循环流化床锅炉固硫灰制备混凝土膨胀剂的材料组成设计及性能研究

发布时间：2018-01-18 03:13

本文关键词：循环流化床锅炉固硫灰制备混凝土膨胀剂的材料组成设计及性能研究　出处：《华南理工大学》2013年硕士论文　论文类型：学位论文

【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。
[Abstract]:Circulating fluidized bed (CFB) boiler combustion has become clean coal-fired power generation technology vigorously developing in our country, the sulfur ash desulfurization of circulating fluidized bed boiler (hereinafter referred to as CFB fbcf) emissions than ordinary coal high, and its composition and structure are different from fly ash by using fly ash, may have a greater harm therefore, sulfur ash CFB as one of the largest industrial solid wastes new, is an urgent problem to use its resources. According to the sulfur ash CFB containing f-CaO, CaSO4 and Al2O3 activity in preparation of calcium oxide - calcium sulphoaluminate composite expansive agent component, this paper used the preparation of concrete expansive agent system for the utilization of sulfur dust CFB, reduce environmental pollution, has important significance.
This paper studied the use of CFB sulfur ash and calcined calcium oxide, gypsum concrete composite expansive agent, explore the expansive agent content on properties of material and the influence of expansive agent performance. The results show that the calcium oxide calcined at different temperature, the expansive agent group in Chengdu will have a significant impact on the expansion properties of gypsum type little.1400 ~ C of calcium oxide calcined affect the expansion performance of the most suitable for the preparation of compound expansion agent, suitable content of 20%-30% composite expansion admixture performance to meet the standards; when the content of calcined calcium oxide, sulfur ash and gypsum content ratio changes will affect the formation of ettringite, when the expansion agent in nSO3/nAl2O3 about 3 can generate ettringite most, the largest expansion rate. Sulfur ash in composite expansion to provide expansion source of reactants and partial expansion agent to increase the strength of the source, especially the late strength, at the same time The lower alkali content avoids the destruction of the structure by the alkali aggregate reaction.
Based on the research on the analysis of the composition in meet the expanding range of sulfur ash calcined calcium oxide - gypsum three component phase diagram formed by the requirements of the standard, the rate of expansion can be changed in the range of 0.029%-0.129%. The 30%f-CaO, 40%CFB fbcf, 30%CaSO4 compound expansion agent can achieve the largest expansion rate the type, suitable for the preparation of high performance concrete expansive expansive agent, and can be expansionagentmixing lower (6%-8%) to meet the expansion rate of the standard.
Established in this paper can be used to guide the design of the CFB composite expansive agent composed of sulfur ash, expansive agent and expansion of the relationship between the performance model: ideally, 7d age standard samples per 1mol of ettringite produces about 9.06% limited expansion ratio, 1mol calcium hydroxide produces about 1.52% limited expansion ratio. For the component the fluctuation of CFB fbcf can use its composition and then calculate the expansion rate of value generation expansion sources, also can be designed with specific expansion rate of expansion agent. For expansive agent content, the relationship between compressive strength and expansion rate of the three can be used to quantify the equation. Used to guide the design of expansive agent content.
This thesis adopts XRD to quantitatively analyze the expansion of products and combined with the SEM analysis, discusses the mechanism of compound expansion agent, analyzed that the dissolution precipitation reaction and local chemical reaction of two kinds of ways of forming are ettringite and calcium hydroxide, calcium oxide in the calcining expansion agent dissolved Ca2 +, OH-, SO42- and AlO2- CFB soluble solid sulfur ash and gypsum, calcium hydroxide precipitation crystallization good rod-shaped ettringite crystallization and complete in the hole. The needle shaped ettringite edge and surface precipitation of calcium hydroxide, in the solution of SO42- and AlO2- on the surface of calcium hydroxide crystals generated directly, in line with the local chemical reaction mechanism, which is generated by calcium hydroxide crystals should also be local chemical reaction. Common two kinds of morphology of ettringite expansion. The expansion of high content of calcium oxide agent 20%-30%, ettringite is still the main compound expansion agent Expansion source.
The research results not only achieve the resource utilization of sulfur fixing ash and high added value, but also lay a theoretical foundation for developing a high-performance expansive agent for concrete.

【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU528.042.4

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