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By Miguel Olivas-Martínez

A two-dimensional computational model for the hot filament chemical vapor deposition (HFCVD) process to produce diamond films is presented. The model incorporates the transport of momentum, energy, and mass inside the reaction chamber of a HFCVD reactor. The gas-phase homogeneous reactions were represented by a simplified reaction mechanism. The gas-phase transport equations were coupled to the kinetic expressions representing the catalytic dissociation of the molecular hydrogen at the filament surface and the deposition rate of the diamond film on the substrate. The computational model was solved numerically by means of a commercial software. The model predictions showed good agreement with the experimental data reported in the literature in terms of both temperature and methyl concentration profiles along the filament-substrate center distance. Examples of the potential applications of the present formulation for the design and further optimization of the HFCVD reactor are discussed.

Jan 1, 2006

By Norbert Steiner

For the desulfurization of weak SO2 gas streams, Degussa developed a process using dilute H2SO4 solution containing H2O, instead of conventional gas scrubbing with all solid absorbent medium (limestone, MgO). The process is based on fast reaction of H2O, with SO2 yielding H2SO4 up to 70% strength, depending on off-gas temperature. Compared to the conventional systems with typically < 95% efficiency, independent on the raw gas SO2 concentration, residual SO2 concentrations of less than 20 mg/Nm3 can be easily achieved, corresponding to nearly 100% removal. These features render the H2O, process a very attractive, low capital cost technology to retrofit existing conventional desulfurization plants.

Jan 1, 1996

By Ma Keyi, Yang Xianwan, Zhu Xiaoyun, Guo Zhongcheng, Zheng Yanping

"The oxidation of the Multifunctional Electrodeposited RE-Ni-WP- SiC Composites at high temperature is investigated. The results show that during high temperature oxidation the relationship between the mass change of pure Ni , Ni-W-P, Ni-W-P-SiC or RE-Ni-W-P-SiC coating and the oxidation time follows a mixed curve, i.e. it is approximately a linear relationship when the oxidation time is less than 60 mins while it is a power function relationship when the oxidation time is over 60 mins. The order for the oxidation rate of the four coatings is Ni> Ni-W-P> Ni-WP- SiC>RE-Ni-W-P-SiC. The mass change of Ni-W-P, Ni-W-PSiC or RE-Ni-W-P-SiC coating increases exponentially with a rise of oxidation temperature. The high temperature-oxidation resistance of RE-Ni-W-P-SiC composite coating is 3-4 times that ofNi-W-P alloy coating. The cross section morphologies and Xray diffraction patterns indicate that the high temperature oxidation resistance of RE-Ni-W-P-SiC composite coating is better than any other coatings.1. IntroductionWith the rapid development of modem industries the products in engineering industry are continually challenged by the requirements of long-term and stable working at higher temperature, pressure, speed and under adverse conditions. Consequently, the surface properties of the products, such as the resistance to oxidation at high temperature, the resistance to wear and the resistance to corrosion, should be improved continually."

Jan 1, 2000

By O. Forsén

A new cell construction was designed for the study of the electrochemical behaviour of additives in conditions that simulate real copper, electrorefining. The behaviour of gelatine and thiourea was studied by applying different electrochemical methods, i.e. polarization resistance and voltametric measurements. In this study, individual galvanostatic electrolysis experiments were carried out for 120 hours. The organic additives were introduced to the electrolyte at certain intervals and their concentration was varied in the range &om zero to four ppm. An optical microscope was applied for the examination of copper cathode deposit microstructures. The results show that gelatine has a polarizing effect on the deposition potential of copper whereas even small amounts of thiourea depolarize the electrodeposition of copper. The maximum inhibitor efficiency of gelatine was obtained at a gelatine concentration of slightly lower than two ppm. When both gelatine and thiourea were present in the electrolyte, the depolarizing effect of thiourea exceeded completely the polarizing effect of gelatine. If chloride ions were added to gelatine and thiourea containing electrolyte, the electrochemical behaviour of the system was altered drastically. Chloride ions resulted in the prevailing of polarization effect caused by gelatine while the depolarizing effect of thiourea disappeared in this system. The polarizing effect of gelatine increased until chloride ion concentration of 30 ppm was reached. Also, the above electrochemical phenomena could be detected in the optical examination of copper deposit microstructure.

Jan 1, 1995

By John A. Vallomy

"The CONSTEEL Process introduces a new concept in electric steelmaking by continuously feeding-preheating-melting and refining ferrous scrap or direct reduced iron. The process uses the furnace off-gas and fuel to preheat the scrap in a specially designed preheater. Thermal incineration of the flue gas reduces the carbon monoxide level to the more stringent requirements. Hot water or steam production from heat of flue gas is optional. The tap-to-tap time is set to match the cycle of the caster. The steel is treated via ladle metallurgy. The environment inside and outside of the steelplant is improved by decreasing levels of noise and hazardous emissions. Energy consumption decreases and disturbance to the electric network is eliminated. A CONSTEEL prototype was tested at Nucor Steel, Darlington, SC. A greenfield project is in the completion stage at the Florida Steel plant of Charlotte, NC, USA. The Process PhilosophyThe philosophy of the CONSTEEL Process is not solely to enhance efficiency; this was just a natural result of the change from a batch to a continuous practice. The primary objective in development was four-fold:1) 100% process control2) Rational use of available energy3) Improved environment inside and outside the plant4) Stability of energy input from the power systemIt was to make electric steelmaking more a science than an art and amenable to modern automation.The Basic Concept of CONSTEELThe concept of the process is shown in figure and includes basically a continuous feeding system, a preheater and a melting - refining furnace. A pre-established amount of heat is introduced into the scrap while traveling through the preheater using the sensible and chemical heat contained in the furnace off-gas and additional fuel. Melting-refining is carried out in the electric furnace. Slag formers, slag foaming additions and oxygen are injected to refine the melted steel continuously, to minimize the refractory erosion, to shield the arc, thus optimizing the transfer to the metal bath of the heat generated in the arc, to keep the bath homogeneous in composition and temperature and to produce carbon monoxide (CO) which is fuel for the preheater."

Jan 1, 1988

By Jian Li, S. Penttila, W. Zheng

"Materials selection for Gen IV supercritical water reactor in-core components faces major challenges due to severe operating condition. Beside high-temperature mechanical properties, SCC and general corrosion resistance of commercially available materials are also major focuses in recent research. Recent reports suggest that certain types of surface modifications are beneficial to SCW corrosion resistance. In this study, the effects of surface modifications are investigated, and possible mechanisms for improved corrosion performance are discussed.IntroductionThe current Canadian pressure-tube supercritical water reactor (SCW) design specifies a core outlet temperature of 625°C under 25 MPa of pressure, with peak cladding temperature as high as 850°C. Challenges in materials selection include high-temperature mechanical properties, corrosion resistance, SCC resistance and radiation damage. Most of the SCW corrosion test results available are below 730°C. Early work by Allen [1] summarized the corrosion resistance of alloy groups including Ni-based super alloys, stainless and ferritic/matensitic (F/M) steels that can potentially be used for SCW reactors. F/M steels can only be used at low temperature sites (e.g. down stream piping). At 500°C and 25 MPa, F/M steels develop a thick but mechanically stable oxide layer. However, the long term stability of the surface oxide layer is largely unknown. Ni-based alloys appear to form very thin surface oxide, however pitting was observed in the vicinity of some intermetallic precipitates [2-5], and dissolution of major alloying components could pose significant problems for down stream piping [6]. In addition, concerns of Helium formation due to Ni transmutation prevented this alloy group to be used as fuel cladding. The corrosion resistant austenitic stainless steels (e.g. 316L) are found to be susceptible to localized corrosion such as pitting, intergranular attack and stress corrosion cracking (SCC) [7]."

Jan 1, 2012

By Eric Pirard

Theoretical studies carried out on shape analysis supply mathematical tools to analyze the influence of grain shapes on ore beneficiation. In the case of statistic images like those encountered in applied mineralogy parametrical and harmonical analysis methods are used. It is important that the shape parameters are adapted to the specific processes involved in ore beneficiation, while remaining easy to manipulate. The inertia parameters are considered in the scope of granulometric and gravimetric processes It appears that they are able to distinguish between the resulting products where very popular shape parameters are not. The measured statistics are analyzed through discriminant analysis procedures in order to estimate the importance of morphological differentiation and the aptitude of shape parameters to account for this.

Jan 1, 1989

By E. N. Mounsey

Ausmelt Technology was selected by Bindura Nickel Corporation (BNC) as the basis for a new copper circuit to process nickel plant copper leach residue to blister, anode and finally cathode copper and recover PGM values at the Bindura Smelter Refinery (BSR). The process selected, based on Ausmelt Technology to smelt and convert the residue to matte and blister copper and produce a discard slag, is novel incorporating smelting, converting and slag reduction process steps in a single Ausmelt vessel. The process demands a high quality blister copper product with low levels of arsenic and nickel. This paper reviews the project and the initial operational results to the end of 1997 of the Ausmelt Top Submerged Lancing (TSL) smelter and discusses the implications for the wider TSL converter market.

Jan 1, 1998

By Alan Branham

The Mike deposit is a large, low grade, oxide, gold-copper system found at the intersection of two major faults that bound the Carlin Window, Eureka County, Nevada. Disseminated gold occurs within metamorphosed and hydrothermally altered silty limestone (Silurian-Devonian Roberts Mountains Formation), beneath 182 m (600 feet) of barren Tertiary sediments and tuffs. A supergene copper oxide blanket occurs beneath and locally overlaps the lower portion of the gold zone. Decalcification argillization, silicification, and brecciation are superimposed on earlier calcsilicate hornfels and marbles. Altered dikes and sills intrude the gold zone and are locally auriferous.

Jan 1, 1995

By Zhang Chuanfu, Tan Pengfu

"A thermodynamic model is developed to simulate nickel flash smelting process. In the nickel flash furnace, oxidation of concentrate occurs at one end, and reduction of slag occurs at the other. The model makes use two zones, namely the reaction shaft/settler zone and the appendage zone and accounts for 6 phases (matte, slag, silica, magnetite, Cu-Ni alloy and gaseous phase), 13 elements (Ni, Co, Cu, Fe, S, 0, N, C, H, Si, Al, Mg and Ca) and 33 chemical components in nickel flash smelting system. The compositions of matte, slag and gaseous phases in equilibrium are calculated by using the data of free energies of formation and activity coefficients of components. Two nickel sulfide species are used to allow for the modeling of sulfur-deficient mattes. The model predictions are compared with the known industrail data from Kalgoorlie Nickel Smelter, and excellent agreement is obtained. The model can be a very useful tool for monitoring and optimizing the actual industrial operations of nickel smelting process. The distribution behaviors of Ni, Co, Cu, Fe, S and 0 in the nickel smelting furnace depend on the process parameters such as smelting temperature, volumes of air, the content of the elements~ charge and oil.1. IntroductionThe nickel flash smelting furnace essentially consists of a reaction shaft where nickel sulfide concentrate is partially oxidized with air, a settle zone where matte and slag are allowed to separate, and a slag cleaning end where coke is added to provide for the reduction of the oxidized nickel from slag, and electrodes are used to provide heat.The theoretical model to consider a mass balance for copper flash furnace is developed by S. Goto and R. Shimpo[1][2J. However, this can not be true for nickel flash furnace as a whole since oxidation of concentrate occurs at one end (in the reaction shaft/settler), and reduction of slag occurs at the other (in the appendage). Despite these limitations, an acceptable pseudo-thermodynamic description of the furnace can be achieved using essentially two zones, namely the reaction shaft/settler zone and the appendage zone. Compositions of gas, slag and matte in two zones are calculated."

Jan 1, 1998

By Carlos Eduardo Gomes de Souza, Luis G. S. Sobral, Paulo A. Medeiros da Silva, Selma G. F. Leite, Renata de B. Lima

"The use of mixed cultures of acidophilus microorganisms that act in different temperature ranges, aims at speeding up the digestion of chalcopyrite, highly refractory sulphide mineral, the major mineral in the flotation concentrate of Caraíba Mining Co., with an attractive processing cost. The concentrate under consideration contains mainly chalcopyrite (CuFeS2) and bornite (Cu5FeS4) with contents of, approximately, 70 and 30%, respectively. It was observed in this study, the performance of consortium of mesophiles, moderate and extreme thermophile microorganisms, in the oxidation of the aforementioned sulphides minerals, evaluating operational parameters such as pH of the leaching solution, the reaction temperature and redox potential, with consequent extraction of 80% of the concentrate copper content within 60 days of bioleaching. Such high copper extraction was achieved in column bioleaching tests.INTRODUCTIONThe solubilization of metals by the application of microorganisms from the mineral ores and the subsequent recovery of metals from solution are referred to as bioleaching (Rohwerder, T et al, 2003). This is an economical method for the recovery of metals from minerals; especially lowgrade ores, overburden, and waste from current mining operations which requires moderate capital investment with operating cost (Watling, 2006).Furthermore, bioleaching is generally more environmentally friendly than conventional metal recovery processes such as concentration and smelting. Those physicochemical metal extraction processes generate sulphur dioxide, a toxic emission that is increasingly the target of regulatory legislation (Stott et al., 2000; Olson et al., 2003). Bioleaching of chalcopyrite is the key industry target. The main problem hindering commercial application of chalcopyrite bioleaching is the slow dissolution rate (Fu et al, 2008).Dissolution of acid-soluble sulphide minerals such as sphalerite, and to a lesser extent chalcopyrite, occurs by a combination of ferric iron and proton attack via the polysulphide pathway (Rohwerder et al., 2003)."

Jan 1, 2008

By M. A. Barron, D. Y. Medina, R. T. Hernandez, I. Hilerio

"Chromium Nitride (CrN) thin fihns were deposited on steel AISI 316 substrates with reactive magnetron sputtering method. CrN films were produced under two different conditions. In the first one, the substrate was heated by a d.c. source. At the second coating was applied a negative substrate bias voltage. X ray diffraction, quantitative energy dispersive and scanning electron microscope, were employed to characterize their phases, chemical composition and microstructure. Additionally microhardness was evaluated using a microhardness tester. The results show that the phase formation of CrN thin films in the first case (with temperature) is better. Both coatings presented homogeneous surface. Their compositions shows differences though that gases flow are same. In attention to their hardness, presents an increment if it's compared with hardness substrate.Nomenclature.P Ar =Argon gas pressure during coating.PN2 = Nitrogen gas pressure during coating.Ts = Substrate temperature during coating.T f = Coating melting temperature. (CrN = 1050°C).E=Potential difference.t =Coating time.P=Target power (Cr) in magnetron sputtering de.HV = Vickers hardness.F = Applied charge.d= Average length of longitude of the two diagonals (mm)Introduction.Wear causes losses in materials surface, generating that components of mechanical systems suffer irreversible changes in their properties, causing a faulty operation of the system. It is important to control their effects, measuring and interpreting their causes clearly."

Jan 1, 2013

By Thomas Gliick, Jianming Lu, David Dreisinger

"The recovery of manganese from the Boleo project of Baja Mining is via an acid oxidation and acid reduction process in seawater. Manganese as manganese dioxide is leached into solution as manganese sulphate with the addition of sulphur dioxide gas as a reductant and then precipitated as a manganese carbonate. The use of the manganese carbonate intermediate to produce electrolytic manganese metal (EMM) has been extensively studied. The manganese carbonate can be used in place of natural (MnC03) or reduced ores (MnO) of manganese as a feed to the EMM plant. Manganese carbonate can be dissolved in spent electrolyte from manganese plating, followed by purification using ammonium sulphide precipitation of minor elements and then electrowinning in a selenium free process. The results of small cell testing of manganese electrowinning are reported.IntroductionThe Boleo Project of Baja Mining is a greenfields development currently under construction approximately 5 km north of the town of Santa Rosalia, Baja California Sur, Mexico. The Boleo property is held by the Mexican company, Minera y Metalurgica del Boleo S.A. de C. V. (MMB). MMB is owned 70% by Baja Mining Corp. and 30% by a consortium of Korean companies consisting of KORES - Korea Resources Corporation, LS Nikko Copper, Hyundai Hysco, SK Networks and lljin Copper.The Boleo deposit has Measured and Indicated resources of264.7 million tonnes grading 1.50% copper equivalent (CuEq) & Inferred resources of 159.9 million tonnes grading 1.15% CuEq. The calculation of copper equivalent is based on a combination of metal prices and predicted metallurgical recoveries (Table I). The metallurgical recoveries have been confined by extensive bench and pilot plant testing. Proven and probable reserves are available at Boleo to provide for more than a 30 year mine life. Initially, 25 years of mine life and 23 years of process plant operation have been scheduled in the February 2010 Technical Report Update (www.sedar.com)"

Jan 1, 2012

By Finn Olesen, Melina Garcia, Mark William Kennedy

"Furnace resistance is a function of the complex interrelationship between many factors including: operating practice, slag conductivity, temperature, power intensity, and geometry (electrode shape, diameter, spacing, immersion, slag depth, etc.).Accurate prediction of resistance is critical for success of the overall furnace design. The sizing of electrodes, columns, bus-bars, and transformers are all impacted. Estimation of minimum and maximum resistance or maximum operational current, as well as the maximum operating voltage are of fundamental importance.Various mathematical tools have been developed to assist designers with the selection of furnace dimensions and the prediction of resistance. Elkem found the methods of Downing and Urban 1965 and Westly 1975, to be particularly useful.In the current paper, comparisons are drawn between data from spent aluminum pot lining (SPL) demonstration testing at Elkem Bjolvefossen and predictions based on these classical tools and 3D finite element modeling (FEM) with COMSOL.®"

Jan 1, 2012

By Ali Akbar Mottahedi

Chromate conversion coating is a process for making a complex layer at the surface of zinc galvanized steel which makes the metal more resistant to corrosion, especially at marine atmosphere, and increases the adhesiveness of color. In this work the influences of various compositions on commercial zinc galvanized steel sheet to the color of chromate conversion coating has been investigated at normal temperature and the factors that affect the control and optimization of the process have been determined. A bath composition of 20 g/liter Cr203 and 10 g/liter NaOH and a dipping time of 50 seconds at room temperature (25-30°C) make a desirable color of chromate coating. A slow agitation at a constant pH of I (with additions of NaOH or H2SO4) assures a constant bath condition and develops the color. This kind of coating has more corrosion resistance and this bath condition and composition are also more economical.

Jan 1, 2003

By Muhlis Nezihi Saridede, Burak Birol

"Plastic wastes become a huge problem day after day due to the growth of plastic industry. Hence, plastic wastes are used as a raw material for other industries to eliminate this problem. Polyethylene Terephthalate (PET), which is a commonly used for plastic bottles, may be used as a reductant for iron production because of its C and H content. In this study, composite pellets containing iron ore concentrate, flux and reductant were prepared. Crystallized PET bottles and coke were used as reductant after ground. The prepared pellets were reduced at 1400°C for 30 min. and iron nuggets were produced successfully. Usage of waste PET purely as reductant in composite pellets gives a higher metallization degree and proper carbon content than coke or PET and coke mixture.IntroductionPlastics can be seen everywhere, especially at packaging industry in our common life. The increase of plastic usage ends up with an important problem, the increase of plastic wastes. Many studies have been carried out about usage of plastics as reductant in blast furnace such as Ogaki et al.[1], Heo and Baek [2], Saridede [3], Minoru et al.[4], etc. Besides, Kato et al. [5], Nomura and Kato [ 6] and Rongfang et al. [7] have pointed out the use of plastics in coke ovens regarding to its calorific content. In EAF steelmaking, a mixture of coal/coke and plastics can be used as an energy resource instead of only coal or coke. [8] Also, the usage of PET and PC in self-reducing composite pellets increased the reduction rate. [12]PET (Polyethylene terephthalate ), which is commonly used for soft drink plastic bottles, is an important municipal waste due to its C and H content. Its molecular formula is (C10H8O 4)n. Demir and Dincer showed that PET can be crystallized at 250°C to have the ability to be ground to a size of -100 µm. [11]"

Jan 1, 2011

By Dean G. Heitt

"The Rain and SMZ mines from 1987 to 1994 produced a total of22.0 t of gold from a pre-mine reserve of 14.24 Mt of ore grading 2.13 g/t Au.Gold at Rain is hosted within the basal portion of the Mississippian Webb Formation. ·Mineralization is closely tied to the Rain Fault which is interpreted to be the main feeder for the deposit. Multiple collapse and hydrothermal breccia events provided permeability for the mineralizing fluids in the otherwise unreactive siltstones. Major alteration events include: decalcification and dolomitization of the Devils Gate Limestone; and silicification, baritization, argillization and oxidation of the Webb Fm. Six ore types based on XRD and visual rock chip Jogging have been identified: siliceous ore containing >40% quartz and <30% barite; siliceous-baritic ore containing mostly silica but >30% barite; baritic ore containing >40% barite; argillaceous ore containing >40% total clays (including alunite); calcareous ore containing mostly calcite and dolomite; and carbonaceous ore which has significant pyrite and organic carbon. Metallurgical testing of the oxide leach grade ores found that recoveries, on -1.3 cm crushed material, were greater than 70%. Results also found that Rain ore has strong grind dependency due to silica encapsulation.The Rain leach pad was commissioned in 1988, and to date 9.3·Mt at an average grade of0.65 g/t Au have been placed. Life to date recovery, through December 1995, is approximately 51 %, for a total of3.87 t of gold produced. Two major factors have contributed to the low leach recoveries at Rain when compared with the metallurgical testing: 1) More argillaceous ore than expected was placed on the pad especially late in the mine life and 2) approximately 50% of the tons placed were run-of-mine with no agglomeration."

Jan 1, 1997

By Ma Ying

The continuous directional solidification technique of five kinds of special ZA alloys with eutectic, peritectic and eutectoid transformation under the condition of continuous casting by heated mold was studied. The mechanism of surface defects appearing in ZA alloy line was discussed and the structure of some defects were analyzed by SEM. The results show that only when the fitting of various technique factors, pressure head, outlet temperature, pulling speed and cooling condition are reasonable under a certain range, can the ZA alloy smooth line be continuously pulled out. Unreasonable techniques will result in hot tear, rough surface, mush outlet, leaking and other defects. The shape and location of solid-liquid zone have an important influence on the formation of the above defects. When the solid-liquid zone is located in the mould outlet or inner mould, the surface of solidification will protrude into the inner mould. If the remaining liquid cannot counteract the solidification contraction, a rough surface will appear. If the solidification surface further into the mould, the ingot in the mould will have a great friction force when pulling and will form a hot tear. When the solid-liquid zone is moved out of mould, the solidification surface will turn into a plane, which easily results in leaking. A vibration or unstable operation will cause an ingot winding during pulling

Jan 1, 2003

By Michael I. Morris

The U.S. Department of Energy&apos;s (DOE&apos;s) Transuranic and Mixed Waste Focus Area (TMFA), funded from fiscal year (FY) 1996 though FY 2002, was tasked with finding solutions for the mixed waste treatment problems of the DOE complex. During TMFA&apos;s initial technical baseline development process, three of the top four technology deficiencies identified were the need for amalgamation, stabilization, and separation/removal technologies for the treatment of mercury-contaminated mixed waste. The Mercury Working Group (HgWG), a selected group of representatives from DOE sites with significant mercury waste inventories, assisted TMFA in soliciting, identifying, initiating, and managing efforts to address these areas. Solicitations and contract awards were made to the private sector to demonstrate both the amalgamation and stabilization processes using actual mixed wastes. The goal was to develop separation and removal processes that will address DOE&apos;s needs. This paper discusses the technology selection process, development activities, and the accomplishments of TMF A through these various activities.

Jan 1, 2003

By Ram V. Ramachandran

As an industry with major potential impacts (both good and bad) on water resources and due to the rising costs of process water, the mining and metallurgical processing industry has a key responsibility to contribute to the overall goal of preserving both the quantity and quality of water available within the watersheds they operate in. As we plan for new and existing mining and metallurgical projects, we need to consider a hierarchy of options to minimize our impact within the watersheds we operate; keeping clean water clean by diverting around our operations; reduction in the amount of water we use; reuse of water wherever possible, and improvements to water quality for recycling and/or release to environment. Technology is needed to treat water to improve its quality for reuse or release to the original watershed. While lime precipitation followed by sulfide polishing is effective for removal of most of the metals, it does little or nothing to remove ammonium ions and anions such as chloride, nitrate, molybdate, arsenate and selenite/selenite. Regulations on sulfate limits in treated discharge water has drawn close attention to the treatment of acid mine drainage (AMD). Management of brine and salt disposal is also posing a problem due to strict regulations and cost of disposal. This paper will: (a) address issues associated with managing water with the objective of maintaining water sheds—status quo-during and after operation (b) discuss potential technologies for advanced water treatment plants.