共查询到16条相似文献,搜索用时 62 毫秒
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提升管循环流化床气,固局部滑落速度的分布 总被引:1,自引:0,他引:1
本研究采用光纤激光多普勒测速仪(LDV),通过两列信号处理系统,同时测定了气体和颗粒局部速度,研究了低密度循环流化床提升管内局部滑落速度的变化规律。实验结果表明,提高颗粒循环速率,在任一径向位置的气固滑落速度均增加;提高气体表观速度,反而使气固之间局部滑落速度减小。由于固体颗粒在近壁区的团聚行为,在近壁区气、固局部滑落速度出现一个极大值。 相似文献
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本文综合分析了文献报道的实验数据,利用快速流态化气固两通道流动模型较好地预测了床层平均空隙率随操作条件及气固物性的变化规律。为了便于工业设计,同时整理得到了床层平均空隙率的经验公式。 与实验值相比,上式平均相对偏差小于±2.4%。 相似文献
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薛惠芳 《化学反应工程与工艺》1992,8(3):302-307
颗粒速度是快速流化床内重要的流体力学参数,直接测定是困难的,一般都是通过测定其他参数,来计算颗粒的速度。本研究在内径6.6cm 和9.7cm,高3m 的快速流化床内测定颗粒的轴向滞留量分布及压头损失,分析床层内颗粒速度及其影响因素,对三种不同颗粒进行测定,将实验数据进行关联,得出颗粒速度的关联式:适用范围:气体流速:1.4~6.0m/s颗粒循环速度:30~130kg/m~2·s颗粒终端速度:0.133~0.880m/s将实验值与计算的结果比较,基本一致。故可认为该式在实验范围内,可用于推算快速流化床内的颗粒速度。 相似文献
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低密度循环流化床反应器床层截面平均颗粒速度的变化规律 总被引:4,自引:0,他引:4
本文在高8m,内径186mm 的循环流化床中采用 FCC 颗粒,利用 TSI 光纤激光多普勒测速仪测定了局部颗粒速度的径向分布,并获得了床层截面平均颗粒速度。实验结果表明:截面平均颗粒速度随操作气速的增大而增大,随固体循环速率的增大而略有减小。由实验数据回归得到了计算本实验条件下低密度速度的经验关联式。论文还从基本流体力学理论出发,在考虑颗粒加速运动的条件下,建立了一维气、固两相流模型,可以用于预测床层截面平均颗粒速度和空隙率的变化规律,模型计算结果和实验数据吻合较好。 相似文献
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本文在φ140mm的气固并流下行快速流化床中,研究了颗粒浓度及颗粒速度的径向分布随操作气速、颗粒循环速率以及床层轴向位置的变化规律。并探讨了颗粒质量通量的径向分布及颗粒流动的均匀性,表明在相同操作条件下,下行快速流化床中气固流动远比上行快速流化床均匀。 相似文献
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《煤化工》2017,(4)
采用PC6D型颗粒浓度测量仪,在多段分级转化流化床冷态实验装置上,测量了提升管中局部固体浓度,对颗粒聚团特性进行了实验研究。结果表明:径向上絮状物的时间分率Fc和絮状物内的颗粒浓度εsc在床层中心区(r/R0.6)较低,而在边壁区(r/R0.8)相对较高。提升管所有截面上各径向位置的Fc和εsc均随表观气速urg的减小和/或固体循环量Gs的增加而增加,轴向上操作条件对底部加速段Fc、εsc的影响明显高于对上部充分发展段Fc、εsc的影响;径向上操作条件对中心区Fc、εsc的影响显著高于对边壁区Fc、εsc的影响。在絮状物颗粒浓度0到εsmf范围内,得出絮状物内的颗粒浓度εsc与该处相应的局部颗粒浓度εs的变化关系式为εsc=3.33εs0.8。 相似文献
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A heterogeneous model for the fast fluidized bed reactor which carries out a gas-solid non catalytic reaction is presented. The hydrodynamics of the fast fluidized bed is characterized by the model of Kwauk et al. (1985) which assumes the existence of two phases; a dense phase and a dilute pneumatic transport phase. For a given solid flowrate, the length of the reactor occupied by each phase depends on gas velocity, particle diameter and density and average voidage within the reactor. The gas-solid reaction is assumed to follow the shrinking core model. The solids are assumed to be completely backmixed in the dense phase and move in plug How in the dilute pneumatic transport phase. The gas phase is assumed to be in plug flow in both phases
For given gas and solid flowrates, the transition from the dense phase flow to the fast fluidized bed (containing two regions) as functions of particle size and density is determined using the model of Kwauk et al. (1985). The numerical solution of the governing mass balance equations show that for given solid and gas flowrates, (and average voidage) the gas phase conversion shows an unusual behavior with respect to particle diameter and density. Such behavior is resulted from the effects of particle diameter and density on the reactor volume occupied by each phase and the effect of particle diameter on the apparent reaction rate. The numerical results show that a fast fluidized bed gives the best conversion at large particle density and for the particle diameter which results the fast fluidized bed to be operated near the pure dense phase flow. 相似文献
For given gas and solid flowrates, the transition from the dense phase flow to the fast fluidized bed (containing two regions) as functions of particle size and density is determined using the model of Kwauk et al. (1985). The numerical solution of the governing mass balance equations show that for given solid and gas flowrates, (and average voidage) the gas phase conversion shows an unusual behavior with respect to particle diameter and density. Such behavior is resulted from the effects of particle diameter and density on the reactor volume occupied by each phase and the effect of particle diameter on the apparent reaction rate. The numerical results show that a fast fluidized bed gives the best conversion at large particle density and for the particle diameter which results the fast fluidized bed to be operated near the pure dense phase flow. 相似文献
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根据在直径0.186m、高8m和直径0.14m、高12m两台快速流化床装置的实验结果,并综合文献研究报道,研究了操作气速、颗粒循环速率、颗粒物性、床层直径以及进口、出口结构等因素对床层截面平均空隙率轴向分布的影响。表明一般情况下,快速流化床截面平均空隙率轴向分布的基本形式是上部空隙率高、下部空隙率低的单调指数函数。在特定的床结构条件下,快速流化床截面平均空隙率轴向分布曲线可能发生变异,即在出口结构有强约束作用时,可能呈反C,在入口结构有弱约束作用时,可能呈S型。 相似文献
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This paper presents an experimental study on the axial and radial distributions of heat transfer coefficients in a fastfluidized bed operated at ambient temperature.The following formula is recommended to correlate the local heat transfer coefficients in fast fluidized beds:where a,n_1 and n_2 are functions of radial positions. 相似文献
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Bubble frequency and velocity in a bubbling fluidized bed are estimated by combining advanced estimation theory and the cross correlation function of pressure measurements. The cross correlation function is shown to be a mathematical function of bubble frequency and velocity. Sequential weighted least squares and a version of Kalman filtering are used to compute optimal estimates of these bubble parameters for fluidization in the bubbling/near slugging regime. The dynamics of both algorithms are studied in response to simulated step changes in fluidizing air flow. 相似文献