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By M. D. Strachan

Technical & Procurement Services Limited (TECHPRO) in Ashford, Kent, UK, have been appointed as Project Managers for the major rehabilitation of the Copper Smelting complex of Nkana Division, Zambia Consolidated Copper Mines Limited, (ZCCM) Zambia. In outline, the overall scope covers three main areas: a) Transfer and implementation of new technology into Zambia for the production of primary copper. b) Replacement of gas collection and gas treatment circuits to guarantee high quality feed to the acid plants. c) Completion of a number of minor projects in the copper smelter and associated utility plants to complement changes in the primary smelting technique. This paper describes the Project Management methodology and style used by TECHPRO to tackle typical problems that arise in retrofit projects of this type. Reference is made specific aspects of the smelter projects to illustrate solutions to the problems. The subjects. addressed highlight the complexities not only of having a -Client 5,000 miles from the Project Office, but also the difficulty of co-ordinating and controlling the performance of min sub-contractors who are also geographically distant.

Jan 1, 1991

By M. I. Kalashnikova

Gipronickel Institute has developed the technology of treatment of difficult to concentrate sulphide Pb-Zn concentrates (Zn-19,9%, Pb-8,4%, Cu-0,34%, Fe-8,8%, Ba-6,8%, S-18,7%, Ag-106 g/tonne). The technology consists of pressure leaching, impurity removal from leaching solution, electrowinning and Pb-Ag containing cake treatment. Despite low zinc content in initial concen-trate the technology allows production of solution which is suitable, after standard procedure of impurity removal, for electrowinning with production of zinc grade SHG. Comparing to the standard technologies the flowsheet developed provides the lesser expenses per zinc unit because of decreasing of liquid to solid ratio at pressure leaching stage. The initial concentrate is characterized along with low content of principal metals by high con-tent of barite, which makes flotation of pressure leaching residue more difficult. That is why in this case the hydrometallurgical treatment was chosen. At optimal parameters of chloride leach-ing found during laboratory experiments the principal components extraction was 99.5% for Pb and up to 92% for Ag.

Jan 1, 2006

By Yang Tian-zu

The separation of precious metals from base metals containing in gold-antimony alloys by selective chlorination leaching under controlling potential was studied in this work. The effects of the consumption of hydrogen peroxide, the concentration of hydrochloric acid, the concentration of sulfuric acid, leaching temperature, leaching time and the liquid-solid ratio in hydrochloric acid system on the leaching efficiencies of the base metals have been investigated. The optimal leaching conditions of the gold-antimony alloys are as follows: hydrochloric acid concentration 4.0mol?L-1, sulfuric acid concentration 1.2mol?L-1, liquid-solid ratio L:S=7.5:1, the leaching temperature 80 0C, leaching time 2h, and the oxidation potential of the leaching system 400±20mV( vs SCE).The leaching efficiencies of copper, nickel and antimony are more than 99% and the gold leaching efficiency is about 0.042% under the above leaching conditions. The base metals containing in the gold-antimony alloy are separated from the precious metals thoroughly.

Jan 1, 2006

By Yuanyuan Wang, Hong Li, Xueting Liu, Hao Bai, Kang Zhou

"Phase change materials are widely used in efficient utilization of energy and new energy technology. Especially, more attention has been paid to composite phase material, which is applied on architectural energy-saving and efficient working fluid. In this paper, stearic acid-silicon dioxide composite material was prepared by sol-gel process from tetraethyl orthosilicate (TEOS) and stearic acid (SA). The material was investigated by Field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) and Differential scanning calorimeter (DSC). The FE-SEM results show that 3D-grids of silicon dioxide were formed clearly and SA was encapsulated in the silicon dioxide shell. The FT-IR results show that there were no chemical reactions between silicon dioxide and SA, which is the chemical property of the composite material, is stable. The DSC results show that the composite phase change material has favorable heat capacity. This material is expected to be used to make a cooling working fluid.1. IntroductionEnergy thermal storage becomes increasingly prominent issue in recent years, because thermal storage has been used in many aspects, for example, it can be added into building materials to improve heat conditioning. Another potential application of thermal storage materials is that the intermittent waste heat can be collected and recycled effectively by using the thermal storage facility. Thus, energy thermal storage plays a significant role in conserving available energy and improving its utilization [1]. Energy thermal storage includes sensible heat storage and latent heat storage. The latent heat storage has great heat density with a constant temperature during the phase change process [2-5]. Large quantities of latent heat storage will be absorbed and released when phase change takes place. Based on the former researches, some phase change material (PCM), such as fatty acid and paraffin waxes, has been proved to have high latent heat storage capacity and appropriate thermal properties [5-6]. However, using the PCM in energy storage systems directly is restricted, e.g. some properties of organic PCM, like form-stability and thermal conductivity, are not good enough to use. Meanwhile, almost all the inorganic PCMs are corrosive and most materials may cause sub cooling and segregation [7-9].The other problem is that the leakage when the temperature reaches the phase change point. Therefore, encapsulated composite phase change material (CPCM) emerged in order to solve the problem of leaking out, minimize the sub cooling and prevent phase segregation. [10-13] However, the easy flammability of fatty acid also has hindered the development of PCM. Accordingly, it has been found out that silicon compounds are environmentally friendly promising substitutes for halogen-containing flame retardants. Especially, silsesquioxanes are excellent in the flame retardancy. So CPCM can be encapsulated with SiO2 acting supporting material."

Jan 1, 2014

By Norihiko Fukatsu, Takashi Iwamoto, Noriaki Kurita, Koji Katahira, Kunihiro Koide, Teruo Ohashi

"The galvanic cell-type hydrogen sensor employing CaZro.9Ino.t03-a. as the solid electrolyte was designed for the measurement of hydrogen activities in molten copper under industrial .conditions. The sensor probe consists of the cap-shaped solid electrolyte with porous platinum electrode on the inside and alumina refractory tube. The gas mixture of the composition 4%H2-0.5%02-Ar was made to flow on the inside electrode. The hydrogen sensor probe was inserted directly into molten copper and the melt was used as the outer electrode. The effect of oxygen activity gradient to EMF was eliminated theoretically by measuring the oxygen activity in the melt simultaneously with an oxygen sensor. The high stability of output and excellent response to the change of hydrogen activity were obtained over the wide range of industrial copper melting conditions.IntroductionIn the metal casting process, hydrogen easily dissolves in molten metals from water vapor in the surrounding atmosphere. Owing to the large difference in hydrogen solubility between liquid and solid metal, dissolved hydrogen becomes a cause of the defects of blowholes in castings or ingots. It is necessary to control the hydrogen content in the molten metals [l]. Using proton-conducting ceramics as a solid electrolyte, high temperature-type hydrogen sensor can be constructed [2]. SrCe03- and BaCe03-based perovskite-type oxides exhibit appreciable proton conduction under hydrogen containing atmosphere at high temperature [3-5]. A hydrogen sensor for molten aluminum using CaZro.91no.103-a. has been developed and widely used in the ·process control in the aluminum melting industry [6,7]. The same type of hydrogen sensor has also been expected in the copper melting industry. .. However, CaZro.91no.103-a shows ·not only proton but also oxide ion conduction in the high temperature and at low oxygen activies like the copper melting· conditions. Then we studied the oxide ion conduction in CaZro.91no.103-a. iit · detail [8]. From the consideration on the EMF of the galvanic cell employing this material as electrolyte, it was shown that the unknown hydrogen activity may be precisely determined from cell potential which is corrected for the effect of oxygen potential gradient And the hydrogen sensor based in this principle was constructed and tested in laboratory-scale [9,10]. We repeated the similar tests in factory-scale and developed the sensor system for practical uses [11, 12]. In this report, the structure and system of the hydrogen sensor for molten copper will be introduced first. The reliability of the sensor will then be demonstrated from the results of experiments for sensor probes carried out in TYK's laboratory."

Jan 1, 2000

By Duck Jae Lee, Kwan Ho Kim, Ji Whan Ahn

"In Korea, reutilization of constructions waste is gaining an increasing attention as generation of construction waste is projected to increase continuously. In current practices, the concrete waste is simply crushed and used as a low application such as paving, back filling, etc. In this study, a new process was developed comprising of heat pretreatment, autogenous milling, and density separation for complete reutilization of concrete waste. Firstly, the concrete waste was crushed using autogenous milling. The coarse size fractions from autogenous milling have a density of 2.5g/cm3 and a water absorption ration 3.0%, which meet the specification of the first class of KS F 2573. The fine size fractions were further separated using a hindered-settling column into two products 1) underflow, 2) overflow. The underflow sample was a high quality fine recycled aggregate which can be used for concrete making, and the overflow sample was an enriched cement material can be also used for CO2 sequestration by mineral carbonation. Introduction Kwan Ho Kim1, Ji Whan Ahn2, Duck Jae Lee1, Hee Chan Cho1 Recently, the importance of resource recycling is gaining a greater attention due to the increasing price of natural resource. Recycling is beneficial for not only the management of waste, but also the reducing of consumption of natural resources and huge energy consumption to treat of natural resource. The construction and demolition waste comprises the major industrial waste generated in Korea. It increased to 54 million tons in 2004, and is projected to increase to over 300 million tons in 2020, as many buildings reach the end of their 30 years life. Among total waste, the proportion of concrete waste was about 30% in Korea. Due to its large volume, recycling of concrete waste is the most important aspect of the waste management. In the current practices, the concrete waste is simply crushed and used as a recycled aggregate. The recycled aggregate has a low quality and most of them are down cycled for usage as paving material, back-filling material, concrete bricks, etc. It cannot be reused for replacement of natural aggregates because cement mortar is not separated perfectly from aggregates. These kinds of recycled aggregates tent to be weaker, more porous and have a higher value of water absorption. When these aggregates are used in concrete making, there are problems of higher total water demand, low compressive strength and durability [1-5]. And recycled fine aggregate is not almost recycled due to its low quality. In this study, a new processing circuit is developed to produce not only highquality recycled coarse aggregates but also fine aggregates and cement material from concrete waste."

Jan 1, 2008

By Olga K. Karakasi, Angeliki Moutsatsou, Ioanna Kavallari

"The present study focuses on the amelioration of the behaviour of high calcium fly ash (HCFA), investigating its application in a new environmental field: oil spill clean up. High calcium fly ash is a by-product of electric power plants, produced annually in large quantities, whose greater amount is landfilled. Some of its properties, such as its chemical and mineralogical composition, its fine particle size, its porosity, floating ability and hydrophobic character make it an attractive material for this purpose. Researches showed that when added to an oil spill, it forms a semi-solid phase, which allows the quite total removal of the oil, but it is not stably retained on the surface. In order to ameliorate its floating ability, the decrease in its specific gravity by mixing with a lighter material is investigated. In the present study the mixing with two materials, already used in oil spill clean up, sawdust and a polymer, has been examined. Addition of 15-25% w/w sawdust to HCFA results in a material with better performance than HCFA or sawdust alone: it has a satisfactory floating ability and allows total removal of oil. Addition of the polymer, however, has resulted in no significant amelioration of the oil sorption behaviour of HCFA, probably because no affinity between HCFA and polymer has been achieved.IntroductionCoal fly ash is a by-product of coal combustion in electric power plants, produced worldwide in huge quantities, approximately 500 million tones annually. High calcium fly ash (HCFA) is classified to class C presenting a (Al2O3 + SiO2 + Fe2O3) > 50%. The production of lignite fly ash in Greece comes up to 13 million tones annually, of which only 12% is used in construction applications, the other being landfilled [5, 6].Besides its limited application worldwide as a construction material, research is focusing on the development of new environmental applications, such as waste stabilisation and solidification, soil and water environmental improvement [9, 12]. For the application of fly ash in further environmental fields several chemical modifications have been applied, in order to improve its properties. Extensive research has been focused on the conversion of both coal and lignite fly ash to zeolite and its further application in environmental field, such as the uptake of inorganic (heavy metals and ammonium [8, 11]) or even organic compounds (methylene blue [15]) from waste water streams, or the use as molecular sieves, to adsorb water molecules, SO2 and NH3 from gas streams, due to the high cation exchange capacity and porosity of the produced zeolithic material. Furthermore, lignite fly ash has been combined with sodium silicate solution, prepared by treatment of rice husk ash, and tetrapropylammonium bromide, to synthesise hydrophobic zeolite ZSM-5 [4]."

Jan 1, 2008

By Jamil M. Khalifeh, Shadia J. Ikhmayies, Bothina A. Hamad

"The structural and electronic properties of cubic d -NbN are investigated using density functional theory (DFT) and all-electron full potential linearized augmented plane wave method (FPLAPW). The equilibrium structural parameters are determined by fitting the total energy as a function of volume to the Murnaghan's equation of state. We calculated the total and partial densities of states (DOS) and compared them with those computed by different authors. Our DOS at Fermi level is found to be very close to the experimental value. The band structure is computed, discussed and used to find the characteristic energy separations. Valence electron density contours are recorded and discussed. We deduced the partial charge densities of different bands and binding energies of valence core levels and compared them with experimental and theoretical results obtained by different authors.IntroductionNiobium nitride has been intensively investigated over the last decades because of its interesting physical properties and technological applications (superconducting microdevices, microelectronic, catalytic probes, and hard coatings) [l]. While the group IV transition metal nitrides (TMN) mainly crystallize in the cubic NaCl structure (Bl type), those of group V and VI nitrides occur as different phases. Thus for niobium nitride, many phases have been reported in the literature: cubic fcc d -NbN, tetragonal ? -Nb4N3, hexagonal d -NbN, hexagonal e -NbN, and low nitrogen content hexagonal ß -Nb2N [l, 2].Structural and electronic properties of niobium nitride were investigated theoretically and experimentally by many authors. For example, in 1975 Schwarz [3] obtained the partial density of states for NbC and NbN from APW band structure calculations. In 1975 Kallne and Pessa [4] studied the electronic structure of Nb, NbC and NbN by using X-ray emission. In 2003 Amriou et al. [5] studied the electronic structure and bonding mechanism of NbC and NbN compounds using first principle total energy calculations using the full-potential linearized augmented plane wave method. Also in 2006 Sanjines et. al [l] studied the electronic structure of the hexagonal~Nb2N, hexagonal' d -NbN, and cubic d -NbN thin fihns by using X-ray photoemission spectroscopy. They [l] also calculated the densities of states for these phases and used them in the interpretation of the experimental valance band spectra. Most of these studies are old and there is a need for more recent studies. According to our knowledge, there are little comprehensive theoretical studies on this subject by using FP-LAPW method [5], which proved its ability to give accurate results. In this work we used the FP-LAPW method to study the structural and electronic properties of the cubic (fee) o-NbN (space group Fm-3m, prototype NaCl) crystal."

Jan 1, 2013

By F. G. Caballero, J. L. Gonzalez-Carrasco, S. Barrius, H. Carreon, M. Lieblich

"The grit blasting is a low-cost technique successfully used to enhance mechanical fixation of the implants through increasing their roughness. As a result of the severe plastic surface deformation, it produces subsurface effects such as grain refinement, hardening and compressive residual stresses which are generally evaluated with destructive techniques. In this research work, non-contacting and contacting thermoelectric power measurements are performed in blasted 316L VM and Ti-6AI-4V specimens using Ah03 and Zr02 particles which yield a coarse and a fine rough surface, respectively. This study correlates the microstructural changes induced by the grit blasting treatment and the limitations and advantages of each of the nondestructive thermoelectric techniques based on the Seebeck effect used to evaluate these biomaterials.IntroductionIt is well known that surface properties play an important role in metallic materials used in bio-medical applications. Since the biological response is correlated directly with surface properties it is comprehensible the intense activity in superficial modification by physics or chemistry methods in this field. Grit blasting, one of the most popular surface modification of metallic biomaterials, enhances the mechanical fixation of the implant through the increase in roughness [1-3]. Roughening is developed by bombarding the surface with a high-velocity jet of ceramic particles, being the final roughness a function of the processing parameters (pressure, distance, time, ... ) and blasting particles (nature, shape, size). As the plastically deformed surface layer tries to expand relatively to the intact interior of the specimen, residual compressive stress gradients develops perpendicular to the surface at shallow depths with a maximum value at a depth in the range of 5 to 60 µm. This surface treatment also may cause subtle variations in the subsurface material properties, such as increased hardness and grain size refinement, which are consequences of the significant plastic deformation through cold work. Blasted affected zones may extend to a depth of up to about 200 µm. The subsurface hardening and the near-surface compressive stress gradient playa beneficial role by retarding fatigue crack nucleation and further growth, ultimately extending the fatigue life of the metallic part [4]. In this work, two non-destructive thermoelectric techniques (NDTT), the non-contacting and contacting thermoelectric power measurements were used to analyze the subsurface induced changes on blasted Ti-6AI-4V and 316L VM specimens using Al2O3 and Zr02 particles. Detailed information on the microstructural induced effects and subsurface mechanical properties were published elsewhere [5-8]. Here the nondestructive evaluation of the involved microstructural changes is used to assess the global subsurface damage. Advantages of using nondestructive techniques during manufacturing are envisaged."

Jan 1, 2012

By Shadia J. Ikhmayies

"Cadmium telluride (CdTe) is a very interesting material that has many applications. Thin films of p-type CdTe can be used as the absorber layer in the heterojunction CdS/CdTe thin film solar cells in which n-type cadmium sulfide (CdS) works as the window layer. A review of the photoluminescence (PL) spectra ofp-type CdTe thin films prepared by different techniques was performed. The presence of defects and impurities such as oxygen and chlorine influence the PL spectrum. Copper and other dopants change the PL spectra and enhance the defects band. Chemical-heat treatment especially with CdCh is known to improve the quality of CdTe thin films because it decreases the Cd vacancies and quenches deep traps, so it enhances the PL signal. A discussion of chemical-heat treatment especially with CdCh, the effect of the ambient atmosphere, and that of the measuring temperature is performed.IntroductionCadmium telluride (CdTe) is a II-VI compound semiconductor that has a cubic zincblende (sphalerite) structure with a lattice constant of 0 A4~11]. Other than all of II -VI semiconductors, CdTe can be made both n- and p-type. But due to self compensation it is not easy to get p-type CdTe films [2]. Polycrystalline CdTe thin films are interesting because they have a lot of applications. Most of the problems associated with the use of these films are attributed to inhomogeneity, self-compensation, and the difficulty of forming a stable and lowresistivity ohmic contact [3]. CdTe technology has been established for a large number of applications, including solar cells, optical and nuclear detectors, and thermal- and radiationimaging devices [3]. At present, the highest demonstrated conversion efficiency for a CdTe based heterojunction (ID), with CdS as a window layer, is 16.5% [4, 5]. CdTe thin films can be prepared by different experimental techniques, such as thermal evaporation [l], electrochemical deposition (ED) [3], close-spaced sublimation (CSS) [3, 4, 6], physical vapor deposition (PVD) [3], chemical molecular beam deposition (CMBD) [7], and close space vapor transport (CSVT) [8].The objective of this paper is to make a review of the photoluminescence (PL) spectra ofp-type CdTe thin films prepared by different techniques and discuss the factors that influence the PL spectra. The composition of the film is very interesting in determining its PL spectrum. Different kinds of defects, impurities and dopants have their finger prints in the PL spectrum. Deposition techniques and deposition parameters such as the deposition temperature and ambient atmosphere also have their influence. Heat and chemical treatments which are known to improve crystallization and reduce the defects change the PL spectrum."

Jan 1, 2013

By Xinghua He, Shujing Zhu

"Cycled fluidized bed ash (CFBA), a significant portion of fly ash produced from coal-fired power plants and rejected from the ash classifying process, has remained unused due to its high free CaO and S03 content. It is necessary to extend research on the method to reduce the expansion and improve the compressive strength by some effective chemical activator. This paper presents experimental results on the expansion by Le chaterlier tester and the compressive strength. Hydraulic ash-zeolite (HAZ) cementitious material was blended as the chemical activator to study the effects of the activator on the expansion and the compressive strength. The results show that HAZ can not only reduce the expansion, but also increase the prisms compressive strength. Scanning electron microscope observation and X-ray diffraction analysis indicate that the main hydrated products of the sample are calcium hydroxide, ettringite, zeolite and calcite, which can explain the results of the expansion and the strength tests.IntroductionNearly 80% of the electricity in China is produced by coal-fired plants, which results in the production of a large quantity of coal combustion residues, among which coal fly ash is the major component. Because of that the air-pollution becomes heavier as time going on. Cycle-fluidized-bed-combustion systems are retrofitted to meet air-emission standards mandated by China Clean Air Act. Cycle fluidized bed ash (CFBA) will present new challenges for coal-combustion byproduct management. The use of cycle-fluidized-bed ash as a cement replacement in concrete is the most attractive one because of its high volume utilization and widespread construction. However, the replacement of cement with cycle fluidized bed ash in Portland cement concrete usually increases the expansion and decreases the early strength of concrete. In many research of this field, most of them were focus on the activation of pozzolanic activity of CFBA and to make all kinds of blend cement. A number of studies had been carried out on the activation of CFBA using chemical activators. These studies involved using different activating methods including alkali activation and sulfate activation 11, 2]. The former involved the breaking down of the glass phases in an elevated alkaline environment to accelerate the reaction [3, 4]. The later is based on the ability of sulfates to react with aluminum oxide in the glass phase of CFBA to produce ettringite that contributes to the strength at early ages [5-7]. With respect to sulfate activation, the use of gypsum and sodium sulfate had been well studied [5-8]. HAZ is one of HAS sub-products which is a patentd chemical activator made by Wuhan University (ZL98113594.3). It had been used to activate CFBA to produce blend cement in many Chinese engineering projects and time has told us that it is a good activator."

Jan 1, 2012

By Guozhu Ye, Mikael Larsson, Eric Burström, Sten Ångström

"Increased use of scrap in steelmaking including scrap use in BOF has a high economic and environmental potential in terms of increased productivity, energy saving and reduced emission of CO2. Preheating and surface cleaning of steel scrap is a concept developed by MEFOS in a four year research program funded by MISTRA, Swedish Foundation of Strategic Environmental Research. The process concept consists of four major steps: 1) Combustion of ASR or other waste fuel and composing of the gas composition. 2) Scrap heating and cleaning in a shaft where the coated zinc is removed as ZnCl2 and scrap is heated to about 600 ºC. 3) Dust separation for recovery of metal zinc. 4) Gas cleaning. This paper will describe the process concept and highlight the major results from preliminary trials around the scrap heating and cleaning shaft.IntroductionSteel is often coated to increase the corrosion resistance. Share of coated and galvanized steel in the world marked is steadily increasing. This results in increased amounts of scrap with different types of coatings. Use of galvanized scrap in EAF plant results in an EAF dust with high content of zinc ferrite and many other impurities like Pb, Hg, Cd and halide. EAF dust is classified as hazardous waste in most of the developed countries and the steel plant has to pay for external treatment for zinc recovery. For use in BOF plant this will result in a BOF dust containing typically 1-5%Zn making it impossible for recycling to the blast furnace.Different approaches for surface cleaning have been investigated in past. Dapper et al. [1] examined the possibility to evaporate Zn, Ni, Cr, Sn from coated materials using chlorine. Chlorinated rinsing of non iron oxides and metals using HCl from combustion of PVC was discussed by Fray [2]. Further studies by Tee and Fray [3-5] have been concentrated on the possibility to vaporize coatings with an air and chlorine gas mixture. The O2:Cl2 ratio in the gas mixture was found to have great importance for control of the process. To avoid the chlorination of iron, this ratio should be kept at a level of 10:1.Scrap pre-heating up to about 600 ºC is a well known method and this alone could save up to 100 kWh per ton steel. The technology has been established since many years and efficient processes were developed in the 90’s. However, no process has fully gained the expected energy savings as the large quantity of the exhaust gas has to be reheated to over 1000 ºC again to destroy the hazardous components like dioxins."

Jan 1, 2008

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 Aichun Dou

Au-Sb alloy sample in which the total amount of Cu and Ni is below 25% (wt. %). In practice, Cu and Ni were difficult to be dissolved in sulphuric acid solution by oxidative leaching under the atmospheric pressure conditions, because of the lower concentration of Cu and Ni in the sample. In this paper, pressure oxidation leaching in sulphuric acid system (POLS) followed by hydrochloric acid leaching (HAL) was employed to remove impurities in the Au-Sb alloy. The effects of variables in POLS on leaching ratios of different metals were investigated in detail. Under the optimal conditions: the concentration of H2SO4 is 1.5 mol/L, liquid-solid ratio is 7:1, the amount of oxidizer is 1.2 times of the theoretical amount, leaching time is 4h and leaching temperature is 427K, the leaching ratios of copper and nickel reached up to 99%, antimony, lead and silver were not dissolved in dilute sulphuric acid solution. The residue from POLS was then treated with hydrochloric acid solution in fixed conditions, the leaching ratio of antimony reached over 92%, the grade of gold in the ultima residue was enriched up to 66%.

Jan 1, 2016

By C. Lupi

Electric arc furnace dust generated during the production of steels is regarded as hazardous waste because of the presence of leachable elements such as Cr, Pb, Cd .... Different processes are available according to the management policy chosen by the steelmaker: disposal. recycle and/or recovery. The feasibility of an hydrometallurgical Zn recovery process on fumes generated during the pyrometallurgical treatment of EAF dust has been investigated. The recovery of metallic iron, chromium and nickel as molten metal provides fumes very rich in zinc oxide ( 63.1% ) and poor in zinc ferrite. This secondary dust is still an hazardous waste and represents the raw material for the recovery of Zn and Pb. The waste material is first leached in 1.5 M sulphuric acid at 30°C to provide a Zn, Fe and Mn rich aqueous solution and a Pb and Ca sulphate rich sludge. The iron is eliminated by precipitation because is harmful to the following electrowinning process. The ftltered and purified leached solution is acidified in order to obtain good electrowinning conditions. A pure cathodic deposit of zinc is then produced in an electrolytic cell at laboratory scale.

Jan 1, 1996

By Michel G. Drouet

Dross, a major by-product of all processes involving molten aluminum, forms at the surface of the molten metal as the latter reacts with the furnace atmosphere. It generally represents 1 to 5 wt% of the melt, depending on the process, and contains on average about 50% free aluminum dispersed in an oxide layer. Since aluminum production is highly energy-intensive, dross recycling is very attractive from both the energy and the economic standpoints. The conventional recycling process using salt rotary furnaces is thermally inefficient and environmentally non-acceptable because of the production of salt slags. Hydro-Quebec has developed and patented a new salt-free technology using a rotary furnace heated by an electric arc between two graphite electrodes, called DROSCAR®. A 600-kW pilot plant in operation at LTEE is in use to demonstrate the process. This process provides aluminum recovery rates over 90%, using a highly energy efficient, environmentally sound production method. In 1994, 400 tonnes of aluminum dross were treated in this facility and several tests on various types of dross have also been conducted in early 1995. A report on the results will be presented.

Jan 1, 1995

By Mikiya Tanaka

Keywords: Solvent extraction, nickel, electroless plating, accelerating effect With the increasing importance of electroless nickel plating technology in many fields such as the electronic and automobile industries, the treatment of spent baths is becoming a serious problem. Although the spent baths are currently treated by a conventional precipitation method, a method with no sludge generation is desired. Previously, we proposed the solvent extraction recovery of nickel from the spent baths by means of solvent extraction using LIX84I as the extractant. However, a problem of this method was that the extraction and stripping of nickel were not fast enough to achieve high efficiencies when the continuous extractor was used. We have overcome this difficulty by finding that the addition of an acidic organophosphorous reagent in small amount into the organic phase markedly promotes the extraction and stripping rates of the nickel. Shaking-out tests using a separatory funnel at 240 spm revealed that the time to reach the equilibria is more than 60 min with only 20 vol% LIX84I, but is reduced to 10 min and 2.5 min by adding 2 vol% DP8R, respectively, during the extraction and the stripping with sulfuric acid.

Jan 1, 2004

By T. Ranki-Kilpinen

In the flash smelting technique, developed by Outokumpu Oyj, off-gases with dust load are directed into the heat recovery boiler (HRB). As the temperature decreases, metallic sulphates become thermodynamically stable. Sulphation of oxidic particles initiates. The release of heat causes an increase in particle temperatures, and soft sulphated particles can stick to the heat transfer surfaces. Dust accretion may form and cause operational problems. The objectives of the project are to study sulphation reaction mechanisms and kinetics of flue- dust particles under HRB conditions, and get more information for the flue-dust treatment possibilities. The sulphation behaviour of synthetic Cu2O particles (37-53 pm) was studied using a fluid-bed reactor of laboratory scale. The experimental parameters in the latest campaign were oxygen and sulphur dioxide contents of 2.5-10 vol-% 02 and 40-60 vol-% SO2 respectively and temperatures of 600-660°C. Samples were examined microscopically (SEM+EDS) and chemical analysis were conducted. The sulphation rate was found to have a maximum at the certain temperature, which was dependent on the gas SO2 content. Regardless of the level of SO2, a rise in oxygen content promoted sulphate formation.

Jan 1, 2002

By Wenying Liu

The effect of aeration on chalcocite heap leaching was studied by analyzing the historical data from two chalcocite heap leach pads located in Chile, one with aeration and the other without aeration. The data showed that the copper leaching kinetics of the aerated heap was greater than that of the unaerated heap within a certain leaching period, after which there was no effect of aeration on the copper leaching kinetics. The total acid consumption per ton of ore processed was higher in the case of aeration, which was supported by the higher pH of the PLS. But the net acid consumption per ton of copper produced was the same in the two cases. Approximately 5% of the total iron added to the unaerated heap was precipitated inside the heap. In contrast, there was no net iron precipitation or generation inside the aerated heap. Bacteria activities were thought to occur even in the unaerated heap, but the extent was much less than in the aerated heap. Given the importance of forced aeration in chalcocite heap bioleaching, mathematical modelling will be applied in the future work to assist the optimization of the aeration system design.

By B. J. Jody

This paper describes a one-step thennal-treatment process, developed at Argonne National Laboratory, to remove all organic contaminants from the glass-fiber waste that is generated during the glass-fonning process. The recovcred glass fibers can then be recycled into new glass fibers or new glass products without adversely impacting the operations of the glass industry or the quality of its products. Our process involves shredding the waste to a manageable size and then processing it at temperatures below its melting point to remove the polymeric-coating layer. The glass industry generates more than 60,000 tons of glass-manufacturing waste annually in the glass-forming process alone. Recycling of this waste stream can keep this non-biodegradable waste out of the landfills. In addition, use of recycled glass lowers energy costs, by an average of about $5 per ton as compared to using virgin raw materials to make virgin glass fibers. This process will also reduce the emission of C02 by 17,400 tons a year and it will also reduce the emission of nitrogen oxides. Economic analysis of our process shows a potential payback of less than 2 years.

Jan 1, 2003