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By Fathi Habashi

The recovery of uranium from wet process phosphoric acid was applied on industrial scale in the 1940's by using octylpyrophosphoric acid as an extractant. Later, more efficient reagents were used, e.g., di(2-ethylhexyl) phosphoric acid and actylphenyl phosphoric acid. In the 1970's the rare earths in Kola phosphate were recovered in Finland and recently (1997) in Norway using HNO, as a leaching agent and di(2-ethylhexyl) phosphoric acid as solvent. It was demonstrated later on laboratory scale that both uranium and rare earths could be extracted from the rock by tributyl phosphate but at different pH values provided that the rock is leached with nitric or hydrochloric acids instead of the commonly used sulfuric. This new concept opens the way to the possibility of treating phosphate rock by in-situ, dump, or vat leaching for the recovery of phosphate values as well as uranium and the rare earths. Another solvent extraction process is used industrially for the purification of phosphoric acid using butyl and amyl alcohols.

Jan 1, 1998

By William Petruk

"Heap leaching is a developing technology for recovering native gold and electrum from low grade deposits and from tailings. Recovery depends on permeability of the rock and ore minerals, size of particles in the heap, and ore textures that influence exposure of gold grains to cyanide solutions. These ore textures include gold-bearing veinlets and microveinlets along fractures and microfractures, gold grains in porous minerals and rocks, and gold graim. occurring along grain boundaries of other minerals. On the other hand, small encapsulated gold grains arc not likely tote exposed even with fine grinding. Most gold grains that occtir along grain boundaries of other minerals can be exposed with a moderate to fine grind, but the. resulting material will be too fine-grained to be permeable in a heap. Such finely ground ore, as well as tailings from flotation operations, can however be prepared for heap leaching by agglomerating the material into porous briquettes. Oxidized and weathered zones above. orebodies are frequently amenable to heap leaching because the gold-bearing pyrite and arsenopyrite have become permeable by conversion to porous iron oxides and ferric oxyhydroxides. A review of ore textures in several types of gold deposits suggests that:(1) the gold in vein deposits would gtmerally be amenable to heap leaching of both oxidized ores and fresh non-refractory ores,(2) the gold in Carlin-type deposits and in volcanogenic massive sulfide deposits is not likely to be amenable to heap leaching fresh ore, but oxidized zones above the orebodies are generally amenable to cyanidation, and(3) the gold in porphyry copper-gold deposits and in Witwatersrand-type deposits would likely be amenable to heap leaching of both fresh and oxidized ores but with high cyanide consumption."

Jan 1, 1997

By B. Mishra

The major waste product of the alkaline extraction of alumina from bauxite [Bayer Process] is known as red-mud. Approximately, a ton of red-mud is produced for every two tons of bauxite that is mined. The red-mud produced from Jamaican bauxite is rich in hematite, alumina and titanium oxide. It has been shown that over 90 wt. pct. alumina can be recovered from red-mud by soda-ash sintering and caustic leaching. Hematite can be carbothermically reduced with a degree of metallization of over 94 pct. At this stage, the product could be charged through the tuyeres in an iron blast furnace or smelted to produce pig iron. The mineralogical characteristics of the reduced product are not amenable to magnetic separation for iron recovery. The problems associated with the use of reduced red-mud as an alternative to direct-reduced iron [DRI] has also been discussed. Special attention has been paid to lower the alkali content of the reduced material. If smelted, the concentration of titanium oxide in the slag will be significantly high justifying its recovery by an acid-leach process. This paper describes the successful efforts of iron and alumina recovery.

Jan 1, 2000

By V. P. Bystrov

Vanyukov process has been developed and investigated in Russia over the last 25 years. It has been established that various kind of material could be treated in Vanyukov process. The results of the pilot plant trials as well as industrial experience are presented in this paper.

Jan 1, 1993

By Rodney J. Ishak

The reduction of Mn3O4 to MnO has been investigated in a thermobalance apparatus. The charge was composed of manganese ore (decomposed by heating/calcination or pre-reduction to mainly Mn304) and coke. The material was charged to a crucible, which was suspended in the balance. CO-gas was distributed through a grid in the bottom of the crucible. Two sizes of ores were used; 2.4-4.8 mm and 6.7-9.5 mm. Coke particles were in the size range 4.8-6.7 mm. Experiments were conducted in the 900-1100°C temperature range. The composition of the product gas was monitored continuously. External mass transport between bulk gas and particle surface does not seem to limit the rate of reduction. Assuming that both diffusion through product layer and chemical reaction at the interface between MnO and Mn304 are rate controlling, the data was tried both in a shrinking core model and in a grain model using regression. The grain model gives the best physical description of the process, because the reactant is in fact a porous medium. With this model the effective diffusivity was calculated to be in the 1.5-6.10-5 m2/s range. The pore size was mainly between 0.1 and 10 um.

Jan 1, 2003

By Leiv Kolbeinsen, Stian Seim, In-ho Jung

"The current work presents new experimental data in the iron-unsaturated region of the FeTiO3-Ti2O3-TiO2 slag system. The samples are prepared by melting pure reactants in a high frequency induction furnace that employs a cold crucible. A similar experimental set-up has been described in literature and proven suitable to investigate high titania slags. The FeO content of the samples range from 3.7 to 21.8 wt% and the Ti2O3 content range from 3.6 to 30.1 wt%. The liquidus temperatures of the samples are measured in-situ by a spectropyrometer and range from 1450 to 1645 °C.In addition, an improved thermodynamic database for the FeO-Ti2O3-TiO2 system has been developed. Ternary parameters have been included and optimized to fit previously published experimental data. This optimization minimizes the discrepancy between experimental data and thermodynamic calculations as previously discussed in literature. New liquidus projection plots are proposed for the FeO-Ti2O3-TiO2 and the FeTiO3-Ti2O3-TiO2 systems.IntroductionIlmenite (FeTiOs) smelting is a relatively small industry world-wide. However, a reasonable focus on the process has been applied in Norway due to the location of one such smelter in Tyssedal, which is located in the western part of Norway. The process is essentially carbothermal reduction, where most of the iron in the ilmenite is reduced to its metallic state, and the titanium oxide is concentrated in the slag product. The metallic iron is sold as a high purity pig iron and finds applications in cast products. The slag concentrate is further processed for the production of TiOvpigment and/or titanium metal. This further processing can be performed through different routes according to the purity of the slag concentrate."

Jan 1, 2012

By W. D. Riley

Engineered Scavenger Compounds (ESCs), developed by the U. S. Bureau of Mines I are a novel class of compounds that can selectively recover a desired element from 'a solid or molten alloy. Lithium titanate (Li2Tip7 or Li20' 3TiO.) is being used as an ESC to recover lithium (Li) from Aluminum-Lithium (AI-Li) alloys. X-ray diffraction measurements have shown that lithium titanate undergoes a phase change from an orthorhombic structure to a hexagonal structure. This change is due to the incorporation of Li in the matrix of the material and the effect of temperature. Although both of the structures are metastable, the hexagonal phase that forms during the scavenging of Li from AI-Li alloys appears to be the more stable phase. Recovering Li from the ESC by electtodeposition does not cause the structure to revert to the orthorhombic phase. Both the orthorhombic and the hexagonal structures of Li.Til07 have similar scavenging capacities for Li. This paper proposes a new mechanism for the phase transformation.

Jan 1, 1991

By L. W. Beckstead

In a conventional zinc refinery plant, zinc concentrates were roasted at 950°C. The calcine was ground and leached in a series of leaching vessels using sulfuric acid. The pH in the first leaching vessel was maintained at 2.5, while the pH of the solution exiting the last vessel was about 5.4. The leached residue typically contained (in percent) 0.1 Ag, 0.2 As, 0.7 Cd, 2 Cu, 15 Fe, 10 Pb, and 15 Zn, and it was classified as hazardous material according to the EP-toxicity test. In order to make the residue non-hazardous, and to recover most of the metal values from the residue, a brine leach process was developed. The process consisted of leaching the zinc leach residue in CaCI, brine solution at pH 2 for 1 hour at 90°C. Silver extraction was about 95 percent, while lead, copper, cadmium, zinc, and iron extractions were about 80, 50, 50, 30, and less than 0.5 percent, respectively. More extreme conditions of acidity could have been used in the leaching stage to increase zinc dissolution, but iron dissolution would have significantly increased which would have complicated subsequent recovery steps. The leached and washed residue passed the EP-toxicity leach test and could be disposed as non-hazardous. Silver, copper, and lead in the leach solution were recovered by zinc cementation, while zinc and cadmium were recovered by sulfide precipitation. The resulting solution can be recycled in the process after magnesium precipitation.

Jan 1, 1993

By Nagy El-Kaddah, Thinium T. Natarajan

A modeling strategy is presented for computing the electromagnetic field and the shape of the molten metal in electromagnetic confinement systems. This strategy involves the use of a hybrid finite element/integral technique to calculate the electromagnetic field and force distribution in the melt. The free surface shape is determined from minimization of electromagnetic, gravitational and surface tension energies using the Lagrange method of multipliers. This approach was applied to model the electromagnetic levitation melting process. The model was found to accurately predict the measured shape of levitated droplets.

Jan 1, 2014

By M. C. Ruiz

In the present study, the size distribution, Fo(v), of organic drops produced in a continuous-mixing vessel has been determined experimentally for various conditions. The organic phase used was a 1: 1 mixture of a salicylaldoxime (LIX 860N-IC) and a ketoxime (LIX 64-IC) in an aliphatic diluent (Escaid 103). The aqueous phase was a copper sulfate solution. The results indicated that an increase in stirring speed, extractant concentration, and pH produced smaller drops. The effect of the stirring speed was the most significant, decreasing the average volume of drops by 57 % for a change from 300 to 400 rpm. On the contrary, an increase in the dispersed phase fraction, copper sulfate concentration, and retention time produced larger drops. Changes in temperature from 23 to 30°C did not affect significantly the drop sizes. In all cases, the experimental drop size distributions could be accurately represented by a lognormal distribution.

Jan 1, 2001

By Jim Sundal

Primary steel manufacturers using electric arc furnaces generate one of the largest hazardous waste streams nationwide. The waste stream, known as electric arc furnace dust, is a listed hazardous waste with the designation K061. Oregon Steel Mills, Inc., (OSM) of Portland, Oregon, has implemented a process known as Glassificationn, which uses KO61 as an ingredient in an onsite recycling process. Because OSM was able to demonstrate that the Glassificationm recycling process beneficially uses all toxic constituents in the electric arc furnace dust and that the recycling process produces marketable products, the process is not subject to Resource Conservation and Recovery Act (RCRA) permit requirements. The marketable products manufactured using Glassificationn include roofing granules, ceramic glazes and colorants, abrasive blasting media and, more recently, synthetic slag fluidizers. The purpose of this paper is to identify the regulatory issues for recycling hazardous waste and demonstrate that OSM glass frit is effective as a slag fluidizer in primary steel manufacturing.

Jan 1, 1994

By Gerardo H. Achurra

During the last years, the Caletones Smelter, like others copper smelters in the world, has evolved from the conventional, inefficient, pollutant and expensive technologies, to modern, environmentally friendly and efficient ones. For this reason' as well as to improve its competitive position this Smelter shut down the reverberatory furnace, started up two big acid plants and has developed some pyrometallurgical technologies. The main facilities of the Caletones Smelting and Converting Process, in the present and the future, are the Teniente Converters, the reactors with a high operational availability that have reached concentrate top process capacities near to 2,400 tpd. These reactors operate in most of Chilean smelters as well as in other smelters in the world such as in Zambia, Peru and Mexico. Since 2000, the Caletones Smelting and Converting Process, has been adapted in two Teniente Converters, four Slag Cleaning Furnaces and four Pierce -Smith Converters. These facilities, together with the operation of two Fluidized Bed Dryers and two Oxygen Plants have allowed to reach concentrate smelting capacities and copper productions of 1,250 ktpy and 380 kfipy, respectively. Associated to EI Teniente Division Expansion Plan, Caletones Smelter, in the first stage, will increase its capacity to 1,440 ktpy in 2004. In the long term, Caletones has different options, such as the processing of 1,600 to 2,000 ktpy of concentrate, producing anodes, white metal or a mixture of them. These options are connected with CODELCO's Smelters & Refineries Strategic Plan, including Mejillones Project. The main challenges of Caletones Smelter are associated to the development and the consolidation of the Continuous and Environmental Friendly Processes, automation and control of different processes and to the improvement of its leadership between other Copper Smelters in the world.

Jan 1, 2003

By Markku Rytkonen, Shaolong Chen, Ilpo Kylmäkorpi, Hannu Mansikkaviita

Though the Peirce Smith (P-S) converter is a traditional type of furnace, continuous improvement in its mechanical and electrical design is still Kumera's approach. Efforts are made particularly on the following aspects: converter head shape for easy fabrication and structural strengthening, oxidation air swivel joint for low pressure drop and low noise level, wind box for even air distribution to tuyeres, drive unit and its control for reliable and handy operation. These improvements have successfully been applied in recent P-S converter deliveries.

Jan 1, 2009

By Yuanbo Zhang, Mingjun Rao, Weiguang Tian, Huimin Tang, Guanghui Li, Lei Ye, Guoshen Liang, Zhiwei Peng, Foquan Gu, Tao Jiang

The amount of slag produced from a typical ferronickel smelting pro- cess is 4 to 6 times that of the metal product, and handling this slag is a huge challenge to the ferronickel industry. The feasibility of a technological route for preparing refractory materials from a ferronickel slag was verified in this study. Based on the thermodynamics analysis, the effect of the sintering temperature on the properties of refractory material from the slag was studied in the presence of magnesia. The results of thermodynamics calculation showed that the reaction of MgO with SiO generated forsterite and enstatite, whereas the reaction between 2 MgO and Fe O /Al O produced corresponding magnesia spinels. The experi- 2 3 2 3 mental results showed that a refractory material with refractoriness of 1580 °C, bulk density of 2.88 g/cm3, compressive strength of 106.9 MPa, and apparent porosityof 5.8%was obtained under the conditions ofmagnesia addition of 15 wt %, sintering temperature of 1350 °C and sintering time of 3 h. With increasing sintering temperature, the bulk density and the compressive strength of refractory material increased but the apparent porosity decreased, mainly attributed to the formation of the liquid phase which promoted the densification of the refractory material. (cid:1) (cid:1) (cid:1)

Mar 1, 2018

By Patricio Barrios

The Rio Tinto Metal (RTMetal) copper smelter, located 5 Km from Huelva, Spain, began operations in 1970. Since then a series of expansions and modifications have allowed a progressive increase in copper production. Environmental considerations having become increasingly important, environmental protection has come to represent an important aspect of the investments in production. As a result, modifications have been carried out in the two existing acid plants: -Modification of the RTM I gas cleaning section to closed circuit. -Substitution of cascade filters and acid lines. -Modification of the RTM I plant to double absorption. The Expansion and Environmental Improvement Project, completed end 1995, will allow 270,000 t Cu and 800,000 t H2SO4 to be produced yearly, at the same time achieving a decrease in specific and overall emissions. RTMetal's goal is to be an efficient smelter, with the avowed intention of respecting the environment and adopting the best available technologies.

Jan 1, 1996

By S. A. Davis

In July of 1996, the Kroll process began production again at TIMET's Henderson, NV, manufacturing facility. This, after being shut down for several years due to low market demand for titanium. Faced with limited pond capacity and increasing costs for water and wastewater disposal and storage; process changes were made to recycle water used to wash Kroll titanium sponge back into the sponge leaching process. This idea was revisited from 1992-93, when three consecutive attempts to recycle water for this application were unsuccessful due to early pump failure. Since it was uncertain why previous attempts failed, a complete understanding of the existing system was first sought. This included reviewing piping and flow diagrams; taking field measurements for all the piping, valves, and fittings; analyzing the wastewater composition; and modeling the fluid dynamics and control of the system. The fluid dynamics of the system were modeled by breaking the piping network up into nodes and applying the Bernoulli equation to each segment. The fluid flowrate control valves were modeled for this purpose also and the models were used to help specify the required processing equipment and control ranges and tolerances. Once the project was completed, an operating procedure was prepared for operation, startup, and shutdown of the washer water recycle system.

Jan 1, 1999

By Stephen Chryssoulis, Stamen Dimov

Detection and quantification of precious metals (Au, Pd, Pt, and Rh) in spinels and silicate minerals is important for establishing the maximum attainable recovery by sulphide flotation. To achieve this goal subpart per billion (ppb) detection limits are required plus the ability to quantify results. Existing quantitative microbeam techniques (EPMA, PIXE, SIMS, TOFLIMS) have limits of detection in the O. l-200ppm range. Time-of-flight resonance ionization mass spectrometry (TOF-RIMS) is a microbeam analytical technique that allows for the identification and quantification of atomic species in very small quantities. It utilizes a tunable laser source for resonant excitation and ionization of a particular element of interest and has some unique features: elemental selectivity, linear response over a large dynamic range and very high sensitivity. The analysis consist of three steps: (i) the solid sample is vaporized by laser ablation to form a plume containing neutral atoms, (ii) the neutral atoms of a specific atomic element in the plume are resonantly excited and ionized by another tunable laser, and finally (iii) the ions created are mass analyzed in a time-of-flight mass spectrometer. A TOF-RIMS mass spectrometer was developed at AMTEL for trace element analysis of Au, Pd, and Rh in minerals. The spectrometer was calibrated using homogeneous CANMET and NIST reference samples covering three orders of magnitude in concentration. Attained minimum detection limits (MDL=2cr of the background) are in the low ppb range.

Jan 1, 1999

By M. Sakamoto, S. Karaswa, Y. Yoneoka, Y. Ohmizo

"The Annaka Refinery has been processing leach residue by Waelz process for 17 years. Recently, the quantity of the leach residue has increased due to a decline in the quality ~f zinc concentrate. Meanwhile, negative factors (e.g. deterioration of water balance due to improved electrolytic power consumption rate) have increased· in the processing of the leach residue.We have implemented various measures in responses to this situation, while striving to increase ·processing capacity and achieve stable operation. AS we have largely completed our assessment of the efficacy of these measures, we report on our recent process improvements.IntroductionWe have been treating leach residue by the Waelz kiln process since 1981. At that time, treatment of only 50,000 tons of leach residue per year was anticipated. However, subsequent process improvements have revised this figure up to 75,000 to 80,000 tons per year.However, today's increased Fe zinc concentrate grade has resulted in increased amounts of leach residue. In addition, improvements have reduced electrolytic power consumption rate of zinc electrolysis, limiting the amount of water that can be used in ·the zinc refining processes and for deaning leach residue. Consequently, we encounter an increasing number of problems and factors adversely affecting leach residue treatment, including increases in water-soluble Zn (WsZn) and. S (S04) in leach residue.To solve these problems, we have taken several measures to ensure long-term continuous operation and treatment of this increased · amount of leach residue. This paper discusses these measures."

Jan 1, 2000

By I. M. Richardson, M. Janssen, I. J. Bennett, V. A. Popovich

The most critical processing step during the manufacture of screen-printed crystalline solar cells is firing aluminium and silver contacts, which generates residual stresses and solar cell bowing. In this paper, an alternative Ag contact formation mechanism is proposed and aspects related to electrical contact properties, residual stresses and layer delamination are investigated. It is found that there are two main processing parameters affecting the uniformity and delamination of the Ag/Si interface, namely the peak firing temperature and the silicon surface roughness. Silicon surface polishing gives a better wetting of the silicon surface by the glass layer, resulting in a good contact and lower incidence of large voids, compared to the case of highly textured surfaces. The non-uniformity in the glass layer and large voids at the Ag/Si interface (in the case of a textured surface) are expected to have a negative effect on the mechanical strength of the solar cell.

Jan 1, 2015

By Walter Curlook

An atmospheric acid leaching process for leaching nickel and cobalt from highly-serpentinized saprolitic fractions of nickel laterite deposits has been developed and patented [I]. The process involves leaching the highly-serpentinized saprolitic portion of the nickel laterite ore profile in strong sulphuric acid solutions at atmospheric pressure and temperatures between 80°C and 100°C, essentially autogenously, to extract over 85% of its contained nickel content and a large proportion of its cobalt content after leaching times of about one hour. The amount of sulphuric acid used in the leaching process is between 80% and 100% by weight of the finely ground highly-serpentinized saprolite ore on a dry weight basis. The metal values are recovered as intermediate products. Key words: Atmospheric Leaching; Nickel Oxide Ores; Laterites

Jan 1, 2004