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基于可视化湿颗粒流化床实验系统,研究了多种Geldart-D类颗粒在不同含液量时的流动特性变化规律,包含流型、床层压降、最小流化速度。实验结果表明:1)在湿流化床内,颗粒出现聚团结块行为,气泡呈现不规则形状;湿颗粒流化过程的稳定性较干颗粒床明显下降,床内近壁面区域易出现局部沟流。2)固定床阶段,由于空隙率的增加,相同气速条件下,湿颗粒床层压降低于干颗粒;基于厄贡公式,得出了湿颗粒固定床床层压降的计算方法。3)湿颗粒的最小流化速度U_(mf)高于干颗粒,且随粒径d_p的增加而增加;导出了预测D类湿颗粒最小流化速度的半经验公式,Re_(mf)=0.279.Ar~(0.5),该式计算结果与实验测量结果偏差小于15%。
Based on the visualized wet particle fluidized bed experimental system, the variation of flow characteristics of various Geldart-D type particles at different liquid contents was studied, including flow pattern, bed pressure drop and minimum fluidization velocity. The experimental results show that: 1) agglomeration of particles occurs in the wet fluidized bed, the bubbles present irregular shapes; the stability of wet granulation fluidization process is significantly lower than that of dry granulation bed, local ditch tends to appear in the near wall area of the bed flow. 2) In the fixed bed stage, the wet granule bed pressure drop is lower than that of the dry granule under the same gas velocity condition because of the increase of the void ratio. Based on the Argon formula, the calculation method of the bed pressure drop of the wet granule is obtained. 3) The minimum fluidization velocity of wet particles, U mf, is higher than that of dry particles and increases with the increase of particle size d p. The semi-empirical formula for predicting the minimum fluidization velocity of wet particles D is derived. Re mf = 0.279 . Ar ~ (0.5), the calculated results and experimental results deviate less than 15%.