Refining of Solid Iron Oxide by Flux

采用na22o - b_2o_3助熔剂，采用助熔剂浸出法（850 ~ 950^ C）和再结晶法（1400 ~ 1450^ C）对细粒铁矿中的杂质进行了脱除。用前一种方法可以除去被分离出来的杂质和矿石表面的杂质。后一种方法对于去除晶粒内部的夹杂物是有效的。硅、铝、钙、镁、锰、钒等杂质的浓度在850 ~ 1450ºC之间随温度升高而降低。这些结果可以解释为再结晶氧化铁的数量增加以及细粒矿石随着温度的升高而破碎。在重结晶法提纯α -Fe_2O_3时，微量元素在na22o - b_2o_3助熔剂与α -Fe_2O_3晶体之间的分配系数是明确杂质行为不可缺少的参数。研究了α -Fe_2O_3晶体与助熔剂之间Mn、Al和Ti的分布随温度和助熔剂组成的变化规律。α -Fe_2O_3晶体的生长不是由Fe_2O_3颗粒的聚集形成的，而是由奥斯特瓦尔德成熟机制形成的。在α -Fe_2O_3晶体生长过程中，Mn、Al和Ti在α -Fe_2O_3表面的吸附使其与助熔剂平衡。本实验不涉及扩散机制。α -Fe_2O_3晶体与Na_2O晶体之间Mn、Al和Ti的分配系数。2B_2O_3在1000^ cc时的通量分别为0.8、0.02和1。Mn的分配系数与温度的关系为负，Al和Ti的分配系数与温度的关系为正。Mn以Mn^<3+>的形式存在于α -Fe_2O_3晶体中。通量中的Fe和Mn分别以Fe^<3+>和Mn^<2+>的形式存在。

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.