稻壳灰中二氧化硅的利用

发布时间：2018-07-29 11:55

【摘要】：随着化石资源日趋匮乏和社会对能源需求不断增长，全球能量消耗从2001年的4.04×1017kW增加到2025年的6.40×1017kW，增长58%。因此，寻找一种可再生和可替代的能源资源已经成为必然的趋势。我国是农业大国，生物质产量大、价格低、可再生，仅稻壳年产量就达8000万吨，在国家优惠政策的支持下，利用稻壳发电技术已经在全国推广，为我国秸秆资源利用和缓解电力紧张做出了贡献。但是由于受到收集、运输、价格的影响，很难维持企业经营，同时大量稻壳灰没有利用不仅造成资源浪费，，而且容易引起灰尘飞扬污染环境，因此，稻壳灰的综合利用具有重要的研究价值。本论文以热解副产的稻壳灰为原料，对其中的硅源进行了提取和利用。首先采用碱溶的方法分离稻壳灰中二氧化硅和炭，分离硅酸钠溶液和炭，炭作为制备活性炭原料。详细研究了固液比、溶出时间、溶出温度以及碱浓度对二氧化硅溶出率的影响，确定了最佳反应条件；在固液比为1:8、溶出温度为100oC、溶出时间为2.5h、NaOH的浓度为10wt%的条件下，二氧化硅的溶出率可以达到93.26wt%，模数为0.82。然后以硅酸钠溶液为原料，采用液相结晶法制备含有结晶水的偏硅酸钠晶体。实验研究了固含量、溶液模数、结晶温度及晶种对偏硅酸钠晶体生成的影响，探讨了反应条件对偏硅酸钠所带结晶水个数的影响。实验结果证明，以酸预处理的稻壳灰为原料，碱溶制备的硅酸钠溶液经浓缩，在不同条件下冷却结晶，可以成功地制取不同的偏硅酸钠产品。在温度为35oC，模数在0.5-0.8范围内均能制备五水偏硅酸钠；固含量为45%-55%硅酸钠溶液室温冷却结晶，在晶种存在下，当模数为0.7时，产品为五水偏硅酸钠一等品，当模数为0.8时，产品为六水偏硅酸钠；在120oC下脱水制备出无水偏硅酸钠粉体。本论文还综述了稻壳灰在不同领域中的应用研究进展。稻壳灰最具发展前景的领域是火山灰材料和吸附剂。稻壳燃烧后形成的稻壳灰中含有大量无定形二氧化硅，这使得稻壳灰具有很好的火山灰活性，这不仅可以使制备出的混凝土具有高强度和高性能，还可以降低混凝土的生产成本。而且，稻壳灰中的二氧化硅和碳都具有一定的吸附能力，以稻壳灰为原料可以生产出高于其自身价值数倍的吸附剂。但是稻壳的燃烧条件对得到的稻壳灰的性能影响很大，因此研究如何获得质量稳定并且性能理想的稻壳灰的燃烧条件是现在科研的重点。如果攻克了控温这一难关，实现大规模化生产，一定会为稻壳灰在未来更多领域的发展开辟出崭新的道路。总之，稻壳灰是一种具有高效的、节能的、可持续发展的、有潜在环保价值、社会价值、经济价值的绿色原材料。稻壳灰拥有如此多的优点使其在未来的研究中能够为当地或者更多区域的可持续发展提供新动力。
[Abstract]:With the increasing shortage of fossil resources and the increasing demand for energy, the global energy consumption increased from 4.04 脳 1017kW in 2001 to 6.40 脳 1017kW in 2025, an increase of 58kW. Therefore, the search for renewable and alternative energy resources has become an inevitable trend. China is a large agricultural country with large biomass production, low price and renewable biomass. The annual output of rice husk alone reaches 80 million tons. With the support of the national preferential policies, the technology of using rice husk to generate electricity has been popularized throughout the country. It has contributed to the utilization of straw resources and the alleviation of power tension in China. However, due to the influence of collection, transportation and price, it is very difficult to maintain business operations. At the same time, a large number of rice husk ash is not only a waste of resources, but also easily causes dust to pollute the environment. The comprehensive utilization of rice husk ash has important research value. In this paper, the silicon source of rice husk ash produced by pyrolysis was extracted and utilized. At first, silica and carbon were separated from rice husk ash by alkali solution, then sodium silicate solution and carbon were separated. Carbon was used as raw material of activated carbon. The effects of solid / liquid ratio, dissolution time, dissolution temperature and alkali concentration on the dissolution rate of silica were studied in detail, and the optimum reaction conditions were determined under the conditions of solid / liquid ratio of 1: 8, dissolution temperature of 100oC, dissolution time of 2.5 h / NaOH concentration of 10 wt%. The dissolution rate of silica can reach 93.26 wtand the modulus is 0.82. Then sodium metasilicate crystal containing crystalline water was prepared by liquid phase crystallization method using sodium silicate solution as raw material. The effects of solid content, solution modulus, crystallization temperature and seed on the crystal formation of sodium metasilicate were studied experimentally, and the effects of reaction conditions on the number of crystal water brought by sodium metasilicate were discussed. The experimental results show that different sodium metasilicate products can be successfully prepared from rice husk ash pretreated with acid by concentrated sodium silicate solution prepared by alkali solution and cooled and crystallized under different conditions. Sodium metasilicate pentahydrate can be prepared in the temperature range of 35oC, the modulus is 0.5-0.8, and the solid content is 45-55% sodium silicate solution cooled at room temperature. In the presence of seed, when the modulus is 0.7, the product is the first grade sodium metasilicate pentahydrate, and when the modulus is 0.8, The product was sodium metasilicate hexahydrate, and anhydrous sodium metasilicate powder was prepared by dehydration under 120oC. This paper also reviewed the application of rice husk ash in different fields. The most promising areas of rice husk ash are pozzolanic materials and adsorbents. The rice husk ash formed after burning contains a large amount of amorphous silica, which makes the rice husk ash have good pozzolanic activity, which can not only make the prepared concrete have high strength and high performance. It can also reduce the production cost of concrete. Moreover, silica and carbon in rice husk ash can be adsorbed to a certain extent, and the adsorbent which is several times higher than its own value can be produced by using rice husk ash as raw material. But the burning condition of rice husk has a great influence on the performance of rice husk ash, so it is the focus of scientific research to study how to obtain the burning condition of rice husk ash with stable quality and ideal performance. If we overcome the difficulty of temperature control and realize large-scale production, it will open a new way for the development of rice husk ash in more fields in the future. In a word, rice husk ash is a kind of green raw material with high efficiency, energy saving, sustainable development, potential environmental protection value, social value and economic value. Rice husk ash has so many advantages that it can provide new impetus for local or more regional sustainable development in future research.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ127.2

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