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By Y. Wong

The quality and quantity of secondary deposits, which include tailings streams and tailings dams, are increasing around the globe. The tailings are already mined, available and liberated to such an extent that the recovery of a valuable product is highly economical in terms of CAPEX & OPEX. The most widely used process for the recovery of these valuable ultra-fine haematite iron particles is the Wet High Intensity Magnetic Separation technique, originally developed by Dr. Jones over 55 years ago. Many of the original machines are still working today. The aim of this paper is to demonstrate the capabilities in terms of grade and yield of using sophisticated magnetic separation modules. All results and figures are obtained from test works, design- and engineering works. Two types of tailings have been identified for processing. Firstly, tailings that have already been deposited in a Tailings Storage Facility, and secondly, live tailings streams from an existing wet iron ore beneficiation plant. In both cases, the technical and practical results are shown along with relevant flow sheets and plant layouts. Finally, this paper highlights the total predicted power- and water consumptions, capital requirements and projected operating expenses. The results show that the operating costs are significantly lower than the mining and processing operations which are required for an equivalent amount of iron ore. The recovery % of iron depends on various factors but is within the 30–50% range, at an equivalent grade to the mainstream product. Another significant benefit is that the magnetic separation process is water positive, meaning that water is released rather than added in the process. The processing of secondary deposits will therefore result in an overall reduction in operating costs, an increase in product yield from a plant, extend the mine life and offer environmental benefits by reducing the tailings footprint and water usage.

Jan 1, 2016

By A. Christoffersson, T. Nillson-Wullf, H. R. Manouchehri

"Mining industry has been the building blocks for human development through millennia and will continue to play its role in sustainability and meeting society’s needs for raw material. In the way towards sustainability, the next generation of efficient and heavy duty of Sandvik’s crushers, CH860 and CH865, are introduced for efficient crushing. As the secondary, tertiary and/or pebble crusher, these new crushers are designed to over perform in tough mining environment. Featuring higher crushing forces relative to the mantel diameter and 500 kW motor, combined with advanced automation system, i.e., sophisticated HydrosetTM and Automated Setting Regulation (ASRTM), combined with overpressure system with dedicated air supply in dust collar, etc., the new crushers provide higher safety, productivity, and reliability with the same foot-print of conventional cone crushers.Since crushers are more energy efficient than mills it makes sense to effort in fine crushing to save energy and protect environment. That has been the logic behind development and introducing stronger and more efficient crushers by Sandvik. The results on crushing hard iron and gold ores by CH865 have proven its efficiency in fine crushing at a higher productivity, availability and reliability rates through increasing throughput for defined size fraction and extended crushing chamber liner life.Within this paper the performance of the CH865 to deal with two different ores are presented discussed with a glance at how the downstream milling process can be benefited by saving energy and reducing the operation cost. In plant practice, the implementation of the new CH865 provides between 25 and 30% of the crushed ore in the size range of first step milling, i.e., < 2 mm, that offers opportunity for reduction in energy consumption in milling and even changing the process plant configuration by directly forwarded that part to gravity separation. Furthermore, potential of converting the rod mill to ball mill to improve productivity has been considered by plant engineers. Furthermore, some potential applications for such efficient crushers are brought into considerations and discussed. The new developments provide about 30% higher crushing force to efficiently deal with competent ores and pebbles. The CH860 and CH865 crushers are well suited to replace conventional secondary and tertiary crushers respectively; nevertheless, CH865 is virtual option for pebble crushing in SAG and AG milling circuits."

Jan 1, 2016

By P. Karimi, A. Amini, H. Abdollahi, A. Mirzaeian

Due to detrimental effects of cyanidation process on the environment in gold industry, application of cyanide alternatives such as thiourea are being highly considered in recent projects. In this study, the extraction of gold from poly metal ore, using thiourea was precisely investigated. The representative sample contained 2.5 ppm Au and 160 ppm Ag. The sample was categorized as oxide gold ore, because the main part of its pyrite was changed to iron oxide and hydroxide such as goethite and lepidocrosite. According to mineralogy, the main gangue mineral was quartz. It shows that gold grains are free and interlocked with quartz matrix. Also, the presence of a high amount of silver in free and sulfide forms and also the low content of other sulfide minerals such as base metal sulfides is a remarkable point of these studies. In the gold extraction process with thiourea, there are several parameters that affect the rate of gold dissolution such as concentrations of thiourea as a gold lixiviant and ferric sulfate as an oxidant, pH and size fraction of feed and leaching time. The influence of these parameters on the gold dissolution rate were investigated and optimized. The results showed that the concentration of thiourea is the most influential parameter which could increase the gold recovery to 71% (at 10 g/kg sample). The optimal amount of ferric sulfate was determined as 6 g/kg sample. Also, the optimal levels of size fraction of feed and pH of solution were 88% under 75 micron and 2 as acidity; respectively. Leaching time was 6 hrs. In addition, this sample was leached with cyanide and the optimized values of size fraction of d88=75 microns, pH=10.45, 2500 ppm of sodium cyanide with time leaching of 24 hours were concluded for maximum recovery of gold in solution. Finally, the results of cyanidation tests were compared to the thiourea dissolution after optimizing all affected parameters in cyanidation process.

Jan 1, 2016

By van der Merwem J. N.

"Coal pillars are prone to scaling over time, and are progressively reduced in size and consequently subjected to increased load and reduced strength. The effective factor of safety therefore reduces. Databases of failed and stable pillars cannot, therefore, be regarded as definitive.More than a decade has passed since the first attempt to predict the lifespan of pillars. This paper presents a review based on the new database and pillar strength equations. The methodology for the analysis is based on the fact that pillars scale. The ultimate safety factor (defined as the ratio between strength and load at the time of failure) is derived, followed by an estimate of the rate of pillar scaling, which results in an estimate of the expected time of failure.It is suggested that the predicted lifespan should not be used as an absolute indicator of expected pillar life, but rather as an index – the pillar life index (PLI) – to complement the safety factor and related probability of failure when evaluating pillar stability. A pillar with a predicted lifespan of less than 500 years would be regarded as being in danger of imminent collapse, while a lifespan of at least 1 000 years should be required for long-term purposes.The differences between this analysis and that published in 2003 constitute a strong case for regular reviews of all the empirically based stability indicators, namely the safety factor, probability of failure, and the PLI. Reviews at 10 year intervals appear to be required.The constants in the proposed method are valid only for the Witbank No. 1, 2 and 4 seams and the Highveld No. 2 and 4 seams.IntroductionIt is well known that over time, coal pillars are prone to scaling, and thus are progressively reduced in size and consequently subjected to increased load and reduced strength. The effective factor of safety therefore reduces and it is quite possible for failure to occur after a long time interval. In fact, scrutiny of the database of failed pillars indicates that failure occurred after periods ranging from 2 to 49 years, and not immediately after mining.The factor of safety for pillars at the time of failure is not the same as that immediately after mining. The concept of the safety factor is based on the pillar strength obtained by statistical analysis of pillar dimensions immediately, or within a month after mining, when the surveys are conducted. Strictly speaking, the safety factor as commonly used is valid only immediately after mining, and it continues to reduce thereafter. The ideal situation would be to base analyses of pillar strength on pillar dimensions at the time of failure, but that is simply not possible because the real dimensions cannot be measured at that time."

Jan 1, 2016

By Srisharan Shreedharan, Gang Huang, Hongqing Song, Sijing Cai, Pinnaduwa H. S. W. Kulatilake

"Subsidence prediction due to ore extraction and backfilling during open stoping operations for an underground iron mine in China is reported in this paper. Geologic complexities including faults and interfaces between different lithologies, and the stoping and backfilling sequence adopted from the mine plans are incorporated in building a 3-D discontinuum numerical model. The stoping was simulated in two vertically stacked horizontal layers (Fig. 6), with a total of 16 stopes. Large displacements of up to 50 cm were predicted by the model along the roof of the stopes, and a maximum surface subsidence of 22.5 cm was predicted by the model . Backfilling was found to control subsequent deformation and subsidence. The extraction of the upper orebody led to relatively higher deformations in extracting the lower orebody. Finally, the predicted subsidences at all locations along a subsidence profile on the surface are shown. INTRODUCTIONThe Luohe iron (pyrite) mine, located in Hefei city, Anhui, is an underground mine in China, being mined through the open stoping and backfilling method. The orebody lies at a depth of about 400 m and has an average thickness of 250 m (Magang Steel Company, 2012a). Discovered in the 1960s, the location has a reserve estimate of 300 million tonnes, which have been mined since 2007. The orebody has been divided by the mining company into an east and a west section to facilitate planning for ore extraction.Figure 1 shows the surface above the underground mine, which is seen to contain many human settlements including villages, pastures and other infrastructure. These locations are sensitive in that they need to be protected from potential adversities due to the underground mining, such as surface subsidence. While it may be near impossible to completely eliminate the subsidence due to ore extraction, operations such as backfilling have been adopted by the mine in an effort to substantially reduce it. Hence, this paper focuses on describing the stability of stopes in the mine and estimates future subsidence in a part of the mining region through numerical modeling."

Jan 1, 2016

By J. Kretschmann, R. Amiri

"The Sangan iron-ore mines (SIOM) in Iran are located in a remote area, near the Afghanistan border. The deposit of SIOM is containing a geological resource of 1.2 billion tons of mostly magnetite with a Fe grade ranging from 27 to 61 %. The Iranian government plans a stepwise development of SIOM in cooperation with private companies to satisfy the growing demand of the Iranian steel industry. Sustainable development (SD) is an influential ethical concept in mining all around the world. However, a successful realization of a SD is not possible without a foundation on the core values and regarding the specific circumstances of the individual mining country. This paper introduces SIOM and describes SD activities undertaken during its development. From the early stages, these activities have been realized to secure the acceptance of the stakeholders in the region. To evaluate their effects, indicators could be filtered as the ones with the highest priority for the stakeholders. Moreover Islamic values and Iranian regulations and their influences on SIOM have been analyzed. Keywords: Iran, Sustainable Mining, SIOM, Evaluation, Islamic Values INTRODUCTION Mining Industry in Iran The Islamic Republic of Iran holds 68 types of minerals, including salt, sand and gravel, gypsum, chrome, lead, zinc, copper, coal, gold, iron etc., with 37 billion tons of proven reserves and more than 57 billion tons of potential reservoirs. Iran is ranked among the 15 major mineral rich countries (1). In accordance with the statistics published by Statistical Center of Iran (SCI), there were 5.316 active mines and 84.922 employees in the whole country in 2012-13 (2) and according to the statistics published by Central Bank of Iran (CBI) in 2011 the share of this sector in the Gross Domestic Product (GDP) of the country was 1.2 per cent (3). Sangan Iron Ore Mines (SIOM) The deposit of SIOM is one of the largest iron-ore deposits in Iran, also considered to be one of the Middle East’s richest deposits, which contains a total geological resource of 1.2 billion tons of mostly magnetite with a Fe grade ranging from 27 to 61%. It is located 300 km southeast from Mashhad, the capital of Khorasan-e-Razavi Province, and 18 km northeast of Sangan town, in Khaf County, at latitude N34°24’, longitude E60°16’ in the north-eastern Khorasan-e-Razavi Province, 30 km west of the Afghanistan border (4) (Figure 1). SIOM is owned by the Iranian Mines and Mining Industries Development & Renovation Organization (IMIDRO). IMIDRO intends to develop an open pit mine complex and supporting facilities in SIOM for the production of about 20 Mtpy of iron oxide concentrate and pellets in four developing phases (5)."

Jan 1, 2016

By N Gkikizas-Lampropoulis

Selection of delay times to optimize fragmentation has been a controversial topic among researchers and blasting practitioners. This paper interprets previous experimental information on the effect of delay on fragmentation with the aid of some new experimental observations of the time of detachment of the free face of the blast as well as results of numerical modelling. It was shown that detachment of the burden occurs at delays shorter than the one which produced optimum fragmentation in the experiments, suggesting some fragmentation improvement due to gas action. In addition, at the spacing to burden ratio of the experiments, the damage zone from an earlier detonating charge extends the distance to the neighboring charge, essentially affecting the burden of some of the holes of the blast, at detonation time. Computer modelling demonstrated that increased spacing results is less overlap of stress induced damage zones meaning that there is less influence of delay on stress wave induced fragmentation. It was also shown that simultaneous initiation results in less back break, while increased back break may result even with short delay times.

Jan 1, 2016

By Lang Tao, Jun Wang, Wei Xiao, Wenqing Qin, Pan Cao, Guanzhou Qiu, Key Lab of Biohydrometallurgy of Ministry of Education, Central South University

"The effect of metal cations on the rutile flotation using styryl phosphoric acid (SPA) as the collector was investigated by micro-flotation test, bench scale flotation test, zeta-potential measurements and adsorption measurements. The micro-flotation results indicated that Fe (?) and Al (?) ions in low concentrations had obvious activation on the rutile flotation, and Pb (?) ions in low concentrations had smaller activation of rutile, but Fe (?), Al (?), Pb (?), Ca (?) and Mg (?) have strong inhibition of rutile flotation in high concentrations. The bench scale flotation results indicated ethylene diamine tetraacetic acid (EDTA), boracic acid, and sodium hexametaphospate can decrease the metal ions concentrations, and increase the recovery of rutile flotation. Adsorption measurements and zeta-potential measurements revealed that Fe (?), Al (?) and Pb (?) ions were adsorbed on the rutile surface, and had interaction with SPA. But when these ions concentration were over the largest adsorption capacity, residual metal ions could occur chemical reaction with SPA.INTRODUCTIONRutile is one of the favored minerals for production of titanium dioxide white pigment, primarily through the chloride manufacturing process (Stanaway 1994; Hou et al., 2013) However, the majority of rutile ores belong to refractory ores, while flotation is one of the most efficient methods to separate fine rutile from gangue (Dolbear et al., 1937). With the flotation development, many effective collectors were successfully applied in the oxide ore. Many reviews have indicated that organic phosphonic acid collectors showed good selectivity on oxide ores such as ilmenite and rutile (Bulatovic & Wyslouzil 1999; Liu & Peng 1999).It is inevitable that many types of metal cations are present in ore pulp. These metal cations significantly influence the flotation of minerals. Liu et al. (2015) showed that Ca2+ and Mg2+ could improve the floatability of spodumene at pH 12.5 and 10.0, respectively. The authors proposed that Ca2+ and Mg2+ ions readily form hydroxy complexes (CaOH(l) and MgOH(l)) and precipitates as (Ca(OH)2 and Mg(OH)2) in strongly alkaline solutions. Fan and Rowson (2000) investigated the effect of Pb(NO3)2 addition as an activator on ilmenite flotation and showed that it could improve ilmenite floatability. The addition of Pb(NO3)2 resulted in an increase of ilmenite zeta potential in both weakly alkaline and acidic aqueous solutions. Mehdilo, Irannajad, and Rezai (2015) studied three kinds of ilmenite of different origins and discovered that both Mg and V had a negative correlation with ilmenite flotation, while the Mn content seemed to correlate positively with flotation efficiency. A number of studies have also showed that Fe3+ can improve the floatability of ilmenite (Fan et al., 2009; Nuri, Mehdilo, & Irannajad, 2014)."

Jan 1, 2016

By K. Webb, M. Hohn

"This paper reviews the evolving Ontario mining regime for mining industry-Aboriginal engagement and its apparent alignment with court decisions, domestic law, emerging international norms, mining industry rules, and mining firm-Aboriginal agreements, drawing on publicly available commentary from government officials, the private sector, and Indigenous communities. This paper provides a preliminary analysis of the potential implications of the new regime, especially for the mining industry and Aboriginal communities and, on that basis, discusses possible future developments.RÉSUMÉ Le présent article analyse le régime minier de l’Ontario pour l’engagement entre l’industrie minière et les Autochtones et son harmonisation avec les décisions des tribunaux, le droit interne, les nouvelles normes internationales, les règles de l’industrie minière et les ententes compagnies minières- Autochtones en se basant sur des commentaires, disponibles publiquement, d’officiels gouvernementaux, du secteur privé et des communautés autochtones. Cet article fournit une analyse préliminaire des implications potentielles du nouveau régime, surtout pour l’industrie minière et les communautés autochtones et, en s’appuyant sur ces données, il traite des futurs développements possibles."

Jan 1, 2016

By Karl Gunnar Holter, Frank Clement

"INTRODUCTION Typically waterproofing of conventionally excavated tunnels has been done by installing pre-fabricated sheet membranes between the primary temporary support lining and the secondary permanent inner lining. The membrane acts as a separation or sliding layer between the linings, which is often desirable. The geotextile installed behind the sheet membrane provides the required drainage and protection of the system. The design of the tunnel lining is strongly influenced and limited by the use of waterproofing sheet membranes. Since primary and secondary linings are separated from each other, forming a double-shell lining system. In that case the secondary lining must be designed for all permanent loads, although the sprayed concrete primary lining continues resists ground and water loads for a long time after construction. Significant progress has been made in sprayed concrete technology over the last two decades, with advanced admixtures, as well as the improved application technology using spraying robots. The development of new admixtures like superplasticizers based on poly-carboxylates, alkali free accelerators and silica fume, enables designers to use permanent sprayed concrete linings (SCL) increasingly for long-term service life. When designed and applied correctly, sprayed concrete can be considered as permanent. The use of spray applied membranes has seen increased use over the last decade in some countries, and demonstrated functionality and cost-effectiveness in several situations. This paper describes the use of the sprayed waterproofing membrane MasterSeal 345, an EVA polymer based product, and the practical experiences from several projects. SPRAY APPLIED WATERPROOFING MEMBRANES The sprayed waterproofing membrane is polymer based and has been especially developed for underground structures. The membrane is applied between primary and secondary concrete linings and develops high bond strength on both sides to the concrete (doubled-bonded)."

Jan 1, 2016

By G. Castillo, J. Mortensen

"INTRODUCTION Molybdenite is typically produced as a co-product in the copper ore flotation process. At the Rio Tinto Kennecott Concentrator (RTKC) in Copperton, Utah, the molybdenite is initially floated with copper sulfides and other value minerals producing a Cu-Mo concentrate. This is then separated in the molybdenum plant by depressing copper sulfides and pyrite and floating only molybdenite. The molybdenum plant in RTKC comprises the rougher circuit and several stages of cleaning to achieve a certain grade requirement of Mo. The rougher circuit is where the first stage of separation occurs. Cu sulfides and pyrite are depressed in the rougher circuit by adding NaSH under nitrogen and in the cleaner circuit by adding NaSH under air. The depression of Cu sulfides (and pyrite) by NaSH is related to the redox activity1. It is important therefore to maintain a reducing potential in the circuit in order to achieve effective Cu-Mo separation. If the rougher circuit is under air, like RTKC’s molybdenum cleaner circuits, it is harder to maintain the target redox potential because NaSH oxidizes rapidly in the presence of air thereby increasing NaSH consumption significantly. CU-MO SEPARATION AND ROLE OF PULP POTENTIAL The collector adsorption on copper sulfide minerals is through an electrochemical mechanism2. The collector changes the surface chemistry of the Cu mineral allowing it to float. Molybdenite, or MoS2, on the other hand, floats readily in the presence of a frother as it is naturally hydrophobic. Usually, hydrocarbon oil extenders such as diesel or burner oil are added to enhance Mo recovery. In order to effectively separate Cu from Mo, the collector complex on the copper surface needs to be destabilized or desorbed using a reducing agent such as NaSH or Nokes. As long as the circuit is under highly reducing conditions, the collector remains detached from the sulfide mineral surface allowing Cu sulfide depression. Therefore, it is important to measure the oxidation-reduction potential (ORP) continually and maintain the reducing condition with addition of NaSH. For a given collector each mineral will have a characteristic potential or electrochemical window for flotation to occur3, therefore, it is necessary to reduce the potential outside of this window in order to effectively separate Cu and Fe sulfides from MoS2 minerals2. In RTKC plant, the target reducing condition is between -450 to -550 mV to effectively destabilize the collector and depress Cu and Fe minerals. Typically the dosage of NaSH used in the molybdenum plant could range from 6 to 30 gallons/min (gpm). The high dosage of NaSH could pose risk of H2S exposure. RTKC wanted to evaluate alternatives to NaSH in order to reduce its consumption and minimize risk of H2S gas generation."

Jan 1, 2016

By Paolo Toscano, Dave Hall

"This paper discusses the project history, process design and layout of the Rainy River Gold Project mill. The circuit consists of a 55 x 83 primary crusher, 15 MW SAG mill and 15 MW ball mill. Both mills are twin pinion with LSS and VFD drives. A pebble crusher is located in the process plant with bypass and stockpile options. Gravity concentration followed by 30 hours of leach residence, carousel CIP, carbon recovery, cyanide destruction and tails disposal in a 1,428 hectare tailings management area (TMA).The Rainy River Gold Project is located approximately 65 km northwest of Fort Frances in north western Ontario. The project is scheduled to be commissioned and reach commercial production in mid-2017. Expected cost is $US877M and is comprised of an open pit mine, process plant, tailings management area and supporting infrastructure. The process plant is designed to produce gold/silver Dore’ bars.The project has been developed on the following timeline:• 1967 – First exploration• 1994 – 17 zone discovered• 2004 – 433 Zone discovered• 2005 – Rainy River Resources Ltd. purchases property • 2006 - ODM zone discovered• 2007 - Cap Zone discovered• 2008 - First NI-43-101 Resource completed• 2012 - PEA completed & Intrepid Zone discovered• 2013 - New Gold acquires Rainy River Resources• 2014 - Updated feasibility study completed & Environmental Assessment report submitted• 2015 - Detailed Engineering >95% complete, EA approved and construction commencesThe property is accessed by provincial highway 600 and is within 17 km of 230 kV power line and railway sidings. Key project criteria are summarized as follows:"

Jan 1, 2016

By P. T. Bissert, T. J. Lutz, J. A. Yonkey, G. T. Homce

"The National Institute for Occupational Safety and Health (NIOSH) has been researching refuge alternatives (RAs) since 2007. Refuge alternatives typically have built-in pressure relief valves (PRVs) to prevent the unit from reaching unsafe pressures. The Mine Safety and Health Administration (MSHA) requires that the PRVs vent the chamber at a maximum pressure of 1.25 kPa (0.18 psi, 5.0 in. H2O), or as specified by the manufacturer. To facilitate PRV testing, an instrumented benchtop test fixture was developed using an off-the-shelf centrifugal blower and ductwork. Relief pressures and flow characteristics were measured for three units: a modified PVC check valve, an off-the-shelf brass/cast iron butterfly check valve, and a commercially available valve that was designed specifically for one manufacturer’s steel pre-fabricated RA and has been adapted for use in built-in-place (BIP) RAs located at one mine. PRVs used in tent style RAs were not investigated. The units were tested with different modifications and configurations in order to check compliance with 30 CFR regulations. BACKGROUND The Mine Improvement and New Emergency Response Act of 2006 (Miner Act) (1) was enacted in the wake of three mine explosions/fires that claimed 19 lives that year. Intended to help improve underground coal mine accident preparedness, the MINER Act includes provisions that target mine safety issues in areas such as emergency response planning, adoption of new technology, training and education, and mine safety standards enforcement. Section 13 of the MINER Act specifically directed the National Institute for Occupational Safety and Health (NIOSH) to provide for research into the effectiveness and viability of refuge alternatives (RAs) for underground coal mines, and the Department of Labor to act on the results of such research as appropriate. These mandates culminated in the 2009 adoption of changes to 30 CFR mining health and safety regulations, requiring underground coal mines to provide mine emergency RAs and associated components, to provide a life-sustaining environment for persons trapped underground. Such RAs can be either self-contained mobile units or built-in-place (BIP) facilities. The regulatory changes also include provisions establishing requirements for the Mine Safety and Health Administration (MSHA) approval of RAs and their components, and among these provisions are numerous criteria for providing a safe breathable atmosphere under positive pressure within the RAs. One specific criterion for maintaining a safe RA atmosphere requires the inclusion of an air pressure relief valve that will activate at a maximum of 1.25 kPa (specified as 0.18 psi, or approximately 5.0 in H2O), or at a pressure as specified by the RA manufacturer, above mine atmospheric pressure in the RA (2)."

Jan 1, 2016

By P. Zhang, K. Liu, L. Ou

"The strength and mechanism of Portland cement prepared from stone coal vanadium slag were studied in this paper. Initially, the slag was used as silicon raw materials to prepare clinker. By blending the prepared clinker with gypsum, waste, and fly ash, a series of different grades cement got well prepared. All of performances of the cement were up to the requirements of China’s national standard. The hydration products and microstructure of cement were identified and analyzed by X-ray diffraction and scanning electron microscopy. With the comparison of cement hydration characteristics at different ages, the strength formation mechanism of cement was clarified. The experimental results suggested that adding the fine materials (mainly waste and fly ash) to replace part of clinker would accelerate cement hydration, as it provided additional surfaces for the nucleation and growth of hydration products. And the hydration products were similar to ordinary Portland cement, mainly containing the amorphous calcium silicate hydrates (C-S-H), acicular ettringite (AFt) and portlandite (CH). With hydration time increasing, the hydration products continuously covered the cement particles, resulting in a thicker surface layer. As a result, it gradually condensed into a dense structure block with small pores and smooth surfaces, which led to higher strength. In conclusion, using the vanadium slag to prepare Portland cement can realize the utilization of solid mineral wastes, which will bring huge ecological and economic benefits.INTRODUCTIONWith the development of China’s mining industry, more and more mineral waste residue is discharged every year. These solid wastes cause varieties of resources and environmental problems on people’s living area. While at the same time, the demands of cement are increasing with the remarkable development of the construction industry. Thus, in recent years, utilization of proper solid waste to prepare cement has become an efficient way to deal with the solid mineral wastes problems (Boncukcuoglu, Kocakeri?M, & Tosunoglu, 2002; Simatupang, Hanafi, Purwasasmita, Imran, & Pane, 2012; Tsakiridis, Papadimitriou, Tsivilis, & Koroneos, 2008; Yun, Yong, Choi, Lee, & Lachemi, 2009)."

Jan 1, 2016

By James A. Finch, Yue Hua Tan, Wei Zhang

"The paper is part of our study of the frother structure-property relationship using bubble rise velocity. Single bubble rise velocity profiles were determined in a 350 cm column for surfactants from the polypropylene glycol (PPG) family. Using velocity at 300 cm, the concentration to reach minimum velocity (CMV) is determined. The CMV is shown to decrease as alkyl chain length (n, number of carbons) increases and as the number of propylene oxide groups (m) increases. Linear correlations log CMV vs. n and m were observed. Taking literature data for critical coalescence concentration (CCC), linear log CMV vs. log CCC correlations were also noted. Mechanisms are briefly discussed, and prediction of CCC made for a commercial polypropylene glycol.INTRODUCTIONAs one of the great enabling technologies of the 20th century, froth flotation is a highly versatile method for physically separating minerals by exploiting differences in wettability (hydrophobicity). Over the last century, flotation reagents have undergone significant developments (Khoshdast and Sam, 2011). One important group of reagents is frothers which are used to reduce bubble size, slow bubble rise velocity and help stabilize froth (Klimpel and Isherwood, 1991).Frothers, originally derived from natural sources (e.g., pine oil and cresylic acid), are largely replaced today by synthetic products which provide more consistent properties. Polyglycols, based on PEO (polyethylene oxide), PPO (polypropylene oxide), or PBO (polybutylene oxide) groups, were first described by Leja and Nixon (1957) and have attracted wide use since then (Farrokhpay 2011). The chemical structure of polyglycols can be represented by a general formula: R(X)mOH, where R = H, or CnH2n+1 and X stands for EO (-C2H4O-), PO (-C3H6O-), or BO (-C4H8O-). The polypropylene glycol ethers (CnH2n+1(PO)mOH) are the most common of these reagents (Pugh, 2007) and the focus of this study.In general, the chemical structure of frother molecules comprises two parts, a non-polar hydrophobic hydrocarbon (alkyl: CnH2n+1) chain and a polar hydrophilic head. By introducing the ether -Olinkage, which acts as another polar site, the propoxy group (-OC3H6-) in the structure makes the frother readily soluble in water (Somasundaran and Wang, 2006), facilitating the industrial use of these frothers. Available as by-products, Dow Chemicals introduced as series of polyglycols, e.g., Dowfroth (DF) 200, 250, 263, and 1012, the most familiar being DF250 (CH3(PO)4OH), a polypropylene glycol methyl ether. While no longer available from Dow, these and other polyglycols are still widely used."

Jan 1, 2016

By Yongjie Bu, Wei Sun, Zhiyong Gao, Yuehua Hu, Hongbiao Tao, Runqing Liu, Central South University

"The flotation behavior of O-isopropyl-N-ethyl thionocarbamate (IPETC) and pH for chalcopyrite and galena was studied through pure mineral test, adsorption quantity determination, solution chemistry calculation and Materials Studio simulation. The results show that the recovery differential value of chalcopyrite and galena is about 20% when pH of the pulp 9.5 and IPETC is 7×10-4 mol/L, the flotability differences of the two minerals is significant. There is competitive adsorption between OH? and IPETC on mineral surfaces, it lead to galena flotability is lower than chalcopyrite flotability. IPETC can remove the hydration layer on mineral surface and adsorb on active sites for collector adsorption, minerals have a better hydrophobicity.INTRODUCTIONCopper and lead are two of the most widely used metals in industrial and living, their applications include building construction, various metal alloys, heat and electricity, machine manufacturing (Zhang et al., 2014). Chalcopyrite and galena are the major source of copper and lead, normally they associated with each other. With the growing use of these resources, high grade and dissemination large particle sizes minerals are less and less, the use of low grade and complex dissemination minerals have to be paid more attention (Chen, Ye, & Li, 2010; Liu, Sun, Hu, & Wang, 2009). As the special properties and complex composition of copper-lead sulfide ore, flotation separation of chalcopyrite from galena effective is a research emphasis and difficulty point in mineral processing (Bruckard, Sparrow, & Woodcock, 2011).In the separation process of chalcopyrite and galena, it is rather important to choose effective collector (Huang, Wang, & Liu, 2014). Enlarging and using the two mineral flotability will be a good basis and start in flotation (Reyes-Bozo et al., 2014). Qin et al. (2013) made a great deal of research on flotation separation of copper/lead concentrate, collector O-isopropyl-N-ethyl thionocarbamate (IPETC), butyl xanthate (BX) and ammonium dibutyl dithiophosphate (ADTP) were investigated, BX and ADTP floated both chalcopyrite and galena well, specific adsorption appeared in the surface of mineral, the problem was the collectors were not selective enough, however IPETC showed better selective."

Jan 1, 2016

By B. Berhe, R. D. Lawrence, J. Hinzer

"The fortunes of mining companies and their implied value are tied to cycles - both economic and commodity – within which they operate. Hence the determination of appropriate future metal prices is one of the most critical factors faced by mineral valuators especially for advanced projects. Price, and hence revenue, is usually the most sensitive input to the valuation model. Empirical studies of past forecasts show that the success rate for commodity price forecasting is very poor. This paper explores various approaches and comments on their strengths and weaknesses. We conclude that careful evaluation of long-term metal prices is a key element and is hardly a luxury that can be left to simple averages or rules of thumb. INTRODUCTION Discounted Cash Flow (""DCF"") analysis, is well suited for the valuation of advanced mineral development assets, for which there are identified mineral resources and some form of economic assessment (Pre-Feasibility or Feasibility Study). The DCF method is also the most commonly used method for determining value for such assets. It provides a means of relating the magnitude of expected future cash flows from profits (or losses) to the magnitude of the initial cash flow (investment) needed for capital expenditures to purchase or to develop an asset for commercial production. The method proves useful in making investment decisions as it allows for the quantification of the Net Present Value (“NPV”), as well as the Internal Rate of Return (IRR) and Payback Period on initial investment capital. Valuation by its very nature is a forward-looking exercise. The DCF method attempts to estimate the NPV of expected future cash flows, by selecting factors that will likely affect future cash flow based on informed analysis. One of the most critical and sensitive factors is the determination of appropriate future commodity prices. “The variables that have the greatest impact on a DCF evaluation are the reserves, the metal prices, and the discount rate.”1 The determination of future commodity prices for valuation purpose or during M&A negotiations is a hotly contested issue. There are a number of analysts, institutions and specialized commercial data suppliers that provide both short and long-term commodities price forecasts. Also, the use of an aggregated mean for all available forecasts, or consensus forecasted prices for valuation purposes is not uncommon. The methods used in making forecasts for each forecaster may vary and in many cases may not be publically disclosed. Nonetheless, the aggregated mean of all forecasted commodity prices of reputed institutions is usually taken to “represent the market’s view of likely future commodity prices.”"

Jan 1, 2016

By Ausenco Engineering Canada

"This paper demonstrates the selection of grinding circuit technology for a number of recent projects including discussion of the key drivers and the role of energy efficiency. Decreasing head grades combined with a strong and sustained increase in operating costs has forced miners to examine increased project size, increased equipment capacity and efficiency improvements in order to reduce their unit operating costs and improve overall project economics. Comminution energy consumption, safety and capital cost considerations play a critical role in the success of projects. This paper presents some key guidelines for a successful and cost effective comminution circuit design and includes a case study on three projects, outlining the issues and the drivers which led to the ultimate circuit selection and the critical role that energy efficiency played.INTRODUCTIONComminution circuits for minerals processing are selected based on their suitability and efficiency in reducing run-of-mine ore to the desired feed size for the downstream process. The input material (ore) properties and downstream process requirements are the key determinants and there are standard approaches for each circumstance.The minerals processing industry has been a fast adaptor of efficiency improvements based on increasing capacity of equipment (e.g. trucks, crushers, mills, pumps) but less successful in adapting radically new technologies that disrupt incumbent flowsheets or processes.The installed power of grinding mills has increased linearly over the past 25 years (Meka & Lane, 2010) and pumps and classification equipment have kept pace. The autogenous grinding (AG) and semiautogenous grinding (SAG) mills displaced stage crushing as a dominant method of coarse rock breakage in many applications causing crusher manufactures to increase the capacity of cone crushers to meet the competitive demand.Examples of new comminution technology in the 20th and 21st centuries are the development and adoption of cyclone classification in the 1940s (Newtech, 2016), AG milling in the late 1950s, vertical grinding mills in the 1980s, high pressure grinding rolls (HPGRs) also in the 1980s and ultrafine milling technology in the 1990s (Meka & Lane, 2010)."

Jan 1, 2016

By Simon Strong, Tim Brown, Luis Ignacio Sanz Vivanco

"One of the most significant technical and practical challenges facing the tunnel construction team on the Legacy Way road tunnel project in Brisbane, Australia was how to erect the pre-stressed precast concrete slabs to form the smoke duct in the tunnel boring machine (TBM) tunnels. An essential part of the tunnel ventilation system, the smoke duct, extends the full length of the 4.6km long twin, two lane tunnels. The vast majority of the tunnels (approx. 4.3km) were constructed using two 12.4m diameter double shield TBMs. The refurbished Herrenknecht machines broke several world records on the way to completing the tunnel excavation works in just over nine months. With the excavation complete the focus turned to solving the complex civil tunnel fit out challenges. A key component of the civil fit out of the tunnels was constructing the smoke duct in the TBM tunnels which was designed as a precast solution. The slabs which each measure 8.62m long by 2.0m wide by 200mm thick and weigh close to 9 tonne need to be erected above cast in situ corbels whilst other tunnel finishing works continue. The space proofing clearance offered by the design to the support corbels below and the precast segmental lining above was in the order of only 100mm. This paper details the events of how the Transcity JV tunnel fit out team, comprising some of Europe and Australia’s leading tunnel construction specialists, drew upon the global strengths of the existing JV member companies and the global reach of leading TBM manufacturer Herrenknecht to develop an innovative system to solve this challenging problem. This globetrotting story, which starts in Australia, visits Europe and mainland China before returning to Brisbane where it all began."

Jan 1, 2016

By X. Song, Q. Zhang

"The development of fracture zones in surrounding rock mass has significant impact on the stability of underground mine roadways. Detection of the fracture zones is of compelling importance for maintaining roadway stability as well as for safe and speedy excavation of the roadways. This paper presents a study conducted at Dong Bao Wei underground coal mine, where the roadways were developed in diabase rock mass. The roadways suffered severe damages, including sloughing and excessive floor heaving. The borehole imaging technique was applied in the study to observe and detect fracture zone development surrounding the roadway openings. Based on the borehole imaging studies, new roadway support systems were proposed to improve the stability. INTRODUCTION At the Dong Bao Wei Coal Mine three main roadways of the west wing were excavated. The three roadways had semicircle arch cross sections and were at a depth of 650 meters, each being about 750 meters in length. The roadways were driven through a section of thick diabase intrusion, which was softened by water with reduced strength and may turn into powder form under weathering. Site investigation indicated that the roadways in diabase intrusion zone were badly damaged due to severe deformation, and very serious roadway sidewall sloughing and spalling accompanied by severe floor heave often occurred.(Figures 1 and 2) In order to ensure the normal use of the roadway, undercuts were excavated. However, this operation seriously affected the roadway construction progress and increased the amount of roadway support operations as well as the roadway maintenance costs. Furthermore, a roof fall accident occurred in nearby drilling site. The investigation indicated insufficient support provided for the roadways which imposed significant safety hazards and would have serious impact to mining production and subsequent mining activities.The support of the main roadways is a critical task and is the focus of the underground opening excavation work at the mine, since more than 40 years of service life is required from these main roadways. For these roadways, large cross sections with high degree of stability and minimal amount of deformation should be maintained. Therefore, providing sufficient and appropriate roadway supports is of significant importance to the coal mine. In this paper, in order to optimize the roadway supporting system, studies were carried out on the geological structures, lithological characters, roof bolt anchoring features and suitable anchoring layers. The studies were aimed at ensuring the stability of mine roadways, reducing the roadway maintenance costs and providing a safe mine passageway for orderly production and progressive development of the mine"

Jan 1, 2016