| Biomass pyrolysis is one of the cutting-edge technologies for the research of bio-energy in the world. Fluidised-bed fast pyrolysis technology has advantages such as high heat transfer rate, uniform bed temperature, short residence time to inhibit second cracking, etc. so has been widely used in the biomass pyrolysis research to obtain high bio-oil yield. Fluidised-bed fast pyrolysis technology can convert biomass into high quality liquid fuel (bio-oil) using continual feeding. Mallee biomass is grown in Australia to combat the existing salinity problem in the Western Australian wheat belt, due to its performance in fast growing, high yield and drought tolerance.In the past research on biomass pyrolysis, a lot of work has been done in maximizing bio-oil yield. However, considering the final use and its request for the oil quality, pyrolysis products distribution, property and chemical composition of bio-oil have been intensively studied in this thesis. For practical production facility, the entire tree (including woody trunk and leaves) will be delivered in the reactor to produce biofuels. Understanding the pyrolysis behaviour of woody trunk and leaves would thus be an important aspect of the biofuel technology development. Based on above described necessarity, the effects of pyrolysis parameters (temperature, particle size of biomass, the removal of AAEM) on mallee woody trunk and leaves pyrolysis products yield and bio-oil composition have been systematically studied. The main research work and conclusions are listed as following:1. This paper presents an investigation of the effect of temperature on yield of pyrolysis products and bio-oil property through characterization method of thermogravimetric analysis, scanning electron microscope, viscosity analysis, elemental analysis, water content analysis and heating value analysis. The research results show that the yields of pyrolysis products were significantly influenced by the pyrolysis temperature. The maximum yield of bio-oil and minimum content of water in bio-oil were achieved at the same pyrolysis temperature range (450-475℃). It was shown that the conditions for maximizing bio-oil yield also led to the formation of the largest amounts of small lignin-derived oligomers as a part of bio-oil, resulting in a bio-oil with the highest viscosity and highest heating value. The increases in oil yield with increasing temperature from350to500℃were mainly due to the increases in the production of lignin-derived oligomers insoluble in water but soluble in CH2C12.2. The effect of particle size on yield of pyrolysis products and bio-oil propoty was studied in a fluidized-bed reactor, and the bio-oil was analyzed by technologies/method of thermogravimetric analysis, UV-fluorescence spectroscopy, viscosity analysis, water content analysis and cold water precipitation analysis. The research results show that the yield of bio-oil decreased as the average biomass particle size was increased from0.3to about1.5mm. Further increases in biomass particle size failed result in any further decreases in the pyrolysis products yield. The viscosity of bio-oil decrease with increasing particle size as well, which paralled the changing trend of bio-oil yield. The increase of water content in bio-oil and and the decrease of the content lignin derived oligmor with increasing particle size could explain the changing trend of bio-oil viscosity. It can be learned from the TGA analysis of the bio-oil that the biomass with larger particle size could result in higer yield of light components in bio-oil.3. The effects of inorganic species in biomass, especially the alkali and alkaline earth metallic (AAEM) species (K, Na, Mg and Ca) on the yield and property of bio-oil from the pyrolysis of biomass was investiated. The bio-oil was characterized by thermogravimetric analysis, UV-fluorescence spectroscopy, viscosity analysis, water content analysis and cold water precipitation analysis. The research results show that AAEM species exist in the wood in two different forms:water-soluble and water-insoluble but acid-soluble. The removal of AAEM species did not result in significant changes in the yields of bio-oil and bio-char. However, the bio-oil properties, e.g.viscosity, were drastically affected by the removal of AAEM species. The water-soluble AAEM species were not as important as the waterinsoluble but acid-soluble AAEM species in influencing the bio-oil composition and properties. It is believed that the acid-soluble AAEM species (especially Ca) were more closely linked with the organic matter in biomass and thus were closely involved in the reactions during pyrolysis. The removal of AAEM species, especially the acid-soluble AAEM species, led to very significant increases in the yields of sugars and lignin-derived oligomers, accompanied by decreases in the yields of water and light organic compounds in the bio-oil.4. The viscous nature of the bio-oil from the pyrolysis of leaves cause the bio-oil condensation and collection system to block easily, necessitating modifications to ensure uninterrupted pyrolysis experiments.The pyrolysis behaviour of mallee leaves at different temperatures has been studied using a modified fluidised-bed reactor. The bio-oils have been characterised with Karl Fischer titration, TGA, UV-fluorescence spectroscopy, FTIR spectroscopy and GC-MS. These results show that the yields and composition/properties of bio-oils from leaves are quite different from those obtained from the pyrolysis of the woody fraction of the same mallee tree species. Both wood and leaves give good yields of bio-oils and therefore are suitable feedstocks for biofuel production. Notably, the amount of water-insoluble compounds present in leaf bio-oils occur in much higher concentration than in wood bio-oils. Eucalyptol is the most abundant simple compound identified in the liquid product. Char yields of leaves are also higher than the woody fraction, partly due to the increased fraction of "extractives", which include other compounds not included in the usual classification of woody biomass. |
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