Search Documents

By Bo Zhou

During secondary aluminum recovery, complex aluminum scraps are melted and refined often in a rotary melting furnace and the aluminum metal has to pass through a molten salt layer and melt down in a bottom aluminum bath. Previous experimental study and industrial observations have indicated that salt shell formation and re-melting on the metal solids in the early stage plays a critical role in the overall melting process of the scrap. In the present paper, mathematical models are developed to simulate the process of salt shell formation and its re-melting, as well as aluminum melting in the molten melt. Influence of the salt layer properties, the residence time of the metal particles in the salt layer, the particle size, the temperature of bulk melt were investigated. Reasonable agreement with the measurement data was reached. The developed melting model will be used to construct a population balance model of the scrap melting behavior for a rotary melting furnace, taking into account the distributed characteristics of the scrap. Finally, an overall process model based on Computational Fluid Dynamics (CFD) for the rotary furnace will be constructed, coupling with the population balance model for the scrap melting.

Jan 1, 2003

By Nico Steenekamp

At Lonrho Platinum in South Africa, ores from both the Merensky and UG2 reefs of the Bushveld Igneous complex are treated by flotation and smelting to produce a nickel-copper matte which serves as a collector for the platinum group metals (PGM' s). The nickel-copper matte was originally shipped to Norway for treatment and recovery of the contained base metals, with the return of the PGM rich concentrate to South Africa. The Lonrho Platinum Base Metal Refinery was commissioned in 1985. The original process employed a Shenitt Gordon design. The converter matte is treated in a refinery which utilises both atmospheric and pressure leaches for the dissolution of base metals to produce nickel sulphate crystals, copper cathode and a PGM concentrate. This paper refers to flowsheet and operating changes as well as improvements within the Base Metal Refinery.

Jan 1, 1999

By James D. O, DeLa&apos

Multicomponent materials are common in nearly all areas of materials science and technology, yet the use of phase diagrams to represent these complex systems is hampered by the requirement of three or more dimensions for explicit graphical representation. In the present work, the "solid-modeling" capabilities of a computer aided design (CAD) system have been applied to the representation of three-dimensional phase diagrams. Relevant phase diagrams for a hypothetical quaternary eutectic system were constructed and used to demonstrate the capabilities of the technique. These capabilities lead to relative ease of phase diagram construction and improved access to qualitative and quantitative information. Results of this work are contrasted and compared to previous efforts toward computer ,representation of phase diagrams. It is concluded that solid-modeling of three-dimensional phase diagrams can be used to advantage in both education and research.

Jan 1, 1991

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 Helena Byrdziak

Polish Copper Industry, located in the Lepica-Glogów region and operated since the 1970's, includes four mines and two smelters, "Legnica" and "Glogów", the latter consisting of "Glogów" I" and "Glogów II" both having different technologies. The "Legnica" and the "Glogów I" smelters using shaft furnaces, so sulfur elimination largely takes place during batchwise converting, resulting in fluctuation SO2-concentration between less than 1% up to 10% in the converter pas W the sulfuric acid plants. The ensuing difficulties of the past have now largely been overcome. Introduction of flash smelting at "Glogów II" with subsequent acid making by double SO2-conversion from the stable process gas, contributed significantly to further reduction Of SO2-emission. In 1994 a new double conversion sulfuric acid plant was installed at "Glogów l" as well as a "Solinox" desulfurisation plant at "Legnica", further reducing SO2 emission considerably, The next step towards this goal under consideration is a semi-dry desulfurization system for the "Glogów I" power station, SO2- abatement measures by KGHM and the results thereby achieved are presented.

Jan 1, 1996

By Shunhong Huang

To improve understanding the effect of heavy metal chromium on soil biota, laboratory incubation experiment was carried out in the soils contaminated artificially with five concentrations of chromate (50, 250, 500, 1000 and 2000 mg kg_1 soil) over time (35 days). The population and diversity of bacteria, fungi and actinomycetes in soils were measured as indicators of soil microbial processes in the disturbances mentioned above. Incubation experiment results elucidated that the population and diversity of microorganisms decreased with increasing Cr (VI) concentration. Furthermore, various microorganisms showed different sensitivity to total Cr contamination. The sensitivity of microbial population to chromium contamination was in the order: actinomycetes >bacteria>fungi. The resulted implied that the microorganism can be used as an indicator of chromium contamination.

Jan 1, 2008

By James R. Myers

A source of clean gas containing sulfur dioxide and sufficient oxygen for conversion to sulfur trioxide is essential to the production of sulfuric acid. SO2 containing gases obtained from roasting sulfide ores are heavily contaminated with inorganic dust and volatile impurities. If not removed, these contaminants will reduce product acid quality, foul the catalyst beds and mist eliminators, and accelerate equipment corrosion. This paper reviews conventional gas cleaning systems for metallurgical acid plants, followed by a discussion of modern systems utilizing DynaWave Scrubber technology. This technology is based on a unique approach togas scrubbing that can concurrently accomplish several gas cleaning/processing tasks. Scrubbing liquid is injected into the gas stream to create a "Froth Zone". This is a region of extreme turbulence, with a very high rate of liquid surface renewal. It efficiently removes both particulate matter and gas contaminants, and is also a cost effective quenching device for gases as hot as 1250 o C.

Jan 1, 1992

By Leonard J. Friedman

Modern smelting systems using continuous, flash and/or oxygen smelting processes have a significant effect on the choice of sulfur dioxide control processes and system arrangements. Based on gases from an enriched air or oxygen smelting furnace and copper converters the paper reviews and analyzes alternate processes and system arrangements for recovery of sulfur dioxide. The work indicates the choice system to include a conventional sulfuric acid plant for converter gas and a liquid SO2 plant to handle the high strength smelting fur¬nace gas. The liquid SO2 plant would be used as a fly-wheel to damper the flow and SO2 concentration variations of the con-verter acid plant. Potential energy recovery alternates and product flexibility are also reviewed.

Jan 1, 1983

By Malcolm J. Harrison

The problems associated with the flow control of abrasive slurries and solids laden fluids creates reliability problems in many mining operations. Conventional valves such as pinch, knife gate and plug types cannot always function reliably in such harsh operating environments. Due to the technological advances in the hard coating industry, ball valves can now be produced with internal surfaces protected from the erosive effects of these applications. Pressures well in excess of the capability of conventional 1000 kPa working pressure valves can now be handled reliably. The significant advantages of minimizing down-time and lowering maintenance costs can now be realized with metal seated ball valves.

Jan 1, 1999

By A. A. Hejja

The first part of this study deals with the importance of surface tension of slags produced in the smelting of sulphide concentrates. Theoretically the method of determining the surface tension of slags was laid down by Boni and Derge. The values obtained experimentally for a series of main oxide components were grouped into a useful correlation incorporating experimental constants for the relevant oxides present in the slag, some of these giving the surface tension value for the particular slag. These estimated values were coupled with or incorporated into the slag viscosity plots to show the correlation between the two factors. This is also important from a refractory attack point of view in the furnace operation. In the second part an attempt is made toward the optimisation of slag composition relevant for electric furnace smelting processes. Using the knowledge of the viscosity and electrical conductivity of the slags at the temperature of furnace operation, the mode of optimisation is based on correlations which utilize the trend of the mostly parabolic plots of viscosities and conductivities. The results obtained by this method agree well with the optimum slag compositions being used in established operations derived from years of practical experience for various slags used in the furnaces. However, due to extensive turbulence in suspension and gas injected bath smelting processes, the outlined methods cannot be used for these processes. Also great caution should be exercised in their application for three electrode circular furnaces with separate slag cleaning.

Jan 1, 1997

By Hideki Yamamoto

A new technology to convert fluoride gas (C2H2F4 ; R-134a) contained in the exhaust gases from semiconductor manufacturing plants and refrigerators directly into a harmless substance have been established, thus, presenting a new concept for the disposal of fluoride gases such as CFCs that are associated with the global warming. Experimental results verify that chemical reactions with metal compounds can take place at substantially lower temperatures of 700- 800K as compared with combustion. treatment temperatures of 1200-1500K. The reaction product is mainly metal fluoride, which chemically is a harmless material. Furthermore, this process is compact, easily controlled, safe and has low running costs. This paper deals with a new chemical reaction method for the harmless disposal of gases effecting the global warming.

Jan 1, 2003

By Anthony C. Mulligan

Metals have historically been used in mining since they offer an excellent combination of hardness, toughness and cost and can be fabricated to form a variety of shapes. However, for many applications the metals used today have limited performance in the environments in which they are needed. This is particularly true for geothermal environments where the brines are highly siliceous causing corrosion and accelerated wear of many components. Geothermal sources are increasingly being explored for their high thermal value as well as possible sources for future minerals. While advanced ceramics have historically been expensive to produce in comparison with metals, they offer significantly greater corrosion resistance and hardness and can improve the overall performance when used in selected ?problem? areas. One of the major drawbacks in the use of ceramics in high impact areas has been their brittle nature and propensity to fracture and spall (fail) when loaded. Recent advances in the fabrication of ceramics have combined hard (strong) ceramics with more ductile ceramics in a architecturally designed microstructure, thus allowing ceramics to perform well in these high impact regions. Additionally, ceramics are significantly more inert to corrosion from either alkaline or acidic environments and can typically be used for significantly longer periods in these environments than their metallic counterparts.

Jan 1, 2006

By Martin B. Schranz

Copper sulfate pentahydrate is recovered from the spent etchant waste stream of a printed circuit board manufacturing facility by cooling crystallization. The fluidized bed crystallizer contains submerged cooling surfaces which are bathed in a stream of air. The air bubbles provide agitation which improve heat transfer, reduce fouling and maintain crystals in suspension. The recently patented apparatus (US 5,523,064) has advantages when compared to a conventional surface cooled crystallizer including capital cost, ease of operation and production of larger more uniform crystals

Jan 1, 1997

By Oleg I. Platonov

The process for desulfurizing coke oven gas in a regenerative system ?scrubber-stripper?, with sour gas being fed to Sulfur Recovery Unit (SRU) and tail gas being recycled to raw coke gas scrubber, has been developed. A key problem of this process is the presence of elemental sulfur in the SRU off-gas, which may deposit on gas-blowing equipment, thus disrupting its operation. A new treatment technology for SRU off-gas that has been worked out for a Claus unit operated by «Russian Metallurgical Company» (RMC) in Magnitogorsk (Russia) is presented. It incorporates a catalytic hydrolysis/hydrogenation stage, where all sulfur-bearing species such as sulfur dioxide, carbonyl sulfide and elemental sulfur are converted to hydrogen sulfide. The SRU in Magnitogorsk comprises three main units: gas re-heater; catalytic hydrolysis reactor and waste gas cooler. Re-heater is required to increase temperature of the process gas up to a level of catalytic conversion (beyond 330-3500C). Oxygen utilized as an oxidizing agent reduces the volume of waste gas to a minimal possible value. The operational data garnered since 16.07.2004 clearly shows that the new technology allows high-level purification of Claus tail gas from elemental sulfur. Unlike SCOT ? process, this technology does not require separate stages for H2S removal and enrichment that tangibly simplifies its implementation at lower capital and operation expenditures.

Jan 1, 2006

By M. A. Gerdel

In carboxylate collector flotation of bastnasite from other semisoluble salt type minerals such as barite various modifiers must be added in order to achieve selective flotation. One such modifier is a lignin sulfonate. It may function in part by acting as a sequestrant for metal ions present, preventing autoactivation in the system by metal ions derived from the minerals themselves. It also functions as a depressant for both bastnasite and barite, chemisorbing on both. However, it is shown that the lignin sulfonate functions as a much stronger depressant for barite than for bastnasite. It is suggested that the; strong depressing action on barite is related to a good fit of the sulfonate into the barite structure.

Jan 1, 1989

By Alex Moyano

The Codelco-Chile is considering different processing options for the projected concentrate from the Alejandro Hales mine (former Mansa Mina mine with high arsenic and antimony content of 6% and 0.6%, respectively), that will produce complex blister copper with high impurities contents, higher than the present values produced at the converting process of the Codelco Norte smelter processing only Chuquicamata concentrates. In order to know both the anodic copper quality and the metallurgical implications when a complex blister copper is processed in the refining process of the CN smelter, the Codelco and IM2 ?task force? evaluated positively the refining process for the complex blister copper by addition of alkaline fluxes at laboratory and industrial scale tests. The promising results of the tests done at laboratory scale at the Tohoku University facilities, allowed a large scale test planning to validate the lab-scale results in 3 refining furnaces of 250 t capacity at the CN smelter. The obtained results demonstrate the industrial technical feasibility to process a complex blister copper in the refining furnaces producing an anodic copper quality suitable for the electrolytic process.

Jan 1, 2006

By Gerald M. Ellis

Exploration for gold .deposits on Hispaniola has taken place sporadically over the years but has expanded in the past decade. There are veintype, disseminated, alluvial and elluvial deposits. Investigations were previously undertaken in Haiti by combined Haitian, Bureau of Mines, and UN geological teams at Grand Bois Limbe(Milot) and Cap Coq areas. Later studies were conducted at the Miches and Moncion districts. Gold occurrences were reported in quartz, silicic-barite veins and gossans. An important deposit ?at Pueblo Viejo is? a disseminated type where extraction is taking place in the oxidized zone. Exploration by Japanese and West German firms with local geologists are described in this paper together with Pueblo Viejo, Miches, Restauracion, Milot, and Meme ?areas where occurrences are known. Copper deposits with associated gold va1ues are also described. These include vein deposits in Central Cordillera and disseminated deposits at Terrier Rouge and Blondin.

Jan 1, 1989

By Florian Kongoli

The optimal operation of the blast furnace depends considerably on the properties of the sinter fed into the furnace. As a result, the optimization of the sintering processes has a direct effect on the overall effectiveness of the iron making processes. In order to produce a good sinter special care needs to be taken in order to assure it has a good permeability and reducibility and it is able to retain these properties for a certain time. If the sinter starts to melt down early in the upper part of the blast furnace, where its solid state reduction is essential, permeability decreases, the gas channels get blocked, reductibility diminishes and serious problems may also follow. Among the factors that influences the above mentioned sinter properties are the oxygen potential and fluxing components. Nevertheless, their effect on the phase relations during sintering and sinter reduction conditions has not yet entirely clarified and confusion exists in literature. This quantification becomes even more important today where many new minor components such as Al2O3 and MgO enter the sinter through raw materials. This work quantifies the effect of oxygen potential and fluxing components such as alumina and magnesia on the liquidus and phase relations of the sinter primary melts in the iron rich portion of CaO-FeO-Fe2O3-SiO2 system at sintering conditions. This is carried out by the means of new type of industrial diagrams in the form of Fe/CaO vs. SiO2 that can directly help the optimization of the sintering processes.

Jan 1, 2006

TiO2 and Ti/TiO2 thin films were deposited on a quartz substrate by laser ablation of Ti02 and Ti targets using Nd:YAG pulsed laser. After sulfurization of the Ti02 film in H2S or CS2 gas at 1273 K for 1 hour, the surface atomic structure was changed. Furthermore, the Ti/TiO2 film was successfully prepared by the subsequent ablation of Ti and TiO2 targets. The morphology and structure of the films were characterized by XRD, XPS and AFM analyses.

Jan 1, 2003

By S. N. Lekakh

Experimental work and thermodynamic simulations of cast iron refining were carried out using various additions of alkali and rare earth metals. The refining reactions for sulfur and oxygen removal were studied for melts treated with Mg, Ca, and Ce. The measured data and the results of the computer simulations were in agreement. Experimental kinetic data, together with the thermodynamic calculations, were used for optimization of the amount and sequence of the addition of nodulizers for ductile iron production.

Jan 1, 2009