| Biomass is a very promising technology to convert solid biomass into liquids (bio-oil) thermochemically, which utilize agricultural wastes more efficiently. Mechanism research of fast pyrolysis is essential for determining the pyrolysis process and equipment as well as pyrolysis parameters, and consquently, affects the yield and characteristics of bio-oil. In the devolatilization characteristics of biomass, residence time of particles and the final volatile yield are most important. The ultimate goal of the study on fast pyrolysis is to commercialize the bio-oil production. Therefore, it is a vital step to analyze the characteristics of bio-oil and to develop the application technology of bio-oil.In the paper, velocity motions of char particles were studied in LEFR at constant temperature by Particle Image Velocimetry (PIV), and residence time was determined. According to PIV experimental results, residence time of particles was calculated at different flow fields. The ratio of paticle and gas residence time was a first-order functional relation with Reynolds number of flow field. Based on similarity criterion and the function, residence time of particles in LEFR can be calculated, which could offer base data for devolatilization characteristics.Fast devolatile experiments were conducted in the LEFR for determing the final volatile yield of four kinds of biomass (wheat straw, corn stalk, peanut shell and cotton stalk) at moderate temperature (773K-923K). The experimental results showed that when the reaction temperature was over 873K, the volatile yield would not change with the increase of temperature and residence time, which is defined as the final volatile yield W∞. Final volatile yield of wheat straw, corn stalk, peanut shell and cotton stalk were 79%,80%,85%,85%, respectively.Analysis methods of physical properties and chemical composition for bio-oil were summarized and analysis results were introduced. Bio-oil derived from corn stalk was analyzed by Gas Chromatography/Mass Spectrum (GC/MS). The results showed that the main components included methanol, water,2-propanone-l-hydroxy-, acetic acid, cyclopenten, furanm, propanoic acid, phenol-2-methl-, etc.. Components in water-soluble fraction were nearly the same at different reaction conditions. After water-soluble fraction was extracted by dichloromethane, more components were analyzed. Most of them were derivatives about cyclopenten, furanm, phenol and water content was reduced greatly.Stabilities of emulsified fuel were investigated by varying bio-oil content, emulsifier types and contents. The characteristics of emulsified fuel with four different content of bio-oil were analyzed and tested on a SD1110 diesel engine. The engine load characteristics and exhaust emission characteristics curves of diesel engine were determined, and then, the fuel economy and exhaust emission characteristics of the engine fueled with the emulsified fuel were analyzed in comparison with that of the pure No.0 diesel oil. The experimental results showed that, the specific fuel consumption was the lowest, when the engine was fueled with the emulsified fuel about 20% volume fraction of bio-oil. CO emission of emulsified fuel was higher than that of diesel oil, and the high concentration of bio-oil was, the more CO emission was. But the NO and smoke emissions of the emulsified fuels were lower than that of the pure No.0 diesel oil. Since the physical and chemical characteristics of the bio-oil/diesel oil emulsified fuels were similar to that of diesel, it could be used to fuel diesel engines. |
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