芒硝制纯碱新方法及其工艺研究
文献类型：学位论文
| 作者 | 王天贵 |
| 学位类别 | 博士 |
| 答辩日期 | 2004 |
| 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 | 李佐虎 |
| 关键词 | 芒硝 纯碱 方法 工艺 石膏 碳酸钙 |
| 其他题名 | A New Manufacturing Process of Soda Ash from Sodium Sulfate |
| 学位专业 | 化学工艺 |
| 中文摘要 | 本文针对铬盐生产中含铬芒硝（NaZSO4）的再生循环利用及铬盐清洁生产工艺中碱的补充，研究了一种芒硝制纯碱新方法，该方法具有一定的普适性。铬盐行业是一个重污染行业，产生大量的废气、废液和废渣，芒硝是固体废物之一。铬盐生产中消耗的大量纯碱和硫酸，绝大部分转化成了含铬芒硝。目前，含铬芒硝只能在脱铬处理后制成硫化碱，不仅不能彻底解决污染问题，经济效益也很差，总体原子经济效益大大降低。此外，芒硝也是许多其它工业过程的废弃物，大多来源于硫酸与纯碱或烧碱的终结产物，都存在类似的问题。当前，清洁生产、资源循环利用、原子经济效益最大化的“3R”现代工业理念已经成为人们的共识。因此，研究芒硝再生循环利用具有重要的经济意义和环保价值。而现有的化学合成制碱法一索尔维制碱法和候氏制碱法都无法将其有效的利用。因此，研究芒硝制碱的新方法具有重要的现实意义。芒硝制纯碱新方法采用了与索尔维制碱法完全不同的原理，它以碳酸钙和芒硝为原料，利用重铬酸钠溶液为转化介质，最终得到纯碱和硫酸钙。主要流程为：用重铬酸钠溶液分解碳酸钙得到铬酸钙沉淀、铬酸钠溶液和二氧化碳气体；铬酸钙与硫酸钠复分解得到铬酸钠溶液和硫酸钙；铬酸钠溶液与二氧化碳反应再生重铬酸钠溶液同时得到碳酸氢钠沉淀；碳酸氢钠脱铬处理得到商品纯碱。研究结果表明，在110℃以上的重铬酸钠浓溶液中碳酸钙可以被完全分解，温度是影响碳酸钙转化率的主要因素，分解反应属于传递和表面反应联合控制，表面反应占主导作用。在60℃以上的硫酸钠浓溶液中，铬酸钙可以很容易地转化为铬酸钠溶液和硫酸钙沉淀，但硫酸钠要过量一倍以上，铬酸钙才能转化完全，转化反应速率受铬酸钙的溶解限制。铬酸钠溶液很容易碳化再生重铬酸钠，二氧化碳分压0.5MPa以上，30％的铬酸钠溶液转化率即可达到75％以上，硫酸钠的存在有利于铬酸钠的转化，碳化反应速率都要经历一个大一小一大一小的过程，碳酸氢钠的析出对反应影响较大。用洗涤加亚铁还原的方法或糖类还原剂高温锻烧的方法都可以将碳酸氢钠中夹带的六价铬还原脱除，锻烧温度是影响还原速率和转化率的主要因素，在600℃以上，几分钟内六价铬就可以完全转化为结晶型、不溶性的三氧化二铬。副产硫酸钙可以制成各种各样的彩色石膏粉，也可以脱除六价铬制得高品质的两水硫酸钙，更可以制成高强石膏或石膏晶须，不会造成环境污染。初步研究表明，新工艺流程合理，技术上可行，为工程放大提供了坚实基础。 |
| 英文摘要 | A new method to produce soda ash from sodium sulfate was developed in this dissertation. The study is to meet the need of recycling and regenerating soda ash from the sodium sulfate, a by-product in the production of chromates, and the need of providing cheaper alkaline subatance for the cleaner production process of chromates. The method can also be used in other fields. Chromium salts industry produces lots of pollutants and sodium sulfate containing chromate is one of them. Sodium sulfate containing chromium (VI) comes from the soda ash and sulfuric acid consumed in the production. At present, it is used to produce sodium sulfide after the removal of chromium (VI), which can not delete the pollution of chromium completely and the profit is poor either. Moreover, sodium sulfate is also a waste of many other industrial processes and similar problems exist. Today, the modem "3R" concept of cleaner production, recycling utilization of the resources and maximum of nuclear economy is commonly accepting by people. Therefore, it has important economic significance and great environmental interests to study the recycling and reuse of sodium sulfate. Still it should has practical value because present chemical methods for producing soda ash—Solvay's process and Dual process, can not utilize sodium sulfate effectively. The new method adopts a different principle from Solvay's process and Dual process. With aqueous sodium dichromate solution being work medium, it uses sodium sulfate and calcium carbonate as raw materials to produce soda ash with gypsum as a by-product. Its process consists of dissolution of calcium carbonate in aqueous sodium dichromate solution to obtain calcium chromate precipitates and aqueous sodium chromate solution and CO2 gas, complex-decomposition of calcium chromate and sodium sulfate solution to get gypsum and aqueous sodium chromate solution, carbonation of aqueous sodium chromate solution to regenerate aqueous sodium dichromate solution and produce sodium bicarbonate, chromium removal and calcination of sodium bicarbonate to obtain soda ash. Experimental results indicate that temperature is the key factor affecting the dissolution and transformation of calcium carbonate and above 110 °C, calcium carbonate can be decomposed almost completely in concentrated sodium dichromate solutions. The dissolution reaction rate is mixed-controlled by diffusion and surface processes, with the latter dominating. Above 60 °C, the reaction of calcium chromate and sodium sulfate is rapid in saturated sodium sulfate solutions. In order to transform calcium chromate completely, the amount of sodium sulfate should be more than twice the stoichiometric value. The complex-decomposition rate is controlled by the dissolution of calcium chromate and increases substantially with increasing temperature. The carbonation of aqueous sodium chromate solution takes place easily and under the circumstance of 0.5MPa partial pressure of CO2 and 30% sodium chromate content, the conversion of sodium chromate can reach 75%. Existence of sodium sulfate in the solution benefits the conversion of sodium chromate. The carbonation rate experiences a variation of high-low-high-low and the precipitation of sodium bicarbonate also affects it. The chromium contained in sodium bicarbonate can be removed by combining washing or recrystallization with ferrous ion reduction or sugar calcination reduction. Calcinating temperature is the key factor affecting the rate and conversion of reduction and above 600 °C, Cr transforms into crystalline, insoluble Cr2O3 in several minutes. The by-product calcium sulfate can be used to make color gypsum, produce gypsum of high-strength after removal of chromium, and make whisker or building gypsum, no risk to pollute the environment. Preliminary study indicates that the new process for manufacturing soda ash from sodium sulfate is reasonable and feasible in technology, which provides a solid basis for the engineering scale. |
| 语种 | 中文 |
| 公开日期 | 2013-09-16 |
| 页码 | 154 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1392]  |
| 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 | 王天贵. 芒硝制纯碱新方法及其工艺研究[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. 2004. |
入库方式： OAI收割
来源：过程工程研究所
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