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By Animesh Jha

Univariant diagrams are constructed for the reduction of nickel and cobalt oxide and sulphide minerals. The results from the carbothermic and hydrogen reduction of sulphide minerals are compared. The importance role of lime and calcium sulphate in controlling the emission of sulphurous- gases during reduction reaction is also explained. The mechanism of carbothermic reduction of nickel sulphide is explained by examining the sulphur exchange and reduction reactions. The phase equilibrium relationships that determine the formation of multicomponent liquid are characterised. Also the governing equilibria for inert atmosphere calcination- roasting of nickel and cobalt sulphide minerals are also described for the metallization of nickel and cobalt.

Jan 1, 1993

By Guo Chen, Jin Chen, Jinhui Peng

In this study, the influences of the green evaluation variables on the characterization of microwave shaft furnaces were systematically investigated. These variables include: resource consumption, environment impact, production cost, processing time and quality of microwave shaft furnaces. A greenness evaluation index, evaluation system and evaluation model of microwave shaft furnaces were established. The analytic hierarchy process and fuzzy comprehensive evaluation were applied to the evaluation process. Resource consumption and environment impact had a statistically significant effect on the green evaluation of microwave shaft furnaces. The results indicated that green evaluation techniques can be applied effectively and efficiently to the process manufacturing of microwave shaft furnaces.

Jan 1, 2015

By C. Gasparrini

Mineralogy may be applied to the selection of appropriate separation techniques, as well as to assist in the evaluation of problems causing loss of metals and other economically important elements during plant processing. Mineralogic studies may thus help develop techniques to optimize metal recoveries. The present paper describes how such factors as the minerals in which the elements of interest are concentrated, their chemistry, the chemistry of the associated minerals, grain size and textural associations with other minerals in the ore, may affect decisions on separation techniques for the recovery of economic elements. A number of case studies are described in which the mineralogical observation of ore samples has revealed the cause of problems experienced in the extraction of select precious and base metals, or has been decisive in the choice of appropriate techniques for recovery.

Jan 1, 1981

By Ma Ying

The continuous directional solidification technique of five kinds of special ZA alloys with eutectic, peritectic and eutectoid transformation under the condition of continuous casting by heated mold was studied. The mechanism of surface defects appearing in ZA alloy line was discussed and the structure of some defects were analyzed by SEM. The results show that only when the fitting of various technique factors, pressure head, outlet temperature, pulling speed and cooling condition are reasonable under a certain range, can the ZA alloy smooth line be continuously pulled out. Unreasonable techniques will result in hot tear, rough surface, mush outlet, leaking and other defects. The shape and location of solid-liquid zone have an important influence on the formation of the above defects. When the solid-liquid zone is located in the mould outlet or inner mould, the surface of solidification will protrude into the inner mould. If the remaining liquid cannot counteract the solidification contraction, a rough surface will appear. If the solidification surface further into the mould, the ingot in the mould will have a great friction force when pulling and will form a hot tear. When the solid-liquid zone is moved out of mould, the solidification surface will turn into a plane, which easily results in leaking. A vibration or unstable operation will cause an ingot winding during pulling

Jan 1, 2003

By Marcela Morvová, Mário Janda, Morva Imrich

"The possibilities of greenhouse gas mitigation using various methods are brought out. The special case of utilization of mixture of CO2 with other greenhouse gases in a synergetic way inside non-thermal plasma based system is described in detail.Measurements on pilot system comprising pyrolysis chamber as alternative energy system (production of hydrogen and liquid tar) were made for various biomass and waste as the input material. The exhaust from this system was treated with non-thermal plasma gap suitable for up to 650Nm3/hour of exhaust gas flow. Condensable portion of exhaust is liquefied in distillation unit; produced hydrogen is stored on-line inside nano sized carbon of our own production.The CO2 removal efficiency varies depending on exhaust composition between 45 to 98%. Other oxides as CO, NOx, SOx and several hydrocarbons and VOC are also removed. The main product connected with CO2 removal is a solid powder of proteinoid nature. There exist strong probability, that precursor of the origin of life on the Earth from primary atmosphere were formed in the similar way as it is present in the electric discharge system used. Our system is equipped with on-line as well as ex-post analysis of all forms of products. We have also developed a system for recuperation of all forms of produced heat. It is stored inside as latent heat of waxes.IntroductionNatural greenhouse effect on the Earth is caused mainly by water vapour with the average absolute concentration about 4%. Other gases able to absorb long-wave radiation and thus this causing greenhouse effect are CO2, CH4, N2O, halocarbons and as precursors ozone and NOX. Some of them we produce and introduce into atmosphere in large quantities during production of energy and in transport. This factor leads to permanent increase of average temperature of air, sea and oceans, so called global warming.Nowadays large amount of data exists showing that the temperature of Earth in the last 150 years has been continually increasing. It represents about 03°C per ten years and the most of climatologist believe, that the increased concentration of greenhouse gases in the atmosphere is responsible for this effect.The most important greenhouse gas is carbon dioxide CO2. Majority of CO2 emissions comes from electric power stations working with fossil fuels, cars and industry. Burning of fossil fuels contribute up to 80% to world wide anthropogenetic emissions of CO2."

Jan 1, 2010

By U B. Pal

Downsizing and decommissioning of nuclear facility operations is increasing the stockpile of various different grades of Radioactive Scrap Iron (RSI). Disposal of this material not only represents significant resource and value lost, but also necessitates long term monitoring for environmental compliance. The latter results in additional recurring expense. It is desirable to be able to decontaminate the RSI to a very low level that can be recycled or used for fabrication of containers for RSI disposal instead of using virgin metal to fabricate the container. Electro-Slag Remelting and Refining (ESR) is often used for decontaminating radioactive contaminated sources of scrap iron such as stainless steel. Non-radioactive oxides of cerium are used to simulate the radioactive oxide contaminants of Uranium and Plutonium. The success of the ESR process is strongly dependent on the capacity of the slag to rapidly incorporate the radioactive contaminant (simulant). In this study we have measured the slag-metal partition coefficient for cerium and investigated the reaction mechanism for the dissolution CeO, in the slag.

Jan 1, 2002

By Huanyu Zhang, Quanqiang Ma, Huiqing Tang

Improvement of the coke quality for blast furnace (BF) iron making by hydrothermal oxidation treatment on coke quality was investigated. Results show that, under subcritical condition, sulfur removal rate is 15% and the weight loss is 3%; under supercritical condition, both sulfur removal rate and mass loss rate increase with the increase of H2O2 concentration. In the experimental conditions, sulfur removal rate and mass loss rates were 45% and 17%, respectively. Hydrothermal oxidation treatment could reduce the CO2 reactivity of the coke and the treatment under supercritical condition is more effective. Hydrothermal oxidation treatment could improve the graphitization of the coke and smoothness of pore boundary in the coke and the treatment under supercritical condition is more effective.

Jan 1, 2016

By Esher Hsu

On July 5, 1997, Environmental Protection Administration of Taiwan publicized the recycling regulation of waste home appliances that include four items, namely, television, refrigerator, washing machine, and air conditioner. It is believed that this regulation pioneers the law enforcement of waste home appliances in the world. The objective of this study is to provide helpful base for amending recycling rates of waste home appliances. This study investigates the collection and recycling costs of waste home appliances in accordance with these newly established routes and facilities, respectively. Cost survey was conducted among collectors and recycling plants of waste home appliances; consequently, the collection and recycling costs were analyzed, correspondingly. Results provide some suggestions regarding recycling route, recycling system, recycling rates paid by manufactures and importers, recycling subsidies to collectors and recyclers. Those suggestions may provide useful policy implications to EPA for the future decision-making regarding the recycling of waste home appliances.

Jan 1, 2003

By Peter A. Spencer

The metallurgical parameters necessary for the design of a carmercial scale bio-oxidation plant have been determined for the treatment of a refractory arsenopyrite concentrate using a moderately thermophilic bacterial culture. The parameters considered were bio-oxidation rate, culture growth rate, nutrients, solids density, level of bio-oxidation, particle size distribution and oxygen uptake rate. The approach for obtaining the optimum values for these parameters is discussed and values based on results fran batch and continuous testing are given. Estimates of the capital and operating costs for a plant treating the carmercial arsenopyrite concentrate have been calculated fran the test data.

Jan 1, 1990

By David J. Howard, Christine Broadbridge, David C. Paine

"High pressure vapor/solid reactions offer an opportunity for novel synthesis and processing of thin film materials and structures for electronic, optical, and magnetic applications. In this paper we review the use of two high pressure techniques that operate from 25 to 1000 atm (2.5 to 100 MPa) to fabricate thin film oxide structures from Si1-xGex deposited on Si wafers. High pressure synthesis enables temperature-independent control of reaction rates in the oxidation of this multicomponent semiconductor system and hence offers the opportunity to form thennodynamically metastable Si1-xGex<h from the alloy. The thermodynamics of the Si-Ge-0 system are reviewed and a method is described that utilizes selective chemical reduction (via H2 gas) of Si1-xGcx<h to form Ge precipitates in an SiO2 matrix. IntroductionAlloys of Si1-xGex grown epitaxially on Si substrates by chemical vapor deposition (CYD) and molecular beam epitaxy (MBE) have been used to create high performance microelectronic devices1. These devices show improved performance over conventional Si technology because they exploit the Si/Si 1-xGex band-gap discontinuity and take advantage of higher hole mobilities in the Ge containing alloys. While a range of devices based on heteroepitaxial systems have been demonstrated, the Si1_xGex alloys are of particular interest because they are most closely compatable with standard Si device processing. One disadvantage of Si-based materials systems is that they are not typically useful emitters of light. This is important since the use of light (rather than electrons) for transmitting and processing signals into, out of, and within Si-based microelectronics would represent a major technological advance in microelectronics-based communication and computer technologies. Nevertheless, through the use of innovative processing techniques it may be possible to use the Si1_xGex/Si heteroepitaxial system in integrated microelectronic/light-wave technologies."

Jan 1, 1994

By F. Sakurai

The enlarged Mitsubishi process in Naoshima has been in steady operation since. May 1991. However, the sulfuric acid plants have been in operation for more than 30 years. The acid plants were modernized between 1999 and 2001 by renewing some of main equipment such as the drying tower and gas heat exchangers, and introducing new technology. At the same time, as an electric energy saving measure, the electric power consumption in the sulfuric acid plant was vastly improved by decreasing the volume of gas treated the installation of low temperature activity catalyst in the 1st pass of the converter and optimization of main gas blower runner. Furthermore, last year, the oxygen plant was replaced and enlarged, and anode production increased from 240,000 to 280,000 tonnes per year with an associated increase of sulfuric acid from 550,000 to 660,000 tonnes per year. This paper describes these recent improvements in the acid plant at Naoshima smelter.

Jan 1, 2002

By W. Persson

The first installation at a copper smelter of a Semtech OPC System for continuous, on-line production control of copper converting in PS converters took place in 1994. At present OPC systems are installed at 19 PS converters. The technology presents to the operator real-time information on the progress of the process he is controlling in the form of optical process parameters, thus facilitating dynamic process control. The optical process parameters are based on time- and wavelength resolved registrations of the light emitted by the off-gas flames and identification of correlation between these parameters and characteristic metallurgical process data. The present paper provides a description of the technology as seen by the furnace operators and a summary of operating experiences made during five years of full-scale, operation at various smelters, reviews influences from the technology on smelter operational practises and comments on recent developments as regards new applications of the technology.

Jan 1, 1999

By Hector Carreon

During fretting, high points or asperities of the mating surfaces adhere to each other and small particles are pulled out, leaving minute, shallow pits and powdery debris. Sometimes these surface conditions are neglected, but they are important in some application such as the aerospace industry. In this research work, non-contacting and contacting thermoelectric power techniques are performed in fretted 7075-T6 and Ti-6Al-4V samples. It has been found that the contacting and non-contacting thermoelectric power measurements are associated directly with the subtle material variations such as work hardening and residual stresses due to plastic deformation produced in the fretting zone but surface topography. Therefore, both techniques could be used for a global characterization of the most relevant fretting induced effects. Potential of these techniques to monitor subsurface changes in other severe surface plastic deformation processes are clearly envisaged.

Jan 1, 2015

By H. Kamiya, H. Hasegawa, M. Nojiri, S. Matsui, Y. Fukuda, M. Tsukada

"The present paper focuses on the action mechanism of anionic polymer dispersants in dense Si3N4 and SiC suspension. An atomic force microscope (AFM) was used to determine the relationship between the macroscopic suspension viscosity and the microscopic adsorbed structure of a polymer dispersant at the solid / liquid interface. The surface interactions within the suspensions were analyzed in various dispersant pH and additive conditions. The addition of an anionic polymer dispersant decreased Si3N4 and SiC suspension viscosity and increased electro-steric repulsion force on the non-oxide surface in solution at pH> 6 which was the isoelectric point of the materials. It was assumed that the increase of repulsive force was promoted by a hydrophobic adsorption of polymer dispersant on the non-oxide particles.IntroductionThe surface of silicon nitride and silicon carbide powders in a water suspension system has quite a complex molecular structure. In the case of Si3N4, hydroxyl and ammonium groups form on the surface and the pH of the suspension is increased from neutral to about 10 due to surface oxidation. The particle surface is negatively charged in alkaline solutions (pH=10), because the isoelectric point of silicon nitride exists in the pH range from 5 to 6. However, in spite of charging the negative surface charge, an anionic polymeric dispersant is generally used for the reduction in slurry viscosity.In dense SiC suspensions, an anionic polymer dispersant is generally used in order to disperse aggregates and reduce the suspension viscosity, too. Since an anionic dispersant is used in alkaline solutions higher than the isoelectric point of silicon carbide, the dispersant adsorbed on the negative charged surfaces of SiC.Few researchers have discussed and estimated the adsorption mechanism and structure of anionic polymeric dispersants on silicon nitride and silicon carbide surfaces. This is because it is difficult to observe the structure and measure the interaction at the solid/liquid interfuce directly. However, new developments in surface-force measurement technology have enabled the determination of non-DLVO type interaction for analyzing aggregation behavior2. The use of the AFM for analyzing the effects of various surfactants and co-polymers on colloidal dispersions and solid surfaces has also begun to rapidly expand to characterize the interaction between solid surfaces."

Jan 1, 2000

By K. L. Hardee

A recent development has emerged which produces a retrofittable, low cost anode by attaching disposable, electrocatalytically active titanium mesh over the existing lead anodes. The coated titanium mesh anode operates at potentials of several hundred millivolts lower than the lead anode, providing significant power savings. The exposed lead surfaces are stabilized since most of the current flows through the titanium mesh. With the minimal lead corrosion, the sludge formation is virtually eliminated and the purity of the plated copper is greatly enhanced. Further savings may be realized by the elimination of non-essential chemicals such as cobalt. Since the combination anode is stable and uniform, the plated copper is also more uniform with minimal formation of dendrites, reducing the shorting. Full-size anodes have been tested for over 6 months in commercial copper electrowinning cells. The laboratory and field performance of the stabilized lead anode will be reviewed, including the voltage characteristics, the lead stability and the copper cathode purity.

Jan 1, 1999

By Ronald C. Askin

Dredging is a common method of remediating ponds containing contaminated wastes. However, dewatering of the dredged solids is usually not well integrated with the dredging phase. As a result, overall project efficiency can be poor. Specifically, since dredges deliver material in a widely varying slurry form and since dewatering presses require the delivered material to be uniform, union of the two systems often results in inconsistent operation of the overall process. In an effort to enhance overall dredging and dewatering process production rates as well as minimize the return of suspended solids in the decant water, a new process was developed to provide a consistent dredged sludge for delivery to the press. This paper discusses modifications made to a conventional dredging and dewatering process to improve production rates and dewatering capabilities. These modifications are applicable to any project where efficient solids dewatering is required and where returning decant water must be visually free of suspended solids.

Jan 1, 1996

By J. P. Downey, L. G. Twidwell

"The high density sludge process (HDS) is a commercially proven acid rock drainage wastewater treatment process that is based on acid neutralization and metal precipitation. Previous studies have established that metal removal efficiencies in precipitation-based wastewater treatment applications can be improved through metal ion adsorption on ferrihydrite and/or aluminummodified ferrihydrite. This study was conducted specifically to determine whether the metals removal efficiencies at an existing industrial facility could be improved by promoting ferrihydrite and/or aluminum-modified ferrihydrite precipitation during the pH adjustment stages of the HDS process. The metal tenors of the treated wastewater samples are compared with those obtained through baseline experiments, which were designed to simulate the conventional HDS operation. The subject metals were: aluminum, arsenic, cadmium, copper, iron, manganese, nickel, and zinc.IntroductionThe HDS process is commercially proven ARD wastewater treatment technology that involves raising the wastewater pH by adding hydrated lime, caustic soda, or another alkaline substance. In addition to neutralizing the acidity, many dissolved metals precipitate as pH is elevated. Waste volume is minimized by capturing and immobilizing the precipitated solids.However, ARD streams characteristically contain multiple dissolved metal species. The response of various metals to pH adjustment in the HDS process is neither uniform nor quantitative, so minor to trace concentrations typically remain in the treated wastewater following solid-liquid separation. The effectiveness and applicability of the process would be improved if a means were found to further reduce the metal concentrations.Previous research and industrial applications have proven that metal ion adsorption on ferrihydrite (FH) and/or aluminum-modified ferrihydrite (AMF) increase metal removal efficiencies. Ferrihydrite and AMF are considered ideal for cation and anion adsorption from an aqueous solution at the appropriate pH [1]. Ferrihydrate adsorption of dissolved heavy metals is widely practiced throughout the world [2, 3]. It is established that FH and AMF effectively adsorb As contained in aqueous solutions [4]. Arsenic removal by adsorption on FH is the U.S. Environmental Protection Agency’s (EPA) Best Demonstrated Available Technology [5]. Twidwell and Leonhard also demonstrated that heavy metals (Cd, Cu, Ni, and Zn) are effectively removed from solution by coprecipitation/adsorption using AMF and FH [6]."

Jan 1, 2008

By J. M. Rapkoch

In late October 1996, an acid plant at a major U.S. copper smelter was faced with unexpected and rapidly increasing pressure drop across the gas cooling tower in the acid plant, indicating a build-up on the packing. This threatened to halt operations if not resolved. Earlier that month, a smaller vessel in the acid plant was found to be completely plugged with lead sulfate. It was feared that a similar fate awaited the gas cooling tower unless the scale build-up was stopped. Although lead sulfate is present in most copper smelter acid plants, this accumulation was unusually severe. An investigation was launched to find the source of the lead, determine how lead is transported to the gas cooling tower, recommend operating practices to prevent such severe scaling, and seek ways to recycle the lead value in the scale covered polypropylene packing. Late in the investigation it was learned that the lead originated from an improperly executed recycling program.

Jan 1, 2000

By A. V. Tarasov

Based on the data available in the literature and the practical experience of new metallurgical plants, a method has been proposed and relevant studies conducted for metallurgical processing of zinc sulfide concentrates. Process conditions and parameters have been identified, which ensure high levels of recovery of zinc into solution. This is achieved by leaching concentrates under the normal pressure at a temperature of >90°C in the presence of ferric iron ions. Sulfide sulfur is converted to elemental sulfur in this process. To produce elemental sulfur it is necessary to maintain oxidizing conditions in the system, characterized by a positive Eh value. In order to eliminate the interfering effect of elemental sulfur formed in the process, it is possible to add surfactants into the concentrate pulp. The proposed technology has certain advantages as compared with the high-temperature pressure leaching and is considered as a basic technology to be applied to increase zinc production at one of the Russian zinc plants.

Jan 1, 2006

By V. M. Paretsky

Most recent developments made in the Gintsvetmet Institute in the field of technologies and equipment for single-stage autogenous smelting of copper sulfide raw materials to produce white metal and blister copper on the basis of oxygen-flame smelting process and separation of highly basic calcium-containing slags have been discussed. This technology includes the oxygen-flame smelting process (KFP Process) to produce highly basic self-disintegrating ferrite-calcium slags with their subsequent flotation to recover copper and a basically new sparging smelting process (FBP Process) to produce combined slags subjected to decopperizing inside the same furnace. Results of special investigations of the slag structure obtained in the KFP and FBP processes and substantiating selection of their chemical and phase composition have been presented. It has been demonstrated that the above processes meet the stringent world-level requirements to advanced technologies with respect to energy conservation and environmental safety with different scales of production and within a wide range of specific conditions of particular operations.

Jan 1, 2006