低温氢还原法生产氧化铬工艺优化
文献类型：学位论文
| 作者 | 尤海侠 |
| 学位类别 | 硕士 |
| 答辩日期 | 2009-05-21 |
| 授予单位 | 中国科学院过程工程研究所 |
| 授予地点 | 过程工程研究所 |
| 导师 | 张懿 |
| 关键词 | 氢还原 铬酸盐 氧化铬 工艺优化 动力学 |
| 其他题名 | Process Optimization for Chromic Oxide Preparation through Hydrogen Reduction of Chromates at Low Temperature |
| 学位专业 | 化学工艺 |
| 中文摘要 | 氧化铬(Cr2O3)是铬盐工业重要产品之一, 工业应用广泛。中国科学院过程工程研究所开发的铬酸钾低温氢还原法氧化铬生产工艺是以氢气作为洁净介质，低温还原铬酸钾中间体，短流程清洁生产氧化铬，反应介质实现了再生循环，具有重大的经济与环保效益。本论文针对铬酸钾低温氢还原法氧化铬生产工艺存在产品杂质含量高、单程收率低的问题，对生产工艺流程进行了优化，并以铬酸钠为原料，对铬酸盐低温氢还原过程的动力学和反应机理进行了研究。 本文主要取得了以下创新性进展： （1）针对铬酸钾晶体中以高铁酸钾形式存在的水溶性铁，提出了强化高铁盐水解沉淀的分离提纯方法，可将铬酸钾晶体中的铁含量由0.74 %和1.04 %降至检测限以下；根据生产过程中碳钢设备引入的铁多为铁磁性三氧化二铁的特点，提出了磁分离的除铁方法，工业生产线采用磁分离设备除铁实验研究结果表明，氧化铬产品中的铁含量可降至0.1 %以下，满足产品质量要求。 （2）提出并优化了示范工程氢还原产物酸洗脱钾工艺。在选定的四种酸—硫酸、硝酸、草酸、铬酸中，以硝酸的脱钾效果最好。针对示范工程氢还原中间产物，硝酸洗涤脱钾的最佳工艺条件为：搅拌速率400 r•min-1，温度80 ℃，液固比5:1，搅拌时间60 min，硝酸浓度0.3 mol•L-1。在此优化条件下，钾脱除率可达到70.4 %，氧化铬直收率由73.9 %提高至86.9 %。 （3）在分析Cr(NO3)3-KNO3-HNO3-H2O体系溶解度数据与相图的基础上，提出采用真空蒸发结晶方法分离硝酸铬副产品、采用冷却结晶方法分离硝酸钾副产品的方法，从而实现了酸洗脱钾液的再生循环。 （4）以铬酸钠为原料，采用TGA/DSC法进行了氢还原动力学研究，研究结果表明：在430 ~ 500 ℃之间，铬酸钠氢还原过程发生的主要反应为Na2CrO4•4H2O + 1.5H2 NaCrO2 + NaOH + 5H2O。用Doyle-Ozawa法和Kissinger法确定了反应的动力学参数，求得反应活化能E为342.47 kJ•mol-1，反应级数n为0.87。 |
| 英文摘要 | As one of the important products of chromate industry, chromic oxide finds wide industrial applications. The chromic oxide manufacturing process proposed by the Institute of Process Engineering, Chinese Academy of Sciences, employs hydrogen as the clean reduction agent, reducing the intermediate product potassium chromate at low temperature and manufacturing chromic oxide through a shorter and cleaner production route than the traditional process. The new process achieves the recovery and recycle of reaction media and exhibits significant economic and environmental benefits. This work aims to resolve the problem of high impurity content and low trivalent chromium yield. The production process parameters were systematically optimized, and the hydrogen reduction kinetics and reaction mechanism for sodium chromate were also investigated. The following innovative progresses were achieved in this work: (1) Through a combined method of deposition with enhancing the hydrolysis of ferrate, the soluble iron in the potassium chromate crystal can be decreased from 0.74 %wt and 1.04 %wt to below the testing limit, respectively. Furthermore, through a magnetic separation method, the iron content in chromic oxide product can be decreased to below 0.1 %wt, which satisfies the quality requirement of chromic oxide product. (2) A new potassium removal process with acid washing of hydrogen reduction products was proposed and optimized. The results showed that the potassium removal effects of nitric acid were the best in four selected kinds of acids, including sulfuric acid, nitric acid, oxalic acid and chromic acid. Under optimized conditions of 400 r•min-1 in stirring speed, 80 ℃ in leaching temperature, 5.0 in liquid-to-solid ratio, 60 min in leaching time, and 0.3 mol•L-1 in nitric acid concentration, the chromic oxide yield can be improved from 73.9 % to 86.9 %. (3) On the basis of solubility data and phase diagram of the Cr(NO3)3-KNO3-HNO3-H2O system, it was proposed that the Cr(NO3)3 byproduct can be separated by vacuum evaporation crystallization，the KNO3 byproduct can be separated by cooling crystallization, and therefore the recovery and recycle of the disposal liquor can be achieved. (4) The hydrogen reduction kinetics was investigated through the TGA / DSC method with sodium chromate as the raw material. The results demonstrated that the main reaction in the hydrogen reduction process of sodium chromate is Na2CrO4•4H2O + 1.5H2 NaCrO2 + NaOH + 5H2O in the temperature range from 430 ℃ to 500 ℃. The reaction activation energy E and reaction order n were determined as 342.47 kJ•mol-1 and 0.87, through the Doyle-Ozawa method and the Kissinger method, respectively. |
| 语种 | 中文 |
| 公开日期 | 2013-09-16 |
| 页码 | 77 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1307]  |
| 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 | 尤海侠. 低温氢还原法生产氧化铬工艺优化[D]. 过程工程研究所. 中国科学院过程工程研究所. 2009. |
入库方式： OAI收割
来源：过程工程研究所
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