共查询到19条相似文献,搜索用时 93 毫秒
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快速流化床中平均滑落速度及絮状物的特性 总被引:3,自引:0,他引:3
本文依据大量实验数据,研究快速流化床的操作条件,气固物性等参数对于床内颗粒平均滑落速度的影响。颗粒聚集为絮状物是快速流化床中气固流动的一个重要特征,文中对等效絮状物的基本特征进行了讨论,根据大量实验数据对絮状物的终端速度、絮状物当量直径,以及絮状物中的粒子个数作了推算,这对认识快速流化床气固接触机理及反应器的设计具有参考价值。 相似文献
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循环流化床提升管中固体颗粒停留时间的分布 总被引:9,自引:1,他引:9
在内径140mm,高10m的循环流化床提升管中,采用磷光颗粒示踪法对床内固体颗粒的停留时间分布进行了测定。在气速1.5~9.0m/s,固体循环量10~140kg/m2s的范围内,实验测得的停留时间分布曲线均有明显的双峰分布。这种双峰分布是由于提升管中弥散颗粒和颗粒团共同作用的结果。本文提出的一维两组分扩散叠加模型可较好地描述提升管中固体的混合行为。考察了在实验条件下,操作条件对固体混合行为的影响。发现:气速及固含对颗粒的轴向Peclet数影响不大,提升管中颗粒的返混主要是由于颗粒团引起的。将研究结果与近期文献报道的其他研究进行了对比 相似文献
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聚团是气固循环流化床(CFB)中最常见的现象,对气固之间的热量和质量传递有重要影响。为了考察循环流化床内不同运动方向聚团速度的特性,采用高速相机对提升管内气固流动进行摄像,并利用Matlab图像处理程序,分离出颗粒聚团区域并计算颗粒的运动速度。采用拉格朗日(Lagrange)法计算聚团速度,并根据聚团运动方向对上行和下行聚团的速度分别研究。研究结果表明:采用拉格朗日法能准确地计算聚团速度,上行聚团速度略大于下行聚团速度,聚团速度主要分布在[?3,3] m?s?1且随表观气速的增加而增加;边壁区域下行聚团数量远大于上行聚团数量,中心区域上行聚团数量略大于下行聚团,下行聚团数量占聚团总数的60%~70%。聚团速度沿轴向高度略有增加,在顶部受出口的影响略有减小。聚团横向移动在边壁区域较小,中心区域较大。 相似文献
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低密度循环流化床局部颗粒速度的轴径向分布的研究 总被引:1,自引:0,他引:1
在高8m,内径186mm的循环流化床中,利用光纤激光多普勒测速仪测量了FCC颗粒的局部速度沿轴径向的分布。实验结果表明:局部颗粒速度沿径向分布是不均匀的,床中心区域分布比较平坦,近壁环形区域分布较陡,颗粒沿轴向运动有较长的加速段。由实验数据回归得到预测低密度循环流化床局部颗粒速度的经验关联式。 相似文献
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循环流化床提升管中颗粒速度的径向分布及其沿轴向的发展 总被引:9,自引:0,他引:9
采用5光纤速度探头对f100mm?5.1m循环床提升管8个高度截面上11个径向位置的局部颗粒速度进行了实验测试,并采用径向不均匀指数(RNI)对颗粒速度径向分布的不均匀性及其沿轴向的变化进行了定量描述。研究结果表明:在高气速、高颗粒循环量操作时,操作条件对颗粒上升速度和下降速度的径向分布的影响在加速段和充分发展段呈现出不同的规律;颗粒上升速度和下降速度沿轴向的变化在核心区和边壁区也表现出不同的趋势。当颗粒循环速率大于200 kgm-2s-1时,颗粒的加速段长度大大延长,以至于大于提升管的高度(15.1m)。颗粒速度径向分布的不均匀性沿轴向是逐渐增大的,并且与截面平均颗粒速度存在很强的相关性。 相似文献
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实验的三相循环流化床以玻璃珠 (dp = 0.48 mm, ρs = 2460 kg(m(3) 和苯乙烯颗粒 (dp = 1.45mm, ρs = 1264 kg(m(3)为固相,空气为气相,水、0.05%、0.20% (mass) CMCS (羧甲基纤维素钠)水溶液为液相.实验研究了液体粘度、表观液体速度、表观气体速度、辅助液体速度及颗粒密度对颗粒循环速度的影响.随着液体粘度的增加,颗粒循环速度增加;随着表观液体速度和辅助液体速度增加,颗粒循环速度都增加;随着表观气体速度的增加,颗粒循环速度减小.低密度颗粒系统同高密度颗粒系统相比,低密度颗粒系统能提前从三相传统流型进入三相循环流型.实验还研究了液体粘度对低密度颗粒的起始液体速度和过渡液体速度的影响,为得到三相循环流化床的流型图提供了可靠的依据. 相似文献
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液固循环流化床中颗粒轴向速度的实验研究 总被引:4,自引:0,他引:4
利用超声多普勒测速仪实验测量了液固循环流化床中不同径向位置处颗粒瞬态轴向速度,研究了其概率密度分布特征。采用瞬态速度的标准偏差衡量瞬态速度的波动程度,考察了不同操作形式下的颗粒时均轴向速度的径向分布以及表观液速和颗粒循环速率等操作条件对速度波动程度和速度均衡径向分布的影响,利用相间作用力对两种分布的特点进行了机理分析,并对液固和气固循环流化床中颗粒的流动行为进行了比较。 相似文献
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Solid particles were dried in the riser of circulating fluidized bed with internals to study the drying kinetics. Experiments were conducted in a circulating fluidized bed, having perforated plates as internals covering wide range in the operating parameters. The effects of various operating parameters, i.e., initial moisture content, temperature, and flow rate, of the heating medium and solid circulation rate on the rate of drying have been critically examined. It has been observed from the present investigation that the presence of internals enhances the solids holdup in the riser of circulating fluidized bed. The drying efficiency of a circulating fluidized bed with internals has been compared with the drying performance of a circulating fluidized bed without internals under the same operating conditions. 相似文献
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Solid particles were dried in the riser of circulating fluidized bed with internals to study the drying kinetics. Experiments were conducted in a circulating fluidized bed, having perforated plates as internals covering wide range in the operating parameters. The effects of various operating parameters, i.e., initial moisture content, temperature, and flow rate, of the heating medium and solid circulation rate on the rate of drying have been critically examined. It has been observed from the present investigation that the presence of internals enhances the solids holdup in the riser of circulating fluidized bed. The drying efficiency of a circulating fluidized bed with internals has been compared with the drying performance of a circulating fluidized bed without internals under the same operating conditions. 相似文献
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This study is devoted to gas-solid mass transfer behavior in heterogeneous two-phase flow. Experiments were carried out in a cold circulating fluidized bed of 3.0m in height and 72mm in diameter with naphthalene particles. Axial and radial distributions of sublimated naphthalene concentration in air were measured with an online concentration monitoring system HP GC-MS. Mass transfer coefficients were obtained under various operating condition, showing that heterogeneous flow structure strongly influences the axial and radial profiles of mass transfer coefficients. In the bottom dense region, mass transfer rate is high due to intensive dynamic behavior and higher relative slip velocity between gas and clusters. In the middle transition region and the upper diluter region, as a result of low mass transfer driving force and the influence of flow structure, mass transfer rate distribution becomes non-uniform. In conclusion, among the operating parameters influencing mass transfer coefficients, the superficial gas velocity is the most important factor and the solid circulation rate should be also taken into account. 相似文献
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三相循环流化床中气泡上升速度的实验研究 总被引:5,自引:1,他引:4
开发了一种新型的光纤探头多相流气泡测试系统,可用于气-液两相和气-液-固三相体系中气泡参数的测定。应用此系统研究了三相循环流环化床中不同径同位置气泡的上升速度分布,气泡上升速度均值的径向布以及操作条件对这现任中分布的影响。 相似文献