 1, 1996

By R. L. Atwood

This paper discusses the metallurgical and Manufacturing input to Merrill-Crowe plants. Topics treated are pregnant solution chemistry, clarification, degassing, zinc addition, product filtration, accounting, and costs.

Jan 1, 1985

By E. Taskin

Diasporic bauxite from the Mugla-Milas region was mechanically activated in a planetary mill for different activation times and the structural changes were examined by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and specific surface area analysis (BET ? Burnauer, Emmett and Teller). Non-activated and activated bauxite samples were leached directly in alkaline (Na2O) solution at atmospheric conditions and the activation procedure led to the amorphization and structural disordering of the diasporic bauxite structure, which increased the dissolution efficiency. Effects of milling speed, liquid/bauxite ratio and leaching time on alumina extraction in direct alkaline leaching of diasporic bauxite were also studied. The alumina extraction was ~7% for non-activated bauxite and ~70% for activated (75 minute) bauxite. Key words: Diasporic bauxite, Mechanical activation, Alkaline leaching, Alumina extraction

Jan 1, 2009

By Christopher J. Bise

INTRODUCTION The control of nuisance water in a mine is extremely important; left uncontrolled, nuisance water can have a severe effect on haulage, ventilation, production, and the health and safety of miners. To control water in mines, a four-step process is followed: (1) prevention, (2) collection, (3) transportation, and (4) treatment. This chapter will be devoted to the collection and transportation of mine water because prevention is usually dictated by pre-mining conditions and initial planning, while treatment is variable and highly site specific. A mine drainage system is nothing more than a collection of gathering points (sumps), machines that impart energy to the fluid (pumps), transportation ducts (pipes), and control devices (fittings, valves, etc.). A pump does not pull the fluid up the suction pipe; atmospheric or external pressure pushes the liquid up the suction pipe to the pump. All references in this chapter will be to centrifugal pumps, due to their popularity for mine drainage. PUMP CHARACTERISTIC CURVES The performance of a pump is plotted on a graph as an indication of its characteristic. To develop the data points, a test facility similar to that shown in Fig. 1 is established. The calibrated Venturi meter is used to measure quantity, the Bourdon gage measures pressure, and the wattmeter measures power input. Various discharge pressures are obtained by throttling with a gate valve in the discharge pipe. Quantity and power are measured at each of these pressure levels, giving the necessary data for plotting the characteristic curves. Fig. 2 shows a typical characteristic curve for a centrifugal pump. Notice that pressure is measured as so many feet of vertical water column above the outlet level, or head. Knowing the quantity (in gallons per minute), head (in feet), and power input (brake horsepower), the pump's efficiency can be plotted based upon the following relationship:

Jan 1, 1986

By F. Allen Meek

The Upshur Complex of Island Creek Coal Corp. consists of approximatly 35.000 acres of both surface and deep mine researves located in Upshur County West Virginia. The principle seams on the researve are the Middle and Lower Kittanning. Other mining in the area during the late 1960's and early 1970's produced surface mines that exhibited severely acidic drainage characteristics both during the mining phase, and after reclamation was completed. The Buckhannon River, the principal drainage for the area, is a high quality, lightly buffered stream, that is periodically stocked with trout. Because past mining had caused post mining acidic discharges and the Buckhannon River was a valuable recreational resource, mining permits for the area were put on hold by regulatory authorities, until solutions to the acid mine drainage questions could be addressed. In 1978, the director of the West Virginia Department of Natural Resources appointed a Task Force consisting of Industry, Regulatory. and Academlc participants. This Task Force was charged with gathering information and evaluating field procedures used during mining to prevent acidic mine drainage. In 1979, the group published a document titled "Suggested Guidelines for Mining in Potentially Acid Producing Overburdens" which summarized material handling and mining procedures that could be employed to help prevent the occurrence of post mining acid mine drainage. In 1982, a Technical Advisory Committee was appointed consisting of well known researchers in the field of acid mine drainage prediction and prevention. The group was charged with the task of conducting research in the field of acid mine drainage prevention. Mining conducted at the Upshur Complex between 1979 and 1986 employed various acid mine drainage preventative techniques recommended in the suggested guidelines manual and techniques concurrently being researched by the Technical Advisory Committee. Costs for the various techniques were documented and the resulting post-mining water monitored. The results of these evaluations are used by Island Creek in the planning of future mining operations in potentially acid prodcuing environments

Jan 1, 1991

By Ebrahim Farrokh

Ghomroud water conveyance tunnel project is under construction using shield Tunnel Boring Machines (TBM) for a total length in excess of 50 km. Phase 1 of the project included 36 km of tunnel divided into four lots (1, 2, 3, and 4) of nine km each. Lots 3 and 4 of this tunnel for a total length of 18 km were combined into one award and have been constructed using a double shield (DS) TBM or one path system. Extreme ground convergence in some sections of the tunnel has stalled TBM performance in early reaches, due to face collapse and shield jammings. This paper presents the latest update on the tunnel progress and impact of ground convergence on machine performance based on the information obtained from field observations. Also, the method and results of tunnel convergence measurements were studied in conjunction with geological parameters and an attempt was made to correlate TBM operational parameters and ground convergence. The result of the analysis indicates a good correlation between machine?s operational parameter and tunnel convergence and can be used as an indicator of the potential for high rates of convergence. An early warning on ground convergence is essential for taking precautionary measures to avoid TBM jamming and related long delays and costs.

By Kenneth F. Wyman

The following report details the successful construction of Contract 2A of the Three Rivers Water Quality Management Program, Intrenchment Creek Combined Sewer Overflow Conveyance System, in DeKalb County for the City of Atlanta, Georgia. The contract required construction of approximately 2878 m (9443 ft) of tunnel bored to an initial diameter of 7.95 m (26 ft 1 in), with provisions to concrete line those portions designated by the engineer to a finished internal diameter of 6.91 m (22 ft 8 in). Flanking the tunnel are two shafts. The upstream shaft was excavated to a nominal diameter of 4.87 m (16 ft) to accommodate a finished internal diameter of 3.66 m (12 ft). This shaft required a transition boot fully concrete lined to final dimensions of 6.91 m (22 ft 8 in) wide, 13.72 m (45 ft) long, and varying in height from 6.91 m (22 ft 8 in) to 12.80 m (42 ft). Associated work necessary to complete the contractual obligations included installation of 22.86 m (75 ft) of cut-and-cover box culvert, 484 m (1589 ft) of open-cut sewer installation in sizes ranging from 0.30 m (12 in) to 1.68 m (5 ft 6 in), one river crossing, 137.46 m (451 ft) of monolithic concrete trapezoidal channel, and installation of 19125 cu m (25000 cu yd) of select fill material compacted and graded to finished contours. The downstream shaft was excavated to a minimum diameter of 12.04 m (39 ft 6 in) and concrete lined to a finished internal diameter of 10.67 m (35 ft). Requirements here included installation of a complete pumping station with all mechanical, electrical, and structural elements necessary for dewatering the tunnel through the controlled use of four 250 hp submersible pumps discharging into the facilities of the Intrenchment Creek Water Pollution Plant. The objective of this project was to collect combined storm runoff and sanitary flows currently coursing through Intrenchment Creek

Jan 1, 1985

By J. Warmbrodt, D. Apel, D. Nutakor, L. Grayson, M. Hilgers

MinerSIM is an augmented reality system with integrated hypermedia that is suitable for training underground miners in the basics of using a jackleg drill to install rock bolts. While statistical evidence shows that rock bolting with such a drill has an inherent level of risk, it is conjectured that this can be mediated with adequate safety training outside of the actual mine environment using a variety of educational media including interactive three-dimensional images, games, animations, and videos to describe the mechanics of rock bolting and its principles. Ultimately, trainees will install rock bolts in an immersive environment mixed with real and virtual images generated via a gaming graphics engine. This paper will discuss considerations, implementation issues, and evaluation methodologies of the MinerSIM system.

Jan 1, 2007

By B. Stewart, R. Li

Coal waste materials inhibit the direct establishment of vegetation due to adverse physical and chemical properties, particularly low water retention and high potential acidity. The Moss #1 coal refuse pile is located in Dickenson County, Virginia, and was idled in the late 1980s with little topsoil resources available for final closure. The refuse was acidic (Total S = 0.38%; pH = 3.6), black in color and high (70%) in coarse fragments. The refuse also had a low water-holding capacity (4.5% in < 2.0-mm fraction). A small plot experiment was established on the refuse pile to evaluate the effects of liming rates (50% and 100% of lime requirements) and topsoil thickness (15, 30 and 60 cm) on vegetative growth and leachate quality. Liming and topsoil amendment increased the surface soil pH from <4.0 to >6.0 over a two-year period, which resulted in greater vegetative cover and biomass than the control plots. All topsoil treatments resulted in greater vegetative cover and biomass than plots treated with lime only. This was due to improved surface soil physical and chemical properties. A topsoil treatment of 60 cm gave the thickest vegetative cover and biomass yield. Such a treatment, however, would be cost-prohibitive at this location. Applica¬tion of 27Mg ha`1 of lime to the refuse surface along with 15 cm of topsoil produced acceptable two-year vegetative cover and biomass, and this appeared to be the optimal treatment for this particular situation. Both liming and topsoil had no affect on leachate pH and the electrical conductivity of leachates collected below the plots. This suggests that surface revegetation will have little effect on the quality of water draining through the pile. Therefore, long-term water-treatment requirements may not be reduced by successfully revegetating the pile surface.

Jan 1, 2000

By Brendan Demich, Brendan Macdonald, Timothy J. Orr, Jonathan K. Hrica, CASSANDRA L. HOEBBEL, Jason Navoyski, Jennica L. Bellanca

Haul truck fatal accidents and injuries continue to be a significant concern for the mining industry. However, the availability of high-quality training materials continues to be limited. Near-miss incident accounts, if packaged well, could help fill this gap, because for every fatality, there are hundreds of reportable accidents and thousands of undocumented near misses. Researchers from the National Institute for Occupational Safety and Health (NIOSH) collected detailed accounts of 21 near-miss incidents in virtual interviews with mineworkers at surface mining operations across the country. From these interviews, researchers created four simulation videos using the Unity game engine. The simulation videos bring these events to life through first-person retelling and various visual perspectives of actual events. Each video exemplifies a critical safety message and a common haul truck hazard. This paper describes the process of taking narratives and turning them into impactful visual stories using graphic simulation. NIOSH plans to co-release these simulation videos with the Mine Safety and Health Administration (MSHA) to the mining industry to raise awareness and ultimately help reduce haul truck-related accidents and fatalities in mining.

Jun 1, 2023