Search Documents

By Harry: Lobb Verakis

Mining operations have made tremendous strides in improving the safety of blasting as shown by the significant and continual decrease in fatalities and serious injuries. Advances in blasting technology and blasting practices have played a significant role in reducing fatalities and injuries. However, even with the decline of fatalities and injuries blast area security continues to be by far the leading factor in blasting accidents. Even though there continues to be an increase in the use of industrial explosives and blasting agents in the U.S.A., the decline in fatalities and injuries from blasting accidents has persisted.

Jan 1, 2010

A portable surface impedance meter has been tested extensively over a wide variety of geological formations both in Australia and elsewhere. It has proved a useful geophysical too] for relatively shallow mapping (i.e less than 100 metres depth) of faults, intrusions, dykes and conductive ore veins and can be used as a depth probe for overburden and glacial ice. Case studies involving coal seam mapping at Collide (Qld. Australia), galena ore vein location at Zeehan (Tas. Australia) and glacial ice probing on the Brewster Glacier (South Island, New Zealand) are detailed. The first results of a similar unit using a lower frequency with consequential increase in depth of penetration will be presented. The application of VLF measurements to monitor blasting in mines and in the location of earthquake epicentres will also he introduced.

Jan 1, 1987

By J. Y. Foley

Platinum-group elements (PGE) are preferentially associated with chromian spinels, including high-iron chromite, magnesian-chromian hercynite, and chromian magnetite in clinopyroxene-rich upper stratigraphic portions of the Tonsina ultramafic complex in southern Alaska. Ratios of Pt:Pt+Pd are proportional to chromium content in the associated chromian spinels. The maximum PGE content of geochemical rock samples from Dust Mountain is greater than 20.000 ppb (>0.6 oz/ton) with minor gold values. The maximum PGE content of tabled chromite concentrates is 3.430 ppb (0.1 oz/ton) at Dust Mountain. 1.029 ppb (0.03 oz/ton) at Sheep Hill, and 1,749 ppb (0.051 oz/ton) at Bernard Mountain. High-iron chromite at Dust Mountain yields tabled chromite concentrates with Cr:Fe ratios between 0.5 and 1.2. Lower PGE contents are found in more chromium-rich chromitites from Sheep Hill and Bernard Mountain that yield concentrates with Cr:Fe ratios between 1.0 and 2.8. Platinum-group minerals include amalgams. arsenides. PGE alloys, and sulfides. These minerals are between 3 and 40 microns in size and are concentrated along grain boundaries and fractures of metasomatically and hydrothermally altered chromian spinel grains.

Jan 1, 1987

By Enever J, Walton R, Wold M

Photoelastic and equivalent material model ling techniques for studying stresses and defor- mations and modes of failure in geological and engineering structures are described. The appli- cation of these techniques to the solution of tunnelling design problems is outlined. Models may contain heterogeneous components to simulate geological and man-made structures and may be two- or three-dimensional. Prototype construc- tion procedures and time dependent behaviour may be modelled. Examples of recent model studies carried out for the design of underground railway tunnels are given. Development of photoelastic and equi- valent material modelling techniques and facili- ties at the CSIRO, Division of Applied Geomech- anics are described, including a biaxial and triaxial frame for testing large scale two and three dimensional equivalent material models and components of full scale prototype structures.

Jan 1, 1976

Several coal preparation plants are presently "automated" to the extent of automatic sequencing and interlocking via digital means, together with closed loop control on various level and density circuits. This paper will explore the potential for second generation automation utilizing on-stream ash analysers and other measuring elements so as to optimize the total metallurgical process. This would enable maxim-ization of recovery, improved product homogeneity and minimum reagent consumption.

Jan 1, 1985

By N. F. Sather

Results of comprehensive trace element analyses of samples of Illinois #5 and #6 seam coals and the unquenched ashes obtained from gasification of these coals in a Lurgi reactor are reported and discussed. Areas where additional background information is needed for assessment of the environmental impact of trace element emissions from coal gasification are identified.

Jan 1, 1976

Two structurally and mineralogically distinct sulphiderich veins cross-cutting the disseminated sulphides of the Nairne Pyrite Member appear to be products of local remobilization of sulphides under fracture-induced free energy gradients during regional metamorphism and tectonic deformation.The contrasting mineralogy of the two vein types may have arisen as a result of differences in the structural orientation of the veins and!or the relative ages of the veins.

Jan 1, 1969

By Peter J. Nicholson

Since the reintroduction of soil mixing to the United States over 10 years ago, the work installed by soil mixing technology has grown dramatically. From an annual turnover of less than ten million dollars per year the volume of soil mixing put in place has grown to an estimated $40 million per year in the year 2000. The majority of work done to date has involved walls, either for excavation support, permanent retaining structures or hydraulic cut-off walls. The other major use for soil mixing has been for mass stabilization of soils whether for isolation of contaminants or for retaining structures. This paper will discuss the uses of and costs of typical soil mix structures. BACKGROUND Soil mixing is defined as the in-situ combining of reagents, typically cement, with native soils, the purpose being to modify or improve the ground. This history of soil mixing covers only the use of cement slurry, aggregated with soil in-situ by mechanical mixing methods only. Soil mixing by use of high-pressure hydraulic means, also known as Jet Grouting, will not be discussed. In addition this will not cover ex-situ (above ground) mixing, or mixing dry reagents with soil. Only mixing applications for building, civil and heavy construction applications will be discussed, with only passing reference made to uses of soil mixing for environmental remediation work.

Jan 1, 2001

By Rob Farnfield, William Birch, Douglas A. Anderson

In the blasting industry, even to the most safety conscious shotfirer, misfires are a constant source of concern. In the United Kingdom, there are two types of misfire, as classified by the Health & Safety Executive. Type A occurs when testing a shot before firing reveals broken continuity that cannot be rectified. However, due to the fact that a majority of quarries use non-electric initiation [i.e. shock tube] that cannot be tested, this type of misfire is very unusual.

Jan 1, 2016

By A. V. Byvaltsev

Adsorption of cyanide complexes of gold, silver, copper, mercury, nickel, cobalt, iron, zinc and cadmium has been studied. Adsorption isotherms of the mentioned metals from individual solutions for different free cyanide concentrations have been obtained. Values of the constants of Freundlich isotherm equation have been calculated. Metal cyanide complexes affinity to activated carbon was determined.

Jan 1, 2014

By John A. Herbst, K. Rajamani

Process improvement is probably the most widespread objective of mineral process plant operators in the late 1980's. An important part of such improvements is dynamic optimization which involves reacting to inevitable plant disturbances in such a way that productivity is maximized at every instant of time. This paper describes the way in which mathematical models can be and have been used in dynamic optimization. Both off-line and on-line model applications are described.

Jan 1, 1989

THE Great Cobar Company Limited owns 1100 acres of freehold, which include the Great Cobar Oopper Mine and smelters, the Cobar Gold Mine, the Cobar-Ohesney Copper Mine, and the Great Peak Gold Mines.ORE OCCURRENCEThe ore-bodies in the first three mines-namely, Great Cobar Copper Mine, Cobar Gold Mine, and Cobar-Ohesney Oopper Mine are, speaking generally, lenticular deposits of evidently more or less complete metasomatic replacements of the country rock along a line of powerful faulting. These lenses vary from 150 ft. to 400 ft. in length, and from 20 ft. to 100 ft. in width.

Jan 1, 1919

By Lynn B. Hales, Randy A. Ynchausti

There is a large economic driving force associated with improving metallurgical performance in mineral processing plants using process control. Because of this and other benefits, control systems of the future will develop towards more sophisticated user friendly computer based systems that use powerful software analysis and control techniques. Auto-tuning, adaptive control and process models will gain expanded use because of their transparent availability to the system designer. Control of individual unit operations will be optimized and coordinated through expert systems that monitor economic conditions and management directives and direct operations accordingly. Plant areas, considered cost centers for years, will be integrated into plant-wide control systems for economic control and optimization. New control hardware, process sensors, control strategies and software development tools will be presented, as well as an overview of the economics driving the continued development of advanced process control systems.

Jan 1, 1993

By J. C. Watts

Ball mill grinding circuit control has received increasing emphasis in the past few years due to such factors as declining ore grades, increasing production costs, and advances in analytical devices and minicomputer technology. Since ball mill circuits have been a traditional bottleneck in mineral processing plant throughput, control systems often improve through- put without requiring additional processing equipment. In addition, much of the variability of the grinding product size and consistency is often removed, allowing better process operation downstream. Among the problems which arise in designing and implementing a process control strategy for ball mill circuits are circuit constraints imposed by processing equipment and local management, proper instrument selection, installation and maintenance, and use of calculated or inferred variables for process measurements. This paper discusses these problems and attempts to identify valid approaches to their solution.

Jan 1, 1979

By Jennifer Pell

Dunsmuir Ventures? Nanuq diamond project is located approximately 250 km northeast of Baker Lake and 170 km north of Chesterfield Inlet. It occurs at the intersection of the Wager Bay shear zone with the Keewatin Arch, a major long-lived crustal uplift. The newly discovered diamondiferous kimberlites at Rankin Inlet, Repulse Bay and on Melville Peninsula also occur along this arch. Kimberlite indicator mineral (KIM) sampling has outlined a distinct KIM train more than 35 km long and 6 km wide. Geomorphological studies, boulder displacements and dispersion of magnetite in tills suggest that glacial transport distances were on the order of 4 to 6 kms only. The presence of multiple sources within the main Nanuq indicator train would account for its length and breadth. A second train has been located on the west central part of the property and anomalous concentrations of KIM occur elsewhere. Pyrope garnets (G9?s and G10?s), diamond inclusion field (DI) eclogitic garnets and DI chromites were confirmed by microprobe analyses. Clinopyroxene thermobarometry indicates a cool geotherm, approximately 35 mW/m2, and that mantle within the diamond stability field was tapped. An aeromagnetic survey has identified a number of anomalies. Those with down ice KIM support will have ground geophysical follow-up and will be tested in a spring 2004 drill program. Dunsmuir is optimistic that this will lead to the discovery of a new kimberlite cluster on the Nanuq property.

May 1, 2004

By Yuanwci Shi

This paper discusses the results of research on the interaction between roof strata and shield supports including the active and passive supporting functions of the shield supports which prevents roof strata separation; pressure distribution on the canopy and under the base plate as measured in the laboratory and underground; comparison between various shield structures regarding their effectiveness on roof and floor control; and determination of optimum support capacity under given geological and mining conditions including hard-tocave roof

Jan 1, 1997

By S Grano, J Ralston

Selective oxidation of minerals was used in this study to separate by flotation the copper sulphide minerals of chalcocite, covellite and chalcopyrite from the arsenic copper sulphide minerals of enargite and tennantite. It was found that a satisfactory separation of these minerals was only possible after selective oxidation of their surfaces in slightly acidic pH conditions, or after oxidation and selective dissolution of the surface oxidation products with a complexant in basic pH conditions.

Jan 1, 2000

By Lewis Gordon, Alan Morrow, Aundra Nix

At the ASARCO Mission Mill, a multivariable, predictive controller was used to optimize parallel grinding circuits, improving throughput and product size. Using a dynamic model of the grinding circuit developed from on-line testing the software manipulates 4 variables to control 14 quality and constraint variables in each circuit. Traditionally, model-based control in grinding is difficult due to ore changes. This is addressed via a novel method to predict mill overload and automatic model switching.

Jan 1, 2000

In a previous study, various pyrite depressants were examined to improve the flotation performance of a copper-sulfide ore. Optimal results from this study were used to examine the effect of elevation on recovery and grade. Tests were conducted at elevations of 3350, 1735, 610 and -760 metres, consisted of five repetitive experiments for statistical analysis, and were performed both with and without airflow control. Tests were also performed in a glove box at Montana Tech to mimic the pressure conditions. Results indicate that both recovery and grade are dependent on pressure via bubble size and airflow suggesting that pressurised flotation cells should be considered for operations, particularly those at high elevation. Economics are extremely favourable for implementation because ensuing capital expenses are inconsequential with minimal time for return-on-investment.

Jan 1, 2005

By Stephanie Trant

Montana Tech has been engaged in fundamental research on the processing of critical materials for more than a decade. Efforts include examining novel reagents for the flotation of Rare Earth Minerals (REMs). For this paper, research results on a collector, salicyl hydroxamic acid (SHA), are presented. Various REMs were examined and include the rare earth oxides (REOs), carbonates (RECs), and phosphates (REPs) of a suite of Rare Earth Elements (REEs). Differences are attributed to solution and surface chemistry, coordination number, and ionic diameter. SHA adsorption follows an ion-exchange process that leads to chemisorbed and surface-precipitated states, depending mostly on pH. Many effects are directly attributed to lanthanide contraction. Results should also be applicable to other REM/collector systems and further suggest that REM flotation should consider dual collectors.