Refining of Solid Iron Oxide by Flux

采用Na_2O-B_2O_3熔剂，采用熔剂浸出(85 0~95 0ﾟC)和重结晶法(14 0 0~14 5 0ﾟC)脱除细粒铁矿石中的杂质。前者可以去除分离出来的杂质和矿石表面的杂质。后一种方法是去除晶内夹杂物的有效方法。在850~1450ﾟC温度范围内，硅、铝、钙、镁、锰、钒等杂质含量随温度升高而降低，这主要是由于再结晶氧化铁含量的增加以及矿粉随温度升高而破碎的结果。实验研究了α-Fe_2O_3晶体与熔剂之间的锰、铝、钛含量随温度和熔剂组成的变化规律。α-Fe_2O_3晶体不是由细小的Fe_2O_3粒子聚集而成，而是按Ostwald熟化机制生长。在晶体生长过程中，通过在α-Fe_2O_3表面的吸附，Mn、Al和Ti与熔剂处于平衡状态。本实验未涉及扩散机制。在1000ﾟC下，锰、铝和钛在α-Fe_2O_3晶体和Na_2O_2B_2O_3熔剂之间的分配系数分别为0.8、0.02和1。结果表明，Mn的分配系数与温度呈负相关，而Al和Ti的分配系数与温度呈正相关。在α-Fe_2O_3晶体中，Mn以Mn^&lt；3+&gt；形式存在。熔剂中的铁和锰分别以Fe^-lt；3+-gt；和Mn^-lt；2+&gt；

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.