The solids flow in the CFB-riser quantified by single radioactive particle tracking |
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Authors: | Shiva Mahmoudi Jan Baeyens Jonathan Seville |
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Affiliation: | University of Warwick, School of Engineering, Coventry CV4 7AL, UK |
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Abstract: | Single radioactive particle tracking was used to measure the overall solids residence time (and its distribution) in the riser of a CFB, operating at superficial air velocities (U) of 1 to 9 ms− 1 and solids circulation fluxes (G) between 20 to 600 kg m− 2s− 1.The results demonstrate that the particle motion and mixing differ according to the operating mode of the riser, with a fairly constant velocity throughout the riser achieved in the dilute or dense riser flow, but with a significant amount of back-mixing for intermediate values of U and/or G. This back-mixing is due to the core-annulus mode of particle flow. Whereas experimental results and theoretical predictions are in fair agreement for the dilute and dense riser flow, the core-annulus regime needs to account for a U and G dependent slip factor (φ), in excess of the commonly proposed value φ = 2, especially at U-UTR < 2 ms− 1.Moreover, the previously published riser operation diagram is confirmed by the experiments, although a further analysis of the core-annulus regime is needed. |
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Keywords: | CFB Riser Solids flow Operating regimes Slip factor |
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