Search Documents

By Z. Q. Yue

Many large rock avalanches and/or landslides have occurred in mountainous regions around the world. Their occurrences are normally rapid and unexpected, which can cause disasters. They have been investigated extensively by many researchers and engineers since the 1903 Frank Slide on Turtle Mountain, Alberta, Canada. They are one of the most peculiar phenomena because the rock debris of more than one million m3 can move over the horizontal distances exceeding those expected from conventional friction physics. This paper presents a gas cause hypothesis responsible for the large rock avalanches. It is the migration and expansion of a certain amount of highly pressurized and dense natural gas mass from deep geological grounds into the mountainous rock mass slopes. The natural gas with high pressure and density can escape from the deep geological ground and flow through faults, weak zones and/or porous channels into the rock mass forming a mountainous slope. The rock mass forming the slope has the high tensile and compressive strength and can resist the initial loading of the gas mass migrated into and stored in their voids, pores, holes, gaps, openings, apertures and cavities. With time, more and more gas mass from deep ground can migrate into and stored in the slope rock mass. Eventually, the peak equilibrium of forces and deformation reaches. The expanding power of the gas in the slope rock mass would instantly and rapidly break, erupt and/or explode them. The compressed and dense gas mass would mix, flow and expand together with the broken rock debris mass and continue offering their remaining expanding powers to the moving and sliding debris mass. As a result, the rock debris of large volume can reach the runout distances exceeding those expected from the conventional friction physics. The gas would escape into the sky and the solid rock debris would remain on the ground spreading over large ground area. The 1903 Frank Slide is examined to show this gas cause and mechanism in mountainous regions.

Jan 1, 2015

"The main purpose of geometallurgy is to develop a model to predict the variability in the mineral processing performance within the ore body. Geometallurgical tests used for developing such a model need to be fast, practical and inexpensive and include as an input data relevant and measureable geological parameters like elemental grades, mineral grades and grain size. Important in each geometallurgical program is to define the number of samples needed to be sent for geometallurgical testing to enable reliable metallurgical forecast. This is, however, a complicated question that does not have a generic answer.To study the question on sampling a simulation environment was built including a synthetic ore body and sampling & assaying module. A synthetic Kiruna type iron oxide - apatite deposit was established based on case studies of Malmberget ore. The synthetic ore body includes alike variability in rock types, modal mineralogy, chemical composition, density and mineral textures as its real life counterpart. The synthetic ore body was virtually sampled with different sampling densities for a Davis tube testing, a geometallurgical test characterising response in magnetic separation. Based on the test results a forecast for the processing of the whole ore body was created. The forecasted parameters included concentrate tonnages, iron recovery and concentrate quality in terms of iron, phosphorous and silica contents.The study shows that the number of samples required for forecasting different geometallurgical parameters varies. Reliable estimates on iron recovery and concentrate mass pull can be made with about 5-10 representative samples by geometallurgical ore type. However, when the concentrate quality in terms of impurities needs to be forecasted, the sample number is more than 20 times higher. This is due to variation in mineral liberation and shows the importance of developing techniques to collect qualitative information on mineral and ore textures in geometallurgy."

Jan 1, 2016

By P. Momni, D. Ersenkal

Equator Principles (EPs) are a set of guidelines developed and adopted by a series of financial institutions for assessing and managing social and environmental issues in project financing. Established in 2003, EPs are now adopted by some 68 financial institutions from 27 countries. As more and more financial institutions join this global initiative, it is important for project owners to have a logical framework embedded into the project lifecycle to reduce the risk of non-compliance which could result in costly delays. This paper outlines a proactive approach for project developers in order to integrate environmental and social aspects into entire project lifecycle.

Jan 1, 2010

By D. J. Archambeault, A. Saigal

Substantial cost savings have been demonstrated by material design changes after initial product development. As more information about a product's operating environment becomes available to a designer, it is possible to consider a more costeffective material that still meets or exceeds the design intent, such as minimum low cycle fatigue life. This is especially true in the aircraft engine industry, where precise operating cycle data is not available until after the first engine is built and tested. A methodology for predicting estimated low cycle fatigue life has been developed to investigate potential material change candidates for an aft cooling plate. A twodimensional macromechanical finite element model (FEM) has been developed using ANSYS and used to determine the effects of varying material properties. It is shown that slight changes in density, coefficient of thermal expansion and modulus of elasticity have profound effects on component and effective stresses, and therefore, estimated low cycle fatigue (ELCF) life. Aerospace

Jan 1, 2006

By N. W. Xu, C. Sha, F. Dai, Y. G. Zhu, B. Li

Underground caverns stability and excavatability of rock masses are of significance in geotechnical engineering, in both design and construction stages. Risks associated with underground group caverns of Houziyan hydropower station in southwestern China are growing as a result of continuous excavation-induced unloading. To improve our understanding of the underground caverns instability and resolve the complex subsurface conditions of the highly fractured rock mass, a high resolution microseismic monitoring system was established in the deep underground caverns, pursuing the relationship between the measured data about microseismic activity and excavation damage zones of surrounding rock mass. Through analyzing the tempo-spatial distribution of microseismic activity, excavation damage zones and potential risk regions in underground caverns were identified. Furthermore, the correlation between microseismic activity and pre-existing geological structures, as well as traditional monitoring was analyzed. In order to validate the correlation between seismicity and potential slip surface of underground caverns, a model was implemented into numerical code to further evaluate the deformation and stability of surrounding rock mass. The monitoring results demonstrate that microseismic events mainly occur at high stress concentration regions, which coincides with the results obtained from numerical analysis. Therefore, the comprehensive method incorporating microseismic monitoring and numerical analysis, as well as traditional monitoring and filed observation has been proven to be very promising in deformation and even instability prediction of surrounding rock mass in underground caverns subject to delineation of potential slip surfaces and excavation damage zones.

Jan 1, 2015

By Ji Wang

Reflective in-seam wave detection has the advantages of a far detection range and wide applicability. It has been successfully used in detection of many abnormal geological structures in work-faces, such as faults and collapse columns. However, a reflective in-seam wave is a dispersion wave. It has weak energy and is always covered by the direct in-seam wave. In the past, underground seismic explorations were not able to image the opposite roadway using reflective in-seam waves. To solve this problem, we propose a new method of reflective in-seam wave imaging based on adaptive dispersion filtering. This method processes the reflective in-seam wave using a filter with the parameter of transmission distance. The degree of similarity of the filtered and the explosion signal is used to estimate the transmission distance and image the reflective objects. We test and verify this method using real underground seismic data. This research is helpful for the detection of coal mine goafs and abandoned roadways in work-faces or in front of tunneling ends.

Aug 1, 2013

By D. Ibarra, J. Jacob, A. G. Guezennec, P. d’Hugues, A. Archane

The lack of adequate gas mass transfer is a rate limiting step in many bacterial leaching processes. Oxygen often becomes a limiting factor because of its low solubility compared to the high demand induced by sulfide oxidation. One way of increasing the solubility of oxygen in water or in media solution is by increasing the driving force, i.e. raising the oxygen partial pressure in the gas stream supplied to the leach pulp. The use of oxygen is a well-known practice in high-temperature bioleaching reactors (above 70°C) whereas air is usually preferred in medium and low-temperature operations in order to avoid too high dissolved oxygen concentrations which could impact negatively the bacterial activity. The purpose of this study was to investigate the use of oxygen-enriched gas in bioleaching reactors at 40°C in order to improve the gas transfer in the system when operating at high solid load (20% and more). Bioleaching experiments were performed on a sulfide-rich tailing waste (pyrite 60%, copper 0.8%, cobalt 0.06 %, gold 1 g/t) using the “BRGM-KCC” bacterial consortia. The reactor used for the tests was designed on the basis of a new bioleaching reactor concept developed by Air Liquide, Milton Roy Mixing and the BRGM which uses floating agitators to inject gases and to mix and to suspend solids in the bioleaching solution. Two types of tests were carried out: with air injection and with oxygen enriched gas mix injection. The aim of this work was to confirm the capacity of bacteria to grow and to dissolve pyrite in this type of bioreactors in oxygenrich atmosphere, and to compare sulfides dissolution rates during both types of bioleaching tests. The results obtained show that the use of oxygen enriched gas mix does not decrease bioleaching performances compared to air injection. High metal extraction yields were achieved (above 80%). No deleterious effect due to oxygen use was observed on the bacteria despite the high level of dissolved oxygen reached in oxygen tests (up to 14 mg.L-1).

Jan 1, 2016

By K. Torigoe, S. Owad, C. Tokoro, Y Tsunazawa

The mechanism of an abrasion process to recover metal values by removing components from printed circuit boards (PCBs) is modeled using a discrete element method (DEM) simulation. To simulate the abrasion process, a model PCB geometry was constructed consisting of bonded particulates. The simulation allowed connections between particles to be broken if the bonding force calculated from DEM exceeded a threshold level. Simulation results were compared with experimental comminution data using an agitation mill with test PCBs on which nine capacitors were surface solder-mounted. Simulation results obtained from the DEM with the anchoring model corresponded to experimental observations.

Jan 1, 2011

Over the years, efficient on-line monitoring of performance and status of an electrolytic copper refining process has been challenging due to the need for complex electrical measurement systems and the management of the enormous volume of data. Recent innovative developments by Kennecott Utah Copper Corporation and Outokumpu Technology in wireless cell voltage and individual cell temperature sensing opens new possibilities to improve and modernize tank house management. This paper describes the powerful Outokumpu CellSenseTM refinery monitoring system for efficient interpretation of data produced by wireless CellSensorTM system with traditional refinery measurements. Examples from commercial tank house installations demonstrate the benefits of the system to improved process control and operation. The Outokumpu CellSenseTM monitoring system is simple to operate and accessible to all the plant operation teams.

Jan 1, 2007

By G. O. Crowell

This paper gives the history of the celestite deposit, now being mined by Kaiser Celestite Mining Ltd., near Sydney, Nova Scotia. Mining and milling procedures are covered, and the regional and local geology of the area are described, including the origin of the celestite.

Jan 1, 1971

By Z. Trojanová

The deformation behaviour of ternary magnesium alloys AJ (Mg-Al-Sr) and AX (Mg-Al-Ca) were investigated in tension as well as compression tests. The samples were deformed at temperatures between 20 and 300 °C and at an initial strain rate of the order 10-4 s 1. The flow stress decreases with increasing temperature. The macroscopic work hardening rate decreases with increasing flow stress and temperature. The stress and temperature dependence of the work hardening rate is a result of the hardening and softening processes. Stress relaxation experiments were performed in order to reveal features of the thermally activated dislocation motion. Internal and effective stress components of the applied stress were estimated. A decrease in the internal stress was observed at elevated temperatures, which indicates recovery process (-es). A more detailed analysis of the estimated values of the activation volume and activation energy helped to interpret the thermally activated processes during plastic deformation. It is concluded that the deformation behaviour of the alloys depends on the activity of non-basal slip that is strongly influenced by temperature.

Jan 1, 2007

By Atulya Verma, Samantha Espley, Nashel Kalaka

Numerical modelling simulations of proposed mining sequences are used to evaluate mining induced stress concentrations and their migration associated with the progress of mining. This analysis is a standard practice for most prospective mining projects at various levels of feasibility study. The studies are usually initiated at the beginning of the mining cycle, on a global scale, and are maintained and updated throughout the life of mine (LoM) to identify or address local issues and the required remedies as and when needed. Developments in numerical modeling techniques along with advancements in computing technology and data storage/management capacity have given rock engineers access to a huge volume of data that needs to be analyzed and assessed. The most common approach to numerically evaluate stress concentrations and migrations in underground mines is to select the points of interest in a given volume such as the back of an excavation or points within pillars around critical infrastructure, and plot the stresses or a derivative of stresses over time to represent life of mine concentrations and migrations of stresses. The problem with this approach is the sharp gradient of stresses close to excavation boundaries. Slight changes in the location of selected points can change the stress concentration and migration patterns substantially and all generalized statements about LoM risk can be challenged in one way or another. For global stresses, the most common current approach of data analysis is by viewing series of pictures representing stress contours. In this approach, it is easy to overlook some critical detail and/or be masked by personal preferences of contour/picture representation. To overcome the problem of representing and analyzing huge volume of stress simulation data, the authors, through their experience at different mining operations, developed a volume-based technique to reliably evaluate mining-induced stress concentrations and migrations. The volume-based approach is for risk-based assessments of adjacent regions in the rockmass, in and around planned stoping excavations. The volume of interest is the entire ore body that is planned to be mined, but it could be just a part of the ore body depending on the specific use case. The risk identifiers are the induced stresses as compared to the strength of the rockmass. Over the LoM, the risk identifiers are tracked versus the corresponding excavation ratio of the zone. This approach is very effective in identifying the stages of mining that are contributing the most to the mining induced stress risk and the results can be used for proactive planning and mitigations measures such as alternative mining sequences, or stope sizes, or extraction methods. The approach has also been very successful in application at mature mines, particularly in assessing the re-initiation of mining in zone that has been dormant for some time. The volume-based approach allows for an assessment of the current state of the rockmass and the identification of future risks when planning resumption of mining activities.

Jan 1, 2023

By L. Byszynski

The results of a three month evaluation of the application of EMEW® technology at the KGHM Glogów II Smelter tank house bleed stream are presented. The current, conven¬tional electrolyte decopperization process has some limitations, including: only a fraction of its production is commercial grade cathode copper, significant operating costs, low current efficiency, low current densities resulting in low copper depletion rate, and arsine gas and sulphuric acid emission. The EMEW® cell technology developed by Electrometals Technologies Ltd. can overcome many of these limitations. Tests were performed on a pilot EMEW® installation comprising 30 cells at ambient temperature on electrolyte bleed, using current densities between 100 and 600 A/m2 , with copper concentrations between 45 and <1g/dm3. Results showed that a high grade copper can be obtained to the level of 7 g/dm3 of copper concentration in electrolyte. The use of EMEW® technology allows the direct and efficient recovery of over 85% of the copper contained in the bleed electrolyte. Glue & thiourea addition were tested in order to improve the parameters of the copper depletion process. The behavior of Arsenic and Bismuth was observed and a means for their elimination from the system proposed. On-line copper concentration monitoring is proposed to improve control and performance.

Jan 1, 2007

By L. Tapia

The main disturbance for stability in primary grinding using SAG mills is related to continuous changes in the ore being fed to the plant, such as size and hardness. Searching for stability is the first step to accomplish, before trying to maximize the mill throughput. The time variability in the characteristics of the ore being fed from the mine to the plant must be known or inferred to perform adaptive changes in the grinding process control. In day to day operation, such information is not available in real time. Transport times and inventories between the mine and the plant complicate the situation. Under this scenario, Minera Los Pelambres implemented a grinding optimization strategy, based on the real time analysis of certain process variables, such as ore size, mill current consumption, pebble generation and throughput. As a result, both grindability and stability indexes are inferred. This is equivalent to inferring the ore characteristics by knowing its effect on the grinding behavior. These two indexes permit control of the SAG mill total charge level and hence, allow optimization of throughput by means of an expert control system.

Jan 1, 2007

By Lev Filippov, Saeed Farrokhpay

"Flotation process has had less success to recover nickel from laterite ores. Nickel in laterite ores is often finely disseminated in various minerals in very fine size. Therefore, fine grinding should be used to liberate nickel containing particles. Particles resulted from fine grinding are often very fine, and recovery of such particles is generally low using conventional flotation methods. One option to overcome this problem is enhancing the particle-bubble interaction by increasing the particle size and forming flocs. Selective flocculation of fine particle can be therefore the key to enhance the flotation performance of low grade laterite ores.INTRODUCTIONThe majority of the world’s nickel resources occur as laterite ores which are complex, low grade and expensive to treat using conventional smelting and high temperature and/or high pressure autoclave methods (Xu et al., 2013). While about 70% of the nickel resources are contained in laterites, only 40% of the world’s nickel production comes from these ores. Researchers have tried to improve the nickel laterite flotation recovery by using a number of feed preparation techniques. For example, in a study on a laterite ore sample from Australia, flotation tests on a narrow sized fraction of 38-75 µm resulted in only a small increase in the nickel content, from 1.0% to 1.4% (Quast et al., 2015a). In fact, no physical separation technique (including flotation) has been able to dramatically upgrade nickel in laterite ores (Quast et al., 2015b). Thus the challenge of processing low grade nickel laterite ores still exists. This paper aims to explore the possibility of applying selective aggregation in pre-concentrating of valuable minerals in nickel laterite ores."

Jan 1, 2016

By Man-Chao He

One of the critical problems involved in deep coalmines is unusual gas emissions. Many researchers agree that there is a relationship between coal gas emissions and geological features such as tectonics or geological disturbances, gas content, properties of the coal and rock and the mininginduced stress state in the coal seam and rock. Thus, the present paper intends to investigate complex mechanical phenomena during the process of gas emission in underground coal-mines. A program of laboratory testing was undertaken to study the effects of temperature and pressure on mechanisms of gas emission. It must be noted that this paper describes new techniques developed to simultaneously measure deformation and gas pressure, as well as flux during the test, taking the characteristics of gas transport into consideration under certain temperature and pressure conditions. The results indicate that under certain temperature and pressure conditions, gases adsorbed to coal start to desorb, and increase the pore pressure. High pressure gases entering coal fractures can generate high tensile stresses near the crack tips, leading to crack propagation and coalescence, which in turn can cause the specimen to dilate. From the experimental viewpoint, these test results may help us discern why mining seismic events can trigger gas emissions.

Aug 1, 2013

By P. J. Urso

"This paper discusses the mining problems encountered at the Fording River coal mine to date, and how they have been solved. All of the production now comes from surface mining, but underground hydraulic mining is planned and briefly described. Other facets of the operation, including markets, equipment and personnel, are covered. IntroductionFording Coal Limited was formed in 1968 to mine and market metallurgical coal resources held by the company in the East Kootenay region of southeastern British Columbia. The company, at its Fording River operations, holds approximately 48,000 acres of coal lands, having an estimated 2.0 to 3.0 billion long tons of metallurgical coal in place. (Although not a point for further discuss ion in this paper, the company also holds approximately 1.0 million acres of mineral rights. These consist primarily of coal in Alberta, potash and coal in Saskatchewan, and minor industrial mineral holdings of limestone, salt and bentonite in the three western provinces.)Fording Coal is owned 60% by Canadian Pacific Investments Ltd. and 40% by Cominco Ltd. Inasmuch as Cominco itself is owned approximately 54% by CPI, it is seen that the effective CPI ownership of Fording is about 82%. The company, originally staffed and managed by Cominco, has been independent since January, 1978, with its own board of directors, management, staff and employees.The company&apos;s head office is in Calgary, Alberta. The Fording River operations are located approximately 45 miles north of the Crowsnest Pass, near the Alberta/British Columbia boundary, only 95 air miles and 200 road miles from Calgary.A contract was signed in 1969 with the Japanese steel mills to provide 45 million long tons of metallurgical coal over IS years, commencing in 1972 at an annual rate of 3 million long tons per year. Despite some start- up difficulties, the mine and plant facilities achieved their rated capacities in 1975, producing and shipping at the 3-million-Iong-ton level. The coal specifications are shown in Table I."

Jan 1, 1980

By T Nakamura, M. Itoh

Most of the used cathode ray tube (CRT) glass in Japan, which contains lead oxide, was exported and recycled in overseas factories of new CRTs. However, domestic treatment and recycling of waste CRT glass has become necessary because overseas CRT factories have shut down and exports of CRT glass have stopped. Some of the waste CRT glass recycled domestically is charged in lead blast furnaces instead of silica flux, because there is no local reproduction route for glass that contains lead. However, the mass of CRT glass that can be treated in this manner is limited because of its high silica content. Consequently, additional treatment methods for waste CRT glass are required so that more can be used as a lead smelting material. In this study, waste CRT glass was treated with hydrofluoric acid to dissolve the silica contained in the glass, and the dissolved lead was recovered by precipitation. Lead metal was recovered by electrodeposition from the prepared hexafluorosilicic acid solution.

Jan 1, 2011

By F. Filzwieser, K. Gamweger

The process of gas purging in molten aluminium has been an industrial practice in Europe for many years. The advantages are a reduction in the hydrogen content and impurities in the melt, as well as a homogenisation of the temperature and chemical analysis in the molten metal. Formerly used lances or impellers are being replaced by porous plugs which are installed at the bottom of the furnace. This special product of RHI Refractories has proven its efficiency in primary melting as well as in die cast, sheet and extrusion plants.

Jan 1, 2004

By J. Peace, J. R. Fletcher

"British Steel has increased its usage of stainless steel for bunker, silo and chute linings to reduce maintenance costs and improve productivity.A generation of low cost 12% Cr steels has been specifically developed to satisfy the needs of hardness, flow promotion and through life costing which are demanded by bulk solids handling industries.The range of stainless steels include:• a very hard martensitic grade which is particularly suitable for high stress applications where impact and abrasion are predominant;• a titanium stabilized duplex steel for structural applications, as well as low friction , medium abrasion resistant wear liner plate; and• a ferritic stainless steel with rubber backing for low stress application where flow promotion of product is the predominant requirement.Industrial applications and experiences along with methods of fixin g the stainless steels will be discussed in conjunction with the relative through-life costs of the products.IntroductionBritish Steel has become one of the most efficient steel manufacturers in the world, with improvements seen in productivity, quality, delivery, performance and response to the needs of the worldwide market place.Part of this success stems from reductions in engineering downtime in the key areas of its operations, by the introduction of better engineering design and the use of enhanced materials where significant cost benefits have been identified.The nature of producing iron and steel requires the use and handling of a number of raw materials with wide ranging properties, each calling for a different approach to solving the difficulties encountered in storing and transporting these materials to their respective point of use. Figure 1 shows steel production for 1988-89 where over 30 million tonnes of raw materials were handled in making 14 million tonnes of liquid steel at British Steel&apos;s five integrated works.Typically solid raw materials include, iron ore, coal, limestone, ferro alloys and scrap. Intermediate products such as coke and sinter create their own specific handling and wear problems.Coals and ores are shipped into the United Kingdom from several sources, and have a great variety of properties. Some coals can be extremely wet and sticky, whereas others are dry and dusty . The ores handled can vary from wet concentrate and fines to heavy angular rubble and pellets. These raw materials are off-loaded, stored and conveyed through British Steel&apos;s own port facilities at Port Talbot, Immingham, Redcar and Hunterston. British Steel also produces the majority of its own coke and all its own sinter. Coke and sinter are frequently handled at elevated temperatures which cause other handling problems."

Jan 1, 1991