水热还原法制备氧化铬清洁工艺的基础性研究
文献类型：学位论文
| 作者 | 姚芝茂 |
| 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 | 氧化铬 铬盐 清洁工艺 水热还原 |
| 其他题名 | Basic Research on the Cleaner Preparation Technology of Chromic Oxide by Hydrothermal Reduction |
| 学位专业 | 化学工艺 |
| 中文摘要 | 氧化铬是铬系列主要产品之一.在钾系一亚熔盐法生产铬盐清洁新工艺研究的基础上,按照新技术体系无废排放、工艺介质内循环和节能的要求,研究开发了以铬酸钾和重铬酸钾为原料,蔗糖为还原剂,水热还原Cr(VI)制备氧化铬的清洁生产新工艺,以取代现行污染严重的铬酐热分解生产氧化铬的传统工艺;通过钾碱介质的再生与循环利用,实现与铬盐清洁生产新工艺主体部分衔接,为铬盐清洁生产新工艺全流程实现废弃物零排放和资源的高效利用奠定了产品工程基础.该论文在以下几个方面取得了新的进展:1.进行了Cr(VI)水热还原过程热力学分析与动力学实验.2.研究了水热法蔗糖还原(重)铬酸钾为水合氧化铬的工艺过程.3.在蔗糖水热还原铬酸钾工艺过程研究的基础上,研究了碳酸化蔗糖水热还原铬酸钾的过程.4.开展了水合氧化铬热分解过程的研究.5.对还原介质处理与钾碱再生进行了研究.6.对蔗糖水热还原铬酸钾和重铬酸钾制备氧化铬的新工艺进行了全流程循环实验. |
| 英文摘要 | Chromic oxide Cr2C>3 is one of important chromium products. In accordance with the requirement of producing no waste, inner-recycling of medium and energy saving for the New Technology of Cleaner Production of Chromium Compounds (NTCPC) and based on the research of new cleaner technology of producing chromates with sub-molten salts of potassium system, a new cleaner process for preparing chromic oxide Cr2C>3 by reduction of Cr(VI) under hydrothermal conditions was developed to substitute the conventional and heavyly polluting preparation process of C^Ch with thermal decomposition of chromic anhydride, by using K2CrO4 and K2Cr2O7 as the chromium source and sucrose as the reducing agent. The process connects with the main frame of the new technology of cleaner production of chromate by recovery and recycle of caustic potash medium and provides the products engineering foundation for completely realizing waste zero emission and comprehensive utilization of mineral resource in the total technological process of chromate clean production. The thesis contains the following main results: Thermodynamical analysis and kinetic experiments for reduction of Cr(VI) under hydrothermal conditions were carried out. The estimation of ArG°(T) showed that the reactions of Cr(VI) with sucrose under hydrothermal conditions with very negative values of ArG°(T) had strong potential for forward reaction. The results of kinetic experiments showed that the effects of temperature and concentration ratio of reactants [Cr]/[Ci2H22On] were very significant. The activation energy of reaction is about 148.5kJ mol"1. The reaction follows first-order kinetics with respect to both Cr(VI) and sucrose. Reduction of potassium chromate and potassium dichromate to chromic oxide hydrate under hydrothermal conditions using sucrose as the reducing agent was investigated. The effects of the stoichiometric mole ratio of sucrose to chromate or dichromate salts (Rm), the isothermal temperature (Tjso) and time (tjs0) on the conversion of Cr6+to Cr3+ were also studied in detail. By using the orthogonal experiment Lc>(34), the order of the above affecting factors was obtained: tjS0<(Rm, TiS0) and the optimum technological conditions were determined. With potassium chromate and potassium dichromate as the raw materials, the conversion of Cr(VI) are 93.7% and 99.5%, Based on the research of reducing potassium chromate with sucrose under hydrothermal conditions, the process of reducing potassium chromate with sucrose to hydrated chromic oxide under hydrothermal and pre-carbonation conditions was investigated. The effects of conditions of carbonation such as CO2 partial pressure Pco2, time tc, temperature Tc and stirring speed Sc on the conversion of Cr(VI) to Cr(III) were studied in detail. The appropriate conditions of carbonation were determined. The experimental results showed that the conversion of Cr(VI) to Cr(III) was 98% under the optimum conditions. Thermal decomposition process of hydrated chromic oxide was investigated. The thermal decomposition of hydrated chromic oxide in air or CO2 atmosphere was studied comparatively by using the techniques of thermal gravimetry, differential thermal analysis, X-ray diffraction analysis, FT-IR spectroscopy and gas adsorption. The results confirmed that there was a reduction-oxidation process of Cr3+-?Cr5+-?Cr3+ during the thermal decomposition either in air or CO2. The presence of O2 favors the transformation process, which leads to the formation of microcrystallites of a-Cr2O3, The medium treatment of the reducing process and the recovery of caustic potash medium were investigated. The effects of CO2 partial pressure, carbonating time and temperature, and stirring speed on CO2 absorption were studied in detail. The optimum conditions of the carbonation of filtrate were determined. Cycle experiments of the total process of new Cr2O3 preparing technology by reducing Cr(VI) with sucrose under hydrothermal conditions were conducted. The results showed that the conversion of Cr(VI) was 97.0%, the recovery of Cr2O3 was 94.5%, and the recovery of K+ was 96.4%. Q2O3 product obtained is green hexagonal tablet-like powder, belonging to hexagonal crystal system. The mean size of Cr2C>3 product is about 2.3 urn. The new cleaner technology of preparing Q2O3 was proposed and the preliminary technical and economic analysis for it was carried out. The results showed that the new technology connected well with the main part of the New Technology of Cleaner Production of Chromate by recovery and recycle of caustic potash medium. The new process showed a promising application prospect as the technique, economy and environmental friendliness are concerned. |
| 语种 | 中文 |
| 公开日期 | 2013-09-16 |
| 页码 | 122 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1375]  |
| 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 | 姚芝茂. 水热还原法制备氧化铬清洁工艺的基础性研究[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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