Refining of Solid Iron Oxide by Flux

点击翻译按钮获取中文摘要

Using the Na_2O-B_2O_3 flux, the impurities in fine grained iron ore were removed by the flux leaching (850-950^ﾟC) and recrystallization methods (1400-1450^ﾟC). The impurities that were isolated and those on the surface of the ore could be removed by the former method. The later method was effective for the removal of inclusions existing inside the grain. The concentrations of impurities for Si, Al, Ca, Mg, Mn and V decreased with increasing temperature between 850 and 1450^ﾟC. These results were explained by the increase in the amount of recrystal lized iron oxide as well as the break up of a fine ore with an increase in temperature.It was found that the partition coefficients of the trace elements between Na_2O-B_2O_3 flux and alpha -Fe_2O_3 crystal were indispensable in order to clarify the impurity behavior in purification of alpha -Fe_2O_3 by recrystallization method. The experiments on the Mn, Al and Ti partitions between alpha -Fe_2O_3 crystal and fluxes have been carried out as a function of temperature and flux composition. Alpha -Fe_2O_3 crystal grew not by clustering of fine Fe_2O_3 particles but by Ostwald ripening mechanism. Mn, Al and Ti were included in equilibrium with flux by adsorption on alpha -Fe_2O_3 surface during crystal growth. No diffusion mechanism was involved in the present experiment. The partition coefficients of Mn, Al and Ti between alpha -Fe_2O_3 crystal and Na_2O.2B_2O_3 flux at 1000^ﾟC were 0.8, 0.02 and 1, respectively. The temperature dependence of partition coefficient of Mn was found to be negative, while that of Al and Ti was positive. Mn was present as Mn^<3+> in alpha -Fe_2O_3 crystal. Fe and Mn in flux were present as Fe^<3+> and Mn^<2+>, respectively.