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Self-cementitious properties of fly ashes from CFBC boilers co-firing coal and high-sulphur petroleum coke 总被引:1,自引:0,他引:1
Self-cementitious properties of fly ash from circulating fluidized bed combustion boiler co-firing coal and high-sulphur petroleum coke (CPFA) were investigated. CPFA was self-cementitious which was affected by its fineness and chemical compositions, especially the contents of SO3 and free lime (f-CaO). Higher contents of SO3 and f-CaO were beneficial to self-cementitious strength; the self-cementitious strength increases with a decrease of its 45 μm sieve residue. The expansive ratio of CPFA hardened paste was high because of generation of ettringite (AFt), which was influenced by its water to binder ratio (W/A), curing style and grinding of the ash. The paste cured in water had the highest expansive ratio, and grinding of CPFA was beneficial to its volume stability. The hydration products of CPFA detected by X-ray diffraction (XRD) and scanning electron microscopy (SEM) were portlandite, gypsum, AFt and hydrated calcium silicate (C-S-H). 相似文献
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The characteristics of deposits from two 100 MWe CFBC boilers firing 100% petroleum coke have been examined using samples over five years. This comprehensive study was done by chemical analysis, X-ray diffraction (XRD) and scanning electron microscopy (SEM) including energy dispersive X-ray (EDX) analysis. 相似文献
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Results of calorimeter tests on Portland cement-silica fume-fly ash mixtures are presented. Data indicate that silica fume accelerates cement hydration at high water/cementitious ratios and retards hydration at low water/cementitious ratios. On the other hand, fly ash retards cement hydration more significantly at high water/cementitious ratios. When silica fume and fly ash are added together with cement, the reactivity of the silica fume is hampered and the hydration of the cementitious system is significantly retarded. 相似文献
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以铝酸盐水泥熟料、硅酸盐水泥熟料和粉煤灰为原料,探讨了掺加少量铝酸盐水泥熟料对硅酸盐水泥及粉煤灰硅酸盐水泥复合体系水化、凝结和硬化性能的影响。结果表明,在硅酸盐水泥及粉煤灰硅酸盐水泥中掺加铝酸盐水泥熟料,可以明显缩短水泥的初、终凝时间,但复合体系的需水量增加;掺加少量铝酸盐水泥熟料(≤3%)可明显提高硅酸盐水泥的早期强度,但后期强度(28d)有所降低;当铝酸盐水泥熟料的掺量达5%时,水泥的各龄期强度均明显降低。少量铝酸盐水泥熟料掺加到粉煤灰硅酸盐水泥中,复合体系的各龄期强度都明显提高,且早期强度的提高幅度较大。 相似文献
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分选与磨细粉煤灰对水泥胶砂性能的影响 总被引:1,自引:0,他引:1
研究了分选与磨细粉煤灰的颗粒分布与形貌的差异及对水泥胶砂性能的影响。研究结果表明:当勃氏比表面积相近,磨细粉煤灰的中位粒径大于分选细粉煤灰,其圆珠状颗粒较少,表面较为粗糙。在相同水胶比的条件下,掺分选粗粉煤灰的水泥胶砂流动度及强度均低;分选粗粉煤灰磨细后,不仅减少了颗粒的粘连,增加了比表面积,而且提高了粉煤灰的反应活性和水泥胶砂流动度及强度,虽其水泥胶砂流动度仍小于掺分选细粉煤灰的水泥,3d水泥胶砂强度也略低,但其28d水泥胶砂强度略高于掺分选细粉煤灰的水泥;在相同水泥胶砂流动度的条件下,掺磨细粉煤灰配制的水泥胶砂3d强度低于掺分选细粉煤灰的水泥,但随着水化龄期的增长,其差距逐步缩小,至60d时可超过后者。 相似文献
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在工业运行的410 t·h-1循环流化床锅炉上进行烟煤、70%烟煤+30%石油焦和50%无烟煤+50%石油焦的燃烧试验,研究了运行参数对SO2排放特性的影响。结果表明,3种燃料均能达到良好的燃烧效果,炉内温度场分布均匀。在相同燃烧条件下,不同燃料SO2排放量与其中的含硫量呈正相关关系。SO2排放量随温度的升高先减小后增大,存在最佳脱硫温度;随钙硫比的增大而减小;随过量空气系数的增大而减小;随飞灰再循环量的增大而减小。对于不同种类的石灰石,大比表面积和高比孔容积的石灰石对SO2有较好的脱除效果。考察了燃用不同燃料的最佳温度、钙硫比和过量空气系数,阐述了飞灰再循环和石灰石微观结构在循环流化床锅炉脱硫中的机理和作用,以期对循环流化床的设计和运行工作提供指导。 相似文献
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粉煤灰中掺入一定量的增活剂,经低温下煅烧,制得的增活粉煤灰达国标规定的一级品要求,28d抗压强度比达92%,水泥中掺入35%的增活粉煤灰,可以生产出42.5R粉煤灰硅酸盐水泥,经济效益和社会效益较好。 相似文献
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The hydration processes in the ternary system fly ash/calcium aluminate cement/calcium sulphate (FA/CAC/C$) at 20 °C were investigated; six compositions from the ternary system FA/CAC/C$ were selected for this study. The nature of the reaction products in these pastes were analysed by X-ray diffraction (XRD) and infrared spectroscopy (FTIR). At four days reaction time, the main hydration reaction product in these pastes was ettringite and the samples with major initial CAC presented minor ettringite but calcium aluminates hydrates. The amount of ettringite developed in the systems has no direct relation with the initial components. 相似文献
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高钙粉煤灰作水泥混合材对安定性的影响 总被引:5,自引:0,他引:5
文章从天然高钙粉煤灰具有f-CaO含量高的特点出发,通过采用正交试验方法进行的试验研究,阐述了利用高钙粉煤灰作为水泥生产混合材料时其f-CaO含量、比表面积和掺入量对水泥安定性的影响。 相似文献
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串联磨技术是近几年发明的比较先进的水泥粉磨技术。在消化吸收串联磨技术的基础上进行工艺改进,利用粉煤灰可以作助磨剂和混合材的两种特性,在生产复合硅酸盐水泥时,将粉煤灰按一定比例分别在一级磨和二级磨中粉磨,使水泥磨产量、出磨水泥质量、粉煤灰掺量都有一定程度的提高。 相似文献
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为了加快煤粉工业锅炉底部粉煤灰的沉降速度和除灰速度,保障锅炉的稳定运行,采用试验的方法研究了粉煤灰特性、粉煤灰燃烧状况和落灰斗结构对粉煤灰沉降速度的影响,重点研究了粉煤灰颗粒的粒径、粉煤灰的燃烧充分性、落灰斗的高度和侧壁倾斜度对沉降速度的影响。结果表明:粒径较小的粉煤灰颗粒沉降速度较慢,粒径小于0.009 mm的粉煤灰颗粒容易造成炉底刮板机内细泥积聚;当煤粉不完全燃烧时,粉煤灰有少部分不溶于水且下降速度慢;粉煤灰的沉降速度随落灰斗侧壁倾斜度的增大和落灰斗高度的减小而减小,因此,设计的落灰斗在空间允许的情况下侧壁倾斜度应为10°以内,并且应该尽量加大落灰斗的垂直高度。 相似文献
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在去年笔者提出的水泥厂发展混凝土掺和料产业的思路基础上,通过试验研究和经济成本分析,进一步探讨了水泥厂以生产、推广使用粉煤灰水泥的模式发展混凝土掺和料产业的技术经济可行性,并在此基础上研制开发了适用于预拌混凝土的专用粉煤灰水泥。 相似文献
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