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By Fathi Habashi

Nitric Acid has been used for over 50 years in the uranium industry and in phosphate fertilizer manufacture. Its application in the treatment of sulfide concentrates is relatively recent. A review of recent developments is given.

Jan 1, 1999

By Bhagyadhar Bhoi, Chitta Ranjan Mishra, Hara Prasanna Mishra

"In the Sukinda Valley of Orissa, India, the total quantity of nickel ore reserves comprising of both lateritic and chromite over burden(COB) have been estimated at around 231 million tonnes containing 0.3 to 0.9% Ni. While mining of one tonne of Chromite ore, around 6-7 tonnes of chromite over burden are removed. These overburden materials are disposed as waste materials, which causes lot of environmental hazards and ecological imbalance. India imports a large amount of nickel and ferro-nickel to meet its growing demands in various sectors. For import substitutions, efforts have been made to produced ferro-nickel from the lean deposits of nickel bearing lateritic ores/ chromite over burden materials by reduction roasting followed by magnetic separation and then the nickel rich magnetic fraction is smelted to produce ferro-nickel. It has been possible to produce ferro-nickel of grade varying from 4-25% nickel.IntroductionDuring mining of chromite ore, large quantities of overburden materials are being generated. The materials amount to approximately 10 million tones per year contain around 0.3-0.9% Ni, 0.02-0.06% Co, 20-50% Fe and 4-9% Cr2O3 depending upon the location and the depth of the mine. These materials presently do not find any application for the extraction of nickel due to lack of a suitable technology. The materials are also unsuitable for ferro-nickel making because of their very high iron to nickel ratio. The country is seriously looking for a suitable technology to utilize these resources as its entire domestic requirements of nickel is met though imports. In this connection, a systematic approach has been made at the Institute of Minerals and Materials Technology, Bhubaneswar to develop a process for ferro-nickel making from this indigenous resource."

Jan 1, 2011

By D. M. Jones

Dust generation data have been obtained from 19 industrial Outokumpu flash furnaces. Statistical analyses of the data have been carried out and the most significant factors affecting dust generation evaluated. The results indicate that dust production may most effectively be minimized by: 1) Minimizing the distance between the molten slag and the furnace roof 2) Optimizing burner design and combustion parameters.

Jan 1, 1996

By A. P. Pavia

Investigation on profitable ways to recover significant quantities of silver remaining dissolved in highly concentrated chloride solutions frequently pass through the development of solvent extraction (SX) routes. In this work, the general pathways involving Ag(I) extraction by dibutylthiourea (DBT) or tetraethylthiuram disulfide (disulfiram, DSF), from concentrated acidic chloride solutions, are investigated. With this purpose, the dependence of Ag(I) distribution coefficient on ligand and chloride concentrations has been analysed. Furthermore, in order to check whether there is some protonation at any site of DBT or DSF after contact with adequate chloride phases, lH NMR has also been used. The collected spectroscopic data suggest that anionic Ag(I) extraction reactions are not likely to occur. Based on the overall results achieved, proposals for the most probable Ag(I) extraction reactions are made.

Jan 1, 2001

By Balladares V. Eduardo

Most of the arsenic contained in copper concentrates is removed in the gas phase during the smelting and converting processes and, according to recent environmental regulations, it is required to fix it in a solid stable form. In this regards, ferric arsenate has been reported as thermal and aqueous stable compound. Therefore, various alternatives for treating gas containing arsenic were considered in this work. From data obtained at laboratory scale on fixation of arsenic using iron oxide, a new process to treat copper concentrates containing arsenic was evaluated. The effect of temperature, oxygen potential and the sample porosity on the fixation of arsenic contained in a gaseous stream was studied, and the iron oxide converted into ferric arsenate was up to 10%. The obtained results suggest a new alternative for gas treatment with an interesting and attractive technical development. The arsenic was retained as ferric arsenate with thermal and aqueous stability, and it allows a safe disposal keeping the environmental restrictions. The kinetics parameters are used to scale up laboratory results to higher processing rates.

Jan 1, 2005

By Hassan Saalman, Mahmoud Mahmoud, Omneya El Hussaini

The Ferruginous sandstone ore was obtained from Ramlet Hemeyir area, Southwestern Sinai, Egypt, was found to contain 10% rare earth elements (REE). A representative sample has been subjected to sulfuric acid agitation leaching. About 93% of the REE content was released by mixing the ground sample to -100 mesh with concentrated H2SO4 at solid/liquid (S/L) ratio of 1/2 for 5h at a temperature ranged from 250 to 300o C. The REE was precipitated from the prepared sulfate leach liquor of pH 1.0 by adding 35% oxalic acid at 25o C. The precipitation yielded 98% REE. For selective separation of yttrium, the rare earth cake was leached with 31.5% nitric acid. Next, the aqueous solution was contacted with di-(2-ethylhexyl) phosphoric acid (D2EHPA) where 98% yttrium extraction was achieved. Stripping was done with hot H2O (80o C). Finally, a precipitation with oxalic acid was done followed by ignition at 950o C. A yield of 95% yttrium oxide was produced.

Jan 1, 2014

By Emmanuel N. Zevgolis

In the present work, a reduction roasting experimental study of Greek nickeliferous laterite samples with a gaseous reducing mixture ? CO:N2- is presented. The effect of parameters such as temperature, ore grain size, and composition of the reducing mixture were examined. It is deduced that the reducibility of intermediate type laterite sample, where iron appears mainly in the form of goethite (a-FeOOH), is considerably higher than that of limonitic type laterite samples, where hematite (a-Fe2O3) is the predominant iron mineral phase. The degree of reduction of the limonitic type laterite samples does not exceed 50%, while it reaches 95% in the case of the intermediate-type laterite sample under the same experimental conditions. Increasing the temperature in the range 750-900°C does not considerably favor the reduction of the limonitic type laterites, whereas decrease of ore grain size of the limonitic-type ore samples and more intense reducing conditions increase the reduction. The considerably higher specific surface area values of the intermediate laterite samples, diminishes the effect of the ore grain size and this can be regarded as the critical parameter leading to the higher reducibility of this ore.

Jan 1, 2009

By B. Wasmund, K. Adham, K. O'Keefe, C. Lee

"Metal chlorides (e.g. iron and nickel) can be pyrohydrolysed at elevated temperatures to yield an HCl rich off-gas and a metal oxide product. Typically, the high energy requirement for pyrohydrolysis is provided by the combustion of a hydrocarbon fuel with air. Here, it is demonstrated that the use of oxygen-enriched combustion can result in lower fuel requirements and higher HCl concentrations. In addition, the oxygen enrichment can result in a smaller volume of off-gas and thus, smaller and less expensive process equipment. This new concept can be applied to both the spray roaster (SR) and the fluidized bed reactor (FBR). Similar to the aircombustion case, the oxygen-enriched process can use a direct contact venturi scrubber, to recover energy from the roaster off gas, but at a higher efficiency. The new process also uses an absorption tower for capturing HCl from the roaster off-gas, but generates a stronger HCl solution than is possible with pyrohydrolysis in air.BackgroundIn recent years, the metallurgical industry has become increasingly involved with developing methods for extracting metals, upgrading products or cleaning metallic products by using hydrochloric acid. These applications of chloride metallurgy often result in metal chloride solutions, which should be processed to regenerate HCl for reuse, and to recover the metal value as a product or by-product oxide [2, 3, 4].The pyrohydrolysis of metal chloride solutions has been done in two types of air roasters: spray and fluidized bed. The existing roasters burn a hydrocarbon fuel in air, to provide the required energy for evaporating the feed solution and to provide an elevated temperature for the chloride pyrohydrolysis to occur, according to the following reactions:"

Jan 1, 2011

By J. A. Brierley

A biooxidation-heap pretreatment process was field tested to evaluate enhancing gold recovery from a preg-robbing sulfidic carbonaceous ore. Newmont Gold Company&apos;s Gold Quarry sulfidic carbonaceous ore was inoculated with an iron-grown culture of Thiobacillus ferrooxidans to form a 495 ton test heap. Biooxidation was conducted for a period of 100 days. The most active period of biooxidation occurred during the first 40 days of pretreatment? About 35 to 40% of the sulfide was oxidized. The extent of biooxidation was considered good as the ore particle size was relatively large 58% >1?9 cm (&apos;/< inch). The larger particle size ore limited the extent of bacterial activity. The field test demonstrated the ability to conduct biooxidation in a small pilot test heap. Thiourea was evaluated for extraction of gold from the biooxidized preg-robbing ore.

Jan 1, 1995

By Mansoor Barati, Leili Tafaghodi Khajavi

"This study involves employing solvent refining as a purification process in which silicon recrystallization takes place from an iron-silicon melt. It is believed that iron will act as the impurity “getter” and purified silicon crystals will grow from the alloy melt, while the impurities are segregated to the liquid alloy. Phosphorous is a problematic impurity to remove since its segregation coefficient in pure silicon is relatively large. To assess the feasibility and efficiency of phosphorous removal through solvent refining, it is critical to study its equilibrium distribution between solid Si and the Fe–Si alloy phase.The distribution of phosphorous between solid silicon and iron-silicon melt at 1210-1310 °C was measured to evaluate the impurity removal potential of each alloy. Interaction parameter between phosphorous and iron was calculated by varying the concentration of phosphorous in silicon.IntroductionAmong various semiconductor materials for manufacture of solar cells, silicon accounts for over 90 percent of today's PV materials [1, 2].The major challenge in producing solar silicon that operates efficiently is to meet purity level requirement through a cost efficient route. Silicon solar cells can play a significant role in answering the world's need for energy if cost reductions can be achieved through manufacturing process. Considerable effort has been made to replace the expensive, complex vapor-phase purification by a simpler and less costly process. One of the refining approaches that have attracted wide research interests is producing low-cost solar grade silicon by purification of metallurgical grade silicon. Since metallurgical processes are selective in removing impurities, a combination of various purification processes can be used to reduce the impurity level in silicon. Considering different thermodynamic characteristics of impurities, each refining step is responsible for lowering specific impurities."

Jan 1, 2012

By Xuerong Wen

The oxidation behavior of TiAl3 intermetallics was investigated as a hnction of time at 1273K in pure dry oxygen. The oxidation experiments were carried out using TGA method. The oxidation scales were analyzed using SEM, EDS and X-ray diffraction methods. The structures of oxides formed at the different oxidation times were analyzed. The mechanism of oxidation of TiAl3 intermetallics was discussed.

Jan 1, 1998

By Z. Yang

The flotation behavior of the. green algae Chlorella vulgaris and a wild Chlamydomonas spp. was studied in the presence of Zn(II) using dodecylammonium chloride as collector. At about pH 6. both organisms readily float as amine concentration approaches lx10-3 kmol/m3. In addition, electrokinetic measurements were made on the organisms as a function of pH in both the presence and absence of Zn(II). It was found that the Zn(II) has a considerably greater effect on the zeta potential of C. vulgaris than on Chlamydomonas. Zn(II) adsorption studies also indicated that C. vulgaris is able to accumulate more Zn from solution than the Chlamydomonas.

Jan 1, 1991

By John B. Cocanour

The U.S. Bureau of Mines (USBM) has developed a laboratory-scale on-line analysis and process control system for a decopperization electrolytic circuit. This system is software driven, running on a 486DX-33 personal computer (PC) utilizing a portable energy- dispersive x-ray fluorescence (XRF) spectrometer as the sample analyzer. The XRF copper reading obtained was used as the control variable through an RS-232 serial interface to the PC for software-based control of feed flowrates. When the copper concentration in the electrolytic cell (as measured by the XRF) deviated from the set point, the feed flowrate to the cell was automatically altered using software-based proportional-integral-differential (PID) computer control to yield the desired copper concentration at the electrolytic cell outlet.

Jan 1, 1994

By Dandan Jian, Christian Karcher

Information of liquid steel flow patterns inside the mold may be obtained from the velocity at the free surface (meniscus). This meniscus flow may be measured using the contactless electromagnetic technique termed Lorentz force velocimetry (LFV). It is based on the measurement of Lorentz forces acting on a magnet system when an electrically conducting metal melt interacts with the field lines stretched by the magnet system. Force sensor and the magnet system form a so-called Lorentz force flowmeter. In this paper we present a series of model experiments that demonstrate the feasibility of using two identical flowmeters that are arranged in a certain distance one behind the other. In this case, surface velocity may be determined by just cross-correlating the two force signals recorded by the two sensors. This technique is called time-of-flight LFV. A special prototype of a respective measuring device, called meniscus velocity sensor (MVS), has been developed to measure local free-surface velocity. In the present paper we describe experimental results of respective measurements in the model test stand LiMeSCo (liquid metal surface velocity correlation). To check the potential of the time-of-flight technique, in a first step we measure surface velocities during solid-body rotation of metallic substances. We observe that small modulations in the signals that are due to the natural unevenness of the solid body can be used to determine surface velocities. In a second step we apply the time-of-flight technique to liquid metal free-surface flow. Here we use the low-melting eutectic alloy GaInSn as a test melt. In this case we observe that the cross-correlations between the signals are much rarer and much weaker than in the solid-body experiments. We conclude that the presence of the localized magnetic fields, produced by the permanent magnets of the flowmeter, give rise to intense deformation of the free surface and the creation of surface waves. The field acts as a magnetic obstacle. We observe that the flow velocity is decreased right underneath the magnetic field and is accelerated in the side regions. This magnetic obstacle effect may restrict the determination of the local surface velocity in application.

Jan 1, 2012

By M. L. Cunha

The lack of control of As and Sb compounds from copper smelters and converters has rendered some chalcopyrite containing arsenopyrite, stibnite and tetrahedrite minerals unusable for metal extraction. In the present investigation, we have studied the carbothennic reduction of Portuguese chalcopyrite mineral concentrate in the presence of lime/CaS04 and CaS04/Si02. Thermodynamic equilibrium calculations were performed to study the distribution of As and Sb between metal and the CaO-Si02-FeO slag phase. The phase equilibrium calculations also show the effect of oxygen partial pressure on the increase in the volume of the slag phase, which helps in lowering the copper metal formation temperature and facilitates a better separation between metal, matte and slag. The reduction reaction kinetics was studied between 850°C and 1100 °C, and the phases formed were identified by X-ray powder diffraction and scanning electron microscopy techniques. The importance of this research for using recycled matte, lean and rich minerals with As and Sb is also explained.

Jan 1, 2001

By Stephanie Trant

Montana Tech has been engaged in fundamental research on the processing of critical materials for more than a decade. Efforts include examining novel reagents for the flotation of Rare Earth Minerals (REMs). For this paper, research results on a collector, salicyl hydroxamic acid (SHA), are presented. Various REMs were examined and include the rare earth oxides (REOs), carbonates (RECs), and phosphates (REPs) of a suite of Rare Earth Elements (REEs). Differences are attributed to solution and surface chemistry, coordination number, and ionic diameter. SHA adsorption follows an ion-exchange process that leads to chemisorbed and surface-precipitated states, depending mostly on pH. Many effects are directly attributed to lanthanide contraction. Results should also be applicable to other REM/collector systems and further suggest that REM flotation should consider dual collectors.

Primary sulphidic gold ores in the Archean provinces of Western Australia can be broadly sub-divided into pyritic, pyrite-telluride, arsenical and antimonial types. Pyritic ores contain only native gold, and are essentially not refractory. Arsenical ores almost always carry some invisible gold, and may vary from mildly to highly refractory. Pyrite-telluride ores contain gold-bearing tellurides, and are refractory to varying degrees. Antimonial ores usually contain aurostibite, and may be very difficult to process. A classification scheme for metallurgical processing, based on mineralogy, is proposed for the ores, and implications for processing are discussed.

Jan 1, 1995

By Juan Hernández Ávila

This work studies the Molybdenum effect on the microestructure, mechanical properties of an as-cast ductile iron. For this study five ductile irons with different amounts of Molybdenum each were made in an induction furnace. In this material nodule count and nodularity is affected by the Molybdenum additions; The iron´s matrix, nodules and the phase were analyzed using scanning electron microscopy detecting Molybdenum only in the matrix. Mechanical properties such as hardness, microhardness, tensile strength and yield strength show increments as the Molybdenum amount is increased. In the same way, ferrite and pearlite phases display a variation in their percentage as the contents of the alloy element increase. This element has a marked influence on the pearlite interlaminar spacing. From the obtained results we conclude that Molybdenum in these quantities dissolves in solid ferrite solution during the solidification process, improving the material´s mechanical properties.

Jan 1, 2009

By A. K. Kyllo

A study has been carried out on the dusts from Hudson Bay Mining and Smelting&apos;s Flin Flon copper smelter. The aim of the work was to determine the mechanisms of dust formation and the deportment of the various constituents. The work concentrated on the copper converters, but the electrostatic precipitators and baghouse also clean the reverberatory furnace off gas, so some mixing will have occurred. The dust composition was found to vary with distance from the furnace, and to be made up of three major components: solidified droplets, unreacted flux, and condensed particles. The solidified droplets were formed from material ejected from the converter during blowing, while the flux was blown out of the converters immediately after charging. The condensed particles contained the majority of the lead and zinc, as well as the volatile impurities. There was also a significant soluble content of the dusts, increasing with distance from the furnace. The condensed material may be separated from the remainder by a simple washing and sizing technique.

Jan 1, 1996

By M. Wenzel, Dang Thanh Tung, Nguyen Anh Duc, Nguyen Huu Luong, Dang Van Sy, N. Kelly, K. Gloe, K. Kretschmer, Phuc Nguyen Le, K. Schnaars, S. Robles M, L. Götzke, J. J. Weigand

The recovery of rare earth metals from secondary sources has attracted much attention due to their ever expanding demand in the high-tech industry. The studies reported here focus on the hydrometallurgical recovery of lanthanum and cerium from spent fluid catalytic cracking (FCC) catalysts in a two-step process: leaching with nitric acid and solvent extraction by tri-n-butyl phosphate (TBP) and di(2-ethylhexyl)phosphoric acid (D2EHPA). The experiments show a high dissolution yield of about 93% lanthanum and 42% cerium in a single leaching step with 2 M (126 g/L) HNO3 at 80 °C; only 11% aluminum has been dissolved simultaneously. In the subsequent solvent extraction step the best results for this leach liquor could be achieved using a 1:1 mixture of 25% (v/v) TBP (0.92 M) and 25% (v/v) D2EHPA (0.76 M) in n-decane without the need for any pH adjustment. In that case La(III) and Ce(III) can be extracted with 60% and 74% yield respectively in one stage from the majority of accompanying matrix elements. In particular no extraction of Al(III) could be observed under these conditions.

Jan 1, 2016