Author: Marko KekkonenPublisher:
ISBN: 9789512243396
Category :
Languages : en
Pages : 2
Book Description
Experimental Study on Solid State Reduction of Chromite with Rising Temperature
Author: Marko KekkonenPublisher:
ISBN: 9789512243396
Category :
Languages : en
Pages : 2
Book Description
Kinetics and Mechanism of Solid State Silica Fluxed Reduction of Chromite with Coal
Author: Hoang Van DuongPublisher:
ISBN:
Category : Chromite
Languages : en
Pages : 220
Book Description
Solid state reduction of an Australian chromite was thermogravimetrically studies at temperatures between 1000-14000C with coals under an argon atmosphere. Temperature had the greatest influence on the reduction followed by chromite particle size and silica addition. The affect of silica on the reduction process was from a temperature of around 13000C, with the formation of a silicate slag. The initial reduction involved the nucleation of metallic iron at lattice defect sites of the chromite. This led to the formation of an iron carbide layer around the chromite. Further reduction of the iron was possible by diffusion of the ionic iron to the surface of the chromite where it was reduced through the carbide phase. A counterdiffusion of chromium and magnesium ions also occurred within the partially reduced zone of the chromite. In the presence of added silica and a temperature of 13000C, subsequent reduction of the chromium and the remaining iron were through the dissolution of these species into the slag. This mechanism resulted in a two stage reduction kinetics which was experimentally observed. The first stage was controlled by the solid state diffusion of the cations. The activation energy was 111 kJmol-1. The second stage was controlled by the dissolution process. The slag contained some chromium and trace amounts of carbon and iron. Some silicon was also reduced at 14000C. The concentrations of carbon and silicon in the alloys were inversely proportional to each other. The reductions of Cr2O3, Fe2O3, and chromite by activated carbon were through the gas phase based on the in situ measurement of the partial pressure of oxygen. The reduction of the Fe2O3 was stepwise which did not show for the Cr2O3 and the chromite systems. The product gas in the reduction of chromite was determined to be mostly of carbon monoxide.ls were.
Kinetic Study on Solid State and Smelting Reduction of Chromite Ore
Author: Marko KekkonenPublisher:
ISBN: 9789516665460
Category :
Languages : en
Pages : 96
Book Description
7th International Symposium on High-Temperature Metallurgical Processing
Author: Jiann-Yang HwangPublisher: Springer
ISBN: 3319480936
Category : Technology & Engineering
Languages : en
Pages : 721
Book Description
The technology, operation, energy, environmental, analysis, and future development of the metallurgical industries utilizing high temperature processes are covered in the book. The innovations on the extraction and production of ferrous and nonferrous metals, alloys, and refractory and ceramic materials, the heating approaches and energy management, and the treatment and utilizations of the wastes and by-products are the topics of special interests. This book focuses on the following issues: •High Efficiency New Metallurgical Process and Technology Fundamental Research of Metallurgical Process •Alloys and Materials Preparation •Direct Reduction and Smelting Reduction •Coking, New Energy and Environment •Utilization of Solid Slag/Wastes and Complex Ores •Characterization of High Temperature Metallurgical Process
Fundamentals of the Solid-state Reduction of Chromite in the Presence of Silica Flux
Author: Peter WeberMetals Abstracts
Author: Fengamentals of the Solid-state Reduction of Chromite in the Presence of Silica Flux
Author: The Solid-state Reduction of Chromite in a Vertical Shaft Furnace
Author: M. J. NiayeshReport of Investigations
Author: An Experimental Study Investigating the Role of Chromite on Affecting the Behaviour of the Platinum Group Elements in Igneous Systems
Author: Craig Stewart FinniganPublisher:
ISBN: 9780494218693
Category :
Languages : en
Pages : 306
Book Description
Experiments were performed to document the role of chromite in affecting the behaviour of the platinum group elements (PGEs) during melting and crystallization. Initial experiments involving diffusive exchange of natural chromite with PGE-saturated basaltic melt revealed platinum group minerals (PGMs; including metal alloys and laurite) as precipitates along the chromite-melt interface. X-ray photoelectron spectroscopy of the glass near the chromite showed lower Fe3+/Fe2+ relative to measurements far removed from the interface, indicating a local zone of reduction The reduction is likely caused by preferential uptake of Fe3+ and Cr 3+ by the chromite relative to the melt. The effect causes the precipitation of PGMs due to their locally lowered solubility. PGM precipitation was also found to occur during spinel growth experiments, which we attribute to the same effect. This process could explain the commonly observed inclusion of PGM in chromite in ophiolites and layered intrusions, and may contribute to the fractionation of the PGEs due to their differential solubilities in silicate melt. Chromite may therefore concentrate and fractionate the PGEs by two different mechansims, one involving physical entrapment of PGMs following local reduction, and the other involving direct solid solution into the chromite lattice. The diffusive exchange technique was also used to measure chromite-melt partitioning of the PGEs, which avoids the problem of PGE contamination during heterogeneous nucleation of chromite in metal-saturated experiments. Run product chromite crystals and glass were analysed by laser ablation---inductively coupled plasma---mass spectrometry (LA-ICP-MS). Partition coefficients were calculated using the composition of chromite margins and coexisting glass. In sulfur-free experiments, chromite-melt partition coefficients (D) for Rh and Ru are large (> 10), and show a progressive decrease with lower fO 2, but still remain> 1. Partition coefficients for Pt are & sim;2 or less, whereas values for Pd are “1 under all conditions studied. Partition coefficients for Os range from 9 to 213, and minimum partition coefficients for Ir are all> 1. Partition coefficients for Ru, Rh and Pt measured at log fS2 of -0.23 are all lower than those measured in S-free experiments at the same or similar fO2. Of Significance, Os and Ru retain their compatibility in chromite in S-bearing experiments at FMQ. Measured partition coefficients confirm that chromite can fractionate Os, Ir, Ru and Rh from Pt and Pd during crystallization, provided the system is sulfur-poor.