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By David G. Dixon

Although the kinetics of leaching processes are of paramount importance in the design and analysis of nearly all hydrometallurgical flowsheets, these concepts remain poorly understood and, as a result, are only rarely applied to mass and heat balance models. In this second of two papers, we demonstrate how simple yet powerful models of leaching kinetics and other rate processes may be added to mass and heat balance models, and apply these concepts using a spreadsheet model of a simplified pyrite autoclaving flowsheet. In particular, we focus on the interpretation and scale-up of batch leaching data, and on simple means for modeling other phenomena commonly associated with leaching, such as reagent depletion, gas-liquid mixing, and the precipitation of oxides and basic salts.

Jan 1, 2002

By Du Sichen, S. Seetharaman, A. Jakobsson

"In the Present paper, the principles of oxygen potential measurements have been discussed along with the design details for oxygen sensors that are used in copper industry. A description of some of commercial probes is presented along with their salient features. The application of these sensors in flash smelting, converter and casting sections of copper production are discussed along with their implications on process optimization.I. IntroductionThe high temperature galvanic cells have come into prominence on account of their numerous applications in both fundamental as well as applied measurements. Since the inception of the oxygen-ion conducting electrolytes like ZrOrCaO·by Kiukkola and Wagner [1], the oxygen concentration cells have been extensively used in laboratories as well as in industries. In metal-production technology, these cells have been used to monitor the oxygen potentials in metallic, slag as well as gas phases and also to control and styr metallurgical processes. The pioneer among the various industrial users of such cells is the copper industry. To-day, high temperature solid electrolyte cells involving oxygen ion conducting electrolytes have become an integral part of copper pyro-refining and continuous casting. In the present paper some of the applications according to the industrial processes are described including the developments that are going on in the European scene."

Jan 1, 1997

By Shu Bin, Lin Chen, Tian-zu Yang, Wei-feng Liu, Wan-da Bin

"Antimony resources are rich in china, its reserves and productions are ranking the first in the world. The Chinese antimony mineral resources are mainly existed in the form of three types, such as stibnite, antimony-gold ores andjamesonite. The antimonial dust that produced from lead smelting process is an important secondary antimony resource. The different process that was adopted to extract antimony depends on the different raw materials. The process of blast furnace volatilization smelting is mainly used to treat stibnite and antimony-gold ores. But jamesonite is treated by the process of roasting-sintering-blast furnace smelting. And antimonial dust is treated in the reverberatory furnace. Many new technologies that are applied in these traditional antimony smelting processes play important roles, such as deleading agent, antimony white production, air-oxidation method, direct-blowing method, bath smelting technology, and so on. At the same time, the development of antimony smelting technology in china is prospected according to the requirement of the state environmental protection.IntroductionThere are five countries that produce antimony in the world, such as china, Tajikistan, Bolivia, Russia, and South africa, but China is the largest country of antimony production in the world. In the world, the antimony productions of 2008, 2009, and 2010 are 182,000 tons, 154,000 tons, and 167.000 tons respectively, but Chinese antimony productions are 166.000 tons, 140,000 tons, and 150,000 tons respectively. So Chinese antimony production was accounted for more than 89% of the world in 2010. It indicates that China have irreplaceable advantages in antimony resource and production all over the world."

Jan 1, 2013

By Yimin Ruan

"An inverse design method is developed to obtain the optimal cooling conditions for the continuous quenching of precipitation hardenable sheet alloys to achieve the required yield strength. The yield strength of a precipitation hardenable alloy is obtained by allowing solute to enter into solid solution at a proper temperature and rapidly cooling the alloy to retain the solute in the solid solution. An aging process may be needed for the alloy to develop the final mechanical properties.The objective of the design is to optimize the quenching process so that the required yield strength can be achieved. With the inverse design method, the required yield strength is specified and the sheet thermal profile at the exit of the quenching chamber can also be specified. The conjugate gradient method is used to optimize the cooling boundary condition during quenching. The adjoint system is developed to compute the gradient of the objective functional. An aluminum sheet quenching problem is presented to demonstrate feasibility of the inverse design method.IntroductionQuenching is a critical step in metal production to achieve desired material properties, such as yield strength, hardness, etc., for precipitation hardenable alloys. In most cases, rapid quenching from the solution heat treatment temperature is necessary to obtain the required material properties, but rapid quenching may cause other problems such as excessive distortions of the quenched materials.In a solution heat treatment, the alloy is heated to a suitable temperature, held at that temperature to allow the soluble alloying elements to enter into the solid solution, and cooled rapidly (quenching) to retain the alloy elements in the solid solution. An aging process, which controls precipitation of fine particles at room (natural aging) or elevated temperatures (artificial aging), is generally followed after the quenching process to develop the final mechanical properties of the heat treated alloys."

Jan 1, 1998

By Eltefat Ahmadi

Iron-free titanium oxycarbonitride (TiOxCyNz) is a promising feedstock for production of titanium tetrachloride (TiCl4) at low temperatures. In this study, the effects of leaching variables such as temperature, time, particle size of staring material and concentration of the leaching solutions were evaluated on iron removal from nitrided Malaysian ilmenite by Becher process. The nitrided ilmenite was prepared by isothermal reduction with graphite at 1200 °C for 3 h in H2-N2 atmosphere. The aerated leaching experiments were conducted at 50–90 °C with addition of 0.3–2.0 wt% of NH4Cl catalyst. The highest extent of iron removal (XFe) was obtained at about 96.2% for the sample leached at 90 °C for 7 h with 2.0 wt% NH4Cl. The iron concentrate and titanium oxycarbonitride product were characterized by ICP-OES, XRD, XRF and SEM-EDX analyses. The results indicated that the aeration leaching process was a successful route to prepare low-iron titanium oxycarbonitride.

By Chris Twigge-Molecey

As emission constraints for metallurgical plants become more difficult to meet; control of major, multi-vessel, flue systems become more critical. Control instabilities can result in significant loss of system capacity or emissions to the environment. This paper will discuss the use of dynamic simulation techniques to optimize both the design and control strategies for these systems. A significant ,safety hazard is associated with pressure excursions from process upsets or equipment failures. Pressure rise rates of up to 10 kPajsec can occur. These cannot-be followed by conventional controls. Fail-safe high speed venting is required to protect both the furnaces and operating personnel'. Design options, sizing techniques and practical problems are discussed.

Jan 1, 1992

By C. P. Broadbent

The process metallurgy of many nickel laterite smelting operations is controlled largely by the physical chemistry of the slag system. Consequently, accurate phase diagram information and physicochemical property data are essential to interpret and predict the behaviour and optimisation of the overall process. The system (SiO2 - MgO - FeO) first described by Bowen et al. between 1914 and 1935 and the system (SiO2 - MgO - FeO - Fe2O3) determined by Muan and Osborne in 1956 are of particular relevance to the study of nickel laterite smelting slags as these systems form a reasonable approximation of many industrial slags. This paper will review the literature for these (and other relevant) phase systems. In addition data available from the ternary and (quasi)ternary phase diagrams will be compared with data obtained from industrial slags. The physico-chemical properties under consideration will include; melting and crystallisation behaviour (solidus and liquidus temperatures), viscosity - temperature relationships, heat flux considerations, electrical conductivity, surface and interfacial tension.

Jan 1, 1993

By Zhangm Mingming

Three samples received from the EAF shop were characterized by chemical, X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM) methods. The objective of this characterization work was to investigate the occurrence of nickel, copper, zinc, sulfur and phosphorus and to identify their origin and associations with iron minerals in the concentrate samples from the mines. The samples were identified as MINERAL, PELLET, and HRD. The latter is the DRI product. All three samples were received as fine powders. The results indicate that, in the mineral sample, magnetite is the major iron oxide mineral with hematite as a second phase based on the OM and XRD studies. Pyrite [FeS2], chalcopyrite [CuFeS2] and bravoite [(Fe,Ni)S2] are the major sulfide minerals. Trace amounts of apatite [Ca5(PO4)3(F,Cl,OH)], wardite [Na4CaAli2(PO4)8(OH)8 6H2O], giniite [Fe;(PO4)4(OH)3 2H2O] and vivianite [Fe3(PO4)2 8H2O] were identified by SEM and XRD. Microscopic studies also indicated that most of the sulfide grains in the mineral sample are present either as liberated fine particles (about 10 microns) or as inclusions within the magnetite and hematite grains. XRD studies revealed magnetite as the major mineral with subordinate amounts of hematite and pyrite confirming the microscopic findings. Copper, nickel, and zinc are mainly present as chalcopyrite, bravoite, and franklinite [(Zn,Mn,Fe)(Fe,Mn)2O4] in trace amounts in the mineral samples, respectively. Impurities carry over to the pellet and HRD samples. Chemical analyses of the three iron-bearing samples indicate that sulfur and phosphorus in the pellet sample exceeded the specification. Since liberated pyrite and chalcopyrite particles were observed in both the mineral and pellet samples, magnetic and flotation processing routes should be effective for sulfide removal but at the cost of iron losses. The high phosphorus content of all three samples indicates that there are phosphates which are difficult to remove by the current concentrating processes (magnetic separation and flotation).

Jan 1, 2012

By A. Block-Bolten

Copper concentrates from northern Peru contain large amounts of arsenic and antimony in the form of sulfosalts like enargite, tennantite and tetrahedrite. These impurities affect up to 30% of Peruvian copper production. Under the sponsorship of the Instituto Geologico Minero y Metalurgico in Lima a project to separate copper from arsenic without pollution of the environment is being carried out at the National University of Trujillo in Peru. The U.N.T. process is unique in the respect of using .low melting salts as solvents, and sulfides of metals with high cation potential as destructors of the complex sulfosalt molecules. Laboratory scale experiments have given encouraging results but interesting and difficult problems developed on scale-up. The process is pyro-hydrometal-lurgical and under certain circumstances its economics are promising.

Jan 1, 1981

By Jack S. McPartland

The recent developments on the concentration and recovery of gold from leached gold thiosulfate solutions by solvent extraction, reduction-precipitation, and electrochemical deposition are reviewed in this paper. Alkyl phosphorus esters have been found to extract gold only in alkaline thiosulfate solutions, The recovery of gold increases with thiosulfate concentration in the aqueous phase and with alkyl phosphorus esters concentration in the organic phase with aliphatic hydrocarbon diluents. The addition of ammonia improves the extraction. The extraction of gold with amines in either aliphatic or aromatic diluent decreased in the following order: primary>secondary>tertiary amines. Increase in the extractant concentration at high pH increased the extraction of gold. At pH < 9, the primary amine, RR&apos;CHNH2 with 1&apos;9-23 carbon atoms is the main extractant with TBP as the synergistic reagent and at pH >9, the primary amine shows a synergistic effect on the extraction of gold&apos; with TBP. TheAu(I) ions in thiosulfate solution are reduced by sodium borohydride (SBH) to metallic gold, with particles in the sub micron range, At an SBH/ Au ratio of 6.25, pH = 6, and at room temperature, the I e ppm Au(I) in a solution of ] 0 gil thiosulfate was completely reduced to metallic gold in about 60 minutes.

Jan 1, 1999

By G. L. Liu

"Deformation Banding ( DB ) in cold rolled mild steel has been experimentally established by microstructure investigation. Deformation banding model includes such deformation mode when it is applied to rolling texture simulation. The cause for the occurrence of deformation banding is the reduction of the total work for plastic deformation through a relaxation of the deformation constraints. In the first DB model, all grains are assumed to band from the first deformation step. Such an unrealistic assumption has been eliminated in the new model by the introduction of a banding criterion based on an energy minimizing approach. The prediction is closer to the measured texture by applying banding criterion and setting critical resolved shear stresses (CRSS) ratio for { 110 } and { 112 } slip modes to 0.85.IntroductionBased on the continuum theory of plastic flow and deformation mechanism of crystallographic dislocation slip, Taylor's FC ( Full Constrain ) theory [1] has been widely used in texture modeling. As the process of cold rolling of sheet materials produces a microstructure consisting of elongated or equiaxed flat grain or cell, the ""lath"" and ""pancake"" relaxed constraints ( RC ) models [2, 3] were introduced as the successful improvements over the classical FC model. It has been also recognized that crystals may split into different orientations during deformation and the term deformation banding is used to describe such deformation processes [4, 5]. Lee et al. [6, 7] pointed out that the success of the RC theory in predicting textures depends on the physical processes of deformation banding. They developed so called Deformation Banding ( DB ) model by considering DB in the longitudinal plane to be accounted for by the RC method and allowing DB in the rolling plane. DB model was applied to simulate the texture development in bee case [8], the predicted bee rolling textures are in reasonable agreement with the measured textures. In the first DB model, however, all grains are assumed to band right upon the first deformation step. A banding criterion was formulated [7] which states that DB will occur if the work used in DB model is less than that in RC model. Such criterion has been incorporated into the original DB model for texture simulation and is referred to as DBC ( Deformation Banding Criterion ) model."

Jan 1, 1998

By Guangliang Wu, Dongchang Huang, Xinbin Liu

Oxidation Kinetics of SPHC was analyzed by TGA, and the curve of oxidation weight gain with different temperature was acquired. It is found that, when the oxidation temperature is between 500 and 600 , all the curves are linear; when the oxidation temperature is above 700 , the curves are close to parabolic. At the temperature of 900 , the oxidation weight gain increases dramatically. The TGA results indicate that the activation energy of SPHC steel is 146.19 kJ/mol at the temperature of 500 900 , and an oxidation kinetic model was set up for variable temperature. Based on the temperature change during rolling process, numerical simulation of oxide scales evolution was carried out for SPHC steel, and the simulation result agreed well with measured ones. It can provide a basis for estimating the scale growth and controlling the temperature on site.

Jan 1, 2016

By Tsembel Darjaa, Toru H. Okabe, Yoshiaki Umetsu

"With the purpose of extracting molybdenum and rhenium from molybdenum sulfide concentrate; .electrolysis of slurry, solvent extraction and ·precipitation operations were carried out. The slurry of the concentrate in 10 mass% NaCl aqueous solution was continuously circulated into a vertical type 10 stack bipolar electrolytic cell consisted of carbon electrode disks, and, the concentrate was dissolved by electrochemically generated oxidizers at 313 K. The current efficiency for molybdenum dissolution was 73 % after 10 hours electrolysis, and the leach solution was found to contain 0.2 mol/l of molybdenum and 4x10-5 mol/l rhenium. This result shows the dissolution is more than 8 times faster than that obtained using a single cell. The leach solution from electro-oxidation was then subjected to a solvent extraction for rhenium which is then recovered as sulfides. After rhenium separation, molybdenum was precipitated by pH adjustment, and solid MoO3 (H2O)x crystals, free of sulfate, were obtained from the leach solution containing large amount of so42-.IntroductionIn the past, electro-oxidation using a bipolar cell was applied for leaching molybdenite concentrate and ores at U. S. Bureau of Mines [1-3] and also at Bhabha Atomic Research Center [4]. In· these previous studies, Moebious type bipolar cells, in which electrode plates were vertically inserted into the free surface of the electrolyte, were employed and its effectiveness was demonstrated.Recently, the present authors studied on leaching of Mongolian molybdenite concentrate, and the effectiveness of leaching of the concentrate by electro-oxidation in alkaline and acidic NaCl solutions was demonstrated [5]. The leaching reaction during the process can be explained by the 18 electron transfer reaction of molybdenite (MoS2) with the oxidizers produced in-situ by electrolysis of NaCl aqueous solution. Further investigation was made with respect to various process parameters for electrooxidation such as pH, pulp density and temperature of the slurry, and the dissolution behavior of minor elements such as iron, copper, and rhenium [6]. Solubilities of molybdenum in the leach solution at, various temperatures and pH .was · studied, and feasibility of molybdenum recovery by hydrolysis of molybdenum species was demonstrated. By adjusting the pH of the leach solution, molybdenum oxides or hydroxides free from sulfate were successfully obtained from the solution containing large amount of sulfate ion. Rhenium present in the concentrate at a level of several tens of mass ppm was found to dissolve into the leach solution, and co-precipitate with the molybdenum compounds. Rhenium in the leach solutions, therefore, has to be recovered before precipitation of molybdenum, otherwise it is lost in the precipitate."

Jan 1, 2000

By Ludwig Hermann

"Phosphorus is required by every cell of living organisms and essential for plant growth. It is a non-renewable resource that must be mined from natural deposits, going gradually into depletion. Abundant secondary resources are available in sewage sludge and meat and bone meal, with the highest exploitable P concentrations in ashes that remain from their widely used combustion with energy recovery. ASH DEC has successfully removed heavy metals and transformed sewage sludge ash into a marketable P fertilizer by application of a thermo-chemical treatment process. Pilot scale investigations in which ash was treated proved that generally heavy metal limits required by fertilizer legislation can be attained. To achieve a high P availability for crops – an essential fertilizer quality feature – was a more challenging R&D task. Our presentation demonstrates the scientific approach and R&D results that lead from assessment of market requirements to licensed products.IntroductionPhosphorus (P) is required by every cell of living organisms. It is one of the major elements for plant nutrition and therefore essential for crop production. P supply in plant nutrition depends entirely on external inputs into soils [1]. This is achieved by P-fertilizers deriving from rock phosphate deposits that are gradually going into depletion. Serious prognoses anticipate that rock phosphate will be the first low running resource in the world [2]. In the EU, last year 2.530 kt of phosphorus (P2O5 in fertilizers) was consumed and only 313 kt (P2O5 in rock phosphate) was mined. Since 2007, rock phosphate prices have increased by 500% because of a tight supply situation [3].For these reasons, P recycling is becoming an increasingly important issue. Suitable secondary raw materials with regard to their high P-content and abundance are sewage sludge and meat and bone meal. In the EU 989 kt P2O5 are accumulated annually in theses materials, of which 632 kt P2O5 are permanently lost to landfills and other forms of disposal. The main reasons for their limited recycling are concerns on heavy metal contents and organic pollutants that may incite health hazards. As an additional shortcoming, the availability of P from these materials to plants is poor and storage and transportation are problematic issues [4, 5]."

Jan 1, 2008

By Jan Yaozhong

The composition and the possible utilization of Ti bearing blast furnace from a titanomagnetite blast furnace smelter were studied. The slag contained about 20% Ti02 and trace Sc. The mineralogical analysis indicated that Ti in the slag is mainly as perovskite. By means of magnetite separation, the Ti containing phase could not be enriched. An effective hydrometallurgical approach was proposed with sulphuric acid leaching. The method proposed for processing the studied slag renders product Ti02 and SC203. Besides the recovery ofTiO2 and SC2O3&apos; the leaching process yields fine grained residues which can used as additives for making cement.

Jan 1, 1996

By Jorge A. S. Tenorio, Chuanwei Zhuo, Joner O. Alves, Yiannis A. Levendis

"The disposal of wastes is a serious environmental problem, since available landfill space is dwindling. Their treatment by pyrolysis or combustion has merit, and the corresponding fuel or power production is of technological interest. However, such processes need a rigid control of emissions. This work addresses the gaseous light hydrocarbons (LHCs) generated during sequential pyrolysis and partial oxidation of unserviceable tires, PET bottles, com wastes (DDGS) and sugarcane bagasse in a two-stage laminar-flow horizontal furnace, kept at 1000 °C. Gas chromatography was used to identify and quantify the components of the emitted gaseous light hydrocarbons. The results showed that the biomass residues generated the highest emissions of aliphatic hydrocarbons, whereas PET generated the most aromatic hydrocarbons. When stainless steel meshes were inserted in the exhaust flow, it was found that hydrocarbon emissions were curtailed; as such meshes catalyzed partial conversion of these carbon-bearing gases to carbonaceous nanomaterials.IntroductionLight hydrocarbons (LHCs) are volatile organic compounds, consisting of hydrogen and carbon with low molecular weight; the most common species are methane, ethane, propane, butane, etc. LHCs are valuable since they are a very important energy resource. However, uncontrolled release of light hydrocarbon gases to the atmosphere should be avoided [l, 2]. In this work, a development is presented for the evaluation of LHCs generated during the controlled pyrolysis/combustion of several wastes in a two-stage laminar-flow horizontal furnace. Samples of unserviceable tires, post-consumer PET bottles and waste residues from the bioethanol industry (DDGS and sugarcane bagasse) were burned. A catalyst system, consisting of stainless steel screens, was tested for its effects on the gaseous emissions."

Jan 1, 2011

By Shuqiang Guo, Gonghui Yang, Xingxing Zhang, Yuyang Bian, Song Chen, Weizhong Ding, Yinhe Liu, Lan Jiang

One of the most promising refractory materials for application is zirconia in melting superalloy. In this work, the properties and phase composition of magnesia partially stabilized zirconia ceramics (MgO-PSZ) under different sintering temperatures were systematically investigated. Commercial magnesia partially stabilized zirconia (MgO-PSZ) powders were selected as the starting materials. The magnesia partially stabilized zirconia phase composition was measured by X-ray diffraction (XRD), the density of sintered samples was tested by vacuum density instrument, the thermal expansion were obtained by thermal dilatometer from ambient temperature up to 1450°C, and the microstructures of MgO-PSZ were characterised by scanning electron microscope (SEM). The results indicated that the properties of thermal expansion, densification, microstructures and phase composition were significantly affected by sintering temperature. Densification was consistent with SEM micrographs of MgO-PSZ at different sintering temperatures.

Jan 1, 2015

By Lifeng Zhang

Printed circuited boards contain considerable quantities of valuable metal, while also containing many environmental pollutants making them unsuitable for landfill. In this study the decomposition of common plastics used in printed circuit boards were studied. Polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC) and polyethylene (PE) were heated in both C02 and argon atmospheres using a thermo-gravimetric furnace (TG) coupled to a mass spectrometer (MS). Soda ash Na2C03 and baking soda NaHC03 were used as reactants. The degradation temperatures and evolved gases are presented for single plastics and mixtures. Mixed plastics are shown to behave as a sum of the individual plastics. The mass loss temperature is the same in CO2 and argon. However, less residue is formed when heated in CO2.

Jan 1, 2008

By Willy Persson

A common feature of the kinds and amounts of impurities present most pyrometallurgical, processes is injection of oxygen to, remove various in the feed. The degree of success of a specific process step relies critically on control of the instantaneous oxygen potential/oxidation stage, throughout the step as well as upon termination of the step. This will, for instance, determine the distribution of impurities between metal and slag. As long as the operation is perturbation free -detailed analysis of all additions and application of advanced models often yield satisfactory control means However, a pyrometallurgical process is seldom free from disturbances, which reduces the accuracy of the static models and leads to inconsistencies in scheduled route might be uncontrollable changes in quality and quantity of feed, operator interventions and shift changes, timing of cranes, lining wear and accretions etc. The implementation of dynamic, control to correct for disturbances and, more generally for process optimization, requires continuous on-line information on, the actual status of the process. The implementation of sensors for continuous process monitoring, e.g., as regards the instantaneously prevailing oxygen potential or oxidation stage, has been hampered by the highly aggressive environment in smelters; This is. where remote-sensing techniques based on optics and spectroscopy, have proven to form invaluable, tools towards the realization of dynamic production control. Since about 15 years Semtch has developed and industrialized a remote-sensing technology, based on ,optics and spectroscopy, for continuous on-line process monitoring and production control of various pyrometallurgical processes. The presentation will discuss applicability aspects with examples and experiences from installations and tests in ferrous and non-ferrous industry. Keywords: Applied spectroscopy, Metallurgy, Process monitoring, Production. Control

Jan 1, 2003

By Gregory A. Knapp

Treatment of industrial wastewaters generally advances with specific chemical concentration and mass-flow targets, established by National Pollutant Discharge Elimination System (NPDES) permits. Treated discharges must also address toxicity to test and receiving water organisms. Various parameters might need consideration during treatment design and planning, such as the known toxicants, hardness, alkalinity, solids, nutrients, metals in both the dissolved and particulate state, and even flow. Since toxicity is used as a "catch all" regulatory monitoring tool, design of treatment systems should focus on the various factors contributing to toxicity.

Jan 1, 1996