Papers by Keyword: Selective Reduction

Abstract: For the development of nickel production in Russia, it is proposed to involve in processing complex natural-alloyed iron-chromium-nickel ores of the Khalilovskoye deposit, which are currently not used due to their poverty, both in iron and nickel. The rough ferronickel obtained by selective carbothermal reduction under laboratory conditions needs dephosphorization (the phosphorus content in the metal can reach 0.7%). In the frame of this work, the dependences of the phosphorus distribution coefficient on the slag basicity and the temperature of the metal were obtained in the course of experiment. Intervals of melting temperatures for calcareous-ferruginous slags were determined experimentally as well. On the basis of the obtained results, the criteria for the selection of the slag mode during dephosphorization of rough ferronickel were formulated: it is necessary to form a slag containing at least 40% CaO and 20% FeO with a basicity of 3.0 ... 3.5; the slag temperature should remain at the level of 1550 ... 1600 ° C, the slag at this temperature has a low viscosity; it is important to create a more complete mixing of the metal and slag for improvement of dephosphorization (by blowing metal with an inert gas or steam).

Abstract: In metallurgy production nickel is an important alloying element used in the production of stainless, heat-resistant, acid-resistant grades of steel. For the development of ferronickel production in the Russian Federation, it is proposed to involve in processing complex poor iron-chromium-nickel ores of the Khalilovskoye deposit, which are not used at the present time. In the frame of this work the dependences of the elements reduction degrees of iron-chromium-nickel ore on the iron extraction degree were studied. These dependencies are necessary for the choice of the composition and development of ferronickel production technology. Burned ore raw materials were subjected to a selective carbothermal reduction in the laboratory electric arc furnace. In the obtained ferroalloy the nickel content decreased from 65 to 3%, phosphorus - from 0.68 to 0.38%, sulfur - from 0.19 to 0.10% with an increase in the reducing agent consumption. With the reduction of 1% iron, the recovery of nickel was only 50%, with 5% - 65–75%, with 20% - 95%. The content of iron oxides in the partially reduced melt with an increase in coke consumption decreased from 61 to 53%, and nickel oxide - from 0.192 to 0.010%. The analysis of the dependences allows us to make a conclusion that it is inappropriate to recover less than 5% of iron due to the low degree of nickel recovery (less than 70%). The rational degree of iron reduction from ore raw materials is 5-10%, which corresponds to the nickel content in the ferroalloy 10-20%, phosphorus - 0.3-0.5%, sulfur - 0.08-0.09%. Obviously, the resulting crude ferronickel needs refining, first of all dephosphorization.

Abstract: This study was conducted to investigate the effect of palm shell charcoal reductant in the selective reduction of nickel ore with the addition of additive at various temperatures and times. In this present work, 10 wt. % of sodium sulfate as additive and 5, 10, 15 wt. % of palm shell charcoal as reductants were used. The reduction of nickel ore was performed at 950oC, 1050oC, and 1150oC for 60, 90, and 120 minutes. A wet magnetic separation method was then carried out to separate the concentrates and tailings. Characterization of reduced ore was performed by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), while the composition of ferronickel in concentrate was identified by X-Ray Fluorescence (XRF). The result showed that the higher temperature reduction, the higher of nickel grade, and its recovery at the concentrate. Nevertheless, the longer reduction time and the more reductant in nickel ore lowering the nickel grade and its recovery in the concentrate. The optimum condition in this selective reduction process was obtained with the addition of 5 wt. % of reductant and 10 wt. % of sodium sulfate in nickel ore, which was reduced at 1150oC for 60 minutes. It resulted in 4.60% and 73.23% for nickel grade and its recovery, respectively.

Abstract: In this paper, Cu/SiO₂ composites with different metal contents were successfully prepared by a selective reduction process. The phase composition and microstructure of composites were analyzed by XRD and SEM, respectively. The results show that spherical copper particles are uniformly distributed in silica matrix. The impedance and permittivity of composites were tested with RF impedance analyzer (0.1~1 GHz). It is indicated Cu/SiO₂ composites exhibit capacitive character. In addition, the dielectric constants get enlarged due to the enhancement of interface polarization.

Abstract: In this paper, thermodynamic analysis on reduction of lateritic nickel ore by CO₂/H₂ mixed gas was performed based on activity theory. Effects of CO₂/H₂ ratio and temperature on selective reduction of laterite ore were investigated. The calculation result shows that the metallization of Fe and Ni could be promoted by each other because of the variation of the Fe and Ni activity, which accounts for the inescapability of Fe metallization. When laterite nickel ore was reduced by mixed gas with a CO₂/H₂ ratio of 9/1 and a gas flow of 100mL/min at 800°C for 1h, a product with a Ni metallization rate over 95% and a Ni/Fe ratio as much as 2.6 was prepared.

Abstract: The metallurgical behavior of adjusted converter slag components during the selective reduction process were investigated by thermodynamic calculating with different modified slag composition, addition of reducing agent and reduction temperature. The activities of main slag components were drawn from the calculated values. The results showed that the activity of SiO₂ increased with increment of its mass fraction in slag. The solubility of SiO₂ increased with increment of temperature. The selective reduction was promoted by selecting the appropriate amount of modifier. Reduction order was elucidated in this paper, Fe was reduced from the slag followed by P, Mn and Si and the reduction rate of Si could reach about 51%. The metal phase was rich in Fe, Si, Mn and P as a result of the selective reduction.

Abstract: The composition change of slag and alloy phases were investigated during the process of selective reduction by thermodynamic calculating the selective reduction of the slag components with different modified slag composition, addition of reducing agent and reduction temperature. The results showed that the process of the selective reduction will be promoted by raising the temperature and the ratio of modifier to slag. The solubility of SiO₂ increased as temperature increased. Selecting the appropriate amount of modifier will promote the selective reduction. In the first stage, Fe was reduced from the slag, followed by the reduction of P, Mn and Si. Finally, Fe-Si-Mn metal was obtained as a result of the selective reduction.