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By Manoj Kumar, Vinay Kumar, Nikhil Dhawan, Manish Wadhwa

"Electronic waste (e-waste) is a collective name given to discarded electronic devices such as Television, Cellular Phones and Personal Computers. Among the heterogeneous metals present in the e-waste are the base metals: copper, aluminium, nickel, tin, zinc, iron and precious metals: gold, silver, palladium, platinum apart from several hazardous and halogens metals. Hence there is a need to recover these metals from electronic scrap by recycling and then re-use, which can meet large amount of metals demand. Hydrometallurgical processing was employed for the recovery of metals from television printed circuit board (TV PCB). Different lixiviants such as hydrochloric acid, Sulphuric acid, and nitric acid were used to understand the dissolution behavior of copper, iron and lead present in the TV PCB. Effect of increasing concentration of nitric acid was also studied. Selective recovery of tin over 95% in the form of tin oxide was precipitated. The precipitated tin oxide was identified by X-ray diffraction technique. Tin oxide of purity more than 99.9% was obtained.IntroductionThe electrical and electronic industries comprising computers, television, mobiles, etc, which are manufactured utilizing printed circuit, boards, capacitors, resistance, soldering material etc. During production, at the end-of service life and degradation due to the advanced version with latest features generate valuable metallic and non-metallic constituents. European Union Council on waste electrical and electronic equipment (WEEE) has classified these into different categories as listed in Table 1 [Streicher-Porte et al., 2005]. Among these the information technology, telecommunications and consumer equipment constitute electronic waste (e-waste) [EC, 2002]. Almost all e-waste consists of an integrated part of printed circuit boards which is a valuable source of several metals such as copper, tin, lead, aluminium, iron, silver, gold, platinum etc. [Relay et al., 1990]."

Jan 1, 2008

By Fathi Habashi

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

Jan 1, 1999

By Derek J. Fray

Electric arc furnace dusts, especially those containing zinc ferrite, are notoriously difficult to process to give valuable products and non-toxic residues. The ideal process would remove and recover the toxic non-ferrous metals as pure metals, of commercial value, and non-toxic residue which can be used as a raw material in the steel industry. From an examination of the thermodynamics of the oxides and chlorides of the various elements in the dust, it is apparent that the chlorides of the toxic non-ferrous elements are more stable than the oxides while the reverse applies to the ferrous elements. This offers the opportunity for a complete separation of the zinc, lead and cadmium from the iron oxide. Results are presented for the chlorination of electric arc furnace dusts under oxidising conditions and the subsequent treatment of the chlorides to recover the pure metals and chlorine which can be recycled back to the reactor.

Jan 1, 1994

By J. L. Jambor

Sulfide-rich tailings accumulated in a 4l-hectare impoundment at the Waite Amulet minesite near Noranda, Quebec, have undergone partial oxidation and destruction of the principal sulfides (pyrite and pyrrhotite) in the vadose zone. Mineralogical studies and whole-rock chemical analyses of 18 samples from 3 boreholes along a cross-section of the tailings pile indicate that the principal chemical manifestations of the alteration are a pronounced depletion in sulfide-sulfur, and an enrichment in total Fe as Fe203' Other elements such as Al, Mn, Mg, Ca, Na, and K in the solids show erratic or inconsistent variations, but a trend to Si enrichment in the oxidation zone is clear. The trend is interpreted to be a relative enrichment whereby the proportion of the stable silicate minerals has increased as a consequence of the consumption of pyrite and pyrrhotite in the oxide zone.

Jan 1, 1989

By J. T. I. Poijärvi

Outokumpu Harjavalta Metals Oy operates copper and nickel smelters, three sulphuric acid plants and nickel refinery at Harjavalta and copper refinery and precious metal plant at Pori. The by-products of these plants are presented in this paper. The by-products of the smelters include products from slag cleaning of flash smelting furnaces and converters, flue dusts and smelter off-gases. Weak acid and sludges from cleaning of smelter off-gases and acids are the by-products of the acid plants. The by-products out of the copper refinery are crystallized metal sulphates and sludges from electrolyte purification, on which a co-production process of the copper tankhouse is based. The main by-products of the precious metals plant are products from anode slime treatment and platinum metal group concentrates in the recovery of precious metals. Sludges from nickel matte leaching and precipitates from solution purification are the by-products of the nickel refinery. The formation, treatment and processing as well as the research work done for the utilization instead of dumping of the by-products in the production of copper and nickel will also be discussed in this paper.

Jan 1, 1995

By Cong Wang, Siyang Long, Pengcheng Zhang, Haibin Zuo

The present study describes central segregation of the High-carbon steel billets of 150mm square and its heredity to the following hot-rolled wire rods, whose sizes are 10mm and 6.5mm in diameter separately. The relationship between center segregation of the billets and solute element distribution of rods, the mechanical properties and microstructure of rods were studied experimentally. The results show that segregation index of C is higher than that of Mn. With the increase of central segregation, the stability of the mechanical property of the rods becomes worse. The formation of carbide network and central martensite in the rolled products can be attributed to the heredity of the as-cast central segregation. The 6.5mm-diameter-rod has higher tensile strength than that of 10mm diameter which might be due to bigger reduction ratio. Thermo Mechanical Control Process (TMCP) should be used together with Billet Centersegregation- controlling (BCSC) to improve the overall properties of rolled products effectively.

Jan 1, 2016

By C. J. Newman

In January 1999, a redesign of the Kennecott Flash Converting furnace settler was initiated to enhance furnace integrity and extend furnace life. This furnace uses Kennecott-Outokumpu Flash Converting technology to produce copper directly from copper matte. A detailed assessment was made of all technology available around the world before making a decision on the design features to be incorporated in the new design. The new design includes the following: redesign of all sidewall cooling elements to include the latest cooling element technology; redesign of the furnace hearth to include a stadium hearth at the reaction shaft end of the furnace; redesign of the furnace hearth to include a stepped hearth design adjacent to the furnace sidewalls; addition of flat settler roof cooling elements .around the reaction shaft; replacement of reaction shaft transition elements with an improved design and improvements to the furnace cooling element monitoring systems. The Flash Converting furnace was shut down on a planned basis in July 2001 to implement these improvements after 29 months of operation, converting more than 1,000,000 tonnes of matte. During the 30 day shut down, the improvements were successfully completed, with furnace start up in August 2001

Jan 1, 2002

By R. Shimpo

Equilibrium calculations by a computer may sometimes fail in giving solutions when the system includes a large number of components and more than three phases, and especially when no definite information about stable phases is given. An improved method of calculation is presented in which the number of phases need not to be initially fixed, phases can appear or disappear in the course of' calculation and a new method is combined with the Newton-Raphson method to obtain solutions easily. The improved method is applied to the copper smelting operation and all the successive stages of the operation are successfully simulated.

Jan 1, 1983

By Jean P. Murray

The extractive metallurgical industry is a major consumer of high-temperature process heat. It is, consequently, a major contributor of C02 emissions and other greenhouse gases derived from the combustion of fossil fuels for heat and electricity generation, or from the process itself. These emissions can be substantially reduced by replacing fossil fuels with solar energy as the source of process heat. Concentrated solar radiation can supply a large amount of thermal energy to endothermic reactions at temperatures exceeding 2000 K. Another potential for C02 emission reduction exists as well. Thermodynamically, the total amount of energy required for metal production at any given temperature is the enthalpy change of the reaction, AH. Of this total, an amount equal to the Gibbs free energy AG must be supplied as high quality energy in the form of electrical work or by using a reducing agent. Many conventional metallurgical electrolytic processes and reducing furnaces are unable to add only the thermodynamically required electricaVchemical energy due to process inefficiencies. Electrical work in excess of AG for the reaction may be used to supply process heat, or excess chemical reducing agent burned to supply process heat. Besides the thermodynamic and economic drawback, this inefficiency results in excess C02 emissions derived from the combustion of fossil fuels. With these practices, energy becomes an important cost element of the metal produced. Highly-concentrated solar energy has the demonstrated potential to separate these two forms of process energies, allowing the addition of only the thermodynamically required high-quality energy while high-temperature solar process heat is provided to the reactor. Examples of metal oxide reduction processes that have been studied experimentally in solar furnaces include the production of Fe, Al, AI/Si alloy, Mg, Zn, Tic, Sic, CaC2, TIN, Si3N4, and AIN by carbothermic reduction of their oxides, and the high-temperature solar- electrothermal reduction of ZnO.

Jan 1, 1999

By Andrew Case

The Port Nickel facility in Braithwaite, Louisiana, is known for pioneering hydrometallurgical processes for the 'separation and recovery of nickel, cobalt and copper. Ten years ago, in 1985, a new CRI-MET process for the recovery of molybdenum, vanadium, nickel, cobalt and alumina from spent catalysts was developed and implemented. Spent- catalysts from the petroleum industry consietute the majority of feed. These are not only a valuable-source of metals, but due to EPA regulations are frequently classified as hazardous under RCRA. Molybdenum and vanadium are selectively leached in an oxidative hydrothermal step. Alumina is then extracted in a caustic digestive leach. The unique technology produces four primary commercial products l molybdenum trioxide, vanadium oxide, aluminum trihydrate and nickel-cobalt concentrate. This paper discusses the process, modifications. during ten years of operation, and the relationship of these modifications to the future of the catalyst recycling business.

Jan 1, 1995

By J. Fraser Forbes

"The meaning of the term ""process control"" has evolved significantly since its widespread use began in the manufacturing industries in the 1940s. Further, the scope of process control applications has drastically increased both in terms of the breadth of industries using process automation technologies and the vertical integration of these technologies within a single industry. This evolution and integration of process control technologies within the manufacturing industries has proceeded to such an extent that process automation is an integral part of modern business practices.This paper will examine the current status of process control technology from simple process regulation through process performance optimization to business planning. Each layer of the operations automation hierarchy will be discussed both in. terms of the current state-of-the-art and the directions in which these technologies are evolving. The key tools and tasks necessary for success at every level of the automation hierarchy will be introduced. Finally, the critical challenges that must be faced in accomplishing the goal of complete Computer Integrated Manufacturing (CIM) will be described.Finally, although this paper addresses issues of practical importance to any manufacturing company, the discussions will be framed in terms of the particular challenges facing and the opportunities available within the materials manufacturing industries."

Jan 1, 2000

By Devon A. Hannan

Thermodynamic modeling calculations were undertaken for the recovery of mercury from HgTe using a vacuum retort reactor. However, discrepancies were noted in the available thermodynamic data which introduced uncertainty in the model results. Consequently, a series of transpiration experiments were first undertaken on the thermal decomposition of HgTe into an inert carrier gas stream according to the following reaction: HgTe(s) Hg(g) + Te(s) From the measured weight loss of the HgTe samples, the Gibhs free energy change for the above volatilization reaction was determined as a function of temperature. The experimentally determined Gibbs free energy values were found to be approximately 30% larger (more posi-tive) than the values available in databases such as HSC Chemistry. By conducting a second-law analysis on the experimental data, the heat of formation of HgTe at 298.15 K and the en-tropyat 298.15 K were determined, which then formed the basis for a new database for the modeling calculations. The results of this study showed that HgTe was more stable at elevated temperatures than was generally indicated in the literature. The new database is given in a for-mat for direct insertion in HSC Chemistry. Using the new database, modeling calculations were conducted to examine the effects of the re-tort pressure and the molar ratio of purge gas to HgTe on the volatilization of mercury from HgTe. A diagram is presented that shows the minimum temperature for 100% volatilization of mercury from HgTe as a function of retort pressure for different molar ratios of purge gas (N2) to HgTe. For example, it was found that the minimum temperature for 100% volatilization could be decreased by 175 K, at a retort pressure of 0.05 bar, if the molar ratio ofN2 to HgTe is increased from 1.0: 1 to 100.0: I.

Jan 1, 2003

By M. Wu, A. Kharicha, A. Ludwig

"The droplet formation during melting of a 400 mm diameter electrode is simulated with a multiphase-MHD approach. The computational model includes a layer of slag and a layer of liquid steel. A VOF approach is used for the interface tracking and a potential formulation is used for the electric and the magnetic field. The Lorentz force and the Joule heating are recalculated at each time step in function of the phase distribution. The first results provided by this model are presented.IntroductionThe Electro-Slag-Remelting (ESR) process is an advanced technology for the production of components of e.g. high quality steels [ 1-9]. An alternating current (Figure 1) is passed from a conventionally melted and cast solid electrode through a layer of molten slag to the baseplate. Because of the electrical resistivity of the slag, Joule heating is generated and the slag transfers this energy to ingot and mould surfaces and to the melting electrode tip. The molten metal produced in the form of droplets passes through the slag and feeds a liquid pool from where directional solidification takes place. The slag and the ingot are contained in a water cooled copper mould. As also the baseplate is water cooled, a heat flow regime is imposed that gives controlled solidification, and this results in improved structure characteristics of ESR ingots.This process involves two liquids, a liquid metal and a liquid slag. Each liquid is subject to a phase change due to melting and/or solidification. From a fluid dynamic point of view, the ESR process is clearly a multiphase process, with free interfaces (slag/pool, gas/slag), and with a mixed area (slag and falling steel droplets) [ 10-15].Physically, the development of the heat and mass transfer at the slag/droplet interface is important for the final ingot quality, composition and cleanliness. Visual observations of the droplet formation just under the electrode being melted is almost impossible. Due to the presence of high temperatures, opacity of the materials, and the presence of the mould it is not possible to directly observe the behaviour the slag/pool interface. Although usually assumed flat [1-9], a previous work [10] using a Volume of fluid (VOF) model has shown that the interface shape between a layer of slag and steel layer in a cylindrical cavity is highly coupled with the distribution of the electric current. A full scale simulation of the ESR process using a VOF model has shown that the shape of the pool interface is likely to be non flat."

Jan 1, 2011

By G. Sterzik, W. A. Jankola, T. L. Salway, D. J. McKay

At Trail, British Columbia, Cominco's zinc leaching and solution purification processes include direct pressure leaching of zinc concentrates, leaching of fume from the lead smelter, leaching of calcine and electrolyte purification. These processes have been adapted to match the unique characteristics of Cominco's integrated zinc and lead operations. Recent modifications include changes to the purification process and iron-residue handling circuits. In 1997, a new five-compartment autoclave, complete with ancillary equipment, was installed in the pressure leaching plant. This paper discusses these changes, the current flowsheet and further improvements.

Jan 1, 2000

By F. Garcia-Carcedo

This research aimed to develop a clean technology for the production of ZnO from residues generated by the steel making industry. Scientific and technologic parameters were both investigated in order to define an industrial methodology allowing the integral recycling of EAF dusts. A reengineering of the Waelz process was perform,~d, aiming to produce a clean fraction of ZnO, fluorine free, as well as a slag enriched in metallic iron, which can be recycled in electric arc furnaces. The technical conditions used to produce the ultra pure fraction of ZnO are described. The magnetic separation of the EAF dust allowing the production of a phase high in iron and recyclable to the electric arc furnace is also discussed. Thermodynamic of the volatilization of all the elements contained in the EAF dust was performed in order to better control the thermal process in the rotary kiln. Tests were run using different reducing agents, weakly or highly reactive, aiming to determine their specific efficiency.

Jan 1, 2000

By Nickolas J. Themelis

The role of copper in the economy will not diminish in the 21st century. Following the tenets of industrial ecology, production and use of copper must take into account both human needs and also how to minimize "collateral" effects on the environment. Dispersive uses will be phased out and post-use recovery of copper will increase. This will result into an advantage for smelting processes that can accommodate mixed metal scrap and waste streams. The bath smelting processes of Noranda and Mitsubishi will continue to make progress but the dominance of the Outokumpu flash smelting will not be challenged until the Noranda reactor overcomes the obstacles to the direct production of copper, thus eliminating the need for a converter.

Jan 1, 1999

By D. J. Droppert

This paper describes the precipitation-production of crystalline scorodite (FeAs04.2H20) from arsenic-rich sulphate-based metallurgical solutions at ambient pressure (95°C). Arsenic is precipitated by means of a controlled precipitation technique in which the supersaturation of the solution is carefully controlled. By controlling the supersaturation in the presence of seed material. the formation of amorphous ferric arsenate is prevented. Scorodite is known to be the most stable As(V) compound and is therefore preferred as host mineral for arsenic immobilization. The effect of the following parameters on the preCipitation behaviour and kinetics of scorodite are discussed: Type of base seed concentration initial [As]. sulphate concentration. neutralization rate. seed recycling and method of Fe(ll!) addition to Fe-deficient arsenic solutions.

Jan 1, 1996

By Yongbin Yang, Meixia Cai, Yufeng Guo, Guanzhou Qiu, Tao Jiang, Jianjun Fan

"A series of sintering and metallurgical experiments were carried out to optimize the blast furnace burden structure in this study. The results indicated that the sinter disintegrated seriously with basicity around 1.4, and after this “turning point”, the sintering properties were improved gradually with the increase of basicity of sinter. Based on the results, an idea was put forward which focused on producing two different kinds of sinter with different basicity. Different with the original burden structure of 85% sinter with basicity 1.4-1.5 + 15% pellets, an alternative new BF burden structure was proposed by the following structure?44% sinter with basicity 1.05 + 44% sinter with basicity 1.87 + 12% pellets. This new alternative BF burden structure has been adopted by some steel plants.IntroductionIn recent years, conventional blast furnace (BF) process was put into operation to produce hot metal in “A” steel plant. “A” steel plant owns two sets of sinter strands at present. Because the sinter production capacity exceeds the actual requirements of BF, a burden structure with 85-90% self-made sinter + 10-15% purchased pellets is adopted to take advantage of the low–cost sinter. But the serious problems encountered with the BF operators are that the sinter disintegrated easily during transportation and storage process. Therefore, the rate of return fines is very high after sinter being screened."

Jan 1, 2012

By Joon H. Jang

At a selected pH, hydrothermal oxidation of chalcopyrite was carried out under controlled F+,, at elevated pressures and temperatures (172-200°C) by balancing the rate of oxygen injection against the rate of consumption. Chalcopyrite was converted to covellite (CuS) and digenite (CU1.8S) with rejection of iron and sulfur to the solution. Covellite forms in the first stage, followed by nucleation and growth of digenite in the second stage. The effects of rapid and slow injection of stoichiometric quantities of oxygen are compared. Both the covellite and digenite form a porous layer occupying the same volume as the original chalcopyrite grain. An electrochemical kinetic model is presented to correlate the observed results.

Jan 1, 1993

By Petrus Christiaan Pistorius, Farzin Fatollahi-Fard

The production of synthetic rutile—a common starting material for most titanium production processes—from iron-rich titanium minerals such as pseudorutile and ilmenite is described. The process for “upgrading” the mineral to synthetic rutile is by carbothermal reduction of the mineral while immersed in a molten salt at high temperature, followed by magnetic separation of the reduced iron. A variety of factors are also investigated, such as particle size of the mineral, the type of mineral, and the molten salt used. The solubility of iron(III) oxide in different molten salts is also experimentally determined.

Jan 1, 2016