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By Kinya Atsumi, Kanjana Khunathai, Hisaya Kato, Hidetka Kawakita, Keisuke Ohto, Katsutoshi Inoue

"Crosslinked microalgae were prepared from the residue generated in the production of biofuel, by crosslinking-condensation in concentrated sulfuric acid. These microalgae were tested for adsorption of various metal ions in hydrochloric acid medium. The crosslinked microalgae exhibited high selectivity for Au(III) over other precious and base metal ions. From an isotherm experiment, the maximum adsorption capacity was evaluated to be 3.25 mol/kg of dry gel for Au(III) which was many times higher than that of the original microalgae residue. SEM and X-ray diffraction confirmed the formation of metallic gold particles, suggesting the occurrence of a redox reaction between surface functional groups on the gel surface and trivalent gold ion.IntroductionSubstantial quantities of precious metals are being used by the electronic industry because of their excellent electrical conductivity and resistance to corrosion. In recent years, recovery of precious metals from secondary sources such as electronic scrap [1,2 ], and leach liquors is being favored because of environmental concerns. Of course, recovery is only practical, if its cost is lower than the value of the metals (gold, platinum and palladium) recovered.Traditional methods of separation and refining do not fulfill this requirement. In order to overcome this problem, attempts have been made in recent years to develop new processes including total leaching in hydrochloric acid containing chlorine gas or hypochlorite, followed by solvent extraction and ion exchange [3]. In the new processes, new solvent extraction reagents or ion exchange resins with high selectivity and high loading capacity are used to simplify the process and to reduce the operating costs."

Jan 1, 2011

By T. S. Bannos

Section 1417 of the Safe Drinking Water Act Amendments enacted by the O.S. Congress prohibits the use of lead containing solders for potable water systems in new construction or when making repairs. The legislature defines "lead-free" solder as containing less than 0.2% lead. In the development of a new solder it was recognized in addition to the lead free requirement, the alloy should perform as well as the popular 50/50 tin lead solder, both in application and properties. Another objective was to have only nontoxic elements. This led to the development of a 4.0% copper, 0.5% silver and 95.5% tin solder. Review of the merits of other alloy systems and the development of the physical properties along with test data are presented for the lead free tin. rich alloy.

Jan 1, 1990

By C. M. Iheagwara

This paper has addressed the issues that constitute major obstacles to the cost- effective and efficient operation of metallurgical vessels from the refractory standpoint. Refractories generally withstand severe conditions of high temperature reactions as well as physical loading/impingement and hence degenerate and need replacement. Scarcity of some refractory materials especially high alumina and magnesite ores in some places, the prohibitive cost and the frequency of replacement of damaged refractories threaten the continued support for metallurgical operations. Some of the causes, prevention and cure for refractory wear have been discussed and rational strategies (short and long term) have been recommended which if implemented should go a long way towards arresting the perennial problems they portend.

Jan 1, 1991

By Yoshiaki Suzuki

Since 1973, Saganoseki Smelter & Refinery had operated two flash smelting furnaces together to produce 330,000 mtpy of copper. However, in 1990's, economical situation required the smelter more increased productivity to remain competitive. The program, to integrate two flash furnaces into one was carried out maintaining the same production. Modifications were done on the pneumatic concentrate drying system, concentrate feeding system, concentrate burner and furnace cooling system, etc. to double the, furnace throughput. A new large cryogenic oxygen plant was constructed replacing two old plants. Single flash smelting furnace operation has started in March 1996. This paper describes about details of modifications and operational results.

Jan 1, 1998

By Ma Shao Xian, Li Dong, Li Zhen Guo

"The new type shaft calciner ( SK-10 Serials) is developed and designed by CADRE itself on the basis of the conventional shaft calciner. The actual application in a number of calcinations plants have proven that they are of very good effect. Calcined coke calcining heated by the shaft calciner has a high quality, lower lost by fire. The shaft calciner needs no additional fuel when it is working. Anode Carbon Plant and calcined coke Plant commonly used the shaft calciner in domestic. The waste heat from the shaft calciner can be recuperated to generate electricity and to make the steam for produce. Exhaust waste heat is recovered by 90% or more. The new type shaft calciner's structure is optimized by computer simulation for fire-wall structure, combustion air to fuel ratio, volatile combustion is fully in use, furnace cooling zone structure, the exhaust smoking structure and calciner heat balance. Furnace structure and production operating parameters has been got the best optimized results. This paper introduces the working principle and characteristics of the shaft calciner - the equipment for calcining of the petroleum coke. It also demonstrates measured process parameters of the new type shaft calciner. Through comparison with the rotary kiln and conventional shaft calciner, it proves its own technical characteristics and advantages: higher capacity, high quality products, provides more energy for power generation, equipment operation and maintenance costs lower.IntroductionChina's petroleum coke market is mainly dominated by the delay raw petroleum coke. Rotary kiln and shaft calciner are the main process equipment for calcined petroleum coke. As the shaft calciner burning less, no external fuel, waste heat utilization is high, long service life, the utilization rate in China is more extensive than the rotary kiln."

Jan 1, 2012

By Xiyun Yang

Magnetite was prepared by hydrogen reduction method. For a conversion to cobalt-modified magnetite, magnetite particles were suspended into a solution containing Co2+ and Fe2+ to precipitate a cobalt ferrite layer on the surface. pH value influences the particle composition directly, the desirable CoFe2O4 is obtained when pH value is 12. The coercivity increases with the increase of cobalt content, cobalt efficiency reaches a maximum value at cobalt content of 2.71wt%. With cobalt modification, magnetite particles have similar lattice constant and squareness ratio to that without cobalt modification. TEM and XPS analyses indicate that acicular morphology is retained during the coating process, the epitaxial growth layer consists of CoFe2O4and 0.3Co2O3CoFe2O4 at cobalt content of 2.71wt% and 5.03wt%, respectively.

Jan 1, 2006

By Matti Leiponen

During the last few years Outokumpu Oy has put forth efforts to develop the material handling in the Pori tankhouse. The final objective is full automation including cell loading. The fully automated material handling provides high quality anodes and cathodes as well as equipment and handling systems capable of very accurate cell loading. The new machines and equipment for accurate cell loading and the methods to produce high quality anodes and starting sheets are described in this paper.

Jan 1, 1987

By Kazuhiro Asai

Nippon Mining and Metals Company has an annual indium production capacity of 30 tons at its Saganoseki smelter and refinery. Lately, indium content in the. zinc smelting dust, one of the main sources, has been on the decrease while the amount of impurity in it on the increase. The present process at Saganoseki does not permit efficient elimination of a large. amount of impurity. Therefore, studies were conducted to improve its recovery process. As a result, a new indium recovery process consisting of leaching, solvent extraction and electrowinning has been developed. The new process was tested at a pilot plant and satisfactory results were obtained. This new process is discussed in this paper.

Jan 1, 1995

By Veneta Groudeva

A pyritic ore containing zinc, lead and copper as? the relevant primary sulfide minerals, .as well as gold and silver finely disseminated in the sulfide matrix, was? leached in percolation columns. Each column contained 30 kg of ore crushed to minus 10 mm. Firstly, zinc and copper were efficiently leached by means of chemolithothrophic bacteria? in acidic sulfate bearing medium. Zinc was leached more rapidly than copper but the final extractions of these metals were similar (about 75% in 300 days). A part of the galena was oxidized to the. insoluble lead sulfate during the leaching. The pyr:ite was, however, relatively slightly attacked. The ore was then leached by means of FeC11 - HCl solutions both in the presence and in the absence of bacteria to solubilize the lead. The chemolithotrophic bacteria grew in media containing both chloride and sulfat~ ions and maintained a high ferric to ferrous ion ratio in the percoiating solutions. The chemical leaching was, however, more efficient since ft was possible to carry it out at higher chloride ion concentrations. About 10% of the lead was leached in this way in 90 days. Finally, the ore was leached by thiourea in the presence of a gold-oxidant (oxone) to extract the gold and silver. Over 60% of the gold and over 55% of the silver were extracted from the ore in 150 days, while. the extractions of these precious metals from an untreated ore sample were lower than 25%.

Jan 1, 1991

By Mariana H. Staia

Thermodynamic calculations based on the free energy minimization method were performed for the system Ti-Fe-Mn-0-C1-C in order to evaluate the chemistry associated with the chlorination of an ilmenitic concentrate using CCl4. In the calculations various weight ratios of FeTi03/ CC14, a , were considered, which varied between 0.32 to 0.98 at temperatures ranging from 673 K to 1273 K , at atmospheric pressure. The results obtained indicated that the operating conditions for a process in a packed bed reactor, which implies the chlorination of both Fe and Ti, are 0.39 < a < .49 at T 1173 K.

Jan 1, 1993

By John P. Hager

One possible approach for the recovery of mercury from acid plant blow-down sludge in smelters is the use of a vacuum retort reactor for the vaporization of the mercury with subsequent collection of metallic mercury in an attached condenser. An experimental study was undertaken to investigate the vaporization of mercury when present as a compound in the Hg-S-O and Hg-Se systems. A transpiration reactor was modified to operate under reduced pressure and with a continuous flow of inert sweep gas. A water-cooled cold finger was inserted into the exit end of the reactor to provide for the rapid quenching of the exit gases and the collection of the mercury. Rates of vaporization were measured at several temperatures for each compound and were generally found to be constant at a given temperature and reactor pressure. The results were used to determine the minimum operating temperature for 100% vaporization of the compound in 60 minutes. For Hg2SO4, HgSO4, and HgSO/2HgO the required temperatures. for a reactor pressure of 50 Torr. were determined to be 634°, 622°. and 603°C. respectively. For HgO, HgSe, and HgS the required temperatures were 557°. 451°. And 382°C. respectively. For HgS the rate of vaporization was also measured at a reactor pressure of 1 00 Torr. The rate of vaporization was found to be slower resulting in an increased vaporization temperature of 423°C. It was also determined that the mercury vapor present in the exit gas stream can back-react with the other gas species to a significant extent and can result in very little condensed metallic mercury. For the vaporization of both HgS and HgSe. the mercury vapor was found to have back-reacted to the extent that virtually none of the vaporized mercury was collected in metallic form. For the vaporization of Hg2S04? HgS04, and HgSO4*2HgO the amount of metallic mercury recovered varied from approximately 50% for HgS04*2HgO to approximately 10% for Hg2S04 and HgS04. Only for HgO was the recovered mercury in primarily elemental form. The application of the results to the operation of a vacuum retort and condenser system is discussed.

Jan 1, 2001

By Mike Adams

A comprehensive pre-feasibility study has been conducted by Companhia Vale do Rio Doce CVRD) for Niquel do Vermelho nickel laterite deposit. Within this study, five integrated flowsheet options were evaluated via batch and pilot campaigns at Lakefield Oretest, over an intensive six-month period from receipt of ore to final reporting. Key technical objectives set by the client included demonstrating the technical viability of the beneficiation of several ore types, processing through integrated pressure acid leach/mixed hydroxide precipitation (PALIMI-IP) and mixed sulfide precipitation (PALIMSP) circuits, and the treatment of barren liquors to meet stringent environmental requirements. Refining of the MHP was by ammonia re-leach and solvent extraction (SX) to produce LME-grade nickel cathodes, NiCO3, NiO and CoS. LME grade nickel and cobalt was also produced by oxidation of the MSP and hydrogen reduction on the leachate. The database and data acquisition system, along with web-based reporting, enabled rapid turnaround on both daily and more comprehensive run reports, making it possible for speedy and confident decisions on operating conditions of the complex flowsheets. The high value of developing such data is emphasized and discussed as pivotal in the successful progression of laterite projects through to sustainable commercial viability. Keywords: Flowsheet, CVRD, Nickel, Piloting, Pressure, Leach, Refining.

Jan 1, 2004

By Steven Wright

The reduction of a slag produced 6om the recycling of lead batteries was studied in a kilogram scale laboratory investigation by reacting with graphite at temperatures of 1180 and 1200°C. Simultaneous reduction of PbO, Fe203, Sb203 and As203 occurred with the Sb and As reporting to the metal while the lead content in the slag was above 2 wt%. The Sb and As distributions between metal and slag were strongly affected by temperature and slag oxidation state. The rates of reduction of PbO and Sb203 increased with increasing slag basicity and temperature and decreased as the PbO content in the slag decreased. The reduction rate of PbO from these slags was similar to other industrial lead slags at the same CaO/SiO2 ratio and temperature. The implications of the behavioural similarities of the antimonous slags during reduction with carbonaceous reductants and other lead slags are briefly discussed.

Jan 1, 1994

By R. K. Mehta

Microorganisms have been increasingly used in applications such as-metal solubillzation, precipitation and recently being used as flocculants. Optimal control and on-line monitoring of these processes occurring in microbial reactors are of extensive interest but often difficult because of the unavailability of a mechanistic model of the process and on-line direct sensors. In this paper a dynamic populatlon balance model of microbial desulfurization will be presented. The influence of certain physical and biological parameters on the leaching rate will be illustrated via computer simulations and an extended continuous-discrete Kalman filter will be Implemented for estimation of unknown states.

Jan 1, 1991

By David Roha, Øyvind Mikkelsen

"Significant resources have been spent throughout the years in the investigation of production of aluminum by carbothermic reduction. Due to the technological challenges involved, the efforts have not yet resulted in a commercial process. An initiative to overcome issues that prevented previous attempts to succeed was taken by Alcoa through the Advanced Reactor Process. The research program has resulted in technical developments which have resolved many of the previous issues. The knowledge about the process has continuously improved through physical and computer modeling as well as by experimentation at various scales. The technical achievements together with improved process understanding have resulted in a reactor design able to continuously operate the process for several weeks at the time, with hundreds of kilograms of alloy in every tap.IntroductionThe Hall-Heroult process has since its invention in the late 19th century, been essentially the only process used for commercial production of primary aluminum. The process has so far proved to be superior to all potential process alternatives and has continuously been improved. Although the Hall-Heroult is a reliable process it also has challenges:"

Jan 1, 2012

By R. Nilsson

In the present work the sulphide capacities of Ca0-Mn0-Si0, ternary slags have been measured in the temperature range 1798 - 1873 K by equilibrating the slag with a gas-mixture containing CO, CO,, SO, and Ar. The results are compared with the data reported in literature. A theoretical model has been developed in the present work where the sulphide capacity is expressed as a function of the slag composition and temperature. The model enables the estimation of sulphide capacities of complex slags with a knowledge of the capacities of simpler systems.

Jan 1, 1994

By J. B. Wiskel, H. Henein

"A study was conducted to establish the effective heat transfer coefficient for a single molten droplet moving in a gaseous medium. Towards this objective, a series of quench experiments were performed on molten droplets of AA6061 aluminum generated with the Impulse Atomization technique (IAP). IAP is a single fluid atomization process capable of producing powders with a predictable mean particle size and a relatively tight standard deviation under controlled atmospheric conditions. Microstructure analysis of the atomized powder was used to establish the extent of pre-quench solidification. A mathematical model was then employed to correlate the Ranz-Marshall and Whitaker equations with the observed particle cooling behaviour. These equations were found to provide a reasonable estimation of the heat transfer conditions only when the variation in gas thermophysical properties across the boundary layer was accounted for in the model. This model formulation of droplet heat transfer has important implications with regards to active sprays and atomization processing operations IntroductionAn understanding of droplet cooling is important in atomization powder production. It is well understood that dendrite arm spacing is inversely proportional to cooling rate during solidificationl1l. Through modification of the heat transfer conditions during metal atomization, the microstructure of a powder maybe tailored to the end user. However, owing to the complexity of gas flow it is difficult to determine a heat transfer coefficient for a moving droplet. This difficulty is further compounded when complex jets and/or streams and their interactions are considered. To provide a base for these more complicated types of analyzes, two approaches have been employed to calculate the effective heat transfer conditions for a single droplet. In one approach, Megardis [ZJ developed a numerical model to investigate the heat transfer process of a free falling droplet undergoing laminar convective cooling. The effective heat transfer coefficient as a function of angular position was determined by numerically solving the fluid and energy equations for the system."

Jan 1, 1999

By Lucas Nana Wiredu Damoah, Lifeng Zhang

"The use of electromagnetic field to remove suspended particles from metals such as aluminum by pushing to the boundary has been well studied. However, the potential of this method is yet to be exploited for the removal of inclusions from silicon. Considering the increasing amount of Top-cut SoG-Si scraps year upon year, there is the need to harness all the potentials of technologies to recycle this materials to ensure sustainability. This study investigates, and discusses new results on the effect of processing parameters such as composition, coil current, and frequency on the removal of inclusions from silicon under high frequency AC electromagnetic field.IntroductionThe solar cell silicon making industry requires pure and clean silicon in order to maximize the conversion potential of the solar cell material. The conversion efficiency of solar cells is limited by minority carrier recombination at dislocations and those intra-granular defects such as impurities, small clusters of atoms, or precipitates [1]. Recent global developments in the energy sector with a drive for the production of clean, reliable, and affordable energy have stirred a rapid growth in the production of photovoltaic (PV) cells.[2] Thus over the years, silicon based PV cells has seen a lot of growth as it has a PV market share of over 90 % [3] either as single-crystalline silicon, or multi-crystalline Si (MC-Si), or amorphous Si [4]. MC-Si produced by directional solidification of solar grade silicon melt dominates the silicon PV market. During the directional solidification process, SiC and Si3N4 particles within the melt are pushed by the solidification front to the top of the ingot which is the last to solidify. Therefore the top of the ingot is cut generating what is known as top-cut solar silicon scraps. The Si3N4 particles are mainly from the coating material at the inside surface of the silica crucible and from the air absorption during solidification process. The SiC particles mainly stem from the carbon reduction process of the primary production of silicon [5]. For sustainability the silicon in the top-cut silicon scraps must be recovered. Therefore methods for removing non-metallic particles, such as SiC and Si3N4, from the silicon are important in order to recycle the top-cut scraps to a useful feedstock for the silicon solar cells manufacturing."

Jan 1, 2012

By K. Pagalthivarthi, P. V. Desai

"During solidification of alloys, many inter-related physical processes, such as melt convection, mass diffusion, heat transport, macrosegregation and melt-undercooling occur. Several research workers have studied one or more of these effects separately. To answer important questions on solidification behavior, an overall approach interrelating the processes is necessaryAs a first step toward accomplishing the overall modeling, the freezing of a binary liquid metal is examined. The various stages during freezing of the alloy are critically described to build a continuum model for the entire process. Diffusive mixture theory is used to write the conservation equations for the liquid and the mushy zones. The concept of local thermodynamic equilibrium in the presence of curvature effects is used to restrict the number of degrees of freedom within the mushy zone. Constitutive equations relating flux quantities and affinities, the governing differential equations and boundary conditions are discussed briefly for the freezing process.IntroductionA solidification study encompasses such facets as solifidication time, microstructure, macrosegregation of the solute, shrinkage effects and soundness of the casting. Influence of one or more of the coupled heat and mass transfer phenomena such as local solute redistribution, thermosolutal convection, melt undercooling at dendrite tips and heat dissipation to the ambient have all been previously examined [1-3J. Several studies have examined the individual facets of alloy solidification as isolated processses. In fact, the transport processes occur simultaneously and a comprehensive model should include their inter-relationships. In particular, some of the existing studies of the mushy zone [4-6J do not emphasize thermodynamic completeness. This work represents an attempt to develop a thermodynamically consistent model of the entire solidification process on physical grounds."

Jan 1, 1986

By Rollie E. Dutton, David A. Stubbs

"A sensor has been developed and tested that is capable of emitting and receiving ultrasonic energy at temperatures exceeding 900°C and pressures above 150 MPa. The sensor works with standard ultrasonic pulser-receivers and has demonstrated the capability of measuring workpiece deformation during hot isostatic pressing (HIP). Details of the sensor design, performance, and coupling of the ultrasound to the workpiece are described. Ultrasonic data acquired by the sensor, in situ, during HIP runs and at elevated temperatures in air are presented.INTRODUCTIONHigh temperature structural components, such as structural castings for jet engines, nickel-base superalloy turbine blades, and ceramic and metal matrix composites made from powders are often densified by hot isostatic pressing (HIP). For powder consolidification, the HIP process involves sealing the powder (and reinforcing fibers for composites) within an evacuated ""Can"" made of a material that softens at high temperatures. A hydrostatic pressure is then applied by pressurizing the inside of the HIP vessel with argon gas (up to 140 MPa). The hydrostatic pressure densities the powder through the elimination of the porosity between the powder particles.This paper presents details of the development and preliminary testing of an ultrasonic displacement sensor that can be used to monitor materials processing, in situ, at temperatures and pressures significantly higher than current ultrasonic displacement sensors. The target processing environment for this sensor is that typically found in a hot isostatic pressure (HIP) vessel, i.e., temperatures exceeding 1000°C and pressures above 138 MP a."

Jan 1, 1997