Effect of Temperature on the Hydrodynamics of Bubbling Fluidized Beds
Advancing the chemical engineering fundamentals
Particulate Systems (T2-3)
Keywords: fluidization, hydrodynamics, particle tracking
Effect of temperature on some hydrodynamic parameters of bubbling gas-solid fluidized beds has been investigated. Despite the fact that most of industrial fluidized bed reactors operate at relatively high temperatures, the majority of studies, concerning solids behavior and hydrodynamic correlations of fluidized beds, have been done at ambient temperature. The lack of information at higher temperatures is related to difficulties associated with measuring techniques under such conditions. In order to explore the fluidized bed hydrodynamics at high temperatures, experiments have been carried out in the present study, at different temperatures (in the range of 25-700 oC) and different superficial gas velocities (in the range of 0.16-0.87 m/s) for sand and alumina. The fluidized bed used in the experiments was 0.078 m ID and 0.75 m height. Time-position trajectory of particles was obtained by the radioactive particle tracking technique using a radioactive tracer in the bed. In each experiment a single tracer was placed into the bed to move freely with the other particles. Movement of the tracer was then monitored for about 5 hours during which the count rates of the tracer at some 820,000 points were acquired. Hydrodynamic parameters such as velocity distribution of bubbles, velocity distribution of ascending and descending clusters, and diffusivity of solids were achieved from the particle trajectories by proper processing of the experimental time-position data. Temperature dependence of these hydrodynamic properties was investigated by comparing the results at different temperature. As expected, this comparison indicates that by increasing the temperature, particles have more chance to be picked up by the bubbles, they move accordingly at a higher velocity and existence of particles in emulsion phase decreases. Velocity of bubbles and clusters in the bed was obtained by plotting the velocity distribution of bubbles and clusters found by the above mentioned algorithm. By comparing the velocity distributions, velocity dependence to temperature has been indicated.
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Presented Monday 17, 16:40 to 17:00, in session Particulate Systems (T2-3).
