| Biomass energy is a renewable, rich and relative clean energy. Crop straw is one of themost important resources of biomass energy. According to the survey, China strawutilization rate is about 33% and only 2.6% after treatment. The incineration of crop strawresults in not only environment pollution but also the waste of resources. So, strawconversion efficiency and development of new energy products become the problems ofagriculture, energy and environment that must be resolved. As an efficient use ofresources, fast pyrolysis of crop straw for liquid has increasingly become one of the hottopics.Cold test device of spout-fluidizing bed with a draft tube has been built. Solidcirculation rate, central fountain height and bed pressure drop were used to evaluate bedconfiguration. The best bed configuration is as follows: the length of draft tube is 0.45m,the diameter of draft tube is 0.045m and the installation height of draft tube is 0.060m.Influences of operating conditions (spouting gas velocity and fluidizing gas velocity)and material (static bed height and the proportion of oilseed rape straw in mixture) onflow characteristics (solid circulation rate, central fountain height, pressure drop,minimum spout-fluidizing gas velocity and flow regime map) were studied and explored.The result shows that fluidization could be well realized in spout-fluidizing bed with adraft tube when oilseed rape straw of 0.85～0.43mm and quart sand of 0.38～0.25m aremixed together with the ratio 1: 4, total weight 500g.Solid circulation rate shows increasing trends as increasing of the operating gasvelocity, increases rapidly first and then slowly with increasing static bed height anddecreases with increasing the proportion of oilseed rape straw in mixture. Oilseed rapestraw circulation rate can reach 3g·s-1 when the spouting gas velocity is about 0.25～0.28m·s-1.Central fountain height increases while operating gas velocity is increasing. A rapidincrease in centre fountain height was measured as the static bed height is below 0.092m,while later on it slowly increases. Central fountain height decreases with increasing theproportion of oilseed rape straw in mixture. Relevance formula about central fountainheight was obtained by multiple nonlinear regressions. The average relative deviation ofcalculated value and experimental value is 3.17%. According to the relationship between bed pressure drop and operating gas velocity,minimum spout-fluidizing gas velocity was obtained. Fluidizing gas can minimize thespouting gas velocity, but it results in an increase in minimum spout-fluidizing velocity.The minimum spout-fluidizing gas velocity increases with increasing static bed heightand the proportion of oilseed rape straw in mixture. Relevance formula about centralfountain height was obtained by multiple nonlinear regressions. The average relativedeviation of calculated value and experimental value is 8.73%.According to the relationship between bed pressure drop and operating gas velocity andthe flow state in the bed, flow regime map were divided into four parts such as fixed bed,partly spout-fluidizing bed, spout-fluidizing bed and carry-over bed. The range ofspout-fluidizing bed decreases with increasing static bed height and increases withenhancing proportion of oilseed rape straw in mixture.A mathematical model about flow characteristics in spout-fluidizing bed with a drafttube was built by two solid particles analysis in the section of spout, fountain, annular andcarry-over. Gas-solids movement was initially explored. The mathematical model canprovide correct guidance for fast pyrolysis and engineering enlargement.
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