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By M. Misra

Acid mine drainage from reactive sulfide tailings is a major environmental concern facing the mining and mineral industries. A preventive technique to control acid mine drainage by agglomeration and encapsulation process is presented in this paper. The reactive tailings are agglomerated using Portland cement type I1 as binder. The cold bonded agglomerates after specified curing period are, strong and resistance to weathering. The leaching and weathering experiments have shown that a significant reduction in the concentration of dissolved metals can be observed with the agglomerates as compared to as- received tailings. Addition of small amount of sodium silicate during agglomeration increases the strength and develop good resistance to weathering by forming a glassy coating and elongated crystals within the agglomerates.

Jan 1, 1993

The oxidation of ferrous ions by oxygen in sulphate solutions is a very slow process, but it tills long been known that the addition of sulphur dioxide increases the rate of reaction very significantly. The kinetics and mechanism of the process were investigated in the laboratory and the results confirmed the advantage of adding small amounts of sulphur dioxide to the oxygen stream for the removal of iron from solutions. The effect of various parameters on the overall rate of iron oxidation and precipitation was studied. In particular, temperature, acidity and composition of the gas mixture were considered and the optimum conditions for the precipitation of goethite were determined.

Jan 1, 1991

By Junji Shibata

Heavier rare earth, which is contained in a small amount in ores such as bastnesite and monazite, has been accumulated as a heavier rare earth residue without doing separation and purification due to the lack of suitable methods. The heavier rare earth residue includes seven rare earth elements such as Tb, Dy, Ho, Y, Er, Tm and Yb. Separation and recovery process of Dy, Y, Tm and Yb from leached solution of the heavier rare earth residue was investigated by using a column method with solvent impregnated resin. The solvent impregnated resin was prepared by impregnation of organophosphorous extractant whose trade name is PC-88A into a macro porous resin, Amberlite XAD-7. It was almost impossible to separate them in simple adosorption and elution steps. However, we attained to individually separate Dy, Y, Tm and Yb from the leached solution first by changing eluent concentration gradually from pH2 to 0.02kmol/m3 HC1 in the elution step, and secondly by using a development column and changing eluerit concentration in the elution step. The separation process flow was proposed for a heavier rare earth residue by using the solvent impregnated resin method.

Jan 1, 1998

By Chang Wei, Fan Zhang, Zhigan Deng, Minting Li, Cunxiong Li, Gang Fan, Xingbin Li

Marmatite is an important resource of zinc, which exist in forms of high iron and high indium. In order to recycle the valuable metal from these ores, the testwork of simultaneous leaching on neutral residue mixed with zinc concentrate of high iron and high indium has been conducted. The primary objectives are to leach the zinc and indium remaining in the neutral leach residue as ferrite using acid, and to reduce the ferric iron in solution to the ferrous by zinc concentrate, thereby extracting the zinc and indium in the zinc concentrate. The results indicated that in the following conditions, mass ratio of neutral residue to zinc concentrate of 1:0.25, particle size of 74-58 μm, initial sulfuric acid concentration of 150 g/L, liquid to solid ratio of 8 L/kg, temperature of 90°C, reaction time of 4h, the leaching efficiency of zinc and indium were over 95%, nearly 90% Fe was Ferrous in the leaching solution. This process effectively extracted zinc and indium and converted Fe3+ into Fe2+ in solution, and simplified the traditional process of reduction after leaching.

Jan 1, 2016

By Yuanbo Zhang, Huanpeng Mi, Guanghui Li, Binjun Liang, Zhiwei Peng, Tao Jiang

Ludwigite ore has not yet been utilized on an industrial scale due to its complex mineralogy and fine mineral dissemination. In this study, sodium salts were employed to enhance the separation of iron and boron by reductive roasting-magnetic separation. It was found that the separation of iron and boron as well as the iron grade and recovery were significantly improved b y the addition of Na2SO4 or Na2CO3. Under the reduction temperature of 1050 °C, reduction time of 60 min and magnetic intensity of 0.1T. Compared with the inexistence of sodium salts, the iron grade and recovery of the magnetic concentrate increased from 83.3% and 88.6% to 93.2% and 95.1%, respectively, by adding 6% Na2CO3. The XRD and microstructure analyses indicated that the iron oxides were transformed into metallic iron and the average metallic iron grains were grown to over 40μm which was beneficial for separation of metallic iron from gangue.

Jan 1, 2016

By Joël P. T. Kapusta, Romeo U. Pagador, Noparut Wachgama, Chumnoom Khuankla

"Thai Copper Industries (TCI) is a custom copper smelter and refinery in Rayong, Thailand, with an annual capacity of 165,000 tons of cathodes. It employs the El Teniente Technology as the primary smelting reactor to produce white metal from copper concentrates. The white metal is further treated in Hoboken Siphon Converters to produce blister copper then refined in anode furnaces before being cast into anodes for electro-refining in the on-site tankhouse.Thai Copper Industries is the first copper smelter to install and successfully operate on a commercial scale with the Air Liquide Shrouded Injection (ALSI™) Technology in the Hokoben converters with sonic injection of oxygen enriched air and nitrogen for cooling of the injector tip areas. Following commissioning and the establishment of operating practices, the performance of the Hoboken converters with ALSI™ Technology produced outstanding results. The unique combination of an El Teniente and Hoboken siphon converters, both of which are bath smelting operations, offers very high blowing and oxygen efficiencies. As a consequence, reverts recycling was accelerated with minimal build up on the mouth, end-plates or even below the siphon that is typical in Hoboken converters.These outstanding results in the Hoboken Siphon Converters with ALSI™ Technology helped the TCI Plant reach a production of about 75% of its capacity within four months despite the fact that the TCI staff is quite young and its converter know-how and experience are not yet fully developed."

Jan 1, 2009

By Andrea Bernardes

Printed circuit boards (PCBs) of varying compositions have been converted by incineration and following melting into an environmental agreeable slag and a copper-nickel-tin alloy, containing the precious metals. The environmental compatibility of the slag was determined according to the German standard DIN 38414 - Part 4; pollutants' concentration in the lixiviates is smaller than the thresholds of drinking water (CE-Standards). Each experiment the charge were 500g scrap from PCBs and ca. 100g slag forming material. The products were a kind of mullite slag, poor on iron, which was recirculated, and an alloy containing up to 0.3% Gold. With a burner to the retort coal gas, the waste gas was burned without soot, and the produced mixed zinc-lead oxide containing silver was collected in the flue dust.

Jan 1, 1997

By Pengfu Tan

In order to understand and control the formation of dioxins and furans in iron ore sinter plants and to possibly avoid expensive end-of-pipe removal stages, thermodynamic calculations on the stability of PCDD/Fs have been combined with sinter process modeling by means of kinetic simulations and computational fluid dynamics. Three thermodynamic databases of PCDD/Fs, derived using the Group Additivity approach and two computational molecular modeling methods, MNDO and PM3, respectively, combined with the SGTE database have been used to model the PCDDIF formation and the PCDD/F isomer distributions in iron ore sintering. The results show very similar conditions for the PCDD/F formation using the different databases. Concerning the isomer distributions of toxic PCDD/Fs, the calculated data derived from the MNDO method showed optimum agreement with measured values from industrial furnaces. The thermodynamic calculations also proved that the isomer distributions found in combustion processes are equilibrium values, while the concentration ratio of PCDDs and PCDFs in the wind boxes does not represent an equilibrium state. A CFD model of iron ore sintering was developed including the kinetics of 15 relevant chemical reactions with the aim of describing the temperature fields and the gas flow patterns in the sintering bed. On the basis of these information and experimental observations reported in the literature possible pathways for the PCDD/F formation in sinter plants have been identified: PCDD/Fs are formed in the critical temperature region of 250 to 450 °C below the combustion zone, are then carried downwards with the gas and condensed close to the bottom of the sinter bed. Transported to the discharge end with the solid mixture, they are again released into the gas phase when the flame front approaches the bottom. PCDD/Fs are also formed in the last wind boxes when the hot off-gases cool down and reach the critical temperature range. Consequently, methods to reduce the dioxin formation reactions are proposed including inhibitor addition to the sinter feed and off-gas quenching.

Jan 1, 2003

By S. J. Buckler

Many chemical and metallurgical processes use submerged gas injection to increase contact area between gas and liquid phases in order to promote faster overall reaction or refining rates. The total interfacial area produced by gas injection through lances, nozzles or tuyeres is both an important design parameter for new vessels and a measurement for estimating the maximum processing capacity of existing equipment. Estimating total interfacial area from submerged injection into industrial pyrometallurgical vessels from existing knowledge is a problem with two aspects. The first difficulty is the difference in behaviour of cold (aqueous) and hot (molten metal) systems, implying that existing models and correlations of gas-liquid behaviour developed in low temperature systems are not necessarily appropriate for estimation of high temperature behaviour. The second difficulty is the issue of scale-up of correlations from laboratory to industrial sized vessels. The work presented in this paper is part of an ongoing experimental investigation, at the GK Williams CRC for Extractive Metallurgy, to quantify the total gas-liquid interfacial area available in pyrometallurgical vessels using chemical measurement methods. The effects of three operating variables, injected gas flow rate, nozzle diameter and nozzle submergence, on total interfacial area are quantified in a IOOL aqueous system - the first stage of a three stage process in examining the implications for scale-up of high temperature, medium-scale results are discussed. The results of work at high, injected gas flow rates (up to 500/min) show that the submerged Froude number is not sufficient for use as the sole variable in a predictive model of total interfacial area. Further work is being undertaken to identify other dimensionless variables that will better represent the gas-liquid characteristics in submerged injection that influence the formation of total interfacial area. The second and third stages of the experimental investigation involve measuring the total interfacial area in a large-scale (1000L) aqueous sodium sulphite and small-medium scale molten metal baths.

Jan 1, 2002

By Dian Adisty, Leiv Kolbeinsen, Eli Ringdalen

In Si and FeSi production, the main Si source is SiO2, in the form of quartz. Reactions with SiO2 generate SiO-gas that further reacts with SiC to Si. During heating, quartz will transform to other SiO2 modifications with cristobalite as the stable high temperature phase. Transformation to cristobalite has been investigated and shown to be a slow process where the rate varies between the investigated quartz types. The effect of quartz versus cristobalite as SiO2 source has been studied for reaction (1) 2SiO2 + SiC = 3SiO + CO, by heating of pellets with SiO2 + SiC in Ar-gas. The reaction was faster with cristobalite than with quartz. Initial experiments indicates that this is the case only in Ar and not in CO-atmosphere The higher specific surface area of cristobalite is believed to contribute to the higher rate. The industrial consequences of the observed difference between quartz types are discussed.

Jan 1, 2014

By A. Vahed

The Goro Nickel Project is situated in the Southern Province of New Caledonia. Inco Limited and Goro Nickel S.A. have developed a process that features the use of pyrohydrolysis to produce nickel oxide. The process treats a blend of laterites by Pressure Acid Leaching followed by solvent extraction of nickel and cobalt using Cyanex 301®. Purified nickel chloride solution is converted to high purity NiO product and 6M hydrochloric acid, which is recycled back to the SX circuit. In co-operation with Andritz AG, spray roaster and fluid-bed pyrohydrolysis technologies were examined for this purpose. Tests were conducted at the Andritz AG pilot plant in Vienna, Austria, and at Goro in larger scale installations. The latter served to establish process engineering design parameters for scale-up. Several process variables were investigated in both technologies and the off-gas characteristics were established. Fluid-bed pyrohydrolysis was selected for the Goro commercial plant, primarily because it produced a granular nickel oxide. The main focus of this paper is to outline the results obtained in pilot plant studies of liquid fueled fluid bed pyrohydrolysis for the Goro Project. Keywords: lnco Goro Nickel, Fluid Bed Pyrohydrolysis, Pilot Plant Tests

Jan 1, 2004

By Tom McCullough

The purpose of this paper is to discuss the implementation and results derived from installing oxy-fuel burners in a l80 ton copper reverbatory melting furnace. Specific results will be discussed in the areas of melt chemistry, furnace modifications, productivity, process enhancements, and the combustion system capabilities.

Jan 1, 1996

By A. Shemi

Tungsten carbide scrap (WC–Co) is material generated from the tungsten carbide manufacturing process and worn out or used carbide parts from industry. Tungsten (W) ores contain about 3 wt% WO3 and their W concentrates about 10– 75 wt% WO3. Tungsten carbide scrap typically contains 40–95 wt% W. The high intrinsic value of W and the fact that the least valuable scrap contains more W than the average tungsten ore makes tungsten carbide scrap a worthy material for re-use. This study has investigated the selective dissolution of the cobalt (Co) binder phase, and recovery of tungsten monocarbide (WC) and Co using an acid leach process. The Co component was selectively leached leaving the WC solid particles intact. Further investigation using a complexing agent-aided acid leach process that takes advantage of organic chelating agents that form a soluble tungsten complex in place of the passive insoluble tungsten oxide is envisaged. The optimal dissolution of the Co binder phase using an inorganic acid in conjunction with an organic complexing agent is a novel approach with the potential of reduced leaching times and possibility of regenerating the unreacted organic acid.

By Chao Li, Lim Hongxu, Yuyue Wang, Xie Yang

"A intergrated process of sulfuric acid leaching, sodium chloride leaching, lead chloride crystallization, lead hydroxide synthesis and roasting was carried out for the recovery of lead, cadmium, copper and zinc from lead smelting dust containing various metals. The results showed that the separation of cadmium, zinc and copper from dust could be obtained after sulfuric acid leaching and corresponding leaching rate were 92.12%, 90.25% and 88.26% respectively. The subsequent sodium chloride leaching carried out for lead with optimized parameters as: sodium chloride concentration 250g/L, leaching temperature 90°C, leaching time 2h, pulp density 33g/L, 0.12mol/L CaCh; The lead compounds crystallization rate reached 86.67%, and then transferred into mPbO·nH2O, the product of 98.66% ß-PbO could be obtained through roasting under 502°C. In the end, a feasible method of ß-PbO preparation from lead containing dust was put forward.IntroductionThe pyro-metallurgy flue dust from smelting lead activities are often stockpiled and pose potential environmental risks due to the heavy toxic elements, such as Pb, Cd, As, Cu, Cl, and Zn which are contained in the dust. With the rapid depletion of rich ore resources in recent years, it has become increasingly more financially attractive to recover valuable metals from previously stockpiled dust, while simultaneously reducing the potential of environmental pollution from toxic elements contained in the dust. Nowadays, pyro-metallurgical and hydrometallurgical routes or both combined methods can be developed to treat secondary materials such as lead ash, leach residues etc. By comparison the hydrometallurgical processes are often considered more eco-friendly.Some chloride leaching processes for recovering lead have been employed using either NaCl, or MgC2 and CaCl2, or FeCl3 [1] The effectiveness of the brine leaching method is based on the formation of complex metal chlorides in concentrated chloride solutions [2] Similarly, Other metals such as zinc, cadmium and copper contained in the flue dust are often treated with sulfuric acid, hydrochloric acid, ammonium solution and sodium hydroxide etc. as lixiviants [3] The metals from leach solutions thus has been obtained by precipitation, ion exchange, solvent extraction or replacement [4]"

Jan 1, 2014

By Pengkai Wang, Huimin Lu, Xiaoxiang Zhang

"In this paper, it was studied an electrochemical reduction process of carbon dioxide in ionic liquids such as 1-n-butyl-3-methylimidazolium hexafluorophosphate ([Bmim] PF6) as the electrolyte. The electrolysis experiments were carried out under current and potential controls. The cathode products contained carbon nanotubes, carbon nanofibers, nanographites, and amorphous carbon. To establish the actual current and potential ranges, the electroreduction of carbon dioxide dissolved in the ionic liquid was studied by cyclic voltammetry on glass-carbon (GC) electrode at room temperature. The electrochemical mechanism of carbon dioxide electroreduction was studied for explanation of all obtained results. Carbon dioxide in ionic liquids was electroreduced, similar to metals oxides being electroreduced in molten salts.IntroductionGlobal warming caused by the increase of carbon dioxide in the atmosphere has become one of the most concerning environment problems, so the solution to this greenhouse effect is very urgent. However, the carbon dioxide is also a cheap and abundant raw material that represents a potential source for the production of chemicals and fuels. Therefore, the development of the technologies that achieve simultaneous reduction and conversion of carbon dioxide to fuels is important. The electrochemical reduction of carbon dioxide is one of the effective approaches to transform CO2. Many investigations have been carried out on the electrochemical reduction of CO2 in both aqueous [1] and non-aqueous [2] electrolyte solutions with different electrodes. The solubility of CO2 in water is very low even under high pressure of CO2, and some investigators have brought focus into the electrochemical reduction of carbon dioxide in organic solvents, because they dissolved much more CO2 than water did. However, the hazardous or toxic properties of organic solvents hinder their use."

Jan 1, 2009

By A. J. Duncan, S. Viswanathan, Q. Han

"Measurements of liquid permeability in the mushy zones of Al-15.42% Cu and Al-8.68% Cu alloy samples have been performed isothermally just above the eutectic temperature, using eutectic liquid as the fluid. A modified method has been developed to determine the specific permeability, Ks, as a function of time during the test from the data collected on these alloys. Factors affecting permeability measurements are discussed. Permeabilties are observed to vary throughout the experiment. This is attributed to rnicrostructural coarsening and channeling that occurs in the sample during the experiment. The permeability is related to the rnicrostructure of the sample using the Kozeny-Carman equation. The correlation between the measured Ks, liquid fraction, gL and the specific solid surface area, Sv, improves markedly when compared to previous studies in which rnicrostructural coarsening was ignored.IntroductionThe permeability of interdendritic liquids flowing through dendritic structures ·is an important parameter needed to predict the level of porosity in castings. The permeability is a component of Darcy's Law, used to estimate the pressure drop due to the resistance to the flow of interdendritic fluid to feed shrinkage. Therefore, much research has focused on measuring the permeability of alloys in the mushy zone (1-10). The Kozeny-Carman equation for liquid permeability in the mushy zones of alloys may be written as"

Jan 1, 1999

By C. M. Antony

The galvanizing process involves the use of accessory equipment in a series of aggressive environments including zinc ammonium chloride flux, molten zinc at 45S°C (850°F), and acid for stripping of adherent zinc. An Fe-Ni-Cr-Co alloy has been identified which combines excellent strength and resistance to molten zinc and acid attack making it suitable for accessory equipment. The alloy was field tested by a commercial galvanizer as basket material and was found to provide improved life compared to original low-alloy steel baskets while cross-section thickness was reduced 44%. Additionally, other associated processing cost savings were realized.

Jan 1, 1992

By Dan Wang, Qian Xu, Guangshi Li, Xionggang Lu, Xingli Zou, Zhongfu Zhou, Hongwei Cheng, Changyuan Lu

The preoxidation of the ore has a profound significance to the concentration, separation and purification of nickel and copper from the lean complex ore. In this paper, the natural Ni-Cu sulfide mineral samples under the elevated temperature condition in air were investigated, as well as under isothermal condition at 600 oC in air. The mineralogical characterization was studied using XRF, ICP and the Rietveld method. The oxidation behavior and the element migration of the Ni-Cu sulfide ore were studied by XRD, SEM-EDS and TG. The XRD Rietveld method was successfully developed in the phase identification and quantification of this complex ore powder sample. The oxidative intermediates (Cu/Ni-ferrite) were detected by XRD, and the process of the element migration was obviously revealed by the line scans using SEM-EDS. It is the preoxidation of this mineral that provides guidance for the extraction of valuable metals from low-grade Ni-Cu sulfide ores in the future.

Jan 1, 2015

By J. A. Holmes

Due to varying and complex mineralogy, the flotation tailings from the Chingola Concentrator have, for some years, contained upwards of 0.4% acid soluble copper. In 1968, an investigation was initiated, to determine a method for recovering this acid soluble copper. This initial investigation concluded with a recommendation to install a leach-solvent extraction-electrowinning plant at Chingola, to treat up to 900 000 tonnes of material per month, for an additional copper production of some 4 500 tonnes per month. The process consists basically of six stages :- Materials reclamation handling and preparation, acid leaching in air agitated pachucas, solid-liquid separation by countercurrent washing in thickeners, solution concentration and purification by solvent extraction, copper recovery by electrowinning, and residue neutralisation and disposal. This paper describes the development of the main parameters for design of each of the six sections, and gives details of the final plant design. Problems encountered in commissioning and initial operations are commented on, particularly insofar as they indicated any errors or misjudgements in the design. The choice of materials of construction is commented on in some detail.

Jan 1, 1976

By James B. Pfeiffer

TETRA Technologies, Inc., has applied its HDSIM metals precipitation system to treat a waste stream containing scrubber blowdown and process water from a smelter operation. The combined stream contained cadmium, lead, selenium, arsenic and zinc, plus some iron and copper. Treatment requirements included meeting stringent mass flow limitations for specific heavy metals. The HDS ? system can reduce the arsenic from 600 ppm to less than one ppm. The process generates a dense sludge that can be reprocessed in a smelter, eliminating the liability associated with landfilling. Flow diagrams and process details are discussed.

Jan 1, 1994