(Ca(OH)2-)NaOH-Na2WO4-H2O和(Ca(OH)2-)NaOH-Na3PO4-H2O体系的热力学与应用
Thermodynamics of(Ca(OH)2-)NaOH-Na2WO4-H2O and(Ca(OH)2-)NaOH-Na3PO4-H2O systems and their application
吕世杰 1李江涛 2刘旭恒 1陈星宇 1何利华 2孙丰龙 1赵中伟2
作者信息
- 1. School of Metallurgy and Environment,Central South University,Changsha 410083,China
- 2. School of Metallurgy and Environment,Central South University,Changsha 410083,China;Key Laboratory of Hunan Province for Metallurgy and Material Processing of Rare Metals,Changsha 410083,China
- 折叠
摘要
白钨矿(CaWO4)碱压煮工艺是我国主流的钨冶炼工艺.但是,该工艺的机理仍不是很明确.本文利用相平衡原理,开展了白钨矿浸出过程、浸出渣洗涤过程、浸出液蒸发结晶过程中的热力学研究.根据浸出热力学平衡相图的分析,发现白钨矿中的钙对杂质的浸出有抑制作用(以磷为例),合理地解释了浸出液中磷等杂质始终维持在较低水平的主要原因.在浸出渣稀释−溶解钨酸钠晶体的过程中,利用热力学平衡相图解释了添加磷酸钠作为抑制剂,抑制二次白钨生成的作用机理,并优化了磷酸钠用量、反应时间、反应温度等对逆反应有抑制效果的工艺参数.在钨酸钠浸出液蒸发结晶钨碱分离过程中添加Ca(OH)2,在回收利用余碱的同时,还可实现溶液中杂质磷的脱除.该过程的热力学平衡相图表明,蒸发结晶结束区域是Ca5(PO4)3OH的稳定区,而CaWO4不稳定,说明了Ca(OH)2的加入不会影响钨的损失.实验结果表明,在蒸发结晶开始时加入理论量的Ca(OH)2,可以去除90％的磷,钨的损失率控制在0.2％以下.
Abstract
The caustic soda autoclaving process for digesting scheelite(CaWO4)is a unique and widely used tungsten(W)metallurgy technology in China.However,some experimental phenomena still need a proper theoretical explanation.In this work,some operational details and the theoretical basis of the technology are reported.During the digestion,some impurities,such as P,As,and Si are also digested.The P impurity was taken as an example.Based on the analysis of thermodynamic equilibrium phase diagram analysis,low levels of P impurities in the leaching solution were obtained.However,during the next dilution of the residue,P was supplemented as an inhibitor to reduce W loss.The inhibition of the reverse reaction mechanism is explained.The washed Na2WO4 solution containing excess NaOH can be reused in the evaporation−crystallization process;meanwhile,the supplemented P should be removed by adding Ca(OH)2.A theoretical analysis of the thermodynamic equilibrium phase diagram shows that there is an area where Ca5(PO4)3OH is stable,but CaWO4 is not.The experimental results show that over 90%of P can be removed by adding the theoretical Ca(OH)2 amount at the beginning of the evaporation-crystallization step.The W loss ratio can be controlled below 0.2%.
关键词
NaOH分解/白钨矿/赝三元相图/蒸发结晶/除磷Key words
NaOH decomposition/scheelite/pseudo-ternary phase diagram/evaporation crystallization/phosphorus removal引用本文复制引用
基金项目
National Natural Science Foundation of China(52174340)
Changsha Outstanding Youth Program,China(kq2009032)
出版年
2023
NETL
NSTL
万方数据