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By Eldon L. Abbott, Rebecca K. Bolan

The Florida Department of Transportation, Florida’s Turnpike Enterprise is studying the feasibility of a 1128 meter (3,700 foot) vehicular tunnel to provide direct access for Port of Miami traffic to/from I-395, I-95, SR-836 (Dolphin Expressway) and Miami International Airport. Both Bored and Immersed Tube tunnels were evaluated and re-evaluated for constructing two, two-lane, 11.9 meter (39-foot) diameter tunnels beneath the Main Shipping Channel lying between Watson Island and the Port of Miami on Dodge Island in Biscayne Bay, Miami, Florida, USA. Bedrock Geology of South Florida is predominately very permeable, vuggy limestone with sand seams and occasional voids. Groundwater inflows in deep cut-and-cover excavations, tunnel buoyancy, grouting, maintenance of Port operations and potential/possible environmental impacts to Biscayne Bay were significant issues.

Jan 1, 2005

By E Mielczarski

Determination of the adsorbed layer composition and structure at molecular and atomic levels and understanding adsorption mechanisms and dynamics are vitally important for the preparation of surface layers with specific functions. Direct information, at a molecular level, about mineral surface composition, its structure and surface distribution is crucial to perform an efficient separation process for mineral beneficiation. This information is equally important for modifying surface properties of industrial minerals for specific applications such as: fillers, composites, weathering resistance, etc. An understanding of the mechanisms and kinetics of the interaction of first adsorbed organic molecules with mineral surfaces is a fundamental requirement for the prediction and control of the macroscopic surface properties governing the efficiency of separation technologies or new material formulations. The developed infrared external reflection technique has a unique ability to study interface phenomena, at a molecular level, on heterogeneous substrates. The variety, precision and reliability of information about the interface phenomena delivered by this technique is superior to any other single technique. The experiments are fast and non-destructive. High sensitivity (starting from 20 per cent of the monolayer) in situ collected information in a multiphase system, even in the region of strong absorption of the substrate, makes this technique a very valuable experimental tool. The complexity of the recorded reflection spectra, their sensitivity to variations of the optical properties of all bulk and surface components and their spatial distribution in the system under investigation, are in fact the major strengths of this technique. A few examples of the application of this multi-diagnostic technique, for monitoring surface modifications of semi-soluble minerals for selective flotation, will be discussed in detail in this paper.

Jan 1, 2005

By F. Barriga-Ordonez, J. A. Finch, L. Calzado, S. R. (Ram) Rao

Sludge, formed by lime treatment of acidic drainage and stored in tailing ponds of the Sudbury region, contains 5-7% Ni, mostly in a mix of hydroxides with Fe (~ 10%), Mg (~ 10%) and Cu (-0.5%), and Ca (-3.5%) as sulphate. Investigations were conducted to recover nickel by a 2-stage process. In the first stage, the sludge was leached with sulphuric acid at pH 3.2. About 90% of the nickel was extracted, producing a solution, which contained mainly nickel (2 g/L) and magnesium (3.7 g/L). In the second stage, nickel was separated by treating with ozone which recovered 99% of the nickel in the Ni(III) oxidation state as -85% pure nickel oxide-hydroxide (NiOOH) precipitate. The oxide settled and filtered readily. A potential use of the product in battery making is suggested. The leach residue contained 0.5% Ni making it less toxic for disposal. Some physical properties of nickel oxy-hydroxide and process parameters including ozone consumption will be discussed.

Jan 1, 2005

By A Nisbett

The largest single operating loss in many hydrometallurgical plants is the poor recovery of leached product in the solids sent to tailings. Any reduction in the concentration of the valuable species in this stream will improve the project economics. Conventional design, to reduce the soluble loss, is to increase the number of wash stages or the wash/water ratio. This approach is limited in effectiveness as it can only reduce the soluble loss to that dictated by the concentration in the returning solution. For copper plants this concentration is set by the recovery in the solvent extraction (SX) plant. When using a single grade of SX feed a single grade of SX raffinate is produced generally with five to seven per cent of the copper still remaining in solution. An alternative approach has been developed by Cognis Corporation and implemented on a number of recent projects using engineering input from Miller Metallurgical Services. The SX plant feed is æsplitÆ into two different streams: a high-grade stream containing up to 75 per cent of the copper and a low-grade stream with the remaining copper. This Split-CircuitÖ concept has significant benefits in terms of both copper recovery and reduction in acid costs. The high-grade stream has the bulk of the copper removed and the raffinate sent directly back to the leach; to fully re-use the acid that has been generated during extraction in the SX process. The recycling of this higher concentrated acid stream considerably reduces the acid in the raffinate sent to washing steps. It represents a significant saving in acid consumed via the tails stream. The low-grade stream has a significantly lower SX feed grade and hence produces a lower raffinate acid and copper concentration. This lowers the economic species in the wash solution and hence reduces the soluble loss accordingly. Other operating improvements are realised with lower neutralisation costs (with the lower acid in the wash stream) and from a decreased need for in-circuit neutralisation to improve SX performance. The SX plant itself is also split into a high-grade extraction and a low-grade extraction stream to enable the low-grade raffinate to be produced. A number of circuit alternatives have been utilised that have provided a range of benefits. The circuit concept has been included into both new and existing plant operation. As a result of this experience other methods of incorporating the concept into a circuit have been developed.

Jan 1, 2005

By P Krauss, S Harpalani

Methane emitted from underground coal mines, along with ventilation air and known as ventilation air methane (VAM), constitutes the largest component of coal mine methane (CMM) emissions. Atmospheric methane, on the other hand, is a potent greenhouse gas with a significant adverse impact on the atmosphere. This has led to the development of various technological alternatives for its use as an energy fuel. Techniques involving oxidation of VAM, usually consisting of very low concentrations of methane, have been validated in the past. Prominent among these technologies are the thermal and catalytic flow reversal reactors, ancillary fuel technologies, lean fuel gas turbines, and concentrators and gasifiers. However, the efficiency of any VAM utilisation technique depends on the amount and concentration of methane in the ventilation exhaust air. Therefore, quantification of VAM emission from a coal mine is the first step towards identifying the most suitable technology for its utilisation for energy production. This paper presents an evaluation of the efficacy of VAM as an energy source. It provides details of a case study aimed at developing a technique to accurately quantify VAM emission from a coal mine. It further discusses the various VAM utilisation techniques available, and presents an economic evaluation of the alternatives. Based on the findings of the study, the most feasible method for VAM utilisation is identified for the mine. The paper summarises the procedure for quantifying VAM emissions and selecting the most suitable utilisation technique.

Jan 1, 2005

By J Czerwinski, M Kasper, M Wyser, N Heeb

The VERT project 1993 - 1998 laid the technical foundation for curtailing the emission of fine particles from diesel engines at Swiss underground workplaces. The targeted maximum was 100 ¦g/m3 EC. Extensive laboratory and field investigations demonstrated that this specification is only attainable with modern diesel particulate filter (DPF) systems that almost eliminate particles in the entire lung penetrating size range from 20 nm to 2.5 ¦m. In January 2000, Switzerland mandated compulsory particle filters in underground workplaces, particularly in tunnelling, irrespective of engine age, size and type. After the implementation, the particle concentration in the respiratory air was below 40 ¦g/m3 EC, compared to earlier values of up to 750 ¦g/m3 EC. Deployed DPFs have proven filtration rates of 99 per cent in the entire size range of alveoli intruding particles. The DPFs are as durable as the engine, suffer no ageing and require minimal maintenance. The failure rate is below three per cent annually. Of the 6000 retrofitted construction machines in Switzerland, about 400 are deployed underground. Prerequisites for this quality are a sophisticated certification procedure, electronic monitoring of DPF operation and meticulous periodic exhaust gas inspection of the engines.

Jan 1, 2005

By Paulo Roberto Pereira

This paper is motivated by the belief that increasing drilling and blasting costs will not necessarily bring about better digging or crushing productivity. As a matter of fact it can be counter productive as the ensuing discussion will show. In the two case studies presented herein when powder factor increased, productivity at a rope shovel and at a primary crusher decreased. Experience has shown that equipment (shovel and primary crusher) productivity increases as the powder factor increases and concurrently operating costs decrease. This is illustrated by Figure 1where the graph shows (assuming drilling costs constant) that for increases in powder factor initially operating costs might fall till a certain point and then they start to go up again. By the same token we need to understand what is the behavior of the operation’s productivity. It seems intuitive productivity goes up for increases in powder factor but when an operation reaches the point of minimum operating cost one could say that productivity reached its maximum. For continuing increases in powder factor can productivity still go up or does it go down? This paper presents two examples where the productivities of a surface coal mine and of a quarry are reduced for increases in powder factor. This indicates that these two operations could be operating to the right of their minimum operating costs and maximum productivity and therefore wasting precious drilling and blasting dollars and resources. Moreover, their productivity is following the red dotted line in Figure 1 and the question becomes can they follow the blue dotted line for increased drilling and blasting costs? The industry owes to itself to determine this minimum operating cost point and what can be done in case that the productivity goes down afterwards despite an increase in drilling and blasting costs. In other words, utilize your drilling and blasting resources correctly. In the two examples that follow single explosive loading strategies make powder factor a valid means of comparing the results of productivity as a function of powder factor. Also, external factors such as equipment operator influence are eliminated due to the long time span considered in the analysis

Jan 1, 2005

Ni and samaria-doped ceria (Ni-SDC) cermet are desirable materials for making a solid oxide fuel cell anode working at intermediate temperature (800°C or lower) due to its good ionic/electronic conductivity at the reduced operating temperature. An advantage of the use of a Ni-SDC anode is the enlargement of the effective reaction zone in the interfacial area between the anode and the electrolyte. As a result of the mixed ionic/electronic conductivity of the anode, the electrode reaction rate is enhanced. Investigations into the properties of the ceria-based anode reveal that the performance of the anode is closely related to its microstructures, which are dependent on the composition and fabrication conditions of the ceramics. In this paper, a method for quantitative characterization and correlation of Ni-SDC cermet microstructures to the performance of an anode is investigated. A series of Ni-SDC anode samples are prepared by screen-printing (SP) and spin-coating (SC) techniques, and different microstructures of the samples are obtained through controlling the SP or SC conditions and the sintering temperature. Individual phases (Ni, SDC and pore) in the tri-phase boundary (TPB) microstructures in the electrode are differentiated and segmented from each other in optical and SEM images based on the differences in refractivity and atomic contrasts among the phases. The geometric properties of the segmented phases are characterized using image analysis methods, so that a quantitative skeleton illustrating the TPB microstructures of the Ni-SDC electrode is obtained. Statistical analysis of the distribution of the three phases in the TPB microstructures is performed and the relationship of the microstructures with the optimum electrode is interpreted in terms of the microstructure analysis data.

Jan 1, 2005

By G. P. Gu

The in-service 90/10 cupro-nickel tubes in a water-chiller system suffered from severe corrosion damage during their relatively short service life causing unexpected down time. In addition to downtime, the environmental risk associated with losing refrigerant was also a concern that initiated this investigation, Microstructural investigation using SEM and electron microprobe indicated that pitting corrosion had resulted in local nickel depletion, During the corrosion process, copper appeared to have re-deposited around the corrosion pits accelerating the local corrosion.

Jan 1, 2005

By M. Menegaki

Restoration of abandoned mine sites is still one of the weak points of mining practice. The latter stands especially for the case of the surface coal and lignite exploitations, where the extended size of the disturbed land and the drastic changes to the geomorphologic features do not facilitate the implementation of a cost effective and environmentally sound reclamation plan. The paper examines the parameters involved towards the legal requirements for the reclamation of the first lignite exploitation in Greece, namely the ?Plakes? mine, located at Euboea, due to the particularities of the site. Then an integrated redesign procedure is presented, aiming at minimizing aesthetic degradation, confronting technical difficulties and preparing the site to accept new uses.

Jan 1, 2005

By D. W. Olson

The estimated value of natural gemstones produced from U.S. deposits during 2004 was $12.9 million. This was a 3-percent increase from that of 2003. U.S. gemstone production included agates, amber, beryl, coral, garnet, jade, jasper, opal, pearl, quartz, sapphire, shell, topaz, tourmaline, turquoise and other gem materials. More than 60 varieties of gemstones have been produced commercially from U.S. mines. But commercial mining of gemstones has never been extensively undertaken in the United States. Most of the deposits have been relatively small compared with other mining operations. In the United States, much of the current gemstone mining is conducted by collectors, gem clubs and hobbyists rather than business organizations.

Jan 1, 2005

By Harumasa Kurokawa

Since the initial start-up, the Toyo Smelter & Refinery has been operating in harmony with the ambient environment, and improvements have been implemented with technologies specifically developed for further protecting the environment. Toyo Smelter & Refinery is now planning to increase the copper production capacity from 280,000 tpy to 450,000 tpy, over a period of several years. In 2003, the first step of this smelter expansion and modernization plan was implemented. The production capacity of the P-S converter was increased dramatically, as it became possible to operate under a ?2 hot-2 blowing? schedule. In 2005, an additional converter will be installed, in order to allow operation under a ?3 hot-2 blowing? schedule. This report will describe the technical improvements on the P-S converters, as well as describe the Toyo expansion program and discuss the technologies applied to the fugitive gas collecting system.

Jan 1, 2005

By Peter W. Lotz

Contents of: ?Sampling for Cyanide in Metallurgical Processes? ?Sampling at process level of operation ?Sampling at environmental level ?Sample stability and integrity issues ?each citing possible objectives, practical example and reasons for surprises Overall recommendations on sampling plans and procedures to maintain sample integrity

Jan 1, 2005

Material sampling theory is well established in mineral process monitoring, improvement and control. It has been much enhanced by fundamental contributions due to Gy. When GyÆs sampling theory is applied to sampling inspection and monitoring, it provides estimates of average quality or extent of contamination. It also provides estimates of uncertainty, but these often ignore uncertainty in estimated variograms or other measures of variability. Risk assessment is often an implied task in sampling inspection and quality monitoring. A valid technique of risk assessment needs to take into account the uncertainty in the variational measures themselves. Standard statistical tolerance limit calculations which do take such uncertainty into account can be adapted to develop a technique for handling uncertainty in variational measures such as the variogram. Data from a published example is used to illustrate the technique.

Jan 1, 2005

By J Naser, M Tuck

This paper reports a computational study using computational fluid dynamics (CFD) in a mine ventilation system. Ambient air is injected to a rectangular mine drive through a circular duct. Moisture evaporates from shaft wall depending on flow properties of air in the drive-duct system. The physical process involves simultaneous momentum, heat and mass transfer. A species transport equation is employed to account for the moisture concentration in air. The momentum equation is solved using standard k- model, while energy and species transport equations are solved using standard expressions for moisture evaporation rate and heat flux from the drive wall. The aim of this paper is to investigate effectiveness of CFD simulation in relation to mine ventilation in a drive where a significant mass transfer phenomenon occurs. Results from simulation are compared with existing data from a site in Victoria.

Jan 1, 2005

In 1997, the Australian coal industry through Standards Australia committee MN-001 Coal and Coke recognised the need to produce a Standard giving some instruction on how to inspect and audit mechanical sampling systems. A Guide was developed by sampling subcommittee MN-001-04 and in 1999 the Standard was released as AS4264.5 æGuide to the Inspection of mechanical sampling systemsÆ Coal and Coke. Since that time the author has assisted with other committees in developing the Guide for other commodities such as concentrates and a generic standard for particulate materials. (AS4433.6 released 2000). The Coal and Coke guide is also currently a work item for ISO Standards. This paper is focused primarily on auditing and inspection procedures for coal mechanical sampling systems. It highlights the need for at least a three level inspection protocol where the operators manning the system maintain operational checks, the operators are regularly supervised by the company managing the system and once per year an independent auditor inspects the whole system to ensure compliance with design and standards. It does not cover short- and long-term maintenance of individual systems. With companies already certified to the ISO9000 series, this guide forms the framework to bring the operation and inspection of their mechanical sampling systems into line with these principles.

Jan 1, 2005

By C. O. Aksoy

There is a long history of coal production in Turkey with electric energy generated from power plants since the 1950s. However, the cost of power generation is high. Therefore, it has become necessary to find a means of decreasing production costs to become more competitive in a global market. This paper attempts to economically minimize the overall operating costs of a dragline-shovel-truck system applied at an open pit mine that has fed the Yatagan power plant since 1979, lowering the lignite production cost, and indirectly, the overall electricity generation unit cost. Systems currently in place, as a result of former optimization studies, are time-consuming and expensive to re-implement to comply with today’s very different geometric and economic conditions affecting mining operations. In such cases, rather than re-optimization, it is more viable to identify the parameters that affect the minimum unit cost, via a cost minimization study, allowing present mine equipment to be utilized more efficiently. Unit cost minimization analyses are subject to the capacity of the pool of mining equipment available, combined with the mining block geometry from pre-stripping onwards. In this overall unit cost minimization study, P&H shovels and CAT 777 trucks with capacities of 15 yd3 and 77 tons, respectively, were used in truck-shovel pre-stripping operations. A 65 yd3 Marion 8050 dragline was used to expose the overburden immediately over the coal seam. Pre-stripping bench heights varied from 8 m to 20 m and dragline bench heights from 20 m and 25 m were evaluated to minimize the unit cost of field operations. Total overburden extended to a depth of 60 m (35 m to 40 m for pre-stripping). Minimization analyses performed on the pre-stripping truck-shovel operation, prior to dragline operations, determined that the shovel bench height should be 15 m requiring a dragline bench height of 25 m.

Jan 1, 2005

By A M. Sherwood

The Otago and Southland lignite deposits represent by far the largest known fossil energy resources in New Zealand. Despite their size they have remained virtually untouched since exploration in the 1970s and 1980s defined their extent. In total there is an estimated 10.9 billion tonnes of lignite in 13 defined fields in Otago and Southland. Much of the exploration work only targeted seams at shallow depth and it is highly probable that there are further resources at depth in the fields that have been explored to date.   L&M Lignite Limited (L&M) holds exploration permits over a number of lignite deposits and is currently engaged in pre-feasibility studies to investigate the potential of the lignites for gasification. L&M is focussing its studies on the Hawkdun and Ashers-Waituna deposits. Coal quality in these deposits, particularly Ashers-Waituna, is highly suitable for gasification. In total the two deposits contain 1647 Mt of potentially recoverable lignite. L&M has engaged a variety of consultants to progress this project. The Hawkdun and Ashers-Waituna deposit databases have been re-evaluated and the resources remodelled. Further drilling has been carried out and the coal quality database has been expanded. The baseline project is to develop a mine to feed a plant that will produce liquids, specifically low-sulphur diesel and naptha, using the Fischer-Tropsch process. The project anticipates a staged development of 10 000 barrel per day units, each requiring mining at the rate of 12 700 tonnes of lignite per day. The production of other products including ammonia-urea, methanol, hydrogen and electric power is also under study.

Jan 1, 2005

By Haydn H. Murray

A hydrothermal bentonite located in the high Sierras in Nevada is being mined and processed for use as a natural dietary supplement. Because hydrothermal clay deposits are normally zoned and not uniform in composition, a special stockpile was constructed to assure uniformity of processed products. The stockpile of clay was layered and rectangular in shape. Channel samples were taken from 10 locations around the stockpile and were mixed and quartered to provide representative samples. The samples were then chemically and mineralogically analyzed. The results showed excellent uniformity. The mineralogy and chemical analyses will be discussed in the paper.

Jan 1, 2005

By M Ljunggren, M Lundh

Dissolved air flotation (DAF) in wastewater treatment as a separation process of submillimetre biological flocs is based on the generation of bubble/floc aggregates. DAF is a complex process but has got advantages, such as allowing a high hydraulic load, compared to sedimentation. A thorough knowledge of the physics of the DAF process is, however, still lacking. This paper will present results of experimental studies on three aspects of significance to the separation process û the flow structure in the flotation tank, rise velocities of aggregates, influence of floc size on the separation efficiency. Flow structure. Measurements were performed in a pilot plant mapping and visualising the velocity field. The dispersion water (bubbles) had a decisive influence on the flow structure due to the effect of the bubbles on the bulk water density. Stratified conditions with a less dense, bubble-containing upper layer and a clear water, denser bottom layer were important for a good separation. A simple model of the stratified flow structure was elaborated making it possible to interpret the function of the aggregate rise velocities. Bubble/floc aggregates. The dynamics of single flocs, bubbles, aggregates were visualised using a borescope + CCD video camera + digital recorder + image analysis. Sequences of video frames made it possible to determine the rise velocities of the single aggregates. These velocities were found to be in the range 1 - 9 mm/s with a tendency for large flocs to have higher rise velocities. Separation versus floc size. The floc size distribution was measured in the DAF process. Data from three different DAF cases showed, that large flocs (> about 100 ¦m) were entirely separated, whereas small flocs experienced a less good separation. It was, moreover, found, that a very significant separation of flocs took place in the very upstream end of the separation zone in a pilot plant case.

Jan 1, 2005