Studies On Biomass Fast Pyrolysis In Bench-scaled Fluidized Bed With The Quality Analysis Of Bio-oil

Biomass is the only clean renewable energy resource that can be liquefied. Bio-oil made from fast pyrolysis of biomass is convenient for being stored and transported with potential to be used as a fossil oil substitute. However, higher viscosity, higher moisture, higher acidity, lower heating value and heat instability are unbeneficial properties of bio-oil to be used as liquid fuel. Thus in this paper, experimental studies were carried out in a bench-scaled fluidized bed reactor. On the one hand, the influences of the parameters such as raw material characteristics and pyrolysis conditions on the yield and quality of bio-oil were studied, on the other hand, the influences of microwave drying on biomass and its pyrolysis products were investigated. The purpose of these studies was to optimize reaction parameters for improving the bio-oil quality and enlarging the application of bio-oil as liquid fuel.At first, the background of energy all over the world, the bio-energy and the fast pyrolysis technique were introduced. As liquid product, the properties of bio-oil and the difficulties on its application were emphasized.Secondly, the system of the bench-scaled fluidized bed and the choices of trial parameters were described, followed by the description of the experimental process.Thirdly, experimental studies on the influences of raw material and the pyrolysis conditions on the yield and quality of bio-oil were performed, which indicated that the raw material sorts, reaction temperature and vapor residence time were key factors. At the same time, the content of cellulose and lignin as well as the ash in biomass were critical parameters, and the pine was most suitable raw material for bio-oil. For getting high quality pine-oil, the favourable reaction temperature was between 450℃and 550℃. The residence time affected the secondary reaction of the vapor, which was important for the yield and the water content of bio-oil.Finally, compared with heated air drying, the influence of microwave drying on raw material characteristics and the mechanism of biomass fast pyrolysis were studied. It was found that microwave drying rate was far faster, moreover, greater the microwave power level was, faster the dehydration rate was. The biomass dried by microwave had greater surface area and more inner paths, which was benefited for the release of volatiles, meanwhile the secondary reaction of pyrolysis products was suppressed because of the shorter contacting time between vapors and char. As a result, the yields of bio-oil and char increased while the yield of gas decreased. The bio-oil from biomass dried by microwave has lower water content and higher heating value, which was good for used as fuel.