Solid Circulation Rate and Gas Leakage Measurements in an Interconnected Bubbling Fluidized Beds

Two-interconnected fluidized bed systems are widely used in various processes such as Fisher-Tropsch, hot gas desulfurization, CO2 capture-regeneration with dry sorbent, chemical-looping combustion, sorption enhanced steam methane reforming, chemical-looping hydrogen generation system, and so on. However, most of two-interconnected fluidized beds systems require riser and/or pneumatic transport line for solid conveying and loopseals or seal-pots for gas sealing, recirculation of solids to the riser, and maintaining of pressure balance. The riser (transport bed) is operated at the high velocity fluidization condition and residence times of gas and solid in the riser are very short. If the reaction rate of catalyst or sorbent is slow, the riser can not ensure sufficient contact time between gas and solid and we have to use two bubbling beds for each reaction to ensure sufficient contact time. In this case, additional riser must be installed for solid circulation. Consequently, conventional two-interconnected fluidized bed systems are very complex, large, and difficult to operate. To solve these problems, a novel two-interconnected fluidized bed system has been developed. This system has two bubbling beds, solid injection nozzles, solid conveying lines, and downcomers. In this study, effects of operating variables on solid circulation rate, gas leakage between two beds have been investigated in a cold mode two-interconnected fluidized bed system. Moreover, long-term operation of continuous solid circulation up to 60 hours has been performed to check feasibility of stable operation.

Authors:

• Ho-Jung Ryu
• Seung-Yong Lee
• Young Cheol Park
• Moon-Hee Park

Keywords:

• Fluidized bed
• Gas leakage
• Long-term operation
• Solid circulation.

References:

[1] J. F. Davidson, R. Clift, and D Harrison, Fluidization, 2nd Ed., Academic
Press, London, 1985, pp. 294-329.
[2] L. F. Diego, F. G. Labiano, P. Gayan, J. Cleaya, J. Palacios, and J. Adanez,
"Operation of a 10kWth chemical-looping combustor during 200h with a
CuO-Al2O3 oxygen carrier," Fuel, vol. 86, pp. 1036-1045, 2007.
[3] H. J. Ryu and G. T. Jin, "Conceptual design of 50kW thermal
chemical-looping combustor and analysis of variables," Energy Engg. J.,
vol. 12, no. 4, pp. 289-301, 2003.
[4] H. J. Ryu and G. T. Jin, "Performance estimation and process selection for chemical-looping hydrogen generation system," Trans. Of the Korean
Hydrogen Energy Society, vol. 16, no. 3, pp. 230-239, 2005.
[5] H. J. Ryu and J. H. Choi, "Effects of temperature and particle density on
particle entrainment in a gas fluidized bed," HWAHAK KONGHAK, vol.
35, no. 2, pp. 173-180, 1997.
[6] E. Johansson, A. Lyngfelt, T. Mattisson, and F. Johnsson, "Gas leakage
measurements in a cold model of an interconnected fluidized bed for
chemical-looping combustion," Powder Technology, vol. 134, pp.
210-217, 2003.
[7] B. Kronberger, E. Johansson, G. Loffler, T. Mattisson, A. Lyngfelt, and H.
Hofbauer, "A two-compartment fluidized bed reactor for CO2 capture by
chemical-looping combustion," Chem. Eng. Technol., vol. 27, no. 12, pp.
1318-1326, 2004.
[8] D. Kunii and O. Levenspiel, Fluidization engineering, 2nd Ed.,
Butterworth-Heinemann, MA, 1991, pp. 71-75.