| Nowadays, along with fossile resource is scarce and the social demand forenergy is increasing. The total world energy consumption is expected to expand by58%between2001and2025, from404quadrillion kW in2001to640quadrillion kWin2025. Thus，Looking for a kind of renewable and alternative energy resources hasbecome an inevitable trend.Our country is an agricultural country, biomass is largeoutput, low price and renewable, only rice husk annual output could reach80milliontons. With the support of national preferential policies, rice husk is used as materialfor power generation technology has been promoted all over the country, which hasmade a great contribution for the straw resource utilization and relieved the strain onthe power for our country. But due to the influence of the collection, transportationand price, it is difficult to maintain business. At the same time, a large number ofunused rice husk ash (RHA) not only caused the waste of resources, but also gave riseto the environmental pollution and dusty in the sky. As a result, it has an importantvalue to research the comprehensive utilization for RHA.In this thesis we use RHA which is the by-products produced by pyrolysis as rawmaterials, and then extracting and utilizing the silicon source.Firstly, we prepared the liquid of silicon dioxide by alkali dissolving methodwith RHA as raw material and evaluated the influence of solid-to-liquid ratio,dissolution time, dissolution temperature and the concentration of alkali ondissolution rate of silicon dioxide. The optimum reaction conditions weresolid-to-liquid ratio=1:8, dissolution temperature=100oC, dissolution time=2.5h, theconcentration of alkali=10wt%. Under this condition, the dissolution rate of silicondioxide was up to93.26%, and the modulus of liquid was0.81. In order to furtherevidence the main material in the obtained filtrate was silicon dioxide, we hadcharacterized it by XRD and FT-IR. And the rest of solid residue could be used forpreparing activated carbon.Then we prepared sodium metasilicate crystal by solvent spun crystalline. We discussed the influence of solid content, modulus, temperature, time and seed crystalon sodium metasilicate crystal and the number of crystal water. The result showed thatRHA after acid pretreatment could prepare Na2SiO3·5H2O successfully at a widerange of reaction conditions, especially when modulus was0.5-0.8at35oC. If solidcontent was45%-55%modulus was0.7, adding seed crystal and cooling at roomtemperature, we could obtain first grade of Na2SiO3·5H2O. When modulus was0.8,Na2SiO3·8H2O was prepared, and adding seed crystal, Na2SiO3·6H2O could beobtained.And at120oC, we can prepare qualified products of Na2SiO3.This thesis also summarizes the recent advances in the comprehensiveapplication of RHA in different areas. It is considered that the most promising areas ofRHA are as pozzolana material and as an adsorbent. After combustion, the presence ofplenty of amorphous SiO2endows RHA with perfect pozzolana activity. It isbeneficial to the development of concrete in the direction of higher strength as well asbetter performance and reduces the cost of manufacture. What is more, SiO2and C inthe RHA both own adsorption capacity. The adsorbent which was produced by RHAas the raw material possesses several times value beyond RHA s own value. But theperformance of RHA was very sensitive to combustion conditions on rice husk, it isimperative to study on how to obtain ideal performance and stable quality of RHA. Ifbreaking down a barrier of controlling temperature and realizing the large-scaleindustrial production, it will open up a new path for the application of the RHA.In summary, RHA is an environmental-friendly power with low-energy,high-efficient, green and potential economic benefits, social benefits andenvironmental benefits. Multiple benefits of RHA can be achieved by future criticalresearch efforts to provide new impetus for the local and regional sustainabledevelopment. |
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