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By L. Bbosa

Positron Emission Particle Tracking (PEPT) and the Discrete Element Method (DEM) are used to investigate Power Draw in a laboratory scale tumbling mill. The mill is run dry in batch mode at different speeds using mono-size charge of glass beads, and is mounted along with a torque transducer to measure power. Particle tracking information from PEPT is used to reconstruct the motion of glass beads and infer the overall charge behavior, while DEM is employed to simulate particle motion and interaction, with collision mechanics calculated using the Hertz-Mindlin contact model. For PEPT and DEM data, the product of torque and average angular velocities in discrete cells are accumulated to obtain mill power. This method is found to be within statistical agreement with measured power for all tests. Spatial distributions plotted from this approach highlight the regions of the mill that draw the greatest power. A second technique to obtain Power Draw from DEM data which sums particle forces against the mill geometry is similarly found to accurately predict mill power with lower statistical error. Keywords: Power Draw, PEPT, DEM

Sep 1, 2012

By B. McFadzean, J. Taguta

The enthalpy of immersion is the heat change arising from the replacement of the solid-gas interface with the solid-liquid interface when a solid surface is immersed in a liquid. Although immersion calorimetry has been established as a valuable and reliable means of determining solid surface properties such as wettability, it has seldom been applied in mineral processing research. In this study, precision solution calorimetry was employed to measure the enthalpies of immersion of different minerals in water. The enthalpies of immersion were then related to the first-order flotation rate constant as determined by the microflotation technique. The same measurements were also made on sulphide minerals whose surfaces were modified to different degrees of hydrophobicity using different percentage coverages of amyl xanthate collector. The enthalpy of immersion technique was capable of distinguishing and ranking minerals according to their wettability. All mineral types and collector-treated minerals conformed to the same relationship that was found between the enthalpy of immersion and the flotation rate constant. This conformed, empirically, to a power law equation. As the enthalpy of immersion decreased, there were large increases in flotation response for very small changes in hydrophobicity. In addition, a critical enthalpy of immersion (CEI) was found, above which no flotation could occur. The scatter in the data points could be corrected for by adjusting the rate constant using the density of the minerals to produce a robust relationship between the rate constant and enthalpy of immersion. These results have shown that the enthalpy of immersion is able to indicate both the natural mineral hydrophobicity and the extent to which collectors can render a mineral hydrophobic. This technique has considerable potential to be used as a sensitive and accurate measure of mineral surface wettability in order to predict flotation performance.

Jan 1, 2018

By Gabriela Pino, Maurício Torem, Diego Veneu

Because of its simplicity, economy and biocompatibility, research regarding the use of microorganism for decontaminating heavy metals produced by many industries is an area of growing interest. Also, there is a stringent need for the control of toxic metals produced during various production processes and released into the aqueous environment in order to avoid damage relevant to soil or groundwater contamination. Among the available treatment technologies, sorptive flotation has been considered as a promising alternative for the wastewater treatment. In the present study Streptomyces lunalinharesii strain was applied as bioreagent for the removal of copper, cadmium and zinc. The removal of those metal ions depends mainly on the respective pH value, influencing the aquatic speciation during the process, as well as the zeta potential of the system and biomass concentration. Langmuir and Freundlich isotherms have been depicted. Dispersed air flotation was applied as the subsequent separation method for harvesting the suspended metal laden microorganisms, following the biosorption of copper, zinc and cadmium. The investigated parameters (in batch mode, laboratory scale) were in this case the saturator pressure, the coagulant concentration and the recycled flow. Applying the optimum defined conditions, over 60% removal of metal ions have been achieved in one stage and simultaneously, quantitative separation of the used (metal-loaded) biomass has been obtained.

Jan 1, 2014

By Y. M. Zhu

Lead in environment often causes a serious health hazard. The removal of Pb2+ from aqueous phase is a beneficial project. In this paper, deposited Saccharomyces cerevisiae (S.c.) was chosen as adsorbent, Pb2+ ions as adsorbate, and the process of biosorption was studied. The dynamics of the adsorption was investigated. The adsorption mechanism of Pb2+ by S.c. cells was also investigated by detecting microstructure, zeta potential under different pH value, FT-IR spectra of the S.c. particles before and after biosorption. It was shown that the biosorption of Pb2+ by deposited S. c. is a rapid process, and the adsorbing equilibrium is reached within 10 minutes. The Zero point of zeta potential of S.c. cells is pH=3.3. When 2.0<pH<3.3, there exists biosorption (biosorption rate 76%~88%), which means static bio-sorption been not the only kind of biosorption. FT-IR spectrum analysis showed that groups on bacteria surface were mainly characteristic groups of protein and amylase; oxo-groups and nitric-groups on S.c. cell surface could chelate with heavy metal ions. Chemical adsorption might exist in the process.

Jan 1, 2014

By A. S. Broesder

"With depletion of global ore deposits, there has been an increasing industry trend towards mining of lower average grade deposits in order to meet global demand, resulting in increased processing cost, energy usage and water usage. Consequently the industry is seeking pre-concentration technologies to reduce costs, increase production in existing operations and potentially enable the economic mining of previously uneconomical deposits. This pre-concentration can also advantage downstream processing and metal recovery. CSIRO has developed a large scale magnetic resonance based technology for the rapid quantitative detection of selected copper, iron and arsenic minerals in bulk ore. The technology is suited to measurement on large primary conveyors for enabling “pod” based sorting. The approach used in high tonnage sorting is to not sense and divert individual rocks, but to instead measure groups of rocks (“pods”) carried continuously on a single primary conveyor that can be diverted by conventional mechanical means. Bulk ore sorting operates by removing barren ore pods from a stream of crushed ore based on a bulk sensor measurement at a pod resolution of ~1 – 10 tonnes. The sorting process is based on the intrinsic variability of grade during the mining process that often occurs at the few tonne scale, and for instance, is common in many porphyry copper deposits. The MR technology has been proven in the laboratory for a wide range of copper, arsenic and iron minerals. A full scale prototype sensing system has been demonstrated in a trial at an Australian copper mine. Implementation trials of commercial MR based bulk sorting systems are progressing during 2018.INTRODUCTION An increasing trend in the mining industry is the exploitation of larger lower-grade deposits to meet global demand. Low-grade deposits involve increased processing cost, energy and water usage and increased tailings. There is therefore growing interest in technologies that enable more efficient extraction of low grade deposits. Water intensity of mining activities in a context of water scarcity, and the environmental and health implications of mine tailings are existing challenges, which are only made worse by the progression to lower grade orebodies. There is therefore also an interest in safer, cleaner and less wasteful extraction and production to ensure community well-being and environmental resilience."

Jan 1, 2018

"The business importance of water for mining companies is unequivocal as it may affect several aspects of mining projects ranging from the life-and-death license to operate to the imperative economic viability. It is thus no wonder that nearly all mining companies acknowledge water-related risks, issues and opportunities in their respective sustainability report. Somehow, this procedure has fostered the idea that water frugality could be the sustainable solution to several water-related issues. The regular exercise of water accounting should then follow as a key strategic requirement. Water accounting is defined as the application of a consistent and structured approach to identifying, measuring, recording and reporting information about water. However, several factors discussed herein have led to the fact that some water accounts are still produced using means (hardware and software) which undermatch the value actually associated with water. The resulting fuzziness about water usage could result in missed opportunities, suboptimal operations or even lead to environmental law violations. This paper subscribes to the distinctive perspective that, once underlying concepts and practical definitions have been standardized under a supported framework, such as the openly available Water Accounting Framework (WAF) published by the Minerals Council of Australia, most of the remaining water accounting issues may be boiled down to accuracy issues and, ultimately, to how much accuracy is valued by the stakeholders. Using the latest WAF document as a baseline for best practices of water accounting and, borrowing concepts from the fields of sensor network design in the process industries and best practices of metal accounting, this paper reviews some essential accuracy issues to be considered when designing or analyzing water accounting systems in mineral processing. The current paper also includes some elements for a promising attempt to include the value of information paradigm inside the water accounting best practices."

Jan 1, 2014

By Olli Haavisto, Heikki Häkkänen, Tommi Kauppinen, Navid Khajehzadeh

Raman analysis is a well-established method for finding the abundant minerals in an ore sample. In this study, Raman spectroscopy is tested as a method for rapid and contactless on-line mineral analysis. Rapidness might enable on-site analysis of rock drillcore, which in turn would lead to more cost-efficient solutions in mineral exploration. This paper discusses the use of Raman analysis to identify minerals and to measure their concentration. The sample set under study consists of rock drillcore collected from Agnico-Eagle Kittilä Mine, Finland. Selected parts of the sample set are measured by Raman spectroscopy and the minerals are identified using reference spectra from a public source. Moreover, the direct measurement of concentration of different minerals with the help of Non-negative least squares (NNLS) optimisation algorithm is considered. The optimisation algorithm was constructed to form a linear combination of reference spectra which best represent the measured spectrum, or an average of measured spectra, from an ore sample. The results show that NNLS can identify abundant minerals in a given sample. Also through this method of analysis the results of a traditional point-count method can be expanded: It was observed that, due to grain size, multiple minerals consistently appear in the spectra measured over an area, which means that point-count method is not a proper way to interpret the spectra. This can be seen as a new result, as formerly the discussion has attended to other methods.

Jan 1, 2014

By I. Gombköto

Mining and mineral processing operations are usually generating huge amount of tailings. These tailings often gives lots of maintenance work in order to protect environmental resources from heavy metals slowly leaching out of tailing are due to Acid Rock Drainage (ARD) process. Handling leakage could be active or passive such as using of Permeable Reactive Barriers (PRB). PRB?s are used worldwide treating underground contaminations, using different type of matrix materials. All generally used matrix material has its advantages and disadvantages such as selectivity, sensitivity of precipitation generation or not satisfying hydraulic conductivity. Nowadays cheap and effective matrix material which is ignorant to pore plugging caused by precipitation within the PRB could be one solution to the demands of the industry. The authors have been carried out an investigation at University of Miskolc on lignite as high humid acid containing material for determining the ability of heavy metal adsorption and pore plugging resistance. Moreover, using hydraulic and chemical simulation methods, complete PRB dimensioning protocol based on new lignite matrix had been introduced. Within the frame of this paper the results are going to be discussed.

Sep 1, 2012

By Pawel Strzalkowski, Marta Baszczynska, Urszula Kazmierczak

The paper presents issues related to interference of mining activities with the environment. Exploitation of mineral resources causes primarily a modification of the landscape. All of the negative impacts on environment are short-lived and last as much as it takes to exploit the raw material. After the mine closure reclamation is necessary during which all aspects that reduce harmful effects of the mining activities on the environment must be taken into account. Current ways of reclamation allow recreating natural environment, which is different from the original and enriched in diverse new values. This requires propositions of new forms of converted land development through a detailed analysis of technical, natural, planning, economic and social sphere requirements. Before making final decisions regarding selection of direction of reclamation, a thorough analysis of the key factors has to be carried out. All steps related to the implementation of the reclamation project are shown in the paper using Limestone Mine "Górazdze" located in the south-western part of Poland as an example. This paper also presents an analysis of current ways of post-mining reclamation towards agricultural and forestry landscape, along with our own suggestion for their extension in order to preserve biodiversity. For choosing optimal solutions the most relevant criteria were considered: existing natural values and possibility of their protection. Taking into account the economic and social aspects, supported by natural potentials, implementation of tourism and recreation in this area were proposed. It was shown that this proposition would not interfere with the current trends of the natural landscaping. Finally, after completion of reclamation and land development in the considered mine area, creation of a geo-park was proposed along with appearance of geotourism in the area. To illustrate the proposed forms of post-mining land development in the form of maps, an ArcGIS(ESRI) software was used.

Jan 1, 2014

By M. S. Eygi

This study covers the investigations based on the electrokinetic and rheological properties to explain the interactions between kaolin minerals and commercially available polyelectrolyte in anionic character. Additional adsorption test were also conducted to support the interaction mechanism. Adsorption tests showed that adsorption densities decrease by increasing the solid content. In-creasing the solids contents from 1% to 30% by weight resulted in the decrease on adsorption from 2.14 mg/g to 1.85 mg/g. Because of its difficulty, the solids ratio at 70% was not studied. However, following to trend of the curve plotted adsorption density-solid ratio, an estimation was made and adsorption density at 70% solid content was extracted from the curve as 1.75~1.80 mg/g. The electrokinetic studies pointed out that the presence of polyelectrolyte increase the zeta potential of kaolin from 40 mV to 60 mV which is reasonable conditions to disperse and stabilize the kaolin slurry and lower the viscosity. When these result of the different tests are combined and considered together, 2 mg/g polyelectrolyte concentration was noted as optimal concentration where adsorption density, viscosity and zeta potential of the slurries give maxima and remain constant after this concentration.

Jan 1, 2014

Opportunities to monitor and control primary grinding mill performance are strongly sought after in the mineral processing industry. Currently, limited on-line information about mill charge motion and content is available to mill operations for control purposes, leading to periods of lower throughput, instability, variable product size and accelerated mill liner and lifter wear. In response to this need, CSIRO has developed an on-line surface vibration monitor for primary grinding mills which produces data that has been shown to provide new information about the mill charge in terms of toe and shoulder position, as well as potentially key features such as the overall charge level, the distribution between rock and balls in the mill, and the impact of the charge on the mill liners and lifters. This paper outlines the key features of the on-line monitor system, particularly those relating to data transmission, data analysis, and the design of the monitor and its independent power supply. It describes the coupling of single vibration sensor data from the CSIRO on-line monitor to the actual operating conditions of a SAG mill and how the vibration response and hence mill operating conditions vary as a function of time, including during mill equipment failures such as a broken discharge grate. Opportunities for improved mill control based on the data from the on-line monitor are also discussed, as well as the implications in terms of mill processing and maintenance performance. Recently a CSIRO monitor was also installed on a ROM ball mill and analysis of the vibration sensor data from this installation is currently underway. Preliminary findings from this installation will be presented along with comparisons of generic information, such as toe position (measurement precision and operation variability) and vibration signal (intensity, sensitivity and operation variability), between this type of primary grinding mill and AG/SAG mills.

Sep 1, 2012

By H. Araneda

Throughout Chile?s history, mining has consistently been a leading industry in the country. The 1990s marked the beginning of a boom in Chile?s mining industry, especially in copper mining, due to both foreign and local direct investment in the sector. Mining?s contribution to the GDP was 15.6% at current prices in 2009, and it accounts for 56% of the country?s exports. Chile?s copper market share reached 35% in 2009. The investment portfolio in mining in Chile for the coming decade has been estimated at 90 billion US dollars. The acute scarcity of human resources currently experienced by the mining sector in Chile will be accentuated in the coming decade as a result of this scenario of investments. The situation is, additionally, similar to the one confronted by other countries involved in the mining industry such as Australia, South Africa, Canada, and in Latin America includes, Peru, Colombia and Brazil. A study carried out by Fundacion Chile, ¨Labor Force in the Chile Mining Industry, Diagnostic and Recommendations, 2011-2020? shows the projected labor shortage for the operation of projects in the development stage, considering only the requirements of the process of extraction, processing, and maintenance. The demand, accumulated incrementally, will be around 115,000 technically skilled workers, professionals, and qualified workers. This figure refers to the operational work force, and does not include the human resources that will be required for the prior stage of the engineering and construction of the projects (brownfield and greenfield). The demand for technically skilled workers and professions for the stages of engineering and construction of the projects that have already received investments is estimated to be 190,000 people for the period 2012-2020. The peak of the demand for engineering is 2012, with a figure that surpasses the 12,000 professionals for all of the engineering specialties. The analysis of the formation of human resources at the tertiary level (where tertiary includes technical/vocational and academic degrees at the undergraduate level) for mining and related majors demonstrates that the programs are scarce with a bias toward theoretical contents and that they are excessively long (40% longer than comparable programs in Australia, Canada, and in OECD countries). The completion rates are low, especially in the technical-vocational programs, which have a completion rate of only around 30%. Finally, the rates of attraction of technically skilled labor and professionals towards careers in mining are insufficient to reduce the identified skill gaps. In the case of university professionals such as geologists, mining engineers and engineers in metallurgy, 80-90% will work in mining. In the case of graduates of relevant majors, that cover skills also utilized by other industries, not only mining?such as maintenance workers, operators of fixed and mobile equipment, etc.?the mining sector appears to be unattractive for reasons such as shift schedules, geographical location of work sites, and other factors. On the basis of the available diagnosis a strategy for the sector has been developed (Workforce Development and Skills Strategy) whose objective is (i) to define a Mining Qualifications Framework to identify the critical roles to be filled (ii) to start, with public resources, a ¨fast-track? training program to assure the availability of at least 28,000 operators (machinery operators, truck drivers, etc.) and maintenance specialists in 2015 (iii) to promote the development of training hubs for mining with learning technologies to train technical labor and professionals on the basis of world class standards (iv) to design and implement a campaign oriented toward the perception of mining as an attractive field of employment opportunity (v) to develop curricular innovations for tertiary education programs, on the basis of international benchmarks. Keynotes: Chile, mining, copper mining, skilled human resources

Sep 1, 2012

During incineration of municipal solid waste (MSW), some heavy metals and other environmentally harmful elements are liberated into bottom ash. The stricter environmental regulations require a higher immobilization efficiency of the ash before its safe disposal and application. Vitrification is one of the promising options, and has the advantages of high destruction efficiency of organics, high immobilization of heavy metals, and large volume reduction. The main components of the vitrified slag are SiO2, CaO, Al2O3, Fe2O3, Na2O and MgO, and the compositions have direct effect on the glass formation during vitrification, and further on the physical and mechanical properties of the slag. To provide essential data for the utilization of bottom ash as vitrified slag, the phase relations and thermodynamic properties of the oxide system need to be systematically investigated. In the present study, the liquidus temperature of the typical vitrified bottom ash slag was determined by using differential scanning calorimetry (DSC) measurement. High temperature equilibrium experiments were conducted to investigate the phase relations of the sub oxide system of CaO-SiO2-Na2O by means of Scanning Electron Microscopy (SEM), Electron Microprobe Analysis (EMPA) and X-ray Diffraction (XRD). The results show that the melting temperature of the vitrified bottom ash is around 930°C. In the CaO-SiO2-Na2O system with less than 50 mol% SiO2, the liquidus temperature de-creases with increasing amounts of Na2O along the tie-line of Na2O-Ca3Si2O7. Two compounds Na2Ca3Si2O8 and Na4Ca8Si5O20 are identified in the oxide system.

Jan 1, 2014

To extract the gold from refractory gold concentrate with high sulfur and arsenic, the gold concentrate was catalytically oxidized to expose the gold for cyanide leaching. The effects of reaction temperature, initial nitric acid concentration, reaction time and initial gold concentrate concentration on the conversion rate were studied. The results show that the appropriate conditions for the catalytical oxidation of this gold concentrate are: reaction temperature of 65 oC; initial nitric acid concentration of 25% (wt.); reaction time of 1.5 hours; initial gold concentrate concentration of 10% (wt.). Under such conditions, the conversion rate of gold concentrate is 92%. The solution can be used to prepare nano-iron oxide red pigment. Gases released in the process can be recycled and reused by oxidation absorption. A chemical background of catalytic oxidation is proposed.

Jan 1, 2014

By John Ralston

"Interfacial chemistry plays a pivotal role in bubble-particle capture, for it controls whether or not attachment occurs. Surface heterogeneity, degree of surface hydrophobicity, bubble nucleation and related phenomena influence the stability of the aqueous wetting film between a particle and an approaching bubble. The latter must be unstable if capture is to occur. Various techniques that may be used to quantify this interfacial, chemistry-dominated behaviour, are described.The efficient capture of specific particles by rising bubbles and the delicate control of interfacial chemistry that leads to selective capture are central issues in froth flotation. For efficient capture to occur between a particle and a bubble, they must undergo a close encounter, a collision process dominated by hydrodynamics. Should this encounter bring the particle and bubble within the range of attractive forces, the intervening liquid film between the bubble and the particle will drain, leading to a critical thickness at which rupture occurs. The liquid-vapour interface then retreats over the solid particle surface until a stable wetting perimeter is established. The particle and bubble are then joined after this attachment process. The particle may only be dislodged from this state if it is supplied with sufficient kinetic energy to exceed the detachment energy in this detachment process. These various events are now well documented and may be followed using high-speed videomicroscopy (Schulze, 1984; Nguyen et al., 2001).The process of collision can now be described quantitatively for single bubbles colliding with bubbles under various flow regimes (Dai et al., 1998) and appropriate scale up is possible for multiple bubble particle collisions occurring under turbulent conditions (Pyke et al., 2002). In this paper we will be concerned with the role of interfacial chemistry and how this influences the attachment process."

Jan 1, 2003

By Svetlana Krashenina, Nebojsa Petrovic, Oscar Lopez

"As easily mined gold deposits are becoming increasingly rare, gold producers are turning to the processing of ores with polymetallic and copper mineralization. These base metals can create metallurgical and waste handling/disposal challenges, which can render the project uneconomic. Base metals such as copper compete for the cyanide reagent used to extract gold, necessitating the need to increase cyanide volumes and consequently, cyanide consumption costs. Copper will also stabilize in tailings water as weak acid dissociable cyanide, a form that is both difficult and costly to destruct. SART (sulphidization-acidification-recycling-thickening) process technology can be applied to remove base metal interferences in gold projects. SART breaks the copper-cyanide complex and precipitates the copper as a saleable copper sulphide concentrate. With the copper removed, the cyanide can be regenerated as free cyanide for recycle to the gold recovery process. This improves cyanide utilization efficiency and mitigates copper presence in tailings. Additionally, copper recovery generates an incremental revenue source to further improve project economics. Engineering Dobersek GmbH together with BioteQ developed a SART and AVR testing program to recover cyanide and maximize operational efficiencies at a gold processing plant in Kazakhstan with high cyanide consumption in the leach circuit. Results from on-site testing demonstrated that up to 99.98% of copper can be removed and precipitated as copper sulphide and 60-90% of cyanide can be recovered from the AVR and recycled for leaching, reducing total overall cyanide use. This paper provides an overview of the testing methodology and results together with a discussion on the potential of SART to improve gold production operations to deliver both environmental and economic benefits."

Jan 1, 2014

By Olgac Kangal, Ali Guney, Gulay Bulut, Guven Onal, Ayhan A. Sirkeci

"This paper presents the results of pilot scale column flotation applications in the two different copper concentrators in Turkey. The Kure Copper Plant is located in the Black Sea Region of Turkey. There are four types of copper ore formations in the Küre region. The so called disseminated ore contains 60-70% siliceous minerals of which Cu content is around 0.5%. The remaining three ore types in the region are generally named “massive ores”. The massive ores may assay up to 15% Cu and the major gangue mineral is pyrite associated with relatively little amount of silica. The main copper mineral in all formations is chalcopyrite that is generally finely disseminated in pyrite therefore satisfactory liberation requires ultrafine grinding especially in the case of the massive ores.A blend of these ores, containing 1.7% Cu on average, is fed to the Küre Copper Concentrator whose capacity is 1.2 million tons of ore annually. Unfortunately, today the plant operates below its designed capacity treating around 550,000 tons of ore per year. The design of Küre Copper Plant was undertaken by the Outokumpu Company of Finland. The operation of the plant is almost automatically controlled and the feed, the concentrate and the tailings are assayed for copper by on-line XRF analysers. The particle size analysers are also connected to the grinding circuit. The feed material is ground almost below 50 µm and the flotation is conducted around pH 11.2 using Hostaflot X-231 (a trade mark of Hoechst) as the collector. Apart from the rougher cells, there are four cleaning stages after which the final concentrate is produced. A very fine grinding requirement for an adequate level of liberation makes successful flotation difficult and consequently the final concentrate can hardly assay above 16% Cu leading to copper losses around 20% in the tailings that contains 0.3% copper."

Jan 1, 2003

Calcium sulfate whiskers are considered to be a prosperous reinforced material in application due to their high mechanical properties. But the hydration occurs easily at moist atmosphere or in aqueous solution. The surface topographies of the calcium sulfate hemihydrate whiskers and the hydrates were analyzed by on-line observation and using XRD. The results indicated the transformation of the crystal type and shape of calcium sulfate hemihydrate whiskers and the reduction of whiskers? aspect ratio. The hydration process of the calcium sulfate hemihydrate whiskers and the effective parameters were further discussed based on FT-IR measurements. The conclusions were obtained that the hydration of calcium sulfate hemihydrate whiskers can be divided into the three phases, namely, initial hemihydration phase, dehydration phase, and coarsening, dissolving and the re-formation of calcium sulfate dehydrate crystal phase. In addition, it was found that in the hydration process of calcium sulfate hemihydrate whiskers the calcium sulfate dihydrate whiskers are formed at first and then converted into the calcium sulfate dihydrate with different crystal shapes, but in the hydration of gypsum hemihydrate the gypsum dihydrate is formed without transition products. The surface active site-calcium ion which has strong trend to react with H2O, the surface ?OH and the inner channels are considered to play important roles in the hydration process of calcium sulfate hemihydrate whiskers.

Jan 1, 2014

By M. Wright, A. H. Mwale

This paper examines the combination of unit technologies in a minerals beneficiation train, and explores the inter-relationship between energy input and water consumption for a given mineralogy and product recovery, as these are two critical environmental issues which affect the overall viability of many minerals plants. In particular, we review constitutive relationships for each of the sub-processes of comminution, flotation, and tailings dewatering, and suggest how these might be integrated into a unified hybrid model, with particle size distribution as the key design variable. Such a model can then be used to explore the trade-offs between different performance objectives (be these technical, economic or environmental) as part of a multiple-objectives optimisation exercise. In this way, it may become practical to envision situations in which concentrate grade and recovery are sacrificed, marginally, in order to reduce energy demand in comminution, and improve overall water recovery. This becomes more relevant as the industry commits to advancing the sustainable development agenda in the face of the increasing life -cycle costs and impacts of minerals processing operations, coupled to declining ore body grades, and the desire to maximise recovery of minor and trace elements. Some specific observations for copper are offered.

Jan 1, 2003

By D. J. Zhao

The reduction and nitridation of preoxidized ilmenite pellets were investigated with the prospect of creating grain refiners containing titanium oxides and titanium nitride dispersoids. All the reduction and nitridation reactions were conducted in a furnace with a thermogravimetric analysis system under a H2-N2 gas mixture of 5 L/min. The ilmenite pellets were reduced at 1100°C for 4 hours under 80%H2-20%N2 gas mixture, and then respectively nitrided at 700°C, 800°C, 900°C and 1000°C for 12 hours under 10%H2-90%N2 gas mixture. The products were characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM), and analyzed by Energy Dispersive Spectrometers (EDS) and Electron Probe Mapping Analysis (EPMA). Iron oxides were reduced into metallic iron, and oxides of titanium were found, but titanium nitride particles were not identified in the products under the prevailing conditions.

Jan 1, 2014