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By Walter Curlook

An atmospheric acid leaching process for leaching nickel and cobalt from highly-serpentinized saprolitic fractions of nickel laterite deposits has been developed and patented [I]. The process involves leaching the highly-serpentinized saprolitic portion of the nickel laterite ore profile in strong sulphuric acid solutions at atmospheric pressure and temperatures between 80°C and 100°C, essentially autogenously, to extract over 85% of its contained nickel content and a large proportion of its cobalt content after leaching times of about one hour. The amount of sulphuric acid used in the leaching process is between 80% and 100% by weight of the finely ground highly-serpentinized saprolite ore on a dry weight basis. The metal values are recovered as intermediate products. Key words: Atmospheric Leaching; Nickel Oxide Ores; Laterites

Jan 1, 2004

By A. M. Ramalho

In the synthesis and sintering processes to obtain superhard materials, such as diamond and cubic boron nitride, deformable ceramic capsule is used as gasket to transmit and support the required high pressures and high temperatures, HPHT. The ceramics materials for these capsules should have special physics and chemical characteristics such as refractoriness, shear strength and compressibility. In this work, Bridgman?s anvil made of hard metal or speed steel was used to characterize some ceramics materials in terms of their maximum compressible thickness. Tests were also performed with different resin polymers used as binding mixture with ceramics powder. Chemical analyses and investigations through scanning electronic microscopic (SEM), X-ray and real tests for the synthesis of diamond were also performed. The results showed that local Brazilian calcite can be successfully used in the manufacture of HPHT gaskets.

Jan 1, 2006

By Li Chen

A new process, i.e. Ball milling--Neural leaching--Oxidation calcinations--Chloridizing distillation--Hydrolysis, was designed to recover germanium from the vacuum furnace slag produced in Shaoguan smelter. The suitable process and operational parameters were determined for the practical production.

Jan 1, 2005

By Tianzu Yang, Weifeng Liu, Lin Chen, Wei Chen, DUCHAO ZHANG

Ni-M (Metal=Cu, Fe, Co, Mn, Zn, Cr) aerogel catalysts were tested for CH4 oxy-CO2 reforming. It was found that the Ni-Co bimetallic aerogel catalyst had the highest activity and stability in methane oxy-CO2 reforming among all the Ni-M aerogel catalysts. It exhibited a steady activity of 79 % (in terms of CH4 conversion) at 750 oC, which is the highest activity under a similar reaction condition as compared with those published in literature. Characterizations for the reduced catalysts indicated the formation of Ni-Co alloy, while other transition metals separated from Ni during the reduction process. Therefore, the active species in the Ni-Co bimetallic catalyst showed a stronger interaction than those in other Ni-M catalysts, which might be one of the main reasons for the better catalytic performance of the catalyst.

Jan 1, 2016

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

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

Jan 1, 2000

By Zvi Rivlin

Classical nucleation theory states that in first order phase transformations, such as liquid to solid transition, nucleation of the product phase starts with the formation of small, unstable clusters (embryos). When the thermodynamic barrier to nucleation is overcome, the embryos grow and attain a critical size, beyond which they are stable, i.e. they become nuclei. If nucle- ation does not occur, the parent, liquid phase remains in metastable equilibrium. At temperature lowers, undercooling increase and atomic mobility decreases. The viscosity change in the undercooled liquid may result in the formation of glassy state. As demonstrated in previous papers [I-21, in solidification involving surface nucleation of the product phase, as the case is in rapid quenching by melt-spinning, both nucleation temperature and nucleation time depend upon the number of atoms available at the isothermal surface in contact with the substrate. As a result of the thinness of the melt-spun ribbons, the embryo clusters that form at the freezing temperature may not be supplied by the amount of atoms necessary for their growth to critical nuclei sizes. In such extreme conditions, the liquid does not crystallize, it forms a metallic glass. A numerical simulation method is proposed for the reactions involved in embryo cluster formation and growth, at the atomic level. The simulation enables the caIcuIation of either the nucleation or the glass transition temperatures. Calculations made for the well-known glass forming CuZr and FeB systems afford prediction of the geometrical and thermodynamically conditions necessary for the formation of either crystalline or amorphous ribbons in melt-spun ribbons.

Jan 1, 1994

By Jian Zhang

From the standpoint of quality, surface cracks normally pose more of a problem than internal cracks. Hypo-peritectic (HP) steel grades are well known for their proneness to surface longitudinal cracking (SLC) during continuous casting. This study analyzed the influences of chemical composition, technique parameter and secondary cooling on the surface longitudinal cracks. Based on the optimized the first and secondary cooling zone water distribution in the process of continuous casting, low cooling water distribution at solidification initial stages and uniform cooling at secondary cooling zone were suggested, which can be used to effectively control the surface longitudinal cracks.

Jan 1, 2010

By C. M. F. Vieira

In the county of Campos dos Goytacazes, north of the State of Rio de Janeiro, Brazil, there is a large production of red ceramic, mainly perforated bricks. A percentage of these bricks are damaged during the firing processing and become a red ceramic waste. This work investigates a possible solution to this environmental problem through the mixture of fired brick wastes, up to 20 wt.%, with clay bodies to produce red ceramics. Cylindrical pressed bodies were fired at temperatures varying from 500 to 1100ºC. After firing, samples were then tested for linear shrinkage, water absorption and mechanical strength. The results showed that brick waste addition did not changed the workability of the clay and that up to 5 wt.% of waste no detrimental effect occurred on the fired properties at all temperatures.

Jan 1, 2010

By V. M. Paretsky

The basic work conducted by Prof. A.Yazawa has demonstrated that in order to ensure single-stage white metal production by autogenous smelting of copper sulfide raw materials, it is most favorable to use highly basic slags, in particular oxide systems CaO-FeO-Fe2O3-Sio2. he special studies have been conducted in the Gintsvetmet Institute to investigate the composition and structure of slags produced on a semi-commercial scale when testing the KFP and FBP processes for white metal smelting, as well as the slag obtained in a full-scale KFP furnace at the Almalyk copper smelter. The investigations conducted have demonstrated why production of high-grade matte or white metal is associated with lower loss of copper in slag in a series: silicate slag I silicate-calcium slag I ferrite-calcium slag.

Jan 1, 2003

By Xiang Sun

Microwave heating has been used in numerous industrial processes due to its great advantages when compared with conventional heating methods. However, microwave heated products can be affected by non-uniform temperature distribution resulting from the mechanisms of microwave heating. To overcome this problem, a critical step is to have a temperature-time profile. In order to characterize and evaluate microwave heating effects, an accurate temperature measurement is needed. This paper discusses the possibility of applying several temperature measurement techniques in microwave processing. Both contact and non-contact methods are introduced and compared.

Jan 1, 2006

By Hui Lu

The structural changes in solutionized AA2618 during natural aging and their effects on subsequent artificial aging were investigated by hardness measurements, X-ray diffraction, differential scanning calorimetry and transmission electron microscopy. The changes in lattice parameter and hardness during natural aging indicate that copper-enriched clusters form in the earliest stage, followed by the formation of magnesium-enriched clusters and coppermagnesium co-clusters. Prior natural aging consistently weakened the hardening during subsequent artificial aging at 180, 200 and 230 °C but had no effects on artificial aging at 150 °C. The decreased age hardening was attributed to the reversion of small clusters/zones that formed during prior natural aging. The lattice parameter exhibited erratic changes with increasing artificial aging time, reflecting the complex sequence of the reversion and precipitation.

Jan 1, 2006

By M. A. Barakat

"Adsorption of heavy metal ions specifically, Cu(II), Zn(II), Mn(II), and Cr(VI) from aqueous solution on synthetic 4A Zeolite was evaluated. The 4A zeolite was synthesized previously by dehydroxylation of low grade Kalabsha Kaolin at 800 °C, and reacted hydrothermally with 2-4 M NaOH solution at 100 °C for 2h. The adsorption capacity of the metal ions were found to be strongly dependent on pH and initial metal ion concentration. At the optimium conditions the adsorption capacity decreased in the order Cu(II) > Zn(II) > Mn(II) > Cr(VI) ions. Almost complete adsorption was achieved for both of Cu(II) and Zn(II) ions at pH > 6, while the adsorption capacity for both Mn(II) and Cr(VI) was 96, and 55.3 % at pH 11 and pH 3, respectively. The results also showed that the grain size of the 4A zeolite has a little effect on the adsorption capacity. The experimental data was compared with two adsorption isotherms, Langmuir and Freundlich isotheroms. The results showed a good agreement of the Langmuir plots with the experimental data.1. IntroductionSeveral industrial wastewater streams may contain heavy metals such as Cr, Cu, Pb, Zn, Co, Ni, Mn, etc. including the waste liquids generated by metal finishing or the mineral processing industries. Heavy metals are considered hazardous pollutants due to their toxicity, even at low concentration, and nonbiodegradability. Increasing level of heavy metals in natural water bodies poses a serious threat to all living species including humans. It is, therefore, essential to reduce the heavy metal concentration in effluents/wastewater before it is discharged into the water bodies [1]."

Jan 1, 2008

By Thomas Weyand, Thomas Claridge, Dale Nickels

"This paper addresses the initial results of a project to evaluate the suitability of copper mining tailings as raw material for the production of structural products using PMET’s patented technology. Preliminary testing indicated that high performance structural products were possible using these materials. A demonstration scale project produced approximately 1,500 bricks in various colors. These products fall under under ASTM C- 73 and were found to present properties suitable for severe weather applications. Although the products in this project were of typical brick dimensions, other products are possible, for example concrete block substitutes or pavers. These products from the PMET process are commercially known as Brixx. This paper will provide operational details of the production process, mineralogy and mechanical properties of the products.INTRODUCTIONPMET has developed process technology that can convert various siliceous waste materials into competent structural products. This technology is the subject of US patent # 6,068,803. In general, the process consists of mixing lime, water and the major feed stock, pressing to form a “green” shape, and curing the product in an autoclave for 6 hours with saturated steam at ~200oC. The curing process forms Tobermorite, which acts as a crystalline binder. Freeport-McMoRan approached PMET to see whether mine tailings from the Sierrita mine, containing significant amounts of clay, might be a suitable feed material for the production of structural products. “Brixx” is the commercial term used to describe the resultant structural product formed in the test work. This paper is a preliminary evaluation of a technology that is being considered by Freeport-McMoRan. This report is not an endorsement by Freeport-McMoRan of the process or products, nor is it a commitment to use this technology."

Jan 1, 2008

By Daniel Bennett

There are few methods currently applied towards on-line bulk mineralogical analysis. Yet on-line knowledge of process mineralogy could potentially provide large benefits, such as increased extraction efficiency or resource optimization. The work described in this paper involves the development of radio frequency methods for bulk mineralogical analysis. Some resonances that occur in the radio frequency spectrum are mineral specific, and potentially allow quantitative estimation of mineralogy in an ore stream. Results will be presented on the specific detection of chalcopyrite. Initial quantitative measurements investigating matrix effects have indicated the feasibility of on-line mineralogical estimation using radio frequency techniques.

Jan 1, 2006

By L. Xia

Sodium silicate(s), also known as “water glass”, are one of the oldest and most widely used industrial chemicals. Its first use in Canadian operations can be traced back to around 1925, which coincided with early use of xanthates in mineral flotation. Silicate functions as a sulphide and non-sulphide gangue mineral dispersant, depressant and modifying reagent in grinding and flotation operations. It is believed that soluble sodium silicate promotes selectivity of value added sulphides against gangue minerals, resulting in both grade and recovery improvement. This paper seeks to link improved grade/recovery to the interaction characteristics of minerals and the sodium silicate. A systematic study was performed with individual mineral species, an artificially designed model ore and the feed ore from a copper flotation operation. The function of sodium silicate was evaluated in the context of colloidal chemistry and linked to mineral surface chemistry. Measurement of pulp rheology and mineral zeta potential identified that sodium silicate works as a dispersant. The dispersion is accomplished by increasing a mineral’s net surface charge, resulting in a change in slurry viscosity. Bench scale laboratory flotation tests suggest that better dispersion leads to a diminished interaction of chalcopyrite with gangue. The improved Cu grade and recovery then are likely in response to an increased accessibility to collector along with a linked increase in particle bubble attachment resulting in better separation efficiency. ToF-SIMS surface chemical analysis of the flotation samples found a higher proportion of sodium silicate on minerals from the flotation tailings relative to the concentrates. Moreover, attachment of sodium silicate appears to be mineral specific; the data indicates that sodium silicate favours the surface of gangue phases over the value sulphides.

By Fumitaka Tsukihashi

Phase diagrams of the CaO-SiO2-FeOx-MgO, Al2O3 systems arc necessary for the analysis of copper smelting reactions and sintering process of iron ore. The effect of MgO and Al2O3 addition on the liquidus of the phase diagram of the CaO-SiO2-FeOx system at low oxygen partial pressure was observed. The liquid phase area changed bi the addition of MgO and Al2O3 with a changing oxygen partial pressure from 10-8 to 10-3 atm (10-3 to 10 2 Pal at 1573K. The effect of Fe3+ / Fe2+ ratio on the melting mechanism is discussed.

Jan 1, 2003

By A. J. Rigby

Refractory linings in converters or anode furnaces used to over-oxidize the blister copper will suffer rapid deterioration, due to prolonged contact with copper oxide-rich slag. Nitrogen stirring with COP KIN porous plugs and use of SEMTECH OPC in converters and anode refining vessels can considerably reduce both refractory wear and processing times. In addition, careful control of the vessel atmosphere and the use of real-time optical process control minimize both slag volume and contact time with the vessel refractory.

Jan 1, 2005

By Sergio N. Monteiro

Wastes generated by our society and the question on how to dispose them is, nowadays, a relevant matter of concern. The objective of the present work was to characterize the technical properties of composites made of discarded jute sackcloth with its coarse wove fabric, serving as reinforcement phase, and polyethylene wastes collected from city dumps, as continuous matrix. Different amounts, up to 30 wt.% of jute plain weave, fabric were press molded at 160°Ctogether with sieved polyethylene particles. The resulting composites displayed mechanical properties that could compete with those of low-density wooden board. Both by presenting a solution to, otherwise, disposed wastes and by helping to prevent deforestation, the investigated composite may be regarded as an environmentally correct material.

Jan 1, 2006

By S. Tanaka

The Tamano Smelter of Hibi Kyodo Smelting Co. Ltd. was commissioned in 1972. Since start up, the anode production capacity has increased from 101,000 tpy to 290,000 tpy, as a result of the application of continuous improvements at each phase of the expansion projects. The Tamano Smelter had developed several innovations, including the original coke combustion technology for Flash Smelting Furnace operations (T-FSF), and has also been able to extend the operating life of the Peirce-Smith converters. This paper will present several improvements implemented at the Tamano Smelter, and will discuss relevant P-S converter operation.

Jan 1, 2005

By Roberto Parra

The classic criteria of the preparation of the charge for the smelting of copper concentrates in at flash furnace considers the mass and energy balance from the chemical and mineralogy composition of the concentrates. The operation parameters fixed with this method don't assure the stability of the operation and the critical problems of the slag quality and dust formation occurs very often. This paper presents the results of a laboratory test that allows the prediction of the behavior of concentrates blends in the view of the minimization of the dust formation and the magnetite control in the slag. The combustion of different copper concentrates and blends were done in a drop tube furnace The results show that the magnetite and dust formation don't have a linear behavior with the weight proportion of the blend and some optimal blends of 2 or 3 types of concentrates can be identified. From the reasonable hypothesis that the qualitative behavior of blends in the drop tube represents the real behavior in the burner, the preparation of the charge with this approach could help to solve those operational problems.

Jan 1, 2003