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By P. J. Bethell

Background Increasingly complex geological conditions, with the presence of high ash binders in the mining horizon were encountered at the A.C. I. Dugout Mine near Price, Utah. This led to the production of high ash coal from the Dugout Mine during 2003 and 2004. This material had poor marketability and posed operating issues for the utilities burning the coal. Ash levels increased from typical levels in the 9-12% range to between 15 and 25%. etween 15 and 25%. Reviews of the mine plan and expected geological conditions indicated that further periods of high ash production could be expected. Action Plan Detailed sampling of the mine high ash production was carried out. The majority of the coal from the Dugout Mine is trucked to the Savage Coal Terminal (SCT) at Wellington, Utah where it is stored in multiple piles by quality. Coal at the mine is segregated by a CoalScan 2600, on-line analyzer into high ash, low ash and rock chute (waste material). From these piles, the material is crushed prior to shipment to SCT. The samples obtained from the various high ash piles were subjected to detailed sizing and washability analysis. Once this information was obtained, alternative circuit configurations were evaluated to process this material into a salable product. Water supplies in the arid terrain where the plant is located are scarce. This factor played a part in the final circuit design.

Jan 1, 2008

By Z. Yang, M. J. Collins, N. E. Tuffrey, R. J. Kalanchey, I. M. Masters

The high elevation of China Western Mining Company (WMC)' s Ganhe refinery, and the high iron content of concentrates produced by the WMC mines, were key factors in the selection of pressure leaching by WMC for their new zinc refinery. This paper describes the results of pressure leaching test work conducted by Sherritt in Fort Saskatchewan with a sample of WMC concentrate from Qinghai Province in China. Results from batch pressure leach tests and a four-day pilot plant campaign are reported. The pilot plant campaign included continuous operation of a two-stage pressure leach circuit, as well as neutralization and iron removal steps, resulting in the production of iron-free zinc sulphate solution. Greater than 98% zinc extraction was achieved in pressure leaching, while producing solution containing about 9 g/L H2SO4 and 2 g/L Fe. Following neutralization and iron removal, the solution contained about 170 g/L Zn and less than 10 mg/L Fe. Overall recovery of sulphur in the zinc concentrate feed to elemental sulphur byproduct was about 85%, while 75 to 80% of the indium in the feed was recoverable from the neutralization residue. The test results highlighted the technical and economic advantages offered by the Sherritt Zinc Pressure Leach Process and provided the required data for the engineering design.

Jan 1, 2008

By Juan Daniel Martínez, Janaina Accordi Junkes, Dachamir Hotza, Tatiana Pineda

"The rice husk combustion in a bubbling and atmospheric fluidized bed reactor was investigated. The results showed the technical viability of producing both heat and amorphous silica from a renewable energy source. This paper presents the characterization of rice husk ash (RHA) obtained under varying fluidization velocities (0.13-0.15 m/s) and rice husk feed (4.5-7.2 kg/h). Characterization techniques include X-ray fluorescence, X-ray diffraction, particle size distribution and scanning electron microscopy. For the employed range of fluidization velocities of rice husk feed no noticeable influence on the chemical composition of produced RHA was observed. After combustion, RHA containing ~93% amorphous silica and <3% unburned char was obtained. RHA primary particles presented sizes from 90 to 100 µm and a tendency for agglomeration in aqueous media. Thus, the potential of this type of reactors with respect to speed, continuity and self-sufficiency energy of the process was shown.IntroductionDue to the increase of the agroindustrial production, the concern with processing by-products, such as rice husk (RH), is growing. For a better material and energy use, allowing a cleaner production and a more maintainable development, RH can be used as renewable fuel in the production plant, for instance, in steam generators. The adequate combustion of RH generates hot gases with low levels of pollutants, as carbon monoxide and particulate material.RH is the protecting coating formed during the growth of the rice grain, composed by four structural layers.1 The main components of the husk are cellulose and hemicelulose (50%) besides lignine (26%) and organic components (4%), as oils and proteins. The remaining amount includes inorganic materials (SiO2, Al2O3, K2O, Na2O, MgO, CaO, Fe2O3, MnO, P2O5).1The rice husk ash (RHA) is the product of the termochemical transformation of RH. The conditions of the different conversion processes (pyrolysis, gasification and/or combustion) determine the physical-chemical characteristics of the final product. RHA corresponds to 14 to 25% RH, depending on the variety of the rice, climate and soil of the producing area.2-4 The main component of RHA, which is generated at moderate combustion temperatures, is amorphous silica (SiO2) in the range from 80 to 97%.4,5"

Jan 1, 2008

By Alhondra de los Santos, Jesús L. Valenzuela, Jose R. Parga

"The present study evaluated the feasibility of using iron species generated by electrocoagulation (EC) as an adsorbent for removal As(III/As(V) from aqueous media. The full potential of EC was evident in that more than 99 percent of arsenic was removed without addition of chemical reagents. The adsorbent iron-species generated by EC was characterized by Chemical Analyses, X-Ray Diffraction and Scanning Electron Microscopy. The experimental data were correlated by employing a Langmuir adsorption isotherm. Thermodynamic parameters such as ?H o , ?S o and ?Go were calculated. The adsorption process was found to be exothermic and spontaneous.1. IntroductionArsenic contamination in potable water supplies is a serious health problem in many countries around the world. Groundwater arsenic contamination in La Comarca Lagunera Mexico was first reported 30 years ago [1]. Arsenic concentration has been found in well water from several communities ranging from 0.25 to 1.0 ppm. The elevated concentration of arsenic in water, above that originating from natural sources, has been attributed to the use of organoarsenical pesticides in the cotton fields and also to the millions of tons of waste slag generated at a local lead smelter [1]. The main arsenic species present in natural waters are arsenate ions 3- 4 AsO (oxidation state V) and arsenic ions H3AsO3, - 2 3 H AsO and 2- 3 HAsO oxidation state III). However, As(V) ions are most prevalent in oxygenated water while As(III) is found for anaerobic conditions, such as in well water or in groundwater. Conventional methods of arsenic removal rely on chemical-based treatment with lime, alum coagulation, iron coagulation and chemical oxidation. Other processes used with varying degrees of success include adsorption onto activated carbon, reverse osmosis, nanofiltration, manganese dioxide, magnetite and ionexchange resins [1-3]. These conventional processes generate a considerable quantity of secondary hazardous waste such as solid sludge, which also pose serious environmental problems. These drawbacks have forced various industries to search for effective, alternative treatment technologies for arsenic with a preference for electrochemical methods."

Jan 1, 2008

By D. Mohapatra

Extraction of Al(III) from aqueous sulfuric acid solutions into organic Cyanex 272®-carbon tetrachloride systems was investigated from a multi-component mixture containing aluminum, cobalt and nickel. Al(III) extraction efficiency was quantitative with 1.0 M Cyanex 272® in two stages at an aqueous: organic (A:O) phase ratio of 1:1 and an equilibrium pH of 3.2. The stripping of Al(III) from the loaded organic (LO) with different acids indicated sulfuric acid to be the best stripping agent. More than 99% stripping of Al(III) from the LO was achieved using 2 M H2SO4 at an A:O phase ratio of 1:1 in a single stage. The stoichiometry of the extracted species of Al(III) was determined by the slope analysis method. The extraction reaction proceeded via the cation exchange mechanism and the extracted species was assumed to be AlA3?3HA, where HA refers to the dimeric and A the anionic form of the extractant, Cyanex 272®. The extraction of Al(III) was studied in the presence of various ions to ascertain the tolerance limit of individual ions.

Jan 1, 2008

By K. L. Morton

Groundwater and associated pore pressure represent elements that can have a negative impact on surface mining and slope stability. Groundwater flow and deformation within a slope influence each other. An increase in pore pressure will result in a decrease of effective stress; and conversely, if the pore pressure decreases, the effective stress increases. Slope analysis and slope design calculations require good information on pore pressure distribution around an open pit excavation. Until recently very little pore pressure data were available and assumptions had to be used. Location and design of measuring points depend on geological and structural setting, geotechnical domains and practicality. Good planning and the use of sensitive point piezometers to measure in situ pore pressures means that real-time data can be collected and used for the construction of flow nets, the determination of pore pressure distribution around an open pit mine, the validation of the dewatering/depressurization requirements, the calculation of the efficiency of the dewatering system and finally the use of pore pressure data in slope stability analysis. The recommended layout for a monitoring system, types and design of piezometers, data collection and use of the pore pressure data are presented.

Jan 1, 2008

By Peter de Kort

Tunnels in urban areas generally require deep excavations in soils under the groundwater table. In The Netherlands uplift loads are generally taken by piles installed into dense sand layers, which are hard to penetrate. To avoid nuisance and damage to the environment, piles often need to be installed using vibration free methods, which also have the advantage of low noise levels during installation. Drilling piles and obtaining a high uplift resistance is a contradiction in itself. Franki has adopted several installation methods based on the injection of grout during drilling and/or post grouting to overcome the difficulty of hard layers. This report presents two projects, situated in Rotterdam and Sneek, where vertical tension piles in floors, subject to high uplift loads, have been used. It also explores a project in Zeebrugge (Belgium), where tension piles are installed at an inclination of 1:1 to anchor a diaphragm wall for a quay construction. Test results presented in this report show, that vibration free and soil displacing piles can be installed in very dense sand layers and that a high uplift resistance can be achieved. It is also shown, that a variety of installation methods is available, even in limited space.

Jan 1, 2008

By Ed Cope

The newly discovered South Arturo deposit is a Carlin-type, breccia-hosted, oxide gold deposit located on the Dee Mine property at the north end of the Carlin Trend in Nevada. The Dee Gold Mine was discovered in 1981 by Dee Delamar, a Cordex geologist. The property was put into production by Rayrock Mines in 1984. During its 16-year mine life, the Dee Mine produced about 18.6 t (600,000 oz) of gold from oxide ore at an average production rate of about 1.24 to 1.55 t/a (40,000 to 50,000 oz/year). In October 1997, Bar-rick Gold Exploration acquired the right to earn a 60-percent interest in the Dee property from Dee Gold Mines through an exploration farm-out agreement. Barrick Gold Exploration began exploration activities on the property in 1998 and vested in its 60 percent operating interest in 2004. However, the discovery hole at South Arturo was not drilled until July 2005 from atop the historic mine dumps located 300 m (985 ft) south of the Dee openpit. The discovery hole (BD-72) encountered a cumulative 75.6 m (248 ft) of oxide mineralization grading 1.9 g/t (0.055 oz/st) gold beneath 260 m (855 ft) of dump material and post mineral Tertiary Carlin Formation volcanic and sedimentary rocks. Oxidation within the deposit extends to depths greater than 610 m (2,000 ft). The deposit has passed the prefeasibility test and is presently in the feasibility stage. Exploration is on-going to enhance or enlarge the known deposit. The current resource for the deposit stands at 40.4 t (1.3 million oz) of gold. The South Arturo discovery is an example of an historic mining property yielding a new discovery through the diligent application of area selection criteria of the model type and persevering when early results were generally negative. Barrick?s original exploration pro-grams on the property were focused on the discovery of deep, high-grade sulfide deposits that would likely be mined by underground methods. As it turns out, South Arturo is mostly oxidized and will be amenable to mining by openpit methods

Jan 1, 2008

By A Rozendaal

Namakwa Sands, a heavy minerals beneficiation business situated along the west coast of South Africa, is a major producer of titanium slag, pig iron, ceramics quality zircon and rutile concentrate to the international export market. The bulk of the economic mineralisation, which includes zircon, rutile, ilmenite and leucoxene is hosted by a late Cainozoic aeolian succession overlying remnant palaeo-strandline sediments. Relatively younger duricrust layers that cement a significant part of the generally unconsolidated ore compounds the challenging processing character of the primary mineralogy. The complex nature and hardness of the duricrust ore influence their mineability negatively, and can potentially destabilise downstream ore preparation processes. Effectively, up to ten per cent of the entire mineral resource is sterilised as the present infrastructure is not geared to treat the hard-mineralised ore. The metallurgical performance of the primary processing stage, which entails wet density separation, is strongly a function of the quality of the heavy mineral assemblage, liberation state of the economic minerals and slimes content. Elevated concentrations of garnet, a gangue contaminant exhibiting similar physical characteristics as the economic minerals, subtract substantially from the recovery performance of the secondary concentration process, which comprises mainly wet magnetic separation. By contrast, the intrinsic mineral purity of the economic fraction governs its successful recovery to saleable products as stringent product quality specifications apply. Improved mine planning through geometallurgical enhancement of the existing mineral resource model is envisaged to benefit the entire Namakwa SandsÆ mineral beneficiation chain, ultimately aiming to optimise mineral resource utilisation.

Jan 1, 2008

By James Goldberg, Sally Zadra, Wiliam Reisz

Early recognition and risk assessment is critical to sustaining a safe and productive blasting operation. While every blasting environment holds inherent risk, highwall blasting in highly congested areas such as Hanson Material Service Corporation’s Romeoville and Thornton quarries in the greater south Chicago metropolitan area can be particularly perilous

Jan 1, 2008

The Río Agrio of northern Patagonia, Argentina, is highly acidic due to inputs of volcanic gases (SO2, HCl, HF) in its headwaters. The watershed includes a hyper-acidic (pH <0.5) volcanic crater lake, a larger glacially carved lake that is also strongly acidic (pH 2.6 to 2.7) and an acidic river that flows for more than 40 km (25 miles) before its pH is completely neutralized. This unique watershed has many geochemical and biological similarities to acid waters caused by mining. This paper describes the Río Agrio watershed and draws a comparison with some famous acid mine waters. Learning more about naturally acidic lakes and river systems could have important applications to the bioleaching of ores or biological treatment of mine waters. Therefore, it should be of interest to the general community of mining and metallurgical engineers.

Jan 1, 2008

By C. R. Copeland

Water sprays are a common method used to reduce particulate matter (PM) emissions. Various factors such as wettability, surface area coverage, fine particle engulfment rates, interparticle adhesion forces, suppressant penetration, and suppressant longevity have all been suggested as critical factors in achieving effective PM control. However, it has not been established which of these factors are the most important. Experimental work indicated that suppressant penetration is the most critical of these factors. Suppressant effectiveness was also improved using hygroscopic reagents which retained moisture, improving longevity. Maximizing suppressant penetration and improving suppressant longevity led to an average 86% reduction in PM10 concentrations in laboratory dust tower tests.

Jan 1, 2008

By Mohammad Nasim

Vertical expansion of existing structures frequently requires foundation retrofitting to enhance the capacity of existing foundations for supporting additional loads. Owing to their small diameter, a variety of suitable drilling methods available for installation, and smaller installation equipment capable of operating under limited headroom conditions, micropiles are often preferred for foundation retrofitting. This paper presents a case history demonstrating application of micropiles to underpin the existing foundation of the Washington D.C. Children?s National Medical Center (CNMC) for its future expansion. Located at 111 Michigan Avenue in northwest Washington, DC, portions of the hospital currently extend five stories above grade and three levels below-grade as parking garages. The hospital intends to expand the surgical wing up to the current build out (five stories) above the remaining portion of the existing parking garage. The original foundations consist of 80-ton Raymond Step-Tapered piles. New loading on the foundations required each Raymond pile to be capable of supporting 150 tons. Results from quick load tests on existing piles indicated that two entire column lines (Column Line A and B) would experience loads beyond their capacity, requiring enhancement of the existing foundation at these locations. The design and construction of the foundation upgrading work was particularly challenging due to various project constraints related to a high groundwater table, micropile installation under limited head room, and ensuring that the parking garage remained fully operational for the entire duration of construction. The paper presents the challenges faced during testing of existing foundations amid a high groundwater table, design developments of underpinning options to support the additional column loads, difficulties and challenges encountered during installation of the micropiles and construction of the micropile pilecaps, and value engineering options developed during various phases of the project. Understanding that micropiles are often a preferred option for foundation retrofitting, the case history is expected to provide a baseline design approach and innovative solutions to typical challenges faced during construction, thereby reducing potential cost overruns during design development and construction of similar future projects.

Jan 1, 2008

By Richard B. Stein

Section 25 has been assembled to give the geological, mining, or metallurgical engineer an overview of some of the important downstream operations that typically follow mining activities. This subject is obviously too broad and complex to be covered in detail within this Handbook. However, the engineer will be interested to learn about the basic fundamentals, and especially how they might affect the economics of the total project from prospecting and mining through to metals recovery and marketing. In this way, it is hoped that the engineer will have a better overall appreciation for the technical and commercial prospects of a mining and metal-producing project.

Jan 1, 2008

By J K. de Wet, G Balassone, J D. Singleton, V Arseneau

The Accha-Yanque zinc belt in southernPeru is a major zinc-lead rich metallogenic province. In the belt are comprised several non-sulfide-type occurrences, extending on the periphery of the Yauri-Apurfmac batholith (Oligocene-Miocene). Zinc mineralisation at Accha (almost fully oxidised) occurs in breccias of sedimentary and tectonic origin in the limestone of the Ferrobamba Fm (Middle to Upper Cretaceous). Non-sulfide association consists mainly of smithsonite and hemimorphite replacing both primary ore minerals and carbonate host rocks. Mn(hydr)oxides and Zn-clays (sauconite), can be locally very abundant. Differences in mineralogy of the ore and gangue minerals, as well as the composition of the host rock can have a profound impact on zinc recovery and reagent consumption, and therefore on the economic value of the deposit. An&nbsp;EXTENDED ABSTRACT&nbsp;is available for download. A full-length paper was not&nbsp;prepared for this presentation.

Jan 1, 2008

By Walter I. Paniagua

A housing complex of 76 buildings is being constructed in the city of Morelia, in western central Mexico; the buildings are 5 levels high, with a shallow concrete slab foundation. Soil conditions include a soft clay stratum, with up to 8 m depth, in a highly seismic area. Pile foundations and micro-piles were considered, but discarded due to economic factors. The alternative of soil improvement with rigid inclusions was used. An FEM (Finite Element Method) analysis was conducted to determine the diameter, spacing, length and arrangement of the inclusions. Construction was implemented with traditional methods: soil boring, and mortar tremied with pipe and the aid of a sock to contain the material (no steel reinforcement was used). So far, 46 buildings have been built, and level measurements for 18 buildings have been recorded since 2006, with resulting good behavior in both total and differential settlements.

Jan 1, 2008

By W. Haibei, Lei. Z., Z. Bangsheng, W. Yufang, J. Kaixi

In 2007 output of zinc was more than 3.71 million tons in China. Some new projects have finished FS and several new zinc plants are building now. In recent ten years it happened great changes in zinc industry. For zinc concentrates one pressure leaching plant was built with capacity 10,000t/a and at least four companies are carrying out FS or engineering design now. Direct atmospheric leaching will put into used in China in 2008 with capacity 100,000t/a. It is estimated that until 2010 the output of direct leaching will be 400,000t/a.

Jan 1, 2008

By B. P. Watson

The Bushveld platinum group metal deposits are two distinct, shallow-dipping stratiform tabular orebodies and strike for many hundreds of kilometres. Mining is extensive, with depths ranging from close-to-surface to 2 000 m. The mining method is a variation of planar open stoping. Pillars are widely used to support the openstopes. Little work has been done in the past to determine pillar strength and pillars have been designed using experience and formulae developed for other hard-rock mines. This has led to oversize pillars with consequential loss of ore or undersize pillars resulting in potential collapses or pillar bursts. This paper describes a back-analysis of pillar failures at Impala Platinum, just north of Rustenburg, and provides insights into pillar behaviour. Strength formulae are presented for Merensky Reef pillars at Impala. These formulae may be used cautiously on other platinum mines with similar geotechnical and geomechanical conditions.

Jan 1, 2008

By Henrique Hesse, Rosana de Cassia de Souza Schneider, Wolmar Alípio Severo Filho, Ezequiel Bavaresco, Rodrigo Klamt, Luciano Roni Silva Lara, Luciano Dornelles

Alkyd resins are used in surface treatment. They are product of the glycerolysis followed by polymerization. In the present work it was studied methods of alkyd resin production from crude glycerol compared with resin produced with pure glycerol. This glycerol corresponds to 10% of the final products in the biodiesel production. The crude glycerol was partially purified with neutralization, flotation and adsorption. The experiments were accomplished with temperature control, inert atmosphere and with several quantities of the substrate. For the products characterization physic-chemistry methods, infrared spectroscopy and hydrogen nuclear magnetic resonance were used. According to the observed results, the resins obtained with crude glycerol have presented similar properties of the classic alkyd resin produced with pure glycerol. The exploitation of the crude glycerol reduces the stages and costs of the process.

Jan 1, 2008

According to the Australian Bureau of Statistics, fatalities from road transport accidents represented an average of over 97 per cent of all transport related accidents between 1997 and 2002. With increasing traffic density, tunnels are becoming a more viable means of providing alternative travel routes to ease areas of congestion in the road transport network. However, unlike open road conditions, a fire incident in the confined space of a tunnel environment may impact upon many users that are remote from the incident location. In this context, designing for an appropriate level of safety in tunnels is therefore an important consideration for achieving consistency in the life safety measures for users of the road transport network. Unfortunately, like fire safety engineering design for buildings, there are presently no clear measures in the design processes to assess the adequacy of the design in terms of attaining the level of safety implicated in the design objectives. This is partly due to the indeterminate nature in which the design objective or the level of performance measure is stated û the intent of the objective is relatively clear but the measure of it is not. Another reason is the lack of a standardised procedure for determining the critical design variables affecting life safety. This is important to ascertain consistency in the use or adoption of the important parameters for design. This paper looks at the processes involved in the fire engineering design of road tunnels that are currently practised. A review of the design processes for fire safety in road tunnels is provided, which includes the range of fire scenarios in a tunnel environment, the traffic flow and composition, the relevant fire protection systems, the ventilation and smoke control system, the egress provisions and the benefits of incorporating fire brigade intervention. A simplified risk assessment approach is developed for a typical road tunnel to assess and evaluate the impact of a range of design parameters on life safety. Using a sensitivity technique, the important variables are then identified and means of reducing design variations associated with them are recommended. The technique may be further refined for use in the development of codes or guidelines in order to develop a suitable means of deriving more consistent design values, and hence achieve better consistency in the overall level of safety in the design.

Jan 1, 2008