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By K. N. Bolatbaev, S. S. Naboichenko

The initial rates of dissolution of pyrite, chalcosine, sphalerite and galena in acidic sulphate solutions under oxygen pressure were measured in the range of Poe = 0.2-1 MPa, 130-180 °C, [H2SO4]0 = 0.2-0.7 M, and in the presence of surface-active agents and agitation producing Re = 4-16 x 103. Reaction orders, activation energies, and values of reaction constants for these oxidation reactions were established. The reactions also were shown to be diffusion-controlled; and the rates demonstrate a linear dependence on the surface area of the sulphides. A surface reaction model, in which oxygen is transported through a solid layer of surface products, has been advanced. The initial stage of high-temperature interaction at pH <7 is suggested to involve a chemical activation of the sulphide surface and is described by the following general reaction: MenSm + H3O+ Men-1 Sm-1 (HS-)s + H2O The subsequent oxidation of surface complex HS- to S0 or SO2-4 occurs with the assistance of Fe(III), Cu(II) ions depending on temperature and the redox potential of the medium, which are defined by oxygen pressure and composition of the reaction mixture, especially concentrations of H2SO4 and metals with variable valence. General process kinetics are complicated due to the formation of by-products on the basis of Fe3+ Pb2+, Cup ions, which displace the kinetics into the diffusion region.

Jan 1, 2004

By S. Ghafarnejad Parto, Å. Rasmuson, A. Fredriksson, M. Mohammadi, K. M. Forsberg, J. Martinez De La Cruz

The present study aims at recovering rare earth elements (REE) in conjunction with the production of fertilizers from an apatite concentrate. Apatite is one of the REE rich minerals ending up in the tailings pond when Luossarvaara-Kiirunavaara AB (LKAB) in Sweden processes Malmberget’s iron ore deposit. Leaching with nitric acid, hydrochloric acid, and sulphuric acid respectively have been studied. The nitric acid route was chosen for further investigations and the optimum acid concentration for leaching of the REE were determined. The leached REE are recovered by solvent extraction using di-(2-ethylhexyl) phosphoric acid (D2EHPA) and 2-ethylhexylphosphonic acid-mono-2-ethylhexyl ester (EHEHPA).

Jan 1, 2014

By Marek Mika

This Paper has been prepared to be presented at the 23rd World Mining Congress & Expo ? Montreal 2013. It presents the idea how to carry out the shaft sinking operation, going through highly water-bearing and very weak rock strata, giving as an example one specific shaft sinking project which is being executed for one of the Polish collieries by our Shaft Sinking Company Content 1. Introduction. 2. Hydrogeological conditions within the area of the shaft. 2.1. Hydrogeological conditions assumed at the stage of designing. 2.2. Hydrogeological conditions encountered in the course of sinking. 3. Designed shaft lining. 4. Procedures for the shaft sinking. 4.1. Designed procedures of the shaft sinking. 4.2. Procedures for preservation and strengthening of the shaft lining and the surrounding rock strata. 5. Technological guidelines for proceeding with the shaft sinking ? selection of special methods. 6. Options for mechanization of work for the selected method. 7. Conclusions.

Aug 1, 2013

By M. Tanaka, H. Narita, T. Fuchikami, K. Morisaku, K. Nagao, T. Yoshida, K. Kuroda

The effect of various N-substituents on the performance of amide-containing tertiary amine compounds in the extraction of Rh(III) from HCl solutions was investigated to optimize the structure of these compounds for industrial use. It was found that N-2-ethylhexyl-bis(N-di-2-ethylhexyl-ethylamide)amine and tris(N-di-2-ethylhexyl-ethylamide)amine, which have long, branched alkyl chains, were suitable for Rh extraction, because they were soluble in a practical diluent (80 vol% n-dodecane?20 vol% 2-ethylhexanol) and stable against highly concentrated HCl/Rh solutions, and showed high selectivity for Rh(III) over Pd(II) and Pt(IV).

Jan 1, 2014

By Hajime Miki, Gde Pandhe Wisnu Suyantara, Shigeto Kuroiwa, Eri Takida, Tsuyoshi Hirajima, Masashi Yamane, Yuji Imaizumi, Mitsuru Sawada, Keiko Sasaki

Selective flotation of molybdenite and chalcopyrite using various oxidation treatments (i.e., ozone treatment, hydrogen peroxide, and Fenton-like reagent) was studied in this work. It was found that ozone treatment produced a depressing effect on both minerals, resulting in a lower separation of both minerals. On the other hand, oxidation treatment using hydrogen peroxide (H2O2) and Fenton-like reagent could deliver selective oxidation on chalcopyrite surface and depress its floatability. However, bench-scale copper- molybdenum (Cu-Mo) flotation tests show that oxidation treatment using H2O2 required a higher dosage of H2O2 and a longer treatment time in order to deliver comparable flotation results to that of conventional Cu- Mo flotation using NaHS treatment. On the contrary, Fenton-like reagent could deliver selective Cu-Mo flotation results comparable to that of NaHS treatment at a lower dosage of H2O2 and a shorter conditioning time. Contact angle measurements and X-ray photoelectron spectroscopy (XPS) analysis were employed to understand the depressing mechanism of these oxidation treatments. It was found that the chalcopyrite surface covered by various oxidation products that render the surface hydrophilic. Meanwhile, the surface of molybdenite was slightly oxidized, making the surface remained hydrophobic. INTRODUCTION Molybdenite (MoS2), the main source of molybdenum, is associated with copper sulfide minerals, mainly chalcopyrite (CuFeS2), as a trace mineral. Molybdenite is a valuable mineral and plays an important role in making the copper-molybdenum (Cu-Mo) processing plant economically viable (Laskowski, Castro, & Ramos, 2013). Therefore, it is important to recover molybdenite efficiently and effectively and separate it from copper minerals. Conventional separation of copper and molybdenum minerals is usually carried out in selective Cu- Mo flotation process using a copper depressant (i.e., sodium hydrosulfide (NaHS), Noke’s reagent, or cyanides) (Ansari & Pawlik, 2007; Bulatovic, 2007). However, this process still suffers due to imperfect molybdenum recovery. Moreover, the copper depressants use in this process are toxic and harmful to the environment. As alternative, various methods have been developed to replace these toxic and hazardous depressants, for example, by synthesizing new non-toxic or low-toxic depressants or by using various oxidation methods such as sodium hypochlorite in an alkaline medium, manganese dioxide, oxygen, and plasma pre-treatment (United States Patent Office Patent No. US 2559104 A, 1951; Patent No. US2238250 A, 1941; Barzyk, Malysa, & Pomianowski, 1981; Hirajima et al., 2014). However, the oxidation phenomenon and mechanisms are still not clear since detailed surface analyses have not done and the plasma pre-treatment method is facing technical issues for industrial scale application.

Jan 1, 2019

By Sadough vanini Ali

Hot deformation behavior of functionally graded steel (FGS) was investigated via conducting hot compression tests at different temperatures and strain rates. Functionally graded steels consist of ferrite, austenite, bainite and martensite layers that are made by diffusion of alloy elements during the melting process. The zenerhollomon parameter has been used to describe the flow stress variations as a function of temperatures and strain rates. The parameter values for all the layers via using the boundary conditions was determined based on composite graded behaviors. Furthermore by applying the rule of phase mixtures, the whole strain rate applied on composite would be the sum of layers strain rates considering the layers volume fraction, while the layers have the same stress. Consequently the composite flow stress for each strain rate and temperature was determined.

Oct 1, 2011

By B. Farabi Khoshmehr

In the present study the effect of Silicate Sodium oxidation agent concentration and Plasma Electrolytic Oxidation (PEO) treatment time were investigated on properties of oxide layer on Aluminum alloy. The phase composition and surface morphology of PEO films were evaluated through x-ray diffraction (XRD) and scanning electron microscopy (SEM). Pin on Plate abrasive machine were used to investigate of were resistance of coating. The results showed that oxide layer which formed on Aluminum surface consist of high temperature a- Al?O? and ?- Al?O? phases. The diffraction peak intensity and percentage of these phases were increased by increasing silicate sodium concentration. Microscopic studies revealed a porous surface for PEO coating. This was affected by silicate sodium concentration and oxidation time. The wear test results showed that the weight loss of PEO coating was reduced due to improvement of their wear resistance.

Oct 1, 2011

"These guidelines set out information on timely disclosure of news releases which are intended to provide, existing shareholders and potential investors, factual information on which a reasoned investment decision can be made.Consider the problems and concerns raised by the following hypothetical news releases:Natural Resource Company""The Company has recently optioned a large and exciting gold property near the ""XXX"" gold discovery area. In describing the property, the Company's independent consultant has said: ""The favourable location of, and some of the results of prior work done on the property give the Company a worthwhile mineral exploration opportunity .... "". The Company proposes to expeditiously conduct a sizeable exploration program on the property as soon as the appropriate financing has been arranged.""Non-Resource Company""Based on discussions with several European countries, the Company anticipates that it will have orders to ship over 200,000 crates of widgets to those European countries over the next two years. These orders, which considerably exceed the Company's forecasts for the first year, represent a projected profit to the Company in excess of $1,000,000 over the next five year period.""GuidelinesTimely disclosure news releases are intended to provide, to both existing shareholders and potential investors, factual information on which a reasoned investment decision can be made. National Instrument 43-101 Standards of Disclosure for Mineral Projects provides requirements for disclosure of a scientific or technical nature for a mineral resource company.The examples do not provide sufficient detail and are misleading because material information is omitted. The following guidelines should be observed when preparing a news release:"

Jan 1, 2003

By S. Rash Ahmadi

One of the most important elements in power plants is rotors and repairing the damaged rotors is very important in view point of economics. One of the most complicated problems in power plants is increasing of stiffness of the turbine rotors. This problem which occurs mainly due to thermal shock or rubbing makes to exit damaged rotor from service. These elements can be repaired effectively by heat treatment methods. Tempering heat treatment is the most common solution for straightening of damaged rotors but it requires having good knowledge about heat treatment parameters (temperature and time) and their affects on fundamental properties of rotors. In this article, a suitable method is introduced in order to modify the increased stiffness in journal part of rotors due to martensite transformation, using heat treatment tempering process.

Oct 1, 2011

By A Sadough Vanini

In this paper large deformation of smart functionally graded beams with initial imperfection and under thermal loadings is considered. Smart beam consist of two types of layers. One layer is made from functionally graded materials and a layer or a set of layers from active materials that usually is made from piezoelectric materials that are bounded on the surfaces of beam. An active controller is used for controlling the deformation and stress in functionally graded layer of beam. A simple Euler- Bernoulli beam theory is used for analyzing of beam. In functionally graded layer the material property vary continuously through the thickness direction and power law model is used for the variation of elastic modulus, heat expansion and heat conduction coefficients. Poisson ratio is assumed to be constant in functionally graded layer. The effects of varying the power law constants and the Gain of controller is considered here. The results are reduced and compared with smart functionally graded beam without initial imperfections.

Oct 1, 2011

By S. Rash Ahmadi

Thin brittle coatings are deposited or developed on component surfaces for different reasons. In many practical applications the coatings are stressed by externally applied loads. Under such conditions, coating failure can occur. In this paper the probability of the extension of surface crack in coated materials due to cylindrical sliding indentation is analyzed. Contact loading problems typically result in multi-axle and strongly inhomogeneous stress fields near the contact surface. This property which strongly affects the stress intensity factors is taken into account in the failure analysis. Edge cracks were selected to model the actually accruing surface flaws. A suitable method is described for calculating the contact stress fields in coating and substrate. The coating is idealized as a brittle-elastic layer of uniform thickness, which is bonded to the surface of a half space. Method of linear elastic fracture mechanics are then used to calculate the load required to cause fracture in the coating.

Oct 1, 2011

By S. A. Sadough vanini

In this paper the influence of temperature on the flow behavior and rheological characteristics of an A356 alloy in the semi-solid state using backward extrusion process are studied experimentally and numerically. Simulation process is done by dynamic explicit in ABAQUS software for each forming condition. A cooling slope treatment was employed in order to obtain a non-dendritic microstructure. Experiments were performed in 5 temperatures and 4 different wall thicknesses. In the low forming speeds, liquid fraction had time to escape from solid phase forward the samples? wall. This condition was the main reason for the segregation phenomenon seen in the base and walls. Viscosities were determined using the force-displacement graphs obtained form back-extrusion tests. As observed experimentally, in a constant temperature, increase of shear rate resulted in decrease of alloy viscosity exponentially. Raising the temperature increases the liquid fraction hence reduces the semi-solid alloy viscosity. The results of experimental and simulation are compared and there is a good adaptation.

Oct 1, 2011

By Sadough vanini Ali

Charpy impact energy of functionally graded steels produced by electroslag remelting in crack divider configuration has been modeled in various strain rates. It has been well known that majority of materials indicate different behaviors under different strain rates and temperatures. Therefore, modifying the elastic-plastic model considering the effects of strain rates and temperature gives us an acceptable prediction of these composites behaviors in impact test. In this investigation, graded steel was divided in to several layers in which the layers have the same strains under the impact. Constitutive equation describing the flow stress variations as a function of strain rates and temperatures, have been used to express the stressstrain behavior of layers. The parameter values of constitutive equation determined for all the layers via using the boundary conditions based on composite graded behaviors which were the characterized ferrite, austenite, bainite and martensitte phases. Consequently by applying the rule of phase mixtures and ascribing the impact energy of each layer to the area of stress-strain curve of the same layer, the whole impact energy of composite is the sum of layers impact energy with considering the layers volume fraction.

Oct 1, 2011

By I. Colquhoun

Current practice tends towards "integrity as an afterthought". That is, integrity is treated as an isolated aspect of operations and maintenance. In fact, this works quite well. But it would work so much better and with less uncertainty if integrity management measures were introduced at the design phase and addressed the entire life-cycle of the pipeline asset. The talk will address the measures and metrics that can be implemented on a new pipeline during design to optimize integrity and deliver a comprehensive operating manual and integrity management program for the pipeline system. This deliverable should describe the risks to be assessed and monitored, and the actions to be taken to control these risk adequately. Properly executed, integrity by design will provide a good working estimate of the life-cycle integrity management costs and maximize system reliability.

Jan 1, 2005

By S. Rash Ahmadi

Welding is highly reliable and efficient metal joining process. In welding the metal adjacent to the weld joint is subjected to severe thermal conditions. As a result, complex changes in metallurgical structure occur in this region. These changes in structure depend on the material and the temperature history experienced. Friction stir welding (FSW) is relatively a new welding process in which, heat is generated by friction between the tool and the workpiece. The amount of heat conducted into the workpiece determines the quality of weld, residual stress and distortion of the workpiece. The objective of the current work is to study the transient temperature in a friction stir welding. So, a three dimensional transient analytical model is used to study the thermal distribution during the welding. Heat input from the tool shoulder alone is considered in the model. The process parameters like axial load, welding speed and tool rotational speed, used in actual FSW process are taken to build the model. This analytical model is very useful for select the optimized affected parameters in friction stir welding. The model illustrates the comprehensive equation including actual affected parameters in FSW and it can be used for different materials. In addition to the above the thermal history finds application in design of welding tools.

Oct 1, 2011

By S. A. Sadough vanini

In this paper, Stress-Strain-Temperature relations for Shape Memory Alloys are studied. Temperature effects on Shape Memory Alloys are different from those related to ordinary materials. In ordinary materials, elastic characteristics can be assumed to be constant in low temperature ranges, and only the deflection arising from temperature changes could be added to the elastic defection. As long as two phases of austenite and martensite could be present in Shape Memory Alloys simultaneously, elastic modulus follows temperature and temperature gradient. In continue a smart actuator is investigated considering a homogeneous cantilever beam. Beam bending is established by using shape memory wires. An initial strain is imposed to shape memory wires in a low temperature, and then, they are installed in the outer surface of the beam. Therefore, since the temperature is imposed in these wires and they cannot have free recovery strain, the compressive recovery stress will be produced in the outer surface. This will result in a deflection in axial direction of the beam. At first, beam deflection is calculated on the basis of theoretical relations and solving the relevant differential equations. Afterwards, experimental tests are performed on an elastomeric beam equipped with shape memory wires. When a voltage is applied, a temperature rise will occur in the wires; then, this temperature rise causes a deflection in the beam. Finally, the theoretical and experimental results? comparison indicates a good conformity. One capability of this actuator is its high flexibility, and by controlling the inlet current, the end-beam deflection can be controlled.

Oct 1, 2011

By Noko S. Phala

The energetics of CO and CO2 hydrogenation to methanol were studied on a gold surface via periodic and cluster DFT calculations. CO hydrogenation appears to be much easier than CO2 hydrogenation on an Au(111) surface. The use of a cluster model does not seem to improve the energetics of CO2 hydrogenation. It is concluded that an active support (e.g. ZnO) will be required to increase the productivity of a gold surface towards synthesis gas conversion. The energetics of CO and H2 adsorption are improved on the cluster model compared to a slab model of an Au(111) surface, suggesting that nanosized gold particles may be beneficial in CO hydrogenation.

Oct 1, 2003

By P. C. Patnaik

Performance of industrial gas turbine engines in terms of power output, reduced cooling and efficiency have been continuously increasing in parallel with aero gas turbines due to the advances made in the development of new materials, protective thermal barrier coatings (TBCs) and the advanced diagnostics to monitor service induced problems such as hot corrosion, thermal and thermo-mechanical fatigue and other operational issues, Environmental attack (hot corrosion or high temperature oxidation) is a common degradation mode in the hot section of the gas turbine, Hot corrosion occurs when Na or K bearing compounds in the environment or in the fuel combine with other contaminants such as S and Pb or V to form corrosive sulphates or vanadates thus attacking the protective oxide on the turbine airfoil, These problems pose far more threat to new turbine engine materials such as directional solidified, single crystals and ceramic matrix composites (CMCs). The CMCs due to their increased temperature capability, when used in the combustion chamber, are likely to reduce the peak temperatures attained during combustion and therefore provide the benefits of reduced emissions of oxides of C and N, These issues will be reviewed critically and their impact will be assessed on gas turbine lives. With respect to alternate fuels, past experience has shown that utilization of residual oils and coal derived fuels in gas turbines have resulted in complex deposition and corrosion processes, In recent years biomass derived alternate fuels have been used either through a gasification cycle or through direct firing of the biomass derived liquid fuel with a view to reduce Green House Gases (GHGs) and improve the climatic conditions. In both cases, the resulting high temperature corrosion processes (in the presence of alkaloids in the fuel) are also very complex, leading to premature removal of hot section components, Technology solutions mitigating these fundamental problems will be reviewed and solutions presented.

Jan 1, 2005

By Antonio Fontana

"Environmental problems encountered with the use of diesel equipment in underground mining operations are discussed. The concept and procedure o implementing the Health Effects Index equation as a means of quantitatively assessing an underground working environment is outlined and sample calculations are present ed. Advantages and disadvantages of utilizing this method are also discussed.IntroductionWith the introduction of diesel-powered mining equipment in the 1960s there arose several question s for the environmental engineer to consider. These included: 1. What are the constituents of diesel exhaust and how can they be detected and evaluated?2. What are the toxicities and long-term health effects of these constituents?3. What is the ventilating volume required to maintain the concentration of these constituents below toxic levels?Diesel engines are a class of reciprocating, internal combustion engines in which relatively high compression ratios are used to generate high air-charge temperatures, which cause ignition of fuel to occur spontaneously. Ideally, perfect combustion of the fuel would produce an exhaust consisting solely of nitrogen (N2), water (H2O), carbon dioxide (CO2) and oxygen (O2). However, because no combustion process is perfect, relatively small quantities of imperfect-combustion products, or pollutants, are also generated. These include hydrocarbons (HC), carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO2), carbon (C) or soot, and sulphur dioxide (SO2).Currently, the Regulations for Mines and Mining Plants, made under the Occupational Health and Safety Act (Section 176), stipulate that weekly tests shall be made to determine the carbon monoxide (CO) concentration in the undiluted exhaust and at the operator&apos;s position, and the nitrogent dioxide (NO2) concentration at the operator&apos;s position. Also, the aldehyde (as HCHO) concentration in the atmosphere, at the operator&apos;s position, is to be measured at least every three months. Threshold limit values (TLVs) have been established for each of the three combustion products, and each is regarded as a separate entity. Consequently, this does not allow for consideration of interactions and possible synergistic effects between the various exhaust components."

Jan 1, 1982

By J. H. Baek, D. W. Lee, B. K. Kim

Nanostructured Cu-Al203 composite powders were synthesized by thermochemical process for an electrode application. The synthesis procedures are 1) preparation of precursor powder by spray drying of solution made from copper and aluminum nitrates, 2) heat treatments to evaporate volatile components in the precursor powder and synthesis of nanostructured CuO+Al2O3, and 3) CuO reduction by hydrogen into Cu. The suggested procedures stimulated the formation of the gamma-Al2O3. The mean particle size of the final composite powders was 20nm, and the electrical conductivity and hardness in the hot-extruded bulk were competitive with Cu/Al2O3 composite by the conventional internal oxidation process.

Jan 1, 2004