Research On The Hydrothermal Reutilization Process Of Biomass Wastes

With the development of economy and rising demand for energy sources, the shortage of energy sources and environment pollution become more apparent. China is a large agricultural country and has abundant biomass wastes resources, such as plant straw, grain husk, which can provide us with renewable materials. Biomass wastes can create sustainable development opportunities as an alternative energy source to chemical raw materials. Hydrothermal technology is a new and hot technology. Use hydrothermal technology to convert biomass wastes into new resources is of very important significance.In this study, we use tubular reactors and a salt bath stove to research the conversion process of rice husk and wheat bran under hydrothermal conditions and use TOC analyzer, scanning electron microscopy, elemental analysis, HPLC and other equipments to analyze the raw materials and reaction products. Seeing about changes of structures on rice husk and wheat bran before and after hydrothermal reaction and the yield of glucose and lactic acid in liquid, we find that after reaction the wheat bran and rice husk suffered a heavily structural damage. Wheat bran has a more complete degradation than rice husk, and its liquid products, as well as reducing sugar and lactic acid production rate are much higher than rice husk. It's because wheat bran has the relatively more hemicellulose and less cellulose and lignin.The reducing sugar yield of wheat bran and rice husk is analyzed. We inspect the effect of reaction time, reaction temperature, oxidizers and other catalysts on the yield of reducing sugar to select a suitable condition for reducing sugar production. The results show that the reaction temperature, reaction time, oxidizers and various additives all have a big impact on reducing sugar yield. At the conditions of the temperature of 300℃, reaction time of 2 min, and deionized water 3.5mL without any additives, the reducing sugar production rates of rice husk and wheat bran are 26.0% and 37.6% respectively. Yields of reducing sugar increase greatly when add ethanol to the reaction. When the ratio of ethanol to water is 7 to 3, the yields of reducing sugar reach the highest value, rice husk, 47.5% and wheat bran, 63.0 %. The productions of lactic acid of glucose, wheat bran and rice husk under hydrothermal conditions are also researched. We investigate the effect of reaction temperature and reaction time on the production rate of lactic acid, and take further study on the yield of lactic acid when add oxidant additives and metal ions in order to find explore the optimal conditions for lactic acid production. The results show that the optimal temperature is 300℃to produce lactic acid. Addition of oxidant reduces the yield of lactic acid. The effect of metal ions on lactic acid production is very complex. Some make promoting performance while other make hindering performance. Overall, the yield of lactic acid is low at our experimental conditions. The highest yield of glucose is 9.5% (with 400ppm Co²⁺), the highest yield of rice husk is 6.7% (with 400ppm Cr³⁺), and the highest yield of wheat bran is 7.4% (without any catalyst).