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| Abstract: |
| Rice husk is an organic silicon source for amorphous nano-silica particles. This paper reports the experimental study on the industrial production of nano-silica by rice husk combustion in a specially-designed 0.7 MW double-circulating fluidized bed (DCFB) based on acid pretreatment process. The physicochemical properties of RHA were characterized by various testing instruments. Results showed that acid pretreatment removed a large amount of metal impurities in the rice husk and thus inhibited the formation of crystalline silica or the agglomeration during the fluidized bed combustion process. The combustion efficiencies were as high as 99.5%. The obtained RHA comprised white fine particles and exhibited an amorphous structure, but factors such as collection point and acid type had certain influences on the quality of RHA. The highest SiO2 purity was greater than 98.6 wt.%, the lowest content of unburned carbon was 0.2 wt.%, the specific surface area reached 178 m2/g, and the pore size reached 5 nm. The circulating fluidized bed combustion of rice husk based on acid pretreatment can prepare nano-silica while providing heat for industrial processes, which is a highly energy-rich process. |
| Key words: rice husk double-circulating fluidized bed acid pretreatment nano-silica rice husk ash |
| DOI：10.11916/j.issn.1005-9113.18131 |
| Clc Number:TK6 |
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| Descriptions in Chinese: |
| 酸预处理稻壳在0.7 MW双循环流化床中燃烧制备纳米SiO2的中试实验 陈佩，别如山 （哈尔滨工业大学 能源科学与工程学院，哈尔滨 150001） 创新点说明：提出一种将稻壳预处理和双循环流化床燃烧相结合连续制备纳米SiO2的新方法，以该方法在稻壳大规模生产纳米SiO2方面取得了突破性进展，同时也解决了流化床中稻壳燃烧出现的结渣和团聚问题。 研究目的： 将酸预处理后的稻壳在双循环流化床锅炉中燃烧，达到大规模连续制备纳米SiO2的目的，在此基础上也解决了稻壳在流化床中燃烧的粘结团聚问题。 研究方法： 首先采用酸对稻壳进行预处理，提前除去稻壳中阻碍稻壳燃烧的碱金属等，而后将酸预处理后的稻壳在特定设计的0.7 MW的双循环流化床（DCFB）中进行燃烧试验。 1) 通过流化床的运行温度情况、燃烧效率以及烟气排放等方面研究预处理后稻壳在流化床中的实际燃烧情况； 2) 采用SEM扫描电镜、TEM透射电镜、X射线荧光光谱仪和比表面积及孔径分析仪等手段对稻壳在DCFB中不同工况燃烧后不同位置所得稻壳灰进行表征； 3) 对比了本实验所得稻壳灰与其它条件所得稻壳灰的理化性能。 研究结果： 实验结果表明，酸预处理除去了稻壳中大量的金属杂质尤其K，抑制了结晶二氧化硅的形成，因此稻壳在0.7 MW双循环流化床中燃烧状况良好，并未出现粘结团聚问题，并且燃烧效率高达99.5%；燃烧后所得的稻壳灰均为白色颗粒，呈无定形结构，SiO2纯度最高可达98.6wt.%以上，残炭含量最低至0.2wt.%以下，比表面积最高为178m2/g，平均孔径为5-6 nm；与其它条件下所得稻壳灰的性能进行对比后发现，在大规模循环流化床中所得稻壳灰的性能处于优良水平。 结论： 酸预处理提前除去稻壳中的碱金属杂质，不仅解决了稻壳在流化床中的燃烧问题，还大幅提高了稻壳灰的质量。相比于实验室电加热炉中纳米二氧化硅的制备，稻壳酸预处理结合循环流化床燃烧的方法即可大规模连续制备纳米二氧化硅，同时也为工业过程提供热量，这是一种高能量富集的过程。 关键词：稻壳，循环流化床燃烧，预处理，纳米SiO2，稻壳灰 |
