The Study Of Efficient Refining Rice Husk To Produce A Series Of Green Chemicals With Microwave Assisted

China is a rice producing country, rice husk are very rich. However, the research of rice husk utilization tends to be emphasis on one aspect of rice husk utilization, are "fighting each other", and don’t comprehensive utilize rice husk. Therefore, this study intends to use step-by-step extraction method with microwave, give full play to the microwave of high heating speed, high selectivity and easy-to-control features, to conduct the study of efficient refining rice husk to produce a series of green chemicals with microwave-assisted.Firstly, the composition of rice husk and pyrolysis characteristics at different heating rates in synchronous thermal analyzer were studied. It can learn about the process and characteristics of rice husk pyrolysis, predicted the rate and degree of difficulty of reaction through the kinetic analysis, give the reference value in the optimization of process parameters in subsequent microwave pyrolysis.Secondly, pyrolysis rice husk with microwave, collected acetic acid and furfural in stages. Use an appropriate amount of phosphate acid to pretreat rice husk with an appropriate method, its acetyl fractures to generate acetic acid with microwave assisted. Then the pentosan decomposes, dehydrates and cyclizes to generate furfural with the further pyrolysis. The content of acetic acid and furfural is detected by the high performance liquid chromatography (HPLC), according to the conversion rate of acetic acid and furfural under different conditions to determine the best process parameters.Then extract rice husk biochar after microwave pyrolysis with water to separate the trace elements and residual sugars, which can be used for the preparation of high-quality plant nutrition salts and the raw materials of microbial fermentation. Finally, the solid residues obtained after the extraction are mixed with clays and other additives according to an appropriate ratio, then compressed into briquettes of biomass to determine the optimum molding ratio, the combustion performance is investigated by the actual combustion experiment. In the end, get a good kind of biomass briquettes.Through the above process, the various resources in rice husk are made full use, the comprehensive utilization of rice husk forms a complete chain of green technology, not only make full use of rice husk to produce a range of high value-added green chemicals, make the waste into treasure, but also reduce the "three wastes" pollution, can also make part of the raw materials and products to re-return to the natural ecological cycle. It full embodies the characteristics and concept of green chemistry and has tremendous value of research and development.The results and conclusions of this study are following:(1)The main component of rice husk is lignocellulose, the total content is62.07%, wherein the highest content is cellulose, reached to29.10%. Rice husk ash content is also higher, reached to16.97%. At a certain heating rate, the process of rice husk pyrolysis is broadly divided into three stages:the dehydration and warm-up phase, the fast pyrolysis with weight loss phase and the carbonization phase. The second stage is the main stage of the pyrolysis process, the majority of the weight loss of the sample occurs here, and the weight loss rate is high. The higher heating rate can promote rice husk pyrolysis. With the increase of heating rate, the pyrolysis reaction frequency factor and the corresponding activation energy reduced, and the decreasing trend of activation energy reinforced, pyrolysis intensity is gradually increased.(2)The contents of acetic acid and furfural are determined by the high performance liquid chromatography (HPLC), which has the advantages of quick analysis, high selectivity and high sensitivity. The quality of pyrolysis liquid increases with the increase of microwave power, the higher microwave power promotes pyrolysis reaction. The phosphate pretreatment contributes to the formation of acetic acid and furfural. The optimum conditions are:10%phosphoric acid soaked rice husk24h. The first step conditions:microwave power is300W, reaction time is12min, the conversion rate of acetic acid and furfural are0.97%and2.7%respectively; the second step conditions:microwave power is600W, reaction time is12min, the conversion rate of furfural is1.68%.(3)There are a certain amount of P, K, Mg, Ca and other trace elements which can be used as plant nutrient inorganic salts and a certain amount of carbohydrate which can be used as raw material for microbial fermentation in water extraction from rice husk biochar. It is feasible that solid residues mixed with clays and other additives are pressed into the biomass briquettes. The optimum molding ratio:solid residues clays ratio is10:4, and adding a certain percentage desulfurization agent and accelerant. The biomass briquettes have lower sulfur content and add CaO as a desulfurization agent, which can reduce the harm of SO2to environment.The ignition performance of the biomass briquettes is good, the ignition time is short, the sustainable burning time is more than2hours. But there is still a clear gap of the sustainable burning time and the actual calorific value compared with commercially available mineral coal briquettes, and the calorific value of unit mass is not large. In industrial production, the combustion performance of the biomass briquettes will be greatly improved by using molding machine to improve the density of the biomass briquettes. Then the biomass briquettes will be developed into a high-quality fuel that can replace the status of mineral coal in a certain extent. It has an important economic, social and environmental significance.