Conference article

Effect of Superficial Gas Velocity on Bubbling Fluidized Bed Behaviour in a Biomass Gasifier

Cornelius Agu
Department of Process, Energy and Environmental Technology, University of South-EasternNorway, Porsgrunn, Norway

Britt M.E. Moldestad
Department of Process, Energy and Environmental Technology, University of South-EasternNorway, Porsgrunn, Norway

Download articlehttps://doi.org/10.3384/ecp20170158

Published in: Proceedings of The 60th SIMS Conference on Simulation and Modelling SIMS 2019, August 12-16, Västerås, Sweden

Linköping Electronic Conference Proceedings 170:24, p. 158-163

Show more +

Published: 2020-01-24

ISBN: 978-91-7929-897-5

ISSN: 1650-3686 (print), 1650-3740 (online)

Abstract

This study investigates the behaviour of bubbling fluidized beds in biomass gasification processes based on the variation of superficial gas velocity at different temperatures and air flow rates. In the paper, the operating window is defined as the gas velocity between the minimum fluidization and slugging velocities, which are computed using the correlations in the literature. The analysis shows that the operating gas velocity depends on the amount of char accumulated in the bed. An increase in the char accumulation results in higher minimum fluidization and slugging velocities of the bed mixture. This therefore suggests that the gas velocity ratio required to achieve the desired operating fluidized bed regime is higher when the biomass accumulation is considered.

Keywords

biomass, gasification, air-fuel ratio, CPFD, bubbling fluidized bed

References

C.E. Agu, C. Pfeifer, and B.M.E. Moldestad. Prediction of void fraction and minimum fluidization velocity of a binary mixture of particles: Bed material and fuel particles. Powder Technology, 349: 99 – 107, 2019(a).

C.E. Agu, C. Pfeifer, L.-A. Tokheim, and B.M.E. Moldestad. Behaviour of biomass particles in a bubbling fluidized bed: A comparison between wood pellets and wood chips. Chemical Engineering Journal, 363: 84 – 98, 2019(b).

C.E. Agu, C. Pfeifer, M. Eikeland, L.-A. Tokheim, and B.M.E. Moldestad. Models for predicting average bubble diameter and volumetric bubble flux in deep fluidized beds. Industrial & Engineering Chemistry Research, 57: 2658 – 2669, 2018.

C.E. Agu, C. Pfeifer, M. Eikeland, L.-A. Tokheim, and B.M.E Moldestad. Measurement and characterization of biomass mean residence time in an air-blown bubbling fluidized bed gasification reactor. Fuel, 253: 1414 – 1423, 2019(c).

M.J. Andrews and P.J. O’Rourke. The multiphase particle-in-cell (MP-PIC) method for dense particulate flows. International Journal of Multiphase Flow, 22: 379 – 402, 1996.

J. Baeyens and D. Geldart. An Investigation into slugging fluidized beds. Chemical Engineering Science, 29: 255 – 265, 1974.

J.S.M. Botterill, Y. Teoman, and K.R. Yuregir. The effect of operating temperature on the velocity of minimum fluidization, bed voidage and general behaviour. Powder Technology, 31: 101 – 110, 1982.

C. Chen, J. Werther, S. Heinrich, H.-Y. Qi, and E.-U. Hartge. CPFD simulation of circulating fluidized bed risers. Powder Technology, 235: 238 – 247, 2013.

S. Ergun. Fluid flow through packed column. Chemical Engineering Progress, 48: 89 – 94, 1952.

Y. Hatate, K. Ijichi, Y. Uemura, M. Migita, and D.F. King. Effect of bed temperature on bubble size and bubble rising velocity in a semi-cylindrical slugging fluidized bed. Journal of Chemical Engineering of Japan, 23: 765 – 767, 1990.

A.C. Kumoro, D.A. Nasution, A. Cifriadi, A. Purbasari, and A.F. Falaah. A new correlation for the prediction of minimum fluidization of sand and irregularly shape biomass mixtures in a bubbling fluidized bed. International Journal of Applied Engineering Research, 9(23): 21561 – 21573, 2014.

D. Kunii and O. Levenspiel. Fluidization Engineering, 2nd ed., Butterworth – Heinemann, Washington Street, USA, 1991.

N. Nemati, R. Zarghami, and N. Mostoufi. Investigation of hydrodynamics of high temperature fluidized beds by pressure fluctuations. Chemical Engineering & Technology, 39: 1527 – 1536, 2016.

T. Otake, S. Tone, M. Kawashima, and T. Shibata. Behaviour of rising bubbles in a gas fluidized bed at elevated temperature. Journal of Chemical Engineering of Japan, 8: 388 – 392, 1975.

R.R. Pattipati and C.Y. Wen. Minimum fluidization velocity at high temperature. Industrial & Engineering Chemistry Process Design and Development 20: 705 – 708, 1981.

S. Shaul, E. Rabinovich, and H. Kalman. Generalized flow regime diagram of fluidized beds based on the height to bed diameter ratio. Powder Technology 228: 264 – 271, 2012.

C. Si and Q. Guo. Fluidization characteristics of binary mixtures of biomass and quartz sand in an acoustic fluidized bed. Industrial & Engineering Chemistry Research 47: 9773 – 9782, 2008.

C.Y. Wen and Y.H. Yu. A generalized method for predicting the minimum fluidization velocity. AIChE Journal 12: 610 – 612, 1966.

Citations in Crossref