Dissertation > Industrial Technology > Chemical Industry > General issues > Chemical processes ( physical processes and physical and chemical processes ) > Basic theory

Hydrodynamic Simularity for Fluidized Beds with Coarse Particle

Author LuoXinJiang
Tutor XuDeLong;FanHaiHong;LiXiaoGuang
School Xi'an University of Architecture and Technology
Course Materials Science
Keywords Fluidized beds Similarity Coarse particle
Type Master's thesis
Year 2005
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In the process of design about industrial fluidized beds, testing results from small model equipment can’t be directly instructed operation of large scale model due to being so-call serious the effect of scale-up. If pilot-plant-scale experiment is done, it will result in a considerable expense. In the addition, fluidized behaviors in gas-solid fluidized beds can’t still entirely be understood on the account of the absence of rigorous measure methods. So the theory of hydrodynamic similarity for fluidized beds with coarse particle is developed by author to get scale-up method and information from large model bed.On the basis of theory of similarity and gas-solid fluidization, the four dimensionless criteria, the Froude number, the Flow number, the ratio of static height to diameter of bed and solid to-gas density ratio, describing similarity of fluidized beds were obtained. The group of criteria of fluidized beds with coarse particle almost includes full integral similarity in fluidized beds.A series of experiment have verified rationality of the group. It is show that these parameters (including the bed expansion ratios, the dimensionless average bed pressure, the standard deviation of pressure fluctuation and the dominant frequency of pressure fluctuation) which reflect on hydrodynamic behaviors should be equal in the two different scale systems of fluidized beds with coarse particle on the condition of the same similarity caritas.It was found experimentally that the Froude and the flow numbers have an influence to the different degree on these parameters, the ratio of static height and diameter of bed serve on little effect to bed expansion ratio, and but impose on the other parameters. A critical point corresponding to the Flow number 1.8 was firstly observed in process of investigating influence of solid-gas density ratio to fluidized behaviors.The solid to gas density ratio can lightly affect similarity below the point, and the reverse is true.The employment of these numbers make it possible to put forward to design a large scale model fluidized bed, and simulate hot pilot-plant-scale experiment on small cold model equipment.

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