Search Documents

By Maryam Ghodrat, Bijan Samali

Disposal of waste syringes in a safe and eco-friendly way has been an issue of considerable scale for decades. The generated amount of waste syringes has escalated with the rapid growth in population and wide acceptance towards single-use medical devices. Some hospitals have their own on-site incinerators ,but recent tightening of air quality regulations and landfill levies led to the closure of manyon-site incinerators. The solution to this problem implicates the development of an environmentally-sound method that would employ these waste materials. This work investigates a thermodynamic modelling approach for incineration treatment of waste plastic syringes in Electric Arc Furnace (EAF) steelmaking. Mass balance was obtained from HSC Chemistry thermochemical package. The results indicate that the rate of iron oxide reduction in the slag is higher when coke is partially replaced by waste plastic syringes. Furthermore, the amount of dust and stack gas emission was reduced by around 0.4% and 1.25% respectively by replacing 20%-weight of pure coke with waste plastic syringes. The study demonstrates part of the coke can be successfully replaced by waste plastic syringes in electric arc furnace to provide additional energy from combustion without affecting the main process.

Mar 1, 2018

By T. K. Bundtzen

Placer gold in the Iditarod and Innoko mining camps of western Alaska is derived from a suite of comagmatic, Late Cretaceous to Early Tertiary, alkali-calcic, meta-aluminous. volcanic-plutonic complexes and peralumi-nous rhyolite sills that intrude Mesozoic flysch. Heavy-mineral concentrates from 42 mining operations and streams draining known mineralized areas in the igneous complexes contain placer gold and a variety of ore minerals derived from epithermal to hypothermal conditions of formation. The minerals include cassiterite, ilmenorutile, samarskite, cinnabar, scheelite, chromite, stibnite, silver sulfosalts, monazite, and zircon. Results of the study show that 1) cinnabar. stibnite, and quartz formed with the bulk of the placer gold in an epithermal lode environment, 2) chromite appears to have originated in mafic phases of monzonite plutons and alkalic basalts, and 3) niobium-tin-tungsten-uranium-silver values may have been derived from stockwork accumulations in cupolas of monzonite plutons.

Jan 1, 1987

By Jochen Petersen

Design and operation of heap leach processes are still largely based on,operator experience and rule of thumb. Although considered a low-cost, low-tech route for mineral extraction, the underlying physical, chemical and biological processes are actually rather complex. Numerous heap leach models have been devised over time, but the majority of these tend to simplify the true process and are of limited use in practise. The modelling approach presented here combines the more conventional reaction-diffusion model with models accounting for equilibrium reactions in solution, bacterial growth kinetics, complex reactions schemes, gas flow, heat conservation, etc. One particular model application is discussed in the context of developing a novel high temperature heap leach processes using thermophile micro-organisms. The complexity of processes such as this can only be appreciated with the aid of a systematic model. For the designing engineer an accessible, personal computer based model should be an indispensable tool for the design and optimisation of efficient heap leach operations.

Jan 1, 2002

By Józef Czemecki

Polish copper concentrates are characterized by high levels of impurities, particularly Pb and As. Two technologies are being used for copper concentrate smelting at KGHM Polska Meidz S.A., namely the shaft furnace process (Legnica Copper Smelter, Glogów I Copper Smelter) and a single-stage process for direct to blister concentrate smelting in a flash furnace (Glogów II Copper Smelter). Both technologies are used at different physical and chemical conditions which results, in different impurities behavior. The paper presents flow sheets for copper production in a plant using the shaft furnace process and in another in which a single stage flash process is used. The metals distribution in particular semi-products is given as well as a method for elimination of impurities from the copper production cycle. Methods are also discussed for alloy and matte converting and copper refining to obtain low Pb and As concentrations in anode copper (0.3% Pb and 1500 ppm As maximum) that are being used in the KGHM Polska Meidz plants. Useful co-operation between the plants using different technologies, aimed at the limiting the effect of undesired impurities on the quality of blister copper produced, is also described.

Jan 1, 1998

By Ayşe Ece Yıldızçelik, Mehmet Buğdaycı, Onuralp Yücel

ZrB2 and TiB2 are significant metal borides. They are being used in various industrial areas from space technology to nuclear industry owing to their physical properties such as high melting point, high thermal/electrical conductivity and low density. Present study was conducted in two main stages: self-propagating high-temperature synthesis (SHS) reactions and leaching. ZrO2, TiO2, B2O3 were used as starting material and Mg was used as a reductant to produce ZrB2-TiB2 powders via SHS. Therefore, it was aimed to determine production parameters, leaching conditions and comprehensive examination of final product features. The samples were characterized by using chemical analysis (AAS), XRD, XRF and SEM/EDS techniques.

Jan 1, 2015

By Jerry D. St. Clair

A multidisciplinary team of scientists and engineers at Wont has been working to understand heavy metal contamination of DuPont process waste streams and technologies for abatement of these metals. As part of this effort, an extensive study was made of a specific waste stream of importance in DuPont's environmental commitment. This 200 gpm stream contains 5-5000 ppm of nickel plus a variety of inorganic and organic constituents. The chemical complexity of the waste rendered conventional. alkaline precipitation ineffective, and only through the simultaneous application of analytical characterization, fundamental chemical understanding, and process engineering did effective technical approaches emerge. In this instance, ion exchange, sulfide precipitation, and caustic digestion ultimately proved successful in reducing the nickel to below the 1 ppm target. The results of this study will be presented, along with key learnings about the process of solving heavy metal contamination problems.

Jan 1, 1994

By Greg Andrews, David Dreisinger

The Foxtrot deposit of Search Minerals contains a range of rare earth element containing minerals including allanite, fergusonite and bastnasite. The Search Minerals Direct Extraction Process for treating these minerals involves coarse crushing of the ore to -6 mesh (3.45 mm), acid treatment at 200 °C in a novel reactor configuration, water leaching, various purification steps to reject iron, aluminum and uranium/thorium (present in small amounts) and finally precipitation of rare earths as an oxalate and calcination to form a mixed rare earth oxide product for refining. The economics of the process are presented.

Mar 1, 2017

By O. C. Gaspar

The mineralogical and textural characteristics of the volcanogenic massive sulphide ores from the Aljustrel and Neves-Corvo deposits have been studied by ore microscopy techniques since 1977. Several ore types have been recognized, and the ore paragenesis, ore textures, and behaviours of different ore types during grinding and concentration processes, have been determined. An ore classification was established for use in metallogenetic studies, ore reserve calculations, selectivity during mining, and control of the ore beneficiation processes. In addition, an empirical method was developed for supplying, on time, the qualitative and semi-quantitative information needed for processing the Aljustrel ores and for optimizing the Neves-. Corvo copper and tin concentrators.

Jan 1, 1991

By Fiseha Tesfaye, Pekka Taskinen

"Thermodynamics of the equilibrium phase assemblage Ago_9Cul.lS-Cu2-xS-CuS have been studied by an EMF -method. The ternary phase was synthesized from the pure Cu2S and Ag2S in vacuum furnace at high-temperature and mixed with appropriate compositions of Cu2S and CuS to form the cathode electrode. The EMF-measurements were made on the solid-state galvanic cell Pt(-) I Ag I RbAg,ils I Ago9Cu1.1S-Cu2-xS-CuS I Pt(+), in a temperature range from 316 K to 498K.Based on the measured EMF vs. T relations, thermodynamic functions (?fG° , ?fS and ?fH°) of stromeyerite (Ag0.9Cu1.1S) in equilibrium with Cu2-xS and CuS have been determined. The obtained experimental values have been compared with the available literature values. New experimentally determined thermodynamic properties of the solid solution (Ag,Cu)2Sss were determined.IntroductionDue to intense mining of high grade sulfide ore minerals in the past, recently, the available sulfide ores are poor in metals and becoming increasingly complex; such that, the production of high grade metals by the conventional pyrometallurgical processes is compromised. Consequently, smelters are in need to modify their operating flow sheets and strategies for processing more complex feed materials economically, while meeting the strict environmental regulations. To make the appropriate modifications, accurate thermochemical data of phases and phase assemblages which exist in these complex ore minerals are essential.Silver-bearing sulfosalts are encountered in ore minerals for the production of base metals and are common sources of silver. Among the silver-based sulfosalts, stromeyerite (Ag0_9Cu1.1S) is relatively common ore mineral in most hydrothermal vein and replacement deposits [1]. Recently, the ternary chalcogenide compound Ago0.93Cu1,07S has been studied, intensively, due to its high ionic conductivity and gradual disorder in the sequential phase transitions [2]. Therefore, accurate knowledge of the thermodynamic properties of stromeyerite has considerable fundamental and practical interest in many aspects of extractive, chemical and physical metallurgy."

Jan 1, 2014

By Jose Hector Figueroa P.

Mexicana de Cananea, S.A de C.V. is a major copper producer mining a large deposit of the disseminated porphyry type considered one of the largest copper resources of the world with 2.7 billion tons of 0.60% copper for the mill plus 4.1 billion tons of averaging 0.26% copper for leaching. Mining of low grade sulfide leach ore, has been an important part of the overall production of the open pit mine which started in 1944. Before this time all the mining in Cananea was by underground methods. The leaching process in Cananea began on the 1920's with in situ operations in the underground mine and small dumps up to the 1950's. Large scale leaching operations began in 1960 and the copper solutions produced were treated in precipitation plants until 1,980 when the first SX/EW Plant was put in operation in Cananea. Leaching action is essentially ferric-bacterial, with no fiesh acid added to the leaching solutions. Traditionally, 5540% copper extraction is recovered fiom ROM, 70- 120 meter high leach dumps in 80 months of leaching. Cananea has successfully improved copper recoveries by implementing several actions that include: 1. Stripping of old dumps. 2. Leaching of old dumps through slotted casing. 3. Crushing conveying leach ore to minus 8 inch and stacking it in 30 meter lifts. As result of these actions, copper recovery has been increased' to about 70% of total copper with actions 1 and 2 and up to 85% in half the time by crushing-conveying the leach ore, based on the same solubility index of the run-of-mine ore. This paper describes the above actions that were implemented to enhance the leaching recoveries from. sulfide leach dumps and the economics of such actions.

Jan 1, 1999

By Jian Li, Tiejun Chun, Jian Pan, Deqing Zhu, Vinicius Mendes

"A study of the coal-based direct reduction behaviors of composite binder magnetite pellets was carried out in a simulating coal-based grate-rotary kiln process. It is shown that preheated pellets possess much better reducibility than fired oxide pellets: 40 min are required for preheated pellets to reach over 90% metallization degree compared to 100 min for fired oxide pellets. The compressive strength of preheated pellets decreases dramatically at the earlier stage of reduction, climbs quickly after reducing for 30min and achieves a high value at the end of reduction. However, the compressive strength of metallized pellets from reducing of fired pellets is much lower, more cracks and fractures being formed. In the preheated pellets, crystallite of metal iron is coarse. In the oxide pellet, a large number of interconnected crystals of metal iron are formed inside pellets, and pellet structure is very compact.IntroductionDirectly reduced iron is an excellent feed in electric arc furnace (EAF) steelmaking, and possesses low tramp element content and steady component. It is generally preferred in the production of high quality steel [1-3]. Nearly 64.44 million tons of DRI were produced in 2009 over the world, over 80% of which were produced by gas-based processes, the left by coal-based processes. However, the DRI capacity was only 600 thousand tons in China in 2009. The EAF steel production has exceeded 40 million tons annually, and most of EAF operate on hot metal as feed [4]."

Jan 1, 2011

By Ben Hogg

Since the development of the top-submerged lance (TSL) technology for copper and lead smelting by the cooperation of Mount Isa Mines (MIM), now owned by Glencore, and the Commonwealth Scientific Industrial Research Organisation (CSIRO) the core of the ISASMELT™technology has always resided in the lance system. Through continuous innovation and operation of our own smelters, first at MIM, subsequently at Mopani, and also at both the Kazzinc Copper and Kazzinc Lead smelters, Glencore Technology have expanded the core equipment supply to enhance the plant operability. The success of Glencore Technology’s expertise can be directly measured by the success of the Kansanshi Copper Smelter plant, which achieved 100% nameplate capacity within three months of start-up. This paper describes the ISASMELT™ core equipment and how it is applied to smelt sulfide materials. It highlights the strength of the ISASMELT™: continuous innovation to facilitate the versatility and continued increased capacity with every plant implementation.

By Edward Rosenberg

The synthesis and characterization of silica polyamine composites modified with a variety of sulfur containing ligands is described. The two most successful ligands in terms of sulfur in-corporation and mercury capture are ethylene sulfide and carbon disulfide. The ethylene sulfide forms either an amino mercaptane or a polysulfide upon reaction with amino groups on the composite. The carbon disulfide undoubtedly forms a dithiocarbamate functional group upon reaction of the amino group under basic conditions. Both materials posses excellent capture kinetics and capacities for mercury, Once captured, the mercury is extremely difficult to remove from the composite materials, even with concentrated acids, and they easily pass the TCLP test. The materials are compared with related thioether modified silica polyamine composites and appropriate potential applications are discussed.

Jan 1, 2003

By Fumito Tanaka

The Mitsubishi process is the sole pyrometallurgical process for the continuous production of blister copper from copper concentrates and has been successfully operated around the world. The development of calcium ferrite slag (CaO-FeOx-Cu20), the so-called "C-slag", has enabled continuous converting from matte to blister copper in the commercial scale operations. Commercial interests in the slag led to many papers over the CaO-FeOx slag. However, CU2O- bearing slag has not been studied well due to experimental difficulties. The authors have quantified the thermodynamic properties ofthe CaO-FeOx-Cu2O system. The results have been utilized to analyze various issues related to the converting furnace, such as the magnetite precipitation from the slag or from blister copper and to develop better controlling criteria for the continuous converting operation.

Jan 1, 2003

By R. Tunold, Y. J. Zhang

"The cathodic kinetics of aluminum deposition from aluminum chloridealkali chloride melts was studied by use of electro-cnemical transient techniques at 700 °C. Aluminum deposited as an insoluble product on a glassy carbon electrode and as a partly soluble product on a tungsten electrode. The deposition was found to be a simple diffusion controlled process involving the exchange of three electrons. The diffusion coefficient of aluminum chloride was calculated - 4.sx10-s cm2 ·S-I in AlCl3 -NaCl-LiCl melts and 2.6x10-s cm2 ·S-' in AlCl3 -NaCl-KCl melts. For AlCl3 -NaCl-CsCl system the diffusion coefficient exhibited some uncertainty due to nucleation. The determined rate constant of aluminum deposition reaction was on the order of 10-' -10-2 cm'S:' Constant potential electrolysis was carried out. TiB2 was well wetted by aluminum. The species of melts penetrated into graphite and glassy carbon but not into tungsten. The diffusion coefficient of species in glassy carbon was evaluated.IntroductionAluminum chloride electrolysis is attractive for its power saving of 30%. Different process to circumvent the conventional chlorization to obtain aluminum chloride economically, such as directly chlorizating mixture of Al~03 and C in a cell with A-shaped laminated bipolar electrodes by rising chlorine (1), or by use of a composite anode (2), will promote the electrolysis technology to be realized industrially. With the appearance of the Alcoa process periodically there are studies on the kinetics of aluminum deposition. Some discrepancies seem to exist on the mechanism of aluminum deposition. Borne studies (3,4,5) showed that the deposition of aluminum was hindered by diffusion process in the melts. M.Gabco et a1. (6) claimed a preceding dissociation of a complex being the rate controlled step. This paper presents our results on the mechanism of aluminum deposition from the study by use of transient techniques and some results from constant potential electrolysis."

Jan 1, 1988

By Yuanyuan Wang, Yuhao Ding, Hao Bai, Kang Zhou, Guangwei Du

"In this paper, the list analysis of GHG emissions of aluminum industry was conducted based on the data from typical electrolytic aluminum plants of a China’s northwest province. The results show that under the conditions of average anode effect coefficient as 0.16 times/(cell• day) and anode duration as 5 minutes per day, equivalent emissions of CO2 reached 1.23 ton per ton of aluminum, in which PFC emissions accounted for about 71%. Compared with foreign advanced level, which is 0.87 ton per ton of aluminum under the conditions of average anode effect coefficient as 0.01 times/(cell•day) and anode duration as 0.46 minutes per day, there is much room for China’s aluminum industry to reduce GHG emissions. Since anode effect plays an important role on PFCs generation in electrolytic aluminum process, how to control anode effect strictly becomes the key factor for remarkable reduction of GHG emissions in China’s aluminum industry.IntroductionTechnology of aluminum electrolysis is a mature and efficient process of aluminum production. Due to the huge demand on aluminum worldwide, so resource consumption, energy consumption and pollutant emissions in the process of aluminum production are still large. The global output of aluminum reached 45193 kt in 2012. A large amount of CO2 and PFCs are produced in the process of aluminum production, and the greenhouse effect and environmental pollution caused by emissions of them is a concern. PFCs belong to a powerful greenhouse gas, thus emission reduction of PFCs is very important for aluminum electrolysis industry. At present, China's aluminum production accounts for about 33% of the world's aluminum production, and controlling PFCs emission has become the key point of pollution control of aluminum electrolysis industry in China [1].Taking the case of a typical electrolytic aluminum plant of a China’s northwest province, this paper studies the list analysis of GHG emissions of aluminum industry in China. GHG emissions of a China’s northwest province were calculated through investigating existing situation of aluminum electrolysis industry in the province, knowing capacity, output, main production technology and equipment level of aluminum electrolysis industry, and using the calculation framework and methods of GHG emissions of aluminum electrolysis industry, which were put forward by the intergovernmental panel on climate change (IPCC), the international aluminum association and other organizations at home and abroad. The list analysis of GHG emissions of aluminum electrolysis industry will offer useful information in promoting emission reduction of GHG in aluminum electrolysis industry, improve the efficiency of energy utilization."

Jan 1, 2014

By N. Kanari

Chalcopyrite concentrates and their pure constituents were chlorinated by C12+N2 between 25 °C and 750 °C. The reaction products were analyzed by SEM, XRD and chemical analysis. The effect of gas flow rate and chlorine content of the gas mixture on the reaction rate were investigated. At room temperature, these solids start to react with chlorine giving metal and sulfur chlorides. Complete reaction is achieved at about 300 °C and the iron and sulfur chlorides were fully volatilized. The chlorination residue is composed of valuable metals' chlorides. A simplified flow - sheet for the treatment of chalcopyrite concentrates by chlorine was suggested.

Jan 1, 1998

By Mototsugu Matsuno

A new process has been developed to treat fly ash generated from municipal incinerators, which contains not only toxic metals such as lead and cadmium, but also dioxins. The process includes the following steps; fly ash is formed into green pellets with some additives and the pellets are then roasted to eliminate or stabilize the toxic metals and to decompose dioxins. A pilot plant with a capacity of approximately 100 kg/hr was used to test the process. The tests verified that heavy metals were either volatilized or stabilized and dioxins were decomposed by high-temperature roasting. The pelletized ash was found to be non-toxic, so that it can be recycled as artificial lightweight aggregate. It was also found that volatilized metals collected as secondary ash can be recycled as smelting resources.

Jan 1, 2003

By W. K. Connor, O&apos

Thermal Treatment Technology Division Albany Research Center, U.S. Dept. of Energy Oregon. This evaluation included a characterization study and direct smelting tests conducted in a bench-scale electric arc furnace (EAF). In contrast to other thermal treatment technologies considered for these wastes (i.e., fluidized bed combustion), direct smelting in the EAF can process 100% of the wastes without prior beneficiation, and utilizes solid oxidant additions (in this case iron ore) rather than air to oxidize the carbon. This solid oxidant addition is advantageous because it results in the production of several value-added furnace products. These products include cast iron resulting from the reduction of the iron oxides, baghouse dust containing virtually all of the zinc from the residues, and a clean (nonhazardous) slag product suitable for recycle as concrete aggregate or construction fill. Offgas from the smelting furnace also holds potential as fuel gas for cogeneration. The direct smelting tests conducted thus far were successful at producing the desired furnace products, exhibiting the potential for complete recycle of the waste pile. A cast iron product of comparable quality to conventional cast irons was produced, at nearly 80% iron recovery to the metal. The slag product was determined to be nonhazardous, based on the EPA TCLP. Lead and zinc partitioning to the dust product was greater than 99%. The material balance over the furnace indicates that for every ton of feed processed, 540 lb. of cast iron, 600 lb. of slag, and 150 lb. of dust would be produced. Energy consumption was roughly 1.10 kWxh/lb of feed material. Prior experience suggests that these figures measured in the bench-scale furnace would translate to 0040 to 0.50 kWxh/lb at the industrial-scale.

Jan 1, 2000

By M. Wallin

Millions of tons of sludge from different metallurgical processes are produced worldwide annually, and the environmental impact of landfilling these often hazardous sludges stresses the need to understand their role as valuable resources. The current work explores the potential of producing a saleable low-phosphorous ferromanganese alloy by utilizing sludge from the silicomanganese industry together with an iron source. The aim of the project is to explore the feasibility and practical challenges related to reduction and dissolution of manganese and silicon from the sludge to liquid metal and slag. Parameters such as ratio of input material as well as the effect of adding limestone and coke to the mixture were explored by thermodynamic calculations and adapted experimentally. Results show that a ferromanganese alloy, in fact, can be formed, while silicon and calcium forms a complex slag that captures a significant amount of impurities.