【摘要】 在提升段净高为4.0 m、内径0.19 m的循环流化床冷态试验台上进行了快速床和气力输送两种流型中径向气体混合的试验研究,试验用物料为河沙,dp=120μm,真实密度ρs=2 400kg/m3。试验台颗粒循环流率(Gs)和流化风速(Ug)可独立控制,根据床层上、下部压力梯度随流化风速的变化关系判断快速流态化的存在区域。采用柱塞流模型,用CO2作为示踪气体进行3种风速下的径向气体混合试验,得出了快速床和气力输送两种流型中气体径向扩散系数Dr随颗粒浓度变化的趋势。研究发现,在气力输送流型中Dr随颗粒浓度增加而减小,在快速床流型中Dr随颗粒浓度增加而增大。结合固体颗粒在不同流型中的存在状态解释了流型对Dr的不同影响作用。更多还原

【Abstract】 On a CFB(Circulating Fluidized Bed) cold-state test rig with a riser section having a net height of 4.0 meters and an inner diameter of 0.19 meters,an experimental study has been performed of the radial gas mixing in the following two flow patterns:i.e.fast bed and pneumatic conveyance.The bed material used in the test was river sand,dp=120 μm and the real density ρs=2400 kg/m3.The particle cyclic flow rate(Gs) and fluidized air speed(Ug) can be controlled independently on the test rig.The variation relationship of the pressure gradient between the upper and lower bed layers with the fluidization air speed can be used to ascertain the zone where a fast fluidization is present.By using a plunger flow model and with CO2 serving as a tracer gas,the radial gas mixing was tested at three air speeds.The tendency of Dr changing with the particle concentration was obtained in the following two flow patterns,the fast bed and pneumatic conveyance.It has been found that in the pneumatic conveyance flow pattern,Dr will decrease with an increase of the particle concentration while in the fast bed flow pattern,Dr will increase with a particle concentration increase.In conjunction with the existence status of solid particles in various flow patterns,the different influence of the flow patterns on Dr can be reasonably explained.更多还原