The partitioning of trace elements between ilmenite, ulvospinel, armalcolite and silicate melts with implications for the early differentiation of the moon

http://digital.csic.es/bitstream/10261/78672/1/Kinetics%20of%20redox%20reactions%20of.....2011.pdf

Kinetics of redox reactions of ilmenite for chemical-looping combustion

A cycle is the quantitative characterization of the flows of a specific material into, within, and from a given system. An anthropogenic elemental cycle can be static (for a point in time) or dynamic (over a time interval). The about 350 publications collected for this review contain a total of 1074 individual cycle determinations, 989 static and 85 dynamic, for 59 elements; more than 90% of the publications have appeared since 2000. The cycles are of varying quality and completeness, with about 80% at country- or territory-level, addressing 45 elements, and 5% at global-level, addressing 30 elements. Despite their limitations, cycles have often been successful in revealing otherwise unknown information. Most of the elements for which no cycles exist are radioactively unstable or are used rarely and in small amounts. For a variety of reasons, the anthropogenic cycles of only perhaps a dozen elements are well characterized. For all the others, with cycles limited or nonexistent, our knowledge of types of uses, lifetimes in those uses, international trade, losses to the environment, and rates of recycling is quite limited, thereby making attempts to evaluate resource sustainability particularly problematic.

Anthropogenic cycles of the elements: a critical review.

Microwave heating has been extensively explored in various fields of materials processing. This technology exhibits unique characteristics including volumetric and selective heating, which eventually lead to many exceptional advantages over conventional processing methods including both energy and cost savings, improved product quality, faster processing and greater eco-friendliness, making microwave heating appropriate for applications in metallurgy. This paper presents a critical review on the use of microwave energy in metallurgy, with emphasis on both fundamentals of microwave heating and recent experimental efforts on extractive metallurgy via pyrometallurgical and/or hydrometallurgical routes. Applications to metallurgical processes for extraction of various metals, including heavy metals (Fe, Ni, Co, Cu, Pb and Zn), light metals (Al and Mg), rare metals (Ti, Mo, W and Re) and precious metals (Au, Ag and Pt), are reviewed and discussed.

Microwave-assisted metallurgy

Pyrometallurgical recycling of electric arc furnace dust

The non-carbothermic zinc pyrometallurgical processing of electric arc furnace (EAF) dust was investigated on a laboratory scale. The main objective of this process was to convert highly stable zinc ferrite (ZnFe2O4), which accounts for more than half of total zinc in the EAF dust, into ZnO and Ca2Fe2O5 by CaO addition. The EAF dust was mixed with CaO powder in various ratios, pressed into pellets, and heated in a muffle furnace in air at temperatures ranging from 700 to 1100°C for a predetermined holding time. All ZnFe2O4 was transformed into ZnO and Ca2Fe2O5 at a minimum temperature of 900°C within 1 h when sufficient CaO to achieve a Ca/Fe molar ratio of 1.1 was added. However, at higher temperatures, excess CaO beyond the stoichiometric ratio was required because it was consumed by reactions leading to the formation of compounds other than ZnFe2O4. The evaporation of halides and heavy metals in the EAF dust was also studied. These components could be preferentially volatilized into the gas phase at 1100°C when CaO was added.

New pyrometallurgical process of EAF dust treatment with CaO addition

Japanese zinc production in 2005 was 6.75×105 t, and domestic demand of zinc was 4.82×105 t. The main use of metallic zinc is in the surface coating of steel and the metal accounts for 62.8% of the domestic demand. The purposes of this study are as follows: (1) to identify the material flow of zinc associated with steel production, and (2) to estimate the environmental effects (energy consumption and CO2 emission reduction) of some intermediate dust treatment processes.The major conclusions are (a) in Japan, 6.16×106 t of blast furnace/converter dust was generated in 2000, and this product contained 2.20×104 t-Zn. 0.433×106 t of EAF dust was generated and this dust contained 8.86×104 t-Zn, and (b) 9.57 MJ of energy is required for producing 1 kg of zinc oxide by the Waelz process using EAF dust, and the estimated amount of CO2 emission in this process is 1.49 kg-CO2. On the other hand, if the LAMS process proposed by the authors is employed, it is estimated that there will be a reduction of 1.70 MJ in energy consumption and a reduction of 0.14 kg-CO2 in CO2 emissions.

Substance flow analysis of zinc associated with iron and steel cycle in Japan, and environmental assessment of EAF dust recycling process

A new EAF dust treatment process named as “Lime Addition and Magnetic Separation Process (LAMS Process)” has been proposed to recover zinc oxide from the dust and to use solid residue as a flux for steel refining. The LAMS Process consists of the reaction of EAF dust with CaO followed by the adequate crushing and high gradient magnetic separation. The basic principle of this process has been established by revealing the phase equilibria in the CaO–Fe2O3–ZnO system where Ca2Fe2O5 can be in equilibrium with pure ZnO rather than ZnFe2O4, which is the major component of EAF dust, at higher CaO region. The conversion of zinc ferrite in EAF dust to ZnO and Ca2Fe2O5 has been experimentally demonstrated by heating the dust with double molar amount of CaO at 1173 and 1373 K. It has also been demonstrated that the formed ZnO and Ca2Fe2O5 can be separated by the strong magnetic field. Therefore, it may be possible to recover ZnO from EAF dust without the carbothermic reduction like Waelz process.

/pdf/new-eaf-dust-treatment-process-with-the-aid-of-strong-1euxld9nv9.pdf

New EAF Dust Treatment Process with the Aid of Strong Magnetic Field

Phase relations in the Fe2O3-FeTiO3-TiO2 system were investigated by equilibrating synthetic samples in evacuated sealed quartz tubes at a temperature of 1373 K. The equilibrium partial pressure of oxygen was measured by the electromotive force (EMF) method in the temperature range of 1273 to 1373 K. The phase diagram and oxygen partial pressure diagram in the titanium-iron-oxygen ternary system were then constructed at 1373 K. Rutile extraction from natural ilmenite ore was discussed from the thermodynamic viewpoint. It is found that rutile can be produced from common natural ilmenite ores not only by the reduction as the conventional titanium-rich slag process but also by an oxidation. Then, the oxidation experiment was conducted in air using Australian ilmenite ore to obtain rutile as one of the coexistent phases. Magnetic separation and leaching experiments for synthesized pseudobrookite and reagent rutile were conducted to confirm the possibility of separation of rutile from pseudobrookite. A new rutile extraction process was then proposed.

Feasibility study of the new rutile extraction process from natural ilmenite ore based on the oxidation reaction

Microwave heating has been applied to the oxidation in the new rutile extraction process developed by the authors in which rutile is extracted from a natural ilmenite ore by oxidation and magnetic separation followed by leaching with diluted acid. Since ilmenite FeTiO3 and pseudobrookite Fe2TiO5 strongly absorb 28 GHz microwave, Australian ilmenite ore mainly composed of FeTiO3 was rapidly heated up to about 1 273 K and oxidized in air with keeping almost constant temperature. As a result, two equilibrium phases of rutile TiO2 and pseudobrookite were quickly formed at microwave power of 1.5 kW. The growth rate of the pseudobrookite phase in the microwave irradiation was found to be much faster than that of the rutile phase in the conventional resistance furnace, indicating a drastic enhancement of the growth rate by the microwave irradiation.

Satoshi Itoh

Papers

New pyrometallurgical process of EAF dust treatment with CaO addition

Substance flow analysis of zinc associated with iron and steel cycle in Japan, and environmental assessment of EAF dust recycling process

New EAF Dust Treatment Process with the Aid of Strong Magnetic Field

Feasibility study of the new rutile extraction process from natural ilmenite ore based on the oxidation reaction

Application of 28 GHz Microwave Irradiation to Oxidation of Ilmenite Ore for New Rutile Extraction Process