Chemical Papers

, Volume 64, Issue 2, pp 154–162 | Cite as

Solid suspension and gas dispersion in gas-solid-liquid agitated systems

  • Anna Kiełbus-Rąpała
  • Joanna KarczEmail author
Original Paper


The aim of the research work was to investigate the effect of superficial gas velocity and solids concentration on the critical agitator speed, gas hold-up and averaged residence time of gas bubbles in an agitated gas-solid-liquid system. Experimental studies were conducted in a vessel of the inner diameter of 0.634 m. Different high-speed impellers: Rushton and Smith turbines, A 315 and HE 3 impellers, were used for agitation. The measurements were conducted in systems with different physical parameters of the continuous phase. Liquid phases were: distilled water (coalescing system) or aqueous solutions of NaCl (non-coalescing systems). The experiments were carried out at five different values of solids concentration and gas flow rate. Experimental analysis of the conditions of gas bubbles dispersion and particles suspension in the vessel with a flat bottom and four standard baffles showed that both gas and solid phases strongly affected the critical agitation speed necessary to produce a three-phase system. On the basis of experimental studies, the critical agitator speed for all agitators working in the gas-solid-liquid systems was found. An increase of superficial gas velocity caused a significant increase of the gas hold-up in both coalescing and non-coalescing three-phase systems. The type of the impeller strongly affected the parameters considered in this work. Low values of the critical impeller speed together with the relatively short average gas bubbles residence time tR in three phase systems were characteristic for the A 315 impeller. Radial flow Rushton and Smith turbines are high-energy consuming impellers but they enable to maintain longer gas bubbles residence time and to obtain higher values of the gas hold-up in the three-phase systems. Empirical correlations were proposed for the critical agitator speed, mean specific energy dissipated and the gas hold-up prediction. Its parameters were fitted using experimental data.


agitation gas-solid-liquid system gas hold-up critical impeller speed power consumption 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Brauer, H., Dyląg, M., & Talaga, J. (1989). Zur Fluiddynamik von gerührten Gas/Feststoff/Flüssigkeits — Systemen. Chemie Ingenieur Technik, 61, 978–979. doi: 1002/cite.330611218.CrossRefGoogle Scholar
  2. Bujalski, W. (1986). Three phase mixing: studies of geometry, viscosity and scale. Thesis, University of Birmingham, Birmingham, UK.Google Scholar
  3. Bujalski, W., Nienow, A. W., & Liu, H. (1990). The use of upward pumping 45° pitched blade turbine impellers in three-phase reactors. Chemical Engineering Science, 45, 415–421. DOI: 10.1016/0009-2509(90)87027-P.CrossRefGoogle Scholar
  4. Chapman, C. M., Nienow, A. W., Cooke, M., & Middleton, J. C. (1983a). Particle-gas-liquid mixing in stirred vessels. Part III. Three phase mixing. Chemical Engineering Research & Design, 61, 167–181.Google Scholar
  5. Chapman, C. M., Nienow, A. W., Cooke, M., & Middleton, J. C. (1983b). Particle-gas-liquid mixing in stirred vessels. Part IV: Mass transfer and final conclusions. Chemical Engineering Research & Design, 61, 182–185.Google Scholar
  6. Dohi, N., Matsuda, Y., Itano, N., Shimizu, K., Minekawa, K., & Kawase, Y. (1999). Mixing characteristics in slurry stirred tank reactors with multiple impellers. Chemical Engineering Communications, 171, 211–229. DOI: 10.1080/00986449908912758.CrossRefGoogle Scholar
  7. Dohi, N., Takahashi, T., Minekawa, K., & Kawase, Y. (2004). Power consumption and solid suspension performance of large-scale impellers in gas-iquid-solid three-phase stirred tank reactors. Chemical Engineering Journal, 97, 103–114. DOI: 10.1016/S1385-8947(03)00148-7.CrossRefGoogle Scholar
  8. Dutta, N. N., & Pangarkar, V. G. (1995). Critical impeller speed for solid suspension in multi-impeller three phase agitated contactors. The Canadian Journal of Chemical Engineering, 73, 273–283. DOI: 10.1002/cjce.5450730302.CrossRefGoogle Scholar
  9. Frijlink, J. J., Bakker, A., & Smith, J. M. (1990). Suspension of solid particles with gassed impellers. Chemical Engineering Science, 45, 1703–1718. DOI: 10.1016/0009-2509(90)87049-X.CrossRefGoogle Scholar
  10. Harnby, N., Edwards, M. F., & Nienow, A. W. (1992). Mixing in the process industries. Oxford, UK: Butterworth-Heinemann.Google Scholar
  11. Jin, B., & Lant, P. (2004). Flow regime, hydrodynamics, floc size distribution and sludge properties in activated sludge bubble column, air-lift and aerated stirred reactors. Chemical Engineering Science, 59, 2379–2388. DOI:10.1016/j.ces.2004.01.061.CrossRefGoogle Scholar
  12. Kamieński, J. (2004). Agitation of multi-phase systems. Warsaw, Poland: WNT. (in Polish)Google Scholar
  13. Karcz, J., & Cudak, M. (2003). Local momentum and heat transfer in a liquid and gas-solid-liquid systems mechanically stirred in a jacketed vessel. 11th European Conference on Mixing, 14–17 October 2003 (Paper P24). Bamberg, Germany.Google Scholar
  14. Kiełbus-Rąpała, A., & Karcz, J. (2009). Influence of suspended solid particles on gas-liquid mass transfer coefficient in a system stirred by double impellers. Chemical Papers, 63, 188–196. DOI: 10.2478/s11696-009-0013-y.CrossRefGoogle Scholar
  15. Kluytmans, J. H. J., Wachem, B. G. M., Kuster, B. F. M., & Schouten, J. C. (2003). Mass transfer in sparged and stirred reactors: influence of carbon particles and electrolyte. Chemical Engineering Science, 58, 4719–4728. DOI:10.1016/j.ces.2003.05.004.CrossRefGoogle Scholar
  16. Kordač, M., & Linek, V. (2006). Mechanism of enhanced gas absorption in presence of fine solid particles. Effect of molecular diffusivity on mass transfer coefficient in stirred cell. Chemical Engineering Science, 61, 7125–7132. DOI:10.1016/j.ces.2006.06.025.CrossRefGoogle Scholar
  17. Lehn, M. C., Myers, K. J., & Bakker, A. (1999). Agitator design for solid suspension under gassed conditions. The Canadian Journal of Chemical Engineering, 77, 1065–1071. DOI:10.1002/cjce.5450770537.CrossRefGoogle Scholar
  18. Littlejohns, J. V., & Daugulis, A. J. (2007). Oxygen transfer in a gas-liquid system containing solids of varying oxygen affinity. Chemical Engineering Journal, 129, 67–74. DOI:10.1016/j.cej.2006.11.002.CrossRefGoogle Scholar
  19. Majířvá, H., Příkopa, T., Jahoda, M., & Machoň, V. (2002). Gas hold-up and power input in two- and three-phase dual-impeller stirred reactor. 15th International Congress of Chemical & Processing Engineering CHISA, 25–29 August 2002. Prague, Czech Republic.Google Scholar
  20. Nienow, A.W., & Bujalski, W. (2001). Studies on agitated three phase systems. 6th World Congress of Chemical Engineering, 23–27 September 2001. Melbourne, Australia.Google Scholar
  21. Nienow, A. W., & Bujalski, W. (2002). Recent studies on agitated three phase (gas-solid-liquid) systems in the turbulent regime. 7th Conference on Mixing, Fluid Mixing 7, 10–11 July 2002. Bradford, UK.Google Scholar
  22. Takenaka, K., Ciervo, G., Monti, D., Bujalski, W., Etchells, A. W., & Nienow, A. W. (2001). Mixing of three-phase systems at high solids content (up to 40% w/w) using radial and mixed flow impellers. Journal of Chemical Engineering of Japan, 34, 606–612. DOI: 10.1252/jcej.34.606.CrossRefGoogle Scholar
  23. Wiedmann, J. A. (1983). Zum Überflutungsverhalten zwei- und dreiphasig betriebener Ruehrreaktoren. Chemie Ingenieur Technik, 55, 689–700. DOI: 10.1002/cite.330550904.CrossRefGoogle Scholar
  24. Zhu, Y., & Wu, J. (2002). Critical impeller speed for suspending solids in aerated agitation tanks. The Canadian Journal of Chemical Engineering, 80, 1–6. DOI:10.1002/cjce.5450800417.CrossRefGoogle Scholar
  25. Zhu, Y., & Wu, J. (2001). Solid suspension in aerated agitation tanks. 6th World Congress of Chemical Engineering, 23–27 September 2001. Melbourne, Australia.Google Scholar
  26. Zwietering, T. N. (1958). Suspending of solids particles in liquid by agitation. Chemical Engineering Science, 8, 244–253. DOI: 10.1016/0009-2509(58)85031-9.CrossRefGoogle Scholar

Copyright information

© Institute of Chemistry, Slovak Academy of Sciences 2009

Authors and Affiliations

  1. 1.Department of Chemical EngineeringWest Pomeranian University of TechnologySzczecinPoland

Personalised recommendations