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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 Pragna N. H. Bhakta

The minerals industry is under political and economic pressure to reduce its processing wastes and minimize their impact on the environment: Recycling is one of the means by which the minerals Industry can reduce the quantities of effluents and residues that are discharged to the environment. The wise use of available resources is not only an environmental necessity but also an economic benefit as natural mineral resources are depleted and/or become more complex. The purpose of this paper is to review the technical and regulatory issues that will help shape the future of minerals recycling over the next ten years. Research and development to address technical issues will be discussed with emphasis on the Bureau of Mines recycling research program.

Jan 1, 1992

By Shunichi Ajima

PT. Smelting Co. was established in February, 1996 to construct and operate the Gresik Smelter and Refinery. The construction work of first Copper Smelter and Refinery in Indonesia was completed in the end of August, 1998 and it was put into the integrated test operation in December, 1998. Gresik Smelter and Refinery is designed to produce 200,000 tpy of copper cathode from copper concentrate supplied from Grasberg Mine of PT. Freeport Indonesia Company in Irian Jaya, Indonesia. As by product 592,000 tpy of sulfuric acid, 382,000 tpy of slag, 31,000 tpy of gypsum and 480 tpy of slime will be produced in the full operation. Major processes applied at Gresik Smelter and Refinery are: Smelter: Mitsubishi Continuous Copper Smelting and Converting Process ( Mitsubishi Process ) Anode Casting: Continuous Casting of Copper Anodes with the Hazelett Twin Belt Caster Refinery: ISA Process Acid Plant: Lurgi Mitsubishi Double Contact Process

Jan 1, 1999

By H. Y. Cho

LS-Nikko Copper Inc, has been operating its Onsan copper smelter since 1979. The smelter began its operation with a designed capacity of 80,000 tpa of copper from concentrates and its smelting capacity was increased to 140,000 tpa of copper by modifying the existing line in 1988. The Mitsubishi Continuous Smelting and Converting Process has been operating since 1998 at the initial capacity of 160,000 tpa of copper. In 2002, the smelting capacity of the Onsan smelter has been increased to 426,000 tpa of copper from concentrate. Now the Onsan smelter has plans to increase its smelting capacity to 500,000 tpa of copper from concentrates by 2010. During the expansion work, the modernization of facilities will be accompanied by an increase in smelting capacity, via the Outokumpu process. This paper reviews the brief history of smelting capacity increase in Onsan smelter and its Outokumpu process modernization plans.

Jan 1, 2006

By H. Aminian

Copper electrowinning (EW) is an important process in connection with the solvent extraction to produce pure and marketable copper cathodes. A phenomenological model was developed to simulate the copper electrowinning process. The simulator is used to predict the operation of the Mines Gaspe pilot plant electrowinning cells put in operation in 1996. Results confirm the potential of the simulator that would subsequently be used for student training, process optimization and assessing the performances of control strategies.

Jan 1, 1999

By J. H. de. Visser

The transfer of molten metal in smelting or refining operations is typically performed in open trough-type launders that are constructed of either water-cooled copper troughs or refractory lined steel jackets. This transfer can be either continuous or batch. Batch operations transfer metal through an open launder. The uncovered launder has many operational and environmental drawbacks. In order to improve workplace hygiene, designs have evolved toward ventilated launder covers that .are connected to secondary exhaust systems that use negative pressure under the cover removing fume and hot gases to secondary fume control devices. In smelting operations, a variety of covers have been employed which insulate the launder and contain the fumes and also provide additional heat along the length of the launder through a series of premix or inspiration-type burners that add combustion products to the normal fume load in the launder. Cover designs have proven to be inadequate in that hinged unventilated covers hinder convenient access while heated ventilated covers are costly to maintain. Covers that employ refractory bricks and overhead enclosure-type exhaust hoods have been somewhat successful, but restrict operator movement and require large volumes of exhaust air. An example is given of a cover and off-gas system for launders that is designed to provide superior insulation and heating capabilities, as well: as better control of the fume gases-and ease of maintenance. The cover system must maintain the balance between maintaining launder heat and fume removal. The construction of the covers must be able to withstand high internal temperatures and maintain its structural properties.

Jan 1, 1999

By Tim Robinson, Georges Houlachi, Michael Moats, Marco Ginatta, Michael Free, David Creber, Neale Neelameggham, George Holywell

"Electrolytic processing is used commercially to recover and/or refine metals such as aluminum, copper, magnesium, nickel, and zinc. There are also new and exciting opportunities to utilize electrometallurgy in the production of titanium, lead, and other metals. This paper reviews some of the main technologies that are used to produce and refine metals as well as some of the recent advances and future directions the electrometallurgy industry may implement to meet the challenges faced now as well as those that are likely to be faced in the future.IntroductionElectrolytic processing is used commercially to recover and/or refine metals that include large scale production for metals such as aluminum, copper, magnesium, nickel, and zinc as well as small scale production for metals such as gold and silver. There are also new and exciting opportunities to utilize electrometallurgy in the production of titanium, lead, and other metals. This paper will focus only on electrometallurgical processing of metals with relatively large production markets."

Jan 1, 2012

By John Demol

Monazite, a rare earth and thorium phosphate mineral, is one of the major minerals processed for extraction of rare earths. Industry practice for treating monazite concentrates is to use either a sulfuric acid bake or caustic conversion route. In the sulfuric acid bake, monazite concentrate is mixed with concentrated sulfuric acid and roasted. The rare earth phosphate mineral is converted to rare earth sulfate which dissolves in a subsequent water leach. As the bake temperature increases above 300 °C, thorium becomes less soluble. Although acid baking is practised in industry, the bake reactions are not well understood. A combination of chemical analysis, XRD and SEM-EDS was used to identify reaction processes occurring during sulfuric acid baking of a 93 wt% monazite concentrate between 200 °C and 800 °C. The effects of these reactions on the leachability of the rare earths, thorium and phosphate were also examined.

By David K. Melgaard

Electroslag Remelting (ESR) is a complex process used to produce high quality specialty alloy materials. The quality can be directly correlated to variances in melt rate and immersion depth. Conventional ESR furnaces control these quantities using two independent control loops using proportional changes in current for melt rate and driving the electrode up and down to match a voltage set point for immersion depth. However it is well known that the control loops are highly coupled, i.e. changing the current to account for melt rate deviations changes the voltage depth relationship and vice verse. In addition the noise in measurements of the ESR process can be considerable, forcing conventional controllers to use highly damped responses. A new model-based controller has been developed to embody the coupling and improve responsiveness by using estimates from a reduced-order linear ESR model and the typical process measurements to control melt rate and immersion depth simultaneously. Kalman filtering is used to optimally combine the model estimates of eight process states and the measurements of voltage, current, position and mass to estimate the instantaneous melt rate and immersion depth. Several ESR melts under steady state and transient conditions were conducted to evaluate the performance of the new controller. This paper will discuss the design of the new ESR model and controller and will present experimental results demonstrating its much improved control and responsiveness. While this controller was developed for the ESR process, the effectiveness of model-based control in managing such a complex process with relatively simple equations suggests the approach could be employed for many other processes as well.

Jan 1, 2006

By A. E. Wraith

The tuyère flow rates of Peirce-Smith converters and bath smelting reactors are rendered particularly sensitive to accretion formation, bath depth variations and the general aerodynamic design of the blast delivery system by the limited pressure-flow properties of the conventional single stage centrifugal blower. This sensitivity is examined in terms of tuyère practice, vessel management and fixed engineering parameters for Peirce-Smith converters and the Noranda Reactor by use of the flow resistance factor, R*. New understanding of the effect of accretion growth on the flow behaviour of individual tuyères shows that blowing rates and hence throughputs could be optimised by careful attention to operating detail even within present plant constraints. The concept of the resistance vector is introduced to elucidate comparisons between different practices and to provide reference standards for optimisation. On this basis, the benefits of introducing quite moderate changes in the pressure-flow properties of the blast delivery system are considered. In view of recent developments in the flexible use of converters as hybrid bath smelting vessels for matte production, the foundation is now laid for a searching consideration of relationships between vessel volume and shape, blowing requirements, tuyère performance and production rates, the detail of which will be examined more appropriately in a forthcoming paper.

Jan 1, 1999

By Todd S. Fayram

The Gordonsville Operation of Pasminco US Inc. along with the Center for Advanced Mineral and Metallurgical Processing (CAMP) at Montana Tech studied, developed and implemented a pilot scale hydrometallurgical facility for the industrial recovery of germanium and gallium. This paper describes the joint testing and engineering program that culminated in this successful process.

Jan 1, 2003

By M. Giunti, R. Hampson, S. Gray, P. Kapoulitsas, J. Clark

In 1997 Pasminco's Port Pirie Lead Smelter began a modernisation of its lead and precious metals refinery operations. Driven by the anticipated closure of its Broken Hill mine, the new refining process replaced the locally developed continuous process, which had been in operation since the 1950's. Commissioning of the new plant was staged, beginning in late 1997, and finishing early in 1999. The new plant provides for batch refining of lead, and the use of vacuum induction retorting and bottom blown oxygen cupel technology in the silver refining area. The project has resulted in an increase of lead production capacity of 11% and allows the treatment of a wider range of concentrates than was formerly possible. The most significant change has been to double the smelter's silver capacity to over 400 tonnes per annum. This paper describes the successful implementation and optimisation of the new refinery, which is now consistently meeting design capacity.

Jan 1, 2000

By F. J. Tavera

A study on the electro kinetics of lead carbonate, silica, and alumina, in aqueous media was carried out at different pH values. The behavior of potential was determined for these species in the pH range between 3 and 12. Homocoagulation of lead carbonate in aqueous media is analyzed at its isoelectrical point. Lead carbonate heterocoagulation is analyzed with silica, alumina, and silica ? alumina mixtures at low pH values. The experimental results are considered for their possible application to treat residual water polluted with lead.

Jan 1, 2006

By Raj Mutharasan

The phenomena of gas-molten metal reactions for the production of metal matrix composites consist typically of a combination of one or more gas transport steps and a liquid gas reaction step. Reaction products include such strength enhancers, grain refiners, or high thermal conductivity phases as TiC, AIN, SIC, Si3N4, TiN in aluminum alloys. Nitrides, carbides and oxides can be produced at various volume fractions and in fairly fine sizes (500 am to 5 um) in laboratory melts by Reactive Gas Injection method (RGI). Gas injection methodology to produce the reinforcements is attractive because it can potentially be scaled to production scales in excess of 10,000 kg/h. For continuous production, the reactant molten metal can be continuously fed into the .crucible where the reactive gas is injected. The molten metal phase reactant may also be involved in a controlling transport step, depending on its concentration and viscosity. It is well known that the reaction product reinforcement size and shape of these phases have significant impact on the physical, mechanical and thermal properties. The current state of knowledge is unable to predict the kinetics and growth of solid reaction products obtained. The primary goal is to develop a fundamental framework for the understanding and prediction of the particle size in such reaction systems. In addition, the role of gas transport, liquid hydrodynamics and decomposition are important issues. A reaction-transport model is being developed using a reaction, transport, and thermodynamic framework, both at macro and at atomistic level to assess gas - liquid interactions.

Jan 1, 1996

By Dachun Liu, Yifu Li, Baoqiang Xu, Yongnian Dai, Bin Yang

"The removal of impurity arsenic from crude tin is one of the major problems in the process of tin refining. Through a thermodynamic analysis on vacuum refining process of crude tin, the vapor pressure of impurity arsenic under different temperatures can be obtained, which demonstrates that it is possible to separate tin and arsenic by the vacuum refining process. This paper attempts to verify the behaviors of impurity arsenic. The experiment result shows that through vacuum distillation, crude tin with 0.16% arsenic can be refined from crude tin with 0.96% arsenic, and about 50% impurity arsenic can be collected in the form of metallic arsenic.PrefaceThe crude tin obtained by the reduction process is insufficiently pure for most applications, even smelting from tin concentrate. Arsenic is a common impurity in crude tin and also one of the predominant elements to affect tin performance. Arsenic is a poisonous metal that has long been linked to an increased risk of cancers, diabetes, thickening of the skin, diseases of the liver and digestive complications, so there is a mandatory limit on the amount of arsenic (<0.015%) in tinfoil wrapper and tin layers for food packaging. Arsenic causes a poor appearance and plasticity, and increases viscosity. The impurities content of crude tin fluctuate over a wide range; a lot depends on composition of tin ore concentrate, treatment method and technological process before reduction smelting. And the content range of arsenic is usually 0.5~4%, but it is higher in some factories."

Jan 1, 2012

By Jiu-ju Cai, Wen-chao Liu, Fei Liu

"The material flow of urban eco-industrial system includes linear flow, recycling flow, branching flow, converging flow, etc., which consequently lead to the system complexity. Comparing the urban eco-industrial system to ecosystem, it can be concluded that this complexity is caused by the system adaptability. In the system, the interaction and adaptability between the agents themselves and between the agents and the environment stimulates the changes of material-flow mode, which lead to the evolvement from traditional industry to the eco-industry. Focusing on the evaluation of this evolvement process, two material-flow models are established in this paper, one of which is for the system itself and the other for the agents in system. The latter model is applied to analyze the interrelationships among mass, energy and pollutant flow in the iron and steel industry, and to make the direction clear to improve the resource and energy efficiency and decrease the environmental load.1 IntroductionIndustrial system is a subsystem of urban system, and they are interconnected and interrelated through material flow. The industrial development causes the urbanization. But the traditional industrial mode, characterized by high consumption, high pollution and low efficiency, also causes the “urban problems”, and leads to the reduction of resources carrying capacity and the increase of environmental load. Nowadays a lot of researches focus on how to realize the sustainable development of industries and cities. Thus comes the urban eco-industrial system guided by industrial ecology.Regarded as a Complex Adaptive System (CAS), the urban eco-industrial system evolves for quite a long time. According to Holland’s description on CAS, CAS consists of adaptive agents, which interact with the environment and other agents, learn and accumulate experiences, and accordingly change their own structures and motion modes. In this way, the evolution of the whole macro system is improved [1]. The evolution from traditional industrial system to urban eco-industrial system is mainly reflected in the variety of internal material flows which include not only linear flows but also recycling flows. Therefore, to construct models which clearly analyze industrial metabolism, is of great importance to evaluate industrial system evolution.The article is organized as follows: Section 2 describes the urban eco-industrial system. Section 3 presents the system-oriented metabolic analysis model and the agent-oriented one, analyze the interrelations of energy flow, material flow and pollutant flow in Chinese iron and steel industry through the latter model, and indicates the directions of improving the resource efficiency and energy efficiency, and decreasing the environmental load. Section 4 concludes."

Jan 1, 2008

By Shadia J. Ikhmayies

"Cadmium sulfide thin films were prepared on glass substrates by the spray pyrolysis technique at a substrate temperature of 490°C. Some of the films were etched by HC1 in distilled water, others were heat treated in nitrogen atmosphere, and another set of films was first etched by HC1 and then annealed. Room temperature impedance spectroscopy measurements on the films were performed using coplanar geometry in the dark and in room light in the frequency range 20 Hz to 1 MHz. The experimental data were represented by complex plane diagrams and showed one well-defined semicircle in the high frequency region. Hence the equivalent circuit that models the CdS: In thin films was found to be a single RC circuit, which indicates the bulk conduction through the grains. The influence of treatments on the electrical properties was investigated.IntroductionCadmium sulfide (CdS) is a brilliant II—VI semiconductor material with a direct band gap of 2.42 eV at room temperature. It has many outstanding physical and chemical properties, which have promising applications in multiple technical fields including photochemical catalysis, gas sensor, detectors for laser and infrared, solar cells, nonlinear optical materials, various luminescence devices, optoelectronic devices and so on [1]. There are different methods to prepare undoped and doped CdS films, such as rf sputtering [2] chemical bath deposition (CBD) [3], pulsed laser deposition (PLD) [4], and spray pyrolysis (SP) [5-11]. Of these methods, spray pyrolysis represents the less expensive option, and can produce large area high-quality low cost thin films [12]."

Jan 1, 2012

By Emily Chen, Randolph Kirchain, Gabrielle Gaustad

"As prices and demand for aluminum metal have increased over the past few years, secondary production has begun to outpace primary aluminum production. However, while recycling of packaging and automotive scrap has continued to increase, aerospace secondary materials remain a largely untapped resource. Shredded or co-mingled aerospace scrap has a high degree of compositional uncertainty due to the prevalence of high copper and high zinc alloy series. Although it is clear that upgrading strategies enable increased usage of aerospace scrap, it is not clear that they would be economic or efficient. Previous studies by the authors have shown that modeling techniques, specifically chance-constrained optimization, provide the ability to evaluate upgrading options in terms of potential aerospace scrap utilization and production cost. Three specific cases are analyzed: a dismantled case, a sorted case, and a shredded or co-mingled case; sensitivity analysis of resulting compositional uncertainty is also presented.IntroductionAluminum recycling has a number of key environmental and economic benefits. Secondary recovery forestalls depletion of non-renewable resources and avoids the deleterious effects of extraction and winning (albeit by substituting some effects of its own). For most metals, the latter provides strong motivation for recycling; for light metals, like aluminum, the motivation is compelling[1]. Fortunately, as prices and demand for aluminum have increased greatly over recent years, secondary production has begun to outpace primary production (Figure 1). However, while the recycling rates of many aluminum products such as used beverage cans and cars have increased over this period, aerospace secondary materials remain a comparatively untapped resource.This untapped resource for scrap aluminum is a very large one; aluminum is the primary aircraft material comprising about 80% of a planes unladen weight[2]. It is used extensively for airframes, landing gear, engine components, propellers, and interior trim. A standard Boeing 747 jumbo jet, for example, contains approximately 75,000 kilograms of aluminum[2]. At an approximate rate of 300 per year, more than 6,000 civil aircraft are forecast to arrive at end-of-life in the next 20 years, potentially creating a large aerospace scrap market[3]. Many military aircraft are already available for possible scrap use, however, most are currently in storage at air force bases around the world[4]. The underutilization of these aerospace scrap materials indicates a lack of economic end-of-life options."

Jan 1, 2008

By F. Begazo

The most common approach to increase production in copper refineries is to increase current densities. However, if these increases are not well thought out beforehand and are not properly and effectively controlled, the end results could be reduced plant performance and a deterioration in cathode quality. Both of these factors result in lower efficiencies and increased costs. At the Ilo Refinery of Southern Peru Copper Corporation, a modernization and expansion program was implemented shortly after the Refinery was purchased from Minero Peru, in 1994. This program was intended to increase production from 195,200 mtpy of cathode to 227,000 mtpy over a 3-year period. Part of this production increase would come from increasing current density. During the period from 1994 to 1997, current density at the Ilo Refinery was increased from 218 A/m2 to 230 A/m2, while plant efficiencies were maintained at consistently high levels. The current efficiencies were maintained at >97.5% and time efficiencies were maintained at >98%. During 1998, additional increases in current density were implemented while the high plant performance was maintained at the same levels. By the end of 1998, the current density was 241 A/m2, while current efficiency and time efficiency of 98% were maintained. This paper describes the control processes used at the Ilo Refinery to maintain high plant performance levels while increasing the current density. Additionally, expected plant performances from extended test programs at current densities up to 280 A/m2, for future production increases, are reviewed and discussed.

Jan 1, 1999

By K. Twite, K. Mujinga, J-M. Dereydt, P. Louis

"GECAMINES is a large mining concern and the world's leading cobalt producer having some of the richest cobalt deposits in the world. Cobalt is associated in the ore with copper as sulphides and oxides and in some locations with nickel too. Specific hydrometallurgical processes have been developed by GECAMINES which had done an important contribution to the development of the cobalt hydrometallurgy.In the Shituru plant, cobalt is obtained from an unique in-pulp electrolysis process, while in Lullu, cobalt is electrolyzed in a clear acidic solution giving a purer deposit. In the beginning of 1996 Shituru started the treatment of mixed Cu-Co-Ni Shinkolobwe hydrates obtained as by-product of an uranium solvent extraction plant. A typical analysis of this feedstock is: 2% Cu, 8% Co and 4% Ni.The nickel sulfide depolarized cementation process developed previously by GECAMINES was inefficient to treat such a high level of nickel contamination and it was decided to produce alloyed Cobalt-Nickel cathodes in the Shituru tankhouse.As anticipated from laboratory tests as previous studies and publications, a lower Ni/Co in the deposit was obtained compared to the Ni/Co ratio solution, despite the nickel reversible electrochemical potential is somewhat higher than the one of cobalt (-0.25 V vs -0.28 V).In this paper, the process flow-sheet and production data are given. Cobalt alloy with 5 - 20 % Ni was obtained at a production level of 300 t per month. The process developed is a new contribution to cobalt hydrometallurgy."

Jan 1, 1997