Issue
Korean Journal of Chemical Engineering,
Vol.16, No.1, 82-88, 1999
SOLIDS FLOW CHARACTERISTICS IN LOOP-SEAL OF A CIRCULATING FLUIDIZED BED
The hydrodynamics of solids (FCC) recycle in a loop-seal (0.08 m) at the bottom of the downcomer (0.08 m-I.D.×4.0 m-high) in a circulating fluidized bed (0.1 m-I.D.×5.3 m-high) have been determined. Solid flow rate through the loop-seal increases linearly with increasing aeration rate. At the same aeration rate, the maximum solid flow rate can be obtained at a loop-seal height-to-diameter ratio of 2.5. The effects of solid inventory, solid circulation rate and gas velocity on pressure balance around the CFB have been determined. At a given gas velocity and solid circulation rate, pressure drops across the downcomer and loop-seal increase linearly with increasing solids inventory in the bed. At a constant solid inventory, pressure drops across the riser and the downcomer increase with increasing solid circulation rate but decrease with increasing gas velocity in the riser. The obtained solid flow rate has been correlated with pressure drop across the loop-seal.
[References]
  1. Basu P, Fraser SA, "Circulating Fluidized Bed Boiler: Design and Operation," Butterworth-Heinemann, Boston, 1991
  2. Cho YJ, Namkung W, Kim SD, Park SW, J. Chem. Eng. Jpn., 27(2), 158, 1994
  3. Dries HWA, "Cocurrent Gas/Solids Downflow in Vertical Cat Cracker Standpipes: Effects of Gas Compression and Solids Compaction," Fluidization, Editors Grace, J.R. and Matsen, J.M., 493, 1980
  4. Ergun S, Chem. Eng. Prog., 48(2), 89, 1952
  5. Knowlton TM, Hirsan I, Hydrocarb. Process., 57, 149, 1978
  6. Knowlton TM, Hirsan I, Leung LS, "The Effect of Aeration Tap Location on the Performance of a J-valve," Fluidization, Editors Davidson, J.F. and Keairns, D.L., Cambridge University Press, 128, 1978
  7. Knowlton TM, "Non Mechanical Solid Feed and Recycle Devices for Circulating Fluidized Bed," CFB Technol. II, Editors Basu, P. and Large, J.F., Pergamon Press, New York, 31, 1988
  8. Kojabashian C, "Properties of Dense-phase Fluidized Solids in Vertical Down-flow," Ph.D. Thesis, Massachusetts Institute of Technology, Cambridge, Massachusetts, U.S.A., 1958
  9. Leung LS, Chong YO, Lottes J, Powder Technol., 49, 271, 1987
  10. Merrow E, Chem. Eng. Process., May, 14, 1985
  11. Namkung W, Cho YJ, Kim SD, HWAHAK KONGHAK, 32(2), 241, 1994
  12. Rhodes MJ, Laussman P, Can. J. Chem. Eng., 70, 625, 1992
  13. Rudolph V, Chong YO, Nicklin DJ, "Standpipe Modeling for Circulating Fluidized Beds," CFB Technol. III, Editors Basu, P., Horio, M. and Hasatani, M., Pergamon Press, New York, 49, 1991
  14. Yang WC, Knowlton TM, Powder Technol., 77, 49, 1993
  15. Zenz FA, Powder Technol., 47, 105, 1986
  16. Zhang JY, Rudolph V, Can. J. Chem. Eng., 69, 1242, 1991