高铝粉煤灰是我国的特色二次资源，年产生量超过2500万吨，其中氧化铝含量可高达50 %，而我国铝土矿资源极为短缺，研发高铝粉煤灰提取氧化铝技术是国家重大需求。高铝粉煤灰中铝硅比（A/S~1.2）低，硅主要以非晶态二氧化硅和结晶态的莫来石（3Al2O3·2SiO2）存在。铝硅分离是高铝粉煤灰利用的关键，且国内外已有大量研究，但已有研究仍存在高铝粉煤灰中结晶态铝硅组分浓碱体系（亚熔盐介质）分解机理尚不明晰、非晶态二氧化硅稀碱脱除效率不高、铝硅湿法分离硅组分利用价值低等问题。为此，本论文围绕高铝粉煤灰中铝硅高效分离及产品高值化，开展了高铝粉煤灰结晶态铝硅组分（莫来石和刚玉）亚熔盐介质分解规律、粉煤灰协同赤泥亚熔盐溶出研究，创新提出了高铝粉煤灰热化学法铝硅深度分离新方法，并系统进行了相关的工艺优化与应用基础研究。本论文取得如下创新性进展：（1）高铝粉煤灰的主要含铝物相为莫来石和刚玉，研究了粉煤灰中莫来石和刚玉在NaOH亚熔盐介质中的分解规律。结果表明，刚玉较莫来石更难分解，在Na2O浓度370 g/L、初始苛性比25条件下，莫来石在120 oC下就开始分解，而刚玉高于180 oC后才开始分解。莫来石和刚玉的分解过程符合收缩核反应模型，且二者的分解过程均属于化学反应控制，相应表观活化能分别为67.46 kJ/mol和161.82 kJ/mol。研究同时发现，高铝粉煤灰亚熔盐介质氧化铝溶出料浆中脱铝渣的棒状结构使其易于液固分离，以此为基础，研究开发了高铝粉煤灰-赤泥协同溶出提取氧化铝新技术，有效解决了亚熔盐法赤泥溶出浆液的过滤难题，浆液过滤速度增大到1.264 m3/(m2?h)。同时高铝粉煤灰-赤泥协同溶出促进了赤泥原料中Na8(Al6Si6O24)(OH)2.04(H2O)2.66向不含铝物相NaCaHSiO4转化，且抑制了溶出渣中1.2Na2O?0.8CaO?Al2O3?2SiO2?H2O的生成，使赤泥中氧化铝提取率由72.14 %提高至91.70 %。（2）研究了高铝粉煤灰主要物相与氟化铵的反应热力学，发现温度高于74 oC时非晶态二氧化硅与氟化铵反应可自发进行。通过研究高铝粉煤灰与氟化铵低温（120~160 oC）反应过程中的粉煤灰颗粒形貌、物相、价键、化学成分等变化规律，发现氟化铵可与非晶态二氧化硅反应，而不与莫来石、刚玉发生反应，建立了高铝粉煤灰低温热化学法脱除非晶态二氧化硅新方法。考察了原料配比、反应温度、反应时间等工艺参数对非晶态二氧化硅分离效果的影响。在优化工艺条件下，二氧化硅脱除率可达59.38 %，脱硅粉煤灰中铝硅比可提高至3.15。机理研究表明，高铝粉煤灰与氟化铵热化学反应破坏了玻璃相中Q4(0Al)结构和活性较低的Si-O-Al配位结构，使非晶态二氧化硅高度转化为易溶于水的氟硅酸铵，反应产物经水溶处理使氟硅酸铵进入液相，实现非晶态二氧化硅高效脱除。同时脱硅液通过氨化处理得到白炭黑产物和氟化铵，氟化铵介质可循环回用。（3）基于高于165 oC时氟化铵能够分解莫来石的反应特性，提出了高铝粉煤灰中结晶态铝硅高温热化学深度分离新方法。在高温分解过程中，铝组分分解转化为刚玉（α-Al2O3），硅组分转化为氟硅酸铵。考察了不同因素对分离过程的影响，获得了优化工艺条件。在优化条件下，得到二氧化硅含量低于0.2 wt%的固相刚玉产物。同时结合物相及成分分析结果明晰了混合焙烧的化学反应历程，且由氟硅酸铵成功制备得到比表面积达到441.8 m2/g纯度高于99 %的白炭黑产品。;High alumina fly ash (HAFA) is a characteristic secondary resource in China, with an annual output of more than 25 million tons, among which the alumina content can be as high as 50 %. However, China is extremely short of bauxite resources, and the technology development of extraction alumina from HAFA is a major national demand. HAFA has a low mass ratio of alumina to silica (A/S~1.2), and silicon mainly exists in amorphous silica and crystalline mullite (3Al2O3·2SiO2). Alumina-silica separation is the key to the utilization of HAFA and has been extensively studied at home and abroad. But there are some problems such as the unclear decomposition mechanism of crystalline alumina-silica component in concentrated alkali system (sub-molten salt medium), the low removal rate of amorphous silica in HAFA, and the low utilization value of silicon components during the alumina-silica separation of HAFA by wet method. To this end, this thesis focused on the efficient separation of alumina and silica in HAFA. The research of the decomposition rule of crystalline alumina-silica component (mullite and corundum) in sub-molten medium, and the synergistic dissolution of HAFA and red mud in sub-molten salt medium were carried out. Meanwhile, a new method for deep separation of alumina and silica in HAFA by thermochemical method was also proposed, and relevant process optimization and application basic research were carried out systematically. The following results and progresses in this thesis were achieved: (1) The main aluminum-containing phases of HAFA are mullite and corundum, and the decomposition rule of mullite and corundum in NaOH sub-molten medium was investigated. The results showed that corundum is more difficult to decompose than mullite. Under the condition of Na2O concentration of 370 g/L and initial caustic ratio of 25, mullite began to decompose at 120 °C, while corundum began to decompose when the temperature was higher than 180 °C. The decomposition process of mullite and corundum were controlled by chemical reaction, and the corresponding apparent activation energies were 67.46 kJ/mol and 161.82 kJ/mol, respectively. At the same time, it was found that the rod-like structure of the dealuminized slag in the dissolution slurry of HAFA sub-molten salt method made it easy to separate the liquid and solid. Based on this, a new method of HAFA-red mud synergistic dissolution extraction of alumina was proposed, which effectively solved the filtration problem of red mud dissolution slurry of sub-molten salt method, and the slurry filtration speed was increased to 1.264 m3/(m2?h). Meanwhile, the synergistic dissolution of HAFA-red mud promoted the conversion of Na8(Al6Si6O24)(OH)2.04(H2O)2.66 to NaCaHSiO4, and inhibited the formation of 1.2Na2O?0.8CaO?Al2O3?2SiO2?H2O in dissolution slag. Finally, the alumina extraction rate in red mud was increased from 72.14 % to 91.70 %. (2) The reaction thermodynamics of the main phase of HAFA with ammonium fluoride were studied. It was found that the reaction of amorphous silica with ammonium fluoride could be carried out spontaneously when the temperature is higher than 74 oC. By studying the changes of the morphology, phase, valence bond and chemical composition of HAFA particles during the reaction of HAFA with ammonium fluoride at low temperature (120~160 oC), it was found that ammonium fluoride could react with amorphous silica without reacting with mullite and corundum, and a new separation technology of amorphous silica in HAFA by low-temperature ammonium fluoride thermochemical method was established. The effects of different factors (ratio of raw materials, reaction temperature and reaction time) on the desilication rate were investigated. Under the optimized conditions, the removal rate of silica could reach 59.38 %, and the A/S of desilicated HAFA was inceased to 3.15. Mechanistic studies showed that the thermochemical reaction of HAFA and ammonium fluoride destroyed the Q4(0Al) structure and the lower activity Si-O-Al coordination structure in glass phase, which made the amorphous silica highly converted into water-soluble ammonium fluorosilicate. When the reaction product was treated with water, the ammonium fluorosilicate was dissolved into water to achieve the efficient removal of amorphous silica. Meanwhile, the desiliconization liquid was subjected to ammoniation treatment to obtain silica product and ammonium fluoride, and the ammonium fluoride could be recycled.(3) Based on the reaction characteristics of ammonium fluoride capable of decomposing mullite at temperatures above165 oC, a new process for high temperature thermochemical reaction separation of crystalline aluminum silicon in HAFA was proposed. In the pyrolysis process, the aluminum component was decomposed and converted into corundum (α-Al2O3), and the silicon component was converted into the by-product of ammonium fluorosilicate. The effect of factors on the separation process were investigated and the optimized conditions were obtained. Under the optimized conditions, the silica content in solid phase corundum product was less than 0.2 wt%. Meanwhile, the reaction process of thermochemical was clarified by analyzing the results of phase and composition, and the nano silica with specific surface area of 441.8 m2/g and over 99 % purity was successfully prepared from ammonium fluorosilicate. Key words: High-alumina fly ash, Alumina-silica separation, Sub-molten salt, Ammonium fluoride