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Hydrodynamics and flow structure, gas and solids mixing behavior, and choking phenomena in gas-solid fluidization

Du, Bing
http://rave.ohiolink.edu/etdc/view?acc_num=osu1110208922

Abstract Details

2005, Doctor of Philosophy, Ohio State University, Chemical Engineering.
In this study, the dynamic flow behavior and gas and solids mixing behavior in the turbulent fluidized beds are investigated by using Electrical Capacitance Tomography (ECT) technique and tracer technique. The ECT study reveals that the time-averaged solids holdup distribution exhibits radial symmetry in the turbulent regime. The addition of 10% fine particles decreases the solids concentration in the emulsion phase. The flow behavior in the turbulent fluidized beds is not appreciably affected by the temperature up to 400 °C. More than one spiral motion of bubble swarms is observed in the bubbling regime for the 0.3 m ID fluidized bed. The gas and solids mixing behavior varies significantly with the flow regimes. A small quantity of fine particles is noted to drastically affect the gas and solids mixing behavior in the turbulent fluidized bed. For Group A particles, the flow in the bed transits from the dilute regime to the turbulent regime when the gas velocity is below Utr or the solids circulation rate is lower than Gs,tr. Such flow transition can be signified as the choking transition. For Group B particles, choking is initiated by the formation of the square-nosed slugs (0.05 m ID column) or the wall slugs (0.1 m ID CFB) when the gas velocity is below Utr or the solids circulation rate is lower than Gs,tr. When the gas velocity is above Utr or the solids circulation rate is higher than Gs,tr, choking is characterized by the formation of open slugs. These regime transitions are characterized as the choking transition. A model based on the movement of the solids blob at the center of the bed is developed to predict the critical lifetime of a solids blob in a circulating fluidized bed. The criterion for the occurrence of choking transition in a circulating fluidized bed for both Group A and Group B particles is given.
Liang-Shih Fan (Advisor)
334 p.
Engineering, Chemical
hydrodynamics; flow structure; mixing behavior; turbulent fluidized bed; circulating fluidized bed; choking; regime transition

Recommended Citations

Citations

  • Du, B. (2005). Hydrodynamics and flow structure, gas and solids mixing behavior, and choking phenomena in gas-solid fluidization [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1110208922

    APA Style (7th edition)

  • Du, Bing. Hydrodynamics and flow structure, gas and solids mixing behavior, and choking phenomena in gas-solid fluidization. 2005. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1110208922.

    MLA Style (8th edition)

  • Du, Bing. "Hydrodynamics and flow structure, gas and solids mixing behavior, and choking phenomena in gas-solid fluidization." Doctoral dissertation, Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1110208922

    Chicago Manual of Style (17th edition)

osu1110208922
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© 2005, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.