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By Zuomei Jin

The Mineralogical form of Silver in a Ag-rich complex ore was determined. In the complex sulfide ore, acidic thiourea leaching resulted in 35% extraction of silver directly. In the same complex sulfide ore, under the effect of ultrasonic treatment, 65% of silver can be ex¬tracted. After the above ore had been roasted and acidically leached of Zn and Cu, the silver extracted from this Pb-Ag residue was 96.8%. The effets of temperature, thiourea and ferric ion concentrations and partical size were examined. The leaching rate of silver from the Pb-Ag residue was diffusion controlled. The activation energy was calculated to be 10. 49%KJ/mole. The kinetic model for the thiourea leaching of silver from Pb-Ag residue was obtained and is given by, The kinetics of silver cementation by aluminium in thiourea solutions was also investigated. The activation energy was calculated to be 65. 13KJ/mole, which is reasonable fora rate-limiting surface reaction.

Jan 1, 1995

By Christine P. Viecelli

As Phelps Dodge Corporation addresses the environmental challenges of the 1990's, water management has become a key element in an overall waste minimization strategy. The Phelps Dodge Hidalgo copper smelter has implemented a comprehensive water management program that includes management of both fresh and process water utilized by its pyrometallurgical operation. Two major technological strategies are being implemented. They are the design, construction and operation of a raw water pre-treatment facility to allow increased evaporation within cooling towers thereby minimizing blow down, and the use of a brine concentrator to treat and recycle significant quantities of process water. The end result of this program is a significant reduction in raw water pumped from the underlying aquifer into the facility as well as a decrease in process water which must be impounded or otherwise treated.

Jan 1, 1992

By Motoyasu Sato

Highly pure pig irons were produced in a multimode microwave reactor from powdered iron ores with carbon as a reducing agent in the nitrogen atmosphere. The grains in compacted powder absorb microwave energy selectively. Microwave-matter interaction creates thermal non-equilibrium state microscopically and enhances chemical reactions and the phase mixing at the grain boundaries very rapidly. The visible light spectroscopic techniques was used to monitor the progress of the reactions. Up to 650°C, the heated powders radiate the continuous spectrum of blackbody emission. The small non-equilibrium hot spots rise, move and finally burst in to brighter light emitting from all over the surface at 650°C. CN molecules and Fe (I) atoms were identified in the recorded spectrum. These bursts are similar to the ?ignition propagation? normally observed in chemical reactions. The line spectra originated from CO molecules have not been detected yet. The solid-solid reaction could be expected between the iron oxides and carbon to produce CO2 directly. A loss in the sample weight was accelerated during the excess-emission. These are the clear evidence that microwaves cause thermally non-equilibrium state and accelerate reduction process. The reduction of iron ore is completed at 1380°C and relatively very pure pig iron was produced. It should be noted that the impurity level of Mg, S, Si, P and Ti is only 5-10% of what is found in the pig irons produced by modern conventional blast furnaces in the steel industries. The necessary amount of carbon needed was 1/2 compared to conventional blast furnace to produce the unit weight of steel, if we applied renewable energy or nuclear power for the microwave excitations.

Jan 1, 2006

By Nobuaki Sato

For decontamination of SO2 containing waste gases from industries such as ferrous and non-ferrous metal companies, desulfurization with hydrogen production by the reaction of Br2 and SO2 was proposed as bromine-sulfur (BS) process. In this process, SO2 is fixed as H2SO4 in the presence of Br2 and H2O forming H2SO4 and HBr. Then hydrogen is produced by the decomposition of HBr and Br2 as byproduct is recycled. The reaction of Br2, SO2 and H2O was found not to occur in liquid phase but to occur in vapor one. The production ratios of H2SO4 and HBr showed a maximum at temperatures around 60 oC. The highest production ratio was obtained at 70 oC with a mixing ratio of Br2:SO2:H2O=1:1:10. The experimental results were discussed with thermodynamic consideration.

Jan 1, 2006

By Adam C. Powell

A new Cahn-Hilliard phase field model of transport-limited electrochemistry describes phase boundary motion due to oxidation and reduction reactions at metal-electrolyte interfaces. Benchmarks demonstrating the accuracy of the method include open circuit voltage and closed circuit current in metallothermic reduction, and linear stability theory in metal electrolysis, including a new stability criterion for reduction of liquid metal from liquid electrolyte. The model is applied here to understanding cathode interface stability in titanium electrolysis e.g. in the SOM process developed with Uday Pal, and to structure evolution in subhalide reduction of titanium dichloride by magnesium developed by Toru Okabe. Potential for application to new fuel cell and battery systems is also discussed.

Jan 1, 2006

By C. Lupi

Zinc impure solutions as spent electrolytes, leach liquors coming from aqueous treatment of both minerals and solid waste, need to be purified before undergoing the treatment to obtain the final product. Solvent extraction is one of the most selective operations particularly when many metallic ions are present in solution. Zinc pure solutions are frequently obtained using DZEHPA as extractant. In this work an investigation on zinc extraction effectiveness of naftenic acid was carried out. After determining the best diluent and the optimal extractant concentration, the partition coefficient was determined as a function of temperature, equilibrium pH and zinc concentration. Finally same batch tests to determine the equilibrium curves at room temperature on exhausted electrolyte coming from zinc cell were carried out by using naftenic acid, D2EHPA and TBP. The pH giving, for each extractant, the best extraction yield was selected in order to compare the equilibrium curves. Experimental results show that all the examined extractants are very effective in zinc extraction if the process conditions are appropriately selected. In order to avoid an impure solution pre- treatment and to obtain the maximum ertraction yield the appropriate solvent can be chosen.

Jan 1, 1998

By D. de la Villa

From 1989 to 1992 Rio Tinto Minera has developed and implemented a productivity program in its Huelva Plant, including Smelter, Acid Plant and Electrorefinery. This Plan was designed in order to increase productivity, reduce emissions and produce a better quality of cathodes. This paper describes investments and operating improvements involved in this project, focusing on Smelter and Acid Plants, and comments the results obtained so far.

Jan 1, 1993

By Yong Xian, Zhaohui Sun, Honggang Zhong, Qijie Zhai, Jie Sun

Vacuum refining is admitted as an effective means to remove impurities in the process of alloy smelting. In this paper, Orthogonal and single factor experiments were carried out to investigate effects of multiple factors, such as superheat degree of the melt, degassing time and vacuum degree, on the vacuum refining process. The results showed that the best removal rate of oxygen and nitrogen is up to 82.71% and 61.3%, respectively, due to high vacuum degassing efficiency. It is found that the superheat degree is minimal impact on the deoxidization rate, in addition, nitrogen removal is controlled by the degassing time. The inclusions exist in the AlV55 alloy are mainly composed of oxides and vanadium-nitrogen compounds.

Jan 1, 2015

By Cecil Harriss

Philip Environmental Services Corporation's (Philip's) innovative fluidized bed thermal desorption system recovers mercury from contaminated soil. Referred to as the Thermal Recycling System, Philip has constructed a mobile thermal desorption system that has a processing rate up to five tons per hour. The system includes a continuous-feed system, all radiant heat, inert gas atmosphere, hot gas filter, two-stage cooling, and a water treatment system. Based on treatability studies, the processed soil can meet cleanup objectives as low as two milligrams per kilogram and passes the mercury toxicity characteristic leaching procedure test.

Jan 1, 1996

By Yosry Attia

Recent emphasis on environmental effects and costs of conventional mining processing, plus success in accelerating bacterial action, suggest that biotechnology be explored for gold ore processing. In our paper, the past experience with organisms in processing gold is reviewed. The use of microorganisms for liberation of gold from sulfide ores as a substitute for fine grinding is discussed. The possibility of accumulation of gold from solutions, such as cyanide solutions, is explored as a potential replacement for such processes, such as carbon-in-pulp or ion exchange. The improvement in engineering technology and kinetics needed to scale-up from laboratory experiments to production scale are outlined.

Jan 1, 1985

By Colin Dessemond

Since 1950, the traditional process has been dominating the production of lithium compounds from spodumene ores to sustain the lithium market because of its economic viability and the markets need for technical grade (99.5% purity) product. This traditional process includes thermal conversion, acid roasting and lithium leaching. However, this process has not been challenged and very few studies have tried to explain its limitation (95% lithium yield) or optimize the thermal treatment. Here, α to β spodumene conversion and lithium extraction were performed in a rotary kiln on a 2 mm to 2 cm spodumene concentrate instead of a micrometric one using a 1050 °C, 30 min conversion treatment and 250 °C, 30 min, 30% H2SO4 excess leaching treatment. X-Ray Diffraction analyses were performed on the converted material to determine the conversion rate by Rietveld analysis. It was observed after thermal treatment that the α-spodumene particles fractured and divided while the impurities remained compact. A sifting was performed after thermal treatment and it was determined that 65% of the initial mass became finer than 180 μm. X-Ray diffraction analyses and lithium content measurement were performed on both fractions and it was determined that the finer fraction had a very high lithium content of 3.24 wt%. Lithium extractions were performed on both fractions separately. While the coarser fraction’s lithium yield was only 61% the finer fraction’s lithium yield went up to 99% without any additional treatment. These observations may open more economical ways for the traditional process by potentially bypassing two third of costly steps such as grinding.

By Gabriel A. Torma

This paper provides infonnation on selected technologies available for remediation of metal contaminated soils and industrial effluent solutions. Because some of the industrial sites are contaminated with organics (solvents, gasolines and oils), an effort has been made to introduce the most frequently used cost-effective cleanup methods, such as "bioventing" and "composting." The microorganisms involved in these processes are capable of degrading organic soil contaminants to environmentally harmless compounds: water and carbon dioxide. Heavy metals and radionuclides contaminated mining and industrial sites can be remediated by using adapted heap and dump leaching technologies, which can be chemical in nature or bio-assisted. The importance of volume reduction by physical separation is discussed. A special attention is devoted to the remediation of soils by leaching (soil washing) to remove heavy metal contaminants, such as chromium, lead, nickel and cadmium. Furthermore, the applicability of biosorption technology in the remediation of heavy metals and radionuclides contaminated industrial waste waters and acidic mining effluent solutions was indicated.

Jan 1, 1996

By Liya Bochkareva, David Hui, Sergey Eremeev, Maksim Kireitseu, Igor Nedavniy

The principal goal of the present paper is to demonstrate an application of modern software engineering tools for modeling virtual reality and molecular dynamics of novel nanocomposites. The main technical components of presented system are I) software and nanoengineering tools for modeling of virtual reality, molecular dynamic and 30 video images of novel diamcindscontaining nanocomposites and 2) Problem tracking system to be used during modeling of virtual reality. A computational scheme and software, which utilizes neural networks and/or Microsoft. Net technique was developed to predict properties of nano-structured materials and optimization and control of nano-devices. Developed software and IT nanoengineering tools can be used by both industrial and private single users. For commercial companies proposed technology may provide better cost-effective alternative to the existing solutions for nanoengineering and modeling their virtual realit. For private users (students, professors, and engineers) proposed technology and IT tools can provide simple and cost-effective solution for nanoengineering while studying, exploring virtual reality and modeling novel nanostructures and its properties leading to an innovation or a discovery. Because of using novel software and methodologies, users can easily operate proposed technologies by available computers and operating systems (Pentium III or IV). In addition, users can upgrade it by their own self-written models, if necessary. The proposed technologies could replace or be used along with technologies for modeling such as 30 max studio and others.

Jan 1, 2004

By P. A. Manohar

This paper describes an implementation of the Potts model for simulation of grain growth in 2D on a distributed-memory parallel architecture. The simulation scheme utilizes a continuous-time, asynchronous parallel version of the n-fold way algorithm. Each Processing Element (PE) carries a piece of the global simulation domain while the virtual topology of the PEs is in the form of a square grid in 2D and Torus in 3D. Different PEs have different local simulated times. Inter-processor communication is carried by the Message Passing Interface (MPI) routines. Sample results for grain growth simulation in 2D are presented for a 840 x 840 global domain size distributed over 16 PEs. The grain growth kinetics obtained in the simulation of pure, isotropic systems is in good agreement with the theory. Grain size distributions obtained in the parallel simulation are well described by the lognormal distribution, thus validating the simulation procedure. Keywords: Metropolis algorithm. n-fold way algorithm, asynchronous parallelization, grain growth

Jan 1, 2003

By Chunhua Liao, Chao Peng, Guangsheng Huo

To get the separation of tungsten and molybdenum, we adjusted the pH of the solution to 7, at which tungstate (WO4 2-) will be polymerized into HW6O21 5-, while molybdate will still exist in the form of MoO4 2-. Two strongly basic anion exchange resins (D201, D213) were experimented for the separation of tungsten and molybdenum. The results of condition experiments indicate that D213 resin performs better in the treatment of lower concentration solution A (WO3 10g/L, Mo 4.12g/L) with a separation factor as high as 10.64. While D201 resin is more suitable for the high concentration solution B (WO3 70g/L, Mo 28.97g/L) with a separation factor of 6.9. The results of column testing performed on D213 resin show that the solution after loading process with a mass ratio of Mo/WO3 = 50 and the desorption solution with a mass ratio of WO3/Mo = 27 can be obtained

Jan 1, 2014

By G. Richards

The Trail smelter of Teck Metals Ltd. produces about 90,000 tonnes of lead per year through two stages of refining following KIVCETTM smelting. Bullion from the KIVCET furnace is first treated in a pyro-refining plant in preparation for Betts electrorefining which makes 99.99% pure lead. Pyro-refining consists of number of integrated unit operations to remove primarily copper, arsenic, antimony and tin. The operation of this plant to meet the specifications for electrorefining requires attention to bullion management and selective use of reagents. The processes used for pyro-refining are reviewed in terms of chemistry and control.

By Seyed Ahmad Jenabali-Jahromi

In this paper a meshless method called Finite Point Method (FPM) is developed to simulate the solidification process of continuously cast bloom steel in both primary and secondary cooling region. The method is based on the use of a weighted least-square interpolation procedure. A transverse slice of bloom as it moves with casting speed is considered as computational domain. The two dimensional heat transfer equation together with temperature dependent thermophysical properties is solved in the computational domain. The present work is verified in the mold region by the comparison of the surface temperature simulated by FPM and finite volume method (FVM) and also comparison of solidified shell thickness simulated by FPM and measured on a breakout bloom. For secondary cooling region the validation is done by comparison of the surface temperature simulated by FPM, FVM and thermovision measurements.

Jan 1, 2009

By Yilin Fang, Alain Bonneville, Timothy. D. Scheibe, Zhijie Xu

"We present a hydro-mechanical model for geological sequestration of carbon dioxide. The model considers the poroelastic effects by taking into account the coupling between the geomechanical response and the fluid flow in greater detail. The simplified hydro-mechanical model includes the geomechanical part that relies on the linear elasticity, while the fluid flow is based on the Darcy's law. Two parts were coupled using the standard linear poroelasticity. Analytical solutions for pressure field were obtained for a typical geological sequestration scenario. The model predicts the temporal and spatial variation of pressure field and effects of permeability and elastic modulus of formation on the fluid pressure distribution.IntroductionIn order to achieve a substantial reduction of CO2 emissions and alleviate the atmospheric carbon problem, massive scale carbon sequestration is required involving millions of tons of carbon dioxide injection over several decades. The geomechanical response is important upon the injection of substantial supercritical carbon dioxide into deep geological formations. Supercritical CO2 is less dense than brine waters and the buoyancy driven flow of CO2 requires the aquifer to be capped by low permeability rock (""caprock"") to prevent the upward migration of C02 (as shown in Fig.1 ). Massive scale injection of C02 changes the overall stress state in the caprock and formation. This change leads to large deformation that can damage the caprock, create fractures, and open new flow paths for supercritical C02. Therefore, a coupled hydromechanical model becomes essential for the caprock integrity analysis."

Jan 1, 2012

By P. Maraboutis

Iron removal by precipitation as jarosite from Fe-Ni-Co sulfate solutions, (synthetic or real, resulting from laterites leaching) has been investigated. Precipitation was carried out at 95 C, and at an initial pH 1.6, which was either kept constant with CaCO3 or Li2CO3 additions, or left to drift with the evolution of the reaction to lower values. The precipitation of K-, NH4- and Na- jarosite was initially examined using synthetic solutions. In all cases, hydronium ions were incorporated into the precipitate as well. Residual iron in solution was lower (0.2-1 g/1) and equilibrium was achieved faster (within 4-8 h) when precipitating K¬jarosite at constant pH, using CaCO3 for neutralization. Nickel and cobalt losses were small. Na- jarosite precipitation was also studied from real solutions with high initial iron content, under constant pH=1.5, controlled with CaCO3 additions, and it was shown that low residual iron concentration in solution (0.3-0.5 g/1) can be achieved again, with relatively small nickel and cobalt losses. The thickening and filtration characteristics of the precipitates were excellent in all cases examined.

Jan 1, 1988

By Yukio Ishikawa

Sumitomo Metal Mining Co,. Ltd. (SMM) has been producing 22,000 t/y of electrolytic nickel at Niihama by nickel matte electrorefining process since 1970. Although the matte electrorefining is an established process and the productivity has been greatly improved in the last 20 years, SMM has intensively developed the chloride process for the nickel production since 1970's. The nickel and cobalt refining process involving solvent extraction and electrowinning from the chloride solution has been successfully developed for the treatment of the mixed sulphide in 1975. The first application of chlorine leach to the anode slime has been succeeded since 1986. Based on those technology, the matte chlorine leach electrowinning process (MCLE) has been developed as an alternation to the relatively old technology of matte electrorefining. The new process offers significant cost down and excellent quality of the product. In 1986, the feasibility of MCLE was confirmed by the test work using the integlated pilot plant. The innovation of the chlorine leach process has been undertaken by this work. The new refining process can be divided into three stages including chlorine leach stage, purification stage and electrowinning stage. More than 99 % of nickel was extracted in atmospheric chlorine leach. Although copper ion was used for electron carrier in the chlorine leach, the excess copper from the feed matte is bled off from the leach circuit by de copperizing electrolysis. The copper ion of the pregnant solution is fixed on nickel matte by the cementation reaction. The nickel matte containing copper is processed in the chlorine leach. In the purification circuit, cobalt, iron and other impurities were removed from the nickel chloride solution. The nickel chloride solution is then fed into the electrowinning cell. Based on the process established, the new plant with a capacity of 330 t/M electrolytic nickel was commissioned in order to obtain the engineering data for design of the full scale plant in 1989. The performance of the plant was fully satisfied and the new process demonstrated the potential application of modern process control.

Jan 1, 1992