| Solid biomass can be converted into liquid fuel through fast pyrolysis, which is convenient to be stored and transported with potential to be used as a fossil oil substitute. In China, agricultural wastes are the main biomass materials, whose pyrolysis process has not been researched adequately compared to forestry wastes. The special attention has been given to the yield of the liquid product in prevalent studies on biomass fast pyrolysis. But the quality of bio-oil usually doesn't meet the general request of liquid fuel. Thus the influences of pyrolysis parameters on the characteristics of bio-oil need to be investigated in detail for finding the approaches to improve the quality of bio-oil. In addition, biomass resources, especially agricultural wastes, are usually not continuous in space and time. So in order to achieve the low-cost and large-scale production of bio-oil, the pyrolysis mode of biomass should conform to the raw materials'characteristics. This thesis is dedicated to the exploitation of Chinese biomass resources through fast pyrolysis in a fluidized bed reactor.As the representative forestry wastes and agricultural wastes in China, pine wood sawdust, peanut shell and maize stalk are involved in this study. The pyrolysis characteristics of three types of biomass materials were studied using a thermogravimetric analysis (TGA) and the pyrolysis model was built. Fast pyrolysis experiments were carried out in a bench-scale fluidized-bed reactor. The bio-oil yields of peanut shell and maize stalk are obviously lower than that of pine sawdust. Compared with pine sawdust, the char yields of peanut shell and maize stalk are higher but the heating value of uncondensable gas is lower. This means that the bio-oil cost may be higher for agricultural wastes if taking the conventional pyrolysis technique. And the characteristic and component analysis results of bio-oil reveal that the quality of bio-oil from agricultural wastes, especially maize stalk, is worse than that from pine, which was proved by the combustion characteristics of three kinds of bio-oils on TGA.In order to improve the quality of bio-oil, the influences of operating conditions (temperature, residence time, and biomass particle size) of the fluidized bed reactor on the yield and quality of bio-oil are studied. The temperature is the most important factor, the bio-oil yields of peanut shell and maize stalk are both highest when the temperature is 450°C, while the highest yield is obtained at 500°C for pine sawdust. And the temperature at which the quality of bio-oil is better is not usually consistent with that at which the yield is highest. For example, the bio-oil from maize stalk pyrolysis at 400°C has lowest oxygen and water content, and has highest heating value. The effects of residence time are similar as temperature, in other words, the quality of bio-oil is not usually best when the yield is highest. Although the particle size has no obvious effect on the yield of bio-oil when which is small than 1mm, the quality of bio-oil is obviously influenced by biomass particle size. Therefore, the better quality bio-oil can be gained by choosing proper operating conditions on the base of biomass characteristics.It is an important aspect to improve the quality of bio-oil that how to decrease the water content of bio-oil. To achieve the aim, it is necessary to dry biomass materials for reducing the raw water content. Microwave drying is a rapid, high-effect, and economical method, which was adopted to dry biomass materials for fast pyrolysis in this thesis for the first time. The drying characteristics of biomass materials using microwave oven was investigated and compared with conventional electrical oven drying. The results indicate that the drying rate for microwave oven is more than 5 times fast than that for electrical oven and a better pore structure is formed during the quick evaporation process. The pyrolysis experiments on TGA and the fluidized bed reactor show that the microwave drying pretreatment is advantageous for biomass pyrolysis and the probability of secondary cracking of volatiles is decreased, and as a result, more bio-oil is obtained with microwave drying. Because of secondary pyrolysis being weaken, the heating value of bio-oil from microwave drying biomass is increased with less water content, and more primary pyrolysis products were reserved in bio-oil. A higher heating value and lower water content are beneficial to bio-oil use as a fuel, and more primary pyrolysis products make bio-oil produce high add-value chemical materials.Microwave heating technology was also directly using in biomass pyrolysis process in this thesis. Because the char from biomass pyrolysis absorbs microwave energy, the temperature of char is higher than the environment temperature. Thus, compared with electrical heating, the pyrolysis process can take place at lower temperature. Therefore, lower temperature pyrolysis can be achieved using microwave heating which is a more saving-energy pyrolysis mode.A kind of mobile biomass pyrolysis system was invented, whose energy demand is fully supplied by biomass resources, which is suitable for dealing with the highly distributed and low energy density agricultural wastes. The cost analysis of the immovable pyrolysis plant reveals that the cost of bio-oil will increase significantly with the increase of the raw material price. And limited by the carrying cost of biomass and the restricted capability of one unit, there exist a optimal collecting radius for the immovable pyrolysis plant to achieve the lowest bio-oil cost in a certain condition. While for the mobile pyrolysis mode, the collecting radius has a far smaller effect on the bio-oil cost compared with the immovable mode. This means that the low-cost and large-scale production of bio-oil can be achieved using the mobile biomass pyrolysis equipment. According to the study results in this thesis, a new scheme of the mobile biomass pyrolysis system and a new type fluidized bed reactor were put forward to utilize Chinese abundant biomass resources using pyrolysis technology. The low-cost and high-value of the bio-oil-based product is the ultimate objective.
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