【作者】 张晓燕；

【导师】 殷素红；

【作者基本信息】 华南理工大学 ， 材料学， 2013， 硕士

【摘要】 循环流化床(CFB)锅炉燃烧已成为我国大力发展的清洁燃煤发电技术，其脱硫产物循环流化床锅炉固硫灰(以下简称CFB固硫灰)排放量比普通燃煤方式高，且其组成、结构有别于粉煤灰，若按粉煤灰使用可能产生较大危害，故CFB固硫灰作为一种新的大宗工业固体废弃物，其资源化利用成为亟待解决的难题。根据CFB固硫灰含有f-CaO、CaSO4和活性Al2O3等制备氧化钙-硫铝酸钙复合膨胀剂的组分，本论文提出用其制备混凝土膨胀剂，对于实现CFB固硫灰的资源化利用，减少环境污染，具有重要的意义。本论文首先研究了利用CFB固硫灰与煅烧氧化钙、石膏配制混凝土复合膨胀剂，探究膨胀剂中原料性状及含量对膨胀剂性能的影响规律。结果表明，不同温度煅烧的氧化钙、膨胀剂的组成都会对膨胀性能产生显著影响，石膏类型对膨胀性能的影响甚微。1400°C煅烧的氧化钙最适宜配制复合膨胀剂，含量为20%-30%时适宜配制性能满足标准的复合膨胀剂；煅烧氧化钙含量一定时，固硫灰与石膏含量比变化会影响钙矾石的生成量，当膨胀剂组成中nSO3/nAl2O3≈3时能生成最多的钙矾石，膨胀率最大。固硫灰在复合膨胀剂中起到提供膨胀源反应物及部分膨胀源、提高强度尤其是后期强度的作用，同时其较低的碱含量避免了碱骨料反应对结构的破坏。在上述研究基础上分析得出了满足标准要求的膨胀剂配方在煅烧氧化钙-固硫灰-石膏三组分相图中围成的范围，其限制膨胀率可在0.029%-0.129%范围变化。其中30%f-CaO、40%CFB固硫灰、30%CaSO4配制的膨胀剂能达到最大的膨胀率，适宜配制对膨胀性能要求较高的Ⅰ型混凝土膨胀剂，且可在较低的膨胀剂掺量下（6%-8%）达到满足标准要求的膨胀率。论文建立了可用于指导复合膨胀剂组成设计的CFB固硫灰组成、膨胀剂组成与膨胀性能之间的关系模型：理想状态下，7d龄期标准试样中每1mol钙矾石约产生9.06%的限制膨胀率、1mol氢氧化钙约产生1.52%的限制膨胀率。对于组分波动较大的CFB固硫灰可以利用其组成计算膨胀源的生成量进而计算出膨胀率值，同时还可以设计具有特定膨胀率的膨胀剂配方。对于组成一定的膨胀剂，其掺量、抗压强度与膨胀率三者之间的关系可以用方程量化表征，用于指导膨胀剂掺量的设计。论文采用XRD对膨胀产物进行定量分析并结合SEM分析，探讨了复合膨胀剂的作用机理，分析认为钙矾石和氢氧化钙均存在溶解沉淀反应和局部化学反应两种形成途径，膨胀剂中的煅烧氧化钙溶出Ca2+、OH-，CFB固硫灰和石膏溶出SO42-和AlO2-，在孔洞处沉淀析出结晶良好的长杆状钙矾石及结晶完整的氢氧化钙。氢氧化钙边缘及表面析出的针状钙矾石，是溶液中SO42-和AlO2-直接在氢氧化钙晶体表面生成的，符合局部化学反应机理，而这部分氢氧化钙晶体也应是通过局部化学反应生成的。两种形貌的钙矾石共同作用产生较高的膨胀。膨胀剂中氧化钙含量为20%-30%时，钙矾石仍然是复合膨胀剂的主要膨胀源。论文的研究结果既实现了固硫灰高附加值的资源化利用，又为开发一种高性能的混凝土膨胀剂奠定了相应的理论基础。更多还原

【Abstract】 The combustion mode of circulating fluidized bed boiler (CFB) has become a cleancoal-fired power generation technology which is developed rapidly in China. The byproductof this technology, circulating fluidized bed boiler (CFB) desulphurization ash, is more thanthe normal way of burning coal, and the unique composition and structure of this materialmake it different from the common ash. As a new massive emissions industrial solid waste,the CFB desulphurization ash can’t be used in the traditional fields for its detriment to theconcrete structure, and the resource utilization of this waste is the most difficult issue to beresolved. Considering there is a lot of calcined CaO, CaSO4and activated Al2O3in the CFBdesulphurization ash, all of which are the essential components of the calciumoxide-sulphoaluminate composite concrete expansion agent, in this paper, the CFBdesulphurization ash was used to prepare the composite concrete expansion agent, which issignificant for achieving the resource utilization of this kind of waste and reducingenvironment pollution.In this paper, the composite concrete expansion agent was prepared by CFBdesulphurization ash mixing with CaSO4and calcined CaO. The effects of performance of rawmaterials and content on the expansive property of expansion agent were researched. Theresults showed that the calcination temperature of CaO and composition of expansion agenthave great impacts on the expansive property, by contrast, crystalline types of CaSO4hadlittle effect. The CaO calcined under1400°C was most suitable to prepare high-performanceexpansion agent, and the suitable CaO content ranged preferably from20%to30%. Under thecondition of certain content of calcined CaO, mass ratio of CFB desulphurization ash toCaSO4had great effect on ettringite production. The production and the expansion ratioreached to a peak value when the molar ratio of SO3to Al2O3was around3. The CFBdesulphurization ash not only provided part of expansion source and reactant in the expansionagent, but also increased the compressive strength, especially for the long-term strength,meanwhile its low alkali content reduced the chance of alkali aggregate reaction.The paper got the feasible prescription of the composite concrete expansion agent in thephase diagram of the tertiary system of calcined CaO, CFB desulphurization ash and CaSO4 based on above research. Restrained expansion ratio ranges from0.029%to0.129%. Takingexpansion ratio as a determinant index, the optimal formula was30%f-CaO,40%CFBdesulphurization ash, and30%CaSO4. Concrete expansion agent made of this proportion issuited to prepare high-standard TypeⅠconcrete expansion agent, besides it can meet standardrequirement of e the concrete expansion agent with a low dosage(6%-8%).A model about the relation between the expansive property and the composition of CFBdesulphurization ash and expansion agent was built, which could guide the future design ofcomposition of composite concrete expansion agent. The results showed that one moleettringite generation and one mole calcium hydroxide generation would separately produce9.06%and1.52%restrained expansion ratio under ideal conditions. Using this model,expansion ratio could be calculated from the expansive component production, while theexpansive component production could be calculated from the variable composition of theCFB desulphurization ash, meanwhile the formula of the expansion agent with a givenexpansion ratio could be designed by this model. For expansion agent of definitecomposition, the relationship between addition、compressive strength and the expansion ratiocould be characterized quantitatively by some equations which have been worked out in thispaperin order to guide the future design of addition of composite concrete expansion agent.The reaction mechanism of the composite concrete expansion agent was researched byQXRD and the SEM. The results showed that both ettringite and calcium hydroxide formedthrough dissolution-precipitation and topochemical reaction. The Ca2+、OH-ions releasedfrom calcined CaO, and SO42-and AlO2-ions released from CaSO4and CFB desulphurizationash dissolved in the solution. In addition, long rod-shaped ettringite crystals andwell-crystallized calcium hydroxide were deposited and crystallized out in the pore of thecement pastes. Peripheral calcium hydroxide crystallizing formed through topochemicalreaction transformed into needle-shaped ettringite through topochemical reaction in thesolution containing a great deal of SO42-and AlO2-ions. Two patterns of ettringite functionedtogether to generate great expansion. The expansion of composite concrete expansion agentcontaining20%to30%calcined CaO originated majorly from the generation of ettringite.This research not only realized the resource utilization of CFB desulphurization ash withhigh added-value, but also laid the theoretical foundation for developing a new concrete expansion agent with high performance.更多还原