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By Zhouhua Jinag

The attempt has been made to manufacture high nitrogen austenitic stainless steels by pressurized electro-slag remelting furnace with maximum nitrogen pressure of 7MPa. To obtain high nitrogen content in steels, the compound electrodes with different nitrogen sources (FeCrN, Si3N4) were prepared. Using the Si3N4 as the nitrogen alloying source, the silicon contents in ingots were prone to be out of the specification range, and the electric current fluctuated greatly and the surface qualities of the ingots were poor. The surface qualities of the ingots were improved using FeCrN as nitrogen alloying source. The sound and compact macrostructure ingot with the maximum nitrogen above 1.0wt% could be obtained. A series of high nitrogen austenitic stainless steels have been successfully developed by this method. The mechanical and pitting corrosion resistance properties of high nitrogen austenitic stainless steels were investigated. The results show that the steels exhibit excellent mechanical and pitting corrosion resistance properties.

Jan 1, 2009

By R. T. Jones

Base metals and platinum group metals can be collected in metallic alloy form, via a wide variety of smelting processes. The recovery, or degree of collection, of the valuable metals is a function of the extent of reduction in the furnace, which, in turn, is indicated by the fraction of iron present in the feed materials that report to the alloy. An equation has been developed that relates the recovery of various metals (such as Ni, Co, Cr, and PGMs) to the recovery of Fe. This recovery equation (for each metal) is characterized by a single parameter (K?) that can either be empirically fitted to the data, or expressed in terms of the equilibrium constant and the ratios of the activity coefficients involved. Data from a number of varied DC arc furnace campaigns are presented to illustrate this behaviour.

Jan 1, 2009

By J B. Pateiro-Fernßndez, M Fuchsschwanz, G Deissmann, S Ahmad

Quang Ninh province is the most significant coal producing region in the north of Vietnam. The Nui Beo Coal Company (NBCC) operates open pit mines in Quang Ninh province and the waste overburden produced is dumped as sidehill fill in the Chinh Bac waste dump site. In the past, no special consideration has been given to the environmental impacts during the dumping operations. The mine waste is transported in trucks from the mine site to the dumping site and the loading, hauling and dumping operations are the main sources of dust emission. Rain events, especially during the rainy season, cause the generation of contaminated surface water as well as seepage of water through the dump at a number of locations. The existence of cracks at the top of the dump can pose serious stability problems with heavy rain events leading to failure of slopes which can potentially disturb vast areas of land currently used for agricultural purposes and human settlement. For sustainable development at the Chinh Bac waste dump site in the future, apart from the social and economic considerations to be assessed, there is an absolute necessity for environmental protection measures to be in place both during and after the dumping of the mine waste overburden. Research Association Mining and Environment in Vietnam (RAME) is working to develop and implement concepts for the mitigation of environmental problems emerging from dust, contaminated water and lacking slope stability to ensure successful rehabilitation of the coal mine waste dumps in the north of Vietnam. Within the framework of RAME, the Institute of Mining Engineering I (RWTH Aachen University) is managing and working to develop the stabilisation concepts for the solid mine waste dump in collaboration with the Chair of Geotechnical Engineering (RWTH Aachen University), Brenk Systemplanung and the Vietnamese group of companies VINACOMIN (Vietnam National Coal-Mineral Industries Group). The most economical and environmentally sound operations, as well as locally adaptable environmental protection measures, are essential for the sustainable development of the dumping operations at Chinh Bac dump. This paper describes the dump site and the sustainable development possibilities with an emphasis on the environmental protection and stability problems at the Chinh Bac waste dump.

Jan 1, 2009

By W Akpan

The Royal Bafokeng community in South AfricaÆs North West Province represents a unique case in Sub-Saharan Africa in terms of its positioning in the natural resource economy. It receives royalties directly from mining firms for the extraction of Platinum Group Metals, which include platinum, ferrochrome, rhodium and palladium. In 2007, royalty income of about R290 million (approximately US$32.2 million) was reported. Such direct revenues have enabled the community to invest in educational, medical and other social infrastructure, thus complementing governmentÆs social provisioning efforts. Indeed, the Bafokeng community owes its present-day modernisation efforts to mineral rights, and in particular, the legal-institutional arrangement that has enabled it to play an active role in South AfricaÆs lucrative extractive economy. However, the distribution of platinum wealth in this community is not only uneven, but also appears to have had little impact on the broader socio-economic conditions in the community. Despite claims by community leaders of heavy investment in education and skills development, the community continues to be faced with very high levels of unemployment, illiteracy, sprawling informal settlements, poor access to medical facilities and malnutrition. This paper examines the sociological paradoxes and contradictions thrown up by the approach adopted to involve community members in the mobilisation of mining royalties for developmental ends. The central argument is that the current æmodelÆ contradicts the communityÆs stated goals of using platinum wealth to drive up broad-based development and modernisation. This is mainly because it leaves out the vast majority of community members, who are uneducated and unskilled. The core analysis is based on pilot data from an ongoing study in the Royal Bafokeng community.

Jan 1, 2009

The last time Mining Engineering presented an issue with a special focus on Canadian Mining (ME, August 2008 pp. 28 to 40) things were going well. A feature story took a look at Xstrata?s Nickel Rim South Mine in Sudbury and the booming Canadian oil sands were discussed at length. Potash prices were soaring, large diamonds were being found and British Columbia was launching plans to find more workers. How things have changed in six short months. What began as a mortgage crisis grew into a credit crisis, then mutated into a financial crisis, that has taken its toll on the value of bonds, loans, stocks, real estate and commodities. Miners that were flying high on unprecedented commodity prices six months ago have begun scaling back with delays, shut downs and layoffs as they struggle to survive this most recent economic downturn.

Jan 1, 2009

By I Mason, A Bray, K Smith, T Sindle

Borehole radar is a proven geophysical technology that can be used to map an orebody ahead of mining. This paper will present a case study, where borehole radar is being used within the mining cycle to map out orebody blocks, both as a strategic and tactical tool. Refined equipment and procedures now enables a slimline borehole radar tool to be deployed on the end of drill rods, making it easier and faster to deploy in an underground mine with minimal impact on the mining process. Boreholes are drilled in advance of mining; cover holes to ensure the competence of the hanging wall and geology holes to determine the location and grade of ore are two such examples. All of these boreholes can be entered using a borehole radar tool to map geology and structure ahead. The radar data can provide images of the orebody as well as help detect potential water bearing structures that could impact on safety at a mining face.

Jan 1, 2009

By R. E. Chaves

San Martin Mine is an open pit, gold heap leach operation located approximately 70 kilometers from the Honduran capital of Tegucigalpa. Mining operations commenced in 2000 and were completed late in 2007, while heap leaching operations continue. Reclamation was executed concurrently with operations to the extent practical. The area has distinct rainy and dry seasons and closure objectives include: prevention and mitigation of acid rock drainage, sediment and erosion control, and mitigation of visual impacts. Final closure is well underway at San Martin and this paper describes the closure processes conducted to date, problems encountered, and the subsequent lessons learned.

Jan 1, 2009

By Eduardo Nunez, Asim Tuzun, Dan Graffi, Glenn MacPherson

"In preparation for the milling of a new nickel and copper mine ore, Nickel Rim South, Xstrata’s Strathcona Mill is undertaking numerous process improvement projects. Within the grinding circuit, several projects are under development and an automated grinding control strategy, consistent with the operating objectives, was identified as a key requirement. The grinding strategy is to maximize the throughput (quantitative objective) while maintaining the cyclone overflow within specifications (qualitative objective).This paper describes the implementation of a robust grinding control strategy using the existing control system. The implemented controls maintain the cyclone overflow density at the desired target, while continually optimising the rod mill feed rate to allow maximum throughput. This approach has the added benefit of improving the stability of the rougher flotation circuit down stream of the grinding and improving energy efficiency of the rod and primary ball mills. This paper discusses the comparison of the before and after the implementation of results.INTRODUCTIONThe grinding process is a size reduction operation used in the mining industry to liberate the valuable minerals from the gangue. Grinding is one of the most important and expensive processes in a concentrator (Xi-song, 2007; Pomerleau 2000; Najim 1995), often accounting for around half of the total operating costs in base metal concentrators (Wills, 1990), which has led to a focus on development and implementation of control and optimisation strategies. The grinding process prepares the ore for the subsequent concentration step, which for sulphide base metal operations, is predominantly flotation. The performance of the concentration (flotation) is very much determined by the feed characteristics of the slurry coming from grinding. The valuable minerals recovery process in flotation is very much influenced by the grinding process and the liberation of the desired minerals from the gangue minerals (McIvor, 1991).The true objective of grinding is to obtain a proper liberation of the minerals as defined by a particle size distribution referenced typically by d80 (80% passing size of product). Besides achieving the desired mineral d80 size, it is clearly desirable to produce as narrow a size distribution as possible to squeeze the maximum amount of the mineral value into the highest recovery region (McIvor, 1991). This is an important criterion for the mill in economically optimizing the grade and recovery for the concentrate product. It is important not to over or under grind, while keeping the specific comminution energy as low as possible (Nunez, 2005) to achieve the target liberation. In other words, maintain an optimal throughput depending on the ore conditions to the capacity of the grinding mills, while providing the flotation process with a constant and narrow size distribution, at a cut size selected to meet the metallurgical requirements (Bascur, 1991)."

Jan 1, 2009

By Patricio Ruz, Gabriel Riveros, Carolina Ramirez, Andrzej Warczok, Rober Treimer

"Continuous converting of copper matte produces slag with high cuprous oxide content. The corrosion of chrome-magnesite refractories with slag of high cuprous oxide content is a major problem. Properties of olivine type of slag make the slag very attractive for matte smelting and converting.Analysis of phenomena determining the slag infiltration into the porosity of a refractory and dissolution of refractory components in the slag allowed for better understanding of the mechanisms of refractory destruction.The results of laboratory scale tests of the olivine slag infiltration into open porosity and corrosion showed dominating effects of slag temperature and cuprous oxide content. The optical and X-ray examination of slag samples permitted the definition of the mechanism of formation of new phases and refractory deterioration. 71"

Jan 1, 2009

By H Bateman, I Cawrse, G Carnes, S Cawrse

In developing mineral resources, the focus typically centres on the management of identified social and environmental impacts and compliance with regulatory requirements. However, opportunities to protect and enhance the environment and communities are most effective in the planning and design phases. Achieving the objective of integrating sustainability considerations as an element of design decision making requires that the design criteria be technically sound, relevant to the project and applicable to desired design outcomes. This is particularly important for projects employing virtual teaming, where design engineers may be geographically dispersed and are unlikely to be familiar with site specific sustainability challenges and opportunities. This paper documents the approach taken by BHP Billiton to incorporate sustainability principles, objectives and guidelines in design criteria for the Olympic Dam Expansion (ODX) project. It describes the range of inputs used in defining sustainability objectives which interface in a framework that is dynamic and transferable to other mining projects and to engineering design in general. The Sustainability in Design Criteria document distils statutory requirements, corporate standards, lessons learned and leading industry practice into a single coherent framework that supports engineers to approach problem solving as a holistic and integrated exercise with a long term perspective. The framework also serves to improve linkages between internal stakeholders by fostering greater communication, collaboration and innovation to deliver more sustainable outcomes through the design process.

Jan 1, 2009

By Malti Goel

"The cost-effective capture of carbon dioxide (CO2) from the point sources for its reduction the atmosphere offers many challenges in materials science. Novel CO2 capturing approaches using chemical, physical and biological methods are in the research stage and are aimed to minimize the cost. Appropriate materials development , which can withstand required temperature or pressure as the case may be for CO2 emanating from coal gas or industrial waste gases form the minimum condition. Other requirements are reclyclability of material and cost of separation. Nano-material composites can be more effective in selective capture of CO2 and can offer solutions for large-scale separation process. Nano-porous material catalysis can enhance the reaction rate of CO2 with other chemicals and thus help in capture of CO2 and convert it into value added products. This paper reviews recent industrial scale developments. In the Indian context, R&D priority areas in CO2 capture process development with a focus on energy industry are presented.IntroductionScience of Climate Change is growing at an enormous pace. With the ultimate goal of stabilization of greenhouse gases in the atmosphere, new scientific approaches are being researched worldwide. A shift in policies from low carbon and no carbon energy sources to fossil fuel sources with capture of carbon and its permanent storage is taking place. The process of carbon capture is both energy and materials intensive and the cost of power generation may increase up to 40% when carbon capture and storage (CCS) technology is implemented. Development of cost effective R&D technology therefore remains the greatest challenge before the scientific community."

Jan 1, 2009

By Thomas Buenger

The Hamburg smelter of Norddeutsche Affinerie AG is situated near the city of Hamburg’s downtown and is therefore particularly subjected to fulfill environmental requirements according to the German legal regulations. Thus, investments related to increasing concentrate throughput are always linked to packages to enhance the emission status of the smelter. This connection between environmental protection and productivity enhancement should be explained by the example of the Peirce-Smith converter plant of the Hamburg smelter. Such outstanding investments can be demonstrated by the transition from scrap charging via boat from the front side to a fully automatic and completely sucked scrap charging system.

Jan 1, 2009

By Claudio Toro, Alex Moyano, Rodrigo Díaz, Hugo Jara, Carlos Caballero, Pedro Morales, Leandro Guzmán

"During 2007, Codelco-Chile carried out industrial tests to validate the Continuous Converting Process in the Teniente Converter of the Codelco Norte smelter.For planning and starting up the tests, a predictive, analytical and dynamic model was developed to support operational decisions. The dynamic model was developed using the METSIM® platform and dynamic data exchange (DDE) to operate smoothly with MS Excel®. The main feature of this real-time model was the on/off-line ability to work and gather data from either the smelter’s PI system® or database, and simulate the operation with or without scheduled events and controls.The main model development aspects, which include thermodynamics, metallurgical and kinetic considerations, slag-type and on-line mass and heat balances of the process, as well as the successful validation of the model, are presented and discussed in the present paper."

Jan 1, 2009

By Peter Chou

A total of 117 slope stabilization drilled piers were installed as part of a major hillside revitalization project. The 110-million dollar development, known as Stratford at Kenwood, included an 18-story upscale senior residential tower, a 3-story healthcare building, and 4-story condominium buildings, offering approximately 580,000 square feet of living space with panoramic views of Downtown Cincinnati, Ohio. In an effort to establish a flatter hillside plateau for the new 4-story condominium and to create a cut and fill balanced jobsite environment, an 800-foot long row of drilled piers and a 600-foot long multi-tiered shear key system was used to terrace existing 1.5H to 3H: 1V steep slopes and support the new fill. These slope stabilization features reduced the amount of spoils needed to be wasted off-site and mitigated the risk of slope instability. An ODOT/FHWA research indicated that spacing of stabilization piers and necessity of top-connecting elements are highly dependent on pier diameter, spacing, soil type, depth to potential failure surface, surcharge loads, and pier deflection. Due to pre-existing deep buried swales, various load combinations, and the complex mechanism of soil arching effects between adjacent piers, both analytical and numerical computer modeling was performed to estimate the loading on each pier. New generation multiplexed, 3-Dimensional, Micro-Electro-Mechanical-System based inclinometers were installed between selected piers to confirm the pier design, and monitor the fill placement, as well as long-term slope stability.

Jan 1, 2009

By Lawrence P. Goldfarb

The City of Alexandria, Virginia, Public Safety Center (PSC) is a 64,000 square foot facility that houses the Police Department, Office of Sheriff and the Office of Magistrate. In addition, the center includes a detention facility for local and federal inmates, operated by the Sheriff. The PSC is composed of a 3-story building to the west and a 6-story building to the east constructed on a landfill in a wetland area in the flood plains of hunting Creek. The existing ground floor of the 3-story building is a floating slab-on-grade, with the interior and exterior columns, exterior walls and upper floors all supported on belled, drilled shafts. Portions of the floating first floor slab have undergone excessive settlement due to the apparent consolidation of the underlying organic soils. The magnitude of the settlements of the floating first floor slab is sufficient to require replacement of the slab and relocation of a portion of the facility. The rehabilitation was complex and required staged construction, consisting of constructing Auger Pressure Grouted (APG) Piles in low overhead conditions. This paper summarizes the geotechnical conditions that lead to the excessive settlement of the floor slab, the construction of the (APG) Pile foundations in low overhead conditions and the evaluation of potential future settlements.

Jan 1, 2009

By Jake Hutchison, Wade Hutchison

The opposition to the project has risen as a result of some political pressures and from public perceptions about the project’s necessity and its impact on the neighborhood. As a result of this controversy, the Underground Conservation Hall was quickly termed “Bredesen’s Bunker” by the Media. Close exposures for blasting, required by the Conservation Hall construction project, have been regulated by specifications that regulate seismic monitoring, pre-blast and post-blast inspections. Planned blasting for the project included blasting to a depth of 30 feet (9.14 meters) within 35 feet (10.67 meters) of the front of the newly renovated Tennessee Executive Residence. Excavation for the project found more competent rock at higher elevations than identified in test drilling which required blasting within 2 feet (0.61 meters) of the side of the Residence.

Jan 1, 2009

By Claudio Toro, Alex Moyano, Jonkion Font, Carlos Caballero, Pedro Morales

"Codelco-Chile in the last decade has carried out industrially-oriented research as an alternative to the traditional batch-type converting process. In a first stage carried out preliminary evaluations in a rearranged Peirce Smith (PS) converter, and then an exploratory test in a “Convertidor Teniente” (Teniente converter, TC) for the Codelco-Chile Continuous Converting Process. However, the validation test for this process in the TC was delayed up to the second quarter of 2007 where the validation studies were done satisfactorily.Thus, the objective of this paper is to present the results of the campaign tests validating the Codelco-Chile Continuous Converting Process in the TC1 of the Codelco Norte smelter.The results of charging the solid or liquid matte or high grade matte (“white metal”) by Garrgun, or by mouth of the 22 m x 5 m TC1 are presented. Some features of the industrially validated process are discussed, and the pilot test results of the matte injection are also presented."

Jan 1, 2009

One of the key issues facing gold producers is the management of cyanide and the implementation of the International Cyanide Management Code. Many operations now use cyanide destruction processes to ensure that the material being discharged to the tailings dam is compliant with regulatory requirements and the International Cyanide Management Code. One of the problems for operations is the quantification of both cyanide species and their reaction products throughout the leach and destruction circuits. Therefore methods have been developed utilizing high performance liquid chromatography (HPLC) to measure free cyanide, cyanide complexes of metals such as copper and iron, and other species formed from reactions in leaching and cyanide destruction, including cyanate, thiocyanate, and sulphur species (eg. sulphite, thiosulphate and sulphate). This enables a complete mass balance for cyanide and sulphur in both leaching and cyanide destruction. This paper outlines the methodology which has been developed and discusses the application of these methods in the fundamental research currently being conducted on the impact of sulphide minerals in cyanidation and cyanide destruction chemistry.

Jan 1, 2009

By M. N. Chandraprabha

This paper discusses the role of mineral-adapted acidiphilic microorganism Acidithiobacillus ferrooxidans on the beneficiation of arsenopyrite containing multisulfides (pyrite and chalcopyrite). Adaptation to minerals altered the surface properties of the microorganism. Bacterial adaptation to arsenopyrite and controlled bacterial adhesion to mineral surfaces lead to selectivity in arsenopyrite separation. Bioremoval of arsenic ions (both arsenite and arsenate ions) by Acidithiobacillus ferrooxidans is also discussed.

Jan 1, 2009

By A. El-Midany

Dolomite impurities are increasing in the currently mined phosphate deposits in Florida. Several research efforts have been conducted in various laboratories around the globe to find methods to economically removing the dolomite. However, a universal and cost-effective process is not now in commercial use. In this paper, a new process for dolomite/apatite separation is presented. The differential solubility of dolomite in slightly acidic solution is utilized to generate micro CO2 bubbles at the dolomite/water interface. Particle (dolomite)/bubble aggregates float to the surface leaving phosphate concentrate with low MgO content. Interestingly, up to 6.0 mm particles can be floated by such micro-bubble/particle aggregates. Different surface-active agents were tested to stabilize the bubbles. Results of these tests are presented, and the mechanisms involved are discussed.

Jan 1, 2009