Search Documents

By R. E. Brewer

Pilot scale flotation tests were conducted with a l?ft-diam column at the Barrick Resources (USA) Mercur mine, Tooele County, UT, to scavenge unleached (0.01 to 0.018 oz/st) gold values from the tailings of a carbon-in-leach (CIL) circuit. The optimal recovery was 35 pct of the unamenable-to-leaching gold, at a grade of 0.353 ounces of gold per short ton, using a mixture of dithiophosphate, xanthate, and diesel fuel as a collector. This was achieved by floating approximately 1.6 wt pet of the CIL tailings. The gold values are believed to be contained in arsenic-bearing minerals, attrited carbon, and carbonaceous material in the ore. Redox potentials were measured with a gold electrode during the conditioning stage prior to flotation. The correlation between flotation recovery and redox potential values could be used to control reagent additions. Treatment of a previously leached and weathered tailings material, averaging about 0.055 ounces of gold per short ton, was also investigated. The tailings were first water leached at approximately 60? C, and the water-leached tailings, containing approximately 0.03 ounces of gold per short ton, were then fed to the column flotation unit. The effects of pH' and sodium sulfide addition on gold flotation recovery and redox potentials were examined. Maximum gold flotation recovery, 36 pct, was achieved at pH 8,5 with a sodium sulfide addition of 0.18 Ib/st. Overall gold recovery by leaching and flotation was in the range of 70 to 80 pet.

Jan 1, 1989

By Patricia A. Wells

In the remelting of scrap, the ultimate goal is to produce clean aluminum while minimizing metal losses. Recently, it has become more difficult to make significant recovery improvements in Reynolds' Reclamation Plants since metal recoveries were nearing the theoretical maximum. In an effort to gain a better understanding of the factors impacting Reynolds remelting process, a series of experiments using a Taguchi-type design was performed. Specifically, the critical variables and interactions affecting metal recovery of shredded, delacquered Used Beverage Containers (UBC) melted in a side-well reverbatory furnace were examined. This furnace was equipped with plunger-style puddlers and metal circulation. Both delacquecing and melting processes operated continuously with downtime only for necessary mechanical repairs. The experimental design consisted of an orthogonal array with eight trials, each using nominal 500;000 lb shred charge volumes. Final recovery results included molten output and metal easily recovered from dross generated during the test.

Jan 1, 1995

By R. Moreau, V. Uspenski, K. Messadek, Y. Delannoy

Experiments and numerical simulations have been carried out to investigate the properties of quasi-2D turbulence. A new mercury model experiment has been built and tested in a uniform magnetic field up to 6T, (Ha~ 1000), ensuring a better two-dimensional behaviour than earlier versions (Alboussiere et al., 1997), limited to 0.2T. The quality of the experimental results has been improved in order to get wave number spectra (instead of frequency spectra) and higher signal over noise ratio (due to the higher magnetic fields). In parallel, some two-dimensional "direct" numerical simulations were performed using a commercially available code to solve a 2-D motion equation involving a source term to model the Hartmann layer. This term is derived from the condition of closure of the electric current, which allows to transfer the Hartmann effect into the 2D-core flow without simulating the layer itself (Sommeria & Moreau, 1982). No subgrid scale modelling is needed in such a two-dimensional situation where most of the energy is carried by the large scales.

Jan 1, 1999

By V. D. Tathavadkar

Natural chromite mineral is a solid solution of spinet end members namely: chromite (FeCr2O4), hercynite (FeA1204), magnetite (Fe3O4), magnesio-chromite (MgCr2O4), (MgA12O4), and magnesio-ferrite (MgFe2O4). A phase transformation in chromite minerals occurs in oxidising conditions during the soda-ash roasting reaction. This phase transformation plays an important role in improving the extraction efficiency of Cr3+ from mineral phase. The extraction efficiency of chromium (Cr3+) from chromite to a water¬soluble sodium chromate (Cr6+) salt depends upon the decomposition kinetics of the spinet phase. An investigation of the phase changes in chromite ores in the absence of sodium carbonate was carried out in air, argon, and in argon +5 % hydrogen gas mixture. The thermodynamics of phase transformation reaction in chromite solid solution phase is discussed using the solution model proposed by Sack and Ghiorso [1]. The microstructural changes and the changes in elemental compositions of different phases were examined by SEM and electron probe microanalysis (EPMA) respectively. The experimental results indicate that the solid solution spinet phase in chromite mineral undergoes spinodal decomposition under the influence of oxygen partial pressure and temperatures. The structure of phases formed and their morphologies suggest that the phase decomposition may be similar to those observed by Burkert et. a]. 121, although the scale of phase separation in chromite appears to be strongly dependent on oxygen partial pressure.

Jan 1, 2001

By J. Bostjancic

As wastewater discharge regulations become more stringent, power plants, manufacturing plants and other industrial sites are looking for ways to reduce makeup water requirements and to recycle and reuse as much wastewater as possible. In some cases, environmental regulations require zero liquid discharge, meaning all wastewater must either be retained on site or reduced to solids for disposal off site. Zero liquid discharge or "closed-loop" wastewater treatment systems using evaporators and other process equipment have been well-accepted in recent years. Often overlooked is the fact that zero discharge is not just the latest fashion--many commercial zero liquid discharge systems have been in operation since the mid-70's. This paper will give specific examples of zero liquid discharge operations from 1974 to the present, showing how evaporation equipment and processes have changed to meet the requirements of industry and environmental regulations.

Jan 1, 1996

By Nelson Collao I.

Loss of the organic phase from solvent extraction circuits is a major cost factor for SXEW operations. Recognized sources of loss include evaporation, entrainment, and biological degradation. The mechanisms for both entrainment and evaporative losses are well recognized. Biological degradation of the organic has not been as extensively evaluated as the other mechanisms but is a major source of loss. This paper discusses the impact of biological degradation on an operating plant, potential mechanisms for degradation, conditions under which biodegradation of plant organic can occur and plant conditions that may assist in promoting biodegradation.

Jan 1, 2003

By Katsunori Yamaguchi

The zinc, lead and alumina contents in copper smelting slag are increasing with the increase in waste recycling. The recovery of base metals such as lead and zinc from copper converter slag is important from both an economical and environmental perspective. As a fundamental study of the metal recovery by reduction process, activity coefficients of ZnO and PbO in the CaO-SiO2-FeOx-5mass%AlO1.5 slag under iron saturation at 1573K are derived from the data of slag-metal equilibrium experiments. On the basis of the obtained data, the activity coefficients of ZnO and PbO in the CaO-SiO2-FeOx-5mass%AlO1.5 slag were compared with those of the CaO-SiO2-FeOx ternary system. Addition of alumina increases activities coefficient of ZnO and PbO in SiO2 rich side of the slag, and decreases them in CaO rich side.

Jan 1, 2006

By Huaming Yang

Infrared materials are a special kind of material widely used in military, biological engineering and chemical industry. However, the problems associated with them such as unstable properties, high cost and a high thermal expansion coefficient seriously restrict the development and the wide application of the traditional infrared materials with the SiC or ZrSiO4 matrix. The ultrafine quartz powder is normally used to prepare the infrared materials by hot-pressing technology. The aim of the paper is to investigate the thermal expansivity, the effect of the SiO2 size and the addition of Al2O3 or Fe2O3 on the infrared emissivity of the quartz matrix of the infrared material (QMIM) in a 8-25um wavelength range. The results indicate that 89% of infrared emissivity and 0.4x 10-5/°C of thermal expansion coefficient of QMIM can be obtained. The affecting mechanism of A1203 and Fe2O3 on the infrared emissivity of QMIM were also discussed.

Jan 1, 2003

By Youqi Fan

Complicated copper oxalate precursor powder was prepared using ammonium oxalate as precipitating agent in the Cu(II)-C2O42--NH3-NH4+-H2O system. The composition and morphology of the powder are characterized by chemical analysis, X-ray Diffraction (XRD), scanning electron microscope (SEM), infrared spectroscopy (IR). The effects of temperature, copper ion concentration, pH value are investigated. It?s indicated by the experimental results that precursor of copper oxalate is prepared below a critical pH value, whereas the precursor turns to be a complicated copper salt combined with NH3 while over the pH value. Probable chemical formula CuC2O4?x(NH3)?yH2O can be assumed which x and y are relation to experimental conditions. Technological parameters, such as temperature, initial copper concentration and solution pH value, have significant effects on particle size, morphology and dispersion of precursor powder. By controlling certain technological conditions, various morphologies of precursor, pie shape, spindle shape and rod shape can be synthesized.

Jan 1, 2009

By K. A. Elbarawy

Processing of Egyptian barite ore with a composition of 85.5% BaSO4; 2.75%SiO2;1.56%Fe2O3 and 5.1% Al2O3 was performed with the aim to prepare pure barium salts. The process took place through pelletization-solid state reduction and leaching steps. Each of these steps was optimized. Pure barium sulphate (99% < 0.82µm) and carbonate (99%<0.75µm )were the final products. This article deals with the reduction process that occur whn coal was added to the ore during pelletization in the ratio of 5:1 stoichiometry. Optimum reduction of pellets of 8-12mm in diameter was achieved after 60 minutes at 1050oC and under a rate of 5 lmin-1 of nitrogen atmosphere, where 87.79% of the ore was reduced. The kinetic studies showed that the reduction process could be modeled according to the core mechanism of diffusion control in which the effective diffusivity is based on the surface area of unreacted ore. The activation energy calculated was 92.7 kJmol-1.

Jan 1, 2006

By Jasper Kwong

The recycling of MgO-C refractories as a slag conditioner in EAF (electrical arc furnace) foaming slags have been evaluated by the Albany Research Center. The amount of MgO in the slags is critical for the foaming quality. Good foaming slags provide the benefits of high energy efficiency and low refractory consumption and require saturation with MgO. A computer model predicting the chemistry of MgO saturated foaming slags was designed to predict suitable amounts of MgO additives from MgO-C spent refractories. This model can also help to reduce the amount of slags and to improve the economics of producing steel. The implementation of this recycling program is underway at steel plants and the experience of recycling spent refractories will be discussed.

Jan 1, 2002

By Y. Ono

In lightweight metal processing such as aluminum (AI) and magnesium (Mg), metal cleanliness is a crucial process parameter for refining, part manufacturing and recycling in order to obtain high quality parts and products. In this paper, techniques for cleanliness evaluation of molten AI and Mg using ultrasonic probes with clad steel buffer rods having high signal-to-noise ratio (SNR) are presented. Due to the high SNR of the ultrasonic probes used, backscattered ultrasonic signals from inclusions, which may be oxide films and/or particles, in molten Mg and those from silicon carbide particles, having an average size of 50f.Ull, added in molten AI are successfully detected with reflection configurations of pulse-echo and/or pitch-catch modes at an ultrasonic frequency of 10 MHz. In addition, relative cleanliness evaluation of molten Al and Mg is demonstrated. In order to establish the procedure and to investigate the optimum system configurations for cleanliness evaluation of molten metals, particle flow simulation system using water and polyvinyl chloride (PVC) particles has been constructed. Counting the number and measuring the size distribution of the PVC particles, having an average diameter of 128um, suspended in water with the PVC volume concentrations of 5ppm and 10ppm are performed with ultrasonic pitch-catch mode. The counted numbers of particles by the presented method and system have good agreement with the calculated results with a count error of less than 10% or two counts. Based on the results obtained with water simulation experiments, the prototype system for cleanliness evaluation of molten Mg by counting and sizing inclusions has been developed. Keywords: Ultrasound, Clad buffer rod, Molten metal, Aluminum, Magnesium, Inclusion detection, Cleanliness measurement, Counting, Sizing

Jan 1, 2003

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 David G. Dixon

A mathematical model is derived in dimensionless form which simulates the effluent concentration response of reagents from spent heaps under both fresh and recycled water rinsing. The model is based on dispersion from isochoric pathways distributed in length and cross-section, oriented normal to convection channels in ideal plug flow. The effects of heap height, rinsate flow, and initial reagent concentration are examined. It is shown that the rinsing cycle undergoes a distinct shift between fast and slow rinsing at a certain time depending on the amount of stagnant solution in the heap, and the distribution of dispersion pathways. Results of preliminary column rinsing tests on both agglomerated and unagglomerated ores are presented which partially validate the model.

Jan 1, 1994

By Xiangwen Wang

Electrodeposition of lead metal from high purity brine electrolytes containing lead chloride (PbCI,) was conducted so as to assess the feasibility of electrowinning lead-metal directly from aqueous chloride electrolytes. Tests were performed at 65 and 80°C (338 and 353°K). Characteristic features of the deposits, on both lead and graphite substrates, were correlated to operating parameters associated with: electrolyte temperature, current density and total lead- concentration. Photomicrographs of these morphological features were obtained by use of Scanning Electron Microscopy (SEM).

Jan 1, 1993

By Hao Rang

The article Is specially to Introduce the recovery process of Nb, Mn, P from slags and reutilization techniques of the remaining slags. Nb-Mn-Fe alloys which contain 14-16% Nb, 40-60% Mn can be obtained after using fire refining process of " Blast Furnace-Revolving Furnace-Electric Furnace -Electric Furnace, "meanwhile, phosphorous slags which the content of phosphorus pentoxide Is 29.21%. Further going through wet metallurgical processing and electrowinning technics to recover grading 99°o metallic manganese. Finally, phosphorous slags are grinded finely to be as phosporous fertilizers to be directly used for farmlands. Small particle size (0-8mm) rich slags are mixed with slight solid additions for balling directly, and taken Into blast furnace with blocky slags all together. The remaining tall slags are fully used as constructional materials, slags cement as well as a serial of wall materials, road materials, ground ornamental materials without burning operation and steam curing. The compressive strength range of those materials is up to 15-30 MPa. There is no more solid waste slags effluent In the full technical process.

Jan 1, 1994

By Stanko Nikolic

Ferrous calcium silicate slags are potentially important for future practice in copper converting operations and processes and can be described by the ?Cu2O?-FeO-Fe2O3-CaO-SiO2 system. Despite its industrial importance the phase equilibria in this system have not been fully investigated. Characterization of this slag system is necessary to improve the design and optimization parameters of new processes, including fluxing and operating temperatures. Experimental methods have been developed to investigate the phase equilibria of these slags at copper saturation and without copper. This technique involved equilibration of samples at a fixed oxygen partial pressure, rapid quenching, and analysis of the compositions of phases using electron probe x-ray microanalysis (EPMA). Liquidus and solidus data are reported for the primary phase fields of spinel, wollastonite and tridymite at 1250oC and an oxygen partial pressure of 10-6atm. The resulting data has been used to construct liquidus isotherms in the ?FeO?-CaO-SiO2 system both in equilibrium with and without molten copper. The experimental results were compared with the predictions of a thermodynamic computer package utilizing a self consistent thermodynamic database. The predictions of the model were in good agreement with the experimental isotherms when projected onto the FeO-CaO-SiO2 section, however the copper concentrations in the liquid phase at copper saturation were lower than predicted using the current database of the model.

Jan 1, 2006

By Joo Hyun Park

A history of the research regarding the spinel in the community of the stainless steels has simply been reviewed, followed by the recent studies for the formation mechanism of the spinel in the ferritic stainless steel melts equilibrated with the highly basic slags and the crystallization behavior of spinel phase in the calcium aluminosilicate melts containing MgO and CaF2 during slow cooling cycles. It has been proposed that the content of aluminum and calcium in the steel melts as well as the basicity and the content of MgO and Al2O3 in the slags are quite important factors affecting the spinel formation in view of the formation mechanism based on the reduction of MgO (or CaO) and Al2O3 in the slags by the aluminum and silicon added to deoxidize the molten steel. The use of magnesia refractory was also recommended. The formation mechanism of spinel from the MgO inclusions readily formed in the steel melts equilibrated with the highly basic slags has newly been proposed on the basis of the ionic exchange reactions at the inclusion/metal interface and the crystal chemistry of oxides. The crystallization behavior of the spinel phase in the calcium aluminosilicate melts was enhanced by the Al2O3 based on the ionic reaction of spinel formation in the oxide melts, while the size of the spinel crystals in the oxide melts decreased by addition of CaF2.

Jan 1, 2006

By K. Tozwa

The electrical conductivity of electrolytes for copper electrorefining and electrowinning processes has been reported by many researchers since 1911. The experimental results show that the conductivity increases with an increase in sulfuric acid concentration and decreascs with an increase in copper concentration. In pure copper sulfate solution, however, the conductivity increases with an increase in the copper concentration. After confirming the conductivity of pure and acidified copper sulfate solutions experimentally, the concentrations of hydrogen ion and free (not hydrated) water in the electrolytes were estimated and it was found that the relation between the conductivity of acidified copper sulfate electrolytes and the products of concentration of hydrogen ion and free water is linear. Accordingly, the conductivity of acidified copper sulfate electrolytes increases with an increase in sulfuric acid concentration and decreases with an increase in copper concentration.

Jan 1, 2003

By Tianzu Yang, Weifeng Liu, Shu Bin, Lin Chen, Wanda Bin

"Vanyukov Process has been mainly applied for processing copper and nickel sulfide ore for more than 30 years. Based on the understanding of the Vanyukov Process, researchers from China introduced the technology into the areas of lead, antimony and bismuth extraction by changing the furnace structure and technical flow, which greatly extended the application area and raised the processing efficiency, thus developed the oxygen-rich side-blow bath smelting (OSBS) technology in 2000. This contribution reviews the history of OSBS technology from four respects: the quantity, the furnace structure, the process flow and the application area. Its potential research direction and industrial application are also summarized.IntroductionVanyukov bath smelting furnace and related bath smelting technology were developed by researchers from Soviet Union who devoted comprehensive research on fundamental theory as well as engineering technology [1,5]. Vanyukov process has been applied for large industrial production since the 1970s and it is still one of the major methods in modem pyrometallurgy process. The appearance ofVanyukov double district furnace and joint double furnace in the past ten years, which are applied for copper smelting, is the most valuable advances of the Vanyukov process [7,8,9]. However, the application ofVanyukov process was limited in copper and nickel sulfide ore smelting, and few countries adopted this process except Soviet Union."

Jan 1, 2013