粉煤灰合成有序介孔纳米材料的CO2辅助沉淀技术及机理研究

Since the large production amount of coal fly ash, the low rate of multipurpose utilization, and the serious environmental pollution in China, it is urgently imperative to study the high-value recycling technology of coal fly ash and clarify its mechanism. For the first time, the candidate proposed an original idea for the recycling of coal fly ash, including (i) the extraction of silicon and aluminum, and (ii) the functional applications of synthesized nano materials. In this work, the fundamental and perspective studies about the co-recycling of silicon and aluminum, and the synthesis of ordered mesoporous nano materials will be carried out as follows: (i) investigate the alkali dissolution method for the extraction of silicon and the limestone sinter method for the extraction of aluminum, clarify the migration and crystalline transformation rule of silicon and aluminum in the chemical reaction processes, and thus achieve the maximum extraction efficiency of both silicon and aluminum; (ii) develop the CO2-assistant precipitation technology and the special reactor, introduce the purified CO2 into the synthesis of ordered mesoporous nano-SiO2 and nano-Al2O3, and further study the purification technique for synthesized nano materials and the recrystallization technology for recycling the by-product (Na2CO3); (iii) investigate the nucleation and aggregation mechanism of primary nano particles, and the formation mechanism of mesopore structure, clarify the H+ release role and the template role of CO2 for the growth of nano particles, and thus directionally adjust and control the specific surface area, pore size and surface hydroxyl group of synthesized nano materials. These series of technologies could not only achieve the high-value recycling of coal fly ash, but also reduce the CO2 emission through the on-site utilization inside the coal-fired power plants; thus, this work would provide the theoretical basis and technical support for the practical application of synthesizing ordered mesoporous nano materials from coal fly ash.

我国粉煤灰产生量大、综合利用率低、环境危害严重，申请人基于粉煤灰高值资源化技术及机理研究的迫切需求，创新性地提出了以协同回收硅铝元素为核心、硅铝产品功能化应用为驱动的粉煤灰资源化理念。拟开展粉煤灰协同回收硅铝元素、合成有序介孔纳米材料的基础性和前瞻性研究：研发碱溶解-石灰石烧结技术逐级、协同回收硅铝元素，阐明硅铝元素在反应体系中的迁移转化规律，协同提高硅铝回收效率；研发CO2辅助沉淀技术及设备，将捕集后CO2原位用于合成有序介孔纳米SiO2或Al2O3材料，并研究纳米材料的纯化技术和回收Na2CO3副产品的重结晶技术；研究纳米原生粒子成核聚集机理及孔隙结构的形成机制，阐明CO2在纳米颗粒形成过程中的释H+作用和模板剂作用，实现对纳米材料比表面积、孔尺寸及表面羟基的定向调控。该系列技术将在燃煤电厂内部实现粉煤灰的高值资源化和CO2的原位减排及利用，并为其产业化应用提供理论支撑。

针对我国燃煤电厂具有粉煤灰产生堆存量大、高值化利用效率低、环境危害严重的问题，提出粉煤灰协同回收硅铝元素、硅铝产品功能化应用的粉煤灰资源化理念。开展粉煤灰协同回收硅铝元素、合成有序介孔纳米材料的基础性和前瞻性研究：研发碱溶解-石灰石烧结技术逐级协同回收硅铝元素、CO2辅助沉淀技术及其孔隙结构的调控技术。项目探究了探究碱溶解技术回收粉煤灰中硅元素过程中的迁移转化机理，通过对于碱溶解过程中反应温度、停留时间、碱灰比、碱液浓度等参数的控制和超声波等强化作用，硅元素回收效率达到54.42%；探究石灰石烧结技术回收脱硅灰中铝元素过程中的晶态转化机理，通过烧结时间和烧结温度的参数的优化，铝元素回收效率达到87.42%。实现对应研究目标。搭建CO2微气泡进样且控温控压反应器，以硅浸出液/铝浸出液作为前驱体采用CO2辅助沉淀合成有序介孔氧化硅和介孔氧化铝，开发了pH调控-纯化-二次沉淀技术同时回收Na2CO3副产品。通过对纳米SiO2形成和团聚过程中硅浓度、CO2流速等参数的调控与优化，阐明了纳米颗粒成核、聚集过程中CO2微气泡的释H+作用和模板剂作用，合成比表面积为190.39-355.45 m2/g，孔尺寸为6.41-15.58 nm和表面羟基2.49-4.04 mmol/g的纳米SiO2介孔产品；通过对石灰石烧结过程中烧结温度和CO2辅助沉淀过程中反应温度的调控与优化和动力学分析，探究铝元素的晶态转化规律和纳米材料形成机制，合成比表面积为166.7-404.3 m2/g，孔尺寸为2.8-15.2 nm的纳米Al2O3材料。在燃煤电厂内部实现了粉煤灰的高值资源化和CO2的原位减排及利用的粉煤灰资源化途径，为粉煤灰乃至大宗硅基工业固废的高值化利用和碳捕集提供可行的技术，进一步提升粉煤灰资源化产品性能及价值，为其产业化应用提供理论支撑。