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By Z. Zak Fang, P. Fan, S. Middlemas

"Titanium dioxide (T1O2) has been widely used as pigment in paints, paper and cosmetic products, as well as high-tech applications such as PV Cells, semiconductors, biomedical devices and air purification. T1O2 pigment is primarily produced by the high temperature chloride process, resulting in considerable CO2 emissions. A novel hydrometallurgical process for making T1O2 pigment without direct CO2 emission is investigated. The new method promises to eliminate direct CO2 emissions, consume significantly less energy, and produce minimal environmental waste. The novel process involves molten salt roasting of titania slag, with subsequent washing, leaching, solution purification, hydrolysis, calcination and post-treatment stages, resulting in high-purity anatase or rutile pigments while realizing significantly reduced environmental impacts. Pigment whiteness is critically sensitive to trace amounts of discoloring impurities such as iron and chromium. Several methods for reducing the levels of these impurities are investigated. Energy consumption and emission models are also developed.IntroductionTitanium dioxide (T1O2) is one of the most commonly used minerals in the chemical manufacturing industry. It has been commercially processed since the early 1900's, and has a wide variety of applications. Pigment is used in paints [1], plastics and paper [2], sunscreen [3], cosmetics and even as a food additive [4]. T1O2 has also been used in photovoltaic cells [5], biomedical devices [6], and in air purification [7]. T1O2 pigment has a refractive index of 2.7, which imparts a high level of opacity (and hence whiteness) to whatever material it is added [8]."

Jan 1, 2012

By M. A. Halim, V. I. Lakshmanan, T. Sheikhzeinoddin, R. Roy

"Chloride metallurgy is emerging as an alternative process for the production of base metals. Process Research ORTECH Inc. (PRO) has been at the forefront of technological development of chloride metallurgy. PRO has developed an innovative technology for the production of high purity titanium dioxide, iron oxide and vanadium pentoxide from ilmenite ores and concentrates. PRO is also developing its proprietary mixed chloride technology for the extraction of vanadium from other sources such as oil shales. In this paper, results from the test work conducted at PRO for the extraction of Ti and V using a mixed chloride lixiviant are presented.IntroductionTitanium and vanadium alloys and compounds have numerous industrial applications. Titanium dioxide is used in paints, plastics, rubber, paper, inks, textiles and a number of other miscellaneous applications. Currently nanosize T1O2 is being investigated for application in the cosmetics industry. Inorganic sunscreens mainly use T1O2 or ZnO particles, which reflect and scatter ultra-violet light. T1O2 nanomaterial is also finding application in smart construction materials and coatings, as a photo-catalytic converter. Nano TiO2 can catalyze the dissociation of NOX gases and other automotive emissions, thereby reducing the smog in urban centers. After the construction material is exposed to sunlight or ultra-violet light, the T1O2 is photo-activated and degrades the pollutants.Titanium metal and titanium dioxide are produced from ilmenite (FeTiOs) or rutile (naturally occurring T1O2) ore. Only about 6% of the titanium resources are used to produce titanium metal and the rest is used to produce T1O2. Many of the titanium ore deposits currently have unacceptable levels of transition metals which limits their processing by conventional routes."

Jan 1, 2012

By Nan Zhang, Gai-feng Xue, Shangchao Liu, Benquan Fu

"The high-magnetization microspheres of Fe3O4 encapsulated with S1O2 and T1O2 layers (Fe3O4@SiO2@TiO2) were prepared. The microspheres were characterized by transmission electron microscopy and scanning electron microscopy. These high-magnetization microspheres could be readily dispersed by shaking whereas they could be rapidly separated from the aqueous solution simply by applying an external magnetic field. The two shells of S1O2 and T1O2 protected the iron oxide well and the microspheres were stable in acid and base solutions. Therefore, they have a good potential for the enrichment of phosphopeptides or photocatalytic activity. They could also be used to remove metal ions from waste water.IntroductionSolid-phase extraction (SPE) is the most commonly used separation technique for its simplicity, consumption of small volumes of organic solvent, and the ability to achieve a higher enrichment factor. The quest for new adsorbents is an important factor in improving analytical sensitivity and precision in SPE techniques. To date, many novel adsorbents, such as nanometer-sized materials, carbon nanotubes, mesoporous materials and magnetic nanoparticles have been employed in SPE.Magnetic polymeric microspheres, an interesting advanced composite material, have received increasing attention in the past few decades because of their unique physical and chemical properties and their potential for use in applications in various fields [1]. Magnetic microspheres consisting of an iron oxide core and a silica shell have attracted particular attention for their unique magnetic response, low cytotoxicity, and chemically modifiable surface. The core-shell magnetic silica microspheres have shown great potential in the fields of biotechnology and biomedicine for applications such as cell labeling and separation, enzyme and protein separations, targeted drug delivery, and magnetic ferrofluids hyperthermia."

Jan 1, 2012

By Hai-Xing Fang, Bing Xie, Hong-Yi Li

"In the duplex melting process, chromium forms chromium spinels, the study of which will help to exploit the Hongge ores (rich in chromium) in the Panzhihua-Xichang area in China. Mimicked chromium slag was synthesized. The oxidation and decomposition mechanism of the Fe-Cr spinels contained was studied in a sodium roasting process. The effects of temperature, roasting time, amount of soda added and filling reagents were investigated. The leaching-reduction-precipitation-calcination procedure to extract Cr2CO3 was optimized. The results showed that the optimized roasting temperature was 1000~1020°C with a stoichiometric Na2CO3 addition and without any filling reagents. Roasted materials were leached with distilled water and were filtered to obtain a chromium-containing solution, which was adjusted to pH 1.60-1.80. A reducing reagent, NaHSO3, was added in a stoichiometric ratio and the solution was then adjusted to pH 7.25~8.25. Maximum Cr2O3 precipitation was obtained and the precipitate was calcined at 1050°C for 2h to obtain Cr2Ü3 with recovery rate over 96%.IntroductionChromium is widely applied in the metallurgical industry, in refractory materials and in the chemical industry with its particular properties of hardness, wear-resistance, high temperature resistance and corrosion resistance [1]. There is no free state of chromium in nature and chromite is the main chromium containing mineral [2], China is poor in chromium resources, despite its large demand, and there are few deposits of high grade of chromite ores except in some regions in Tibet and Xinjiang province [1, 4]. Hongge, one of largest titanomagnetite mines in Panzhihua-Xichang area, is a polymetallic deposit mainly containing iron and titanium; it is also associated with various beneficial elements such as chromium, copper, nickel, etc. [3]. As investigated in Reference 3, the chromium reserves of Hongge ores are so large that it is of great importance to study how to extract the chromium from them."

Jan 1, 2012

By Shaohua Ju, Jin-hui Peng, Ya-jian Wang, Shuai-dan Lu, Li-bo Zhang, Lei Guo

"The granulation of a red mud is of great importance for recycling this material as an adsorbent for waste water or gas. A new granulating process was developed and its effect was evaluated. To reduce the cost of the granulation process, the wet filter cake (containing 25% water) was directly mixed with different cement contents (4%, 6%, 8% and 10% based on wet material). The mixtures were placed in a moist environment for 4 days, and then were washed with deionized water until the pH values of leachants were lower than 9.0. The efflorescence ratio, surface area and particle size of the aged mixture were determined, respectively, by bottle shaking experiments, N2 adsorption and screening. The results showed that the best addition of cement is 2%, and this yielded granulated material with a particle size of less than 2 mm, an efflorescence ratio of 4.83% and a specific surface area of 17.42 m2/g.IntroductionRed mud is a residue of the aluminium industry that is produced during the alkaline extraction of alumina from bauxite by the Bayer process. For every ton of alumina that is produced, the amount of red mud generated can vary from 0.3 to 2.5 tons, depending on the characteristics of the bauxite. In its typical form, red mud is brick red in colour, caustic, about three times as dense as water and, when un-neutralised, has a high pH, typically around pH 13 [1]. It is primarily composed of iron oxide, silica and alumina, along with traces of heavy metals. Red mud particles are quite small; typically 99% will pass through a 0.6 mm sieve and 87% through a 0.038 mm sieve [2],"

Jan 1, 2012

By Peng Peng, Ouo Cheng, Guodong Lai, Lijuan Chu, Zebiao Zhang

"The pressure acid leaching residue of zinc concentrate contains a large quantity of sulfur. The present study attempts to leach sulfur using a mixture of ammonium sulfide and water solution at 25°C. Effects of three leaching variables: ammonium sulfide concentration, leaching time, liquid/solid ratio on the sulfur leaching rate were investigated. The process conditions were optimized using response surface methodology based on the central composite design. From the analysis of variance (ANOVA), the significant factors on response were identified. The optimum conditions for leaching elemental sulfur from pressure acid leaching residue of zinc concentrate were obtained using an ammonium sulfide concentration of 2.5 mol/L, leaching liquid-solid ratio of 6.5:1 and leaching time of 7 min. Under the optimum experimental conditions, a maximum of 98.50% of total sulfur was extracted. The experimental results obtained agreed satisfactorily with the model predictions, with a correlation coefficient (R2) of 0.99.IntroductionSulfur is widely used in agriculture, medicine, rubber, building materials, gunpowder, wine and sugar, and other fields [1]. Currently the world sulfur production is 40Mt, out of which more than 90% is recovered from industrial processes, and 10% is natural [2], This highlights the importance of sulfur recovery. As the pressure leaching technologies [3] continue to mature and are increasingly applied to refining, a large quantity of high-sulfur residue is produced [4-5]. It is desirable to recover sulfur from this residue, so that it is economically advantageous, and reduces environmental pollution [6]."

Jan 1, 2012

By Neil E. Izatt, Ronald L. Bruening, Steven R. Izatt

"IBC has developed environmentally friendly Molecular Recognition Technology (MRT) processes to selectively extract, recover, and purify a wide range of metals from a variety of process streams. The incorporation of MRT into process flow sheets can improve the economics of the processes. MRT separations are effective even at low (mg/L to \i%JV) metal levels. MRT processes are sustainable, being economically viable, energy efficient, and environmentally friendly as well as having a low carbon footprint. Examples of MRT processes will be presented and discussed involving platinum group metals, gold, rhenium, and other metals of interest to the mining community.IntroductionA significant portion of the earth's precious metal resources has been moved during the past century from underground to above ground [1]. This movement has important economic, health, environmental, ecological, and sustainability implications for the earth and its population. There is concern that recycling of certain precious and specialty metals from end-of-life (EOL) electronic wastes (e-wastes), catalyst wastes, mining waste streams, and other waste products such as rechargeable batteries is not adequate to maintain supplies of these metals sufficient for future needs [2-4]. Improved metal recycling rates and more efficient metal recovery from the enumerated wastes would significantly reduce the amount of virgin metals that must be mined to support our lifestyle [5]. More efficient separation procedures in ore processing flow sheets and more effective recovery of metals from low-grade waste streams would reduce metal loss in the mining industry."

Jan 1, 2012

By Hande Cavus, Ibrahim Yusufoglu, Cem Kahruman

"In this study, ammonium tetramolybdate (ATM) was obtained as the intermediate product of ammonium heptamolybdate tetrahydrate (AHM). The thermal decomposition mechanism of ATM was investigated under nonisothermal and isothermal conditions in air and inert gas atmospheres. Nonisothermal experiments were carried out by TGA/DTA/MS while TG was used for isothermal conditions. Characterization of the decomposition products were carried out by XRD and FT-IR. The thermal decomposition of ATM in air proceeds in a single step and forms M0O3 while [(ÍÇ4)2è]ïïï83Ìïè3 and molybdenum suboxide (Ìïè3.÷, ÷=0.025) were obtained in the first and the second steps of thermal decomposition in He, respectively. Activation energies, frequency factors and kinetic model equations were determined for thermal decomposition reactions. Fractional conversion-time diagrams were compared with diagrams drawn according to kinetic model equation.IntroductionM0O3 is usually used as catalyst in industry [1]. AHM is the basic source to produce molybdenum containing catalysts used in petrochemistry [2]. The oxides of Li, V, W, Te, Bi and Sn are doped in M0O3 to produce catalysts, which find commercial applications in the industry. The properties of M0O3 are affected by dissolution, settling, calcination, drying and thermal decomposition processes [1]. There are several studies in the literature about the thermal decomposition of AHM and the characterization of the decomposition products in different gas atmospheres and at various heating rates [3-19]."

Jan 1, 2012

By Guodong Lai, Shixing Wang, Lijuan Chu, Jinhui Peng, Zebiao Zhang

"The beneficiation of poor manganese ores containing phosphate gangue is very difficult by conventional processes, because of the similarities in the physico-chemical properties of the constituent minerals. The shaking table gravity concentration process and concentrated strong acid selective intensified leaching process were used for dephosphorisation of Yunnan manganese ore. The leaching process was effective. The effects of intensified leaching time, solid-liquid ratio and particle size were investigated. The relevant leaching factors were optimized as -0.125+0.088 mm particle size with 68% nitric acid for 24 h when using a solid-liquid ratio of 1:1 at room temperature and atmospheric pressure. Under these conditions, the P/Mn ratio was reduced from 0.0107 to 0.0056, and the grade of manganese was increased from 12.32% to 42.76%. The dissolution of manganese during leaching was negligible.IntroductionManganese and its compounds are widely used in the iron and steel industry as deoxidation and desulfurization agents and as alloying additives [1-2]. Because of the increase in demand, low grade refractory manganese ores are becoming a new source. Many Chinese manganese ores are high in phosphorus, which cannot be used directly for metallurgical purposes. This occurs because phosphorus enters into the metal phase during smelting and its presence sharply deteriorates the mechanical properties of the metal [3-4].Kanungo and Sant [3] investigated the dephosphorization of phosphorus-rich manganese ores by selective leaching with dilute hydrochloric acid. They observed that leaching with dilute hydrochloric acid (0.1-0.6M) could reduce the phosphorus contents to the specified limit of 0.12%. Ye [5] investigated dephosphorization of high-phosphorus manganese ore of the Huayuan type. Using high intensity magnetic separation, roasting and leaching with acid for dephosphorization, as used in the industry, a 40.15% manganese concentrate with a P/Mn ratio of 0.0037 was obtained. Yimin [6] investigated magnetic separation followed by inverse flotation of high-phosphorus manganese ore, and found that the P/Mn ratio could be reduced from 0.046 to 0.002."

Jan 1, 2012

By M. A. Rabah, F. E. Farghaly, M. A. Motaleb

"Wastewater from industrial galvanization industry was reclaimed under current flow stream conditions. Results showed that the raw water contains 0.7 % by weight total suspended solids (TSS) causing turbidity amounting to 30. Measurements of Zeta potential as a function of pH revealed that solid separation takes place at pH 9. Addition of H2O2 to the polmer solution helps to oxdize ions of iron and zinc metals toinsoluble ferric oxide and zinc hydroxide to a higher state of oxidation. Addition of 5 mg/L of cationic magna flocculants polymeric solution helps the rapid separation of the turbidity. Separation of floccules so formed takes place by filtration. Addition of peroxide ions to the turbid wastewater confirms the physical stability of the flocs so formed. Impurity flocculation takes place in few seconds. Maximum temperature for safe solid removal was <30°C. The treated water was pure and safe for recycling or use in domestic purposes.IntroductionStocks and et. al. [1] show that the galvanizing process introduces spent pickling acid waste production, but its major constituent, could be used. Survey of the operational procedures adopted and the acid wastes produced by UK Galvanizers are reported. Various methods to recovery spent acid of suitable composition and to eliminate zinc contamination was considered. Application of the Kleingarn acid management system reduces waste volume, saves hydrochloric acid (HCl) and increases component throughput whilst, in conjunction with zinc elimination, could allow recycling of the majority of galvanizer’s acid wastes.Dahab [2]; Kerney [3] reported recycling of galvanizing products, including pickleliquor. Kerney suggested a mobile treatment plant for recycling pickling acids. Dahab found that pollution reduction could be achieved by relatively simple operational changes to the process that gave fairly short payback times.Rozenblat and et. al.[4] studied the extraction of zinc (II), iron(III) and iron(II) with Tributyl phosphate (TBP) from hydrochloric acid solutions containing high zinc(II) concentration. Two technological approaches for the separation are considered. Firstly, the selective extraction of iron(III) (iron(II) is oxidized to iron(III)) over zinc(II) with TBP deficiency. Secondly, iron(III) reduction to iron(II) followed by zinc(II) selective extraction with an excess of TBP. Prior stripping, the organic phase was washed with small amounts of water. Scrubbing of TBP solutions containing iron(III) contaminated with zinc(II) gives always a mixture of zinc(II) and iron(III) which must be recycled to the extraction step in continuous process. The following technological concept is proposed: reduction of iron(III) to iron(II), extraction of zinc(II) with 5-10 volume excess of TBP, washing of TBP phase contaminated with iron(II) with small volumes of water and recycling of the scrubbings and stripping of zinc with water."

Jan 1, 2008

By Tracy Morris, Weldon Read, Luis Navarro

"During the leaching of anodic slimes, tellurium dissolves into the leach liquor together with copper and must be removed before the solution is sent to liberator cells for copper recovery. Prior to the installation of autoclaves, tellurium was precipitated using raw slimes that caused a recirculation of tellurium in the leaching circuit. After autoclaves were installed the old leach tanks were converted into tellurium reactors utilizing copper chips, steam and agitation to form a copper telluride precipitate. Tellurium levels of less than 10 rng/L are achieved in a timely manner.IntroductionThe electrolytic refining of copper consists of an electrolytic cell provided with an anode of impure copper, a cathode of substantially pure copper (starter sheet) and an electrolyte made of copper sulfate and sulfuric acid [1]. When a direct electrical current is passed between the anode and cathode inside the cell, the impure copper anode dissolves in the electrolyte and pure copper is plated onto the cathode. During this operation, many of the impurities are deposited on the bottom of the cell as an anodic slime residue composed of insoluble chemical compounds. Slimes are a major source of rare and precious metals in the copper industry [2-5],In the Amarillo Copper Refinery (ACR), the anodic copper slimes are sent to the Precious Metals department in order to extract and then refine the gold, silver, platinum and palladium from them. The remaining impurities, in the form of a soda slag or copper slag are sent to the Hayden smelter for further processing. Copper telluride is sent to the Selenium/Tellurium department inside the plant for selenium and tellurium recovery. During the leaching process of the anodic slimes, copper, tellurium, and other metal species in the slimes are dissolved into leach liquor that cannot be returned to the tankhouse unless the tellurium concentration is below 10 mg/L."

Jan 1, 2012

By Tracy Morris, Weldon Read, Luis Navarro

"Bismuth is a recognized contaminant in the electrolytic refining of copper that can render many cathodes to be outside ASTM standards and unsuitable for copper rod and other downstream products if not carefully controlled. This paper portrays the performance of Molecular Recognition Technology (MRT) for bismuth removal at the Amarillo Copper Refinery (ACR) and describes how the highly selectivity gel has been successfully used to achieve good bismuth removal and how many pit falls and draw backs have been overcome.IntroductionASARCO operates one of the largest copper refineries in the world at Amarillo, Texas. The main feed for this refinery is produced at the Hayden smelter in Arizona. During the operation of this smelter a variety of metals are carried as impurities in the copper anodes because of the diversity of concentrates and residue products used as raw materials in the smelter feed mix. Even though the impurities are concentrated enough to be detected at the smelter, it is difficult to remove them completely. A simple way to control impurities at the smelter is to minimize the addition of material with a high concentration of impurities to the charge in order to reduce the output of this metal species. All this leads us to have a ""refinery problem"" [1,2,3]."

Jan 1, 2012

By Takashi Nagai, Hideaki Sasaki, Masafumi Maeda

"The production of solar cells is increasing dramatically and the shortage of polycrystalline silicon for these cells has become a serious problem, making development of a low-cost production process for solar grade silicon essential. An electron beam melting technique is known to be effective for the removal of phosphorus from molten silicon. Although the phosphorus is removed by preferential evaporation in this process, the rate of removal is not sufficient, and its improvement requires thermodynamic information on phosphorus in the molten silicon. In this research, the vapor pressure of phosphorus in equilibrium with a siliconphosphorus alloy was measured by double Knudsen cell mass spectrometry with a system blowing gas into the Knudsen cell. The activity of phosphorus in silicon, the Gibbs energy change of the dissolution of phosphorus in silicon, and other factors were estimated from the results. Using these data, we provided guidelines on how this process can be improved.IntroductionSolar energy is in great demand since it is inexhaustible and cleaner than that from conventional energy resources. Silicon is the material most widely used to convert solar energy into electricity. Figure 1 shows the recent production of solar cells. High purity silicon for solar cells, namely solar grade silicon (SOG-Si), has been commercially supplied mainly from off-grade high purity silicon in the semiconductor industry. However, production of solar cells has increased rapidly in recent years, and the shortage of SOG-Si has become a serious problem, so that a new processes which can produce SOG-Si economically are required.Directional solidification was applied to remove transition metal elements such as Fe or Ti by segregating them from the remaining melt. However, such solidification is useless for phosphorus because the segregation coefficient of phosphorus is nearly unity. Numerous approaches have been made in an attempt to produce a resource of low cost SOG-Si from metallurgical-grade silicon (MG-Si). [1,2]"

Jan 1, 2012

By Ibrahim Yusufoglu, Ahmet Orkun Kalpakli, Cem Kahruman, Sedat Ilhan

"The effects of oxalic acid concentration, temperature, stirring rate and particle size on the dissolution rate of synthetically prepared calcium molybdate were investigated. Dissolution of calcium molybdate in oxalic acid solutions takes place as a series - parallel type reaction. In the first reaction step, which proceeds according to the ""Langmuir - Hinshelwood Mechanism"", calcium aqua oxalato molybdate is formed as a complex chelate intermediate product. In the second reaction step, molybdic acid is formed during the slow hydrolysis of calcium aqua oxalato molybdate, and it reacts rapidly with oxalic acid to form the polymeric hydrogen oxalate dimolybdate chelate as an end product. Activation energies were calculated as 41.4 and 49.9 kJ mol-1 for the first and zero order reactions. The fractional conversion versus time relationship can be given by the following equation.IntroductionMolybdenum is used widely in electric-electronic, metal working, aerospace and aeronautic, nuclear, glass and petrochemical industries because of its high melting temperature and resistance against chemical effects. However, the largest molybdenum consumers are the iron-steel and super alloy industries where molybdenum is used as an alloying element. Industrially important molybdenum minerals are limited to molybdenite (M0S2), powellite (CaMo04) and wulfenite (PbMo04), which are considered as primary molybdenum resources. Secondary molybdenum resources are spent catalysts and scrap [1-4].Molybdenum has been produced by pyrometallurgical processes in the past. Since it is possible to process low grade molybdenum ores and industrial wastes by hydrometallurgical processes, which are more environmentally friendly than pyrometallurgical processes, the importance of the use of hydrometallurgical processes has increased in the molybdenum production industry."

Jan 1, 2012

By D. W. Collins

Several organic and inorganic substances are widely used to control deposit structure and morphology during the electroprocessing of copper. Methods for monitoring the levels of thiourea, glue and guar gum during electrorefining and electrowinning have been successfully developed under the trade names of Reatrol and CollaMat. Other instrumental methods have been developed for additives and decomposition products associated with the electroplating of copper and other metals. Generally, these methods have been found to be either insufficiently sensitive or lacking in the desired selectivity for some or all of the additives. These procedures have mostly employed DC techniques; i.e., cyclic voltammetry, Tafel analysis, etc. In this work, chronopotentiometry (CP) and AC voltammetry were used to examine the interaction of glue, guar gum, thiourea and chloride during the electroplating of copper onto a platinum electrode. In addition, the interactions between the additives have been explored. It was found that glue in pure electrolyte (H2S04 and CuS04 only) had no effect on the chronopotentiogram. Glue was only active if chloride ions were present. The addition of thiourea resulted in several different chronopotentiograms depending on the presence of either chloride or chloride and glue. Thiourea used in conjunction with glue and chloride showed a significant increase in the polarization during copper deposition when compared to the electrolyte containing only glue and chloride. The use of a modified channel electrode further increased the sensitivity of CP. The use of AC voltammetry was explored as a technique to monitor some of the additives. AC voltammograms have more spectral detail then their DC counterparts and it is possible to monitor some of the additives at very low concentrations with AC techniques.

Jan 1, 1999

By John Jiang, Yeonuk Choi, Olivia Wang, Gus Van Weert

"As part of a general review of processing double refractory ores through Barrick Gold's autoclaves/CIL facility at Goldstrike, Nevada, blanking the gold cyanide adsorbing native carbon in the ore with hard (m.p. >55°C) paraffin wax was proposed. To avoid interference from other ore constituents in the exploratory testwork, commercial activated carbon was substituted for native carbon in the ore to establish the best conditions for de-activation of carbon with molten wax.IntroductionDouble refractory gold ores present two barriers to gold extraction. The first is generally a physical barrier: the gold is encapsulated or dispersed in a matrix which is impervious to the gold lixiviant. In most cases, including the Goldstrike deposit, this involves a pyrite or arsenopyrite matrix, although minor gold may also be dispersed in competent silica (quartz) or iron oxides. Gold can be rendered accessible by oxidative destruction of such sulphide matrices. At Goldstrike this is practised by roasting and autoclave oxidation (POX). It is the latter route to which this paper refers.The second barrier refers more correctly to gold recovery. Gold may be extracted from the autoclave oxidized solids with cyanide, forming a gold cyanide complex. One characteristic of this complex is that it adsorbs on graphitic surfaces. This behaviour is used advantageously on a large scale by gold millers, who use man made activated carbon particles to remove the gold from solution during leaching: the Carbon-In-Leach, or CIL process. The gold bearing carbon particles are larger than the ore solids and can be separately recovered by screening. Goldstrike uses the CIL technology to recover gold after autoclave oxidation."

Jan 1, 2012

By W. G. Davenport

Chapter 6 examined autotherrnal smelting of pure chalcopyrite concentrate with 50 mass% O2-50 mass% N2 blast. It showed that production of 1500 K products with this blast requires: 181 kg of pure oxygen 337 kg of air per tonne, of concentrate. It also showed that the grade of matte produced with this blast is 58% Cu. This chapter re-examines autotherrnal smelting by asking: (A) WHAT COMPOSITION BLAST (MASS% 02 -MASS% N2), 298 K, WILL AUTOTHERMALL Y PRODUCE 65% Cu MATTE 1500 K FROM PURE CHALCOPYRITE CONCENTRATE? (B) HOW MUCH PURE OXYGEN AND AIR WILL BE NEEDED? These are important questions for flash? smelting because furnace operators usually want to send specific composition matte to converting. This chapter shows how a specified matte can be produced autotherrnally with 298 K oxygen-air blast. Later chapters show how it can be done with hot blast, hydrocarbon combustion, different concentrates etc.

Jan 1, 2001

By Klaus Gamweger

There are different reasons for purging a metal bath. The operations are varied, for example the purging gas can be used as a reactive gas being part of the metallurgical process or as an inert gas using the rising gas bubbles for agitation only. The different purposes for agitation, chemical and thermal homogenization or a preferential movement of the slag to the slag skimming door have to be considered. It depends on the furnace type and its dimensions as well as the process characteristics what the focus is on. For an optimized arrangement of numbers and position of all single plugs in the furnace, mathematical modeling - the CFD Computational Fluid Dynamics method - is used. This paper shows how the operation of purging plugs can influence the metallurgical process of an anode furnace by the example of Jinchuan Copper in China. The potentials for savings in energy consumption as well as in time for oxidation and reduction are presented.

Jan 1, 2006

By W. G. Davenport

Chapter 10 showed that any given smelting task, e.g. production of 65% Cu matte, 1500 K, from CuFeS2, can be done with many different combinations of: blast%02 hydrocarbon fuel blast temperature. This chapter repeats the Chapter 10 calculations but reports the results in terms of the mass industrial oxygen mass hydrocarbon fuel blast preheat energy combinations that will produce 65% Cu matte, 1500 K, from CuFeS2 concentrate. It also determines the energy inputs equivalent to these combinations.

Jan 1, 2001

By V. Bojarevics, K. Pericleous

"A number of different methods have been developed for noncontact electromagnetic treatment of liquid metal and to investigate the melting/solidification processes. Applying AC magnetic field in terrestrial conditions, along with the buoyancy and thermo-capillary forces, results in turbulent flow. The use of a homogenous DC magnetic field allows damping both of the turbulence and the large scale flow at different rates leading to surprising results at some stages. The dynamic interaction of the turbulent flow with the oscillating interface needs to be accounted if it is required to levitate liquid metal of up to few kilograms without the contact to container walls. At the high values of magnetic field some oscillation modes are damped quickly, while others are modified with a considerable shift of the oscillating droplet frequencies and the damping constants from the non-magnetic case. Numerical models are used to investigate behavior of liquid metal suspended in high DC magnetic fields providing microgravity-like conditions with laminar viscosity and heat transfer to the surroundings.IntroductionSince the early Electro Magnetic (EM) levitation experiments [1] in AC magnetic field it became apparent that the levitated liquid metal is prone to oscillation and instability. The EM and electrostatic levitation experiments with liquid metal droplets show difficulties related to confinement stability and a need for complex correction functions to establish a correlation between the measurements and the droplet material properties [2,3]. Intense internal fluid flow is visually observed, apparently being in the turbulent regime for earthbound conditions."

Jan 1, 2012