铬酸盐多元水盐体系相图及相分离基础性研究
文献类型：学位论文
| 作者 | 崔金兰 |
| 学位类别 | 博士 |
| 答辩日期 | 2000-11 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 张懿 |
| 关键词 | 相图 清洁工艺 铬盐 多元水盐体系 相分离 |
| 其他题名 | Basic research on phase diagrams and phase separation of multi-component chromate aqueous solution system |
| 学位专业 | 清洁工艺 |
| 中文摘要 | 铬、铝等两性元素含氧根的多元复杂水盐体系相平衡与相图研究是两性元素化工-湿法冶金新过程开拓的重要理论依据，但国内外的相关研究却极少，铬系近于空白。本文研究了熔盐液相氧化法铬化工清洁生产新过程的多元水盐体系相图-热力学优化-分离新方法，首次构筑了难度很大的相关相图，填补了铬系相平衡的空白。建立了铬氧酸根复杂多元新体系的相分离研究方法，在铬化工清洁工艺中，为工艺路线的设计、工艺参数的优化提供了有力依据。对铬酸钾清洁工艺中的KAlO_2-K_2CO_3-KOH混合物进行了有效分离，得到质量合格的氢氧化铝产品，实现了铬化工的多组份深度利用。其主要内容如下：1.测定了Na_2CrO_4-(NH_4)_2CrO_4-H_2O体系在20 ℃和50 ℃的溶解度以及(NH_4)_2CrO_4-NH_4HCO_3-H_2O体系和Na_2CrO_4-NaHCO_3-H_2O体系在25 ℃和40 ℃的溶解度数据。根据溶解度数据，分别绘制了各自相应的相图，为实际复杂体系相分析提供了依据。2.测定了25 ℃时Na_2CrO_4-NaHCO_3-H_2O体系平衡溶液的密度、粘度、电导率和pH值等物化常数，并运用经验公式对该平衡溶液的密度进行了理论计算，计算值与实验值能很好吻合。3.测定了Na~+, NH_4~+ || HCO_3~-, CrO_4~(2-)-H_2O体系 25 ℃和40 ℃时的溶解度，并构筑了相应的相图。分析相图和计算可以知道，碳酸化母液组成点在P_3点(NaHCO_3, (NH_4)_2CrO_4与NH_4HCO_3的共饱点)附近时，钠转化率最大；碳酸化取出液温度越高，钠转化率越低；提高氨盐比(NH_3/Na_2CrO_4)能够提高钠转化率。4.KOH-K_2CrO_4-H_2O体系，KOH-KAlO_2-H_2O体系和KOH-K_2CrO_4-KAlO_2-H_2O体系相平衡研究结果表明，较低的氢氧化钾浓度有利于铝酸钾结晶析出，一定范围内，较高的氢氧化钾浓度有利于铬酸钾结晶析出，因此，通过控制氢氧化钾浓度可以使铬酸钾-铝酸钾-氢氧化钾得以分离。5.测得了KOH-K_2CrO_4-K_2CO_3-H_3O体系相图。并将有饱和碳酸钾共存与无碳酸钾共存时，铬酸钾在氢氧化钾水溶液中溶解度进行对比，表明碳酸钾对铬酸钾的盐析作用非常强烈，进一步说明碳酸钾的存在对铬酸钾从反应体系中的分离是非常有利的。6.熔盐液相氧化法生产铬盐的高碱介质可经冷却结晶分离后再循环，所得复盐经洗涤、脱硅、晶种分解，得到质量合格的氢氧化铝产品，实现多组份综合利用。 |
| 英文摘要 | Phase equilibrium and phase diagrams of complex multi-component aqueous salt system of oxygen acids of amphoteric elements such as chromium and aluminum are the important theoretical bases for developing a new chemical-hydrometallurgical process. However, the related studies on this field were seldom reported, particularly the chromate system was nearly blank. The present paper mainly focuses on the phase diagrams of multi-component aqueous salt system, optimization of thermodynamics and new separation methods in the clean production process for chromium salts via the molten salt liquid phase oxidization. Some complecated phase diagrams of chromate system were worked out for the first time. A phase separation research method for the new complex multi-component chromate systems was established, which was a base for designing technological flow sheet and optimizing parameters in clean technology of chromium chemical industry. Meanwhile, the mixture of KAlO_2-K_2CO_3-KOH obtained by clean technology of potassium chromate was separated successfully to obtain qualified Al(OH)_3 product and deeper utilization of the components in chromium chemical industry was realized. The main points are as follows: 1. Solubility of the Na_2CrO_4-(NH_4)_2CrO_4-H_2O system at 20 ℃ and 50 ℃, and solubility data of the (NH_4)_2CrO_4-NH_4HCO_3-H_2O system and Na_2CrO_4-NaHCO_3-H_2O system at 25 ℃ and 40 ℃ were determined, respectively. Corresponding phase diagrams were plotted according to the solubility data, which offers a base for phase analyses of the real complex systems. 2. Some physical chemical constants, such as density, viscosity, conductivity and pH of equilibrium solution in the Na_2CrO_4-NaHCO_3-H_2O system at 25 ℃ were determined. And density of th equilibrium liquid phase has been calculated by using empirical equation, and the calculated results were in agreement with the experimental ones. 3. Solubility of the Na~+, NH_4~+ || HCO_3~-, CrO_4~(2-) -H_2O system at 25 ℃ and 40 ℃ were studied, and the corresponding phase diagram was constructed. It was clear by analyzing the phase diagram and calculation that, conversion percentage of Na~+ reached the maximum near the point P_3 (cosaturated point of NaHCO_3, (NH_4)_2CrO_4 and NH_4HCO_3). The higher the end temperature of carbonation was, the lower the conversion of Na~+ was. Increasing of the ratio of ammonia to salt (NH_3/Na_2CrO_4) could improve the conversion of Na~+ 4. Research results of phase equilibrium for the KOH-K_2CrO_4-H_2O system, the KOH-KAlO_2-H_2O system and the KOH-K_2CrO_4-KAlO_2-H_2O system revealed that lower concentration of KOH was beneficial for the crystallization of KAlO_2, and within a certain range, higher concentration of KOH was favorable for the crystallization of K_2CrO_4. Therefore, the mixture of K_2CrO_4-KAlO_2-KOH could be separated by control of concentration of KOH. 5. Phase diagram of the KOH-K_2CrO_4-K_2CO_3-H_2O system was determined. Meanwhile, solubility of K_2CrO_4 in aqueous solution of KOH saturated with K_2CO_3 was compared with that in aqueous solution of KOH without K_2CO_3, and the salt-out effect of K_2CO_3 on K_2CrO_4 was very strong, i.e. the presence of K_2CO_3 was very favorable for the separation of K_2CrO_4 from reaction system. 6. The high concentration of KOH medium was cooled, separated and recycled in the production process of chromium salts via the molten salt liquid phase oxidization. On the other hand, the double salt obtained was washed, desilication, and eventually the qualified product of Al(OH)_3 could be obtained by seed crystal decomposition, and the comprehensive utilization of multi-component was realized. |
| 语种 | 中文 |
| 公开日期 | 2013-09-26 |
| 页码 | 124 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1926]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 崔金兰. 铬酸盐多元水盐体系相图及相分离基础性研究[D]. 中国科学院研究生院. 2000. |
入库方式： OAI收割
来源：过程工程研究所
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