A kinetic study of the leaching of a low-grade niobium–tantalum ore by concentrated KOH solution

A kinetic study of the leaching of a low-grade niobium–tantalum ore by concentrated KOH solution under atmospheric pressure has been investigated. The effects of reaction temperature, KOH concentration, agitation speed, particle size and alkali-to-ore mass ratio on the dissolution rate of niobium were examined. It was found that the dissolution rate of niobium is significantly influenced by the temperature, particle size and concentration of KOH solution. The experimental data were well interpreted with a shrinking core model under diffusion control through the product layer. By using the Arrhenius expression, the apparent activation energy for the dissolution of niobium was evaluated. Finally, on the basis of the shrinking core model, the following rate equation was established:$1-3(1-X_{\text{b}}{)}^{2/3}+2(1-X_{\text{b}})=\frac{k_0}{R^2}{\mathrm{e}}^{-\frac{72200}{R\prime T}}·t\text{.}$     

Electrochemical properties of gadolinium on liquid gallium electrode in LiClKCl eutectic

This work presents the electrochemical properties of gadolinium(Gd), a significant rare earth element in spent nuclear fuel(SNF), in the LiCl-KCl eutectic. To explore thermodynamic properties of Gd at the liquid gallium(Ga) electrode, experiments were performed both on the inert tungsten(W) and liquid gallium(Ga) electrode at different temperatures in a range from 723 to 823 K, which show that the Gd metal can be oxidized to Gd(Ⅲ) by exchanging of 3 electrons. Electrochemical techniques including cyclic voltammetry(CV), open circuit potential(OCP), potentiostatic electrolysis and galvanostatic electrolysis were utilized to detect the electrochemical behavior and evaluate standard apparent potential of the Gd(Ⅲ)/Gd couple,and E_(Gd(Ⅲ)/Gd)~*=-3.456 + 6.2×10~(-4)T(±0.046)( vs Cl_2/Cl~-) is obtained.In addition, electromotive force(EMF) and coulometric titration were employed to calculate the activity and activity coefficient of Gd in metal Ga. After calculation, the activity is 1.791×10~(-15) at 723 K and function of activity coefficient and temperature is lgγ = 3.485-10927/T(±0.0875).     

罩式退火炉炉内气体流场的仿真研究

由于外部气体渗入炉内易造成钢卷被氧化,为了寻求避免钢卷退火时发生表面氧化的方法,采用流体分析软件FLUENT对罩式退火炉炉内的流场进行分析,结果表明:分流板对气体的扰动作用是造成气体涡流场的直接原因;当钢卷外径过小时,分流板对气体的扰动作用较强,易于造成外部气体渗入;当钢卷外径大于分流板外径时,分流板对气体的扰动作用减弱;当钢卷外径大于2300mm时,钢卷周围不再出现涡流场;钢卷外径控制在2400±100mm范围内为最佳。     

表面改性对JT-235浮选铜钼矿的影响

难选铜钼矿难于浮选的原因主要是矿物表面被氧化。通过对铜钼矿表面改性,然后采用新型浮选剂JT-235进行浮选,研究结果表明,经过电场改性后,铜钼矿石铜回收率达到79%,钼回收率增加到75%;经过碱改性后,铜回收率增加到89%,钼回收率增加到84%;经过盐酸改性后,铜回收率最高达到83．5%,钼回收率达到80%。改性方法简单可行,成本增加不大。     

某含银氧化铅、锌矿石浮选试验研究

该铅锌矿石,铅锌氧化率高,含泥量大,给铅锌选别回收带来困难。经试验研究,采用先硫后氧工艺流程及符合环保要求的药剂制度,获得铅精矿品位56.59%,回收率89.91%,锌精矿品位40.13%,回收率75.19%,铅精矿含银品位1539g/t,回收率78.16%。     

南钢DF钢夹杂物分析研究

对南钢转炉厂生产DF钢中的夹杂物进行了研究，结果表明现有工艺制度下吹氩精炼效果不明显，氩后钢中的夹杂物含量为865．78mg／kg；大于300μm的夹杂物，主要成分为Si—Al，或Si—Al—Mn；80～300μm夹杂物，主要成分为Si—Al-Mn，且Si较高，Mn较低；小于80μm的夹杂物，主要成分为Si—Al—Mn，并且含Mn较高：改变钢液脱氧制度及控制吹氩搅拌，可使氩后钢中及铸坯中的夹杂物含量分别降低到203．38mg/kg、59．8mg／kg。     

时效处理对904L超级奥氏体不锈钢腐蚀性能的影响

利用电化学方法研究了904L超级奥氏体不锈钢不同时效下腐蚀性能的变化情况。研究结果表明:904L超级奥氏体不锈钢发生钝化时,致钝电流密度小,电位范围广,因此它容易获得钝化,这主要与904L含有较高含量的Cr、Mo合金元素有关;随着时效温度逐渐接近钢的析出敏感温度以及随着时效时间的延长,904L超级奥氏体不锈钢耐腐蚀性能明显下降。     

一种新的加热炉状态识别算法

最小距离法是一种应用非常广泛的状态识别算法,但其在使用过程中要求待识别样本必须符合类内距离较小、类间距离较大这一前提条件,否则将会造成识别错误.针对最小距离法存在的问题,提出了一种基于人工神经网络的改进最小距离法,并将该方法应用于加热炉工况的状态识别.结果表明,该方法具有识别速度快、识别率高的优点,完全能够满足工业生产过程的需要.     

板塘花岗岩矿地质特征及成因浅析

板塘花岗岩矿位于广东河源,是以花岗岩为主的非金属矿床。矿体产于罗浮-龙川岩体,呈岩基产出,岩性主要为黑云母花岗岩。矿体形态简单,分布均匀、连续、完整,厚度比较稳定。根据矿体产出特点,初步认为矿床成因类型属于S型花岗岩。     

宝钢炼钢厂碳钢线网络化控制系统剖析

宝山钢铁股份有限公司不锈钢分公司炼钢厂碳钢线网络控制系统由三种不同类型的网络组成,第1种是连接PLC、操作站和数据库站的冗余FL-Net控制网;第2种是连接操作站、数据库站和L2的工业Ethernet网;第3种是现场总线,分为PE-Link和T-Link两种。PLC站间通信通过PE-Link相连,而PLC与远程I/O、VVVF变频器、智能MCC、智能化仪表的通信通过T-Link相连,使整个系统结构简洁、紧凑,具有强大的远程控制管理能力,大大节省了维护工作量,同时提高了系统运行的可靠性。