高铝粉煤灰非晶相协同活化与深度分解基础研究

High alumina coal fly ash (HAFA), as the primary solid waste, is mainly generated in the north of Shanxi and middle-west of Inner Mongolia. About 50 million tons HAFA is emitted annually, and it consists of >40% Al2O3 and >40% SiO2, which is regarded as an important alternate resource of bauxite. However, due to its low Al/Si mass ratio and inert reactivity of amorphous silicate, HAFA can not be directly applied in the preparation of Al-Si composite and extraction of alumina. In terms of the above problems, the characteristics of mineral phase (crystal and amorphous phases) and atomic coordinate (Al/Fe/Ti/Ca-O-Si) ought to be investigated in detail, and the effects of interface structure between crystal and amorphous phases and atomic coordinate (Al/Fe/Ti/Ca-O-Si) on the reactivity of amorphous Si-O are identified. Based on the results, a novel method “synergistic activation-deep desilication” is provided. During the synergistic activation process, the mechanical/chemical/microwave synergistic activation is adopted to enhance the transition of Al/Fe/Ti/Ca-O-Si coordinate for the elevation of reactivity of amorphous silicate, and the reactivity will be elevated 10 times. During the deep-desilication process, a special capture agent will be designed and selected to avoid the side-reaction of zeolite formation, and the deep decomposition of amorphous silicate will be accomplished. As a result, the desilication ratio will be elevated to 60% approximately which will make the Al/Si mass ratio reach to 3.0, and the content of Al2O3 will be elevated to above 70%, simultaneously, the content of Na2O will be controlled to below 0.5%. This desilicated HAFA, as a raw Al-material, will be provided to alleviate the shortage of bauxite. At the same time, this technology will provide theoretical basis and technical support for the high-value comprehensive utilization of the other Si-rich industrial solid waste.

高铝粉煤灰作为西北大型能源基地的重要固体废弃物，排放量巨大，且铝硅资源丰富，可作为铝土矿的重要替代资源。但由于其原料铝硅比低、非晶相SiO2反应活性差且难分离等问题，增加了铝硅复合材料制备和氧化铝提取等高值化利用过程能耗/物耗。针对上述问题，本研究以粉煤灰的矿相界面结构特征、Al/Fe/Ti/Ca-O-Si原子配位结构特点分析为切入点，通过机械/化学/微波多场多介质协同活化和定向捕捉剂螯合控铝手段，开展非晶相惰性硅氧配位键活化转型、铝硅钠界面副反应调控等基础研究，明确非晶相硅氧键活化与分解之间耦合作用机制，建立粉煤灰非晶相/晶相温和协同活化-副反应调控与深度分离新方法，大幅降低非晶相活化分离过程介质损耗，实现非晶相SiO2高效活化与深度分离，铝硅比有望提高至3.0以上，形成非晶相协同活化–深度分离新工艺，为高铝粉煤灰等其他含硅工业固废高值化利用提供理论基础和技术支撑。

高铝粉煤灰作为西北大型能源基地的典型固废废弃物，年排放量超过5000万吨，因建材化利用途径受限，目前主要以堆存为主，造成了严重的环境污染。针对粉煤灰铝硅比低、杂质高、反应活性低等问题，从原子尺度研究了铁、钙、钛、铝硅配位结构的赋存形态与其反应活性的关联性，结合核磁分析和分子模拟计算，明确了非晶相中铝硅配位结构反应活性Q4（3Al）> Q4（2Al）> Q4（1Al），杂质反应活性Ca>Fe>Ti。基于配位结构活性分析，开发了碱磨活化脱硅和酸磨活化脱硅两套工艺，结合表征和实验结果分析活化机理，表明通过机械化学外场协同活化解离惰性Al-O-Si配位结构，促进氢铝原子置换，产生大量活性硅羟基结构，提高硅氧配位的碱反应活性；同时破坏颗粒包裹结构，产生晶格畸变，增加铝硅酸盐的非晶态程度，提高整体反应活性。进一步开展了活化脱硅过程热力学和动力学研究，热力学分析结果表明沸石的自发的吉普斯自由能△G<0，且远低于硅铝碱溶反应△G；脱硅动力学分析结果表明脱硅过程前期受表面反应控制，后期因沸石自发生成附着于颗粒表面，受固膜扩散控制影响。经过系统的工艺优化，粉煤灰反应活性提高10倍以上，脱硅率近60%，钠含量<0.5%，为粉煤灰资源高值化利用提供优质原料。该技术目前已应用于3000t/年高铝粉煤灰制备莫来石耐火材料和千吨级气化渣制备高模数水玻璃示范装置，支撑煤基固废铝硅分质高值利用技术开发，可拓展应用至其他含硅固废资源化利用技术开发，应用前景广泛。