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By Melvin A. Jennings

Ion-exchange technology for precious metals recovery is at a turning point. Some very exciting technology has been developed in the past five years which should lead to commercialization of the process. Ion-exchange will allow not only for the recovery of gold and silver, but also will allow for the recovery of cyanide form plant tailings. This process may soon be competitive with Merrill-Crowe for silver and once this occurs, it will become the process of choice.

Jan 1, 1991

By Michael Zinigrad

The quality of metallic materials depends on their composition and structure and these are determined by various physico-chemical and technological factors. To effectively prepare materials with required composition, structure and properties it is necessary to carry out a research in two parallel directions: Comprehensive analysis of thermodynamics, kinetics and mechanisms of the processes taking place at the solid-liquid-gaseous phase interface during welding processes and development of mathematical models of the specific welding technologies. We have developed unique method of mathematical modeling of phase interaction at high temperatures. This method allows us to build models taking into account the thermodynamic characteristics of the processes, the influence of the initial composition and temperature on the equilibrium state of the reactions, the kinetics of heterogeneous processes, the influence of the temperature, composition, hydrodynamic and thermal factors on the velocity of the chemical and diffusion processes. The model can be implemented in the optimization of various technological processes in welding, surfacing, casting as well as in manufacturing of steels and non-ferrous alloys, materials refining, alloying with special additives, removing of non-metallic inclusions.

Jan 1, 2003

By Daoxin Wu

In this paper, the rutile TiO2 were prepared under air, Ar and H2 calcination atmosphere by low temperature hydrolysis using Tetrabutyl titanate (C16H36O4Ti) as raw material. Powers were characterized by X-ray diffraction, UV-vis diffuse reflectance and X-ray photoelectron spectroscopy. The influence of the calcination atmosphere on the photocatalytic reactivity of rutile TiO2 for oxygen production was investigated. The photocatalytic reactivity of rutile TiO2 prepared under air, Ar and H2 atmosphere was compared under ultraviolet and visible light radiation with Fe3+ (c=8.0mmol.L-1) as electron acceptor. The results showed that rutile TiO2 prepared under Ar and H2 atmosphere had higher photocatalytic activity for oxygen production than that prepared under air atmosphere. The oxygen production rates under ultraviolet irradiation were 427.5, 378.2 and 357.0µmol.l-1h-1 respectively when rutile TiO2 was prepared under Ar, H2 and air atmosphere. The oxygen production rates under visible light irradiation were 78.2, 52.2 and 13.5µmol.l-1h-1 respectively when rutile TiO2 was prepared under Ar, H2 and air atmosphere.

Jan 1, 2008

By Dean G. Heitt

"The Rain and SMZ mines from 1987 to 1994 produced a total of22.0 t of gold from a pre-mine reserve of 14.24 Mt of ore grading 2.13 g/t Au.Gold at Rain is hosted within the basal portion of the Mississippian Webb Formation. ·Mineralization is closely tied to the Rain Fault which is interpreted to be the main feeder for the deposit. Multiple collapse and hydrothermal breccia events provided permeability for the mineralizing fluids in the otherwise unreactive siltstones. Major alteration events include: decalcification and dolomitization of the Devils Gate Limestone; and silicification, baritization, argillization and oxidation of the Webb Fm. Six ore types based on XRD and visual rock chip Jogging have been identified: siliceous ore containing >40% quartz and <30% barite; siliceous-baritic ore containing mostly silica but >30% barite; baritic ore containing >40% barite; argillaceous ore containing >40% total clays (including alunite); calcareous ore containing mostly calcite and dolomite; and carbonaceous ore which has significant pyrite and organic carbon. Metallurgical testing of the oxide leach grade ores found that recoveries, on -1.3 cm crushed material, were greater than 70%. Results also found that Rain ore has strong grind dependency due to silica encapsulation.The Rain leach pad was commissioned in 1988, and to date 9.3·Mt at an average grade of0.65 g/t Au have been placed. Life to date recovery, through December 1995, is approximately 51 %, for a total of3.87 t of gold produced. Two major factors have contributed to the low leach recoveries at Rain when compared with the metallurgical testing: 1) More argillaceous ore than expected was placed on the pad especially late in the mine life and 2) approximately 50% of the tons placed were run-of-mine with no agglomeration."

Jan 1, 1997

By Jaroslav Horskoý, Miroslav Raudenský, Bogdan Filipic, Božidar Sader

This paper describes main elements and practical use of the computational system for automated setting of optimized casting conditions in the continuous casting of steel. The system consists of the heat transfer model of the process, empirical metallurgical criteria, and optimization algorithm. The physical model of the, strand temperature distribution relies on the classical Bennon-Incropera mixture continuum formulation for the convective-diffusive heat transport. Fluid flow effects are considered through enhanced thermal conductivity of the liquid phase. The model is solved by the operator-splitting Crank-Nicolson finite volume version of the Voller-Swaminathan scheme. The solution procedure is coupled with the IDS solidification analysis package. Boundary conditions for the strand cooling rely on combination of the generic and plant-specific mold, spray, and roll heat transfer coefficients ' by coping the effects of the casting speed, casting temperature, casting powder, mold oscillation mode, steel grade, water or air-mist spray type, running water, trapped water on the rolls, and radiation. The caster safety and productivity and the quality of the strand are related to nine empirical metallurgical criteria. The criteria ensure the caster safety and economy as well limit the internal, longitudinal, and transversal surface cracking possibility. The problem of finding optimum casting parameter values is stated as a minimization problem based on the analytical form of the cooling criteria evaluated from the steady-state temperature distribution of the strand. To solve the optimization problem, a genetic algorithm is employed. The algorithm explores process parameters settings heuristically by applying the principles of biological evolution. It starts with a random set of solutions and iteratively improves them through selection and variation. Solutions are evaluated by running the heat transfer model of the process and extracting the values of the empirical metallurgical criteria.

Jan 1, 2000

By Jorge A. S. Tenório, Pedro F. A. Prado, Denise C. R. Espinosa

There has been an increasing push to develop environmentally sound recycling processes of electronic waste (WEEE), including end-of-life photovoltaic modules, to reclaim materials such as silver which is both valuable and pollutant to human health and wildlife. However, process sustainability and economic feasibility of PV panels recycling is strongly tied to the materials separation step, which currently presents challenges due to use of high temperature treatments and strongly acidic solutions. A method using an easily accessible solvent — isopropanol— dissolved the silicone-based encapsulant of crystalline silicon PV modules in 2 days at room temperature, separating the module into semiconductor wafer, glass, ribbon and backsheet.

Mar 1, 2017

By Dong Hoon Han

The simultaneous sulfation by sulhr dioxide and oxygen of CaO and MgO in calcined CMA (calcium magnesium acetate) were investigated. he experiments were carried out in the temperature range from 700 to 830 "C and at the SO2 concentrations of 0.3 to 1 mol %. The oxygen concentration was kept at 5 %. Each sample was calcined completely before the temperature was lowered to the sulfation temperature. According to the ranges of partial pressure of sulhr dioxide and temperature, there exist three regions for the sulfation reaction: region I in which neither oxide is sulfated, region I1 in which only CaO is sulfated, and region 111 in which both oxides are sulfated. It was shown that the MgO in calcined CMA is sulfated at a rate comparable to that of CaO by forming a mixed sulfate phase. Thus, unlike MgO contained in other desulhrization materials, the MgO content in calcined CMA can be fully utilized for flue gas desulhrization.

Jan 1, 1999

By Matsufumi Takaya, Yukihiro Sakamoto

"Electric field emission properties from CVD diamond fabricated using pulse-modulated microwave plasma CVD were studied. Diamond was synthesized by microwave plasma CVD apparatus equipped with a pulse-modulated microwave power supply. Pulse conditions were varied from 1 to 10 seconds for pulse periods and from 0.1 to lHz for pulse frequency either. Surface morphologies of the deposits were differed by pulse frequency and duty cycle. As a result, FE properties prepared by different pulse duty cycle were different from continuous film which synthesized using continuous microwave significantly. Highest current density was obtained from the uneven morphology diamond film prepared at 17.5% pulse duty cycle.FE properties of the CVD diamond were depended on surface morphologies that related to the pulse conditions.1. IntroductionDiamond has excellent physical and chemical properties as an industrial material. Especially, hydrogen terminated diamond had the negative electron affinity (NEA) 1) and CVD diamond has this NEA property either as deposited 2). So the electron emission source to the FED is expected as one of this application of CVD diamond as cold cathode of electric devices. We studied on FE properties of various CVD diamond, pulse microwave plasma CVD diamond showed better property than those of other CVD diamond 3).This report studied on· the effect of the duty-cycle of pulse modulate microwave condition on FE properties of the diamond fabricated by pulse modulated microwave plasma CVD."

Jan 1, 2000

By Tullio Corsini

Scrap battery recovery process, developed by Engitec Impianti S.p.A., is improved transforming batches operations in continuous. Benefits expected: constant and better quality of the products; easier and more reliable control of the operating parameters, reduction of manpower requirements. Paste will content less sulfate, particularly in soluble form. Sodium sulphate is obtained with higher and constant purity.

Jan 1, 1993

By Milton Blander

A review of concepts and theories for predicting thermodynamic solution properties of multi- component high temperature liquid solutions is reviewed. During the last 50 years the ability to predict :such properties for molten salts, silicates and metals based on the generally known properties of the lower order (often binary) systems has been developed and shown to provide predictions which are quite useful in science and technology. There are many gaps in our understanding of these high temperature solutions, especially for metals, and considerably more work is needed.

Jan 1, 1996

By Michael Zinigrad

The quality of metallic materials depends on their composition and structure and these are determined by various physico-chemical and technological factors. To effectively prepare materials with required composition, structure and properties it is necessary to carry out a research in two parallel directions: Comprehensive analysis of thennodynamics, kineties and mechanisms of the processes taking place at the solid-liquid-gaseous phase interface during welding processes and development of mathematical models of the specific welding technologies. We have developed unique method of mathematical modeling of phase interaction at high temperatures. This method allows us to build models taking into account the thennodynamic characteristics of the processes, the influence of the initial composition and temperature on the equilibrium state of the reactions, the kinetics of heterogeneous processes, the influence of the temperature, composition, hydrodynamic and thennal factors on the velocity of the chemical and diffusion processes. The model can be implemented in the optimization of various technological processes in welding, surfacing, casting as well as in manufacturing of steels and non-ferrous alloys, materials refining, alloying with special additives, removing of non-metallic inclusions.

Jan 1, 2003

By Andrew Case

The Port Nickel facility in Braithwaite, Louisiana, is known for pioneering hydrometallurgical processes for the &apos;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 Banqiu Wu

Zirconium carbide powder has been synthesized from zircon concentrate and methane using a high temperature plasma reactor, a non-transferred DC plasma torch was used as heat source. A high temperature filter consisting of graphite felt was designed, built and operated to separate the zirconium carbide from silicon carbide during the process. Characterization of the collected powders was done by wet chemical analysis using Atomic Absorption (AA), Scanning and Transmission Electron Microscopy (SEM and TEM) and by X-Ray Diffraction (XRD). It was found that the zirconium carbide purity was around 95% with silicon carbide being the primary impurity. The powders had particle sizes between 30 and 80 nm. The effect of several experimental variables are presented as well as temperature and velocity profiles calculated in the reactor.

Jan 1, 1997

By J. P. Evans

The modem copper smelter today utilizes tonnage oxygen for smelting concentrates, generating a high strength S02 off-gas leaving the smelter vessel. This gas stream, which also contains any unreacted oxygen, plus C02, N2 and H20, also carries with it the volatilized portion of heavy metals in the feed, plus partly oxidized sulfide concentrates. The time/temperature history and subsequent treatment of this off-gas stream emerging from the smelting furnace exit up to the acid plant can influence the partitioning and segregation of heavy metals in the off-gas circuit. Depending on this history, the type and characteristics of the chemical and physical reactions which. occur in the gas handling system can be influenced. This fact can also be used as a tool to adjust the separation of copper from heavy metals. In this paper, the impact of different time/temperature histories of the gas, due to different furnace geometries .and design, on the subsequent formation and characteristics of the smelter dust is examined. Based on the available data, several case histories drawn from examples using both bath and flash smelting technologies are analyzed from this perspective.

Jan 1, 1992

By J. P. Evans

The modem &apos;copper smelter today utilizes tonnage oxygen for smelting concentrates. ,generating a high strength S02 off-gas leaving the smelter vessel. This gas stream. which also contains any unreacted oxygen, plus CO2; N2 and H20. also carries with it the volatilized portion of heavy metals in the feed, plus partly oxidized sulfide concentrates, The time/temperature history and subsequent treatment of this off-gas stream emerging from the smelting furnace exit up to the acid plant can influence the partitioning and segregation of heavy metals, in the off-gas circuit. Depending on this history. the type and characteristics of the chemical and physical reactions which occur in the gas handling system &apos;can be influenced. This fact can also be used as a tool to adjust the separation of copper from heavy metals. In this paper, the impact of different time/temperature histories of the gas, due to different furnace geometries and design. on the subsequent formation and characteristics of the smelter dust is examined. Based on the available data. several case histories drawn from examples using both bath and flash smelting technologies are analyzed from this perspective.

Jan 1, 1992

By Kampe. S. L., Baker. Andrew H., Tony Zahrah

"Experimental heats of reaction for the formation of several Al3Ti + TiB2 intermetallic composite formulations have been determined utilizing bomb calorimetry. To overcome the kinetic constraints and achieve ignition in these formulations, a boron (B)/potassium nitrate (KNO3) initiation aid was incorporated within the blended reactant compact. The heat contribution from the initiation aid was regressed to provide estimates of the heat of reaction of the nominal formulations. Powder x-ray diffraction was utilized to identify the products of the reaction and discern any differences between the predicted equilibrium products of the formulation and the actual products.IntroductionReaction synthesis is a technique for the creation of ceramics, intermetallics, and in-situ composite materials [1]. Reaction synthesis is defined by its self, propagating mechanism, where the energy liberated from a localized reaction within a green powder compact is enough to carry the bulk reaction to completion. Achieving a self, propagating state can be achieved in variations of two primary methods of initiation: uniform volumetric heating and directional propagation [2].Uniform volumetric heating involves subjecting a green compact of the unreacted formulation to uniform heating in a furnace to encourage diffusion to initiate the reaction (Figure 1a) throughout the bulk material. Directional propagation utilizes a point heat source at one section of a green compact of unreacted formulation (Figure 1b). The localized exothermic reaction at one point in the compact then initiates the reaction in the section of the compact adjacent to it and fully propagates throughout the entire compact until completion. Initiation of the localized reaction is generally associated with the melting of the constituent with the lowest melting point, with instantaneous initiation of the reaction usually occurring close to that melting point [1]. This melting point can be high in some systems of interest, such as the titanium (Ti) and boron (B) system in equation 1:"

Jan 1, 2011

By R. C. Chaturvedi, S. B. Padwal

"Padwal and Chaturvedi have developed the model based on M-K theory, considering Hosford's yield criterion and critical thickness strain criterion"" to predict the sheet metal forming limits under simple (constant) strain ratio paths. This analysis has been extended in this paper to predict the sheet metal forming limits under complex strain paths. The effects of exponent ""a"" in Hosford's yield criterion and strain paths on the forming limits under complex strain paths are studied using this analysis. The predictions of the present analysis are compared, both for simple and complex strain paths, with experimental results of Ishigaki for A.K. steel and also with the predictions of Rao and Chaturvedi's model. The quantitative analysis of the error in predicting the forming limits has also been carried out using a method suggested by the authors earlier.1. INTRODUCTIONThe constant strain ratio condition has been assumed in the theories developed for prediction of forming limit diagrams (FLO). In actual forming operation, this condition is seldom satisfied. Even in the case of simple single stage press formed components, the strain path becomes curved and non-linear. In the case of pressings with complex shapes, or multiple stages of forming, the changes in strain path are more pronounced and even abrupt.Experimental study of the forming limits, under two stage strain paths, by Ishigaki [1], has shown that the forming limits are path dependent. It has been observed that the forming limits lower than that under simple strain paths, may be obtained under certain strain paths (when the first stage strain path is either equibiaxial tension or uniaxial tension, followed by the second stage strain path as plane strain). Rasmussen's work [2J, on the theoretical study of forming limits under curvilinear strains paths, has shown that a large drop in formability can result from very small changes in strain path. Thus if a deformation process gives rise to failures due to plastic instability, the failure is not necessarily due to insufficient formability of the material. In such cases, FLOs based on constant strain ratio path should not be used directly in predicting the success or failure of the forming operation. Thus the knowledge of forming limits under complex strain paths is of great importance to the interpretation of press-shop problems."

Jan 1, 1994

By S. Ferlay

"The main purpose of the ZIMA VAL project (Label EUREKA EU1367 and LIFE ENV/F/000278) is to demonstrate industrial scale recovery and recycling of the main components of used dry batteries (zinc, manganese dioxide, mercury, and stainless steel) into high added value products. The originality of the ZIMA VAL process resides in:1- the use of hydrometallurgy2- alkaline treatment implementation (highly selective) for zinc and mercury3- electrochemical recovery of high quality products.4- the recycling of all the battery components (zinc, mercury, manganese dioxide, stainless steel) ·5- low operating and investment costs.The process consists of physical classification, mechanical dismantling, hydrometallurgy and electrochemistry. The purpose of the demonstration plant in FALAISE (Calvados - France) is to define the technical and technological parameters of an industrial unit for the treatment of 2400 tonnes per year of used batteries."

Jan 1, 2000

By Duclerc Fernandes Parra, Vijaya Kumar Rangari, Washington Luiz Oliani, Danilo Marin Fermino, Ademar Benevolo Lugao, Nilton Lincopan, Luiz Gustavo Hiroki Komatsu

Polyethylene is widely used for packing applications. Different grades of polyethylene, LLDPE and LDPE play a major role in the film blowing industry. The use of nanoclay in polymer matrices (non-polar) requires the use of a compatibilizer agent, ethylene graft maleic anhydride copolymer (PE-g-MA), which acts as a bridge for nanoclay-matrix-interaction. In our study, blown films of LLDPE, LDPE, and their blends were produced using a twin screw extruder. The combination of PEs as matrix, montmorillonite (MMT) and silver nanoparticles (AgNPs) intended to improve mechanical and thermal properties. Nanocomposites films with 1 wt% of montmorillonite and 0.5–1.0 wt% silver nanoparticles were prepared by blow extrusion and evaluated. Nanoclay intercalation/exfoliation degree was investigated by X-ray diffraction spectroscopy (XRD) and scanning electron microscopy (SEM). Mechanical and thermal properties were evaluated. The results showed optimum dispersion at intercalation/exfoliation levels for polyethylene nanocomposite (PENC), slight increasing in mechanical and especially improvement in thermal properties.

Mar 1, 2017

By Duan Xin-hui, Wang Xin, Peng Jin-hui, C. Srinivasakannan, Zhang Li-bo

The work attempts to optimize the process of preparation of modified semi-coke from semi-coke using phosphoric acid (H3P04) as the activating agent using the response surface methodology (RSM). The influences of three major dependent variables, the impregnation ratio, activation time, and activation temperature were assessed on the independent variables yield and the iodine number. The empirical relationship between the dependent and the independent variables were established using the quadratic response surface models, which were utilized to optimize the process parameters. The significance of each of the parameters and interaction among the parameters on the independent variable was assessed based on analysis of variance (ANOVA). The process variables were varied within the range of impregnation ratio (IR) from 1.5 to 4, activation time from 30 to 90 min and activation temperature from 550 'C to 650 'C. The optimized process conditions were estimated to be an IR of 2.29, activation time of 32 min, and an activation temperature of 605°C respectively using the process optimization tool. The BET surface area of modified semi-coke of the optimized sample was estimated to be 915m2/g, with the pore volume of0.71cm3/g, with an average pore diameter of 3.09 nm, with micropore volume fraction being 52.36%. The scanning electron microscope (SEM) images were utilized to visualize the surface pore structure.

Jan 1, 2013