Study On Stability And Fractional Condensation Of Bio-oil

Biomass is a kind of renewable clean energy with tremendous potential for development. Biomass pyrolysis technology can convert biomass to tri-state product: combustible gas, bio-oil and biochar. Among them, the bio-oil can be used for energy and chemical industries. Therefore, the research on physicochemical properties of bio-oils is important. In this study, different components of bio-oil by fractional condensation system was classified and the stability properties of bio-oil were explored by aging test.Rice husk was selected as raw material for pyrolysis. Pyrolysis products is condensed by fractional condensation system, and the fractional condensation system is set to four sections, with the condensing temperature controlled at 100 ~ 150 ?, 50 ~ 90 ?, 0 ? and-20 ?. The yield, pH value, water content and elemental analysis of different components were analyzed in order to determine the enrichment regularity of the moisture, acids and other substances. The effects of condensation temperature change on enrichment regularity of different components were explored through adjusting the condensation temperature of the first section and the second section. It is found that: the oil yields of the second and third section are relatively high, and the first section has a lower yield but enriched more in heavy component. therefore, the oil of the first condensation section has a relatively high calorific value and carbon content, which is more suitable to be used as fuel. The oil of second and third condensation sections are more suitable for other purposes, such as hydrogen reforming.The stability of bio-oil is poor, so the storage and transportation of bio-oil are very difficult, and this shortcoming greatly limits the promotion of the use of bio-oil. In this study, the 70 ~ 120 ? grade-oil and single-grade-oil are used in an aging test. In the aging test the viscosity, pH value, water content of the two oils are tested and the changes of oil component in aging process were explored through the GC-MS analysis. The aging mechanism of the bio-oil was analyzed based on changes of the composition. Results showed that esterification reaction, hydration reaction, polymerization reaction, acetal and ketal reactions occur at the aging process of bio-oil. In addition, the experiment also found that the stability of the grade-oil is better.To further improve the pH and stability of the bio-oil, ethanol and ethyl acetate were used as additives for bio-oil modification. Results showed that ethanol was involved in the reaction of aging process of bio-oil, and it effectively inhibited the aging reactions by reacting with ketones, aldehydes and acids. The ethyl acetate achieved the same goal for improving the stability of bio-oil through dilution and dissolution. In addition, the experiments also demonstrated that the composite additive made by ethanol and ethyl has a better improvement effect than those two single additives.