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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 Yanjie Liang

Elemental sulfur and volatilization kiln slag(VKS)containing heavy-metal produced by smelter factories were used to produce sulfured building material. The effects of heating mode, material proportion (MSulfur:MVKS), size of waste particles and ratio of aggregate to filler(A/F) on the mechanical properties and leaching toxicities of solidified stuff were investigated. The optimal conditions for the solidification are stepped heating mode, 3:7 ratio of MSulfur to MVKS, particle size less than 150µm and 3/17 ratio of A/F. Under the above optimal conditions, the compressive strength of solidified stuff rises to 35 MPa, and water absorption is down to 4%-6%.Furthermore, when NaOH is applied as an additive in the process of solidification, the 2+concentrations of most heavy metals except Pb have reached the national leaching toxicity standard. The results of X-ray diffraction reveal that sulfured solidification is caused by the physical encapsulation rather than chemical transformation.

Jan 1, 2010

By Huimin Lu, Shi Zhou, Lisha Yang

"The Zeolitic imidazolate frameworks (ZIFs) were successfully synthesized by applying a combination of ionothermal synthesis and microwave energies for rapid synthesis. The synthesis was proceeded under various conditions including different raw materials, reaction temperature as well as microwave irradiation time. Zeolitic imidazolate frameworks (ZIFs), also known as coordination polymers, are new type of porous materials formed by inerratic polyhedral in three-dimensional. They are the ideal crystalline substances for gas separation and storage. The assynthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and C02 adsorption test. Results illustrated that the synthesized samples had stable structure, high thermal stability (up to 530 °C) and C02 adsorption capacity (10.2 cm3/g at 0°C under ambient pressure). This novel method also showed great advantage with high energy efficiency, safe synthesis conditions, and rapid crystallization time (60 minutes).IntroductionNowadays, carbon dioxide capture has become imperative due to the global warming caused by the increase of C02 in the atmosphere, especially produced by the concentrated sources such as power plants [1]. Zeolitic imidazolate frameworks (ZIFs), also known as coordination polymers, are ideal crystalline substances for gas separation and storage due to their structure diversity, high thermal and chemical stability [2-5]. They are formed by inerratic polyhedra in threedimensional with large cages and small apertures. Traditionally, ZIFs are synthesized by solvothermal method in a sealed autoclave under autogenous pressure [6-9]. However, in order to generate the products, the solvothermal temperature should not be lower than 100°C according to the sovlothermal mechanism. Moreover, at such a temperature, molecules with a low boiling point (such as water) may generate high pressure in reactor which might cause danger [9]. Thus the synthesis requires the equipment to possess resistance to autogenous pressure and corrosion. Further, conventional solvothermal methods need a long time to prepare products, usually a few days, which is a large energy consumption and inefficiency. So it is interesting to synthesis ZIFs through other ways under mild reaction condition with high energy efficiency."

Jan 1, 2012

By Gabriel Zarate

Mantoverde is a heap leach-SX-EW plant that was commissioned in December 1995 at a production rate of 42,130 tonnes of copper per year and 5.4 million tonnes of ore per year. Copper production was steadily increased reaching a maximum of 62,239 tonnes in 2012 for an ore throughput of 10,5 million tonnes. In order to get these production and throughput rates, a number of changes have been made in the metallurgical parameters of the plant operation since the start up, among them particle size, heap height, acid addition distribution in curing and leaching solution, leach cycles and pad type. Most of the modifications have been implemented after carrying out extensive column test work programs. The modifications implemented and the results obtained, as well as the test work programs carried out, are discussed in this paper.

By Wenbo Luo, Jilai Xue, Tiepeng Li, Jun Zhu

Sodium silicate solutions for producing silica have been ultrasound treated to enhance the precipitation process in laboratory scale. Higher precipitation rate was found with ultrasound treated solutions than those without ultrasound. The obtained SiO2 powder products were characterized using XRD, SEM, BET and laser particle size analyzer. The particle size distribution and the specific surface area of the powder products varied with the power input level and the processing time of the ultrasonic treatment. The results indicate that the efficiency of the precipitation process can be improved optimally when the ultrasound is conducted into the solutions before the nucleation stage.

Jan 1, 2015

By Jun Li

Rate processes of silver cyanidation were studied with the objective of understanding the reaction mechanism. The research was divided into three sections: anodic dissolution of silver in cyanide solutions, cathodic reduction of oxygen on silver surfaces and the direct leaching of silver in oxygenated cyanide solutions. The charge transfer steps plus the diffusion of reactants from bulk solutions to the silver surface were identified as rate-limiting and the rates of both anodic and cathodic reactions can be calculated using the Butler-Volmer equation and Fick's first law. Based on mixed potential theory and the results of electrochemical studies, a comparison of the rate obtained from direct leaching with that predicted from the calculation is made. Calculated results agree well with the experimental data.

Jan 1, 1992

By J. B. Cocanour

Pioneering work at the U.S. Bureau of Mines (USBM) has produced a personal computer (PC)-based, software-driven video photometric color sensor for real time process control of metallurgical streams. The video photometer is an inexpensive optical sensor which operates in the visual area of the electromagnetic spectrum and collects color information through plastic optical fiber. The red, green, and blue (R/G/B) voltage components of the color video signal are digitized and characterized through software and then presented as the control variable for software-based proportional-integral-differential (PID) control. This sensor has been successfully employed in the control of a laboratory copper electrolytic circuit. With this sensor, copper solutions were analyzed on-line without the need for sample removal, dilution, mixing or reagent addition, thereby allowing for the real time control of the circuit.

Jan 1, 1994

By Laurence Whitty-Léveillé

Proper handling of the radioactive fraction associated with the production of rare earth elements (REEs) in the mining industry is essential for a sustainable environment and human health. Actinides, such as uranium and thorium, have similar chemical properties to REEs, and are often co-dissolved in current hydrometallurgical processes. This causes radioactive contamination of the infrastructure through the extraction cycle. The present study optimizes, through experimental design, a sequential leaching procedure with Na2CO3/NaHCO3 and HCl for the rapid and selective dissolution of REEs and actinides. Optimization focuses on the main operating parameters (time, temperature, and concentration); different types of minerals, REE composites, and ores; on achieving maximal leaching yield; and on minimizing dissolution of the gangue metals (Fe, Si, and Ca). The final sequential procedure was rapid (1 h), effective, and led to the segregation of Th, U, and REEs with limited dissolution of the gangue metals.

By Yongbin Yang

Cathodic reduction of oxygen is a process involved in many fields. As is well known, the mechanism of oxygen reduction usually varies considerably with electrode substrates. In this paper, cathodic reduction of oxygen on gold electrode was studied by linear sweep voltammetry with regards to cyanide leaching of gold. As the results shows, the electron transfer number increases as potential shifted negatively and decreases as pH value increases. Besides, the increment of electron transfer number as a function of potential decreases when pH value increases. When pH increases to 13.0, the volt-ampere curve exhibits a relative flat section with currents approximate to the limit current density of a 2e process. By varying dissolved oxygen concentration, the electron transfer number was calculated for pH11.0 at different potentials, the results being 2.387e, 2.732e, 2.982e, and 3.227e at, -0.35V, -0.40V, -0.45V, and 0.50V, respectively. The calculated current densities are in good conformity with measured results.

Jan 1, 2010

By D. A. Horne, V. R. Daiga

Certain steel mill wastes contain significant amounts of zinc oxide due to the use of galvanized scrap during the steel making process. Typically electric arc furnace (EAF), and basic oxygen process (BOP) flue dusts contain 20 to 30% zinc oxide and 40 to 50% iron oxides, along with smaller quantities of lead and cadmium. These materials can be recovered from the flue dusts by using a proven rotary hearth furnace (RHF) process. By-products of the recycling operation include a crude zinc oxide fume, which is captured in a baghouse filtering system, and sponge iron that may be recycled into the steel making operation. Crude zinc oxide properties plus the operating experience from two commercial RHF installations utilizing MR&E's DRyIron™ Process will be presented.

Jan 1, 2000

By N. G. Azeredo

This work dealt with the evaluation of engineering structural clay brick samples that were sintered at estimated temperatures of 700 and 800°C. They were collected in a red-brick plant in Campos dos Goytacazes, RJ, Brazil. From a lot, a sample already sintered in its kiln at 700°C were collected and also a sample from the same lot only dried by the air, which were then sintered at 800°C controlled temperature. The samples were subjected to Brazilian Standard tests (ABNT NBR 15270:2005) to determine their geometric, physical and mechanical properties. In order to be classified as structural clay brick it is required minimum 3.0 MPa for the characteristic compressive strength (fbk) to be suitable for up to five floors structural building applications. We also used the Weibull Probability Plot and Weibull Maximum Likelihood Estimation to evaluate distribution parameters in order to compare the results of compressive strength obtained in the tests.

Jan 1, 2015

By Jewel A. G. Gomes

Green rust (GR) are layered Fe(II)-Fe(III) double hydroxides, having a pyroaurite-type structure consisting of positively charged hydroxide layers and hydrated ions in interlayers. This special feature of GR is very efficient for wastewater treatment as the pollutants are easily taken in or exchanged with the anions in the interlayers. It can be simply and cost-effectively produced by electrocoagulation (EC). Chicken processing plant (CPP) produces large amount of wastewater containing variety of readily biodegradable organic compounds, fats, and proteins. The possible re-use of properly treated CPP wastewater would be economic and environment friendly. In this study, we present our work on treatment of CPP wastewater using EC, specifically for the removal of COD. Analysis of the EC-treated water for reuse in the same plant is discussed considering the U.S.EPA regulations. Two types of EC-reactors were used for this purpose. To better understand the treatment mechanism, EC-floc was also characterized using XRD and SEM-EDS.

Jan 1, 2010

By Chen Chen, Wang Yanze, Hong Xin

Furnace superalloy was applied in harsh environment within the erosion of high temperature and oxidizing atmosphere. With plasma powder surfacing technology, iron-based alloy powder was sprayed on the surface of 310S stainless steel to form oxidation layer that increases the oxidation resistance and reduces the cost of materials. With optimum technological parameters, in this paper, oxidation test of 100 hours on iron-based cladding alloy and furnace alloy were carried out at 1200 . The technique of XRF, XRD and EDS were used to characterize composition, oxide morphologies and surface mechanical properties. The results showed that Element composition of cladding layer formed by Plasma powder surfacing was well distributed. Its oxidation weight gain rate of 100 hours was 0.4552g/m2h, belonged to antioxidant level. The oxidation weight gain rate of furnace alloy was 1.4617g/m2h, belonged time-antioxidant level. And on the mechanical comparison test, surfacing alloy is relatively excellent than furnace alloy.

Jan 1, 2016

By Varadarajan Seshadri

Geometallurgical characterization of iron ore which is a raw material for Iron making as in the case of charcoal blast furnaces operating in Brazil or for production of agglomerates such as iron ore sinter which serves as burden material for blast furnces of high productivity or pellets extensively used in the direct reduction processes all over the world in the iron and steel industry. Selection of proper raw material after due characterization should lead to an improvement of the productivity of the respective processes The usual classification of quality of iron ore is uniquely based on chemical analysis, granulometric and physical parameters. However not much emphasis has been given to the structural characteristics which also are important in the processes. Different typological categories of Brazilian iron ores have been used in the characterization . For instance, several kinds of hematite crystals like specularite, martite and microgranular hematite, etc with variable crystal sizes are found in the different ore types. They are also composed of different of fabrics and types of accessorial mineralogical constituents and have different porosities, pore diameters, etc which influence the cold and the hot agglomeration stages of the ore fines, and also chracteristics such as reducibility, decrepitation etc, important for assessment of quality of iron ores. . The first step for attaining a good characterization of ores is to know in detail about the structure of the deposit, shape of the body, types of iron ores and their distribution. This requires a geological-structural study and the mapping of the bodies using mineralogical criteria for typological classification of ores. followed by structural characterization of materials in stages of mining, comminution, screening and concentration processes. In this contribution a geometallurgical approach for quality control of Brazilian iron ores for sintering and pelletizing processes is highligted.

Jan 1, 2006

By L. J. Lutz

The U.S. Bureau of Mines has developed an electrorefining process to recover Ni, Co, Cr, and other metals from mixed and contaminated superalloy scrap. The superalloy scrap is cleaned then directly electrodeposited as a Ni -Co deposit. The process recovers approximately 90 pct of the Ni-Co available from the scrap as a 99t pct pure Ni-Co alloy. During electrorefining the electrolyte undergoes a purification process which results in Cr and other refractory metals reporting to the purification residue. Operating data is given for a 3-L compartmented electrolytic cell. Techniques for the removal of Fe, Cr, and trace impurities from the recycled electrolyte are outlined. The economics of a facility producing 15 mt/d of a Ni-Co alloy are also discussed.

Jan 1, 1993

By F. H. Froes, O. N. Senkov, N. Srisukhumbowornchai

"Mechanical alloying (MA) and thermohydrogen processing (THP) approaches were used to synthesize amorphous or nanocrystalline powders of the titanium-aluminide-based alloys and composites. Fully dense samples with nanocrystalline and bimodal structures were produced from these powders by hot isostatic pressing. The stability of the microstructures during continuous heating at high temperatures was studied. Characterization techniques including X-ray diffraction, scanning and transmission electron microscopy, energy dispersive spectroscopy, and differential thermal analysis were used in this work.IntroductionAs performance demands increase, so do the demands for enhanced mechanical property combinations at reduced overall weight; and reduced weight can most efficiently be realized by the use of low-density metals with high specific strength, such as titanium alloys and titanium-aluminum intermetallics [l]. The TiAl-based alloys are attractive for high temperature applications, however, they exhibit poor ambient temperature ductility and fracture toughness [2-4]. Incremental improvements can be obtained using ingot metallurgy processing [1,2] but more substantial developments require ""far from equilibrium"" (FFE) synthesis [5-8] which allows development of novel constitutional and microstructural effects, leading to enhanced physical and mechanical properties. Improved ductility of titanium aluminide intermetallics can be achieved by disordering, grain refinement and deoxidation of the matrix, while good elevated temperature properties are achieved due to a dispersion of fine, thermodynamically stable, second phase particles.The approaches for producing nanocrystalline and amorphous TiAl-based alloys and composites used in this work included FFE powder metallurgy techniques such as rapid solidification, mechanical alloying and thermohydrogen processing. The rapid solidification (RS) technique allows extension of solubility limits, production of novel phases, and much more refined microstructures (down to nanostructure or even amorphous range) than is possible using the ingot metallurgy technique [9]. Mechanical alloying (MA) is a process in which heavy working of powder particles results in intimate alloying by repeated deformation, fracturing and welding. This process can produce greater departure from FFE than RS, leading to greater refinement effects; and additionally allows production of a dispersion of second phase particles [10]. Thermohydrogen processing involves hydrogen as a temporary alloying element in titanium to facilitate processes, refine microstructure, and improve final mechanical properties [11]; it was used in the present work to improve MA process. The combination of these three processes was expected to control the final microstructure even better than either process used alone."

Jan 1, 1998

By A. Barba, M. P. Gómez, F. Puertas, M. Palacios, M. F. Gazulla, S. Martínez-Ramírez, I. García-Díaz

"The present study explores the reactivity and burnability of cement raw mixes containing fired red or white ceramic tile wastes or combinations of the two as alternative raw materials. The results showed that the new raw mixes containing these wastes are technically viable. The reactivity and burnability of the new raw mixes have been evaluated; confirming very good results when the particle size of wastes was less than 90 µm. The chemical and mineralogical compositions of the new clinkers were comparable to clinker manufactured with conventional raw materials. The mix of red and white ceramic tile waste was found to perform as well or better than each type of waste separately, a promising indication that separation of the two would be unnecessary for these purposes.IntroductionPortland cement clinker production consumes large amounts of energy (850 kcal/kg clinker) and has a considerable environmental impact. This involves massive quarrying for raw materials (limestone, clay etc), as it takes 1.7 tonnes to produce one tonne of clinker, as well as the emission of greenhouse and other gases (NOx, SO2, CO2) into the atmosphere. Around 850 kg of CO2 are emitted per tonne of clinker produced.The cement industry is looking for solutions to these problems, to attain sustainability and comply with the Kyoto Protocol commitments [1,2]. For that reason, experimental ways are being explored to develop cements whose manufacture is less energy-intensive, less damaging to the surrounding environment and with lower tendency to emit polluting gas. One of the reach this objective is the use of industrial waste and by-products as alternative materials for cement manufacture. Such alternative materials may partially replace fuel [3,4], conventional raw materials [5-8] or clinker in the final composition of the cement [9]."

Jan 1, 2008

By Rod Samuels, Rupert Allen, Thomas Harper

"Viceroy Resource Corporation of Vancouver, B.C., has recently developed and brought into production the Brewery Creek Mine, an open-pit heap leach gold mine, located 55km east of Dawson City in Yukon, Canada. Mineable reserves are 15.2 million tonnes of ore grading 1.45 grams/tonne, containing 22 tonnes (707,315 oz) of gold. Ore processing employs the heap leach technology using run-of-mine ore. Highlights of 1996 activity included construction of a 158,000 m2 of leach pad, placing 1.9 million tonnes of ore at a grade of 1. 46 gpt to the leach pad, construction and successful commissioning of the ADR plant, and pouring of the first gold bar on November 15th.Permitting of this mine has drawn significant attention because of the innovated heap leach technology; although this technology has been proven in other jurisdictions, it has not been used at such extreme northern sites where winter temperatures routinely reach -45°C for extended periods.ABSTRACT ONLY"

Jan 1, 1997

By Guo Xueyi

The morphological characteristics of the nickel particles electrodeposited from chloride dominant aqueous solution was investigated. The effects of the electrolyte constituents, the parameters for the electro-deposition on the morphology of the nickel particles were addressed. It is evidenced that not only the particle size but also the morphology of the deposited nickel particles strongly depend on the electrolyte constituents and technical operation conditions. The electro-crystallization mechanism of the metallic nickel particles deposited at high current density was elucidated. The ultra-fine nickel particles with flake, nodular or dendrite shape may be produced by controlling the duration for electro-deposition.

Jan 1, 2003

By Thomas E. P. Wechsler

The limiting factor for most pyro-metallurgical processes in secondary cop- per melting is the time required to heat and melt the product. American Combustion's proprietary PYRETRON variable £uel/air/oxygen combustion system improves the throughput of existing scrap melting and heating furnaces for copper and copper alloy production by increasing the rate of heat transfer from the flame to the product. The increased productivity and energy savings obtained from this technology can result in sizable reductions in operating costs for smelting operations.

Jan 1, 1991