赤泥铝硅深度分离协同种分母液高效循环基础

The deep separation of aluminum and silicon in the red mud is of great significance to the reduction and the resource utilization of the solid waste from the alumina industry. In order to extract alumina from the bulk typical Bayer red mud, this project will investigate the phase transformation from sodalite/cancrinite to CaNaHSiO4, the reaction and the chemical limit of the Fe’s isomorphous substitution to Al between the various hydrate garnet solids, and the interaction between the above two reactions. And a new method for the desilication from the Sub-molten Salt leached liquor and the synchronous desalination from the Bayer mother liquor is established. Furthermore, this project will mainly study the mechanism and the chemical regulation methods for the deep separation of aluminum and silicon in the red mud, and the mechanism and the regulation methods for the synchronous desilication- desalination. Also, the autocatalysis of the separation of aluminum and silicon and the extraction limit of alumina to the Sub-molten Salt system will be clarified. It is to achieve the efficient recycle of the Sub-molten Salt leaching liquor and the desalination of the Bayer mother liquor under the normal temperature and pressure, through the new technology of the evaporation-crystallization process subsequent from the synchronous desilication- desalination. And the circulation efficiency of the Bayer mother liquor will also be largely increased. This project aims at constructing a new full hydrometallurgical alkali technology for the extraction of alumina, which provides a scientific guidance for the economic and efficient treatment of the China’s bulk characteristic complex resources containing alumina.

赤泥铝硅深度分离对氧化铝工业固体废弃物的减排及资源化利用意义重大。本项目拟以大宗典型拜耳法赤泥的提铝过程为研究对象，考察亚熔盐法铝硅分离过程方钠石/钙霞石物相转变、水化石榴石物相间的铁铝同晶取代及限度，研究两种提铝过程的交互影响，建立亚熔盐溶出液脱硅协同拜耳系统种分母液排盐新方法。重点研究铝硅深度分离机制及其化学场调控方法、同步脱硅-排盐规律及其调控方法，阐明亚熔盐体系铝硅分离自催化现象及提铝反应限度。通过协同脱硅排盐-蒸发-结晶新技术路线，实现亚熔盐溶出介质的高效循环与常温常压下种分母液排盐，并大幅提高种分母液的循环效率。本项目旨在构建全湿碱法氧化铝提取新技术，对经济高效处理我国大宗特色复杂含铝资源具有科学指导意义。

赤泥是氧化铝工业的固体废弃物，目前全国每年排放量约1亿吨，大量赤泥的有效处置与综合利用一直是全世界氧化铝工业的主要难题之一。赤泥铝硅深度分离对赤泥的减排及资源化利用意义重大。项目以我国北方拜耳法氧化铝厂产出的低铁拜耳法赤泥为研究对象，研究了赤泥铝硅深度分离过程。表征了合成脱硅剂及其在高碱铝酸钠溶液脱硅过程的结构与性质变化，提出了低成本、操作温和的高碱脱硅技术。研究了NaOH-Al(OH)3-Na2CO3-H2O体系相平衡，获得了高碱铝酸钠体系中碳酸钠的蒸发结晶动力学以及水合铝酸钠的冷却结晶动力学。通过项目的实施，查明了拜耳法赤泥在亚熔盐介质中的两种提铝过程，即方钠石族化合物向不含铝组分的硅酸氢钠钙物相转变，以及体系有氧化铁存在的条件下发生的水化石榴石物相中铁取代铝的同晶取代反应，阐明了硅酸氢钠钙对水化石榴石同晶取代反应的促进作用，揭示了温度场、石灰组分在拜耳法赤泥铝硅深度分离反应中的作用。对于高分子比、高碱铝酸钠溶液体系结晶析出水合铝酸钠的结晶过程，证实了大颗粒的长大主要由晶体生长过程引起、小颗粒的长大则主要由聚结过程控制。获得了NaOH-Al(OH)3-Na2CO3-H2O体系相平衡数据及物相分区，查明了碳酸钠结晶介稳区和结晶动力学方程；基于全过程物流优化设计，建立了亚熔盐溶出-稀释-停留脱硅-蒸发结晶的新技术路线，实现了高碱、高分子比含硅铝酸钠溶液实际体系的深度脱硅，脱硅过程条件温和，并可与拜耳种分母液混合排盐，可省去拜耳系统强制效蒸发系统，并实现亚熔盐介质的高效循环，协同实现种分母液向高分子比铝酸钠溶出介质的转变，放大试验中亚熔盐循环介质分子比高于32。