钾系亚熔盐法铬盐清洁工艺的分离工程应用基础研究与优化
文献类型：学位论文
| 作者 | 徐红彬 |
| 学位类别 | 博士 |
| 答辩日期 | 2003 |
| 授予单位 | 中国科学院过程工程研究所 |
| 授予地点 | 中国科学院过程工程研究所 |
| 导师 | 张懿 |
| 关键词 | 亚熔盐 清洁工艺 铬酸钾 盐析结晶 固液相平衡 平均离子活度系数 |
| 其他题名 | Applied Fundamental Research on the Separation Operations in the Chromate Cleaner Production Process Based on Potassic Sub-molten Salt Techniques |
| 中文摘要 | 铬化工为无机化工重点行业之一，其污染问题引起广泛社会关注。中国科学院过程工程研究所开拓的亚熔盐铬化工清洁生产新工艺，大幅度降低了反应温度和能耗，提高了主元素铬的利用率，实现了铬铁矿资源的全组分深度利用和铬渣零排放。分离工程问题在清洁工艺过程中占有重要地位。实现铬酸钾中间体的结晶分离为清洁工艺源头减废的关键环节；伴生元素铝的脱除程度直接影响到清洁工艺过程铬系列产品的质量；钾系亚熔盐电解质溶液体系固液相平衡预测方法的建立将为工艺过程高效相分离的实现提供有力的辅助研究手段。本文紧密结合清洁工艺特点，对以上分离过程关键问题进行了应用基础研究和工艺优化。本论文在以下几个方面取得了新的进展：（1）建立了钾系亚熔盐多组分电解质溶液体系固液相平衡预测方法，在缺乏固液相平衡基础数据的情况下，可利用多组分体系中各种组分的单一电解质溶液的固液相平衡关系，预测多组分的固液相平衡，为清洁工艺相关电解质溶液体系的相分离问题研究提供理论基础和指导；（2）在氢氧化钾介质浓度40％以上、略低于沸点的条件下，从晶／渣悬浮液中结晶分离铬酸钾中间体，经简单重力分级，可得到80％以上的分离效率，大大减少了铬渣的洗涤负荷，使铬渣中水溶性六价铬含量由传统工艺的1％降至微量，从而实现铬化工的源头污染控制；（3）考查了液相氧化反应和稀释一结晶过程中，各操作参数对铬酸钾结晶相分离效率的影响。稀释一结晶过程最佳操作工艺条件确定为：20％氢氧化钾溶液进行正向稀释、搅拌转速150 mill-1、缓慢稀释，可实现无需添加晶种的结晶过程；（4）研究了液相氧化反应系统中单一及协同杂质积累对铬酸钾结晶相分离效率的影响，并提出了消除杂质积累效应的方案。配合示范工程，考查了液相氧化一液固分离一晶渣洗涤过程中，铬、铝、硅、氢氧化钾在各工艺物流中的分配情况；（5）结合清洁工艺流程特点，将盐析结晶分离新方法引入到铬酸钾粗晶和铁渣的分离过程中，测定了操作温度范围内铬酸钾在氢氧化钾中的超溶解度，确定了铬酸钾盐析结晶的介稳区，研究了铬酸钾盐析结晶成核时溶液过饱和速率和最大过饱和度之间的动力学关系，分析了盐析剂加入速度对晶体平均粒度的影响；通过对实际体系的工艺计算和实验研究，讨论了盐析结晶分离过程各工艺参数之间的关系，并分析了其在清洁工艺过程中实施的可行性；（6）借鉴传统铬盐生产工艺中通过调整溶液pH值脱除杂质铝的方法，结合清洁工艺过程特点，提出了重铬酸钾产品的深度脱铝方案。通过控制碳酸化反应转化率在85％-95％，可除去碳化液中的杂质铝，实现碳酸化过程的同步除铝。重铬酸钾产品重结晶过程在重铬酸钾溶解液中引入铬酸钾溶液，调整混合溶液pH值到6.0左右，可使杂质铝沉淀析出，实现重铬酸钾产品精制。 |
| 英文摘要 | Chromium compounds are basic chemicals essential to many industries. The serious environmental problems resulted from the traditional process have spawned wide public concerns. The Institute of Process Engineering, Chinese Academy of Sciences has recently developed a new cleaner manufacturing process for chromium compounds. Based on the sub-molten salt techniques, the cleaner process significantly decreases the reaction temperature and energy consumption, remarkably improves the utilization efficiency of the main element chromium, and successfully achieves the comprehensive utilization of chromite resources and the zero emission of chromium-containing residue. Separation-related problems are of great importance for the cleaner process. Achieving effective crystallization separation of the intermediate K^CrCU is the key issue to reduce the environmental pollution at the source. The content of trivalent aluminum determines in part the quality of the K.2Cr2O7 product. The construction of thermodynamic solid-liquid equilibrium prediction method for the sub-molten salt system helps to effectively achieve the related phase separations. Upon close combination with the cleaner process, this thesis aims to carry out applied fundamental research and process optimization on the above separation-related issues. In this thesis, the following achievements and progresses were exhibited: (1) A solid-liquid phase equilibrium prediction method was proposed for the potassic sub-molten salt multi-component electrolyte systems. This method can be used to predict the multi-component solid-liquid phase equilibrium of sub-molten salt system with only the assistance of single electrolyte solid-liquid equilibrium data, and is capable of providing instructions for solving the separation problems in the cleaner process where the experimental data are absent for multi-component solid-liquid equilibrium. (2) It was found that, the K2CrO4 intermediate can be crystallized and separated from the suspension system containing the leaching liquor, K2OO4 crystal, and ferrite-enriched residue when the concentration of KOH medium is above 40% by weight and the temperature is slightly below its boiling point. Simply after gravitational settling, separation efficiency of some 80% can be achieved. This greatly reduces the loads in leaching and washing the chromium-containing residue, decreases the content of soluble hexavalent chromium in the residue from 1% in the traditional process to almost zero, thus achieving the source pollution control in the chromate chemical industry. The effects of various operation parameters in the liquid-phase oxidation and diluting process on the phase separation efficiency of the K^CrCU crystal were examined. The optimum operation conditions for the diluting process were determined as: adding 20%wt of aqueous KOH solution as the diluent into the liquor system to be diluted, slowly diluting, stirring at 150 min"1, without crystal seeds added. The accumulation effect was examined of single and multiple impurities on the conversion rate of chromium and phase separation efficiency of K2CrO4 crystal for the recycle process of sub-molten salt medium. Accordingly, two measures were proposed to counteract the impurity accumulation effect. The distribution of the main components among the process flows were analyzed for the requirement of the demonstration project. (5) With accordance to the flow characteristics of the cleaner process, the salting-out crystallization method was introduced into the separation process of K2CrO4 crude crystal and chromite ore processing residue. The solubilities and supersolubilities of K2CrO4 in aqueous KOH solution were determined. Therefore, the meta-stable zone of the salting-out crystallization was obtained. Experimentally, the kinetic relationship of the maximum supersaturation and the supersaturation rate when nucleation occurs was found, and the effects of the diluent feeding flow rate on the mean crystal particle size were discussed. The relationship was discussed among the various technical parameters during the salting-out crystallization process of K2Cr04 in the KOH aqueous solution. Based on the experimental results on the real system, the applicability and feasibility of the salting-out crystallization operation were discussed. (6) Inspired by the aluminum removal method in the traditional chromate production process, a new approach was proposed to removing trivalent aluminum from the K^C^Ch product by adjusting the pH value of the liquor. The trivalent aluminum in the system can be removed by controlling the conversion rate at the range of 85% to 95% during the carbonation of K^CrCU. The coupling of carbonation of K2CrO4 and removal of trivalent aluminum is thus achieved. The trivalent aluminum in the system can be further precipitated by adding certain amount of K2CrO4 to the K2Cr2O7 dissolution liquor and controlling the pH value of the liquor at approximately 6.0 during the recrystallization process of K.2Cr2O7. Thereby, the refinement of the product K2O2O7 is achieved. |
| 语种 | 中文 |
| 公开日期 | 2013-09-16 |
| 页码 | 125 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1399]  |
| 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 | 徐红彬. 钾系亚熔盐法铬盐清洁工艺的分离工程应用基础研究与优化[D]. 中国科学院过程工程研究所. 中国科学院过程工程研究所. 2003. |
入库方式： OAI收割
来源：过程工程研究所
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