Rice husk is a by-product of rice processing. According to statistics, there are more than 56million tons rice husks in our country. Rice husk is not very hygroscopic because it contains amount of lignin and silica, which lead to it hardly d
Research on the Comprehensive Utilization of Rice Husk
Rice husk is a by-product of rice processing. According to statistics, there are more than 56million tons rice husks in our country. Rice husk is not very hygroscopic because it contains amount of lignin and silica, which lead to it hardly decay in fields. More and more rice husks packed and turned into wastes which were hardly to deal with. They were not only environmental pollutions but also easily to cause fire. All over the world have devoted to the comprehensive utilization of rice husk and gained statisfied effect. Rice husk power generation is not only helpful to solve pollution problems but also to the development of energy. Activated caobon and silica white could be obtained from rice husk ash and it is favorable to the development of our national economy. In this article, the preparation, characterization of high specific surface area activated carbon and nano-silica white were studied systematically. The obtained nano-silica white was modified by hexadecanol and became more affinitive to organic polymer materials. The nono-silica could be turned to tridymite by chemical process using solvent-thermal method at low temperature. Finally, according to the composition of rice husk, the rice husks were hydrolyzed step by step. Xylose, HBS lignin, glucose and nano-silica could be obtained by this method. This method developed a new way for the comprehensive utilization of rice husk.Taking rice husk as raw material and separating carbon and silica by treating rice husk ash with alkali liquor, the residue were activated by phosphoric acid and sodium hydroxide respectively, activated carbon with different properties were prepared. When phosphoric acid was used as the activated reagent, the best process condition is at 500oC, the specific surface area of activated carbon is about 1200m2/g, and the iodine number is about 850mg/g. By altering dose of activating agent, activating temperature, time and various activating process conditions, effective control of porous carbon’s specific surface area and pore distribution will be achieved, which paves the way for further development and utilization of rice husk ash. We also used sodium hydroxide as the activated reagent, By altering dose of activating agent, activating temperature, time and various activating process conditions, different properties activated carbon were obtained, the best process conditions is at 800oC, and according to the result of our experiments, a more reasonable mechanism of alkali activation.Taking rice husk ash as raw material and water glass is obtained by treating rice husk ash with alkali liquor. Firstly, amount of CO2 were pumped in water glass to formed microcrystalline seed at 80 oC water bath, and then sulfate were dropped into to form precipitation. Using improved chemical precipitation method, it could successfully prepare nano- silica particles in about 20-30nm diameter and each index could reach to national standard requirement. This simple and economic method has widened rice husk ash’s application range. Every factor should be considered in order to utilize biomass resources comprehensively. So a new route was designed for the treating of waste water in the silica white preparing process. The calcium sulfate dihydrate was obtained using the waster water and calcium chloride solution as the reagent. The calcium sulfate dihydrate was put into at autoclaves at 130oC, and the calcium sulfate whisker was obtained. This method solved the problems of waste water drainage, and prepared CaSO4 whisker which had higher application value. The whole process is cyclic and had any waste water drainage. this is a breakthrough in the biomss comprehensive utilization.The silica white obtained from rice husk ash were hydrophilic, so the silica white had bad compatibility with organic compounds when it was used in organic compounds. In this article, a new modified method was used to get hydrophobic surface. Debasing reaction was carried out at lower temperature in a mild system to modify silica that is obtained from rice husk ash by hexadecanol in situ and to prepare superhydrophobic silica particles. Surface wettability in inorgic materials can also be controlled by alkyl’s length. This simple experimental method can be further extended to other inorganic material’s surface modification. In order to study the mechanism of this modification, every reaction condition was studied systematically and a reasonable mechanism was proposed. This method is simple convenient and were very meaningful for other inorganica materials’surface modification.Usually, amorphous silica needs high temperature to change to tridymite or quartz. In this article, amorphous silica was treated in glycol at 196oC and it turned to tridymite by this chemical process. In order to study the mechanism of this phase transition, every reaction condition was studied systematically and a reasonable mechanism was proposed. Firstly, the amorphous silica went through a reversible process, and then the crystal seed formed as the pentacoordinate silica hydrolyzed. Secondly, when sufficient energy was supported, the crystal seed began growing and finally tridymite formed. This method is simple convenient and were very meaningful for other oxides’phase transition.The components of the rice hull were extracted and hydrolyzed in steps according to their characteristics. Firstly, the hemicellulose was hydrolyzed in dilute acid with refluxing under atmospheric pressure. High yield of xylose solution was obtained. Then the residue was cooked by 80 % of glycol under pressure. After 4 h of cooking at 200 oC, high boiling solvent lignin (HBSL) was extracted. The residue after HBSL extraction was subject to the third-step-hydrolysis in sulfuric acid (2mol/L). 90 % of cellulose was hydrolyzed after 6 h of pressure reaction at 130 oC. Glucose solution, the feedstock for fuel ethanol production, was obtained. Lastly, the final residue was calcined at 800 oC to produce nano-size silicon dioxide. The particle size was 30-90 nm, and the whiteness reached to 99%. The advantages of this study were as follow. By hydrolyzing the hemicellulose and lignin firstly, the fixation effect of lignin on the cellulose was eliminated, and the crystalline of the cellulose was destroyed. As a result, 90-100% of cellulose could be hydrolyzed. Additionally, by using the components of rice hull, such as hemicellulose, lignin and silicon, to produce furfural, surfactants and silicon dioxide, more than 90% of rice hull could be utilized.In conclusion, a new method was proposed for the comprehensive utilization of bio-resources like rice hull. Many good achievements with important social and economic significance were obtained.