| 题名 | 铝酸钠溶液分解过程晶体附聚调控研究 |
| 作者 | 徐荣广 |
| 学位类别 | 硕士 |
| 答辩日期 | 2012-05-24 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 王志 |
| 关键词 | 铝酸钠溶液 铝氧水合物 附聚 砂状化 超细化 |
| 其他题名 | Agglomeration Adjustment of Crystal Precipitation from Sodium Aluminate Solutions |
| 学位专业 | 化学工程 |
| 中文摘要 | 不管是制备砂状氧化铝还是超细氢氧化铝，必须严格调控产物粒度。由于晶体附聚对产物粒度的贡献远大于晶体生长，因此，要实现新型一水软铝石和传统三水铝石产品的砂状化或纳微化，以获得合适粒度的产物，必须调控晶体附聚。本文研究了影响铝酸钠溶液分解过程晶体附聚的关键影响因素及调控机制，重点解析了游离碱、碳酸钠、二氧化硅及有机添加剂对分解过程晶体附聚的作用规律。 (1)基于铝酸钠溶液分解过程中结合碱与游离碱的作用差异，研究了游离碱对晶体生长和附聚的影响。结果表明，游离碱对晶体附聚抑制作用随其浓度增大而增强，由于晶体表面活性位点容易受到游离碱侵蚀，导致这些起粘结作用的物质减少，从而晶体附聚受到抑制；当温度、游离碱浓度、晶粒活性和转速提高时，晶体溶解速率加快，导致晶体附聚受到的抑制作用越强；基于溶解-结晶模型，获得了AlOOH和Al(OH)3在游离碱液中溶解速率与游离碱浓度和晶体表面积的数学关系：Dm∝At1.5且Dm∝CFC。 (2)基于有机添加剂对溶液结晶过程液-固界面性质调控作用，研究了有机添加剂对铝酸钠溶液结晶和附聚的影响规律。葡萄糖和葡萄糖酸钠可完全抑制铝酸钠溶液的分解，可作为控制反应进度的调整剂；阴离子表面活性剂抑制铝酸钠溶液分解及晶体附聚，可促进产物颗粒纳微化；聚乙二醇类非离子表面活性剂可促进铝酸钠溶液分解及晶体附聚，有助于产物颗粒砂状化，当PEG1000添加量为1 g/L时分解率最高(32.39%)，添加量为5 g/L时附聚度最大(275)；温度越低分解率越高，但温度过低或过高不利于晶体附聚，75~85℃时晶体附聚效果较好，有利于获得砂状铝氧水合物。 (3)由于分解过程主副产物界面性质随分解深度变化而改变，研究了碳分过程伴生副产物碳酸钠对晶体附聚的影响。结果表明，晶种分解过程中主体铝酸根离子缓慢变化时，碳酸钠抑制溶液分解及晶体附聚；NaAlO2-AlCl3反应过程中主体铝酸根离子快速变化时，碳酸钠显著抑制晶体附聚，但随着溶液离子强度增大，抑制作用反而下降；依据铝酸根离子缓慢变化以及快速变化过程中碳酸钠对晶体附聚的影响规律，综合分析认为，碳分过程副产物碳酸钠将会抑制晶体附聚，从而导致产物粒度细化。 (4)铝酸钠溶液中二氧化硅含量直接影响着分解过程与产品质量。铝酸钠溶液耦合分解制备一水软铝石过程中，溶液硅量指数越高，产物中二氧化硅含量越低；晶种活性及二氧化硅含量越高，产物中二氧化硅含量也越大；在高硅量指数范围内(A/S：600~800)，二氧化硅的增加抑制了晶体附聚。 |
| 英文摘要 | Particle size of products must be adjusted and controlled, no matter sandy boehmite or superfine aluminum hydroxide was obtained. Since the influence of crystal growth on particle size is less than that of crystal agglomeration, therefore, crystal agglomeration should be adjusted and controlled to obtain sandy or ultrafine boehmite and aluminum hydroxide with desirable size. Important parameters and adjustment mechanism for agglomeration of crystal precipitation from sodium aluminate solutions were studied, and researches focused on effects of free alkali, sodium carbonate, silicon dioxide and organic additives on crystal agglomeration. (1) Based on the differences in effects of free and combined alkali on precipitation from sodium aluminate solutions, the effects of free alkali on crystal growth and agglomeration were investigated. Results showed that agglomeration was inhibited by free alkali, and the inhibitory effect became stronger with increasing the concentration of free alkali (CFC); crystal that freshly formed in sodium aluminate solution can make small particles agglomerate as binder, and was eroded by free alkali, so agglomeration of crystal was inhibited. Crystal continuously dissolved due to erosion of free alkali, and higher temperature, higher CFC, higher rotating speed, and crystal particle with higher activity favored erosion of crystal. Based on dissolution-crystallization model and experimental data, the orders of erosion rate with respect to CFC and crystal surface were estimated to be 1 and 1.5, respectively. (2) Based on the effect of additives on solid-liquid interfaces in crystallization process, effects of organic additives on crystallization and crystal agglomeration in sodium aluminate solutions were studied. Results showed that precipitation of sodium aluminate solutions was totally inhibited by glucose and sodium D-gluconate. Precipitation from sodium aluminate solutions and crystal agglomeration was inhibited by anionic surfactant, making product ultrafine. Precipitation ratio and product size was promoted by PEG nonionic surfactant, which would make product sandy; maximum precipitation ratio (32.39%) was obtained at PEG concentration of 1 g/L, while maximum agglomeration degree (275) was obtained at PEG concentration of 5 g/L. Lower temperature favored precipitation, but too low or too high temperature inhibited crystal agglomeration, and crystal agglomeration was enhanced at 75~85℃, which is helpful for obtaining sandy alumina hydrate. (3) Considering the interfacial properties of main product and by-product changed with decomposition depth, the effect of associated by-product of sodium carbonate during carbonation process on crystal agglomeration was investigated. The results showed that sodium carbonate inhibited precipitation of sodium aluminate solutions and crystal agglomeration during seeded precipitation process, in which the main aluminae ions changed slowly; crystal agglomeration was inhibited strongly in the reaction between NaAlO2-AlCl3, in which the main aluminate ions changed rapidly, however, the inhibiting effect decreased with ionic strength increasing. It can be inferred that crystal agglomeration was inhibited greatly by sodium carbonate formed in carbonization process, which made product ultrafine. (4) Silicon dioxide in sodium aluminate solutions directly affected precipitation process and product quality. During the process of coupling precipitation boehmite from sodium aluminate solutions, the higher silicon index of solution, the lower content of silicon dioxide in the product, which is similar to the result of conventional aluminum hydroxide. The content and properties of silicon dioxide in seed affected content of silicon dioxide in the product. Within high silicon index(A/S：600~800), agglomeration of boehmite and gibbsite was inhibited with a little increase of content of silicon dioxide. |
| 语种 | 中文 |
| 公开日期 | 2013-09-25 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1832]  |
| 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 | 徐荣广. 铝酸钠溶液分解过程晶体附聚调控研究[D]. 中国科学院研究生院. 2012. |
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