循环碳氨法生产铬盐清洁工艺的基础性研究
文献类型：学位论文
| 作者 | 刘昌见 |
| 学位类别 | 博士 |
| 答辩日期 | 1999-12-24 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 张懿 |
| 关键词 | 铬盐 清洁工艺 碳氨循环转休 相图 |
| 其他题名 | Clean Process of Chromates Production by Recycling Ammonia and Carbon Dioxide |
| 中文摘要 | 本文针对铬盐工业的严重污染问题，研究了以氨和二氧化碳为循环介质，由铬酸钠转化为得铬酸钠、重铬酸铵及铬酐等铬盐产品的物理化学基础问题及其清洁生产新过程。研究了Na~+, NH_4~+//CrO_4~(2-), HCO_3~--H_2O体系相平衡规律，发现在体系上存在NaNH_4CrO_4·2H_2O的结晶区；以铬酸钠为盐析剂的盐析冷析方法可以较完全地使母液I中的铬酸铵以铬酸铵钠结晶的形式析出；铬酸铵钠复盐晶体在温度低于180 ℃时的首先分解为铬酸钠和重铬酸铵，高于180 ℃时，热分解产物为铬酸钠、重铬酸钠和三氧化二铬的混合物，铬酸铵钠复盐在低于180 ℃的第一、第二步分解反应由相界面反应控制，动力学符合收缩圆柱体方程：1-(1-α)~(1/2) = kt，反应的活化能为51.76kJ/mol，高于180 ℃的第三步分解反应动力学符合Prout-Tompkins方程：-ln(1-α) = kt；以铬酸铵钠复盐晶体热分解得到的铬酸钠和重铬酸铵混合物经结晶分离可以制备高附加值的重铬酸铵产品，在120 ℃、铬酸钠饱和条件上蒸氨得到的溶液经蒸发浓缩至沸点达到145 ℃，分离除去铬酸钠，冷却结晶可以制备高质量的重铬酸钠产品；探讨了由重铬酸铵、氧化钙制备铬酸钙，再经碳化、水解制备铬酐的方法。在整个工艺中除目标产品外，其它物质全部实现内循环，无含铬芒硝与硫酸氢钠产生，钠离子返回液相氧化系统循环利用，是一全新的清洁生产工艺。 |
| 英文摘要 | The physical chemistry and a clean process of conversion of sodium chromate into sodium dichromate, ammonium dichromate, chromium oxide etc. using ammonia and carbon dioxide were investigated in the present thesis. The solubility and phase equilibrium of Na~+, NH_4~+//CrO_4~(2-), HCO_3~--H_2O system were determined firstly. The results showed that crystal zone of NaNH_4CrO_4·2H_2O double salt existed in phase diagram of both Na~+, NH_4~+//CrO_4~(2-)-H_2O system and Na~+, NH_4~+//CrO_4~(2-), HCO_3~-H_2O system. (NH_4)_2CrO_4 in mother liquid can be separated completely by salt-out with Na_2CrO_4 crystal. The mechanism and kinetics of thermal decomposition of NaNH_4CrO_4·2H_2O crystal were investigated by TG-DTG, DTA and XRD. Results indicated that below 180 ℃ the thermal decomposition products were the mixtures of sodium chromate and ammonium dichromate, but above 180 ℃ the final thermal decomposition products were the mixtures of sodium chromate, sodium dichromate and Cr_2O_3. The kinetics of thermal decomposition reaction below 180 ℃ obeys the shrink cylinder equation: 1 - (1-α)~(1/2) = kt, and the activation energy of reaction was 51.76kJ/mol. The kinetics of the third step reaction of thermal decomposition above 180 ℃ obeys the modified Prout-Tompkins equation: -ln(1-α) = kt. From the decomposition products - the mixture of sodium chromate and ammonium dichromate, ammonium dichromate can be obtained by recrystallization. Sodium dichromate can be produced by evaporation of ammonia from the solution of sodium chromate and ammonium dichromate, and 120 ℃ and excess sodium chromate were optimal conditions. Calcium chromate can be produced by the reaction of ammonium dichromate with calcium oxide, chromium oxide can be produced by carbonation of calcium chromate and then hydrolyzition of calcium dichromate. In the whole process, sodium chromate can be converted into objective products including sodium dichromate, ammonium dichromate, chromium oxide etc., and ammonia, carbon dioxide, wastewater and other by-products can be recycled in this process. |
| 语种 | 中文 |
| 公开日期 | 2013-09-27 |
| 页码 | 130 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1994]  |
| 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 | 刘昌见. 循环碳氨法生产铬盐清洁工艺的基础性研究[D]. 中国科学院研究生院. 1999. |
入库方式： OAI收割
来源：过程工程研究所
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