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By G. Belardi

A study has been conducted to assess a new wet beneficiation treatment for the recovery of the sulphuric-acid-soluble titanium oxide contained in the waste from an Italian TiO2-pigment facility. The waste is produced during treatment of a Ti-enriched slag and contains as main components TiO2 (54%, of which 42% acid-soluble and 12% insoluble), SiO2 (27%) and A1203 (6%). Eighty percent of the material is finer than 50pm. The first step was to ascertain the possibilities offered by size classification, wet gravity separation, froth flotation and wet high-intensity magnetic separation to improve the grade and recovery of Ti02 and reduce the SiO2 content. The next step was to optimize the operating conditions of the various separations and assemble them into a complete flow- sheet. Beneficiation ensures potentially 70% recovery of the TiO2 with a concentrate grade of 80%.

Jan 1, 1998

By Jenq-Gong Duh, Jyh-Wei Lee

"Hard chromizing process is a method for developing a surface modified coating providing wear, corrosion resistance and high temperature surface protection. Two carbon steels with 0.45 wt% and 0.95 wt% carbon contents, respectively, were chromized with pack cementation process at 950'C for 4 and 9 hours, respectively. The phase transformation and microstructure phenomena of chromized coating layer and matrix of two steels were studied with X-ray diffractometer and electron probe microanalyzer. (Cr,Fe)23C6 and (Cr,Fe)7C3 carbides and (Cr,Fe)2N1-x nitride phases were observed on the chromized surfaces. The thickness of chromized layers obeyed the parabolic rate law. The mechanism and diffusional kinetics of the chromizing process were proposed. The diffusivity of chromium in the (Cr,Fe)7C3 carbide phase was calculated using the moving boundary method.IntroductionChromizing process is one of the surface treatment technologies that can produce a chromium contained surface layer with sufficient corrosion and wear resistance on the steel matrix [1-7]. The relatively low cost and no ""line-of-sight"" restrictions are main advantages of chromizing. Adequate bonding strength of these coatings to the substrate was reported [7]. Chromizing process can be classified into soft chromizing and hard chromizing [2]. Soft chromizing is applied to steels containing less than 0.1wt% carbon through which chromium will be diffused. High temperature oxidation resistance improvement is the main purpose of soft chromizing process. On the contrary, the hard chromizing can be applied to steel containing more than 0.3wt% carbon, and very hard chromium nitride and carbide layers will be formed on the surface, which are very resistant to wear, corrosion and temperature [5-7]. In the previous studies on the Fe-Mn-Al-Cr alloy [5,7] and carbon steels [6], the thickness (X) of chromizing layers was analyzed and found the parabolic rate Jaw prevailed:"

Jan 1, 2004

By Patrick R. Taylor

The synthesis of high-purity ultra-fine barium strontium titanate powders (BST: BaO6Sro.4TiO3) has been performed in a non-transferred are D.C. thermal plasma reactor. Slurries of aqueous solutions of dissolved barium and strontium nitrates and solid titanium dioxide powders were used as precursors. Oxygen and argon were used as carrier gases, and pure argon and combinations of argon and nitrogen were used as plasma gases. The plasma torch power was varied, as well as the oxygen flow rate and the total molar concentration of the precursors. A graphite plate was designed to protect the torch electrode and lower the level of impurities in the product. A thermochemical analysis of the Ba(NO3)2-Sr(NO3)2-TiO2-H2O-O2 system was performed to predict the conditions for the formation of BST and the feasibility of the reaction, The powders collected from the different sections of the reactor were characterized using Transmission and Scanning Electron Microscopy, X-Ray Diffraction, and ICP chemical analysis. The powders produced showed high conversion to BST, ultra-fine particle size (< 30 rim) and high purity, which makes this a potential process to produce ceramic materials for electronic devices.

Jan 1, 2003

By Y. H. Liu

Several foaming aluminum samples of different density were prepared in a semi?industrial scale experimental system, Their properties such as the energy absorption characteristics, mechanical properties, heat conductivity and acoustical properties were measured. The results showed that the foaming aluminum with a density of 0.5 to 0.6 g/em3J has the best energy absorption and this makes it suitable as the ensuring bar of the automobiles and also as a cushion material for the engine. The foaming aluminum with a density of 0.25 to 0.4 g/em3 has the best acoustical properties and heat conductivity resistance, which is suitable for the door filling material, the ceiling and the partition or the car engine.

Jan 1, 2003

By A. G. Jackson, Mark D. Benedict, Steven R. LeClair, Yang Cao, David M. Conrad

"Electronic Prototyping (EP) represents a new and powerful medium that many in science and technology view as the research paradigm of the future. Actually, EP has many handles, sometimes referred to as simulation-based design involving more long term objectives such as virtual reality, but regardless of the 'spin', the direction of EP is an enhanced visual paradigm to enable a new set of tools for engineers and scientists alike. Tools to not only automate, visualize and compute otherwise intractable problems but to enable augmentations of our ability to perceive that which is interesting and new -""a virtual version of a process"" [1] prodding us on the pathways of materials and process discovery.IntroductionActually there are many reasons to apply sensors to materials, such as smart or adaptive materials/structures, and new materials synthesis/processing [1], only some of which are motivated by improved product quality and/or productivity. Although U.S. Air Force applications of sensors to materials processing represent but one of many perspectives, hopefully it is a perspective which will engender new ideas and insights in addressing future challenges in materials research. To provide context and establish need for future sensor applications in materials processing, we will utilize on one of several Air Force vistas or '21st-Century' objectives."

Jan 1, 1997

By Mike Adams

Comprehensive pilot testwork has been conducted on BHP Billiton&apos;s Ravensthorpe nickel laterite deposit over a fifteen-month period at Lakefield Oretest. Some 228 tonnes of ore were processed in a beneficiation pilot-plant comprising scrubbing, attrition scrubbing, screening and thickening over sixteen pilot runs with an average mass closure of 99.2%. This produced a suitable feed for hydrometallurgical piloting over seven runs covering 1,680 hours of operation. The integrated EPAL® (enhanced pressure acid leach) circuit comprised a limonite pressure acid leach front end discharging into a saprolite atmospheric leach circuit and subsequently to induced jarosite precipitation, counter-current decantation, iron removal, mixed hydroxide precipitation, and manganese removal. The pilot plant met its key objectives in demonstrating the flowsheet&apos;s technical viability, and generating raw data inputs for the project feasibility study. Rapid, intensive data capture, collation and reporting helped solve key flowsheet issues. The pilot plant also demonstrated its value as a risk management tool in the resolution of numerous engineering, metallurgical and materials selection issues at a manageable scale. A disciplined approach to experimental planning, operation and management was a significant contributor to the overall success of the campaign. Keywords: Ravensthorpe, Nickel, Piloting, Beneficiation, Pressure, Leach

Jan 1, 2004

By Jian Ye

Recycling of aluminum scrap, such as Used Beverage Container (UBC) scrap is steadily increasing. In secondary remelting of such scrap, it is a common practice to use protective molten salt cover. An appropriate salt protects metal from oxidation, promotes coalescence of the suspended metal droplets, and separates clean metal from the oxide contamination. The molten salt also reacts with metal. This causes metal loss and change of resulting metal composition. In this paper, role of molten salt fluxes in melting of UBC scrap is discussed, and selection criteria for molten salt are provided.

Jan 1, 1995

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 Gabriel A. Torma

This paper provides infonnation on selected technologies available for remediation of metal contaminated soils and industrial effluent solutions. Because some of the industrial sites are contaminated with organics (solvents, gasolines and oils), an effort has been made to introduce the most frequently used cost-effective cleanup methods, such as "bioventing" and "composting." The microorganisms involved in these processes are capable of degrading organic soil contaminants to environmentally harmless compounds: water and carbon dioxide. Heavy metals and radionuclides contaminated mining and industrial sites can be remediated by using adapted heap and dump leaching technologies, which can be chemical in nature or bio-assisted. The importance of volume reduction by physical separation is discussed. A special attention is devoted to the remediation of soils by leaching (soil washing) to remove heavy metal contaminants, such as chromium, lead, nickel and cadmium. Furthermore, the applicability of biosorption technology in the remediation of heavy metals and radionuclides contaminated industrial waste waters and acidic mining effluent solutions was indicated.

Jan 1, 1996

By W. Zhao

Several years ago, Reddy and Blander presented upriori model for calculating the sulfide capacity of binary silicate melts. It is modified now to apply to CaO-AlO 1.5 melts at different temperatures and compositions. Our predictions are in very good agreement with the available experimental data. From a comparison of binary calcium aluminate and calcium silicate systems, higher sulfide capacities are obtained in aluminate systems. The sulfur can be removed from hot metal more effectively by adding aluminate melts.

Jan 1, 1995

By Philippe Charlier

Recycling of aluminium contained in used aseptic beverage cartons is a difficult task which has nevertheless to be tackled by our modern societies. Techniques have earlier been developed by the paper and pulp industry for the recycling of the board fibres from collected post-consumer beverage cartons. A joint technical feasibility study by Granges and a leading beverage carton producer has dealt with different techniques for handling residues from repulping facilities. The aluminium obtained can be used as raw material for the production of thin gauge foil, thus closing the recycling loop.

Jan 1, 1995

By M. T. Ernett

Significant amounts of arsenic are often present in effluents arising from the mining of sulfide ores for the extraction of metals such as copper, gold, lead and zinc. The arsenic is usually removed from the process effluent by co-precipitation with iron because of its common occurence in the mined ore bodies and the excellent adsorptive property of the precipitated hydrous ferric oxide compound. There has been controversy, however, over the long-term stability of the arsenic-bearing ferrihydrite which is produced. This paper presents the results of laboratory studies which indicate that the cations of calcium, magnesium, zinc, cadmium and lead, increase the pH range of effective arsenic adsorption in the Fe-As precipitate from 4-7 to 4-9. The increase in the pH range is similar for all of the added cations investigated. Sulphate ions are shown to have a minimal effect on the residual dissolved arsenate concentration. Silicate ions reduce the adsorptive capacity of ferrihydrite if they are present before the arsenic is adsorbed.

Jan 1, 1994

By C. Schwandt

Recent research work has led to the development of a new electrochemical hydrogen sensor, which is based on a proton conducting solid electrolyte in conjunction with a self-contained solid hydrogen reference standard and is operated at elevated temperatures. The incorporation of the internal hydrogen reference renders the sensor versatile and user-friendly and makes it attractive for practical exploitation. The present article focuses on the utilisation of the sensor as the integral part of a probe for the quantitative determination of hydrogen in molten aluminium and aluminium alloys. The main features of the sensor and the probe as well as the measuring technique are discussed. Experimental results obtained with the novel analyser in trials under industrial conditions are presented and highlight the good performance of the device.

Jan 1, 2003

By Volker Uhlenwinkel

The design of a free fall atomizer as well as the process parameters affect the particle mass flux distribution in the spray cone. The mass flux distribution is important in spray forming because of its influence on the deposit shape and enthalpy input into the deposit. In this article the effect of different process parameters on the mass flux distribution is shown. Furthermore, different melts were atomized with the same atomizer. An empirical correlation will be introduced to predict the mass flux in the spray cone. This correlation will be compared with experimental results.

Jan 1, 1999

By Taiping Lou

The coarsening process of precipitates in non-equilibrium systems was studied, and then a physical model of coarsening was proposed. The coarsening process of CaO&apos;TiO2 in MgO-TiO2-Al2O3-SiO2-CaO-CaF system was investigated. It is shown that the coarsening process by the model predicting is agreed with the experimental results.

Jan 1, 2000

By M. Z. Mubarok

Effect of single addition of a lignin-based biopolymer additive, DP 2782, at various dosages as well as in combination with thiourea on cathode polarization during copper deposition was investigated by performing potentiodynamic and galvanostatic measurements using a potentiostat. The result of electrochemical measurements was compared with the behaviour of cathode deposition with glue and thiourea additives. Surface micro-appearance of the copper deposit after 1 h galvanostatic scan under current density of 330 A/m2 and various additive type and dosage was evaluated by scanning electron microscopy (SEM) examination. It was found that the addition of 2.5 mg/l biopolymer gave sufficiently polarizing effect of copper deposition. SEM examination of the cathode surface after galvanostatic scan revealed that the combination of the biopolymer with thiourea (2.5 and 3.5 mg/l) resulted in a compact deposit which is comparable with that resulted from the test with glue and thiourea.

By A. V. Tarasov, S. D. Klushin

493 The most common method for minimizing the copper content of residual slag in the process of autogenous smelting of sulfide raw materials is treatment of molten slag in an electric furnace, with optional addition of solid reducing agents, such as coke, and/or sulfiding agents such as pyrite. A drawback of this technique is the fact that the final slag produced still contains 0.5% or more Cu. We have tested a method for treating molten slag obtained as a result of autogenous smelting by a gaseous mixture of sulfur dioxide and methane at a ratio of. SC:SO2 = 0.75 :1.0 in the presence of oxygen. Interaction reaction within the SO2-O2-CRi system proceeded at a high rate at 1373 to 1573 K to form reducing and sulfiding agents: H2S, S, COS, CO, CO2, H2, H2O. The gas mixture requirement was about 100 to 150 Nm3 per 1 tonne of slag. A decrease in the ferric iron concentration (Fe3+) from 10-15% down to 2-3% resulted in lower solubility of copper in slag, and agitation of the melt with gas stream accelerated. the separation of the sulfide phase and slag. Removal of copper from slag was performed in a pilot unit within the second V anyukov furnace zone where slag arrived with a copper content of 0.8-1.3%. The temperature of molten slag was maintained within 1523 to 1573 K. The copper content of the final slag was at a level of0.12 to 0.14%. The matte sent to converting was a mixture of bottom matte from the smelting zone and the slag treatment zone. It had a copper content of about 50 to 55%. Process gases from both furnace zones were combined and sent to the acid plant for sulfur recovery. This process was offered for commercial use at two copper smelters in Russia and CIS.

Jan 1, 2000

By Cyro Takano

An alternative use for recycling of waste from bag house of iron ore sinter plant was tested by producing and evaluating" at laboratory scale, the self reducing cold bonded pellets. This waste was characterized and the self-reducing pellets were produced using anthracite coal fines as reductant and Portland cement or hydrated lime/Blast Furnace slag as binder. It was used the molar ratio of Fe2O3/C (fix) equal to 3. Evolution of cold strength with curing time, for different contents of binder, was evaluated. Cold strength of 200N/pellet was obtained, for sinter dust, after 10 days of curing. Suitable hot strength was also presented and no decrepitation and swelling were observed. Good fractional reduction was obtained at 950°C and 1137°C. These results show that this material may be used by the Self-Reducing Processes for hot metal production, as an alternative route for this dust destination.

Jan 1, 1996

By Carl W. Dalrymple

A wide variety of contaminants (heavy metals, suspended solids, colloids, oils, organics) have been successfully removed from wastewater using an electrocoagulation process. An innovative electrocoagulation system is described. This process involves a procedure which subjects dissolved and suspended wastewater contaminants to the simultaneous addition of metal ions in the presence of direct current. During the treatment process Ionic and other charged particles in the wastewater are neutralized with oppositely charged ions generating the coagulation of contaminants: The process Is called CURE, and&apos; presented here with application to wastewaters containing mainly heavy metals.

Jan 1, 1995

By H. Bernier

The Noranda Inc., CCR Division, copper refinery located in Montreal-East, Québec, Canada, has expanded over the years to reach a capacity of 410,000 metric tons of cathode production per year. The expansion process resulted in nine, parallel, 200 m. long bays each equipped with its overhead cranes and manually operated washing machines. Anode scrap washing and piling was done manually. The mechanization of the tank house involved the elimination of 18 cells at one end of each of the bays in order to install transfer conveyors where anode scrap and cathode loads are deposited by the bay cranes. The cathode loads are brought by new transverse cranes to new machines where cathodes are washed, piled in predetermined bundle weights, check weighed, strapped then shipped in trucks or railroad cars. Suspension bars are automatically removed, stacked in magazines and sent back to the starting sheet machines. Anode scrap loads are brought to machines located near the anode furnaces where they are washed and piled in bundles for easy charging. The mechanization has eliminated numerous hazardous jobs and has realized a reduction of 0.2 man-hours/ton. After these modifications, the refinery production capacity now stands at 370,000 metric tons per year.

Jan 1, 1987