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Kinetic Behaviour of Solid/Solid Separation of Ultrafine Particles in Aqueous Suspension

Sep 13, 2010

By Steve Tadolini

Underground roof falls can have devastating effects on the safety of operations personnel, and equipment, and seriously impact production. Immediate steps are usually taken to danger off and secure the area while clean-up efforts are designed and implemented. A critical step, often overlooked due to production demand, is the determination of - why the roof fall occurred so that additional occurrences can be avoided in future developments or what measures can be taken to identify areas that have similar ?symptoms?? Forensic engineering includes the investigation of materials, products, structures or components that fail or do not operate/function as intended. The authors define forensics in ground control engineering as the study of evidence discovered while examining underground roof falls by applying expert observational techniques and established mining engineering principles to determine the probable cause, hypothesize solutions, and design engineering safeguards to prevent reoccurrences. Simply stated, the primary steps in the forensics of underground roof fall techniques are: ? Assess regional and local conditions prior to the event. ? Assess post-event conditions. ? Hypothesize plausible ways in which the pre-event conditions ? became the post-event conditions.Search for evidence that either denies or supports the various ? hypotheses.Apply engineering skill to relate the various facts and evidence into a cohesive scenario of how the event may have occurred. This paper details the proposed technique by utilizing a roof fall case study that required the examination of five primary factors: mine design parameters, excavation geology, method of excavation, method of support, and mining cycle times.

Jan 1, 2009

By James A. Finch

"I offer a personal view of what the next 30 years holds for mineral processing. Re-stating that mineral processing will remain a vibrant industry in raw material production, growth opportunities in waste management are identified. The processing sequence familiar now (mining -mineral processing -extraction) will become more interwoven. In situ processing (i.e., milling underground) will evolve from concept to demonstration. Opportunities to exploit physical properties altered in chemical (pyro-and hydro-) processing will present themselves. In primary grinding, the path to AG/SAG milling will progress with little deviation but opportunities in regrinding are wide open. Flotation will see the trend to designing bubble/particle reactors accelerate simultaneously with a vigorous response from mechanical cell suppliers. Gravity separation remains a bastion of the lone inventor but I anticipate that the new lines will come from the waste management business. I finish by examining the ""research cycle"", identifying growth in small ""high tech"" companies and university research centres.IntroductionI have been asked to offer a personal view of""where we are going in mineral processing?"". Gazing into crystal balls is quite a cottage industry as we approach the end of the millennium. Academics are often asked to assume the role of visionary, I presume because it is considered in their mandate, to reflect and philosophize (or, less charitably, because they are considered to have the time). Since this is the 30th Annual Canadian Mineral Processors Operators Conference, I am tempted to suggest the next 30 years as my frame of reference. This is about equivalent to one engineer's career or, given it takes typically 15 years to go from concept to realization in mineral process engineering (Napier-Munn, l 997a), about 2 ""invention cycles"". With this length of cycle, much that is familiar now will remain so over the 30 years.Research and development (R&D) is in response to need. The overarching need in mining is to find new ore bodies. Process developments cannot compensate for a depleting deposit or a declining commodity price. Mineral processing R&D is characterized by incremental gains, aimed at pushing the mine down the cost per tonne league table. Breakthroughs are the exception (flotation at the turn of the century was one). This must be kept in mind when trying to predict the future in our business."

Jan 1, 1998

By G C. Sen

All mining and quarrying operations that employ blasting to fragment and move broken ground have a price to pay for æby-productsÆ such as vibration and noise. These æby-productsÆ cannot be eliminated but they can be controlled and modern blasting techniques have improved to the point that excessive environmental restrictions can be adhered to whilst maintaining acceptable production rates and quality. Accurate measurement is the key to control, and as the environmental limits are becoming tighter, the proper way to measure vibrations from blasting operations becomes an integral part of the mining or quarrying operations. The basic vibration monitoring system consists of a primary sensor connected to a data logger and computer software for the analysis of the signal received and recorded. Currently, as with all fields of measurement, much improvement has occurred over the past decade, and electronic devices are much more accurate and reliable. Data analysis has also improved considerably with the computing power that is available to field operatives today. Mounting the primary sensor has been often overlooked in supposed æstandardsÆ with procedures such as double sided tape, resting on a flat surface provided the vibration level is less than a given amount. But if it is worth going to the expense of the monitoring equipment and manpower, surely it is worth a little extra effort to ensure the primary sensor is coupled to the ground effectively. The primary sensor must move with the ground and measure this movement; so if the primary sensor is allowed to move without respect to the ground (ie poor coupling to the ground) then a false record of the physical event will be measured. This scenario can easily be a practical reality if the primary sensor coupling method to the ground is not effective. In this study a number of mounting methods were fabricated and connected to similar data monitors and a series of ænormalÆ production blasts were used as the vibration source. These mounting devices were measured against an in-house procedure (the æstandardÆ) and the relative merits compared. A laboratory investigation was also carried out to look at the physical parameters of the æsoil and their effect on vibration attenuation of the in-house standard method.

Jan 1, 1999

By W. G. Willson, D. E. Walsh, B. Irwin

Low-rank coal (LRC) drying processes are generally categorized by operating temperature, drying environment and type of feed (either sized or ground coal). Within these broad categories, drying processes differ according to the type of drying equipment and methods of quenching and stabilizing the dried products. This paper focuses on the produce quality of various LRC drying processes including conventional low and high temperature evaporative drying and non-evaporative, hydrothermal drying. The former may be preferred if the dried product can be utilized immediately, but moisture reabsorption, spontaneous heating and fines production during handling are problems associated with longer term storage, transportation and utilization. Methods for reducing these problems are discussed. Hydrothermal processing is an advanced technology featuring high pressure, non-evaporative drying, which solves stability problems by producing a liquid feel.

Feb 24, 1997

By V. Galla

Waste rock facilities (WRF) generally have a large footprint depending on the strip ratio the mine plan provides. Considerable planning is involved during the initial phase of the mine plan regarding the location of the WRF. As the mining operations are commenced the locations of the WRF change accordingly with the variations in the mine plan involving feedback and support from local communities and stakeholders. Waste rock facilities management becomes challenging when the area available for placement is limited due to terrain topography, environmental and permitting constraints. Risks associated in the design of waste rock facilities constitute particle size of rock, chemistry associated with the rock for reactivity and stability of the over all facility. This paper will provide some insights on designing, scheduling and managing a WRF. Emphasis on geotechnical, geophysics and geochemistry aspects of waste rock with reference to design, construction process and scheduling of WRF are also presented. Design improvements in the reclamation slope of WRF for erosion control will be discussed. Continuous improvement (CI) methodology will be introduced in the process of WRF operations. Current practices and future recommendations towards sustainability and consistency in operating WRF will be discussed in conclusion.

Jan 1, 2011

By D. V. Gaffney

This report presents the results of a three-phase investigation of the feasibility of using cemented coal waste in active underground coal mines to prevent mine subsidence. Coal caste was broadly defines to include waste from both coal preparation plants and coal-fired power plants. Underground systems with potential for cemented backfill are determined through identification of current mining methods and available technologies for cemented backfilling and consideration of materials and systems constraints upon mining and backfilling integration technical concerns including operation, health and safety, materials utilization, environmental impact, applicability and techni¬cal status are assessed for six (6) systems which were identified as potentially feasible. Two (2) of these systems are conceptualized in a hypothetical case history and developed to further assess their operational and economic feasibility. Comparisons of costs among both systems and with costs of surface disposal are presented. Also presented are the conclusions reached concerning the present feasibility of using cemented backfill in active coal mines and potential avenues for further research. Appendices contain further consideration for design of cemented mixtures to be used in backfilling, the results of laboratory testing of mixtures rich varying concentrations c: waste products and cementing agents, and an annealed bibliography

Jan 1, 1981

By S. Uddin

An integrated device has been developed to measure sedimentation potential, conductivity and pH simultaneously of particulate systems. Maxwell?s model was used to calculate volume fraction of solid from the conductivity data. In this approach, all system variables are known and zeta potential can be calculated from Smoluchowski?s equation. The technique is validated by comparing zeta potential vs. pH for alumina and silica suspensions with electrophoresis measurements. The technique was extended to mixed alumina/silica systems. Sufficient column height along with size difference between the two minerals allowed gravity fractionation during settling. Sedimentation potential measured over time identified the transition from one mineral to the next. Using XRD analysis the results supported the correlation between surface charge and sample composition. This is a step towards characterizing surface charge of mixed systems of interest in mineral processing.

Jan 1, 2010

By J. T. Jordaan

Paper written on project work carried out in partial fulfilment of B. Eng (Mining Engineering) degree This paper addresses the critical parameters that need to be considered when designing a mechanized bord-and-pillar mining layout for a narrow tabular steep dipping orebody. These parameters are : ?Reef dip ?Reef width ?Geological structures within the orebody ?Physical dimensions of the selection of machines ?Gradeability of the selection of machines. The main objective in designing such a layout is to maximize machine efficiencies whilst minimizing dilution. This methodology was then applied in the design of a mechanized bord-and-pillar mining layout for a given piece of ground (Vlakpoort and Moddergat) using a given selection of machines. This piece of ground contains the PGM bearing UG2 Reef with an average thickness of 124 cm and dipping at 18°withadverse strike and dip changes. Two bord-and-pillar layouts were designed for this area. Layout 1 is characterized by the use of strike conveyors to convey ore on strike with an average LHD hauling distance of 35 m. Layout2 uses LHDs for all on strike conveyance of ore with an average hauling distance of 75 m. These two layouts were then technically and financially compared. It was concluded that layout 1 is theoretically superior but layout 2 was chosen due to its greater flexibility and probability of operational success. Layout 2 was also compared to conventional mining and it was concluded to be more economically feasible. However the latter is a proven mining method in these conditions and has a lower risk operational failure. Bord-and-pillar mining has some favourable promises such as improving labour difficulties, lowering operating costs and providing safer working conditions. The success of mechanized bord-and-pillar mining in narrow tabular steep dipping orebodies will depend on the extent of the research and development efforts which need to create and innovate technologies to overcome some of the current limitations stated in the above-mentioned parameters.

Jan 1, 2003

By J. C. Willett, J. R. Sanfilipo, P. D. Warwick

The U.S. Geological Survey has conducted an assessment of the Nation’s coal deposits that potentially could be mined during the next 30 or more years. For the Gulf Coastal Plain region, the assessment includes reviews of the stratigraphy, coal quality and resources, and coalbed methane potential of the Cretaceous, Paleocene, and Eocene coal deposits in the region. The results of these efforts are a series of digital maps, text, and tables published in CD-ROM format. Although abundant coal resources are available in the Gulf Coast region, coal quality issues may limit large-scale development in the future. Additional data are required to better evaluate the coalbed methane resource potential for the Gulf Coast region.

Jan 1, 2001

By P. Brad Marchant

"To properly evaluate bioleaching as a commercial alternative for sulphide concentrate oxidation, to enhance cyanidation response, it was necessary to define and optimize critical operating variables outside of the laboratory under less than ideal conditions. A complete bioleach testing laboratory was installed at Equity Silver Mines to aid in pilot plant flowsheet development.A continuous pilot scale bioleach circuit was constructed to provide data for meaningful valuation of biotechnology on a plant scale. The important operating and design parameters for pilot plant testing are described. Plant scale feasibility and design considerations, to treat a refractory pyrite/arsenopyrite concentrate produced from flotation tailing, are discussed. 1.0 BACKGROUNDEquity Silver Mines Limited is located 37 km southeast of Houston in central British Columbia. A 70% owned subsidiary of Placer Development Limited, Equity is Canada's largest open pit silver producer. Ore reserves were estimated at 28 million tonnes grading 106 g Ag/t, 0.96 g Au/t, and 0.38% Cu from two pits, the Southern Tail and the Main Zone. Detailed geology and mineralogy has been described previously(1,2).The concentrator flowsheet consists of conventional crushing, grinding, flotation, and dewatering circuits processing 5 300 tonnes per day of new mill feed. The resultant Cu/Ag/Au concentrate is trucked to Prince Rupert for shipment to market. Mill tailing reports to a closed circuit pond from which mill process water is recycled. Details of the concentrator process have been reported( 2,3).Production in the Southern Tail pit, from July 1980 to March 1984, resulted in mill tailing averaging 0.9 g Au/t and slightly more than 20 g Ag/t. Historic data indicate that unrecovered gold is associated with arsenopyrite and silver losses with unliberated tetrahedrite or minor silve,, bearing sulphosalts. Main Zone mill tailing, which commenced production in March 1984, contains approximately 0.5 g Au/t which is probably associated by majority with silver bearing minerals and pyrite while silver losses, 30-40 g Ag/t, are associated with unliberated silver and antimony bearing minerals."

Jan 1, 1985

Population growth, social inequality, pollution, global warming, poverty, overexploitation of natural resources and biodiversity loss, are a few examples of the many challenges facing the world today. Sustainable development is about meeting these challenges and improving the standard of living for the benefit of the maximum number of people. These issues concern governments, communities, environmental and social action groups and individuals all over the world. Business too, has a fundamental role to play in delivering sustainable development. In particular, sustainable development is becoming increasingly recognised as a critical issue for the oil and gas industry to address and act upon. BP is committed to positively respond to the challenges posed by the objective of sustainable development.

Jan 1, 2002

By Bruce Hebblewhite

Australia’s Minerals Tertiary Education Council (MTEC) has achieved several successes during its first three years of operation. This initiative was developed through the Minerals Council of Australia, in conjunction with three partner universities involved in mining engineering education. The partner universities are the University of New South Wales (UNSW); Curtin University, the West Australian School of Mines (WASM); and the University of Queensland (UQ). The collaboration between these partner universities and industry has led to the development of shared course material, cross-institutional teaching arrangements, and the development of a number of flexible, distance-based delivery programs. This article then discusses future initiatives. Importantly, the challenge is the future initiative planned to cement this collaboration by the formation of a “virtual” national school of mining engineering: Mining Education Australia (MEA). This will provide a common third and fourth year program to all three universities beginning in 2007. The common program will involve innovative teaching and learning arrangements, greater student exchange potential and a more significant input by industry into the education process.

Jan 1, 2006

Mineral exploration and mining in New Zealand has had almost five years of new legislation. The requirement for different consents is a challenging, time consuming, expensive exercise but in most cases the new procedure is working, although the matter of obtaining access to land is still a major issue. Priority is critical. After lodgment of an application for a minerals permit there are many other matters to address such as identifying land owners, occupiers and administrators, preparation of access applications, consultation and preparation of various resource consent applications.

Jan 1, 1996

By James D. Noll, Eileen Birch

In a previous study, the e?cacy of commercial and prototype impactors for sampling diesel particulate matter (DPM) in coal mines was investigated. Laboratory and ?eld samples were collected on quartz-?ber ?lters and analyzed for organic and elemental carbon. Coal dust contributed a minimal amount of elemental carbon when commercial cascade impactors and prototype impactors, designed by the University of Minnesota (UMN) and the US Bureau of Mines (BOM), were used to collect submicrometer dust fractions. Other impactors were not as e?ective at excluding coal dust. The impactors evaluated in that study were either not commercially available or were multi-stage, expensive, and di?cult to use for personal measurements. A commercial version of the BOM impactor, called the DPM Cassette, was recently introduced by SKCs. Tests were conducted to evaluate the performance of the DPM Cassette for measuring diesel-source elemental carbon in the presence of coal dust. Bituminous coals from three mines in two di?erent coal provinces were examined. The dust particle diameters were small and the coal dust contained a high percentage of carbon, there by giving a worst-case condition for non-anthracite coal mines. Results for the DPM Cassette were essentially identical to those obtained by the BOM impactors in a previous study. At a respirable coal dust concentration of 5.46mg m3, which is 3.8 times the regulatory limit, the DPM Cassette collected only 34µg m3 of coal-source elemental carbon.

By D. Hopkins, D. Türler, R. D. Giauque, W. B. Davis, M. Karaca

In a highly collaborative research and development project with mining and university partners, sensors and data-analysis tools are being developed for rock-mass characterization and real-time measurement of mineral content. Determining mineralogy prior to mucking in an open-pit mine is important for routing the material to the appropriate processing stream. A possible alternative to lab assay of dust and cuttings obtained from drill holes is continuous on-line sampling and real-time x-ray fluorescence (XRF) spectroscopy. Results presented demonstrate that statistical analyses combined with XRF data can be employed to identify minerals and, possibly, different rock types. The objective is to create a detailed three-dimensional mineralogical map in real time that would improve downstream process efficiency.

Jan 1, 2002

By M Furche, U Noell, C Grissemann, J A. Meima, T Graupner, A Romero-Baena

The mining residues at the abandoned copper mine site Pe±a de Hierro, located at the headwaters of the Rio Tinto, contribute substantially to the pollution of the river with high loads of Fe, As, Pb, Zn and Cu. The pH of the outflow ranges from 0.5 to 2.4 in the dry and wet season, respectively. One heap composed of alternating layers, which were deposited parallel to the slope, was investigated in detail. Unsorted blocky to fine materials including gossan material, pyritic volcanics, ashes from pyrite combustion and slate were observed here. The top of the heap has a gentle slope and a hill contouring channel-rip morphology. The initially rugged surface was smoothed by heavy rainfalls filling up the pores of the blocky material with fines. These fines are capable of storing the water for a prolonged time, providing an extended reaction time close to surface in a dry climate at extremely low pH conditions (one to four). All minerals, pyrite, mica, barite and even quartz (probably due to F released from dissolved mica) have been digested and silica gel precipitates have formed a stable and quasi impermeable 100 ¦m layer with very low porosity (<5 area per cent, estimated using scanning electron microscopy (SEM) imaging). The silica layer itself is covered by Fe-oxy-hydroxide (ie FeOOH) coating (10 ¦m) and seals a 1 - 5 mm thick stable hardpan. This hardpan covers the channels and part of the rips almost entirely, guiding the rainwater subhorizontally towards slopes and sinkholes. By geoelectrical measurements, a 3D-resistivity model of the internal structures and the bedrock relief underlying the heap was generated. Internal structures relate to lithological changes in a number of layers. Zones of low resistivity may be attributed to washed-in fines within the mega pore system, whilst zones of high resistivity close to the surface probably reflect the advanced stage of drying beneath aging hardpans. The water movement at the surface was investigated by an artificial precipitation experiment with monitoring of the subsequent changes in resistivities.

Jan 1, 2008

By Greg Smith

This paper documents the use of bench testing equipment developed to enhance the understanding of, and improve upon, common roof bolt support systems. Most roof bolt systems consist of components that are covered within the scope of ASTM (American Society for Testing and Materials) standards. However, ASTM does not specify testing methods or performance standards for complete roof bolt ?systems?. It only designates testing methods and minimum performance standards for roof bolt ?components?. Improved understanding and continuous improvement of these systems is essential given the enormous impact that they have on the safety and profitability of underground mining operations. Bench testing equipment has been developed that effectively measures and records multiple points of deformation in a rock bolt support system while load is being applied. With this testing capability, an improved understanding of component and system stress distribution can be obtained and devices and methods for visual load indication can be developed. This paper is formatted as case studies where testing was performed to demonstrate load versus deformation profiles and to develop system improvement products.

Jan 1, 2012

By W. McMahon

Following the Sago Mine accident, the Mine Safety and Health Administration (MSHA) asked the U.S. Army Engineer Research and Development Center to study several possible methane explosion scenarios in the Sago coal mine. The study used a 1-ft resolution map of the mine to produce a 3-dimensional (3-D) model of a portion of the mine, including the sealed area where the explosion occurred. An advanced 3-D computational fluid dynamics (CFD) code was used to calculate the explosion pressures within the sealed area, on the mine seals, and in nearby regions of the mine. Based on the best available information on methane concentrations and assumptions on homogeneity and on layering and mix composition, three separate initial conditions of methane-air concentrations and location were studied. This paper discusses the CFD modeling technique, the results of the calculations, the challenges of conducting this type of modeling, and the advantages and limitations of CFD modeling of accident investigations of mine explosions.

Jan 1, 2009

Under the Town and Country Planning Act 1977 the Ministry of Works and Development has a responsibility for providing information to local and regional planning authorities on public works and matters of national development and importance, for the exercise of their responsibilities under this Act. One such matter which has recently become a source of concern is the development of South Island lignite. In 1979 the Ministry of' Energy produced a position statement outlining a programme of' research leading to the possible extraction of lignite in Southland or Central Otago for conversion into about 50 per cent of New Zealand's liquid fuel requirements by 1995. Understandably this possibility has caused considerable concern at the local level, expressed particularly by bodies such as Federated Farmers and the local authorities. In the absence of any factual knowledge short of mere conjecture been able to recommend to local authorities is that they limit their planning period to ten years. After this time more information regarding the size, nature, location and certainty of the proposal will permit a more accurate assessment of the implications of the York. While on holiday earlier this year I took the opportunity to visit opencast mining areas in Germany and England to gain an appreciation of the scale of impacts involved and discuss with those concerned the procedures used in planning for such operations. What follows is a brief description of these operations, a comparison with the likely development in this country and the extraction of what may be some relevant principles of' operation for the planning of an environmentally acceptable project. Please note that the views expressed in this paper are mine alone and are not necessarily those of the Ministry of Works and Development.

Jan 1, 1981